MEDICAL
Gift of
Harold E. Eraser, M.D
o
TEXT. BOOK OF ANATOMY
PUBLISHED BY THE JOINT COMMITTEE OF HENRY FROWDE AND HODDER & STOUGHTON
AT THE OXFORD PRESS WAREHOUSE, FALCON SQUARE, LONDON, E.G.
CUNNINGHAM'S
^
TEXT-BOOK
OF
ANATOMY
EDITED BY
ARTHUR ROBINSON, M.D., F.R.C.S. ED.
PROFESSOR OF ANATOMY, UNIVERSITY OF EDINBURGH
V
FIFTH EDITION
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FIRST EDITION 1902
SECOND EDITION 1905
THIRD EDITION 1909
FOURTH EDITION 1913
REVISED FOURTH EDITION 1915
FIFTH EDITION 1918
/.
r
TO
Sir William burner, It.C.B.
F.R.S., M.B., LL.D., D.C.L., D.Sc.
IN RECOGNITION OF
HIS EMINENCE AS AN ANATOMIST
AND HIS INFLUENCE AS A TEACHER
THIS VOLUME
IS DEDICATED
BY THOSE OF HIS FORMER PUPILS AND ASSISTANTS
WHO HAVE CONTRIBUTED
TO ITS PAGES
PRINTED FOR THE JOINT COMMITTEE OF HENRY FROWDE, HODDER & STOUGHTON, OXFORD PRESS
WAREHOUSE, FALCON SQUARE, LONDON, B.C., BY R. & R. CLARK, LTD., EDINBURGH,
GREAT BRITAIN.
All rights reserved
PREFACE TO THE FOURTH EDITION.
THE fourth edition of Cunningham's Text-book of Anatomy has lacked during its
preparation the able guidance of its original editor, but the various contributors
have attempted to maintain the standard of excellence which was Professor
Cunningham's ideal.
The deaths of Professor Cunningham, Professor Birmingham, and Professor
A. H. Young have necessitated changes in the authorship of several of the articles.
Every section has been fully revised; some have been partially and others
have been completely rewritten.
In the majority of the sections numerous additional illustrations have been
added, or the original illustrations have been replaced by new figures better
adapted to their purpose, and colour has been largely used, particularly in diagrams.
The sections originally written by Professor Cunningham were the Central
Nervous System, the Eespiratory System, and the Ductless Glands. The account
of the Central Nervous System has been revised and largely rewritten by
Professor Elliot Smith of Manchester. The Kespiratory System has been revised
and partly rewritten by Professor Berry of Melbourne ; and the section dealing
with the Ductless Glands has been rewritten by Professor A. Campbell Geddes
of Dublin.
The description of the Alimentary System, originally written by Professor
Birmingham, has been revised and partially rewritten by Professor Waterston of
King's College, London.
With regard to the sections dealing with General Embryology and the
Vascular System, in the original preparation of which I was associated with my
senior colleague and friend, Professor A. H. Young, I have completely rewritten
the account of General Embryology, and have revised and partially rewritten the
account of the Vascular System.
It may be found, where the sections written by various authors overlap one
another, that there occur, in this as in previous editions, different accounts of
certain phenomena concerning which our knowledge is still in an indefinite stage,
and it must be understood that the authors of the various sections are solely
responsible for the opinions expressed in their own sections.
The Basle anatomical terminology has been adopted throughout, except in
those cases where the results of recent researches have shown that the terms of
that nomenclature are incorrect, or where the terms themselves did not conform
with the principles of the terminology.
It is scarcely necessary, to-day, to urge reasons for the use of the Basle
nomenclature, for it is now generally recognised, not only that it is based on
vi
PKEFACE. vii
sound general principles, but also that it is, at the same time, less cumbrous and
more definitely instructive than the terminology previously in use in this country.
One of the recognised functions of a preface is to give the editor the
opportunity of expressing his thanks to those who have assisted in the production
of the work, and I gladly avail myself of this function.
My thanks are due to all the authors for their courtesy and consideration. To
Mr. J. Keogh Murphy, F.K.C.S., for the preparation of an extremely useful glossary
and index, and for ever-ready help and many valuable suggestions. To Dr. E. B.
Jamieson for assistance in the revision of the text, and for the preparation of
specimens from which some of the new illustrations were made.
I am also greatly indebted to Professor Keibel, and to Mr. Gustav Fischer of
Jena for permission to copy eight figures from Normentaflen zur Entwicklungs-
geschichte des Menschen ; to Professor Gustav Ketzius for permission to use
figures from his monographs; and to Professors Mall, Felix, and Tandler for
permission to utilise the results of their work in the preparation of diagrams.
Most of the new figures in this edition have been drawn by Mr. J. T.
Murray with his usual skill and appreciation, and the remainder have been prepared
by Mr. Frank Butterworth from designs made by the authors of the articles in
which the figures appear.
AETHUE EOBINSON.
EDINBURGH, April 1913.
PREFACE TO THE FOURTH EDITION, REVISED.
THE whole of the text of this edition has been carefully revised, and alterations
which seemed to be necessitated by advancing knowledge have been made.
As in the case of the fourth edition I am greatly indebted to Dr. E. B.
Jamieson for his invaluable assistance.
AETHUE EOBINSON.
October 6. 1914.
PREFACE TO THE FOURTH EDITION, THIRD
IMPRESSION, REVISED.
THE whole of the text has again been revised, and mistakes to which attention has
been directed have been corrected.
Notes have been appended to some of the sections drawing attention to the
bearing of recent observations on statements made in the text.
Parts of the Vascular System have been rewritten, and in that section some of
the old figures have been replaced, partly by drawings made by Mr. J. T. Murray
from recent dissections, and partly by diagrams illustrating points not well shown
by dissections.
I am indebted for the dissections from which the drawings were made to
Dr. E. B. Jamieson and Mr. A. E. Maclean.
AETHUE EOBINSOK
June S, 1917.
--LJ
v*V "
Oliver Sheppard, R.H.A.,fecit.
DANIEL JOHANNES CUNNINGHAM ADHUC LOQUITUR.
DEMONSTRATOR OF ANATOMY, UNIVERSITY OF EDINBURGH, 1874-1882.
PROFESSOR OF ANATOMY, ROYAL COLLEGE OF SURGEONS, DUBLIN, 1882-1883.
PROFESSOR OF ANATOMY, TRINITY COLLEGE, DUBLIN, 1883-1903.
PROFESSOR OF ANATOMY, UNIVERSITY OF EDINBURGH, 1903-1909.
LIST OF CONTRIBUTORS
RICHARD J. A. BERRY, M.D., F.R.C.S. Ed.,
Professor of Anatomy, University of Melbourne.
(The Respiratory System.)
A. FRANCIS DIXON, M.B., D.Sc. (Dubl),
Professor of Anatomy, Trinity College, Dublin.
(Tlie Uro-genital System.)
A. CAMPBELL GEDDES, M.D.,
Professor of Anatomy, University of Montreal.
(The Ductless Glands.)
DAVID HEPBURN, M.B., F.R.S.E.,
Professor of Anatomy, University College, Cardiff.
(Arthrology.)
ROBERT HOWDEN, M.A., M.B.,
Professor of Anatomy, University of Durham.
(The Organs of Sense and the Integument.)
A. M. PATERSON, M.D., F.R.C.S.,
Professor of Anatomy, University of Liverpool.
(Myology, The Spinal and Cerebral Nerves, Ttie Sympathetic Nervous System.)
ARTHUR ROBINSON, M.D., F.R.C.S. Ed.,
Professor of Anatomy, University of Edinburgh.
(General Embryology, The Vascular System.)
G. ELLIOT SMITH, M.D., F.R.S.,
Professor of Anatomy, University of Manchester.
(The Central Nervous System.)
HAROLD J. STILES, M.B., F.R.C.S. Ed.,
Surgeon to the Royal Hospital for Sick Children, Edinburgh.
(Surface and Surgical Anatomy.)
ARTHUR THOMSON, LL.D., M.A., M.B., F.R.C.S.,
Professor of Human Anatomy, University of Oxford.
(Osteology.)
DAVID WATERSTON, M.A., M.D., F.R.C.S. Ed.,
Professor of Anatomy, University of St. Andrews.
(The Digestive System.)
CONTENTS.
GLOSSARY OF VARIATIONS BETWEEN INTERNATIONAL AND OLD TERMINOLOGY
INTRODUCTION .
PAGE
xvii
GENERAL EMBRYOLOGY.
The Animal Cells
Reproduction of Cells ...
Amitotic and Mitotic Division of
Cells .'
The Ovum
Its Structure
Its Maturation
The Spermatozoon
Fertilisation
Segmentation
Formation of Blastula . . . .
Ectoderm and Entoderm . . .
Embryonic Area . . . .
Extra-Embryonic Coelom ...
Differentiation of the Embryonic
Area
Neural Groove .....
Formation of Notochord and Secondary
Mesoderm
The Paraxial Mesoderm ....
Mesodennic Somites ....
Early Stages in Development of the
Nervous System ....
Nerve Ganglia and Chromaffin
Tissues
Differentiation of the Neural Tube .
Fate of Walls of Primitive Brain
Vesicles
Fate of Cavities of Primitive
Brain
Folding off of the Embryo ...
Professor ARTHUR ROBINSON.
PAGE : PAGE
7 | Formation of the Embryo ... 39
8 Development of the Limbs ... 39
Primitive Alimentary Canal . . . 41
9 The Fore -Gut Pharynx and Stoma-
13 todaeum 42
13 Visceral Clefts and Arches . . 43
15 Rudiments of Respiratory System . 44
17 External Ear, Tympanic Cavity,
20 and Auditory Tube ... 44
21 The Tongue 45
21 Derivatives of the Mid-Gut ... 47
21 The Hind-Gut, Anal Passage, and Post-
22 anal Gut 48
22 Derivatives of the Stomatodaeum
The Nose and Mouth ... 48
23 The Internal Ear 50
23 Protection and Nutrition of the Embryo
during its Intra-uterine Existence 53
24 Foetal Membranes and Appendages . 53
28 Chorion 53
28 Amnion ...... 54
Body-Stalk 54
30 Allantois 54
Umbilical Cord .... 55
32 Yolk-Sac or Umbilical Vesicle . . 55
33 The Placenta 56
Primitive Vascular System and Foetal
33 Circulation 63
Summary of the External Features of
36 the Human Embryo and Foetus at
37 different periods of Development . 74
OSTEOLOGY.
The Skeleton 81
Composition. of Bone . 82
Structure of Bone .... 83
Ossification and Growth of Bones . 85
The Vertebral Column .... 87
A Typical Vertebra ....
Cervical Vertebrae . . . . 90
Thoracic Vertebrae .... 93
Lumbar Vertebras .... 95
False or Fixed Vertebrae . . .96
The Sacrum 96
The Coccyx 99
The Vertebral Column as a whole . 100
Professor ARTHUR THOMSON.
Development of the Vertebral Column . 102
The Cartilaginous Column . . .102
Ossification of the Vertebrae ... 104
The Sternum 106
The Ribs 109
The Costal Cartilages . . . .113
The Thorax as a whole . . . . 113
The Bones of the Skull . ... 115
Frontal Bone 115
Parietal Bones . . . . .118
Occipital Bone .... 120
Temporal Bones .... 125
Sphenoid Bone 133
CONTENTS.
XI
Ethmoid Bone . . .
Inferior Conchae
The Lacrimal Bones
The Vomer .....
Nasal Bones . .
Sutural Bones ....
Bones of the Face ....
Maxillae
Palate Bones ....
Zygomatic Bones
Mandible
The Hyoid Bone ....
The Skull as a whole
The Skull from the Front
The Skull from the Side .
Posterior Aspect of the Skull .
Upper Aspect of Skull
Base of the Skull .
The Skull in Section
Upper Surface of the Base of
Skull
Medial Sagittal Section of
Skull .....
Nasal Fossae .
Nasal Septum ....
Air-sinuses in connexion with
Nasal Fossae ....
Frontal Sections of the Skull .
Horizontal Section of the Skull
Sexual Differences in the Skull
The Skull at Birth
Differences due to Age .
Bones of the Upper Extremity
Clavicle
Scapula .....
Humerus .
the
the
the
PAGE
139
142
143
144
145
145
146
146
150
153
154
158
159
160
164
171
171
172
179
179
183
183
185
185
186
192
193
194
197
197
197
200
204
THE ARTICULATIONS OR JOINTS.
Syndesmology 299
Synarthroses 299
Diarthroses or Movable Joints . . 300
Structures which enter into the
Formation of Joints . . . 301
The Different Kinds of Movement
at Joints 303
The Development of Joints . . 304
Morphology of Ligaments . . 305
Ligaments of the Vertebral Column and
Skull 305
Articulation between the Atlas and
Epistropheus .... 309
Articulation between the Atlas and
the Cranium .... 310
Mandibular Joint ..... 312
Cranial Ligaments not directly asso-
ciated with Articulations . . 313
The Joints of the Thorax . . .313
Joints of the Heads of the Ribs . 313
Costo-transverse Joints . . . 314
Articulations between the Ribs and
their Cartilages . . . .315
Interchondral Joints . . . 315
Sterno-costal Joints . . . .315
Sternal Articulations . . . 317
The Articulations of the Superior Ex-
tremity 317
THE MUSCULAR SYSTEM.
The Muscular System .... 363
Fasciae 364
Description of the Muscles . . . . 365
PAGE
Ulna 210
Radius 214
The Carpus . . . . ,217
The Carpus as a whole . . .222
The Metacarpus .... 223
The Phalanges 226
Sesamoid Bones .... 228
Bones of the Lower Limb . . . 228
The Pelvic Girdle and the Lower Ex-
tremity 228
The Hip Bone 228
The Pelvis 235
The Femur 239
The Patella . . . . . 245
The Tibia 246
The Fibula 250
Tarsus 254
Talus 254
Calcaneus 259
Navicular Bone of the Foot . . 261
Cuneiform Bones .... 261
Cuboid Bone 263
The Tarsus as a whole . . .264
The Metatarsus 265
Phalanges of the Foot . . .267
Sesamoid Bones of the Foot . . 269
Appendices
Architecture of the Bones of the
Skeleton 270
Variations in the Skeleton . . 275
Serial Homologies of the Vertebras . 283
Measurements and Indices employed
in Physical Anthropology . . 284
Development of the Chondro-cranium
and Morphology of the Skull . 290
Morphology of the Limbs . . . 294
Professor DAVID HEPBURN.
Articulations of the Clavicle . . .317
Sterno-clavicular Joint . . . 317
Acromio-clavicular Joint . . .318
Ligaments of the Scapula . . 320
Shoulder-joint . . . . . 320
Elbow-joint 323
The Radio-ulnar Joints .... 326
The Radio-carpal Joint .... 328
Carpal Joints 329
Intermetacarpal Joints . . . 332
Carpo-metacarpal Joints . . . 332
Metacarpo-phalangeal Joints . . 333
Interphalangeal Joints .... 334
Articulations and Ligaments of the Pelvis 334
Lumbo-sacral Joints . . . 335
Sacro-iliac Joint . . . 335
Symphysis Pubis 337
Articulations of the Inferior Extremity 339
The Hip-joint 339
The Knee-joint .... 342
The Tibio-fibular Joints . . . 349
The Joints of the Foot . . .351
The Ankle-joint .... 351
The Intertarsal Joints . . .354
The Tarso-metatarsal Joints . . 359
Intermetatarsal Joints . . . 360
Metatarso-phalangeal Joints . . 360
Interphalangeal Joints . . . 361
Professor A. MELVILLE PATERSON.
Appendicular Muscles ... . 365
Fasciae and Superficial Muscles of the
Back 365
Xll
CONTENTS.
PAGE
Fasciae of the Back .... 365
The Superficial Muscles of the Back . 365
The Fasciae and Muscles of the Pectoral
Eegion 369
Fasciae of the Pectoral Eegion . . 369
Muscles of the Pectoral Region . . 369
Fasciae and Muscles of the Shoulder . 373
Muscles of the Shoulder . . .373
Fasci ae and Muscles of the Arm . . 378
Fasciae and Muscles of the Forearm and
Hand .... .382
The Muscles of the Front and Medial
Aspect of the Forearm . . .385
Superficial Muscles ....
Intermediate Layer .... 388
Deep Layer . . . . . . 388
Short Muscles of the Hand . . .391
Muscles of the Thumb .... 392
Muscles of the Little Finger . . .393
The Interosseous Muscles of the Hand . 394
The Muscles on the Dorsal Surface of the
Forearm 395
Superficial Muscles .... 396
Deep Muscles ..... 398
The Lower Limb 402
Fasciae and Muscles of the Thigh and
Buttock 402
Fasciaa of the Thigh and Buttock . . 402
Muscles of the Thigh and Buttock . 405
The Muscles on the Anterior Aspect of
the Thigh 405
The Muscles on the Medial Side of the
Thigh 411
The Muscles of the Buttock . . .414
The Muscles on the Posterior Aspect of
the Thigh 418
The Fasciae and Muscles of the Leg and
Foot 422
Fasciae of the Leg and Foot . . . 422
The Muscles on the Front of the Leg and
Dorsum of the Foot . . . 424
THE CENTRAL NERVOUS SYSTEM.
ELEMENTS OP THE CENTRAL NERVOUS
SYSTEM . . . . . . 497
Outline of Development of the Central
Nervous System .... 499
Neurone Theory 503
Nerve Components . . . 505
Nerve-cells ... 506
Nerve-fibres 508
Neuroglia 511
The Nature of the Brain . . .512
THE SPINAL MEDULLA .... 517
Internal Structure of Spinal Medulla 523
Characters presented by the Spinal
Medulla in its Different Regions . 524
Component Parts of the Gray Matter
of the Spinal Medulla . . .527
Component Parts of the White Matter
of the Spinal Medulla . . .531
THE ENCEPHALON OR BRAIN . . 539
General Appearance of the Brain . 539
Parts of Encephalon. derived from the
Hind-brain 543
Medulla Oblongata .... 543
Pons 548
The Fourth Ventricle . ' . . 549
Internal Structure of Medulla Ob-
longata and Pons . . . .551
Internal Structure of the Pons . 565
PAGE
The Muscles on the Lateral Side of the Leg 426
The Muscles on the Posterior Aspect of
the Leg 428
The Muscles in the Sole of the Foot . 432
Axial Muscles 437
The Fasciae and Muscles of the Back . 437
The Fasciae of the Back .... 437
The Muscles of the Back . . . 438
First Group . . ... .438
Second Group 439
Third Group 442
Fourth Group ..... 444
The Fasciae and Muscles of the Head
and Neck 446
Fasciae of the Head and Neck . . 446
The Muscles of the Head . . . 448
Superficial Muscles .... 448
The Muscles of the Scalp . . .448
The Muscles of the Face . . .450
The Fasciae and Muscles of the Orbit . 452
Muscles of Mastication .... 454
The Muscles of the Neck . . . 458
The Muscles of the Hyoid Bone . . 458
The Muscles of the Tongue . . .462
The Muscles of the Pharynx . . . 464
The Muscles of the Soft Palate . . 466
Deep Lateral and Praevertebral Muscles
of the Neck 467
The Muscles of the Thorax . . .470
Muscles of Respiration .... 470
Fasciae and Muscles of the Abdominal Wall 474
Fasciae of the Abdominal Wall . . 474
The Muscles of the Abdominal Wall . 476
Fasciae and Muscles of the Perineum
and Pelvis 485
Fasciae of the Perineum .... 485
The Muscles of the Perineum . . 486
The Fasciae of the Pelvis . . . 489
Muscles of the Pelvis .... 493
The Development and Morphology of .
the Skeletal Muscles . . 495
Professor G. ELLIOT SMITH.
The Cerebellum 570
The Structure and Connexions of the
Cerebellum 576
The Mesencephalon . . . .581
Internal Structure of the Mesence-
phalon 584
The Deep Connexions of the Cerebral
Nerves attached to the Medulla
Oblongata, Pons, and Mesence-
phalon 592
Prosencephalon or Fore-brain . . 607
Development of Parts derived from
Fore -brain 6(
Parts derived from the Dience-
phalon ...... 609
Thalamus 609
Hypothalamic Region . . . 613
Pineal Body 614
Trigonum Habenulae . . . 614
Corpora Mamillaria . . . .615
Hypophysis 615
Third Ventricle . . . .616
Cerebral Connexions of the Optic
Tract 619
Parts derived from the Telencephalon . 620
Cerebral Hemispheres . . . 620
The Connexions of the Olfactory
Nerves . 623
CONTENTS.
XI 11
The Cerebral Commissures and the
Septum Pellucidum . . . 628
The Corpus Callosum . . . 629
The Lateral Ventricle . . .632
Basal Ganglia of the Cerebral Hemi-
sphere 637
Intimate Structure of Cerebral Hemi-
sphere 644
The Cerebral Cortex . . . . .644
The Neopallium .... 645
The White Matter of the Cerebral
Hemispheres ..... 647
THE PERIPHERAL NERVOUS SYSTEM.
SPINAL NERVES
Development of the Peripheral Nerves .
Development of the Sympathetic System
Development of the Cerebral Nerves
677
679
681
682
685
687
688
690
690
The Spinal Nerves .
Posterior Rami of the Spinal Nerves
Posterior Rami of the Cervical Nerves
Posterior Rami of the Thoracic Nerves
Posterior Rami of the Lumbar Nerves
Posterior Rami of the Sacral and Coccy-
geal Nerves 691
Morphology of the Posterior Rami . 691
Anterior Rami of the Spinal Nerves . 692
Cervical Nerves 692
Cervical Plexus ' 694
Phrenic Nerve 699
Morphology of the Cervical Plexus . 700
Brachial Plexus 700
Branches of Brachial Plexus . . 701
Anterior Thoracic Nerves . . 703
Musculo-cutaneous Nerve . . 704
Median Nerve 705
Ulnar Nerve 708
Medial Cutaneous Nerve of the Fore-
arm 709
Medial Cutaneous Nerve of the
Arm 710
Axillary Nerve 710
Radial Nerve 710
Superficial Ramus of Radial Nerve . 712
Deep Ramus of Radial Nerve . . 712
Subscapular Nerves . . . ' . 713
Thoracic Nerves 713
Lumbo-sacral Plexus . . . .718
Lumbar Plexus 719
Obturator Nerve .... 722
Femoral Nerve 724
Sacral Plexus ..... 727
Sciatic Nerve . ... 728
The Nerves of Distribution from the
Sacral Plexus .... 728
ORGANS OF SENSE AND THE INTEGUMENT.
The Sulci and Gyri of the Cerebral
Hemispheres ..... 653
The Acoustic Area and Fibre Tracts 657
The Visual' Area and Fibre Tracts . 658
The Parietal Region of the Brain . 662
The Frontal Region .... 665
Weight of the Brain .... 667
Meninges of the Encephalon and Spinal
Medulla 667
Dura Mater . . . .667
Arachnoidea . . . . .670
Pia Mater 673
Professor A. MELVILLE PATERSON.
Common Peroneal Nerve .
Deep Peroneal Nerve
Superficial Peroneal Nerve
Tibial Nerve
Medial Plantar Nerve ...
Lateral Plantar Nerve
Pudendal Plexus
Pudendal Nerve ....
Morphology of the Pudendal Plexus
Morphology of the Limb-plexuses .
Distribution of Spinal Nerves to Muscles
and Skin of Limbs
Variations in Position of the Limb-
plexuses
Significance of the Limb-plexuses .
SYMPATHETIC NERVOUS SYSTEM .
Cervical Part of Sympathetic Trunk
Superior Cervical Ganglion
Middle Cervical Ganglion
Inferior Cervical Ganglion
Thoracic Part of Sympathetic Trunk .
Abdominal Part of Sympathetic Trunk
Pelvic Part of Sympathetic Trunk
Sympathetic Plexuses ....
Coeliac and Pelvic Plexuses
CEREBRAL NERVES ....
Olfactory Nerves ....
Oculo-motor Nerve .
Trochlear Nerve
Trigeminal Nerve
Abducens Nerve
Facial Nerve
Acoustic Nerve .
Glossopharyngeal Nerve
Vagus Nerve .
Thoracic Plexuses of
Accessory Nerve
Hypoglossal Nerve .
Development of Cerebral Nerves
Morphology of Cerebral Nerves
769
770
771
781
781
784
785
786
789
791
791
795
796
Professor ROBERT HOWDEN.
OLFACTORY ORGAN
Cartilages of Nose .
Nasal Cavity ....
ORGAN OF SIGHT .
Bulb of the Eye .
Sclera
Cornea
Vascular and Pigmented Tunic
Retina
Refracting Media of Eyeball .
Eyelids
Lacrimal Apparatus
Development of the Eye
AUDITORY ORGAN .
799
800
801
806
806
807
808
810
814
819
821
824
825
827
External Ear 827
Auricle 827
External Acoustic Meatus . . 830
Tympanic Cavity ... .832
Tympanic Antrum and Mastoid Air-
cells 836
Auditory Tube 837
Auditory Ossicles .... 838
Internal Ear 843
Osseous Labyrinth 843
Membranous Labyrinth .... 846
Development of Labyrinth . . 853
ORGANS OF TASTE 854
THE INTEGUMENT OR SKIN . . .856
b
XIV
CONTENTS.
Appendages of the Skin .
Development of the Skin
Appendages .
and its
PAGE [ PAGE
858 Endings of Nerves of General Sensa-
tion 863
861 Special End Organs .... 863
THE VASCULAR SYSTEM.
Structure of Blood-vessels
THE HEART
The Chambers of the Heart .
Structure of the Heart ....
Pericardium
ARTERIES
Pulmonary Artery .....
The Systemic Arteries ....
Aorta . . . . .
Thoracic Aorta . . .
Abdominal Aorta .....
Branches of the Ascending Aorta .
Coronary Arteries ....
Branches of the Arch of the Aorta
Innominate Artery ....
The Arteries of the Head and Neck
Common Carotid Arteries
External Carotid Artery
Branches of External Carotid Artery
Internal Carotid Artery
Branches of Internal Carotid Artery
Vertebral Artery .
Arteries of the Upper Extremity .
Subclavian Arteries ....
Branches of the Subclavian Artery .
Axillary Artery . . . . .
Branches of the Axillary Artery
Brachial Artery .....
Branches of Brachial Artery
Kadial Artery
Ulnar Artery
The Arterial Arches of the Wrist and
Hand . . . .
Branches of Descending Thoracic Aorta
Visceral Branches of the Descending
Thoracic Aorta ....
Parietal Branches of the Descending
Thoracic Aorta ....
Branches of Abdominal Aorta
The Paired Visceral Branches of the
Abdominal Aorta
The Unpaired or Single Visceral
Branches of the Abdominal Aorta
Parietal Branches of the Abdominal
Aorta
Common Iliac Arteries .
Hypogastric Artery ....
Branches of the Posterior Division .
Branches of the Anterior Division .
Visceral Branches ....
Parietal Branches of the Anterior
Division .....
The Arteries of the Lower Extremity .
The External Iliac Artery
The Femoral Artery ....
Popliteal Artery .....
Posterior Tibial Artery .
Plantar Arteries ....
Anterior Tibial Artery . . ' .
THE VEINS
The Pulmonary Veins . . .
Systemic Veins
Coronary Sinus and Veins of Heart
Superior Vena Cava and its Tribu-
taries ......
Azygos Veins
868
870
873
878
880
882
882
884
884
884
885
887
887
888
888
888
888
891
891
900
902
905
909
909
910
914
916
917
918
919
921
923
924
925
925
927
927
928
933
935
936
938
939
939
940
944
944
946
951
952
954
955
958
958
959
959
960
960
Professor ARTHUR ROBINSON.
Innominate Veins .... 962
Veins of the Head and Neck . . .964
The Veins of the Scalp . . .967
Veins of the Orbit, Nose, and Infra-
temporal Eegion .... 968
Venous Sinuses and Veins of the
Cranium, and its Contents . . 969
Diploic and Meningeal Veins . . 969
Veins of the Brain .... 970
Sinuses of the Dura Mater . . 972
Veins of the Spinal Medulla . . 977
Veins of the Superior Extremity . . 977
Deep Veins of the Upper Extremity 977
Axillary Vein 977
The Superficial Veins of the Superior
Extremity 978
Inferior Vena Cava and its Tributaries 980
Common Iliac Veins . . . 983
Veins of the Lower Extremity . . 985
Deep Veins of the Lower Extremity 986
Superficial Veins of the Lower Extre-
mity 990
The Portal System . ... . .988
Mesenteric and Splenic Veins . . 992
THE LYMPH VASCULAR SYSTEM . . 993
The Terminal Lymph Vessels . . 996
Lymph Glands of the Head . . .998
Lymph Glands of the Neck . . . 1000
Lymph Vessels of the Head and Neck . 1003
Lymph Glands of the Superior Extre-
mity 1006
Lymph Vessels of the Superior Extre-
mity 1009
The Lymph Glands of the Thorax . 1010
The Lymph Vessels of the Thorax . 1013
Lymph Glands and Vessels of the In-
ferior Extremity .... 1013
Lymph Vessels of the Inferior Extremity 1014
Lymph Glands of the Pelvis and Ab-
domen 1015
Lymph Vessels of the Pelvic Viscera . 1017
Lymph Glands of the Abdomen . . 1019
DEVELOPMENT OF THE BLOOD-VASCULAR
SYSTEM 1025
The Primitive Aortae and Primitive
Heart 1025
The Primitive Veins . . . 1026
Development of Heart, of first part of
Aorta, and of Pulmonary Artery . 1031
Division of Heart into its different
Chambers, and Division of Aortic
Bulb 1033
The Aortic Arches Formation of
Chief Arteries .... 1027
Primitive Dorsal Aortae Formation
of Descending Aorta . . . 1028
Branches of Primitive Dorsal Aortae 1029
Arteries of Limbs . . . .1031
Development of the Veins . . 1035
The Vitelline and Umbilical Veins . 1036
Formation of the Portal System . 1036
The Anterior Cardinal Veins . . 1038
The Posterior Cardinal Veins, the
Subcardinal Veins, and the Inferior
Vena Cava 1040
Veins of Limbs . 1042
CONTENTS.
xv
PAGE
MORPHOLOGY OF THE VASCULAR SYSTEM 1042
The Segmental Arteries and their
Anastomoses 1042
Aorta, Pulmonary Artery, and other
Chief Stem Vessels . . . 1046
The Limb Arteries .... 1047
Morphology of the Veins . . . 1047
ABNORMALITIES AND VARIATIONS OF
THE VASCULAR SYSTEM . . 1049
Abnormalities of the Heart . . . 1050
Abnormalities of Arteries . . . 1050
THE RESPIRATORY SYSTEM.
The Organs of Respiration and Voice . 1061
The Larynx 1061
Cartilages of the Larynx . . 1062'
Articulations, Ligaments, and Mem
branes of the Larynx . . 1065
Cavity of the Larynx . . . 1068
Muscles of the Larynx .... 1072
Trachea 1078
THE DIGESTIVE SYSTEM.
Digestive System, General Arrangement of 1 103
Mouth 1106
Palate and Isthmus Faucium . . 1110
Teeth 1113
Permanent Teeth . . . .1115
Deciduous Teeth . . . .1121
Structure of the Teeth . . .1122
Tongue 1124
Glands .1131
Salivary Glands . . . .1133
The Pharynx 1140
The Palatine Tonsils . . .1145
The (Esophagus 1150
Structure of the (Esophagus . . 1153
The Abdominal Cavity . . . .1155
Subdivisions of the Abdominal
Cavity . . ... . . 1158
The Peritoneum 1160
Stomach . . .... 1163
Relations and Connexions of
Stomach 1169
Position of Stomach . . . .1172
Structure of the Stomach . . 1174
THE URINO-GENITAL SYSTEM.
THE URINARY ORGANS .... 1257
The Kidneys 1257
The Ureters 1265
The Urinary Bladder . . ' . .1271
The Urethra (Female) .... 1284
THE MALE REPRODUCTIVE ORGANS . 1286
The Testis 1286
The Deferent Duct .... 1289
Descent of the Testis .... 1295
Spermatic Funiculus .... 1296
Scrotum 1297
Penis 1298
Prostate 1301
Bulbo-urethral Glands . . . .1304
The Male Urethra .... 1304
THE FEMALE REPRODUCTIVE ORGANS . 1310
THE DUCTLESS GLANDS.
The Chromaphil and Cortical Systems 1341
The Suprarenal Glands . . .1343
Ductless Glands of Entodermal Origin . 1347
The Thyreoid Gland . . 1347
The Parathyreoid Glands . . 1348
PAGE
The Branches of the Aorta . . 1050
The Arteries of the Head and Neck . 1053
The Arteries of the Upper Limb . 1054
The Iliac Arteries and their Branches 1055
The Arteries of the Lower Limb . 1056
Abnormalities of Veins .... 1057
The Superior Vena Cava . . . 1057
The Veins of the Upper Extremity . 1058
The Inferior Vena Cava . . . 1058
The Veins of the Lower Extremity . 1059
Abnormalities of the Lymph Vessels . 1059
Professor RICHARD J. A. BERRY.
Bronchi ....... 1082
Thoracic Cavity ..... 1083
Pleurse ....... 1084
Mediastina ...... 1089
The Lungs ....... 1091
Root of the Lung .... 1096
Structure of the Lungs . . . 1098
Development of the Respiratory Apparatus 1099
Professor DAVID WATERSTON.
Intestines . . . . .
Structure of Intestines . .
Duodenum
Liver ..... .
Structure of Liver . . .
Vessels of Liver . . .
Gall-Bladder and Bile Passages .
Pancreas. .....
Jejunum and Ileum ...
Large Intestine . . . .
Caecum and Vermiform Process .
Colon . . . . . .
Rectum
Anal Canal
Peritoneum . . . . .
Development of Digestive System .
Development of the Teeth . .
Morphology of Teeth ...
Development of the Pharynx' .
of the (Esophagus, Stomach,
Intestines
of the Peritoneum ...
of the Liver and Pancreas .
and
1177
1178
1182
1187
1198
1199
1201
1203
1208
1210
1213
1219
1224
1228
1234
1244
1244
1248
1248
1249
1252
1254
Professor A. FRANCIS DIXON.
Ovary ....... 1310
Uterine Tubes ..... 1314
Uterus ....... 1316
Vagina ....... 1321
Female External Genital Organs . . 1324
Larger Vestibular Glands . . 1327
Development of the Urino-genital
Organs ...... 1327
The Wolffian Duct and Embryonic
Secretory Organ .... 1329
The Ureter and Permanent Kidney 1331
The Urethra ..... 1332
Sexual Glands and Generative Ducts 1333
External Genital Organs . . . 1335
The Mammary Glands . . . . 1336
Development of the Mammae . . 1339
Professor A. CAMPBELL GEDDES.
The Thymus ..... .1350
Ductless Glands associated with the
Vascular System .... 1352
Spleen ....... 1352
Glomus Coccygeum .... 1353
XVI
CONTENTS.
SURFACE AND SURGICAL ANATOMY.
HAROLD J. STILES, F.R.C.S. Ed.
PAGE
Head and Neck 1357
Cranium ...... 1357
Face 1374
Neck 1385
Thorax 1395
The Lungs and Pleura . . . 1398
The Heart and Great Vessels . . 1403
Abdomen 1407
The Anterior Abdominal Wall . 1407
Abdominal Cavity . . . .1411
The Abdominal Viscera . . . 1415
Male Perineum 1427
Prostate . . . . . . . 1429
Female Pelvis 1434
Back . 1436
The Upper Extremity
Shoulder .
Axilla
Arm .
Elbow
Forearm and Hand .
The Lower Extremity .
The Buttock .
The Back of the Thigh
The Popliteal Fossa .
The Front of the Thigh
The Knee .
The Leg .
The Foot and Ankle
PAGE
1444
1444
1446
1447
1449
1450
1455
1455
1456
1457
1458
1460
1461
1463
INDEX. ... 1467
A GLOSSARY
OF THE
INTERNATIONAL (B.N.AJ
ANATOMICAL TERMINOLOGY
GENEKAL TEEMS.
TERMS INDICATING SITUATION AND DIRECTION.
Longitudinalis
Verticalis
Anterior
Posterior
Ventral
Dorsal
Cranial
Caudal
Superior
Inferior
Proximal is
Distalis
Sagittalis
Frontalis
Horizontalis
Medianus
Medialis
Lateralis
Intermedius
Superficialis
Profundus
Externus
Internus
Ulnaris
Radialis
Tibial
Fibular
Longitudinal
Vertical
Anterior )
Posterior/
Ventral \
Dorsal J
Cranial \
Caudal J
Superior)
Inferior /
Proximal)
Distal J
Sagittal
Frontal
Horizontal
Median
Medial \
Lateral /
Intermediate
Superficial \
Deep J
External "1
Internal J
Ulnar \
Radial/
Tibial \
Fibular/
Referring to the long axis of the body.
/Referring to the position of the long axis of the body in the
I erect posture.
Referring to the front and back of the body or the limbs.
{'Referring to the anterior and posterior aspects, respectively, of
the body, and to the flexor and extensor aspects of the
limbs, respectively.
( Referring to position nearer the head or the tail end of the long
axis. Used only in reference to parts of the head, neck,
I or trunk. Cephalic is sometimes used instead of cranial.
(Used in reference to the head, neck, and trunk. Equivalent to
\ cranial and caudal respectively.
/Used only in reference to the limbs. Proximal, nearer the
I attached end. Distal, nearer the free end.
/Used in reference to planes parallel with the sagittal suture of
\ the skull, i.e. vertical antero-posterior planes.
/ Used in reference to planes parallel with the coronal suture of
I the skull, i.e. vertical transverse planes.
Used in reference to planes at right angles to vertical planes.
/Referring to the median vertical antero-posterior plane of the
\ body.
f Referring to structures relatively nearer to or further away from
\ the median plane.
/ Referring to structures situated between more medial and more
\ lateral structures.
f Referring to structures nearer to and further away from the
( surface.
(Referring, with few exceptions, to the walls of cavities and
hollow organs. Not to be used as synonymous with
| medial and lateral.
f Used in reference to the medial and lateral borders, respectively,
\ of the forearm and hand.
/Used in reference to the medial and lateral borders, respectively,
( of the leg and foot,
xvii
XV111
GLOSSAKY.
THE BONES.
B.N.A. TERMINOLOGY.
Vertebrae
Fovea costalis
superior
Fovea costalis inferior
Fovea costalis trans-
versalis
Radix arcus vertebrae
Atlas
Fovea dentis
Epistropheus
Dens
Sternum
Corpus sterni
Processus xiphoideus
Incisura jugularis
Planum sternale
Ossa Cranii.
Os frontale
Spina frontalis
Processus zygomati-
cus
Facies cerebralis
Facies frontalis
Pars orbitalis
Os parietale
Linese temporales
Sulcus transversus
Sulcus sagittalis
Os occipitale
Canalis hypoglossi
Foramen occipitale
magnum
Canalis condyloideus
Sulcus transversus
Sulcus sagittalis
Clivus
Linea nuchfe suprema
Linea nuchse superior
Linea nuchse inferior
Os sphenoidale
Crista infratemporalis
Sulcus chiasmatis
Crista sphenoidalis
Spina angularis
Lamina medialis pro-
cessus pterygoidei
Lamina lateralis pro-
cessus pterygoidei
Canalis pterygoideus
[Vidii]
Fossa hypophyseos
OLD TERMINOLOGY.
Vertebrae
Incomplete facet for
head of rib, upper
Incomplete facet for
head of rib, lower
Facet for tubercle of
the rib
Pedicle
Atlas
Facet for odontoid
process
Axis
Odontoid process
Sternum
Gladiolus
Ensiform process
Supra-sternal notch
Anterior surface
Bones of Skull.
Frontal
Nasal spine
External angular
process
Internal surface
Frontal surface
Orbital plate
Parietal
Temporal ridges
Groove for lateral
sinus
Groove for sup. longi-
tudinal sinus
Occipital
Anterior condyloid
foramen
Foramen magnum
Posterior condyloid
foramen
Groove for lateral
sinus
Groove for sup. long.
sinus
Median part of upper
surface of basi-occi-
'pital
Highest curved line
Superior curved line
Inferior curved line
Sphenoid
Pterygoid ridge
Optic groove
Ethmoidal crest
Spinous process
Internal pterygoid
plate
External pterygoid
plate
Vidian canal
Pituitary fossa
B. N. A. TERMINOLOGY.
Sulcus caroticus
Conchse sphenoidales
Hamulus ptery-
goideus
Canalis pharyngeus
Tuberculum sellae
Fissura orbitalis
superior
Os temporale
Canalis facialis [Fal-
lopii]
Hiatus canalis facialis
Vagina processus sty-
loidei
Incisura mastoidea
Impressio trigemini
Eminentia arcuata
Sulcus sigmoideus
Fissura petrotym-
panica
.Fossa mandibularis
Semicanalis tubae
auditivae
Os ethmoidale
Labyrinthus eth-
moidalis
Lamina papyracea
Processus uncinatus
Os lacrimale
Hamulus lacrimalis
Crista lacrimalis pos-
terior
Os nasale
Sulcus ethmoidalis
Maxilla
Facies anterior
Facies infratempor-
alis
Sinus maxillaris
Processus frontalis
Processus zygomati-
cus
Can ales alveolares
Canalis naso-lacri-
malis
Os incisivum
Foramen incisivum
Os palatinum
Pars perpendicularis
Crista conchalis
Crista ethmoidalis
Pars horizontalis
OLD TERMINOLOGY.
Cavernous groove
Sphenoidal turbinal
bones
Hamular process
Pterygo - palatine
canal
Olivary eminence
Sphenoidal fissure
Temporal Bone
Aqueduct of Fal-
lopius
Hiatus Fallopii
Vaginal process of
tympanic plate
Digastric fossa
Impression for Gas-
serian ganglion
Eminence for sup.
semicircular canal
Sigmoid fossa
Glaserian fissure
Glenoid cavity
Eustachian tube
Ethmoid
Lateral mass
Os planum
Unciform process
Lachrymal Bone
Hamular process
Lachrymal crest
Nasal Bone
Groove for nasal
nerve
Superior Maxillary
Bone
Facial or external
surface
Zygomatic surface
Antrum of Highmore
Nasal process
Malar process
Posterior dental
canals
Lachrymal groove
Premaxilla
Anterior palatine
foramen
Palate Bone
Vertical plate
Inferior turbinate
crest
Superior turbinate
crest
Horizontal plate
GLOSSAKY.
xix
B.N.A. TERMINOLOGY.
OLD TERMINOLOGY. B.N.A. TERMINOLOGY.
OLD TERMINOLOGY.
Os zygomaticum
Malar Bone Incisura radialis
Lesser sigmoid cavity
Processus temporal is
Zygomatic process Crista interossea
External or interos-
Processus fronto-
Frontal process
seous border
sphenoidalis
Facies dorsalis
Posterior surface
Foramen zygoma-
Temporo-malar canal
Facies volaris
Anterior surface
tico-orbitale
Facies medialis
Internal surface
Foramen zygomatico-
Malar foramen
Margo dorsalis
Posterior border
faciale
Margo volaris
Anterior border
Mandibula
Inferior Maxillary
Radius
Radius
Bone
Tuberositas radii
Bicipital tuberosity
Spina mentalis
Genial tubercle or
Incisura ulnaris
Sigmoid cavity
spine
Crista interossea
Internal or interos-
Linea obliqua
External oblique line
seous border
Linea mylohyoidea
Internal oblique line
Facies dorsalis
Posterior surface
Incisura mandibulse
Sigmoid notch
Facies volaris
Anterior surface
Foramen mandibulare
Inferior dental fora-
Facies lateralis
External surface
men
Margo dorsalis
Posterior border
Canalis mandibulae
Inferior dental canal
Margo volaris
Anterior border
Protuberantia men-
Mental process
talis
Carpus
Carpus
The Skull
as a Whole.
Os naviculare
Os lunatum
Scaphoid
Semilunar
Ossa suturarum
Wormian bones
Os triquetrum
Cuneiform
Foveolae granulares
Pacchionian depres-
Os multangulum
Trapezium
(Pacchioni)
sions
majus
Fossa pterygo-pala-
Spheno-maxillary
Os multangulum
Trapezoid
tina
fossa
minus
Canalis pterygo-
Posterior palatine
Os capitatum
Os magnum
palatinus
canal
Os hamatum
Unciform
Foramen lacerum
Foramen lacerum
Choanae
medium
Posterior nares
Lower Extremity.
Fissura orbitalis su-
perior
Sphenoidal fissure
Os coxse
Linea glutsea an-
Innominate Bone
Middle curved line
Fissura orbitalis in-
ferior
Spheno-maxillary
fissure
terior
Linea glutsea pos-
Superior curved line
terior
Upper Extremity.
Spina ischiadica
Spine of the ischium
Clavicula
Clavicle
Incisura ischiadica
Great sacro-sciatic
Tuberositas coracoi-
dea
Impression for conoid
ligament
major
Incisura ischiadica
notch
Lesser sacro-sciatic
Tuberositas costalis
Impression for rhom-
minor
notch
boid ligament
Tuberculum pubicum
Spine of pubis
Ramus inferior ossis
Descending ramus of
Scapula
Scapula
pubis
pubis
Incisura scapularis
Supra-scapular notch
Ramus superior ossis
Ascending ramus of
Angulus lateralis
Anterior or lateral
pubis
pubis
angle
Ramus superior ossis
Body of ischium
Angulus medialis
Superior angle
ischii
Ramus inferior ossis
Ramus of ischium
Humerus
Humerus
ischii
Sulcus intertubercu-
Bicipital groove
Pecten ossis pubis
Pubic part of ilio-
laris
pectineal line
Crista tuberculi
External lip
Facies symphyseos
Symphysis pubis
major is
Crista tuberculi
Internal lip
Pelvis
Pelvis
minoris
Pelvis major
False pelvis
Facies anterior medi-
Internal surface
Pelvis minor
True pelvis
alis
Apertura pelvis min-
Pelvic inlet
Facies anterior later-
External surface
oris superior
alis
Linea terminalis
Margin of inlet of
Margo medialis
Internal border
true pelvis
Margo lateralis
External border
Apertura pelvis min-
Pelvic outlet
Sulcus nervi radialis
Musculo-spiral groove
oris inferior
Capitulum
Epicondylus medialis
Epicondylus lateralis
Capitellum
Internal condyle
External condyle
Femur
Fossa trochanterica
Linea intertrochan-
Femur
Digital fossa
Spiral line
Ulna
Ulna
terica
Incisura semilunaris
Greater sigmoid
Crista intertrochan-
Post, inter trochau-
cavity
terica
teric line
XX
GLOSSARY.
B.N.A. TERMINOLOGY.
Condylus medialis
Condylus lateralis
Epicondylus medialis
Epicondylus lateralis
Tibia
Condylus medialis
Condylus lateralis
Eminentia inter-
condyloidea
Tuberositas tibiae
Malleolus medialis
Fibula
Apex capituli fibulae
Malleolus lateralis
OLD TERMINOLOGY.
Inner condyle
Outer condyle
Inner tuberosity
Outer tuberosity
Tibia
Internal tuberosity
External tuberosity
Spine
Tubercle
Internal malleolus
Fibula
Styloid process
External malleolus
B.N.A. TERMINOLOGY.
OLD TERMINOLOGY.
Bones of the Foot.
Talus
Calcaneus
Tuber calcanei
Processus medialis
tuberis calcanei
Processus lateralis
tuberis calcanei
Os cuneiforme pri-
mum
Os cuneiforme se-
cundum
Os cuneiforme ter-
tium
Astragalus
Os calcis
Tuberosity of os calcis
Inner } A .
I tuberosities
Outer J of os calcis
Inner cuneiform
Middle cuneiform
Outer cuneiform
THE LIGAMENTS.
Ligaments of the Spine.
Lig. longitudinale
anterius
Lig. longitudinale
posterius
Lig. flava
Membrana tectoria
Articulatio atlanto
epistrophica
Lig. alaria
Lig. apicis dentis
Anterior common liga-
ment
Posterior common liga-
ment
Ligamenta subflava
Posterior occipito-axial
ligament
Joint between the atlas
and the axis
Odontoid or check liga-
ments
Suspensory ligament
The Ribs.
Lig. capituli costae
radiatuin
Lig. sterno - costale
interarticulare
Lig. sterno - costalia
radiata
Lig. costoxiphoidea
Anterior costo - verte-
bral or stellate liga-
ment
Interarticular chon-
dro - sternal liga-
ment
Anterior and posterior
chondro -sternal liga-
ment
Chondro-xiphoid liga-
ments
The Jaw.
Lig. temporo-mandi-
bulare
Lig. spheno - mandi-
bulare
Lig. stylo - mandi-
bulare
Upper
Lig. costo-claviculare
Labrum glenoidale
Articulatio radio -
ulnaris proximalis
Lig. collaterale ulnare
Lig. collaterale
radiale
Lig. annulare radii
Chorda obliqua
Articulatio radio -
ulnaris distalis
External lateral liga-
ment of the jaw
Internal lateral liga-
ment of the jaw
Stylo - maxillary liga-
ment
Extremity.
Rhomboid ligament
Glenoid ligament
Superior radio - ulnar
joint
Internal lateral liga-
ment of elbow -joint
External lateral liga-
ment
Orbicular ligament
Oblique ligament of ulna
Inferior radio - ulnar
joint
Discus articularis
Recessus sacciformis
Lig. radio - carpeum
volare
Lig. radio - carpeum
dorsale
Lig. collaterale carpi
ulnare
Lig. collaterale carpi
radiale
Articulationes inter-
carpeee
Lig. accessoria volaria
Lig. capitulorum ossium
metacarpalium
transversa
Lig. collateralia
Triangular fibre -
cartilage
Membrana sacci-
formis
Anterior ligament of
the radio-carpaljoint
Posterior ligament of
the radio - carpal
joint
Internal lateral liga-
ment of the wrist-
joint
External lateral
ligament of the
wrist- joint
Carpal joints
Palmar ligaments of
the metacarpo -
phalangeal joints
Transverse metacar -
pal ligament
Lateral phalangeal
ligaments
The Lower Extremity.
Lig. arcuatum
Lig. sacro-tuberosum
Processus falci-
form is
Lig. sacro-spinosum
Labrum glenoidale
Zona orbicularis
Ligamentum ilio -
femorale
Lig. ischio-capsulare
Lig. pubo-capsulare
Lig. popliteum obli-
quum
Lig. collaterale
fibulare
Lig. collaterale
tibiale
Lig. popliteum arcu-
atum
Meniscus lateralis
Subpubic ligament
Great sacro - sciatic
ligament
Falciform process
Small sacro - sciatic
ligament
Cotyloid ligament
Zonular band
Y-shaped ligament
Ischio-capsular band
Pubo-femoral ligament
Ligament of Winslow
Long external lateral
ligament
Internal lateral liga-
ment
Arcuate popliteal liga-
ment
External semilunar
cartilage
GLOSSAEY.
xxi
B.N.A. TERMINOLOGY.
Meniscus medialis
Plica synovialis patel-
laris
Plicae alares
Articulatio tibio - fibu-
laris
Lig. capituli fibulae
Syndesmosis tibio-fibu-
laris
Lig. deltoideum
Lig. talo - fibulare an-
terius
Lig. talo-fibulare pos-
terius
OLD TERMINOLOGY.
Internal semilunar
cartilage
Lig. mucosum
Ligamenta alaria
Superior tibio - fibular
articulation
Anterior and posterior
superior tibio-fibular
ligaments
Inferior tibio - fibular
articulation
Internal lateral liga-
ment of ankle
Anterior fasciculus of
external lateral liga-
ment
Posterior fasciculus of
external lateral liga-
ment
B.N.A. TERMINOLOGY.
Lig. calcaneo-fibulare
Lig. talo - calcaneum
laterale
Lig. talo - calcaneum
mediale
Lig. calcaneo - navi-
culare plantare
Lig. talo -na vie ulare
Pars calcaneo-
navicularis
Pars calcaneo- j
cuboidea J catum
OLD TERMINOLOGY.
Middle fasciculus of
external lateral liga-
ment
External calcaneo-
astragaloid liga-
ment
Internal calcaneo-
astragaloid liga-
ment
Inferior calcaneo -
navicular ligament
Astragalo - scaphoid
ligament
Superior calcaneo - sca-
phoid ligament
Internal calcaneo-cu-
boid ligament
THE MUSCLES.
Muscles of the Back.
Superficial.
Levator scapulae Levator anguli scapulae
Muscles of the Chest.
Serratus anterior Serratus magnus
Muscles of Upper Extremity.
Biceps brachii
Lacertus fibrosus
Brachialis
Triceps brachii
Caput mediale
Caput laterale
Pronator teres
Caput ulnare
Brachio-radialis
Supinator
Extensor carpi radi-
alis longus
Extensor carpi radi-
alis brevis
Extensor indicis pro-
prius
Extensor digiti quinti
proprius
Abductor pollicis
longus
Abductor pollicis
brevis
Extensor pollicis
brevis
Extensor pollicis
longus
Lig. carpi transversum
Lig. carpi dorsale
Biceps
Bicipital fascia
Brachialis anticus
Triceps
Inner head
Outer head
Pronator radii teres
Coronoid head
Supinator longus
Supinator brevis
Extensor carpi radialis
longior
Extensor carpi radialis
brevior
Extensor indicis
Extensor minimi
digiti
Extensor ossis meta-
carpi pollicis
Abductor pollicis
Extensor primi inter-
nodii pollicis
Extensor secundi
internodii pollicis
Anterior annular
ligament
Posterior annular
ligament
Muscles of Lower Extremity.
Tensor fasciae latas Tensor fasciae femoris
Canalis adductorius Hunter's canal
(Hunteri)
Trigonum femorale
(fossa Scarpae ma-
jor)
Canalis femoralis
Annulus femoralis
M. quadriceps
femoris
Rectus femoris
Vastus lateralis
Vastus intermedius
Vastus medialis
M. articularis genu
Tibialis anterior
Tendo calcaneus
Tibialis posterior
Quadratus plantae
Lig. transversum
craris
Lig. cruciatum cruris
Lig. laciniatum
Retinaculum muscu- -\
lorum peronaeorum I
superius
Retinaculum muscu- |
lorum peronaeorum I
inferius J
Scarpa's triangle
Crural canal
Crural ring
Quadriceps
Rectus femoris
Vastus externus
Crureus
Vastus internus
Subcrureus
Tibialis anticus
Tendo Achillis
Tibialis posticus
Accessorius
Upper anterior an-
nular ligament
Lower anterior an-
nular ligament
Internal annular liga-
ment
External annular
ligament
Axial Muscles.
Muscles of the Back.
Serratus posterior
superior
Serratus posterior in-
ferior
Splenius cervicis
Sacro-spinalis
Ilio-costalis
Lumborum
Dorsi
Cervicis
Longissimus
Dorsi
Cervicis
Capitis
Serratus posticus
superior
Serratus posticus in-
ferior
Splenius colli
Erector spinae
Ilio-costalis
Sacro-lumbalis
Accessorius
Cervicalis ascendens
Longissimus
Dorsi
Transversalis cervicis
Trachelo-mastoid
XX11
GLOSSAKY.
B.N.A. TERMINOLOGY. OLD TERMINOLOGY. -HOOT* T.*+.aral TV/Tnonioc f *T A /.ir
Spinalis Spinalis
Dorsi Dorsi
JWW* MVW*M *M&tiM9\**W0 V* -L1\^V>A.
B.N.A. TERMINOLOGY. OLD TERMINOLOGY.
Cervicis Colli
Scalenus anteiior Scalenus anticus
Capitis Capitis
Scalenus posterior Scalenus posticus
Longus capitis Rectus capitis anticus
Semispinalis- Semispinalis
major
Dorsi Dorsi
Rectus capitis an- . Rectus capitis anticus
Cervicis Colli
terior minor
Capitis Complexus
Multifidus Multifidus spinae
Muscles of Thorax.
Transversus thoracis Triangularis sterni
Muscles of Head and Neck.
Diaphragma, pars Diaphragm, lumbar
lumbalis part
Epicranius Occipito-frontalis
Crus mediale ^ Crus and origin
Galea aponeurotica Epicranial aponeu-
Crus intermedium I from internal ar-
rosis
Crus laterale ) cuate ligaments
Procerus Pyramidalis nasi
Arcus lumbo- Ligamentum arcu-
Pars transversa Compressor naris
costalis medialis atum internum
(nasalis)
(Halleri)
Pars alaris (nasalis) Dilatores naris
Arcus lumbo- Ligamentum arcu-
Auricularis anterior Attrahens aurem
costalis lateralis atum externum
Auricularis posterior Retrahens aurem
(Halleri)
Auricularis superior Attollens aurem
Orbicularis oculi Orbicularis palpe-
Muscles of the Abdomen.
brarum
Pars lacrimalis Tensor tarsi
Ligamentum inguin- Poupart's ligament
Triangularis Depressor anguli oris
ale (Pouparti)
Quadratus labii su-
Ligamentum lacunare Gimbernat's ligament
perioris
(Gimbernati)
Caput zygomaticum Zygomaticus minor
Fibrae intercrurales Intercolumnar fibres
Caput infraorbitale Levator labii superi-
Ligamentum inguin- Triangular fascia
oris
ale reflexum (Col-
Caput angulare Levator labii superi-
lesi)
oris alaeque nasi
Annulus inguinalis External abdominal
Zygomaticus Zygomaticus major
subcutaneus ring
Caninus Levator anguli oris
Crus superius Internal pillar
Quadratus labii in- Depressor labii infer i-
Crus inferius External pillar
ferioris oris
Falx (aponeurotica) in- Conjoined tendon
Mentalis Levator menti
guinalis
Platysma Platysma myoides
M. transversus ab- Transversalis muscle
Sterno-thyreoid Sterno-thyroid
dominis
Thyreo-hyoid Thyro-hyoid
Linea semicircularis Fold of Douglas
(Douglasi)
Annulus inguinalis Internal abdominal
Muscles and Fascia of the Orbit.
abdominalis ring
Fascia bulbi Capsule of Tenon
Septum orbitale Palpebral ligaments
Perineum and Pelvis.
Rectus lateralis Rectus externus
Transversus perinei Transversus perinei
Rectus medialis Rectus internus
superficialis
M. sphincter urethrae Compressor urethras
membranaceae
Muscles of the Tongue.
Diaphragma urogeni- Deep transverse
tale muscle and compres-
Genio-glossus Genio-hyo-glossus
sor urethrse
Longitudinalis Superior lingualis
Fascia diaphragmatis Deep layer of triangu-
- superior
urogenitalis lar ligament
Longitudinalis Inferior lingualis
superior
inferior
Fascia diaphragmatis Superficial layer of
Transversus linguae Transverse fibres
urogenitalis in- the triangular liga-
Verticalis linguae Vertical fibres
ferior ment
Arcus tendineus White line of pelvis
fasciae pelvis
Muscles of the Pharynx.
Ligamenta pubo - Anterior and lateral
prostatica true ligaments of
Phary ngo - palatinus Palato- phary ngeus
bladder
M. uvulae Azygos uvulae
Fascia diaphragmatis Visceral layer of
Levator veli palatini Levator palati
pelvis superior pelvic fascia
Tensor veli palatini Tensor palati
Fascia diaphragmatis Anal fascia
Glosso-palatinus Palato -glossus
pelvis inferior
GLOSSARY.
XXlll
THE NERVOUS SYSTEM.
Spinal Medulla.
B.N.A. TERMINOLOGY.
Fasciculus anterior pro-
prius (Flechsig)
Fasciculus lateralis
proprius
Nucleus dorsalis
Pars thoracalis
OLD TERMINOLOGY.
Anterior ground or
basis bundle
Lateral ground bundle
Clarke's column
Dorsal part of spinal
medulla
Paramedian furrow
Sulcus intermedius
posterior
rhe Brain or Encephalon is divided into parts as follows :
B.N.A. TERMINOLOGY.
Column se anteriores, etc .
Fasciculus cerebro -
spinalis anterior
Fasciculus cerebro -
spinalis lateralis
(pyramidalis)
Fasciculus cerebello -
spinalis
Fasciculus antero-later-
alis superficialis
OLD TERMINOLOGY.
Anterior grey horns, etc.
Direct pyramidal tract
Crossed pyramidal
tract
Direct cerebellar tract
Gowers' tract
RHOMBENCEPHALON = Myelencephalon (medulla oblongata) (after-brain) 1
Metencephalon (pons and cerebellum) (hind-brain) ) Postel>lor primary vesicle.
'MESENCEPHALON (mid- brain peduncles, corpora quadrigemina, etc. ) Middle primary vesicle
Thalamus (optic thalamus).
Thalamencephalon <^-Metathalamus (geniculate bodies).
Epithalamus (pineal body, etc.).
CEREBRUM^
Diencephalon =
(inter-brain)
PROSENCEPHALON
(fore-brain)
Telencephalon
Mamillary portion of hypothalamus.
Posterior part of 3rd ventricle.
Optic portion of hypothalamus (hypophysis).
"r
1
1
i
Nucleus
n
rate are equal, the tissue or organ is in a state of equilibrium. As soon as the
death-rate exceeds the multiplication rate, decay and atrophy set in ; and when
the decay and atrophy have proceeded to such an extent that an important tissue
or organ can no longer perform its proper functions, general death ensues.
General decay and death are, therefore, the natural results of the loss of
multiplication power of the cells of the body, but life may persist after multiplica-
tion power is lost, so long as the cells last produced retain their capabilities, and
death may result whilst multiplication power
of the cells is retained, if the newly produced
cells are incapable of performing their proper
functions. Nevertheless, speaking generally,
it may be said that cell multiplication is
a vital necessity, and it takes place in two
ways (1) by amitotic and (2) by mitotic division
of pre-existing cells.
Amitotic Division. The phenomena of
amitotic division, so far as they are known, are
much simpler than those of mitotic division.
First the nucleus is constricted and divided ;
then the cell body is constricted and divided,
and two similar daughter cells, each half the
size of the mother cell, are produced. The part
played by the centrosome during the process
is not definitely known, but each daughter cell
eventually possesses a centrosome. The appar-
ently simple process of amitofcic division occurs
at some periods of growth, and the more com-
plicated process of mitotic division at other
periods, but the laws which govern the alterna-
tions are unknown.
Mitotic Division ; Mitosis, or Karyokin-
esis. Mitotic or karyokinetic division is not
Only the more complicated, but it appears also FlG - 4. SCHEMA OP ANIMAL CELL IN EARLY
to be the more important form of cell division. PART OF PROPHASE OF HoMOTYPE MlTOSIS '
It takes place in all rapidly growing tissues,
especially in the embryonic and foetal stages
of life, and it is the main form of cell division
which occurs in the earliest embryonic periods.
There are, however, two forms of mitosis, the
homotype and the heterotype. Of the two,
homotype is so much the more common that it
may be looked upon as the ordinary form, for
heterotype mitosis appears to be limited to one
of the two cell divisions which occur during
the maturation of the germ cells, and to
some of the cell divisions which are associated
with the production of malignant tumours.
Homotype Mitosis. The phenomena of
homotype mitosis occur in four phases, (1)
the prophase, (2) the metaphase, (3) the anaphase, and (4) the telophase.
The Prophase. During the prophase both the centrosome and the nucleus
undergo very obvious transformations.
The centrosome and its contained centriole divide into two parts, of which one
passes to one pole and the other to the opposite pole of the nucleus.
The nuclear transformations concern the nucleolus, the chromatic substance,
and the nuclear membrane.
The nucleolus disappears. In some cases it passes from the nucleus into the
cytoplasm, where it breaks up ; in other cases the details of its disappearance are
entirely unknown.
FIG. 3. SCHEMA OF ANIMAL CELL IN
RESTING STAGE.
Daughter
centrosome x^
Nucleus with
chromatic/'
substance in
skein form! .-.'
Achromatic
spindle
Daughter centrosome
Achromatic
spindle
Chromosomes L'l^--
at equator '/ '
of spindle y/:;
V-
FIG. 5. SCHEMA OF ANIMAL CELL AT COM-
PLETION OF PROPHASE OF HOMOTYPE
MITOSIS.
10
HUMAN EMBKYOLOGY.
Daughter centrosome
Chromosomes
dividing into
equal parts
PHASE OF HOMOTYPE MlTOSIS.
Daughter centrosome
Chromosomes at ^-
pole of spindlex^
Achromatic / f.
spindle y.
The chromatic substance is aggregated to form first a fine and afterwards a
thicker thread or spirem. At the same time, a spindle of achromatic fibrils appears
between the two daughter centrosomes, and the nuclear membrane disappears.
As soon as the achromatic spindle is definitely established the chromatic
thread breaks up into a number of segments, the chromosomes, which arrange
themselves around the equator of the achromatic spindle.
The chromosomes may be V-shaped, rod-like, cuboidal or spheroidal, and each
may be a single structure, or it may consist of
two or four parts which are closely bound to-
gether. There is evidence which tends to sup-
port the belief that, whether the chromosome
appears to consist of one, two, or more seg-
ments, its constituent particles are derived
partly from the maternal and partly from the
paternal ancestor of the cell ; and it is believed
that the maternal and paternal portions undergo
similar division during the last three phases of
mitosis. In any case, whether the chromosomes
are single or compound structures, each becomes
FIG. 6. SCHEMA OF ANIMAL CELL IN META- attached to, or very closely associated with, one
of the fibrils of the achromatic spindle.
At the end of the prophase the nucleus
as such, and the nucleolus, have entirely dis-
appeared, and the cell body contains, in their
place, two centrosomes, an achromatic spindle,
and the chromosomes. The centrosomes lie at
the opposite poles of the achromatic spindle
with the granules of the protoplasm grouped
radially around them, and the chromosomes are
grouped round the equator of the achromatic
spindle.
The Metaphase. During the metaphase
each chromosome divides into two equal parts,
the rods or loops dividing longitudinally ; and
the division, in all cases, commences at the
point where the chromosome is in relation with
the fibrils of the achromatic spindle.
The Anaphase. In the anaphase the halves
of the chromosomes, i.e. daughter chromosomes,
move towards the opposite poles of the achro-
matic spindle, and when they reach the vicinity
of the daughter centrosomes the anaphase ends
and the telophase begins.
The Telophase. At the end of the anaphase,
or the commencement of the telophase, a con-
striction appears around the periphery of the
FIG. S.-SCHBMA OF ANIMAL CELL AT END OF Cell > at the level of the e ^>
spindle /reXj
lies in the region of the larger deutoplasmic granules by which its presence is
frequently obscured.
The Mitochondria. These minute particles can be demonstrated by suitable
methods of fixation and staining.
The Maturation of the Ovum. The process of maturation consists of two
mitotic divisions, of which the first is hetero-
typical, and results in the reduction of the
number of chromosomes, and the second is
homotypical. The phenomena of the two
divisions differ in some of their details from
those of ordinary cell divisions, therefore a
short account of them is necessary.
In the prophase of the first maturation
division, the centrosome, the nucleolus, and
the nucleus vanish, and an achromatic spindle
appears at one pole of the oocyte, where it
lies, at first, parallel with the surface ; and
the chromosomes are gathered around its
equator. The number of the chromosomes
is only half the typical number, and they
are probably twin chromosomes (p. 11).
There are no centrosomes at the poles of the
spindle. After a short time the spindle
rotates until it lies at right angles to its
original position, and one pole, surrounded
by a small amount of the cytoplasm, forms
a projection, the first polar projection, on the
surface of the oocyte (Fig. 14).
During the metaphase the twin chromo-
somes divide. In the anaphase the daughter
chromosomes travel to the opposite poles of
the spindle, and at the end of the anaphase
one-half of the daughter chromosomes lies
in the first polar projection and the other
half in the body of the oocyte (Fig. 16).
In the telophase the first polar projection
is separated from the body of the oocyte and
oocyte I ceases to exist, being converted
into an oocyte of the second order, or oocyte
II, and the first polar body, each of which
contains half the typical number of chromo-
somes.
The second maturation division occurs
without the intervention of a resting stage,
i.e. without the reappearance of a nucleus
in oocyte II. A new achromatic spindle
appears with the daughter chromosomes at
its equator ; it rotates, and one pole, sur-
rounded by a small amount of cytoplasm,
projects on the surface of the oocyte as the
second polar projection (Fig. 17). In the
metaphase the daughter chromosomes divide
homotypically into equal parts, and during
the anaphase the grand- daughter chromo-
somes move towards the poles of the spindle,
one-half entering the second polar projection and the other half remaining
in the body of the oocyte. During the telophase the second polar projection is
separated as the second polar body and the larger remaining part of the oocyte
II becomes the mature ovum (Figs. 1*7 and 18).
Chromosomes
which remain in
oocyte II
FIG. 16. SCHEMA OF MATURATION OF OVUM AT
END OF THE ANAPHASE OF THE FIRST DIVI-
SION. Two chromosomes (paternal or maternal)
lie in the first polar bud and two in the larger
part of the ovum which becomes oocyte II.
Oolemma
First polar body -
Second polar bud
Chromosomes of
oocyte II
Achromatic
spindle
FIG. 17. SCHEMA OF MATURATION OF OVUM AT
THE COMMENCEMENT OF THE METAPHASE OF
THE SECOND DIVISION.
16
HUMAN EMBEYOLOGY.
Simultaneously with the division of the oocyte II into the second polar body
and the mature ovum, the first polar body may divide into two parts. When
that occurs four cells are present within the oolemma at the end of the matura-
tion, i.e. the relatively large mature ovum and the three polar bodies (Fig. 19).
The details of the maturation of the human ovum are unknown, and the above
account is based upon the phenomena which occur in other mammals. In mammals
two polar bodies are invariably formed, but in many the first does not divide into
two parts simultaneously with the formation of the second. The significance of
the differences which occur is not at present fully understood.
Each of the four descendants of the oocyte I contains half the typical number of
chromosomes, and those in the mature ovum
soon become enclosed in a new -formed
nucleus, which is called the female promicleus.
When the process of maturation is com-
pleted, the mature ovum differs from a
typical animal cell, inasmuch as it probably
possesses no centrosome and its nucleus con-
tains the chromatic substance of only half
the typical number of chromosomes.
The first maturation division always
occurs whilst the oocyte is still in the ovary
and before the spermatozoon has entered
it. The second division takes place in the
FIG. is. SCHEMA OF MATURATION OF OVUM AT upper or middle part of the uterine tube, and
END OF ANAPHASE OF SECOND DIVISION a i ways a ft er the spermatozoon has entered
The chromosomes 01 oocyte 11 have separated , ^ ,
the oocyte.
If the mature ovum does not meet with
a spermatozoon it passes through the genital
passages and is cast off and lost; or it
breaks down, whilst still in the genital pas-
sages, into a detritus which disappears ; but
if it meets and unites with a spermatozoon
/-"//. '^K" \ a zygote is formed, from which a new indi-
I I $ FA vidual may arise, and in that case the polar
( ^S?' bodies persist until the zygote has undergone
J ; one or two divisions; but sooner or later they
.// disappear, probably breaking down into frag-
Femaiepro- \\< ments which are absorbed by the cells of the
nucleus in. " V /
Second polar bud with chromosomes
Chromosomes of second polar bud '
Oolemma :-<$d3HB[^te
First polar body _;'_.
Achromatic /./.-
spindle , //~"^
Chromosome?
which remain ir
mature ovuir
into equal parts which have passed to the
opposite poles of the spindle.
Second
Parts of first polar
Parts of first polar
body S,
Oolemma /'/
fex
mature ovum
Spermatocytes. When the male germ
FIG. 19.-SCHEMA OF MATURATION OF OVUM. cells reach the P eri d f r wth the ^ are
END OF TELOPHASE OF SECOND DIVISION where called spermatocytes of the first order, or
the four descendants of oocyte I are the mature spermatocytes I, which Correspond, mor-
ovum, with half the original number of ^holnmpallv with OOCvtPS I (Tiff 10")
chromosomes, and three polar bodies. . pnOlOglCaiiy, Wit ocyufc
The spermatocytes he in the walls of
the tubules of the testes or male sex glands, where their descendants become
converted into spermatozoa.
They differ from the oocytes I in three important respects : (1) they have no
protective membrane corresponding with the oolemma of the oocyte ; (2) they are
not enclosed in follicles ; (3) the spermatocytes are not surrounded by definite
encircling layers of cells similar to the cells of the stratum granulosum.
As the spermatocytes lie in the walls of the tubules of the testes they are inter-
mingled with other cells, the supporting and nurse cells, amidst which they undergo
their maturation divisions, and their descendants become embedded in the nurse
cells, where they are converted into spermatozoa. To a certain extent, therefore,
the nurse cells may be looked upon as corresponding with the cells of the ovular
cumulus which surround the growing oocyte.
After it has reached its full growth each spermatocyte I, like each oocyte I, can
produce only four descendants, and the descendants, as in the case of the oocyte I,
THE SPEKMATOZOON. 17
are formed by two successive mitotic divisions, of which the first is heterotypical
and produces reduction of the chromosomes, and the second is homotypical.
The two divisions differ from the corresponding divisions of the oocytes in three
important respects : (1) centrosomes are present ; (2) the four grand-daughter cells
produced are of equal size and presumably of equal value, so far as capability of
uniting with a mature ovum to form a zygote is concerned ; (3) each of the four
grand-daughter cells possesses two centrosomes.
In the prophase of the first or heterotype division the nucleus and nucleolus
disappear in the ordinary way. The centrosome divides, and an achromatic spindle
appears, which has the daughter centrosomes at its poles and half the typical
number of chromosomes at its equator. The chromosomes are twin chromosomes.
During the metaphase the two segments of each twin chromosome separate from
each other. In the anaphase they travel to the opposite poles of the achromatic
spindle, and consequently, when the cell divides in the telophase, each daughter
cell or spermatocyte II contains a centrosome and half the typical number of
chromosomes.
The second maturation division, which takes place without the intervention of
a resting stage, is of the homo type form. The centrosome divides, a new achromatic
spindle appears, and the daughter chromosomes gather at its equator. In the
metaphase the chromosomes divide into equal parts, which travel to the opposite
poles of the spindle during the anaphase, and when the telophase is completed the
grand-daughter cells, which are called spermatids, possess a centrosome and half the
typical number of chromosomes. In the resting stage which follows, the chromatic
particles become enclosed in a new-formed nucleus, and the centrosome, if it -has
not already divided, separates into two parts, one which lies nearer the nucleus and
is called the anterior centrosome, and another, farther from the nucleus, termed the
posterior centrosome (Fig. 22). Numerous mitochondria are present, and an in-
definite structure, called the accessory body, is also found in the cell protoplasm.
A spermatid, therefore, differs from a typical animal cell not only because it
possesses the chromatic substance of only half the typical number of chromosomes,
but also because it possesses an accessory body and two centrosomes.
From Spermatid to Spermatozoon. The reader will have noted that the
female gametes become mature and ready for conjugation with male gametes
directly after the second maturation division is completed. In the case of the
male germ cells, however, the spermatids which result from the second maturation
division have still to undergo a complicated process of transformation before they
become converted to spermatozoa or mature male gametes. The process of
transformation takes place in association with the nurse cells in which the
developing spermatozoa become embedded.
The details of the process of transformation are difficult to follow, and the
knowledge regarding them is still to some extent indefinite. Certain points,
however, are well established ; but before they are considered it is necessary that
the reader should be acquainted with the anatomy of an adult spermatozoon.
THE SPEKMATOZOOK
A spermatozoon is a minute organism consisting of a head, a neck, a body,
a tail, and an end-piece. Its total length is about 50 /x, that is, its length is
about the same as the diameter of the nucleus of the ovum.
The head has the form of a laterally compressed ovoid. It is separable into
anterior and posterior portions, and the anterior portion is more or less completely
covered by a head-cap, which culminates in a sharp ridge. The length of the head
is about 4*5 /z.
The neck is an extremely short constricted region which intervenes between
the head and the body. At its anterior end, where it joins the head, there is a
deeply staining anterior centrosome, and at its posterior end a similarly deep-
staining posterior centrosome, from which a deep-staining axial filament extends
posteriorly through the body and tail into the end-piece (Fig. 21).
2
18
HUMAN EMBEYOLOGY.
Head
Body
Tail
Head"
NeckT
BodyJ
End piece
FIG. 20. HUMAN SPERMATOZOA and its sheath as they pass from
(after Retzius). the body into the uil
A, Side view ; B, Front view.
consists of prolongations of the axial filament and its
sheath, and it ends in the short thin end-piece.
The Transformation of the Spermatid into the
Spermatozoon. As the transformation progresses the
nucleus of the 'Spermatid becomes the head of the
spermatozoon. The axial filament grows out from the
posterior centrosome of the spermatid, which divides
into two parts, one of which becomes the posterior Endpi ece|
centrosome of the neck of the spermatozoon, whilst the
other becomes the end-ring of the body of the sperrna- FlG . 2 i. -STRUCTURE OF A HUMAN
tOZOOn. SPERMATOZOON (after Meeves).
The anterior centrosome of the spermatid becomes
the anterior centrosome of the
.- Nucleus - - T^-L |\ Head nucleus. . /_
Anterior / \\^/ '\ Anterior centrosome^,
centrosom e ~ ~f - - ' ; :|
Posterior centrosome _ -j
Body--
End ring
The Body. The body is a little longer than the head, and its constituent parts
are : (1) a portion of the axial
filament ; (2) a portion of the
axial sheath ; (3) the spiral
sheath ; (4) the mitochondrial
sheath ; (5) the end-ring.
The axial sheath is a thin
layer of protoplasm immediately
surrounding the axial filament.
The spiral sheath consists of
a spiral fibril embedded in in-
different protoplasm, and the
mitochondrial sheath, which sur-
rounds the spiral sheath, is
formed by protoplasm contain-
ing numerous mitochondria.
The end-ring closes the pos-
terior ends of the spiral and
mitochondrial sheaths, and it is
perforated by the axial filament
Head cap
Ant. centrosome
Post, centrosome
Axial filament
. Spiral sheath
Mitochondria!
sheath
End ring
Axial filament
.Sheath of axial
filament
Posterior ,,_| ^
centrosome
Axial filament
Tail
can only be surmised.
neck of the spermatozoon. The
cytoplasm of the spermatid forms
the axial sheath, the indifferent
protoplasm of the spiral sheath
and mitochondrial sheath. The
origin of the spiral filament and
the origin of the head-cap are
uncertain, but it is stated that,
in some animals, the head-cap is
formed from the accessory body,
which is not shown in Fig. 22.
The Object of the Reduction
of the Chromosomes. The most
striking phenomenon of the pro-
cess of the maturation of the
gametes is the reduction of the
chromosomes. The constancy of
the reduction tends to emphasise
its importance, but, as we have
no definite knowledge of the
functions of the chromatic sub-
stance, the object of the reduction
The evidence which has been accumulated tends to the
Tail
Nucleus f
Anterior
centrosome -_
Posterior
centrosome""
End ring- - X^
Tail
FIG. 22. SCHEMA OF TRANSFORMATION OF SPERMATID
INTO SPERMATOZOON (after Meeves, modified).
THE SPEEMATOZOON. 19
conclusion that the particles of the chromatic substance are the bearers of
hereditary tendencies and capabilities. 1 If this is the case, then they are the
means by which ancestral possessions, in the morphological sense, are transmitted
from generation to generation. There is evidence also, first ascertained by Mendel
and substantiated and increased in recent years by his followers, which lends
probability to the belief that the tendency carriers form two main groups : (1)
those which carry certain tendencies ; (2) those which carry opposite tendencies.
The bearers of tendencies and the bearers of their opposites are allelomorphic
or alternative to each other, and are called allelomorphs. Thus the particles
which bear tallness and dwarfness respectively are allelomorphs, that is, they are
alternative to each other.
Further, the facts which are known suggest the idea that in the primitive gerrn
cells, and their descendants which contain the typical number of chromosomes, the
character-bearing particles are arranged in pairs of which both elements may bear
the same tendencies, or one may bear one tendency and the other the opposite.
For example, if red and blue be supposed to be opposite tendencies carried by
different particles or allelomorphs, then the germ cells of any given animal, male
or female, may contain either a pair of red-bearing particles, a pair of blue-bearing
particles, or a red and a blue bearing particle associated together as a pair.
The reduction of the chromosomes during the maturation divisions of the germ
cells is an admitted fact, and it is believed that the reduction is a necessary
preliminary to the union of a male and a female gamete to form a zygote from
which a new individual may arise. It is assumed that the purpose of the
reduction is the segregation of the different tendency bearers from each other
in order that they may enter into new combinations. If this assumption is
correct, then every mature germ element or gamete contains only one element of
any given pair of tendency bearers, in the supposititious case under consideration,
either the red or the blue bearer, but not both ; and the object of the reducing
division is the segregation of the allelomorphs in order that they may enter into
new and possibly into different combinations, producing new and possibly varied
results.
If, in the case of any given group of animals, the mature germ cells of some of
both sexes contain the blue-bearing particles and others the red-bearing particles,
it necessarily follows that three possible results may ensue when impregnation
occurs, that is when two mature germ cells unite to form a zygote.
(1) A female gamete bearing red tendency particles may fuse with a male
gamete bearing red tendency particles ; (2) a female gamete bearing blue tendency
particles may meet and fuse with a male gamete bearing blue tendency particles ;
(3) a female gamete bearing red tendency particles may meet and fuse with a male
gamete bearing blue tendency particles. The constitution of the zygotes formed
may be stated as follows :
EK BB EB,
and the character of the individual developed from the zygote will vary according
to the combination. If two red tendency bearing gametes meet, the individual
will be red ; if two blue tendency bearing gametes meet, the individual produced
will be blue ; but when a gamete bearing red tendency particles unites with a
gamete bearing blue tendency particles the individual will be either red or blue
or a combination of the two, the result depending upon the relative potency or
dominance of the two tendencies.
Further exposition of this interesting subject would be out of place in a text-
book of anatomy, but it is of such great importance in association with the trans-
mission of hereditary characteristics and hereditary diseases that every medical
student should make himself familiar with its possibilities by consulting the works
of Bateson, Punnet, and other writers and observers who are attempting to solve
the complicated problems which it presents.
1 It must be understood that this function, if it exists, does not prevent the chromatic particles possessing
other functions, and that there is no evidence that the potency of a tendency depends upon amount of chro-
matic substance.
20
HUMAN EMBKYOLOGY.
FERTILISATION.
Fertilisation is the term applied to the union of the male with the female gamete
to form a zygote which contains the typical number of chromosomes (Fig. 23).
The meeting of the gametes and their union take place, normally, in the upper
or middle part of the uterine tube.
The details of the process are unknown in the case of the human subject, but
in many animals it has been noted that as the spermatozoon approaches the ovum
the latter shows signs of excitement, and a small prominence, called the cone of
attraction, appears on its surface. At the same time its pronucleus undergoes
changes of form. As the two gametes meet the spermatozoon pierces the oolemma
which surrounds the ovum and passes through the cone of attraction into the body
of the ovum.
In some cases apparently only the head, neck, and body of the spermatozoon
effect an entrance, but in others the whole spermatozoon enters the body of the ovum.
After the entrance occurs and before the second polar body is formed, the parts of
Spermatozoon
Parts of first polar body X
Second
polar body
Polar bodies
Centrosome with
male pronucleus
;Male pronucleus
^.Female
pronucleus
Oolemma
jSC,Body of
/ mature ovum
Polar bodies
Polar bodies
Male pronucleus^
Centrosome with ^
male pronucleus -j
pronucleus
Oolemma
Centrosome
First
segmenta-
tion nucleus
-rf - Centrosome
FIG. 23. SCHEMA OF THE FERTILISATION OF THE MATURE OVUM AND THE FORMATION OF THE ZYGOTE.
the spermatozoon which have entered remain quiescent. After the second polar
body is formed they disappear and are replaced by a nucleus which contains half the
typical number of chromosomes and which is accompanied by two centrosomes. At
this period the impregnated ovum contains two pronuclei, both of which contain
half the typical number of chromosomes ; but the female pronucleus has no accom-
panying centrosomes.
Shortly after the appearance of the male pronucleus the two pronuclei unite
and then the zygote, formed by the union of the male and female gametes,
consists of a cell body enclosing a nucleus called the first segmentation nucleus ; and
two centrosomes.
The first segmentation nucleus is the product of the union of the male and the
female pronuclei. It contains the typical number of chromosomes, half being
derived from the male and half from the female gamete ; and it is accompanied by
two centrosomes, both of which appear to be derived from the male gamete, though
their exact origin has not yet been definitely established. The zygote and the
polar bodies which are still present are enclosed within the oolemma.
SEGMENTATION.
21
Polar bodies
Oolemma
Polar bodies
Oolemma
SEGMENTATION.
Immediately after its formation the zygote is separated, by a series of consecu-
tive mitotic divisions, into a large number of cells which are grouped together
in the form of a solid spherical mass, called a morula on account of the mulberry-
like appearance of its surface. This period of division
is called the period of segmentation (Figs. 24-2*7).
The segmentation divisions are of the homotype
form, and there is evidence which tends to the con-
clusion that the earliest divisions, by which the zygote
is divided first into two and then into four parts, are
quantitatively and qualitatively equal. After a time,
however, the divisions result in the formation of cells
of different sizes and different capabilities, definite
and circumscribed functions being allocated to certain
groups of cells and their descendants. It is probable FIG. 24.-SEGMENT OF ZYGOTE
that at this time cells are set apart which are the pro-
genitors of the germ cells of the next generation, and
which therefore retain all the capabilities of their
ancestors. These cells are the means by which the
species is reproduced and the hereditary tendencies
are transmitted from generation to generation. At the
same time other cells are set apart for the production
of the tissues and organs of the individual which will
be produced from the zygote, and in which the germ
cells and their descendants will be lodged and protected
till they attain their maturity.
After the morula is established one of the first
definite changes which occurs in its constitution is
the differentiation of its cells into an outer layer
and an inner mass (Fig. 26).
In the human subject, as in many other mammals,
the cells of the outer layer constitute the trophoblast
or trophoblastic ectoderm, which plays a most im-
portant part in the nutrition of the embryo and fcetus.
It enters into the formation of the chorion, or outer-
most envelope of the growing zygote, which is sub-
sequently differentiated into a placental and a non- FM . 26 ._ gMMENTATIONOpZY60T] ,
placental portion and which serves, in the nrst in-
stance, both as a protective and a nutritive covering.
In many mammals the cells of the inner mass
soon separate into two main groups, the ecto-mesoderm
and the entoderm ; but it appears probable that, in the
human subject, they differentiate into three groups,
ecto-mesoderm, primary mesoderm, and entoderm.
In the majority of mammals, immediately before or
as the differentiation of the inner mass occurs, a cavity
appears in the zygote. As soon as the cavity appears
the morula is converted into a blastula and the cavity
enlarges until it separates the inner mass from the
outer layer, except at one pole of the zygote, where the
inner mass and the outer layer remain in contact.
The cavity is called the segmentation cavity. It
would appear, however, from the evidence at present
available, that this primitive cavity never exists in the human subject, for as the
main part of the inner mass separates from the outer layer the cells of the primary
mesoderm segment of the inner mass proliferate rapidly and form a jelly-like tissue
which completely fills the space which would otherwise become the segmentation
cavity. At the same time the ecto-mesodermal and entodermal segments of the
Morula Stage.
Trophoblast
Ecto-mesoderm
Ectoderm *
Entoderm'
Primary mesodertn
FIG. 27. DIFFERENTIATION OF
ZYGOTE AND CELLS (Hypothetical).
22
HUMAN EMBEYOLOGY.
Trophoblast
Extra-,
embryonic
entoderm
Primary mesoderm
Plasmodial trophoblast
Cellular trophoblast
Amniotic ectoderm
Embryonic %
ecto-mesoderm T
inner mass become converted into hollow vesicles by the appearance of cavities in
their interiors (Fig. 29).
When the above-mentioned changes have occurred the zygote consists of three
spheres, one large and two small. The large sphere is bounded by the tropho-
blast ; it contains the two small spheres and the
jelly-like mass of primary mesoderm derived from
the primary mesoderm segment of the inner mass
(Fig. 29).
The two small vesicles lie ex-centrically in the
interior of the larger vesicle. The larger and more
external of the two is the ecto-mesodermal vesicle.
It is separated from the trophoblast, peripherally,
and the entodermal vesicle, centrally, by the sur-
rounding primary mesoderm.
The early appearance of the mesoderm in the
FI. 28.-FURTHER DIFFERENTIATION Z 7g ote and its insinuation at so early a period be-
OF ZYGOTE (Hypothetical). tween the ectoderm and the entoderm are peculiar-
ities limited to the human subject. In most mammals
the mesoderm does not appear until the
embryonic area and its primitive streak are
defined.
The Embryonic Area. The area where
the two inner vesicles he in apposition with
each other is the region of the zygote from
which the embryo will be formed ; it is
called, therefore, the embryonic area, and at
the time of its definition it consists of three
layers, ectoderm, primary mesoderm, and
entoderm. It is uncertain whether the
mesoderm which is present in the area at
this period takes part in the formation of
the embryo or is replaced at a later period
by mesoderm derived from the cells of the
ecto-mesodermal vesicle; the
latter certainly forms a large part
of the mesoderm of the embryo.
The Extra - Embryonic
Ccelom. The extra - embryonic
coelom is a space which appears
as two clefts, one on each side of
the embryonic area, in the primary
mesoderm (Fig. 30). The clefts
fuse together round the periphery
of the embryonic area, and the
single space so formed expands
rapidly until the mesoderm which
originally filled the greater part
of the larger vesicle becomes con-
verted into a thin layer which
lines the inner surface of the
trophoblast and covers the outer
surfaces of the epithelial walls of
the extra-embryonic parts of the
two inner vesicles (Fig. 32).
The extra -embryonic coelom does not extend into the embryonic area, and
it never completely separates the ecto-mesodermal vesicle from the inner surface
of the trophoblast ; on the contrary, the primary mesoderm on the outer surface
of the ecto-mesodermal vesicle retains its continuity with the mesoderm on the
inner surface of the trophoblast until the termination of intrauterine life, and
Extra-
embryonic
entoderm
FIG. 29. SCHEMA OF DIFFERENTIATION OF
ZYGOTE (Bryce's Ovum).
Plasmodial trophoblast
Cellular trophoblast \
Amniotic ectoderm -V-*
Amnion cavity^
Embryonic
ecto-niesoderm^
Extra-embryonic <^1
creloin j
Primary mesoderm;-
FIG. 30. SCHEMA OF DIFFERENTIATION OF ZYGOTE
(Peter's Ovum).
THE EMBRYONIC AREA. 23
it takes part, as will be seen later, in the formation of the umbilical cord, which
connects the foetus with the placenta (p. 54).
The Differentiation of the Embryonic Area. As the embryonic area is the
area of contact between the ecto-mesodermal and the entodermal vesicles it is, at
first, circular in outline. As growth continues the area becomes oval, and a linear
streak, the primitive streak, appears in that part of the oval which becomes the
posterior part of the area (Fig. 31).
At the same time the position of the mesoderrnal elements of the wall of the
ecto-mesodermal vesicle is revealed, for the primitive streak is a thickened ridge of
cells which grows from the ecto-mesoderm and projects against the entoderm in the
posterior part of the embryonic area, pushing aside the primitive mesoderm which
intervened between the adjacent parts of the walls of the ecto-mesodermal and the
entodermal vesicles. The deeper cells of the ridge, those next the entoderm, are
the mesoderrnal elements of the primitive ecto-mesoderm, and, by proliferation,
they form the larger part, if not the whole, of the embryonic mesoderm and also an
organ, called the notochord. The mesoderm produced from the primitive streak
may be termed the secondary mesoderm.
Immediately after the formation of the primitive streak a groove, the neural
groove, appears in the anterior
part of the embryonic area. Embryonic area.
It is formed by the longi- t plasmc "
tudinal folding of a thickened Ch ] ceiiuiar
Mesoderm lining-,
plate of ectoderm, the neural I of trophobiast va
plate, which is the rudiment Mesoderrn of amnion; Jf
of the whole of the central
and peripheral portions of the Neural fold
nervous system, except per-
haps the olfactory nerves, and Ectoderm of ammon
the end organs of the sensory Neurenteric canal
nerves. From it also are de-
rived the cells of the primitive primitive streak
sheaths of the nerve -fibres
and the chr omaffin cells of the M ?a?anic) SSr
supra-renal glands and other
chromamn bodies. A
rpi -i , i 11 f fv, FIG. 31. SCHEMA OF DORSAL SURFACE OF EMBRYONIC AREA OF
ZYGOTE AFTER THE REMOVAL OF PART OF THE CHORION AND
neural groove are called the PART OF THE AMNION.
neural folds.
Almost from the first the anterior ends of the neural folds are united together
a short distance posterior to the anterior end of the embryonic area. Their
posterior ends, which remain separate for a time, embrace the anterior part of the
primitive streak. In the meantime, however, a groove, the primitive groove, has
appeared on the surface of the primitive streak. The anterior end of the primitive
groove deepens, until it forms a perforation which passes, through the anterior end
of the streak and the subjacent entoderm, into the cavity of the entodermal vesicle.
As this perforation passes from the floor of the posterior part of the neural groove
into that part of the entodermal vesicle which afterwards becomes the primitive
enteron or alimentary canal, it is called the neurenteric canal. The neurenteric
canal is but a transitory passage, and it disappears in man and other mammals
before the neural groove is converted into a closed neural tube.
After the appearance of the primitive groove and the neurenteric canal the
posterior ends of the neural folds converge, across the anterior part of the primitive
streak and groove, and fuse together posterior to the neurenteric canal. The
primitive streak is thus divided into two portions. (1) An anterior portion, which
lies at first in the floor of the neural groove, and, later, in the floor or ventral wall
of the posterior end of the spinal medulla; and (2) a posterior portion, which
remains on the surface and takes part in the formation of the median portion of
the posterior end of the body, forming the perineum, and the median part of the
ventral wall of the body, from the perineum to the umbilicus. It is through the
24
HUMAN EMBEYOLOGY.
Anterior end of neural fold
Plasmodial trophoblast
Cellular trophoblast
Amnion cavity [blast
Mesoderm lining of tropho-
Mesodenn of amnion
Ectoderm of amnion
Allantoic diverticulum
entoderm vesicle
Mesoderm covering of
entoderm vesicle
eurenteric canal
,vity of entodermal vesicle
FIG. 32. SCHEMA OF SAGITTAL SECTION OF ZYGOTE ALONG
LINE A IN FIG. 31.
Chorion <
Plasmodial trophoblast
Cellular trophoblast
Neural groove
perineal section of the posterior part of the primitive streak that, at a later period
of embryonic life, the anal and urogenital orifices of the body are formed.
The Formation of the
Notochord and the Secondary
Mesoderm. The notochord
and the secondary mesoderm are
formed from the primitive
streak; the notochord from its an-
terior extremity, and thesecond-
[Body stalk mesoderm ary mesoderm from its lateral
^Extra-embryonic coeiom margins and posterior end.
Entoderm As soon as the primitive
streak is established its anterior
end becomes a node or centre
of growth by means of which
the length and, to a certain
extent, the breadth of the body
are increased. The portion of
the body formed by the activity
of the anterior end of the streak
is the dorsal portion, from the
back part of the roof of the nose,
anteriorly, to the posterior end
of the trunk. The perineum
and the ventral wall of the
body, from the perineum to the
umbilicus, are formed from the
posterior part of the primitive
streak. Nevertheless, the
primitive streak undergoes little
or no increase in length; in-
deed, as growth continues, it
becomes relatively shorter as
contrasted with the total length
of the embryonic region, for the
new material, formed by its
borders and its anterior ex-
tremity, is transformed into
the tissues of embryo as rapidly
as it is created.
The Notochord. The
notochord or primitive skeletal
axis is formed by the prolifera-
tion of cells from 'the anterior
end of the primitive streak.
On its first appearance it is a
narrow process of cells, the head
process, which projects forwards
from the anterior boundary of
the neurenteric canal, between
the ectoderm and the entoderm.
Shortly after its appearance the
head process wedges its way
between the entoderm cells, and
from that period onwards, as
the posterior parts are formed,
by continued proliferation from the front end of the primitive streak, they are at
once intercalated in the dorsal wall of the entodermal sac, where they remain,
forming a part of the dorsal wall of the entodermal cavity (Fig. 33), for a
V Mesoderm lining of trophoblast
Amnion cavity
Extra-embryonic coeiom
Mesoderm of amnion
Ectoderm of amnion
Mesoderm covering
entoderm
Entoderm
Cavity of entodermal
vesicle
Notochord
FIG. 33. SCHEMA OF TRANSVERSE SECTION OP ZYGOTE ALONG
LINE B IN FIG. 31.
Primitive streak
Primitive groove
Plasmodial trophoblast
Cellular trophoblast
Mesoderm lining of
trophoblast
-Chorion
Extra-embryonic coeiom
-. Mesoderm of amnion
Ectoderm of amnion
Amnion cavity
Mesoderm covering
"entoderm
' Entoderm
^Cavity of entodermal vesicle
FIG. 34. SCHEMA OP TRANSVERSE SECTION OF ZYGOTE
LINE C IN FIG. 31.
ALONG
THE MESODEEM AND NOTOCHOED. 25
considerable time. At a later period the notochordal cells are excalated from the
entoderm, and then they form a cylindrical rod of cells which occupies the median
plane, lying between the floor of the ectodermal neural groove and the entodermal
roof of the primitive alimentary canal, which, in the meantime, has been more or
less moulded off from the dorsal part of the entodermal sac (Fig. 37). For a still
longer time the caudal end of the notochord remains connected with the anterior
end of the primitive streak, and its cephalic end is continuous with the entoderm
of a small portion of the embryonic area, which lies immediately in front of the
anterior end of the neural groove and which becomes bilaminar by the disappearance
of the primary mesoderm. This region, because it afterwards forms the boundary
membrane between the anterior end of the primitive entodermal canal and the
primitive buccal cavity or stomatodseum, is called the bucco-pharyngeal membrane
(Fig. 55, p. 42). It disappears about the third week of embryonic life, and immedi-
ately afterwards the anterior end of the notochord separates from the entoderm,
but the posterior end remains continuous with the primitive streak, until the for-
mation of the neural tube is completed.
After a time the cylindrical notochordal rod is surrounded by secondary
mesoderm which becomes converted into the vertebral column of the adult. As
the vertebral column is formed the notochord is enlarged in the regions of the inter-
vertebral fibro-cartilages and for a time assumes a nodulated appearance (Fig. 60).
Ultimately the notochord disappears, as a distinct structure, but remnants of
it are believed to exist as the pulpy centres of the intervertebral fibro-cartilages.
The extension of the notochord into the region of the head is of interest from a
morphological, and possibly also from a practical point of view. It extends
through the base of the cranium from the anterior border of the foramen magnum
into the posterior part of the body of the sphenoid bone. Its presence in the
posterior part of the skull suggests that that region was, primitively, of vertebral
nature. As the notochord passes through the occipital portion of the skull it
pierces the basilar portion of the occipital region first from within outwards and then
in the reverse direction. It lies, therefore, for a short distance, on the ventral
surface of the rudiment of the occipital bone, in the dorsal wall of the pharynx,
and it is possible that some of the tumours which form in the dorsal wall of the
pharynx are due to the proliferation of remnants of its pharyngeal portion.
The Differentiation of the Secondary Mesoderm. It has already been
noted that a portion of the inner mass of the human zygote becomes converted
directly into mesoderm which may be called, for convenience, primary mesoderm.
It was stated also that the wall of the larger of the two inner vesicles of the
zygote consists of ecto-mesoderm, that term being intended to convey the idea
that the cells of the wall of the larger inner vesicle were the progenitors of both
ectodermal and mesodermal cells.
As soon as the larger of the two inner vesicles is formed two areas of its
wall are defined : (1) the part in contact with the smaller inner or entodermal
vesicle and (2) the remainder. As future events prove, the cells of the larger
area, which is not in contact with the entodermal vesicle, simply produce
ectodermal descendants which line the inner surface of a sac-like covering of the
embryo termed the amnion ; they are, therefore, the predecessors of the amniotic
ectoderm.
The cells of the larger inner vesicle, which lie adjacent to the smaller entoderm
vesicle, and are merely separated from the entoderm by a thin layer of primary
mesoderm, take part in the formation of the embryo ; forming, with the entoderm,
the embryonic area from which the embryo is evolved. These cells are the fore-
runners of both ectoderm and mesoderm, and as the mesoderm developed from
them is differentiated after the formation of the primary mesoderm it may be
termed secondary mesoderm or primitive streak mesoderm ; the latter term being
applied because it is differentiated in a linear region called the primitive streak
(p. 23). It is the formation and fate of this primitive streak mesoderm which is
now to be considered.
At first the embryonic area is circular in outline, at a later period it becomes
ovoid, and in the narrower or caudal portion of the ovoid area a linear thickening
HUMAN EMBRYOLOGY.
Mesoderm of.
ainnion
Ectoderm of
amnion
Neural crest
Eoof-plate
Lateral wall of
neural groove
Floor-plate
Mesoderm of
entoderm vesicle
Entoderm
Cavity of
entoderm vesicle
vity
FIG. 35. TRANSVERSE SECTION OF A ZTGOTE, showing early stage
of embryonic secondary mesoderm before the appearance of the
embryonic parts of ccelom.
^Amnion cavity
Paraxial
erm
Embryonic
ccelom
Trophoblast of '
chorion
Mesoderm of
chorion
Mesoderm of
amnion -
Ectoderm of
amnion -
Neural crest^
Roof- plate
Lateral wall of^
neural groove^.
Floor-plate
Entoderm
Mesoderm of
ntoderm vesicle^
Cavity of
ntoderm vesicle
FIG. 36.- TRANSVERSE SECTION OF A ZYGOTE, showing early
stage of development of embryonic coelom and differentiation
of mesoderm.
Neural crest*
Trophoblast of chorion
Paraxial mesoderm
Notoeho:
QSO. of yolk-sac
ntoderm of yolk-sac
Intermediate cell tract
Splanchnic and
somatic layers of
lateral plate meso.
Embryonic
coelom
> Amnion
cavity
Extra-embryonic
coelom
Alimentary canal
Yolk-sac
FIG. 37. TRANSVERSE SECTION OF A ZYGOTE, showing union of
intra- and extra-embryonic parts of coelom and separation of
embryonic mesoderm into paraxial bars, intermediate tracts,
and lateral plates, with separation of lateral plates into
somatic and splanchnic layers by the intra-embryonic part of
the coelom.
appears ; this is the primitive
streak(Figs.31, 34). It is formed
by the proliferation of the ecto-
mesodermal cells of the wall of
the larger inner vesicle. The
deeper cells of the streak, which
displace the primary mesoderm
from the median plane, and thus
come into contact with the
entoderm, are the rudiments
of the secondary or primitive
streak mesoderm (Fig. 34).
The superficial cells form part
of the surface ectoderm of the
embryo.
At the anterior end of the
primitive streak the mesoder-
mal elements of the streak fuse
with the subjacent entoderm
and through the fused mass
a perforation, the neurenteric
canal (p. 23), is formed (Fig.
32).
The canal itself soon dis-
appears, but the cells of its
walls form a nodal growing
point, and by their proliferation
the length and breadth of the
embryonic area are increased.
The mesoderm cells proliferated
from the cephalic border of the
nodal point are the rudiments
of the notochord, which has
already been considered (p.
24).
It is uncertain whether or
not the mesodermal cells
budded off from the nodal point
blend with the cells of the
primary mesoderm, but there
can be little doubt that they
form by far the greater part,
if not the whole, of the perma-
nent mesoderm of the embryo.
Either by displacement or
by union with the primary
mesoderm the secondary meso-
derm forms a continuous sheet
of cells, in the embryonic area, on
each side of the median plane.
Each of the lateral sheets
is thickest where it abuts
against the notochord and the
wall of the neural groove, and
thinnest at its peripheral
margin, where it is continuous
with the primary mesoderm of
the extra-embryonic area (Fig.
35).
THE MESODEKM.
27
Plasmodial trophoblast
Cellular trophoblast
- Mesoderm lining
trophoblast
.
-Chorion
iak \ Mesoderm covering
lK' x-'*
entoderm vesicle
At the cephalic end of the embryonic area the medial margins of the
mesodermal sheets fuse together across the median plane, forming a transverse
bar of mesodermal cells which may be called the pericardial mesoderm (Fig. 48),
because the pericardial sac, which envelops the heart, is afterwards developed
from it. The area in which this mesoderm lies may be named the pericardial
region of the embryonic area (Fig. 48).
Between the bar of pericardial mesoderm, the cephalic end of the neural
groove, and the medial margins of the mesodermal plates lies a small segment of
the embryonic area from which the primary mesoderm entirely disappears, leaving
the ectoderm and entoderm in contact. This is the bucco-pharyngeal area. It
afterwards becomes the bucco-pharyngeal membrane (Figs. 50, 55), which separates
the primitive mouth or stomatodseum from the cephalic end of the primitive
entodermal alimentary canal. As already stated, the bucco-pharyngeal membrane
disappears during the third week, when the stomatodseum and the primitive
alimentary canal become A
continuous with each other.
Between the bucco-
pharyngeal area and the
cephalic end of the primi-
tive streak the medial
margins of the mesodermal
plates are separated from
one another by the noto-
chord and the neural
groove (Fig. 36), and still
more caudally they are ^^^R \\\ j f [ I/r~-^^^B Mesoderm of amnion
united with the sides of
the streak (Fig. 34).
After the permanent
mesodermal plates are de-
finitely established a series
of clefts appear in their
peripheral margins. The
clefts, on each side, soon
fuse together to form the
bilateral rudiments of the
embryonic ccelom (Fig. 36).
The septum of cells at
the lateral border of the
embryonic area on each
side, which, for a time,
separates the embryonic
from the extra-embryonic ccelom, soon disappears, and the ccelom then forms a
continuous cavity (Fig. 37).
The embryonic ccelom also extends medially, but the medial extension ceases
whilst the cavity is still at some distance from the median plane, except at the
cephalic end of the embryonic area, where the two lateral halves of the embryonic
ccelom become continuous with one another through the interior of the pericardial
mesodermal bar (Figs. 49, 55).
As the embryonic ccelom is forming and extending, a longitudinal constriction
appears in each lateral half of the mesoderm, a short distance from its medial
border. This constriction separates each plate into three parts : (1) a medial bar, the
paraxial mesoderm, which lies at the side of the neural groove and the notochord (Fig.
37) ; (2) the constricted portion, which is called the intermediate cell tract ; and (3)
the part lateral to the constriction, which is called the lateral plate (Fig. 37).
The embryonic ccelom is confined, as a rule, in the human subject, to the lateral
plate, which it divides into a superficial layer, next the ectoderm, the somatic
mesoderm, and a deeper layer, next the entoderm, the splanchnic mesoderm.
The medial borders of the somatic and splanchnic mesoderm are continuous
Mesodermal somites
(paraxial mesoderm)
Ectoderm of amnion
Mesoderm of body-stalk
FIG. 38. SCHEMA OF DORSAL ASPECT OF EMBRYO, showing partial
closure of neural groove.
Portions of the choriou and amnion have been removed.
The neural folds have fused, except in the cephalic and caudal regions,
both the cephalic and the caudal ends of the embryo have been bent
ventrically and thirteen mesodermal somites have been formed.
28
HUMAN EMBEYOLOGY.
with one another round the medial border of the coelom. The lateral border of the
somatic mesoderm is continuous, at the margin of the embryonic area, with the
mesoderm which covers the outer surface of the amnion, and the lateral border
of the splanchnic layer is continuous with the mesoderm on the wall of the
extra-embryonic or yolk-sac portion of the entodermal sac.
The Paraxial Mesoderm. Each paraxial mesodermal bar soon assumes the form
Trophoblast cellular layer
Plasmodial trophoblast x
Neural tube
Mesoderm of chorion
Mesodermal somite
Notochord
Intermediate cell tract
Amnion cavity
Amnion
Somatic mesoderm
Coelom
Splanchnic mesoderm
Primitive gut
Extra-embryonic coelom'
Wall of yolk-sac
Cavity of yolk-sac
FIG. 39. TRANSVERSE SECTION OF THE ZYGOTE SHOWN IN FIG. 38, showing the differentiation
of the mesoderm.
of a triangular prism with the apex directed ventro- medially, towards the notochord,
and the base dorso-laterally, towards the surface ectoderm.
The cephalic portion of each paraxial bar, as far caudalwards as the middle
of the hind-brain, remains unsegmented, but the remainder is cut into a number of
Chorion
Scleratogenous mesoderm
Muscle plates
Cutis lamella
Wolfflan duct "
Intermediate cell tract
Amnion
Amnion cavity
Neural tube
Spinal ganglion
_ Sympathetic ganglion
Aorta
Intra-embryonic coelorn
_ Extra-embryonic coelom
.. Gut
Coelom
Umbilicus
.. Yolk-sac
FIG. 40. SCHEMA OP A TRANSVERSE SECTION OF A ZYGOTE, showing differentiation of mesoderm and
extension of amnion.
segments, the mesodermal somites, by a series of transverse clefts (Fig. 38). The
irst cleft appears in the region of the hind-brain, and the others are formed
sively, each caudal to its predecessor. Only three or four somites lie in the
THE MESODEEM.
29
region of the head ; the remainder are in the body area of the embryonic region.
The segmentation of the paraxial bars commences before their elongation is com-
pleted, and the posterior somites are separated off as the paraxial bars are extended
by the continued proliferation from the nodal point at the anterior end of the
primitive streak.
When they are first defined the somites are solid masses of cells, but in a short
time a cavity the co3lom of the somite or myoccele is developed in each mass.
Mesoderm of amnion ~~~~-
Ectoderm of amnion *
Neural crest
Roof-plate
Lateral wall of neural
groove
Floor-plate
Mesoderm of
entoderm vesicle
Entoderm
Cavity of entoderm
vesicle
Amnion cavity
Notochord
Mesoderm of
chorion
Trophoblast of
chorion
FIG. 41.
A. Transverse section of a zygote, showing the constituent parts.
B. Diagram of embryonic area showing parts of neural plate and primitive streak.
The apical portion of the hollow mesodermal somite is its scleratogenous segment.
The cells of the scleratogenous section of the somite undergo rapid proliferation.
Some of the newly formed scleratogenous cells invade the myocoele ; others migrate
towards the notochord ; finally, the scleratogenous cells separate from the remainder
of i the somite, and as they increase in number they migrate along the sides of
Trophoblast of chorion
Mesoderm of chorion
Mesoderm of amnion
Ectoderm of amnion
Neural crest
Roof-plate
Lateral wall of
neural groove
Floor-plate
Primitive Entoderm
streak Mesoderm of
entoderm vesicle
Cavity of entoderm
vesicle
Amnion cavity
^Paraxial
mesoderm
Notochord
FIG. 42.
A. Diagram of a transverse section of a zygote, showing the formation of a neural groove in the embryonic area.
B. Diagram of a surface view of the embryonic area of the same zygote.
the notochord and the neural tube, which has been formed in the meantime from the
neural groove, and join with their fellows of the opposite side, and with their
cephalic and caudal neighbours. In this way is formed, around the neural tube
and the notochord, a continuous sheath of mesoderm, the membranous vertebral
column, from which are differentiated, in later stages, the vertebral column and its
ligaments, and the membranes of the brain and the spinal medulla.
30
HUMAN EMBKYOLOGY.
After the separation of the scleratogenous segments of the mesodermal somites,
the remainders of the somites, each of which consists of a flat plate with incurved
dorsal and ventral margins, constitute the muscle plates from which the striped
muscle fibres are derived.
In the opinion of some observers the outermost portion of each of the above -described plates
is developed into subcutaneous connective tissue cells ; consequently it is spoken of as the cutis
lamella. According to this view the muscle cells are formed from the innermost cells and the
incurved margins of the plates.
The Intermediate Cell Tracts. The intermediate cell tracts are the rudiments
of the internal organs of the genital system and the temporary and permanent
urinary system, with the exception of the urinary bladder and the urethra.
The Lateral Plates. From the cells of the lateral plates are formed the lining
endothelial cells of the great serous cavities of the body the pleurae, the peri-
cardium, and the peritoneum ; the majority of the connective tissues, with the
exception of those of the vertebral column and the head, the greater part or
all the mesoderm of the limbs, and, probably, the unstriped muscle fibres of the
walls of the alimentary canal and the blood-vessels.
Position of otic
vesicle
Neural crest
Trophoblast of chorion
iraxial mesoderm
Embryonic
arc
Intermediate cell tract
Splanchnic and
somatic layers of
'lateral plate meso.
_Etnbryonic
coelom
Amnion
Neural crest
Caudal neuropore
Notochord
Mesoderm of
yolk-sac /
Entoderm of yolk-sac
S^xtra-em-
bryonic coelom
Alimentary canal
Yolk-sac
FIG. 43.
A. Diagram of a transverse section of a zygote, in which the neural tube has formed but has not separated
from the surface ectoderm.
B. Diagram of embryonic area of same zygote. Compare with surface view of embryo in Fig. 38.
The Cephalic Mesoderm. It has already been noted that the mesoderm of the
head becomes segmented only in the region of the caudal part of the hind-brain,
where four cephalic mesodermal somites are formed on each side. From the
scleratogenous portions of these somites are developed the occipital part of the skull
and the corresponding portions of the membranes of the brain, and from their
muscle plates the intrinsic muscles of the tongue.
The unsegmented part of the cephalic mesoderm gives rise to the remaining
muscles and connective tissues of the head region.
Early Stages of the Development of the Nervous System. No definite trace
of the nervous system is present until the primitive streak has formed and the
embryonic area has passed from a circular to an elongated form. Then an area of
thickened ectoderm, the neural plate, appears in the anterior part of the embryonic
area. It commences a short distance posterior to the anterior end of the area,
and its posterior extremity embraces the anterior end of the primitive streak. Its
lateral margins fade into the surrounding ectoderm, and, in the earliest stages,
cannot be definitely defined ; but, as the elongation of the plate continues coinci-
dently with the elongation of the embryonic area, the lateral margins of the plate
are elevated as the mesoderm beneath them thickens, and so they become distinct.
THE EAELY NEKVOUS SYSTEM.
31
As the lateral margins of the neural plate are raised the plate is necessarily folded
longitudinally, and the- sulcus so formed is called the neural groove. Each side
wall of the neural groove, formed by the corresponding half of the neural plate, is
a neural fold. At a very early period the neural folds unite anteriorly to form the^
anterior boundary of the neural groove, and, somewhat later, they unite posteriorly,*
caudal to the neurenteric canal and across the anterior end of the primitive streak.
After the lateral boundaries and the anterior and posterior extremities of the neural
groove are defined, the lateral margins of the neural folds converge until they meet
and fuse in the median plane, and the neural groove is thus converted into the
neural tube, which possesses a floor or ventral wall, formed by the central part of
Neural crest
Primitive ganglion
Surface ectoderm
^Floor- plate -
(1)
Roof-plate
Ependyma cells
'osterior nerve-root
Posterior
nerve-root
Anterior
nerve-root
Sympathetic
ganglion
Chromamn cells
Basal lamina with
neuroblasts
(3)
Roof-plate
Surface ectoderm
Spinal
ganglion
Sympathetic
ganglion
Chromamn cells
Central canal
Ependyma cells
Mantle layer
Peripheral
layer
Gut
Anteriorlnerve-root
Sympathetic ganglion -
Chromamn cells
Gut
Roots of
sympathetic
ganglion
Sympathetic nerve
(4) Secondary sympathetic ganglion
FIG. 44. DIAGRAMS illustrating the formation of (1) the rudiments of the primitive ganglion from the neural
crest. (2) The differentiation of different parts of the primitive ganglion into permanent ganglion root,
sympathetic ganglion, and masses of chromaffin cells. (3) The formation of the anterior and posterior
nerve-roots. (4) The differentiation of the walls of the neural tube into ependymal matter and
peripheral layers.
The cells of the primitive ganglion which form the primitive sheaths of the nerves are not shown in the
diagrams.
the original neural plate and called the basal plate or floor-plate ; a dorsal wall or
roof-plate, and two lateral walls formed by the lateral parts of the neural plate.
The fusion of the lateral margins of the neural plate to form the roof-plate
of the neural tube commences in the cervical region, and from there extends
cranialwards and caudalwards, therefore the last parts of the roof-plate which
are formed are its anterior and its posterior extremities ; consequently, for a time,
the neural canal, which is the cavity of the tube, opens on the surface at its
anterior and posterior ends; the anterior opening being called the anterior
neuropore, whilst the open part at the posterior end is termed the posterior
neuropore (Fig. 43). Eventually, however, about the third week of embryonic
32 HUMAN EMBKYOLOGY.
life both apertures are closed and, for a time, the neural canal becomes a completely
closed cavity.
As the margins of the neural groove rise and converge they carry with them
the adjacent ectoderm to which they are attached, and which forms part of the
surface covering of the embryo ; consequently, when the lateral margins of the
folds meet and unite, the tube, which is completed by their fusion, is embedded in
the body of the embryo, but, for a time, its dorsal wall is attached to the surface
ectoderm by a ridge of cells, formed by the fused lateral margins of the neural
plate. This ridge is called the neural crest (Figs. 41-44).
The neural crest is the rudiment of the cerebral and spinal nerve ganglia, the
sympathetic ganglia, the chromaffin cells of the chromaffin organs, and the cellular
sheaths of the peripheral nerves; whilst the walls of the neural tube become
transformed into the various constituent parts of the central nervous system, the
brain and spinal medulla, the retinae of the eye-balls, and the optic nerves. 1
The Formation of the Nerve Ganglia, the Chromaffin Tissues, and the
Primitive Nerve Sheaths. The primitive ganglia grow as cell buds from the
neural crest which, for a time, connects the dorsal wall of the neural tube with
the surface ectoderm. In the body region they correspond in number with the
spinal nerves and with the primitive segments into which the* mesoderm becomes
divided, but in the cephalic region their arrangement is more irregular, and some
of the ganglia of the cerebral nerves receive additional cell elements from the
surface ectoderm.
Simultaneously with the appearance of the cell buds which form the primitive
ganglia, the neural crest disappears, and directly after the ganglia are formed they
lose their connexion with both the neural tube and the surface ectoderm and
become isolated cell clumps. At this period, therefore, the nervous system
consists of the neural tube and the primitive ganglia.
After the primitive ganglia have lost their connexion with the neural tube
they increase in size by the proliferation of their constituent cells, and they
migrate ventrally along the sides of the neural tube, but the migration ceases
before the ventral ends of the ganglia reach the level of the ventral wall of
the tube. As the migration proceeds clumps of cells are budded off from the
ventral ends of the ganglia. These secondary cell buds are the rudiments of
the sympathetic ganglion cells and of the chromaffin tissue which is found in
the sympathetic nerve plexuses, the medulla of the suprarenal glands, and in the
carotid glands. In the first instance the secondary cell buds which form the
sympathetic ganglia wander ventrally and medially, from the ventral ends of
the primitive ganglia, until they attain the positions afterwards occupied by the
ganglia of the sympathetic trunks on the ventro-lateral aspects of the vertebral
column. From the primary sympathetic ganglia, buds of cells are given off; these
buds wander still further ventrally to become the cells of the ganglia of the cardiac,
coeliac, and other great ganglionic nerve plexuses, as well as to form the
chromaffin cells of the chromaffin organs.
The exact manner in which the cells of the primitive sheaths of the nerves
originate from the primitive ganglia is not known, but it has been shown by
Harrison, in the case of the frog, that if the primitive ganglia are destroyed,
the primitive sheaths of the nerves are not formed. Presumably, therefore, in the
frog the cellular sheaths of the nerves are derived from cells produced by the
primitive ganglia, and it may be assumed that they have a similar origin in
the human subject.
After the rudiments of the sympathetic system, the chromaffin cells, and the
cellular sheaths of the nerves have separated, the remains of the primitive ganglia
become the permanent spinal and cerebral nerve ganglia.
In the early stages these ganglia are completely isolated structures which lie
along the sides of the neural tube between the lateral walls of the tube medially,
and the mesoderm somites laterally.
Some time after the ganglia of the cerebral and spinal nerves become isolated
1 It is stated that some of the sympathetic nerve-cells are derived from the ventral parts of the lateral
walls of the neural tube, but the evidence on this point is not entirely satisfactory.
THE NEUKAL TUBE. 33
their cells give off processes which become nerve- fibres. These fibres grow out
both from the dorsal and the ventral ends of the ganglia, and, together with the
ganglia, they form, in the cranial region, certain of the cerebral nerves, and, in
the spinal region, the posterior roots of the spinal nerves.
The fibres which grow out of the dorsal ends of the ganglia enter the walls
of the neural tube, and by their means the ganglia regain connexion with the
tube.
The fibres which grow out from the ventral end of each spinal ganglion unite
with the fibres of the corresponding anterior nerve-root, which, in the meantime,
has grown out from the cells of the ventral part of the lateral wall of the spinal
portion of the neural tube, and form with them a spinal nerve-trunk.
The Differentiation of the Neural Tube. Before the neural groove is con-
verted into a closed tube, an expansion of its anterior part indicates the separation
of the neural rudiment into cerebral and spinal sections, the dilated portion being
the rudiment of the brain and un dilated part the rudiment of the spinal medulla.
Whilst the cerebral portion is still unclosed, three secondary dilatations of its
walls indicate its separation into three sections, the primitive fore-brain, the
mid-brain, and the hind-brain ; the primitive fore-brain being the most cephalward
or anterior and the hind-brain the most caudal or posterior of the three (Fig. 38).
Shortly after the three segments of the brain are defined, and before it becomes
a closed tube, a vesicular evagination forms at the cephalic end of each lateral
wall of the primitive fore-brain region. These evaginations are the primary optic
vesicles, and they are the rudiments of the optic nerves, the retinae, and the
posterior epithelium of the ciliary body and the iris of the eye -ball.
When the cerebral portions of the neural folds meet and fuse dorsally the
cerebral dilatations become the primitive brain vesicles, each vesicle possessing
its own cavity and walls, but the cavities of the three vesicles are continuous with
one another, and the cavity of the hind-brain vesicle is continuous, caudally, with
the central canal -of the spinal part of the neural tube.
After the primitive brain vesicles are formed, a diverticulum grows out from
the cephalic end of the primitive fore-brain vesicle. This is the rudiment of the
secondary fore-brain. Its cephalic end soon divides into two lateral halves, which
are the rudiments of the cerebral hemispheres of the adult brain (Fig. 45).
After their formation the cerebral hemispheres expand rapidly in all direc-
tions. They soon overlap the primitive fore-brain and mid-brain (Fig. 63), and,
eventually, the hind-brain also, and each gives off from the cephalic end of its
ventral wall a secondary diverticulum, the olfactory diverticulum, which becomes
converted, later, into the olfactory bulb and olfactory tract.
When they first appear the rudiments of the cerebral hemispheres are con-
nected together, across the median plane, by a part of the cephalic end of the
wall of the secondary fore-brain dilatation, which is called the lamina terminalis.
This primitive connexion between the two cerebral hemispheres persists through-
out the whole of life, and it is supplemented, at a later period, by the formation
of three secondary commissures, the corpus callosum and the fornix, which grow
across the space between the cerebral hemispheres and connect their medial walls
together, and the anterior commissure wjiich grows through the lamina terminalis
and connects the temporal portions of the two hemispheres.
The Fate of the Walls of the Primitive Brain Vesicles. The primitive
hind-brain, which is also called the rhombencephalon, is separated in the later
stages of development into two parts. (1) A caudal portion which is connected
with the medulla spinalis, and which becomes the medulla oblongata or myelen-
cephalon of the adult brain. (2) A cephalic portion which is continuous at one
end with the medulla oblongata and at the other with the mid-brain. The ventral
wall of the cephalic portion of the primitive hind-brain is ultimately converted
into the pons, and its dorsal wall differentiates into two parts a caudal part
which becomes the cerebellum ; and a cephalic part which is converted into the
anterior medullary velum and the brachia conjunctiva. The brachia conjunctiva
connect the cerebellum with the ventral part of the mid-brain. The pons and
cerebellum form the metencephalon of the adult, whilst the brachia conjunctiva
3
34
HUMAN EMBKYOLOGY.
MID-
CHORDA
DORSALIS
and the anterior medullary velum constitute parts of the isthmus rhombencephali
(Figs. 45, 63).
The ventral portion of the primitive mid-brain is converted into the two
peduncles of the cerebrum of the adult brain, and the dorsal portion is transformed
into four rounded elevations, the colliculi or corpora quadrigemina.
The transformations which take place in the region of the primitive fore-brain
or prosencephalon are numerous and complicated; therefore its ventral, lateral,
and dorsal walls require separate consideration.
By the expansion of its cephalic (anterior) extremity is formed the secondary
fore-brain, which becomes divided, as already explained, into the two secondary
vesicles which are the rudiments of the cerebral hemispheres of the completed brain.
After the formation of the rudiments of the cerebral hemispheres, which
constitute the tel-
M : i o ^ encephalon of the
adult, the primi-
tive fore-brain and
the undivided
stalk of the second-
ary fore-brain
diverticulurn be-
come the dience-
phalon.
The cephalic
or anterior end of
the diencephalon
is closed by the
lamina terminalis
(see p. 33), in
association with
which are subse-
quently developed
FIG. 45. DIAGRAMS TO ILLUSTRATE THE ALAR AND BASAL LAMINA. In both two columns
cases the embryonic brain is represented in mesial section (His). which run dorSO-
A. The different subdivisions of the brain are marked off from each other by dotted ventrally, the
lines, and the dotted line running in the long axis of the neural tube indicates tne co lumns of the
separation of the alar from the basal lamina of the lateral wall. .
B. Medial section through the brain of a human embryo at the end of the first -11 ' \
month. Dotted lines mark off the different regions and also the alar and basal tenor pillars;, and
laminae from each other. two transverse
H, Buccal part of hypophysis cerebri ; RL, Olfactory lobe ; C.STR, Corpus striatum ; Commissures, One
A, Entrance to optic stalk ; 0, Optic recess ; I, Infundibular recess ; T, Tuber Q which connects
cinereum ; M, Mamillary eminence. together the two
cerebral hemispheres and is called the anterior commissure, whilst the other is
the optic chiasma in which the medial fibres of the optic nerves decussate.
From the cephalic or anterior end of the ventral wall of the diencephalon a
diverticulurn is projected ventrally towards the dorsal wall of the primitive mouth.
The ventral end of this diverticulurn becomes the posterior lobe of the hypophysis
(O.T. pituitary body) of the adult, the dorsal end becomes the tuber cinereum, and
the intermediate part is the infundibulum which connects the tuber cinereum of
the adult brain with the posterior lobe of the hypophysis.
Caudal to the hypophyseal diverticuium a single elevation appears in the
ventral wall of the diencephalon. It is the corpus mamillare, which afterwards
separates into the paired corpora mamillaria of the adult brain.
Still more caudally the ventral wall of the diencephalon takes part in the
formation of the substantia perforata posterior, which lies between the two
peduncles of the cerebrum and is partly developed from the cephalic or anterior
end of the ventral wall of the primitive mid-brain.
The greater part of the dorsal wall of the diencephalon is ultimately reduced
to a single layer of epithelial cells, but near its caudal end a diverticuium is
projected dorsally. This is the epiphysis or pineal body, which remains quite
THE NEUKAL TUBE.
35
rudimentary in man as contrasted with many other animals. At a later period
two transverse bands of fibres appear in the dorsal wall of the diencephalon, one
in front of and the other immediately behind the root of the epiphyseal recess.
The anterior band is the dorsal or habenular commissure, and the posterior is the
posterior commissure of the adult brain.
These structures, collectively, together with a small diverticulum of the
Spongioblast
s Roof-plate
Spongioblast
Floor- plate '
FIG. 46.
epithelial roof, which appears
anterior to the dorsal com-
missure, and is called the
supra-pineal recess, constitute
the so-called epithalamus.
Each lateral wall of the
diencephalon is differentiated
into a dorsal and a ventral
part. The dorsal part forms
a large gray mass called the
thalamus, and on the posterior
end of the thalamus are de-
veloped two rounded eleva-
tions the medial and the At Diagram of a transverse section of a spinal medulla which has
lateral geniculate bodies, _ not differentiated into groups of cells.
, . , ... B. Diagram of a transverse section of a spinal medulla showing
Which Constitute the meta- positions of germinal cells.
thalamus of the adult brain.
The ventral or basal portion of the lateral wall of the diencephalon, together
with the adjacent part of the ventral wall, forms the hypothalamus of the fully
developed brain.
The Fate of the Spinal Portion of the Primitive Neural Tube. The
spinal portion of the neural tube, during the first three months of in tra- uterine
life, develops equally in its whole extent, but after that period a longer cephalic or
anterior (superior in the erect posture) and a shorter caudal portion are recognisable.
The cephalic portion undergoes still further development and is converted into
the spinal medulla of the adult,
but in the smaller caudal or
posterior portion retrogressive
changes occur, and it is trans-
formed into the non-functional
filum terminale of the completed
medulla spinalis.
Histological Differentiation
of the Walls of the Neural Tube.
In the earliest stages of its de-
velopment the walls of the neural
tube consist of a mass of nucleated
protoplasm, more or less distinctly
differentiated into cell areas, of
columnar form, which extend be-
tween and are connected with an
internal limiting membrane, bound-
ing the neural canal, and an ex-
ternal limiting membrane, which
surrounds the whole tube. At
Columnar cells of roof-plate
Peripheral layer - -
Neuroblasts
Mantle layer
Spongioblast
Ependyma cells
Neuro blast ;~
Columnar cells of floor-plate
FIG. 47. SHOWING ELEMENTS OF CENTRAL NERVOUS SYSTEM.
this time the outline of a transverse section of the primitive neural tube is
somewhat ovoid. The cavity of the tube is compressed laterally into a dorsti-
ventral cleft, which is bounded by dorsal, ventral, and lateral walls. In the
dorsal and ventral walls, called respectively the roof- and floor-plates, the columnar
character of the primitive epithelial elements of the medulla spinalis is retained
throughout the whole of life, but the peripheral parts of some of the cells are
converted into fibrils.
In the lateral walls of the embryonic medulla spinalis some of the cells soon
36 HUMAN EMBKYOLOGY.
assume a spherical form. These spherical cells have large deeply staining nuclei,
and they are termed germinal cells.
For many years it was believed that the germinal cells were the predecessors
of the primitive nerve elements or neuroblasts, and that the remaining cells, called
spongioblasts, became transformed into the reticular sustentacular tissue of the
central nervous system. It appears, however, from the results of more recent
researches, that some of the descendants of the germinal cells become spongioblasts
whilst others become neuroblasts or primitive nerve-cells. Moreover, there
appear to be two groups of germinal cells ; the descendants of one group are
directly transformed into the ependyrnal or lining cells of the central canal, whilst
those of the other group form in the first instance indifferent cells, some of whose
descendants become neuroblasts and others spongioblasts. The fate of the cells
present before the germinal cells appear, and which do not become germinal cells, is
uncertain, but they probably take part in the formation of the spongioblastic tissue.
It is believed, therefore, that all the nerve- cells are the descendants of the
germinal cells, and that the spongioblasts which become developed into the cells
of the neuroglia or sustentacular reticulum are derived partly from the non-
germinal cells of the primitive neural tube and, partly, they are descendants of
the germinal cells.
As differentiation proceeds three layers and two membranes are gradually
defined in the walls of the neural tube : (1) a central layer of columnar ependyma
cells immediately surrounding the central canal ; (2) an intermediate or mantle
layer consisting of neuroblasts and their processes, the nerve-fibres, intermingled
with spongioblasts ; (3) a peripheral reticular layer consisting, at first, of processes
of the bodies of the spongioblasts. The membranes are an external limiting
membrane, surrounding the exterior of the tube, formed by the fused outer ends
of the spongioblastic cells, and an internal limiting membrane bounding the
central canal and continuous with the inner ends of the ependyma cells. Through-
out the whole of the spinal medulla and the brain, the ependyma cells become
transformed into the columnar ciliated cells which line the cavities of the adult
brain and spinal medulla. The mantle layer becomes converted into the gray
matter of the adult central nervous system.
The peripheral reticular layer, in the spinal region, becomes permeated by
nerve-fibres, which are merely processes of the nerve-cells, and it is thus converted
into the white matter of the adult spinal medulla. In the brain region it is
either transformed in the same way into white matter, or it remains in a more
rudimentary condition as a thin peripheral layer of neuroglia on the surface
of the gray matter. On the other hand, in the brain region white matter is
formed internal to the gray matter by the growth of nerve-fibres which insinuate
themselves between the mantle layer externally and the bodies of the ependyma
cells internally.
As the histological differentiation of the walls of the neural tube is proceeding
each lateral wall is divided into a dorsal part, the alar lamina, and a ventral part,
the basal lamina, by a sulcus-like dilatation of the central canal called the sulcus
limitans. After the limiting sulci are formed the parts of the walls of the neural
tube are a roof-plate, a floor-plate, and two lateral walls, each of which consists of
an alar lamina, essentially sensory in function, and a basal lamina, essentially motor
in function (Fig. 44).
The Fate of the Cavities of the Primitive Brain. The cavity of the spinal
portion of the primitive neural tube becomes the central canal of the spinal
medulla of the adult. The cavities of the primitive brain vesicles are transformed
into the ventricles, foramina, and aqueduct of the adult brain. The cavities of
the telencephalic divisions of the secondary fore-brain become the right and left
lateral ventricles of the adult brain. The cavity of the undivided portion of the
secondary fore-brain vesicle, together with the cavity of the primary fore-brain,
become the third ventricle or cavity of the diencephalon, and the apertures of
communication between the third ventricle and the cerebral hemispheres are
the interventricular foramina (O.T. foramina of Monro).
The cavity of the hind-brain vesicle becomes the fourth ventricle, and the
THE FOKMATION OF THE EMBKYO. 37
cavity of the primitive mid-brain is converted into the aqueductus cerebri, which
connects the third with' the fourth ventricle.
After the anterior and posterior neuropores (p. 31) are closed, the cavity of
the neural tube is, for a time, a completely enclosed space. Subsequently the
mesoderm, which in the meantime has surrounded the tube, becomes differentiated,
in its immediate neighbourhood, into three membranes. The innermost of the
three is closely connected with the walls of the neural tube and is called the
pia mater. The outermost, known as the dura mater, is dense and resistant, and
the intermediate membrane is a thin lamella called the arachnoid.
As the membranes are formed, spaces are differentiated between them. The
space between the dura mater and the arachnoid is the subdural space, and that
between the arachnoid and the pia mater is the subarachnoid space.
After a time a median perforation, the median aperture of the fourth ventricle
(O.T. foramen of Magendie), and two lateral perforations pierce the dorsal wall
of the fourth ventricle and the pia mater which covers it, and thus the fourth
ventricle becomes connected with the subarachnoid space. It is stated also that
a perforation passes through the medial wall and the covering pia mater of a
portion of each lateral ventricle which is called its inferior horn, throwing those
portions of the lateral ventricles also into communication with the subarachnoid
space, but it is doubtful if the statement is correct.
THE FOKMATION OF THE EMBEYO.
Mesoderm of amnion,
Primitive streak
Body stalk
Allantoic
'diverticulum
from entoderm
vesicle
Notochord
The transformation of the relatively flat embryonic area into the form of the
embryo is due, in the first instance, to the rapid extension of the median part
of the area, as contrasted with
the slower growth of its mar-
gins, and the later modelling
of the various parts of the
embryo is due to different rates
of growth in different parts of
the embryonic region.
By the rapid proliferation
of cells from the nodal grow-
ing point, at the cephalic end
nf fV,a T* ' V a at V fk FlG ' 48 ' SCHEMA OF SAGITTAL SECTION OF EMBRYONIC AREA AND
eaK, tne AMNION BEFORE THE FOLDING OF THE AREA HAS COMMENCED.
cephalo-caudal length of the
area is increased, whilst
the cephalic and caudal
ends of the area remain
relatively fixed, conse-
quently the area be- Region of
comes folded longitu- ne a u ? e p r or f"
dinally. At the same
time, the cephalic end
Of the neural groove is Buoco-pharyngeal/ /
, , f? , -, membrane i Pericardium
pushed away from the
Amnion^cavity
Neural tube\
Ectoderm of amnion
Amniotic mesoderm
Chorionic
mesoderm
Region of
posterior
neuropore
Cloacal
- membrane
Body stalk
^ Allantoic
diverticulum
Hind -gut
Mid-gut
Fore-gut (heart not shown)
nodal point, until it lies
at first dorsal and then
cephalad to the cephalic
border of the area. As
a result of this move-
ment the bucco-pharyn-
geal and the pericardial areas become reversed in position, and a cephalic or head
fold is formed. This fold is bounded, dorsally, by what is now the cephalic portion
of the embryo, ventrally, by the reversed pericardial region, and its cephalic
end is formed by the extremity of the head region and the bucco-pharyngeal
membrane.
FIG. 49. SCHEMA OF SAGITTAL SECTION OF EMBRYONIC AREA SHORTLY
AFTER THE FOLDING HAS COMMENCED. The pericardial mesoderm is
carried into the ventral wall of the fore-gut and the coelom has extended
through it. The cephalic end of the neural tube and the caudal pait of
the primitive streak are bent ventrally, and the latter now forms the
cloacal membrane.
38
HUMAN EMBKYOLOGY.
The growth at the nodal point not only produces a head fold, but at the same
time it forces the cephalic end of the primitive streak caudally over the caudal
end of the embryonic area, thus forming a tail fold.
As the head and tail folds of the embryo are produced by the longitudinal
increase of the embryonic area, transverse growth of the area results in the forma-
tion of right and left lateral folds (Figs. 37, 39), and as the various folds are
formed the embryo rises, like a mushroom, into the interior of the amnion cavity.
The portion of the entodermal sac which is enclosed within the hollow embryo,
formed by the folding of the embryonic area, is the primitive entodermal alimentary
canal. The part which remains outside the embryo is the yolk sac, and the passage
of communication between the two is the vitello-intestinal duct.
That portion of the primitive entodermal alimentary canal which lies in the
head fold is termed the fore-gut, the part in the tail fold is the hind-gut, and the
intermediate portion which is in free communication with the yolk-sac is the
mid-gut.
As the extension of the embryonic area and its folding proceed the margin of
the area, which remains relatively stationary, becomes the margin of an orifice, on
Spinal part of neural tube
Notochord
Fore -gut
Hind-brairt ^><^"\ \
Mid-gut
Amnion cavity
Ectoderm of amnion
Mesoderm of amnion
Hind-gut
Mid -brail
Stomatodaeunf'
Pericardium (heart not shown
Rudiment of liver
i
i
I
I
Umbilical orifice
Mesoderm of yolk-sac
Entoderm
iculum
FIG. 50. SCHEMA OF SAGITTAL SECTION OF EMBRYO AFTER THE FOLDING HAS DEFINED BOTH THE
FORE-GUT AND HIND-GUT AREAS.
the ventral aspect of the embryo, through which the primitive alimentary canal
of the embryo and the intra-embryonic part of the ccelom communicate,
respectively, with the yolk sac and the extra-embryonic portion of the coelom.
This orifice is the primitive umbilical orifice.
Not only does the primitive alimentary canal communicate with the yolk
sac, and the intra-embryonic with the extra-embryonic ccelom, at the margin of
the umbilical orifice, but also the body walls of the embryo, formed by the
somatopleure, becomes continuous, at the same margin, with the wall of the amnion.
The young embryo is connected also with the inner surface of the chorion by
a band of tissue which is part of the median portion of the caudal part of the wall
of the amnion sac. The mesoderm in this region is thickened, and contains in its
interior a diverticulum, allantoic diverticulum, which is primarily derived from the
entodermal sac, but is afterwards connected with the hind-gut. This strand con-
sists of ectoderm and mesoderm, and it contains not only the allantoic diverticulum
but also the blood-vessels passing between the embryo and the chorion. It was
called, by His, the body stalk, but the term is not fortunate, for it takes no
part in the formation in the body of the embryo. On the other band, its
mesodermal and entodermal constituents represent a diverticulum from the wall
of the hind-gut, present in many mammals and known as the allantois ; it might
with advantage, therefore, be termed the allantoic stalk.
At first the umbilical orifice is relatively large as contrasted with the total size
THE LIMBS. 39
of the embryo, but as the embryo rapidly extends, in all directions, from the
margin of the orifice, the latter soon becomes relatively small. Ultimately the
various parts of the margin of the orifice are approximated until they fuse together,
closing the opening and forming a cicatrix on the ventral wall of the abdomen
which is known as the umbilicus or navel.
THE EMBEYO.
Whilst the embryonic area is being folded into the form of the embryo, the
neural groove on the surface of the area is being converted into the neural tube.
After the neural tube is completely closed and separated from the surface, during
the third week, the embryo is an elongated organism possessing a larger cephalic
end, a smaller caudal end, attached by the body stalk to the chorion (Fig. 49), a
continuous and unbroken dorsal surface, a ventral surface separated into cephalic
and caudal portions by the umbilical orifice, two lateral surfaces right and left, and
it contains within its interior three cavities : (1) The cavity of the neural tube,
which becomes the cavities of the brain and the spinal medulla (Fig. 50) ; (2) the
primitive alimentary canal, which is a portion of the entodermal vesicle constricted
off during the folding of the embryonic area (Figs. 37, 40); (3) the embryonic
ccelom. The coelom consists of right and left portions which communicate at
the margin of the umbilicus with the extra-embryonic coelom, and with each other
through the pericardial portion of the intra-embryonic ccelom in the ventral wall
of the fore-gut of the embryo (Figs. 49, 90).
At this period the embryo is easily distinguished from the remainder of the
zygote, and it is so far developed that indications of its general plan of organisa-
tion are discernible.
It has, as yet, no limbs, but the general contour of the head and body are
defined. It possesses a notochord or primitive skeletal axis, afterwards replaced
by the permanent vertebral column. On the dorsal aspect of the notochord lies
the neural tube, which is the rudiment of the future brain and the spinal medulla.
At the sides of the neural tube and the notochord are the mesodermal somites
and the nerve ganglia (Figs. 40, 43).
Ventral to the notochord is the primitive alimentary canal (Fig. 50), closed at
its cephalic end by the bucco-pharyngeal membrane, and at its caudal end by
what was originally the caudal portion of the primitive streak, but which is now
called the cloacal membrane because it separates the caudal end of the hind-gut,
which becomes the entodermal cloaca, from the amniotic cavity (Fig. 50).
At the sides of the primitive alimentary canal are the right and left lateral
parts of the coelom, and between the dorsal angle of each half of the coelom and
the mesodermal somites of the same side lies the intermediate cell tract which is
the rudiment of the greater part of the genito-urinary system (Figs. 39, 40).
Ventral to the fore-gut is the pericardial mesoderm, traversed by the pericardial
portion of the ccelom, which is connected dorsally, on each side, with the corre-
sponding lateral portions of the coelom ; and ventral to the hind-gut is the cloacal
membrane. Between the pericardial region at the one end and the cloacal
membrane at the other lies the umbilical orifice, through which the mid-gut
communicates with the yolk sac, the intra-embryonic part of the coelom with
the extra-embryonic coelom, and the allantoic diverticulum with the cloaca (Figs.
39, 50).
THE LIMBS.
When it is first defined the embryo is entirely devoid of limbs (Fig. 51).
During the third week a superficial ridge appears on each side, along the line
of the intermediate cell tract in the interior. This is the Wolffian ridge, and
upon it the rudiments of the fore and hind limbs, the limb buds, are formed,
as secondary elevations ; the fore-limb buds preceding the hind-limb buds in time
of appearance (Fig. 52).
40
HUMAN EMBEYOLOGY.
Shortly after it has appeared, each limb bud assumes a semilunar outline ; it
projects at right angles from the surface of the body, and it possesses dorsal and
ventral surfaces, and cephalic or preaxial, and caudal or postaxial borders. The
FIG. 51. VIEW OF DORSAL ASPECT OF A
HUMAN EMBRYO 1*38 mm. LONG, before
the . appearance of the limbs. (From
Keibel and Elze, Normaltafeln.)
FIG. 52. DORSAL LATERAL VIEW OF
A HUMAN EMBRYO 2*4 mm.
LONG. The Wolffian ridge is seen
at the lateral border of the meso-
dermal somites. (Keibel and
Elze, Normaltafeln.)
bud is the rudiment of the distal segment of the future limb, the hand in the case
of the fore-limb, and the foot in the case of the hind-limb.
As the limb-rudiment increases in length the more proximal segments of the
limb are differentiated, the forearm and arm in the case of the fore-limb, and the
leg and the thigh in the case of
the hind -limb. At the same
time the limbs are folded ven-
trally, so that their original
ventral surfaces become medial
and their original dorsal surfaces
lateral, and the convexities of
the elbows and knees are directed
laterally. At a later period, on
account of a rotation which takes
place in opposite directions in the
fore- as contrasted with the hind-
limbs, the convexity of the elbow
is turned towards the caudal end
of the body and that of the knee
towards the cephalic end. It is
only at much later periods of de-
X velopment, as the erect posture is
assumed, that the convexity of the
FIG. 53. LATERAL VIEW OF A HUMAN EMBRYO 2-1 mm. greatest elbow is directed dorsally and the
length, showing limb buds projecting from the Wolffian ridge. pnTlv f jV o f the knee ventrallv
(Keibel and Elze, Normaltafeln.) Onvexity C illy.
The terminal or distal seg-
ment of each limb is, at first, a flat plate with a rounded margin, but it soon differenti-
ates into a proximal or basal part and a more flattened marginal portion. It is
along the line where these two parts are continuous that the rudiments of the digits
appear. They become evident as small elevations on the dorsal surface of the limb
bud about the fifth week ; they extend peripherally, and by the sixth week the
fingers project beyond the margins of the hand segment, but the toes do not attain
to a corresponding stage of development until the early part of the seventh week.
THE PEIMITIYE ALIMENTAEY CANAL.
41
The nails are later developments. They appear at the third month and reach
the ends of the digits at' the sixth month.
Each limb bud is essentially an extension of a definite number of segments of
the body. It consists, at first, of a core of mesoderm covered by ectoderm. As it
grows the anterior branches of the
spinal nerves of the corresponding
segments are prolonged into it,
together with a number of blood-
vessels. The nerves remain as the
nerves of the fully developed limb,
but the blood-vessels are reduced
in number and are modified until
a smaller number of permanent
main trunks is established.
The greater part, if not the
whole, of the mesodermal core of
the primitive limb-rudiment seems
to be produced by the somatic
mesoderm of the lateral plate.
As the development proceeds it is
differentiated into the cartilagin-
ous, muscular, and other connective
tissue elements which are the rudi-
ments of the skeletal framework
and the muscles and fasciae of the
adult limb.
It is not yet decided whether
or not the muscle elements of the
mesodermal core are derived from
the lateral plate mesoderm, or from
muscle cells which have migrated
into the limb, from the muscle
plates of the segments from which
the limb is formed and from which muscles of the body wall are developed ; and
although it is generally believed that the bone which replaces the cartilaginous
skeletal rudiments is produced by mesodermal cells, it has been asserted that the
bone-producing cells originate in the ectoderm and migrate from the surface into
the interior.
FIG. 54. LATERAL VIEW OP A HUMAN EMBRYO 9 '5 mm.
LONG. (Keibel and Elze, Normaltafeln.)
Note that the limb rudiments no longer project at right angles
from the side of the body but that they are bent ventrally.
THE EAELIEE MODIFICATIONS OF THE PEIMITIVE ENTODEEMAL
ALIMENTAEY CANAL AND THE FOEMATION OF THE STOMA-
TODJEUM AND PEOCTOD^EUM.
The greater part of the permanent alimentary canal is derived from the ento-
dermal sac and is therefore lined by entoderm cells. This part is enclosed in the
embryo as the latter is folded off from the remainder of the zygote (Fig. 50), but
the cephalic and caudal portions of the alimentary canal are formed by the
enclosure of part of the external space and are, therefore, lined by ectoderm.
The cephalic part is a portion of a space called the stomatodseum which lies,
at first, between the ventrally bent extremity of the head and the bulging
pericardial region (Fig. 50). At a later period it is enclosed laterally by the rudi-
ments of the maxillae or upper jaws, and caudally by the mandibular rudiments.
When it first appears the stomatodseum is separated from the cephalic end of
the entodermal portion of the primitive canal by the bucco-pharyngeal membrane,
but when that septum disappears, during the third week, the stomatodseum
communicates with the fore-gut. Subsequently, it is separated into nasal and
oral portions, and the oral portion forms that part of the mouth in which the gums
and teeth are developed.
The caudal part of the permanent canal is formed by the elevation of a surface
42
HUMAN EMBEYOLOGY.
fold round a pit-like hollow called the proctodseum (Fig. 60), which is separated
from the caudal part of the ento-
smodiai trophobiast dermal portion of the alimentary
canal, until about the fourth
ellular trophoblast
Fore-gut Notpchord
Amiiion cavity^
Neural tube "
Ccelomv
a
Mesodermofchorion anal jg^^gg^^ a portion Of the
fammon more extensive cloacal mem-
aiuniou
>- Body stalk
brane mentioned on p. 39.
Peri
cardium
Hind-gut
Wall of yolk-sa
FIG. 55. SAGITTAL SECTION OF ZYGOTE SHOWN IN FIG. 38.
Differentiation of the
Fore-gut.
Derivatives of the Lateral
Wall. Shortly after the fore-
gut is enclosed, and whilst it is
still separated from the stomato-
daeum by the bucco-pharyngeal
membrane, its cephalic extremity
dilates to form the primitive
pharynx and thereafter, a series
of eight pouches are formed in its
walls, five in each lateral wall ; the
pharyngeal or branchial pouches ;
two in its ventral wall, one near
the cephalic extremity, the rudiment of the thyreoid gland, and a second situated
more caudally, which is the germ of the respiratory system, that is, of the larynx,
the trachea, the bronchi, and the epithelial lining of the lungs. The eighth pouch,
Seessel's pouch, is formed in the dorsal wall, immediately caudal to the dorsal end of the
bucco-pharyngeal membrane, and it projects into the floor of the primitive cranium.
Ext. ear{
1st Branchial
cleft
2nd Branchial
pouch
2nd Branchial. }
cleft
3rd Branchial
pouch "
4th Branchial
pouch -
4th Branchial ..
cleft
Pharyngo-branchial duct,
|5th Branchial bar /
5th Branchial pouch
Separating membrane / /
- 1st cleft = tympanum / /
and tube V
Tonsil
Lower Upper-
- parathyreoid parathyreoid
Upper Lower -_^
-parathyreoid parathyreoid
.Thyreoid gland '
**" Thymus
- - Hyoid bone
- - Thyreo-glossal duct
Thyreoid cartilage
\
Thymus
FIG. 56. SCHEMA showing the branchial pouches, the branchial clefts, the branchial bars, and the thyreo-
glossal duct and some of their derivatives. I., II., III., IV., and V., the five branchial bars.
Simultaneously with the formation of the pharyngeal pouches internally a
series of clefts appear externally. They correspond in position with the first four
pharyngeal pouches, and they are called the pharyngeal or branchial clefts.
By means of the pharyngeal pouches and clefts the lateral boundary of the
cephalic part of the fore-gut, on each side, is divided into a series of bars, the
pharyngeal or branchial bars, five in number, but the fifth is distinctly visible only
in the inner aspect of the pharynx.
THE PEIMITIVE ALIMENTAEY CANAL.
43
The first of the pharyngeal bars is the rudiment of the maxillary and mandibular
regions. It is called the mandibular arch. The second is the hyoid arch, and the
remainder are the branchial arches proper.
When they first appear, the arches extend from the level of the dorsal wall of
the fore-gut to the pericardium but, as growth proceeds, and the neck is developed
between the head and the pericardium, the ventral ends of the arches of opposite
sides meet in the ventral wall of the primitive pharynx. The growth of the mandi-
Rudiment of respiratory system
Ectoderm of embryo |
Ectoderm of amnion
Mesoderm of amnion
Thyreo-glossal d
Hind-brai
Medulla spinalis
Notochord
t Dorsal pancreas rudiment
Peritoneal part of coelom
Seessel's pouch
Mid- brain
Peritoneal part of
coelom
loaca
Rathke's pouch
Cerebral hemisphere
Pericardium /
Rudiment of liver |
Septum transversum
Rudiment of gall-bladder
Ventral pancreas rudiment
Vitello-intestinal duct
FIG. 57. SCHEMA OF A LONGITUDINAL SECTION OP AN EMBRYO. (After Mall, modified,
dorsal and ventral divertricula for alimentary canal. The heart is not shown.
oacal membrane
'ail-gut diverticulum
horion
Allan toic
diverticulum
Showing
bular and the hyoid arches soon greatly exceeds that of the branchial arches proper,
and the latter gradually recede from the surface until, on each side, they lie at the
bottom of a depression, the precervical sinus, which is overlapped by the caudal
border of the hyoid arch. As the overgrowth of the hyoid arch continues the open-
ing of the precervical sinus to the surface is reduced to a narrow channel, the precer-
vical duct. Afterwards this is obliterated, the sinus becomes the precervical vesicle,
1st cleft '
2nd cleft-
cleft "
Precervical duct'
4th cleft '
Branchial duct
Precervical_
sinus
Precervical
duct
4th pouch
FIG. 58. SCHEMA showing the formation of the precervical sinus, the branchial ducts, and the
precervical sulcus.
but the position of the original aperture of the precervical duct is temporarily
indicated by a sulcus, the precervical sulcus which soon disappears. The precervical
vesicle lies at the side of the third pharyngeal cleft, and it is associated with
the second and fourth clefts by narrow canals, the branchial ducts, which are the
remains of the branchial clefts. Ultimately the precervical vesicle and the branchial
ducts disappear, but it has been suggested that before the vesicle disappears a
part of the lobe of the thymus of the same side is formed from its wall.
44 HUMAN EMBEYOLOGY.
The portion of the wall of the primitive pharynx which lies between each
pair of visceral arches and separates the clefts externally from the pouches
internally is called the separating membrane. In the earliest stages it consists of
ectoderm, mesoderm, and entoderm ; then, for a time, the mesoderm disappears to
re-appear again between the two epithelial strata at a still later period.
Bound the margins of the dorsal part of the first pharyngeal or mandibular
cleft are formed a series of tubercles which develop into the auricle of the external
ear, and the cavity of the cleft becomes the external acoustic meatus (see p. 52).
The first pharyngeal pouch and the adjacent part of the cavity of the primitive
pharynx becomes the tympanic cavity and the auditory (O.T. Eustachian) tube. A
part of the cavity of%the second pharyngeal or hyoid pouch is represented in
the adult by the supra-tonsillar recess, which lies in the side wall of the pharynx
above the palatine tonsil (Fig. 56).
The third pharyngeal pouch opens like the first and second directly into the
cavity of the fore -gut, but the fourth and fifth pouches lie in the lateral wall of a
common recess which opens by a single aperture, the pharyngo-branchial duct, into
the cavity of the primitive pharynx (Fig. 56).
The cavities of the third, fourth, and fifth pouches ultimately disappear, but
before the disappearance takes place diverticula which, at first, are hollow but, after-
wards, become solid are given off from the ventro-lateral parts of each, and solid
epithelial outgrowths, the epithelial bodies, are formed from the dorso-lateral walls
of the third and fourth pouches (Fig. 56).
The ventral diverticulum from the third pouch, on each side, forms the main
part of the corresponding lobe of the thymus, and the ventral diverticulum of
the fourth pouch either takes part in the formation of the thymus or it entirely
disappears. The rudiment of the thymus is formed in the neck, but as the gland
differentiates it extends and it migrates caudally, until its cephalic end lies near
the caudal end of the thyreoid gland, at the level of the sixth ring of the trachea,
and its caudal end is in the thorax at the level of the fourth costal cartilage.
The epithelial bodies derived from the third and fourth pharyngeal pouches
form the structures known in the adult as the parathyreoid bodies. That derived
from the third pouch migrates caudally more rapidly than its fellow formed from
the fourth pouch; consequently the parathyreoid derived from the fourth
pharyngeal pouch lies at the middle of the dorsal border of the corresponding lobe
of the adult thyreoid gland, and the parathyreoid formed from the third pharyngeal
pouch is situated at the caudal end of the corresponding lobe of the thyreoid gland
and close to the cephalic end of the thymus.
The diverticulum formed from the ventral part of the fifth pharyngeal pouch is
the ultimo-branchial body. After it separates from the pouch it becomes solid and
is associated with the corresponding lobe of the thyreoid gland, but, apparently,
in the human subject, it takes no part in the formation of that gland.
Derivatives of the Ventral Wall. The diverticulum from the ventral wall
of the primitive fore-gut, which is situated nearest the cephalic or anterior end
of the gut, is the rudiment of the thyreoid gland. It commences in the median
plane, between the ventral ends of the mandibular and hyoid arches, and grows
ventrally, into the substance of the neck, then turns caudally, ventral to the
cartilages which form in the second, third, and fourth arches, from which the
hyoid bone and the cartilages of the larynx are developed. When the caudal
end of the diverticulum reaches the region where the cephalic or anterior portion
of the trachea will be formed it becomes bilobed, and thus is differentiated
into the isthmus and the two lobes of the permanent gland. The stalk of the
diverticulum, which extends from what becomes the oral part of the primitive
pharynx to the isthmus of the gland, is the thyreoglossal duct. Its cephalic
end remains as the foramen caecum, which is situated in the dorsum of the tongue,
at the junction of the ventral two- thirds with the dorsal third. The caudal end
sometimes persists and is transformed into the third or pyramidal lobe of the
thyreoid gland, which is attached to the dorsal border of the isthmus (Figs. 56, 61).
The more caudally situated diverticulum from the ventral wall of the fore-gut
is the rudiment of the respiratory system (Figs. 59, 60). When it first appears
THE PKIMITIVE ALIMENTAKY CANAL.
45
it has the form of a longitudinal groove bounded at its cranial end and laterally by
an elevated ridge, named' by His the furcula (Fig. 59). The caudal end of the groove
soon dilates into a pouch, and then the pouch and groove are separated by a con-
striction, which passes from the caudal
towards the cranial end, from the more
dorsal part of the fore -gut, which be-
comes the oesophagus. The constricting
process ceases before the separation
reaches the cranial extremity of the re-
spiratory rudiment, which remains, there-
fore, in communication with the pharynx
and forms the permanent laryngeal aper-
ture. The tube formed by the separation
of the groove is differentiated into the
larynx and the trachea, and the caudal
terminal dilatation SOOn divides into two FlG - 59. VIEW OF FLOOR OF PKIMITIVE PHARYNX,
u 1^'^u n, 4-Vm ..T,rJ4 showing the furcula with the groove, from which
lateral lobes, each of which is the rudi- arise t | e cavities of the laryn * the ' trachea) the
ment of the epithelial lining bronchi and bronchi, and the alveoli of the lungs,
the lung of the corresponding side.
The Tongue. The tongue is formed by four separate rudiments which lie in the
ventral part of the cranial end of the primitive pharynx. Two of these are eleva-
tions formed on the caudal surfaces of the ventral ends of the mandibular arches,
Tuberculum impar
Sinus arcuatus
Furcula
Ccelon:
Pancreas
Stomach
Bile-duct
Small intestine
Caecum
Liver
Lung
Intestinal loop
Large intestine
.rNotochord
(Esophagus
Trachea X.
Vertebra
Heart
Wolffian duct
Kidney
Mouth
~ Proctod^um
Hind-brain ^^^^^^ ^^^^^^
Allantoic diverticulum
Mid-brain | Vitello-intestinal duct
Fore-brain
FIG. 60. FURTHER DEVELOPMENT OF THE ALIMENTARY CANAL, AS SEEN IN A HUMAN EMBRYO
ABOUT FIVE WEEKS OLD (Diagrammatic).
The tongue is well formed, the trachea and oesophagus are separated, the bronchi have commenced to branch ;
the duodenal curve is well formed, and the caecum has appeared in the loop of the mid-gut. The
cloaca is partially separated into genito-urinary and rectal portions.
one on each side. The third is a median elevation, the tuberculum impar, which is
situated immediately caudal to the conjoined ventral ends of the mandibular arches,
46
HUMAN EMBKYOLOGY.
and the fourth, called the copula, formed by the conjoined ventral ends of the second
arches, is separated from the tuberculum impar by the orifice of the thyreoid
rudiment (Fig. 61).
The two lateral elevations on the mandibular arches unite to form the greater
part of the ventral or anterior two-thirds of the tongue, upon which all the papillae
Mandibular rudiments
/ Tuberculum
impar
Foramen
Furcula
Aperture of larynx
Labiodental sulcus
Mandibular rudiment
Tuberculum impar |
Hyoid rudiment
Germ and
subst. -
eburnea
Foramen ^
caecum
Precervical sinus
Aperture of larynx
FIG. 61. SCHEMA showing stages in the development of the tongue.
are developed. The tuberculum impar either disappears or it forms the median
part of the anterior two-thirds of the organ. The posterior or dorsal third of
the tongue, which lies in the ventral or anterior wall of the permanent pharynx,
is formed from the copula of the second arches. It follows from what has been said
Rudiment of respiratory system
Notochord
Medulla spinalis
Ectoderm of embryo ^^*\
Rudiment of
thyreoid gland
Hypophysi
Rathke's pouch
Ectoderm of amnion /
Mesoderm of amnion
Cerebral
hemisphere
I
Pericardium
Liver diverticulum branching in septum transversum
,' Stomach
Dorsal pancreas rudiment
Ventral pancreas rudiment
"V. Peritoneal part of coelum
x^,. Caecum
Peritoneal part of
coelum
kWolffian duct
Rectum
r Tail gut
Genito-urinary
chamber
Cloacal membrane
Allantoic
diverticulum
Chorion
v ( Umbilical cord
^ Placental mesoderrn
Yolk-sac
Septum transversum
I
FIG. 62. SCHEMA showing further stages in the development of the diverticula from the primitive gut and
modifications of the mid-gut and the mid-gut regions. The heart is not shown. (After Mall, modified. )
that the commencement of the thyreoid rudiment, which persists in the adult as
the foramen csecum of the tongue, must lie at the junction of the dorsal third with
the ventral two-thirds. In many cases it appears to lie in the dorsal end of the
ventral two-thirds, a position which may be associated with the fact that, in some
cases, the rudiment of the thyreoid passes through the substance of the tuberculum
THE PRIMITIVE ALIMENTARY CANAL.
impar and not from between the tuberculum impar and the ventral ends of the
hyoid arches.
Derivative of the Dorsal Wall (Seessel's Pouch). The dorsal diverticulum
from the cranial end of the fore-gut, to which the above term is applied, enters the
base of the occipital region of the primitive head. The ultimate fate of the pouch
is unknown in the human subject, but it has been suggested that it is represented
by a depression in the mucous membrane of the cranial part of the pharynx, close
to the pharyngeal tonsil, which is known as the pharyngeal bursa.
The reader who has followed this description will have noted that from the
cranial portion of the fore-gut are formed the caudal or inferior part of the mouth
(with the exception of the lips, teeth, and gums), the pharynx, the thyreoid gland,
the thymus, the parathyreoids, the respiratory organs, and the oesophagus. The
more caudally situated portion of the fore-gut is differentiated into the stomach
and the first and second parts of the duodenum.
The stomach is formed from the part of the fore-gut immediately adjacent to
Rudiment of thyreoid gland Trachea
Notochord
Medulla spinalis
Ectoderm of embryo
Foramen ctecum
i Oesophagus
Stomach
Pancreas rudiment
Peritoneum
Cerebellar part
of hind-brai
Hypophysis .
Mid-brain
Mesoderm of .
amnion
Ectoderm of
amnion
Cerebral hemisphere
toneum
Descending
colon
uctus deferens
rinary bladder
reter
todoeum
<3enito-urinary
chamber
Allan toic
diverticulum
Chorion
Mandibular arch
Pericardium
Liver diverticulum
Mesoderm of placenta
! Yolk-sac
Diverticulum of peritoneum
FIG. 63. SCHEMA showing complete separation of cloaca into dorsal and ventral parts and the temporary
ventral hernia of a portion of the gut through the umbilical orifice. The heart is not shown. (After
Mall, modified.)
the oesophagus, and the duodenum from the more caudally placed portion, which
is directly continuous with the mid-gut.
The Liver and Pancreas. When the embryo is about three weeks old and has
attained a length of 2*5 mm. a ventral diverticulum appears in the ventral wall of
the duodenal part of the fore-gut, and when the age of the embryo is about four
weeks and its length increased to about 4 mm. a diverticulum is formed in the
dorsal wall a little nearer the cranial end. The ventral pouch is the rudiment of
the liver, the gall bladder, the bile- ducts, and a portion of the pancreas, and the
remainder of the pancreas is formed from the dorsal diverticulum (Figs. 57, 62, 63).
The Derivatives of the Mid-Gut. The mid-gut is that part of the primitive
alimentary tract which lies between the more definitely enclosed fore-gut and
hind-gut, and it is in free communication with the yolk-sac by the vitello-intestinal
duct. It is transformed into the greater part of the small intestine.
The Derivatives of the Hind-Gut. The parts formed from the hind-gut
are : (1) The terminal part of the ileum ; (2) the whole of the large intestine,
except a small portion of the anal canal ; (3) the urachus, the urinary bladder, the
urethra in the female, and the greater part of the urethra in the male. 1
1 T. B. Johnston, Journ. ofAnat., Oct. 1913 ; H. v. Berenberg-Gossler, Anat., Heft. 1913.
48 HUMAN EMBEYOLOGY.
As development proceeds the mid-gut and the cephalic (anterior) part of the
hind-gut form a U-shaped tube which possesses a cranial (anterior) and a caudal
(posterior) limb, and a ventral extremity which is connected with the yolk-sac
by a narrowed and elongated canal, the vitello-intestinal duct (Fig. 5*7).
Upon the caudal limb of the loop, about the middle of its dorso-ventral height,
an enlargement appears which is the rudiment of the csecum and vermiform process
of the adult. After this rudiment has formed the caudal limb of the loop under-
goes rotation, being carried first to the left, then cranially, and finally to the right.
As it is carried to the right it crosses the cranial (later ventral) aspect of the
cranial limb of the loop, and when the rotation is completed the regions of the
jejunum and ileum, the csecum, the ascending and the transverse colon are
defined.
After the rotation has occurred the tubular intestine formed from the mid-gut
and the anterior part of the hind-gut, undergoes rapid elongation and is thrown
into a number of coils.
When the embryo has attained the length of 10 mm., and is a little over a
month old, the greater portion of the coiled gut passes through the umbilical
orifice into an expansion of the coelom formed in the proximal part of the umbilical
cord (see p. 47) (Fig. 63), which has replaced the allantoic or body-stalk as the
medium by which the embryo is attached to the chorion. The herniated coils
remain in the root of the umbilical cord until the embryo is about 40 mm. long,
and about ten weeks old, when they return to the abdomen, and the coelomic
space in the umbilical cord disappears.
The Derivatives of the Posterior Part of the Hind-Gut. When the caudal
portion of the hind-gut is first enclosed its terminal extremity and its ventral
wall are bounded by the caudal portion of the primitive streak, which is bent
ventrally during the folding -off of the embryo.
The terminal part of this portion of the gut becomes expanded, forming
a chamber called the entodermal cloaca, into the ventral parts of which the
ducts of the primitive kidneys, the pronephric or Wolfl&an ducts, open, one on each
side.
The ventral part of the cephalic end of the cloaca is continuous with the
allantoic diverticulum, and the dorsal part with a tubular portion of gut which
forms the descending and possibly also the iliac and pelvic portions of the colon.
As the temporary tail is formed and projected first caudally and then ventrally,
by the growth energy of the nodal point situated at the caudal end of the neural
tube, a diverticulum of the caudal end of the dorsal part of the cloaca is prolonged
into it, forming the tail gut. This soon becomes shut off from the cloaca. It
entirely disappears before the temporary tail is absorbed into the caudal end of
the body (Figs. 57, 62, 63).
At a later period the cloaca itself is separated into a dorsal part, the rectum,
and a ventral part, the urino-genital chamber, by the formation of a septum, which
commences in the angle between the allantoic diverticulum and the ventral wall
of the cloaca, and is prolonged caudally till it reaches and fuses with the internal
surface of the cloacal membrane, which thus becomes separated into urino-genital
and anal portions, both of which disappear about the eighth week.
In both sexes the urino-genital section of the cloaca is separable into three
parts : (1) a cranial part, which is converted into the urachus or middle umbilical
ligament ; (2) an intermediate part, which becomes the urinary bladder ; and
(3) a caudal part, which, in the female, is transformed into the urethra and the
vestibule of the vagina, whilst in the male it is developed into the urethra.
Derivatives of the Stomatodaeum. When the stomatodseum is first definitely
established, it is bounded cranially (anteriorly) by the caudal surface of the
ventrally bent terminal part of the head, caudally by the conjoined ventral ends of
the mandibular arches, and laterally by the dorsal parts of the mandibular arches,
and the maxillary processes, which grow ventrally from the dorsal parts of the
mandibular arches. The space is open ventrally, and it is closed dorsally by the
bucco-phaTyngeal membrane, which separates it from the fore-gut (Fig. 55).
THE STOMATODJEUM
40
Stomatodseum
Globular process
Olfactory pit
Lateral
nasal
process
Maxillary
64. ANTERIOR VIEW OF BOUNDARIES OF
STOMATOD^UM BEFORE COMPLETION OF PRIMI-
TIVE UPPER LIP.
The bucco-pharyngeal membrane disappears about the third week, and about
the twenty-first day a diverticulum from the stomatodaeum is projected into the
caudal surface of the head, from the point
where that surface originally joined the
dorsal end of the external surface of the
bucco-pharyngeal membrane. The diver-
ticulum is Rathke's pouch. The cranial
extremity of the pouch comes into relation
with the hypophyseal diverticulum from
the floor of the third ventricle, and dilates.
The stalk which connects the dilated
terminal part of the diverticulum with
the stomatodseum disappears, and the
terminal vesicle becomes the anterior lobe
of the hypophysis (O.T. pituitary body)
(Figs. 57, 62, 63).
The Separation of the Stomatodseum
into Nose and Mouth. In the cephalic FIQ
boundary of the stomatodseal space lies
the ventral end of the head, which is
called the fronto-nasal process.
In the fronto-nasal process, on each side of the median plane, is situated a
shallow pit, the olfactory pit, and by the pits the process is divided into a median
part, the median nasal process, and two lateral parts, the lateral nasal processes.
Further, the margin of the median process is divided by a median cleft into
right and left globular processes (Fig. 64).
The orifices of the olfactory pits are directed laterally, therefore the lateral nasal
processes lie dorsal to the median nasal process in the cranial boundary of the
stomatodaeal space, and as their margins increase in height the pits deepen (Fig. 69).
At this period the cranial boundary of the stomatodaeum is divided by the
median sulcus and the olfactory pits into four projections the two globular processes,
each of which lies between the median
sulcus and an olfactory pit, and the
two lateral nasal processes, which form
the dorso-lateral borders of the olfactory
pits. The lateral boundaries are formed
by the maxillary processes and the dorsal
parts of the mandibular bars, and the
caudal boundary is formed by the medi-
ally turned and conjoined ventral parts
of the mandibular bars. Immediately
cranial to the maxillary process, on each
side, is the projecting eye ; and leading
from it, between the maxillary process
and the lateral nasal process, is the
naso-lacrimal sulcus.
As growth proceeds and each maxil-
lary process grows ventrally, its ex-
- Cerebral hemisphere
-Lens
Lateral nasal process
-Maxillary process
-Mandibular arch
-Hyoid arch
-Third arch
Pericardial region
FIG. 65. SCHEMA OF ANTERIOR VIEW OF THE HEAD f rA t n jf v f 11<; p q w iP Aam nr
OF A HUMAN EMBRYO SHOWING THE COMPLETION T 6mit S 6S 71 i faudal or P S -
OF THE PRIMITIVE UPPER LTP. tenor border of the lateral nasal process,
and then, carrying the lateral nasal
process with it, it fuses with the globular process of the same side.
After the fusion of the maxillary processes, and the posterior or caudal
borders of the lateral nasal processes, with the globular processes has occurred/
the olfactory pits are completely separated, for a time, from the stomatodseum,
and they lie in the ledge which now forms the cranial boundary of the stomato-
dseum. This ledge consists of the two globular processes, fused into a single mass,
and the two maxillary processes, the caudal or posterior l edges of the lateral nasal
1 Inferior in erect posture.
4
50
HUMAN EMBRYOLOGY.
Anterior nasal orifice
processes being shut off from the margin of the ledge by the maxillary processes
(Fig. 65).
After the ledge is completed the dorsal ends of the olfactory pits are separated
from the stomatodseum by a thin membrane, but this soon disappears, and the pits
open again into the stoniatodaeal space, through apertures which are called the
primitive choanse.
After the formation of the primitive choanae a ledge grows from the medial
surface of each maxillary process towards the median plane, caudal to the choanae.
These ledges, the palatine processes, meet and fuse during the third month of fcetal
life, the fusion commencing ventrally and being completed dorsally in the region
of the uvula. As the ledges meet and fuse, the stomatodseum is separated into a
cranial and a caudal portion. The cranial
part is the nasal cavity ; it is soon divided
into two lateral halves by a septum which
passes caudally from the base of the
cranium. The caudal portion of the
stomatodseum blends with the ventral
part of the primitive pharynx and it
forms the vestibule of the mouth and its
derivatives, and the gums and teeth.
The details of the process by which
the primitive lips are separated into the
permanent lips, and the gums are defined,
are described in the section dealing with
Hypophyseal depression the digestive System.
FIG. 66. PORTION OF THE HEAD OF A HUMAN The Derivative of the Proctodaeum.
EMBRYO ABOUT 2 MONTHS OLD (His). The lips The proctodseum is a surface depression
:rXw7rm ^Mbie^thUatte 6 , ' T t which owes its origin to the elevation of
palatine processes are growing inwards from the the Surface round the margin of the anal
maxillary processes. membrane. It forms the lowest portion
of the pars analis recti of the adult.
Urino-genital System. The formation of the internal parts of the urino-genital
system from the intermediate cell tract, the urino-genital chamber, and the
differentiation of the external genitals in the region of the cloacal membrane are
described in the account of the urino-genital system.
The development of the auditory organ is so intimately associated with the
development of the pharyngeal portion of the primitive gut that a short considera-
tion of the chief phenomena may with advantage be introduced here ; but for the
details of the development of the internal; middle, and external portions of the ear
the student must refer to the account of the development given in association with
the description of the auditory organ.
Palatine
process
THE INTERNAL EAR, THE TYMPANUM AND AUDITORY TUBE,
AND THE EXTERNAL EAR.
In the human subject, as in other mammals, the auditory organ consists of the
internal ear or labyrinth, the middle ear or tympanum, with which is associated the
auditory tube (O.T. Eustachian) ; and the external ear, which consists of the external
acoustic meatus with the auricle at its lateral end.
The internal ear itself consists of two parts the cochlea, which is the true organ
of hearing, and the vestibule and the three semicircular canals connected with it,
which are associated with the recognition of alterations in the position of the head,
and, therefore, with the recognition and maintenance of equilibrium.
The whole of the internal ear is lined with ectodermal epithelium, the auditory
epithelium, which is derived from the surface of the head of the embryo. It is
recognisable in embryos of about 2 '6 mm. (Fig. 67) as a thickened and slightly
depressed plate of ectodermal cells which lies on the surface of the head, in the
region of the hind-brain, dorsal to the second branchial cleft. As development
THE INTEKNAL EAR
51
proceeds the plate is gradually invaginated into the substance of the head, and is
Hind -brain Auditory ganglion
/ / Rudiment of otic vesicle
Xa^C^^^S-^^^X /
Paraxial mesoderm
Hyomandibular cleft
SoM
S P M1 '
First cephalic aortic arch
SpMz
FIG. 67. TRANSVERSE SECTION OP A BAT EMBRYO.
Showing the relation of the paraxial mesoderm of the head to the lateral plates, the commencement of the
formation of the otic vesicles and hyomandibular clefts, and the relation of the primitive heart to the
pericardium and fore-gut.
EC. Ectoderm. SoM. Somatic mesoderm. SpM. Splanchnic mesoderm.
transformed into a pear-shaped vesicle, the otic vesicle, which remains for a time in
communication with the ex- HB
terior by means of a short
tubular stalk, the recessus
labyrinthi, which is subse-
quently converted into the
ductus endolymphaticus. 1
After it is separated from
the surface the otic vesicle
alters its position, until its
ventral end lies in close re-
lation to the dorsal wall of
the pharynx, and, at the same
time, it undergoes alteration
of shape. The ventral part
of the vesicle grows towards
the median plane, along the
ventral wall of the hind-brain.
It forms the cavity and the
lining epithelium of the coch-
lea; but it remains in con-
nexion with the dorsal part
by means of a narrow tube,
the canalis reuniens, and as it
grows in length it becomes
converted into a spiral tube.
The portion of the dorsal
section of the primitiv e vesicle,
which lies to the lateral side
of the recessus labyrinthi, first
HM
FIG. 68. TRANSVERSE SECTION THROUGH THE HEAD
OP AN EMBRYO.
Showing the rudiments of the three parts of the ear and their
relation to the hyomandibular cleft.
BV. Blood-vessels.
C. Cochlea.
EM. Ext. acoustic meatus.
ET. Auditory tube.
HB. Hind-brain.
HM. Hyomandibular cleft.
N. Notochord.
0V. Otic vesicle.
P. Pharynx.
Kecessus labyrinthi.
Semicircular canal.
Tympanum.
RL.
SC.
T.
expands and
1 See note 3, p. 79.
then becomes compressed and
52
HUMAN EMBEYOLOGY.
constricted into the form of three flat purse-like diverticula which, by the partial
obliteration of their cavities, become converted into the three semicircular canals (see
Sense Organs). The more ventral part of the dorsal section of the vesicle is divided,
by a constriction of its lateral wall, into a dorsal part, the utricle, which remains in
connexion with the semicircular canals, and a ventral part, the saccule, which is
united to the cochlea by the canalis reuniens. The apex of the constriction which
separates the utricle from the saccule passes into the mouth of the ductus endo-
lymphaticus, which is thus transformed into the Y-shaped canal which connects
the utricle with the saccule. At a later period the closed extremity of the ductus
endolymphaticus dilates and forms a small saccule, the saccus endolymphaticus.
In the adult the saccus endolymphaticus lies in the posterior fossa of the skull,
in relation with
the posterior
surface of the
petrous part of
the temporal
bone and ex-
ternal to the
dura mater.
The tympa-
num and the
auditory tube
(O.T. Eustachian)
are developed
from the first
visceral pouch.
The ventral
part of the pouch
disappears at an
early stage. The
dorsal extremity
expands and is
converted into
the cavity of
the tympanum,
whilst the stalk
of connexion
with the pharynx
is gradually con-
stricted off from
its lateral to-
wards its medial
end, and is converted into the auditory tube. The constriction commences when
the embryo has attained a length of about 20 mm., that is about the beginning of
the eighth week, and is completed about the end of that week when the embryo
is about 25 mm. long.
After the auditory tube is defined it grows rapidly in length, and cartilage
appears in its walls during the fourth month.
As the tympanic cavity increases in size the auditory ossicles stapes, incus, and
malleus, which are differentiated from the dorsal ends of the cartilages of the first
and second branchial arches, are invaginated into it.
The membrana tympani, which separates the tympanum from the external
acoustic meatus, is formed from the separating membrane which intervenes
between the first branchial pouch and the first cleft. It consists, therefore, of an
external covering of ectoderm, an internal lining of entoderm, and an intervening
layer, of fibrous tissue, derived from the mesoderm.
The external ear is developed from the cavity and the boundaries of the first
branchial cleft. The cavity of the cleft is transformed into the cavity of the
external acoustic meatus, and on the mandibular and on the hyoid margins of the
FIG. 69. FIGURES, MODIFIED FROM His, ILLUSTRATING THE FORMATION OF
THE PINNA.
1. Tuberculum tragicum = Tragus.
2. ,, auterius helicis
3. ,, intermedium helicis
4. Cauda helicis
5. Tuberculum anthelicis = Antihelix.
Helix.
6. Tuberculum antitragicum = Anti-
tragus.
7. Tuberculum lobulare = Lobule.
HM. Hyomandibular cleft.
0V. Otic vesicle.
THE MEMBRANES AND APPENDAGES OF THE FCETUS. 53
cleft three eminences appear. From the eminences on the two arches, and the
skin immediately posterior to the eminences on the hyoid arch, are formed the
various parts of the auricle, but the exact part played by the individual
eminences in the human subject is as yet a matter of some doubt.
THE PROTECTION AND NUTRITION OF THE EMBRYO DURING
ITS INTRA-UTERINE EXISTENCE.
Whilst it is passing down the uterine tube, and for a brief period after it
enters the uterus, the zygote, or impregnated ovum, depends for its nutrition
upon the yolk granules (deutoplasm) embedded in its cytoplasm, and upon the
fluid medium surrounding it which is secreted by the walls of the uterine tube
and the uterus.
As the human ovum is very small, and as it contains but little deutoplasm, its
nutrition is practically dependent, almost from the first, upon external sources
of supply. The urgent necessity for the formation of adequate arrangements
whereby the external sources may be utilised leads to the early establishment
of an intimate connexion between the zygote and the mother, which is one of the
characteristic features of the development of the human embryo.
During the third week after fertilisation, as the embryo is beginning to be
moulded from the embryonic region, and before the paraxial mesoderm commences
to separate into mesodermal somites, a primitive heart and the rudiments of
some well-defined blood-vessels are distinguishable in the embryo; but the
details of the development of the vascular system and the establishment of the
embryonic circulation cannot be well understood until the formation and structure
of a group of closely associated extra-embryonic organs or appendages, derived
from the zygote, has been considered.
This group includes the chorion, the placenta, the amnion, the umbilical cord,
and the yolk-sac.
THE MEMBRANES AND APPENDAGES.
The Chorion. It has already been noted that when the zygote becomes a
blastula it consists of three vesicles, a large vesicle enclosing two smaller vesicles
and a mass of primary mesoderm (Fig. 29).
The wall of the large vesicle is composed of trophoblast (trophbblastic ectoderm),
and its inner surface is in direct contact with the primary mesoderm.
A little later a cavity, the extra-embryonic ccelom, appears in the primary
mesoderm, separating it into two layers, .one lining the inner surface of the tropho-
blast and the other covering the outer surfaces of the two inner vesicles (Figs.
70, 71).
As soon as the extra-embryonic coelom is established the chorion is formed ;
it consists of the trophoblast and its inner covering of mesoderm.
In the meantime the trophoblast has differentiated into two layers, an inner
cellular layer, and an outer plasmodial layer. In the plasmodial layer cell
territories are not denned, and it consists, therefore, of nucleated protoplasm.
The differentiation of the trophoblast into two layers occurs after the zygote
is embedded in the mucous membrane of the uterus which is modified for its
reception and which, after the modification has occurred, is called the decidua.
As development proceeds the trophoblast increases in thickness and it invades the
decidua. As this invasion occurs the plasmodial layer of the trophoblast becomes
permeated with spaces which are continuous with the lumina of the maternal
blood-vessels in the decidua, and are filled with maternal blood.
By means of the spaces the plasmodial trophoblast is separated into branching
processes which intervene between ' the blood-filled spaces. The processes are
the primary chorionic villi, and they soon develop -cellular interiors (Fig. 72).
After a time the primary villi are invaded by the chorionic mesoderm, and are
thus converted into the secondary chorionic villi, which become vascularised by the
54
HUMAN EMBEYOLOGY.
growth of foetal vessels into the foetal mesodermal cores. The secondary villi,
therefore, consist of a mesodermal core covered by a layer of cellular trophoblast
and a layer of plasmodium, the latter lying outside the former. Still later the
secondary villi send out numer-
_-4 ; Mesoderm of amnion
- Ectoderm of amnion
Allantoic diverticulum
of entoderm vesicle
Body stalk mesoderm
Extra-embryonic ccelom
Entoderm
Mesoderm covering of
entoderm vesicle
Neurenteric canal
Cavity of entodermal vesicle
FIG. 70. SCHEMA OF SAGITTAL SECTION OF ZYGOTE ALONG LINE A.
( Plasmodial trophoblast Neural groove
Chorion { Cellular trophoblast
\ Mesoderm lining of trophoblast^
Amnion cavity
Extra-embryonic coelom
Mesoderm of amnion -
Ectoderm of amnio
Mesoderm covering
entoderm
Entoderm
Cavity of entodermal
vesicle
ous branches into the blood
[blast spaces,and thus increase greatly
Mesoderm lining of tropho- in Complexity (FigS. 75, 76, 77).
development progresses
still further a part of the chorion
is converted into the fcetal
portion of an organ called the
placenta, and thus the chorion
is divided into placental and
non - placental regions. Upon
the placental part the villi con-
tinue to increase, but they dis-
appear entirely from the non-
placental part, which is then
called the chorion Iseve (Fig.
The Amnion, the Body-
Stalk (Allantoic Stalk), and
the Umbilical Cord. The
amnion is formed from that
portion of the wall of the larger
of the two inner vesicles of the
zygote, the ecto - mesodermal
vesicle (p. 22), which does
not take part in the formation
of the embryo. It consists of
ectoderm cells covered exter-
nally by a layer of extra-em-
bryonic mesoderm, and it is
continuous with the margin
of the embryonic area (Figs.
70, 71).
The cavity of the ecto-
mesodermal vesicle, enclosed
between the amnion and the embryonic area, is the cavity of the amnion ; it
is filled with fluid, which raises the amnion in the form of a cupola over the
embryonic region (Fig. 70).
The Body-Stalk (Allantoic Stalk). It has been noted already that the mesoderm
of the median part of the posterior or caudal portion of the amnion becomes
Notochord
FIG. 71. SCHEMA OF TRANSVERSE SECTION OF ZYGOTE ALONG
LINE B (Fig. 31).
Plasmodi
trophoblast
Plasmodial
tropho
Cellular
trophobl
Mesoder:
Ectode
of amnion
Plasmodial
trophoblast
Cellular
trophoblast
Efferent vessel
of villus
Fused mesod
of c
and amnio:
Ectoderm/
of amnion
'Afferent vessel of villus
Fused mesoderm of
r - "amnion and chorion
Ectoderm of amnion
FIG. 72. SCHEMA OF THREE STAGES IN THE FORMATION OP A CHORIONIC VILLUS.
thickened. In the thickened strand lies the allantoic diverticulum of the
entodermal vesicle (Fig. 70), whilst through it, on either side of the allantoic
diverticulum, pass the umbilical arteries and veins, by means of which blood is
conveyed between the embryo and the chorion.
This segment of the wall of the amnion vesicle was termed by His the
body-stalk. It takes no direct part in the formation of the embryo, and as it
THE MEMBKANES AND APPENDAGES.
55
Afferent vessel
of vil
Plasmodial trophoblast
Cellular
trophoblast
Afferent vessel
of villas
Mesoderm
.. of villus
Efferent vessel
of villus
contains the rudimentary allantoic diverticulum and represents the much more
highly developed allantois of other forms, it would, perhaps, be better to term it the
allantoic stalk. For the present purpose it is important to note that the blood-
vessels which pass through the body-stalk enter or leave the body through the
umbilical orifice, which is, at first, a relatively large aperture (Fig. 50).
As the embryonic area is folded into the form of the embryo the amnion
increases in extent, filling more and more of the extra-embryonic coelom, and the
embryo rises into the interior of its cavity. In other words, the walls of the amnion
bulge ventrally round the cranial and caudal extremities and the lateral borders
of the embryo (Figs. 75, 76, 77). As the distension of the amnion still continues,
the ventral bulging, round the margin of the umbilical orifice, becomes more pro-
nounced, the yolk-sac is forced farther
and farther away from the embryo, the
vitello-intestinal .duct is elongated, and
it is surrounded by a hollow tube. The
cavity of the tube is an elongated part of
the extra-embryonic coelom, and its walls
are formed by the amnion (Figs. 57, 62, 63).
The caudal wall of the tube neces-
sarily consists of the elongated body-stalk
(allantoic stalk).
As the distension of the amnion still
continues, the walls of the tube are forced
nrrflinQt tViP virplln inrpqfinfll rlnor anrl FlG - 73. SCHEMA OF A TRANSVERSE SECTION OF A
SECONDARY CHORIOKIC VILLUS. A loop of the
the amniOtlC mesoderm fuses With the afferent vessel has been cut at two points.
mesoderm of the vitello-intestinal duct.
When the fusion is completed, a solid cord, the umbilical cord, is formed (Figs.
77, 78, 80). It consists of an external covering of amniotic ectoderm, and a core
of mesoderm in which lie the two umbilical arteries of the body-stalk, a single
umbilical vein formed by the fusion of the two primitive veins, and the remains
of the vitello-intestinal duct and the vitelline vessels. The proximal end of the
umbilical cord is connected with the embryo; the distal end is attached to the
chorion, and in its neighbourhood lies the now relatively small vesicular yolk-sac
(Fig. 62).
As the amnion grows still larger, all that part of its outer surface which does
not take part in the formation of the umbilical cord is ultimately pressed into
contact with the inner surface of the chorion, with .which it fuses, and the cavity
of the extra-embryonic part of the coelom is obliterated (Fig. 78).
The outer wall of the zygote now consists of the fused chorion and amnion,
and it contains in its interior the amniotic cavity and the embryo, which is attached
to the chorion by the umbilical cord.
When it is first formed the umbilical cord is comparatively short, but, as the
amniotic cavity increases, the cord elongates, until it attains a length of from
18 to 20 inches, a condition which allows the embryo to float freely in the
fluid in the amniotic cavity, whilst its nutrition is provided for by the flow and
return of blood, through the umbilical cord, to and from the placenta, where
interchanges take place between the maternal and the foetal blood.
The Yolk-Sac or Umbilical Vesicle. When the embryonic area is folded into
the form of the embryo, the entodermal vesicle is differentiated into three parts :
(1) a part enclosed in the embryo, where it forms the primitive entodermal
alimentary canal; (2) a part which lies external to the embryo in the extra-
embryonic coelom this is the yolk-sac or umbilical vesicle ; (3) the third portion is
the vitello-intestinal duct, which connects the primitive alimentary canal and the
yolk-sac together (Figs. 40, 62).
The walls and the cavity of the yolk sac are, therefore, continuous with the
walls of the primitive alimentary canal, and the structural features of the two are
identical, each consisting of an internal layer of entodermal cells and an external
layer of splanchnic mesoderm.
Free communication between the yolk-sac and the primitive alimentary canal
56 HUMAN EMBKYOLOGY.
appears to exist in the human subject till the embryo is three weeks old and
about 2 '5 mm. long. During the fourth week the vitello-intestinal duct is
elongated into a relatively long narrow tube, which is lodged in the umbilical cord
and the yolk-sac, which has become a relatively small vesicle, is placed between
the outer surface of the amnion and the inner surface of the chorion, in the region
of the placenta (Fig. 62). During the latter part of the fourth or the early part of
the fifth week, when the embryo has attained a length of about 5 mm., the vitello-
intestinal duct separates from the intestine and commences to undergo atrophy,
but remnants of it may be found in the umbilical cord up to the third month.
The yolk-sac itself persists until birth, when it is, relatively, a very minute
object which lies either between the amnion and the placenta or between the
amnion and the chorion laeve.
At a very early period, before the paraxial mesoderm has commenced to divide
into mesodermal somites, a number of arteries, the primitive vitelline arteries, are
distributed to the yolk-sac from the primitive arterial trunks of the embryo, the
primitive aortse, and the blood is returned from the yolk-sac 'to the embryo by a
pair of vitelline veins (Fig. 81).
After a time the arteries are reduced to a single pair, and after the two primi-
tive dorsal aortse have fused into a single trunk, the pair of vitelline arteries
also becomes converted into a single trunk, which passes through the umbilical
orifice along the vitello-intestinal duct to the yolk-sac (Fig. 83).
The vitelline veins also pass through the umbilical orifice on their way to the
heart of the embryo, and they become connected together, in the interior of the
body of the embryo, by transverse anastomoses, which are described in the account
of the development of the vascular system.
After the umbilical cord is formed, the extra-embryonic parts of the vitelline
veins disappear, and can no longer be traced in the cord. The same fate overtakes
the extra-embryonic and a portion of the intra-embryonic part of the vitelline
artery, and the remainder of the artery persists as the superior mesenteric.
THE PLACENTA.
The placenta is an organ developed for the purpose of providing first the
embryo and later the foetus with food and oxygen, and for removing the effete
products produced by the metabolic processes which take place in the growing
organism. It is formed partly from the zygote and partly from the mucous
membrane of the uterus of the mother.
In the placenta the blood-vessels of the embryo of the earlier stages and
the foetus of the later stages and the blood of the mother are brought into close
relationship with one another, so that free interchanges may readily take place
between the two blood streams; and the modifications and transformations of
the uterine mucous membrane and the chorion of the zygote, by which this
intimate relationship is attained, constitute the phenomena of the development of
the placenta.
The details of the development of the human zygote for the first ten or twelve
days after the fertilisation of the ovum are not known, but the knowledge of what
happens in other mammals justifies the belief that during that time the zygote is
formed, in the ovarian, or the middle part of the uterine tube, by the union of a
spermatozoon with the mature ovum. During the first ten to fourteen days after
its formation it passes along the uterine tube, towards the uterus, whilst, at the same
time, it undergoes the divisions which convert it into a morula.
The Formation of the Placenta. Before the zygote reaches the uterus the
mucous membrane which lines the cavity of that organ undergoes changes, in
preparation for its reception and retention, and when the changes are completed
the modified mucous membrane is known as the uterine decidua.
The changes which take place are, for the most part, hypertrophic in character ;
the vascularity of the mucous membrane is increased, mainly by the dilatation of
its capillaries; the tubular glands of the membrane are elongated, they become
THE PLACENTA.
Decichia basalts
Blood-vessels
Muscular wall
of uterus
Uterine
tube
Trophoblast
Inner mass of cells
Unchanged layer
Dilated part of gland
Inner part of
gland
tortuous, and dilatations form in their walls a short distance from their outer closed
extremities. At the same time the interglandular tissue increases in amount, and
as a result of the various processes the decidua is thicker, softer, more spongy, and
more vascular than the mucous membrane from which it was evolved.
Partly on account of the dilatation of the deep part of the glands and partly
on account of differences in texture of the internal as contrasted with the external
part of the decidua, the membrane may be looked upon as consisting of three
layers. (1) An internal layer, next the cavity, the stratum compactum. (2) An
intermediate layer, the stratum spongiosum, formed largely by the dilated parts
of the glands. (3) An external layer, the unchanged layer, in which lie the com-
paratively unaltered outer ends of the glands.
When the zygote, in the morula stage, reaches the uterus, from the tenth to
the fourteenth day, it acts as a parasite, it eats its way through the epithelium on
the surface of the decidua, and implants itself in the stratum compactum.
The zygote may penetrate the decidua at any point of the wall of the uterine
cavity, but it usually
enters at some point of
the dorsal or the ventral
wall. The entrance gener-
ally takes place between
the mouths of adjacent
glands, which are pushed
aside, and the zygote be-
comes at once surrounded
by the interglandular
tissue of the stratum com-
pactum of the decidua.
The aperture through
which it passes may be
closed by a nbrinous plug
or its margins may con-
verge rapidly and fuse
together.
The portion of the de-
cidua in which the zygote
is embedded is thicker
than the other parts of the
membrane, and it is separ-
ated by the zygote into an
internal part, the decidua
capsularis, and an external
part, the decidua basalis.
The junction of the decidua
capsularis with the decidua
basalis is the decidua marginalis, and the remainder of the decidua, by far the larger
portion, is the decidua vera.
As soon as the zygote becomes embedded in the decidua its trophoblast under-
goes rapid proliferation. The superficial part of the growing trophoblast becomes
converted into a mass of nucleated protoplasm, the plasmodial or syncytial layer,
but the inner part remains more or less distinctly cellular.
The plasmodial portion of the trophoblast invades and destroys the surrounding
maternal tissue, and at the same time spaces appear in its substance. As the
plasmodium destroys the walls of the dilated maternal blood-vessels, channels are
made through which the maternal blood flows into the spaces in the plasmodium,
and thus maternal blood begins to circulate in the trophoblast of the zygote.
In the meantime the extra-embryonic ccelom has appeared in the primary
mesoderm of the zygote, and the outer layer of the mesoderm has associated itself
with the trophoblast to form the chorion.
The spaces in the plasmodium enlarge rapidly after the maternal blood
Cavity
cervix uter
74. SCHEMA OF A FRONTAL SECTION OP THE UTERUS, showing
the various parts of the decidua and a zygote embedded in the
decidua.
58
HUMAN EMBKYOLOGY.
Intervillous space
Maternal blood-vessel
Spongy layer
| Placental area
if I Unchanged layer of decidua
Stratum spongiosum
Muscular wall of uterus
Uterine tube
Secondary villus
Amnion cavity
Amnion
Mesodenn linin
trophobl
Trophoblas
Unchanged part of
gland"
Dilated part of
gland*
Cavity of uterus
Body-stalk
antoic diverti-
um
Primitive streak
JSTeurenteric canal
Cavity of
entoderm sac
JJxtra-embryonic
coelom
Decidua capsularis
Decidua vera
Embryonic
begins to circulate within them and the plasmodium becomes divided into
three series of
parts. (1) The
parts which lie
between adjacent
blood spaces, the
primary chorionic
villi. (2) The parts
which lie in con-
tac t with the
mesoderm of the
chorion, and which
form with the
mesoderm the
chorion plate. (3)
The parts which
cover the maternal
tissues and form
the outer boun-
daries of the blood
spaces, the basal
layer. The blood
spaces themselves
are called the in-
tervillous spaces
(Figs. 76, 79).
After a time
each primary
villus differenti-
ates into a cellular core and plasmodial periphery, and thereafter the villi are invaded
by the mesoderm of
the chorion and are
thus converted into
secondary villi (Fio-.
76).
The first-formed
villi are non-vascular,
but by the time 'the
secondary villi have
developed the um-
bilical arteries have
grown through the
body-stalk (allantoic
stalk) into the meso-
derm of the chorion,
and branches from
them enter the nieso-
dermal cores of the
villi, which thus be-
come vascular.
When the second-
ary villi are fully
developed each con-
sists of a vascular
mesodermal core con-
tinuous with the
mesoderm of the
chorion The meso- FlG- 76 -~ ScHEMA OF A FRONTAL SECTION OF A PREGNANT UTERUS AT THE
PERIOD OF THE FORMATION OF THE EMBRYO. Note extension of amnion
dermal Core IS Covered as contrasted with stage shown in Fig. 75.
FIG. 75. SCHEMA OF A SECTION OF A PREGNANT UTERUS AFTER THE FORMATION
OF THE INTERVILLOUS SPACES.
Unchanged layer Maternal blood-vessels
Placental area
Spongy layer ^r~ ^* ^. /I Intervillous spaces
Absorbing
chorionic villi
Uterine tube
Trophoblast
of chorion
Amnion
Amnion w.
cavity
Trophoblast*
Decidua
capsularis
Decidua vera :
Spongy layer
Extra-em bryoui
THE PLACENTA.
59
by a layer of cellular trophoblast, Langhan's layer, which lies next the mesoderm,
and a layer of plasmodium external to the cellular layer. The proximal end
of each villus is continuous with the chorion plate of the intervillous spaces,
formed by the chorion, and the distal extremity is connected with the plasmodial
basal layer of the trophoblast, which forms the outer boundary of the intervillous
spaces and which is fused with the maternal decidual tissue.
After a time branches are projected from the sides of the secondary villi
into the intervillous spaces. In this way two sets of secondary villi are
differentiated, (1) the anchoring villi (Fig. 79), which cross from the chorion to the
Intervillous space
Yolk-sac
Secondary villus
Anchoring villus
Maternal
artery
Umbilical cord-
Decidu
Temporari
herniated sim.... _ mf^-m .
intestine
Decidua capsulari
Trophoblast ot&M
chorion Iseve
Pancreas^
Uterine tube
Unchanged part of
uterine gland
Dilated part of
uterine gland
Decidua capsularis
~* Trophoblast
Mesoderm lining
of chorion Iseve
Mesoderm of amnion
Ectoderm of amnion
Amnion cavity
ium (heart not shown)
FIG. 77. SCHEMA OF A SECTION OF A PREGNANT UTERUS AFTER THE FORMATION OF THE UMBILICAL CORD.
Note that the expanding amnion has almost obliterated the extra-embryonic coalom which lies between
it and the chorion.
basal layer of trophoblast and are attached to the latter by cell columns, which are
the remains of the primary villi which have not been penetrated by the foetal
mesoderm, and (2) free or absorbing villi (Fig. 76), which extend from the sides of
the original secondary villi into the blood, in the intervillous spaces.
Whilst the trophoblasfcic invasion of the compact layer of the decidua is
proceeding, not only are the interglandular elements of the decidua destroyed, but
the walls of the glands also, and, as a consequence, some of the glands in the
decidua basalis open for a time into the intervillous spaces, and become filled with
blood which passes from the spaces into the gland cavities. In many cases,
however, before the glands are destroyed their walls are converted into solid
strands of cells, and thus the cavities of their more external undestroyed portions
are converted into closed spaces.
In the early stages the trophoblast is differentiated in a similar manner over
60
HUMAN EMBEYOLOGY.
the whole of the surface of the zygote, and thus, for a time, the whole of the
surface of the chorion is covered with villi. As the embryo grows, and the
amnion and the extra- embryonic ccelom are distended, the zygote increases in size,
and the capsular portion of the decidua is stretched till its vascular supply is
interfered with and the villi associated with it undergo atrophy and disappear.
When these degenerative changes have occurred, the portion of the chorion in
association with the thinned decidua capsularis presents a relatively smooth
surface, and is known as the chorion Iseve. Whilst the decidua capsularis is being
stretched and thinned, and the associated portion of the chorion is being reduced
to the condition of a non-villous region, the decidua basalis increases in thickness ;
at the same time the villi associated with it increase in size and in the complexity
of their branches. The portion of the chorion from which these large villi spring
is termed the chorion frondosum. It is this portion of the chorion which takes
Placental area
Intervillous space
Spongy layer
Umbilical
cord
Muscular wall of uterus
x'Amnion cavity
Uterine tube
Compact layer of decidua
- Trophoblast
Fused mesoderm
of chorion and
amnion
Ectoderm of
Button
Spongy layer
Rectum
Small intestine
, Amnion cavity
Liver
Stomacl
Trachea
FIG. 78. SCHEMA OP A SECTION OF A PREGNANT UTERUS AFTER FUSION OF AMNION AND CHORION.
part in the formation of the so-called foetal portion of the placenta, the maternal
part of that organ being formed by the decidua basalis.
The placenta, therefore, is formed partly by the zygote and partly by maternal
tissues, but the interchanges between the foetal and the maternal blood take place
in the substance of the zygote through the trophoblast which covers the surfaces
of the villi.
As the growth of the embryo and the distension of the amnion continue,
the outer surface of the amnion is gradually forced against the inner surface of
the chorion, with which it fuses. When this fusion is completed the extra-
embryonic ccelom is obliterated and the zygote contains only one extra-embryonic
cavity, the amniotic cavity, in which the foetus floats in the amnion fluid (Fig. 78).
At this period the amnion cavity is bounded by a wall formed by the fused
amnion chorion and decidua. In the meantime the chorion has differentiated into
the chorion Iseve, fused with the decidua capsularis, and the chorion frondosum,
fused with the decidua basilis. As the distension of the amnion proceeds to a
still greater extent, the part of the wall of the cavity formed by the fused amnion
chorion Iseve and the decidua capsularis projects more and more into the cavity
THE PLACENTA.
61
of the uterus, until it is forced against the surrounding wall of the uterine cavity,
where it fuses with the decidua vera, and thus the cavity of the uterus is
obliterated. This fusion takes place towards the end of the second month, and as
soon as it has occurred the discoid mass of placental tissue is continuous at its
margin with the fused amnion, chorion, and decidua vera (Fig. 78).
After the second month the foetus lies in the amnion cavity, which is bounded
by the fused chorion and uterine wall, except at the lower end of the uterus, where,
over the orificium internum, the cavity of the body of the uterus communicates with
the cavity of the neck of the uterus ; there the amniotic cavity is bounded by a mem-
brane formed by the fused amnion chorion Iseve and the decidua capsularis only.
And at the end of pregnancy this portion of the membrane is ruptured by the
increased pressure of the amnion fluid produced by the contraction of the muscular
wall of the uterus (Fig. 88).
Unchanged part of uterine gland
Muscular wall of uterus | ( Maternal vein
Maternal artery
Decidua basilis unchanged part
Anchoring villus
Decidua-stratum spongiosum
Unchanged part of uterine gland
J Maternal blood of intervillous space
Trophoblast covering septum of stratum I
\ { Intervillous space compactum of decidua
* Septum of stratum compactum
ibilical gut
.Vena unibili-
calis impar
uibilical artery
Umbilical cord
Unchanged layer
Spongy layer
Ectoderm of amnion
''used mesoderm of amnion and chorion
Compact layer Trophoblast of chorion
FIG. 79. SCHEMA OF STRUCTURE OF COMPLETED PLACENTA.
Completion of the Placenta. It has already been stated that each secondary villus
consists of a vascular mesodermal core covered by a cellular and a plasmodial
layer of trophoblast, the latter lying next the maternal blood in the intervillous
spaces. As development proceeds and the intervillous spaces become larger, the
villi become longer and more complicated, and at the same time the cellular layer
of the trophoblast largely disappears, until in the majority of the villi the
plasmodial layer alone covers the vascular mesodermal core.
In still later stages, degenerative changes occur not only in the villi, but
also in the chorionic plate of the intervillous spaces and in the basal trophoblast
which closes the spaces externally. One of the results of the degenerative pro-
cesses is the deposit of fibrinoid material in the place originally occupied by the
trophoblast, the object of this process is still unknown ; another is the adhesion
of the fibrinous layers on the surfaces of adjacent villi, and the fusion of the
villi thus connected into masses of intermingled fibrinous and vascular tissue.
When the chorionic part of the placenta is completed it consists of (1) the
62
HUMAN EMBKYOLOGY.
chorion plate closing the intervillous spaces internally; (2) the villi; (3) the
intervillous spaces ; and (4) the basal layer of the trophoblast, which closes the
intervillous spaces externally, and is perforated by the maternal vessels passing to
and from the spaces.
The maternal portion of the completed placenta consists from within outwards
of (1) the basal layer of the decidua ; (2) the remains of the spongy layer of the
decidua ; and (3) the unchanged layer.
Placenta
Spongy layer
Yolk sacs
Umbilical cord
Ectoderm of
amnion
Fused mesoderm of_
amnion and chorion
Trophoblast
Spongy layer of decidua .
Muscular wall of uterus _
Compact layer of decidua
Uterine tube
- Amnion cavity
-^Spongy layer of
decidua
Fused mesoderm of amnion and chorion
FIG. 80. SCHEMA OF PREGNANT UTERUS IMMEDIATELY AFTER BIRTH OF THE CHILD, showing commencing
separation of the placenta. Part of the umbilical cord is shown in section and part in surface view. The
blue streaks in the former part indicate the position occupied by the vitello-intestinal duct in earlier stages.
The basal layer of the decidua is the remains of the compact part of the decidua
basalis of earlier stages. It is fused internally with the basal plate of the tropho-
blast, and is continuous externally with the spongy layer. The spongy layer con-
sists of a series of cleft-like spaces. These spaces are the compressed remains of
the earlier dilated portions of the glands of the stratum spongiosum, from which
the epithelial lining has, to a great extent, disappeared. The spongy layer is con-
tinuous externally with the unchanged layer, in which lie the unaltered outer
parts of the glands and the intervening interglandular tissue.
THE PEIMITIVE VASCULAE SYSTEM. 63
The maternal blood-vessels pass from the muscular wall of the uterus into the sub-
mucous tissue, and thence into the placenta, where they traverse the maternal portion
and the basal plate of the deciclua and open into the intervillous spaces. The
arteries usually open on or near the septa and the veins in the intermediate areas.
In addition, however, to the constituent parts already described, the chorionic
part of the placenta contains some strands of maternal tissue, and in the maternal
part there are portions of trophoblast.
The parts of the decidua found in the chorionic part of the placenta are a series
of fibrous strands, the remains of parts of the stratum compactum which were not
destroyed by the trophoblastic invasion. They are continuous externally with
fibrous strands of the maternal part of the placenta, and serve to separate the
placenta into a series of lobes, from 15 to 20 in number.
The portions of trophoblast met with in the maternal part of the placenta are
variable pieces of plasrnodium which appear to have wandered from the general
mass. They may be found in any of the strata of the maternal part, and even
in the submucous tissue.
At the end of pregnancy, when intra-uterine life terminates, the fused amnion
chorion and decidua capsularis are ruptured, in the region of the internal orifice of
the uterus, and the amniotic fluid is expelled through the vagina. Next the foetus
is extruded, and as soon as it is born it becomes a child. After the child is born
it remains attached to the placenta by the umbilical cord (Fig. 80), which is usually
ligatured in two places and then divided, between the ligatures, by a medical man
or an attendant. Afterwards the placenta is expelled from the uterus.
Detachment of the placenta is probably caused by contraction of the muscular
substance of the uterus, and it takes place by rupture of the strands of the spongy
layer of the decidua (Fig. 80). As the detached placenta is expelled the decidua
vera is torn through along the line of the spongy layer, and the fused amnion and
chorion Iseve and the inner part of the decidua vera, which are attached to the
margin of the placenta and which constitute the membranes, are expelled with it.
At birth the placenta weighs about 500 grm., it has a diameter of about
16 to 20 cm., and is about 3 cm. thick. Its inner surface is covered with the amnion
which fused with the chorion towards the end of the second month of pregnancy.
Its outer surface is rough, it is formed by the remains of the spongy layer of the
decidua, and is divided into a number of areas by a series of fissures which
correspond in position with the septa by which the organ is divided into lobes.
THE PKIMITIVE VASCULAE SYSTEM AND THE
FCETAL CIECULATION.
As the zygote travels along the uterine tube, from the ovarian towards the
uterine end, it exists either upon the yolk granules derived from the ovum or
upon substances absorbed from the fluids by which it is surrounded. After it
enters the uterus it must depend, for a time, upon the same sources of nutriment,
but as it penetrates the decidua it is probable that the cells of the trophoblast
actually devour the cells of the decidua which they invade. This, source of food
is only sufficient for a short period, whilst the zygote remains relatively small,
and substances absorbed by its surface cells can be transmitted easily to all parts.
Whilst the period exists, however, not only are the decidual tissues utilised as
a food-supply, but fluids are absorbed from them and transmitted into the interior
of the zygote to fill the expanding cavities of the amnion and the coelom.
In all probability the fluids passed into the zygote contain nutritive materials
which suffice for the requirements of the embryonic and non-embryonic parts of
the zygote so long as both consist of comparatively thin layers of cells, but when
the embryonic area increases in thickness, and begins to be moulded into the
embryo, its association with adjacent fluids becomes less intimate, and as the
development of its various parts progresses, a supply of food and oxygen is required
which is greater than can be provided by osmosis from the adjacent fluid media.
Thus an imperative necessity arises for a method of food-supply adequate to the in-
creasing requirements upon which the continued development and growth depend.
64 HUMAN EMBEYOLOGY.
To meet this necessity the blood vascular system is formed. The system is
essentially an irrigation system. In its earliest stages it consists of a series of
vessels, the blood-vessels, all of which contain a corpuscle-laden fluid, called blood.
The blood is kept circulating, in the early stages, by the rhythmical contraction
of the walls of the vessels, but, after a short time, parts of the vessels are
developed into a muscular organ called the heart. After the heart is established
the continuance of the circulation of the blood depends upon the regular con-
tractions of the muscular substance of its walls.
The corpuscular portions of the blood and the walls of the blood-vessels are
formed from the cells of the zygote, but it is obvious, in the early stages at all
events, that the fluid portion of the blood must be obtained from the mother. It
is necessary, therefore, both for this purpose and for the facilitation of interchanges
between the foetal and maternal blood streams, that the foetal blood-vessels should
be brought into close association with the maternal blood at an early period. It is
for this purpose, among others, that large spaces appear in the trophoblast ; that
the spaces become filled with blood from maternal vessels which have been opened
up by the destructive action of the trophoblast cells ; and that the spaces are
afterwards invaded by the chorionis villi, which carry in their interiors branches
of the blood-vessels of the embryo. As soon as the intimate relationship between
the chorionic villi and the maternal blood is established fluids can readily pass
from the^ maternal to the foetal vessels, and there can be no doubt that both food
and oxygen pass from the maternal to the foetal blood through and by the agency
of the trophoblastic epithelium, whilst, at the same time, waste products of foetal
metabolism pass from the foetal to the maternal blood.
The germs of the vascular system are a series of cells arranged in strands
which constitute, collectively, the angioblast. They appear between the entodermal
and the mesoderrnal layers of the wall of the yolk-sac, and, therefore, entirely outside
the embryo ; but it is not certain whether they are derived from the mesoderm or
from the entoderm.
Origin of Blood Corpuscles. After a time the angioblast separates into two
parts, (1) the peripheral cells of the strands which form the endothelial walls of the
primitive blood-vessels, and (2) the central cells which become the primitive blood
corpuscles or mesamoeboids (Minot).
The mesamoeboids are colourless cells with large nuclei and a relatively small
amount of protoplasm; from them are formed, either by transformation or
division, (1) the erythrocytes, which are coloured blood corpuscles, and (2) nucleated
colourless corpuscles. The erythrocytes are nucleated cells with a homogeneous
protoplasm which contains the substance, called haemoglobin, upon which the
yellowish-red colour of the cells depends, and from them are derived the fully
developed red corpuscles.
The primitive erythrocytes, the ichthyoid cells of Minot, are transitory structures
in mammals, but they are the permanent red blood cells of the ichthyopsida (fishes
and amphibia). They are succeeded by the sauroid blood cells (Minot), which
represent the permanent corpuscles of reptiles and birds, and which are distinguish-
able from the ichthyoid cells by their smaller size and more deeply-staining nuclei.
The sauroid blood cells are replaced by the blood plastids, which are young non-
nucleated red corpuscles. According to some observers the blood plastids are
sauroid cells which have lost their nuclei, whilst other investigators believe the
blood plastids to be the nuclei of sauroid cells. Whatever their origin, they become
converted into permanent red blood corpuscles by transformation from the spherical
to a cup-shaped and later to a biconcave form.
The young red blood cells are therefore the ichthyoid cells, those progressively
older are sauroid cells, blood plastids, and blood corpuscles.
The colourless, nucleated corpuscles white blood corpuscles are much less
numerous than the coloured corpuscles in the adult blood. They appear to be
derived from the mesamoeboids, though it is possible that they are also formed by
ordinary mesoderm cells, and as regards those formed from mesamoeboids it is not
certain whether a rnesamceboid cell can by division produce both erythrocytes and
white corpuscles, or whether it must produce one or the other. (See note 5, p. 79.)
THE PKIMITIVE VASCULAE SYSTEM
65
1st aortic
arch
Common trunk formed
by umbilical and
yolk-sac veins
ena umbilicalis
impar
Umbilical arteries
Vitelline Arteries
The primitive mesanioeboids are formed in the wall of the yolk-sac, and
there some of them produce erythrocytes ; many, however, migrate into the
embryo, where some of them take part in the formation of the walls of the em-
bryonic blood-vessels, and others become enclosed in the liver, the lymph glands,
and the bone marrow, where they become foci for the formation of blood corpuscles.
During the first two months the primitive forms of red blood cells predominate.
In the Second month Dorsal intersegmental branches
the sauroid cells in- Dorsal aort*
crease considerably
in number, and from
the third month the
blood plastids become
more and more
numerous, until, at
the eighth month
(Minot), the majority
of the blood cells
are blood plastids
undergoing conver-
sion into blood cor-
puscles. At this time
the colourless cells
are present in a very FIG. SI. SCHEMA OF CIRCULATION OP AN EMBRYO, 1*35 MM. LONG, WITH Six
distinct minority. SOMITES - < After Felix ' modifie(L)
Formation of the Primitive Blood Vascular System of the Embryo. The earliest
stage of the formation of the heart and blood-vessels in the human subject are not
known, but, judging by what occurs in other mammals, it is probable that the first-
formed vessels appear in the splanchnic mesoderm before the embryonic area
begins to fold. It is presumed that they are formed by aiigioblastic cells which
have migrated into the embryonic area from the walls of the yolk-sac. From
their seat of origin they extend towards the caudal end of the embryonic area, one
on each side of the notochord, and from the caudal end of the embryonic region
they pass along the body-stalk into the chorion. (See note 5, p. 79.)
As the cephalic
Dorsfal intersegmental branches end of the embryonic
aort8e area is folded, to
enclose the fore-gut,
the corresponding
parts of the primi-
tive arteries are bent
into a c-shaped form.
The ventral limb of
the c, which lies in
the dorsal wall of the
pericardium and the
ventral wall of the
fore-gut, is the primi-
tive ventral aorta. The
bend of the c is the
first aortic arch, which
passes along the
lateral margin of the
bucco-pharyngeal membrane. The dorsal limb of the c is the cranial part of the
primitive dorsal aorta. The primitive dorsal aorta passes posteriorly into the tail
and gives off in the region of the tail fold the primitive umbilical artery, which runs
along the body-stalk to the chorion.
The caudal parts of the primitive ventral aortae are the rudiments of the heart.
At first they lie, quite separate from each other, in the dorsal wall of the pericardium,
but soon they approach one another and fuse together to form a single tubular
5 .
Anterior cardinal
ve;
1st aortic arch
Heart
Stem formed by union of
lateral umbilical and
vitelline veins
| Vena umbilicalis
impar
Umbilical arteries
Vitelline veins
FIG. 82. SCHEMA OF VASCULAR SYSTEM OF AN EMBRYO, 2 '6 MM. LONG, WITH
FOURTEEN SOMITES. (Arteries after Felix, modified.)
66
HUMAN EMBKYOLOGY.
Yolk-sac artery
(later = superior
raesenteric)
2nd aortic arches
1st aortic arches
Anterior cardinal veins
Sinus venosus
Umbilical
arteries
Vena umbilicalis impar
heart. The more cranially situated parts of the primitive ventral aortse remain
separate and take part in the formation of ventral roots of. the aortic arches.
Before the single heart is formed other blood-vessels have appeared, which
return blood from the chorion and the yolk-sac to the heart. These vessels are
the primitive veins. Two veins pass from the chorion into the body-stalk, where
they fuse together to
Posterior cardinal veins form the VCIia Umbilicalis
impar. This divides, at
the caudal end of the
embryo, into the two
lateral umbilical veins,
which run to the heart,
one along each lateral
margin of the embryo.
In an embryo 1/3 mm.
long (Eternod), in which
the paraxial mesoderm
had not yet commenced
to segment into meso-
dermal somites, each
lateral umbilical vein
received, as it entered
the embryo, a large
efferent vein from the yolk-sac. This condition, if regular, is very transitory. After
a very short time the connexion of the vitelline veins with the caudal ends of the
lateral umbilical veins is lost, and the blood is returned from the yolk-sac directly
to the heart by two vitelline veins, one on each side, which run along the sides
of the vitello-intestinal duct and receive the lateral umbilical veins close to the
heart (Fig. 81).
In the meantime a number of branches have been developed from both the
dorsal and the ventral walls of the 7th pair of inter .
primitive dorsal aortse; the former segmentai arteries
are the somatic pre-segmental and inter-
segmental arteries, and the latter are
the primitive vitelline arteries.
In a human embryo which has de-
veloped six distinct mesodermal somites
the vitelline arteries form a plexus on
the sides of the hind-gut area of the
wall of the entodermal vesicle, from
which the umbilical arteries appear
FIG. 83. SCHEMA OF VASCULAR SYSTEM OF AN EMBRYO WITH TWENTY-
THREE SOMITES. (Arteries after Felix, modified. )
Vertebral
arteries
1st pair of inter-
segmental arteries
1st cephalic aortic arch
f-ephalic aortic arch
3rd cephalic aortic arch
4th cephalic aortic arch
6th cephalic aortic arch
Bulbus cordis
Ventricle
Atrium
to spring (Felix). The plexus is re-
presented in Fig. 81 by the bulbous
dilatations. The vessels which enter
this plexus arise from the ventral
aspects of the primitive dorsal aortse,
some distance from their caudal ends.
It is probable, however, that the
caudal ends of the primitive dorsal
aortse are connected with the caudal
part of the plexus at the points of
origin of the umbilical arteries, though
the connexions are not" visible in the sections of the embryo mentioned (Fig. 81).
Practically the same condition is present in an embryo 1/6 mm. long possessing
fourteen distinct somites, except that the main rootlets of the umbilical artery, on
each side, are situated farther caudalwards than in the younger embryo, and lie in
the region of the most caudal somites (Fig. 82).
Further Development of the Arterial System. When the embryo possesses
twenty-three mesodermal somites, but is still devoid of limbs, the arterial system has
Sinus venosus
FIG. 84. DIAGRAM showing stage of five aortic arches.
THE PEIMITIVE VASCULAK SYSTEM.
67
3rd arches
4th arches
5th arches
6th arches
Dorsal aorta
'Pulmonary arteries
External carotids / /
Ventral root of 3rd arch /
Ventral root of 4th and 5th arches i
Truncus arteriosus
85 __ ScHEMA OF AoBTIC ARCHES OF AN EMBRYO, 9 MM. LONG. (After
Tandler, modified.) The second and third arches have atrophied and
the transitory fifth has appeared.
advanced considerably in development. Two aortic arches, on each side, now connect
the cephalic end of the heart with the primitive dorsal aorta. The umbilical artery
and vitelline arteries are quite separate, and each umbilical artery springs, by a
number of roots which anastomose together, from the caudal part of the corre-
sponding dorsal aorta. The vitelline arteries are still numerous, but that which rises
opposite the twelfth mesodermal somite is becoming the main artery of the yolk-sac ;
eventually its proximal 2nd arches atrophied
part is transformed into
the superior mesenteric
artery of the foetus.
When the embryo
has attained a length of
5 mm., and is about five
weeks old, it possesses
about thirty-eight
mesodermal somites, and ist arches atropwe
five aortic arches are
present on each side.
Commencing from the
cranial end, they are
the first, second, third,
fourth, and sixth; the
fifth arch appears sub-
sequently between the
fourth and the sixth. All five arches pass to the corresponding dorsal aorta, but
the three most caudal, on each side, spring from the cranial end of the heart, which
is now called the aortic trunk, whilst the two most cranial rise from a common stem
which constitutes their ventral roots, and which springs, also, from the aortic trunk
(Fig. 84). A little later the aortic trunk gives off only two branches on each
side, (1) a stem common to the first five arches, for the fifth has now appeared, and
(2) the sixth arch (Fig. 85). The fifth arch is very transitory. Whilst it is present
it runs from the
common ven-
tral stem, caudal
to the fourth
arch, to the
dorsal part of
the sixth arch.
It soon disap-
pears, and no
traces of it are
left in the adult
(Fig. 85).
The portion
of the common
ventral stem
which lies
caudal to each
of the arches is
Internal carotid
Internal carotid !
[nternal carotid ;
External carofTid y '
External carotid
Arch of aorta
j Right subclavian artery
i Left subclavian artery
i
Right subclavian artery
| Union of ductus arteriosus
- with aorta
' Union of dorsal roots of
6th arches
Left 6th arch
. Right pul-
"monary artery
-Left pulmonary artery
"Innominate artery
-Right 6th arch
Left common carotid
Right common carotid
Left 6th arch
Ascending aorta
FIG. 86. SCHEMA OF PART OF THE ARTERIAL SYSTEM OF A FLeft lumbar vein
Placenta
Umbilical arteries
Inferior mesenteric artery '
Common iliac artery*
External iliac artery
Umbilical artery -
FIG. 88. DIAGRAM OF THE FCETAL CIRCULATION.
A little later two veins are formed, one on each side, which return blood from
the body wall and the primitive limbs. They are the posterior cardinal veins, and
as soon as they are established they join the caudal ends of the anterior cardinal
veins to form the ducts of Cuvier, which then open directly into the posterior part
of the heart which is called the sinus venosus (Fig. 83). Shortly afterwards the
common stems of the vitello-umbilical veins are absorbed into the sinus venosus,
forming its right and left horns. When this has happened six veins open into
70 HUMAN EMBKYOLOGY.
the sinus venosus, three on each side the two ducts of Cuvier, the two vitelline
veins, and the two lateral umbilical veins (Fig. S3).
The anterior cardinal veins and their tributaries, and cross anastomoses which
form between them, are transformed into some of the cranial blood sinuses, the
internal jugular veins, the innominate veins, and the cephalic (upper) part of the
superior vena cava. The right duct of Cuvier becomes the caudal part of the
superior vena cava, and the left is converted into the oblique vein of the left
atrium (O.T. oblique vein of Marshall) (Fig. 88).
A portion of the abdominal part of the right posterior cardinal vein is replaced
by the right subcardinal vein, and from this and a transverse anastomosis between
it and the opposite subcardinal vein is formed that part of the inferior vena cava
which extends from the renal veins to the liver, and a part of the left renal vein.
From the remains of the cardinal veins and transverse anastomoses between them
are formed (1) the azygos, the hemiazygos, and the accessory hemiazygos veins ;
(2) the inferior vena cava, caudal to the renal veins ; (3) the common iliac veins ;
(4) the hypogastric veins; and (5) the parts of the left lumbar veins which
pass dorsal to the aorta (Fig. 88).
The cephalic end of the inferior vena cava is formed from the cephalic extremity
of the right vitelline vein and a caudal outgrowth from it which unites with the
right subcardinal vein (Fig. 88).
Details of the history of the transformations of the cardinal veins, the vitelline
and umbilical veins, and the formation of the cranial part of the inferior vena cava
are given in the account of the further stage of the development of the vascular
system.
The Primitive Heart. The primitive heart is formed in the dorsal wall of the
pericardium, ventral to the fore-gut, by the fusion of the caudal parts of the
primitive ventral aortse, and shortly after its formation it is divided into five
primitive chambers. The most caudal of the five, which receives the main primitive
veins, is the sinus venosus, the second is the atrium, the third the ventricle, the
fourth is the bulbus cordis, and the fifth and most cranial is the truncus aorticus,
which discharges its contents into the ventral roots of the aortic arches (Fig. 84).
During the period which intervenes between the time when the embryo is
8 mm. and 1*7 mm. long, that is between the fifth and the eighth weeks, the greater
part of the sinus venosus is absorbed into the atrium ; the ventricle and the atrium
are each divided into right and left chambers by the formation of an interatrial
and an interventricular septum ; the bulbus cordis is absorbed partly into the
ventricle and partly into the truncus aorticus, and the truncus aorticus is separated
into the ascending part of the aorta and the stem of the pulmonary artery. When
these changes are completed the heart consists of right and left atria and right
and left ventricles. The ventricles are entirely separated from one another by
the interventricular septum, but there is an orifice of communication between the
right and left atria (Fig. 88).
The right atrium receives blood from the superior and inferior vense cavse, and
from the walls of the heart, by the coronary sinus, which is a remnant of the
transverse part and left horn of the sinus venosus. The blood which enters through
the superior vena cava and by the coronary sinus, passes through the right atrio-
ventricular orifice into the right ventricle, but the whole, or the greater part, of the
blood which enters by the inferior vena cava passes through the foramen ovale,
which lies in the interatrial septum, into the left atrium.
The blood which enters the right ventricle is ejected into the pulmonary artery.
A small portion of it passes by the right and left branches of the artery into the
lungs, and is returned to the left atrium by the pulmonary veins, but by far the
greater part passes through the ductus arteriosus into the aorta, which it enters at
a point immediately beyond the origin of the left subclavian artery (Fig. 88).
The blood which enters the left atrium, through the foramen ovale, mixes,
in the left atrium, with the blood which is returned by the pulmonary veins;
then it passes through the left atrio-ventricular orifice into the left ventricle,
by which it is forced into the aorta. Some of this blood passes into the
innominate artery, and so, by its right subclavian branch, to the right upper
THE CCELOM. 71
extremity, and by its right common carotid branch to the right side of the head
and neck ; another part enters the left common carotid artery and is distributed to
the left side of the head and neck, and some passes, through the left subciavian
artery, to the left upper limb. The remainder mixes with the blood which enters
the aorta, from the right ventricle, through the pulmonary artery and the ductus
arteriosus. Part of this mixed blood is distributed to the body and the viscera,
and the lower limbs, and the remainder passes through the umbilical arteries to the
placenta (Fig. 88).
The Foetal Circulation. When the fcetal circulation is thus fully established,
purified oxygenated blood, returning from the placenta, enters the body of the
foetus by the umbilical vein and passes to the liver. Some of it enters the liver,
but the greater part passes, through a channel called the ductus venosus, to the
inferior vena cava, where it mixes with the venous blood returning from the
lower limbs and the abdominal region, including the liver. This mixed, but,
as contrasted with the blood in the superior vena cava, comparatively pure blood
enters the right atrium and passes through it and through the foramen ovale into
the left atrium, thence to the left ventricle and through the left ventricle into
the aorta. A portion of this comparatively pure blood is distributed to the head
and neck and the upper limbs. The remainder unites with the stream of venous
blood poured into the aorta through the ductus arteriosus. Part of it is distributed
to the body and the lower limbs, and part is sent to the placenta to be purified
and oxygenated (Fig. 88).
The remaining part of the blood stream is formed by the blood returned from
the head and neck, the upper part of the body and the upper limbs, by the
superior vena cava, and from the walls of the heart by the coronary sinus. It
is the most venous and impure blood in the body. After entering the right
atrium it passes into the right ventricle, and thence into the pulmonary artery.
A very small part of it is passed to the lungs, by the right and left branches
of the pulmonary artery ; the remainder goes through the ductus arteriosus into
the aorta, where, beyond the origin of the left subciavian artery, it mixes with the
much purer blood which entered the aorta from the left ventricle.
At birth; when the placental circulation ceases, the lungs become the organs
through which oxygen enters and carbonic acid leaves the blood; the foramen
ovale in the interatrial septum closes, and the ductus arteriosus is obliterated.
The course of the circulation and the condition of the blood in the different regions
is, therefore, considerably altered.
On account of the cessation of the placental circulation all the blood which
enters the right atrium is entirely venous, and, as the foramen ovale is closed,
it all passes into the right ventricle, which forces it into the pulmonary artery.
As the ductus arteriosus is closed, all the blood which enters the pulmonary
artery must now pass through the lungs, where it is aerated, and whence it is
returned, by the pulmonary veins, as oxygenated blood, to the left atrium. It
passes from the left atrium to the left ventricle, which forces it through the
aorta and its branches to all parts of the head, neck, body, and limbs; and
now, for the first time, all parts receive blood of the same quality.
THE CCELOM.
It has already been pointed out that there are two parts of the ccelom, the
extra-embryonic and the intra-embryonic. Both are clefts separating an outer from
an inner layer of mesoderm.
The Extra-embryonic Coeloxn. The extra-embryonic coelom appears in the
primary mesoderm and separates it into a parietal and a visceral layer. The
parietal layer covers the inner surface of the trophoblast and forms with it the chorion.
It covers also the outer surface of the auinion. The visceral layer covers the outer
surface of the extra-embryonic portion of the wall of the entodermal cavity.
The extra-embryonic and intra-embryonic parts of the coslom are at first
saparate from one another (Fig. 36), then they become continuous, for a time, in the
region of the umbilical orifice (Fig. 37), but are separated from one another again
56
72
HUMAN EMBKYOLOGY.
when the umbilical orifice closes. The extra-embryonic portion is entirely
obliterated when the outer surface of the expanding amnion fuses with the inner
surface of the chorion (compare Figs. 77 and 78).
The Intra- embryonic Ccelom. The intra-embryonic coelom appears as a series
of cleft-like spaces in the margin of the embryonic mesoderm. The spaces fuse
together to form a fl -shaped cavity (Fig. 89) which separates the peripheral part
of the embryonic mesoderm into a parietal or somatic, and a visceral or splanchnic,
layer. The bend of the D -shaped cavity lies in the
margin of the cephalic part of the embryonic region,
and it has no direct communication with the extra-
embryonic coelom, but the greater part of each stem
of the cavity, on account of the disappearance of its
lateral wall, soon opens, laterally, into the extra-
-peritoneal canal em bryonic CCelom.
The transverse portion of the n -shaped cavity, which
extends across the cephalic end of the embryonic area
and connects the two limbs together, is the pericardial
cavity. The adjacent part of each lateral limb of the
cavity is the pleuro-pericardial canal, it becomes a pleural
cavity, and the remaining portions of the two limbs
SCHEMA OF INTRA- unite ventrally, as the umbilical orifice closes, to form
EMBRYONIC C(ELOM SEEN FROM r v, p ei ny u npritnnpal pa-n-i-Hr
ABOVE BEFORE THE FOLDING OF l "H* Pineal Cavity.
THE EMBRYONIC AREA. As the head fold forms, the pericardial part of the
cavity is carried ventrally and caudally into the ventral
wall of the fore-gut (Fig. 90). The mesoderm which originally formed its peri-
pheral boundary, but which now lies in the cephalic boundary of the umbilical
orifice, becomes thickened, and forms the septum transversum (Figs. 90, 91, 93).
Alimentary
canal
Alimentary
canal
I 1 Pleuro-
Peritoneal
coelom
FIG. 89.
Pericardium
Opening into pleuro-
peritoneal canal
Pleuro-peritoneal canal
Peritoneum
Spinal medulla
ore -gut
_ Pleuro-pericardial
canal
Spinal medulla
Dorsal mesentery
Alimentary canal
Peritoneum
pinal medulla
Fore-gut
Pleuro-
pericardial canal
Heart
Pericardial
cavity
FIG. 90. SCHEMATA OF EMBRYONIC CCELOM AFTER FOLDING OF EMBRYONIC AREA BUT BEFORE THE
SEPARATION OF THE VARIOUS PARTS. D from above ; A, B, and C at levels of line A, B, and C in Fig. D.
At the cephalic end of its dorsal wall, on each side, the pericardial cavity is still
continuous with the two lateral parts of the coelom ; and each lateral part, which
THE CCELOM.
lies dorsal to the pericardium, and between the fore -gut medially and the body
laterally, is still a pleuro-pericardial canal.
The Separation of the Pericardial, Pleural, and Peritoneal Parts of the
Coelom. In the lateral wall of each
pleuro-pericardial canal, near its
cephalic end, lies the duct of Cuvier,
passing towards the heart ; and a
lung bud containing a primitive
bronchial tube grows, from the medial
wall, into the cavity of each pleuro-
Spinal medulla
-Li\ Alimentary canal
Oesophagus
/Lung bud
Opening into pericardium
Duct of Cuvier
Pleuro-pericardial canal
.. Lung bud
Commencing lateral
i , part of diaphragm
Septum transversum
- -Peritoneum
^ ^
FIG. 91. SCHEMA OF LATER STAGE OF DIFFERENTIATION
OF CCELOM. A, from above. B, transverse section cut FIG. 92. SCHEMA OF A TRANSVERSE SECTION
level of lung bud in A. AT THE LEVEL OF THE LUNG BUD IN FIG. 91.
pericardial canal (Fig. 91). As the lung buds grow the cavities of the pleuro-
pericardial canals increase in size, and each passes ventrally, round the side of
the pericardium towards the ven-
tral wall of the body, until it is
separated from its fellow of the op-
posite side only by a median meso-
derm-filled interval, which becomes
the anterior mediastinum and the
anterior part of the superior media-
pieurai cavity stinum (Fig. 94). At the same time
closed aperture between the cavitv of each pleuro-pericardial
pleura and pericardium . -, ,-, i T i
Duct of Cuvier canal, and the growing lung bud
in its interior, grow towards the
cephalic end of the embryo (Fig.
B-
Lung
Bronchus
Lateral part of
diaphragm converging
towards dorsal
mesentery
Septum transversum
Peritoneum
Spinal medulla
(Esophagus
FIG. 93. SCHEMA OF STILL LATER STAGE OF CCELOM
DIFFERENTIATION. The pleurae are separated from the
pericardia, but still communicate with the peritoneum.
FIG. 94. SCHEMA OF TRANSVERSE
SECTION OP EMBRYO AT LEVEL OF
LINE B, Fig. 93, showing ventral ex-
tension of the pleurae.
93). As it passes cephalwards the growing lung lies to the lateral side of the
duct of Cuvier, which is thus forced against the cephalic end of the pleuro-
perieardiaj[ canaj, compressing it towards the median plane, against the sides
74 HUMAN EMBRYOLOGY.
of the trachea and the oesophagus, until its cavity is obliterated. When this
occurs the pericardial cavity is entirely shut off from the remainder of the coelom,
and it becomes a completely closed space (Fig. 93).
As the closure of the pericardial cavity is taking place two wing-like folds of
mesoderm, connected ventrally with the septum transversmn and laterally with
the body walls, appear, caudal to the lungs (Figs. 91, 93). These folds are the
rudiments of the lateral parts of the diaphragm, and each passes medially until it
fuses with the mesoderm of the side wall of the fore-gut and with the dorsal
mesentery. When this fusion is completed the cavity of the portion of the coelom
surrounding the lung, the original pleuro-pericardial canal, is separated from the
more caudal part of the coelom, which now becomes the peritoneal cavity.
Only the broad outlines of the processes by which the pleuro-peritoneal canals
are separated from the pericardium and the peritoneum are mentioned in the
preceding paragraphs. The details of the processes are too complicated for
description in an ordinary text-book of anatomy.
The Formation of the Diaphragm. There are four main parts of the
diaphragm, a ventral, a dorsal, and a right and a left lateral.
The ventral part is formed from the septum transversurn, which is gradually
differentiated into a caudal, an intermediate, and a cephalic part. The caudal part
is transformed into (1) the mesodermal tissue of the liver, which grows towards
the abdomen, (2) the falciform and coronary ligaments, and (3) the small omenturn.
The cephalic part becomes the caudal or diaphragmatic wall of the pericardium.
The intermediate part is transformed into the ventral portion of the diaphragm.
The dorsal part of the diaphragm is developed from the mesoderm of the dorsal
mesentery of the fore-gut. Each lateral part is derived from a lateral ingrowth
which springs ventrally from the septum transversum and laterally from the body
wall. The two lateral portions grow towards the median plane till they fuse
with the dorsal portion ; but in some cases, especially on the left side, the fusion
is not completed. In such cases an aperture of communication remains, between
the pleural and the peritoneal cavities, through which a portion of the abdominal
contents may pass into the pleural sac, constituting a diaphragmatic hernia.
SUMMAEY OF THE EXTERNAL FEATUKES OF THE HUMAN EMBEYO
AND FOETUS AT DIFFERENT PERIODS OF DEVELOPMENT.
During the first fourteen days after the impregnation of the ovum the human zygote
descends through the uterine tube, assumes the morula condition, enters the uterus,
penetrates into the decidua compacta, and differentiates into three vesicles and a mass of
primitive mesoderm ; but, probably, it is not until the beginning of the third week, if
Bryce's calculations are correct, that a definite embryonic area is present. By that time
the zygote is an ovoid vesicle measuring 2'4 by 1-8 mm. Its wall is formed by the
trophoblast, and it contains two inner vesicles, the ecto-mesodermal and the entodermal
vesicles. The inner vesicles are surrounded by a mass of primary mesoderm in which
the extra-embryonic portion of the coelom is beginning to appear. At this period the
embryonic area is the region where the walls of the two inner vesicles lie in relation with
one another, and it is *19 mm. long (Fig. 30).
By the eighteenth or nineteenth day the area has attained a length of 1-17 mm. and
it is -6 mm. broad. It is pierced, about the centre of its length, by the neurenteric canal ;
the primitive streak has appeared on the dorsal surface of the area ; the primitive groove
is distinct, and the neural groove is indicated. The body-stalk is bent dorsally, at right,
angles with the area, and it contains the allantoic diverticulum, which has already been
projected from the wall of the entodermal vesicle (Fig. 95).
During the next twenty-four hours the length of the embryonic area increases to 1*54
mm.; the neurenteric canal is moved caudally, to a point well behind the middle of the
length of the area, and the posterior part of the area is bent ventrally, forming the
posterior boundary of the hind-gut region and indicating the position of the future cloacal
membrane. The head fold has begun to form, and the pericardial region lies in the
ventral wall of the rudimentary fore-gut (Fig. 96).
By the middle of the third week the head and tail folds are distinctly formed andl
THE HUMAN EMBEYO AT DIFFERENT PERIODS.
75
the length of the embryo is 1'9 ram., the neural folds are well developed, the neural
groove is still completely open, and six pairs of mesodermal somites are visible (Fig. 97).
In the next few days the length increases to 2 '5 mm., the neural groove closes except
in the cranial and caudal regions, the number of mesodermal somites is increased to four-
teen pairs, and the cranial region begins to bend ventrally as the cervical flexure forms
(Fig. 98).
By the end of the first month the greatest length of the embryo is about 2'6 mm.,
the head is bent at right angles to the body, the Wolffian ridges have appeared along
the ventral margins of the mesodermal somites and indications of the limb rudiments
FIG. 95. FRASSI'S ZYGOTE. Estimated to be 18-19
days old (Bryce). The embryonic area is 1*17
mm. long and '6 mm. broad. Copied from Nor-
maltafeln, Keibel and Elze, representing a recon-
struction. The chorion is not shown. The upper
part of the amnion is cut away, and the dorsal
aspect of the embryonic area is seen from above.
In the centre of the area is the neurenteric
canal and caudal (inferior in the Fig. ) to it is the
primitive groove. Cephalwards of the neurenteric
canal is the neural groove, in the middle of the
neural plate. At the lower (caudal) end of the
Fig. is seen a section of the body stalk containing
the allantoic diverticulum, and the nodulated
area seen at the upper and right lateral part of
the Fig. is a portion of the yolk-sac.
FIG. 96. SPEE'S ZYGOTE. (From Keibel and Elze's
Normaltafeln.} Length of embryonic area 1'54 mm.
Estimated age 19-20 days (Bryce). At the lower
end of the Fig. (caudal end of the embryo) is seen
a portion of the chorion attached to the embryo by
the body stalk. A portion of the amnion is still
attached to the margin of the embryonic area, and
the dorsal surface of the embryonic area is exposed.
In the median plane of the area is the neural groove,
and at the caudal end of the groove is the neur-
enteric canal. The caudal part of the area is bent
ventrally, and upon it is the remains of the primitive
groove. The yolk-sac is seen at the upper and
right part of the Fig.
are present. The rudiments of the otic vesicles have appeared as slight depressions in
the region of the hind-brain. The anterior and posterior neuropores are still open
(Fig. 99).
In the latter part of the fourth or the beginning of the fifth week the embryo attains
a length of about 5 mm., when measured from the vertex of the head to the base of the
tail, the mesodermal somites increase to thirty-five ; the rudiments of the fore- and hind-
limbs become quite distinct; the otic vesicles sink into the interior of the head but
remain connected with the surface by the recessus labyrinthi, the tail becomes a very
definite appendage, and the bulgings caused by the otic vesicles are quite obvious on
the surface of the head. The cervical flexure remains acute, and the head bends at right
angles upon itself in the region of the mid-brain, forming the cephalic flexure, with the
result that the frontal extremity of the head is turned caudally (Fig. 100).
By the end of the fifth week the length of the embryo has increased to 1 1 mm. (OR) l
1 CR indicates the crown-rump or crown-breech measurement which corresponds with the sitting
height (Mall).
76
HUMAN EMBEYOLOGY,
(Mall). Forty-three mesodermal somites are present, but only about twenty-one are visible
on the surface. During the fifth week the lens of the eye appears as a thickening of the
surface ectoderm ; sinks into the interior of the eyeball ; becomes a vesicle and separates
from the surface. The three segments of the fore-limb become visible, and the rudiments
of the fingers appear. The hind-limb is less advanced ; the thigh segment is not distinct,
and the rudiments of the toes are not yet visible. The third arid fourth visceral arches
disappear from the surface and lie in the depths of the precervical sinus, a depression
between the neck and the anterior part of the body ; this is overlapped, superficially, by
the caudal margin of the second arch, which grows tailwards and forms the operculum of
FIG. 97. KRCEMER - PFANNENSTIEL Zr-
GOTE. (From Keibel and Elze's
Normaltafdn. ) The embryonic
region is folded into the form of an
embryo, which is 1 '9 mm. long, and
it is possibly about three weeks old.
At the lower end of the Fig. (the
caudal end of the embryo) are seen
portions of the chorion and body-
stalk. The cerebral portion of the
neural rudiment is defined. Six
pairs of mesodermal somites are
present, but there are no signs of
limbs.
FIG. 98. BALLE'S EMBRYO.
(From Keibel and Elze's
JVormaltafeln.) Length after
hardening in alcohol 2*5
mm. The neural groove
is closed from the sixth
somite to within a short
distance of the caudal end,
but it is open anteriorly.
The hind-, mid-, and fore-
brain regions and the optic
vesicle can be distinguished.
At the lower end of the
Fig. is the body-stalk, and
at the right side a part of
the yolk-sac.
FIG. 99. PFANNENSTIEL'S EM-
BRYO. (From Keibel and
Elze's Nornudtafeln.} Length
of embryo about 2 '6 mm.
The rudiment of the otic
vesicle is seen in the Fig.
above the second branchial
cleft. The heart and peri-
cardium from the bulging
eminence below the head and
the Wolffian ridge is seen at
the lateral border of the meso-
dermal somites.
the sinus (Figs. 101, 102). During the fifth week the head grows rapidly, and becomes
relatively very large as contrasted with the body.
During this week also the olfactory pits appear, and grow dorsally in the roof of the
stomatodseum, separating the median from the lateral nasal processes ; the median process
is divided into the two globular processes ; and the maxillary processes of the mandibular
arches, growing towards the median plane, fuse with the lateral nasal and the globular
processes, so completing the lateral parts of the primitive cranial lip (Figs. 64, 65, 66).
The nodular outgrowths which form the rudiments of the auricles appear on the
margins of the hyo-mandibular cleft and fuse together, and by the end of the week traces
of the tragus, the helix, and the antitragus are visible (Fig. 103).
By the seventh week the embryo has attained a length of 17 mm. (CR). The cervical
flexure has begun to unfold. The rudiments of the eyelids have appeared. The globular
processes have fused together, but there is still a distinct notch in the middle of the
cephalic or upper lip. The margins of the auricles are now well defined ; the hands are
THE HUMAN EMBRYO AT DIFFERENT PERIODS.
77
R 100. SIDE VIEW OF AN EMBRYO, measuring about
5 > mm. from the root of the neck to the. base of the tail,
I ,nd about 47 mm. from the crown or mid-brain region
I ,o the base of the tail, that is to the breech or rump.
I From Keibel and Elze's Normdttafeln.) The neural
I ube is closed. The limb buds are quite distinct, and
1 he maxillary process of the mandibular bar has grown
I orward below the eye (dorsal to the eye in the Fig.).
FIG. 101. EMBRYO OF 7 '2 MM., CR MEASUREMENT. 8 '5 mn
greatest length. (From Keibel and Elze's Normaltafeln. ) Tl
fore-limb is distinctly in advance of the hind-limb. Tl
second branchial arch has begun $to overlap the third an
fourth and to enclose the precervical sinus. The tip of th
maxillary process is in contact with the lateral and medij
nasal processes at the margins of the olfactory pit.
EMBRYO, 7*2 mm. (CR), and 8 mm. greatest length.
.From Keibel and Elze's Normaltafeln.} The limbs have
>egun to fold ventrally. The second arch has completely
overlapped the third and fourth which now lie in the
trecervical sinus, and the sinus still opens on the surface
it the posterior border of the second arch. The lens of
he eyeball is very evident, and rudiments of the auricle
'f the external ear have appeared on the mandibular or
irst, and the hyoid or second arch.
FIG. 103. EMBRYO, 10'9 mm. (CR) and 11 '5 mm. greates
length. (From Keibel and Elze's Normaltafeln). The pre
cervical sinus is closed and additional rudiments of th<
auricle of the external ear are present on the first am
second arches. The anterior nares are no longer visibh
from the side.
78
HUMAN EMBEYOLOGY.
folded medially ; the tips of the fingers are free, and the palms rest on the cranial part
of the distended abdomen. The thighs and the toes have appeared, and the tail has
begun to fuse with the caudal end of the body (Fig. 104).
At the end of the eighth week, when the embryo becomes a foetus, it has attained a
length of about 25 mm. (CR). The auricles project from the sides of the head, the tail
has almost disappeared from the surface, and the toes are free from one another. The
cervical flexure is now very slight, and although the head is still relatively large, the
disproportion between it and the body has begun to decrease (Fig. 105).
Third Month. The head grows less rapidly, and, though it is still large, it is relatively
smaller in proportion to the whole body. The eyelids close, and their margins fuse
FIG. 104. EMBRYO (CR) greatest length 18'5 mm.
Probably between seven and eight weeks old. (From
Keibel and Elze's Normaltafeln.} The abdomen
is very prominent on account of the rapid increase
of the liver. The digits of the hand and foot are
distinct but not separated from one another. The
margin auricle of the external ear is completed. The
eyelids have begun to form.
FlG. 105. HOMAN FCETUS EIGHT AND A HALF
WEEKS OLD. (After His. )
GE. Genital eminence ; UC. Umbilical cord.
together. The neck increases in length. The various parts of the limbs assume their
definite proportions, and nails appear on the fingers and toes. The proctodseum is formed
and the external generative organs are differentiated, so that the sex can be distinguished
on external examination. The skin is a rosy colour, thin and delicate, but more consistent
than in the preceding stages. By the end of the third month the total length of the foetus,
excluding the legs, is 7 cm. (2| in.), including the legs, 9-10 cm. (3|-4 in.), and it weighs
from 100-125 grammes (31-4J oz.).
Fourth Month. In the fourth month the skin becomes firmer, and fine hairs are
developed. The disproportion between the fore- and hind-limbs disappears. If the foetus
is born at this period it may live for a few hours. Its total length from vertex to heels
is 16-20 cm. (6f-8 in.), from vertex to coccyx 12-13 cm. (4i-5i in.), and it weighs from
230-260 grammes (81-94 oz.).
Fifth Month. The skin becomes firmer, the hairs are more developed, and sebaceous
matter appears on the surface of the body. The legs are longer than the arms, and the
umbilicus is farther from the pubis. At the end of the month the total length of the
THE HUMAN EMBEYO AT DIFFEKENT PEEIODS. 79
foetus, from vertex to heels, is 25-27 cm. (10-10- in.), from vertex to coccyx 20 cm.
(8 in.), and its average weight is about half a kilogramme (1 T V Ibs.).
Sixth Month. The skin is wrinkled and of a dirty reddish colour. The hairs
are stronger and darker. The deposit of sebaceous matter is greater, especially in the
axillae and groins. The eyelashes and eyebrows appear. At the end of the month the
total length of the foetus, from vertex to heels, is from 30-32 cm. (12-12f in.), and its
average weight is about one kilogramme (2i Ibs.).
Seventh Month. The skin is still a dirty red colour, but it is lighter than
in the previous month. The body is more plump on account of a greater deposit of sub-
cutaneous fat. The eyelids re-open, and the foetus is capable of living if born at this
period. Its total length at the end of the month, measured from vertex to heels, is 35-36
cm. (14-14f in.), and its weight is about one and a half kilogrammes (3J Ibs.).
Eighth Month. The skin is completely covered with sebaceous deposit, which
is thickest on the head and in the axillae and groins,, and its colour changes to a bright
flesh tint. The umbilicus is farther from the pubis, but it is not yet at the centre of the
body. The total length of the foetus, from vertex to heels, is 40 cm. (16 in.), and its weight
varies from 2 to 2J kilogrammes (4J-5| Ibs.).
Ninth Month. The hair begins to disappear from the body, but it remains
long and abundant on the head. The skin becomes paler, the plumpness increases, and
the umbilicus reaches the centre of the body. At the end of the ninth month, when the
foetus is born, it measures about 50 cm. from vertex to heels (20 in.), and it weighs from
3-3 kilogrammes (6^-7^- Ibs.).
The age of a foetus may be estimated, approximately, by Hasse's rule, viz., Up to the fifth
month the length in centimeters, the lower limbs being included, equals the square of the age
in months, and after the fifth month the length in centimeters equals the age multiplied by five.
NOTE 1. Evidence is gradually accumulating which tends to show that the reduction of the number of
chromosomes may take place during the last divisions of the germ mother cell, that is before the growth of
the oocyte or spermatocyte I commences, and therefore before maturation commences.
NOTE 2. There is evidence which points to conclusions somewhaf different from those stated on p. 14,
regarding the dentoplasm in mammalian ova, but it is not yet sufficient or sufficiently conclusive to justify its
incorporation in a text-book account.
NOTE 3. The recent observations of G. Fineman, Anat. Hefte, 159 H. (53 B. H.), 1915, show that the
ductus endolymphaticus is not derived from the original canal of communication with the exterior, but is
formed independently by a process of evagination.
NOTE 4. Evidence which has accumulated since this statement was made tends to show that blood
corpuscles and the endothelial cells which form the walls of the primitive blood-vessels are derived from
different ancestors, the endothelial cells from mesenchyme cells, and the red blood corpuscles form angioblasts
which may be derived, as some observers believe, from mesenchyme cells, or, as others think more probable,
from entoderm cells.
NOTE 5. The origin of the white blood corpuscles is still uncertain ; according to some investigators they
and the red corpuscles have common ancestors and the same ancestors may produce endothelium also ; this
is the so-called monophyletiq view. It appears probable, however, that, in some vertebrates, the white
corpuscles are derived from one set of mesoderm cells, the red corpuscles from another, and the endothelium
of the blood-vessels from a third set of mesodermal cells, each set of mesoderm cells being capable of pro-
ducing only one kind of descendant ; tliis is the polyphyletic view.
OSTEOLOGY.
THE SKELETON.
By ARTHUR THOMSON, F.RC.S.
Professor of Anatomy, University of Oxford.
THE term skeleton (from the Greek, o-KeAeros, dried) is applied to the parts which
remain after the softer tissues of the body have been disintegrated or removed,
and includes not only the bones, but also the cartilages and ligaments which bind
them together. In the restricted sense of the word the skeleton denotes the
osseous framework of the body. It is in this sense that it is generally employed in
human anatomy.
The skeleton serves to support the softer structures which are grouped around
it, and also affords protection to many of the delicate organs which are lodged
within its cavities. By the articulation of its several parts, its segments are con-
verted into levers which constitute the passive portion of the locomotory system.
Kecent research has also proved that certain cells found in bone -maf row are
intimately associated with the development and production of some of the
corpuscles of the blood.
Bone may be regarded as white fibrous tissue which, having become calcified
has undergone subsequent changes, so as to be converted into true osseous tissue.
Most probably all bone is of membranous origin, but it may pass through a stage
in which cartilage plays an important part in its development. In many instances
the cartilage persists, and is not converted into bone, as in the case of the articular
cartilage which clothes the joint surfaces, the nasal septum, the cartilages of the
nose, and the cartilages of the ribs. A persistence of the membranous condition
is met with in man in the case of the tentorium cerebelli, which in some groups
of animals ( Garni vora) is converted into a bony partition.
Skeletal structures may be derived from each of the three layers of the
trilaminar blastoderm. The exo-skeleton includes structures of ectodermal, and
some of mesodermal origin, in the shape of hair, nails, feathers, teeth, scales, armour-
plates, etc., whilst the endo-skeleton, with which we are more particularly concerned,
is largely derived from the mesodermal tissue, but also .includes the notochord, an
entodermal structure which forms the primitive endo-skeleton, around which the
axial skeleton is subsequently developed in the Vertebrata. The endo-skeleton is
divisible into an axial portion, appertaining to the trunk and head, and an appen-
dicular part, associated with the limbs. It also includes the splanchnic skeleton,
which comprises certain bones developed in the substance of some of the viscera,
such as the os cordis and os penis of certain mammals. In man, perhaps, the
cartilaginous framework of the trachea and bronchi may be referred to this
system.
The number of the bones of the skeleton of man varies according to age.
Owing to a process of fusion taking place during growth, the number in the adult
is less than the number in the child. The following table does not include the
sesamoid bones, which are frequently developed in tendons, the most constant
ossicles of this description being those in relation to the metacarpo-phalangeal
joint of the thumb, and the metatarso-phalangeal joint of the great toe.
81 6
82 OSTEOLOGY.
The table represents the number of bones distinct and separable during adult
life :
Single Bones. Pairs. Total.
The vertebral column . 26 ... 26
The skull ... 6 8 22
Axial skeleton . . The sternum . . 1 ... 1
The ribs . . .... 12 24
The hyoid bone . . 1 ... 1
f The upper limbs . 32 64
Appendicular skeleton ( The 1( ^ er limbs 31 62
The ossicles of the ear . . . .... 3 6
~34 ~86 1J06
Bones are often classified according to their shape. Thus, long bones, that is to
say, bones of elongated cylindrical form, are more or less characteristic of the limbs.
Broad or flat bones are plate-like, and serve as protective coverings to the structures
they overlie ; the bones of the cranial vault display this particular form. Other
bones, such as the carpus and tarsus, are termed short bones ; whilst the bones of the
cranial base, the face, and the vertebrae, are frequently referred to as irregular bones.
Various descriptive terms are applied to the prominences commonly met with
on a bone, such as tuberosity, eminence, protuberance, process, tubercle, spine,
ridge, crest, and line. These may be articular in their nature, or may serve as
points or lines of muscular and ligamentous attachment. The surface of the bone
may be excavated into pits, depressions, fovece, fossce, cavities, furrows, grooves, and
notches. These may be articular or non-articular, the latter serving for the recep-
tion of organs, tendons, ligaments, vessels, and nerves. In some instances the
substance of the bone is hollowed out to form an air space, sinus, or antrum.
Bones are traversed by foramina and canals ; these may be for the entrance and exit
of nutrient vessels, or for the transmission of vessels and nerves from one region to
another. A cleft, hiatus, or fissure serves the same purpose ; channels of this kind
are usually placed in the line of a suture, or correspond to the line of fusion of the
primitive portions of the bone which they pierce.
Composition of Bone. Bone is composed of a combination of organic and
inorganic substances in about the proportion of one to two.
Organic matter (Fat, etc., Collagen) . . . 31 '04
Mineral matter
Calcic phosphate . . . . 58-23'
Calcic carbonate . . . . 7 '3 2
Calcic fluoride . . . 1-41 V 68'97
Magnesic phosphate . . . 1'32
Sodic chloride '69
100-00
The animal matter may be removed by boiling or charring. According to the
completeness with which the fibrous elements have been withdrawn, so the brittle-
ness of the bone increases. When subjected to high temperatures the earthy
matter alone remains. By soaking a bone in acid the salts may be dissolved out,
leaving only the organic part. The shape of the bone is still retained, but the
organic substance which is left is soft, and it can be bent about in any direction.
The toughness and elasticity of bone depends therefore on its organic constituents,
whilst its hardness is due to its mineral matter.
Bone may be examined either in the fresh or dry condition. In the former
state it retains all its organic parts, which include the fibrous tissue in and around
it, the blood-vessels and their contents, together with the cellular elements found
within the substance of the bone itself, and the marrow which occupies the lacunar
spaces and marrow cavity. In the dried or macerated bone most of these have
disappeared, though a considerable portion of the organic matter still remains,
even in bones of great antiquity and in a more or less fossil condition. Con-
sidering its nature and the amount of material employed, bone possesses a remark-
able strength, equal to nearly twice that of oak, whilst it is capable of resisting a
STKUCTUEE OF BONE. 83
greater crushing strain ; it is stated that a cubic inch of bone will support a weight
of over two tons. Its elasticity is remarkable, and is of the greatest service in
enabling it to withstand the shocks to which it is so frequently subjected. In
regions where wood is scarce the natives use the ribs of large mammals as a sub-
stitute in the construction of their bows. Its hardness and density vary in different
parts of the skeleton, and its permanency and durability exceed that of any other
tissue of the body, except the enamel and dentine of the teeth. The osseous remains
of a race over eighty centuries old have been excavated in Egypt.
Structure of Bone (Macroscopic). To obtain an idea of the structure of a
bone it is necessary to examine it both in the fresh or 'recent condition and in the
macerated state. In the former the bone is covered by a membrane which is with
difficulty torn off, owing to the abundance of fine fibrils which enter the substance
of the bone from its deep surface. This membrane, called the periosteum, overlies
the bone, except where the bone is coated with cartilage. This cartilage may form
a bond of union between contiguous bones or, in the case of bones united to each
other by movable joints, may be moulded into smooth articular surfaces called the
articular cartilages. The attachment of the various ligaments and muscles can also
be studied, and it will be noticed that where tendon or ligament is attached, the
bone is often roughened to form a ridge or eminence ; where fleshy muscular fibres
are attached, the bone is, as a rule, smooth. In the macerated condition, when
the cartilage and fibrous elements have been destroyed, it is possible, however,
to determine with considerable accuracy the parts of the bone covered with
articular cartilage, since the bone here is smooth and conforms generally to the
curves of the articular areas of the joint ; these areas are referred to as the
articular surfaces of the bone. The bone, stripped of its periosteal covering,
displays a dense surface finely pitted for the entrance of the processes derived from
the periosteum, which thus establish a connexion between the bony substance and
that vascular layer ; here and there, more particularly in the neighbourhood of the
articular extremities, these pits increase in size and number and allow of the trans-
mission of small blood-vessels. If careful examination is made, one or two foramina
of larger size will usually be noticed. These vascular foramina or canals allow the
passage of arteries of considerable size into the interior of the bone, and are called
the canales nutricii or nutrient canals or foramina of the bone. There are also
corresponding channels for the escape of veins from the interior.
In order more fully to ascertain the structure of bone it will be necessary to
study it in section. Taking first a long bone, such as one meets with in the
limbs, one notices on longitudinal section, that the bone is not of the same
density throughout, for, whilst the external layers are solid and compact, the
interior is made up of loose spongy bone called sulstantia spongiosa (cancellous
tissue). Further, it will be observed that in certain situations this spongy substance
is absent, so that there is a hollow in the interior of the bone called the medullary
cavity. In the recent condition this cavity is filled with the marrow and is hence
often called the marrow cavity. This marrow, which fills not only the marrow cavity
but also the interstices between the fibres of the spongy substance, consists largely of
fat cells, together with some marrow cells proper, supported by a kind of retiform tissue.
The appearance and constituents of the marrow differ in different situations. In the
medullary cavity of long bones the marrow, as above described, is known as medulla
ossium flava (yellow marrow). In other situations, viz., in the diploe of the cranial
bones (to be hereafter described), in the spongy tissue of such bones as the vertebrae,
the sternum, and the ribs, the marrow is more fluid, less fatty, and is characterised
by the presence of marrow-cells proper, which resemble in some respects colourless
blood corpuscles. In addition to these, however, there are small reddish-coloured
cells, akin to the nucleated red corpuscles of the blood of the embryo. These cells
(erythroblasts) are concerned in the formation of the coloured corpuscles of the
blood. Marrow which displays these characteristic appearances is distinguished
from the yellow variety, already described, by being called the medulla ossium rubra
(red marrow). The marrow met with in the spongy tissue of the cranial bones of
aged individuals often undergoes degenerative changes and is sometimes referred to
as gelatinous marrow.
84 OSTEOLOGY.
A better idea of the disposition of the bony framework of a long bone can be
obtained by the examination of a section of a macerated specimen. In such a
specimen the marrow has been destroyed and the osseous architecture of the bone
is consequently better displayed.
Within the body of the bone is seen the marrow cavity extending towards, but not
reaching, either extremity of the bone. This cavity is surrounded on all sides by
a loose spicular network of bone, which gradually increases in compactness until it
reaches the circumference of the shaft, where it forms a dense surrounding wall. In
the shaft of a long bone the thickness of this outer layer is not the same throughout,
but tends to diminish as we approach the extremities, nor is it of uniform thickness
on all sides of the bone. All the long bones display curves in varying degree, and
it is a uniform rule that the thicker dense bone is found along the concave surface
of the curve, thus assisting in materially strengthening the bone. Towards the
extremities of the long bone the structure and arrangement of the bone undergoes
a change. There is no marrow cavity, the spongy tissue is not so open and
irregular, and the external wall is much thinner than in the shaft ; indeed in many
instances it is little thicker than stout paper. A closer examination of the arrange-
ment of this spongy tissue throughout the bone suggests a regularity in its
arrangement which might escape notice ; and if, in place of one bone only being
examined, sections of other bones are also inspected, it will be observed that the
spicules of this tissue are so arranged as best to withstand the strains and stresses
to which the bone is habitually subjected.
From what has been said it will be obvious that the arrangements above
described are those best adapted to secure the maximum of strength with the
minimum of material, and a consequent reduction in the weight of the skeleton.
The same description applies, with some modification, to bones of flattened form.
Taking as an example the expanded plate-like bones of the cranial vault, their
structure, as displayed on section, exhibits the following appearance : The outer
and inner surfaces are formed by two compact and dense layers, having sandwiched
between them a layer of spongy tissue called the diploe, containing red marrow.
Note that there is no medullary cavity, though in certain situations and at certain
periods of life the substance of the diploe may become absorbed and converted, by
the evagination of the mucous membrane of the respiratory tract, into air-spaces
or air-sinuses.
Structure of Bone (Microscopic). True bone differs from calcified cartilage or
membrane in that it not merely consists of the deposition of earthy salts within its
matrix, but displays a definite arrangement of its organic and inorganic parts.
Compact bone merely differs from loose or spongy bone in the denseness of its
tissue, the characteristic feature of which is the arrangement of the osseous
lamellae to form what are called Haversian systems. These consist of a central or
Haversian canal, which contains the vessels of the bone. Around this the osseous
lamellae are arranged concentrically, separated here and there by interspaces called
lacunas, in which the bone corpuscles are lodged. Passing from these lacunae are
many fine channels called canaliculi. These are disposed radially to the Haversian
canal, and pass through the osseous lamellae. They are occupied by the slender
processes of the bone corpuscles. Each Haversian system consists of from three to
ten concentric rings of osseous lamellae.
In addition to the lamellae of the Haversian systems there are others which are
termed the interstitial lamellae; these occupy the intervals between adjoining
Haversian systems, and consist of Haversian systems which have undergone a process
of partial absorption. Towards the surface of the bone, and subjacent to the peri-
osteal membrane which surrounds the shaft, there are lamellae arranged circum-
ferentially; these are sometimes referred to as the outer fundamental lamellae.
The periosteal membrane which surrounds the bone, and which plays so important
a part in its development, sends in processes through the various Haversian systems,
which carry with them vessels and cells, thus forming an organic meshwork
around which the earthy salts are deposited.
Ossification of Bone. For an account of the earlier development of the
skeleton the reader should consult a manual of embryology. Concerning the
OSSIFICATION AND GKOWTH OF BONES. 85
subsequent changes which take place, these are dependent on the conversion of the
scleratogenous tissue into- membrane and cartilage. A characteristic of this tissue
is that it contains elements which become formed into bone-producing cells, called
osteoblasts. These are met with in the connective tissue from which the membrane
bones are formed, whilst they also appear in the deeper layers of the investing
tissue of the cartilage (perichondrium), and so lead to its conversion into the bone-
producing layer or periosteum. All true bone, therefore, may probably be regarded
as of membranous origin, though its appearance is preceded in some instances by
the deposition of cartilage ; in this case calcification of the cartilage is an essential
stage in the process of bone formation, but the ultimate conversion into true bone,
with characteristic Haversian systems, leads to the absorption and disappearance of
this primitive calcified cartilage. In considering the development of bone an
inspection of the skeleton of a foetus will enable the student to realise that much
of what is bone in the adult is preformed in cartilage, whilst a part of the fully
developed skeleton is represented only by membrane: hence, in regard to this
ossification, bones have been described as of cartilaginous and membranous origin.
If the development of a long bone is traced- through successive stages from the
cartilaginous condition in which it is preformed, it will be noticed that ossification
begins in the body ; the part of the bone ossified from this centre is referred to as
the diaphysis, and, since it is the first to appear, the centre is spoken of as the primary
centre of ossification. As yet, the ends of the body are cartilaginous knobs, but
at a later stage one or more ossific centres appear in these cartilaginous extremities.
These centres, which are independent of the diaphysis and appear much later, at vari-
able periods, are termed secondary centres, and from them the epiphyses are formed.
If there is more than one such centre at the end of a bone, the associated centres
unite, and at a later stage the osseous mass so formed joins with the body or
diaphysis, and in this way the formation of the bone is completed. Complete
fusion by osseous union of the epiphyses with the diaphyses occurs at variable
periods in the life of the individual. Prior to this taking place, the two are bonded
together by a cartilaginous layer which marks the position of the epiphyseal line.
If the bone is macerated at this stage of growth, the epiphysis falls away from the
diaphysis. In the case of the articular ends of bone it will be noticed that the
surfaces exposed by the separation of the epiphysis from the diaphysis are not
plane and smooth, but often irregular, notched, and deeply pitted, so that when the
two are brought together they interlock, and, as it were, dovetail into each other.
In this way the extremities of the bone as yet ununited by osseous growth are,
during youth and adolescence, able to withstand the shocks and jars to which during
life they are habitually subjected. A long bone has been taken as the simplest
example, but it by no means follows that these epiphyses are confined to the
articular extremities of long bones. They are met with not only in relation to the
articular surfaces of bones of varied form, but also occur where bones may be
subjected to unusual pressure or to the strain of particular muscles. For this
reason epiphyses of this nature have been called pressure and traction epiphyses
(Parsons). There occur, however, secondary independent centres of ossification,
which cannot be so accounted for. Possibly these are of phylogenetic interest
only, and may accordingly be classed as Atavistic.
Ossification in Membrane. Membrane bones are such as have developed
from fibrous tissue without having passed through a cartilaginous stage. Of this
nature are the bones of the cranial vault and the majority of the bones of the
face, viz., the maxillse, zygomatic (malar), nasal, lacrimal, and palate bones, as well as
the vomer. The medial lamina of the pterygoid process (internal pterygoid plate)
is also of membranous origin. In the course of the development of a bone from
membrane, as, for example, the parietal bone, the fibrous tissue corresponding to
the position of the primary centre becomes osteogenetic, because here appear the
bone-forming cells (osteoblasts), which rapidly surround themselves with a bony
deposit more or less spicular in arrangement. As growth goes on these osteoblasts
become embedded in the ossifying matrix, and remain as the corpuscles of the
future bone, the spaces in which they are lodged corresponding to the lacunae and
canaliculi of the fully developed osseous tissue. From the primary centre ossifica-
86 OSTEOLOGY.
tion spreads eccentrically towards the margins of the bone, where ultimately the
sutures are formed. Here the growth rendered necessary by the expansion of the
cranium takes place through the agency of an intervening layer of vascular
connective tissue rich in osteoblasts ; but in course of time the activity of this is
reduced until only a thin layer of intermediate tissue persists along the line of the
suture ; this may eventually become absorbed, leading to the obliteration of the suture
by the osseous union of the contiguous bones. Whilst the expansion of the bone in all
directions is thus provided for, its increase in thickness is determined by the activity
of the underlying and overlying strata. These form the periosteum, and furnish
the lamellse which constitute the inner and outer compact osseous layers.
Ossification in Cartilage. Cartilage bones are those which are preformed in
cartilage, and include most of the bones of the skeleton. Their growth is often
described as endochondral and ectochondral, the former term implying the
deposition of membrane bone in the centre of the cartilage, while the latter
signifies a deposit of membrane bone on the surface of the cartilage, the osteo-
genetic layer on the surface of the cartilage being named the perichondrium till
once bone has been formed, when it is called the periosteum.
In a cartilage bone changes of a similar nature occur. The cartilage, which may
be regarded histologically as white fibrous tissue + chondro-sulphuric acid and a
certain amount of lime salts, undergoes the following changes : First, the cartilage
cells being arranged in rows, become enlarged ; secondly, the matrix between the
cartilage cells becomes calcified by the deposition of an additional amount of lime
salts ; thirdly, the rows of cells become confluent ; and, fourthly, into the spaces so
formed extend the blood-vessels derived from the vascular layer of the periosteum.
Accompanying these vessels are osteoblasts and osteoclasts, the former building up
true bone at the expense of the calcified cartilage, the latter causing an absorption of
the newly formed bone, and leading to its conversion into a marrow cavity, so that
in due course all the cartilage or its products disappear. At the same time that this
is taking place within the cartilage, the perichondrium is undergoing conversion into
the periosteum, an investing membrane, the deeper stratum of which, highly vascular,
furnishes a layer of osteoblast cells which serve to develop the circumferential
lamellse of the bone. It is by the accrescence of these layers externally, and their
absorption internally through the action of the osteoclast cells, that growth takes
place transversely. A transverse section of the shaft of a long bone shows this
very clearly. Centrally there is the marrow cavity, formed primarily by the
absorption of the calcified cartilage; around this the spongy tissue produced
by the partial erosion of the primary periosteal bone is disposed, whilst externally
there is the dense envelope made up of the more recent periosteal growth.
Growth of Bone. The above description, whilst explaining the growth of bone
circumferentially, fails to account for its growth in length ; hence the necessity in
long bones for some arrangement whereby ossification may take place at one or both
extremities of the body. This zone of growth is situated where the ossified body
becomes continuous with the cartilaginous epiphysis. In addition, within these
epiphysial cartilages calcification of the cartilage takes place centrally, just as in the
diaphysis. The two parts of the bone, viz,, the diaphysis and epiphysis, are thus
separated by a layer of cartilage, sometimes called the cartilage of conjuga-
tion, as yet uncalcified, but extremely active in growth owing to the invasion
of vessels and cells from a vascular zone which surrounds the epiphysis. The
nucleus of the epiphysis becomes converted into true bone, which grows
eccentrically. This arrangement provides for the growth of the shaft towards
the epiphysis, and the growth of the epiphysis towards the shaft; so that as
long as the active intervening layer of cartilage persists, extension of growth in
a longitudinal direction is possible. As might be expected, experience proves that
growth takes place more actively, and is continued for a longer time, at the end
of the bone where the epiphysis is the last to unite. In consequence, surgeons
sometimes term this the " growing end of the bone." Subsequently, however, at
variable periods the intervening layer of cartilage becomes calcified, and true bony
growth occurs within it, thus leading to complete osseous union between the shaft
and epiphysis. When this has taken place all further growth in a longitudinal
VEETEBEAL COLUMN. 87
direction, ceases. In cases where the epiphysis enters into the formation of a joint,
the cartilage over the articular area persists and undergoes neither calcification nor
ossification.
Vascular, Lymph, and Nervous Supply of Bone. From what has been
said it will be gathered that the vascular supply of the bone is derived from the
vessels of the periosteum. These consist of fine arteries which enter the surface of
the diaphysis and epiphysis ; but in addition there is a larger trunk which enters the
diaphysis and reaches the medullary cavity. This is called the nutrient artery of
the bone. The direction taken by this vessel varies in different bones. In the
upper limb the artery runs dis tally in the case of the burner us and proximally
in the radius and ulna; in the lower limb the nutrient vessel of the femur is
directed towards the proximal extremity of the shaft, whilst in the tibia and fibula
it follows a distal course. The direction of the nutrient artery in the bone is
a mechanical result of the unequal growth of the two extremities of the bone.
During the greater part of intra-uterine life the principal nutrient arteries of the
ng bones are directed towards the distal extremity of the limb. In the process
development the point of entrance of the artery is turned away from the
iphysis which furnishes the greatest amount of bone, and thus, together with
e nutrient canal, acquires an obliquity directed towards the extremity of the
ne which develops last (Piollet, J. de I'Anat. et de la Phys., 1905, p. 57).
It may assist the memory to point out that when all the joints are flexed, as
the position occupied by the foetus in utero, the direction taken by the vessels
the same, and corresponds to a line passing from the head towards the tail-end
if the embryo. Consequently, in the upper limb the vessels run towards the
elbow, whilst in the lower limb they pass from the knee.
The veins which permeate the spongy texture of the bone are large and thin-
walled. They do not accompany the arteries, and, as a rule, in long bones they
escape through large openings near the articular surfaces. In flat bones they occupy
hannels within the diploe, and drain into an adjacent sinus, or form communica-
ns with the superficial veins of the scalp.
The lymph vessels are mainly periosteal, but enter the bone along with the
ood-vessels and become perivascular.
The nerves which accompany the arteries are probably destined for the supply of
e coats of these vessels. Whether they end in the bony tissue or not is unknown.
The attention of anatomists has long been directed to the elucidation of the laws
hich regulate bone-growth. Our present knowledge of the subject may be briefly
mmarised in the following generalisations :
1. In bones with a shaft and two epiphyses, the epiphysis towards which the
trient artery is directed is the first to unite with the shaft.
2. In bones with a shaft and two epiphyses, as a rule the epiphysis which com-
nces to ossify latest unites soonest with the shaft. (The fibula is a notable
exception to this rule.)
3. In bones with a shaft and one epiphysis the nutrient artery is directed
towards the end of the bone which has no epiphysis. (This arrangement holds
good in the case of the clavicle, the metacarpus, metatarsus, and phalanges.)
4. When an epiphysis is ossified from more than one centre, coalescence takes
place between the separate ossific nuclei before the epiphysis unites with the shaft.
Highly suggestive, too, are the following propositions That ossification first
commences in the epiphysis which ultimately acquires the largest relative propor-
tion to the rest of the bone, and that the ossification of the epiphysis is also
correlated with its functional importance. In cases of long bones with only one
epiphysis, the epiphysis is placed at the end of the bone where there is most
movement.
COLUIYINA VERTEBRALIS.
The vertebral column of man consists of thirty-three superposed segments
or vertebrae. In the adult, certain of these vertebrae have become fused together
in the process of growth to form bones, the segmental arrangement of which
88 OSTEOLOGY.
is somewhat obscured, though even in their fully developed condition
sufficient evidence remains to demonstrate their compound nature. The
vertebrse so blended are termed the fixed or false vertebrae, whilst those between
which osseous union has not taken place are described as the movable or true
vertebrae. This fusion of the vertebral segments is met with at each extremity
of the vertebral column, more particularly the lower, where the column is modified
to adapt it for union with the girdle of the lower limb, and where also man's
degenerated caudal appendage is situated. But a partial union of the vertebral
segments also takes place at the upper end of the column, between the highest
two vertebrse, in association with the mechanism necessary to provide for the
movements of the head on the column.
For descriptive purposes the vertebral column is subdivided according to the
regions through which it passes. Thus the vertebrae are described as cervical
(vertebrse cervicales), thoracic (vertebras thoracales), lumbar (vertebrse lurnbales),
sacral (vertebrse sacrales), and coccygeal (vertebrse caudales), according as they
lie in the regions of the neck, thorax, loins, pelvis, and tail. The number of
vertebrse met with in each region is fairly constant, though, as will be hereafter
pointed out, variations may occur in the number of the members of the different
series. The vertebrse in man are thus apportioned *7 cervical, 12 thoracic, 5 lumbar,
5 sacral, and 4 or 5 coccygeal ; the former three groups comprise the true or mov-
able vertebrse, the latter two the false or fixed vertebras. The vertebral formula
may be thus expressed :
Movable or True Vertebras. Fixed or False Vertebrae.
Cervical. Thoracic. Lumbar. Sacral. Coccygeal.
7 12 5 5 4 =33.
The vertebrae, though displaying great diversity of characters in the regions above
enumerated, yet preserve certain features in common. All possess a solid part,
corpus vertebrae or body (centrum); all have articular processes by which they
articulate with their fellows ; most have muscular processes developed in connexion
with them ; whilst the majority display a vertebral foramen formed by the union
of a bony arcus vertebrse (vertebral arch) with the body. These common characters
may best be studied by selecting for description an intermediate member of
the series. For this purpose one of the middle or lower thoracic vertebrse
may be chosen.
A typical vertebra may be described as consisting of a body composed of
a mass of spongy bone, more or less cylindrical in form. The size and shape of
the body is liable to considerable variation according to the vertebra examined.
The superior and inferior surfaces of the body are very slightly concave dorso-
ventrally and from side to side, due to the thickening of the bone around its
margins. In the recent condition these surfaces afford attachment for the inter-
vertebral fibro-cartilages, which are placed like pads between the bodies of the
movable members of the series. The circumference of the body, formed as it is
of more compact bone than the interior, is usually slightly concave from above
downwards, though the dorsal surface becomes flat, where the body forms the
anterior boundary of the vertebral foramen, at which point it is usually slightly
concave from side to side. The vertical surfaces of the body are pierced here and
there by foramina for the passage of nutrient vessels, more particularly on the
dorsal surface, where a depression of considerable size receives the openings
of the canals through which some of the veins which drain the body of the bone
escape. Connected with the body posteriorly there is a bony vertebral arch,
which, by its union with the body, encloses a foramen of variable size, called the
vertebral foramen. When the vertebrae are placed on the top of each other these
foramina form, with the uniting ligaments, a continuous canal vertebral canal
in which the spinal medulla, with its coverings, is lodged. The vertebral arch,
which is formed by the union of the roots of the vertebral arches (pedicles) and
laminae, besides enclosing the vertebral foramen, also supports the spinous and trans-
verse processes, which may be regarded as a series of levers to which muscles are
VEETEBKAL COLUMN.
89
Superior
articular process Boot of the vertebral arch
Spinous process
attached, whilst others are articular and assist in uniting the different vertebrae
together by means of a, series of movable joints. The roots of the vertebral
arches (O.T. pedicles) are the bars of bone which pass from the dorsum of the
body of the vertebrae, one on each side,
to the points where the articular pro-
cesses are united to the arch. Each
root is compressed from side to side, Fovea costaiis superior
and has rounded superior and in- Fovea costaiis y$fifciK^k^ Bod y
ferior borders. Since the vertical
breadth of the roots is not as great
as the height of the body to which
they are attached, it follows that
when the vertebrae are placed one
above the other a series of intervals
is left between the roots of the
vertebral arches of the different
vertebrae. These spaces, enclosed
anteriorly by the bodies of the verte-
brae and their intervertebral fibro-
cartilages and posteriorly by the
coaptation of the articular processes,
form a series of holes communicat-
ing with the vertebral canal ; they
are called the intervertebral foramina,
and allow the transmission of spinal
nerves and vessels. As each inter-
vertebral foramen is bounded above
and below by one of the roots of
the vertebral arch, the grooved
surfaces in correspondence with the
upper and lower borders of the roots
are called the incisurae vertebrales
superior et inferior (upper and lower
intervertebral notches). Posteriorly,
the two roots of each vertebral arch
are united by two somewhat flattened
plates of bone the laminae which
converge towards the median plane,
and become fused with the root of
the projecting spinous process. The
vertical lengths or heights of the
laminae and their sloping arrangement are such, that, when the vertebrae are
articulated together, they leave little space between them, thus enclosing fairly
completely the vertebral canal, of which they form the posterior wall. The edges
and inner surfaces of the laminae are rough for the attachment of the ligaments
which bind them together.
The muscular processes are three in number, viz., two processus transversi
one on either side and one central or median, the processus spinosus. The
transverse processes project laterally on either side from the arch at the point
where the root of the vertebral arch joins the lamina. The spinous process extends
backwards in the median plane from the point of fusion of the laminae. The
spinous processes display much variety of length and form.
The articular processes (zygapophyses), four in number, are arranged in pairs
one superior, the other inferior ; the former are placed on the upper part of the arch
where the roots of the arch (pedicles) and laminae join, the latter on the lower part
of the arch in correspondence with the superior. Whilst differing much in the
direction of their articular surfaces, the upper have generally a backward tendency,
whilst the lower incline forwards.
Fovea cos-
taiis trans-
versal is
Superior articular
process
Root of the
vertebral arch
Fovea costaiis
inferior
Body
FIG. 106. FIFTH THORACIC VERTEBKA, (A) as viewed
from the right side, (B) as viewed from above.
90
OSTEOLOGY.
THE TRUE OR MOVABLE VERTEBRAE.
Vertebras Cervicales.
The cervical vertebrae, seven in number, can be readily distinguished from
all the other vertebrae by the fact that their transverse processes are pierced by
a foramen. The highest two, and the lowest, require special description; the
remaining four conform to a common type.
Their bodies, the smallest of all the true vertebrse, are oblong in shape, the
transverse width being much longer than the antero- posterior diameter. The
superior surface, which slopes from behind forwards and downwards, is concave
from side to side, owing to the marked projection of its lateral margins. Its
anterior lip is rounded off, whilst its posterior edge is sharply defined. The inferior
surface, which is more or less saddle-shaped, is directed downwards and backwards.
It is convex from side to side, and concave from before backwards, with a slight
rounding off of the projecting anterior lip. The vertical diameter of the body is
small in proportion to its width. The anterior surface is flat in the middle line,
but furrowed laterally. The posterior surface, which is rough and pierced by many
small foramina, is flat from side to side and above downwards ; it forms part of
Bifid spine
Superior articular process Superior notch
Foramen transversarium
jratnen transversarium
Anterior tubercle A
Spinous process
Inferior notch
Inferior articular process
B
FIG. 107. FOURTH CERVICAL VERTEBRA, (A) from above, and (B) from the right side.
the anterior wall of the vertebral foramen. The lateral aspect of each body, par-
ticularly in its upper part, is fused with a root of the arch and with the costal
part of a transverse process, and forms the medial wall of a foramen transversarium.
The roots of the vertebral arches, which spring from the posterior half of the
lateral aspects of the body, about equidistant from their superior and inferior
margins, are directed horizontally backwards and laterally. The superior and
inferior notches are nearly equal in depth. The laminae are long, and about as
high as the bodies of the bone. The vertebral canal is larger than in the thoracic
and lumbar regions ; its shape is triangular, or more nearly semilunar.
The transverse processes, so called, are pierced by the foramen transversarium
(vertebrarterial or transverse foramen). They consist of two parts the part behind
the foramen, which springs from the vertebral arch and is the true transverse
process, and the part in front, which is homologous with a rib in the thoracic
portion of the column. These two processes are united laterally by a bridge of bone,
which thus converts the interval between them into a foramen, and they terminate,
beyond the bridge, in two tubercles, known as the anterior and posterior tubercles.
The general direction of the transverse processes is laterally, slightly forwards,
and a little downwards, the anterior tubercles lying medial to the posterior. The
two tubercles are separated above by a groove directed laterally, downwards, and
forwards ; along this the spinal nerve trunk passes. The foramen transversarium
is often subdivided by a spicule of bone. In the recent condition and in the cases
of the upper six vertebrse it is traversed by the vertebral artery and vein.
The spinous processes, which are directed backwards, are short, compressed
vertically, and bifid. The articular processes are supported on cylindrical masses of
CEEVICAL VERTEBE^.
91
bone fused with the arch where the roots of the vertebral arches and the laminae
join. These cylinders are sliced away obliquely above and below, so that the superior
articular facets, more or less circular in form, are directed upwards and backwards,
whilst the corresponding inferior surfaces are turned downwards and forwards.
The Atlas or First Cervical Vertebra. This bone may be readily recognised
by the absence of the body and spinous process. It consists of two lateral masses,
which support the articular and transverse processes. The lateral masses are them-
selves united by two curved bars of bone, the anterior and posterior arches, of which
the former is the stouter and shorter. Each lateral mass is irregularly six-sided,
and so placed that it lies closer to its fellow of the opposite side in front than
behind. Its upper surface is excavated to form an elongated oval facet called the
superior articular fovea, which is concave from before backwards, and inclined
obliquely medially ; not infrequently this articular surface displays indications of
division into two parts. The superior articular fovese are for the reception of the
condyles of the occipital bone.
The inferior articular fovese or facets are placed on the inferior surfaces of
the lateral masses. Of circular form, they display a slight side-to-side con-
cavity, though flat in the
antero- posterior direction.
Their disposition is such
that their surfaces incline
downwards and slightly
medially. They rest on the
superior articular processes
of the second cervical 2
vertebra or epistropheus.
Springing from the an-
terior and medial aspects
of the lateral masses, and
uniting them in front, is a
curved bar of bone, the
arcus anterior (anterior arch);
compressed on each side,
and thickened centrally
so as to form on its an-
terior aspect the rounded
tuberculum anterius (an-
terior tubercle). In corre-
spondence with this, on the posterior surface of this arch is a circular facet
(fovea dentis) for articulation with the dens of the epistropheus.
The medial surface of the lateral mass is rough and irregular, displaying a
tubercle for the attachment of the transverse ligament of the atlas, which passes
across the space included between the two lateral masses and the anterior arch,
thus holding the dens of the epistropheus in position. Behind each tubercle there
is usually a deep pit, opening into the bottom of which are the canals for the
nutrient vessels.
Laterally to the lateral mass, and principally from its upper half, the transverse
process arises by two roots which include between them the foramen trans-
versarium. The transverse process is long, obliquely compressed, and down-turned ;
the anterior and posterior tubercles have fused to form one mass.
The posterior arch arises in part from the posterior surface of the lateral mass,
and in part from the posterior root of the transverse process. Compressed from
above downwards anteriorly, where it bounds a groove which curves around the
posterior aspect of the superior articular process, which groove is also continuous
laterally with the foramen transversarium, the posterior arch becomes thicker
medially, at which point it displays posteriorly a rough irregular projection the
tuberculum posterius (posterior tubercle), the feeble representative of the spinous
process. A prominent little tubercle, arising from the posterior extremity of the
superior articular process, overhangs the groove above mentioned, and not in-
1. Posterior arch.
2. Transverse process.
3. Tubercle for transverse
ligament.
4. Anterior arch.
5. Anterior tubercle.
10
FIG. 108. THE ATLAS FROM ABOVE.
6. Surface for articulation with dens.
7. Superior articular surface.
8. Foramen for vertebral artery.
9. Groove for vertebral artery.
10. Posterior tubercle.
92
OSTEOLOGY.
frequently becomes developed so as to form a bridge of bone across it, converting
the groove into a canal through which the vertebral artery and the posterior ramus
of the suboccipital nerve pass a condition normally met with in many animals.
It is noteworthy that the grooves traversed by the highest two spinal nerves lie
behind the articular processes, in place of in front, as in other parts of the column.
The ring formed by the lateral masses and the anterior and posterior arches is
of irregular outline. The anterior part, cut off from the rest by the transverse
ligament, serves for the lodgment of the dens of the epistropheus ; the larger
part behind corresponds to the upper part of the vertebral canal.
Epistropheus or Second Cervical Vertebra. This is characterised by the
presence of the tooth-like dens (O.T. odontoid process) which projects upwards from
the superior surface of the body. Slightly constricted where it joins the body, the
dens tapers to a blunt point superiorly, on the sides of which there are surfaces for
the attachment of the alar ligaments. When the atlas and epistropheus are articulated
this process lies behind the anterior arch of the atlas, and displays on its anterior
surface an oval or circular facet which rests on that on the posterior surface of the
anterior arch of the atlas. On the posterior aspect of the neck of the dens there
is a shallow, groove in which lies the transverse ligament of the atlas, which
holds the dens in position.
Dens Groove for transverse ligament of the atlas
Superior articular
surface
Dens
Spine
Foramen
vertebral
artery
Inferior articular
process
Spine
A
bral artery Transverse process
B
Inferior articular
process
FIG. 109. EPISTROPHEUS (O.T. Axis), (A) from behind and above, (B) from the left side.
The anterior surface of the body has a raised triangular surface, which ends
superiorly in a ridge passing upwards to- the neck of the dens. The roots of the
vertebral arches are concealed above by the superior articular processes ; inferiorly,
they are deeply grooved. The laminae prismatic on section are thick and strong,
ending in a stout, broad, and bifid spinous process, the under surface of which is
deeply grooved, whilst its sides meet superiorly in a ridge. Placed over the
roots of the vertebral arches and the anterior root of the transverse processes are
the superior articular surfaces. These are more or less circular in shape, slightly
convex from before backwards, flat from side to side, and are directed upwards
and a little laterally. They are channelled inferiorly by the foramina trans-
versaria, which turn laterally beneath them. The grooves by which the second
cervical nerves leave the vertebral canal cross the laminae immediately behind
the superior articular processes. The inferior articular processes agree in form
and position with those of the remaining members of the series, and are placed
behind the inferior intervertebral notches. The transverse process is markedly
down-turned, and its lateral extremity is not bifid.
The sixth cervical vertebra often displays an enlargement of the anterior
tubercle on the transverse process, called the carotid tubercle from the circumstance
that the carotid artery may be conveniently compressed against it. It is necessary
to add, however, that the tubercle is not always well developed.
THOKACIC VEKTEBR^, 93
The seventh cervical vertebra (vertebra prominens) receives the latter name
from the outstanding natureof its spinous process, which ends in a single broad tubercle.
This forms a well-marked surface projection at the back of the root of the neck.
The transverse processes are broad, being flattened from above downwards ; they
project considerably beyond those of the sixth. The maximum width between
their extremities agrees with that between the transverse processes of the atlas,
these two constituting the widest members of the cervical series. The anterior
tubercle is very small and is placed near the body. The foramen transversarium is
small and does not as a rule transmit the vertebral artery. Usually a small vein
passes through it. Not infrequently the costal element is separate from the true
transverse process, thus constituting a cervical rib.
Vertebras Thoracales.
The thoracic vertebrae, twelve in number, are distinguished by having facets
on the sides of their bodies for the heads of the ribs, and in most instances also
articular surfaces on their transverse processes for the tubercles of the ribs (Fig.
124, p. 111).
The body is described as characteristically heart-shaped, though in the upper
and lower members of the series it undergoes transition to the typical forms of the
cervical and lumbar vertebrae, respectively. Its an tero- posterior and transverse
measurements are nearly equal ; the latter is greatest in line with the facets for
the heads of the ribs. The bodies are slightly thicker behind than in front, thus
adapting themselves to the anterior concavity which the column displays in this
region. The bodies of the second to the ninth thoracic vertebrae inclusive, each
possess four fovese costales or costal facets, a superior and larger pair placed on the
superior margin of the body, close to the junction of the root of the vertebral arch
with the body, and an inferior and smaller pair situated on the inferior edge, close
to and in front of the inferior intervertebral grooves.
When contiguous vertebrae are articulated, the upper pair of facets of the lower
vertebra coincide with the lower facets of the higher vertebra, and, together with the
intervening intervertebral nbro-cartilage, form an articular cup for the reception of the
head of a rib. Of these facets on the body the upper pair are the primary articular
surfaces for the head of the rib ; the lower are only acquired secondarily. Moreover, these
facets, though apparently placed on the body, are in reality developed on the sides of the
roots of the vertebral arches behind the line of union of the roots with the body (neuro-
central synchondrosis), as will be explained hereafter.
The roots of the vertebral arches (O.T. pedicles) are short and thick, and
directed posteriorly and slightly upwards. The superior vertebral notch is faintly
marked ; the inferior is deep. The laminae are broad, flat, and sloping, having sharp
superior and inferior margins. When the vertebrae are superposed the latter
overlap the former in an imbricated manner. The vertebral foramen is smaller
than in the cervical and lumbar regions, and nearly circular in shape.
The spinous processes vary in length and direction, being shorter and more
horizontal in the upper and lower members of the series, longest and most oblique
in direction towards the middle of this part of the column. Nearly all have a down-
ward inclination, and are so arranged that they overlap one another. Triangular in
section where they spring from the vertebral arch, they become compressed from side
to side towards their extremities, which are capped by more or less distinct tubercles.
The transverse processes are directed backwards and laterally, and a little upwards.
They gradually decrease in size and length from above downwards. Each has a
somewhat expanded extremity, the anterior surface of which, in the case of the upper
ten vertebr.83, is hollowed out in the form of a circular facet for articulation with
the tubercle of the rib which rests in the upper facet of the vertebra to which the
transverse process belongs. The superior articular processes are vertical, and have
their surfaces directed backwards, slightly upwards, and a little laterally; the
inferior, correspondingly forwards, downwards, and medially.
Certain of the thoracic vertebrae display characters by which they can readily
94
OSTEOLOGY.
be recognised. These are the first, tenth, eleventh.
FIG. 110. FIRST, NINTH, TENTH, ELEVENTH, AND TWELFTH
THORACIC VERTEBRA FROM THE LEFT SIDE.
1. Inferior articular process, with
laterally turned facet.
2. Single facet for head of Xllth rib ;
no facet on transverse process.
3. Single facet for head of Xlth rib ;
no facet on transverse process.
4. Single facet for head of Xth rib.
5. Occasional facet for head of Xth
rib.
6. Facet for head of IXth rib.
7. Facet for head of Ilnd rib.
8. Single facet for head of 1st rib.
and twelfth, and sometimes
the ninth.
The first thoracic ver-
tebra resembles the seventh
cervical in the shape of its
body, and the length and
direction of its spine. There
is a circular facet on either
side of the body for the head
of the first rib, and one facet
on each side at the inferior
border of its body, to com-
plete the socket for the head
of the second rib. Its trans-
verse processes are long, and
the superior intervertebral
notch is better marked than
in other members of the
thoracic series. The superior
articular surfaces are directed
backwards and upwards, not
laterally as in the lower
members of the series.
The ninth thoracic
vertebra occasionally has
only the upper pair of facets
on its body ; at other times it
conforms to the usual type.
The tenth thoracic ver-
tebra may have only one
complete costal facet on each
side for the tenth rib, though
sometimes the articular socket
may be completed by the
ninth thoracic vertebra. The
facet on the transverse pro-
cess is generally small, and
sometimes absent.
The eleventh thoracic
vertebra has a complete
circular facet on the lateral
side of each root of the
vertebral arch for articula-
tion with the eleventh rib.
Its transverse processes are
9. Facet on transverse process for short and stunted, and have
tuberosity of 1st rib. no facets
10. Facet on transverse process for mi ,i.u +1,^
tuberosity of IXth rib. Lne twelfth thOraClC
11. Facet on transverse process for Vertebra has a single facet
tuberosity of xth rib, in this on eac h roo fc o f the vertebral
marked" "^ wel1 aroh for the twelfth rib. Its
S. Superior^ Tubercles fMamillary. transverse prOCCSSeS, short
I. Inferior
E. Lateral
(corre-
sponding
to
_J Accessory.
| Transverse
and stunted, have no facets,
of lumbar anc ^ are ^ r ken up into
smaller tubercles, called the
lateral, superior, and inferior tubercles. These are homologous with the trans-
verse, mamillary, and accessory processes of the lumbar vertebrae. Indica-
tions of these processes may also be met with in the tenth and eleventh
thoracic vertebrae. The twelfth thoracic vertebra may usually be distinguished
LUMBAK VEETEBE^E.
95
from the eleventh by the arrangement of its inferior articular processes, which
resemble those of the lumbar series in being turned laterally ; but the eleventh
occasionally displays the same arrangement, in which case it is not always easy
to distinguish between them.
Mamillary process
Vertebrae Lumbales.
The lumbar vertebrae, five in number, are the largest of the movable vertebrae.
They have no costal articular facets, nor are their transverse processes pierced by
a foramen. In this way they can be readily distinguished from the members of
the cervical and thoracic
series. Spinous process
The body is kidney-
shaped in outline, and
of large size, exhibiting a
gradual transition from BLli Inferior articular process
the thoracic form in the
higher segments. The
transverse diameter is
usually about a half
greater than the antero-
posterior. The anterior
vertical thickness is
slightly greater than the
posterior, being thus
adapted to the anterior
convex curve of the
column in this region.
The roots of vertebral
arches (O.T. pedicles),
directed horizontally back-
wards, are short and stout ;
the superior notches are
shallow, but deeper than
in the thoracic region ; the
inferior grooves are deep.
The laminae are broad and
nearly vertical, sloping but
little. They support on
their inferior margins the
inferior articular processes.
The vertebral foramen is
large and triangular.
The spinous processes,
spatula shaped, with a
thickened posterior mar-
gin, project backwards and
slightly downwards. The
transverse processes, more
slender than in the thor-
acic region, pass horizon-
tally laterally, with a
slight backward inclination and usually with an upward tilt. Arising from the
junction of the roots of the vertebral arches with the laminae in the higher
members of the series, they tend to advance so as to become fused with the lateral
side of the root and posterior aspect of the body in the lower two lumbar vertebrae.
In these latter vertebras the superior intervertebral grooves are carried obliquely
across the superior surfaces of the bases of the transverse processes. The transverse
processes lie in line with the lateral tubercles of the lower thoracic vertebrae, with
Body
Superior articular process
I
Mamillary process
Transverse process
Body
Spinous process
Inferior articular process
FIG. 111. THIRD LUMBAR VERTEBRA, (A) from above,
and (B) from the left side.
96 OSTEOLOGY.
which they are serially homologous, and are to be regarded as representing the
costal elements. Placed on their bases posteriorly, and just lateral to and inferior to
the superior articular processes, are the small accessory processes, which are in series
with the inferior tubercles of the lower thoracic vertebrae. The superior articular
processes are stout, oval, curved plates of bone, fused in front with the roots and
laminae, and having their concave articular surfaces vertical and turned medially.
Laterally, and on their posterior edge, the bone rises in the form of an elongated
oval tubercle, the processus mamillaris (mamillary process); these are in
correspondence with the superior tubercles of the lower thoracic transverse
processes.
The inferior articular processes lie on either side of the root of the spinous
process, supported on the inferior margin of the laminae. Their articular surfaces,
oval in outline, convex from side to side, and plane from above downwards, are
turned laterally. The inferior articular processes are much closer together than the
superior ; so that when the vertebras are articulated the superior articular processes
of the lower vertebra embrace the inferior articular processes of the higher vertebra.
The fifth lumbar vertebra is characterised by the size of its body, which is
the largest of all the vertebrae. Further, the inferior surface of the body is cut
away at the expense of its posterior part : hence the thickness of the body in
front much exceeds the vertical diameter behind. By its articulation with
the first sacral segment the inferior border of the body of this bone assists
in the formation of the sacro-vertebral angle. The transverse process is pyra-
midal in form, and stouter than those of the other lumbar vertebrae. It arises
by a broad base from the side of the back of the body, as well as from the
pedicle, and is directed laterally and a little backwards and upwards. Its upper
surface is slightly grooved by the superior intervertebral notch. A deep notch
separates it posteriorly from the superior articular processes, which are less
in-turned than in the other members of the series, their articular surfaces being
directed more backwards than inwards, and displaying less concavity. The inferior
articular processes are further apart than is the case with the other members of
the series ; they lie in line with the superior. The spinous process is shorter and
narrower than the other lumbar spines, particularly so in the female. The
vertebral canal is somewhat compressed at its lateral angles.
THE FALSE OR FIXED VERTEBRAE.
Os Sacrum.
The sacrum, of roughly triangular shape, is formed normally by the fusion of
five vertebrae. The anterior surface of the bone is slightly hollow from side to side
and concave from above downwards, the curve being usually most pronounced
opposite the third sacral segment. The central part corresponds to the bodies
of the sacral vertebrae, the lines of fusion of which are indicated by a series of
four parallel ridges which cross the median part of the bone at gradually diminish-
ing intervals from above downwards; on each side these ridges disappear on
the medial walls of the four anterior sacral foramina. The size of these holes
decreases from above downwards. The upper and lower border of each foramen
is formed by a stout bar of bone, of which there are five on each side, corre-
sponding in number with the vertebrae present. These unite laterally so as
to form the pars lateralis (O.T. lateral mass), thus enclosing the foramina to the
lateral side, though there the edge is not abrupt, but sloped so as to pass gradually
into the canal. The large anterior rami of the sacral nerves pass through these
foramina and occupy the shallow grooves. The bone is broadest across the first
sacral vertebra, tends to narrow opposite the second, and again usually increases
in width opposite the third. When this condition is well marked, the edge has
a notched appearance (sacral notch) which assists in the interlocking of the sacro-
THE SACKUM.
97
iliac joint ; this feature is common in the Simiidae and some of the lower races
of mankind (Paterson). ,The surface of bone between and lateral to the first,
second, third, and fourth foramina affords attachment to the fibres of origin of
the piriformis, which may in some instances extend on to the bodies of the second
and third segments (Adolphi), whilst on the edge lateral to and below the fourth
foramen the coccygeus is inserted.
The posterior surface is rough and irregular. Convex from above downwards, it
displays in the median plane the crista sacralis media, a crest whereon are seen four
elongated tubercles the spines of the upper four sacral vertebrae. Lateral to these
the bone forms a groove the sacral groove the floor of which is made up of the
confluent laminae of the corresponding vertebrae. In line with the intervals between
the spines, and wider apart above than below, another series of tubercles is to be
Superior articular processes Transverse process of first sacral vertebra
Ala
Anterior sacral
foramen
Inferior lateral angl
Groove for fifth sacral nerve
Coccygeal articular surface
FIG. 112. THE SACRUM (anterior view).
seen. These are due to the fusion of the articular processes of the sacral vertebrae,
which thus form faint interrupted ridges on each side of the bone (cristse sacrales
articulares). Normally, the spine of the lowest sacral segment is absent, and the
laminae do not coalesce medially, thus leaving a gap in which the sacral canal
is exposed (hiatus sacralis) ; whilst inferiorly the tubercles corresponding to the
inferior articular processes of the last sacral vertebra form little down-projecting
processes the sacral cornua by means of which the sacrum is in part united
to the coccyx. Just wide of the articular tubercles are the posterior sacral
foramina, for the transmission of the posterior rami of the sacral nerves.
These are in correspondence with the anterior foramina, so that a probe can be
passed directly through both openings; but be it noted that the posterior are
much smaller, and their margins much sharper, than is the case with the anterior.
The surface of the pars lateralis (lateral mass) lateral to the posterior sacral
foramina is rough and irregular, owing to the presence of four more or less elevated
tubercles, which constitute the lateral ridges on either side of the bone (cristae sacrales
7
98
OSTEOLOGY.
laterales), and which are serially homologous with the true transverse processes
of the lumbar vertebrae. The posterior surface of the bone furnishes an extensive
surface for the origin of the sacro-spinalis, whilst the edge of the bone lateral to
the third and fourth foramen gives attachment to the glutaeus maximus.
The base of the bone displays features more in accordance with a typical
vertebra. Centrally, and in front, is placed the body, the superior surface of which
articulates with the last lumbar vertebra through the medium of an intervertebral
fibro-cartilage. The anterior margin is thin and projecting, overhanging the
general concavity of the pelvic surface of the bone, and forming what is called the
promontory. Posterior to the body, the sacral canal, of triangular form but slightly
compressed dorso-ventrally, is seen, whilst still more posteriorly is the short spinous
Superior aperture of
sacral canal
Superior articular process
Auricular
surface
Articular
process
Spinous process
Transverse process
Posterior sacral foramen
Inferior lateral angle
Inferior aperture of sacral canal
Groove for fifth sacral nerve
Coccygeal articular surface
FIG. 113. THE SACRUM (posterior view).
process, forming the highest tubercle of the median crest. Spreading out from
the sides, and partly from the back of the body on each side, is a fan-shaped mass
of bone, the upper surface of which is slightly concave from side to side, and convex
from above and behind downwards and forwards. This, the ala sacralis, corresponds
to the thick upper border of the lateral part, and is formed, as will be explained
hereafter, by elements which correspond to the roots of the vertebral arches (O.T.
pedicles) and the transverse processes of the sacral vertebrae, together with superadded
structures the sacral ribs. The lateral margin of the lateral part, as seen from above,
is sharp and laterally convex, terminating posteriorly in a prominent tubercle
the highest of the series of elevations seen on the posterior surface of the bone, which
have been already described as serially homologous with the true transverse processes
of the lumbar vertebrae. Fused with the dorsal surface of each lateral part, and
separated from it laterally by a narrow but deep notch, is the superior articular process.
This supports a vertical articular surface, which is of circular or oval form, and con-
cave from side to side, having a general direction backwards and a little medially.
The borders of the sacrum are thick above, where they articulate with the ilia,
THE COCCYX.
99
thin and tapering below, where they furnish attachments for the powerful sacro-
tuberous ligaments (O.T. . great sacro-sciatic). The iliac articular surfaces are
described as auricular in shape (facies auricularis), and overlie the lateral parts
formed by the first three sacral vertebrae, though this arrangement is liable to con-
siderable variation. Posterior to the auricular surface the bone is rough and pitted
by three distinct depressions for the attachment of the strong sacro-iliac ligaments.
Inferiorly, the edge formed by the lateral parts of the fourth and fifth sacral
vertebrae becomes gradually thinner, and at the inferior lateral angle changes its
direction and sweeps medially towards the body of the fifth sacral segment.
The apex, or lower end of the sacrum, is formed by the small oval body of the
fifth sacral vertebra, which articulates with the coccyx.
The sacral canal follows the curve of the bone ; more or less triangular in shape
above, it becomes compressed and flattened dorso-ventrally below. Inferiorly, its
posterior wall is deficient owing to the imperfect ossification of the laminae of the
fifth, and, it may be, of the fourth sacral segments. Passing obliquely downwards
and laterally from this canal into the lateral parts on either side are the four pairs
of intervertebral foramina, each of which is connected laterally with a V-shaped
canal which terminates in front and behind in the anterior and posterior sacral
foramina. The posterior limb of the V is shorter and narrower than the anterior.
The female sacrum is proportionately broader than the male, its curves are
liable to great individual variation ; usually it is flattened above, and somewhat
abruptly curved below, as contrasted with the male sacrum, in which the curve is
more uniformly distributed throughout the bone. In the female the absolute
depth of the curve is less than in the male. The iliac articular surface of the
female sacrum is smaller than, and of a different shape from, that of the male ; in
the majority of cases it only extends over two sacral segments, whereas in the male
it invariably includes a part, and at times the whole of the third segment (Derry).
The variation in the proportions of the breadth to the length of the sacrum is
expressed by the formula
breadth x 100
= Sacral Index. Sacra with an index above
length
100 are platyhieric and are generally characteristic of the higher races, those with
an index below 100 are dolichohieric and are more commonly met with in the lower
races of men. The average European index is 112'4 for males and 116'8 for females.
Os Coccygls.
The coccyx consists of four sometimes five, less frequently three rudimentary
vertebrae, which tend to become fused. The first piece is larger than the others ;
it has an oval hollow
facet on its superior sur-
face, which articulates
with the body of the last
sacral segment. Pos-
teriorly, two processes,
cornua coccygea, which
lie in series with the
articular processes of the
sacrum, extend upwards
and unite with the sacral
cornua, thus bridging
over the notch for the
exit of the fifth sacral
FIG. 114. THE COCCYX.
nerve, and converting
it into a foramen, the A " Posterior Surface ' R Anterior Surface '
last Of the intervertebral L T ' lsverse P rocess - 2 ' Transverse process. 3. For Sacrum. 4. Cornu.
series. From the sides of the body project rudimentary transverse processes, which
may, or may not, unite with the sacrum close to the lower lateral angles ; in the
latter case the fifth anterior sacral foramina are enclosed. Inferiorly, the body of the
bone articulates with the succeeding vertebra. The second coccygeal vertebra displays
100 OSTEOLOGY.
slight traces of a transverse process and the rudiments of roots of the vertebral
arch. The succeeding segments are mere rounded or oval-shaped nodules of bone.
Fusion between the lower elements occurs normally in middle life, whilst union between
the first and second segments occurs somewhat later. It is not unusual, however, to find
that the first coccygeal vertebra remains separate from the others. Though very variable,
as a rule, fusion occurs more commonly in the male, and at an earlier age, than in the
female. Szawlowski has recorded a case in which a curved process arose from the ventral
surface of the first coccygeal segment. He regards this as possibly the homologue of a
ventral arch (Anat. Anz. Jena, vol. xx. p. 320).
From the posterior surface of the coccyx the glutaeus maximus arises, whilst
to it is attached the filum terminate of the spinal medulla. To its borders are
attached the coccygei and levatores ani muscles ; and from its tip spring the
fibres of the sphincter ani externus.
THE VERTEBRAL COLUMN AS A WHOLE.
When all the vertebrae are articulated together, the resulting column displays
certain characteristic features. The division of the column into a true or movable
part, comprising the members of the cervical, thoracic, and lumbar series, and
a false or fixed portion, including the sacrum and coccyx, can be readily
recognised. The vertebrae are so disposed that the bodies form an interrupted
column of solid parts anteriorly, which constitutes the axis of support for the
head and trunk; whilst the vertebral arches posteriorly provide a canal for the
lodgment and protection of the spinal medulla and its membranes. In the movable
part of the column both the anterior supporting axis and the vertebral canal are
liable to changes in their disposition, owing to the movements of the head and
trunk. Like the bodies and vertebral arches, the spinous and transverse processes
are also superposed, and fall in line, forming three series of interrupted ridges
one (the spinous) placed centrally and behind, the others (the transverse) placed
laterally. In this way two vertebral grooves are formed which lie between the
central and lateral ridges. The floor of each groove is formed by the laminae and
articular processes, and in these grooves are lodged many of the muscles which
serve to support and control the movements of the column.
Further, the column so constituted is seen to display certain curves in an
antero- posterior direction. These curves are, of course, subject to very great
variation according to the position of the trunk and head, and can only be satis-
factorily studied in a fresh specimen ; but if care is exercised in the articulation
of the vertebras, the following characteristic features may be observed, assuming, of
course, that the column is erect and the head so placed that the axis of vision is
directed towards the horizon. There is a forward curve in the cervical region,
which gradually merges with the backward thoracic curve ; this becomes con-
tinuous below with an anterior convexity in the lumbar region, which ends more
or less abruptly at the union of the fifth lumbar with the first sacral vertebra,
where the sacrum slopes suddenly backwards, causing the column to form a
marked projection the sacro-vertebral angle. Below this, the anterior concavity of
the front of the sacrum is directed downwards as well as forwards. Of these four
curves, two the thoracic and sacral are primary, they alone exist during foetal
life ; whilst the cervical and lumbar forward curves only make their appearance
after birth the former being associated with the extension and elevation of the
head, whilst the latter is developed in connexion with the use of the hind limb in
the hyper-extended position, which in man is correlated with the assumption of
the erect posture ; this curve, therefore, only appears after the child has begun to
walk. For these reasons the cervical and lumbar curves are described as secondary
and compensatory.
Not infrequently there is a slight lateral curvature in the thoracic region, the
convexity of the curve being usually directed towards the right side. This may
be associated with a greater use of the muscles of the right upper limb, or may
depend on the pressure exercised by the upper part of the thoracic aorta on the
THE VERTEBKAL COLUMN AS A WHOLE.
101
vertebrae of the thoracic region, thus causing a slight lateral displacement, together
with a flattening of the side of the fifth thoracic vertebra (impressio aortica) as was
first pointed out by Wood (Journ. Anat. and Physiol.
vol. iii.). Above and below this curve there are slight
compensatory curves in the opposite direction.
The line which unites the tips of the spinous pro-
cesses is not a repetition of the curves formed by the
bodies. This is due to the fact that the length and
direction of the spinous processes vary much in different
regions ; thus, in the neck, with the exception of the
second, sixth, and seventh, they are all short (absent in
the case of the atlas). In the thoracic region the spinous
processes, though long, are obliquely placed a circum-
stance which much reduces their prominence ; that of
the seventh thoracic vertebra is usually the longest
and most slanting. Below that point their length
gradually decreases, and their position more nearly
approaches the horizontal. In the loins the spinous
processes have all a slight downward direction.
The spinous processes of the -upper three or four
sacral vertebrae form an osseous ridge with interrupted
tubercles. The ridge formed by the vertebral spines
is an important determinant of the surface form, as
it .corresponds to the median furrow of the back,
and there the individual spines may be felt and
counted from the seventh cervical down to the sacral
region. That is best done when the back is well
bent forwards.
Taken as a whole, the spinous processes of the movable
vertebrae in man have a downward inclination a character
which he shares with the anthropoid apes and a few other
animals. This character serves to distinguish his column from
those of lower mammals in which the spines of the lumbar
vertebrae are directed head wards towards the "centre of motion,"
which is usually situated near the caudal extremity of the
thorax, where a vertebra is placed the direction of whose
spine is vertical to the horizontally disposed column ; this
vertebra is often referred to as the anticlinal vertebra.
As viewed from the front, the vertebral bodies
increase in width from the second cervical to the
first thoracic; thence a reduction in breadth takes
place to the level of the fourth thoracic, below which
there is a gradual increase in their transverse dia-
meters until the sacrum is reached. There a rapid
reduction in width takes place, terminating inferiorly
in the nodules of the coccyx.
The transverse processes of the atlas are wide and
outstanding. The succeeding four cervical vertebrae
have transverse processes of nearly equal width ; the
seventh, however, displays a marked increase in its
transverse diameter, and is about equal in width to
the first thoracic vertebra. Below this a gradual and
regular diminution in width characterises the trans-
verse processes of the thoracic vertebrae, until in the
case of the eleventh and twelfth they are merely
represented by the small lateral tubercles. In the
lumbar region the transverse processes again appear outstanding, and of nearly
equal length.
The transverse diameter of the lateral parts of the first sacral vertebra forms
the widest part of the column. Below that, a decrease in width occurs until the
FIG. 115. VERTEBRAL COLUMN
FROM THE LEFT SIDE.
102
OSTEOLOGY.
level of the third sacral segment is reached, at which point the transverse diameter
is somewhat abruptly diminished, a reduction in width which is further suddenly
accentuated opposite the fifth sacral segment.
As viewed from the side, the bodies display a gradual
increase in their antero-posterior extent until the second
lumbar vertebra is reached, below which, that diameter is
slightly reduced. In the sacral region the reduction in
the antero-posterior diameter is great in the first and
second sacral segments, more gradual and less marked in
the last three segments. The facets for the heads of the
ribs in the upper thoracic region lie on the sides of the
bodies ; those for the tenth, eleventh, and twelfth are placed
farther back on the roots of the vertebral arches.
The intervertebral foramina increase in size from above
downwards in the movable part of the column, being largest
in the lumbar region. In the sacral region they decrease
in size from above downwards. In the cervical region the
highest two cervical nerves pass out behind the articular
processes of the atlas and epistropheus, and lie, therefore,
behind the corresponding transverse processes of those
vertebrae. The succeeding cervical nerves pass out through
the intervertebral foramina, which are placed between the
transverse processes and anterior to the articular processes.
In the thoracic and lumbar vertebras the intervertebral
foramina lie anterior to both the articular and transverse
processes. The arrangement of the intervertebral foramina
in the sacrum has been already sufficiently explained.
The vertebral canal for the lodgment of the spinal medulla
and its meninges is largest in the cervical and lumbar
regions, in both of which it assumes a triangular form ;
whilst it is narrow and circular in the thoracic region.
These facts are correlated with the movements of the
column which are most free in those regions where the
canal is largest, i.e. the neck and loins.
The average length of the vertebral column is from 70
to 73 centimetres, or from 27 to 28J inches. Of this the
cervical part measures from 13 to 14 cm. ; the thoracic, 27 to
29 cm.; lumbar, 17 to 18 cm.; and the sacro-coccygeal, 12
to 15 cm. The individual differences in the length of the
column are less than one might expect, the variation in height
of different individuals being often largely dependent on the
length of the lower limbs. In the female the average length
of the column is about 60 centimetres, or 23 J inches, and the
curve in the lumbar region is usually more pronounced.
DEVELOPMENT OF THE VERTEBRAL
COLUMN.
The Cartilaginous Column.
As has been already stated (p. 37), the neural tube
and the notochord are enveloped by a continuous sheath of
mesodermal tissue which forms the membranous vertebral
column. It is by the chondrification of this that the car-
tilaginous column is developed. This process commences
about the end of the first or the beginning of the second
month of foetal life. In correspondence with each vertebral segment, two
symmetrical nodules of cartilage appear on either side of the notochord; these
rapidly surround and constrict it. By their fusion they constitute the body of a
THE CAKTILAGINOUS COLUMN.
103
cartilaginous vertebra, and are so disposed that they alternate in position with the
muscle plates which are lying on either 'side. In this way a vertebral body corre-
sponds in position to the caudal half of the anterior myotome, and the cephalic
half of the posterior myotome, the intermyotomic intervals, which contain the
connective tissue plates separating the muscle segments, lie in line laterally
with the mid -points of the sides of the cartilaginous vertebrae. It is by chondri-
fication of these intersegmental layers that in certain regions the ribs are
ultimately developed. Meanwhile, the scleratogenous tissue between the chondri-
fying vertebral bodies undergoes little change and persists as the intervertebral
fibro-cartilage. Here the embedded notochord undergoes but slight compression and
enlarges, so that if a length of the column be examined in longitudinal section
the notochord displays a moniliform appearance, the constricted parts correspond-
ing to the bodies, the enlarged portions to the fibre-cartilages. The former
disappear at a later stage when ossification begins, but the latter persist in
the adult as the pulpy core in the centre of the intervertebral fibro-cartilage.
The portions of the scleratogenous tissue which lie lateral to the notochord
have next to be considered ; these extend dorsalwards around the vertebral canal,
and ventralwards beneath the notochord. The former is sometimes called the
vertebral bow, the latter the hypochordal bow. The vertebral bow begins to
chondrify on each side, and forms the lateral portions of the cartilaginous vertebral
Vertebral canal
Vertebral bow
Notochord
Sheath
Hypochordal bow
Body of vertebra
Hypochordal
bow
Notochord
^
FIG. 117. THE DEVELOPMENT OF THE MEMBRANOUS BASIS OF A VERTEBRA (after Keith).
A, in transverse section. B, in horizontal section, showing the relation of the vertebrae to the
primitive segments.
arch, the extremities of which usually unite dorsally about the fourth month of
foetal life ; if from defective development this union should fail to occur a
deformity known as spina bifida is the result.
From the cartilaginous vertebral arch, so formed, arise the chondrified rudiments
of the spinous, transverse, and articular processes.
The chondrification of the vertebral arch is variously described as being in-
dependent of the body or an extension from it ; in any case, union between it and
the body is rapidly effected.
The scleratogenous tissue between the cartilaginous vertebral arches which does
not undergo chondrification persists as the ligaments uniting the vertebral laminae.
As regards the so-called hypochordal bow, for the most part it disappears.
By some it is regarded as being represented by a fibrous strand in' the inter-
vertebral fibro-cartilage on the cephalic side of the vertebra to which it
belongs. It is, however, noteworthy that in the case of the atlas vertebra there
is an exception to this arrangement; for here the hypochordal bow chondrifies
and subsequently by ossification forms the anterior arch of that bone an arch
which lies ventral to, and embraces the dens of the epistropheus (q.v. p. 91).
It is only in the thoracic region that the ribs, developed as stated above by the
chondrification of the intersegmental septa, attain their full dimensions. In the
cervical, lumbar, and sacral regions they exist only in a rudimentary or modified
form, as has been described elsewhere. In the construction of the chest wall the ribs
are supported ventrally by the sternum, as to the development of which there is some
difference of opinion. Euge has described this bone as formed by the fusion of two
cartilaginous bands produced by the coalescence of the expanded ends of the first five
104 OSTEOLOGY.
or seven cartilaginous ribs. Paterson, on the other hand, regards the sternum as
arising independently of the ribs by the union of a right and left sternal bar in the
median ventral line. There are also reasons for supposing that the presternum is
intimately associated with the development of the ventral part of the shoulder girdle.
Ossification of the Vertebrae. The vertebrae are developed by ossification of
the cartilage which surrounds the notochord and which passes dorsally over the sides of
the vertebral canal. The centres for the bodies first appear in the lower thoracic vertebrae
about the tenth week. An oval nucleus develops in each body. At first it is placed
dorsal to the notochord, but subsequently surrounds and causes the disappearance of
that structure. Occasionally, however, the primitive centre appears to be formed by
the coalescence of two primary nuclei. Support is given to this view by the occasional
occurrence of vertebrae in which the body is developed in two collateral halves, or in cases
where only one-half of the body persists (Turner) ; normally, however, it is impossible to
make out this division. From these single nuclei the bodies are developed, the process
extending up and down the column until, by the fifth month, all the bodies possess ossific
nodules, except the coccygeal segments. About the seventh week a single centre appears in
the vertebral arch on either side. These commence first to ossify in the upper cervical region
and extend rapidly downwards throughout the column. They first appear near the bases
of the superior articular processes, and extend backwards into the laminae, laterally into
the transverse processes, and forwards into the roots of the vertebral
Centre arches. These latter project anteriorly and form a considerable portion
. for of the postero-lateral aspects of the body, from which, however, they
" are separated by a cartilaginous strip the neuro-central synchondrosis
which does not entirely disappear until about the fifth or sixth year.
It is important to note that in the thoracic region the costal facets lie
sntre for behind the neuro-central synchondrosis, and are therefore borne on the
body lateral aspects of the roots of the vertebral arches. Fusion of the
laminae in the median plane posteriorly begins, after birth, in the lumbar
FIG. 118. OSSIFICATION . -, r , , , 7 , ',. .
OF VERTEBRAE region and extends upwards, so that by the mteentn month or there-
abouts the arches in the cervical region are completed posteriorly. In
the sacral region ossification is slower, the vertebral canal not being enclosed till the
seventh to the tenth year. The spinous processes are cartilaginous at birth, but they
become ossified by the extension into them of the bony laminae.
At puberty certain secondary or epiphyseal centres make their appearance ; these are
five in number. One caps the summit of the spinous process, except in the cervical
region. A single- centre on each side appears at the extremity of the transverse
process, and in the thoracic region assists in forming the articular surface for the tubercle
of the rib. Two epiphysial plates are formed one for the superior, and the second for the
inferior surface of the body, including also that part which lies posterior to the neuro-central
synchondrosis and is formed by the root of the vertebral arch ; from these the thickened
circumference of both upper and lower aspects of the body are derived. Fusion of these
centres with the rest of the bone is not complete till the twenty -fifth year.
In the cervical region independent centres are described as occurring in the anterior
roots of the transverse processes of the sixth and seventh vertebrae. These correspond to
the costal element, and may occasionally persist in the form of cervical ribs. Elsewhere
they are formed by lateral extensions from the root of the vertebral arch.
In the lumbar region the transverse process of the first lumbar vertebra is occasionally
associated with an independent costal centre, which may blend with it, or persist as a
lumbar rib. The mamillary processes are derived from separate centres. The vertebral
arch of the fifth lumbar vertebra is occasionally developed from two centres on each side,
as is demonstrated by the fact that the arch is sometimes divided by a synchondrodial
joint running obliquely across between the superior and inferior articular processes.
(See ante, p. 91; also Fortschritte auf dem Gebiete der Rontgenstrahlen. Erganzungsheft i. ;
"die Entwickelung des menschlichen Knochengerustes wahrend des fotalen Lebens,"
von Lambertz.) At the eighteenth year there are two epiphyses at the end of the costo-
transverse process of the fifth lumbar vertebra ; one caps the transverse element, the other
caps the costal element (Fawcett).
Atlas. The lateral masses, transverse processes, and posterior arch are developed
from two centres one on each side which correspond with the centres from which the
vertebral arches of the other members of the series are developed. These make their
appearance about the seventh week, and do not unite posteriorly till after the third
year. Their point of union is sometimes preceded by the formation of a distinct spinal
OSSIFICATION OF THE VEETEBE^E.
105
nucleus (Quain). The transverse processes are completed by epiphyses about the eight-
eenth year (Fawcett). The, anterior arch is developed from centres variously described
as single or double, which appear in the hypochordal arch of cartilage described by
Froriep (Arch. f. Anat. u. Physiol., Anat. Abth. 1886) which here persists. In this
cartilage ossification commences during the first year of life. Union with the lateral
masses is delayed till six or eight years after birth. The lateral extremities of the
anterior arch assist in forming the anterior part of the superior articular processes.
Epistropheus. The epistropheus ossifies from five primitive centres. Of these, two
one on each side appear about the seventh week, and form the articular and transverse
processes, together with the laminae and spinous process. One, or it may be two, nuclei
appear in the inferior part of the body about the fifth month. The superior part of the
body, including a small part of the superior articular process, and the base of the dens,
19
Cervical vertebra.
1. Centre for body.
2. Superior epiphysial plate.
3. Anterior bar of transverse process developed by
lateral extension from root of vertebral arch.
4. Neuro-central synchondrosis.
5. Inferior epiphysial plate.
Lumbar vertebra.
6. Body.
7. Superior epiphysial plate.
8. Epiphysis for mamillary process.
9. Epiphysis for transverse process.
10. Epiphysis for spinous process.
11. Neuro-central synchondrosis.
12. Inferior epiphysial plate.
Tlwracic vertebra.
13. Centre for body.
14. Superior epiphysial plate, appears about puberty ;
unites at 25th year.
15. .Neuro-central synchondrosis does not ossify till
5th or 6th year.
16. Appears at puberty ; unites at 25th year.
17. Appears at puberty ; unites at 25th year.
18. Appears about 6th week.
Epistropheus.
19. Centre for transverse process and vertebral arch ;
appears about 8th week.
20. Synchondroses close about 3rd year.
27 SI
FIG. 119. OSSIFICATION OF VERTEBRA.
21. Centre for summit of dens ; appears 3rd to 5th
year, fuses 8th to 12th year.
22. Appears about 5th or 6th month ; unites with
opposite side 7th to 8th month.
23. Synchondrosis closes from 4th to 6th year.
24. Inferior epiphysial plate ; appears about puberty,
iinites about 25th year.
25. Single or double centre for body ; appears about
5th month.
Atlas.
26. Posterior arch and lateral masses developed from
a single centre on either side, which appears
about 7th week. In this figure the posterior
arch is represented complete by the union
posteriorly of its posterior elements.
27. Anterior arch and portion of superior articular
surface developed from single or double centre,
appearing during 1st year.
Thoracic vertebra.
28. Epiphysis for transverse process ; appears about
puberty, unites about 25th year.
29. Epiphysis appears about puberty ; unites about
25th or 27th year.
30. Centre for vertebral arch on either side ; appears
about 6th or 7th week, the laminae unite from
birth to 15th month. The arch is here shown
complete posteriorly.
31. Centre for body ; appears about 6th week, unites
with vertebral arch from 5th to 6th year.
are developed from two laterally-placed nuclei which appear shortly after, and fuse together
at the seventh or eighth month, so that at birth the bone consists of four pieces. Fusion
between these parts takes' place in the following order : The dens unites with the body
and lateral parts about the third or fourth year ; union between the two lateral portions
posteriorly and- the body and lateral parts anteriorly, is complete at from four to six years.
The summit of the dens is developed from a separate centre, occasionally double,
which appears from the third to the fifth year, and fuses with the rest of the bone from
the eighth to the twelfth year. About puberty an annular epiphysis is developed on the
inferior surface of the body, with which it is completely united during the twentieth to
the twenty-fifth year. Some authorities state that a few granules between the base of the
dens and the superior surface of the body represent the superior epiphysial plate ; but
106
OSTEOLOGY.
as fusion between the dens and the body occurs before the time for the appearance of
these secondary epiphysial plates, this can hardly be regarded as correct. The line of
fusion of the dens with the body is denned by a small disc of cartilage which persists
within the substance of the bone till an advanced period of life.
A pair of epiphyses placed over the tubercles of the spinous process, if not always
present, are at least frequent.
Sacrum. Each of the sacral segments is ossified from three centres : one for the
body, and two for the vertebral arch that for the body, which makes its appearance in the
first three sacral vertebrae about the end of the third month, about the fifth to the
eighth month for the last two segments. From the two centres for the vertebral arches,
which make their appearance about the fifth or sixth month in the higher segments,
the laminae, articular processes, and the posterior half of the alee on either side are
developed. The sacral canal is not enclosed till the seventh to the tenth year, the
laminae usually failing to meet in the lowest segment, and occasionally, to a greater or
less extent, in some of the higher segments. The anterior portion of the lateral parts is
developed from separate centres which represent the costal elements (Gegenbauer). These
appear about the sixth to the eighth month, and may develop in relation to the upper
four sacral segments ; more usually they are met with in connexion with the first three,
and exceptionally they may be found only in the upper two. It is by fusion of these
with the posterior arches that the lateral parts,
which support the hip bones, are formed. The
costal elements fuse about the second to the fifth
year with the vertebral arches, prior to their
union with the bodies ; and the segments of the
lateral parts unite with each other sooner than
the union of the bodies is effected. The latter
only takes place after puberty by the fusion of
the epiphysial plates, a pair of which make their
appearance between the bodies of each segment.
The lower segments begin to unite together about
the eighteenth year, but fusion between the first
and second sacral vertebra is r* ,r? leted ^
VERSE EPIPHYSES AT THE EIGHTEENTH the twenty-fifth year or after. In addition to the
YEAR. foregoing there are costal and transverse epi-
physes. According to Fawcett they are arranged
as follows. Costal epiphyses : The costal pro-
cesses of the I. and II. sacral segments bear at their
--T.I
T., Epiphysis of transverse process.
C.V., Ventral epiphysis of costal process.
C.D., Dorsal epiphysis.
The numbers indicate the segments to which lateral d inferiorly two such epiphyses, one
the epiphyses belong. , J , ,, , J , . . .
dorsal and one ventral ; these, by their fusion
and expansion mainly in an upward direction, form a plate the auricular facet. The
III. and IV. costal processes have only one epiphysis each, viz., the ventral. All these
appear about the eighteenth year. Transverse epiphyses : Epiphyses are developed on all
the transverse processes of the sacral vertebrae except the II. Those of the IV. and V.
play an important part in the moulding of the lower lateral region of the sacrum. Thus, the
transverse epiphysis of the IV. segment becomes comma-shaped by downward and lateral
growth, the head of the comma fuses with the costal epiphvsis of the III. sacral segment,
which in turn unites with the epiphysis of the transverse process of the V. segment,
the ultimate result being a Z-like arrangement on the posterior and inferior aspect of the
sacrum. The extremities of the superior spinous processes are occasionally developed from
independent epiphyses. On making a median section of an adult bone the persistence of
the intervertebral fibro-cartilages between the bodies is indicated by a series of oval cavities.
Coccygeal Vertebrae. These are cartilaginous at birth. Each has a separate
centre ; the first appears from the first to the fourth year, the second from the sixth to
the tenth year, the third and fourth segments at or about puberty. Secondary centres,
for the coccygeal cornua and epiphysial plates for the bodies are also described. Fusion
of the various segments begins below and proceeds upwards, but is liable to great indi-
vidual variation. In advanced life the coccyx is often ossified to the sacrum.
THE STERNUM.
The sternum occupies the middle of the upper part of the thoracic wall
anteriorly. It is connected on each side with the cartilages of the first seven ribs,
and supports, superiorly, the clavicles. It consists of three parts, named respectively
THE STEKNUM.
107
Incisura jugularis
Clavicular facet
III. Rib cartilag
the manubrium or handle ; the corpus sterni or body ; and the processus xiphoideus
(or xiphoid cartilage). Of 'these the body is formed by the fusion in early life
of four segments or sternebrse.
The manubrium or superior part, usually separate throughout life from the
rest of the bone, though occasionally fused with it, is of a flattened triangular
form. The anterior surface, slightly saddle -shaped, affords attachment to the
fibres of the pectoralis major and sterno-mastoid muscles. It is bounded above by
a thick border, the lateral parts of which are hollowed out obliquely to form the
facets (incisurse claviculares) for the sternal ends of the clavicles ; around the
facets, which have an upward, lateral,
and slightly backward direction, the bone
is faintly lipped. In the interval be-
tween these two facets there is a slight
notch (incisura jugularis) which forms the
floor of the characteristic hollow seen
at the root of the neck anteriorly the
supra - sternal notch. The borders are
excavated immediately below the clavi-
cular facets for the reception of the
cartilages of the first ribs. Below this,
the margin of the bone slopes medially,
and is sharp, except inferiorly, where it
presents a facet which supports a part of
the second costal cartilage. Around this
the bone is usually lipped anteriorly. The
upper angles correspond to the ridge
separating the clavicular facets from the
first costal facets : whilst the lower angle,
which may be regarded as cut across trans-
versely, forms the surface which is united
by cartilage to the body of the sternum.
The anterior edge of this surface is usually
prominent. The posterior aspect of the
manubrium is smoother than the anterior,
is pierced by numerous foramina, and IV - Rib cartila e
is slightly concave from side to side and
above downwards. Here are attached
some of the fibres of the sterno-hyoid and
sterno-thyreoid muscles.
The body or middle part of the
sternum, usually twice the length and
from half to two- thirds the width of
the manubrium, displays evidence of its VI . Rib cartilage
composite nature. If the planum sternale,
(anterior surface) which is slightly convex
from above downwards, and faintly con-
cave from side to side, is carefully ex-
amined, three ill-marked ridges may be
seen crossing it transversely ; these corre-
spond to the lines of fusion between the
four primitive segments. To this surface
of the bone the great pectoral muscles are
extensively attached on either .side of the
median plane. The borders are thick and interrupted at points corresponding
to the transverse lines already mentioned by U-shaped hollows, the edges of which
are more or less projecting. These are for the reception of the cartilages of the third,
fourth, and fifth ribs. The superior border is united to the manubrium above, and
forms with it an angle of variable degree the angulus sterni (sternal angle).
A small facet is formed at the expense of the lateral extremity oft this
V. Rib cartilage
VII. Rib cartilag
Processus xiphoideus
FIG. 121. THE STERNUM (anterior view).
108
OSTEOLOGY.
border, and in conjunction with the facet on the inferior edge of the manubrium
forms a recess on either side, in line with the articulation between the manubrium
and body, into which the cartilage of the second rib fits. The inferior border of the
body is curved, and is united in the middle line with the xiphoid process, whilst on
either side it is pitted to receive the cartilages of the sixth and seventh ribs, the
latter being in part supported by the xiphoid process. The middle line of the body
of the sternum anteriorly corresponds to the floor of the medial surface furrow, which
runs down the front of the chest in the interval between the two great pectoral
muscles. The posterior surface is slightly concave from above downwards, and
displays faint indications of three transverse lines in correspondence with those
placed anteriorly. It is in relation with the pleura and pericardium, and affords
attachment at its inferior extremity, on each side, to a transversus thoracis muscle.
The xiphoid process displays many varieties of form and structure. It
is a pointed process of cartilage, supported by a core of bone connected above
with the inferior end of the body of the sternum, and having its lower extremity,
to which the linea alba is attached, free, tt lies somewhat posterior to the plane
of the anterior surface of the manubrium, and forms a floor to the V-shaped
interval between the cartilages of the seventh ribs. In this way a depression is
formed, the surface hollow in correspondence with which is called the pit of the
stomach or infrasternal depression. To the sides of this process are attached the
aponeuroses of the abdominal muscles, whilst posteriorly the fibres of the diaphragm
and transversus thoracis muscles derive attachment from it. It remains partly
cartilaginous until middle life, at which time it generally undergoes ossification,
particularly at its upper part, becoming fused with the body. Of varied form,
it may be met with of spatula -shape, bifid, circular, pierced in the centre, or
twisted and deflected to one or other side, or turned forward.
The sternum as a whole is broadest above, where the first rib cartilages are
attached. It becomes narrow opposite the second rib cartilages, but again expands
until the level of the fifth rib cartilage is reached, below which it is rapidly
reduced in width and ends
below in the pointed xiphoid
process. Its position in the
body is oblique from above
downwards and forwards; its
axis, if prolonged upwards,
would touch the vertebral
column opposite the third
or fourth cervical vertebra.
Though liable to changes in
position by the rising and fall-
ing of the chest wall, its upper
extremity corresponds to the
level of the lower border of the
second thoracic vertebra, whilst
the lower end of the xiphoid
process usually falls in line
with the fibro - cartilage be-
tween the tenth and eleventh
thoracic vertebrae.
At birth.
At 3 years.
FIG. 122. OSSIFICATION OP THE STERNUM.
In this figure the second as well as the third segment of the body
possesses two centres.
1. Appears about 5th or 6th month. 2. Appear about 7th month ;
unite from 20 to 25. 3. Appear about 8th or 9th month ; third seg-
ment unites with second about puberty ; fourth segment unites with
third in early childhood. 4. Appears about 3rd year or later.
In women the sternum as a whole
is usually narrower and shorter than
in men, and its position less oblique.
On the other hand, Paterson has
shown that the male manubrium is
proportionately wider and shorter
than the female, whilst the male body is proportionately longer and narrower than the female.
Ossification. The cartilaginous sternum, developed from the fusion, in the median
plane, of two cartilaginous bands uniting the anterior extremities of the cartilages of the
first eight ribs, according to the researches of Ruge and more recently of Eggeling, begins
THE RIBS 109
to ossify about the sixth month of foetal life. About this time a single centre appears
in the manubrium; at birth this is well developed. Two centres placed vertically
have also been recorded. Secondary epiphyses have been described in connexion with
the clavicular facets ; these do not unite with the rest of the manubrium till adult life
is reached. The body, formed by the fusion of four segments, is ossified from independent
centres, either single or double, for each segment. These appear the highest as early as
the sixth month of intrauterine life in some cases even before the manubrium has begun
to ossify (Lambertz), the lowest towards the end of full term. The common arrange-
ment met with at birth is a single centre for the first, and double centres for each
of the succeeding segments. Union between these segments occurs rather irregu-
larly, and is liable to much variation. The fourth unites with the third segment in
early childhood, the third with the second about puberty, whilst the fusion of the second
with the first segment may not be complete till the twentieth or twenty-fifth year.
The xiphoid process usually ossifies from a single centre, which may appear as early as
the third year, though often very much later. The xiphoid process usually unites with the
body about forty or fifty, and in exceptional cases osseous union between the body and
manubrium may occur in advanced life.
According to Paterson the manubrium or presternum is developed in association with
the shoulder girdle and becomes only secondarily associated with the ventrally growing ribs.
COSTJE RIBS.
The ribs, of which there are twelve pairs, form a series of curved osseous
bands which support the thoracic wall; posteriorly they articulate with the
thoracic vertebrae; anteriorly, each rib is provided with a costal cartilage. The
first seven ribs articulate with the sternum by means of their cartilages, and
are termed the costse verse, true or vertebro-sternal ribs. The lower five ribs are
not so supported, and are described as the costse spurise (false ribs). Of these the
eighth, ninth, and tenth are united by their cartilages to the cartilage of the
seventh rib, and are called the vertebro-chondral ribs, whilst the last two ribs are
free at their anterior extremities, and are named the floating or vertebral ribs.
A typical rib consists of a capitulum costse (head), a collum costse (neck), a
tuberculum costse (tubercle), and a corpus costse (shaft), on which, near its posterior
end, is the angulus costse (angle).
The head, placed on the posterior or vertebral end of the bone, is somewhat
expanded. Medially, its articular surface is wedge-shaped and divided into two
parts, a superior and inferior, by a ridge or crest (crista capituli), to which the inter-
articular ligament of the head of the rib is attached. Of these two facets the
inferior is usually the larger, and articulates with the superior facet on the body
of the vertebra in numerical correspondence with it, whilst the superior facet is for
the corresponding area on the inferior part of the body of the vertebra above.
The head is supported by a more or less constricted bar of bone, the neck, which
lies anterior to the transverse process of the lower of the two vertebrae with which
the rib articulates, and thus assists in the formation of the costo-transverse cleft.
The neck is continuous with the shaft laterally, at which point there is a well-marked
tubercle on its posterior surface. The anterior surface of the neck is smooth ; its
posterior aspect is rough, and pierced by numerous small holes for vessels. Here is
attached the ligament of the neck of the rib. Not uncommonly the superior border
of the neck is lipped and ridged (crista colli costse), especially in the case of the sixth,
seventh, and eighth ribs, and affords attachment to the anterior and posterior costo-
transverse ligament. The inferior border is continuous with the costal groove laterally.
The tubercle consists of an articular and a non-articular part ; the former is
medial and inferior to the latter. Its articular surface, of rounded or oval shape,
is directed downwards, posteriorly, and a little medially, and rests upon a facet on the
transverse process of the vertebra in numerical correspondence with the rib. The
non-articular part, most prominent in the upper ribs, has the fibres of the ligament
of the tubercle of the rib attached to it. It is usually separated from the superior
border of the neck and shaft by a groove, in which lies the lateral division of the
posterior ramus of a thoracic nerve.
The body is thin, flattened, and band-like. Its length varies much ;
110
OSTEOLOGY.
Head Neck
Tubercle
Angle
Articular part
of tubercle
-Costal groove
the seventh and eighth, which are usually the longest, are from two and
a half to three times the length of the first and twelfth ribs respectively. The
bodies are curved so as to adapt them to the form of the thoracic wall. More acute
in the upper members of the series, where the shafts are shorter, the curve opens
out in the middle and lower parts of the thorax, where the diameters of that cavity
are greater. The curve, however, is not uniform. Including the whole length of
the bone, it will be seen to be most accentuated towards the posterior part, where,
in correspondence with the point at which the bend is most pronounced, there
is a rough ridge placed obliquely across the outer surface of the shaft for the
attachment of the
slips of the ilio-cos-
talis muscle ; this
bend is the angulus
costse. The distance
between the angle
and the tubercle is
greatest on the eighth
rib ; above that, the
width between these two points gradually decreases until, in
the case of the first rib, the two coincide. Below the level
of the eighth rib the distance slightly diminishes in con-
formity with the general narrowing of the thorax below
that level. Towards the anterior extremity of the rib
where the digitations of the serratus anterior and external
oblique muscles are attached to its outer surface the curve
of the body is somewhat more pronounced, and is referred
to as the anterior angle.
Combined with the curve, there is in many of the ribs
a twist. This may best be understood if the student will
take a strip of stiff paper and bend it in the form of the
curve of the rib. If, after he has done this, he pulls down
the anterior end and turns up the posterior end of the strip,
he will have imparted to the strip of paper a twist similar
to that met with in the rib. This appearance is best
seen in the middle members of the series, notably in the
seventh and eighth ribs, above and below which it gradually
becomes less marked. It is the occurrence of this twist
which prevents the extremities of the ribs, together with
the body, from resting on the same plane surface. To this
rule there are certain notable exceptions, viz., the first and
second, the twelfth, and not infrequently the eleventh.
The body has two surfaces, internal and external,
and two borders, a superior and an inferior. The external
surface, which is smooth, conforms to the general vertical
convexity of the thorax, being directed upwards in the
first rib, upwards and outwards in the higher ribs, out-
wards in the middle series, and outwards and slightly down-
wards in the tenth, eleventh, and twelfth. The internal sur-
faces are arranged conversely and are covered with the parietal
pleura. Towards the sternal end of the middle ribs, at the
anterior angle where the downward twist is most marked,
there is often an oblique line across the outer surface.
The upper border of the body is thick and rounded be-
hind, thinner and sharper in front; to it are attached the
fibres of the internal and external intercostal muscles.
The lower border is grooved behind at the expense of the inner surface, and is
overhung laterally by a sharp margin. Anteriorly this sulcus costalis (costal groove)
fades away, and its lips coalesce to form a rounded edge. The intercostal vessels
and nerve are lodged in this groove, whilst its lips afford attachment to the
Nutrient foramen.
Shaft
i
For costal cartilage
THE KIBS.
Ill
Facets on head
Neck
Nori -articular
part of tubercle
Articular part of tubercle
for transverse process of
vertebra
Angle
external and internal intercostal muscles respectively. On the floor of the groove
may also be seen the openings of the canals for the transmission of the nutrient
vessels, which are directed towards the vertebral end of the rib.
The anterior or sternal extremity of the body, often slightly enlarged, displays
an elongated oval pit into which the costal cartilage is sunk.
Peculiar Ribs. The first, second, tenth, eleventh, and twelfth ribs all display
characters by which they can be readily recognised.
The first rib can be easily
distinguished from the others
by its size, curvature, and
flattened form, as well as by
the great proportionate width
of its body. The head,
which is of small size, has a
single oval or circular facet,
which is directed medially
and slightly backwards for
articulation with the side of
the body of the first thoracic
vertebra. The neck is flat- FIG. 124. FIFTH RIGHT RIB AS SEEN FROM BEHIND.
tened from above downwards,
and is slightly down-turned towards the end which supports the head. Its anterior
border is rounded and smooth; its posterior edge rough for the attachment of
ligaments. At the point where the neck joins the body posteriorly, a prominent
tubercle curves upwards and backwards. The inner and lower surface of this
process has a small circular facet which
rests on a corresponding articular sur-
face on the transverse process of the
first thoracic vertebra. The angle coin-
cides with the tubercle, and thus assists
in emphasising its prominence. The
surfaces of the body of the rib are
directed upwards and downwards, its
borders inwards and outwards. If the
finger is run along the thin inner
border, a distinct spine or tubercle can
be readily felt about an inch or an inch
and a quarter from its anterior ex-
tremity. This is the tuberculum scaleni
(scalene tubercle of Lisfranc), which also
forms an elevation on the upper sur-
face of the shaft and affords an attach-
ment for the scalenus anterior muscle.
There is a shallow, oblique groove
crossing the superior surface of the
shaft in front of this, for the lodgment
of the subclavian vein ; whilst behind
the tubercle there is another groove,
usually better marked and passing
obliquely forwards, for the subclavian
artery (sulcus subclavise). In this
groove, behind and below the artery, is
lodged that part of the first thoracic
nerve which contributes to the forma-
tion of the brachial plexus. According
to Wood Jones the development of the groove depends upon the size of the nerve
passing over it. The space on the upper surface of the rib between this latter
groove and the tubercle posteriorly is somewhat rough, and affords attachment to
ithe fibres of the scalenus medius muscle. In manyjspecirnens these features are
FIG. 125. FIRST AND SECOND RIGHT RIBS AS SEEN
FROM ABOVE.
112
OSTEOLOGY.
but faintly marked. The anterior extremity of the rib is thickened and often ex-
panded for the reception of its costal cartilage, which is not infrequently ossified.
Here, on the upper surface, are attached the cos to-clavicular ligament and the sub-
clavius muscle. The inferior surface of the rib is smooth and is covered with
pleura. The outer convex border, thin in front, is usually thick and rough behind
the subclavian groove, where it has attached to it the fibres of the first digitation of
the serratus anterior. Along this edge, also, are attached the external and internal
intercostal muscles of the first intercostal space. The inner concave border is
thin, and has connected with it the aponeurotic expansion known as Sibson's fascia.
The second rib may be distinguished by the sharpness of its curve ; the absence
of any twist on its body, so that it can be laid flat on the table ; the oblique direction
of the surfaces of its body, the outer being directed upwards and outwards, whilst
the inner is turned downwards and inwards ; and the presence of a well-marked,
rough, oval area about the middle of its external surface and lower border for part of
the first, and the whole of the second digitation of the serratus anterior muscle.
The head has two facets, and the angle is close to the tubercle posteriorly.
The tenth rib has usually only a single articular facet on the head, and may or
may not have a facet on the tubercle.
The eleventh and twelfth ribs are recognised by their length. The head of
each is usually large in proportion to the body; it supports a single facet for
articulation with the eleventh or twelfth thoracic vertebrae. The tubercles are ill-
developed and have no articular facets. The angle is faintly marked on the
eleventh, scarcely per-
ceptible on the twelfth.
The anterior extremities
of both are narrow and
pointed and tipped with
cartilage. The costal
groove is absent in the
twelfth, and but slightly
seen in the eleventh.
The twelfth is consider-
ably shorter than the
eleventh rib.
Ossification. Os-
sification begins in the
cartilaginous ribs about
the sixth week, and rapidly
extends along the body, so
that by the end of the
third month it has reached
the permanent costal car-
tilage. The sixth and
seventh ribs are the earli-
est to ossify ; the first
rib being the last (Lam-
bertz). At puberty, or
before, secondary centres
appear. One for the head.
In the first rib there is one
epiphysis for the tubercle.
In the second to the sixth
ribs inclusive there are
two epiphyses for the
tubercle, one for the ar-
ticular part and one for
the non-articular part. In the remaining ribs which have articular tubercles there is only
one epiphysis (Fawcett). By the twenty-fifth year fusion between the epiphyses and the
body is complete.
FIG. 126. THE THORAX AS SEEN FROM THE FRONT.
THE THOKAX AS A WHOLE.
113
THE; COSTAL CARTILAGES.
The costal cartilages, of which there are twelve pairs, are bars of hyaline cartilage
united to the anterior extremities of the ribs, into which they are recessed and held in
position by the periosteum. Through these cartilages the first seven ribs are con-
nected directly with the sternum by means of synovial joints corresponding to the
notches along the margins of the breast bone. To this there is an exception in the
case of the first rib, the cartilage of which is directly blended with the manubrium
sterni. The eighth, ninth, and tenth are connected indirectly with the sternum
by their union with each other, and their articulation, through the medium of
the eighth, with the seventh rib cartilage, whilst the eleventh and twelfth
cartilages tip the ribs to which they belong, and lie free in the muscles cf the
flank. The costal cartilages increase in length from the first to the seventh,
below which they become shorter. The first inclines obliquely downwards and
medially to unite with the superior angle of the manubrium. The second lies more
or less horizontally. The third to the seventh gradually become more and more
curved, inclining downwards from the extremities of their respective ribs, and then
turning upwards to reach the sternum. The tenth cartilage articulates by means of
a synovial joint with the
ninth, the ninth with the
eighth, and the eighth with
the seventh. There are also
surfaces for the articulation of
the seventh with the sixth,
and sometimes for the sixth
with the fifth.
THE THORAX AS A
WHOLE.
The bony and cartilaginous
thorax is barrel-shaped, being
narrower above than below,
and compressed from before
backwards. Its posterior wall
is longer than its anterior, and
its transverse width, which
reaches its maximum opposite
the eighth or ninth rib, is
much in excess of its sagittal
diameter. This is largely
owing to the forward projec-
tion of the thoracic part of
the vertebral column into the
thoracic cavity.
The anterior wall is
formed by the ribs and rib
cartilages, together with the
sternum. The posterior wall
comprises the thoracic part of
the vertebral column and the
ribs as far as their angles.
Owing to the posterior curve
of the ribs, and the projection
forwards of the vertebral
bodies, the antero- posterior
diameter of the thoracic cavity is considerably greater on each side of the median
plane than in the median plane, thus allowing for the lodgment of the rounded
8
FIG. 127. THE THORAX AS SEEN FROM THE RIGHT SIDE.
114 OSTEOLOGY.
posterior parts of the lungs. For the same reason the furrow on each side of
the spinous processes of the thoracic vertebrae is converted into a broad groove
(vertebral groove), the floor of which is in part formed by the ribs as far as their
angles. The grooves so formed are each occupied by the fleshy mass of the sacro-
spinalis muscle.
The side walls are formed by the costal arches. The ribs, which run
obliquely from above downwards and forwards, do not lie parallel to each other,
but spread somewhat, so that the intervals between them (intercostal spaces) are
wider in front than behind.
The superior aperture or inlet, formed by the body of the first thoracic vertebra
behind, the arch of the first rib on either side, and the upper border of the
manubrium sterni in front, is contracted and of reniform shape, measuring on an
average from 10 to 12 cm. transversely and 5 cm. in an antero-posterior direction.
The plane of the inlet is oblique from behind downwards and forwards, so that in
expiration the superior border of the sternum lies on a level with the fibro-cartilage
between the second and third thoracic vertebrae.
The inferior aperture, of large size, is bounded in the median plane behind by the
twelfth thoracic vertebra ; passing thence the twelfth ribs slope laterally, downwards
and forwards. A line carried horizontally forwards from the tip of the twelfth rib
touches the end of the eleventh rib, and then curving slightly upwards reaches
the cartilage of the tenth rib. Thence it follows the confluent margins of the
cartilages of the tenth, ninth, eighth, and seventh ribs, finally reaching the xiphoid
process, where it forms, with the costal margin of the opposite side, the infrasternal
angle, the summit of which coincides with the xiphi-sternal articulation ; in
expiration this joint usually lies on a level with the intervertebral fibro-cartilage
between the ninth and tenth thoracic vertebrae, and corresponds with the surface
depression familiarly known as the pit of the stomach. The inferior aperture of
the thorax is occupied by the vault of the diaphragm.
In the foetal condition the form of the thorax differs from that of the adult. It is
compressed from side to side in this respect resembling the simian type. Its antero-
posterior diameter is relatively greater than in the adult. At birth, changes in form take
place dependent on the expansion of the lungs ; during subsequent growth, the further
expansion of the thoracic cavity in a transverse direction is correlated with the assumption
of the erect posture, and the use of the fore-limbs as prehensile organs.
Sexual Differences. The thorax of the female is usually described as being pro-
portionately shorter and rounder than the male. It also tends to narrowness in the
lower segment. It is hardly necessary to point out that the natural form is often
modified by the use of tight or ill-fitting corsets.
mi TM- T j Transverse diameter x 100 , > ,, , -, . ,, . ,.
The Thoracic Index = taken at the level of the junction
Antero-posterior diameter
of the xiphoid process with the body expresses the proportions of these diameters. That
of the female is on an average lower than the male, indicating a more rounded form.
THE SKULL.
(In view of the vast amount of accurate knowledge the medical student is now called upon to
acquire, it is, in the opinion of the writer of this article, desirable that less stress should be laid
upon the details of the disarticulated bones of the skull and more emphasis placed on the study
of the skull as a whole.
It has hitherto been the custom to disarticulate the bones of the skull, imposing on the
student the task of again reconstructing it, much after the manner of a Chinese puzzle. In this
way a minute acquaintance with, the forms and articulations of the individual bones became
necessary, and the student's memory was burdened with a mass of detail of little or no practical
or scientific value, for in regard to the latter aspect of the subject the points of phylogenetic and
ontogenetic interest are best illustrated by a consideration of the details of the evolution of the
skull and the development and ossification of its parts. With possibly the exception of the
temporal bones and the mandible, the author holds that most of the useful information relating
to the skull can best be studied in the complete cranium, or in sections of it made in different
planes. By this method the student acquires a more intimate knowledge of its structure and
topography, and is consequently better equipped to deal with the regions he may have to explore
in the living.
THE FRONTAL BONE. 115
With this object in view, the writer of this article has given more space to the description of
the skull as a whole and in section than is usually the case. Such a plan has doubtless given
rise to some repetition ; at the' same time it renders more complete, and, it is hoped, also more
useful from a practical standpoint, the account supplied.
It must, however, be borne in mind that a text-book of Anatomy serves the double purpose
of a " Manual " of instruction and a work of reference. In view of this, the author has furnished
a detailed account of the disarticulated cranial bones, such as has been hitherto supplied in works
of a like kind.
The student, however, must not assume on this account that this section of the article should
be neglected. He will find most of the more important details described in the article on the
skull as a whole ; but he would do well to supplement his knowledge by a reference to the more
detailed account for information regarding the development, ossification, and variations of the
individual bones.
OSSA CRANII.
(The Bones of the Skull.), 1
The term skull (cranium) is commonly employed to signify the entire
skeleton of the head. This comprises the bony envelope which surrounds
the brain (cranium cerebrale), and the osseous structures which support the face
(ossa faciei).
The cranium cerebrale is composed of the occipital, the sphenoid, the ethmoid,
the frontal, the two parietals, and the two temporals, the inferior nasal conchse
(O.T. inferior turbinated bones), the lacrimals, the nasal, and the vomer fifteen
bones in all.
The bones of the face (cranium viscerale, ossa faciei) include the following :
One single, viz., the mandible, and six bones, arranged in pairs, viz., the
maxillae, zygomatic (O.T. malar), palate seven bones in all.
The hyoid bone is usually described along with the skull. If, in addition, the
bones of the middle ear, three on each side (malleus, incus, and stapes), are in-
cluded, the skeleton of the head consists of twenty-nine bones.
THE SEPARATE BONES OF THE SKULL.
Os Frontale.
The frontal bone, situated in the anterior part of the cranium, is a single
bone formed by the fusion in early life of two symmetrical halves. It consists
of a frontal part, which corresponds to the region of the forehead ; an orbital part,
which enters into the structure of the roof of the orbits ; and a nasal part, which
assists in forming the roof of the nasal cavities.
Pars Frontalis. The frontal part is the shell-like portion of the bone which
rises upwards above the orbital arches. Its external surface is rounded from side
to side and from above downwards. This convexity is most pronounced about
1J inches above the orbital arches on either side of the median plane, constituting
what ^are known as the frontal tuberosities. These mark the original sites of
the centres from which the bone ossifies. The inferior margin oi' this part is
formed on either side of the median plane by the curved supraorbital margin,
the lateral and medial extremities of which constitute the zygomatic process
(O.T. external angular) and the medial angular process, respectively. The
latter, which descends to a lower level than the former, articulates with the
lacrimal bone, and is separated from its fellow by a rough articular surface
the nasal notch for the nasal and maxillary bones. The curve of the supra-
orbital margin varies in different individuals and races ; towards its medial third
1 In catalogues of craniological collections the terms used are as follows :
Skull = entire skeleton of head, including the mandible.
Cranium = the skull, minus the mandible.
Calvaria = that part of the skull which remains after the bones of the face have been removed
or destroyed.
116 OSTEOLOGY.
it is crossed by a groove, often (25 per cent., Krause) converted into a foramen the
supraorbital notch or foramen. Through this there pass the supraorbital nerve and
artery. Sometimes (16 per cent., Loja) a series of grooves, radiating upwards and
laterally, indicate the course of the nerve (Dixon). Above the supraorbital margin
the character of the bone displays marked differences in the two sexes : in the male,
above the interval between the two medial angular processes, there is usually
a well-marked prominence, called the glabella ; from this the fulness extends
laterally above the supraorbital margin, varying in degree and extent, and forming
the elevations known as the arcus superciliares (superciliary arches). The pro-
minence of these naturally reacts on the character of the supraorbital margins,
which are thicker and more rounded in the male than in the female. Passing
upwards over the glabella, the remains of the suture which originally separated
the two halves of the frontal bone can usually be seen ; above this point all trace
of the suture is generally obliterated.
Extending from the zygomatic process is a well-marked ridge, which
Frontal tuberosities
A
Temporal surface ^-Temporal line
^__ ..==, ^ -Superciliary arch
Zygomatic process (O.T.
Lateral angular process)- ^ m
^^ / \ ifP^BPB ^Glabella and remains of frontal suture
Supraorbital notch IfMclj^^ Medial angular process
' For articulation with nasal bone wj
>. Frontal spine
Fio. 128. THE FRONTAL BONE (Anterior View).
curves upwards and slightly medially, then, turning backwards, it arches
across the lateral aspect of the bone. This is the linea temporalis, which serves
to separate the anterior surface of the frontal portion of the bone from its
temporal aspect. The latter (facies temporalis) forms the floor of the upper and
anterior part of the temporal fossa, and serves for the attachment of the temporal
muscle. r
Pars Orbitalis. The orbital part of the bone consists of two transversely
curved plates, each having the form of a sextant ; their medial edges, which are
irregular and formed of cellular bone, lie parallel to each other, and are
separated in their posterior half by the incisura ethmoidalis (ethmoidal notch),
in which the ethmoid bone is lodged. The edges of the notch on either side
are grooved in front and behind by the anterior and posterior ethmoidal foramina,
which are completed when the ethmoid is in situ. The anterior transmits the
anterior ethmoidal branch of the naso-ciliary nerve and the anterior ethmoidal
vessels ; the posterior, the posterior ethmoidal vessels and nerve. Anterior to the
ethmoidal notch is the nasal notch, from the centre of which the nasal process
projects downwards and forwards to terminate in the frontal spine, which lies
between, and articulates with the nasal bones and perpendicular part of the
THE FKONTAL BONE.
ethmoid. On each side of the root of this process the nasal part of the bone
is grooved obliquely from above downwards and forwards, and enters into the
formation of the narrow roof of the nasal cavity. Anteriorly the nasal notch
is limited by a rough, U-shaped serrated surface, the medial part of which
articulates with the nasal bones, whilst on each side the frontal processes of the
maxillae are united with it. Behind this, amid the broken cells, the passages
leading into the frontal sinuses are readily distinguished, and here the medial
edges of the orbital plates articulate with the lacrimal bones. The orbital part
is thin and brittle. Anteriorly, it is bounded by the supraorbital margin, just within
which, midway between the medial angular process and the supraorbital notch, there
is a Small shallow depression (fovea trochlearis), often displaying a spicule of bone
arising from its edge (trochlear spine), which affords attachment to the pulley of
the superior oblique muscle of the eyeball. Laterally, the orbital part is overhung by
the supraorbital margin and the zygomatic process, and in the hollow so produced
(fossa glandulce lacrimalis) the lacrimal gland is lodged. The extremity of the
zygomatic process articulates with the frontal process of the zygomatic bone
For articulation with
small wing of sphenoid
Foveolse
granu lares
Sagittal sulcus and attach-
ment of falx cerebri
Groove for meningeal artery
Orbital surfac
Temporal surface
Zygomatic process (O.T.
Lateral angular)
Surface for articula-
tion with great wing
of sphenoid
Fossa for the lacrimal
gland
Ethmoidal foramina
Ethmoidal notcl
Frontal sinus
Nasal surface
Supraorbital notch
Trochlear pit
Nasal notch
Frontal spine
FIG. 129. THE FRONTAL BONE AS SEEN FROM BELOW.
Behind this the irregular edge of the orbital surface is united with the great wing
of the sphenoid by a triangular area, which also extends on to the inferior aspect
of the temporal surface of the frontal bone. The apex of the orbital surface,
for the space of about half an inch, articulates with the small wing of the sphenoid.
The cerebral surface of the bone forms a fossa in which lie the anterior and
inferior parts of the frontal lobes of the cerebrum, the gyri of which impress their
form on the inner table of the bone. Here, too, on each side of the median plane,
may be seen depressions, called foveolae granulares, for the lodgment of arachnoideal
.granulations (O.T. Pacchionian bodies). Descending from the centre of the upper
margin of the bone is a median groove, the sagittal sulcus ; narrowing below, this
ends in a ridge the frontal crest which nearly reaches the anterior part of the
ethmoidal notch, where it terminates in a small orifice, the foramen caecum, placed
usually in the suture between the anterior part of the ethmoid and the frontal.
This foramen may, or may not, transmit a small vein from the nose to the com-
mencement of the superior sagittal sinus. This sinus, which is interposed between
the layers of the falx cerebri, is at first attached to the frontal crest, but subse-
quently occupies the sagittal sulcus. Deeply concave from side to side and from
above downwards, the lateral parts of the fossa are seen to be traversed by small
grooves for the anterior branches of the middle meningeal arteries. Below, the
118
OSTEOLOGY.
orbital parts bulge into the floor of the fossa, so that the ethmoidal notch appears
in a depression between them. On each side of the notch faint grooves for the
meningeal branches of the ethmoidal vessels may be seen. The circumference of the
fossa is formed by the serrated edges of the bone which articulate with the parietals
above, and on each side below with the great and small wings of the sphenoid.
Connexions. The frontal articulates with twelve bones, viz., posteriorly, with the parietals
and sphenoid ; laterally, with the zygomatic bones ; inferiorly and medially, with the nasals,
maxillse, lacrimals, and ethmoid.
Ossification. Ossification begins in membrane from one centre for each half. This
makes its appearance about the sixth or seventh week in the region above the processus
zygomaticus. From these the two halves of the frontal
part of the bone are developed, and by extension
medially and posteriorly from their lower part the
orbital parts are also formed. Serres, Rambaud
and Renault, and v. Ihering describe the occurrence
of three pairs of secondary centres somewhat later :
one pair for the frontal spine, on either side of the
foramen caecum ; a centre on either side in cor-
respondence with the position of each trochlear
pit ; and a centre for each zygomatic process.
Fusion between these secondary and the primary
centres is usually complete about the sixth or seventh
month of foetal life. At birth the two symmetrical
halves of the bone are separated by the metopic
suture, obliteration of which, commencing as a rule on
a level with the frontal tubera, gradually takes place,
FIG. 130. OSSIFICATION OF THE FRONTAL so that about the fifth or sixth year it is more
or less completely closed, traces only of the suture
, Metopic suture still open, b, Position of b emg i e ft above and below. In about 8 per cent:
^l t^*ft^JS3 <* Europeans however, the suture persists in the
e, Centres for nasal spine. adult (see ante). At birth the supraorbital notches
lie near the middle of the supraorbital margins.
Traces of the frontal sinuses may be met with about the second year, but it is only
about the age of seven that they can be definitely recognised. From that time they
increase in size till the age of puberty, subsequent' to which time they attain their
maximum development.
lOssa Parietalia. ] L
The parietal bones, two in number, are placed one on each side of the vault
of the cranium. Each articulates with its fellow of the opposite side, the frontal
anteriorly, the occipital posteriorly, and the temporals and sphenoid inferiorly.
Each bone possesses a parietal and cerebral surface, four borders, and four angles.
The parietal surface, convex from above downwards and from before backwards,
displays towards its centre a more or less pronounced elevation, the tuber parietale
(parietal tuberosity). This marks the position of the primitive ossific centre, and
not infrequently corresponds to the point of maximum width of the head. At a
variable distance from the inferior border of the bone, and more or less parallel to
it, two curved lines can usually be distinguished. The linea temporalis superior
(superior temporal line) serves for the attachment of the temporal fascia ; the linea.
temporalis inferior (inferior temporal line) defines the attachment of the temporal
muscle, the extent and development of which necessarily determine the position of
the line. The surface below the lines enters into the formation of the floor of the
temporal fossa, and is called the planum temporale; it also affords origin to the
temporal muscle, and is often faintly marked by grooves which indicate the
course of the middle temporal artery.
Above the superior temporal line the bone is covered only by the tissues of the
scalp. Near its superior border, and about an inch from its occipital angle,
is the small parietal foramen, through which pass a small arteriole and an
emissary vein.
THE PAKIETAL BONES.
119
The cerebral surface is concave from before backwards and from above down-
wards. It is moulded over the surface of portions of the frontal, parietal, occipital,
and temporal lobes of the cerebrum, and displays impressions corresponding to the
arrangement of the gyri of those portions of the brain. It also presents a series
of well-marked grooves for the lodgment of the veins which accompany the
branches of the middle rneningeal artery (F. Wood Jones) ; these radiate from the
sphenoidal angle of the bone, the best marked running upwards at some little
distance behind and parallel to its anterior border. Close to the superior margin
there is a series of depressions for arachnoideal granulations, and there also the bone is
channelled so as to form a groove (sulcus sagittalis), which is completed by articulation
with its fellow of the opposite side. Within the groove lies the superior sagittal
venous sinus, and to its edges the falx cerebri is attached. Close to the mastoid
angle there is also a curved groove, the transverse sulcus, in which the highest
portion or bend of the transverse venous sinus is lodged.
Parietal tuberosity
Parietal
foramen
Frontal angle
Superior temporal line
Inferior temporal line
Sphenoidal
angle
For articulation with the
great wing of the sphenoid
For articulation with
the squamous part of
the temporal
Mastoid angle v For articulation with the mastoid part of the temporal
FIG. 131. THE RIGHT PARIETAL BONE (Parietal Surface).
The anterior, superior, and posterior borders are deeply serrated. The anterior
border articulates with the frontal bone, forming with it the coronal suture. In
the superior part of this suture the frontal bone overlaps the parietal, while the
parietal overlies the frontal below. The posterior border is united with the
occipital bone to form the lambdoid suture. The superior border articulates with
its fellow of the opposite side by means of the sagittal suture ; in the interval
jtween the two parietal foramina this suture is usually simple in its outline,
"he frontal angle is almost rectangular, and corresponds to the site of the anterior
fontanelle. The occipital angle, usually more or less rounded, corresponds in
sition to the posterior fontanelle. The inferior border (margo squamosus) is
irved, and shorter than the others ; it lies between the sphenoidal and mastoid
ingles. Sharp and bevelled at the expense of its outer table, it displays a fluted
mgement, and articulates with the squama temporalis of the temporal bone,
sphenoidal angle, pointed and prominent, articulates with the great wing
)f the sphenoid. It is wedged into the angle formed by the union of that bone
ith the frontal, and is bevelled at the expense of its inner table anteriorly,
8 a
120
OSTEOLOGY.
whilst inferiorly it is thinned at the expense of its outer table. The mastoid
angle is a truncated angle lying between the inferior and posterior borders.
It is deeply serrated, and articulates with the mastoid part of the temporal
bone. Not infrequently there is a channel in this suture which transmits an
emissary vein.
Connexions. The parietal bone articulates with, its fellow, with the frontal, occipital,
mastoid and squama temporalis of the temporal, and with the sphenoid. Occasionally the
Depressions for arachnoideal granulations (O.T. Pacchionian bodies)
Frontal angle
Sphenoidal angle
Grooves for middle meningeal
artery and accompanying
venous sinuses
Mastoid angle
Groove for transverse sinus (O.T. lateral sinus)
FIG. 132. THE RIGHT PARIETAL BONE (Cerebral Surface).
sphenoidal angle may not reach the great wing of the sphenoid, being separated from it by the
articulation of the squama temporalis of the temporal with the frontal (Appendix B).
Ossification.- Ossification takes place in membrane by two centres which appear,
one superior to the other, about the end of the second month (Toldt) ; these gradually
unite during the fourth month and correspond in position to the future tuber parietale ;
from this, ossification spreads in a radial manner towards the edges of the bone,
where, however, the membranous condition still for some time persists, constituting the
fontanelles. These correspond in position to the angles of the bone. Ossification is also
somewhat delayed in the region of the parietal foramina, constituting what is known as the
sagittal fontanelle, a membranous interval which is not infrequently apparent even at birth.
Os Occipitale.
The occipital bone, placed at the posterior and lower part of the cranium,
consists of four parts, arranged around a large oval hole, called the foramen
occipitale magnum or foramen magnum. At birth these parts are all separate.
The expanded curved plate posterior. to the foramen is the squama occipitalis
or tabular part. The thick rod-like portion anterior to the foramen is the basilar
part. On either side the foramen is bounded by the lateral or exoccipital parts.
THE OCCIPITAL BONE. 121
The squamous or tabular part in shape somewhat resembles a Gothic
; arch, and is curved from, side to side and from above downwards. It forms
il inferiorly a small portion of the middle of the posterior boundary of the foramen
< magnum, and unites, on each side of that, with the lateral parts of the bone.
I About the centre of the parietal surface of the squama there is a prominence
the external occipital protuberance, which varies considerably in its distinct-
ness and projection, and serves for the attachment of the ligamenturn nuchae.
From the protuberance, on each side, two lines curve towards the lateral angles
of the bone. These are known respectively as the linea nuchse suprema and linea
nuchae superior (highest and superior curved lines). To the upper of the two the
galea aponeurotica (O.T. epicranial aponeurosis") is attached, whilst the lower serves
r for the origin of the trapezius and occipitalis muscles and the insertion of the sterno-
) mastoid and splenius capitis muscles. The two lines together serve to divide the
external surface of the squama occipitalis into an upper or occipital plane (planum
occipitale), covered by the hairy scalp, and a lower or nuchal plane (planum nuchale),
i serving for the' attachment of the fleshy muscles of the back of the neck. As a rule
I the occipital part bulges backwards beyond the external occipital protuberance ;
exceptionally, however, the latter process is the most outstanding part of the bone.
The nuchal plane, irregular and rough, is divided into two halves by a
median ridge the crista occipitalis externa (external occipital crest), which extends
I from the external occipital protuberance above to the posterior border of the foramen
magnum below. Crossing the nuchal plane transversely, about its middle, is the
inferior nuchal line, which passes laterally and forwards on each side towards
I the corresponding lateral margin of the bone. The areas thus marked out serve
I for the attachment of the semispinalis capitis (O.T. complexus), obliquus capitis
superior, and rectus capitis posterior major and minor muscles.
The cerebral surface of the squamous part, concave from side to side and from
above downwards, is subdivided into four fossae by a crucial arrangement of grooved
ridges called the eminentia cruciata. In the upper pair of fossae are lodged the
occipital lobes of the cerebrum, whilst the hemispheres of the cerebellum occupy
j the lower pair. Near the centre of the eminence is the internal occipital
protuberance, an irregular elevation, the sides of which are variously channelled
i according to the disposition of the grooves. Leading from this to the posterior
margin of the foramen magnum is a sharp and well-defined ridge, the internal oc-
cipital crest, which serves for the attachment of the falx cerebelli, a process of dura
mater which separates the two cerebellar hemispheres. Passing upwards from the
internal occipital protuberance there is usually a well-marked ridge, to one or other
side of which, more frequently the right (with the bone in the normal position and
viewed from behind), there is a well-defined groove, the sulcus sagittalis, the lateral lip
of which is generally less prominent. Placed in this groove is the superior sagittal
venous sinus, and attached to the lips is the falx cerebri. At right angles to the
foregoing, and at the level of the internal occipital protuberance, with which they
become confluent, are two transverse grooves, the sulci transversi. These grooves,
which have more or less prominent edges, lie between the upper and lower pairs of
fossse, and serve for the attachment of the tentorium cerebelli as well as the lodgment
of the transverse sinuses. Commonly the right transverse groove is confluent with
the groove to the right side of the median ridge, but exceptions to this rule are not
infrequent. The angle formed by the union of the venous sinuses lodged in these
grooves constitutes the confluens sinuum (O.T. torcular Herophili), which may
accordingly be placed to one or other side of the internal occipital protuberance,
more frequently the right ; in some cases, however, it may occupy a central position.
The superior angle, more or less sharp and pointed, is wedged in between the
two parietal bones, its position corresponding to the site of the posterior fontanelle.
Each lateral angle articulates with the posterior extremity of the mastoid portion
of the corresponding temporal bone. The superior borders, much serrated, articu-
late with the parietal bones, forming the lambdoid suture ; and the lateral borders,
extending from the lateral angles to the jugular process inferiorly, are connected
with the medial sides of the mastoid portions of the temporals.
The lateral (or exoccipital) parts of the occipital bone are placed on
122
OSTEOLOGY.
either side of the foramen magnum ; on their inferior surfaces they bear
the occipital condyles by means of which the skull articulates with the atlas.
Of elongated oval form, the condyles are so disposed that their anterior
extremities, in line with the anterior margin of the foramen magnum, lie closer
together than their posterior ends, which extend as far back as the middle
of the lateral borders of the foramen. Convex from before backwards, they
are skewed so that their surfaces, which are nearly plane from side to side, are
directed slightly laterally. Each is supported on a boss of bone, pierced by the
canalis hypoglossi (hypoglossal canal), which opens obliquely from within outwards
and forwards on the floor of a fossa, situated just lateral to the anterior part
of the condyle. The canal transmits the hypoglossal nerve, together with
a meningeal branch of the ascending pharyngeal artery and its companion
Highest nuchal lin
External occipital protuberance
Superior nuchal line
Inferior
nuchal.,
line >
Canalis condy-
loideus
Jugular process
Jugular notch
Condyle
Pharyngeal tubercle
FIG. 133. THE OCCIPITAL BONE AS SEEN FROM BELOW.
veins. Behind the condyle is placed the fossa condyloidea, in the floor of which
the canalis condyloideus (condyloid canal) frequently opens. Through this a
vein passes which joins the transverse sinus. The fossae lodge the posterior
margins of the superior articular processes of the atlas in extension of the head.
The edge of the foramen magnum immediately posterior to the condyle is often
grooved for the passage of the vertebral artery around it. Jutting laterally
from the posterior half of the condyle is a stout bar of bone, serially homologous
with the vertebral transverse processes ; this is the processus jugularis ; deeply
notched in front (jugular notch) its anterior border is free and rounded, and
forms the posterior boundary of the jugular foramen. Curving laterally from this
margin, in line with the hypoglossal canal, there is often a small pointed projection,
the processus intrajugulare, which serves to divide the jugular foramen into two
compartments. Laterally, the jugular process articulates by means of a synchon-
drosis with the jugular surface of the petrous part of the temporal bone. Its
posterior border is confluent with the inferior and lateral portion of the occipital
squama, and its under surface is rough and tubercular for the attachment of the
THE OCCIPITAL BONE. 123
rectus capitis lateralis muscle. The superior aspect of the lateral part displays on
either side of the foramen magnum an elevated surface of oval form, the tuberculum
jugnlare ; this corresponds to the part of the bone which bridges over the canal
for the hypoglossal nerve. Its upper surface in many instances displays an oblique
groove running across it; in this are lodged the glosso-pharyngeal, vagus, and
accessory nerves. The jugular process is deeply grooved superiorly for the lower
part of the transverse blood sinus, or sigmoid sinus, which here turns round the
anterior free edge of the process into the jugular foramen. Joining this, close to
its medial edge, is the opening of the canalis condyloideus, when it exists.
The basilar part of the occipital bone extends forwards and upwards
from the foramen magnum. Its anterior extremity is usually sawn across, as,
Groove for superior sagittal sinus and falx cerebri Superior angle
Cerebral fossa x ,i>tmmi
^ggagmffi^fcg-^
\X^B^ESM|^H ^*Wli Internal occipital
Depression for confluens ^j^C / protuberance
sinuum (O.T. tor-
cular Herophili)"
Groove for trans verse
sinus and tcntorium
cerebelli
Lateral angle
Internal occipital
crest
Jugu.ar process
^K mr/^^^ X Canalis condyloideus
BHHl ^|B ""' 'f JF Tuberculum jugulare
ve for inferior petrosal sinus -
^^^^^^^^^^^ ""^Basilar groove
Basilar part
FIG. 134. OCCIPITAL BONE (Cerebral Surface).
after adult life, it is necessary to sever it in this way from the sphenoid, the
cartilage uniting the two bones having by that time become completely ossified.
Broad and thin posteriorly, it narrows at the sides and thickens vertically in front
where on section it displays a quadrilateral form. Projecting from its inferior
surface some little distance anterior to the foramen magnum is the pharyngeal
tubercle to which the fibrous raphe of the pharynx is attached ; on each side of
this the longus capitis and rectus capitis anterior muscles are inserted. The
superior surface forms a broad and shallow groove which slopes upwards and
forwards from the thin anterior margin of the foramen magnum ; in this rests the
medulla oblongata. On each side its lateral edges are faintly grooved for the
inferior petrosal venous sinuses, below which the lateral aspect of the bone is rough
for the cartilage which unites it to the sides and apex of the petrous part of the
temporal bone.
The foramen magnum, of oval shape, so disposed that its long axis lies in the
124
OSTEOLOGY.
sagittal plane, is of variable size and form. The plane of its outlet differs somewhat
in individual skulls; in most instances it is directed inferiorly and slightly
forwards. Anteriorly the condyles encroach upon it, and narrow to some extent its
transverse diameter. To its margins are attached the ligaments which unite it
with the atlas and epistropheus. Through it pass the lower part of the medulla
oblongata where it becomes continuous with the spinal medulla, the two vertebral
arteries, the accessory nerves, and the blood-vessels of the meninges of the superior
part of the spinal medulla.
Connexions. The occipital bone articulates with the two parietals in front and above, with
the sphenoid in front and below, with the two temporals on either side, and with the atlas
by means of its condyles.
Ossification. The major part of the bone ossifies in cartilage, the upper part of the
squamous part (interparietal) alone developing in membrane. The basilar part begins to
ossify about the sixth week of foetal life by the appearance of two centres, one in front of
the other ; the anterior, according to Albrecht, constitutes the basiotic, the posterior the
basi-occipital. These two centres which there is some reason to believe may themselves
be formed by the fusion of pairs placed laterally rapidly unite, so that the occurrence of
one centre alone is frequently described. From this the anterior part of the margin of the
foramen magnum is formed, together with a portion of the anterior end of the occipital
condyle on either side. It helps also to close up the front of the hypoglossal canal.
Union with the condylic parts is complete about the fourth or fifth year. Ankylosis
between the basi-occipital and the sphenoid takes place about the twenty-fifth year.
The lateral, condylic, or exoccipital parts begin to ossify from a single centre about
the end of the second month of foetal life. The notch for the hypoglossal canal appears
about the third month. From this centre is formed the posterior three-fourths of the
occipital condyle. The exoccipital is usually completely fused with the squamous part
by the third year or earlier.
As already noted, the squamous part consists of two parts the one above the occipital
crest, the other below it; the former develops in
membrane, the latter in cartilage. In a three-months
foetus this difference is very characteristic. The
cartilaginous part (supra-occipital) begins to ossify
from two centres (four according to Mall) about the
sixth or seventh week, which rapidly join to form an
elongated strip placed transversely in the region of
the occipital protuberance. The centres for the
superior part (interparietal) appear later. According
to Maggi (Arch. Ital. Biol. tome 26, fas. 2, p. 301),
they are four in number, of which two placed on
either side of the median plane appear about the
second month. The other pair, placed laterally, are
seen about the third month ; fusion between these
takes place early, but their disposition and arrange-
ment explain the anomalies to which this part of the
bone is subject. The medial pair may persist as
separate ossicles, or fuse to form the pre-interparietals,
whilst the lateral pair may remain independent of the
supra-occipital as a single or double interparietal
bone, the former, owing to the frequency of its
occurrence in Peruvian skulls, being sometimes
called the "os Incce." Union between the supra-
FIG. 135,-OssiFicATioN OF THE OCCIPITAL occipital and the i nt erparietal elements occurs about
a, Basilar centre; b, Exoccipital; c, Ossicle the third r f Urth m nth ' bu * evidence of their
of Kerkring ; d, Supra- occipital (from car- separation is frequently met with even in the adult
tilage) ; e, Fissure between supra-occipital by the persistence of a transverse suture running
and interparietal ; /, Interparietal (from inwards from each lateral angle of the squamous part,
m arietlLs ne) 5 9t Fi * SUre betW6en intei " or ' as above mentioned > th ere may be an os Incse.
The supra -occipital forms a small part of the
median part of the posterior border of the foramen magnum, though here a small inde-
pendent centre, known as the ossicle of Kerkring, is occasionally met with. Other
independent centres are sometimes seen between the supra-occipital and the exoccipitals.
THE TEMPOEAL BONES. 125
At birth the occipital consists of four parts the interparietal and supra-occipital
combined, the basi-occipital, and the exoccipitals one on either side.
Ossa Temporalia.
The temporal bone lies about the centre of the inferior half of either side
of the skull, and enters largely into the formation of the cranial base. It is
placed between the occipital behind, the parietal above, the sphenoid in front, and
the occipital and sphenoid medially and below. At birth it consists of three parts
a superior and lateral part, the squama temporalis or squamous portion ; a medial
and posterior portion, the petro-mastoid, which contains the parts specially associated
with the sense of hearing, together with the organ associated with equilibration ;
and an inferior or tympanic part, from which the floor and anterior wall of the
external acoustic meatus is formed.
The squamous part consists of a thin shell-like plate of bone placed
vertically, having a medial (cerebral) and a lateral (temporal) surface and a
semicircular upper border. Inferiorly, behind, and medially it is fused in early
life with the petro-mastoid portion by means of the squamoso-mastoid and the
petro-squamosal sutures, traces of which are often met with in the adult bone ;
whilst below and in front it is separated from the tympanic and petrous parts by
the petro-tympanic fissure. Its temporal surface, smooth and slightly convex, enters
into the formation of the floor of the temporal fossa, and affords attachment to
the temporal muscle. Near its posterior part it is crossed by one or more ascending
grooves for the branches of the middle temporal artery. In front and below there
springs from it the processus zygomaticus. This arises by a broad attachment,
the surfaces of which are inferior and superior ; curving laterally and forwards, it
then becomes twisted and narrow, so that its sides are turned medially and
laterally and its edges directed upwards and downwards. Anteriorly it ends in an
oblique serrated extremity which articulates with the temporal process of the
zygomatic bone. Posteriorly the edges of the zygomatic process separate and are
termed its roots. The superior edge, which becomes the posterior root, sweeps back
above the external acoustic meatus, and is continuous with the supra-mastoid
crest, which curves backwards and slightly upwards, and serves to define the limit
of the temporal fossa posteriorly. Internally this ridge corresponds to the level of
the floor of the middle cerebral fossa. The inferior edge turns medially and
constitutes the anterior root; the inferior surface of this forms a transversely
disposed rounded ridge, the tuberculum articulare (O.T. articular eminence), behind
which there is a deep hollow, the fossa mandibularis, limited posteriorly by the
tympanic plate, and crossed at its deepest part by an oblique fissure, the petro-
tympanic fissure. This cleft, which is closed laterally, transmits about its middle
the tympanic branches of the internal maxillary artery, and lodges the anterior
process of the malleus. At its medial end the lips of this fissure are frequently
separated by a thin scale of bone, a downgrowth from the tegmen tympani
of the petrous part, which here separates the tympanic from the squamous elements,
forming in its descent the major part of the lateral wall of the osseous auditory
tube, which lies just medial to it. Between this scale of bone and the posterior
edge of the fissure there is a canaliculus, which transmits the chorda tympani
nerve. The part of the mandibular fossa in front of the petro-tympanic fissure,
as well as the articular tubercle, articulates with the condyle of the mandible,
through the medium of the interposed articular disc. The part of the fossa
behind the fissure is non-articular and lodges a portion of the parotid gland. At
the angle formed by the divergence of the two roots of the zygoma, in correspond-
ence with the lateral part of the articular tubercle, there is a rounded tubercle ;
to this are attached the fibres of the temporo-mandibular Ligament of the mandibular
joint. In front of the medial end of the articular tubercle there is a small
triangular surface, limited anteriorly by the edge of the anterior root, and medially
by a thick serrated margin which articulates with the temporal aspect of the
great wing of the sphenoid ; this area forms part of the roof of the infra-temporal
(O.T. zygomatic) fossa. Just anterior to the external acoustic meatus and projecting
126
OSTEOLOGY.
downwards from the inferior surface of the posterior root there is a conical process,
called the post-glenoid tubercle, which forms a prominent anterior lip to the lateral
extremity of the petro-tympanic fissure ; it is the representative in man of a
process which is developed in some mammals and prevents the backward displace-
ment of the mandible. By some anatomists it is referred to as the middle root
of the zygomatic process.
The zygomatic process by its inferior margin and medial surface gives origin to
the masseter muscle, whilst attached to its superior edge are the layers of the
temporal fascia. Behind the external acoustic meatus, and below the supramastoid
crest, the squainous element extends downwards as a pointed process, which assists
in forming the roof and posterior wall of the external acoustic meatus, where
it unites inferiorly with the tympanic part and forms the lateral wall of a hollow
within called the tympanic antrum. In the adult this process is occasionally
Groove for middle
temporal artery
Temporal surface
Parietal notch
Supra-meatal spine
Zygomatic process
Tuberce at root of zygoma
Tuberculum articulare
Remains o
masto-squamosal
suture
Mastoid process
External acoustic meatus Tympano- External processus^
mastoid acoustic styloidei
fissure process
Styloid process
FIG. 136. THE RIGHT TEMPORAL BONE SEEN FROM THE PARIETAL SIDE.
The squamo-zygomatic part is coloured blue ; the petro-mastoid, red.
The tympanic part and styloid process are left uncoloured.
sharply defined posteriorly by an oblique irregular fissure, the remains of the masto-
squamosal suture. Immediately above and behind the external acoustic meatus
there is often a little projecting spur of bone, the spina suprameatum (supra-
meatal spine).
The angular recess between this process and the supramastoid crest is of interest
surgically, a-nd is known as Mace wen's triangle. The same authority has pointed out that
the masto-squamosal suture frequently remains open till puberty and occasionally after,
and may be of importance as a channel along which infective processes may extend.
The cerebral surface of the squamous part, less extensive than the parietal aspect
owing to the bevelling of the parietal border, is marked by the impression of the
gyri of the temporal lobe of the cerebrum, and is limited below by the petro-
squamosal suture, the remains of which can frequently be seen. It is crossed in
front by an ascending groove for the posterior branch of the middle meningeal
artery and its accompanying vein, branches from which course backwards over the
bone in grooves more or less parallel to its parietal border.
The parietal border of the squamous part is curved, sharp, and scale-like, being
THE TEMPORAL BONES.
127
i bevelled at the expense of its inner table, except in front, where the margin is thick
' and stout. There it articulates with the great wing of the sphenoid, its union with
ithat bone extending to near the anterior part of the summit of the curve, behind
which it is united to the parietal, overlapping the squamous border of that bone ;
i posteriorly the free margin of the squamous part ends at an angle formed between
it and the mastoid process called the incisura parietalis.
Pars Tympanica. The tympanic part of the temporal bone forms the anterior,
i lower, and part of the posterior wall of the external acoustic meatus. Bounded
in front and above by the petro-tympanic fissure, it forms the posterior wall of the
| non-articular part of the mandibular fossa. Fused medially with the petrous part, its
lower edge, sharp and well defined medially, splits to enclose the root of the
projecting styloid process, and is hence called the vagina processus styloidei
(sheath of the styloid process). Laterally it unites with the anterior part of the
Groove for middle
meningeal artery
Arcuate eminence or
eminence of superior
semicircular canal
Parietal notch
Groove for superior
petrosal sinus
Petro-squamous suture
Carotid canal ^^^^Groove for sigmoid
_ sinus
"^^^^in x yJ^5>''
Styloid proces
Inner surface of mastoid process
Groove for inferior petrosal sinus
FIG. 137. THE RIGHT TEMPORAL BONE (Cerebral aspect).
The squamous part is coloured blue ; the petro-mastoid part, red.
The styloid process and the zygoma are left uncoloured.
mastoid process, and higher up with the descending process of the squamous part, from
both of which it is separated by the tympano-mastoid fissure, through which the
auricular branch of the vagus escapes. Its free border, which forms the anterior,
lower, and part of the posterior border of the external acoustic meatus, is usually
somewhat thickened and rough, and serves for the attachment of the cartilaginous
part of the external acoustic meatus.
The meatus acusticus externus (external acoustic meatus) is directed obliquely
inwards and a little forwards, and describes a slight curve, the convexity of which
is directed upwards ; of oval form, its long axis, close to its orifice, is nearly vertical,
but, as it passes inwards, inclines somewhat forwards so as to give a twist to the
canal. The depth of the canal to the attachment of the membrana tympani
averages from 14 to 16 mm. The superior margin of the outer orifice overhangs
considerably the lower edge, but owing to the obliquity of the inner aperture, to
which the membrana tympani is attached, the superior wall of the osseous canal
only exceeds the length of the lower wall by one or two millimetres.
Pars Petrosa et Pars Mastoidea. The petro-mastoid part of the temporal
128 OSTEOLOGY.
bone, of pyramidal form, is fused to the medial aspect of the tympanic and
squamosal portions, extending behind them, however, to form the well-marked and
prominent mastoid process, which lies posterior to the external acoustic meatus.
This process forms a nipple-like projection, the size of which differs considerably
in different individuals. Usually larger in the male than in the female, its rough
lateral surface and inferior border serve for the insertions of the sterno-mastoid,
splenius capitis, and longissimus capitis muscles. Within and below its
pointed extremity there is a deep groove (incisura mastoidea), usually well marked,
which gives origin to the posterior belly of the digastric muscle ; whilst lying to the
medial side of this, and separated from it by a more or less well-defined rough ridge,
there can oftentimes be seen a narrow, shallow furrow, which indicates the course
of the occipital artery. The medial surface of the mastoid portion forms, in part, the
side wall of the posterior cranial fossa, in which the cerebellar hemispheres are lodged.
Coursing across this aspect of the bone there is a broad curved groove, the con-
vexity of which is directed forwards and lies in the angle formed by the base of the
petrous part and its fusion with the mastoid portion. The depth to which the bone
is here channelled varies considerably, and is important from a surgical standpoint,
as herein lies the sigmoid portion of the transverse venous sinus. Anteriorly
che mastoid is fused with the descending process of the squamosal above, and below,
where it is united with the tympanic, it enters into the formation of the posterior
wall of the external acoustic meatus and the cavity of the tympanum. Above,
its free margin is rough and serrated, and articulates with the mastoid angle
of the parietal; behind and below it articulates by a jagged suture with the
occipital. Traversing this suture, or near it, is the mastoid foramen, which
transmits a vein from the transverse sinus to the cutaneous occipital vein, together
with a small branch of the occipital artery.
The petrous part (pyramis) of the petro-mastoid is of the form of an elongated
three-sided pyramid. By its base it is united obliquely to the inner sides of the
squamosal and tympanic parts. Its apex is directed medially, forwards, and a little
upwards. Its three surfaces are arranged as follows : The anterior looks upwards,
slightly forwards, and a little laterally, and forms part of the floor of the middle
cranial fossa. The posterior is directed backwards and medially, and forms part of
the anterior wall of the posterior cranial fossa. ' The inferior is seen on the under
surface of the base of the skull, and is directed downwards. The margins or angles
are named respectively anterior, superior, and posterior.
The anterior margin is short, and forms an acute angle with the anterior part of
the squamous part; within this angle is wedged the spinous part of the great wing
of the sphenoid. Here, too, the osseous part of the auditory tube (canalis musculo-
tubarius) may be seen leading backwards and laterally from the summit of the angle
to reach the anterior part of the cavity of the tympanum in the interior of the bone.
On looking into it, the canal is seen to be divided into two unequal parts by
an osseous partition, the septum tubse. The upper compartment, the smaller of
the two (semicanalis m. tensoris tympani), lodges the tensor tympani muscle,
whilst the lower (semicanalis tubse auditivae) forms the osseous part of a channel
(the auditory tube), which serves to conduct air from the pharynx to the
tympanic cavity.
The posterior margin is in part articular and in part non-articular. Pos-
teriorly and laterally it corresponds to the upper margin of an area on the inferior
surface with which the extremity of the jugular process of the occipital articulates.
In front of that it is irregularly notched, and forms the free anterior edge of the
jugular foramen, medial to which it has a sharp curved border, often grooved,
reaching to the apex. This groove, which is completed by articulation with the
side of the basi-occipital, lodges the inferior petrosal venous sinus.
The superior margin is a twisted edge which is continuous with the upper
margin of the sulcus for the transverse sinus posteriorly, and anteriorly and
medially reaches the apex of the bone. Eunning along it there is usually a
well-marked groove for the superior petrosal venous sinus, and near its medial
extremity it is slightly notched for the passage of the trigeminal nerve. Along
the entire length of this border the tentorium cerebelli is attached.
THE TEMPOKAL BONES.
129
On the inferior surface of the petrous part, which is bounded in front by the
anterior border medially, the tympanic plate laterally, and behind by the posterior
border, the following structures are to be noted: Springing from and sur-
rounded by its sheath is the slender and pointed processus styloideus, the length
of which varies much. Projecting downwards and slightly forwards and medially,
it affords attachments for the stylo-glossus, stylo-hyoid, and stylo-pharyngeus
muscles, as well as the stylo-hyoid and stylo-mandibular ligaments. Just behind
it, and between it and the mastoid process, is the foramen stylomastoideum, which
lies at the anterior end of the mastoid groove, and transmits the facial nerve and
the stylo-mastoid artery. Just medial to the styloid process there is a deep, smooth,
excavated hollow, the fossa jugularis, which is converted into a foramen (jugular)
by articulation with the occipital bone. Behind and lateral to the fossa there is a
small quadrilateral surface
Temporal surface
Infra-temporal or zygomatic surface
Canal for chorda tympani
Auditory tube
Carotid canal
Tuberc
Tuberculu
articulare
Mandibular
fossa
Petro-tynipamc
exte^a-l fissure
Tympanic plate
Ext. acoustic meatus
Styloid. process
Sheath of styloid
process
Mastoid process
Mastoid notch for
digastric muscle
Groove for
occipital artery
Groove for
inferior
petrosal sinus
Aqueduct of cochlea
external orifice of)
nal for the
nic nerve
'Jugular fossa
Canal for auricular
branch of vagus
tympar
Jugular surface
of variable size, which is
united to the extremity of
the jugular process of the
exoccipital by a synchon-
drosis. Inside the fossa, on
its lateral part, or placed
on its lateral border, is the
opening of a small canal
(canaliculus mastoideus),
which passes laterally to
open into the canalis facialis,
and transmits the auricular
branch of the vagus, which
ultimately escapes through
the petro-mastoid fissure
(vide ante). In front of
the iuerular fossa and separ- Petro-mastoid fissure
Stylo-mastoid
ated from it by a sharp foramen
crest, and just medial to the
tympanic plate, is the circu-
lar opening of the inferior
orifice of the canalis caroti-
cus (carotid canal). Directed
at first upwards, this canal
bends at a right angle and
turns for wards and medially,
lying parallel to the anterior
angle ; reaching the anterior
part of the apex of the bone,
it opens in front by an
oblique ragged orifice.
Through the canal the internal carotid artery, accompanied by a plexus of
sympathetic nerves, passes into the cranium. On the ridge of bone separating the
jugular fossa from the carotid canal is the opening of the canaliculus tympanicus,
through which the tympanic branch of the glosso - pharyngeal nerve passes to
reach the tympanum. Within the orifice of the carotid canal other small openings
(canaliculi carotici tympanici) may be noticed which afford passage to the tympanic
branches of the internal carotid artery and carotid sympathetic plexus.. Occupy-
ing the interval posteriorly and medially between the jugular fossa and the carotid
canal is a V-shaped depression on the floor of which and close to the posterior
border is the orifice of the apertura externa aquaeductus cochleae (aqueduct of
the cochlea). In the fossa is lodged the petrous ganglion of the glosso-pharyngeal
nerve, and the aqueduct transmits a tubular prolongation of the dura mater,
which forms a channel of communication between the perilymph of the cochlea
and the subarachnoid space. A small vein also passes through it. In front
of and medial to the orifice of the carotid canal the inferior surface of the
9
F;G. 138. THE RIGHT TEMPORAL BONE SEEN FROM BELOW.
The squamo-zygomatic part is coloured blue ; the petro-mastoid, red.
The tympanic portion and styloid process are left uncoloured.
130
OSTEOLOGY.
apex of the bone corresponds to a rough quadrilateral surface which forms the
floor of the carotid canal, and also serves for the attachment of the cartilaginous
part of the auditory tube as well as the origin of the levator veli palatini muscle ;
elsewhere it has attached to it the dense fibrous tissue which fills up the cleft
(petro-basilar fissure) between it and the basilar part of the occipital bone.
The anterior surface of the petrous part bears the impress of the gyri of the
lower surface of the temporal lobe of the cerebrum, which rests upon it ; in addition,
there is a distinct but shallow depression (impressio trigemini) near the apex,
corresponding to the roof of the carotid canal ; in this is lodged the semilunar
ganglion on the sensory root of the trigeminal nerve. Lateral to the middle
of the anterior surface, and close to its superior border, is the elevation
(eminentia arcuata), more or less pronounced, which marks the position of the
superior semicircular canal, here developed within the substance of the bone. A little
Tympanic antruin, the medial
wall of which is related to the
lateral semicircular canal
'edial part of posterior wall of external
acoustic meatus left in situ
Points to the recessus epitympanicus
Mastoid air-cells
Facial nerve
Facial canal laid open, displaying the facial nerve within
FlG. 139.
Preparation to display the position and relations of the tympanic antrum. The greater part of the posterior
wall of the external acoustic meatus has been removed, leaving only a bridge of bone at its medial ex-
tremity ; under this a bristle is displayed, passing from the tympanic autrum through the iter to the
cavity of the tympanum.
in front of this, and in line with the angle formed by the anterior border and the
squamous part, is the slit-like opening of the hiatus canalis facialis, within the
projecting lip of which two small orifices can usually be seen. These are the
openings of the canalis facialis; if a bristle is passed through the more medial
of the two openings it will be observed to pass into the bottom of the internal
acoustic meatus, if into the more lateral, it will pass through the facial canal,
and, provided the channel be clear, will appear on the inferior surface of the
bone at the stylo-mastoid foramen. Leading forwards and medially from the
hiatus towards the anterior border is a groove ; in this lies the greater superficial
petrosal nerve, which passes out of the hiatus. A small branch of the middle
meningeal artery also enters the bone here. A little lateral to the hiatus is
another small opening (apertura superior canalis tympanici), often difficult to see ;
from this a groove runs forwards which channels the upper surface of the roof of
the canal for the tensor tympani muscle. Through this foramen and along this
groove passes the lesser superficial petrosal nerve. Behind this, and in front of
the arcuate eminence, the bone is usually thin (as may be seen by holding it up to
the light falling through the external acoustic meatus), roofing in the cavity
THE TEMPOEAL BONES.
131
within the bone called the tympanum and forming the tegmen tympani. Laterally
the line of fusion of the petrous with the squamous part is often indicated by a faint
and irregular petro-squamous fissure.
Posterior Surface. The most conspicuous object on the posterior surface of the
petrous part of the bone is the meatus acusticus interims (internal acoustic meatus), about
8 mm. deep in the adult. This has an oblique oval aperture, and leads laterally
and slightly downwards into the substance of the bone, giving passage to the acoustic
and facial nerves, together with the nervus intermedius and the auditory branch of
the basilar artery. The canal appears to end blindly ; but if it is large, or still better,
if part of it is cut away, its fundus will be seen to be crossed by a horizontal ridge, the
falciform crest, which divides it into two fossae, the floors of which (laminae, cribrosse)
are pierced by numerous small foramina for the branches of the acoustic nerve and
the vessels passing to the membranous labyrinth, whilst in the anterior and upper
part of the higher fossa the orifice of the canalis facialis, through which the
facial nerve passes, is seen leading in the direction of the hiatus canalis facialis
(vide supra). Lateral to the internal acoustic meatus and above it, close to the
superior border, an irregular depression, often faintly marked, with one or two small
foramina opening into it, is to be noticed. This is the fossa subarcuata, best seen
in young bones (see Fig. 143 C), where
it forms a distinct recess, which is
bounded above by the bulging caused by
the superior semicircular canal, within
the concavity of which it is placed ; it
lodges a process of the dura mater.
Below and lateral to this, separated
from it by a smooth, elevated curved
ridge, is the opening of the apertura
externa aquaeductus vestibuli (aqueduct
of the vestibule), often concealed in a
narrow curved fissure overhung by a
sharp scale of bone. In this is lodged
the saccus endolymphaticus,
internal developed as an evagi nation
from the otocyst, together
with a small vein. The ridge
above it corresponds to the
upper half of the posterior
External acoustic
meatus
Osseous part of the
auditory tube
acoustic
meatus
Vestibule
Canalis facialis
Fenestra vestibuli cut across i i
nestra cochin cut arross semicircular canal.
Superior opening of the canal for the
tympanic branch of glosso-pharyngeal
FIG. 140. VERTICAL TRANSVERSE SECTION THROUGH THE LEFT
TEMPORAL BONE (Anterior Half of Section).
Connexions. The temporal
bone articulates with the zygomatic,
sphenoid, parietal, and occipital
bones, and by a movable joint with
the mandible. Occasionally the temporal articulates with the frontal, as happens normally in
the anthropoid apes ; although the region of the pterioii is characterised by an X-like form,
in the lower races of man there is no evidence that the occurrence of a fronto-squamosal
suture is more frequent in the lower than the higher races, its occurrence being due to the
inanner of fusion of the so-called epipteric ossicles with the surrounding bones.
Ossification. The temporal bone of man represents the fused periotic, squamosal,
and tympanic elements ; the two latter are membrane or investing bones, whilst the
former is developed in cartilage around the auditory capsule. The cartilages of the
I. and II. visceral arches are also intimately associated with its development, as will be
ftpewhere explained (Appendix E). The human temporal bone is characterised by the
large proportionate size of the squamosal, the comparatively small size of the tympanic,
the absence of an auditory bulla, and the exceptional development of the mastoid process.
Ossification commences in the ear capsule in the fifth month, and proceeds so rapidly
that by the end of the sixth month the individual centres aTe more or less fused. Of
these, one, the Pro-otic (Huxley), which appears in the vicinity of the eminentia arcuata,
s the most definite in position and form ; from this a lamina of bone of spiral form
is developed, which covers in the medial limb of the superior semicircular canal, and
forms the roof of the internal acoustic meatus, together with the commencement of the
9a
132
OSTEOLOGY.
facial canal. Reaching forwards, it extends to the apex of the petrous part ; whilst
laterally it forms part of the medial wall of the tympanum, surrounds the fenestra vesti-
buli, and encloses within its substance portions of the cochlea,
vestibule, and superior semicircular canal. Another centre, the
Opisthotic, appears in the vicinity of the promontory on the
medial wall of the tympanum, surrounds the fenestra cochleae,
forms the floor of the vestibule, and extends medially to complete
the floor of the internal acoustic meatus. Surrounding the cochlea
inferiorly and laterally, it completes the floor of the tympanum,
and ultimately blends with the anterior and inferior part of the
tympanic ring. The carotid
Canal at first grooves it, and is Lateral semicircular canal
then subsequently surrounded
by it. According to Lambertz
the lamina spiralis of the cochlea
ossifies in membrane. The roof
of the tympanum is formed from
a separate centre, the Pterotic,
which extends backwards to-
wards the superior semicircular
canal, and encloses the tympanic
part of the facial canal ; later-
ally this centre unites by suture
with the squamosal, and sends
down a thin process, which ap-
pears between the lips of the
petro - tympanic fissure, and
forms the lateral wall of the
auditory tube. Nuclei, either
single or multiple, Epiotic, appear
Superior semicircular
canal
Vestibule into
openings of
semicircular canals
Internal
acoustic meatus
Fenestra vesti-
buli cut across
Fenestra cochleae
cut across
Opening leading
into tympanic
antrum
Canalis facialis
Canalis stapedii
Tympanum
External
acoustic meatus
FIG. 141. VERTICAL TRANSVERSE SECTION THROUGH THE LEFT
TEMPORAL BONE (Posterior Half of Section).
in the base of the
Osseous part or'the auditory tube
Styloid process
broken off
Mandibular
petrous part, and envelop the
posterior and lateral semi-
circular canals. It is by ex-
tension from this part that
the mastoid process is ulti-
mately developed. The
styloid process, an inde-
pendent development from
the upper end of the carti-
lage of the second visceral
arch, is ossified from two
centres. The upper or basal
appears before birth, and
rapidly unites with the petro-
mastoid, the tympanic plate
internal acoustic encircling it in front. This
meatus represents the tympanohyal
of comparative anatomy. At
birth, or subsequent to it,
another centre appears in the
cartilage below the above :
this is the stylohyal. Anky-
losis usually occurs in adult
life between the tympanohyal
and stylohyal, the union of
the two constituting the so-
called styloid process of
human anatomy.
The centre from which the
squamo-zygomatic develops
appears in membrane about
the end of the second month. Situated near the root of the zygoma, it extends forwards
and laterally into that process, medially to form the floor of the infra-temporal fossa, and
upwards into the squamosal. From this latter there is a downward and backward exten-
Groove for
membrana
tympani
External
acoustic
meatus
Mastoid air-cells -
Carotid canal
Tympanum
Cochlea
Vestibule, fenestra
vestibuli cut across
Superior semicircular
canal
Canalis facialis
Lateral semicircular canal
Fia. 142. HORIZONTAL SECTION THROUGH THE LEFT TEMPORAL BONE
(Lower Half of Section).
THE SPHENOID BONE.
133
sion, which forms the post-auditory process ; this ultimately blends with the posterior limb
of the tympanic ring, being separated from it in the adult by the petro-mastoid fissure. It-
forms the lateral wall of the tympanic antrum, and constitutes the anterior and upper part
of the mastoid process in the adult. About the third month a centre appears in the outer
membranous wall of the tympanum : from this the tympanic ring is developed. Incom-
plete above, it displays two free extremities. Of these, the anterior is somewhat enlarged,
and unites in front with the mandibular portion of the squamo-zygomatic, being separated
from it by the petro-tympanic fissure and the downgrowth from the tegmen tympani ; the
posterior joins the post -auditory process of the squamo-zygomatic above mentioned.
Below, it blends medially with the portion of the petro-mastoid which forms the floor of
the tympanum and ensheathes the tympanohyal behind. From the medial surface of
the ring below there is an extension medially and forwards which forms the floor of the
osseous part of the auditory tube, as well as the lateral wall and half the floor of the
carotid canal. From the lateral side of the lower part of this ring two tubercles arise ;
A B C
The squamo-zygomatic part is coloured blue ; the petro-mastoid red. The tympanic ring is left uncoloured.
143. A. THE PARIETAL SURFACE OF THE RIGHT TEMPORAL BONE AT
IRTH. B. THE SAME WITH THE SQUAMO-ZYGOMATIC PORTION REMOVED.
ae lettering is the same in both A and B.) a, Tympanic ring, b, Medial wall
of tympanum, c, Fenestra cochleae, d, Fenestra vestibuli'. e, Tympanic
antrum. /, Mastoid process, g. Masto - squamosal suture, with foramen
for transmission of vessels, h, Squamo-zygomatic, removed in figure B
to show how its descending process forms the lateral wall of the
tympanic antrum.
C. CEREBRAL SURFACE OF THE RIGHT
TEMPORAL BONE AT BIRTH.
a, Squamo-zygomatic. b, Petro-
squamosal suture and foramen (just
above the end of the lead line).
c, Subarcuate fossa, d, Aquaeductus
vestibuli. e, Aquaeductus cochleae.
f, Internal acoustic meatus. g,
Upper end of carotid canal.
these grow laterally, and so form the floor of the external acoustic meatus. The interval
between them remains unossified till about the age of five or six r after which closure takes
place. This deficiency may, however, persist even in adult life (see Appendix B, Temporal).
At birth the temporal bone can usually be separated into its component parts. The
lateral surface of the petrous part not only forms the medial wall of the tympanum, but is
hollowed out behind and above to form the inner side of the tympanic antrum, the
outer wall of which is completed by the post-auditory process of the squamo-zygomatic.
As yet the mastoid process is undeveloped. It only assumes its nipple-like form about the
second year. Towards puberty its spongy substance becomes permeated with air spaces,
which are in communication with and extensions from the tympanic antrum. Occasionally
this pneumatic condition is met with in early childhood. The external acoustic meatus
is unossified in front and below, the outgrowth from the tympanic ring occurring
subsequent to birth. The mandibular fossa is shallow and everted; the jugular fossa is
ill-marked ; whilst the subarcuate fossa is represented by a deep pit, the so-called
floccular fossa of comparative anatomy. The hiatus of the facial canal is an open groove,
displaying at either end the openings of the medial and lateral portions of the facial canal.
Os Sphenoidale.
The sphenoid bone lies in front of the basilar part of the occipital medially,
and the temporals on either side. It enters into the formation of the cranial,
orbital, and nasal cavities, as well as the temporal, infra-temporal, and pterygo-
96
134
OSTEOLOGY.
palatine fossse. It consists of a body with three pairs of expanded processes,
the great wings, the small wings, and the pterygoid processes.
The corpus (body), more or less cubical in form, is hollow, and contains within
it the two large sphenoidal air sinuses. These are separated by a partition, which
aiuditory tube
^ Petrosal process
Pterygoid canal
Superior orbital
fissure
Lateral lamina of the
pterygoid process
Medial lamina of the
pterygoid process
Spina angularis
\ Lingtitersph^noi d alls
Scaphoid fossa
Pterygoid fossa
Pterygoid notch
Hamulus of medial pterygoid lamina
FIG. 144. THE SPHENOID SEEN FROM BEHIND.
is usually deflected to one or other side of the median plane. Each sinus extends
laterally for a short distance into the root of the great wing, and downwards and
laterally towards the base of the pterygoid process of the same side. They com-
Superior orbital
fissure
Optic foramen /
Temporal
surface
Infra-temporal / _,
surface Foramen
rotundum
Pterygoid canal
Pterygoid notch
Orbital surface
Infra- temporal crest
Angular spine
Spheno-maxillary surface
Lateral pterygoid lamina
__ Hamulus of medial
pterygoid lamina
FIG. 145. THE SPHENOID SEEN FROM THE FRONT.
municate by apertures with the upper and posterior part of the nasal cavities. In the
adult the posterior aspect of the body displays a sawn surface due to its separation
from the basi-occipital, with which in the adult it is firmly ankylosed. The superior
surface, from the anterior angles of which the small wings arise, displays an appear-
ance comparable to that of an oriental saddle (sella turcica). Over its middle there
is a deep depression, the fossa hypophyseos, in which is lodged the hypophysis
(O.T. pituitary body). Behind, this is overhung by a sloping ridge, the dorsum sellse,
the posterior surface of which is inclined upwards, and is in continuation with
THE SPHENOID BONE. 135
the basilar groove of the occipital bone, supporting the pons and the basilar
artery. Anteriorly and laterally the angles of this ridge project over the fossa
hypophyseos in the form of prominent tubercles, called the processus clinoidei
posteriores (posterior clinoid processes). To these are attached the tentorium
cerebelli and interclinoid ligaments. In front of the fossa hypophyseos there is a
transverse elevation, the tuberculum sellse, towards the lateral extremities of which,
and somewhat behind, there are oftentimes little spurs of bone, the processus
clinoidei medii (middle clinoid processes). In front of the tuberculum sellse is the
sulcus chiasmatis, which passes laterally on either side to become continuous,
between the roots of the small wings, with the optic foramina.
This groove is liable to considerable variations, and apparently does not always serve for the
lodgment of the optic chiasma. (Lawrence, " Proc. Soc. Anat.," Journ. Anat and Physiol.
vol. xxviii. p. 18.)
In front of the sulcus chiasmatis, from which it is often separated by a thin sharp
edge, the superior surface continues forwards on the same plane as the upper surfaces
of the small wings, and terminates anteriorly in a ragged edge, which articulates with
the lamina cribrosa of the ethmoid, and has often projecting from it, in the median
plane, a pointed process, the sphenoidal spine. The lateral aspects of the body are fused
with the great wings, and in part also with the roots of the pterygoid processes.
Curving along the side of the body, above its attachment to the great wing,
is an f- shaped groove, the sulcus caroticus (carotid groove), which marks the
position and course of the internal carotid artery. Posteriorly, the hinder margin
of this groove, formed by the salient lateral edge of the posterior surface of the
body, articulates with the apex of the petrous portion of the temporal bone, and
is hence called the petrosal process ; just above this, on the lateral border of the
dorsum sellae, there is often a groove for the abducent nerve.
The anterior surface of the body displays a vertical, median crista sphenoidalis
(sphenoidal crest), continuous above with the . sphenoidal spine, and below with
the pointed projection called the sphenoidal rostrum. This crest articulates in front
with the perpendicular plate of the ethmoid. On each side of the median plane
are seen the irregular openings leading into the sphenoidal air sinuses, the thin
anterior walls of which are in part formed by the absorption of the sphenoidal
conchse (O.T. turbinated bones) with which in early life they are in contact. With
exception of a broad groove leading downwards from the apertures above mentioned,
which enters into the formation of the roof of the nasal cavity of the corre-
sponding side, the lateral aspects of this surface of the bone are elsewhere in
articulation with the labyrinths of the ethmoid and the orbital processes of the
palate bones. The sphenoidal rostrum is continued backwards for some distance
along the inferior surface of the body, where it forms a prominent keel which
fits into the recess formed by the alee of the vomer. The edges of the alae
serve to separate the rostrum from the incurved vaginal processes at the roots of
the medial plates of the pterygoid processes. Posteriorly, the inferior surface of the
body of the sphenoid is rougher, and covered by the mucous membrane of the roof
of the pharynx ; here, occasionally, a median depression may be seen which marks
the position of the inferior extremity of a foetal channel, called the canalis
craniopharyngeus.
Alae Parvae. The small wings are two flattened triangular plates of bone
which project forwards and laterally from the anterior and upper part of the body
of the bone, with which they are united by two roots which enclose between
them the optic foramina for the transmission of the optic nerves and ophthalmic
arteries. Of these roots, the posterior springs from the body just wide of the
tuberculum sellae, separating the carotid groove behind from the optic foramen
in front ; laterally this root is confluent with the recurved posterior angle of the
small wing, forming the projection known as the processus clinoideus anterior
(anterior clinoid process), which overhangs the anterior part of the body of the
bone and affords an attachment to the tentorium cerebelli and interclinoid liga-
ments. The anterior root, broad and compressed, unites the upper surface of the
small wing with the anterior and upper part of the body. Laterally, the lateral
136 OSTEOLOGY.
angle terminates in a pointed process which reaches the region of the pterion and
there articulates with the frontal, and may come in contact with the great wing.
The superior aspect is smooth, and forms, in part, the floor of the anterior cranial
fossa. The inferior surface constitutes part of the posterior portion of the upper
wall of the orbit, and also serves to roof in the superior orbital fissure (O.T. sphenoidal
fissure), which separates the small wing from the great wing below. The anterior
edge is ragged and irregular, and articulates with the orbital parts of the
frontal. The posterior margin, sharp and sickle-shaped, , separates the anterior
from the middle cranial fossa, and corresponds to the position of the stem of the
lateral cerebral fissure on the inferior surface of the cerebrum.
Alae Magnae.: The great wings, as seen from above, are of a somewhat
crescentic shape and form a considerable portion of the floor of the middle
cranial fossa. If the medial convex edge of the crescent be divided into fifths, the
posterior fifth extends backwards and laterally beyond the body of the bone,
presenting a free posterior edge, which forms the anterior boundary of the
foramen lacerum. This border ends behind in the horn of the crescent, from
which a pointed process projects downwards, called the spina angularis ; this is
wedged into the angle between the petrous and squamous parts of the temporal
bone. The medial surface of the posterior border and spine is furrowed for the
cartilaginous part of the auditory tube (sulcus tubae), whilst on the medial side of
the spine the course of the chorda tyrnpani nerve is indicated by a groove (Lucas).
The second fifth of the convex border of the crescent is fused to the side of the
body and united below with the root of the pterygoid process. The angle formed
by the union of the great wing with the side of the body posteriorly corresponds
to the posterior end of the carotid groove, the lateral lip of which is formed by a
projecting lamina called the lingula. The remaining three-fifths of the convex
border is divisible into two nearly equal parts ; the medial is a free, curved, sharp
margin, which forms the inferior margin of the superior orbital fissure, the cleft
which separates the great wing from the small wing, and which establishes a
wide channel of communication between the middle cranial fossa and the cavity
of the orbit, transmitting the oculomotor, trochlear, ophthalmic division of the
trigeminal, and the abducent nerves, together with the ophthalmic veins. Wide of
the superior orbital fissure this edge becomes broad and serrated, articulating
with the frontal bone medially, and at the part corresponding to the anterior
horn of the crescent, by a surface of variable width, it unites with the sphenoidal
angle of the parietal bone. The lateral border corresponds to the concave side
of the crescent, and is serrated for articulation with the squamous part of the
temporal, being thin and bevelled at the expense of its parietal surface above and
laterally, and broad and thick behind as it passes towards the angular spine.
The internal or cerebral surface is concave from behind forwards, and, in its anterior
part, from side to side also; it forms a considerable part of the floor of the
middle cranial fossa, and bears the impress of the gyri of the extremity of the
temporal lobe of the cerebrum, which rests upon it ; towards its lateral side it is
grooved obliquely by an anterior branch of the middle meningeal artery.
The following foramina pierce the great wing : Close to and in front of the alar
spine is the foramen spinosum, for the transmission of the middle meningeal
artery and its companion vein, together with the nervus spinosus from the man-
dibular division of the trigeminal nerve. In front of and medial to this, and close
to the posterior free border, is the foramen ovale, of large size and elongated
form. This gives passage to the motor root and mandibular division of the
trigeminal nerve, and admits the accessory meningeal branch of the middle
meningeal artery ; a small emissary vein from the cavernous sinus usually passes
through this foramen, and occasionally also the lesser superficial petrosal nerve.
Near the anterior part of the root of the great wing, and just below the sphenoidal
fissure, is the foramen rotundum, of smaller size and circular form. Through this
the maxillary division of the trigeminal nerve escapes from the cranium. Occasion-
ally there is a small canal the foramen of Vesalius which pierces the root of
the great wing to the medial side of the foramen ovale. This opens below into
the scaphoid fossa at the base of the medial pterygoid lamina, and transmits a
THE SPHENOID BONE. 137
small vein. Occasionally there is a small foramen (canaliculus innominatus)
to the medial side of the, foramen spinosum for the transmission of the small
superficial petrosal nerve.
The external surface of the great wing enters into the formation of the walls of
the orbital, temporal, infra-temporal, and pterygo-palatine fossae by three well-
defined areas ; of these the upper two, i.e. the orbital and the temporal, are separated
by an oblique jagged ridge, the margo zygomaticus (zygomatic border), for articula-
tion with the fronto-sphenoidal process of the zygomatic bone. Occasionally the
lower part of this ridge articulates with the zygomatic process of the maxilla.
The facies orbitalis (orbital surface) lies to the medial side of this crest and
is directed forwards and a little medially ; of quadrilateral shape, it forms the
posterior and lateral wall of the orbit ; plane and smooth, it is bounded posteriorly
by the sharp inferior free margin of the superior orbital fissure, towards the medial
extremity of which a pointed spine (spina recti lateralis), for the attachment
of the inferior common ligament of origin of the ocular muscles, can usually
be seen. It is limited superiorly by the edge of a rough triangular area which
articulates with the frontal bone ; anteriorly by the zygomatic border ; whilst
inferiorly a free, well-defined oblique margin constitutes the posterior and lateral
boundary of the fissura orbitalis inferior (inferior orbital fissure), which separates
this part of the bone from the orbital surface of the maxilla. Below this border
there is a grooved surface which leads medially toward the orifice of the foramen
rotundum. In the articulated skull this forms part of the posterior wall of the
pterygo-palatine fossa.
To the lateral side of the zygomatic border, which bounds it in front, is the
facies temporalis (temporal area), concavo-convex from before backwards. It slopes
medially below, where it is separated from the spheno-maxillary area by a well-
marked muscular ridge, the crista infratemporalis (infra-temporal crest). Behind, the
temporal surface is bounded by the margin of the great wing which articulates
with the squamous part of the temporal (margo squamosus), and above by the edge
which unites it with the sphenoidal angle of the parietal and with the frontal bone.
The temporal surface enters into the formation of the floor of the fossa of the same
name, and affords an extensive attachment to the fibres of origin of the temporal
muscle. The facies sphenomaxillaris (spheno-maxillary surface), the third of the
areas above referred to, is situated below the infra-temporal crest, and corre-
sponds to the under surface of the posterior half of the great wing ; it extends
as far back as the angular spine and posterior border. Opening on it are seen
the orifices of the foramen spinosum and ovale. It is slightly concave from side
to side, and is confluent medially with the lateral surface of the lateral pterygoid
plate. In front, it is bounded by a ridge which curves upwards and laterally
from the anterior part of the lateral pterygoid plate to join the infra-temporal crest.
In the articulated skull this ridge forms the posterior boundary of the pterygo-
maxillary fissure. The spheno-maxillary surface overhangs the infra-temporal
fossa, and affords an origin for the superior head of the external pterygoid muscle.
The processus pterygoidei (pterygoid processes) spring from the inferior surface
of each lateral aspect of the body as well as from the under side of the roots
of the great wings, and pass vertically downwards. Each consists of two laminae,
the lateral and medial laminae of the pterygoid process, fused together anteriorly, and
enclosing between them posteriorly the pterygoid fossa.
The lateral pterygoid plate, thin and expanded, is directed obliquely back-
wards and laterally, its lower part being often somewhat everted. Its posterior
edge is sharp, and often has projecting from it one or two spines, to one of which
(processus pterygospinosus) the pterygo-spinous ligament, which stretches towards
the angular spine, is attached. Laterally it furnishes an origin for the inferior
head of the external pterygoid muscle, and on its medial side, where it forms the
lateral wall of the pterygoid fossa, it supplies an attachment for the internal
pterygoid muscle.
The medial pterygoid plate is narrower and somewhat stouter. By its
medial aspect it forms the posterior part of the lateral wall of the nasal cavity ;
laterally it is directed towards the pterygoid fossa. Its posterior edge ends
138 OSTEOLOGY.
below in the bamulus pterygoideus (pterygoid booklet), which, reaching a lower level
than the lateral plate, curves backwards and laterally, furnishing a groove on
its lower surface in which the tendon of the tensor veli palatini muscle glides ;
superiorly, the sharp posterior margin of the medial plate bifurcates, so as to
enclose the shallow scaphoid fossa from which the tensor veli palatini muscle
arises, and wherein may occasionally be seen the inferior aperture of the foramen
Vesalii. To the medial edge of this fossa, as well as to the posterior border of
the medial pterygoid plate, the pharyngo-basilar fascia is attached. Here, too,
the cartilage of the auditory tube is supported on a slight projection, and the
pharyngo-palatinus muscle receives an origin, whilst the superior constrictor of
the pharynx arises from the inferior third of the same border and from the
pterygoid hamulus. Superiorly and medially the medial plate forms an incurved
lamina of bone, the processus vaginalis (vaginal process), which is applied to the
inferior surface of the lateral aspect of the body, reaching medially towards the
root of the rostrum, from which, however, it is separated by a groove, in which, in
the articulated skull, the ala of the vomer is lodged. The angle formed by the
vaginal process and the medial edge of the scaphoid fossa forms a projection called
the pterygoid tubercle, immediately above which is the posterior aperture of the
pterygoid canal, through which the nerve and artery of the canal (O.T. Yidian) are
transmitted. On its inferior surface the vaginal process displays a groove (sulcus
pterygopalatinus), which in the articulated skull is converted into the pbaryngeal
canal by its union with the palate bone. In front, at its root, the pterygoid
process displays a broad smooth surface (facies spbenomaxillaris), which is confluent
above with the root of the great wing around the foramen rotundum, and forms
the posterior wall of the pterygo-palatine fossa. Here, to the medial side of the
foramen rotundum, is seen the anterior opening of the pterygoid canal. Below,
the pterygoid laminae are , separated by an angular cleft, the pterygoid fissure ;
in this is lodged the pyramidal process of the palate bone, the margins of which
articulate with the serrated edges of the fissure.
Connexions. The sphenoid articulates with the occipital, temporal, parietal, frontal,
ethmoid, sphenoidal conchae, vomer, palate and zygomatic bones, and occasionally with the
maxillae.
Ossification. The sphenoid of man is formed by the fusion of two parts, the pre-
sphenoid and the post-sphenoid, each associated with certain processes. In most mammals
the orbito-spbenoids or small wings fuse with the pre-sphenoid, whilst the alisphenoids or
great wings, together with the medial pterygoid lamina, ankylose with the post-sphenoid.
The ossification of these several parts takes place in cartilage, with the exception of the
medial pterygoid lamina, which is developed from an independent centre in the connective
tissue of the side wall of the oral cavity (Hertwig).
At the end of the second month a centre appears in the root of the great wing between
the foramen ovale and foramen rotundum; from this the ossification spreads laterally and
c b a b c backwards and also downwards into the lateral
^^^^^i rf^) pterygoid lamina. According to Fawcett the
^H 5>^tr3/ks^i=v^^^[ pterygoid laminae or the common root of the
N>x. ^i IT -'-li j '
X ^vS3r^9E3^8H two I amm8e m the adult is practically the
^\^^^^St^JSm. -/ on ly P ar t f the ala temporalis preformed in
^*~/& cart ^ a e > t ^ ie wno ^ e f the lateral pterygoid
NI ^ I ^^^|^^^>' lamina and that part of the alisphenoid pro-
Jlrm iT^ jected into the orbital and temporal fossae are
ossified in membrane ; so too are the foramen
PIG. HG.-OSSIFICATION OF THE SPHENOID. ovale *^ foramen spinosum. Meanwhile two
i. -j * ^ ^-^ centres appear about the same time in the
a, Pre-spnenoid ; o, Orbito-spheuoids ; c, Ahsphenoids ; i r -j - -\ ' c j.-u
d, Medial pterygoid lamina; e, Basi-sphenoid. basi-sphenoid in relation to the floor of the
fossa hypophyseos and on either side of the
cranio-pharyngeal canal, around which they ossify, ultimately leading to the obliteration
of that channel. Somewhat later a spbenotic centre appears on each side, from which
the lateral aspect of the body and the lingula are developed. Fusion between these
four centres is usually complete by the sixth month.
In the pre-sphenoid a pair of lateral nuclei make their appearance about the middle of
the third month, just lateral to the optic foramina; from each of these the orbito-
THE ETHMOID BONE. 139
sphenoids (small wings) and their roots are developed. About the same time another
pair of centres, placed medial to the optic foramina, constitute the body of the pre-
sphenoid. At first the superior surface of the body of the pre-sphenoid is exposed in the
interval between the orbito-sphenoids, but by the ultimate coalescence of the medial borders
of the orbito-sphenoids to form the jugum sphenoidale the body of the pre-sphenoid is
almost completely covered over superiorly. By the coalescence of these in front, and
their ultimate union with the basi-sphenoid behind, a cartilaginous interval is enclosed,
of triangular shape, which, however, becomes gradually reduced in size by the ingrowth
of its margins so as to form two medially placed foramina, as may be frequently
observed in young bones one opening on the surface of the tuberculum sellee, the other
being placed anteriorly. (Lawrence, " Proc. Soc. Anat.," Journ. Anat. and Physiol. vol.
xxviii. p. 19.)
As has been seen, the medial pterygoid laminae are developed in membrane and are the
first parts of the sphenoid to ossify. (Fawcett, Anat. Anz., vol. xxvi. 1905, p. 280.) Each is
derived from a single nucleus which appears about the ninth or tenth week, and fuses with
the inferior surface of the great wing, there forming a groove which is converted into the
pharyngeal canal when the alisphenoid and medial pterygoid laminae fuse later with the
body of the post-sphenoid. The hamulus, however, chondrifies before it ossifies during
the third month. Fawcett also regards the lateral pterygoid plate as of membranous
origin.
At birth the sphenoid consists of three parts : one comprising the orbito-sphenoids
together with the body of the pre-sphenoid and the basi-sphenoid, the others consisting of
the alisphenoids, one on each side. Fusion of the latter with the former occurs near the
end of the first year. The dorsum sellse at birth consists of a cartilaginous plate which
separates the body of the post-sphenoid from the basi-occipital. This slowly ossifies, but
the cartilage does not entirely disappear till the age of twenty-five, by which time bony
ankylosis of the basi-cranial axis is complete. For a considerable time the under surface
of the body of the pre-sphenoid displays a bullate appearance, with the 'sides of which
the sphenoidal conchae articulate. It is only after the seventh or eighth year is reached
that the spongy tissue within this part of the bone becomes absorbed to form the
sphenoidal sinuses,
The sphenoidal conchae, or bones of Bertin, best studied in childhood, are formed
by the fusion of four distinct ossicles (Cleland), the centres for which appear in the later
months of utero-gestation. Each bone consists of a hollow, three -sided pyramid, the
apex of which is in contact with the anterior part of the vaginal process of the medial
pterygoid lamina, whilst the base fits on to the posterior surface of the labyrinth of the
ethmoid. The inferior surface of each forms the roof of the corresponding nasal cavity,
and completes the formation of the spheno-palatine foramen, whilst the lateral aspect is
united with the palate borte and forms the medial wall of the pterygo-palatine fossa, and
occasionally constitutes a part of the orbital wall posterior to the lamina papyracea of
the ethmoid. The superior surface of each sphenoidal concha is applied to the anterior
and inferior surface of the body of the pre-sphenoid on the corresponding side of the
rostrum. It is by the absorption of this surface that the contained sphenoidal sinus is
ultimately extended. In the bases of the pyramids are formed the apertures through which
the sinuses open in to the nasal cavity in the adult. Up to the age of five these ossicles
remain independent, but subsequently, owing to their firm ankylosis with the surrounding
bones, they are merely represented in the adult disarticulated skull by the irregular frag-
ments adherent to the separated borders of the ethmoid, palate, and sphenoid bones.
Os Ethmoidale.
The ethmoid bone lies in front of the sphenoid, and occupies the interval
between the orbital parts of the frontal, thus entering into the formation of the
anterior cranial fossa as well as the medial walls of the orbits and the roof and medial
and lateral walls of the nasal cavities. The bone, which is extremely light, consists
of two cellular parts the labyrinth! ethmoidales (ethmoidal labyrinths), which are
united superiorly to a median lamina perpendicularis (perpendicular plate) by a thin
horizontal lamina which, from its perforated condition, is called the lamina cribrosa
(cribriform plate). The general arrangement of the parts of the bone resembles the
capital letter T ; the median plate corresponds to the vertical limb, the cribriform
plate to the horizontal limb of the T, whilst the ethmoidal labyrinths may be
140
OSTEOLOGY.
Middle meatus
FIG. 147. THE ETHMOID SEEK FROM BEHIND.
regarded as comparable to the enlarged down-turned extremities of the horizontal
limb of the letter.
The study of this bone will be much facilitated by cutting through the cribriform plate on
one side of the perpendicular plate, thus removing the ethmoidal labyrinth of one side and
exposing more fully the central perpen-
Alar process Crista galli didllar lamina.
The perpendicular plate, of ir-
regular pentagonal shape, forms the
superior part of the nasal septum.
Its superior border projects above the
level of the cribriform plate so as to
form a crest, which is much elevated
anteriorly, where it terminates in a
thick, vertical, triangular process,
called the crista galli, the interior of
which is filled with fine spongy
bone, but is occasionally pneumatic.
The superior edge of this process
is sharp and pointed, and affords
attachment to the falx cerebri.
In front of this process there is
a groove which separates the pro-
cessus alares (alar processes) which
project from the crista galijon either side. By articulation with the frontal bone
this groove is converted into a canal, the foramen caecum ; this, however, is not
always blind, but frequently transmits a vein to the roof of the nose. The
posterior border of the perpendicular plate is thin, and articulates with the crest of
the sphenoid. The posterior inferior border in the adult is ankylosed with the
vomer ; and the anterior inferior border, which is usually thicker than the others,
unites with the carti-
laginous nasal septum.
The anterior superior
border articulates with
the spine of the frontal
bone and with the
median crest formed by
the union of the two
nasal bones. The per- ( rbit
pendicular plate, which
is usually deflected to
one or other side, has
generally smooth sur-
faces, except above, where
they are channelled by
short and shallow
grooves leading to the
foramina which pierce the cribriform plate; these are for the lodgment of the
olfactory nerves.
The ethmoidal labyrinth is composed of exceedingly thin bone, enclosing
a large number of air-cells ; these are arranged in three groups an anterior, a
middle, and a posterior, the walls of which have been broken in front, above,
behind, and below, in the process of disarticulation. Laterally they are closed
in by a thin oblong lamina, the lamina papyracea or orbital plate, which forms
a part of the medial wall of the orbit, and articulates above with the orbital
part of the frontal, which here roofs in the ethmoidal cells. (The line of this
suture is pierced by two canals, the anterior and posterior ethmoidal foramina,
both of which transmit small ethmoidal vessels and nerves. In front, the lamina
papyracea articulates with the lacrimal bone ; whilst below, by its union with
Anterior and posterior
ethmoidal grooves
Alar process
Infundibulum
Middle meatus-
Middle concha of the nose
Perpendicular plate
Uncinate process
FIG. 148. THE ETHMOID SEEN FROM THE RIGHT SIDE.
THE ETHMOID BONE.
141
Superior conch
of the nose
Cribriform
plate
Anterior ethmoidal
groove
Uncinate process
jthe orbital surface of the maxilla, the air-sinuses in both situations are completed.
( Posteriorly, the lamina papyracea articulates with the sphenoid, and, at its posterior
! inferior angle for a variable distance, with
. the orbital process of the palate bone, both
of which serve to close in the air-cells.
The medial aspect of the ethmoidal labyrinth
displays the convoluted conchae of the nose,
usually two in number, though occasion-
ally there may be three rarely more. In
cases where there are two conchse or ethmo-
turbinals 1 they are separated posteriorly
by a deep groove. A channel is thus
formed in the posterior part of the lateral
and upper aspect of the nasal cavity, called
the superior meatus, which is roofed in bv ^
J FIG. 149. SECTION SHOWING THE NASAL ASPECT
the concha nasalis superior (superior concha), O p THE LEFT LABYRINTH OF THE ETHMOID.
whilst its floor is formed by the superior
surface of the concha nasalis media (middle concha). The posterior ethmoidal cells
open into this meatus. In front of the superior meatus, which only grooves the
posterior half of this aspect of the bone, the surface is rounded from above
downwards and before backwards, and forms the medial wall of the anterior and
middle ethmoidal cells. Kunning obliquely from above downwards and backwards
over the medial surface of the superior concha, are a number of fine grooves con-
tinuous above with the foramina in the cribriform plate ; these are fewer and
more scattered in front, do not pass on to the middle concha, and are for the
olfactory nerves.
The middle concha is nearly twice the length of the superior. Its
anterior extremity is united for a short distance to the ethmoidal crest on the
medial side of the frontal
process of the maxilla. By
its thickened, free convoluted
border it overhangs a deep
groove which runs along the
inferior surface of the ethmoidal
labyrinth. This is the middle
meatus of the nose. It receives
the openings of the middle eth-
moidal cells, which project in to the
meatus, forming a rounded ele-
vation called the ethmoidal bulla.
In front of and below the bulla
is a groove, the hiatus semilunaris,
Lacnmal process .P ' '
which by articulation above with
adjacent bones is converted into
a canal, the infundibulum, which
^inferior concha runs upwards and forwards and
forms a channel of communication
Maxillary process Ethmoidal process .,, ,-, f , -, j ,-,
with the frontal sinus and the
FIG. 150. SHOWING THE ARTICULATION OF THE INFERIOR . ,, t n n
CONCHA WITH THE ETHMOID. anterior ethmoidal cells. Curving
downwards, backwards, and a
little laterally from the roof of the anterior part of this meatus, in front of
the infundibulum, is the processus uncinatus. This bridges across the irregular
opening on the medial wall of the maxillary sinus, and articulates inferiorly with
the ethmoidal process of the inferior concha. The posterior extremity of the middle
concha articulates with the ethmoidal crest on the perpendicular part of the
palate bone.
The lamina cribrosa (cribriform plate) is the horizontal lamina which con-
Crista galli
Lamina papyracea
Alar process
Perpendicu-
lar plate
Uncinate process
1 So called to distinguish them from the maxillo-turbinals and naso-turbinals of comparative anatomy.
142
OSTEOLOGY.
Alar process
Crista galli v
nects the ethmoidal labyrinths with the perpendicular plate. It occupies the
interval between the orbital parts of the frontal bone, roofing in the nasal cavities
inferiorly, and superiorly forming, on each side of the crista galli, two shallow
olfactory grooves, in which, in the recent con-
dition, the olfactory bulbs of the cerebrum
are lodged. Numerous foramina for the trans-
mission of the olfactory nerves pierce this
fflitfor Mao-ciliary part o f tne k one . tnose to tne me dial and
lateral sides of the groove are the largest
and most regular in their arrangement.
Along the lateral edges of the cribriform plate
two notches can usually be distinguished;
when articulated with the frontal bone these
form the medial openings of the ethmoidal
foramina. Leading forwards from the anterior
of these there is often a groove which crosses
to the side of the crista galli, where it ends
in a slit which allows of the transmission of
the anterior ethmoidal nerve to the nose.
Posteriorly, the cribriform plate articulates
with the spine of the sphenoid.
Connexions. The ethmoid articulates with the
sphenoid and sphenoidal conchae, the frontal, the
two nasals, two maxillae, two lacrimals, two inferior conchse, two palates, and the vomer.
Ossification takes place in the cartilage of the nasal capsule. Each labyrinth has
one centre, which appears about the fourth or fifth month in the neighbourhood of the
lamina papyracea. According to Fawcett ossification first commences in a process which
passes outside the naso-lacrimal duct to reach the frontal process of the maxilla. From this
the laminae around the ethmoidal air-cells are formed, which are complete at birth, the
air-sinuses in this instance not being formed by the absorption of spongy bone. From
these centres the conchse are also developed, and these too are ossified at the ninth month.
At birth the ossified labyrinths are united to the cartilaginous septum by a
fibrous layer. Two centres make their appearance in the septal cartilage on either side
of the root of the crista galli about the end of the first year ; from these, the crista galli
and the perpendicular plate are ossified, as well as the medial part of the cribriform plate,
the lateral portions of which are derived from a medial extension of the labyrinths.
Ossification is usually complete about the fifth or sixth year. About the twenty-fifth
year bony union has taken place between the cribriform plate and the sphenoid, but
ankylosis between the perpendicular plate and the vomer is not usual till the fortieth or
forty-fifth year.
Conchas Nasales Infcriores.
The inferior conchae (O.T. inferior turbinated bones) are two shell-like laminae
of bone lying along the lower part of the lateral wall of the nasal cavity on either
Lamina
papyracea
Cribriform plate Ethmoidal labyrinth
FIG. 151. THE ETHMOID SEEN FROM ABOVE.
Lacrimal process
Ethmoidal process
Ethmoidal process
Lacrimal process
Maxillary process
B
FIG. 152. THE EIGHT INFERIOR CONCHA. A, Medial Surface ; B, Lateral Surface.
side. Of elongated form, the bone displays two curved borders enclosing a medial
and lateral surface.
The superior or attached border is thin and sharp in front and behind, where
THE LACEIMAL BONES. 143
ij.t articulates with the inferior conchal crests on the medial surface of the body
inf the maxilla and the perpendicular part of the palate bone, respectively. Be-
tween these two articulations the central part of the superior border rises in the
t'orm of a sharp crest, the anterior part of which forms the upstanding lacrimal
process which articulates above with the descending process of the lacrimal bone,
as well as with the edges of the naso-lacrimal groove of the maxilla, thus com-
pie ting the osseous canal of the naso-lacrimal duct. The posterior end of this crest
is elevated in the form of an irregular projection called the ethmoidal process. This
j unites with the uncinate process of the ethmoid bone (see Fig. 150). Spreading
downwards from the middle of the superior border, on its lateral side, is a thin
'irregular plate of bone, the maxillary process, which partially conceals the lateral
iconcave surface of the bone, and, by its union with the medial wall of the
maxillary sinus, assists in the completion of the partition which separates that
cavity from the inferior nasal meatus.
The inferior or free border, gently curved from before backwards and turned
slightly laterally, is rounded and full, and formed of bone which is deeply pitted
land of a somewhat cellular character. The anterior and posterior extremities of
jthe bone, formed by the convergence of the superior and inferior borders, are thin
i and sharp ; as a rule the posterior end is the more pointed of the two. The medial
surface projects into the nasal cavity ; convex from above downwards, and slightly
.curved from before backwards, it forms the floor of the middle meatus. It is
rough and pitted, and displays some scattered and longitudinally directed vascular
grooves. The lateral surface overhangs the inferior meatus of the nose. Concave
;from above downwards, and to some extent from before backwards, it is directed
towards the lateral wall of the nasal cavity. It is smooth in front, where it
.corresponds to the opening of the canal for the naso-lacrimal duct; behind and
1 towards its inferior border it is irregular and pitted. In the disarticulated bone
this surface is in part concealed by the downward projecting maxillary process.
Connexions. The inferior concha articulates with the maxilla, lacrimal, ethmoid, and
palate bones.
Ossification. The inferior concha (the maxillo-turbinal of comparative anatomy)
is derived from the cartilage forming the lateral wall of the nasal capsule, the upper
portion of which forms the ethmo - turbinals. It ossifies, however, from a separate
(centre, which appears about the fifth month of foetal life, and later contracts a union
by a horizontal lamella on its lateral side with the maxilla.
Ossa Lacrimal ia.
The lacrimal bone, a thin scale of bone about the size of a finger-nail, forms part
of the medial orbital wall behind the frontal process of the maxilla. Irregularly
quadrangular, it has two surfaces a medial and lateral and four borders.
Its lateral or orbital surface has a vertical ridge, the crista lacrimalis pos-
terior (posterior lacrimal crest), running downwards upon it. In front of this is
ithe sulcus lacrimalis (lacrimal groove) for the lodgment of the lacrimal sac. The
medial wall of this groove descends below the level of the
bulk of the bone, and forms the descending process, which orbital surface
helps to complete the osseous canal for the naso-lacrimal
duct, and articulates inferiorly with the inferior concha.
The inferior end of the lacrimal crest terminates in a hook-
like projection, the hamulus lacrimalis (lacrimal booklet),
which curves round the posterior and lateral edge of
ithe naso-lacrimal notch of the maxilla, and thus defines
the upper aperture of the canal for the naso-lacrimal duct.
To the free edge of the crest, behind the lacrimal groove, are
attached the reflected portion of the medial palpebral liga- FlG i53._R IGHT LACRIMAL
ment and the lacrimal part of the orbicularis oculi, the crest BONE (Orbital Surface),
being sometimes thickened at the site of this attachment.
The part of the bone behind the lacrimal crest is smooth and continuous with the
\ surface of the lamina papyracea of the ethmoid. The medial surface is irregular and
144
OSTEOLOGY.
cellular above ; it closes in some of the anterior ethmoidal cells and helps to
complete the infundibulum. Where it is smoother it forms a part of the
lateral wall of the middle meatus of the nose immediately behind the frontal
process of the maxilla, and above the inferior concha. The superior border
articulates with the orbital part of the frontal; the anterior edge with the
posterior border of the frontal process of the maxilla, with which it completes
the lacrimal groove for the lodgment of the lacrimal sac. The inferior margin
articulates with the orbital surface of the maxilla, and in front by its descending
process with the inferior concha. Posteriorly the bone articulates with the
anterior border of the lamina papyracea of the ethmoid.
Connexions. The lacrimal bone articulates with fou-r bones the frontal, ethmoid, inferior
concha, and the maxilla.
Ossification. The lacrimal is developed from a single centre, which makes its
appearance about the end of the second or the beginning of the third month of intra-
uterine life in the membrane around the cartilaginous nasal capsule.
Palate
Maxilla
FlG. 154. TflE VOMER AS SEEN FROM THE
RIGHT SIDE.
Vomer.
The vomer or ploughshare bone, a bone of irregular quadrilateral shape, is
placed in the posterior part of the nasal septum. It has four borders and two
surfaces. The superior border, which can
Groove for readily be distinguished by the presence
ias ne?ve tm Groove on either side of an everted lip or ala,
WL> / ^JJ 3 ?!^ 1 s ^P es from behind upwards and forwards,
and articulates with the inferior surface
of the body of thfe sphenoid, the pointed
rostrum of which is received into the
groove bounded by the projecting alae.
Laterally these alas are wedged in between
the sphenoidal processes of the palate
bones in front, and the vaginal processes
at the root of the medial laminae of the
pterygoid processes behind. The posterior border, which slopes from behind down-
wards and forwards, is free, and forms a sharp, slightly curved edge; this con-
stitutes the posterior margin of the nasal septum, and
serves to separate the openings of the choanae (O.T.
posterior nares). The inferior border, more or less
horizontal in direction, articulates with the nasal
crest formed by the maxillae and palate bones. The
anterior edge is the longest ; it slopes obliquely from _
-, -, j j ^ j T j i i r Vomer at Birth, displaying its forma-
above downwards and forwards. In its upper half ti0 n by two Osseous Lamime united
it is ankylosed to the perpendicular plate of the inferioriy. The figure to the right
ethmoid ; in its lower half this margin is grooved for exhibits the appearance of the bone,
the reception of the septai cartikge of the nose. L"int?^^ ^
The anterior extremity of the bone forms a trun-
cated angle, which articulates with the posterior border of the incisor crest of
the maxillae, and sends downwards a pointed process which passes between
the incisor foramina. The right and left surfaces of the bone are smooth and
covered by mucous membrane. It is not uncommon to find them deflected to
one or other side. A few vascular grooves may be noticed scattered over these
surfaces, and one, usually more distinct than the others, running obliquely down-
wards and forwards, indicates the course of the naso-palatine nerve.
Connexions. The vomer articulates with the sphenoid, the ethmoid, the palates, and the
maxillae. In front it supports the septai cartilage.
Ossification. The vomer commences to ossify in membrane at the end of the
second month. A nucleus appears on each side of the middle line, below the nasal
septum, medial to the plane of the anterior paraseptal cartilages and posterior to them.
During the third month the nuclei, which have increased in height and length,
FIG. 155.
THE NASAL BONES.
145
(fuse at their lower edges, and by forward growth invade the posterior end of each
[anterior paraseptal cartilage,, thus forming a deep groove in which the septal cartilage
I is lodged (Fawcett). As growth goes on the groove becomes reduced by the further
{ fusion of the lateral plates and the absorption of the cartilage, until the age of puberty,
by which time the lateral laminae have united to form a median plate, the primitively
divided condition of which is now only represented by the eversion of the alae and
j the grooving along the anterior border. According to Fawcett, the ossification of the
| Jacobsonian cartilage produces a hitherto undescribed element in the formation of the
; osseous nasal septum.
Ossa Nasal ia.
The nasal bones, two in number, lie in the interval between the frontal
processes of the maxillae, there forming the bridge of the nose. Each bone
j is of elongated quadrangular form,
I having two surfaces an inner and
i outer and four borders. The outer
surface, somewhat constricted about a
its middle, is convex from side to a
side, and slightly concavo-convex from J>
above downwards. Near its centre ' |
there is usually the opening of a
nutrient canal.
The inner surface is not so ex-
tensive as the outer, as the superior
and anterior articular borders encroach
somewhat upon it above. Concave
from side to side, and also from above
downwards, it is covered, in the recent
condition, by the mucous membrane of the nose. Eunning downwards along this
surface is a narrow groove (sulcus ethmoidalis) which transmits 'the anterior
ethmoidal nerve. The anterior or medial border, thin below, is thick above,
and, in conjunction with its fellow at the opposite side, with which it
articulates, forms a median crest posteriorly, which is united to the spine of the
frontal, the perpendicular plate of the ethmoid, and the septal cartilage of the nose,
in that order from above downwards. The posterior or lateral border, usually
the longest, is serrated and bevelled to fit on to the anterior edge of the frontal
process of the maxilla. The superior border forms a wide toothed surface, which
articulates with the medial part of the nasal notch of the frontal bone anteriorly ;
whilst, posteriorly, it rests in contact with the root of the nasal process of the same
bone. The inferior border is thin and sharp, and is connected below with the lateral
cartilage of the nose, and is usually deeply notched near its medial extremity.
Connexions. The nasal bone articulates with its fellow of the opposite side, with the frontal
above, posteriorly with the perpendicular plate of the ethmoid and with the frontal process of the
maxilla. It is also united to the septal and lateral cartilages of the nose.
Ossification. The nasal bones are each developed from a single centre, which
makes its appearance, about the end of the second month, in the membrane covering the
anterior part of the cartilaginous nasal capsule. Subsequent to birth the underlying
cartilaginous stratum disappears, persisting, however, below in the form of the lateral
nasal cartilage, and behind as the septal cartilage of the nose.
B
FIG. 156. THE RIGHT NASAL BONE.
A, Lateral side ; B, Medial side.
Ossa Suturarum (O.T. Wormian).
Along the line of the cranial sutures and in the region of the fontanelles, isolated
bones of irregular form and variable size are occasionally met with. These are the once so-
called Wormian bones, named after the Danish anatomist Wormius. They are now called
ossa suturarum (sutural bones). Their presence depends on the fact that they are either
developed from distinct ossific nuclei, or it may be from a division of. the primary ossific
deposit. Their occurrence may also be associated with certain pathological conditions
10
146
OSTEOLOGY.
which modify the development of the bone. They usually include the whole thickness
of the cranial wall, or they may only involve the outer or inner tables of the cranial
bones. They are most frequent in the region of the lambda and the lambdoid suture.
They occur commonly about the pterion, and in this situation are called epipteric bones
(Flower). By their fusion with one or other of the adjacent bones they here lead to the
occurrence of a fronto-squamosal suture. Their presence has also been noted along the
line of the sagittal suture, and sometimes in metopic skulls in the inter-frontal suture.
They are occasionally met with at the asterion and more rarely at the obelion. They
appear less frequently in the face, but their presence has been noted around the lacrimal
bone, and also at the extremity of the inferior orbital fissure, where they may form an
independent nodule wedged in between the great wing of the sphenoid, the zygomatic, and
the maxillary bones.
OSSA FACIEI.
The bones of the face, seven in number, comprise two maxillae, two palates,
two zygoma tics, with the mandible or lower jaw.
'Frontal process
Lacrimal groove
The Maxillae.
The maxillae, of which there are two, unite to form the upper jaw. Each
consists of a body, with which are connected four projections, named respectively
the zygomatic, frontal, alveolar, and palatine processes.
The body (corpus) is of pyramidal form, and contains within it a hollow called
the maxillary sinus. It has four surfaces a facial or antero-lateral, an infra-
temporal or postero-lateral, an orbital or supero- lateral, and a nasal or medial
and four processes the malar, frontal, alveolar, and palatine.
Surfaces. The facies anterior (antero-lateral surface) is confluent below with
the alveolar process. Above, it is separated from the orbital aspect by the
margo infraorbitalis (infra-orbital margin), whilst medially it is limited by the free
margin of the nasal notch, which ends below in the pointed spina nasalis anterior
(anterior nasal spine). Posteriorly it is separated from the infra-temporal surface by
the inferior border of
the zygomatic process.
The facial aspect of the
bone is ridged by the
sockets of the teeth
(juga alveolaria). The
ridge corresponding to
the root pf the canine
tooth is usually the
most pronounced; med-
ial to this/ and over-
lying the roots of the
incisor teeth, is the
shallow incisive fossa,
whilst placed laterally,
3 J on a higher level, is
the deeper canine fossa,
the floor of which is
formed in part by the
projecting zygomatic
process. Above this,
and near the infra-
orbital margin, is the
infra -orbital foramen,
the external opening of the infra-orbital canal, which transmits the infra-orbital
nerve and artery.
Anterior
nasal spine
Canine fossa
Tuberosity
FIG. 157. THE RIGHT MAXILLA (Lateral View).
THE MAXILLAEY BONES.
147
Ridge for middle
concha
Middle meat
Anterior nasal
spine
Alveolar
process
Nasal crest
FIG. 158. THE RIGHT MAXILLA (Medial Aspect).
The infra - temporal or postero - lateral surface is separated above from
'the orbital aspect by a rounded free edge, which forms the anterior margin
of the inferior orbital
fissure in the articulated Frontal P rocess
; skull. Inferiorlyand an-
| teriorly it is separated
i from the anterior surface
by the zygomatic process
and its free lower border.
Medially it is limited by
a sharp, irregular margin
with which the palate
bone articulates. This
surface is more or less
convex, and is directed
towards the infra-tem-
poral and pterygo-pala-
tine fossae. It is pierced
in a downward direction
by the apertures of the
alveolar canals (foramina
alveolaria), two or more
in number, which trans-
mit the corresponding
nerves and vessels to the
molar teeth. Its lower
part, slightly more pro-
minent where it over-
hangs the root of the third molar, is often called the tuber maxillare (maxillary
tuberosity).
The planum orbitale (orbital surface), smooth and plane, is triangular in shape
and forms part of the floor of the orbit. Its anterior edge corresponds to the
infra-orbital margin; its posterior border coincides with the anterior boundary
of the inferior orbital fissure. Its thin medial edge, which may be regarded
as the base of the triangle, is notched in front to form the sulcus lacrimalis
(lacrimal groove), behind which it articulates with the lacrimal bone for a short
distance, then for a greater length with the lamina papyracea of the ethmoid,
and terminates posteriorly in a surface for articulation with the orbital process
of the palate bone. Its lateral angle corresponds to the base of the zygomatic
process. Traversing its substance is the infra-orbital canal, the anterior opening of
which has been already noticed on the anterior aspect of the body. Behind, however,
owing to deficiency of its roof, the canal forms a groove which lips the edge of the
bone which constitutes the anterior boundary of the inferior orbital fissure. If this
canal be laid open, the orifices of the middle and anterior alveolar canals will be
seen, which transmit the corresponding vessels and nerves to the premolar, canine
and incisor teeth.
The facies nasalis (nasal surface) of the body is directed medially towards the
nasal cavity. Below, it is confluent with the superior surface of the palatine process ;
anteriorly it is limited by the sharp edge of the nasal notch ; above and anteriorly it
is continuous with the medial surface of the frontal process ; behind this it is deeply
channelled by the lacrimal groove, which is converted into a canal by articulation
with the lacrimal and inferior conchal bones. The channel so formed conveys the
naso-lacrimal duct from the orbital cavity above to the inferior nasal meatus below.
Behind this groove the upper edge of this area corresponds to the medial margin
of the orbital surface, and articulates from before backwards with the lacrimal,
lamina papyracea of the ethmoid, and the orbital process of the palate bone. The
posterior border, rough for articulation with the palate bone, is traversed obliquely
from above downwards and slightly medially by a groove, which, by articulation
with the palate bone, is converted into the pterygo-palatine canal, which transmits
10 a
148 OSTEOLOGY.
the greater palatine artery and anterior palatine nerve. Towards its upper and
posterior part the nasal surface of the body displays the irregular, more or less
triangular, opening of the maxillary sinus. This aperture which, in the articulated
skull opens into the middle meatus of the nose, is much reduced in size by articula-
tion with the lacrimal, ethmoid, palate, and inferior conchal bones. In front of
the lacrimal groove the nasal surface is ridged horizontally by the crista conchalis
(inferior conchal crest), to which the inferior conchal bone is attached. Below this
the bone forms the lateral wall of the inferior nasal meatus, receiving the termina-
tion of the lacrimal groove. Above, and for some little distance also on the
medial side of the frontal process, it constitutes the smooth lateral wall of the
atrium of the middle meatus.
Processes. The processus zygoma ticus (zygomatic process), which is
placed on the antero-lateral surface of the body, is confluent anteriorly with
the facial surface of the body; posteriorly, where it is concave from side to
side, with the infra-temporal surface; whilst superiorly, where it is rough and
articular, it forms the apex of the triangular orbital surface, and supports the
zygomatic bone. Inferiorly, its anterior and posterior surfaces meet to form an
arched border, which fuses with the alveolar process opposite the root of the first
molar tooth, and serves to separate the anterior from the infra-temporal surfaces of
the body.
The processus frontalis (frontal process) arises from the upper and anterior
part of the body. It has two surfaces one lateral, the other medial. The lateral is
divided into two by a vertical ridge (crista lacrimalis anterior), which is the upward
extension of the infra-orbital margin. The narrow strip of bone behind this ridge
is hollowed out, and leads into the lacrimal groove below. Posteriorly the edge
of the frontal process here articulates with the lacrimal, and so forms the fossa for
the lodgment of the lacrimal sac (fossa sacci lacrimalis). In front of the vertical
crest, to which the medial palpebral ligament is attached, the lateral surface is
confluent below with the facial surface of the body, and forms the side of the root of
the nose. Here may often be seen a vascular groove entering the bone. Its anterior
edge is rough, or grooved, for articulation with the nasal bone. Superiorly the
summit of the process is serrated for articulation with the nasal notch of the
frontal bone. The medial surface of the frontal process is directed towards the
nasal cavity. It is crossed obliquely from below upwards and backwards by a ridge
the agger nasi or ethmoidal crest which is considered to be a vestige of the naso-
turbinal which is met with in some mammals. Below this the bone is smooth and
forms the upper part of the atrium of the middle meatus, whilst the ridge
itself articulates posteriorly with the anterior part of the middle conchal bone,
formed by the inferior concha of the ethmoid bone.
The processus alveolaris (alveolar process) projects from the inferior surface
of the body of the bone below the level of the palatal process. Of curved form, it
completes, with its fellow of the opposite side, the alveolar arch, in which are
embedded, in sockets or alveoli, the roots of the teeth of the maxilla ; ordinarily
in the adult, when dentition is complete, each alveolar process supports eight teeth.
Piercing the medial surface of the alveolar border behind the incisor teeth two
small vascular foramina are usually visible. When any or all the teeth are shed
the alveoli become absorbed, and the process may under these circumstances be
reduced to the level of the plane of the palatine process. Posteriorly the alveolar
process ends below the maxillary tuberosity of the body ; anteriorly it shares in the
formation of the intermaxillary suture.
The processus palatinus (palatine process), of the form of a quadrant, lies in
the horizontal plane; it has two surfaces superior and inferior and three borders,
a straight medial, a more or less straight posterior, and a curved lateral, by which
latter it is attached to the medial side of the body and alveolar process as far back
as the interval between the second and third molar teeth. Its inferior surface,
together with that of its fellow, forms the anterior three-fourths of the vaulted
hard palate ; it is rough and pitted for the glands of the mucous membrane of the
roof of the mouth, and is grooved, near the alveolar margin, by one or two
channels which pass forward from the pterygo - palatine canal and transmit the
THE MAXILLAEY BONES. 149
anterior palatine nerve and greater palatine artery. Its superior surface,
smooth and concave from side to side, forms the floor of the corresponding
nasal cavity. Its medial border, broad and serrated, rises in a ridge superiorly, so as
to form with its fellow of the opposite side the nasal crest, which is grooved
superiorly to receive the inferior border of the vomer. In front of its articulation
with the vomer this ridge rises somewhat higher, being named the incisor crest,
anterior to which it projects beyond the free border of the nasal notch, and
together with its fellow forms the pointed projection called the anterior nasal
spine. These parts support the septal cartilage of the nose. Immediately to the
lateral side of the incisor crest the superior surface of the palatine process is
pierced by a foramen which leads downwards, forwards, and a little medially, to
open into a broad groove on the medial border of the bone immediately behind
the central incisor tooth. When the two maxillae are articulated, the two grooves
form the oval foramen incisivum, into which the two afore-mentioned foramina open
like the limbs of a Y ; these are called the foramina of Stensen, and represent the
channels by which in lower animals the organs of Jacobson open into the mouth.
In man they afford a means of establishing an anastomosis between the vessels of
the mouth and nose. In front and behind these, and lying within the fossa and
in the line of the suture, are the smaller foramina of Scarpa, which transmit the
naso-palatine nerves, the right nerve usually passing through the posterior foramen,
the left through the anterior. The posterior border of the palatine process, which is
sharp and thin, falls in line with the interval between the second and third molar,
and articulates with the horizontal part of the palate bone.
Sinus Maxillaris. The maxillary sinus lies within the body of the bone, and
is of corresponding pyramidal form, its base being directed towards the nasal cavity,
with the middle meatus of which it communicates, its summit extending laterally
into the root of the zygomatic process. It is closed in anteriorly, posteriorly, and
above by the thin walls which form the anterior, infra -temporal, and orbital
surfaces of the body. Inferiorly it overlies the alveolar process in which the molar
teeth are implanted, more particularly the first and second, the sockets of which
are separated from it by a thin layer of bone.
The angles and corners of this cavity are frequently groined by narrow ridges
of bone, one superiorly corresponds to the relief formed by the infra-orbital canal.
A vascular and nervous groove is often exposed, curving along the floor of the
maxillary sinus just above the alveoli of the teeth. The interior of the cavity is
lined by an extension from the mucous membrane of the nose.
Connexions. The maxilla articulates with the nasal, frontal, lacrimal, and ethmoid
bones above, laterally with the zygomatic, and occasionally with the sphenoid, posteriorly
and medially with the palate, whilst on its medial side it unites with its fellow of the opposite
side, and also supports the inferior concha and the vomer.
Ossification. The maxillae (proper) are developed in the connective tissue around
the oral aperture of the embryo. Ossification commences in membrane from one centre in
the neighbourhood of the canine tooth germ. From this centre growth takes place
rapidly in several directions, viz., upwards on the lateral side of the nasal capsule to form
the posterior part of the frontal process, backwards to form the zygomatic process,
downwards to form the lateral wall of the alveolar process, and medially to form
the palatine process. From the latter a process descends downwards on the medial
side of the teeth to form the medial wall of the alveolar process. At first a large gap
intervenes between the greater part of the palatine process and the zygomatic process,
but bridges of bone ultimately connect the two, separating the various tooth germs,
and so forming the tooth sockets. About the fourth month the maxilla invades a
small lateral cartilaginous process of the nasal capsule (Mihalkovics), and incorporates
it within itself. The infra-orbital nerve is at first placed considerably above the orbital
surface of the maxilla, and only comes in contact with it in the second month when
a groove is formed on the bone, which by the uprising of its lateral wall and its folding
over medialwards finally encloses the nerve and forms the infra-orbital canal and fora-
men. This account of the ossification of the maxilla, which differs considerably from
that given in previous editions, is based on the work of Mall and Fawcett. In the early
stages of the development of the bone the alveolar groove, in which the teeth are
105
150
OSTEOLOGY.
developed, lies close below the infra-orbital groove, and it is not till later that they
become separated by the growth of the maxillary sinus, which first makes its
appearance as a shallow fossa to the medial side of the
orbito-nasal element about the fourth month. In the
adult bone the course of the infra-orbital canal and
foramen indicates the line of fusion of the orbito-nasal
and zygomatic elements, whilst the position of the
anterior palatine canal serves to determine the line of
union of the incisive with the palatine elements. In
addition to the foregoing centres, Rambaud and Renault
describe another, the infra -vomerine, which, together
with its fellow, is wedged in between the incisive and
the palatine elements beneath the vomer, thus explaining
the Y-shaped arrangement of the foramina of Stensen,
which open into the incisive foramen.
The premaxillae, which in most vertebrates are in-
dependent bones lying in front of the maxillse, constitute
in man and apes the portions of the maxilla which
lie in front of the incisive foramen, and support the
superior incisor teeth. Each premaxilla is developed
from two centres : a facial, which ultimately contains
the incisor and canine teeth, and forms the anterior part
of the hard palate, as well as the anterior half of the
frontal process of the complete maxilla (Fawcett) ; and
a palatine centre (infra vomerine of Rambaud and
Renault) which forms the medial wall of the correspond-
ing canal of Stensen. The former develops very early,
either before or after the maxilla (Mall), and fuses almost
~ at once with the maxilla along the alveolar margin ; the
A, Lateral side ; B, Medial side ; C, , , , & , .,. '
Under side, a, Nasal process ; 6, latter appears about the twelfth week, and soon fuses
Orbital plate ; c, Anterior nasal spine ; with the facial centre. The line of fusion of the pre-
d t Infra-orbital groove ; e, Infra-orbital maxillae with the maxillae proper can be readily seen
foramen; /Anterior palatine groove; in young s k u lls, and occasionally also in the adult. It
a, Palatine process ; h, Premaxillary J , . , J , ,
suture ; t, Alveolar process. corresponds to a suture which passes on the palate
obliquely laterally and forwards, from the incisive
foramen to the interval between the lateral incisor and the canine tooth. In cases
of alveolar cleft palate the adjacent bones fail to unite along the line of the suture.
In some instances, however, the cleft passes outwards between the central and lateral
incisor teeth, and this condition suggests the explanation that the premaxillary element is
derived from two centres a lateral and a medial. The researches of Albrecht and
Warinski support this view. The latter anatomist further observes that the lateral
cleavage may lead to a division of the dental germ of the lateral incisor tooth, and so
explain the occurrence of the supernumerary incisor which is occasionally met with. In
this way the different varieties of cleft palate are readily explained ; median cleft palate
being due to failure of union between the two premaxillary bones. Lateral cleft palate
may be of two types : the cleft in one case passing forwards between the central and
lateral incisor, and being due to the non-union of the two elements from which the
premaxilla is primarily developed ; the other, in which the cleft passes between the
lateral incisor and the canine, or between the lateral incisor and a supernumerary in-
cisor, owing to the imperfect fusion of the premaxilla laterally with the maxilla.
FIG. 159. OSSIFICATION OF THE
MAXILLA.
Ossa Palatina.
The palate bone, of irregular shape, assists in the formation of the lateral
wall of the posterior part of the nasal cavity, the posterior portion of the hard
palate, the orbit, the pterygo^-palatine, the infra-temporal, and the pterygoid fossae.
It consists of horizontal and vertical parts, united to each other like the limbs of
the letter L. At their point of union there is an irregular outstanding process,
called the pyramidal process, whilst capping the summit of the vertical part and
separated by a deep cleft are two irregular pieces of bone, called the sphenoidal and
orbital processes.
THE PALATE BONES.
151
The pars horizontalis (horizontal part) has two surfaces and four borders.
As its name implies, it is horizontal in position, and forms the posterior third of
the hard palate. ' Its superior surface, which is smooth, is slightly concave from side
to side, and forms the floor of the posterior part of the nasal cavity. Its inferior
! surface, rougher, is directed towards the mouth, and, near its posterior edge, often
displays a transverse ridge for the attachment of a part of the aponeurosis of the
tensor veli palatini muscle. The anterior border articulates by means of an irregular
suture with the posterior edge of the palatine process of the maxilla. The posterior
margin is free and concave from side to side ; by its sharp edge it furnishes
attachment to the aponeurosis of the soft palate. The medial border is upturned,
and when it articulates with its fellow of the opposite side it forms superiorly
a central crest continuous in front with the nasal crest of the maxilla; it
supports the posterior part of the inferior border of the vomer, and projecting
beyond the line of the posterior border forms the posterior nasal spine. The
lateral border fuses with the vertical part, forming with it a right angle.
The posterior extremity of this edge is grooved by the foramen palatinum
majus.
Sphenoid
Pter
palatine
Orbital process
Ethmoid
Orbital surface
For maxilla
Orbital process
Sphenoid
Surface towards
maxillary sinus
terygoid
Dr lateral
)terygoid
lamina
yramidal
process
.rface for attach. Surface Pterygo-palatine sulcus
>f pterygoideus for maxilla
internus
Maxillary
Maxillary process
process
Nasal crest
Horizontal
part
Orbital surface
Ethmoid
Crista ethmoidalis
Spheno-palatine notch
Crista
conchal is
Sphenoidal
process
Superior
meatus
Middle meatus
Inferior meatus
Pterygoid fossa
Pyramidal
process
Posterior For medial
nasal spine pterygoid lamina
B
FIG. 160. RIGHT PALATE BONE.
A, As seen from the Lateral Side ; B, As viewed from the Medial Side.
The pars perpendicularis (perpendicular part) is very much broader below
than above. Composed of thin bone, particularly at its superior part, it is liable
to be broken in the process of disarticulation, so that it is somewhat uncommon to
meet with a perfect specimen. It may be described as possessing two surfaces
and four borders. Its medial surface, which is directed towards the cavity of the
nose, is crossed horizontally, about its middle, by the crista conchalis (conchal crest)
with which the posterior end of the superior border of the inferior conchal bone
articulates ; above and below this, it enters into the formation of the lateral wall
of the middle and inferior meatuses of the nose, respectively. Near the superior
extremity of the perpendicular part, and below the processes which spring from it,
there is another ridge more or less parallel to that already described. This is the
crista ethmoidalis (ethmoidal crest), and with this the posterior extremity of the middle
concha articulates. The lateral surface, which forms the medial wall of the pterygo-
palatine fossa, is channelled by a vertical groove (sulcus pterygopalatinus), converted
into the pterygo -palatine canal by articulation with the maxilla. This canal, called
at its lower end the greater palatine foramen, transmits the posterior palatine nerve
and greater palatine vessels. Anteriorly the lateral surface projects forwards to a
variable extent, and helps to close in the maxillary sinus by its maxillary process.
The anterior border is a thin edge, of irregular outline, which articulates above with
the ethmoid, with the posterior edge of the maxillary process of the inferior conchal
bone about its middle, and below with the maxilla. The posterior border, thin above,
152
OSTEOLOGY.
Orbital process
Sphenoid
Sphenoidal process
Pharyngeal groov
Middle meatus
Orbital
^X surface
Spheno-pala-
tine notch
Crista conchalis
Inferior meatus
Nasal crest
Posterior
nasal
spine
Ho
horizontal plate
For medial pterygoid lamina
FIG. 161. THE EIGHT PALATE BONE.
As seen from behind.
Pyramidal
process
Pterygoid
fossa
where it articulates with the anterior part of the medial pterygoid lamina, expands
below into the pyramidal process. The inferior border of the vertical part is con-
fluent with the lateral edge of the horizontal
part; posteriorly, and immediately in front
of the tuberosity, it is notched by the lower
extremity of the greater palatine foramen.
The superior border supports the orbital
and sphenoidal processes; the former
the anterior is separated from the latter
by a notch (incisura sphenopalatina), which
is converted into the spheno-palatine fora-
men by the articulation of the palate bone
with the inferior surface of the sphenoid.
Through this communication between the
pterygo-palatine fossa and nasal cavity pass
the spheno-palatine artery and the nasal
branches of the spheno-palatine ganglion.
The processus pyramidalis (pyra-
midal process) is directed backwards and
laterally from the angle formed by the
perpendicular and horizontal parts, and
presents, on its posterior surface, a central
smooth vertical groove, bounded on each side by rough articular furrows which
unite above in a V-shaped manner with the upper thin posterior edge. These latter
articulate with the anterior parts of the lower portions of the medial and lateral ptery-
goid laminae, while the central groove fits into the wedge - like interval between the
two pterygoid laminae, thus entering into the formation of the pterygoid fossa. The
lateral surface of the pyramidal process is rough above, where it is confluent with the
lateral surface of the perpendicular part which articulates with the tuberosity of
the maxilla ; below, there is a small, smooth, triangular area which appears between
the tuberosity of the maxilla and the lateral surface of the lateral pterygoid lamina,
and so enters into the medial wall of the infra-temporal fossa. Passing through
the pyramidal process in a vertical direction are the foramina palatina minora
(lesser palatine foramina) for the transmission of the lesser palatine nerves and
vessels.
The processus orbitalis (orbital process), shaped like a hollow cube, surmounts
the anterior part of the vertical plate. The open mouth of the cube is usually directed
backwards and medially towards the anterior part of the body of the sphenoid, with the
cavity of which it commonly communicates; the anterior part of the cube articulates
with the medial end of the angle formed by the orbital plate and infra- temporal
surface of the maxilla. Of the- remaining four surfaces, one directed forwards
medially articulates with the ethmoid. The others are non-articular : the superior
enters into the formation of the floor of the orbit ; the lateral is directed towards
the pterygo-palatine fossa ; whilst the inferior, which is confluent with the medial
surface of the vertical part, is of variable extent, and overhangs the superior
meatus of the nose.
The processus sphenoidalis (sphenoidal process), much smaller than the
orbital, curves up wards, medially, and backwards from the posterior part of the summit
of the perpendicular part. Its superior surface, which is grooved, articulates with the
anterior part of the inferior surface of the body of the sphenoid and the root of the
medial pterygoid lamina, thereby converting the groove into the pharyngeal canal,
which transmits an artery of the same name together with a pharyngeal branch
from the spheno-palatine ganglion. Its lateral side enters into the formation of part
of the medial wall of the pterygo-palatine fossa. Its medial curved aspect is
directed towards the nasal cavity, whilst its medial edge is in contact with the ala
of the vomer.
Connexions. The palate bone articulates with its fellow of the opposite side, with the
ethmoid, vomer, sphenoid, maxilla, and inferior concha.
THE ZYGOMATIC BONES.
153
Ossification. The palate bone ossifies in membrane at the side of the nasal segment
of the bucco-nasal cavity, medial to the descending palatine nerves, at a time when each
half of the developing palatine shelf is hanging down by the side of the tongue. When
the palatine shelf becomes horizontal, as it does in the fifth week, bone extends into it
to form the horizontal plate. From this common centre all parts of the palate bone
develop but the orbital process may be ossified from an independent centre, which either
fuses with the palate bone, or with the sphenoid, or with the ethmoid.
Ossa Zygomatica.
The zygomatic bone (O.T. malar) underlies the most prominent part of
the cheek, and is hence often called the cheek-bone. Placed to the lateral side
of the orbital cavity, it forms the sharp lateral border of that hollow, and serves
to separate that space from the temporal and infra- temporal fossae which lie behind ;
below, it rests upon and is united to the maxilla; behind, it enters into the for-
mation of the zygomatic arch, which bridges across the temporal fossa.
As viewed from the lateral side, the bone is convex from side to side, and has
four processes, of which three are prominent. These are the fronto r sphenoidal
Fronto-sphenoidal process
Fronto-sphenoidal process
Temporal border
Zygomatico-
orbital foramen
Masseteric
border
Maxillary
border
Zygomatico-
facial canal
For articulation
with maxilla
Orbital process
Temporal
process
Infra-
temporal
surface
A B
FIG. 162. THE RIGHT ZYGOMATIC BONE. A, Lateral Side; B, Medial Side.
(processus frontosphenoidalis), the marginal or pointed extremity of the maxillary
border, and the temporal (processus temporalis). The -most elevated part of the
convex malar surface (facies malaris) forms the malar tuberosity.
The temporal process ends posteriorly in an oblique edge, which articulates
with the extremity of the zygomatic process of the temporal bone. The fronto-
sphenoidal process, the most prominent of the three, is united superiorly to
the zygomatic process of the frontal bone. The edge between the frontal and
temporal processes is thin and sharp"; it affords attachment to the temporal fascia,
and near its upper end there is usually a pronounced angle (processus marginalis),
formed by a sudden change in the direction of the border of the bone. It is just
below this point that the zygomatico-temporal branch of the zygomatic nerve
becomes cutaneous. The inferior margin of the temporal process is somewhat
thicker and rounded ; it extends downwards and forwards towards the inferior
angle, where the bone articulates with the maxilla, and is there confluent with the
ridge which separates the facial from the infra -temporal aspect of the maxilla.
This edge of the bone is sometimes called the masseteric border, since it affords
attachment to the fibres of origin of the masseter muscle. Sweeping downwards, in
front of the fronto-sphenoidal process, is a curved edge which terminates inferiorly
in a pointed process. This border forms the lateral and, in part, the inferior margin
of the orbital cavity. Between the anterior extremity of the masseteric edge and
the pointed anterior angle there is an irregular suture by which the bone is
joined to the maxilla. The opening of the foramen zygomaticofaciale (zygomatico-
154 OSTEOLOGY.
facial foramen) is seen on the lateral surface of the bone ; its size and position
are very variable.
The medial aspect of the bone is distinguished by a curved elevated crest, called'
the orbital process, which extends medially and backwards, and is confluent
laterally with the orbital margin. This process has two surfaces one anterior,
which forms a part of the lateral and lower wall of the orbit, and one posterior,
which is directed towards the temporal fossa above and the infra- temporal fossa
below. The free edge of the orbital process is thin and serrated ; a little below
its middle it is usually interrupted by a non-articular notch, which corresponds
to the anterior extremity of the inferior orbital fissure. The part above this
articulates with the great wing of the sphenoid, the portion below with the orbital
surface of the maxilla. Behind the orbital process the medial surface of the bone is
concave from side to side, and extends backwards along the medial aspect of the
temporal process and upwards over the posterior half of the medial side of the
frontal process, thus entering into the formation of the infra- temporal and temporal
fossae respectively. The orbital surface of the orbital process usually displays the
openings of two canals (foramina zygomatico - orbitalia) one which traverses the
bone below the orbital margin and appears on the front of the bone as already
described, .the other which passes obliquely upwards and laterally through the
orbital process and appears in the temporal fossa, to the medial side of the frontal
process (foramen zygomaticotemporale). The former
transmits the zygomatico-facial branch, the latter the
zygomatico- temporal branch of the zygoma tic nerve.
Just under the orbital margin and a short distance-
below the zygoma tico-frontal sutures there is usually
^^=^^^*^-^= a * a gmall tubercle serving for the attachment of the
lateral palpebral raphe. (Whitnall, Journ. Anat.
Club-shaped process ^ PhyM., Vol. xlv.)
B * low ^e orbital process there is a rough tri-
angular area, bounded laterally by the maxillary
border. This articulates with the zygomatic process of the maxilla, and occasionally
forms the lateral wall of the maxillary sinus.
Connexions. The zygomatic bone articulates with the frontal, sphenoid, maxilla, and
temporal bones.
Ossification. The zygomatic ossifies in membrane. Its basis appears about the tenth
week as a thin ossifying lamina which corresponds to the orbital margin, attached to
which there is a backward expansion corresponding to the body of the bone ; from this
posteriorly there extends the element of the temporal process. On the medial side, and
lying within the angle formed by the orbital and temporal elenients, there appears a
secondary thickening, which develops into a cup -shaped layer which fits into the recess
and ultimately forms the surface of the bone directed to the temporal fossa. Below
the orbital margin on the medial side, and extending backwards towards the temporal
process, is another secondary thickening, which forms a club-shaped nodule, the thick
end of which is directed forwards, whilst posteriorly it forms, in part, the lower margin
of the body and temporal process. The overlap of these several parts leads to the
formation of grooves which may persist in the adult as sutures. (Karl Toldt, junr.,
Sitzsbr. des Akad. des Wiss., Wien, July 1902.) Regarding the ossification of this bone
there are great differences of opinion ; not a few anatomists describe it as developed from
a single centre. Support, however, is given to its origin from multiple centres owing to
the frequency with which in the adult it is met with in a divided condition.
lYlandibuIa.
The mandible or lower jaw, of horse-shoe shape, with the extremities up-
turned, is the only movable bone of the face. Stout and strong, it supports
the teeth of the lower dental arch, and articulates with the base of the cranium,
by the joints, on either side, between its condyles and the mandibular fossse of the
THE MANDIBLE.
155
temporal bones. The anterior or horizontal part, which contains the teeth, is
called the corpus mandibulae, (body) ; the posterior or vertical portions constitute the
rami mandibulse.
The body displays in the median plane, in front, a faint vertical ridge, the
symphysis, which indicates the line of fusion of the two symmetrical halves from
which the bone is primarily developed. In-
feriorly this ridge divides so as to enclose, in
well-marked specimens, a triangular area the
protuberantia mentalis (mental protuberance),
the centre of which is somewhat depressed, thus
emphasising the inferior angles, which are
known as the tubera mentalia (mental tubercles).
The lateral surface is crossed by a faint, elevated
ridge, the linea obliqua (oblique line), which
runs upwards and backwards from the mental
tubercle to the lower part of the anterior
border of the ramus, with which it is conflu-
ent. From this
ridge arise the m.
quadratuslabiiin-
ferioris and the tri-
angular muscle.
A little above this,
midway between 3 _
the upper and /
lower borders of ^
the mandible, and
in line with the
root of the second
premolar tooth,
the bone is pierced
by the mental fora-
men; this is .the
anterior opening
of the inferior
alveolar canal, which traverses the body of the bone. Through this aperture
the mental vessels and nerves reach the surface. The upper border supports
the sixteen teeth of the mandible. It is thick behind and thinner in front, in
correspondence with the size of the roots of the teeth. Anteriorly the sockets
of the incisor and canine teeth produce a series of vertical elevations (juga
alveolaria), of which that corresponding to the canine tooth is the most prominent.
When this is outstanding it gives rise to a hollowing of the surface between
it and the symphysis, often referred to as the incisor fossa ; frequently, however,
this is only faintly marked. Below the oblique line the bone is full and rounded,
and ends below in the basis mandibulsB (inferior border). This slopes laterally
at the sides, and forwards in front, where it is thick and hollowed out on either
side of the symphysis to form the digastric fossae, to which the anterior
bellies of the digastric muscles are attached; narrowing somewhat behind
this, the base again expands opposite the molar teeth, and finally becoming
reduced in width, terminates posteriorly at the angle formed between it and
the posterior border of the ramus. The medial surface of the body is crossed
by the mylo-hyoid line. This slants from above downwards and forwards
towards the lower part of the symphysis. It serves for the origin of the
mylo-hyoid muscle, and also, just behind the last molar tooth, furnishes an
attachment to the superior constrictor of the pharynx. Below the posterior part
of this ridge the surface is hollowed to form a fossa for the lodgment of the
submaxillary gland. Above the anterior part of the mylo-hyoid line the bone is
smooth and usually convex. Here the sublingual gland lies in relation to it.
In the angle formed by the convergence of the, two mylo-hyoid lines,, and in
Fia. 164. THE MANDIBLE AS SEEN FROM THE LEFT SIDE.
1. Mental tubercle.
2. Mental protuberance.
3. Symphysis.
4. Coronoid processes.
5. Condyloid processes.
6. Neck.
7. Angle.
8. Oblique line.
9. Mental foramen.
156
OSTEOLOGY.
correspondence with the back of the lower part of the symphysis, there is a
raised tubercle surmounted by two laterally placed spines, the mental spines.
Occasionally these are again subdivided into an
upper and lower pair, or it may be that the lower
pair may fuse to form a rough median ridge. To
the upper pair of spines the genio-glossi muscles
are attached, whilst the lower pair serve for the
origin of the genio-hyoid muscles. Immediately
above the tubercle there is a median foramen for
the transmission of a nutrient vessel, and close
to the alveolar border opposite the intervals be-
tween the central and lateral incisors, there are
two little vascular canals.
The ramus mandibulse passes upwards from
the posterior part s
of the body, form-
ing by the junc-
tion of its pos-
terior border with
the base of the
booly the angulus
mandibulae (angle),
which is usually
rounded and more
everted, i ^^~^^T < H^^^r^ 10
FIG. 165. THE MEDIAL SIDE OF THE RIGHT HALF OF THE MANDIBLE.
5. Coronoid process.
or
The lateral sur-
face of the ramus
affords attach-
ment to the mas-
10. Fossa for submaxillary
gland.
11. Mylo-hyoid line.
12. Digastric fossa.
Mental spines.
Seter muscle, and 2. Surface in relation to 6. Condyloid process.
When that muscle the sublin g ual g land - 7. Mandibular foramen.
, ,-, T 3. Alveolar border. 8. Mylo-hyoid groove.
is powerfully de- 4 . Lingula . 9 . Ang i e .
veloped the bone
is usually marked by a series of oblique curved ridges, best seen towards the
angle. About the "middle of the deep or medial surface is the large opening
(foramen mandibulare) of the inferior alveolar canal, which runs downwards
and forwards to reach the body, and transmits the inferior alveolar vessels
and nerve. This aperture is overhung in front by a pointed scale of bone, the
lingula mandibulae, to the edges of which the spheno-mandibular ligament
is attached. Behind the lingula and leading downwards and forwards for
an inch or so from the opening of the inferior alveolar canal is the sulcus
mylohyoideus (mylo-hyoid groove), along which the mylo-hyoid artery and nerve
pass. Behind and below this groove the medial surface of the angle is rough for
the attachment of the internal pterygoid muscle. Superiorly the ramus supports
the coronoid process in front, and the condyloid process behind, the two being
separated by the wide incisura mandibulae (mandibular notch), over which there pass
in the recent condition the vessels and nerve to the masseter muscle. The
coronoid process, of variable length and beak-shaped, is limited behind by a thin
curved margin, which forms the anterior boundary of the mandibular notch. In
front its anterior edge is convex from above downwards and forwards, and becomes
confluent below with the anterior border of the ramus and the oblique line.
To the medial side of this edge there is a grooved elongated triangular surface,
the medial margin of which, commencing above near the summit of the coronoid
process, leads downwards along the medial side of the root of the last molar tooth
towards the mylo-hyoid line. Behind this ridge the thickness of the ramus
is much reduced. The temporal muscle is inserted into the margins and medial
surface of the coronoid process. The posterior border of the ramus is continued
upwards to support the capitulum mandibulae (condyle), below which it is some-
what constricted to form the collum mandibulae (neck), which is compressed from
THE MANDIBLE.
157
before backwards, and bounds the mandibular notch posteriorly. To the medial side
of the neck, immediately below the condyle, there is a little depression (fovea ptery-
goidea) for the insertion of' the external pterygoid muscle. The convex surface of
the condyle is transversely
elongated, and so disposed
that its long axis is in-
clined nearly horizontally
medio - laterally and a
little forwards. The con-
vexity of the condyle is
more marked in its antero-
posterior than in its trans-
verse diameter, and tends
slightly to overhang the
mandibular notch. The
medial and lateral ends of
the condyle terminate in
tubercles which serve for
the attachment of part of
the articular capsule of
the joint.
FIG. 166. DEVELOPMENT OF THE MANDIBLE.
A, As seen from the medial side ; B, from the lateral side ;
C, showing accessory (metaplastic) cartilages (blue).
(In A and B Meckel's cartilage is coloured blue.)
Ossification. Its de-
velopment, is intimately as-
sociated with Meckel's carti-
lage, the cartilaginous bar of
the first visceral or man-
dibular arch. Meckel's car-
tilages, of which there are
two, are connected proxi-
mally with the periotic capsule and cranial base. These distal ends meet, but do, not
fuse, in the region of the symphysis. Ossification takes place chiefly from membrane,
in part from primordial cartilage (Meckel's cartilage), and also in part from accessory
(metaplastic) cartilages, which have no connexion with Meckel's cartilage, but arise
in the membrane from which the greater part of the bone is formed. Before ossifica-
tion commences three structures are seen lying side by side in the mandibular arch of the
. embryo. These are, from medial to lateral side, Meckel's cartilage, the inferior alveolar
nerve, which anteriorly divides into its two terminal branches, viz., the incisor and
mental nerves, and a dense connective tissue which stretches from before backwards
from close to the mid-line anteriorly to near the acoustic region posteriorly. Ossification
hi membrane commences about the fortieth to forty-fifth day in the angle between the
incisor and mental nerves ; it extends rapidly backwards under the mental nerve, which
grooves its upper surface, and is ultimately enclosed within the mental foramen. At the
same time the outer alveolar wall is formed by the extension of this ossifying membrane
bone, from which later, about the third month, is developed by backward growth the
angle and ramus, the latter surmounted by a well-defined coronoid process. About the
forty-fifth day the inner alveolar wall, the so-called splenial element, is formed by an
ingrowth from the anterior part of the floor of the mental groove. This passes below the
, incisor nerve and passes up between it and Meckel's cartilage, which it subsequently
; overlaps, extending rapidly forwards and backwards to end posteriorly in the lingula
anterior to the point of origin of the mylo-hyoid nerve. The mandible, in point of time,
is the second bone to ossify, being preceded only by the clavicle. Ossification in
MeckeVs cartilage. This commences a little later than the first formation of the coronoid
process, opposite the first and second incisor tooth germs, not by independent ossification,
but by invasion of osteoblasts from the neighbouring membrane bone. The cartilage
becomes surrounded by shelves of bone projected medially both above and below it
from the main membrane bone. A bony tube is thus formed which extends from near
the mid -line anteriorly to the second milk tooth posteriorly. Within these limits
Meckel's cartilage becomes incorporated within the mandible. The extreme anterior
end of the cartilage does not, however, undergo ossification, and the posterior end, save
that part concerned in the formation of the malleus and incus, degenerates and ultimately
disappears. Ossification in accessory cartilages. These appear at the following sites : one,
158 OSTEOLOGY.
a carrot-like mass, at the condyle ; the large end forms the condyle ; the tapering enc
is wedged into the ossifying ramus under the root of the coronoid process. This cartilag*
appears about the eleventh week. About the thirteenth week a strip of cartilage appear;
along the anterior border of the coronoid process. Along the anterior end of the alveola]
walls close to the middle line, and turning down the symphysial surface of the mandibL
to end below in the region of the future digastric impression, another mass of cartilag<
appears about the fourteenth week. All the above cartilages are ossified by invasior
from the surrounding membrane bone and are not therefore independent centres. L
is possible that the symphysial cartilages may be occasionally independently ossifieq
and thus give rise to the ossa mentalia when they exist. From what has been statecl
it thus appears that under normal conditions each half of the mandible ossifies from om j
centre only. The above account is based on the researches of Low l and Fawcett. 2
In a third or fourth month foetus the cartilage can be traced from the under surface
of the anterior part of the tympanic ring downwards and forwards to reach the jaw, tc]
which it is attached at the opening of the mandibular canal ; from this it may be tracec j
forwards as a narrow strip applied to the medial surface of the mandible, which it sensibl}
grooves. The proximal end of this furrow remains permanently as the mylo-hyoic
groove. The part of the cartilage between the tympanic ring and the mandible dis-l
appears, and its sheath becomes converted into fibrous tissue, and persists in the adult
as the spheno-mandibular ligament, its proximal end being continuous, through the*
petro-tympanic fissure, with the slender process of the malleus, with the development oij
which bone it is intimately associated. I. Chaine (Comptes fiendus, Biologie, 1903)
takes exception to this view and regards the spheno-mandibular ligament as thcj
remnant of a muscular slip.
At birth the mandible consists of two halves united at the syrnphysis by fibrous!
tissue ; towards the end of the first, or during the second year, osseous union between the j
two halves is complete. In infancy the mandible is shallow and the rami proportionately
small ; further, owing to the obliquity of the ramus, the angle is large, averaging about 150.
The mental foramen lies near the lower border of the bone. Coincident with the eruption
of the teeth and the use of the mandible in mastication, the rami rapidly increases in size,
and the angle becomes more acute. After the completion of the permanent dentition iti
approaches more nearly a right angle varying from 110 to 120. The body of the bone
is stout and deep, and the mental foramen usually lies midway between the upper and>
lower borders. As age advances, owing to the loss of the teeth and the consequent!
shrinkage and absorption of the alveolar border of the bone, the body becomes narrow and j
attenuated, and the mental foramen now lies close to the upper border. At the same time
the angle opens out again (130 to 140), in this respect resembling the infantile condition.
In old age the coronoid process and the condyle form a more open angle with each other
than in the young adult.
Os Hyoideum.
The hyoid bone, though placed in the neck, is developmentally connected
with the skull. It lies between the mandible above and the larynx below,
and is connected with the root of the tongue. Of
U-shaped form, as its name implies (Greek v and
etSos, like), it consists in the adult of a central
part, or body, with which are united two long pro- }
cesses extending backwards the greater cornua
one on each side. At the point where these
are ossified with the body, the lesser cornua, which
project upwards and backwards, are placed.
The body is arched from side to side and
compressed from before backwards, so that its
surfaces slope downwards and forwards. Its
~ " AS SEEN Anterior surface displays a slight median ridge, on
either side of which the bone is marked by the
attachment of the mylo-hyoid muscles. Its posterior surface, deeply hollowed, is
concave from side to side and from above downwards. Herein lie a quantity of
1 Journal of Anatomy and Physiology, vol. xliv. p. 82. 2 Graduation Thesis, Edinburgh, 1906.
Pn 4- o YI r\ Q
THE SKULL AS A WHOLE. 159
fat and a bursa, which separates this aspect from the thyreo-hyoid membrane. The
upper border, usually described with the anterior surface, is broad ; it is separated
from the anterior aspect by a transverse ridge, behind which are the impressions
for the attachment of the genio-hyoid muscles. Its posterior edge is thin and
sharp ; to this, above, are attached the genio-glossi, whilst behind and below the
thyreo-hyoid membrane is connected with it. The inferior border is well defined
and narrow ; it serves for the attachment of the omo-hyoid, sterno-hyoid, thyreo-
hyoid, and stylo-hyoid muscles.
The greater cornua are connected on either side with the lateral parts of the
body. At first, union is effected by synchondroses, which, however, ultimately
ossify. These cornua curve backwards, as well as upwards, and terminate in more or
less rounded and expanded extremities. Compressed laterally, they serve for the
attachments laterally of the thyreo-hyoid and hyo-glossi muscles, and the middle
constrictor of the pharynx from below upwards, whilst medially they are con-
nected with the lateral expansions of the thyreo-hyoid membrane, the free edges of
which are somewhat thickened, and connect the extremities of the greater cornua
with the ends of the superior cornua of the thyreoid cartilage below.
The lesser cornua, frequently cartilaginous in part, are about the size of grains
of wheat. They rest upon the upper surface of the bone at the junctions of the
greater cornua with the body. In youth they are separated from, but in advanced
life become ossified with, the rest of the bone, from which they are directed upwards,
backwards, and a little laterally. Their summits are connected with the stylo-
hyoid ligaments ; they also serve for the attachment of muscles.
Connexions. The hyoid is slung from the styloid processes of the temporal bones by the
stylo-hyoid ligaments. Inferiorly it is connected with the thyreoid cartilage of the larynx by
the thyreo-hyoid ligaments and membrane. Posteriorly it is intimately associated with the
epiglottis.
Ossification. In considering the development of the hyoid bone it is necessary to refer
to the arrangement and disposition of the cartilaginous bars of the second and third visceral
tarches. That of the second visceral arch, the hyoid bar or Reichert's cartilage, as it is
sometimes called is united above to the petrous part of the temporal, whilst ventrally it is
joined to its fellow of the opposite side by an independent median cartilage. Chondrifica-
tion of the third visceral arch only occurs towards its ventral extremity, forming what is
known as the thyreo-hyoid bar. This also unites with the median cartilage above mentioned.
In these cartilaginous processes ossific centres appear in certain definite situations.
Towards the end of foetal life a single centre (by some authorities regarded as primarily
double) appears in the median cartilage, and forms the body of the bone (basihyal).
About the same time ossification begins in the lower ends of the thyreo-hyoid bars, and
from these the greater cornua are developed (thyreo-hyals). During the first year the lower
ends of the hyoid bars begin to ossify and form the lesser cornua (cerato-hyals). The
cephalic ends of the same cartilages meanwhile ossify to form the styloid process
(stylohyal) on either side and one of the auditory ossicles called the stapes, whilst the
intervening portions of cartilage undergo resorption and become converted into the
.fibrous tissue of the stylo-hyoid ligaments, which in the adult connect the lesser cornua
'with the styloid processes of the temporal bone. The greater cornua fuse with the body
in middle life ; the lesser cornua only at a more advanced period. Variations in the
course of development lead to interesting anomalies of the hyoid apparatus. The lesser
cornua may be unduly long or the stylo-hyoid ligament may be bony ; in this case the
cartilage has not undergone resorption, but has passed on to the further stage of ossifica-
tion, thus forming an epihyal element comparable to that in the dog. The ossified
stylo-hyoid ligament, as felt through the pharyngeal wall, may be mistaken for a
foreign body. (Farmer, G. W. S., Brit. Med. Journ. 1900, vol. i. p. 1405.)
THE SKULL AS A WHOLE.
The skull as a whole may be studied as seen from the front (norma frontalis)
from the side (norma lateralis), from the back (norma occipitalis), from above
(norma verticalis), and from below (norma basalis).
160 OSTEOLOGY.
The Skull from the Front (Norma Frontalis).
In front, the smooth convexity of the frontal bone limits this region above
whilst inferior ly, when the lower jaw is disarticulated, the teeth of the maxilla
form its lower boundary. The large openings of the orbits are seen on either side
whilst placed centrally, and at a somewhat lower level, is the apertura piriformij
(anterior nasal aperture) leading into the nasal cavity.
The frontal region, convex from above downwards and from side to side, if
limited laterally by two ridges, which are the anterior extremities of the temporal
lines. Superiorly the fulness of the bone blends with the convexity of the vertex
Inferiorly the frontal bone forms on each side the arched superior border of the
orbit (margo supraorbitalis). The space between these borders corresponds to the
root of the nose, and here are seen the sutures which unite the frontal with
the nasal bones medially, and with the frontal process of the maxilla or
each side, called the naso-frontal and fronto-maxillary sutures, respectively. The
supra-orbital margin is thin and sharp laterally, but becomes thick and more
rounded towards its medial end, where it forms the medial angular process ant,
unites with the frontal process of the maxilla and the lacrimal bone in th(
medial wall of the orbit. This arched border is interrupted towards the media!
side by a notch (incisura supraorbitalis), sometimes converted into a foramen, foi
the transmission of the supra-orbital nerve and artery. In the median plane, jusl
above the naso-frontal suture, there is often the remains of a median suture
(sutura frontalis), which marks the fusion of the two halves from which the bom
is primarily ossified. Here also a prominence, of variable extent the glabella if
met with; from this there passes out on each side above and over the orbita
margin a projection called the superciliary arch.
The orbital fossae, of more or less conical form, display a tendency to assuim
the shape of four-sided pyramids by the flattening of the superior, inferior, anc
lateral walls. The base, which is directed forwards and a little laterally
corresponds to the orbital aperture. The shape of this is liable to individual anc
racial variations, being nearly circular in the Mongoloid type, whilst it displays i
more or less quadrangular form in Australoid skulls. The superior margin, at
has been already stated, is formed by the frontal bone between the zygomatic anc
medial angular processes. The lateral and about half the inferior margins arc
formed by the sharp curved edge between the facial and orbital surfaces of the;
zygomatic bone. The medial border and the remainder of the inferior margir
are determined by the lateral surface of the frontal process of the maxilla, anc
the sharp edge separating the facial from the orbital surface of the same bone
Three sutures interrupt the continuity of the orbital margin zygomatico-fronta:
laterally, the fronto-maxillary medially, both lying about the same level, and th(
zygomatico-maxillary inferiorly. The apex of the space is directed backwards anc
medially, so that the medial walls of the two orbits lie nearly parallel to eacl
other, whilst the lateral walls are so disposed as to form almost a right angle witl;
each other. The depth of the orbit measures, on an average, about two inche.'
(5 cm.). At the apex there are two openings ; the larger, known as the superio]
orbital fissure (O.T. sphenoidal), passes from the apex of the space laterally and *
little upwards for the distance of three-quarters of an inch or so, between th<
roof and lateral wall of the orbit. The medial third of this fissure is broad anc
of circular form. Laterally it is considerably reduced in width. Through this
the oculomotor, trochlear, ophthalmic division of the trigeminal, and the abducent
nerves enter the orbit, whilst the ophthalmic veins pass backwards through it
Above and medial to the medial end of the sphenoidal fissure there is a smalle:
circular opening, the optic foramen, for the transmission of the optic nerve anc
ophthalmic artery.
The roof of the orbit, which is very thin and brittle towards its centre
is formed in front by the orbital part of the frontal bone, and behind by ;
small triangular piece of the small wing of the sphenoid, which surrounds th<
optic foramen and forms the upper border of the superior orbital fissure. Laterally
THE FKONT OF THE SKULL. 161
face is separated from the lateral wall by the superior orbital fissure
18
3f>
FIG. 168. THE FRONT OF THE SKULL.
The nasal bones, lamina papyracea of the ethmoid, vomer, inferior concha, zygomatic, and parietal bones are
coloured red. The sphenoid, lacrimal, perpendicular part and middle concha of the < thmoid, a
mandible are coloured blue.' The maxill* are coloured yellow,
left uncoloured.
The frontal and temporal bones are
1. Mental protuberance.
2. Body of mandible.
3. Ramus of mandible.
4. Anterior nasal spine.
5. Canine fossa.
6. Infra- orbital foramen.
7. Zygomatico-facial foramen.
8. Orbital surface of maxilla.
9. Temporal fossa.
10. Lamina papyracea of ethmoid.
11. Superior orbital fissure.
12. Lacrimal bone and groove.
13. Optic foramen.
14. Ethmoidal foramina.
15. Temporal line.
16. Supra-orbital notch.
17. Glabella.
18. Frontal tuberosity.
19. Superciliary arch.
20. Parietal bone.
21. Naso-frontal suture.
22. Pterion.
23. Great wing of sphenoid.
24. Orbital surface of great wing
of sphenoid.
25. Squamous part of the temporal.
26. Left nasal bone.
27. Zygomatic bone.
28. Inferior orbital fissure.
29. Zygomatic arch.
30. Apertura piriformis, displaying
nasal' septum and inferior and
middle conchse.
31. Mastoid process.
32. Incisor fossa.
33. Angle of jaw.
34. Mental foramen.
35. Symphysis meiiti.
posteriorly, anteriorly by an irregular suture between the orbital part of the
162 OSTEOLOGY.
frontal and the upper margin of the orbital surface of the great wing of the
sphenoid, lateral to which the zygomatic process of the frontal articulates with the
zygomatic bone, often forming a ridge which limits the fossa for the lodgment of
the lacrimal gland inferiorly (Whitnall). Medially the roof is marked off from the
medial wall by a suture, more or less horizontal in direction, between the orbital
plate of the frontal and the following bones, in order from before backwards, viz.,
the frontal process of the maxilla, the lacrimal bone, and the lamina papyracea of
the ethmoid. In the suture between the last-mentioned bone and the frontal
there are two foramina, the anterior and posterior ethmoidal foramina ; both trans-
mit ethinoidal vessels and the ethmoidal branches of the naso-ciliary nerve as
well. The roof is concave from side to side, and to some extent also from before
backwards. About midway between the fronto-maxillary suture and the supra-
orbital notch or foramen, but within the margin of the orbit, there is a small
depression, occasionally associated with a spine (fovea vel spina trochlearis), for the
attachment of the cartilaginous pulley of the superior oblique muscle of the
eyeball. Under cover of the zygomatic process the roof is more deeply exca-
vated, forming a shallow fossa for the lodgment of the lacrimal gland (fossa
glandulae lacrimalis). In front, the roof separates the orbit from the frontal sinus,
and along its medial border it is in relation with the ethmoidal air-cells. The
relation to these air spaces is variable, depending on the development and size of
the sinuses. The rest of the roof, which is very thin, forms by its upper surface
part of the floor of the anterior cranial fossa, in which are lodged the frontal
lobes of the cerebrum.
The floor of the orbit is formed by the orbital surface of the maxilla, together
with part of the orbital surface of the zygomatic bone, and a small triangular
piece of bone, the orbital process of the palate, which is wedged in posteriorly.
Laterally, for three-quarters of its length posteriorly, it is separated from the lateral
wall, which is here formed by the great wing of the sphenoid, by a cleft called the
inferior orbital fissure. Through this there pass the maxillary division of the
trigeminal nerve on its way to the infra-orbital canal, the zygomatic branch of
the maxillary nerve, the infra-orbital vessels, a branch connecting the inferior
ophthalmic vein with the pterygoid plexus, and some twigs from the spheno-
palatine ganglion. By means of this fissure the orbit communicates with the
ptery go -palatine fossa behind, and the infra - temporal fossa to the lateral side,
though in the recent condition the fissure is bridged over by the involuntary
orbitalis muscle of Muller. Medially the floor is limited from behind forwards
by the suture between the following bones, viz., the orbital process of the palate
below with the body of the sphenoid above and behind, and the lamina papyracea
of the ethmoid above and in front anterior to which the orbital surface of the
maxilla below articulates with the lamina papyracea of the ethmoid and the
lacrimal above and in front. At the anterior extremity of this line of sutures
the medial edge of the orbital plate of the maxilla is notched and free between
the point where it articulates with the lacrimal posteriorly and the part from
which its frontal process arises. Here it forms the lateral edge of a canal, down
which the membranous naso-lacrimal duct passes to the nose. The floor of the
orbit is thin behind and at the sides, but thicker in front, where it blends with
the orbital margin. Passing in a sagittal direction through its substance is the
infra-orbital canal, the roof of which is usually deficient behind, where it becomes
continuous with a broad, shallow groove, which leads forwards from the anterior
margin of the inferior orbital ' fissure. This canal (canalis infraorbitalis) opens on
the anterior surface of the maxilla immediately below the orbital margin (foramen
infraorbitale) and transmits the maxillary division of the trigeminal nerve, together
with the infra-orbital vessels. The floor forms a thin partition which separates the
orbit from the maxillary sinus, which lies beneath it. Medially it completes the
lower ethmoidal air-cells, and separates the orbit from the middle meatus of the
nasal cavity.
The lateral wall of the orbit, which is the strongest, is formed by the orbital
surface of the great wing of the sphenoid and the superior part of the orbital surface
of the zygomatic bone. Above it, behind, is the superior orbital fissure, whilst below,
THE FKONT OF THE SKULL. 163
and extending much farther forward, is the inferior orbital fissure. The posterior
portion of this wall, formed by the great wing of the sphenoid, serves as a partition
between the orbit and the anterior extremity of the middle cranial fossa, in which
is lodged the pole of the temporal lobe of the cerebrum. In front of this, and
behind the line of the spheno-zygomatic suture, this wall is strengthened on its
outer aspect by its confluence with the cranial wall. Still more anteriorly, the
lateral wall separates the orbit from the temporal fossa. The anterior margin
of the lateral wall is stout and formed by the zygomatic bone, behind which,
formed in part by the orbital process of the zygomatic bone and the zygomatic
edge of the great wing of the sphenoid, it forms a fairly thick partition between
the orbit in front and the temporal fossa behind. Crossing this surface from
above downwards, close to the anterior extremity of the inferior orbital fissure,
is the suture between the zygomatic bone and the great wing of the sphenoid
(sutura sphenozygomatica). This wall is pierced in front by one or two small
canals (foramina zygomatico-orbitalia), which traverse the zygomatic bone and
allow the transmission of the zygoniatico- temporal and zygomatico-facial branches
of the zygomatic portion of the maxillary division of the trigeminal nerve. A
small tubercle, which can be more readily felt than seen, is situated just within
the orbital margin near the middle of the anterior part of this wall, and indicates
the site of attachment of the lateral palpebral raphe (Whitnall).
The medial wall of the orbit is formed from before backwards by a small part
of the frontal process of the maxilla, by the lacrimal, and by the lamina papyracea
of the ethmoid, posterior to which is a small part of the lateral aspect of the
body of the sphenoid in front of the optic foramen. Above, the orbital part of
the frontal bone forms a continuous suture from before backwards with the bones
just enumerated; whilst below, the lacrimal and the lamina papyracea of the
ethmoid articulate with the orbital plate of the maxilla ; posteriorly the posterior
extremity of the lamina papyracea and the anterior part of the body of the sphenoid
articulate with the orbital process of the palate. The orbital surface of the
lacrimal bone is divided into two by a vertical ridge the lacrimal crest (crista
lacrimalis posterior) which forms in front the posterior half of a hollow, the
fossa sacci lacrimalis, the anterior part of which is completed by the channelled
posterior border of the frontal process of the maxilla. In the fossa is lodged the
lacrimal sac, whilst passing from it and occupying the canal, of which the upper
opening is at present seen, is the membranous naso- lacrimal duct. The lower
part of the fossa separates the orbit from the anterior part of the middle meatus
of the nasal cavity. To the medial side of the upper part of the fossa for the
lacrimal sac lie the anterior ethmoidal cells, the passage leading from the nose to
the frontal sinus (infundibulum ethmoidale), and the part of the bone behind the
lacrimal crest forms the thin partition between the orbit and the ethmoidal cells.
Behind, where the body of the sphenoid forms part of the medial wall of the orbit,
the sphenoidal air sinus is in relation to the apex of that space, though here the
partition wall between the two cavities is much thicker.
The skeleton of the face on its anterior surface is formed by the two maxillae,
the frontal processes of which have been already seen to pass up to articulate
with the medial angular processes of the frontal bone, thus forming the lower
halves of the medial margins of the orbits. Joined to the maxillae laterally are
the zygomatic bones, which are supported by their union with the temporal
bones posteriorly through the medium of the zygomatic arches. The suture
which separates the zygomatic from the maxilla (sutura zygomaticomaxillaris)
commences above about the centre of the inferior orbital margin and passes
obliquely downward and laterally, its inferior end lying in vertical line with
the lateral orbital margin. The two maxillae are separated by the nasal cavities,
which here open anteriorly. Above, the two nasal bones are wedged in between
the frontal processes of the maxillae ; whilst below the apertura piriformis, the
maxillae themselves are united, in the middle line by the intermaxillary suture
(sutura intermaxillaris).
The apertura piriformis (piriform aperture) (O.T. nasal aperture or
anterior nares), which lies below and in part between the orbits, is of variable
11 a
164 OSTEOLOGY.
shape and size usually piriform, it tends to be long and narrow in Europeans, as
contrasted with the shorter and wider form met with in the negroid races. Its
edges are formed below and on either side by the free curved margin of the
body and the frontal process of the maxilla ; and above, and partly at the sides,
by the free border of the nasal bones. In the median plane, inferiorly, corresponding
to the upper end of the intermaxillary suture there is an outstanding process
the anterior nasal spine, formed by the coalescence of spicules from both maxillae ;
arising from this, and passing backwards and upwards, is a thin bony partition
the osseous septum of the nose. Often deflected to one or other side, it divides
the cavity of the nose (cavum nasi) into a right and a left half. Projecting into these
chambers from their lateral walls can be seen the medial surfaces and free borders
of the middle and inferior conchse, the spaces below and between which form the
inferior and middle meatuses of the nose, respectively.
Below the orbit, and to the lateral side of the piriform aperture, the anterior or
facial surface of the body of the maxilla is seen ; this is continuous inferiorly
with the lateral surface of the alveolar process, in which are embedded the roots
of the upper teeth.
A horizontal line drawn round the maxillse on the level of a point midway
between the lower borcler of the piriform aperture and the alveolar edge corre-
sponds to the plane of the hard palate. Below that the alveolar process separates the
cavity of the mouth from the front of the face ; whilst above, the large air space,
the maxillary sinus, lies within the body of the maxilla.
The zygomatic bone forms the lower half of the lateral and lateral half of
the lower border of the orbit. Its lateral aspect corresponds to the point of
greatest width of the face, the modelling of which depends on the flatness or
projection of this bone.
When the mandible or lower jaw is in position, and the teeth in both jaws are
complete, the lower dental arch will be seen to be smaller in all its diameters than
the upper, so that when the jaws are closed the upper teeth slightly overlap the
lower both in front and at the sides. Exceptionally, a departure from this arrange-
ment is met with.
Lateral Aspect of the Skull (Norma Lateralis).
Viewing the lateral aspect of the skull, in the first instance without the mandible,
it is seen to be formed in part by the bones of the cranium, and in part by the
bones of the face. A line drawn from the fronto-nasal suture to the tip of the mastoid
process serves to define roughly the boundary between these portions of the skull.
Of ovoid shape, the cranium is formed above by the frontal, parietal, and occipital
bones from before backwards ; whilst below, included within these are the sphenoid
and temporal bones. The sutures between these several bones are arranged as
follows : Commencing at the zygomatic process of the frontal, the suture between
that bone and the zygomatic bone is first seen ; tracing this backwards and a little
upwards, the lower edge of the frontal next articulates with the upper margin of the
great wing of the sphenoid for a distance varying from three-quarters of an inch to
one inch. Here the posterior border of the frontal turns upwards and slightly back-
wards, forming with the parietal the sutura coronalis (coronal suture). The lower
border of the parietal bone, which is placed immediately behind the frontal, articulates
anteriorly with the posterior part of the superior border of the great wing of the
sphenoid. The extent of this suture (sutura sphenoparietalis) is liable to very great
individual variation at times being broad, in other instances being pointed and
narrow, whilst occasionally the parietal does not articulate with the sphenoid at all.
Behind the spheno-parietal suture the parietal articulates with the squamous part
of the temporal (sutura squamosa), the posterior extremity of which is about one
inch behind the external acoustic meatus. Here the suture alters its character and
direction, and in place of being scaly, becomes toothed and irregular, uniting, for the
space of an inch or so, the mastoid angle of the parietal with the mastoid process of
the temporal bone. This suture (sutura parietomastoidea) is more or less horizontal
in direction, and lies in line and on a level with the superior border of the
zygomatic arch. At a point about two inches behind the external acoustic
LATEKAL ASPECT OF THE SKULL.
165
meatus the posterior border of the parietal bone turns obliquely upwards and
backwards, and forms with the squamous part of the occipital bone the strongly
denticulated sutura lambdoidea (lambdoid suture). Inferiorly this suture is con-
tinued obliquely downwards between the occipital bone and the posterior border of
the mastoid portion of the temporal, where it forms the sutura occipitomastoidea
FIG. 169. NORMA LATERALIS OF THE SKULL.
The occipital, sphenoid, and lacrimal bones and the'mandible are coloured blue. The parietal, zygomatic,
md nasal bones are coloured red. The temporal, frontal, ethmoid, and maxillary bones are left uncoloured.
1. Mental foramen.
2. Body of the mandible.
3. Maxilla.
4. Ramus of mandible.
5. Zygomatic arch.
6. Styloid process.
7. External acoustic meatus.
8. Mastoid process.
9. Asterion.
10. Superior nuchal line of occipital
bone.
11. External occipital protuberance.
12. Lambdoid suture.
13. Occipital bone.
14. Lambda.
15. Obelion placed between the two
parietal foramina.
16. Parietal bone.
17. Lower temporal line.
18. Upper temporal line.
19. Squamous part of temporal
bone.
20. Bregma.
21. Coronal suture.
22. Stephanion.
23. Frontal bone.
24. Pterion.
25. Temporal fossa.
26. Great wing of sphenoid.
27. Zygomatic bone.
28. Zygomatico-facial foramen.
29. Lacrimal bone.
30. Nasal bone.
31. Infra-orbital foramen.
32. Piriform aperture and anterior
nasal spine.
(occipito- mastoid suture), much simpler and less serrated than the two previ-
ously mentioned. These three sutures just described meet in triradiate fashion
at a point called the asterion.
Anteriorly the curve of the squamous suture is continued downward between
the anterior edge of the squamous part of the temporal and the posterior border of
the great wing of the sphenoid ; inferiorly it lies in plane with the middle of the
zygomatic arch
166 OSTEOLOGY.
The sutures around the summit of the great wing of the sphenoid are arranged
like the letter H placed obliquely, the cross.-piece of the H corresponding to the
spheno-parietal suture. When this is short, and becomes a mere point of contact,
the arrangement then resembles the letter X. This region is named the pterion.
Curving over the lateral region of the calvaria in a longitudinal direction is
the temporal line. This is often double. The lower line marks the limit of the
attachment of the temporal muscle, whilst the upper ridge defines the attachment
of the temporal fascia. Commencing in front at the zygomatic process of the
frontal, the line sweeps upwards and backwards across the inferior part of that
bone, and then crossing the coronal suture at a point called the stephanion
it passes on to the parietal, over which it curves in the direction of its mastoid
angle. Here it is continued on to the temporal bone, where it sweeps forwards
to form the supra -mastoid crest, which serves to separate the squamous from
the mastoid portion of the temporal bone laterally. Carried forwards, this ridge
is seen to become continuous with the upper border of the zygomatic arch above
the external acoustic meatus. In front, the temporal ridge separates the temporal
fossa from the region of the forehead ; above and behind, it bounds the temporal
fossa which lies within its concavity, and serves to separate that hollow from
the surface of the calvaria which is overlain by the scalp. Above the level of
the temporal lines the surfaces of the frontal and parietal bones are smooth, the
latter exhibiting an elevation of varying prominence and position, but usually
situated about the centre of the bone, called the tuber parietale (parietal tuberosity).
A slight hollowing of the surface of the parietal behind and parallel to the coronal
suture is not uncommon, and is referred to as the post-coronal depression.
As seen in profile, the part of the calvaria behind and below the lambdoid suture
is formed by the squamous part of the occipital bone. In line with the zygomatic
arch this outline is interrupted by the external occipital protuberance or inion.
The projection of this point is variable ; but its position can usually be easily
determined in the living. Passing forwards from it, and blending anteriorly with
the posterior border of the mastoid process of the temporal bone, is a rough crest,
the linea nuchae superior (superior nuchal or curved line), a little above which
there is often a much fainter line, the linea niichse suprema (highest curved line) ;
this affords attachment to the galea aponeurotica. These two lines serve to
separate the part of the cranium above, which is covered by scalp, from that
below, which serves for the attachment of the fleshy muscles of the back of the
neck, the latter surface (planum nuchale) being rough and irregular as con-
trasted with the smooth superior part (planum occipitale). The fulness of these
two parts of the occipital bone varies much. There is frequently a pronounced
bulging of the planum occipitale, and the position of the lambda can often be
easily determined in the living ; similarly the planum nuchale may be either com-
paratively flat or else full and rounded. These differences are of course associated
with corresponding differences in the development of the cerebral and cerebellar
lobes, which are lodged in relation to the cerebral aspect of these parts of the bone.
The further description of the planum nuchale is best deferred till the external
aspect of the base of the skull is studied.
Fossa Temporalis. Within the limits of the temporal lines the side of the
cranium slopes forwards, medially, and down wards, thus leaving a considerable interval
between its lower part and the zygomatic arch. This space or hollow is called the
temporal fossa ; bounded above and behind by the temporal lines, its inferior limit
is defined by the level of the zygomatic arch. Deepest opposite the angle formed
by the frontal and temporal processes of the zygomatic bone, the fossa becomes
shallow towards its circumference.
Its floor or medial wall, which is slightly concavo-convex from before backwards
about mid-level, is formed above by the temporal surface of the frontal, behind
by the sphenoidal angle of the parietal, as well as the lower portion of that
bone, below the temporal line ; below and in front by the temporal surface of the
great wing of the sphenoid, and behind and below by the squamous portion of the
temporal bone. Inferiorly, the floor is limited in front by the free inferior border
of thft crrp.at wino- of thp, srVhp.noirl whir.h forms the utmer boundarv of the pterygo-
LATEKAL ASPECT OF THE SKULL. 167
palatine fossa; behind that, by a rough ridge, the infra -temporal crest, which
crosses the lateral surface of the great wing of the sphenoid, to become continuous
posteriorly with a ridge on the lower surface of the squamous part of the temporal
from which the anterior root of the zygomatic process springs. Anteriorly the
temporal fossa is separated from the orbit by the zygomatic process of the frontal
above, and by the orbital process of the zygomatic and its junction with the lateral
border of the great wing of the sphenoid between its orbital and temporal surfaces.
Laterally and in front, the fossa is overhung by the backward projection of the
fronto-sphenoidal process of the zygomatic bone, and it is under cover of this, and
within the angle formed by the frontal and orbital processes of the zygomatic
bone, that we see the opening of the zygomatico-temporal foramen, which pierces
the orbital plate of the zygomatic bone and transmits the zygomatico-temporal
branch of the zygomatic nerve a filament of the maxillary division of the
trigeminal nerve. The anterior part of the inferior orbital fissure opens into the
lower part of the temporal fossa, and thus establishes a communication between it
and the orbit. If the floor of the fossa is carefully examined, some more or
less distinct vascular grooves may be seen. One passing upwards over the
posterior part of the squamous temporal, immediately in front of and above
the external acoustic meatus, is for the middle temporal artery; two others,
usually less distinct, pass up, one over the temporal surface of the great wing of
the sphenoid, the other over the anterior part of the squamous part of the temporal ;
these are for the anterior and posterior deep temporal branches of the internal
maxillary artery. Inferiorly the temporal fossa communicates with the infra-
temporal fossa, beneath the zygomatic arch, the two being separated by an
imaginary horizontal plane passing medially at the level of that bony bridge. The
fossa contains the temporal muscle with its vessels and nerves, together with the
zygomatico-temporal branch of the zygomatic nerve and some fat ; all of which are
enclosed by the fascia which stretches over the space from the upper temporal line
above to the superior border of the zygomatic arch below. The extent and depth
of the fossa depends on the size of the temporal muscle, the development of which
is correlated with the size and weight of the mandible.
Springing from the front and lower part of the squamous part of the temporal
is the zygomatic process of that bone ; it has two roots, an anterior and a posterior,
between and below which are placed the mandibular fossa in front, and the
opening of the external acoustic meatus behind. Of compressed triangular form,
the process at first has its surfaces directed upwards and downwards, but
curving laterally and forwards, it twists on itself, so that its narrowed surfaces
are now turned laterally and medially, and its edges upwards and downwards;
passing forwards, it expands somewhat, and ends in an oblique serrated surface,
which unites with the temporal process of the zygomatic bone completing the
zygomatic arch. It is the superior edge of this bridge of bone which forms the
posterior root. The inferior border, turning medially, forms the anterior root, and
serves to separate the temporal from the infra-temporal surface of the squamous part
of the temporal, blending in front with the infra-temporal crest on the lateral surface
of the great wing of the sphenoid. The inferior surface of this root is convex from
before backwards, and is thrown into relief by the mandibular fossa, which passes
up behind it. In this way a downward projection, which is called the tuberculum
articulare (O.T. eminentia articularis), is formed.
The spina angularis of the sphenoid (angular spine) lies immediately to the
medial side of the articular part of the mandibular fossa. Its size and projection
vary. It is well to remember its relation to the condyloid process of the mandible
when that bone is in position ; lying, as it does, to the medial side and a little
in front of that process, it affords attachment to the spheno-mandibular liga-
ment. As will be seen hereafter, the anterior extremity of the osseous part of the
auditory tube lies just to its medial side.
A noteworthy feature about the articular part of the mandibular fossa is
the thinness of the bony plate which serves to separate it from the middle
cranial fossa above. The vaginal process is a crest of bone which runs obliquely
forwards from the front and medial side of the mastoid process, just below the
168 OSTEOLOGY.
external acoustic meat us, to the angular spine of the sphenoid. Passing downward
and slightly forwards from the centre of this, and ensheathed by it in front and a
the sides, is the pointed styloid process, the length of which is extremely variable.
In the recess between the posterior root of the zygoma and the upper curve<
edge of the meatus there is usually a depression, though in some instances thi
may be replaced by a slight bulging of the bone. If from the posterior root o
the zygoma a vertical line be let fall, tangential to the posterior edge of the meatus
a small triangular area is mapped off which has been named by Macewen the supra
meatal triangle. Surgically this is of importance, as it is the spot selected in whicl
to trephine the bone to reach the tympanic antrum.
In the suture between the posterior border of the mastoid part of the tempora
and the squamous part of the occipital, there is usually a foramen (mastoid) fo
the transmission of an emissary vein from the transverse sinus within the cranium t
the cutaneous occipital vein of the scalp ; this opening, which may be double, varie
greatly in size, and is usually placed on a level with the external acoustic meatus.
Fossa Infratemporalis. The side of the cranium in front of the anterior roo
of the zygomatic process of the temporal bone is deeply hollowed, forming th
infra -temporal fossa. The student must bear in mind that, in examining thi
space, the ramus and coronoid process of the mandible form its lateral wall
but this bone for the present being withdrawn, enables us to get a better vie\
of the boundaries of the space. In front its anterior wall is formed by th
convex posterior or infra-temporal surface of the maxilla, which rises behind th
socket for the last molar tooth to form the tuber maxillare (maxillary tuberosity
Anteriorly, the infra- temporal surface of the maxilla is separated from its anterio
aspect by the rounded inferior margin of the zygomatic process which support
the zygomatic bone. This latter curves laterally and backwards, forming part of th
upper and anterior wall of the fossa. On the medial surface of this wall will be see]
the suture uniting the zygomatic and maxillary bones (sutura zygomaticomaxillaris
which runs obliquely upwards and medially to reach the lateral extremity of th
inferior orbital fissure, the inferior border of which forms the superior boundary o
the infra-temporal surface of the maxilla. On this aspect of the bone are t
be seen the openings of the foramina alveolaria, two or more in number, whicl
transmit the nerves and vessels to the upper molar teeth. The medial wall of th
infra-temporal fossa is formed by the lateral surface of the lateral pterygoid lamina
the width and shape of which varies greatly ; its posterior border is thin and sharj
and often furnished with spiny points, to one of which the pterygo-spinous ligamenl
which stretches from this border to the angular spine of the sphenoid, is attached
It occasionally happens that this ligament becomes ossified. Anteriorly the latera
pterygoid lamina is separated from the maxilla above by an interval called tb
pterygo-maxillary fissure. Below this the bones are apparently fused, but a carefu
inspection of the skull, together with an examination of the disarticulated bones
will enable the student to realise that, wedged in between the two bones at thi
point, is a part of one of the smaller bones of the face, the pyramidal process of th
palate bone (O.T. tuberosity of palate bone).
The inferior border of the lateral pterygoid lamina is usually curved am
slightly everted. Superiorly, where the lateral pterygoid lamina is generally
narrower, it sweeps upwards to become continuous with the broad inferior surfaci
of the great wing of the sphenoid ; this, which overhangs in part the infra- tempora
fossa superiorly, is limited laterally by the infra-temporal crest, which separates iti
infra- temporal from its temporal surface. The infra- temporal surface of the grea
wing of the sphenoid is limited in front and below by the edge which forms th<
superior boundary of the inferior orbital fissure, whilst behind it reaches as fa:
back as the medial extremity of the petro-tympanic fissure, where it terminates ii
the angular spine. It is from this point that the suture (sutura sphenosquamosa
curves forwards and upwards to reach the region of the pterion. The infra-tempora
surface of the great wing of the sphenoid, and the lateral surface of the lateral
pterygoid plate, alike afford extensive attachments for the external pterygoic
muscle, whilst the former is pierced by minute canals for the transmission o:
emissary veins. Occasionally a larger vascular foramen is present (foramen Vesalii)
LATERAL ASPECT OF THE SKULL. 169
through which a vein runs from the cavernous sinus within the cranium to the
pterygoid venous plexus situated in the infra -temporal fossa. Immediately
behind the root of the external pterygoid plate there is a large oval hole, the foramen
ovale, and behind that, and in line with the angular spine, is the smaller foramen
spinosum. These two foramina cannot usually be seen in a side view of the skull,
and are better studied when the base is examined ; they are mentioned, however,
because they transmit structures which here pass to and from the cranium, viz., the
mandibular division of the trigeminal nerve, together with its motor root, and the
accessory meningeal artery through the foramen ovale, and the middle meningeal
artery and its companion vein through the foramen spinosum. A part of the
squamous part of the temporal also forms a small portion of the roof of this fossa ; it
consists of a triangular area immediately in front of the tuberculum articulare, and
between it and the anterior root of the zygomatic process of the temporal, which is
here curving medially and forwards, to become continuous with the infra-temporal
crest. Medially this surface is continuous with the infra- temporal surface of the
great wing of the sphenoid, separated from it, however, by the posterior part of the
spheno-squamosal suture.
When the mandible is in position, the infra-temporal fossa is concealed by the
ramus of the mandible, the medial surface of which, in its upper half, forms the
lateral wall of that space. Viewed from the lateral side, the ramus of the mandible
displays considerable differences in different skulls. These are mainly due to varia-
tions in its width and in the nature of the angle which it forms at its fusion with
the body of the bone. A considerable interval separates the posterior border of the
ramus from the front of the mastoid process. Within this space may be seen the
free inferior edge of the tympanic plate (vaginal process), from which, just below
the external acoustic meatus, the styloid process of the temporal bone is observed
passing downwards and slightly forwards. The width and height of the coronoid
process vary much, oftentimes reaching the level of the top of the condyle. Its
extremity, when the lower jaw is closed, lies just within the anterior part of the zygo-
matic arch ; at other times it rises to a much higher level, so that its point may be
seen above the level of the upper border of the zygomatic arch. The posterior
edge of the coronoid process forms the anterior border of the mandibular notch,
and limits in front the interval left between the lower border of the posterior half
of the zygomatic arch and the upper hollowed edge of the ramus. On looking into
this interval, the floor of the infra-temporal fossa may be seen, formed anteriorly by
the lateral pterygoid lamina ; whilst posteriorly it is possible to pass a probe right
across the base of the skull from one mandibular notch to the other, the shaft of
the probe lying immediately behind the pterygoid processes of the sphenoid, and
crossing the foramina ovalia, through which the mandibular divisions of the tri-
geminal nerves pass.
The ramus and coronoid process are so placed as to occupy a position inter-
mediate between the zygomatic arch laterally and the lateral pterygoid lamina
medially; their medial surface, therefore, forms the lateral wall of the infra-temporal
fossa. On a level with the surface of the crowns of the teeth of the mandible,
and situated about the middle of this aspect of the ramus, is the mandibular
foramen, the superior opening of the canalis mandibulas (mandibular canal), which
traverses the body of the bone. Through this foramen there pass the inferior
alveolar branch of the mandibular division of the trigeminal nerve, together
with the inferior alveolar artery and its veins. As will now be seen, when the
mandible is in position, the infra -temporal fossa is closed in laterally by the
ramus of the mandible. In front there is an interval between the anterior border
of the ramus and the infra-temporal surface of the maxilla, through which pass
the buccinator branch of the trigeminal nerve and the communicating vein
between the pterygoid plexus and the anterior facial vein. Above, in the
interval between the mandibular notch and the inferior border of the zygomatic
arch, there pass from the fossa the vessels and nerves which supply the masseter
muscle. Between the posterior border of the ramus and the styloid process there
enter and leave the large vessels which are found within the space. Superiorly
under cover of the zygomatic arch, the infra-temporal fossa communicates with the
170
OSTEOLOGY.
temporal fossa, whilst inferiorly it is continuous with the infra-maxillary region.
Medially, on the floor of the fossa there is an f -shaped fissure, the horizontal
limb of which corresponds to the inferior orbital fissure, forming a channel of
communication between the fossa and the orbit, through which passes the zygomatic
branch of the maxillary division of the trigeminal nerve ; whilst the vertical cleft is
the pterygo-maxillary fissure, which leads into a small fossa placed between the front
of the root of the pterygoid process of the sphenoid and the back of the maxilla,
called the pterygo-palatine fossa.
The following foramina open into the infra-temporal fossa the foramen ovale,
foramen spinosum, foramina' alveolaria, mandibular foramen, minute foramina for
the transmission of emissary veins ; of these one of large size is occasionally
present, the foramen of Vesalius.
Fossa Pterygopalatina. This space, which corresponds to the angular
-14
24 23 22
FIG. 170. FRONTAL SECTION THROUGH THE PTERYGO-PALATINE FOSSA OP THE RIGHT SIDE.
The sphenoid is coloured red. The maxilla and vomer are coloured blue. The palate bone and
middle and inferior conchae are left uncoloured.
A. Anterior Wall. B. Posterior Wall. C. Diagrammatic representation of a horizontal section across the
1. Spheno-palatine foramen.
2. Apex of orbital cavity.
3. Inferior orbital fissure.
4. Inferior orbital fissure.
5. Pterygo-maxillary fissure.
6. Alveolar foramina.
7. Part of pterygoid fossa.
fossa.
8, 9, 10. Pterygo-palatine and
palatine canals.
11. Foramen rotundum.
12. Superior orbital fissure.
13. Optic foramen.
14. Sphenoidal sinus.
15. Pharyngeal canal.
16. Pterygoid canal.
17. Spheno-palatine foramen.
18. Pterygo-palatine fossa.
19. Infra-orbital groove.
20. Inferior orbital fissure.
21. Pterygo-maxillary fissure.
22. Foramen rotundum.
23. Pterygoid canal.
24. Pharyngeal canal.
interval between the pterygo-maxillary and inferior orbital fissures, and which
lies between the maxilla in front and the root of the pterygoid process behind,
is bounded medially by the perpendicular part of the palate bone, which separates
it from .the nasal cavity, with which, however, it communicates by means of
the spheno-palatine foramen, which lies between the orbital and sphenoidal
processes of the palate bone and the inferior surface of the body of the sphenoid.
Opening into this fossa, above and behind, are the foramen rotundum, the
pterygoid canal and the pharyngeal canal, in that order from lateral to medial
side, whilst below is the superior orifice of the pterygo-palatine canal, together with
openings of the lesser palatine canals. Its roof is formed by the inferior surface of
the body of the sphenoid and the orbital process of the palate bone. Anteriorly
it lies in relation to the apex of the orbit, with which it communicates by means
of the inferior orbital fissure ; whilst laterally, as already stated, it communicates
with the infra-temporal fossa through the pterygo-maxillary fissure.
UPPEK ASPECT OF THE SKULL. 171
Posterior Aspect of the Skull (Norma Occipitalis).
The view of the cranium as seen from behind includes the posterior halves of
the two parietal bones above, the squamous part of the occipital bone below, and the
mastoid portions of the temporal bones on either side, inferiorly. The shape of this
aspect of the skull varies much, but ordinarily the greatest width corresponds to the
level of the parietal tuberosities. The sutures on this view of the calvaria display a
triradiate arrangement, one limb of which is vertical, and corresponds to the posterior
part of the interparietal or sagittal suture. The other two limbs pass laterally
and downwards in the direction of the mastoid processes, uniting the two parietal
bones in front with the occipital bone behind ; these constitute the A- g haped
lambdoid suture. The point of confluence of the sagittal and lambdoid sutures is
called the lambda. This can generally be felt in the living, owing to the tendency
of the squamous part of the occipital to project slightly, immediately below this spot.
About one inch and a quarter above the lambda the two small parietal foramina are
seen, through which pass the small emissary veins of Santorini, which connect the
intra-cranial venous system with the superficial veins of the scalp. These small
holes lie about T V of an inch apart on either side of the sagittal suture, which
here, for the space of about an inch, displays a simplicity of outline in striking
contrast with its serrated arrangement elsewhere. The term obelion is applied to
a point on the sagittal suture in line with the two parietal foramina. The lambdoid
suture is characterised by great irregularity of outline, and not infrequently chains
of separated ossicles are met with in it, the ossa suturarum (sutural bones). The
squamous part of the occipital bone is divided into two parts by the superior nuchal
or curved line, the central part of which forms the external occipital protuberance or
inion. The part above, called the planum occipitale or occipital surface comes within
our present consideration ; the part below, called the planum nuchale or the nuchal
surface, though seen in . perspective, had best be considered when the base is
examined. A little above the level of the superior curved line the occipital surface
is crossed on either side, by a faint lunated line, the linea nuchse suprema (highest
nuchal or curved line), to which are attached the occipitales muscles and the galea
aponeurotica. The projection of the occipital surface varies much in individual
skulls ; most frequently it overhangs the external occipital protuberance, forming a
distinct boss ; exceptionally, however, the latter may be the most projecting part of
the bone. The extremity of the superior nuchal line on either side corresponds to
the position of the asterion (p. 285). Lateral to these points the outline of the
skull is determined by the downward projection of the mastoid processes, the medial
surfaces of which are deeply grooved by the mastoid notches for the attachment of
the posterior bellies of the digastric muscles, thus causing these processes to appear
more pointed when viewed from this aspect.
Upper Aspect of Skull (Norma Verticalis).
This is the view of the calvaria as seen from above. It is liable to great
diversities of form. Thus, its shape may vary from an elongated oval to an outline
more nearly circular. These differences have been classified, and form important
distinctions from a craniometrical standpoint, the rounder varieties being
termed the brachycephalic, whilst the elongated belong to the dolichocephalic group.
Another noteworthy point in this view is the fact that in some instances the
zygomatic arches are seen, whilst in others they are concealed by the overhang
and bulge of the sides of the anterior part of the cranium. The former condition is
described as phaenozygous, the latter as cryptozygous, and each is more or less closely
associated with the long or round varieties of head-form respectively.
The sutures displayed have a T-shaped arrangement. Placed medially between
the two parietal bones is the sagittal suture. This is finely denticulated, except in
the region of the obelion, though, of course, this will not be apparent if obliteration
of the suture has taken place through fusion of the two parietal bones. Posteriorly
the sagittal suture unites with the lambdoid suture at the lambda, which marks
in the adult the position of the posterior fontanelle of the foetus. Anteriorly it
terminates by joining the transverse suture which separates the frontal bone
172 OSTEOLOGY.
anteriorly from the parietals posteriorly; this latter is called the coronal suture, and the
point of junction between the sagittal and coronal sutures is known as the bregma ;
this corresponds in position to the anterior fontanelle of the foetus. The summit
of the vault of the calvaria corresponds to a variable point in the line of the sagittal
suture, and is named the vertex. The coronal suture is less denticulated centrally than
laterally. Occasionally there is a persistence of the suture (metopic) which unites
the two halves of the frontal bone ; under these conditions the line of the sagittal
suture is carried forward to the fronto-nasal suture, and a skull displaying this
peculiarity is described as metopic. Behind the coronal suture may occasion-
ally be seen the post-coronal depression, and in some instances the vault of the
calvaria forms a broad, slightly elevated crest along the line of the sagittal suture.
On either side the temporal ridges can be seen curving over the lateral and superior
aspects of the parietal bones. As the lower of these crosses the coronal suture in
front it marks a spot known as the stephanion, useful as affording a fixed point
from which to estimate the bi-stephanic diameter. The interval between the
temporal ridges on either side will vary according to the form of the skull and the
development of the temporal muscle. In this view of the calvaria a small part of
the lambdoid suture on either side of the lambda is visible posteriorly.
Basis Cranii Externa (Norma Basalis).
The external or inferior aspect of the base of the cranium i.e. the skull without
the mandible includes a description of the under surfaces of the skeleton of the
face (cranium viscerale) and the cranium (cranium cerebrale). The former includes
the hard palate formed by the maxillse and palate bones, the superior alveolar arch,
and the bodies of the maxillse as seen from below ; whilst laterally, and united with
the bodies of the maxillse, the zygomatic bones are displayed, curving backwards
to form the anterior halves of the zygomatic arches. In the median plane, passing
from the upper surface of the hard palate, is the osseous septum of the nose,
here formed by the vomer, which is united above to the under surface of the body
of the sphenoid.
The under surface of the cranium is pierced by the foramen occipitale magnum
for the transmission of the spinal medulla and its membranes. In front of this a
stout bar of bone extends forwards in the median plane, formed by the union of the
body of the sphenoid in front with the basilar part of the occipital bone behind.
In adult skulls all trace of the fusion of these two bones has disappeared ; when
union is incomplete, it indicates that the skull is that of a person below the age of
twenty-five. The sphenoid comprises that part of the calvaria which forms the roof
and sides of the apertures which lie on either side of the nasal septum above the
hard palate the choanae. Laterally the inferior surfaces of the great wings of the
sphenoid extend as far forward as the posterior border of the inferior orbital fissure ;
whilst posteriorly they reach as far as the angular spine, lateral to which the
spheno-squamosal suture, separating the great wing of the sphenoid from the
squamous portion of the temporal, curves forwards and upwards, medial to the
tuberculum articulare, to reach the floor of the temporal fossa, along which its course
has been already traced (p. 168). On a level with the front of the foramen
magnum the jugular process of the occipital bone forms an irregular curved border,
which sweeps laterally to terminate at a point just medial to the root of the
styloid process. Here, in line with the spheno-squamosal suture, from which, how-
ever, it is separated by a considerable interval, its extremity turns backwards, and
may be traced at first medial to, and then turning upwards, behind the mastoid
process of the temporal bone, separated from this latter by the occipito-mastoid
suture. The bone behind the foramen magnum, which is included between the
two occipito-mastoid sutures, comprises the nuchal surface of the squamous portion
of the occipital bone, an area which is limited behind by the superior nuchal line,
which separates it from the occipital surface of the same bone. The remaining
portions of the base of the calvaria, as at present exposed, are formed by the
squamous and tympanic portions of the temporal bone, together with the petro-mastoid
part of the same bone, the latter of which is wedged in between the great wing of
BASE OF THE SKULL.
173
IS
16
38
1 39
FIG. 171. INFERIOR SURFACE OF BASK OF SKULL.
jcipital, vomer, maxillary, and zygomatic bones are coloured red. The temporal and palate bones, blue.
The sphenoid and parietal bones, and the teeth, are left uncoloured.
eternal occipital crest,
iperior nuchal line of
the occipital bone,
foramen magnum,
ipital condyle.
stoid notch,
[astoid process.
1 '. External acoustic meatus.
8. Styloid process.
9. Mandibular fossa.
10. Foramen spinosum.
11. Angular spine of the
sphenoid.
12. Foramen ovale.
13. Lateral pterygoid lamina.
14. Hamulus of medial
pterygoid lamina.
15. Nasal septum.
16. Posterior nasal spine.
17. Horizontal part of palate bone.
18. Palatine process of maxilla.
19. Incisive foramen.
20. Intermaxillary suture.
21. Greater palatine foramen.
22. Zygomatic process of maxilla.
23. Inferior orbital fissure.
24. Infra-temporal fossa.
25. Zygomatic arch.
26. Left choana.
27. Pterygoid fossa.
28. Scaphoid fossa.
29. Foramen lacerum.
30. Opening of osseous part of auditory tube.
31. Carotid canal.
32. Jugular fossa.
33. Stylo-mastoid foramen.
34. Jugular process of occipital bone.
35. Groove for occipital artery.
36. Mastoid foramen.
37. Canalis condyloideus.
38. Inferior nuchal line of occipital bone.
39. External occipital protuberance.
174 OSTEOLOGY.
the sphenoid in front and the occipital bone behind. Stretching forwards from the
squamous part of the temporal in front is seen the zygomatic process which, by its
union with the zygomatic bone, completes the formation of the zygomatic arch.
Palatum Durum. Studying next the various parts in detail, the hard palate
may be first examined. Of horse-shoe shape as a rule, it presents many varieties of
outline and size. Formed by the palatine processes of the maxillae in front
and the horizontal parts of the palate bones behind, its circumference in front
and at the sides corresponds to the superior alveolar arch, in which are embedded
the sixteen teeth of the two maxillse ; posteriorly the edge of the hard palate is
thin, presenting in the median plane a pointed process, the posterior nasal spine,
on either side of which the posterior free border is sharp and lunated. The vault
of the palate, which is concave from side to side, and from before backwards, varies
in depth according to the projection and development of the alveolar processes.
When the teeth are shed and the alveoli are absorbed, the palate becomes shallow
and flat. Kunning throughout its entire length in the median plane is the
median palatine suture, which separates the palatine processes of the maxillse
in front and the horizontal parts of the palate bones behind. A little behind
the central incisor teeth, and in the line of this suture, is a little pit, the
foramen incisivum. At the bottom of this may be seen the openings of some
small canals, varying in number from one to four; these are usually described
as arranged in two pairs, the one pair placed side by side, the other lying in the
median plane in front and behind. The former are called the foramina of Stenson,
and transmit the terminal twigs of the greater palatine arteries which ascend to
reach the nasal cavities. The latter, called the foramina of Scarpa, open, the
anterior into the left, the posterior into the right nasal cavity, and afford passage for
the fine filaments of the left and right naso-palatine nerves, respectively. About
half an inch (12 mm.) in front of the posterior nasal spine the median palatine
suture is crossed at right angles by the transverse palatine suture. This, which
indicates the line of union of the palatine processes of the maxillse with the
horizontal parts of the palate bones, passes transversely laterally on either side until
it reaches the medial aspect of the base of the alveolar process, along which it
turns backwards, to disappear within the foramen palatinum majus (greater palatine
foramen), the aperture of which lies just medial to the root of the dens serotinus
(wisdom molar). Through this there pass the greater palatine artery and the
large anterior palatine nerve. Leading from this foramen is a groove which
curves forwards immediately to the medial side of the alveolar arch ; not infrequently
the medial edge of this groove forms a thin and sharp ridge on the surface of the
palate. In this groove are lodged the afore-mentioned vessels and nerves. The
surface of the palate in front of the transverse suture is rough, pitted for the palatine
glands, and pierced by numerous small vascular foramina ; the part of the palate
behind the suture, formed by the under surface of the horizontal part of the palate
bone, is much smoother. From this there rises, just posterior to the greater
palatine foramen, a thin sharp crest, which curves medially immediately in
front of the posterior free edge ; to this are attached some of the tendinous fibres
of the tensor veli palatini muscle.
Pterygoid Processes. Buttressed against the posterior extremities of the
alveolar arch are the pterygoid processes of the sphenoid. If carefully examined,
these will be seen not to lie in actual contact with the maxillae, but to be separated
from them by the triangular wedge-shaped pyramidal processes of the palate
bones. It is these latter which are pierced by the foramina palatina minora (lesser
palatine canals), which lie just behind the greater palatine foramen, and through
which pass the lesser palatine nerves. As here displayed, the pterygoid processes of
the sphenoid lie on either side of the opening of the choanse (O.T. posterior nares) ;
each consists of two laminae, a medial and a lateral ; the latter is the broader,
and is directed backwards and slightly laterally. Its lateral surface has been
already studied in connexion with the infra- temporal fossa (p. 168). Medially it is
separated from the medial pterygoid lamina by the pterygoid fossa, wherein is lodged a
considerable part of the internal pterygoid muscle. The floor of the fossa is formed
in greater part by the coalescence of the two pterygoid laminae ; but at the level of
BASE OF THE SKULL. 175
the hard palate the pyramidal process of the palate bone appears wedged in
between the two plates, and so enters into the formation of the floor of the
pterygoid fossa. The medial pterygoid lamina separates the nasal cavity from the
pterygoid fossa; to the posterior edge of the medial pterygoid lamina are attached the
pharyngeal aponeurosis, the superior constrictor of the pharynx, and the pharyngo-
palatinus muscle. Above, the posterior border of this plate is channelled to form
the small scaphoid fossa, which curves laterally over the summit of the pterygoid
fossa, and furnishes a surface for the origin of the tensor veli palatini muscle. The
sharp medial margin of this fossa, continuous below with the posterior border of
the medial pterygoid lamina, extends upwards, and on either side of the body of
the sphenoid forms a blunt pointed process, the pterygoid tubercle, which extends
backwards towards the apex of the petrous part of the temporal bone. Just
lateral to this, and concealed by it, is the posterior extremity of the pterygoid
canal, through which pass the artery and nerve of the canal. The medial surface
of the medial pterygoid lamina is directed towards the nasal cavity. Superiorly
this surface curves medially to meet the inferior surface of the body of the sphenoid,
forming on either side a lipped edge, the vaginal process, between which the alse
of the vomer, which here forms the nasal septum, are wedged. Between the two
a small interval, however, is occasionally left, which forms on either side the basi-
pharyngeal canal. A little lateral to the line of union of the vaginal process with
the vomer is the opening of the pharyngeal canal. This lies between the inferior
surface of the vaginal process and the sphenoidal process of the palate bone, which
here articulates with the inferior surface of the body of the sphenoid. The
pharyngeal branch of the spheno-palatine ganglion and the pharyngeal branch of
the internal maxillary artery pass through this canal. Inferiorly the pterygoid
processes project below the level of the hard palate. The medial plate ends in a
slender recurved process, called the hamulus pterygoideus, which turns backwards
and laterally (this is frequently broken off in skulls which have been roughly
handled). It reaches as low as the level of the alveolar margin, and lies just
within and behind the posterior extremity of the alveolar process. It can readily
be felt in the living by placing the finger against the soft palate behind and just
within the gum around the root of the dens serotinus (O.T. wisdom tooth). On
the front of and below this process the tendon of the tensor veli palatini muscle
glides in a groove.
. The choanae (O.T. posterior nares) lie between the two pterygoid processes.
Of a shape much resembling two Gothic windows, their bases or inferior boundaries
are formed by the horizontal part of the palate bone. Laterally they are bounded
by the medial surfaces of the medial pterygoid laminae, whilst above, the lateral
side of the arch is formed by the vaginal processes of the same laminae ; medially
they are separated by the thin vertical posterior border of the vomer, whilst,
above, the everted alae of the same bone form the medial sides of the arch. The
plane of these apertures is not vertical but oblique, corresponding usually to a line
drawn from the bregma above through the last molar tooth of the maxilla below.
Their size varies considerably, but the height is usually equal to twice the width.
The region of the cranium which lies lateral to the maxilla and lateral
pterygoid lamina corresponds to the infra-temporal fossa, which has been already
described, as it is seen from the side (Lateral Aspect of the Skull, p. 168). Viewed
from below, the infra-temporal fossa is bounded in front by the infra-temporal
surface of the body of the maxilla and the medial surface of the zygomatic bone.
The roof, which is traversed by the spheno-squamosal suture, is formed in front by
the inferior surface of the great wing of the sphenoid, and behind by a small
triangular surface of the under side of the squamous part of the temporal bone,
immediately in front of the tuberculum articulare.
Circumscribed laterally and behind by the anterior root of the zygoma, which
curves forward to become continuous in front with the infra-temporal crest crossing
the lateral surface of the great wing of the sphenoid, the roof of the fossa is
separated from its anterior wall by the inferior orbital fissure, which is so inclined
that with its fellow of the opposite side it forms an angle of 90. Superiorly the
infra-temporal fossa communicates freely with the temporal fossa medial to the
176 OSTEOLOGY.
zygomatic arch, though the student must bear in mind the fact that when the
mandible is in position the lateral limits of the space are very much reduced (p. 168).
The inferior surface of the great wing of the sphenoid is here V-shaped. The
angle corresponds to the spine, the lateral limb to the spheno-squamosal suture,
whilst the medial limb corresponds to a narrow cleft, the fissura spheno-petrosa,
which separates it from the petrous portion of the temporal bone, to which it is
united in the recent condition by a synchondrosis. Along the line of this latter
fissure the edges of the adjacent bones (sphenoid and petrous part of the temporal) are
bevelled so as to form a groove, which extends from the root of the medial pterygoid
lamina medially, to the medial side of the base of the angular spine laterally, where
the groove ends by entering an osseous canal. In the groove (sulcus tubae auditivae)
the cartilaginous part of the auditory tube is lodged, whilst the osseous canal
includes the bony part of the same tube, together with the tensor tympani muscle,
which is lodged in a separate compartment immediately above it. The anterior
extremity of the cartilaginous part of the auditory tube is supported by the
posterior edge of the medial pterygoid lamina, which is often notched for its recep-
tion. Between the root of the lateral pterygoid lamina and the angular spine there
are two foramina which lie immediately in front of the sulcus tubse auditivse.
Of these the larger and anterior is the foramen ovale, through which pass the!
motor root, and mandibular division of the trigeminal nerve, together with the|
accessory meningeal artery. The smaller, which, from its position immediately in
front of the angular spine, is called the foramen spinosum, transmits the middle
meningeal artery and vein, and sympathetic plexus surrounding the artery. Th<
lesser superficial petrosal nerve here passes through the base of the skull to join
the otic ganglion either through a small foramen (canalis innominatus) placec
between the foramen ovale and the foramen spinosum, or through the foramen
ovale or through the spheno-petrosal fissure. The position of the suture between
the basi-occipital and basi-sphenoid corresponds to a line connecting the tips of th(
pterygoid .tubercles at the root of the medial pterygoid laminae.
Occasionally in the centre of this line there is a small pit with a foramen leading from it. Tlii
probably represents the lower end of the cranio-pharyngeal canal.
The inferior surface of the basilar part of the occipital bone (basi-occipital
stretches between the body of the sphenoid in front and the anterior margin o
the foramen magnum behind ; projecting from its centre is a slight elevation, tht
pharyngeal tubercle, to which the pharyngeal raphe, together with the centra
part of the anterior atlanto-occipital membrane, is attached. It should be noted
that when the atlas is in position the pharyngeal tubercle lies in line with th(
tubercle on the anterior arch of that bone. Curving laterally and backward
from the pharyngeal tubercle, on either side, is an irregular ridge (crista muscularis)
in front and behind which are attached the longus capitis and rectus capitis anterio
muscles. On either side of the basi-occipital, in front, there is an irregular opening
of variable size ; this is placed between the root of the pterygoid process anteriorly
the apex of the petrous portion of the temporal bone laterally, and the latera
edge of the basi-occipital and basi-sphenoid medially. It is called the foramei
lacerum. Opening into it in front, just lateral to the pterygoid tubercle, is th<
pterygoid canal, whilst, in correspondence with the apex of the petrous part of th <
temporal, the large orifice of the carotid canal may be seen entering it behind an<
from the lateral side. In the recent condition the lower part of the foramen lacerur
is occupied by fibro-cartilage, over the upper surface of which the internal caroti*
artery and greater superficial petrosal nerve pass to reach their respective foraminr
whilst a small meningeal branch of the ascending pharyngeal artery occasional!
enters the cranium through it. Leading laterally from the foramen lacerum in th
direction of the angular spine of the sphenoid is the spheno-petrosal fissure, whic
lies at the bottom of the sulcus tubae auditivae, and disappears from view within th
bony part of the auditory tube. Passing backwards from the foramen lacerum thei
is a fissure between the lateral side of the basi-occipital and the posterior an
medial border of the petrous part of the temporal bone. This, which is called tt !
petro-occipital fissure, opens posteriorly into the jugular foramen. In the recer
BASE OF THE SKULL. 177
condition the fissure is filled up with cartilage. The inferior surface of the
petrous bone included between these two fissures is rough and irregular, and
affords attachments near its apex to two small muscles, the levator veli palatini
and the tensor tympani. Immediately behind the angular spine the petrous
part of the temporal is pierced by a circular hole, the inferior opening of the
carotid canal. This passes upwards, and then turns medially and forwards towards
the apex of the bone, where it may again be seen opening into the lateral and upper
side of the foramen lacerum. Laterally the wall of the vertical part of this canal,
which is usually very thin, separates it from the cavity of the tympanum, as may be
seen by holding the skull up to the light and looking into the external acoustic
meatus. The carotid canal transmits the internal carotid artery, together with
the sympathetic plexus around it. It is noteworthy that the two carotid canals
he in line with the anterior edges of the two external acoustic meatuses.
The jugular foramen is an opening of irregular shape and variable size placed
between the petrous part of the temporal in front and the jugular process of
the occipital bone behind. The former is excavated into a hollow called the
jugular fossa, which forms a roof to the upper and lateral part of the space, whilst
the latter, by a curved edge, either rounded or sharp, constitutes its posterior
border. There is often considerable difference in the size of the jugular foramina ;
that on the right side (with the skull in its normal position) is usually the larger.
The foramen is occasionally subdivided into two by spicules of bone which bridge
across it. Lodged within the fossa is the bulb of the internal jugular vein, in front
of which the inferior petrosal sinus passes down to join the internal jugular vein
below the foramen. Effecting an exit between the two veins, in order from
before backwards, are the glosso-pharyngeal, vagus, and accessory nerves. Small
meningeal branches from the ascending pharyngeal and occipital arteries also
enter the foramen. The two jugular foramina lie in line with a line drawn through
the centres of the two external acoustic meatuses. Following the direction of
a line connecting the angular spine of the sphenoid and the mastoid process of the
temporal, and placed immediately lateral to the apertures of the carotid canal
and jugular foramen, is the vaginal process of the tympanic plate of the temporal
bone, the edge of which is sharp and thin, and serves to separate the inferior surface
of the petrous part of the temporal from the non-articular part of the mandibular
fossa. Springing from this crest immediately lateral to the jugular fossa, and
in line with the middle of the external acoustic meatus, is the styloid process
of the temporal bone. Its relation to the jugular foramen is of great importance
as the internal jugular vein lies close to its medial side.
Immediately behind the root of the styloid process, medial to and in line with
; ; the front of the mastoid process, is the stylo-mastoid foramen, which is the inferior
aperture of the canalis facialis. Through it the facial nerve passes out and the
stylo-mastoid branch of the posterior auricular artery passes in. The medial
surface of the mastoid process is deeply grooved at its base for the origin of the
I posterior belly of the digastric muscle. Medial to this, and running along, just
wide of the occipito-mastoid suture, is a shallow groove in which the occipital
>;: artery is lodged. Just medial to the stylo-mastoid foramen is the synchondrosis
J between the extremity of the jugular process of the occipital bone and the petrous
part of the temporal. The jugular process is a bar of bone which limits the jugular
I fossa posteriorly and abuts on the occipital condyles medially ; its inferior surface is
y convex from before backwards and affords attachment to the rectus capitis lateralis
muscle. The occipital condyles are placed between the jugular processes and the
foramen magnum. Limited in front by a rounded thickening which becomes
confluent with the anterior border of the foramen magnum, they form by their
medial sides the lateral boundaries of that aperture on its anterior half. Laterally
they are continuous with the jugular processes, in front of which they overhang
a fossa which is pierced behind by the canalis hypoglossi, through which passes
the hypoglossal nerve, together with a small vein and occasionally a small meningeal
branch derived from the ascending pharyngeal artery.
The posterior condylic fossae are situated just behind the posterior extremities of
the condyles. Not infrequently the floor of each is pierced by the condyloid canal,
12
178 OSTEOLOGY.
through which the posterior condylic vein emerges. The base of the skull behind
the jugular processes and condyles of the occipital bone is formed by the nuchal
surface of the squamous part of that bone. Posteriorly this surface is bounded
by the superior nuchal or curved line, in the centre of which is placed the projecting
external occipital protuberance. Laterally the squamous part of occipital bone is
separated from the mastoid portion of the temporal bone by the occipito-mastoid
outure, which curves backwards and laterally, from the extremity of the jugular
process in front, around the base of the mastoid process behind. In front and in
the median plane this plate of bone is pierced by the foramen occipitale magnum, the
anterior half of which has been already seen to lie between the occipital condyles.
Usually of oval form, though in some cases it tends to approach the circular,
the plane of this opening is inclined downwards and slightly forwards. The
extreme anterior edge of the foramen is sometimes called the basion, whilst the
extreme posterior margin is termed the opisthion. The lower border of the medulla
oblongata, where it becomes continuous with the spinal medulla, is lodged within
the foramen, together with the meninges which cover it, whilst the vertebral
arteries and the spinal portions of the accessory nerves pass upwards through it.
The anterior and posterior spinal arteries, some small veins, and the roots of the
first cervical nerves, also traverse it from above downwards.
The student will, no doubt, experience considerable difficulty in bearing in mind the relative
positions of the various foramina and processes which he has studied on the inferior surface of the
base of the skull.
If a line be drawn on either side from the incisive foramen in front, through the stylo-
mas toid foramina posteriorly, it will be found to cut or pass near to the following objects : On
the hard palate it will lie close to the greater and lesser palatine foramina. It will then pass
between the hamulus and the lateral pterygoid lamina, overlying the foramen ovale, the foramen
spinosum, the opening of the osseous part of the auditory tube and the angular spine of the
sphenoid ; behind this it will cut through the root of the styloid process and define laterally the
limits of the jugular fossa. After passing through the stylo-mastoid foramen, if the line be
prolonged backwards it will usually be found to pass over the mastoid foramen in the occipito-
mastoid suture. Another line of much value is one drawn across the base of the skull from the
centre of one external acoustic meatus to the other. This will be found to pass through the
root of the styloid process, the jugular foramen, the hypoglossal canal ; it then crosses the front
of the occipital condyles, and corresponds with the anterior edge of the foramen magnum.
A line which may be found useful is one drawn from the stylo-mastoid foramen of one side to
the greater palatine foramen of the opposite side. This will be seen to overlie, from behind
forwards, the lateral part of the jugular foramen and the inferior opening of the carotid canal.
The line indicates the direction of the carotid canal, and cuts the foramen lacerum anteriorly ; in
front of this it usually corresponds to the position of the posterior aperture of the pharyngeal canal.
Mandible and Atlas in Position. The examination of the base of the skull
is incomplete unless the student examines it with the mandible and atlas in
position. The relation of the ramus of the mandible to the infra-temporal fossa
has been already sufficiently studied (p. 169); one or two points, however, may be
emphasised. The angular spine of the sphenoid lies just medial to the condyle of the
mandible when that structure is in position in the articular part of the mandibular
fossa, and it is noteworthy that immediately to the medial side of the angular
spine is the commencement of the osseous part of the auditory tube. The root of
the styloid process occupies the centre of the interval between the mandibular
ramus and the front of the mastoid process.
Anteriorly the arcade formed by the body of the mandible adds greatly to the
depth of the hard palate. In this space are lodged the tongue and the structures
which form the floor of the mouth. The medial surface of each side of the body of
the mandible is traversed by the mylo-hyoid line, which commences posteriorly
just behind the root of the last molar tooth and runs downwards and forwards
towards the symphysis in front.
When the atlas is in articulation with the occipital bone it is well to recognise
the relation of its transverse processes to the surrounding structures. The
extremities of these processes lie in line with the ends of the jugular processes of
the occipital bone, and thus come to be placed just medial to and immediately below
and slightly in front of the tips of the mastoid processes. They can thus be easily felt
in the living subject. Anteriorly they are separated by a short interval from
the styloid processes, and the stylo-mastoid foramina lie immediately in front and
THE UPPEE SUEFACE OF THE BASE OF THE SKULL. 179
slightly to the lateral side of their extremities. The student will note that there
is no hole in the jugular process of the occipital bone corresponding to the arterial
foramen in the transverse process of the atlas through which the vertebral artery
passes. The course of this vessel over the upper surface of the posterior arch
behind the superior articular processes of the atlas will be seen to coincide with
the posterior condylic fossse and the margins of the foramen magnum immediately
medial thereto, where a slight grooving of the edge often indicates the course of
the artery. In front the anterior tubercle of the atlas falls in line with the
pharyngeal tubercle on the under surface of the basi-occipital, and the student must
not overlook the fact that the anterior surface of the cervical column does not
coincide with the anterior margin of the foramen magnum, but lies nearly half an
inch in front of that, in a frontal plane passing immediately in front of the
external acoustic meatuses. Behind, the upper surface of the posterior arch of the
atlas overlaps the posterior margin of the foramen magnum, and it is by the
apposition of these two surfaces that extension is checked at the occipito-atlantal
articulation.
THE SKULL IN SECTION.
By the removal of the skull-cap the cerebral aspect of the cranial cavity is exposed.
The deep surface of the cranial vault is grooved in the median plane for the superior
sagittal sinus, on either side of which are seen numerous depressions for the lodgment
of arachnoideal granulations. On holding the bone up to the light, the floor of these
little hollows is oftentimes seen to be very thin. A short distance in front of the
lambda, and on either side of the sagittal suture, are the cerebral openings of the
parietal foramina. The inner tables of the frontal and parietal bones are grooved
for the meningeal arteries. The principal branch of the middle meningeal runs more
or less parallel to and at a variable distance behind the line of the coronal suture.
Along the bottom of these grooves small foramina may be seen for the passage of
nutrient arteries to the bone, and the floor of the sagittal sinus is likewise pierced
by small apertures for the transmission of veins.
Basis Cranii Interna.
Cranial Fossae. The upper surface of the base of the skull is divided into
three fossse, of which the cerebrum occupies the anterior and middle, whilst in the
posterior is lodged the cerebellum.
The anterior fossa is defined posteriorly by the sharp, thin edge of the small
wings of the sphenoid, which curve laterally and slightly upwards, as well as back-
wards, to reach the region of the pterion laterally. The floor is formed from before
backwards, in the median plane, by the superior surface of the ethmoid and the
anterior part of the body of the sphenoid ; laterally it is constituted by the orbital
'parts of the frontal and the small wings of the sphenoid. On these the inferior
surface of the frontal lobes of the cerebrum rests. In front the fossa is divided
in the median plane by the frontal crest, to which the falx cerebri is attached.
This is confluent below with the anterior part of the crista galli, from which,
however, it is separated by the foramen caecum, which usually transmits a small
vein from the nose. On either side of the crista galli there are grooves which
vary considerably in depth and width: therein are lodged the olfactory bulbs.
The floor and sides of the groove are pierced by numerous foramina ; of these the
largest number transmit the olfactory nerves from the nasal cavity. In front an
elongated slit, placed on either side of the crista, affords a passage to the nose for
the anterior ethmoidal branch of the naso-ciliary nerve and a small branch of
the anterior ethmoidal artery which accompanies it. To the lateral side of the
olfactory groove and the cribriform plate, the anterior fossae communicate on either
side by means of the two ethmoidal foramina with the cavities of the orbits. The
anterior foramen transmits the anterior ethmoidal nerve and the anterior ethmoidal
artery ; the posterior affords passage to the posterior ethmoidal artery and nerve
(O.T. spheno-ethmoidal nerve of Luschka). Lateral to the olfactory groove, the
floor of the fossa, which here corresponds to the roof of the orbit, is very thin, as may
180 OSTEOLOGY.
be seen by holding the skull up to the light ; it is convex from side to side, and bears
the impress of the gyri of the inferior surface of the frontal lobes of the cerebrum,
which rest upon it. In front and at the side .there are a number of vascular
grooves for the branches of the anterior and middle meningeal arteries.
The middle fossa, which in form may be compared to the wings of a bird
united by the body, is bounded in front by the curved thin posterior edge of the
small wings of the sphenoid ; posteriorly, by the line of attachment of the tentorium
cerebelli, extending from the posterior clinoid process along the superior margin of
the petrous portion of the temporal bone. The median part of the fossa, which is
narrow, corresponds to the fossa hypophyseos and the tuberculum sellae of the sphenoid.
It is limited anteriorly by a line connecting the anterior margins of the two optic
foramina, and is overhung behind by the dorsum sellse. In this area are lodged
the structures which lie within the interpeduncular fossa on the base of the brain.
The floor of the lateral parts of the fossa on each side is formed by the great wing
of the sphenoid in front, the squamous part of the temporal bone to the lateral side,
and the anterior surface of the petrous part of the temporal behind. In the hollows
so formed the temporal lobes of the cerebrum are lodged. On either side of the
tuberculum sellse are seen the optic foramina ; these pass into the orbital cavities
and transmit the optic nerves and ophthalmic arteries. Immediately behind these
openings the anterior and middle clinoid processes are sometimes united, so as to
enclose a foramen. Through this the internal carotid artery passes upwards.
Leading backwards from this, along the side of the body of the sphenoid, is the
carotid groove, which turns downwards near the apex of the petrous part of the
temporal, to become continuous with the carotid canal, which here opens on the
posterior wall of an irregular aperture, placed between the side of the body of the
sphenoid and the summit of the petrous part of the temporal, called the foramen
lacerum. Through the medial angle of this opening the carotid artery accompanied
by its plexus of veins and sympathetic nerves passes upwards. Eunning through
the fibrous tissue, which in life blocks up this opening, the greater superficial petrosal
nerve, coming from the hiatus facialis, passes downwards and forwards to reach
the posterior orifice of the canalis pterygoideus, which is placed on the anterior and
inferior border of the foramen lacerum. A small meningeal branch of the
ascending pharyngeal artery also passes upwards through this foramen. In front
and to the lateral side of the foramen lacerum, and separated from it by a narrow
bar of bone, is the foramen ovale ; through this pass both roots of the mandibular
nerve, the accessory meningeal artery, and some emissary veins. Somewhat lateral
and posterior to this is the foramen spinosum for the transmission of the middle
meningeal vessels, together with a recurrent branch (nervus spinosus) from the
mandibular nerve. Leading from the lateral extremity of the, foramen lacerum
there is a groove which passes laterally, backwards, and slightly upwards on the
superior surface of the petrous part of the temporal to end in the hiatus facialis
(a cleft opening into the canalis facialis), which gives passage to the greater
superficial petrosal branch derived from the ganglion geniculi on the facial nerve,
together with the small petrosal branch of the middle meningeal artery. Just
lateral to the hiatus facialis there is another small foramen for the transmission of
the lesser superficial petrosal nerve. Overhung by the posterior border of the lesser
wing of the sphenoid is the superior orbital fissure, the cleft which separates the
small from the great wings of the sphenoid, and which opens anteriorly into the
hollow of the orbit ; through this pass the oculomotor, trochlear, ophthalmic division
of the trigeminal, and abducent nerves, together with the ophthalmic veins as well
as the sympathetic filament to the ciliary ganglion and the small orbital branch
of the middle meningeal artery. Just below its medial extremity is the foramen
rotundum for the passage of the maxillary nerve to the pterygo- palatine fossa.
Behind this, and between it and the foramen ovale, the foramen Vesalii may
occasionally be seen, through which a vein passes to reach the pterygoid plexus.
The lateral parts of the middle fossa are moulded in conformity with the
gyri of the temporal lobes, but towards its medial part the splitting of the
dura mater in the region of the cavernous sinus serves to separate the cranial
base from the inferior surface of the cerebrum. As may be seen by transmitted light,
30
JO
28
FIG. 172. BASE OP THE SKULL SEEN FROM ABOVE.
The frontal and occipital bones are coloured red ; the ethmoid and temporal bones, blue ; the
parietal, orange ; and the sphenoid is left uncoloured.
1. Frontal bone. 24.
2. Slit for anterior ethmoidal nerve. 25.
3. Anterior ethmoidal foramen.
4. Posterior ethmoidal foramen. 26.
5. Optic foramen. 27.
6. Foramen for internal carotid artery formed by
anterior and middle clinoid process. 28.
7. Small wing of sphenoid.
8. Anterior clinoid process, in this case united on its
medial side to the middle clinoid processes. 29.
9. Posterior clinoid process. 30.
10. Foramen ovale.
11. Groove for middle meningeal artery. 31.
12. Foramen spinosum. 32.
13. Hiatnsjianalis facialis. 33.
14. Line of petro-squamosal suture. 34.
15. Internal acoustic meatus. 35.
16. Groove for superior petrosal sinus. 36.
17. Groove for sigmoid part of transverse sinus. 37.
18. Jugular foramen.
19. Canalis hypoglossi. 38.
20. Groove for transverse sinus. 39.
.21. Internal occipital protuberance. 40.
'22. Ridge for attachment of falx cerebri. 41.
23. Fossa for the lodgment of the occipital lobes of
the brain.
Ridge for the attachment of the falx cerebelli.
Fossa for the lodgment of the left cerebellar
hemisphere.
Foramen occipitale magnum.
Groove for the sigmoid sinus turning into the
jugular foramen.
Groove for the inferior petrosal sinus running
along the line of suture between the petrous
part of the temporal and the basi-occipital.
Depression for the_aeiailunar ganglion.
Middle cranial fossa for lodgment of the temporal
lobes of the brain.
Foramen laceruni.
Carotid groove.
Dorsum sellse of sphenoid.
Leads into foramen rotundum.
Fossa hypophyseos.
Tuberculum sellae of the sphenoid.
Anterior cranial fossa for lodgment of frontal lobes
of the brain.
Cribriform plate of ethmoid.
Crista galli of ethmoid.
Foramen caecum.
Crest for attachment of falx cerebri.
12 a
182 OSTEOLOGY.
the floor of the lateral parts of the fossa is thin as it overlies the temporal, infra-
temporal, and mandibular fossae. The grooves for the lodgment of the branches oj
the middle meningeal artery leading from the foramen spinosum are readily seen
one, coursing backwards a little below the line of the squamoso-parietal suture
is specially well marked. Amongst other features may be noticed the depressioc
for the lodgment of the semilunar ganglion overlying the apex of the petroui
part of the temporal; behind and to the lateral side of the hiatus facialis, the
arcuate eminence, indicating the position of the superior semicircular canal ; anc
immediately anterior and slightly to the lateral side of this the tegmen tympani,
which roofs in the cavity of the tympanum, the thinness of which can readily be
demonstrated if light be allowed to fall through the external acoustic meatus.
The posterior fossa is larger and deeper than the others. In front it is limitec
by a line on either side leading backwards and laterally from each posterior clinoic
process along the superior border of the petrous part of the temporal bone, where
laterally and posteriorly it becomes confluent with the superior lip of the transverse
groove for the transverse sinus, ending posteriorly in the middle line at the internal
occipital protuberance. Along the line thus indicated the process of dura matei
called the tentorium cerebelli, which roofs in the posterior fossa, is attached. The
floor of the fossa, in which the cerebellar hemispheres, the pons, and medulla oblongata
are lodged, is formed by the petrous and mastoid portions of the temporal bone
with part of the body of the sphenoid and the basilar portion of the occipital bone
wedged in between them. Above the mastoid part of the temporal a small part oJ
the mastoid angle of the parietal enters into the constitution of the side wall oi
the fossa. Behind and within these the lateral parts and inferior portions of the
squamous part of the occipital complete the floor. In the median plane the floor
of the fossa is pierced by the foramen magnum, in which lies the lower part of the
medulla oblongata, together with its membranes, and through which pass upwards
the vertebral arteries and the accessory nerves. On either side of the foramen
magnum, and a little in front of a transverse line passing through its centre, is
the opening of the canalis hypoglossi for the passage of the hypoglossal nerve,
a small meningeal branch from the ascending pharyngeal artery and an emissary
vein. Overhanging the opening of the canalis hypoglossi there is a thickened
rounded bridge of bone, to the lateral side of which is placed the irregular opening
of the jugular foramen. The size of this is apt to vary on the two sides, and the
lumen is frequently subdivided by a spicule of bone which runs across it ; the
posterior and lateral rounded part of the foramen is occupied by the transverse
sinus, which here joins the internal jugular vein. A meningeal branch from the
ascending pharyngeal or occipital artery also enters the skull through this com-
partment. The anterior and medial part of the foramen is confluent with the groove
for the inferior petrosal sinus, which turns downwards in front of the spicule above
referred to. The interval between the portions of the foramen occupied by the two
veins allows the transmission of the glosso-pharyngeal, vagus, and accessory nerves
in this order from before backwards. About a quarter of an inch above and to
the lateral side of the anterior part of the foramen jugulare the posterior surface of
the petrous portion of the temporal bone is pierced by the internal acoustic
meatus, through which the facial and acoustic nerves, together with the nervus
intermedius, and the auditory branch of the basilar artery, leave the cranial cavity.
Behind the jugular foramen and close to the margin of the foramen magnum
the opening of the canalis condyloideus, when present, may be seen. This gives
passage to a vein which joins the vertebral vein inferiorly. The inner aperture of the
mastoid foramen is noticed opening into the groove for the transverse sinus, a little
below the level of the superior border of the petrous part of the temporal. Through
it passes an emissary vein which joins the occipital vein laterally; the mastoid
branch of the occipital artery also enters the cranial cavity through this foramen.
The posterior fossa is divided into two halves posteriorly by the internal occipital
crest, to which the falx cerebelli is attached, the floors of the hollows on either side
of which are often exceedingly thin and are for the lodgment of the hemispheres of
the cerebellum. The grooves for the following blood sinuses are usually distinct
the superior petrosal running along the superior border of the petrous part of the
MEDIAN SAGITTAL SECTION OF THE SKULL. 183
temporal, the inferior petrosal lying along the line of suture between the petrous
part of the temporal and the basilar part of the occipital bone; the occipital
sinus grooving the internal occipital crest ; and the transverse sinus curving for-
wards and laterally from the internal occipital protuberance, across the cerebral
surface of the squamous part of the occipital, to reach the mastoid angle of the
parietal bone, in front of which it turns downwards and medially to reach the
jugular foramen, describing a sigmoid curve, and grooving deeply the inner surface
of the mastoid and posterior aspect of the petrous portions of the temporal bone.
Before it terminates at the jugular foramen it again reaches the occipital bone and
channels the upper surface of the jugular process of that bone. Slight grooves for
meningeal arteries are also seen some pass upwards, whilst others turn downwards
and are occupied by branches from the posterior offsets of the middle meningeal
arteries.
Median Sagittal Section of the Skull.
Such a section should be made a little to one or other side of the median plane, so as to pass
through the nasal cavity lateral to the septum ; one-half will then display the nasal septum in
position, whilst in the other the lateral wall of the nasal cavity of that side will be exposed.
The form of the cranial cavity is, of course, subject to many variations dependent
on individual and racial peculiarities. The following details are, however, worthy
of note. The posterior border of the foramen magnum (opisthion), and consequently
the floor of the posterior cranial fossa, occupies the same horizontal plane as the
hard palate. The anterior border of the foramen magnum (basion) lies a little
higher, so that the plane of the foramen is, in the higher races at least, oblique, and
is directed downwards and slightly forwards. From the basion a line passing
upwards and forwards to reach the suture between the sphenoid and ethmoid
passes through the basi-cranial axis formed by the basi-occipital, the basi-sphenoid,
and the presphenoid. The basi-cranial axis is wedge-shaped on section posteriorly,
whilst anteriorly it is of considerable width, and has within it the large sphenoidal
air sinus. Its upper surface leads upwards and forwards with a varying degree of
obliquity from the basion to the overhanging edge of the dorsum sellse, in front of
which the sella turcica, the floor of which is quite thin, is well seen in the section.
From the tuberculum sellse the floor of the anterior fossa follows a more or less
horizontal direction, corresponding pretty closely to the level of the axis of the orbital
cavity. The roof of the orbit is seen to bulge upwards to a considerable extent into the
floor of the anterior fossa ; whilst the floor of the middle fossa sinks to a level corresponding
to that of the under surface of the basi-cranial axis, where it forms the roof of the choanae.
The maximum length of the skull is measured from the glabella (a point between
the superciliary arches) to the occipital point posteriorly. It is noteworthy that the
maximum occipital point does not necessarily correspond to the external occipital pro-
tuberance (inion). The greatest vertical height usually corresponds to the distance from
the basion to the bregma (point of union of the sagittal with the coronal suture), though
to this rule there are many exceptions. On looking into the posterior fossa the hypo-
glossal canals and jugular foramina and the internal acoustic meatus are seen in line,
sloping from below upwards. The internal acoustic meatus lies in a vertical plane,
passing through the basion. The grooves for the middle meningeal artery and its
branches are very obvious. The anterior groove curves forwards and laterally, and
reaching the cerebral surface of the pterion, passes towards the vertex at a variable
distance behind and more or less parallel to the coronal suture. From this grooves pass
forwards across the suture to reach the frontal bone. Another groove curves upwards
and backwards a little below the line of the parieto-squamosal suture. From this an
upwardly directed branch radiates on the cerebral surface of the parietal bone, in the
region of the parietal tuberosity, whilst a lower branch passes backwards some little
distance above the lambdoid suture, and gives offsets which curve downwards and
medially over the cerebral surface of the squama occipitalis of the occipital bone.
Cavum Nasi. In the section through the nasal cavity the structures which form
its lateral wall can now be studied. These are the nasal bone ; the frontal process
of the maxilla ; the lacrimal bone ; the labyrinth of the ethmoid, comprising the
superior and middle conchal bones ; the perpendicular part of the palate bone ;
the inferior conchal bone ; and the medial surface of the medial pterygoid lamina.
184
OSTEOLOGY.
The roof as seen in the section is formed by the nasal and frontal bones, the cribri-
form plate of the ethmoid, the body of the sphenoid and the sphenoidal conchse,
the sphenoidal process of the palate and the ala of the vomer. The floor, which is
42 41 40 39
FIG. 173. MEDIAL ASPECT OF THE LEFT HALF OF THE SKULL SAQITTALLT DIVIDED.
The frontal, maxillary, and sphenoid bones are coloured red ; the parietal, nasal and palate bones, blue ; the
basilar part of occipital, yellow, and squama occipitalis, purple. The ethmoid and inferior concha,
together with the left ala of the vomer, are left uncoloured.
1. Suture between parietal and temporal bones. 24.
2. Remains of the subarcuate fossa. 25.
3. Grooves for branches of the middle meningeal 26.
artery. 27.
4. Dorsum sellse. 28.
5. Sella turcica. 29.
6. Anterior clinoid process.
7. Optic foramen. 30.
8. Sphenoidal sinus. 31.
9. Nasal surface of superior concha. 32.
10. Cribriform plate of ethmoid. 33.
11. Nasal surface of middle concha.
12. Frontal sinus. 34.
13. Nasal bone near spine of frontal. 35.
14. Nasal bone. 36.
15. Frontal process of maxilla.
16. Middle meatus of nose. 37.
17. Directed towards opening of maxillary sinus.
18. Nasal surface of inferior concha. 38.
19. Inferior meatus of nose. 39.
20. Anterior nasal spine. 40.
21. Foramen incisivum.
22. Palatine process of maxilla. 41.
23. Horizontal part of palate bone. 42.
Posterior nasal spine.
Hamulus of medial pterygoid lamina.
Lateral pterygoid lamina.
Superior meatus of nose.
Spheno-palatine foramen.
Pterygo - spinous ligament almost completely
ossified to enclose a foramen.
Styloid process of temporal bone.
Angular spine of sphenoid.
Mastoid process.
Basion (mid-point of anterior border of foramen
magnum).
Internal acoustic meatus.
Canalis hypoglossi.
Groove for inferior petrosal sinus leading into
jugular foramen.
Opisthion (mid-point of posterior border of
foramen magnum).
Groove for sigmoid sinus.
Opening of mastoid foramen.
For transverse sinus and attachment of tentorium
cerebelli.
Fossa for lodgment of cerebellar hemisphere.
Internal occipital protuberance.
nearly horizontal from before backwards, is formed by the palatine processes of the
maxillae and palate bones. On sagittal section the nasal cavity appears some-
what triangular in shape with the angles cut off; the base corresponds to the
floor ; the apertura piriformis and choana to the truncated anterior and posterior
MEDIAN SAGITTAL SECTION OF THE SKULL. 185
angles, respectively ; the superior angle is cut off by the cribriform plate ; whilst the
sides correspond to the frontal and nasal bones anteriorly, and the sphenoidal
conchas, sphenoidal process of the palate, and the ala of the vomer posteriorly.
The cavity is therefore deep towards its middle, but gradually becomes shallower in
front and behind where the piriform aperture and choana are situated. The
piriforni opening of the nose, which is of half-heart shape, is larger than that of
the choanse (O.T. posterior nares), and is directed forwards and downwards ; the
choanas are of rhomboidal form, and slope backwards and downwards. The inferior
meatus is the channel which is overhung by the inferior concha, and its floor is
formed by the side- to-side concavity of the upper surface of the hard palate. Open-
ing into it above, under cover of the anterior part of the inferior concha, is the canal
for the naso-lacrimal duct ; whilst its floor is pierced in front near the middle
line by the canalis incisivus. The middle meatus is the hollow between the
middle and inferior conchas; it slopes from above downwards and backwards,
and is overhung by the free curved edge of the middle conchas, beneath which
there is a passage called the infundibulum, leading upwards and forwards to open
superiorly into the frontal sinus, as well as into some of the anterior ethmoidal cells.
Under cover of the centre of the middle concha and continuous with the
infundibulum in front there is a curved groove, the hiatus semilunaris, into
which open one or more orifices from the maxillary sinus. Above this groove
there is a rounded eminence, the bulla ethmoidalis, overlying the middle
ethmoidal cells, which usually open on its surface. The superior meatus, about
half the length of the middle meatus, is placed between the superior and middle
conchas in the posterior and upper part of the cavity ; it receives the openings of
the posterior ethmoidal cells. Near its posterior extremity the spheno - palatine
foramen pierces its lateral wall, and brings it in relation with the pterygo-
palatine fossa. The sphenoidal sinus opens on the roof of the nose, above the
level of the superior conchas, into a depression called the spheno-ethmoidal recess.
Septum Nasi. If the opposite half of the section in which the osseous nasal
septum is retained be now studied, it will be seen to be formed by the crests of
the maxillary and palate bones below, on which rests the vomer, the posterior
border of which being free, forms the posterior edge of the nasal septum, which
slopes obliquely upwards and backwards towards the inferior surface of the body of
the sphenoid. Here the vomer articulates with the rostrum of the sphenoid. In
front of this the vomer articulates with the perpendicular part of the ethmoid, and
between them anteriorly there is an angular recess into which the cartilaginous
septum fits. Superiorly and anteriorly the osseous septum is completed by the
articulation of the perpendicular part of the ethmoid with the nasal spine of
the frontal, together with the nasal crest formed by the union of the nasal bones ;
whilst posteriorly and superiorly the perpendicular plate of the ethmoid articulates
with the median sphenoidal crest of the sphenoid. In most instances the osseous
septum is not perfectly vertical, but is deflected towards one or other side.
Air-sinuses in Connexion with the Nasal Cavities. Connected with the
nasal cavities are a number of air-sinuses. These are found within the body of
the sphenoid, the labyrinth of the ethmoid, the orbital process of the palate bone,
the body of the maxilla, and the superciliary arch of the frontal bone.
The sphenoidal sinus, of variable size, occupies the interior of the body of the
sphenoid. In some cases it extends towards the roots of the pterygoid processes.
In front it is formed in part by the absorption of the sphenoidal conchas and
is divided up into two cavities by a sagittally placed partition, which, however,
is frequently displaced to one or other side. It opens anteriorly into the roof
of the nose in the region of the spheno-ethmoidal recess.
The ethmoidal sinuses are placed between the lateral aspects of the upper part
of the nasal cavities, and the cavities of the orbits, from which they are separated
by thin and papery walls. These air-spaces are completed by the articulation of
the ethmoid with the maxilla, lacrimal, frontal, sphenoid, and palate bones, and
are divided into three groups an anterior, middle, and posterior. The latter
communicates with the superior meatus ; the anterior and middle open either
independently or in conjunction with the infundibulum into the middle meatus.
186
OSTEOLOGY.
Frontal sinus
Crista galli of ethmoid
Cribriform plate of ethmoid
Sphenoidal sinus
l/f
HL Fossa hypophyseos
Dorsum sella?
of sphenoid
The sinus in the orbital process of the palate bone either communicates with the
sphenoidal sinus, or else assists in closing in some of the posterior ethmoidal cells.
Its communication with the nasal cavity is through one or other of these spaces.
The maxillary sinus lies to the lateral side of the nasal cavity, occupying the
body of the maxilla. Its walls, which are relatively thin, are directed upwards to
the orbit, forwards to the face, backwards to the infra-temporal and pterygo-palatine
fossae, and medially to the nose. In the latter situation the perpendicular part
of the palate bone, the un-
cinate process of the ethmoid,
the maxillary process of the
inferior concha, and a small
part of the lacrimal bone
assist in the formation of
the thin osseous partition
which separates it from the
nasal cavity. The floor corre-
sponds to the alveolar border
of the maxilla, and differs
from the other walls in being
stout and thick ; it is, how-
ever, deeply pitted inferiorly
by the alveoli for the teeth.
The sinus opens by a
narrow orifice in the floor
of the hiatus semilunaris
into the middle meatus.
Occasionally there are two
Angular spine Openings.
The frontal sinuses lie,
one on either side, between
the inner and outer tables of
the frontal bone over the root
of the nose, and extend
FIG. 174. THE NASAL SEPTUM AS SEEN FROM THE LEFT SIDE. laterallv under the SUPer-
The frontal, maxillary, and sphenoid bones are coloured red ; the nasal, ciliary arches. The parti-
vomer, and basi- occipital blue ; the perpendicular part of the ethmoid fjrvQ which SGDirates them
is usually central, though it
communicates with the nose
through a passage called the infundibulum, which opens inferiorly into the
anterior part of the corresponding middle meatus, below the ethmoidal bulla and
continuous with the hiatus semilunaris.
The fact should not be overlooked that the air-spaces within the temporal
bone, viz., the tympanic cavity and the mastoid air-cells, are brought into com-
munication with the naso-pharynx through the auditory tubes. Further details
regarding the air-sinuses and the mode of their growth will be found under the
description of the individual bones.
Frontal Sections.
The relations of many parts of the cranium are best displayed in a series of frontal
(coronal) sections.
By sawing off a thin slice from the front of the lower part of the frontal bone
above, and carrying the section downwards through the medial wall of the orbit and
the frontal process of the maxilla, into the piriform aperture below, a number of important
relations are revealed (see Fig. 175). In the frontal region the extent and arrange-
ment of the frontal sinuses are displayed. The partition between the two sinuses,
be it noted, is usually complete and central in position, though it may occasionally be
perforated or oblique. The sinuses are hardly ever symmetrical, the right being
usually the smaller of the two. (Logan Turner, Edin. Med. Journ. 1898.)
The infundibulum on either side, leading from the frontal sinus above to the middle
Vomer of sphenoid
Lateral pterygoid lamina
Hamulus of medial
pterygoid lamina
Foramen incisivum
and the horizontal part of the palate bone are left uncoloured.
may be deflected to one or other side. Each
FKONTAL SECTIONS OF THE CEANIUM.
187
meatus below, is seen with the middle concha medial to it, and the anterior ethmoidal
cells to its lateral side above. If the section passes through the canal for the naso-
lacrimal duct the continuity of that channel leading from the orbit above to the inferior
meatus of the nose below is clearly shown. Its medial wall above, by which it is separated
from the cavity of the nose, is formed by the thin lacrimal bone ; below, it passes under
cover of the inferior concha to open into the anterior part of the inferior meatus. It is
FIG. 175. PART OF THE FRONTAL, NASAL, AND MAXILLARY BONES REMOVED IN ORDER TO
DISPLAY THE RELATION OP THE VARIOUS CAVITIES EXPOSED.
The frontal and maxillary bones, where cut, are coloured blue ; the ethmoid and the inferior concha red ;
the lacrimal and vomer yellow.
1. Frontal sinus.
2. Septum of frontal sinus deflected towards the right.
3. Infundibulum leading from sinus to middle meatus.
4. Anterior ethmoidal air-sinuses.
5. Middle concha.
6. Eed line in upper part of osseous canal for naso-
lacrimal duct, laid open throughout its entire
length on the right side.
7. Cavity of maxillary sinus laid open.
8. Middle meatus of nose.
9. Inferior meatus of nose.
10. Inferior concha.
11. Nasal septum.
12. Canal for naso-lacrimal duct laid open through-
out its entire length.
13. Anterior nasal spine.
separated from the maxillary sinus laterally by a thin lamina of bone. The cavity of
the maxillary sinus is seen to extend upwards and forwards so as to pass over the lateral
side as well as slightly in front of the canal for the naso-lacrimal duct.
The lower margins of the middle conchae lie pretty nearly on a level with the
most dependent parts of the orbital margins, whilst the lower borders of the inferior
conchse are placed a little above the lower margin of the piriform opening on a level
with the lowest point of the zygomatico-maxillary suture.
Such a section will reveal any deflection of the nasal septum should it exist, and will
also show that but a narrow cleft separates the upper part of the septum, on either side,
from the medial surface of the superior conchee.
The next section (Fig. 176) passes through the anterior part of the temporal fossa just
188
OSTEOLOGY.
behind the zygomatic process of the frontal bone above ; inferiorly it passes through
the alveolar process of the maxilla in the interval between the first and second molar
teeth. The cranial, orbital, nasal,
J and maxillary cavities are all ex-
posed, together with the roof of
the mouth.
The anterior cranial fossa is
deepest in its centre, where its
floor is formed by the cribriform
plate of the ethmoid ; this corre-
sponds to the level of the zygo-
matico-frontal suture laterally.
On either side the floor of the
fossa bulges upwards, owing to
the arching of the roof of the
orbit. Of the orbital walls, the
lateral is the thickest and stoutest ;
the superior, medial, and inferior
walls, which separate the orbit
from the cranial cavity, the eth-
moidal cells, and the maxillary
sinus, respectively, are all thin.
The cavity of the maxillary
sinus lying to the lateral side of
the nasal cavity is well seen.
Its roof, which separates it from
the orbital cavity, is thin and
traversed by the infraorbital
canal. Its medial wall, with
which the inferior concha articu-
lates, is very slender, and forms
the lateral walls of both the
middle and inferior meatuses of
the nose. Its lateral wall is
stouter where it arches up to
bracket the temporal process of
the zygomatic bone. Its floor,
which rests upon the superior
surface of the alveolar border of
the maxilla, sinks below the level
of the hard palate. The fangs
of the teeth sometimes project
into the floor of the cavity.
The nasal cavities are narrow
above, where they lie between
the orbital cavities, from which
they are separated by the cells
within the labyrinth of the
ethmoid. The roof which cor-
responds to the cribriform plate
is narrow, and lies between the
18. Alveolar process of maxilla. sep tum medially and the laby-
19. Groove for posterior palatine . r , , ., -, . i
rmth on either side.
At the level of the orbital floor
the nasal cavities expand later-
ally, the middle meatus running
16
22 21 20 19
FIG. 176. FRONTAL SECTION PASSING INFERIORITY THROUGH
THE INTERVAL BETWEEN THE FIRST AND SECOND MOLAR TEETH.
The frontal and maxillary bones, where cut, are coloured blue ;
the ethmoid, inferior conchse, and zygomatic red ; the vonier yellow.
1. Groove for sagittal sinus.
2. Crest for attachment of falx
cerebri.
3. Crista galli of ethmoid.
4. Cribriform plate of ethmoid.
5. Perpendicular part of eth-
moid, assisting in the forma-
tion of the nasal septum.
6. Labyrinth of ethmoid con-
sisting of the ethmoidal cells.
7. Lamina pap yracea of ethmoid.
8. Middle meatus of nose.
9. Middle concha.
10. Opening from middle meatus
into maxillary sinus.
11. Orbital surface of maxilla.
12. Zygomatico-frontal suture.
13. Infra- orbital groove.
14. Maxillary sinus.
15. Canal for the anterior alveolar
nerve and vessels exposed.
16. Inferior concha.
17. Inferior meatus of nose.
21.
nerve and greater palatine
vessels.
20. Palatine process of maxilla.
Maxillary crest forming part
vlrtg m P a rt of nasa, longitudinally in the angle formed
septum. by the labyrinth of the ethmoid
with the body of the maxilla,
overhung by the middle concha. This channel is seen to have the ethmoidal
cells superior to it, the orbital cavity above and to the lateral side, the maxillary sinus
laterally, whilst its floor is formed by the superior surface of the inferior concha.
The inferior meatus, much more roomy, runs along under cover of the inferior
FKONTAL SECTIONS OF THE CKANIUM.
189
;oncha. Laterally it is related to the maxillary sinus, whilst its floor is formed by the
:oncave superior surface of the hard palate.
The hard palate is arched below, whilst its superior surface is concave upwards on
;ither side of the median crest which
;upports the nasal septum. The sides
>f the arch below correspond to the
nedial surfaces of the alveolar processes
ind fall in line with the lateral walls
>f the nasal cavities superiorly. The
lummit of the arch lies a quarter of
in inch above the level of the floor
>f the maxillary sinus.
The next section (Fig. 177) passes
Jirough the pterygo - palatine and
temporal fossse inferiorly, and cuts the
;ranial vault about half an inch in
I'ront of the bregma. The floor of
.he anterior cranial fossa is seen to be
brmed by the upper surface of the
>ody and small wings of the sphenoid,
md is almost horizontal. At the median
>lane the sphenoidal sinuses are exposed,
-eparated by a thin bony partition, on
dther side of which the openings by
vhich they communicate with the nasal
Cavities are seen. The section passes in
ront of the optic foramen, the groove
>f which may be seen on the inferior
urface of the small wing of the sphe-
iioid close to the body, and lays open
he superior orbital fissure which here
eads forwards into the orbit, and which,
nferiorly and laterally, is continuous
v r ith the cleft between the maxilla and
i he lower edge of the great wing of the
phenoid the inferior orbital fissure.
?his also leads into the orbit.
The nasal cavities, now much dimin-
shed in height, are roofed in above by
1 he inferior surface of the body of the
: phenoid and the alse of the vomer,
/hilst the lateral walls are seen to be
: ormed by the thin perpendicular parts
>f the palate bones, lateral to which
he rounded posterior surface of the
aaxilla is directed backwards, here
orming the anterior wall of the
)terygo - palatine fossa the space
v r hich lies between the anterior part of
he pterygoid process behind and the
naxilla anteriorly. As will be seen,
he medial wall of this space is formed
>y the perpendicular part of the palate,
vhich is, however, deficient above im-
I nediately below the inferior surface of
I he body of the sphenoid. In the in-
erval between the orbital process, which ^ oSflLre.
10
'20
FIG. 177. FRONTAL SECTION PASSING THROUGH THE
PTERYGO-PALATINE FOSSA.
1. Depression for arach-
noideal granulation.
2. Groove for sagittal sinus.
3. Crista galli of ethmoid.
4. Opening of sphenoidal
sinus into superior
meatus of nose through
10. Zygomatic process of
maxilla.
11. Surface of maxilla which
forms the anterior wall
of the pterygo-palatine
fossa.
12. Spheno-palatine foramen.
spheno - ethmoidal re- 13. Opening of pterygo-pala-
part of
tine canal.
14. Perpendicular
palate bone.
15. Pterygoid fossa.
surface of great wing 16. Superior meatus of nose.
17. Middle meatus of nose.
cess.
5. Superior orbital fissure.
6. Part of middle fossa
formed by cerebral
of sphenoid.
7. Zygomatic crest of great 18. Inferior meatus of nose.
19. Inferior concha.
ft , -. " *J. Xi-llCllUl V7L UiLcH llOdULC. 2t\) , .Middle COllCIlil.
'Ont 01 the section, and the 9. Zygomatic process of 21. Maxillary crest and vomer
phenoidal process, which lies behind, temporal. forming nasal septum.
his forms the spheno-palatine fora-
nen. Laterally the section has passed through the inferior orbital fissure, which is
ontiimous above with the pterygo-palatine fossa. Inferiorly the section passes through
he line of fusion of the pterygoid processes with the pyramidal process of the palate
190
OSTEOLOGY.
bone and the union of the latter with the maxilla. Just above this the opening of tin
pterygo-palatine canal, which leads from the pterygo-palatine fossa to the inferior surfaci
of the hard palate, is visible; whilst inferiorly a small portion of the lower part of thi
pterygoid fossa is cut through
Within the choanse the middl<
and inferior conchae are seen
the inferior border of the forme:
corresponds to the level of th<
superior border of the zygomatii
arch, whilst the attached edge of thi
latter to the perpendicular part o
the palate lies in the same horizonta
plane as the inferior margins of tha
arch. Note also that the media
pterygoid laminae lie considerably
within the lines of the medial sur
faces of the alveolar border, am
reach some little distance below thi
level of the hard palate.
The next section (Fig. 178
passes through the maudibular fossi
just behind the tuberculum articu
lare; superiorly, it cuts the vaul
half an inch behind the bregma. Thi
middle cranial fossa is shown ij
section, the floor of which descend
as low as the level of the inferio
surface of the body of the sphenoid
corresponding laterally to a hori
zontal plane passing through thi
superior edge of the posterior roo
of the zygoma. The body of thi
sphenoid rises a finger's breadtl
above this in the median plane ; thi
cavity within it is exposed, whils
on either side and below is seei
the groove for the internal carotk
artery, leading upwards from th<
medial part of the foramen lacerum
which is here divided. To thi
lateral side of the groove is seei
28 i i ' ' Z6 the prominent edge of the lingula
immediately below which is thi
FIG. 178. FRONTAL SECTION OF THE SKULL PASSING THROUGH THE noqtpri or a>rtnrP of thp ntewmnit
MANDIBULAR FOSSA JUST BEHIND THE TUBERCULUM ARTICULARE. P oste 7 ri o r apertur
canal, the inferior edge of which ii
15.
in part concealed by the
tubercle. Immediately lateral tc
the foramen lacerum the foramen
1. Crista galli of ethmoid.
2. Posterior cliuoid process.
3. Optic foramen.
4. Anterior cliuoid process.
5. Orbital part of frontal.
6. Small wing of sphenoid.
7. Suture between squamous pterygoid canal. ,
part of the temporal, and 19. Postero - lateral margin of Dna g e (
parietal bones. lateral pterygoid lamina. Overlie the root of the lateral ptery
20. Groove for carotid artery.
21. Pterygoid fossa.
22. Scaphoid fossa.
23. Hamulus of medial ptery
goid lamina.
24. Inferior concha.
of sphenoid in
of spine.
16. Foramen ovale.
17. Lingula.
18. Anterior margin of foramen ovale is seen separated from the
lacerum and opening of sur f ace O f the section by a narrow
nrawnrmH raiial v
Here it is seen tc
8. Superior orbital fissure.
9. Cerebral surface of great
wing of sphenoid.
10. Foramen rotundum.
1 1 . Squamous part of temporal.
12. Posterior root of zygomatic
process.
13. Tuberculum articulare.
14. Maudibular fossa.
26'
goid lamina. The section passes
just in front of the foramen spin-
osum, and here is visible the stoul
suture between the great wing oi
the sphenoid and the squamous parl
of the temporal bone. The man-
27. Openingofsphenoidalsinus. dibular fossa of the temporal boj
28. Dorsum sellae. is cut on either side, and in i
deepest part is separated from tiu
middle cranial fossa by but a thin lamina of bone. The thinness of the squamous part o:
the temporal and the manner in which it is sutured to the parietal is also well displayed.
FKONTAL SECTIONS OF THE CKANIUM.
191
The next figure (Fig. 179). displays the anterior surface of the section immediately
jhind that above described. In the centre is seen the body of the sphenoid, and the
osterior wall of the sinus is now exposed ; on either side the apex of the petrous part of the
mporal abuts upon the side of the body of the sphenoid, and the large orifice of the carotid
inal is seen opening on to the
Dsterior wall of the foramen
.cerum, which is here divided.
i the recess between the lateral
all of the carotid canal and the
oine of the sphenoid is the
roove leading into the osseous
art of the auditory tube, in front
f which the base is pierced by
le foramen spinosum. Lateral
h the angular spine, the man-
ibular fossa is divided and its
iin roof displayed. Crossing it
;an aversely is seen the petro-
nnpanic fissure which divides
lie fossa into an articular and
on- articular part. The floor of
be middle cranial fossa is here
pen to be formed by the upward
rlope of the anterior surface of
he petrous part of the temporal,
rhich is pierced by the hiatus
analis facialis, and the foramen
pr the lesser superficial petrosal
[ erve. On the upper surface of
[he summit of the petrous part
If the temporal the depression
pr the lodgment of the semi-
Lmar ganglion is well seen on
fither side.
The last section, the an-
lerior surface of which Fig.
[80 is a representation, passes
fertically through the base
Immediately in front of the root
[f the styloid process. In the
[aedian plane the basi-occipital is
j.ivided a little in front of the
Interior extremities of the oc-
I ipital condyles ; its upper sur-
face is concave from side to side
rnd forms a wide groove for the
[nedulla oblongata and pons.
|)n either side there is a narrow
interval between the lateral edge
[if the basi-occipital and the
X)sterior border of the petrous
Ibart of the temporal, which in
H)
1213 14
4.
5.
7.
12.
15 16 17 18 19 20 21 22 23
FIG. 179. ANTERIOR SURFACE OF THE SECTION OF THE SKULL
IMMEDIATELY BEHIND THE PRECEDING SECTION.
. Impressio trigemini on apex of 13. Angular spine of the sphenoid.
petrous bone. 14. Styloid process.
Squamo-parietal suture. 15. Canalforauricularbranchofthe
vagus with opening of carotid
canal in front and above it.
16. Position of osseous opening of
auditory tube.
17. Jugular foramen.
18. Medial wall of open carotid
canal.
19. Canalis hypoglossi.
20. Condyle of occipital bone.
21. Petro-occipital suture.
22. Posterior wall of sphenoidal
sinus.
23. Position of pharyngeal tubercle.
24. Anterior margin
magnum.
25. Occipital condyle.
Groove for posterior branch of
middle meningeal artery.
Eminence of superior semi-
circular canal (eminentia
arcuata).
Hiatus facialis.
Posterior root of zygomatic
process of temporal.
Leads into external acoustic
meatus.
Mandibular fossa.
Tympanic plate.
of foramen
foramen.
Roof of carotid canal.
: ife is occupied by dense fibrous
issue ; running along the upper 10. Mastoid process.
j ;urface of this suture is the in- H- Leading into stylo -mastoid
! erior petrosal sinus. Laterally
i -he section passes through the
'.emporal bone, dividing the cavity of the tympanum and laying open the external acoustic
: neatus. To the medial side of the tympanic wall the cochlea is exposed, whilst above and
'ateral to it the canalis facialis is twice divided, the section passing posterior to the
Single formed by its genu. Below the cochlea, and separated from it and the medial part
!>f the floor of the tympanum, the carotid canal is in part exposed. Above the tympanum
' ! s the epitympanic recess ("attic") leading into the tympanic antrum, the whole being
192
OSTEOLOGY.
roofed in by the thin tegmen tympani, which separates it from the middle cranial fossa.
The obliquity of the medial end of the external acoustic meatus, together with the
groove for the attachment of
the tympanic membrane, is
well seen, and the thickness of
the upper wall of that passage
is also noteworthy. The floor
of the meatus, formed by the
tympanic plate, which separ-
ates it from the mandibular
fossa, is much thinner, but inj
the region of the root of the
styloid process there is a mass-
ing together of dense bone.
HORIZONTAL SECTION.
Figure 181 represents a
horizontal section passing
through the face a little below
the level of the inferior orbital
margin, cutting through the
root of each pterygoid process
posteriorly. The nasal cavities
and the maxillary sinuses are
thus exposed. The nasal cavity
is divided slightly below the
inferior edge of the middle
concha along the line of the
middle meatus. The thin
partition, which here separates
the nose from the maxillary
sinus, is cut through, and the
aperture into the sinus laid
open. In front of this, the
canal for the naso-lacrimal duct
is cut across, and its relations
to the maxillary sinus in front
and to the lateral side, and
to the nose medially, are well
displayed. The form of the
maxillary sinus, as exposed, is
triangular, the summit of the
triangle being directed later-
ally towards the root of the
zygomatic process. Its anterior
wall, which is here stout, is
pierced obliquely by the infra-orbital canal which at this point reaches the facial surface
of the maxilla at the infra-orbital foramen. Its posterior wall, thin and convex backwards,
is directed towards the infra-temporal fossa laterally, and to the pterygo-palatine fossa
medially, where it lies in front of the pterygoid processes. The latter fossa has been cut
across and is seen to correspond to the interval between the posterior and superior
surface of the maxilla, and the anterior aspect of the root of the pterygoid process.
Laterally, it is seen to communicate with the infra-temporal fossa by means of the pterygo-
maxillary fissure which is here cut across ; medially, it opens into the nose by the spheno-
palatine foramen, which is also divided. On one side the anterior orifice of the pterygoid
canal is seen opening on to the posterior wall of the fossa. On the other side, the
canal has been laid open, by removing its lower wall, so as to expose its whole length
as it leads backward to the anterior edge of the foramen lacerum. In the middle
line, the nasal septum, here formed by the vomer and perpendicular part of the ethmoid,
is shown in section. A line passing through the inferior orbital fissures cuts the zygo-
matic arch where the zygomatic process of the temporal articulates with the zygomatic
bone.
16
10 11 12 13 14
FIG. 180. VERTICAL SECTION THROUGH THE SKULL IMMEDIATELY
IN FRONT OF THE ROOT OF THE STYLOID PROCESS.
10. Inferior opening of carotid
1. Cochlea.
2. Entrance to the antrum.
3. Sulcus tympanicus.
4. Tympanic bone.
5. Tympano-mastoid fissure.
6. Part of mandibular fossa.
7. Tympanic cavity (floor).
8. Styloid process.
9. Jugular fossa.
opening
canal.
11. Jugular foramen.
12. Canalis hypoglossi.
13. Occipital condyle.
14. Foramen magnum.
15. Basi- occipital.
16. Squamous part of occipital
bone.
SEXUAL DIFFERENCES IN THE SKULL.
193
12
.13
31 30 29
27 26 25 24
FIG. 181. HORIZONTAL SECTION OF THE SKULL A LITTLE BELOW THE LEVEL OF THE
INFERIOR ORBITAL MARGIN.
Canal for naso-lacrimal duct.
2. Middle concha.
3. Nasal septum.
4. Middle meatus of nose.
5. Naso-lacrimal duct.
6. Infra-orbital canal.
7. Opening into maxillary sinus from the middle
meatus of tl^ nose.
8. Eoof of maxillary sinus.
9. Inferior orbital fissure.
10. Passing through pterygo-maxillary fissure
into pterygo - palatine fossa and ending
opposite opening of foramen rotundum.
11. Infra- temporal crest of great wing of sphenoid.
12. Zygomatic arch.
13. Squamous part of temporal.
14. Inferior surface of great wing of sphenoid.
15. Cut pterygoid process.
16. Tubevculum articulare.
17. Foramen ovale.
18. Mandibular fossa.
19. Foramen spinosum.
20. Spine of sphenoid.
21. Petro-squamosal fissure.
22. Opening of bony canal of auditory tube.
23. Carotid canal.
24. Upper opening of carotid canal (foramen
lacerum).
25. Anterior opening of pterygoid canal.
26. Eoof of pterygo-palatine fossa just above
spheno- palatine foramen.
27. Superior concha.
28. Superior meatus of the nose.
29. Placed in position of spheno - palatine
foramen.
30. Placed in the pterygo-palatine fossa
near the upper part of the pterygo-
maxillary fissure.
31. Pterygoid canal laid open.
SEXUAL DIFFERENCES IN THE SKULL.
Whilst it is a matter of difficulty, in all cases, to determine with certainty the sex of
a skull, the following points of difference are usually fairly characteristic. The female skull
is, as a rule, smaller than the male. In point of cranial capacity it averages about a tenth
less than the male of corresponding race. Undue stress must not be laid on these facts,
since the female in bulk and stature measures on an average less than the male. It is
lighter, smoother as regards the development of its muscular ridges, and possesses less
prominent mastoid processes. In the frontal region, the superciliary arches are less pro-
nounced, and this imparts a thinness and sharpness to the upper orbital margin, which is
fairly characteristic, and can best be appreciated by running the finger along that edge of
bone. For the same reason, the forehead appears more vertical and the projections of the
13
194 OSTEOLOGY.
frontal tuberosities more outstanding, though it is stated that the frontal and occipital
regions are less capacious proportionately than in the male. The vertex in the female is
said to be more flattened, and the height of the skull consequently somewhat reduced. In
the male the edge of the tympanic plate is generally sharp, and divides to form the sheath
of the styloid process, whilst in the female the corresponding border is described as being
rounder and more tubercular.
Whilst it is true that no one of these differences is sufficiently characteristic to enable
us to pronounce with certainty on the matter of sex, it is the case that, taken together,
they usually justify us in arriving at a conclusion which, as a rule, may be regarded as
fairly accurate. In some instances, however, it is impossible to express any definite
opinion.
THE SKULL AT BIRTH.
THE SKULL AT BIRTH.
195
morphological significance, and are not more readily accounted for on the assumption
that they are mere irregularities in the ossification of the occluding membrane.
The sagittal fonticulus is occasionally seen in the skull at birth as a transverse
fissure or angular cleft, notching the sagittal margins of the parietal bones,
transversely to the line of the sagittal suture, and in correspondence with the
position of the parietal foramina, the medial margins of which may, as yet,, be
unossified and formed merely by the membranous layer uniting the two bones.
Frequently at birth all evidence of the previous existence of this fonticulus
is absent.
Most striking at birth is the occurrence of outstanding bosses, tubera parietalia,
on the surface of the parietal bones. These overlie the position of the primary
ossific centres from which these bones are originally developed, and correspond to
Fonticulus frontalis
Tuber frontale
Cartilaginous
septum nasi
Fossa sacci
lacrimalis
Elevations corresponding
?: to the position of the
dental sacs
FIG. 182. FRONTAL ASPECT OF THE SKULL AT BIRTH.
greatest maximum width of the calvaria. They mark the position of what in
the adult are known as the tubera parietalia, though, be it noted, that in the adult
i condition these reliefs need not necessarily correspond to the greater breadth of
:the head.
In like manner the sites of the centres from which the lateral portions of the
frontal part of the frontal bone are developed are readily recognised by the presence
of the frontal bosses, which impart to the child's forehead its bulging appearance,
and correspond in later life to the position of the frontal tuberosities. As yet the
two halves of the frontal part of the frontal bone are ununited, being separated
.by the frontal or metopic suture (sutura frontalis), which lies in direct continuation
anteriorly with the line of the sagittal suture. The frontal suture is, as a rule,
more or less completely fused by the sixth year.
The size of the infant's skull at birth varies considerably, and is to a large
xtent dependent on the bulk and development of the child. The size of the skull
in female infants is absolutely smaller than in the case of male children, though
not necessarily proportionately smaller, since the weight of female children at
irth is on the average absolutely less than male foetuses at full term.
196 OSTEOLOGY.
In viewing the skeleton of the face the observer is struck with the large
proportionate size of the orbital and nasal apertures. The former are circular in
outline, with sharp crisp margins. Under cover of the zygomatic process of the
frontal bone the roof and lateral wall of the orbit is deeply recessed. The fossa
sacci lacrimalis is oftentimes directed more towards the facial aspect than towards
the orbital cavity. The superior and inferior orbital fissures are proportionately large,
and the latter, in the macerated skull, forms a wide channel of communication
with the fossa infratemporalis. The nasal aperture, apertura piriformis, is cordate
in form, and exhibits a greater proportionate width than is met with in the adult ;
its inferior margin is not far beneath the level of the inferior orbital margins.
The vertical depth of the maxillae is small, and as yet the processus alveolaris is
imperfectly developed, its inferior edge lying but little below the level of the
inferior border of the arcus zygomaticus. Sunk in the alveolar border at this
Position of fonticulus frontalis
Tuber parietale
Position of
-fonticulus
occipitalis
Cartilaginous
nasal septum -0| ISfc^ ^^F Suture between
TL . interparietal and
supra-occipital parts
of occipital bone
Fonticulus mastoideus
FIG. 183. LATERAL ASPECT OF THE SKULL AT BIRTH.
stage may be seen the relatively large hollows in which the dental sacs are lodged.
Within the body of the maxilla the maxillary sinus is represented by a shallow
groove, disposed in relation to the middle meatus of the nose. For this reason the
space separating the orbital floor from the palatine surface of the bone is small,
but is later increased to its adult proportions by the enlargement of the maxillary
sinus and the consequent expansion of the body of the maxilla.
Viewed from the inferior surface, the hard palate is shallow, owing to the poor
development of the alveolar border. The sutures between the ossa incisiva and
the processus palatini of the maxillae are readily recognisable, and the vertical
height of the choanse is seen to be relatively small, owing to the perpendicular parts
of the palate bones not having reached their adult proportions.
The mandible consists of two parts united, in the median plane in front, by
fibrous tissue to form the symphysis. The alveolar border is deeply grooved for
the reception of the dental sacs, whilst the remaining substance of the body of
the bone is but slightly developed. The foramen mentale pierces the bone about
midway between its superior and inferior borders.
THE CLAVICLE. 197
The ramus is proportionately wide, and forms with the body an angle which is
very obtuse.
The coronoid process rises considerably above the level of the capitulum, and
comes into close relationship with the crista infratemporalis.
The capiturum, which is proportionately more expanded than in the adult,
occupies the somewhat laterally -directed shallow mandibular fossa of the temporal
bone.
On viewing the lateral aspect of the skull, the meatus acusticus externus, as
such, is not seen ; it is replaced by the slender annulus tympanicus, which supports
the tympanic membrane. This ring of bone, incomplete above, is united by its
extremities superiorly to the inferior surface and lateral aspect of the squamo-
zygomatic part of the temporal bone. The ring itself is disposed so that it slopes
downwards, forwards, and medially ; as yet it fails to enter into the formation of
the posterior wall of the fossa mandibularis, and only at a later stage does it grow
laterally to form the floor of the external acoustic meatus. Through the ring
the labyrinthic wall of the cavum tympani is seen ; exposed on this surface are
the promontory, the fenestra vestibuli, and the fenestra cochleae.
Posterior to the tympanic ring the sutura squamosomastoidea, still open, is seen
separating the pars mastoidea from the squama temporalis of the temporal bone.
On turning the skull over so that its inferior surface is exposed, the partes laterales
of the occipital bone are seen separated in front from the pars basilaris by a
suture, which runs through the occipital condyle on either side. Posteriorly an
open suture, which curves backward and laterally on each side of the posterior
margin of the foramen ovale, separates them from that part of the squama
occipitalis which is developed in cartilage. The squama occipitalis at this stage
exhibits a lateral cleft on each side, passing backwards from the fonticulus
mastoideus, which serves to indicate the line of union of the parts which are
developed in cartilage and membrane respectively. The latter, the superior,
sometimes separate, constitutes the os interparietale.
DIFFERENCES DUE TO AGE.
At birth the face is proportionately small as compared with the cranium, constituting
about one-eighth of the bulk of the latter. In the adult the face equals at least half the
cranium. About the age of puberty the development and expansion of some of the air-
sinuses, more particularly the frontal sinus, lead to characteristic differences in form in
both the head and face.
The eruption of the teeth in early life and adolescence enables us to determine the
age with fair accuracy. After the completion of the permanent dentition, the wear of the
teeth may assist us in hazarding an approximate estimate. The condition of the sutures,
too, may guide us, synostosis of the coronal and sagittal sutures not as a rule taking place
till late in life. Complete obliteration of the synchondrosis between the occipital bone
and sphenoid may be regarded as an indication of maturity. In old age the skull
usually becomes lighter and the cranial bones thinner. The alveolar borders of the
maxillae and mandibles become absorbed owing to the loss of the teeth. This gives
rise to a flattening of the vault of the hard palate and an alteration in the form of the
mandible, whereby the mandibular angle becomes more obtuse.
THE BONES OF THE SUPERIOR EXTREMITY.
Clavicula.
The clavicle, or collar bone, one of the elements in the formation of the
shoulder girdle, consists of a curved shaft, the extremities of which are enlarged.
The medial end, since it articulates with the sternum, is called the sternal
extremity ; the lateral extremity, from its union with the acromion of the scapula,
is known as the acromial end.
The extremitas sternalis (sternal end) is enlarged, and rests upon the disc
198
OSTEOLOGY.
of fibro-cartilage which is interposed between it and the clavicular facet on the
upper and lateral angle of the manubrium sterni. It is also supported by a small
part of the medial end of the cartilage of the first rib. Its articular surface, usually
broader from above downwards than from side to side, displays an antero-posterior
convexity, whilst tending to be slightly concave in a vertical direction. The edge
around the articular area, which serves for the attachment of the capsule of the
ACROMIAL
ARTICULAR SURFACE
TUBEROSITAS CORACOIDEA .
FIG. 184. THE EIGHT CLAVICLE SEBN FROM ABOVE.
sterno-clavicular articulation, is sharp and well defined, except below, where it is
rounded.
The body exhibits a double curve, being bent forwards in the medial two-
thirds of its extent, whilst in its lateral third it displays a backward curve. Of
rounded or prismatic form towards its sternal end, it becomes compressed
and flattened at its acromial extremity. It may be described as possessing two
surfaces, a superior and an inferior, separated by anterior and posterior borders, which
are well defined towards the
lateral extremity of the bone,
but become wider and less
well marked medially where
they conform more to the
cylindrical shape of the bone.-
The superior surface, which is
smooth and subcutaneous
throughout its whole length,
is directed upwards and for-
wards. The anterior border,
which separates the superior from the inferior surface in front, is rough and tubercular
towards its medial end for the attachment of the clavicular fibres of the pectoralis
major, whilst laterally, where it becomes continuous with the anterior margin of
the acromial end, it is better defined, and bears the imprint of the origin of the
fibres of the deltoid muscle ; here, not uncommonly, a projecting spur of bone,
called the deltoid tubercle, may be seen. The posterior border is broad medially,
FIG. 185. THE UPPER SURFACE OF THE RIGHT CLAVICLE
WITH MUSCLE ATTACHMENTS.
TUBEROSITAS COSTALIS
TUBEROSITAS CORACOIDEA
F IG> 186. THE EIGHT CLAVICLE SEEN FROM BELOW.
where it is lipped superiorly to furnish an attachment for the clavicular fibres of the
sterno-mastoid muscle ; behind and below this the sterno-hyoid and sterno-thyreoid
muscles are attached to the bone. Laterally, the posterior border becomes more
rounded/and is confluent with the posterior edge of the acromial end at a point
where there is a marked outgrowth of bone from its inferior surface, the
tuberositas coracoidea. Into the lateral third 'of this border are inserted the
THE CLAVICLE. 199
upper and anterior fibres of the trapezius muscle. The inferior surface, in-
clined downwards and backwards, is marked close to the sternal end by
an irregular elongated
impression (tuberositas
costalis), often deeply
pitted, for the attach-
ment of the costo-
clavicular ligament, which
Unites it tO the Cartilage ^k^SBiiB^SBIII^' Costo-clavicular ligament
of the first rib. Lateral
to this the shaft is
fharmpllprl V>V < o-rnmrA FlG> 187> ~ THE UNDER SUKFACE OP THE RIGHT CLAVICLE WITH THE
by a groove ATTACHMENTS OF THE MUSCLES MAPPED OUT.
which terminates close
to the coracoid impression ; into this groove the subclavius muscle is inserted.
The acromial end of the bone is flattened and compressed from above down-
wards, and expanded from before backwards ; its anterior edge is sharp and well
defined, and gives attachment to the deltoid muscle, which also spreads over part
of its upper surface. Its posterior margin is rougher and more tubercular, and
provides a surface for the insertion of the trapezius. The area of the superior
surface between these two muscular attachments is smooth and subcutaneous. The
lateral edge of this forward-turned part of the bone is provided with an oval facet
(facies articularis acromialis) for articulation with the acromion of the scapula ; the
margins around this articular area serve for the attachment of the capsule of the
joint. The inferior surface of the acromial end of the bone is traversed obliquely
from behind forwards and laterally by a rough ridge or line called the trapezoid
ridge. The posterior extremity of this ridge, as it abuts on the posterior border
of the bone, forms a prominent process, the tuberositas coracoidea; to these,
respectively, are attached the trapezoid and conoid portions of the coraco-clavicular
ligament.
The morphology of the clavicle is of special interest. Its presence is associated with
the freer use and greater range of movement of the fore-limb, such as are necessary for
its employment for more specialised actions than those of mere progression. In conse-
quence of these requirements, the limb, and with it the scapula, become further removed
from the trunk, and so the support which the blade bone received through the union of
its coracoid element with the sternum, as in birds and reptiles, and to some extent in the
lowest mammals, is withdrawn. Some substitute, however, is necessary to meet the
altered conditions, and in consequence a new element is introduced in the form of a
clavicle. The origin of this bone appears to be intimately associated with the precoracoid
element met with in amphibia or reptiles, but whereas the precoracoid is always laid
down in cartilage, which, however, not infrequently disappears, the clavicle develops in
the membrane overlying the precoracoid cartilage. In the course of its development it
may become intimately associated with the remains of that cartilage. Thus, it is probable
that the articular discs at the sterno-clavicular and acromio-clavicular joints, as well
as the sternal articular end of the clavicle, represent persistent portions of the primitive
cartilage, whilst it is possible that the supra-sternal ossicles occasionally present may
be also derived from it. In this way, in its most specialised form, a secondary support is
established between the sternum and scapula, which serves as a movable fulcrum, and
greatly enhances the range of movement of the shoulder girdle.
Nutrient Foramina. The foramina for the larger nutrient vessels, offsets of the transverse
scapular artery, of which there may be one or two directed laterally, are usually found about
the middle of the posterior border, or, it may be, opening into the floor of the groove for the
subclavius muscle.
Ossification. The clavicle in man is remarkable in commencing to ossify before any
other bone in the body ; this occurs as early as the fifth or sixth week of fo3tal life.
The shaft is ossified from two primitive centres (Mall). These are preceded by a curved
rod of connective tissue on the interior of which are developed two masses of a peculiar
precartilaginous nature, one, the sternal, placed medially, lies above and Overlaps in
front the acromial mass, which is placed laterally. In each of these near their approxi-
mated ends a centre of ossification appears. These, subsequent to the fusion of the
200
OSTEOLOGY.
two independent precartilaginous masses, coalesce and form a bridge of bone uniting the
two primary ossific centres. At a later stage cartilage cells appear in the medial
extremity of the sternal pre-
Sternal epiphysis ossifies about Primary centres appear about nflrfilno-inmi mac a^rl ofill
20th year ; fuses about 25th year 5th or 6th week of fetal life
later in the lateral end of
the acromial mass. By the
growth and subsequent ossifi-
cation of the cartilage so
formed the clavicle increases
in length (Fawcett).
A secondary centre ap-
pears at the sternal end about
the age of twenty or later, and fusion rapidly occurring between it and the shaft,
ossification is completed at the age of twenty-five or thereabouts.
The Scapula.
The scapula, or shoulder blade, is of triangular shape and flattened form.
It has two surfaces, costal or ventral, and dorsal. From the latter there springs
a triangular process called the spine, which ends laterally in the acromion;
CLAVICULAR ARTICULAR SURFACE
FIG. 188. OSSIFICATION OP THE CLAVICLE.
MEDIAL ANGLE
SUPRA-SPINOUS FOSSA
SPINE
VERTEBRAL MARGIN
[NFRA-SPINOUS FOSSA
ARTERIAL FORAMEN
ACROMION
ACROMIAL ANGLE
HEAD AND GLENOID CAVITY
NECK
^GREAT SCAPULAR NOTCH
GROOVE FOR CIRCUMFLEX SCAPULAR ARTERY
AXILLARY MARGIN
INFERIOR ANGLE
Fia. 189. THE DORSAL SURFACE OF THE RIGHT SCAPULA.
whilst from its superior margin there arises a beak-like projection called the
coracoid process. The bone overlies the postero -lateral aspect of the thoracic
framework, reaching from the second to the seventh rib.
THE SCAPULA.
201
LONG HEAD
OF TRICEPS
GROOVE FOR CIRCUM-
FLEX SCAPULAR
ARTERY
The body of the bone, which is thin and translucent, except along its margins
j nd where the spine springs from it, has three margins and three angles. Of these
I Margins the vertebral (margo vertebralis) is the longest; it stretches from the
j ledial angle above to the inferior angle below. Of curved or somewhat irregular
;| utline, it affords a narrow surface for the insertion of the leva tor scapulae, rhom-
inoideus minor, and rhomboideus major muscles.
The superior margin, which is thin and sharp, is the shortest of the three. It
uns from the medial angle towards the root of the coracoid process, before
I eaching which, however, it is interrupted by the scapular notch, which lies very
i.i lose to the medial side of the base of that process. This notch, which is converted
Into a foramen by a ligament,
Jin occasionally by a spicule
. if bone, transmits the supra-
,;capular nerve, whilst the
I rans verse scapular artery
| uns above it. Attached to
{he superior margin, close to
U he notch, is the posterior belly
I f the omo-hyoid. The axillary
i. nargin, so called from its rela-
i ion to the hollow of the axilla
jj armpit), is much stouter than
dther of the others ; it ex-
pends from the lateral angle
libove to the inferior angle
| )elow. The upper inch or so
| >f this border, which lies im-
mediately below the glenoid
Articular cavity, is rough and
ubercular (tuberositas infra-
rlenoidalis), and affords at-
tachment to the long head of
he triceps. Below this it is
usually crossed by a groove
jvhich marks the position of
i he circumflex scapular artery.
The medial angle is sharp
ind more or less rectangular ;
Lhe inferior angle is blunter
Lnd more acute; whilst the
lateral angle corresponds to
hat part of the bone which
3 sometimes called the head,
md which supports the glenoid cavity and the coracoid process.
The glenoid cavity is a piriform articular area, slightly concave from above down-
vards and from side to side ; its border is but slightly raised above the general surface
| md affords attachment in the recent condition to the labrum glenoidale, which helps
o deepen the socket in which the head of the humerus rests. Below, the margin
>f the glenoid cavity is confluent with the infra-glenoidal tuberosity, whilst, above,
It blends with a tubercle (tuberositas supraglenoidalis), to which the long head
)f the biceps muscle is attached. Springing from the upper part of the head,
jn line with the superior margin, is the processus coracoideus (coracoid process).
The base of this is limited laterally by the glenoid edge, whilst medially it
s separated from the superior margin by the scapular notch. Eising upwards
or a short space, it bends on itself at nearly a right angle, and ends in a process
; ;vhich is directed laterally and slightly forwards, overhanging the glenoid cavity
ibove and in front. Compressed from above downwards, it has attached to
: ts upper surface near its angle the conoid ligament, lateral to which there is a rough
irea for the trapezoid ligament. Attached to its dorsal border is the coraco-
SCAPULAR SLIP OF LATISSIMUS
DORSI
FIG. 190. THE DORSAL SURFACE OF THE RIGHT SCAPULA
WITH THE ATTACHMENTS OF THE MUSCLES MAPPED OUT.
202
OSTEOLOGY.
GLENOID
CAVITY
ligament, Whilst at ACROMION CLAVICULAR ARTICULAR
its extremity and towards CORACOID PROCESS
the front of its ventral
border, is the combined
origin of. the biceps and
coracobrachialis, together
with the insertion of the
pectoralis minor. The col-
lum scapulae (neck) is that
somewhat constricted part
of the bone which supports
the head ; it corresponds in
front and behind to a line
drawn from the scapular
notch to the infra-glenoidal
tuberosity.
The body of the bone
has two surfaces, a dorsal
(facies dorsalis) and a costal
(fades costalis). The former
is divided into two fossse by
an outstanding process of
triangular form, called the
spina scapulae. The at-
tached border of this crosses
the dorsal surface of the body obliquely in a direction
CORACOBRACHIALIS AND
SHORT HEAD OF
BICEPS PECTORALIS MINOR
OMO-HYOID
MKDIAL ANGLE
NECK
ARTERIAL FORAMEN
LONG HEAD
OF TRICEPS
SUBSCAPULAR FOSSA -
AXILLARY BORDER
FIG. 192. COSTAL SURFACE OF THE RIGHT SCAPULA WITH THE
ATTACHMENTS OF MUSCLES MAPPED OUT.
INFERIOR ANGLE
FIG. 191. THE RIGHT SCAPULA
SEEN FROM THE FRONT. '
laterally and slightly upwards,
extending from the vertebral
border, near the lower limit of its
upper fourth, towards the centre
of the posterior glenoid edge,
from which, however, it is separ-
ated by the great scapular notch,
which here corresponds to the
dorsal aspect of the neck. Within
this notch the transverse scapu-
lar vessels and the supra-scapular
nerve pass to the infra-spinous
fossa. The surfaces of the spine,
which are directed upwards and
down wards, are concave, the upper
entering into the formation of the
supra -spinous fossa, which lies
above it, the lower forming the
upper wall of the infra-spinous
fossa, which lies below it. The
two fossse are in communication
THE SCAPULA. 203
rith each other round the 'free lateral concave border of the spine, where that
urves over the great scapular notch. The dorsal free border of the spine is
ubcutaneous throughout its entire length. Its upper and lower edges are
trongly lipped, and serve the superior, for the insertion of the trapezius;
he inferior, for the origin of the deltoid. The intervening surface varies in
ridth broad and triangular where it becomes confluent with the vertebral border,
,b displays a smooth surface, over which the tendinous fibres of the trapezius play ;
.arrowing rapidly, it forms a surface of varying width which blends laterally with
I flattened process, the two forming a compressed plate of bone which arches across
She great scapular notch above and behind, and then curves, upwards, forwards, and
literally to overhang the glenoid cavity. The medial border of this process is con-
iinuous with the upper margin of the spine, and is gently curved. The lateral
order, more curved than the medial, with which it is united in front, is confluenj;
rith the inferior edge of the spine, with which it forms an abrupt bend, termed the
.cromial angle. The bone included between these two borders is called the acromion.
)f compressed form, it much resembles the acromial end of the clavicle, with which
b articulates by means of a surface (facies articularis acromii) which is placed on
bs medial border near its anterior extremity. The superior surface of the acromion,
rhich is broad and expanded, is subcutaneous, and is directed upwards and dorsally,
,nd in the normal position of the bone laterally as well. Its medial edge, where
lot in contact with the clavicle, has attached to it the fibres of the trapezius,
whilst its lateral margin affords origin to the central part of the deltoid. At its
nterior extremity it is connected with the coracoid process by means of the coraco-
.cromial ligament. Its inferior surface is smooth and overhangs the shoulder-joint.
The supra-spinous fossa, of much less extent than the infra-spinous, is placed
,bove the spine, the upper surface of which assists in forming its curved floor ; in
b is lodged the supraspinatus muscle. The scapular notch opens into it above,
vhilst below and laterally it communicates with the infra-spinous fossa by the
;reat scapular notch, through which the transverse scapular artery and supra-
capular nerve pass to reach the infra-spinous fossa.
The infra-spinous fossa, overhung by the spine above, is of triangular form. The
.xillary margin of the bone limits it in front, whilst the vertebral margin bounds it
ehind ; the greater part of, this surface affords origin to the infraspinatus muscle,
xcepting a well-defined area which skirts the axillary margin and inferior angle of
he bone, and which affords an attachment to the fibres of origin of the teres minor,
["his muscle extends along the dorsal surface of the axillary margin in its superior
wo-thirds, reaching nearly as high as the glenoid edge ; whilst a crescentic surface,
vhich occupies the inferior third of the axillary border and curves backward round
he dorsal aspect of the inferior angle, furnishes an origin for the teres major
nuscle. Here also, near the inferior angle, are occasionally attached some of the
ibres of the latissimus dorsi muscle.
The facies costalis (costal aspect) of the body is hollow from above downwards
ind from side to side, the greatest depth being in correspondence with the spring of the
spine from the dorsal surface. Its medial boundary, which is formed by the anterior
ipped edge of the vertebral margin, affords attachment to the fibres of insertion of
ihe serratus anterior along the greater part of its extent. The area of insertion of
Ms muscle is, however, considerably increased over the ventral aspects of the
nedial and inferior angles respectively. Eunning down from the head and
jaeck above to the inferior angle below, there is a stout rounded ridge of bone,
vhich imparts a fulness to the costal aspect of the axillary margin and increases the
! iepth of the costal hollow ; to this, as well as to the floor of the fossa, the sub-
ncapularis muscle is attached. The tendinous intersections of this muscle leave
it-heir imprint on this surface of the bone in a series of three or four rough lines
which converge towards the neck.
Tie scapula of man is characterised by the greater proportionate length of its base
one ossified, if we except the occasional presence (22 per cent.) of an ossific centre in the
,iead. (H. R. Spencer, Journ. Anat. and PhysioL vol. xxv. p. 552.) The centre for the
>ody makes its appearance early in the second month of intra-uterine life. Within the
irst six months after birth a centre usually appears for the head ; this is succeeded by
>ne for the greater tubercle during the second or third year. These soon coalesce ; and
\ . third centre for the lesser tubercle begins to appear about the end of the third year,
;>r may be delayed till the fourth or fifth year. These three centres are all blended by
he seventh year, and form an epiphysis, which ultimately unites with the body about
he age of twenty-five. It may be noticed that the proximal end of the diaphysis i
ionical and pointed in the centre, over which the epiphysis fits as a cap, an arrangement
vhich thus tends to prevent its displacement before union has occurred. The first centre
o appear in the distal extremity is that for the capitulum about the second or third
'ear. This extends medially, and forms the lateral half of the trochlear surface, the
Centre for the medial half not making its appearance till the eleventh or twelfth year.
210
OSTEOLOGY.
OLECRANON
Separate centres are developed in connexion with the epicondyles ; that for the lateral
appears about the twelfth year, and, rapidly coalescing with the centres for the capitulum
and trochlea, forms an epiphysis, which unites with the body about the sixteenth or
seventeenth year. The centre for the medial epicondyle
appears about the fifth year ; it forms a separate epi-
physis, which unites with the body about eighteen or
nineteen. These two epiphyses at the distal end of
the bone are separated by a down-growth of the
shaft, which lies between the medial epicondyle and
the trochlea, and forms part of the base and medial
side of the latter process.
/(JORONOID PROCESS ml , -,. 1 . . , , ..
1 he epicondylic process when present is developed
from the diaphysis, and has been observed to be
already well ossified by the third year. (" Proc. Anat.
Soc." Journ. Anat. and Physiol. 1898.)
"INCISURA SEMILUNARIS
INCISURA
RADIALIS
-TUBEROSITY
"BlCIPITAL HOLLOW
The Ulna.
-POSTERIOR BORDER
-INTEROSSEOUS BORDER
Of the two bones of the forearm, the ulna,
which is placed medially, is the longer. It con-
sists of a large proximal extremity supporting
the olecranon and the coronoid process ; a body
or shaft tapering distally; and a small rounded
distal end called the head.
Proximal Extremity. The olecranon lies in
line with the body. Its dorsal surface, more or
less triangular in form, is smooth and subcutane-
ous and covered by a bursa. Its proximal aspect,
which forms with the posterior surface a nearly
rectangular projection the tip of the elbow
furnishes a surface for the insertion of the tendon
of the triceps brachii muscle, together with a
smooth area which is overlain by the same
tendon, but separated from it by a bursal sac.
To the volar (anterior) crescentic border of this
process are attached the fibres of the posterior part
of the capsule and a portion of the ulnar collateral
ligament of the elbow-joint. The volar (anterior"
surface is articular, and enters into the formation
of the semilunar notch.
The processus coronoideus (coronoid pro'cess) if
a bracket-like process, which juts forwards froir
the volar and proximal part of the shaft, and if
fused with the olecranon proximally. By itfj
proximal surface it enters into the formation o:j
the semilunar notch, whilst its volar aspect :
which is separated from its proximal side by t\
sharp irregular margin, slopes distally anc
dorsally to become confluent with the vola?
surface of the body. Of triangular shape, this .
area, which is rough and tubercular, terminate!!
inferiorly in an oval elevated tubercle (tuberositai
ulnae), into which the tendon of the brachiali \
muscle is inserted. Of the lateral margins oi
the coronoid process, the medial is usually th<
better defined. Proximally, where it joins th<
proximal border, thereis generally a salient tubercle
to which one of the heads of origin of the flexor digi
torum sublimis muscle is attached, whilst distal to this point the medial bordel
furnishes origins for the Dronator teres, and occasionally for the flexor pollici
-HEAD
.ARTICULAR CIRCUM-
FERENCE FOR RADIUS
^GROOVE FOR EXT. CARPI
ULNARIS
STYLOID PROCESS
FIG. 202. THE RIGHT ULNA AS VIEWED
FROM THE LATERAL SIDE.
THE ULNA.
211
OLECRANON
INCISURA SEMILUNARI
CORONOID PROCESS
INTEROSSEOUS
CREST
longus muscles, from above downwards. The smooth medial surface of the
coronoid process merges with the olecranon dorsally, and with the medial surface
of the body distally.
The incisura semihmaris (O.T.
greater sigmoid cavity), for articulation
with the trochlea of the humerus, is a
semicircular notch, the proximal part of
which is formed by the volar surface of
the olecranon, whilst distally it is com-
pleted by the proximal surface of the
coronoid process. Constricted towards
,its deepest part by the notching of
its borders, the articular surface is
occasionally crossed by a narrow im-
pression which serves to define the ole-
cranon proximally from the coronoid
distally. The articular area is divided
'into a medial portion, slightly con-
cave transversely, and a lateral part,
transversely convex to a slight degree,
: by a longitudinal smooth ridge which
3xtends from the most prominent part
of -the border of the olecranon proxirn-
illy to the most outstanding point
'of the coronoid process distally. The
margins of the semilunar notch are
sharp and well defined, and serve, with
the exception of the area occupied by
the radial notch, for the attachment of
the capsule of the elbow-joint.
The radial notch(O.T. lesser sigmoid
cavity), placed on the radial side of
'the coronoid process, is an oblong
irticular surface for the reception of
'she head of the radius. It encroaches
bn the distal and lateral part of the
sernilunar notch, so as to narrow it
Considerably. Separated from it by
i rectangular curved edge, it displays
i surface which is plane proximo-
listally, and concave from before
Backwards. .Its volar extremity is
larrower and more pointed than its
'lorsal, and becomes confluent with
: /he anterior edge of the coronoid pro-
jess, at which point the annular liga-
nent, which retains the head of the
'adius in position, is attached in front.
.ts dorsal border, wider and more out-
Standing, lies in line, and is continuous
ivith the interosseous margin of the
'haft. Dorsal to this border, the annu-
ar ligament is attached posteriorly.
The body of the ulna (corpus ulnae),
;rtiich is nearly straight, or but slightly
urved, is stout and thick proximally,
:;radually tapering towards its distal extremity. It may be divided into three
irfaces, a volar (O.T. anterior), a dorsal or posterior, and a medial, by three
veil -defined borders, an interosseous crest, a dorsal margin, which latter is
TUBEROSITY
BlCIPITAL HOLLOW
INTEROSSEOUS
BORDER
OR CREST"
HEAD
STYLOID
PROCESS
FIG. 203. THE RIGHT RADIUS AND ULNA SEEN
FROM THE VOLAR ASPECT.
212
OSTEOLOGY.
FLEXOR DIGITORUMSUBLIMIS
PKONATOR TERES
BRACHIALIS \
FLEXOR POLLICIS LONGUS "\ N
BICEPS
subcutaneous throughout its whole length, and a volar margin (O.T. anterior
border).
The crista interossea (interosseous crest) is crisp and sharp in the proximal
three-fourths of the body, but becomes faint and ill-defined in the distal
fourth. To this, with the exception -only of the part which forms the dorsal
boundary of the hollow in which the tuberosity of the radius is disposed when
the two bones are articulated, is attached the interosseous membrane which
connects the two bones of the forearm. The dorsal margin, of sinuous out-
line, curving laterally above, and slightly medially below, is continuous proxim-
ally with the triangular subcutaneous area on
the back of the olecranon, being formed by the
confluence of the borders which bound that sur-
face ; well marked above, it becomes faint and more
rounded below, but may be traced distally to the
dorsal surface of the base of the styloid process. To
this border is attached an aponeurosis common to
the flexor carpi ulnaris, extensor carpi ulnaris, and
flexor digitorum profundus muscles. A noteworthy
feature in connexion with this part of the body is
the fact that it is subcutaneous, and can easily be
felt beneath the skin throughout its whole length.
The volar or anterior surface corresponds to
the front and medial side of the body. It ie
described as consisting of two surfaces, a volai
and a medial, which are separated by a rounded
volar margin, which extends from the tuber-
osity proximally towards the styloid process
distally. The prominence of this ridge varies
in different bones, being well marked in bones
of a pronounced type, but corresponding merely
to the rounding of the surfaces in poorly
developed specimens. The volar aspect of the
bone affords an extensive origin to the flexor
digitorum profundus muscle, which clothes its
volar and medial surfaces in its proximal three-
fourths, reaching as far back as the dorsal border,
and extending proximally as high as the medial
side of the olecranon process. Immediately distal to
the radial notch there is a hollow triangular area ;
limited dorsally by the proximal part of the inter-
osseous crest, and defined in front by an oblique
line which extends distally and backwards
from the lateral margin of the coronoid process.
In this hollow the tuberosity of the radius rests
when the forearm is in the prone position, and
to its floor are attached the fibres of origin of
the supinator muscle. The distal fourth of the
FIG. 204. VOLAR ASPECT OF BONES OF body is crossed by the fibres of the pronator quad-
THE EIGHT FOREARM WITH MUSCULAR rafcug musc l ej which derives its origin from a
ATTACHMENTS MAPPED OUT. ,, , n -, F. -,
more or less well -denned crest, which winds
spirally distally and backwards towards the volar surface of the root of the styloid
process, and is continuous proximally with the volar margin.
The dorsal surface of the body lies between the dorsal margin and the in-
terosseous crest. At its proximal part it is placed behind the semilunar and
radial notches, extending on to the lateral side of the olecranon. Here an area
corresponding to the proximal third of the length of the bone is marked off dis-
tally by an oblique ridge which leaves the interosseous crest about an inch or
more distal to the dorsal edge of the radial notch. Into this somewhat
triangular surface the fibrp.a of the anconaeus are inserted. Distal to this the
BRACHIO-
RADIALIS
THE ULNA.
213
posterior surface is subdivided by a faint longitudinal ridge, the bone betwee
which and the interosseous crest furnishes origins for the abductor pollicis longus,
extensor pollicis longus, and extensor indicis proprius muscles, in order proximo-
distally. The surface of bone between the dorsal margin and the afore-mentioned
longitudinal line is smooth and overlain by the extensor carpi ulnaris muscle, which,
however, does not arise from it.
The distal extremity of the ulna presents a rounded head (capitulum ulnae),
from which, on its medial and dorsal aspect, there projects distally a cylindrical
pointed process called the styloid process. To the extremity of this latter is attached
the ulnar collateral ligament of the carpus, whilst on the volar aspect it has
connected with it the antero-medial portion of the capsule of the wrist-joint. The
antero-lateral half of the circumference of the head is furnished with a smooth
narrow convex articular surface, which fits into the ulnar notch of the radius.
Its distal surface, flat and semilunar in shape, and separated from the root of
the styloid process by a well-marked groove, rests on the upper surface of the
triangular articular disc of the wrist, the apex of which is attached to the groove
just mentioned. The margins of the head, to the volar side and dorsal to the
radial articular surface, have attached to them the volar and dorsal distal radio-
ulnar ligaments. The dorsal and medial surface of the styloid process is channelled
by a groove which separates it from the dorsal surface of the head, and extends
proximally some little way upon the dorsal surface of the distal end of the body.
In this is lodged the tendon of the extensor carpi ulnaris muscle. The pro-
portionate length of the ulna to the body height is as 1 is to 6'26-6*66.
Nutrient Foramina. A foramen, having a proximal direction, for the nutrient artery of the
body opens on the volar surface of the bone from two to three inches distal to the tuberosity.
Vascular canals of large size are seen proximal and dorsal to the radial notch, just dorsal to
the notched lateral border of the semilunar notch. At the distal end of the bone similar openings
are seen in the groove between the styloid process and the distal articular surface of the head.
Connexions. The ulna articulates proximally with the trochlea of the humerus. On the
lateral side it is in contact with the radius at both proximal and distal ends, the proximal radio-
ulnar articulation being formed by the head of the radius and the radial notch of the ulna, the
distal radio-ulnar joint comprising the head of the ulna, which fits into the ulnar notch of the
radius. Between these two joints the bodies of the bones are united by the interosseous membrane.
The distal surface of the head of the ulna does not articulate with the carpus, but rests on
the proximal surface of the interposed articular disc. The ulna is superficial throughout
its entire extent. Proximally the olecranon
process can be readily recognised, particularly
when the elbow is bent, as in this position the
olecranon is withdrawn from the olecranon
1 fossa of the humerus in which it rests when the
joint is extended. Distal to this the subcutane-
ous triangular area on the back of the olecranon
can be easily determined, and from it the
posterior border of the bone can readily be
traced along the line of the " ulnar furrow "
to the styloid process. With the hand
.supine this latter process can be felt to the
medial side and slightly behind the wrist.
When the hand is pronated, the distal end
1 of the radius rolls round the distal extremity
of the ulna, and the antero-lateral surface of
the head of the latter bone now forms a well-
l marked projection on the dorsum of the wrist
^in line with the cleft between the little and
' ring fingers.
Ossification. The ulna is ossified
from one primary and two or more secondary
centres. The centre for the body appears
early in the second month of foetal life. At
birth the body and a considerable part
of the proximal extremity, including the
coronoid process, are ossified, as well as part
of the distal extremity. The olecranon and
'the distal surface of the head and the styloid process are cartilaginous. About ten
years of age a secondary centre appears in the cartilage at the proximal end of the bone, and
Fuses with shaft about 16 years
Appears about 10 years
Appears about 6 years
Fuses with shaft 20-23 years
At Birth. About 12 years. About 16 years.
FIG. 205. THE OSSIFICATION OP THE ULNA.
214
OSTEOLOGY.
OLECRANON
SUBCUTANEOUS
SURFACE
-HEAD
NECK
TUBEROSITY
INTEROSSEOUS
CREST
POSTERIOR
OBLIQUE LINE
forms an epiphysis which unites with the body about sixteen. In this connexion Fawcet
(Proc. Anat. Soc. Great Britain and Ireland, 1904, p. xxvii) has described the occurrenc
of two ossific centres in th
olecranon. One, the mor
volar, the "beak centre," enter
into the formation of th
proximal end of the artici
lar surface of the semiluna
notch, the other centre, nc
in any way forming it. j
scale-like centre appears in th
cartilage of the head abou
the sixth year, from which th
distal surface of that part c
the bone is developed, and b
the extension of which th
styloid process is also ossified
this epiphysis does not unit
with the shaft till the twer
tieth or twenty -third yeai
Independent centres for th
styloid process and for th
extreme edge of the olecrano:
have also been described. Th
student may here be warnei
that the epiphysial line b<
tween the shaft and proxima
or olecranon epiphysis doe
not correspond to the cor
stricted part of the semiluna
notch, but lies considerabl;
proximal to it.
The Radius.
The radius, or latera
bone of the forearm, ii
shorter than the ulna, witl
which it is united on thi
medial side. Proximally i
articulates with the hum
erus, and distally it supports
the carpus. It consists o:
a head, a neck, a tufoerosity
a body, and an expandec
distal extremity. The bod}
is narrow proximally, but in
creases in all its diameter;
distally.
Proximal Extremity
The capitulum (head) i
disc-shaped and provide*
with a shallow concave sur
face (fovea capituli radii
proximally for articulatioi
with the capitulum of th:
humerus. The circumfei;
ence of the head (circum
ferentiaarticularis) issmoot"-
and is embraced by the annular ligament. On the medial side it is usually muc'i
broader, and displays an articular surface, Diane in the proximo-distal direction
HEAD
STYLOID PROCESS
Ext. poll,
long.
Ext. poll, brevis
Ext. carpi rad.
longus
Ext. carpi rad.
brevis
STYLOID PROCESS
GROOVE FOR EXT. Ext. dig. commun.
CARPI ULNARIS and ext. indicis proprius
FIG. 206. THE RIGHT RADIUS AND ULNA SEEN FROM THE DORSAL
ASPECT
THE EADIUS.
215
TRICEPS
which rolls within the radial notch of the ulna in the movements of pronation
and supination. The character of the lateral half of the circumference differs from
the medial, in being narrower, and rounded proxinio-distally.
The collum radii (neck) is the constricted part of the body which supports the
head, the overhang of the latter being greatest towards the lateral and dorsal side.
Distal to the neck, on the medial side, there is an outstanding oval -prominence,
the tuberositas radii (radial tuberosity). The dorsal part of this is rough for
the insertion of the biceps tendon, whilst the volar
half is smooth and covered by a bursa which inter-
venes between it and the tendon.
The body (corpus radii), which has a lateral
curve and is narrow proximally and broad distally,
is wedge-shaped on section. The edge of the wedge
forms the sharp medial interosseous crest of the bone
(crista interossea), whilst its base corresponds to the
thick and rounded lateral border over which the
volar or anterior surface becomes confluent with the
dorsal or posterior surface.
The interosseous crest, faint proximally where it
lies in line with the dorsal margin of the tuber-
osity, becomes sharp and prominent in the middle
third of the bone. Distal to this it splits into two
faint lines, which lead to either side of the ulnar
g notch on the distal end of the bone, thus includ-
ing between them a narrow triangular area into which
the deeper fibres of the pronator quadra tus muscle
are inserted. To this crest, as well as to the
* dorsal of the two divergent lines, the interosseous
membrane is attached.
The lateral surface (once described as the
lateral border) is thick and rounded proximally,
but becomes thinner and more prominent distally,
where it merges with the base of the styloid
process. About its middle the anterior and posterior
oblique lines become confluent with it, and here,
placed between them, is a rough elongated impres-
sion which marks the insertion of the pronator teres
muscle. Proximal to this, and on the
RADIAL EXTENSORS lateral surface of the neck, the
supinator muscle is inserted, whilst
distally this surface is overlain by
the tendons of the brachio-radialis
and the extensor carpi radialis longus
and brevis muscles.
The volar or anterior surface
(facies volaris) is crossed obliquely
by a line which runs from the
f,,^,^;^ rHstallv and latprallv
tuberosity CfcStoJly ana later
towards the middle of the lateral
i surface of the body. This, often called the anterior oblique line, serves for the attach-
I ment of the radial head of origin of the flexor digitorum sublimis muscle. Proximal
to it, the volar aspect of the bone has the fibres of the supinator muscle inserted
into it, whilst distal and medial to it, extending as far as the distal limit
i of the middle third of the bone, is an extensive surface for the origin of the
i flexor pollicis longus muscle. In the distal fourth of the bone, where the volar
aspect of the body is broad and flat, there is a surface for the insertion of the
pronator quadratus muscle, which also extends dorsally to the interosseous ridge.
The dorsal or posterior surface (facies dorsalis) is also crossed by an
oblique line,, less distinct than the anterior. This serves to define the proximal
ABDUCTOR POLLICIS
LONGUS AND EXTENSOR
POLLICIS BREVIS
EXTENSOR DIGITORUM COMMUNSI
AND EXTENSOR INDICIS PROPRIUS
EXTENSOR POLLICIS LONGUS
, FIG. 207. DORSAL ASPECT OF BONES OF RIGHT FORE-
ARM WITH ATTACHMENTS OF MUSCLES MAPPED OUT.
216 OSTEOLOGY.
limit of the origin of the abductor pollicis longus muscle. Proximal to this, the
dorsal aspect of the neck and proximal part of the body is overlain by the fibres
of the supinator muscle which become attached to this surface of the bone in its
lateral half. Distal to the posterior oblique line the dorsal surface in the proximal
part of its medial half gives origin to the abductor pollicis longus and the extensor
pollicis brevis muscles, in that order proximo-distally.
The distal extremity, which tends to be turned slightly forwards, has
a somewhat triangular form. Its distal carpal articular surface, concave from
before backwards, and slightly so from side to side, is divided into two facets
by a slight an tero- posterior ridge, best marked at its extremities where the
volar and dorsal margins are notched; the lateral of these areas, of triangular
shape, is for articulation with the navicular, whilst the medial, quadrilateral in
form, is for the os lunatum. The volar border, prominent and turned forwards,
is rough at its edge, where it serves for the attachment of the volar part of the
capsule of the wrist-joint. The dorsal border is rough, rounded, and tubercular,
and is grooved by many tendons ; of these grooves the best marked is one which passes
obliquely across its dorsal surface. This is for the tendon of the extensor pollicis
longus muscle. The lateral lip of this groove is often very prominent, and forms
an outstanding tubercle. To the medial side of this oblique groove there is a broad
shallow furrow in which the tendons of the extensor digitorum communis and
extensor indicis proprius muscles are lodged, whilst to its lateral side, and between
it and the styloid process, there is another broad groove, subdivided by a faint
ridge into two, for the passage of the tendons of the extensor carpi radialis brevis
medially and the extensor carpi radialis longus laterally. The styloid process
lies to the lateral side of the distal extremity ; broad at its base, it becomes
narrow and pointed distally where by its medial cartilage -covered surface
it forms the summit of the distal triangular articular area. The lateral surface
of this process is crossed obliquely distally and forwards by a shallow groove,
the volar lip of which is sharp and well marked, and serves to separate it
from the volar surface of the bone, whilst the dorsal lip is often emphasised
by a small tubercle above. The tendon of the brachio-radialis muscle is inserted
into the proximal parts of both lips, and also spreads out on to the floor of the groove,
whilst the tendons of the abductor pollicis longus and the extensor pollicis brevis
muscles lie within the groove. To the tip of the styloid process is attached the
radial collateral ligament of the wrist. -On the medial side of the distal extremity
is placed the incisura ulnaris (ulnar notch) for the reception of the head of the
ulna. Concave from before backwards, and plane proximo-distally, it forms
by its inferior margin a rectangular edge which separates it from the distal
carpal surface. To this edge the base of the articular disc is attached, a
structure which serves to separate the distal articular surface of the head of
the ulna from the carpus. The volar and dorsal edges of the ulnar notch, more
or less prominent, serve for the attachment of ligaments.
The proportionate length of the radius to the body height is as 1 is to G'VO-'Z'll.
Nutrient Foramina. The openings of several small nutrient canals may be seen in the
region of the neck. That for the body, which has a proximal direction, is usually placed on the
volar surface of the bone, medial to the anterior oblique line, and from an inch and a half to
two inches distal to the tuberosity. The dorsal surface of the distal extremity of the bone is
pierced by many small vascular foramina.
Connexions. The radius articulates with the capitulum of the humerus in the flexed
position of the elbow, with the ulna to its medial side by the proximal and distal radio-ulnar
joints, and with the navicular and lunate bones of the carpus distally. Proximally, the head of
the bone can be felt in the intermuscular depression on the lateral side of the back of the elbow ; here
the bone is only covered by the skin, superficial fascia, and the thin common tendinous origin of
the extensor muscles, as well as the ligaments which support it. Its position can best be ascer-
tained by pronating and supinating the bones of the forearm, when the head will be felt rotating
beneath the finger. The distal end of the bone is overlain on the volar and dorsal aspects by the
flexor and extensor tendons, but its general form can be readily made out. The styloid process
lying to the lateral side of the wrist in line with the extended thumb can easily be recognised ;
note that it reaches a more distal level than the corresponding process of the ulna. The lateral
border of the lower third of the body can be distinctly felt, as here the bone is only overlain by
tendons.
Ossification. The centre for the body makes its appearance early in the second
THE CAEPUS.
217
month of intra-uterine life. At birth the
Fuses with shaft 18-20 years body is well formed ; its proximal and distal
extremities are capped with cartilage, and
the tuberosity is beginning to appear. A
secondary centre appears in the cartilage
of the distal extremity about the second or
third year; this does not unite with the
body until the twentieth or twenty-fifth
year, somewhat earlier in the female. From
this the carpal and ulnar articular surfaces
are formed. The centre for the head
appears from the fifth to the seventh year,
and fuses with the neck about the age of
eighteen or twenty. It forms the capitular
articular surface and combines with the neck
to form the area for articulation with the
radial notch of the ulna. A scale-like
Appears about
2-3 years
Unites with shaft 20-25 years
At Birth. About 12 years. About 16 years.
FIG. 208. THE OSSIFICATION OF THE EADIUS.
epiphysis capping the summit of the
tuberosity has been described ; this ap-
pears about the fourteenth or fifteenth
year, and rapidly fuses
with that process.
THE BONES OF
THE HAND.
I. METACARPAL
SESAMOID BONES
The bones of the hand,
twenty -seven in number, may
be conveniently divided into
three groups :
(1) The bones of the wrist or
carpus eight in number.
(2) The bones of the palm or
metacarpus five in number.
(3) The bones of the fingers
and thumb or phalanges -four-
teen in number.
The Carpus.
The ossa carpi (carpal bones)
are arranged in two rows : the
first, or proximal row, comprises
from radial to ulnar side, the navi-
cular (O.T. scaphoid), os lunatum
(O.T. semi-lunar), os triquetrum
(O.T. cuneiform), and os pisiforme
or pisiform ; the second or distal
row includes the greater mult-
angular (O.T. trapezium), lesser
multangular (O.T. trapezoid), os
capitatum (O.T. os magnum), and
OS HAMATUM
OS TRIQUETRUM
PISIFORM
V. METACARPAL
FIG. 209. THE BONES OF THE RIGHT WRIST AND HAND
SEEN FROM THE VOLAR ASPECT.
218
OSTEOLOGY.
OS CAPITATUM
LESSER MULTANGULAR
NAVICULAR
ABDUCTOR POLLICIS BREVIS
GREATER MULTANGULAR
OPPONENS POLLICIS
ABDUCTOR POLLICIS LONGUS
FLEXOR CARPI RADIALIS
M.I.
ADDUCTOR/ OBLIQUE HEAD
POLLICIS 1 TRANSVERSE HEAD
Os LUNATUM
OS HAMATUM
OS TR1QUETRUM
FLEXOR CARPI ULNARIS
PISIFORM
ABDUCTOR DIGITI QUINTI
FLEXOR DIGITI QUINTI
BREVIS
FLEXOR CARPI ULNARIS
OPPONENS DIGITI
QUINTI
VOLAR
INTEROSSEI
FIG. 210. VOLAR ASPECT OP BONES OF THE RIGHT CARPUS
AND METACARPUS WITH MUSCULAR ATTACHMENTS MAPPED OUT.
os hamatum (O.T. unciform). Irregularly six-sided, each of these bones possesses
non-articular volar and dorsal surfaces. In addition, the marginal bones are non-
articular along their ulnar and radial aspects according as they form the medial or
lateral members of the series.
Os Naviculare(O.T. Scaphoid). Thenavicularis the largest and the most lateral
bone of the first row.
Its volar surface,
rough for the attach-
ment of ligaments, is
irregularly triangu-
lar. The distal
angle on the lateral
side forms a projec-
tion called the tuber-
osity; this can be
felt at the base of
the root of the thumb.
Its proximal surface
is convex from side to side and
before backwards for articula-
tion with the radius. This area
extends considerably over the
dorsal surface of the bone.
Its distal surface is convex
from before backwards, and ex-
tends on to the dorsal aspect of
the bone, slightly convex from
side to side ; it is divisible into two areas, the lateral for articulation with the greater
multangular, the medial for the lesser multangular- The lateral surface is narrow
and rounded and forms a non-articular border, which extends from the radial articular
surface proximally to the tuberosity distally. The medial surface is hollowed out in
front for articulation with the head of the capitate bone. Proximal to this it displays
a small semilunar-
shaped facet for the os
lunatum. The dorsal
non - articular surface
lies between the lateral
articular surface proxi-
mally and the surface for EXTENSOR CARPI
the greater and lesser
multangular bones dis-
tally. It is obliquely
grooved for the attach-
ment of the dorsal liga-
ments of the wrist. The
navicular articulates
with five bones the
radius, the os lunatum,
the capitate, the lesser
multangular, and the
greater multangular.
Os Lunatum (O.T.
Semilunar Bone). So
called from its deeply
excavated form, the os lunatum lies between the navicular on the lateral side and
the os triquetrum on the medial. Its volar surface, of rhombic form and consider-
able size, is rough for the attachment of ligaments ; its proximal surface, convex from
side to side and from before backwards, articulates with the radius and in part
with the distal surface of the articular disc of the wrist. Its distal aspect, deeply
OS TRIQUETRUM
PISIFORM
OS HAMATUM
OS LUNATUM
OS CAPITATUM
NAVICULAR
EXTENSOR CARPI RADIALIS BREVIS
LKSSER MULTANGULAR
GREATER MULTANGULAR
EXTENSOR CARPI RADIALIS LONGUS
ABDUCTOR POLLICIS LONGUS
FIG. 211. DORSAL ASPECT OF BONES OF THE RIGHT CARPUS AND
METACARPUS WITH MUSCULAR ATTACHMENTS MAPPED OUT.
THE CAEPUS.
219
NAVICULAB
LESSER MULTANGULAR
GREATER MULTANGULAR
OS TRIQUETRUM
PISIFORM
OS HAMATUM
V. METACARPAL
I. META-
CARPAL
FIRST
hollowed from before backwards, is divided into two articular areas, of which
the lateral is the larger; this is for the head of the capitate bone; the medial,
narrow from side to side, articulates with the os hamatum. Its lateral surface,
crescentic in shape, serves for articulation with the navicular, and also for the
attachment of the interosseous ligaments which connect it with that bone. Its
medial surface, of quadrilateral form, is cartilage -covered for articulation with the
os triquetrum, and the edge which separates this from the proximal surface has
attached to it the interosseous ligament which unites these two bones. The
rough dorsal non-articular surface is much smaller than the volar ; by this
means the volar and dorsal sur- o s CAPIT
faces of the bone can readily be os LUN
determined. The os lunatum
articulates with five bones the
navicular, the radius, the os
triquetrum, the os hamatum,
and the capitate bone.
Os Triquetrum (0 . T. Cunei-
form). This bone may be
recognised by the small oval
or circular facet on its volar
surface for the pisiform. This
is placed towards the distal part
of the volar surface, which
is elsewhere rough for liga-
ments. The bone is placed
obliquely, so that its surfaces
cannot be accurately described
as distal, proximal, etc. ; but for
convenience of description, the PHALANX
method already adopted is ad-
hered to. The proximal surface
has a convex rhombic area
for articulation with the distal
surface of the articular disc
in adduction of the hand,
though ordinarily it does not
appear to be in contact with
that structure. To the medial
side of this it is rough for liga-
ments. The distal surface is
elongated and concavo-convex
from radial to ulnar side ; here
the bone articulates with the os
hamatum. The lateral surface,
broader in front than behind,
articulates with the os lunatum.
The medial surface, rounded and
rough, is confluent proximally
and dorsally with the proximal
and dorsal aspects of the bone. The dorsal surface, rounded and smooth laterally,
is ridged and grooved medially for the attachment of ligaments. The os triquetrum
articulates with three bones, viz., the pisiform, the os hamatum, and the os lunatum.
Os Pisiforme. About the size and shape of a large pea, the pisiform bone
rests on the volar surface of the os triquetrum, with which it articulates by
an oval or circular facet on its dorsal aspect. The rounded mass of the rest of
the bone is non-articular, and inclines distally and laterally so as to overhang
the articular facet in front and laterally. The mass of the bone is usually
separated from the articular surface by a small but distinct groove. Into the
summit of the bone the tendon of the flexor carpi ulnaris muscle is inserted, and
FIG. 212. THE BONES OF THE RIGHT WRIST AND HAND
SEEN FROM THE DORSAD ASPECT.
220
OSTEOLOGY.
Capitate
Greater
multangular
Radius -
Os lunatum
Radius
here also the transverse carpal ligament is attached. The ulnar artery and nerve
are in immediate relation with the lateral side of the bone.
Os Multangulum Majus (O.T.
Trapezium). The greater mult-
angular is the most lateral bone of
the distal row of the carpus. It
may be readily recognised by the
oval saddle-shaped facet on its
distal surface for articulation with
the metacarpal bone of the thumb.
From its volar aspect there rises a
prominent ridge, medial to which is
a groove along which the tendon
of the flexor carpi radialis muscle
passes. The ridge furnishes an
attachment for the transverse
carpal ligament, as well as for some
of the short muscles of the thumb.
The proximal surface has a half-
oval facet for the navicular, lateral
to which it is rough, and becomes
FIG. 213. THE RIGHT NAVICULAR BONE. , . .,, .
. rr , , continuous with the non-articular
NOTE. The bone is represented in the centre of the figure 7 7 , . ,
in the position which it occupies in the right hand viewed ^WTOl aspect, Which serves for
_ from the volar aspect. The views on either side, and above the attachment of ligaments. On
~and below, represent respectively the corresponding surfaces fa medial surface there are two
of the bone turned towards the reader. P -\ *\ M> i
facets ; the proximal is a half-oval,
concave proximo-distally, and very slightly convex from volar to dorsal side, and
is for articulation with the lesser multangular; the distal, small and circular,
and not always present, is for articulation with the lateral side of the base of the
second metacarpal bone. The
dorsal surface, of irregular
outline, is rough for the attach-
ment of ligaments. The greater
multangular articulates with
four bones, the navicular, lesser
multangular, and the first and
second metacarpal bones.
Os Multangulum Minus
(O.T.Trapezoid Bone). With
the exception of the pisiform,
the lesser multangular is the
smallest of the carpal bones.
Its rough volar surface is small
and pentagonal in outline.
By a small oblong area on its
proximal surface it articulates
with the navicular. Distally,
by a somewhat saddle-shaped
surface, it articulates with the
base of the second metacarpal.
Separated from this by a rough NOTE. The bone is represented in the centre of the figure in the
Os hamatum
Os triquetrum Tj
Os hamatum
Capitate
Radius
Radius
Navicular
FIG. 214. THE RIGHT Os LUNATUM.
position which it occupies in the right hand viewed from the
volar aspect. The views on either side, and above and below,
represent respectively the corresponding surfaces of the bone
turned towards the reader.
V-shaped impression prolonged
from its volar aspect, is the
area on the lateral surface for
articulation with the greater
multangular ; this is obliquely grooved from before backwards and distally. The
medial facet, for articulation with the capitate, is narrow proximo-distally, and
deeply curved from before backwards. The dorsal surface of the bone, which is rough
and non-articular, is much larger than the volar aspect. The mass of the bone,
THE CAEPUS.
221
The lesser
Os hamatum
Pisiform
multangular
Os lunatum
FIG.
Os triquetrum
216. THE RIGHT PISIFORM
BONE.
Articular
of wrist
IS tor FlG * 215 ' THE KlGHT Os TRIQUETRUM.
third NOTE / Tte k n e is represented in the centre of the figure
in the position which it occupies in the right hand
viewed from the volar aspect. The views on either
side, and above and below, represent respectively
the corresponding surfaces of the bone turned
towards the reader.
dorsally, is directed distally and towards the medial side,
articulates with four bones the greater
multangular, navicular, and capitate
bones, and the second metacarpal.
Os Capitatum (O.T. Os Magnum).
This is the largest of the carpal bones.
Its volar surface is rough and rounded.
The proximal portion of the bone forms
the head, and is furnished with convex
articular facets which fit into the hollows
on the medial surface of the navicular
and distal surface of the os lunatum; that
for the latter is medial to and separated
by a slight ridge from the navicular artic-
ular area. The distal surface, narrow to-
wards its volar border and broad dorsally,
is subdivided usually into three facets by
two ridges that towards the lateral side
is for the base of the second metacarpal ;
the inter-
mediate
facet is for
the
metacarpal ;
whilst the
medial facet
of the three,
NOTE. The figure to the left repre- not always present, very small and placed near the dorsal
bTne 8 ; ^that to' ihfright the side of the bon6 ' is for the fourth metacarpal. The lateral
dorsal view. surface of the body has an articular area for the lesser
multangular, not infrequently separated from the navic-
ular surface on the head by a rough
line, to which the interosseous ligament
connecting it with the navicular is at-
tached. The medial surface of the body
has an elongated articular area, usu-
ally deeply notched in front ; or it may
be divided anteriorly into a small cir-
cular area near the dorsal edge, and
a larger posterior part. This latter
articulates either singly or doubly with
the os hamatum, the interosseous liga-
ment which unites the two bones
being attached either to the notch or
to the surface separating the two articu-
lar facets. The dorsal surface is rough
for ligaments; it is somewhat constricted
below the head, the articular surface of
which sweeps round its proximal border.
The capitate bone articulates with
seven bones the os hamatum, the os
lunatum, the navicular, the lesser mult-
angular, and the second, third, and
Navicula
FIG. 217. THE RIGHT GREATER MULTANGULAR BONE.
NOTE. The bone is represented in the centre of the figure ^ , -,
fourth metacarpal bones; occasionally
in the position which it occupies in the right hand
viewed from the volar aspect. The views on either
the fourth metacarpal does not ar-
ide, and above and below, represent respectively ticulate with the Capitate.
Os Hamatum (O.T. Unciform
B one ). The os hamatum can be readily
distinguished by the hook-like process (hamulus) which projects from the distal and
222
OSTEOLOGY.
medial aspect of its volar surface.
Capitate bone
II. Metacarpal
Navicular
Greater
multangular
To this is attached the transverse carpal
ligament as well as some of the
fibres of origin of the short muscles
of the little finger. The medial
side of the hamulus is sometimes
grooved by the deep branch of the
ulnar nerve. ( Anderson, W.,"Proc.
Anat. Soc." Journ. Anat. and
Physiol. vol. xxviiip. 11.) The volar
surface, rough for ligaments, is
somewhat triangular in shape
Proximally and towards the medial
side there is an elongated articular
surface for the os triquetrum,
convex proximally and concave
distally. The lateral aspect of the
bone is provided with a plane elon-
gated facet, occasionally divided
into two for articulation with the
capitate bone (see above). Where
F,G. 218.-THB EIGHT LESSKR MULTANGULAR BONE. the P"! and lateral surfaces
. meet, the angle is blunt, and has
NOTE. The bone is represented in the centre of the figure in *
the position which it occupies in the right hand viewed a narrow tacet which articulates
from the volar aspect. The views on either side, and with the OS lunatum. Distally
above and below, represent respectively the corresponding ^ere are two articular facets
surfaces of the bone turned towards the reader. L i i ^
separated by a ridge; these are
slightly concave from before backwards, and are for articulation, the lateral with
the fourth, and the medial
with the fifth metacarpal
bone. The dorsal surface,
more or less triangular in
shape, is rough for liga-
ments.
The os hamatum articu-
lates with five bones viz.,
the capitate, os lunatum, os
triquetrum, and the fourth
and fifth metacarpals.
IV. Metacarpa
I. Metacarpal
III. Metacarpal
Os lunatum
The Carpus as a ~
Whole.
When the carpal bones
are articulated together
they form a bony mass, the
dorsal surface of which is
convex from side to side.
Anteriorly they present a
grooved appearance, con-
cave from side to side.
This arrangement is further
emphasised by the forward
projection, onthe medial side,
of the pisiform and hamulus
of the os hamatum, whilst
laterally the tuberosity of
the navicular and the ridge
of the greater multangular help to deepen the furrow 'by their elevation.
Os lunatum
Navicular
Os hamatum-
FIG. 219. THE RIGHT CAPITATE BONE.
NOTE. The bone is represented in the centre of the figure in the
position which it occupies in the right hand viewed from the
volar aspect. The views on either side, and above and below,
represent respectively the corresponding surfaces of the bone turned
towards the reader.
To these
THE METACAEPUS. 223
four points the transverse carpal ligament is attached, which stretches across from
side to side, and thus
converts the furrow into
a canal through which the
flexor tendons pass to reach
V. Metacarpal^ ^ \~^$JJSB . ^~~^ -J v - Metacarpal the fingers.
/Capitate bone
Os lunatuin
FIG. 220. THE EIGHT Os HAMATUM.
NOTE. The bone is represented in the centre of the figure in the position
which it occupies in the right hand viewed from the volar aspect.
The views on either side, and above and below, represent respectively
the corresponding surfaces of the bone turned towards the reader.
FIG. 221. RADIOGRAPH OP THE
HAND AT BIRTH.
It will be noticed that whilst the
primary centres for the metacarpus
and phalanges are well ossified, the
carpus is still entirely cartilaginous.
Compare this with the tarsus at
birth, in which the tarsus is shown
in part already ossified.
Ossification. At birth the carpus is entirely cartilaginous. An exceptional case is
figured by Lambertz, in which the centres for the capitate and triquetral bones were already
present. The same authority states that it is not uncommon to meet with these centres
in the second month after birth. According to Debierre (Journ. de VAnat. et de la
Physiol. vol. xxii. 1886, p. 285), ossification takes place approximately as follows :
Capitate bone .
Os hamatum
Os triquetrum .
Os lunatum
Greater multangular.
Navicular
Lesser multangular .
Pisiform .
11 to 12 months.
12 to 14 months.
3 years.
5 to 6 years.
6 years.
6 years.
6 to 7 years.
10 to 12 years.
The same observer failed to note the appearance of a separate centre for the hamulus
of the os hamatum, and records the occurrence of two centres for the pisiform.
The Metacarpus.
The metacarpal bones form the skeleton of the palm, articulating proximally
with the carpus, whilst by their distal extremities or heads they support the bones
of the digits. Five in number, one for each digit, they lie side by side and
slightly divergent from each other, being separated by intervals, termed interosseous
spaces. Distinguished numerically from the lateral to the medial side, they all
display certain common characters ; each possesses a body or shaft, a base or carpal
extremity, and a head or phalangeal end.
The bodies, which are slightly curved towards the volar aspect, are narrowest
towards their middle. The dorsal surface of each is marked by'two divergent lines
which pass distally from the dorsum of the base to tubercles on either side of the
224
OSTEOLOGY.
Head
Shaft
Head
Tubercle
head. The surface included between the two lines is smooth and of elongated
triangular form. On either side of these lines two broad shallow grooves wind
spirally on to the volar surface, where they are separated
by a sharp ridge which is continuous with a somewhat
triangular surface which corresponds to the volar aspect
of the base. The grooved surfaces on either side of the
shaft furnish origins for the interossei muscles. Close to
the volar crest is the opening of the nutrient canal, which
is directed towards the proximal extremity, except in the case
of the first metacarpal bone.
The capitulum (head) is provided with a surface for
articulation with the proximal phalanx. This area curves
farther over its volar than its dorsal aspect. Convex from
before backwards and from side to side, it is wider anteriorly
than posteriorly ; notched on its volar aspect, its edges form
two prominent tubercles, which are sometimes grooved for
the small sesamoid bones which may occasionally be found
on the volar surface of the joint. On either side of the head
of the bone there is a deep pit, behind which is a prominent
tubercle ; to these are attached the collateral ligaments of the
metacarpo-phalangeal joints.
The bases,
all more or less
wedge-shaped in
Fia. 222. FIRST RIGHT r f . , ,
METACARPAL BONE. form, articulate
with the carpus;
they differ in size and shape according
to their articulation.
Of the five metacarpal bones, the
first, viz., that of the thumb, is the
shortest and stoutest, the second is the
longest, whilst the third,
fourth, and fifth display a
gradual reduction in length.
The medial four bones
articulate by their bases
with each other, and are
united at their distal ex-
tremities by ligaments.
They are so arranged as to
conform to the hollow of
the palm, being concave
from side to side anteriorly,
and convex posteriorly. The
first metacarpal differs from
the others in being free at capitate bone
its distal extremity, whilst
its proximal end possesses
only a carpal articular facet.
The first metacarpal
bOne iS the Shortest and Lesser multangular
Stoutest of the series. Its FIG. 223. SECOND RIGHT METACARPAL BONE.
body 18 compressed from NOTE. The bone is represented in the centre of the figure in the
haoVwarrU Ttfi head position which it occupies in the right hand viewed from the volar
Lesser
multangular
Greater
multangular
v vl spect. The views on either side, and below, represent respectively
01 large Size, IS but Slightly tne corresponding surfaces of the bone turned towards the reader.
convex from side to side, and
is grooved on its volar aspect for the sesamoid bones. The base is provided with
a saddle-shaped surface for articulation with the greater multangular, and has no
facets on its sides. Laterally there is a slight tubercle to which the abductor pollicis
THE METACAEPUS.
225
longus muscle is attached. The canal for the
nutrient artery is directed towards the head of
the bone.
The second metacarpal bone is recognised
by its length and its broad and deeply notched
base for articulation with the lesser multangular.
It has a small half-oval facet for the greater mult-
angular on the lateral side of its base, whilst
on its medial aspect it
presents a narrow vertical
strip for the capitate, in
front of which there are
two half-oval surfaces for
the third metacarpal. To
the dorsal aspect of the
base is attached the tendon
of the extensor carpi
radialis longus muscle,
whilst the flexor carpi
radialis is inserted into the
volar surface.
The third metacarpal
bone can usually be re-
cognised by the pointed
styloid process which
springs from the dorsum of
its base, towards the radial
Medial
side
Insertion
of exten-
sor carpi
radialis
brevis
Styloid process
Capitate bone
Metacarpal
Proximal
FIG. 224. THIRD EIGHT METACARPAL BONE.
NOTE. The bone is represented in the centre of the figure in the position
which it occupies in the right hand viewed from the volar aspect,
views on either side, and below, represent respectively
spending surfaces of the bone turned towards the reader.
The
the corre-
Medial side
IV. Metacarpal
Proxima
FIG. 225. FOURTH EIGHT METACARPAL BONE. Fia. 226. FIFTH EIGHT METACARPAL BONE.
NOTE. The bone in each figure is represented in the centre of the figure in the position which it occupies in the
right hand viewed from the volar aspect. The views on either side, and below, represent respectively th
corresponding surfaces of the bone turned towards the reader.
side. On the proximal surface of the base there is a facet for the capitate.
On the lateral side there are two half-oval facets for the second metacarpal. On
the medial side there are usually two small oval or nearly circular facets for the
15
226 OSTEOLOGY.
fourth metacarpal. The extensor carpi radialis brevis muscle is inserted into the
dorsum of the base.
The fourth metacarpal bone may be recognised by a method of exclusion. It
is unlike 'either the first, second, or third, and differs from the fifth, which it
resembles in size, by having articular surfaces on both sides of its base. Proximally
there is a quadrilateral surface on its base for articulation with the os harnatuui.
On its lateral side there are usually two small oval facets for the third metacarpal.
Of these facets the dorsal one not infrequently has a narrow surface for articula-
tion with the capitate. On the medial side there is a narrow articular strip for the
base of the fifth metacarpal.
The fifth metacarpal bone can be recognised by its size and the fact that it
has an articular facet only on one side of its base, namely, that on its lateral side
for the fourth metacarpal. The carpal articular surface is saddle-shaped, and there
is a tubercle on the medial side of the base for the insertion of the extensor carpi
ulnaris muscle.
As has been already pointed out, the openings of the arterial canals are usually seen on the
volar surfaces of the metacarpals, those of the medial four bones being directed proximally towards
the base or carpal end, differing in this respect from that of the first metacarpal, which is directed
distally towards the head or phalangeal extremity. The opening of the latter canal usually
lies to the medial side of the volar aspect of the body.
Ossification. The metacarpal bones are developed from primary and secondary
centres but there is a remarkable difference between the mode of growth of the first and
the remaining four metacarpals, for whilst the body and head of the first metacarpal
are developed from the primary ossific centre, and its base from a secondary centre, in
the case of the second, third, fourth, and fifth metacarpals the bodies and bases are de-
veloped from the primary centres, the heads in these instances being derived from the
secondary centres. In this respect, therefore, as will be seen hereafter, the metacarpal
bone of the thumb resembles the phalanges in the manner of its growth, a circumstance
which has given rise to considerable discussion as to whether the thumb is to be regarded as
possessing three phalanges and no metacarpal, or one metacarpal and two phalanges. Broom
(Anat. Anz. vol. 28), by a reference to reptilian forms, offers an explanation in regard to the
difference in the mode of ossification of the first metacarpal on the ground that the most
movable joint is that between the first metacarpal and the carpus, whereas on the other
digits the most movable joints are those between the metacarpals and phalanges. In
consequence those ends of the bones which enter into the formation of the joints where
movement is most free are the ends where the epiphyses will appear. This is in accordance
with the law to be suggested in connexion with the fibula. The primary centres for the bodies
and bases of the second, third, fourth, and fifth metacarpals appear in that order during the
ninth or tenth week of intra-uterine life, some little time after the terminal phalanges
have begun to ossify ; that for the body and head of the metacarpal bone of the thumb a
little later. At birth the bodies of the bones are well formed. The secondary centres from
which the heads of the second, third, fourth, and fifth metacarpals and the base of the
first are developed, appear about the third year, and usually completely fuse with the
shafts about the age of twenty. There may be an independent centre for the styloid
process of the third metacarpal, and there is usually a scale-like epiphysis on the head of
the first metacarpal which makes its appearance about eight or ten, and rapidly unites
with the head. The occurrence of a basal epiphysis in the second metacarpal bone has
been noticed.
Phalanges Digltorum Manns.
The phalanges or finger bones are fourteen in number three for each finger,
and two for the thumb ; and they are named numerically in order from the
proximal toward the distal ends of the fingers.
Phalanx Prima. The first phalanx, the longest and stoutest of the three, has a
semi-cylindrical body which is curved slightly forwards. The volar surface is flat,
and bounded on either side by two sharp borders to which the fibrous sheath of the
flexor tendons is attached. The dorsal surface, convex from side to side, is overlain
by the extensor tendons. The proximal end, considerably enlarged, has a simple oval
concave surface, which rests on the head of its corresponding metacarpal bone. On
either side of this the bone displays a tubercular form, and affords attachment to
THE PHALANGES.
227
interossei
in.
Phalanx,
ungual or
terminal
II. Phalanx
the collateral ligaments of the metacarpo-phalangeal joint, and also to the
muscles. The distal end is much smaller than the
proximal; the convex articular surface is divided into
two condyles by a central groove.
Phalanx Secunda. The second phalanx resembles
the first in general form, but is of smaller size. It
differs, however, in the form of its proximal articular
surface, which is not a simple oval concavity, but is an
oval area divided into two small, nearly circular con-
cavities by a central ridge passing from volar to dorsal edge ;
these articulate with the condylic surfaces of the proximal
phalanx. Into the margins of its volar surface near
the proximal end are inserted the split portions of the
tendon of the flexor digitorum sublimis, whilst on the
dorsal aspect of the proximal end the central slip of the
extensor digitorum communis muscle is attached.
Phalanx Tertia. The third or terminal or ungual
phalanx is the smallest of the three ; it is easily recognised
by the spatula-shaped surface on its distal extremity which
supports the nail. The articular surface on its proximal
end resembles that on the proximal end of the second
phalanx, but is smaller. On the volar aspect of this
end of the bone there is a rough surface for the insertion
of the tendon of the flexor digitorum profundus muscle.
The dorsal surface of the same extremity has attached to
it the terminal portions of the tendon of the extensor
digitorum communis muscle. The phalanges of the
thumb resemble in the arrangement of their parts the
first and third phalanges of the fingers.
The arterial canals, usually two in number, placed on either
side of the volar aspect and nearer the distal than the proximal
end of the bone, are directed towards the finger-tips. FIG. 227. THE PHALANGES OF
THE FINGERS (Volar Aspect).
Ossification. The phalanges are ossified from primary
and secondary centres. From the former, which appear as early as the ninth week of
I. Phalanx
Shaft
Hi
'
f
FIG. 228. RADIOGRAPHS OF FOETAL HANDS.
1. About ten weeks. Here the ossific nuclei of the terminal phalanges and the medial four metacarpal bones
are seen. . ,
2. A little later. The centre for the metacarpal for the thumb is now present, as also the centres for the proximal
row of phalanges. The centres of the medial row of phalanges have appeared in the case of the nude
and ring fingers.
3. During the third month. All the primary centres for the metacarpal bones and phalanges are
developed.
4. About the fourth to fifth month.
5. About the sixth to seventh month.
foetal life, the body and distal extremities are developed ; whilst the latter, which begin
to appear about the third year, form the proximal epiphyses which unite with the bodies
15 a
228 OSTEOLOGY.
from eighteen to twenty. Dixey (Proc. Roy. Soc. xxx. and xxxi.) has pointed out that
the primary centre in the distal phalanges commences to ossify in the distal part of
the bone rather than towards the centre of the body. This observation has been
confirmed by Lambertz, who further demonstrates the fact that ossification commences
earlier in the distal phalanges than in any of the other bones of the hand. Of the
other phalanges, those of the first row, beginning with that of the third finger, next
ossify, subsequent to the appearance of ossific centres in the shafts of the metacarpal
bones, whilst the second or middle row of the phalanges is the last to ossify about
the end of the third month. Sewell has recorded a case in which the proximal phalanx
had a distal as well as a proximal epiphysis.
Ossa Sesamoidea.
Two little oval nodules (sesamoid bones), which play in grooves on the volar
aspect of the articular surface of the head of the first metacarpal bone, are constantly
met with in the tendons and ligaments of that metacarpo-phalangeal articulation.
Similar nodules, though of smaller size, are sometimes formed in the corresponding
joints of the other digits, more particularly the index and little finger ; as Thilenius
has pointed out (Morph. Arbeiten, vol. v.), these are but the persistence of cartilaginous
elements which have a phylogenetic interest.
THE BONES OF THE INFERIOR EXTREIYIITY.
THE PELVIC GIRDLE AND THE PELVIS.
The pelvic girdle is formed by the articulation of the two hip bones with
the sacrum dorsally, and their union with each other ventrally, at the joint called
the symphysis pubis.
Os Coxae.
The hip bone (os coxae) (O.T. innominate) is the largest of the " flat " bones of
bhe skeleton. It consists of three parts the os ilium, the os ischium, and the os pubis
primarily distinct, but fused together in the process of growth to form one large
irregular bone. The coalescence of these elements takes place in and around the
acetabulum, a large circular articular hollow which is placed on the lateral side of the
bone. The expanded wing-like part above this is the os ilium ; the stout V-shaped
portion below and behind it constitutes the os ischium ; while the <-shaped part to
the medial side, and in front and below, forms the os pubis. The two latter portions
of the bone enclose between them a large aperture of irregular outline called the
foramen obturatum (obturator foramen), which is placed in front and below, and to
the medial side of the acetabulum.
The ilium, almost a quadrant in form, consists of an expanded plate of bone,
having a curved superior border, the crista iliaca (iliac crest). Viewed from the
side, this forms a curve corresponding to the circumference of the circle of which
the bone is the quadrant ; viewed from above, however, it will be seen to display
a double bend convex anteriorly and laterally, and concave posteriorly and
laterally. The iliac crest is stout and thick, and for descriptive purposes is
divided into a labium externum (external lip), a labium internum (internal lip), and
an intermediate surface (linea intermedia), which is broad behind, narrowest about
its middle, and wider again in front. About 2 \ inches from the anterior extremity
of the crest the external lip is usually markedly prominent and forms a projecting
tubercle, which can readily be felt in the living. Attached to these surfaces and
lips anteriorly are the muscles of the flank, whilst from them posteriorly the
latissimus dorsi, quadratus lumborum, and sacro-spinalis muscles derive origins.
The crest ends in front in a pointed process, the spina iliaca anterior superior
(anterior superior iliac spine). To this the lateral extremity of Poupart's inguinal
ligament is attached, as well as the sartorius muscle, which also arises from the
edge of bone immediately below it, whilst from the same process and from the
THE HIP BONE.
229
anterior end of the external lip of the iliac crest the tensor fasciae latae muscle
takes origin.
The anterior border of the ilium stretches from the anterior superior iliac spine
to the margin of the acetabulum below. Above, it is thin ; but below, it forms
a thick blunt process, the spina iliaca anterior inferior (anterior inferior iliac
spine). From this the rectus femoris muscle arises, whilst the stout fibres of the
CREST OF THE ILIUM
ANTERIOR OLUTEAL LINE
POSTERIOR
OLUTEAL LINE
POSTERIOR
SUPERIOR
SPINE
POSTERIOR INFERIOR SPINE
ACETABULAR NOTCH
Groove for obturator extern us
ISCHIAL SPINE
LESSER SCIATIC NOTCH
SCIATIC TUBEROSITY
ANTERIOR
SUPERIOR SPINE
INFERIOR OLUTEAL
LINE
NTERIOR INFERIOR
SPINE
ACETABULUM
L1O-PECTINEAL EMINENCE
SUPERIOR RAMUS
F PUBIC BONE
PUBIC TUBERCLE
REST OK PUBIC
BONE
BODY OF PUBIC
BONE
INFERIOR RAMUS OF ITBTC BONE
INFERIOR RAMUS OF ISCHIUM
FIG. 229. THE RIGHT HIP BONE BEEN FROM THE LATERAL SIDE.
ilio-femoral ligament of the hip-joint' are attached to it immediately above the
ace tabular margin. Posteriorly, the crest terminates in the spina iliaca posterior
superior (posterior superior iliac spine). Below this, the posterior border of the bone
is sharp and irregularly notched, and descends to a prominent angle, the spina iliaca
posterior inferior (posterior inferior iliac spine). In front of the posterior inferior
iliac spine the edge of the bone becomes thick and rounded, and sweeps forwards
and downwards, round a wide notch called the incisura ischiadica major (greater
sciatic notch), to join the posterior border of the ischium behind the acetabulum.
15 &
230
OSTEOLOGY.
ARTORIUS
TENSOR FASCIA LA.T.E
REFLECTED HEAD
OF RECTUS FEMOR1S
STRAIGHT HEAD OF
RECTUS FEMORIS
The ilium has two surfaces, medial and lateral. The lateral surface is divided
into two parts, viz., a lower, ace tabular, and an upper, gluteal part. The lower forms
a little less than the upper two-fifths of the acetabular hollow, and is separated
from the larger gluteal surface above by the upper prominent margin of the arti-
cular cavity. The gluteal surface, broad and expanded, is concavo-convex from
behind forwards. It is traversed by three rough gluteal (O.T. curved) lines, well seen
in strongly developed bones, but often faint and indistinct in feebly marked speci-
mens. Of these the linea glutsea inferior (inferior gluteal line) curves backwards
from a point immediately above the anterior inferior spine towards the greater sciatic
notch posteriorly ; the bone between this and the acetabular margin is marked by
a rough shallow groove, from which the reflected head of the rectus femoris muscle
arises. The linea glutsea
.EXTERNAL OBLIQUE anterior (anterior gluteal
line) commences at the
crest of the ilium,
about one inch and a
half behind the anterior
superior iliac spine, and
sweeps backwards and
downwards towards the
upper and posterior
part of the greater
sciatic notch. The sur-
face between this line
and the preceding
furnishes an extensive
origin for the glutseus
minimus muscle. The
linea glutsea posterior
(posterior gluteal line)
leaves the iliac crest
about two and a half
inches in front of the
posterior superior iliac
PYRAMIDALIS j i_ j j
RECTUS ABDOMINIS spine, and bends down-
wards and slightly for-
wards in a direction
anterior to the posterior
inferior spine. The
area between this and
the anterior gluteal line
is for the origin of the glutseus medius muscle, whilst the rough surface immediately
above and behind it is for some of the fibres of origin of the glutseus maximus
muscle.
The medial surface of the ilium is divided into two areas which present very
characteristic differences. The posterior or sacral part, which is rough, displays, in
front, a somewhat smooth, auricular surface (facies auricularis) which is cartilage-
coated in the recent condition, and articulates with the sacrum.
This area is said to be proportionately smaller in the female, whilst curving round in front
of its anterior margin there is often a groove, for the attachment of the fibres of the anterior
sacro-iliac ligaments, called the pre-auricular sulcus. According to Derry this groove is better
marked in the female, and may be regarded as characteristic of that sex.
Above and behind this there is an elevated irregular area, the tuberosity (tuber-
ositas iliaca), which is here and there deeply pitted for the attachment of the strong
interosseous and posterior sacro-iliac ligaments. Above this the bone becomes con-
fluent with the inner lip of the iliac crest, and here it affords an origin to the sacro-
spinalis and multifidus muscles, and some of the fibres of the quadratus lumborum.
The anterior part of the medial aspect of the bone is smooth and extensive ; it
GEMELLUS INFER
GEMELLUS SUPERIOR
PECTINEUS
SEMIMEMBRANOSU
BICEPS AND
SEMITENDINOSUS
QUADRATUS FEMORIS
ADDUCTOR LONGUS
GRACILIS
ADDUCTOR BREVIS
^^
ADDUCTOR MAGNUS
FIG. 230. LATERAL ASPECT OP THE RIGHT HIP BONE WITH THE
ATTACHMENTS OF THE MUSCLES MAPPED OUT.
THE HIP BONE.
231
is subdivided by an oblique ridge, called the ilio-pectineal line (linea arcuata),
which passes forwards and downwards, from the most prominent point of the
auricular surface towards the medial side of the ilio-pectineal eminence, which
is placed just above and in front of the acetabulum and marks the fusion of the
CREST OF THE ILIUM
ILIUM
TUBEROSITY
FOR
SACRO-ILIAC
LIGAMENTS
SUPERIOR RAMUS
OF OS PUBIS
OBTURATOR GROOVE
PUBIC
TUBERCLE
CREST
OF OS PUBIS
SYMPHYSIS
ossis PUBIS
LESSER SCIATIC NOTCH
ISCHIUM
TUBER ISCHIADICUM
(ISCHIAL TUBEROSITY)
INFERIOR RAMUS OF os PUBIS RAMUS OF ISCHIUM
FIG. 231. THE RIGHT HIP BONE (Medial Aspect).
ilium with the os pubis. Above this the bone forms the shallow iliac fossa,
from the floor of which the iliacus muscle arises, whilst leading from the
fossa, below and in front, there is a shallow furrow, passing over the superior
acetabular margin, between the anterior inferior iliac spine on the lateral side an
the ilio-pectineal eminence medially, for the lodgment of the tendinous and fleshy
part of the ilio-psoas muscle. If held up to the light the floor of the deepest part
15 o
232 OSTEOLOGY.
of the iliac fossa will be seen to be formed of but a thin layer of bone. A nutrient
foramen of large size is seen piercing the bone towards the posterior part of the
fossa. Below and behind the ilio-pectineal line the medial surface of the ilium
forms a small portion of the wall of the pelvis minor ; the bone here is smooth, and
rounded off posteriorly into the greater sciatic notch, where it becomes confluent with
the medial aspect of the ischium. This part of the bone is proportionately longer
in the female than in the male, and forms with the ischium a more open angle.
Just anterior to the greater sciatic notch there are usually the openings of one or
two large vascular foramina. From this surface arise some of the posterior fibres
of the obturator internus muscle.
The ischium constitutes the lower and posterior part of the hip bone.
Superiorly its body (corpus) forms somewhat more than the inferior two-fifths of
the acetabulum together with the bone supporting it behind and medially. Below
this, the superior ramus passes downwards and backwards as a stout three-sided
piece of bone, from the inferior extremity of which a compressed bar of bone, called
the inferior ramus, extends forwards at an acute angle. This latter unites in front
and above with the inferior ramus of the pubis, and encloses the aperture called
the obturator foramen.
Superiorly, and on the lateral aspect of the ischium, the acetabular surface is
separated from the bone below by a sharp and prominent margin, which is,
however, deficient in front, where it corresponds to the acetabular notch (O.T. cotyloid
notch) leading into the articular hollow; the floor of this notch is entirely
formed by the ischium. Below the prominent acetabular margin there is a
well-marked groove in which the obturator externus lies. Beneath this the
antero-lateral surface of the superior and inferior rami furnishes surfaces for the
attachments of the obturator externus, quadratus femoris, and adductor magnus
muscles. The postero-lateral surface of the ischium forms the convex surface on
the back of the acetabulum. The medial border of this is sharp and well defined,
and is confluent above with the border of the ilium, which sweeps round the greater
sciatic notch. From this border, on a level with the lower edge of the acetabulum,
there springs a pointed process, the spina ischiadica (ischial spine), to which are
attached the sacro - spinous ligament and the superior gemellus muscle.
Inferior to this, the postero-lateral surface narrows rapidly, its medial border
just below the spine being hollowed out to form the incisura ischiadica minor (lesser
sciatic notch). The lower part of this surface and the angle formed by the two
rami are capped by an irregularly rough piriform mass called the tuber ischiadicum
(ischial tuberosity). This is divided by an oblique ridge into two areas, the upper and
lateral for the tendon of origin of the semimembranosus muscle, the lower and medial
for the conjoined heads of the biceps and semitendinosus muscles. Its prominent
medial lip serves for the attachment of the sacro-tuberous ligament, whilst its
lateral edge furnishes an origin for the quadratus femoris muscle ; in front and
below, the adductor magnus muscle is attached to it.
The medial surface of the body and superior ramus of the ischium form in part
the wall of the pelvis minor. Smooth and slightly concave from before backwards,
and nearly plane from above downwards, it is widest opposite the level of the ischial
spine. Below this, its posterior edge is rounded and forms a groove leading to the
lesser sciatic notch, along and over which the tendon of the obturator internus
passes. To part of this surface the fibres of the obturator internus are attached,
whilst the medial aspect of the spine supplies points of origin for the coccygeus and
levator ani muscles, as well as furnishing an attachment to the " white line " of the
pelvic fascia. The medial surface of the inferior ramus of the ischium is smooth,
and so rounded that its' inferior edge tends to be everted. To this, as well as to its
margin, is attached the crus penis, together with the ischio-cavernosus, obturator
internus, transversus perinei, and sphincter muscle of the membranous urethra.
In the female, structures in correspondence with these are found.
The anterior part of the hip bone is formed by the os pubis ; it is by means of
the union of this bone with its fellow of the opposite side that the pelvic girdle is
completed in front.
The pubis (os pubis) consists of two rami a superior (ramus superior ossis
THE HIP BONE.
233
pubis) and an inferior (ramus inferior ossis pubis). The broad part of the bone
formed by the fusion of these two rami is the body.
The body of the os pubis has two surfaces. Of these the posterior or postero-
superior is smooth, and forms the anterior part of the wall of the pelvis minor ;
hereto are attached the leva tor ani muscle and pubo-prostatic ligaments, and
on it rests the bladder. The anterior or antero-inferior surface is rougher, and
furnishes origins for the gracilis, adductor longus, adductor brevis, and some of
the fibres of the obturator externus muscles. The medial border is provided with
an elongated oval cartilage-covered surface (facies symphyseos) by means of which
it is united to its fellow of the opposite side, the joint being called the symphysis
pubis. The superior border, thick and rounded, projects somewhat, so as to over-
hang the anterior surface. It is called the crest. Medially this forms with the
medial border or symphysis the angle, whilst laterally it terminates in a pointed
process, the pubic tubercle (O.T. pubic spine). From the crest arise the rectus
RECTUS FEMORIS (straight head of origin)
RECTUS FEMOKIS (reflected head of origin)
ATTACHMENT OF
ILIO-FEMORAL LIGAMENT ADDUCTOR LONGUS (origin)
PYRAMIDALIS ABDOMINIS (origin)
RECTUS ABDOMINIS (origin)
SEMIMEMBRAN- \ ' S < //Jf \ GRACILIS (origin)
osus (origin)
QUADRATUS |T %/,j;' 'Ifts^. ^ ^ //* JB ADDUCTOR BREVIS (origin)
FEMORIS (origin)
BICEPS AND
SEMITENDINOS
(origin)
FIG. 232. MUSCLE ATTACHMENTS TO THE LATERAL SURFACE OF THE Os PUBIS AND ISCHIUM.
abdominis and pyramidalis muscles, and to the tubercle is attached the medial
end of the inguinal ligament. Passing upwards and laterally from the lateral
side of the body towards the acetabulum, of which it forms about the anterior
fifth, is the superior ramus. This has three surfaces: an an tero- superior, an
antero-inferior, and an internal or posterior. The antero- superior surface
is triangular in form. Its apex corresponds to the pubic tubercle; its anterior
inferior border to the crista obturatoria (obturator crest), leading from the pubic
tubercle to the upper border of the acetabular notch ; whilst its sharp postero-
superior border trends upwards and laterally from the tubercle, and is continuous
with the iliac portion of the ilio-pectineal line just medial to the ilio-pectineal
eminence, forming as it passes along the superior ramus the pubic portion of
that same line (pecten ossis pubis). On this line, just medial to the ilio-pectineal
eminence, there is often a short sharp crest which marks the insertion of the
psoas minor. The base of the triangle corresponds to the ilio-pectineal eminence
above and the upper margin of the acetabular notch below. Slightly hollow
from side to side, and convex from before backwards, this surface provides an
origin for, and is in part overlain by, the pectineus muscle. The posterior
or poster o -superior surface of the superior ramus is smooth, concave from side to
side, and slightly rounded from above downwards; by its sharp inferior curved
border it completes the obturator foramen, as seen from behind. The antero-
234 OSTEOLOGY.
inferior surface forms the roof of the broad sulcus obturatorius (obturator groove)
which passes obliquely downwards and forwards between the lower margin of
the antero-superior surface in front and the inferior sharp border of the posterior or
internal surface behind. The inferior ramus of the os pubis passes downwards and
laterally from the lower part of the body. Flattened and compressed, it unites with
the inferior ramus of the ischium, and thus encloses the obturator foramen, whilst in
correspondence with its fellow of the opposite side it completes the formation of
the pubic arch. Anteriorly it furnishes origins for the gracilis, adductor brevis,
and adductor magnus muscles, as well as some of the fibres of the obturator
externus muscle. Its medial surface is smooth, whilst its lower border, rounded
or more or less everted, has attached to it the anterior part of the crus penis and
the arcuate (O.T. subpubic) ligament.
The acetabulum is the nearly circular hollow in which the head of the thigh
bone fits. As has been already stated, it is formed by the fusion of the ilium and
ischium and pubis in the following proportions : the ilium a little less than
two-fifths, the ischium somewhat more than two -fifths, the pubis constituting
the remaining one-fifth. It is so placed as to be directed downwards, laterally,
and forwards, and is surrounded by a prominent margin, to which the capsule and
labrum glenoidale of the hip-joint are attached. Opposite the obturator foramen
this margin is interrupted by the incisura acetabuli (acetabular notch) ; immediately
lateral to the ilio-pectineal eminence the margin is slightly hollowed, whilst
occasionally there is a feeble notching of the border above and behind. These
irregularities in the outline of the margin correspond to the lines of fusion of the
ilium and pubis and the ilium and ischium respectively. The floor of the ace-
tabulum is furnished with a horseshoe-shaped articular surface, which lines the
circumference of the hollow, except in front, where it is interrupted by the ace-
tabular notch. It is broad above; narrower in front and below. Enclosed by
articular surface there is a more or less circular rough area (fossa acetabuli)
continuous in front and below with the floor of the acetabular notch. This, some-
what depressed below the surface of the articular area, lodges a quantity of fat,
and provides accommodation for the intra-articular ligament of the joint (ligamentum
teres). As may be seen by holding the bone up to the light, the floor of this part of
the acetabulum is usually thin. The major part of the non- articular area is
formed by the ischium, which also forms the floor of the acetabular notch.
The foramen obturatum (obturator foramen) lies in front of, below, and
medial to the acetabulum. The margins of this opening, which are formed
in front and above by the os pubis, and behind and below by the ischium, are
sharp and thin, except above, where the antero-inferior surface of the superior ramus
of the pubis is channelled by the obturator groove. Below, and on either side of this
groove, two tubercles can usually be seen. The one, situated on the edge of the
ischium, just in front of the acetabular notch, is named the posterior obturator
tubercle ; the other, placed on the lower border of the posterior surface of the
superior ramus of the os pubis, is called the anterior obturator tubercle. Between
these two tubercles there passes a ligamentous band, which converts the groove
into a canal along which the obturator vessels and nerve pass. Elsewhere in the
fresh condition the obturator membrane stretches across the opening from margin
to margin. The form of the foramen varies much, being oval in some specimens,
in others more nearly triangular; its relative width in the female is greater
than in the male.
Nutrient foramina for the ilium are seen on the floor of the iliac fossa, just in front of the
auricular surface ; on the pelvic aspect of the bone, close to the greater sciatic notch ; and on
the gluteal surface laterally, near the centre of the anterior gluteal line. For the ischium, on its
pelvic surface, and also laterally on the groove below the acetabulum. For the pubis, on the
surface of the body, and deeply also from the acetabular fossa.
Connexions. The hip bone articulates with the sacrum behind, with the femur to the
lateral side and below, and with its fellow of the opposite side medially and in front. Each
of its three parts comes into direct relation with the surface. Above, the iliac crest assists in
forming the iliac furrow, which serves to separate the region of the flank from that of the
buttock. In front, the anterior superior iliac spine forms a definite landmark ; whilst behind,
the posterior superior iliac spines will be found to correspond with dimples situated on
either side of the median plane of the root of the back. The symphysis, the crest, and tubercle of
THE PELVIS.
235
Appears about
later end of 2nd
m. of foetal life
Appears about 15
years ; fuses 22-25
years
the pubis can all be distinguished in front, though overlain by a considerable quantity of fat,
whilst the position of the tuberosities of the ischia, when uncovered by the great gluteal
muscles in the flexed position of the thigh, can readily be ascertained. In the perineal region
the outline of the pubic and ischial rami can easily be determined by digital examination.
Ossification commences in the ilium about the ninth week of intra-uterine life;
about the fourth month a centre appears below the acetabulum for the ischium, the os
pubis being developed from a centre which appears in front of the acetabulum about the
fifth or sixth month. At birth the form of the ilium is well defined ; the body and part
of the tuberosity of the ischium are ossified, as well as the superior ramus and part of
the body of the os pubis. All three parts enter into the formation of the sides of the
acetabulum, and by the
third year have con verged
to form the bottom of that
hollow, being separated
from each other by a tri-
radiate piece of cartilage,
in which, about the
twelfth year, independent
ossific centres make their
appearance, which may
or may not become fused
with the adjacent bones.
In the latter case they
unite to form an inde-
pendent ossicle, the os
acetabuli, which subse-
quently fuses with and
forms the acetabular part
of the os pubis. By the
age of sixteen the ossifica-
tion of the acetabulum is
usually completed, whilst
the rami of the ischium At Birth - About 12 or 13 y ear s-
and os pubis commonly FIG. 233. OSSIFICATION OF THE HIP BONE.
unite about the tenth
year. Secondary centres, seven in number, make their appearance about the age of
puberty, and are found in the following situations : one for the anterior inferior iliac spine ;
one for the ventral two-thirds of the iliac crest and the anterior superior iliac spine
which grows backwards, one for the posterior superior iliac spine and dorsal third of the
iliac crest which grows forwards these two unite about the twentieth year ; a scale-like
epiphysis over the tuberosity of the ischium ; a separate epiphysis for the spine of the
ischium ; (?) a point for the tubercle and another for the angle of the os pubis. Fusion
between these and the primary centres is usually complete between the twenty-second and
twenty-fifth years. Le Damany states that the proportionate depth of the acetabular
cavity at the sixth month* of foetal life is greater than at birth. In the third year a rapid
increase in its depth again takes place correlated with the assumption of the erect position.
Parsons (Journ. Anat. and Physiol, vol. xxxvii. p. 3 15) regards the ischial epiphysis as
the homologue of the hypo-ischium in reptiles, and suggests that the epiphysis over the
angle of the pubis may represent the epipubic bone of marsupials.
Appears about
4th m. of foetal
Appears about 15
years ; fuses 22-
25 years
At Birth.
Appears about
15 years ; fuses
22-25 years
Appears about
12 years
Appears
.^ about 18
years
Appears
about 18
Unite about 10 years
The Pelvis.
The pelvis is formed by the union of the hip bones with each other in
front, and with the sacrum behind. In man the dwarfed caudal vertebrae
(coccygeal) are curved forwards and so encroach upon the limits of the pelvic
cavity inferiorly. The pelvis is divided into two parts by the ilio-pectineal lines,
which curve forwards from the upper part of the lateral parts of the sacrum
behind to the roots of the pubic tubercles in front. The part above is called
the pelvis major, and serves by the expanded iliac fossae to support the abdominal
contents; the part below, the pelvis minor contains the pelvic viscera,
and in the female forms the bony canal through which at full term the fostus is
expelled.
236
OSTEOLOGY.
The pelvis minor is bounded in front by the symphysis pubis in the median
plane, and by the body and rami of the os pubis on each side, laterally by the smooth
medial surfaces of the ischia and ischial rami, together with a small part of the
ilium below the iliac portion of the ilio-pectineal line. Springing from the posterior
margin of the ischium are the inturned ischial spines. Behind, the broad curved
FIG. 234. THE MALE PELVIS SEEN FROM THE FRONT.
anterior surface of the sacrum, and below it, the small and irregular coccyx, form
its posterior wall. Between the sides of the sacrum behind, and the ischium and
ilium in front and above, there is a wide interval, called the greater sciatic notch,
which is, however, bridged across in the recent condition by the sacro-tuberous and
sacro-spinous ligaments, which thus convert it into two foramina the larger above
FIG. 235. THE FEMALE PELVIS SEEN FROM THE FRONT.
the spine of the ischium, the greater sciatic foramen ; the lower and smaller below
the spine, called the lesser sciatic foramen.
Apertura Pelvis Superior. The upper opening of the pelvis minor is bounded in
front by the symphysis pubis, with the crest of the pubis on each side ; laterally
by the ilio-pectineal lines ; and behind by the sacral promontory. The circum-
ference of this aperture is often called the brim of the pelvis ; in the male it is
THE PELVIS. 237
heart-shaped, in the female more oval. The antero -posterior or conjugate diameter
is measured from the sa,cro-vertebral angle to the symphysis pubis ; the oblique
diameter from the sacro-iliac joint of one side to the ilio-pectineal eminence of
the other; whilst the transverse diameter is taken across the greatest width of
the pelvic aperture.
Apertura Pelvis Inferior. The lower opening is bounded anteriorly by the arcus
pubis (pubic arch), formed in front and above by the bodies of the ossa pubis, with the
symphysis between them, and the inferior pubic rami below and on either side.
These latter are continuous with the ischial rami, which pass backwards and
laterally to the ischial tuberosities, which are placed on either side of this aperture.
In the median plane behind, the tip of the coccyx projects forward ; and in the
recent condition the interval between this and the ischial tuberosities is bridged
across by the sacro-tuberous ligament, the inferior edge of which necessarily
assists in determining the shape of the outlet.
As the anterior wall of the cavity, formed by the symphysis pubis, measures
from \\ to 2 inches, whilst the posterior wall, made up of the sacrum and coccyx, is
from 5 to 6 inches in length, it follows that the planes of the inlet and outlet are
not parallel, but placed at an angle to each other. The term axis of the pelvis is
given to lines drawn at right angles to the centres of these planes. Thus, with the
pelvis in its true position, when the figure is erect, the axis of the upper opening
corresponds to a line drawn downwards and backwards from the umbilicus towards
the tip of the coccyx below, whilst the axis of the lower opening is directed down-
wards and slightly backwards, or downwards and a little forwards, varying
according to the length of the coccyx. Between these two planes the axis of the
cavity, as it passes through planes of varying degrees of obliquity, describes a curve
repeating fairly closely the curve of the sacrum and coccyx.
Position of the Pelvis. The position of the pelvis in the living, when the figure is
erect, may be approximately represented by placing it so that the anterior superior iliac
spines and the symphysis pubis lie -in the same vertical plane. Under these conditions
the plane of the upper opening is oblique, and forms with a horizontal line an angle of from
50 to 60. The position of the pelvis depends upon the length of the ilio-femoral ligaments
of the hip-joint, being more oblique when these are short, as usually happens in women in
whom the anterior superior iliac spines tend to lie in a plane slightly in advance of that
occupied by the symphysis pubis. In cases where the ilio-femoral ligament is long a
greater amount of extension of the hip-joint is permitted, and this leads to a lessening of
the obliquity of the pelvis. This condition, which is more typical of men, results in the
anterior superior iliac spines lying in a plane slightly posterior to the plane of the sym-
physis, whilst the angle formed by the plane of the inlet and the horizontal is thereby
reduced. Bearing in mind the oblique position of the pelvis, it will now be seen that the
front of the sacrum is directed downwards more than forwards, and that the sacral pro-
montory is raised as much as from 3 to 4 inches above the upper border of the symphysis
pubis, lying higher than the level of a line connecting the two anterior superior iliac spines.
From the manner in which the sacrum articulates with the ilia, it will be noticed that the
weight of the trunk is transmitted downwards through the thickest and strongest part of
the bone (see Architecture, Appendix A) to the upper part of the acetabula, where these
rest on the heads of the femora.
Sexual Differences. The female pelvis is lighter in its construction than that of
the male ; its surfaces are smoother, and the indications of muscular attachments less
marked. Its height is less and the splay of its walls not so pronounced as in the male,
so that the female pelvis has been well described as a short segment of a long cone as
contrasted with the male pelvis, which is a long segment of a short cone. The cavity of
the pelvis minor in the female is more roomy, and the ischial spines not so much inturned.
The pubic arch is wide and rounded, and will usually admit a right-angled set-square
being placed within, so that the summit touches the inferior surface of the symphysis pubis,
whilst the sides lie in contact with the ischial rami. In the male the arch is narrow and
angular, forming an angle of from 65 to 70. The greater sciatic notch in the female is
wide and shallow. The distance from the posterior edge of the body of the ischium to the
posterior inferior iliac spine is longer, measuring on an average 50 mm. (2 inches) in the
female, as contrasted with 40 mm. (If inches) in the male. The angle formed by the
ischial and iliac borders is more contracted and acute in the male as compared with the
238
OSTEOLOGY.
female, in whom it is wider and more open. In the female the acetabulum is proportion-
ately smaller than in the male.
The upper opening in the female is large and oval or reniform, as compared with the
cribbed and heart-shaped aperture in the male. The sacro-vertebral angle is more pro-
nounced in the female, and the obliquity of the upper opening greater. The sacrum is
shorter and wider. The posterior superior iliac spines lie wider apart ; the pubic crests
are longer; and the pubic tubercles are separated by a greater interval than in man.
The outlet is larger ; the tuberosities of the ischia are farther apart ; and the coccyx does
not project forward so much. The curve of the sacrum is liable to very great individual
variation. As a rule the curve is more uniform in the male, whilst in the female it tends
to be natter above and more accentuated below. There is a greater proportionate width
between the acetabular hollows in the female than in the male. Of much importance
from the standpoint of the obstetrician are the various diameters of the pelvis minor.
In regard to this it is worthy of note that the plane of "greatest pelvic expansion"
extends from the union between the second and third sacral vertebrae behind, to the
middle of the symphysis pubis in front, its lateral boundaries on either side correspond-
ing with the mid-point of the medial surface of the acetabulum ; whilst the plane of
"least pelvic diameter" lies somewhat lower, and is denned bylines passing through
the sacro-coccygeal articulation, the ischial spines, and the lower third of the symphysis
pubis (Norris). Subjoined is a table showing the principal average measurements in the
two sexes :
PELVIS MAJOR.
Males.
Females.
Maximum distance between the iliac crests
Distance between the anterior superior iliac
spines
Distance between the last lumbar spine and
the front of the symphysis pubis
11| in., or 282 mm.
9^ in., or 240 mm.
7 in., or 176 mm.
10| in., or 273 mm.
9| in., or 250 mm.
7 in., or 180 mm.
PELVIS MINOE.
MALES.
FEMALES.
Upper
Lower
Upper
Cavity.
Lower
Opening.
Opening.
Opening. \
Opening.
Greatest.
Least.
Antero-posterior (conju-
4 in., or
3| in., or
4 in., or
5 in., or
4 in., or
4| in., or
gate) diameter
101 mm.
95 mm.
110 mm.
127 mm.
110 mm.
115 mm.
Oblique diameter .
4| in., or
3^ in., or 5 in., or ...
4iy in., or
120 mm.
88 mm.
125 mm.
115 mm.
Transverse diameter
5 in., or
3 in., or
5^ in., or
4 in., or
4f in., or
4 in., or
127 mm.
88 mm.
135 mm.
125 mm.
110 mm.
110 mm.
Growth of the Pelvis. From the close association of the pelvic girdle with the lower limb
we find that its growth takes place concurrently with the development of that member. At
birth the lower limbs measure but a fourth of the entire body length ; consequently at that time
the pelvis, as compared with the head and trunk, is relatively small. At this period of life the
bladder in both sexes is in greater part an abdominal organ, whilst in the female the uterus has
not yet sunk into the small pelvic cavity, and the ovaries and uterine tubes rest in the iliac
fossae. The sacro-vertebral angle, though readily recognised, is as yet but faintly marked.
Coincident with the remarkable growth of the lower limbs and the assumption of the erect
position when the child begins to walk, striking changes take place in the form and size of tht
pelvis. These consist in a greater expansion of the iliac bones, necessarily associated with the
growth of the muscles whicn control the movements of the hip, together with a marked increase
in the sacro-vertebral angle due to the development of a forward lumbar curve ; at the same time
the weight of the trunk being thrown on the sacrum causes the elements of that bone to sinl
to a lower level between the hip bones. The cavity of the pelvis minor increases in siz>
proportionally, and the viscera afore-mentioned now begin to sink down and have assumed
position, within the pelvis by the fifth or sixth year. The extension of the thighs in th
upright position necessarily brings about a more pronounced pelvic obliquity, whilst the stoutnes
and thickness of the ilium over the upper part of the acetabulum is much increased to withstan
the pressure to which it is obviously subjected. Coincident with this is the gradual developmer
THE FEMUR
239
HEAD
of the iliac portion of the ilio-pectineal line, which serves in the adult to separate sharply the
pelvis major from the pelvis minor. This part of the bone is remarkably strong, as will be shown
(see Architecture, Appendix A), and serves to
transmit the body weight from the sacrum to
the thigh bone. The sexual differences of the
pelvis, so far as they refer to the general con-
figuration of this part of the skeleton, are as
pronounced at the third or fourth month of
foetal life as they are in the adult. (Fehling,
Ztschr. f. Geburtsh. u. GynaeJc. Bd. ix. and x. ;
A Thomson, Journ. Anat. and Physiol vol.
xxxiii. p. 359.) The rougher appearance of
the male type is correlated with the more
powerful muscular development.
The Femur.
The femur or thigh bone is remark-
able for its length, being the longest
OBTURATOR INTBRNUS
PIRIFORMIS /
VASTUS MEDIALIS
LATERAL EPICONDYLE
LATERAL CONDYLE PATELLAR MEDIAL CONDYLE
SURFACE
FIG. 226. THE RIGHT FEMUR SEEN FROM THE FRONT.
medially, and slightly forwards.
FIG. 237. ANTERIOR ASPECT OF PROXIMAL POR-
TION OF THE RIGHT FEMUR WITH ATTACHMENTS
OF MUSCLES MAPPED OUT.
bone in the body. Proximally the femora
are separated by the width of the pelvis.
Distally they articulate with the tibiae
and patellae. In the military position
of attention, with the knees close to-
gether, the bodies of the thigh bones
occupy an oblique position.
For descriptive purposes the bone is
divided into a proximal extremity, com-
prising the head, neck,
and two trochanters ; a
body; and a distal ex-
tremity, forming the ex-
pansions known as the
condyles.
The cap ut femoris
(head) is the hemi-
spherical articular sur-
face which fits into the
acetabulum. Its pole
is directed upwards,
A little below the summit, and usually somewhat
ADDUCTOR
TUBERCLE
240
OSTEOLOGY.
HEAD
PIT FOR LIG. TERES
NECK
TROCHANTERIC FOSS;
GREATER
TROCHANTER
Tubercle of
quadratus
INTERTROCHAN-
TERIC CREST
GLUTEAL TUBEROSITY
ARTERIAL FORAMEN
behind it, is a hollow, oval pit (fovea capitis femoris) for the attachment of the
ligamentum teres. Piercing the floor of this depression! are seen several foramina
through which - vessels
pass to supply the head
of the bone ; the proximal
epiphysis thus having a
double blood supply, viz.,
from the neck distally,and
through the medium of the
ligamentum teres proxi-
mally. The circumfer-
ence of the head forms
a lip with a wavy outline,
more prominent above
and behind than in front.
The head is supported
by a stout compressed
bar of bone, the collum
femoris (neck), which
forms with the proxi-
mal end of the body
an angle of about 125
degrees, and is directed
proximally, medially, and
a little forwards. Its
vertical width exceeds its
antero-posterior thickness.
Constricted about its
middle, it expands medi-
ally to support the head,
whilst laterally, where it
joins the shaft, its vertical
diameter is much in-
creased. Anteriorly it is
clearly defined from the
shaft by a rough ridge
which commences above
on a prominence, some-
times called the tubercle
of the femur, and passes
obliquely downwards and
medially. This constitutes
the upper part of the
linea intertrochanterica
(intertrochantericline), and
serves for the attachment
of the ilio- femoral liga-
ment of the hip -joint.
Posteriorly, where the neck
unites with the body,
there is a full rounded
ridge passing from the
trochanter major proxi-
mally to the trochanter
minor distally; this is
the crista intertrochan-
terica (intertrochanteric crest). A little proximal to the middle of this ridge there is
usually a fulness which serves to indicate the proximal limit of attachment of the
quadratus femoris muscle, and is called the tubercle for the quadratus. Laterally the
ADDUCTOR
TUBERCLE
MEDIAL
EPICONDYLE
MEDIAL
CONDYLE
Surface for^,
attachment
of posterior
cruciate ligament
MBDIAL
EPICONDYLIC LINE
LATERAL EPICONDYLIC LINE
POPLITEAL PLANE
LATERAL EPICONDYLE
Surface for attachment of
ant. cruciate ligament
LATERAL CONDYLE
INTERCONDYLOID FOSSA
FIG. 238. THE RIGHT FEMUR SEEN FROM BEHIND.
THE FEMUR
241
neck is embedded in the medial surface of the tro-
chanter major, by which,, at its upper and dorsal
part, it is to some extent overhung. Here is situ-
ated the trochanteric fossa, into which the tendon of
the obturator externus is inserted. Passing nearly
horizontally across the back of the neck there is a
faint groove leading into this depression ; in this
the tendon of the obturator externus muscle lies.
Distally the neck becomes confluent with the tro-
chanter minor behind, and is continuous with the
medial surface of the body in front. The neck is
pierced 'by many vascular canals, most numerous at
the proximal and dorsal part. Some are directed
proximally towards the head, whilst others pass
in the direction of the trochanter major.
The trochanter major (greater trochanter) is
a large quadrangular process which caps the proxi-
mal and lateral part of the body, and overhangs
the root of the neck above and behind. Its lateral
surface, of rounded irregular form, slopes up-
wards and medially, and is separated from the
lateral surface of the body distally by a more or
less horizontal ridge. Crossing it obliquely from
the posterior superior to the anterior inferior angle
is a rough line which serves for the insertion of the
HEAD
OBTURATOR EXTERNUS
OBTURATOR INTERNUS
PIT FOR
LIG. TERES"
NECK
.TROCHANTERIC FOSSA
INTERTROCHANTERIC CREST
LESSER TROCHANTER
GREATER
TROCHANTER
SPIRAL LIN
PECTINEAL LINE
ARTERIAL FORAMEN
LlNEA ASPERA
FIG. 240. DORSAL VIEW OF THE PROXIMAL PART OF
THE RIGHT FEMUR.
FIG. 239. DORSAL ASPECT OF THE
PROXIMAL PORTION OF THE RIGHT
FEMUR WITH THE ATTACHMENTS OF
MUSCLES MAPPED OCT.
glutseus medius muscle; both
proximal and distal to this the
surface of the bone is smoother
and is overlain by bursse. The
ventral surface, somewhat oblong
in shape, and inclined obliquely
from below upwards and medi-
ally, is elevated from the general
aspect of the body, from which
it is separated in front by
an oblique line leading upwards
and medially to the tubercle at
the upper end of the superior
part of the intertrochanteric
line. This surface serves for the
insertion of the glutseus mini-
mus. The superior border is
curved and elevated ; into it
are inserted the tendons of the
obturator internus and gemelli
muscles medially and in front,
and the piriformis muscle above
and behind. The dorsal border
is thick and rounded, and forms
the upper part of the inter-
trochanteric crest. The angle
formed by the superior and
dorsal borders is sharp and
pointed, and forms the tip of
the trochanter overhanging the
trochanteric fossa, which lies
immediately below and medial
to its medial surface.
16
242 OSTEOLOGY.
The lesser trochanter (trochanter minor) is an elevated pyramidal process
situated at the dorsal side of the medial and proximal part of the body, where that
becomes continuous with the distal and dorsal part of the neck. Confluent
above with the intertrochanteric crest, it gradually fades away into the dorsal
aspect of the body below. The combined tendon of the ilio-psoas is inserted into-
this process and into the bone immediately below it.
The body (corpus femoris), which is characterised by its great length, is cylin-
drical in form. As viewed from the front, it is straight or but slightly curved ; as
seen in profile, it is bent forwards, the curve being most pronounced in its proximal
part. The body is thinnest at some little distance proximal to its middle ; distal
to this it gradually increases in width to support the condyles ; its antero-
posterior diameter, however, is not much increased distally. Its surfaces are
generally smooth and rounded, except behind, where, running longitudinally
along the centre of its curved dorsal aspect, there is a rough-lipped ridge, the
linea aspera. Most salient towards the middle of the body, the linea aspera
consists of a medial lip and a lateral lip, with a narrow intervening rough
surface. Proximally, about 2 to 2J inches from the trochanter minor, the linea
aspera is formed by the convergence of three lines. Of these the lateral is a rough,
somewhat elevated ridge, called the gluteal tuberosity which commences proxim-
ally, on the back of the body, lateral to and on a level with the trochanter minor,
and becomes continuous distally with the lateral lip of the linea aspera. This
serves for the bony insertion of the glutaeus maximus, and is occasionally de-
veloped into an outstanding process called the trochanter tertius. The medial
lip of the linea aspera is confluent proximally with a line which winds round
the body proximally and forwards, in front of the trochanter minor, to become
continuous with the intertrochanteric line (see p. 240). The whole consti-
tutes what is known as the spiral line, and extends from the anterior part of
the trochanter major proximally to the linea aspera distally. Intermediate in
position between the spiral line in front and medially, and the gluteal ridge
laterally, there is a third line, the pectineal line, which passes distally from
the trochanter minor and fades away into the surface between the two lips of
the linea aspera. Into this the pectineus muscle is inserted. About the junction
of the middle with the distal third of the body the two lips of the linea aspera
separate from one another, each passing in the direction of the epicondyle of the
corresponding side. The lines so formed are called the medial and lateral epi-
condylic lines, respectively, and enclose between them a smooth triangular area
corresponding to the back of the distal third of the body ; this, called the planum
popliteum (popliteal surface), forms the floor of the proximal part of the popliteal fossa.
The continuity of the proximal part of the medial epicondylic line is but faintly
marked, being interrupted by a wide and faint groove along which the popliteal artery
passes to enter the fossa of that name. Distally, where the line ends on the proxi-
mal and medial surface of the medial epicondyle, there is a little spur of bone
called the adductor tubercle, to which the tendon of the adductor magnus is attached,
and behind which the medial head of the gastrocnemius muscle takes origin.
The linea aspera affords extensive linear attachments to many of the muscles of the thigh.
The vastus medialis arises from the spiral line proximally and the medial lip of the linea aspera
distally. This muscle overlies but does not take origin from the medial aspect of the body. |
The adductor longus is inserted into the medial lip about the middle third of the length of the ;
body. The adductor magnus is inserted into the intermediate part of the line, extending to :'
the level of the trochanter minor, where it lies medial to the insertion of the glutaeus maximus. \
Distally, its insertion passes on to the medial epicondylic ridge, reaching as far as the adductor
tubercle. The adductor brevis muscle is inserted into the linea aspera proximally, between the
pectineus and adductor longus muscles medially and the adductor magnus laterally. Distal to
the insertion of the glutseus maximus the short head of the biceps arises from the lateral lip as well
as from the lateral epicondylic line ; in front these also serve for the origin of the vastus lateralis
muscle. There is frequently a small tubercle which marks the distal attachment of the lateral i
intermuscular septum on the lateral condylic line, about two inches from the condyle.
Immediately proximal to this there is often a groove for a large muscular artery which pierces
the septum at this point (Frazer).
The canals for the nutrient arteries of the body, which have a proximal direction, are usually i
two in number, and are placed on or near the linea aspera the proximal one about the level of the
junction of the middle and proximal third of the bone, the distal some three or four inches distal i
THE FEMUR
243
MEDIAL
HEAD OF GAS
TROCNEMIUS
PLANTARIS
LATERAL
HEAD OF GAS-
TROCNEMIUS
POSTERIOR CRUCIATE
LIGAMENT
ANTERIOR CRUCIATE
LIGAMENT
ATTACHMENTS
OUT.
OF MUSCLES
to this usually on the medial side of the body, immediately in front of the medial lip of the
linea aspera.
The anterior and lateral aspects of the body are covered by, and furnish surfaces
for, the origins of the vastus lateralis and vastus intermedius. The medial aspect is
covered by the vastus medialis.
The distal extremity of the femur comprises the two condyles and epicon-
dyles. The condyles are two recurved processes of bone, each provided with an
articular surface, and separated behind by a deep
intercondyloid fossa. United in front, where their
combined articular surfaces form an area on which
the patella rests, the two condyles differ from each
other in the following respects : If the body of the
bone is held vertically, the medial condyle is seen
to reach a more distal level than the lateral ; but,
as the femur lies obliquely in the thigh, the con-
dyles are so placed that their distal surfaces lie in
the same horizontal plane. Viewed on their distal
aspect, the medial condyle is seen to be the
narrower and shorter of the two. The lateral
condyle is broader, and advances farther forward
and to a more proximal level on the anterior sur-
FIQ. 241. POSTERIOR ASPECT OF DISTAL face of the shaft. The intercondyloid fossa reaches
PORTION OF THE EIGHT FEMUR WITH forwards as far as a transverse line drawn through
- MAPPED the centre Qf the ^^ condyle Itg gides are
formed by the medial and lateral surfaces of the
lateral and medial condyles respectively, the latter being more deeply excavated,
and displaying an oval surface near its distal and anterior part for the attachment
of the posterior cruciate ligament of the knee-joint. On the posterior and proximal
part of the medial surface of the lateral condyle there is a corresponding surface for
the attachment of the anterior cruciate ligament. The floor of the notch, which is
pierced by numerous vascular canals, slopes proximally and
dorsally towards the popliteal surface on the back of the
body, from which it is separated by a slight ridge (linea inter-
condyloidea) to which the posterior part of the capsule of the
knee-joint is attached.
Epicondyles. The cutaneous aspect of each condyle (i.e.
the lateral surface of the lateral condyle and the medial
surface of the medial condyle) presents an elevated rough
surface called the epicondyle, the medial (epicondylus medialis)
projecting more prominently from the line of the body ; capped
proximally by the adductor tubercle, it affords attachment
near its most prominent point to the
fibres of the tibial collateral ligament of
the knee-joint. The epicondylus lateralis
(lateral epicondyle), less pronounced Surface for t he
and lying more in line with the lateral attachment of
, , . , n i i i i the fibular col-
surlace of the body, is channelled behind lateral ligament
by a curved groove, the distal rounded
lip of which serves to separate it from
the distal articular surface. This groove
ends in front in a pit which is placed
just distal to the most salient point of the
tuberosity ; hereto is attached the tendon of the popliteus muscle, which, in the
extended position of the joint, overlies the distal lip of the groove, which is often
indented for it, but slips into and occupies the groove when the joint is flexed.
Dorsal to the most prominent part of the lateral epicondyle, and just proximal to
the pit for the attachment of the popliteus, the fibular collateral ligament of the
knee-joint is attached, whilst proximal to that there is a circumscribed area for
the origin of the tendinous part of the lateral head of the gastrocnemius muscle.
Groove for
tendon of
popliteus
FIG. 242. DISTAL END OF THE RIGHT FEMUR
(Lateral Side).
244
OSTEOLOGY.
PATELLAR SURFACE
The articular surface on the distal extremity is divisible into three parts
that which corresponds to the distal surface of the body and is formed by the
coalescence of the two condyles in front ; and those which overlie the distal and
posterior aspects of each of those processes. The former is separated from the latter
by two shallow oblique grooves which traverse the articular surface from before
backwards, on either side, in the direction of the anterior part of the intercondyloid
fossa. These furrows are the impressions in which fit the anterior parts of the
medial and lateral menisci of the knee-joint, respectively, when the knee-joint
is extended. The anterior articular area or patellar surface is adapted for
articulation with the patella. Convex proximo-distally, it displays a broad and
shallow central groove, bounded on either side by two slightly convex surfaces.
Of the two sides, the lateral is the wider and more prominent, and rises on the
front of the bone to a more proximal level than the medial, thus tending to
prevent lateral dislocation of the patella. The condylar or tibial surfaces are convex
from side to side, and convex from before backwards. Sweeping round the distal
surface and posterior extremities of the condyles, they describe a spiral curve more
open in front than behind. The medial condylar articular surface is narrower
than the lateral, and
when its distal aspect is
viewed it is seen to de-
scribe a curve around a
vertical axis. Along the
lateral edge of this, and
in front, where it bounds
the intercondyloid fossa, is
a semilunar articular area,
best seen when the bone
is coated with cartilage.
This articulates with the
medial edge of the patella
in extreme flexion of the
joint. The articular sur-
face of the lateral con-
dyle is inclined obliquely from before backwards and slightly laterally. The
surfaces of the condyles proximal to the articular area posteriorly are continuous
with the popliteal surface of the shaft. The area from which the medial head of the
muscle springs is often elevated in the form of a tubercle placed on the distal part
of the popliteal surface of the body, just proximal to the medial condyle.
The proportionate length of the femur to the body height is as 1 is to 3 -5 3-3 '9 2.
Arterial Foramina. Numerous vascular canals are seen in the region of the neck, at
the bottom of the trochanteric fossa, in the fossa for the ligamentum teres, on the inter-
trochanteric crest, and on the lateral surface of the greater trochanter. The nutrient arteries for
the body pierce the bone in a proximal direction on or near the linea aspera. Both the back
and the front of the distal end of the body display the openings of numerous vascular canals,
and the floor of the intercondyloid fossa is also similarly pierced.
Connexions. The femur articulates with the hip bone proximally and the tibia and patella
distally. The lateral surface of the greater trochanter determines the point of greatest hip width
in the male, being covered only by the skin and superficial fascia and the aponeurotic insertion of
the glutaeus maximus. In the erect position the tip of the trochanter corresponds to the level of
the centre of the hip -joint. When the thigh is flexed the trochanter major sinks under cover
of the anterior fibres of the glutseus maximus. In women the hip width is usually greatest at
some little distance distal to the trochanter, due to the accumulation of fat in this region. The
body of the bone is surrounded on all sides by muscles. Its forward curve, however, is account-
able to some extent for the fulness of the front of the thigh. The exposed surfaces of the condyles
determine to a large extent the form of the knee. In flexion the articular edges can easily be
recognised on either side of and distal to the patella.
Sexual Differences. According to Dwight, the head of the femur in the female is propor-
tionately smaller than that of the male.
Ossification. The body begins to ossify early in the second month of foetal life, and at
birth displays enlargements at both ends, which are capped with cartilage. If at birth the
distal cartilaginous end be sliced away, a small ossific nucleus for the distal epiphysis will
usually be seen. This, as a rule, makes its appearance towards the latter end of the ninth
Impression
of medial
meniscus
Semilunav facet
for medial edge
of patella in
extreme flexion
MEDIAL
IBIAL SURFACE
LATERAL
TIBIAL SURFACE T "_ _, M E DIAL CONDYLE
Surface of attachment of posterior
cruciate ligament
FIG. 243. DISTAL ASPECT OF DISTAL END OF THE EIGHT FEMUR.
LATERAL CONDYLE
INTERCONDYLOID FOSSA
THE PATELLA.
245
Appears about
early part of
first year
Fuses with shaft
about 18-19 years
Appears about
2-3 years
Usually appears in
the 9th month of
foetal life
At birth.
Fuses with shaft about 20-22 years
About 12 years. About 16 years.
FIG. 244. OSSIFICATION OF THE FEMUR.
month of foetal life, and is of service from a medico-legal standpoint in determining the age
of the foetus. According to -Hartman, it is absent in about 12 per cent, of children at
term, and may appear as early as the eighth month of foetal life in about 7 per cent. The
proximal extremity, entirely
cartilaginous at birth, com-
prises the head, neck, and
trochanter major. A centre
appears for the head during
the early part of the first
year. It is worthy of note
that this epiphysis has a
double blood - supply one
through the neck, the other
through the ligamentum
teres. That for the tro-
chanter major begins to
ossify about the second or
third year, whilst the neck
is developed as a proximal
extension of the body, which
is, however, not confined to
the neck alone, but forms
the distal circumference of
the articular head, as may
be Seen in bones up to the Usually appears in Usually appears
age of twelve or sixteen; the 9th month of before birth
after that, the separate epi-
physis of the head begins to
overlap it so as to cover it
entirely when fusion is com-
plete at the age of eighteen
or twenty.
The epiphysis of the greater trochanter unites with the body and neck about eighteen or
nineteen, whilst the epiphysis for the trochanter minor, which usually makes its appearance
about the twelfth or thirteenth year, is usually completely fused with the body about
the age of eighteen. The epiphysis for the distal end, although the first to ossify, is not
completely united to the body until from about the twentieth to the twenty-second year.
It is worthy of note that the line of fusion of the body and distal epiphysis passes
through the adductor tubercle, a point which can easily be determined in the living.
The distal end is the so-called "growing end of the bone."
The Patella.
The patella, the largest of the sesamoid bones, overlies the front of the knee-
joint in the tendon of the quadriceps extensor. Of compressed form and
somewhat triangular shape,, its distal angle forms a peak, called the apex
patellae, whilst its proximal edge, or base (basis patellae), broad, thick, and
sloping forwards and a little distally, is divided into two areas by a transverse
line or groove ; the anterior area so defined serves for the attachment of the
common tendon of the quadriceps extensor muscle, whilst the posterior, of com-
pressed triangular shape, is covered with synovial membrane. The medial and lateral
borders, of curved outline, receive the insertions of the vastus medialis and lateralis
muscles, respectively, the attachment of the vastus medialis being more extensive
than that of the vastus lateralis. The anterior surface of the bone, slightly convex
in both diameters, has a fibrous appearance, due to its longitudinal striation, and
is pierced here and there by the openings of vascular canals. Oftentimes at the
superior lateral angle there is a well-defined area for the tendinous insertion of the
vastus lateralis. The posterior or articular surface is divided into two unequal
parts (of which the lateral is the wider) by a vertical elevation which glides in the
furrow of the patellar surface of the femur, and in extreme flexion passes to occupy
the intercondyloid fossa. The lateral of the two femoral surfaces is slightly concave
in both its diameters; the medial, though slightly concave proximo -distally, is
246
OSTEOLOGY.
LATERAL ARTICULAR FACET
Surface for the ligamentum patellae
FIG. 245, THE RIGHT PATELLA.
A. Anterior Surface. B. Posterior Surface.
usually plane, or somewhat convex transversely. Occasionally, in the macerated
bone, indications of a third vertical area are to be noted along the medial edge of
the posterior aspect. This defines the part of the articular surface which rests on
the lateral border of
the medial condyle in
extreme flexion. In
the recent condition,
when the femoral sur-
face is coated with
cartilage, a more com-
plex arrangement of
facets may be in some
cases displayed (as in-
dicated in Fig. 244).
Lament (Journal of
Anat. and PhysioL,
1910, vol. xliv. p. 149)
has shown that these
areas undergo con-
siderable variation in
their arrangement in races who habitually adopt the squatting posture.
Distal to the femoral articular area the posterior surface of the apex is rough
and irregular ; the greater part of this is covered with synovial membrane, the liga-
mentum patellae being attached to its summit and margins, reaching some little
distance round the borders on to the anterior aspect of this part of the bone.
Ossification. The patella is laid down in cartilage about the third month of foetal
life. At birth it is cartilaginous, and the tendon of the quadriceps is continuous with the
ligamentum patellae over its anterior surface, and can easily be dissected off. About the
third year an ossific centre appears in it and spreads more particularly over its deeper surface.
Two centres, vertically disposed, have also been described. Ossification is usually com-
pleted by the age of puberty.
The Tibia.
The tibia is the medial bone of the leg. It is much stouter and stronger than its
neighbour the fibula, with which it is united proximally and distally. By its
proximal expanded ex-
rrprmfv it qnivnnrtq thp Surface for attachment of anterior TUBEROSITY (O.T. Tubercle)
Llty It Supports tne extremity of medial meniscus ^^ Sn f ,
condyles of the femur, * " I Ijjmk /""-t ^enSy of
While distally it Shares EMINENTIA ^**&A i$&*^L lateral meniscus
, -. f. J . n . , INTERCONDYLOIDEA X
m the formation ol the
ankle-joint, articulat-
ing with the proximal
surface and medial side
of the talus.
The proximal ex-
tremity comprises the
medial and lateral con-
dyles (O.T.tuberosities),
the intercondyloid emi-
nence (O.T. spine), and
the tuberosity.
Each condyle is
provided on its proximal aspect with an articular surface (facies articularis
superior), which supports the corresponding femoral condyle, as well as the
interposed meniscus. Of these two condylic surfaces the medial is the larger. Of
oval shape, its long axis is placed antero-posteriorly ; slightly concave from before
backwards and from side to side, its circumference rises in the form of a sharp and
well-defined edge. The lateral condylic surface is smaller and rounder. Slightly
concave from side to side, and gently convex from before backwards, its circumfer-
Surface for attach, of
SYNOVIAL COVERED ^M 1^T\ ^B^^" ^post. extremity of
SURFACE ^BS^y POSTERIOR INTER- la teral meniscus
Surface for attach, of post. / CONDYLOID FOSSA
extrem. of medial meniscus Post, cruciate ligament
FIG. 246. THE PROXIMAL SURFACE OF THE PROXIMAL EXTREMITY
OF THE RIGHT TIBIA.'
THE TIBIA.
247
ice is well defined in front, but is
convexity of its posterior part,
jtween the two condylic surfaces
le bone is raised in the centre
form the intercondyloid eminence
which consists of two intercondyloid
tubercles separated by an oblique
groove, in the anterior part of which
lies the anterior cruciate ligament.
The medial tubercle (tuberculum
intercondyloideum mediale), the
higher, is prolonged backwards and
laterally by an oblique ridge to
which part of the posterior cornu
of the lateral meniscus is attached.
The lateral tubercle (tuberculum
intercondyloideum laterale) is more
pointed and not so elevated. In front
of and behind the intercondyloid
eminence the articular areas are
separated by two irregular V-shaped
surfaces, the intercondyloid fossae.
The anterior intercondyloid fossa,
the larger and wider, furnishes areas
for the attachment of the menisci on
either side, and for the anterior
cruciate ligament immediately in
front of the intercondyloid emin-
ence. The floor of this space is
pierced by many nutrient foramina.
The posterior intercondyloid fossa is
concave from side to side, and
slopes downwards and backwards.
The lateral meniscus is attached
near its apex to a surface which
rises on to the back of the inter-
condyloid eminence; the medial
meniscus is fixed to a groove which
runs along its medial edge, and the
posterior cruciate ligament derives
an attachment from the smooth
posterior rounded surface.
The lateral condyle is the
smaller of the two. It overhangs
the body to a greater extent than
the medial, though this is- obscured
in the living by its articulation
with the fibula. The facet for the
fibula, often small and indistinct,
is placed postero- laterally on the
distal surface of its most projecting
part.' Antero-laterally the imprint
caused by the attachment of the
trachis iliotibialis (O.T. ilio-tibial
band) is often quite distinct. Curv-
ing distal ly and forwards from the
fibular facet there is often a definite
ridge for the attachment of the
expansion of the biceps tendon ;
rounded off behind, thus markedly increasing
INTERCONDYLOID
Tractus iliotibialis EMINENCE
LATERAL
HEAD
NECK
MEDIAL
CONDYLE
ANTERIOR CREST
POSTERIOR PART
OF MEDIAL
SURFACE
ANTERIOR PART OF
MEDIAL SURFACE
SUBCUTANEOUS
SURFACE
LATERAL
MALLEOLUS
*^r
FIG. 247. THE RIGHT TIBIA AND FIBULA AS SEEN
FROM THE FRONT.
The anterior part of the medial surface of the fibula is coloured
blue. The posterior part of the medial surface of the fibula
is coloured red. The lateral or peroneal surface of the fibula
is left uncoloured.
248
OSTEOLOGY.
BICEPS
FlBULAR
COLLATERAL
LIGAMENT OF KNEE
distal to this the areas for the origins of the peronseus longus and extensor digitorum
longus are often crisply defined. The circumference of the medial condyle is grooved
postero-medially for the insertion of the tendon of the semi-membranosus.
In front of the condyles, and about an inch distal to the level of the condylic sur-
faces, there is an oval elevation called the tuberosity of the tibia. The proximal
half of this is smooth and covered by a bursa, while the distal part is rough and
serves for the attachment of the ligamentum patellae.
Considered in its entirety, the proximal extremity of the tibia is broader
transversely than antero-posteriorly, and is inclined backwards so as to overhang
the shaft posteriorly.
The corpus tibiae (body) is irregularly three -sided, possessing a medial, a
lateral, and a posterior surface, separated by an anterior crest, a medial margin, and
a lateral or interosseous crest. It is narrowest about the junction of its middle
and distal thirds, and expands proximally and distally to support the extremities.
Running along the front of the bone there is a gently-curved, prominent margin,
the crista anterior, confluent proximally with the tuberosity, but fading away distally
on the anterior surface of the
distal third of the bone, where
it may be traced in the direc-
tion of the anterior border of
the medial malleolus. This
is the anterior crest or
shin, which is subcutaneous
throughout its entire length.
To the medial side of this is
a smooth, slightly convex
surface, which reaches the
medial condyle proximally,
and distally becomes con-
tinuous with the medial sur-
face of the medial malleolus.
This is the medial or sub-
cutaneous surface of the body,
FIG. 248. ANTERIOR ASPECT OF THE PROXIMAL PORTIONS OF THE which is covered only by skin
MA BIOHT LEG WI ATTACHMENTS OF MC8CLES and superficial fascia, except
in its proximal fourth, where
the tendons of the sartorius, gracilis, and semitendinosus muscles overlie it,
they pass towards their insertions. This surface is limited posteriorly by ttu
medial margin, which passes from the medial and distal surface of the medi*
condyle proximally to the posterior border of the medial malleolus distally. Tl
margin is rounded and indefinite proximally and distally, being usually bes
marked about its middle third. To the lateral side of the anterior crest is th
lateral surface of the bone ; it is limited behind by a straight vertical ridge, the
crista interossea (interosseous crest), to which the interosseous membrane, whicl
occupies the interval between the tibia and the fibula, is attached. This
commences near the middle of the lateral and distal surface of the lateral condyle
and terminates about two inches from the distal extremity by dividing into tw(
lines, which separate and enclose between them the surface for articulation wit!
the distal end of the fibula, and the area of attachment of the interosseom
ligament, which here unites the two bones. In its proximal two-thirds th<
lateral surface provides an extensive origin for the tibialis anterior. Distally,
where the anterior crest is no longer well defined, the lateral surface '
forwards on to the front of the body, and is limited by the anterior margii
of the distal articular surface. Over this the tendon of the tibialis anterior,
and the combined fleshy and tendinous parts of the extensor hallucis propriuf
and extensor digitorum longus muscles pass obliquely distally. The posteri<
surface of the body lies between the interosseous crest laterally and the medi*
margin on the medial side. Its contours are liable to considerable variatioi
according to the degree of side to side compression of the bone. It is usually full
THE TIBIA. 249
and rounded proxinially, and flat distally. Proximally it is crossed by the
linea poplitea (popliteal line), which runs distally and medially, from the fibular
facet to the medial border on a level with the junction of the middle with
the proximal third of the body. To this line the deep transverse fascia is
attached, whilst distal to it, as well as from the medial border of the bone
distally, the soleus muscle takes origin. Into the bulk of the triangular area
proximal to it the popliteus muscle is inserted. Arising from the middle of the
popliteal line there is a vertical ridge, which passes distally and divides the
posterior aspect of the body into two surfaces a lateral for the tibial origin of
the tibialis posterior muscle, and a medial for the flexor digitorum longus muscle.
The distal third of this surface of the body is free from muscular attachments,
but is overlain by the tendons of the above muscles, together with that of the flexor
hallucis longus. A large nutrient canal, having a distal direction, opens on the
posterior surface of the body a little distal to the popliteal line and just lateral
to the vertical ridge which springs from it.
The distal extremity of the tibia displays an expanded quadrangular form.
It is furnished with a saddle-shaped articular surface on its distal surface (facies
articularis inferior), which is concave from before backwards and slightly convex
from side to side. This rests upon the upper articular surface of the body
of the talus, and is bounded in front and behind by well-defined borders. The
anterior border is the rounder and thicker, and is oftentimes channelled by a
groove for the attachment of the anterior ligament of the joint ; further, it is occa-
sionally provided with a pressure facet caused by the locking of the bone against
the neck of the talus in extreme flexion. Laterally the edge of the articular area
corresponds to the base of the triangle formed by the splitting of the interosseous
ridge into two parts. Where these two lines join it, both in front and behind, the
bone is elevated into the form of tubercles, in the hollow between which (incisura
fibularis) the distal end of the fibula is lodged, being held in position by powerful
ligaments. The cartilage-covered surface occasionally extends for some little
distance proximal to the base of the triangle. Medially there is a process projecting
distally, and called the medial malleolus, the medial aspect of which is subcutaneous
and forms the projection of the medial ankle. Its lateral surface is furnished
with a piriform facet (facies articularis malleolaris), confluent with the cartilage-
covered area on the tarsal surface of the distal extremity ; this articulates with a
corresponding area on the medial surface of the body of the talus. Distally
the malleolus is pointed in front, but notched behind for the attachment of the
deltoid or tibial collateral ligament of the ankle. Eunning obliquely along the
posterior surface of the malleolus there is a broad groove (sulcus malleolaris) in which
the tendons of the tibialis posterior and flexor digitorum longus muscles are
lodged ; whilst a little to the fibular side of this, and running distally over
the posterior surface of the distal extremity of the bone, there is another groove,
often faintly marked, for the lodgment of the tendon of the flexor hallucis longus
muscle.
The proportionate length of the tibia to the body height is as 1 is to 4 < 32-4 > 80.
Arterial Foramina. Nutrient canals are seen piercing the proximal extremity of the bone
around its circumference and proximal to the tuberosity. The floors of the intercondyloid fossae
are also similarly pierced, and there is usually a canal of large size opening on the summit of
the intercondyloid eminence. Two or three foramina of fair size are seen running proximally
into the substance of the bone a little distal to and to the medial side of the tuberosity, while the
principal vessel for the body passes distally into the bone on its posterior surface, about the
level of the junction of the proximal and middle thirds. The medial surface of the medial
malleolus, as well as the anterior and posterior borders of the distal extremity, are likewise
pitted by the orifices of small vascular channels.
Connexions. Proximally the tibia supports the condyles of the femur, and is connected in
front with the patella by means of the patellar ligament. Articulating laterally with the fibula
proximally and distally, it is united to that bone throughout nearly its entire length by the inter-
osseous membrane. The anterior crest and medial surface can be readily examined, as they are
subcutaneous, except proximally, where the medial surface is overlain by the thin tendinous
aponeuroses of the muscles passing over the medial side of the knee. The form of the distal part
of the knee in front is determined by the condyles on either side crossed centrally by the liga-
mentum patellae. Distally the medial malleolus forms the projection of the medial ankle, which
is wider, not so low, less pointed, and extends further forwards than the projection of the lateral
250
OSTEOLOGY.
Fuses with shaft about 20-24 years
May appear
Appears independently
before birth about 11 years
ankle. The front and back of the distal end of the bone are crossed by tendons, which mask
to a certain extent its form.
Ossification. The body begins to ossify early in the second month of intra-uterine
life. At birth it is well formed, and capped proximal ly and distally by pieces of cartilage,
in the proximal of which the centre
for the proximal epiphysis has al-
ready usually made its appearance.
From this the condyles and tuber-
osity are developed, though some-
times an independent centre for the
latter appears about the eleventh
or twelfth years, rapidly joining with
the already well-developed mass of
the rest of the epiphysis. Complete
fusion between the proximal epi-
physis and the body does not take
place until the twentieth or the
twenty-fourth year. The centre for
the distal articular surface and the
medial malleolus makes its appear-
ance about the end of the second
year, and union with the shaft
is usually complete by the age of
eighteen. Lambertz notes the occa-
sional presence of an accessory
nucleus in the malleolus. The prox-
imal end is the so-called "growing
end of the bone."
Appears about 1J years
Fuses about 18th year
At birth. About 12 years. About 16 years.
FIG. 249. OSSIFICATION OF THE TIBIA.
The Fibula.
The fibula is a slender bone with two enlarged ends. It lies to the lateral
side of the tibia, with which it is firmly united by ligaments, and nearly equals that
bone in length.
The first difficulty which the student has to overcome is to determine which is the proximal
and which the distal extremity of the bone. This can easily be done by recognising the fact that
there is a deep pit on the medial aspect of the distal extremity immediately behind the triangular
articular surface. Holding the bone vertically with the distal extremity downwards and so
turned that the triangular articular area lies in front of the notch already spoken of, the
subcutaneous non-articular aspect of the distal extremity will point to the side to which the
bone belongs
The proximal extremity or head of the fibula (capitulum fibulae), of irregular
rounded form, is bevelled on its medial surface so as to adapt it to the form of the
distal surface of the lateral condyle of the tibia. At the border where this
surface becomes confluent with the lateral aspect of the head there is a pointed
upstanding eminence called the apex capituli fibulae; to this the short fibular
collateral ligament is attached, as well as a piece of the tendon of the biceps,
which is inserted into its anterior part. Immediately to the medial side of this,
and occupying the summit of the medial sloping surface, there is an articular area
(facies articularis capituli), of variable size and more or less triangular shape. This
area articulates with the lateral condyle of the tibia. The long fibular collateral
ligament, together with the remainder of the tendon of the biceps muscle which
surrounds it, is attached to the lateral and proximal side of the head in front
of the apex capituli. On the front and the back of the head there are usually
prominent tubercles'. The anterior of these is associated with the origin of the
peronaeus longus muscle ; the posterior furnishes an origin for the proximal fibres
of the soleus, and serves to deepen the groove, behind the proximal tibio-fibular
joint, in which the tendon and fleshy part of the popliteus muscle play.
The constricted portion of the body distal to the head is often referred to as
the neck ; around the lateral side of this the common peroneal nerve winds.
THE FIBULA
251
MEDIAL CONDYLIC
SURFACE
INTERCONDYLOID EMINENCE
LATERAL CONDYLIC
SURFACE
POPLITEAL
NOTCH
APEX OF
THE HEAD
The body of the fibula (corpus fibulae) presents many varieties in the details
of its shape and form, being ridged and channelled in such a way as greatly
to increase the difficulties of the student in recognising the various surfaces
described. It is described as
possessing three surfaces, named
the lateral, the medial, and the
posterior. The surfaces are separ-
ated from one another by three
borders or crests, named medial,
HEAD lateral, and anterior ; and, in
addition, the medial surface is
traversed longitudinally by a
ridge called the interosseous crest,
which divides it into an anterior
and a posterior part. The most
important point is first to de-
termine the position of the
LATERAL CREST
INTEROSSEOUS
CREST
GROOVE FOR
TENDONS OF
LATERAL
MALLEOLUS
LONGUS AND
TALUS - BBKVIS
GROOVE FOR,
FLEXOR HALLUCIS
LONG US
FIG. 250. THE RIGHT TIBIA AND FIBULA SEEN PROM
BEHIND.
The Posterior surface of the fibula is coloured red ; the
lateral surface is left uncoloured.
SEMIMEMBRANOSUS
SOLEUS'
TlBIALIS POSTERIOR
FLEXOR HALLUCIS LONGUS
PERON^US LONGUS
AND BREVIS
FIG. 251. POSTERIOR ASPECT OF THE
BONES OF THE LEG WITH ATTACH-
MENTS OF MUSCLES MAPPED OUT.
252
OSTEOLOGY.
APEX CAPITULI
FACET FOR TIBIA.
HEAD-
NECK.
INTEROSSEOUS CREST
NUTRIENT FORAMEN
(in this case directed
proximal ly)
INTEROSSEOUS
CREST"
ROUGH SURFACE
FOR INTER-
OSSEOUS"
LIGAMENT
FACET FOR TALUS
LATERAL
MALLEOLUS
FIG. 252. RIGHT FIBULA AS
SEEN FROM THE MEDIAL SIDE.
The anterior part of the medial
surface is coloured ]olue ; the
posterior part of the medial
surface is coloured red.
anterior crest. If the bone is held in the position which
it normally occupies in the leg, it will be noticed that
the lateral surface of the distal extremity is limited in
front and behind by two lines, which converge
and enclose between them a triangular subcutaneous area
which lies immediately proximal to the lateral malleolus.
From the summit of the triangle so formed a well-
defined ridge may be traced along the front of the body to
reach the anterior aspect of the head. This is the anterior
crest.
The interosseous crest, so named because the inter-
osseous membrane is -attached to it, is the ridge which
lies just medial to the anterior crest, or towards the
tibial side on the anterior aspect of the bone. It is not
so prominent as the anterior crest, and it extends from
the neck of the bone to the apex of a rough triangular
impression that lies proximal to the articular surface
on the medial aspect of the distal end. The interval
between the anterior and interosseous crests is the
anterior part of the medial surface. This interval is, as
a rule, of considerable width in the distal half of the
bone, but the two crests tend to run much closer
together proximally; indeed, it is not uncommon to
find that they coalesce to form a single crest.
The posterior part of the medial surface is the
elongated area behind the proximal three-fourths or
four-fifths of the interosseous crest. It is limited
posteriorly by the medial crest, a sharp, salient ridge,
which commences at the medial margin of the posterior
aspect of the head, but does not reach the distal end of
the bone ; for the distal end of the medial crest curves
forwards and joins the interosseous crest about three or
four inches from the distal extremity of the body ;
therefore, the posterior part of the medial surface is not
represented in the distal part of the body. On the
proximal third of this surface there is frequently found
an oblique ridge which begins near the interosseous
crest at the level of the neck and extends distally and
backwards to join the medial crest. When the proximal
part of the medial crest is indistinct this ridge may be
mistaken for it.
The lateral surface, which is separated from the
medial surface by the anterior crest, is often hollowed
out in its middle part, and it is twisted, so that its
proximal part is directed somewhat forwards, while its
distal part turns backwards and becomes continuous
distally with the broad, shallow groove which occupies
the posterior surface of the lateral malleolus. The
lateral surface is limited posteriorly and separated from
the posterior surface of the body by the lateral crest,
which is usually sharp and well defined except at its
extremities, where it tends to become smooth and
rounded. Its proximal end joins the head distal to and
in front of the apex capituli, and terminates distally at
a point just proximal to the pit on the medial surface
of the distal extremity. In its proximal third or
fourth the lateral crest is often rough where fibres oi
the soleus muscle arise from it.
The posterior surface forms the remainder of the
THE FIBULA. 253
body. It is the district bounded laterally by the lateral crest and medially by
the medial crest and the, distal fourth or fifth of the interosseous crest. It is
twisted in the same degree as the lateral surface ; and, therefore, while its proximal
part is directed backwards, its distal part is directed medially and is in line with
the medial surface of the malleolus. The nutrient foramen is situated on the
posterior surface, at or near the middle of the body near the medial crest, and
is directed towards the distal end of the bone.
The anterior crest gives attachment to the anterior intermuscular septum, and,
at its distal end, to the ligamentum transversum cruris, while the posterior inter-
muscular septum is attached to the lateral crest. These septa enclose the peroneus
longus and brevis muscles, which arise from the lateral or peroneal surface, and
separate them from the muscles on the front and the back of the leg. The inter-
osseous membrane is attached to the whole length of the interosseous crest. The
anterior part of the- medial surface provides origin for the extensor halluciis, the
extensor digitorum longus and the peroneus tertius; while the tibialis posterior
arises from the posterior part of the medial surface. The medial crest is the fibular
attachment of a strong sheet of fascia which covers the tibialis posterior, and
separates it from the flexors of the toes. The soleus muscle arises from the
proximal third of the posterior surface, while the flexor hallucis longus takes
origin from its distal two -thirds.
The distal extremity of the fibula, or lateral malleolus, is of pyramidal
form. Its medial surface is furnished with a triangular articular area (facies
articularis malleoli), plane from before backwards, and slightly convex proximo-
distally, which articulates with a corresponding surface on the lateral side of the
body of the talus. Behind this there is a deep pit, to which the posterior
talo- fibular ligament is attached. Proximal to the articular facet there is a rough
triangular area, from the summit of which the interosseous crest arises ; to this
are attached the strong fibres of the distal interosseous ligament which binds
together the opposed surfaces of the tibia and fibula. The lateral surface of the
distal extremity forms the elevation of the lateral malleolus which determines the
shape of the projection of the lateral ankle. Bounded from side to side and proximo-
distally, it terminates in a pointed process, which reaches a more distal level than
the corresponding process of the tibia, from which it also differs in being narrower
and more pointed and being placed in a plane nearer the heel. Proximally, this
surface, which is subcutaneous, is continuous with the triangular subcutaneous
area so clearly defined by the convergence of the lines which unite to form the
anterior crest. The anterior border and tip of the lateral malleolus furnish
attachments to the anterior talo-fibular and calcaneo - fibular ligaments. The
posterior surface of the lateral malleolus, broad proximally, where it is confluent
with the lateral or peroneal surface, is reduced in width distally by the presence
of the pit which lies to its medial side. This aspect of the bone is grooved (sulcus
malleolaris) by the tendons of the peronseus longus and brevis muscles, which
curve round the posterior and distal aspects of the malleolus.
The proportionate length of the fibula to the body height is as 1 is to 4'37-4'82.
Arterial Foramina. Numerpus minute vascular canals are seen piercing the lateral surface of
the head, and one or two of larger size are seen on the medial surface immediately anterior to the
proximal articular facet. The canal for the nutrient artery of the body, which has a distal
direction, is situated on the posterior surface of the bone about its middle. The lateral
surface of the lateral malleolus displays the openings of many small canals, and one or two larger
openings are to be noted at the bottom of the pit behind the distal articular surface.
Connexions. The head and lateral malleolus, and part of the body immediately proximal to
the latter, are subcutaneous. The remainder of the body is covered on all sides by the muscles
which surround it. Proximally the bone plays no part in the formation of the knee-joint, but
distally it assists materially in strengthening the ankle-joint by its union with the tibia and it;
articulation with the talus. In position the bone is not parallel to the axis of the tibia, but
oblique to it, its proximal extremity lying posterior and lateral to a vertical line passing through
the lateral malleolus.
Ossification. The body begins to ossify about the middle of the second month of
foetal life. At the end of the third month there is but little difference in size between it
and the tibia, and at birth the fibula is much larger in proportion to the size of the
254
OSTEOLOGY.
Appears about
3-4 years
tibia than in the adult. Its extremities are cartilaginous, the distal extremity not being
as long as the medial malleolar cartilage of the tibia. It is in this, however, that an
ossific centre first appears about the end of the second year, which increases rapidly
in size, and unites with the body in about nineteen years. The centre for the proximal
epiphysis begins to ossify about the third or fourth year, and union with the body is
not complete until a period somewhat later than that for the distal epiphysis. The mode
of ossification of the distal extremity is an
Fuses with shaft , . ,-, -, -. , , . . ,
about 20-24 years exception to the general rule that epiphyses
which are the first to ossify are the last to unite
with the body. This may possibly be accounted
for by the fact that the distal end is functionally more
important than the rudimentary proximal end, since in
man alone, of all vertebrates, does the lateral malleolus
reach beyond the level of the medial malleolus. Its
early union with the body is doubtless required to
ensure the stability of the ankle-joint necessitated
by the assumption of the erect position.
In its earlier stages of development it has been stated,
on the authority of Leboucq, Gegenbaur, and others, that
the fibula as well as the tibia is in contact with the femur.
This is, however, denied by Grunbaum (" Proc. Anat Soc.,"
Journ. Anat. and PhysioL, vol. xxvi. p. 22), who states that
after the sixth week the fibula is not in contact with the
femur, and that prior to that date it is impossible to
differentiate the tissue which is to form femur from that
which forms fibula.
Appears about
2nd year
Fuses with shaft
about 19 years
At About About
birth. 12 years. 16 years.
FIG. 253. OSSIFICATION OF FIBULA.
BONES OF THE FOOT.
The bones of the foot, twenty-six in number, are arranged
in three groups : the tarsal, seven in number ; the rneta-
tarsal, five in number ; the phalanges, fourteen in number.
Comparing the foot with the hand, the student will be
struck with the great proportionate size of the tarsus as compared with the carpus, and the
reduction in size of the bones of the toes as compared with the fingers. The size of the meta-
tarsal segment more nearly equals that of the metacarpus.
The Tarsus.
The tarsus consists of seven bones (ossa tarsi) the talus or astragalus,
calcaneus, navicular or scaphoid, three cuneiforms, and the cuboid. Of irregular
form and varying size, they may be described as roughly cubical, presenting for
examination dorsal and plantar surfaces, as well as anterior, posterior, medial,
and lateral aspects.
The Talus.
The talus (O.T. astragalus) is the bone through which the body weight is
transmitted from the leg to the foot. Proximally the tibia rests upon it, whilst
on either side it articulates with the medial and lateral malleolar processes of the
tibia and fibula respectively ; inferiorly it overlies the calcaneus, and anteriorly it
articulates with the navicular. For descriptive purposes the bone is divisible into
three parts the corpus tali (body) blended in front with the collum tali (neck),
which supports the caput tali (head).
The dorsal surface of the body is provided with a saddle-shaped articular
surface (trochlea tali), broader in front than behind, for articulation with the distal
surface of the tibia. The medial edge of the trochlea is straight ; whilst the lateral
border, which is sharp in front and more rounded behind, is curved medially pos-
teriorly, where it is bevelled to form a narrow, elongated, triangular facet, which
is in contact with the transverse or distal tibio-fibular ligament during flexion of
the ankle. (Fawcett, Ed. Med. Journ., 1895.) Over the lateral border the cartilage-
covered surface is continuous laterally with an extensive area of the form of a
quadrant. This is concave from above downwards, and articulates with the medial
THE TALUS.
255
surface of the lateral malleolus. The distal angle of this area is prominent and
somewhat everted, and sometimes referred to as the processus lateralis tali (lateral
process). The medial aspect of the body has a comma -shaped facet, confluent
with the dorsal articular surface, over the medial edge of the trochlea ; this
CALCAKEUS
Surface of talus
for articulation
with fibula
CUBOID
Surface of talus for
articulation with tibia
NAVICULAR
THIRD
V. METATARSAL . _
SECOND I CUNEIFORMS
FIRST J
I. METATARSAL
SESAMOID BONE
THIRD OR TERMINAL PHALANX
FIG. 254. DORSAL SURFACE OF THE BONES OF THE EIGHT FOOT.
articulates with the lateral surface of the medial malleolus. Below this facet
the bone is rough and pitted by numerous small openings, and just below the tail
of the comma there is a circular impression for the attachment of the deep fibres
of the deltoid ligament (talo-tibial fibres). On the plantar surface of the body
there is a deep concave facet, called the posterior calcanean facet (facies calcanea
256
OSTEOLOGY.
articularis posterior), which is of more or less oval or oblong form and is
placed obliquely from behind forwards and laterally ; this rests upon a corre-
sponding surface on the dorsal aspect of the calcaneus. In front of this, and crossing
the bone from the medial side laterally and forwards, is a deep furrow (sulcus tali),
CALCANEUS
SUSTENTACULUM TALI
Surface of talus in
blue rests on the planter
calcaneo-navicular
ligament
XAVICULAR
FIRST
CUNEIFORM
I. METATARSAL
SESAMOID BONE
FIRST OH PROXI-
MAL PHALANX
BOID
SECOND CUNEIFORM
THIRD
CUNEIFORM
I V. METATARSAL
THIRD OR TERMINAL PHALANX
FIG. 255. PLANTAR SURFACE OF THE BONES OF THE RIGHT FOOT.
the floor of which is pierced by numerous large canals. It serves for the attach-
ment of the strong interosseous ligament which unites the talus with the calcaneus,
and separates the facet already described from a smaller oval articular area having
a slightly convex surface, which lies immediately in front of it. This is call*
the middle calcanean facet (facies articularis calcanea media), and articulates witl
THE TALUS.
257
the dorsal surface of the sustentaculum tali of the calcaneus. Posteriorly the
body is provided with two tubercles, separated by a groove ; the lateral of these
(processus posterior tali) is usually the larger, and is occasionally a separate ossicle
(os trigonum). To it is attached the posterior talo-fibular ligament of the ankle-
joint. The groove, which winds obliquely from above downwards and medially
over the posterior surface of the bone, lodges the tendon of the flexor hallucis
longus muscle.
The head, of oval form, is directed forwards and medially. Its anterior surface
Abductor digit! quinti
(origin)
Quadratus plantae
(origin)
Long and short plantar (
ligaments (
Tibialis posterior (part of
insertion)
Peronseu.s brevis
(insertion)
Flexor digiti qninti
brevis (origin)
Oblique head of abductor
hallucis (origin)
Flexor digitorum brevis. (origin)
Abductor hallucis (origin)
Attachments of
plantar calcaneo-
navicular ligament
Flexor hallucis brevis
(origin)
Tibialis posterior (part
of insertion)
Peronseus longus
(insertion)
Tibialis anterior
(insertion)
FIG. 256. MUSCLE-ATTACHMENTS TO LEFT TARSUS AND METATARSUS (Plantar Aspect).
convex from side to side and from above downwards, and articulates with the
tavicular bone (facies articularis navicularis). Inferiorly this surface is confluent
yith the middle calcanean facet, but in well-marked specimens, or when the bones
are articulated, it will be seen that a small area in front of, and lateral to the
middle calcanean facet rests upon an articular surface on the dorsal surface of the
anterior portion of the calcaneus, and is called the anterior calcanean facet (facies
articularis calcanea anterior). On the medial and plantar surface of the head there is
a cartilage-covered surface which does not articulate with any bone, but rests on
the dorso-lateral surface of the plantar calcaneo-navicular ligament, and is sup-
ported on the medial side by the tendon of the tibialis posterior muscle. (Fawcett,
Ed. Med. Journ., 1895, p. 987.)
OSTEOLOGY.
The neck, best seen on dorsal surface, passes from the front of the body and
10
Fm. 257. THE RIGHT TALUS. A. Dorsal surface ; B. Plantar surface.
1. GROOVE FOR FLEX. HALLUCIS LONG.
2. MEDIAL TUBERCLE.
3. TROCHLEA.
4. BODY.
5. FOR ARTICULATION WITH MEDIAL
MALLEOLUS.
6. HEAD.
7. FOR ARTICULATION WITH NA VICULAR.
8. NECK.
9. FOR ARTICULATION WITH LATERAL
MALLEOLUS.
10. SURFACE AGAINST WHICH THE
POSTERIOR TALO-FIBULAR LIGA-
MENT RESTS.
11. PROCESSUS POSTERIOR.
12. PROCESSUS POSTERIOR.
13. POSTERIOR, MIDDLE, AND ANTERIOR
FACETS FOR CALCANEUS.
14. FOR ARTICULATION WITH NAVI-
CULAR.
15. SURFACE RESTING ON PLANTAR
CALCANEO-NA VICULAR LIGA-
MENT.
16. SULCUS TALI.
17. GROOVE FOR FLEXOR HALLUCIS
LONOUS.
IS. MEDIAL TUBERCLE.
inclines towards the medial side. It is confluent with the medial surface in front
L6
JO
C D
FIG. 258. THE RIGHT TALUS. C. Seen from the lateral side ; D. Seen from the medial side.
1. PROCESSUS POSTERIOR.
2. GROOVE FOR FLEXOR HALLUCIS
LONGUS.
3. MEDIAL TUBERCLE.
4. SURFACE AGAINST WHICH THE
POSTERIOR TALO-FIBULAR LIGA-
MENT RESTS.
5. TROCHLEA FOR TIBIA.
6. FOR ARTICULATION WITH
LATERAL MALLEOLUS.
7. NECK. 8. HEAD.
9. FOR ARTICULATION WITH
NAVICULAR.
10. SULCUS TALI.
11. ANTERIOR, MIDDLE, AND
POSTERIOR FACETS FOR CAL-
CANEUS.
12. BODY.
13. SURFACE RESTING ON PLANTAR
CALCANEO - NAVICULAR LIGA-
MENT.
14. FOR ARTICULATION WITH NAVI-
CULAR.
15. HEAD.
16. NECK.
17. TROCHLEA FOR TIBIA.
18. FOR ARTICULATION WITH MEDIAL
MALLEOLUS.
19. BODY.
20. IMPRESSION FOR DELTOID LIGA-
MENT.
21. MEDIAL TUBERCLE.
22. GROOVE FOR FLEXOR HALLUCIS
LONGUS.
23. PROCESSUS POSTERIOR.
24. SULCUS TALI.
25. POSTERIOR AND MIDDLE FACETS
FOR CALCANEUS.
of the medial malleolar facet, and laterally forms a wide groove, which becomes
continuous on the plantar surface with the lateral end of the interosseous groove.
THE CALCANEUS.
The Calcaneus,
259
The calcaneus is the largest of the tarsal bones. It supports the talus on its
dorsal surface and articulates with the cuboid anteriorly. On the plantar aspect and
behind, its posterior extremity, or tuberosity (tuber calcanei), forms the heel, on
which so large a proportion of the body weight rests. The long axis of the bone
inclines forwards and a little laterally and upwards.
The dorsal surface of the calcaneus is divisible into two parts a posterior non-
articular part and an anterior articular portion. The length of the former varies
according to the projection of the heel ; rounded from side to side, it is slightly con-
cave from before backwards. In front of this there is a convex articular area of
variable shape (facies articularis posterior), sometimes nearly circular, at other times
oval and occasionally almost triangular. This is directed upwards and forwards,
and articulates with the posterior calcanean facet on the plantar surface of the
talus. Anterior to this facet the bone is deeply excavated, forming a fossa from
FOB CUBOID
FOE CUBOID
Surface for
attachment
Ian tar
calcaneo-
cuboid
ligament
/ofp:
S o.alci
SUSTENTA-
CULUM
TALI
GROOVE FOR
FLEXOR
HALLUCIS
LONOUS
Surface for
attachment
of long
plantar liga-
ment
MEDIAL
PROCESS
FIG. 259. THE RIGHT CALCANEUS.
TUBEROSITY
B
A. Seen from above ; B. Seen from below.
which a groove (sulcus calcanei) leads backwards and medially around the antero-
medial border of the articular surface. When the calcaneus is placed in contact
with the talus, this groove coincides with the sulcus on the plantar surface of
the talus, and so forms a canal or tunnel (sinus tarsi) in which the strong
interosseous ligament which unites the two bones is lodged. To the front and
medial side of this groove there is an elongated articular facet directed obliquely
from behind forwards and laterally, and concave in the direction of its long axis.
This is frequently divided into two smaller oval areas by an intermediate non-
articular surface. Of these facets the posterior (facies articularis media) articulates
with the middle calcanean facet on the plantar surface of the talus, whilst the
anterior (facies articularis anterior) supports the plantar surface of the head of the
talus (facies articularis calcanei anterior). The lateral side of the anterior extremity
of the dorsal surface of the bone is rough, and to this is attached the origin of
the short extensor muscle of the toes.
The plantar surface of the bone is slightly concave from before backwards, and
convex from side to side. The plantar aspect of the tuberosity is provided with two
tubercles, a medial (processus medialis tuberis calcanei) and a lateral (processus laterahs
tuberis calcanei), of which the former is the larger. From the medial process the short
flexor of the toes and the abductor hallucis muscle arise, whilst from both tubercles
260
OSTEOLOGY.
POST.
MID.
SULCUS
CALCANEI
TROCHLEAR PROCESS
LATERAL PROCESS
spring the fibres of origin of the abductor digiti quinti muscle. On the anterior part
of the plantar surface there is an elevated elongated tubercle, which terminates
somewhat abruptly just behind the anterior border of this aspect of the bone, giving
rise at times to a notch. From the tubercle spring the fibres of the long plantar
ligament, whilst the notch serves for the attachment of the deeper fibres of the
plantar calcaneo-cuboid ligament. The two heads of origin of the quadratus plantse
muscle arise from the bone on either side of the long plantar ligament.-
The medial surface of the calcaneus is crossed obliquely, from above downwards
and forwards, by a broad groove of considerable depth ; along this pass many of
the structures which enter the sole of the foot from the back of the leg. The
groove is overhung in front and
FACETS FOR TALUS above by a projecting bracket-
like process, called the sustenta-
culum tali. The plantar surface
of the sustentaculum is chan-
nelled by a groove in which is
lodged the tendon of the flexor
hallucis longus muscle; whilst
its medial border, to which is
attached a' part of the deltoid
ligament (tibio-calcanean fibres)
of the ankle, is overlain by the
tendon of the flexor digitorum
longus. To the anterior border
of the sustentaculum isattached
the plantar calcaneo-navicular
ligament, and placed on its
dorsal surface is the articular
facet already referred to (facies
articularis media). Posteriorly
the medial surface of the bone
is limited inferiorly by the pro-
jection of the medial process of
the tuber calcanei, and above
by the medial lipped edge of
the tuber osity.
The lateral surface, broad
behind and narrower in front,
is of flattened form. Springing
from it, just below the lateral
end of the sinus tarsi, is the
trochlear process, often in-
distinctly marked. To this
the fibres of the inferior retina-
culum of the peroneal tendons
are attached ; whilst in grooves,
above and below it, pass the
tendons of the peronaeus brevis and longus muscles respectively. To the upper
and posterior part of this surface are attached the fibres of the calcaneo-fibular
ligament of the ankle.
The anterior extremity is furnished with a saddle-shaped surface on its anterior
aspect for articulation with the cuboid. This facet is concave from above down-
wards, and slightly convex from side to side ; its edges are sharply defined, except
medially, and serve for the attachment of ligaments.
The posterior extremity, called- the tuber calcanei (tuberosity), forms the
projection of the heel. Of oval form and rounded surface, it rests upon the two
processes or tubercles inferiorly and is divisible into three areas. Of these the highest
is smooth and crescentic, and is covered by a bursa ; the intermediate is also fairly
smooth, and is defined inferiorly by an irregular line, sometimes a definite ridge,
ANT.
FACETS FOR TALUS
MID.
POST.
SUSTENTACULUM
TALI
LATERAL PROCESS
D
MEDIAL PROCESS
FIG. 260. THE RIGHT CALCANEUS. C. Seen from the lateral
side ; D. Seen from the medial side.
THE CUNEIFORM BONES.
261
FOR SECOND CUNEIFORM
the edges of which are striated. Into this surface the tendo calcaneus is inserted.
The lowest surface is rough and striated, and is confluent below with the medial
and lateral processes; this is overlain by the dense layer of tissue which forms
the pad of the heel.
Os Naviculare Peclis.
The navicular bone (O.T. scaphoid), of compressed piriform shape, is placed on
the medial side of the foot, between the head of the talus posteriorly and the
three cuneiform bones anteriorly. The bone derives its name from the oval or
boat-shaped hollow on its posterior surface, which rests upon the head of the
talus. Its anterior aspect is furnished with a semilunar articular area, which is sub-
divided by two faint ridges into three wedge-shaped facets for articulation,
medio-laterally, with the first, second, and third cuneiform bones. The dorsal
surface of the bone,
convex from side to
side, is rough for the
attachment of the liga-
ments on the dorsal
aspect of the foot. On
its plantar aspect the
bone is irregularly con-
cave ; projecting down-
wards and backwards
from its lateral side
there is often a pro-
minent spur of bone,
the plantar process, to
which is attached the
plantar calcaneo-navicular ligament. The lateral surface is narrow from before
backwards, and rounded from above downwards. In 70 per cent, of cases (Manners
Smith) it is provided with a facet which rests upon a corresponding area on
the cuboid. Behind this, in rare instances, there is a facet for the calcaneus. The
medial surface of the bone projects beyond the general line of the medial border
of the foot, so as to form a thick rounded tuberosity (tuberositas ossis navicularis),
the position of which can be easily determined in the living. To the medial and
plantar surface of this process an extensive portion of the tendon of the tibialis
posterior muscle is inserted.
' FOR HEAD OK
PLANTAR PBOCESS TALUS
u PLANTAR PROCESS
O
TUBEROSITY
FIG. 261. THE RIGHT NAVICDLAR BONE.
A. Seen from behind. B. Seen from the front.
The Cuneiform Bones.
The cuneiform bones, three in number, are placed between the navicular
posteriorly and the bases of the first, second, and third metatarsal bones anteriorly,
for which reason they are now named the first, second, and third cuneiforms
(O.T. internal, middle, and external). More or less wedge-shaped, as their name
implies, the first is the largest, whilst the second is the smallest of the group.
Combined, they form a compact mass, the posterior surface of which, fairly regular
in outline, rests on the anterior surface of the navicular ; whilst anteriorly they
form a base of support for the medial three metatarsals, the outline of which is
irregular, owing to the base of the second metatarsal bone being recessed between
the first and third cuneiforms, as it articulates with the anterior surface of the
shorter second cuneiform.
The first cuneiform bone, the largest of the three, lies on the medial border
of the foot between the base of the metatarsal bone of the great toe anteriorly,
and the medial part of the anterior surface of the navicular posteriorly. In form
the bone is less characteristically wedge-shaped than its fellows of the same
name and differs from them in this respect, that whilst the second and third
cuneiforms are so disposed that the bases of their wedges are directed upwards
towards the dorsum of the foot, the first cuneiform is so placed that its base is
262
OSTEOLOGY.
III. METATARSAL
SECOND CUNEIFORM
directed towards the plantar aspect ; further, the vertical diameter of the bone is not
the same throughout, but is much increased at its anterior or metatarsal end. The
ii. METATARSAL dorsal and medial surfaces are confluent, and
. METATARSAL form a convexity from above downwards, which
is most pronounced inferiorly, where it is turned
round the plantar side of the foot to become con-
tinuous with the plantar or inferior aspect, which
is rough and irregular. On the anterior part of
the medial aspect of the bone there is usually a
distinct oval impression, which indicates the
surface of insertion of a portion of the tendon
of the tibialis anterior muscle. Elsewhere this
surface is rough .for ligamentous attachments.
The lateral surface of the bone, quadrilateral in
FIG. 262. ANTERIOR SURFACES OF THE shape, is directed towards the second cunei-
THREE CUNEIFORM BONES OF THE form; but as it exceeds it in length, it also
RIGHT FOOT. comes in contact with the medial side of the
base of the second metatarsal bone. Kunning along the posterior and dorsal
edges of this area is an n-shaped articular surface, the anterior and dorsal part of
which is for the base of the second metatarsal bone, the remainder articulating
with the medial
side of the second
cuneiform. The
non-articular part
of this aspect of
the bone is rough
for the attachment
of the strong inter-
osseous ligaments
which bind it to
the second cunei-
form and second
metatarsal bones.
The posterior sur-
face of the bone
is provided with a piriform facet which fits on the most medial articular area of
the navicular. Here the wedge-shaped form of the bone is best displayed.
Anteriorly the vertical diameter of the bone is much increased, and the facet for the
base of the metatarsal bone of the great
THIRD CUNEIFORM toe is consequent i v much larger than
that for the navicular. This metatarsal
facet is usually of semilunar form, but not
infrequently is more reniform in shape,
and may in some cases display complete
separation into two oval portions.
The second cuneiform is of a typical j
wedge shape, the base of the wedge being
ii. METATARSAL dj rec t e d towards the dorsum of the foot ;
FIG. 265. THE RIGHT FIG. 266. THE RIGHT shorter than the others, it lies between
SE r c ND CUNEIFORM SECOND CUNEIFORM th articulating with the base of thef
(Medial Side). (Lateral Side). & , . -
second metatarsal in front, and the
middle facet on the anterior surface of the navicular behind. Its dorsal
surface, which corresponds to the base of the wedge, conforms to the round-
ness of the instep, and is slightly convex from side to side, affording attachments
for the dorsal ligaments. Its plantar aspect is narrow and rough, forming the edge
of the wedge ; with this the plantar ligaments are connected. The medial surface,
quadrilateral in outline, is furnished with an r-shaped articular area along its
posterior and dorsal borders in correspondence with the similar area on the latera,
side of the first cuneiform. The rest of this aspect is rough for ligaments
IMPRESSION
FOR TENDON
OF TIBIALI
ANTERIOR
FIG. 263. THE RIGHT FIRST
CUNEIFORM (Medial Side).
FIG. 264. THE RIGHT FIRST
CUNEIFORM (Lateral Side).
II. FIRST
METATARSAL CUNEIFORM
THE CUBOID BONE. 263
The lateral surface displays a facet arranged along its posterior border, and usually
somewhat constricted in the middle ; this is for the third cuneiform. In front of
this the bone is rough for the interosseous ligaments which bind the two bones
together. The posterior surface is provided with a triangular facet slightly concave
from above downwards ; this rests on the intermediate articular surface on the
anterior aspect of the navicular. In front the bone articulates by means of a
wedge-shaped facet with the SECOND CUNEIFORM CUBOID IV METATARSAL
base of the metatarsal bone
of the second toe.
The third cuneiform,
intermediate in size between
the first and second, is also
of a fairly typical wedge
shape ; though its antero-
posterior axis is not straight
but bent, so that the anterior
P' i i FIG. 267. RIGHT THIRD FIG. 268. RIGHT THIRD
CUNEIFORM (Medial Side). CUNEIFORM (Lateral Side).
slightly medially. Its dorsal
surface, which corresponds to the base of the wedge, is slightly convex from
side to side, and provides attachments for the dorsal ligaments. Its inferior
or plantar aspect forms a rough blunt edge, and serves for the attachment of
the plantar ligaments. Its medial surface, of quadrilateral form, displays two narrow
articular strips, placed along its anterior and posterior borders respectively, each
somewhat constricted in the middle. The anterior facet articulates with the lateral
surface of the base of the second metatarsal bone, the posterior with the lateral
surface of the second cuneiform. The rough non-articular surface, which separates
the two elongated facets, serves for the attachment of ligaments. The lateral
aspect of the bone is characterised by a large circular or oval facet, placed near
its posterior border, for articulation with the cuboid ; in front of this the anterior
border is lipped above by a small semi-oval facet for articulation with the media]
side of the base of the fourth metatarsal. The rest of the bone around and
between these facets is rough for ligaments. Posteriorly the bone is furnished with
a blunt, wedge-shaped facet for articulation with the corresponding area on the
anterior surface of the navicular. Below this the surface is narrow and rough for the
attachment of ligaments. The anterior surface of the bone articulates with the
base of the third metatarsal by an area of triangular shape
Os Cuboideum.
The cuboid lies on the lateral side of the foot, about its middle, articulating
with the calcaneus posteriorly and the fourth and fifth metatarsal bones anteriorly.
Its dorsal surface, plane in an antero-posterior direction, is slightly rounded from
I side to side, and provides attachment for ligaments. Its plantar aspect is tra-
versed obliquely from the lateral side medially and forwards by a thick and prominent
: ridge, the lateral extremity of which, at the point where it is confluent with the
lateral surface, forms a prominent tubercle (tuberositas ossis cuboidei), the anterior
and lateral surface of which is smooth and facetted to allow of the play of
a sesamoid bone which is frequently developed in the tendon of the peronseus
i longus muscle. Anterior to this ridge there is a groove (sulcus peronsei) in which
the tendon of the peronseus longus muscle is lodged as it passes across the plantar
surface of the bone. Behind the ridge the bone is rough, and serves for the
attachment of the plantar calcaneo-cuboid ligament, the superficial fibres of which
: pass forwards and are attached to the summit of the ridge. The lateral aspect of
the bone is short and rounded, and is formed by the confluence of the dorsal and
plantar surfaces : it is more or less notched by the peroneal groove which turns round
its plantar edge. The medial surface of the bone is the most extensive ; it is easily
recognisable on account of the presence of a rounded or oval facet situated near
264
OSTEOLOGY.
TUBEROSITY
GROOVE FOR PERON^US
LONG US
A
GROOVE FOR TUBEROSITY
PERON.EUS LONGUS
B
its middle and close to its dorsal border. This is for articulation with the lateral
side of the third cuneiform ; anterior and posterior to this the surface is rough for
ligaments. Not infrequently, behind the facet for the third cuneiform, there is
NAVICULAR a small articular
THIRD CUNEIFORM (occasional) surface for the
navicular, as is the
case normally in
the gorilla, whilst
posteriorly and on
the plantar aspect
the projecting in-
ferior angle is
sometimes pro-
vided with a facet
on which the head
of the talus rests.
(Sutton, " Proc.
Anat. Soc./' Journ. Anat. and Physiol. vol. xxvi. p. 18.) The anterior surface is oval or
conical in outline ; sloping obliquely from the medial side laterally and backwards,
it is divided about its middle by a slight vertical ridge into two parts, the medial of
which articulates with the base of the fourth metatarsal bone, the lateral with that
of the fifth. The posterior surface, also articular, has a semilunar outline, the convex
margin of which corresponds to the dorsal roundness of the bone. The inferior
lateral angle corresponds to the tubercle on the lateral border of the bone, whilst
the inferior medial angle forms a pointed projection which is sometimes called
the calcanean process. This surface articulates with the calcaneus by means of a
saddle-shaped facet, which is convex from side to side, and concave from dorsal
to plantar margins.
The tarsus as a whole may be conveniently described as arranged in two
FIG. 269. THE RIGHT CUBOID BONE.
A. Lateral Side. B. Medial Side.
FIG. 270. RADIOGRAPHS OF THE Ff the bone impart an elasticity to it, which is of much service in reducing the effects of the
hocks to which it is so frequently subjected.
The Scapula. For so light and thin a bone, the scapula possesses a remarkable rigidity. This
.3 owing to the arrangement of its parts. Stout and thick where it supports the glenoid cavity
. 272 OSTEOLOGY.
and coracoid process, the rest of the bone is thin, except along the axillary margin ; but strength is
imparted to the body by the manner in which the spine is fused at right angles to its dorsal surface.
The Humerus. The body consists of a layer of compact bone surrounding a long medullary
cavity. The outer shell, thickest in the distal third of the bone, gradually thins until it reaches
the proximal epiphysial line, where it forms a layer no thicker than stout paper. Distally
the external shell is thicker and stouter than it is proximally, until it reaches the epicondyles,
distal to which the articular surfaces are formed of a layer of compact spongy bone. The proximal
end of the medullary cavity is surrounded by loose spongy tissue, the fibres of which arch inwards
from the inner surface of the compact outer layer, whilst at the distal end the spongy tissue
which springs from the outer shell sweeps distally in a radiating fashion on either side
of the olecranon fossa towards the epicondyles. Proximal to the olecranon fossa there is a
number of laminae of dense bone which arch across from one side to the other, the con-
vexity of the arches being directed distally. The proximal epiphysis, formed of spongy
bone, is united to the body by a wavy line, concave laterally and convex medially, leading
from the base of the greater tuberosity on the lateral side to the distal articular edge on the medial
side. The mass above this includes the head and the two tubercles. The spongy tissue of the
head is fine, and is arranged generally in lines radial to its surface ; that of the greater tubercle
is more open, and often displays large spaces towards its interior, which in old bones communi-
cate freely with the medullary cavity of the body. The general direction of the fibres is
parallel to the lateral surface of the tuberosity. The distal articular end is formed of fine spongy
tissue, more compact towards the surface, and arranged in lines more or less at right angles to its
articular planes. In the adult the principal nutrient canal, viz., that which opens on the
surface near the insertion of the coraco-brachialis, traverses the outer compact wall of the body
obliquely distally for a distance of two and a quarter inches before it opens into the
medullary cavity.
The Ulna. The weakest parts of the bone are the constricted portion of the semilunar
notch, and the body in its distal third, the bone being most liable to fracture at these
points. On section the medullary cavity is seen to extend proximally as high as the base of the
coronoid process ; distally it reaches the proximal end of the distal fifth of the bone. The walls of
the body, which are formed of dense bone, are much thicker on the dorsal surface than on the
volar. Proximally they are continuous with the volar surface of the coronoid process and the
dorsal surface of the olecranon, where they are composed of layers of looser texture, which, however,
gradually become thinner as the points of these processes are reached. Distally they gradually
taper until the head and styloid process are reached, round which they form a thin shell, con-
siderably thickened, however, in the region of the groove for the extensor carpi ulnaris muscle.
The bulk of the proximal extremity is formed of loose spongy bone, arranged in a series of arcades,
stretching from the interior to the dorsal wall over the proximal end of the medullary canal.
Proximal to the constricted part of the semilunar notch the bone displays a different structure ;
here it is formed of spongy bone, of closer texture, arranged generally in lines radiating from the
articular surface. At the point of constriction of the semilunar notch the layer immediately
subjacent is much denser and more compact.
The distal fifth of the bone is formed of loose spongy bone, the fibres of which have a general
longitudinal arrangement ; towards its extremity the meshes become smaller.
The Radius. The neck is the narrowest part of the bone ; here fracture may occur, though
not commonly. The point at which the bone is usually broken is about one inch proximal to the
distal extremity. This is accounted for by the fact that the radius supports the hand at the
radio-carpal articulation, and 'the shocks to which the latter is subjected, as in endeavouring to
save oneself from falling, are naturally transmitted to the radius. On section, the medullary
cavity is seen to extend to the neck ; distally, it reaches to the level of the distal fifth of
the bone. Its walls are thick as compared with the diameters of the bone, particularly along the
interosseous border, thus imparting rigidity to the curve of the body ; these walls thin out
proximally and distally. Proximally, the surface of the tuberosity is formed of a thin shell of
bone, which, however, thickens again where it passes on to the neck. The proximal extremity
is formed of spongy bone arranged in the form of arcades, reaching distal to the level of the
tuberosity medially, but not extending distal to the level of the neck laterally. Beneath the
capitular articular surface there is a dense layer, thickest in the centre, and thinning towards
the circumference ; this is overlain by a very thin layer of less compact bone.
The distal fifth of the body and distal extremity are formed of loose spongy bone
arranged more or less longitudinally. Immediately subjacent to the carpal articular surface
the tissue is more compact, and displays a striation parallel to the articular plane. The nutrient
canal of the shaft pierces the volar wall of the proximal part of the medullary cavity obliquely :
running proximally for half an inch.
The Carpus. The bones are formed of fairly compact spongy tissue, surrounded by a thin
shell of denser bone. They are very vascular, and their non-articular surfaces are pierced bj
many foramina.
The Metacarpus. Similar in arrangement to that of long bones generally, though it ma)
be noted that the compact walls of the body are thicker in proportion to the length of the bon<
than in the other long bones of the upper extremity.
The Phalanges. Each phalanx has a medullary cavity, the walls of the body being formed o
dense compact bone, especially thick along the dorsal aspect. The extremities are made up o
spongy bone within a 'thin dense shell.
ARCHITECTURE OF THE BONES OF THE SKELETON. 273
The Hip Bone. As a flat bone the os coxae consists of spongy tissue between two com-
pact external layers. These, latter vary much in thickness, being exceptionally stout along
the ilio-pectmeal line and
the floor of the iliac fossa
immediately above it.
The gluteal aspect of the
ilium is also formed by
a layer of considerable
thickness. The spongy
tissue is loose and cellular
in the thick part of the
ilium and in the body
of the ischium ; absent
where the floor of the
iliac fossa is formed by
the coalescence of the
thin dense confining
layers ; fine grained and
more compact in the
tuberosity of the ischium,
the iliac crest, and the
floor of the acetabulum,
in which latter situation
it is striated by fibres
which are directed radi-
ally to the surface
again being crossed at
TROCHANTERIC FOSSA
POSTERIOR SURFACE
OF NECK
Base of trochanter minor
cut through
GREATER
TROCHANTER
Interior of tro-
chanter major
containing loose
spongy tissue
(scraped away)
Compact tissue
with dense core
forming the
calcar femorale
Space containing loose spongy
tissue (scraped away) between the
calcar and the base of the tro-
chanter minor
POSTERIOR SURFACE
OF NECK
of that hollow, these
right angles by others
which are arranged circumferentially. This spongy
tissue forms a more compact layer over the surface
of the upper and posterior portion of the acetabular
articular area. The bottom of the floor of the acetab-
ulum varies in thickness ; in most cases it is thin,
and in exceptional instances the bone is here deficient.
The same condition has been met with in the iliac
FIG. 278. DISSECTION SHOWING THE CALCAR
FEMORALE.
A slice of bone has been removed from the pos-
terior aspect of the proximal part of the shaft
of the femur, passing through the trochanter
major superiorly and the trochanter minor
inferiorly and to the medial side. The
loose spongy tissue has been scraped away,
leaving the more compact tissue with the
dense core forming the calcar femorale. By
a similar dissection from the front the an-
terior surface of the calcar may be exposed.
ANTERIOR fossa, where absorption of the thin bony plate
has taken place.
The Femur. The body has a medullary
cavity which reaches the root of the lesser
trochanter proximally. Distally it extends to
within 3^ inches of the distal articular surface.
In. the proximal half the outer compact wall is
very thick, but distal to the middle of the body
it gradually thins until it reaches the condyles,
over which it passes as a thin, hardly definable
external layer. Proximally, it is especially
thick along the line of the linea aspera, and
here the large nutrient canal may be seen pass-
ing obliquely towards the proximal end in the
substance of the dense bone for the space of two
inches. In the proximal end of the body the
osseous lamellae springing from the sides of
the medullary cavity arch inwards towards the
centre, intersecting each other in a manner
comparable to the tracery of a Gothic window.
The lower wall of the neck is thick distally, near
the trochanter minor, but thins rapidly before
it reaches the head. From this aspect of the neck there spring a series of oblique lamellae
which pass proximally and upwards, spreading in fan-shaped manner into the under surface of
the head. These are intersected above by lamellae which arch medially from the lateral side of the
CALCAR FEMORALE
TROCHANTER
MINOR
FIG, 279. SECTION THROUGH HEAD AND NECK OF
FEMUR TO SHOW CALCAR FEMORALE.
274 OSTEOLOGY.
shaft distal to the greater trochanter, as well as from the inner surface of the thin but compact
outer shell of the upper surface of the neck, the whole forming a bracket-like arrangement which
assists materially in adding to the strength of the neck. Further support is afforded by the
addition of a vertical layer of more compact bone within the spongy tissue of the neck.
Distally, as may be seen in Fig. 278, this is. continuous with the dense posterior wall of the body
below ; whilst proximally it sweeps up beneath the lesser trochanter, from which it is separated
by a quantity of loose spongy tissue, to fuse proximally with the posterior dense wall of the
neck above and medial to the intertrochanteric crest. It may be regarded as a continuation
proximally of the posterior wall of the body beneath the trochanteric epiphysis. When
studied in section (see Fig. 279), the central dense core of this partition exhibits a spur-like
appearance : hence the name calcar femorale applied to it. It is of surgical importance in cases
of fracture of the neck of the femur. (R. Thompson, Journ. Anat. and PhysioL, vol. xlii. p. 60.)
From it, stout lamellae having a vertical direction arise. The spongy tissue of the head and
greater trochanter is finely reticulated, that of the distal part of the neck and proximal part of
the shaft being more open in its texture. Passing vertically through this tissue there is a
vascular canal, the orifice of which opens externally on the floor of the trochanteric fossa.
The spongy tissue of the distal part of the body is more delicate and uniform in its
arrangement, displaying a more or less parallel striation in a longitudinal direction. Subjacent
to the articular surface the tissue is rendered more compact by the addition of lamellae disposed
in curves in harmony with the external aspect of the bone.
The Patella. The bone consists of a thick dense layer anteriorly, which thins towards the
edges on either side and distally ; proximally, it corresponds to the area of insertion of the quadriceps.
The femoral articular surface is composed of a layer of compact bone, thickest in correspondence
with the vertical elevation. Sandwiched between these two layers is a varying thickness of
spongy tissue of fairly close grain, the striation of which on cross section runs in parallel lines
from back to front ; on vertical section the tissue appears to be arranged in lines passing radially
from the deep surface of the femoral area to the more extensive anterior dense plate.
The Tibia. The body of the bone is remarkable for the thickness and density of the
osseous tissue which underlies the anterior crest. The posterior wall is stout, but the medial and
lateral walls are thinner. The several walls are thickest opposite the middle of the body, and
thin out proximally and distally where the body unites with the epiphyses. The medullary
cavity, narrow and circular in the middle of the bone, increases in all its diameters proximally and
distally, and reaches to within 2^ to 3 inches of either extremity. Proximally the arrangement
of the lamellae of the spongy tissue resembles a series of arches springing from the dense outer
walls. These form a platform on which the proximal epiphysis rests, the spongy tissue of which
displays a more or less vertical striation. This is much more compact under the condylic
surfaces, the superficial aspect of which is formed by a thin layer of dense bone. The intercon-
dyloid eminence and the tuberosity are also formed of compact tissue, whilst the circumference of
the condyles is covered by a thinner and less dense wall. In the distal end of the body the spongy
tissue, of a loose and' cellular character, is arranged in vertical fibres, blending with the closer
tissue of the distal epiphysis, the articular surface of which is covered by a thin but dense layer.
In the adult bone the nutrient canal for the body is embedded in the dense posterior wall for
the space of two inches.
The Fibula. A medullary cavity runs throughout the length of the body, reaching the
neck proximally, and extending to a point about 2^ inches from the distal extremity of the
lateral malleolus. The lateral wall of the body is usually considerably thicker than the medial.
The head is formed of loose spongy bone, enclosed within a very thin dense envelope. The
spongy tissue of the distal extremity is more compact, and acquires considerable density on the
surfaces underlying the articular area and the pit behind it. The canal for the nutrient artery of
the body opens into the medullary cavity about an inch distal to its external aperture.
The Bones of the Foot. A longitudinal section through the articulated bones of the foot
reveals the fact that the structure of the spongy substance of each individual bone is determined
by the stress to which it is habitually subjected. In this connexion it is necessary to refer to the
arched arrangement of the bones of the foot, a subject which is also treated in the section which
deals with the Joints. The summit of the arch is formed by the talus, on which rests the tibia.
Subjected as the talus is to a crushing strain, it is obvious that this load must be distributed
throughout the arch, of which the calcaneus is the posterior pillar, whilst the heads of the meta-
tarsal bones constitute the anterior pillar. It is found, consequently, that the lamellae of the
spongy tissue of the talus are arranged in two directions, which intercross and terminate
below the dorsal articular surface. Of these fibres, some sweep backwards and downwards
towards the posterior calcanean facet, beyond which they are carried in the substance of the cal-
caneus in a curved and wavy manner in the direction of the heel, where they terminate ; whilst
others, curving downwards and forwards from the trochlea of the talus, pass through the
neck to reach the articular surface of the head, through which in like manner they may be
regarded as passing onwards through the several bones which constitute the anterior part of the
arch, thus accounting for the longitudinal striation as displayed in the structure of the navi-
cular, cuneiform, and metatarsal bones. In the calcaneus, in addition to the foregoing arrange-
ment, another set of curving fibres sweep from back to front of the bone beneath the more com-
pact tissue which forms its under shell. These are obviously of advantage to prevent the spread
of the bone when subjected to the crushing strain. In the sustentaculum tali a bracket-like
VAKIATIONS IN THE SKELETON. 275
arrangement of fibres is evident, and the plantar surface of the neck of the talus is further
strengthened by lamellae arranged vertically.
In the separate bones the investing envelope is thin, though under the articular surfaces
there is a greater density, due to the accession of lamellae lying parallel to the articular planes.
The stoutest bony tissue in the talus is met with in the region of the plantar surface of the
neck, whilst in the calcaneus the greatest density occurs along the floor of the sinus tarsi.
The Metatarsus. In structure and the arrangement of their lamellae the metatarsal bones
agree with the metacarpus.
The Phalanges. In their general structure they resemble the bones of the fingers.
APPENDIX B.
VARIATIONS IN THE SKELETON.
Cervical Vertebrae. Szawlowski records the presence of an independent rib element in the
transverse process of the fourth cervical Vertebra. (Anat. Anz. Jena, vol. xx. p. 306.)
Atlas. The foramen transversarium is often deficient in front. Imperfect ossification occa-
sionally leads to the anterior arch, and more frequently the posterior arch, being incomplete. The
superior articular surfaces are occasionally partially or completely divided into anterior and
posterior portions. In some instances the extremity of the transverse process has two tubercles.
The transverse process may, in. rare cases, articulate with a projecting process (paroccipital or
paramastoid) from the under surface of the jugular process of the occipital bone (see p. 278). An
upward extension from the medial part of the anterior arch, due probably to an ossification of
the anterior occipito-atlantal ligament, may articulate with the anterior surface of the summit of
the dens of the epistropheus. Allen has noticed the articulation of the superior border of the
posterior arch with the posterior border of the foramen magnum. Cases of partial or complete
fusion of the atlas with the occipital bone are not uncommon (see p. 278).
Epistropheus. In some instances the summit of the dens articulates with a prominent
tubercle on the anterior border of the foramen magnum (third occipital condyle, see p. 278).
Bennett (Trans. Path. Soc. Dublin, vol. vii.) records a case in which the dens was double,
due to the persistence of the primitive condition in which it is developed from two centres,
Occasionally the dens fails to be united with the body of the epistropheus, forming an os
odontoideum comparable to that met with in the crocodilia. (Giacomini, Romiti, and Turner.)
The foramen transversarium is not infrequently incomplete, owing to the imperfect ossification
of the posterior root of the transverse process. Elliot Smith has recorded a case in which there
was fusion between the atlas and epistropheus without any evidence of disease.
Seventh Cervical Vertebra. The foramen transversarium may be absent on one or other
side.
Thoracic Vertebrae. Barclay Smith (Journ. Anat. and Physiol. Lond. 1902, p. 372) records
five cases in which the superior articular processes of the twelfth thoracic vertebra displayed
thoracic and lumbar characteristics on opposite sides. Duckworth (Journ. of Anat. and Physiol.
vol. xlv. p. 65) has described a first thoracic vertebra, in which a bony process, arising from the
front of the root of the transverse process, curves forwards and medially so as almost to enclose a
foramen like that of the cervical vertebrae. The ventral surface of this process articulates with
the neck of the first rib.
Lumbar Vertebrae. The mamillary and accessory processes are sometimes unduly de-
veloped. The vertebral arch of the fifth lumbar vertebra is occasionally interrupted on either
side by a synchondrosis which runs between the upper and lower articular processes. In
macerated specimens the two parts of the bone are thus separate and independent. The
anterior includes the body, together with the roots of the vertebral arches and. the transverse
and superior articular processes ; the posterior comprises the inferior articular processes, the
laminae, and the spine. (Turner, Challenger Reports, vol. xvi.) Fawcett has seen the same con-
dition in the fourth lumbar vertebra. Szawlowski and Dwight record instances of the occurrence
of a foramen in the transverse process of the fifth lumbar vertebra (Anat. Anb. Jena, vol. xx.),
and Ramsay Smith describes a case in which the right transverse process of the fourth lumbar
vertebra of an Australian sprang from the side of the body in front of the root of the vertebral
arch, being unconnected either with the arch or articular process.
Sacrum. The number of sacral segments may be increased to six or reduced to four (see
p. 276). Transition forms are occasionally met with in which the first sacral segment displays
on one side purely sacral characters, i.e. it articulates with the hip bone, whilst on the
opposite side it may present all the features of a lumbar vertebra. Through deficiency in the
development of the laminae, the sacral canal may be exposed throughout its entire length, or
to a greater extent than is normally the case. (Paterson, Roy. Dublin Soc. Scientific Trans.
vol. v. Series II.) Szawlowski and Barclay Smith record the occurrence of a foramen in the
lateral part of the first sacral vertebra. (Journ. of Anat. and Physiol. Lond. voL xxxvi. p. 372.)
Vertebral Column as a Whole. Increase in the number of vertebral segments is usually
276 OSTEOLOGY.
due to differences in the number of the coccygeal vertebrae ; these may vary from four
which may be regarded as the normal number to six. The number of presacral or movable
vertebrae is normally 24 (7 C, 12 Th, and 5 L) ; in which case the 25th vertebra forms the
first sacral segment (vertebra fulcralis of Welcker). The number of presacral vertebrae may
be increased by the intercalation of a segment either in the thoracic or lumbar region without
any alteration in the number of the sacral or coccygeal elements : thus we may have 7 C, 13 Th,
and 5 L, or 7 C, 12 Th, and 6 L, or it may be reduced by the disappearance of a vertebral segment
thus, 7 C, 12 Th, and 4 L. Such an arrangement presupposes developmental errors either
of excess or default in the segmentation of the column. On the other hand, the total number of
vertebral segments remaining the same (24 or 25), we may have variations in the number of those
assigned to different regions due to the addition of a vertebral segment to one, and its consequent
subtraction from another region. Thus, in the 24 presacral vertebrae, in cases of the occurrence of
cervical ribs the formula is rearranged thus 6 C, 13 Th, and 5 L, or, in the case of a lumbar
rib being present, the formula would be 7 C, 13 Th, 4 L, as happens normally in the gorilla and
chimpanzee. Similarly, the number of the presacral vertebrae (24) may be increased by the
withdrawal of a segment from the sacral region 7 C, 12 Th, 6 L, and 4 S or diminished by an
increase in the number of the sacral vertebrae, as in the formula 7 C, 12 Th, 4 L, and 6 S. .In-
crease in the number of sacral segments may be due to fusion with a lumbar vertebra, or by the
addition of a coccygeal element : the latter is more frequently the case. This variability in the
constitution of the sacrum is necessarily correlated with a shifting tailwards and headwards of
the pelvic girdle along the vertebral column. Rosenburg considers that the 26th, 27th, and 28th
vertebrae are the primitive sacral segments, and that the sacral characters of the 25th vertebrae
(the first sacral segment in the normal adult column) are only secondarily acquired. He thus
supposes that during development there is a Ijeadward shifting of the sacrum and pelvic girdle,
with a consequent reduction in the length of the presacral portion of the column. This view is
opposed by Paterson (Roy. Dublin Soc. Scientific Trans, vol. v. Ser. II.), who found that ossification
took place in the alae of the 25th vertebra (first adult sacral segment) before it made its appear-
ance in the alae of the 26th vertebra. He thus assumes that the alae of the 25th vertebra may
be regarded as the main and primary attachment with the ilium. His conclusions, based on a
large number of observations, are at variance with Rosenburg's views, for, according to his opinion,
liberation of the first sacral segment is more common than assimilation with the fifth lumbar
vertebra, and assimilation of the first coccygeal vertebra with the sacrum is more common than
liberation of the fifth sacral, thus leading to the inference that the sacrum tends to shift tail-
wards more often than headwards. Dwight (Anat. Anz. Jena, vol. xxviii. p. 33), after a study of
this question, whilst admitting that some of these variations may be reversive, denies that there
is any evidence that they are progressive, and further states that after the occurrence of the
original error in development, there is a tendency for the vertebral column to assume as nearly
as possible its normal disposition and proportions.
Sternum. The sternum is liable to considerable individual variations affecting its length
and direction. The majority of bones are asymmetrical, displaying irregularities in the levels of
the clavicular facets. The higher costal facets may be closer together on one, usually the right
side, than the other, whilst the synchondrosis sternalis is often oblique, sloping somewhat to the
right. According to Birmingham, these are the result of the strain thrown on the shoulder by
pressure either directly applied or through the pull of a weight carried in the hand.
Sometimes the sternum articulates with eight rib cartilages. This may happen on one or
both sides, but when unilateral, much more frequently on the right side a condition by some
associated with right-handedness. It is, however, more probably a persistence of the primitive
condition of the cartilaginous sternum, in which each half is connected with the anterior
extremities of the first eight costal arches. In some rare cases only six pairs of ribs articulate
by means of their costal cartilages with the sternum. Recently Lickley has brought forward
evidence to show that the seventh rib is undergoing regressive changes. (Anat. Anz. vol. xxiv.
p. 326.)
Occasionally the presternum supports the first three ribs ; in other words, the manubrium
has absorbed the highest segment of the body. Keith has pointed out that this is the condition
most commonly met with in the gibbon, and regards its occurrence in man as a reversion to the
simian type. As far as is at present known, its occurrence seems more common in the lower
races. Through errors of development the sternum may be fissured throughout, due to failure
of fusion of the cartilaginous hemisterna. The two ossified halves are usually widely separated
above, but united together below by an arthrodial joint. The heart and pericardium are thus
uncovered by the bone. Occasionally this condition is associated with ectopia cordis, under
which circumstances life is rendered impossible. Through defects in ossification the body of the
sternum may be pierced by a hole, usually in its lower part, or through failure of fusion of the
collateral centres one or more of the segments of the body may be divided longitudinally.
Sometimes small ossicles are found in the ligaments of the sterno-clavicular articulation.
These are the so-called episternal bones, 'the morphological significance of which, however, has
not yet been satisfactorily determined. They are by some regarded as the homologues of the
interclavicle or episternal bone of monotremata, whilst by others they are considered to represent
persistent and detached portions of the pre-coracoids.
Ribs. The number of ribs may be increased or diminished. Increase may occur by the addition
of a cervical rib due to the independent development of the costal element in the transverse
process of the seventh cervical vertebra. This may happen on one or both sides. The range of
development of these cervical ribs varies ; they may unite in front with the sternum, or they may
VARIATIONS IN THE SKELETON.
be fused anteriorly with the cartilage of the first rib, or the cervical rib may be free. It may
in some instances be represented mainly by a ligamentous band, or its vertebral and sternal
ends may be alone developed, the intermediate part being fibrous. At times the vertebral end
only may be formed, and may be fused with the first rib, thus leading to the formation of a
bicipital rib such as occurs in many cetaceans. (For a detailed account of this anomaly see Wingate
Tod's paper in the Journ. o/ Anat. and Physiol vol. xlvi. pp. 244-288.) Increase in the number of ribs
may also be due to the ossification of the costal element which is normally present in the embryo
in connexion with the first lumbar vertebra. (Rosenberg, Morph. Jahrb. i.) Reduction in the
number of ribs is less common. The twelfth rib rarely aborts ; in some cases the first rib is
rudimentary. Cases of congenital absence of some of the ribs have been recorded by Hutchinson,
Murray, and Ludeke. Fusion of adjacent ribs may occur. (Lane, Guy's Hosp. Reports, 1883.)
In this way, too, the occurrence of a bicipital rib is explained. This anomaly occurs most
usually in connexion with the first rib, which either fuses with a cervical rib above or with the
second rib below.
Variations in form may be in great part due to the occupation of. the individual and the con-
stricting influence of corsets. Independently of these influences, the ventral part of the body is
sometimes cleft so as to appear double ; at other times the cleft may be incomplete so as to form
a perforation. Occasionally adjacent ribs are united towards their posterior part by processes
having an intermediate ossicle between (Meckel), thus recalling the condition normally met with
in birds ; more usually, however, the bony projections are not in contact.
The number of true or vertebro-sternal ribs may be reduced to six, or increased to eight (vide
ante, p. 276). Dwight (Journ. of Anat. and Physiol. vol. xlv. p. 438) describes a series of cases in
which the interval between the transverse process of the first thoracic vertebra and the neck of
the first rib is bridged across or converted into a linear cleft by a dorsal extension from the neck
of the rib.
Costal Cartilages. Occasionally a costal cartilage is unduly broad, and may be pierced by a
foramen. The number of costal cartilages connected with the sternum may be reduced to six or
increased to eight (see p. 276). In advanced life there is a tendency towards ossification in the
layers underlying the perichondrium, more particularly in the case of the first rib cartilage, in
which it may be regarded as a more or less normal occurrence.
Frontal Bone. The variation most frequently met with is a persistence of the suture
which unites the two halves of the bone in the infantile condition : skulls displaying this peculiarity
are termed metopic. The researches of various observers Broca, Ranke, Gruber, Manouvrier,
Anoutchine, and Papillault (Rev. mens. de I'ecole d'Anthropol. de Paris, anne"e 6, n. 3) point to the
more frequent occurrence of this metopic suture in the higher than in the lower races of man ; and
Calmette asserts its greater frequence in the brachy cephalic than the dolichocephalic type.
Separate ossicles (ossa suturarum) may occur in the region of the anterior fontanelle. The fusion
of these with one or other half of the frontal explains how the metopic suture is not always in
line with the sagittal suture (Stieda, Anat. Anz. 1897, p. 227) ; they occasionally persist, however,
and form by their coalescence a bregmatic bone. (G. Zoja, Bull. Scientific, xvii. p. 76, Pa via.)
Turner (Challenger Reports, part xxix.) records an instance of direct articulation of the frontal
with the frontal process of the maxilla in a Bush skull, and other examples of the same anomaly,
which obtains normally in the skulls of the chimpanzee and gorilla, have been observed. (Journ.
Anat. and Physiol. vol. xxiv. p. 349.)
There is sometimes a small arterial groove just medial to the supra-orbital notch or foramen,
and occasionally the latter is double, the lateral aperture piercing the orbital margin wide of
its middle point. Frequently the bone corresponding to the floor of the lacrimal fossa displays a
cribriform appearance.
Schwalbe (1901) records the presence of small independent ossicles (supra-nasal bones) in the
anterior part of the metopic suture. The same anatomist has also directed attention (Zeit. f.
Morph. und Anthr. vol. iii. p. 93) to the existence of the metopic fontanelle, first described by
Gerdy, and the occurrence of metopic ossicles (ossa interfrontalia) and canals.
Parietal. A number of cases have been recorded in which the parietal is divided into an
upper and lower part by an antero-posterior suture parallel to the sagittal suture. Corami
(Atti d. XL Congr. Med. Internaz. Roma, 1894, vol. v.) records a case in which the parietal was in-
completely divided into an anterior and posterior part by a vertical suture. A tripartite
condition of the bone has also been observed (Frasetto). The parietal foramina vary greatly
in size, and to some extent in position. They are sometimes absent on one or other side,
or both. They correspond in position to the sagittal fontanelle. Sometimes the ossification
of this fontanelle is incomplete and a small transverse fissure remains. The parietal foramen
represents the patent lateral extremity of this fissure after its edges have coalesced.
Occasionally in the region of the anterior fontanelle an ossicle of variable size may be met witli.
This is the so-called pre-interparietal bone. According to its fusion with adjacent bones
may disturb the direction of the sagittal suture.
Occipital. The torus occipitalis transversus is the term applied to an occasional eleva-
tion of the bone which includes the external occipital protuberance and extends laterally along
the superior curved line. Occasionally an emissary vein pierces the bone opposite the occipital
protuberance. In about 15 per cent, of cases the hypoglossal canal is double. Mu<
three or even four foramina may be met with. The most striking of the many variations to
which this bone is subject is the separation of the upper part of the squamous part
occipital to form an independent bone the interparietal bone, called also, from the
278 OSTEOLOGY.
of its occurrence in Peruvian skulls, the os Incce. By a reference to the account of the ossi-
fication of the bone, the occurrence of this anomaly is explained developmentally. In
place of forming a single bone the interparietal is occasionally met with in two symmetrical
halves, and instances have been recorded of its occurrence in three or even four pieces. In
the latter cases the two anterior parts form the pre-interparietals. Not uncommonly the
internal occipital crest is split and furrowed close to the foramen magnum for the lodgment of
the vermis of the cerebellum, and is hence called the vermiform fossa. Instances are
recorded of the presence of a separate epiphysis between the basi-occipital and the sphenoid,
the os basioticum (Albrecht) or the os pre-basi-occipitale. An oval pit, the fovea bursse or
pharyngeal fossa, is sometimes seen in front of the tuberculum pharyngeum. This marks the
site of the bursa pharyngea. Occasionally the basilar part is pierced by a small venous
canal. The articular surface of the condyles is sometimes divided into an anterior and posterior
part. The so-called third occipital condyle is an outstanding process arising from the anterior
border of the foramen magnum, the extremity of which articulates with the dens of the
epistropheus. Guerri has recorded a case, in which in a fostal skull, there were two projecting
tubercles in the position of the third occipital condyle, independent of the basi-occipital portions
of the condyles. (Anat. Anz. vol. xix. p. 42.) This appears to confirm the view of Macalister
that there are two different structures included under this name one a medial ossification in
the sheath of the notochord, and the second, a lateral, usually paired process, caused by the
deficiency of the medial part of the hypochordal element of the hindmost occipital vertebra,
with thickenings of the lateral parts of the arch. Springing from the under surface of the
extremity of the jugular process, a rough or smooth elevated surface, or else a projecting process,
the extremity of which may articulate with the transverse process of the atlas, is sometimes
met with. This is the paroccipital or paramastoid process. The size and shape of the foramen
magnum varies much in different individuals and races, as also the disposition of its plane.
Elliot Smith has called attention to the asymmetry of the cerebral fossae, which is correlated
with asymmetry of the occipital poles of the cerebral hemispheres. Numerous instances of fusion
of the atlas with the occipital bone have been recorded. Many are, no doubt, pathological in
their origin ; others are associated with errors in development. Interesting anomalies are those
in which there is evidence of the intercalation of a new vertebral element between the atlas and
occipital, constituting what is termed a pro-atlas.
Temporal Bone. The occurrence of a deficiency in the floor of the external acoustic meatus
is not uncommon in the adult. It is met with commonly in the child till about the age of five,
and is due to incomplete ossification of the tympanic plate. The line of the petro-squamosal
"suture is occasionally grooved for the lodgment of a sinus (petro-squamosal) ; sometimes the
posterior end of this is continuous with a canal which pierces the superior border of the bone
and opens into the transverse sinus. Anteriorly the groove may pass into a canal which pierces
the root of the zygoma and appears externally above the lateral extremity of the petro- tympanic
fissure. These are the remains of channels through which the blood passed in the foetal condition
(see ante). Kazzander has recorded a case in which the squamous part of the temporal was
pneumatic, the sinus reaching as high as the parietal and the squamoso - sphenoidal suture.
Symington has described a case in which the squamous part was distinct and separate from
the rest of the temporal bone in an adult; whilst Hyrtl has observed the division of the
squamous part of the temporal into two by a transverse suture. The zygomatic process has been
observed separated from the rest of the bone by a suture close to its root (Adacni). P. P. Laidlaw
(Journ. Anat. and Physiol. vol. xxxvii. p. 364) describes a temporal bone in which there was
absence of the internal acoustic meatus and of the stylo-mastoid foramen. The jugular fossa
also was absent, and there was partial absence of the groove for the transverse sinus, associated with
the presence of a large mastoid foramen. An instance of a rudimentary condition of the carotid
canal is also referred to in the same volume by G. H. K. Macalister.
G. Caribbe (Anat. Anz. vol. xx. p. 81) notes the occurrence in idiots and imbeciles of a more
pronounced form of post-glenoid tubercle, and associates it with regressive changes in the develop-
ment of the temporal bone.
Sphenoid. Through imperfect ossification the foramen spinosum and foramen ovale are
sometimes incomplete posteriorly. Le Double (Bull, et mtm. de la Soc. d'Anth. de Paris, 5 e se"r.
vol. iii. p. 550) records a case in which the foramen rotundum and the superior orbital fissure
were united so as to form a single cleft.
Through deficiency of its lateral wall, the optic foramen, in rare instances, communicates
with the superior orbital fissure. Duplication of the optic foramen is also recorded as a rare
occurrence, the artery passing through one canal, the nerve through the other. Persistence of
the cranio- pharyngeal canal is also occasionally met with. Owing to the ossification of fibrous
bands which frequently connect the several bony points, anomalous foramina are frequently
met with. Of such are the carotico-.clinoid formed by the union of the anterior and middle
clinoid processes, the pterygo-spinous foramen enclosed by the ossification of the ligament con-
necting the angular spine with the lateral pterygoid lamina, and the porus crotaphitico-
buccinatorius similarly developed by the ossification of ligament immediately below and lateral
to the inferior aperture of the foramen ovale.
Ethmoid. The size of the lamina papyracea is liable to considerable variations. In the lower
races it tends to be narrower from above downwards than in the higher, in this respect resem-
bling the condition met with in the anthropoids. The lamina papyracea may fail to articulate
with the lacrimal owing to the union of the frontal with the frontal process of the maxilla
VARIATIONS IN THE SKELETON. 279
in front of it. (Orbito-maxillary-frontal suture. A, Thomson, Journ. Anat. and Physiol.
vol. xxiv. p. 349.) Division of the lamina papyracea by a vertical suture into an anterior and
posterior part has been frequently recorded. The number of the conchse may be increased from
two to four, or may be reduced to one. (Report of Committee of Collect. Invest., Journ. Anat
and Physiol. vol. xxviii. p. 74.)
Maxillae. Not infrequently there is a suture running vertically through the bar of bone
which separates the infra-orbital foramen from the infra-orbital margin. Through imperfections
in ossification, the infra-orbital canal may form an open groove along the floor of the orbit.
Duckworth records four instances of a spinous process projecting inwards into the apertura
piriformis from the lower part of the nasal notch. A case has been described (Fischel) in which
there was complete absence of the premaxillae, together with the incisor teeth.
A not uncommon anomaly is the occurrence of a rounded elongated ridge extending along
the interpalatal or intermaxillary sutures on the under surface of the hard palate. This is called
the torus palatinus, and is of interest because its presence has given rise to the assumption that it
was due to a pathological growth. (See Stieda, Virchow's Festschrift, vol. i. p. 147.)
The sulcus lacrimalis may be constricted towards its centre.
A part of the maxillary sinus may be constricted off anteriorly and, owing to its relation to
the naso-lacrimal duct, is called the recessus lacrimalis.
Underwood (Journ. Anat. and Physiol. vol. xliv. p. 359) records the occurrence of all but
complete septa dividing the cavity of the maxillary sinus.
Zygomatic Bone. Cases of division of the zygoma tic bone by a horizontal suture have been
recorded, as well as instances of its separation into two parts by a vertical suture. Owing to the
supposed more frequent occurrence of this divided condition in Asiatics the zygomatic has been
named the os Japonicum. Barclay Smith (" Proc. Anat. Soc.," Journ. Anat. and Physiol., April 1898,
p. 40) describes a case in which the zygomatic bone was divided into two parts, an upper and
lower, by a backward extension of the maxilla, which articulated with the zygomatic process of
the temporal, thus forming a temporo-maxillary arch. Varieties of a like kind have also been
described by Gruber and others. Cases have been noted where, owing to deficiency in the develop-
ment of the zygomatic, the continuity of the zygomatic arch has been incomplete.
Nasal Bones. The size and configuration of the nasal bones vary greatly in different races,
being, as a rule, large and prominent in the white races, and flat and reduced in size, as well as
depressed, in the Mongolian and Negro stock. Complete absence of the nasal bones has been
recorded, and their division into two or more parts has also been noted. Obliteration of the
internasal suture is unusual ; it is stated to occur more frequently in negroes, and is the
recognised condition in adult apes.
Duckworth has recorded a case (Journ. Anat. and Physiol. vol. xxxvi. p. 257) of undue extension
downwards of the nasal bone, which may be perhaps accounted for on the supposition that the
lower part is a persistent portion of the premaxilla.
Lacrimal. The lacrimal is occasionally absent. In some cases it is divided into two
parts ; in others replaced by a number of smaller ossicles. In rare instances the hamulus may
extend forwards to reach the orbital margin, and so bear a share in the formation of the face, as in
lemurs (Gegenbauer). In other instances the hamulus is much reduced in size. Occasionally
the lacrimal is separated from the lamina papyracea of the ethmoid by a down-growth from
the frontal, which articulates with the frontal process of the maxilla, as is the normal disposition
in the gorilla and chimpanzee. (Turner, Challenger Reports, " Zoology," vol. x. Part IV. Plate I. ;
and A. Thomson, Journ. Anat. and Physiol, London, vol. xxiv. p. 349.)
Inferior Concha. A case in which the inferior conchte were absent has been recorded
by Hyrtl.
Vomer. Owing to imperfect ossification there may be a deficiency in the bone, filled up
during life by cartilage. The separation of the two lamellae along the anterior border varies
considerably, and instances are recorded where they were separated by a considerable cavity
within the substance of the bone. Instances of an extension forwards of the sphenoidal air
sinus into and separating the laminae of the bone have also been described. The spheno-vomerine
canal is a minute opening behind the rostrum of the sphenoid, and between it and the alaa of the
vomer, by which the nutrient artery enters the bone.
Palate Bones. The occurrence of a torus palatinus may be noted (see Variations of Maxilla).
Mandible. Considerable differences are met with in the height of the coronoid process :
usually its summit reaches the same level as the condyle, or slightly above it ; occasionally, how-
ever, it rises to a much higher level; in other cases it is much reduced. These differences
naturally react on the form of the mandibular notch. The projection of the mental protuberance
is also liable to vary. Occasionally the mental foramen is double, and sometimes the mylo-hyoid
groove is for a short distance converted into a canal There is often a marked eversion of the
angle of the mandible, which Dieulafe homologises with the angular apophysis met with in
lemurs and carnivora.
Clavicle. The clavicles of women are more slender, less curved, and shorter than those of
men. In the latter the bone is so inclined that its acromial end lies slightly, higher or on the same
level with the sternal end. In women the bone usually slopes a little downward and laterally.
The more pronounced curves of some bones are probably associated with a more powerful
development of the pectoral and deltoid muscles, a circumstance which also affords an explana-
tion of the differences usually seen between the right and left bones, the habitual use of the right
18 b
280 OSTEOLOGY.
upper limb reacting on the form of the bone of that side. The influence of muscular action,
however, does not wholly account for the production of the curves of the bone, since the bone
has been shown to display its characteristic features in cases where there has been defective de-
velopment or absence of the upper limb (Reynault). Partial or complete absence of the clavicle
has been recorded. W. S. Taylor exhibited an interesting case of this kind at the Clinical
Society of London, October 25, 1901. Sometimes there is a small canal through the anterior
border of the bone near its middle for the transmission of one of the supra-clavicular nerves.
Scapula. The most common variation met with is a separated acromion. In these
cases there has been failure in the ossific union between the spine and acromion, the
junction between the two being effected by a layer of cartilage or by an articulation possessing a
joint cavity. The condition is usually symmetrical on both sides, though instances are recorded
where this arrangement is unilateral. Very much rarer is the condition in which the coracoid
process is separable from the rest of the bone. The size and form of the scapular notch differs.
In certain cases the superior border of the bone describes a uniform curve reaching the base
of the coracoid without any indication of a notch. In some scapulae, more particularly in
those of very old people, the floor of the subscapular fossa is deficient owing to the absorption of
the thin bone, the periosteal layers alone filling up the gap.
At birth the vertical length of the bone is less in proportion to its width than in the adult.
Humerus. As has been stated in the description of the bone, the olecranon and coro-
noid fossae may communicate with each other in the macerated bone. The resulting supra-
trochlear foramen is most commonly met with in the lower races of man, as well as in the
anthropoid apes, and in some other mammals. The occurrence of a hook -like spine, called the
epicondylic process, which projects in front of the medial epicondylic ridge, is not uncommon.
Its extremity is connected with the medial epicondyle by means of a fibrous band, underneath
which the median nerve, accompanied by the brachial artery, or one of its large branches, may
pass, or in some instances, the nerve alone, or the artery unaccompanied by the nerve. This
arrangement is the homologue in a rudimentary form of a canal present in many animals,
notably in the carnivora and marsupials. In addition to the broad radial groove already
described, and which is no doubt produced by the twisting or torsion of the body, there is
occasionally a distinct narrow groove posterior to it, which marks precisely the course of the
radial nerve as it turns round the lateral side of the body of the bone.
Ulna. Cases of partial or complete absence of the ulna through congenital defect have
been recorded. Rosenm tiller has described a case in which the olecranon was separated from the
proximal end of the bone, resembling thus in some respects the patella. In powerfully developed
bones there is a tendency to the formation of a sharp projecting crest corresponding to the inser-
tion of the triceps.
Radius. Cases of congenital absence of the radius are recorded; in these the thumb is
not infrequently wanting as well
Carpus. Increase in the number of the carpal elements is occasionally met with, and
these have been ascribed to division of the navicular, os lunatum, os triquetrum, capitate, lesser
multangular, and os hamatum. Of these the most interesting is the OS centrale, first described
by Rosenberg, and subsequently investigated by Henke, Leboucq, and others. This is met with
almost invariably as an independent cartilaginous element during the earlier months of fcetal
life, and occasionally becomes developed into a distinct ossicle placed on the back of the carpus
between the navicular and capitate bones and the lesser multangular. Its significance depends
on the fact that it is an important component of the carpus in most mammals, and is met
with normally in the orang and most monkeys. Ordinarily in man, as was pointed out by
Leboucq, it becomes fused with the navicular, where its presence is often indicated by a small
tubercle, a condition which obtains in the chimpanzee, the gorilla, and the gibbons. Dwight
has described a case in which there was an os subcapitulum in both hands. The ossicle lay
between the base of the middle metacarpal bone and the capitate bone, with the lesser multangular
to its radial side. (Anat. Anz. vol. xxiv.) Further addition to the number of the carpal elements
may be due to the separation of the styloid process of the third metacarpal bone and its persistence
as a separate ossicle.
Reduction in the number of the carpus has been met with, but this is probably due to
pathological causes. Morestin (Bull Soc. Anat. de Paris, tome 71, p. 651), who has investigated
the subject, finds that ankylosis occurs most frequently between the bases of the second and
third metacarpal bones and the carpus, seldom or never between the carpus and the first meta-
carpal, or between the pisiform and os triquetrum. Instances of complete fusion of the os
lunatum and triquetral bones, without any apparent pathological change, have been recorded
in Europeans, Negroes, and an Australian.
Metacarpal Bones. As previously stated above, the styloid process of the third
metacarpal bone appears as a separate ossicle in about 1/8 per cent, of cases examined. (" Fourth
Annual Report of the Committee of Collect. Invest. Anat. Soc. Gt. Brit, and Ireland," Journ.
Anat. and Physiol. vol. xxviii. p. 64) In place of being united to the third metacarpal,
the styloid process may be fused with either the capitate bone or the lesser multangular, under
which conditions the base of the third metacarpal bone is without this characteristic apophysis.
Phalanges. Several instances have been recorded of cases in which there were three phalanges
in the thumb. Bifurcation of the terminal phalanges has occasionally been met with, and examples
of suppression of a phalangeal segment or its absorption by another phalanx have also been de-
scribed. (Hasselwander, Zeits. fur Morph. u. Anthr. vol. vi. 1903.)
VARIATIONS IN THE SKELETON. 281
Hip Bone. Some of the anomalies met with in the hip bone are due to ossification of the
ligaments connected with it ; in other cases they depend on. errors of development. Failure
of union between the pubic and ischial rami has also been recorded. Cases have occurred where
the obturator groove has been bridged across by bone, and one case is noted of absence of the
acetabular notch on the acetabular margin. In. rare cases the os acetabuli (see Ossification)
remains as a separate bone. Berry (Journ. Anat. and Physiol. vol. xlv. p. 202) has drawn attention
to the occurrence of a small accessory articular facet, situated on the rough non-articular area im-
mediately behind the auricular surface of the ilium, which articulates with a depressed facet on the
posterior surface of the sacrum to the lateral side of the first posterior sacral foramen, in the neigh-
bourhood of the transverse process of the second sacral segment. This he homologises with the
normal articulation between the ilium and sacral transverse processes found in many lower animals.
Femur. Absence of the fovea on the head of the femur for the attachment of the liga-
mentum teres has been recorded. This corresponds with the condition met with in the orang.
Not infrequently there is an extension of the articular surface of the head on to the anterior and
upper aspect of the neck ; this is a " pressure facet " caused by the contact of the iliac portion
of the acetabular margin with the neck of the bone, when the limb is maintained for long periods
in the flexed position, as in tailors, and also in those races who habitually squat (Lane, Journ.
Anat. and Physiol. vol. xxii. p. 606).
The occurrence of a trochanter tertius has been already referred to. Its presence is not
confined to individuals of powerful physique, but may occur in those of slender build, so far
suggesting that it is not to be regarded merely as an indication of excessive muscular develop-
ment. The observations of Dixon (Journ. Anat. and Physiol. voL xxx. p. 502), who noted the
occurrence of a separate epiphysis in three cases in connexion with it, seem to point to its
possessing some morphological significance. Occasionally the gluteal tuberosity may be replaced
by a hollow, the fossa hypotrochanterica, or in some cases the two may co-exist.
The angle of the neck is more open in the child than in the adult, and tends to be less
when the femoral length is short and the pelvic width great conditions which particularly
appertain to the female. There is no evidence to show that after growth is completed any
alteration takes place in the angle with advancing years (Humphry).
The curvature of the body may undergo considerable variations, and the appearance of the
posterior surface of the bone may be modified by an absence of the linea aspera, a condition
resembling that seen in apes ; or by an unusual elevation of the bone which supports the ridge
(femur a pilastre), produced, as Manouvrier has suggested, by the excessive development of the
muscles here attached.
Under the term " platymerie" Manouvrier describes an antero-posterior compression of the
proximal part of the body, frequently met with in the femora of prehistoric races.
Patella. Cases of congenital absence of the patella have been recorded.
F. C. Kempson (Journ. Anat. and Physiol. vol. xxxvi.) has recently drawn attention to the
condition described as emargiiiation of the patella. In specimens displaying this appearance the
margin of the bones is concave from a point about half an inch to the lateral side of the middle
line, to a point half-way down the lateral margin of the bone ; here there is usually a pointed
spine directed proximally and laterally. The condition appears to be associated with the insertion
of the tendon of the vastus lateralis. G. Joachimstal (Archiv u. Atlas der normalen und patholo-
gischen Anatomie in typischen R&ntgenbildern, Bd. 8) figures a case in which on both sides the
patella was double in an adult, the distal and much the smaller portion was embedded in the
ligamentum patellae.
Tibia. The tibia is often unduly compressed from side to side, leading to an increase in its
antero-posterior diameter as compared with its transverse width. This condition is more
commonly met with in the bones of prehistoric and savage races than in modern Europeans.
Attention was first directed to this particular form by Busk, who named the condition
platyknemia. The general appearance of such tibiae resembles that seen in the apes, and
depends on an exceptional development of the tibialis posterior muscle, though, as Manouvrier
has pointed out, in apes this is associated with the direct action of the muscle on the foot, as in
climbing, whereas in man, as a consequence of the bipedal mode of progression, the muscle is
employed in an inverse sense, viz., by steadying the tibia on the foot, and thus providing a fixed
base on which the femur can move. This explanation, however, is disputed by Derry (Journ.
Anat. and Phys. vol. xli. p. 123). Such platyknemic tibiae are occasionally met with in the
more highly civilised races, and are, according to Manouvrier, associated with habits of great
activity among the inhabitants of rough and mountainous districts.
Another interesting condition is one in which the proximal extremity is more strongly recurved
than is usual. This retroversion of the head of the tibia was at one time supposed to represent
an intermediate condition in which the knee could not be fully extended so as to bring the axis
of the leg in line with the thigh ; but such opinion has now been upset by the researches of
Manouvrier, who claims that it is the outcome of a habit not uncommon amongst peasants and
countrymen, viz., that of walking habitually with the knees slightly bent.
Habitual posture also leaves its impress on the form of the tibia, and in races m which the
use of the chair is unknown, the extreme degree of flexion of the knee and ankle necessitated by
the adoption of the squatting position as an attitude of habitual rest is associated with an increase
in the convexity of the lateral condylic surface, and the appearance, not infrequently, of a
pressure facet on the anterior border of the distal extremity, which rests in that position on the
neck of the talus. Cases of congenital absence of the tibia have been frequently described,
amongst the most recent being those recorded by Glutton, Joachimsthal, Bland-Sutton, and Waitz.
282 OSTEOLOGY.
Fibula. The fibula may be ridged and grooved in a remarkable manner, as is the case in
many bones of prehistoric races. This is probably associated with a greater development and
perhaps with more active nse of the muscles attached to it.
The proximal articular facet varies much in size. Bennett (Dublin Journ. Med. Sc., Aug.
1891) records a case in which it was double, and also notes the occurrence of specimens in which
it was absent and in which the head of the bone did not reach the lateral condyle of the tibia.
Many instances of partial or complete absence of the bone have been published. (Lefebre,
Contribution a I'e'tude de I'absence congSnitale du perqng, Lille, 1895.)
Talus. The anterior calcanean facet is sometimes separated from the middle by a non-
articular furrow. The posterior process, often largely developed, is occasionally (2*6 per cent.)
a separate ossicle forming what is known as the os trigonum (Bardeleben) ; or it may be
united to the body of the talus by a distinct synchondrosis. A smooth articular surface may
occasionally be found on the medial side of the proximal surface of the neck. This is a pressure
facet dependent on -the frequent use of the ankle-joint in a condition of extreme flexion, and
is caused by the opposition of the bone against the anterior edge of the distal end of the tibia.
The form of the bone at birth differs from that of the adult in that the medial splay of the
neck on the body is more pronounced, forming on an average an angle of 35 as compared with
a mean of 12 in the adult ; moreover, the articular surface for the medial malleolus extends
forwards along the medial side of the neck, and to some extent overruns its superior surface.
This is doubtless a consequence of the inverted position of the foot maintained by the foetus
during intra-uterine life. In these respects the fo3tal bone conforms to the anthropoid type.
For a detailed study of the varieties of this bone, see K. B. S. Sewell. (Journ. Anat. and Physiol.
voL xxxviii.)
Calcaneus. The trochlear process is occasionally unduly prominent, constituting the sub-
malleolar apophysis of Hyrtl, and cases are recorded of the calcaneus articulating with the
navicular. (Morestin, H., Bull de la Soc. Anat. de Paris, 1894, 5 e se"r. t 8, n. 24, p. 798 ; and
Petrini, Atti del XL Gongr. Med. Internaz. Roma, 1894, vol. ii., "Anat." p. 71.) Pfitzner (Morpho-
logische Arbeiten, vol. vi. p. 245) also records the separation of the sustentaculum tali to form
os sustentaculi. (See also P. P. Laidlaw, Journ. Anat. and Physiol. vol. xxxviii. p. 133.)
Navicular. According to Manners Smith this bone displays more variety of form the
any other of the tarsal bones. He accounts for this both on morphological and mechanic
grounds. He regards the tuberosity as probably of threefold origin, an apophysial, an epiphysir
and a sesamoid element, the latter being the so-called sesamoid bone in the tendon of the
tibialis posterior. Cases are recorded where the tuberosity has formed an independent ossicle.
Cuneiform Bones. Numerous cases of division of the first cuneiform bone into doi
and plantar parts have been recorded ; the frequent division of its metatarsal articular facet is
doubt correlated with this anomalous condition. T. Dwight has described (Anat. Anz. vol. xx.
p. 465) in two instances the occurrence of an os intercunetforme. The ossicle so named lies on
the dorsum of the foot at the posterior end of the line of articulation between the first and
second cuneiform bones.
Cuboid. Blandin has recorded a case of division of the cuboid. Occasionally there is a
facet on the lateral surface of the bone for articulation with the tuberosity of the fifth metatarsal
(Manners Smith).
Tarsus as a Whole. Increase in the number of the tarsal elements may be due to the
occurrence of division of either the first cuneiform or the cuboid bone, or to the occasional
presence of an os trigonum. Cases of separation of the tuberosity of the navicular bone have
been recorded, and instances of supernumerary ossicles between the first cuneiform and
second metatarsal bone have been noted. Stieda mentions the occurrence of a small ossicle
in connexion with the articular surface on the anterior and upper part of the calcaneus, and
Pfitzner notes the occurrence of an os sustentaculi. For further information on the variations
of the skeleton of the foot, see Pfitzner. (Morphologische Arbeiten, vol. vi. p. 245.)
The possibility of an injury having been the cause of the occurrence of some of these so-called
supernumerary ossicles must not be overlooked. The use of the Rontgen rays has proved that
accidents of this kind are much more frequent than was at first supposed.
The reduction in the number of the tarsus is due to the osseous union of adjacent bones. In
many instances this is undoubtedly pathological, but cases have been noticed (Leboucq) of fusion
of the cartilaginous elements of the calcaneus and talus, and the calcaneus and navicular
in foetuses of the third month.
Metatarsal Bones. Several instances of separation of the tuberosity of the fifth metatarsal
(os Vesaleanum) have been recorded, whilst numerous examples of an os intermetatarsum between
the bases of the first and second metatarsal bones have been recorded by Gruber and others.
The tubercle on the base of the first metatarsal for the attachment of the peronaeus longus tendon
is occasionally met with as a separate ossicle. An epiphysis over the spot where the tuberosity
of the fifth metatarsal rests on the ground has been described. (Kirchner, Archiv klin. Chir. B 80.)
Phalanges. It is not uncommon to meet with fusion of the second and third phalanges,
particularly in the fifth, less frequently in the fourth, and occasionally in the second and third
toes. The union of the phalangeal elements has been observed in the foetus as well as the
adult (Pfitzner). The proportionate length of the phalanges varies much ; in some cases the
ungual phalanges are of fair size, the bones of the second row being mere nodules, whilst in other
instances the reduction in size of the terminal phalanges is most marked.
SEETAL HOMOLOGIES OF THE VEETEBE.E.
283
APPENDIX C.
TRUE TRANSVERSE
PROCESS
FORAMEN TRANS-
VERSARIUM
COSTAL PROCESS
XEURO-CENTRAL SYNCHONDROSIS
CERVICAL
i^^ TRUE TRANS-
VERSE PROCESS
COSTAL PROCESS
RACIC
NSVERSE
ROCESS
FORAMEN TRANSVERSARIUM
NEURO-CENTRAL SYNCHONDROSIS
RIB
LUMBAR
SERIAL HOMOLOGIES OF THE VERTEBRAE.
It is a self-evident fact that the vertebral column consists of a number of segments or verte-
brae all possessing some characters in common. These vertebrae or segments undergo modifications
according to the region they oc-
cupy and the functions they are
called upon to serve, so that their
correspondence and identity is
thereby obscured. There is no
difficulty in recognising the homo-
logy of the bodies and vertebral
arches throughout the column.
According to some anatomists the
vertebral arch is the more primi-
tive element in the formation of a
vertebra, whilst others hold that
the bodies are the foundation of the
column. Be that as it may, we find
that in the higher vertebrates, at
least, the bodies are the parts which
most persist. They are, however,
subject to modifications dependent
on their fusion with one another.
This occurs in the cervical part
of the column where the body
of the first cervical or atlas has
for functional reasons become
fused with the body of the
second or epistropheus to form
the dens of that segment. For
similar reasons, and in association
with the union of the girdle of
the hind -limb with the column,
the bodies of the vertebrae which
correspond to the sacral segment
become fused together to form a
solid mass. In the terminal por-
tion of the caudal region the bodies
alone represent the vertebral seg-
ments.
As regards the vertebral arch,
this in man becomes
deficient in the lower
sacral region, and absent
altogether in the lower
coccygeal segments. The
spinous processes are
absent in the case of the
first cervical, lower
sacral; and all the coc-
cygeal vertebrae, and
display characteristic
differences in the cervi-
cal, thoracic, and lum-
bar regions, which have
been already described.
The articular processes
(zygapophyses) are
secondary develop-
ments, and display great
diversity of form, deter-
mined by their func-
tional requirements. It
is noteworthy that, in
the case of the upper
front of the foramina of exit of
COSTAL ELEMENT (RIB)
SACRAL
.!. MKNT
OCCASIONAL FORAMEN
IHAXSVERSARIUM
NEURO-CENTRAL SYNCHONDROS]
COSTAL ELEMENTS
80. DIAGRAM TO ILLUSTRATE THE HOMOLOGOUS PARTS OF THE VERTEBRA.
he bodies are coloured purple ; the vertebral arch and its processes, red ; the costal
elements, blue. A, from above. B, from the side.
two cervical vertebras, they are so disposed as to lie in
upper two spinal nerves, and by this arrangement the weight of the head is transmitted to
solid column formed by the vertebral bodies, and not on to the series of vertebral arches. 1 _t IB m
regard to the homology of the transverse processes, so called, that most difficulty a
284 OSTEOLOGY.
thoracic region they can best be studied in their simplest form ; here the ribs which Gegenbauer
regards as a differentiation from the inferior or haemal arches, in opposition to the view advanced
by others that they are a secondary development from the fibrous intermuscular septa articulate
with the transverse processes and bodies of the thoracic vertebrae through the agency of the
tubercular (diapophyses ) and capitular (parapophyses) processes respectively, the latter being
placed, strictly speaking, on the vertebral arch behind the line of the neuro-central synchondrosis.
An interval is thus left between the neck of the rib and the front of the transverse process ;
this forms an arterial passage which corresponds to the foramen transversarium in the transverse
processes of the cervical vertebrae, the anterior bar of which is homologous with the head and
tubercle of the thoracic rib, whilst the posterior part lies in series with the thoracic transverse
process. These homologies are further emphasised by the fact that in the case of the seventh
cervical vertebra the anterior limb of the so-called transverse process is developed from an
independent ossific centre, which occasionally persists in an independent form as a cervical rib.
In the lumbar region the lateral or transverse process is serially homologous with the
thoracic ribs, though here, owing to the coalescence of the contiguous parts, there is no arterial
channel between the rib element and the true transverse process, which is represented by the
accessory processes (anapophyses), placed posteriorly at the root of the so-called transverse
process of human anatomy. Support is given to this view by the presence of a distinct costal
element in connexion with the transverse process of the first lumbar vertebra, which accounts
for the occasional formation of a supernumerary rib in this region. The cases of foramina in the
transverse processes of the lumbar vertebrae (see p. 275) are also noteworthy as supporting this view.
In the sacrum the lateral part of the bone is made up of combined transverse and costal
elements, with only very exceptionally an intervening arterial channel. In the case of the
upper three sacral segments the costal elements are largely developed and assist in support-
ing the ilia, and they are called the true sacral vertebras ; whilst the lower sacral segments,
which are not in contact with the ilia, are referred to as the pseudo-sacral vertebrae.
The anterior arch of the atlas vertebra is, according to Froriep, developed from a hypochordal
strip of cartilage (hypochordal spange).
APPENDIX D.
MEASUREMENTS AND INDICES EMPLOYED IN PHYSICAL ANTHROPOLOGY.
(1) Craniometry.
The various groups of mankind display in their physical attributes certain features which are
more or less characteristic of the stock to which they belong. Craniology deals with these
differences so far as they affect the skull. The method whereby these differences are recorded
involves the accurate measurement of the skull in most of its details. Such procedure is included
under the term craniometry. Here only the outlines of the subject are briefly referred to ;
for such as desire fuller information on the subject, the works of Broca, Topinard, Flower, and
Turner may be consulted.
The races of man display great variations in regard to the size of the skull. Apart altogether
from individual differences and the proportion of head -size to body-height, it may be generally
assumed that the size of the skull in the more highly civilised races is much in excess of that
displayed in lower types. The size of the head is intimately correlated with the develop-
ment of the brain. By measuring the capacity of that part of the skull occupied by the
encephalon, we are enabled to form some estimate of the size of the brain. The cranial capacity
is determined by filling the cranial cavity with some suitable material and then taking the
cubage of its contents. Various methods are employed, each of which has its advantage. The use
of fluids, which of course would be the most accurate, is rendered impracticable, without special
precautions, owing to the fact that the macerated skull is pierced by so many foramina. As a
matter of practice, it is found that leaden shot, glass beads, or seeds of various sorts are the most
serviceable. The results obtained display a considerable range of variation. For purposes of
classification and comparison, skulls are grouped according to their cranial capacity into the
following varieties :
Micro-cephalic skulls are those with a capacity below 1350 c.c., and include such well-known
races as Andamanese, Veddahs, Australians, Bushmen, Tasmanians, etc.
Mesocephalic skulls range from 1350 c.c. to 1450 c.c., and embrace examples of the following
varieties : American Indians, Chinese, some African Negroes.
Megacephalic skulls are those with a capacity over 1450 c.c., and are most commonly met
with in the more highly civilised races : Mixed Europeans, Japanese, etc.
Apart from its size, the form of the cranium has been regarded as an important factor in
the classification of skulls ; though whether these differences in shape have not been unduly
emphasised in the past is open to question.
The relation of the breadth to the length of the skull is expressed by means of the cephalic
index which records the proportion of the maximum breadth to the maximum length of the
skull, assuming the latter equal 100, or
Max. breadth x 100 _
TUT i ii. = Cephalic index.
Max. length
285
MEASUEEMENTS AND INDICES.
The results are classified into three groups :
1. Dolichocephalic, with an index below 75 : Australians, Kaffirs, Zulus Eskimo Fiiian*
2. Mesaticephalic, ranging from 75 to 80 : Europeans (mixed), Chinese, Polynesians (mixed)'
3. Brachycephahc, with an index over 80 : Malays, Burmese, American Indians Anda-
manese.
In order to provide for uniformity in the results of different observers, some system is neces-
sary by which the various points from which the measurements are taken must correspond
Whilst there is much difference in the value of the measurements insisted on by individual
anatomists, all agree in endeavouring to select such points on the skull as may be readily deter-
mined, and which have a fairly fixed anatomical position. The more important of these " fixed
points " are included in the subjoined table :
VERTEX
BREOMA
OBELION
LAMBDA
MAXIMUM OCCIPITAL
POINT
INI ON
ASTERION
STEPHANION
PTERION
OPHRYON
GLABELLA
NASION
\ N ^\~~\V DACRYON
RHINION
JUGAL POINT
AKANTHION
PROSTHION
(ALVEOLAR POINT)
POGONION
Nasion. The middle of the naso-frontal suture.
Grlabella. A point midway between the two superciliary ridges.
Ophryon. The central point of the narrowest transverse diameter of the forehead, measured
from one temporal line to the other.
Inion. The external occipital protuberance.
Maximum Occipital Point. The point on the squamous part of the occipital in the sagittal
plane most distant from the glabella.
Opisthion. The middle of the posterior margin of the foramen magnum.
Basion. The middle of the anterior margin of the foramen magnum.
Bregma. The point of junction of the coronal and sagittal sutures.
Rhinion. The most prominent point at which the nasal bones touch one another.
Alveolar Point or Prosthion. The centre of the anterior margin of the upper alveolar
margin.
Subnasal Point. The middle of the inferior border of the piriform (anterior nasal) aper-
ture at the centre of the anterior nasal spine.
Akanthion. The most prominent point on the nasal spine.
Vertex. The summit of the cranial vault.
Obelion. A point over the sagittal suture, on a line with the parietal foramina.
Lambda. The meeting-point of the sagittal and lambdoid sutures.
Pterion. The region of the antero-lateral fontanelle where the angles of the frontal, parietal,
squamous part of the temporal, and great wing of sphenoid lie in relation to one
another. As a rule, the sutures are arranged like the letter H, the parietal and
great wing of sphenoid separating the frontal from the squamous temporal. In
other cases the form of the suture is like an X ; whilst in a third variety the
frontal and squamous part of the temporal articulate with each other, thus separating
the great wing from the parietal.
Asterion is the region of the postero-lateral fontanelle where the lambdoid, parieto-mastoid,
and occipito-mastoid sutures meet.
Stephanion. The point where the coronal suture crosses the temporal line.
Dacryon. The point where the vertical lacrimo-maxillary suture meets the fronto-nasal
suture at the inner angle of the orbit.
286 OSTEOLOGY.
Jugal Point. Corresponds to the angle between the vertical border and the margin of the
temporal process of the zygomatic bone.
Supra-auricular Point. A point immediately above the middle of the orifice of the
external acoustic meatus close to the edge of the posterior root of the zygoma.
G-onion. The lateral side of the angle of the mandible.
Pogonion. The most prominent point of the chin as represented on the mandible.
The measurements of the length of the skull may be taken between a variety of points the
nasion, glabella, or ophryon in front, and the inion or maximum occipital point behind. Or the
maximum length alone may be taken without reference to any fixed points. In all cases it is
better to state precisely where the measurement is taken. The maximum breadth of the head is
very variable as regards its position ; it is advisable to note whether it occurs above or below the
parieto-squamosal suture. The inter-relation of these measurements as expressed by the cephalic
index has been already referred to. The width of the head may also be measured from one asterion
to the other, biasterionic width, or by taking the bistephanic diameter.
The height of the cranium is usually ascertained by measuring the distance from the basion
to the bregma. The relation of the height to the length may be expressed by the height or
vertical index, thus
Height x 100 _ ,. ...
-T- = Vertical index.
Length
Skulls are classified in accordance with the relations of length and height as follows :
Tapeinocephalic index below 72. Chamsecephalic index up to 70.
Metriocephalic index between 72 and 77. Orthocephalic index from 70-1 to 75.
Akrocephalic index above 77 (Turner). Hypsicephalic index 75-1 and upwards
(Kollmann, Ranke, and Virchow).
The horizontal circumference of the cranium, which ranges from 450 mm. to 550 mm., is
measured around a plane cutting the glabella or ophryon anteriorly, and the maximum occipital
point posteriorly. The longitudinal arc is measured from the nasion in front to the opisthion
behind ; if to this be added the basi -nasal length and the distance between the basion and the
opisthion, we have a record of the vertico-median circumference of the cranium. This may further
be divided by measuring the lengths of the frontal, parietal, and occipital portions of the
superior longitudinal arc. In this way the relative proportions of these bones may be
expressed.
The measurements of the skeleton of the face are more complex, but, on the whole, of greater
value than the measurements of the cranium. It is in the face that the characteristic features of
race are best observed, and it is here that osseous structure most accurately records the form and
proportions of the living.
The form of the face varies, like that of the cranium, in the relative proportions of its length
and breadth. Generally speaking, a dolichocephalic cranium is associated with a long face, whilst
the brachycephalic type of head is correlated with a rounder and shorter face. This rule, how-
ever, is not universal, and there are many exceptions to it.
The determination of the facial index varies according to whether the measurements are made
with or without the mandible in position. In the former case the length is measured from the
ophryon or nasion above to the mental tubercle below, and compared with the maximum
bizygomatic width. This is referred to as the total facial index, and is obtained by the
formula
Ophryo-mental length x 100 .
- T^T- = Total facial index.
Bizygomatic width
More usually, however, owing to the loss of the mandible, the proportions of the face are
expressed by the superior facial index. This is determined by comparing the ophryo-alveolar or
naso-alveolar length with the bizygomatic width, thus
Ophryo-alveolar length x 100
* 4r- r- = Superior facial index.
Bizygomatic width
The terms dolichofacial or leptoprosope and brachyfacial or chamoeprosope have been
employed to express the differences thus recorded.
Uniformity in these measurements, however, is far from complete since many anthropologists
compare the width with the length = 100.
The proportion of the face-width to the width of the calvaria is roughly expressed by the use of
the terms cryptozygous and phsenozygous as applied to the skull. In the former case the
zygomatic arches are concealed, when the skull is viewed from above, by the overhanging and
projection of the sides of the cranial box ; in the latter instance, owing to the narrowness of the
calvaria, the zygomatic arches are clearly visible.
The projection of the face, so characteristic of certain races (Negroes for example), may be
estimated on the living by measuring the angle formed by two straight lines, the one passing from
the middle of the external acoustic meatus to the lower margin of the septum of the nose ; the
other drawn from the most prominent part of the forehead above to touch the incisor teeth
below. The angle formed by the intersection of these two lines is called the facial angle
(Camper), and ranges from 62 to 85. The smaller angle is characteristic of a muzzle-like
MEASUKEMENTS AND INDICES. 287
projection of the lower part of the face. The larger angle is the concomitant of a more vertical
profile. The degree of projection, of the maxilla in the macerated cranium is most commonly
expressed by employing the gnathic or alveolar index of Flower. This records the relative
proportions of the basi-alveolar and basi-nasal lengths, the latter being regarded as = 100,
thus
Basi-alveolar length x 100
= Gnathic index.
Basi-nasal length
The results are conveniently grouped into three classes :
Orthognathous, index below 98 : including mixed Europeans, ancient Egyptians, etc.
Mesognathous, index from 98 to 103 : Chinese, Japanese, Eskimo, Polynesians (mixed).
Prognathous, index above 103 : Tasmanians, Australians, Melanesians, various African
Negroes.
Unfortunately, however, little reliance can be placed on the results obtained by this method,
since it takes no account of the proportion of the third or facial side of the gnathic triangle.
For a further discussion of this matter see Thomson and Maclver, Races of the Thebaid (Oxford :
Clarendon Press, 1905).
The form of the piriform aperture in the macerated skull is of much value from an ethnic
standpoint, as it is so intimately associated with the shape of the nose in the living. The
greatest width of the aperture is compared with the nasal height (measured from the nasion
to the lower border of the aperture) and the nasal index is thus determined :
Nasal width x 100 .
= Nasal index.
Nasal height
Skulls are
Leptorhine, with a nasal index below 48 : as in mixed Europeans, ancient Egyptians,
American Indians, etc.
Mesorhine, with an index ranging from 48 to 53 : as in Chinese, Japanese, Malays, etc.
Platyrhine, with an index above 53 : as in Australians, Negroes, Kaffirs, Zulus, etc.
The form of the orbit varies considerably in different races, but is of much less value from the
standpoint of classification. The orbital index expresses the proportion of the orbital height to
the orbital width, and is obtained by the following formula :
Orbital height xlOO
Orbital width
The orbital height is the distance between the upper and lower margins of the orbit at the
middle ; whilst the orbital width is measured from a point where the ridge which forms the
posterior boundary of the lacrimal groove meets the fronto-lacrimal suture (Flower), or from
the dacryon (Broca) to the most distant point from these on the anterior edge of the lateral
border of the orbit.
The form of the orbital aperture is referred to as
Megaseme, if the index be over 89 ;
Mesoseme, if the index be between 89 and 84 ;
Microseme, if the index be below 84.
The variations met with in the form of the palate and dentary arcade may be expressed by
the palato-maxillary index of Flower. The length is measured from the alveolar point to a
line drawn across the posterior borders of the maxillae, whilst the width is taken between
the outer borders of the alveolar arch immediately above the middle of the second molar
tooth. To obtain the index, the following formula is employed :
Palato-maxillary width x 100 = p alato . maxillary index .
Palato-maxillary length
For purposes of classification Turner has introduced the following terms :
Dolichuranic, index below 110.
Mesuranic, index between 110 and 115.
Brachyuranic, index above 115.
As is elsewhere stated the size of the teeth has an important influence on the architecture of
the skull. Considered from a racial standpoint, the relative size of the teeth to the length of
the cranio-facial axis has been found by Flower to be a character of much value. The dental
length is taken by measuring the distance between the anterior surface of the first premolar and
the posterior surface of the third molar of the upper jaw.
To obtain the dental index the following formula is used :
Dental length x 100 _ pental index
Basi-nasal length
288 OSTEOLOGY.
Following the convenient method of division adopted with other indices, the dental indices
may be divided into three series, called respectively
Microdont, index below 42 : including the so-called Caucasian or white races.
Mesodont, index between 42 and 44 : including the Mongolian or yellow races.
Megadont, index above 44 : comprising the black races, including the Australians.
Many complicated instruments have been devised to take the various measurements required,
but for all practical purposes the calipers designed by Flower or the compas glissitre of Broca are
sufficient.
As an aid to calculating the indices, the tables published in the Osteological Catalogue of the
Royal College of Surgeons of England, Part I., Man; Index -Tabellen zum anthropometrischen
Gebrauche, C. M. Furst, Jena, 1902 ; or the index calculator invented by Waterston will be found
of much service in saving time.
(2) Indices and Measurements of other Parts of the Skeleton.
In addition to the indices employed to express the proportions of the cranial measurements,
there are others similarly made use of to convey an idea of the proportions of different parts of
the skeleton. Of these the following may be mentioned as those in most common use :
Scapula. At birth the form of the human scapula more closely resembles the mammalian
type in that its breadth, measured from the glenoid cavity to the vertebral border, is greater in
comparison with its length than in the adult. This proportion is expressed as follows :
Breadth from glenoid cavity to vertebral border x 100 ~
, . J . . . . . = Scapular index.
Length irom medial to inferior angle
The index ranges from 87 in African pygmies, which therefore have proportionately broader
scapulae, to 61 in Eskimos. The average European index is about 65.
Hip Bone. The relation of the breadth of this bone to its height is computed as
follows :
Iliac breadth x 100
Ischio-iliac height
= Innominate index.
Man as compared with the apes is distinguished by possessing proportionately broader and
shorter hip bones. The index in man ranges from 74 to 90.
Pelvis. The form of the human pelvis is characterised by an increased proportionate width
and a reduced proportionate height or length. The relation of these diameters is expressed by
the formula :
Greatest breadth ^^^ou^r nf the iliac crests = Pelvic b"^'^^ index
The average index for white races is 73.
Pelvic Cavity. The measurements usually taken are those of the superior aperture. In
man there is a proportionate increase in the transverse diameter as compared with lower forms :
Antero-posterior diameter (conjugate) from mid-point of sacral promontory
to the posterior margin of pubic symphysis x 100
.j . , , rp *-^T. - TT^ = Pelvic or brim index,
Greatest transverse width between ilio-pectineal lines
Turner has classified the indices into three groups :
Dolichopellic, index above 95 : Australians, Bushmen, Kaffirs.
Mesatipellic, index between 90-95 : Negroes, Tasmanians, New Caledonians.
Platypellic, index below 90 : Europeans and Mongolians generally.
Vertebral Column. A characteristic feature of man's vertebral column is the pronounced
lumbar curve associated with the erect posture in the living. Apart from the consideration of
the interposition of the intervertebral fibre-cartilage between the segments, the bodies of the
lumbar vertebrae influence and react on the curve by exhibiting differences in their anterior and
posterior vertical diameters. Advantage has been taken of this to endeavour to reconstruct
the lumbar curve from the dried and macerated bones, but it must be borne in mind that habitual
posture or increased range of movements may yield results which are possibly misleading.
Thus there is reason for believing that the squatting position, when habitually adopted, may give
rise to a compression of the anterior parts of the bodies of the vertebrae which it might be
assumed was associated with an absence of or flattening of the lumbar curve, which in fact did
not exist during life.
The quality of the curve is estimated from the macerated bones by an index which is com-
puted as follows :
Sum of posterior vertical diameters of the bodies of five lumbar
vertebra, x 100 _ . General lumbar index .
Sum of anterior vertical diameters of the bodies of five lumbar
vertebrae
MEASUKEMENTS AND INDICES. 289
The results are classified as follows :
Kurtorachic, index below 98, displaying a forward convexity : includes Europeans
generally, Chinese.
Orthorachic, index between 98 and 102, column practically straight : includes examples
of Eskimo and Maori.
Koilorachic, index above 102, displaying a backward convexity : includes Australians
Negroes, Bushmen, and Andainanese.
Sacrum. Man's sacrum is characterised by its great breadth in proportion to its length
These relations are expressed as follows :
Greatest breadth of base of sacrum x 100
Length from middle ^f promontory to middle of anterior inferior border of = Sacra * m ^ex.
fifth sacral vertebrae
The diverse forms are grouped as follows :
Dolichohieric, index below 100, sacra longer than broad : includes Australians, Tasmanians
Bushmen, Hottentots, Kaffirs, and Andamanese.
Platyhieric, index above 100, sacra broader than long : includes Europeans, Negroes
Hindoos, North and South American Indians.
Limb Bones. The proportionate length of the limb bones to each other and to the body
height is of practical interest. It is a matter of common knowledge that the forearms of Negroes
are proportionately longer than those of Europeans. Great differences, too, are met with in the.
absolute and proportionate length of the lower limbs, nor must the relation of these to body
height be overlooked. An enumeration of the more important of these indices, and the manner
of their computation, will suffice. The proportion of the length of the radius to the length of
the humerus is expressed as follows :
Length of radius x 100
. , f , = Kadio-humeral index.
Length of humerus
Sub-divided into three groups :
Brachykerkic, index less than 75 : includes Europeans, Lapps, Eskimo.
Mesatikerkic, index between 75-80 : Chinese, Australians, Polynesians, Negroes.
Dolichokerkic, index above 80 : Andamanese, Negritoes and Fuegians, Bonindae in general.
he proportion of the length of the tibia to the femur is computed by the formula
of tibia from surface of condyle to articular surface for talus x 100 ,
Oblique length of femur ^bio-femoral index.
sub-divided into two groups :
Brachyknemic, index 82 and under : includes Europeans and Mongolians generally.
Dolichoknemic, index 83 and over : includes Australians, Negroes, Negritoes, American -
Indians.
te proportion of the length of the upper limb to that of the lower limb is obtained thus :
Lengths of humerus + radius x 100
-f-f = Intermembral index.
Lengths of femur + tibia
A comparison between the relative lengths of the upper segments of the limbs is obtained by
the following formula :
Plal
Tra
Length of humerus x 100
= Humero-femoral index.
Length of femur
tymeria (see p. 281). The amount of compression of the femur is estimated as follows :
ittal diameter of shaft immediately distal to lesser trochanter x 100 __. , . j n( i ex
ransverse diameter of shaft immediately distal to lesser trochanter
Platyknemia (see p. 281) The degree of compression of the tibia is estimated by the
formula
Transverse diameter of shaft at level of nutrient foramen x 100 __. j. v k ne mic i n dex
Antero-posterior diameter of shaft at level of nutrient foramen""
The index ranges from 60 in a Maori tibia to 80 to 108 in modern French tibiae.
For further and more detailed information relating to the various measurements and indices
employed by the physical anthropologist, the reader is referred to Topinard's Elements d'Anthro-
pologie ; Sir W. Turner's Challenger Memoirs, Part 47, vol. xvi. ; and Duckworth's Morphology
and Anthropology.
19
290
OSTEOLOGY.
APPENDIX E.
DEVELOPMENT OF THE CHONDRO-CRANIUM AND MORPHOLOGY OF
THE SKULL.
As has been already stated, the chorda dorsalis or notochord extends headwards to a point
immediately beneath the anterior end of the mid-brain. In front of this the head takes a bend
so that the large fore-brain overlaps the anterior extremity of the notochord. At this stage of
development the cerebral vesicles are enclosed in a membranous covering derived from the mesen-
Crista Galli
Pars ethmoidalis
Lamina cribrosa
Orbito-sphenoid
Superior orbital fissure
Alisphenoid
Carotid canal
Meatus acusticus
internus
Subarcuate fossa-
Jugular foramen
Canalis hypoglossi
Foramen magnum
Orbital portion of orbito-sphenoid
t Optic foramen
Tuberculum sell*
(Olivary process)
[ Sella turcica
Dorsum sellae
7- Pars petrosa
Superior semicircular cam
Pars mastoidea
Supra-occipital
Occipital fontanelle
FIG. 282. VIEW OF THE CHONDRO-CRANIUM OP A HUMAN FOETUS 5 CM. IN LENGTH FROM VERTEX
COCCYX (about the middle of the third month) ; the cartilage is coloured blue. The line to the rig
of the drawing shows the actual size.
chyme surrounding the notochord ; this differentiated mesodermal layer is called the primordic
membranous cranium. From it the meninges which invest the brain are derived. In lowei
vertebrates this membranous capsule becomes converted into a thick -walled cartilaginous envelope,
the primordial cartilaginous cranium. In mammals, however, only the basal part of this capsule
becomes chondrified, the roof and part of the sides remaining membranous. In considering the
chondrification of the skull in mammals, it must be noted that part only of the base is traversed by
the notochord, viz., that portion which extends from the foramen magnum to the dorsum sellae of the
sphenoid. It is, therefore, conveniently divided into two parts one posterior, surrounding the
notochord, and hence called chordal, and one in front, into which the notochord does not extend,
and hence termed prechordal. These correspond respectively to the vertebral and evertebral
regions of Gegenbauer. In the generalised type, a pair of elongated cartilages called the para-
chordal cartilages appear on either side of the chorda in the chordal region, similarly in the
prechordal region two curved strips of cartilage named the prechordal cartilages, or the
trabeculae cranii of Rathke, develop on either side of the cranio-pharyngeal canal. In the
human embryo, however, this symmetrical arrangement has not hitherto been observed. In
man, chondrification of the cranial base commences early in the second month and attains its
maximum development about the end of the third month, at which time the chordal part of
the chondrocranium consists of a ring of cartilage, the ventral part of which is formed by the
fusion of two parachordal cartilages, so forming around the chorda dorsalis, a central axial part,
MOKPHOLOGY OF THE SKULL.
291
which comprises the basilar portion of the occipital bone. From this there pass extensions
which form the lateral parts of the occipital bone, and serve to unite the occipital plate, as this
part of the cartilaginous base' is 'sometimes called, to the cartilaginous auditory capsules on
either side. These latter are formed by the chondrification of the cochlear and canalicular parts
of the labyrinth, which do not develop at the same rate, so that the part around the semi-
circular canals is completed much sooner than the cochlear portion ; in consequence, at the end
of the second month, the facial nerve and the genicular ganglion lie in a groove, to be subse-
quently converted into a canal, on the vestibular part of the capsule.
The dorsal part of the ring consists of a thin cartilaginous plate, the tectum posterius, from which
is developed the only part (i.e. the inferior part of the occipital squama) of the cranial vault
preformed in cartilage. In the membranous tissue from which this plate is developed chondrifica-
tion at first begins, on either side, by an extension from the posterior aspect of the pars lateralis
of the occipital; growing rapidly forwards this ultimately unites with the posterior and dorsal
borders of the cartilaginous auditory capsule, from which it is for some time separated by a
narrow membranous interval. At a later stage the cartilages of either side unite, dorsal to the
foramen magnum, to form the tectum posterius or the tectum synoticum (Keibel and Mall).
To the axial part of this portion of the chondrified base the chorda dorsalis has the following
Basi-sphenoid centres
Pre-sphenoid centre
^ Frontal
Orbito-sphenoid
- Ali-splienoid
' Ali- sphenoid
Squamous part
of temporal
). 283. OSSIFICATION ON BASE AND LATERAL WALLS OF SKULL OF FOUR AND A HALF MONTHS'
FCETUS (Schultze's method). Cartilage, blue ; cartilage-bone, black ; membrane-bone, red.
relations : in front of the foramen magnum it runs for a short distance in a groove on the dorsal
surface of the occipital plate, then pierces the cartilage so as to lie ventral to it in the retro-
pharyngeal tissue, again enters the chondro - cranium by passing dorsalwards in the suture
between the occipital plate and sphenoidal cartilage and ends dorsal to the latter cartilage.
The prechordal portion of the cartilaginous basis cranii in man displays the following features :
at the third month it is irregularly diamond-shaped in outline, its posterior angle is wedged in
between the two auditory capsules and is related to the anterior part of the axial portion of the
occipital plate. The anterior angle forms the ventral end of the nasal capsule, whilst the lateral
angles extend over the orbital cavities and correspond to the tips of the alse orbitales of the
sphenoid.
Within this area chondrification takes place as follows (Bardeen). In the region of the
posterior angle, above referred to, a cartilaginous nodule appears anterior and ventral to the end
of the chorda dorsalis ; from this arises the cartilaginous body of the sphenoid, the further
development of which is associated with its union with the anterior end of the median portion
of the occipital plate and the formation there, by the appearance of an independent transverse
strip of cartilage, of the dorsum sellse of the sphenoid ; whilst from its anterior and superior
surface on either side there extend forwards strips of cartilage which surround the hypophyseal
pocket, and unite in front of it to form the anterior part of the body of the sphenoid, thereby
enclosing the hypophyseal canal, which, at first wide, is gradually closed by the chondrification
of its walls. It may, however, remain open.
j.y a
292 OSTEOLOGY.
The region occupied by the ala temporalis is slow to chondrify. According to Fawcett, the
only part of it which is preformed in cartilage is that which corresponds to the root of the two
pterygoid laminae in the adult : this is, perforated by the maxillary division of the trigeminal
nerve. According to the same authority, the whole of the lateral pterygoid lamina and that
part of the ala temporalis projected into the orbital and temporal fossae are ossified in membrane.
So, too, are the foramen ovale and foramen spinosum.
The ala orbitalis, at first much larger than the ala temporalis, is described as chondrifying in
the following way. The process begins by the appearance of cartilage posterior to the position
of the optic foramen ; medially this fuses with the lateral aspect of the anterior part of the body
of the sphenoid, laterally it extends into the orbital plate, with the independent cartilaginous
centre of which it unites. The foramen opticum is completed by the extension of the cartilage
from the side of the anterior extremity of the body of the sphenoid, in front of the nerve, to
reach the orbital plate. These three centres fuse to form a single piece of cartilage during the
third month.
Anterior to the orbito-sphenoids, the base of the skull is intimately associated with the nasal
capsule, and is the last part of the chondro-cranium to become cartilaginous, this change not
being effected till the third month. The roof of the capsule is formed by the coalescence of
cartilaginous elements appearing, first in the nasal septum by an extension of the cartilage from
the ventral surface of the body of the sphenoid and secondly by an independent centre in each
lateral wall of the capsule. At first the nasal capsule is open dorsally on either side of the nasal
septum in correspondence with the olfactory bulbs, but during the third month the wall of the
capsule corresponding to the cribriform plate commences to chondrify around the perforating
nerve-fibres, and so the lamina cribrosa is preformed in cartilage. Laterally strips of cartilage
(cartilago ethmosphenoidalis) pass backwards from the lateral edges of the cribriform plate to
unite it with the anterior edges of the alae orbitales of the sphenoid.
By the third month the nasal capsule has become cartilaginous. As has been stated above,
the nasal septum chondrifies by an extension forwards of the ventral part of the body of
the cartilaginous sphenoid. On either side of the ventral margin of this septum anteriorly are
developed the paraseptal cartilages, which in man persist till after birth. These are connected
posteriorly by means of a connective tissue bridge with small pieces of cartilage the posterior
paraseptal cartilages, which are in turn associated with the paranasal cartilages posteriorly,
and there in part form the floor of the recessus terminalis or cupola of the cartilaginous nasal
capsule (Fawcett). In man, owing to the deficiency of the lamina transversalis anterior, the
fenestra narina and the fenestra basalis which pierce the floor of the nasal capsule, on either
side of the septum, become confluent and form the fissura rostroventralis of Gaupp. Meanwhile
the lateral walls of the nasal capsule are chondrifying independently, forming the paranasal
cartilages. These become subsequently united anteriorly with the nasal septum to form the
tectum nasi or roof of the nose. At first this is open posteriorly where it is in relation with
the olfactory bulb, but later, as has been already described, the tissue around the nerve filaments
chondrifies to form the cartilaginous lamina cribrosa. The inferior concha is derived from the
cartilage of the lower and lateral part of the nasal capsule, from which, however, it becomes
isolated about the seventh month. Above and behind this the middle and superior conchae,
the ethmoidal turbinals, become chondrified, as well as the cartilaginous rudiments which
subsequently form the agger nasi, the bulla ethmoidalis, and the concha sphenoidale or
ossiculum Bertini.
Throughout life certain parts of the cartilaginous nasal capsule persist as the cartilaginous
nasal septum and the cartilages of the alae of the nose, whilst other parts are absorbed and
are replaced by surrounding bones of membranous origin.
The various foramina met with in the cranial base are formed either as clefts in the line of
union of the several cartilaginous elements, or through inclusion by means of bridging processes
derived from these same elements.
From the ventral surface of this cartilaginous platfornr formed, as described, by the union
of the trabeculse, parachordal cartilages, and cartilaginous auditory capsules is suspended the
cartilaginous framework of the visceral arches, which play so important a part in the develop-
ment of the face, an account of which is elsewhere given.
A consideration of the facts of comparative anatomy and embryology appears to justify the
assumption that the mammalian skull is of twofold origin that, in fact, it is composed of two
envelopes, an outer and an inner, primarily distinct, but which in the process of evolution have
become intimately fused together. The inner, called the primordial skull, is that which has
just been described, and consists of the choiidro-cranium and the branchial skeleton. The outer,
which is of dermic origin, includes the bones of the cranial vault and face which are developed
in membrane. This secondary skull, which first appears in higher fishes as ossified dermal plates
overlying the primary skull, acquires a great importance in the mammalia, as owing to the
expansion of the brain and the progressive reduction of the chondro-cranium, these dermal bones
become engrafted on and incorporated with the primordial skull, and act as covering bones to
the cavities of the cranium and face ; for it may be well to point out that these dermal or
membrane bones are not necessarily external in position, as over the cranial vault, but also
develop in the tissues underlying the mucous membrane of the cavities of the face.
Advantage is taken of this difference in the mode of development of the bones of the skull to
classify them according to their origin into cartilage or primordial bones, and membrane or
secondary bones. These differences in the growth of the bone must not be too much insisted
on in determining the homologies of the bones of the skull, as it is now generally recognised that
MOKPHOLOGY OF THE LIMBS. 293
all bone is of membranous origin, and that whilst in some cases cartilage may become calcified
it never undergoes conversion, into true bone, but is replaced by ossific deposit derived from a
membranous source. In the subsequent growth of the skull, parts of the cartilaginous cranium
persist as the septal and alar cartilages of the nose, whilst for a considerable period the basi-
sphenoid and basi-occipital are still united by cartilage. The cartilage also which blocks the
foramen lacerum may be regarded as a remnant of the chondro-cranium.
Whilst in many instances the primordial and secondary bones remain distinct in the fully-
developed condition, they sometimes fuse to form complex bones, such as the temporal and
sphenoid.
Various theories have been advanced to account for the mode of formation of the skull. The
earliest of these was called the vertebrate theory, which assumed that the cranium was built up
of a series of modified vertebrae, the bodies of which corresponded to the basi-cranial axis, whilst
the vertebral arches were represented by the covering bones of the cranium. In view of the more
recent researches regarding the composite origin of the skull above referred to, this theory was
necessarily abandoned. It gave way to the suggestion of Gegenbauer that the primordial
cranium has arisen by the fusion of several segments equivalent to vertebrae, the number of
which he determined by noting the metameric arrangement of the cerebral nerves, of which he
concluded there were nine pairs, arranged much like spinal nerves, both as to their origin and
distribution. The olfactory and optic nerves, though frequently referred to as cerebral nerves,
are excluded, since from the nature of their development they are to be regarded as meta-
morphosed parts of the brain itself. Gegenbauer therefore assumed that that portion of the
cranial base which is traversed by the nine pairs of segmentally arranged cerebral nerves must
be formed by the fusion of nine vertebral segments ; and as the region where the nerves escape
corresponds to the part of the chondro-cranium traversed by the notochord, he calls it the
vertebral portion of the cranial base, in contradistinction to the trabecular or non-vertebral part
which lies in front. This latter he regards as a new formation adapted to receive the greatly-
developed brain and afford protection to the organs of sight and smell.
As has been pointed out by Hertwig, there is an essential difference between the development
of the axial cartilaginous skeleton of the trunk and head. The former becomes segmented into
distinct vertebrae alternating with intervertebral ligaments ; whilst the latter, in order to attain
the rigidity necessary in this part of the skeleton, is never so divided. It follows from this that
the original segmentation of the head is only expressed in three ways, viz., in the appearance of
several primitive segments (myotomes), in the arrangement of the cerebral nerves, and in the
fundament of the visceral skeleton (visceral arches). According to Froriep, the mammalian
occipital corresponds to the fusion of four vertebrae, and there is some reason for supposing that
in some classes of vertebrates the occipital region of the primordial cranium is increased by
fusion with the higher cervical segments.
The form of skull characteristic of man is dependent on the large proportionate development
of the cranial part, which contains the brain, and the reduction in size of the visceral part
(face), which protects the organs of special sense. This leads to a decrease in the mass and
projection of the jaws, as well as a reduction in the size of the teeth. Associated with the
smaller mandible there is a feebler musculature, with a reduced area of attachment to the sides
of the skull. In this way the disappearance of the muscular crests and fossae, so characteristic
of lower forms, is accounted for. At the same time the fact that the skull is poised on the
summit of a vertical column, leads to important modifications in its structure. The disposition
of parts is such that the occipito-vertebral articulation is so placed that the fore and hind parts
of the head nearly balance each other, thus obviating the necessity for a powerful muscular and
ligamentous mechanism to hold the head erect.
Another noticeable feature in connexion with man's skeleton is the prolonged period during
which growth may occur before maturity is reached ; this is associated with a more complete
consolidation of the skull, since bones, which in lower forms remain throughout life distinct, are
in man fused with each other, as exemplified in the case of the presphenoid and postsphenoid,
the occipital and the interparietal, to mention one or two instances among many. It is
noteworthy, however, that during ontogeny the morphological significance of these bones is
clearly demonstrated by their independent ossification.
The points of exit of the various cerebral nerves remain remarkably constant, and in their
primitive condition serve to suggest the segmental arrangement of the cartilaginous chondro-
cranium already referred to. Owing to the very great modifications which the mammalian skull
has undergone in the process of its evolution, it may be pointed out that the passage of the
nerves through the dura mater a derivative, the readers may be reminded, of the primordial
membranous cranium (see ante) alone represents the primitive disposition of the nerves. Their
subsequent escape through the bony base is a later and secondary development. In some cases
the two, membranous or primary and the osseous or secondary foramina, correspond. In other
instances the exit of the nerves through the dura mater does not coincide with the passage
, through the bone.
Of interest in this connexion it may be pointed out that the foramina and canals which
traverse the skull are either situated in the line of suture between adjacent bones or in the line
of fusion of the constituent parts of which the bone pierced is made up. For example, the
superior orbital fissure is situated between the orbito and alisphenoids ; the hypoglossal canal
between the basi and exoccipitals ; the jugular between the petrous, basi, and exoccipital ;
the optic between the orbito-sphenoid and the presphenoid ; the pterygoid between the alisphenoid,
medial pterygoid lamina, and the lingula.
195
294
OSTEOLOGY.
APPENDIX F.
MORPHOLOGY OF THE LIMBS.
Development and Morphology of the Appendicular Skeleton.
The paired limbs first appear in the
human embryo about the third week as
small buds on either side of the cephalic
and caudal ends of the trunk. That these
outgrowths are derived from a large number
of trunk segments is assumed on the ground
that they are supplied by a corresponding
number of segmental nerves, and the circum-
stance that they are more particularly
associated with the ventral offsets of these
nerves would point to the conclusion that
they belong rather to the ventral than the
dorsal surface of the body.
At first the surfaces of these limb buds
are so disposed as to be directed ventrally
and dorsally, the ventral aspect correspond-
ing to the future flexor surface of the limb,
the dorsal to the extensor side. At the
same time, the borders are directed head-
wards (pre-axial), and tailwards (post-axial).
As the limbs grow, they soon display
evidence of division into segments corre-
sponding to the hand and foot, forearm ai
leg, upper arm and thigh. Coincident wit!
this (about the second month) the cartil-
aginous framework of the limb is beii
differentiated. The disposition of the
cartilages furnishes a clue to their homo-
logics. In the fore-limb the radius ai
thumb lie along the pre-axial borders, anc
correspond to the tibia and great toe, whicl
are similarly disposed in the hind-limb
whilst the ulna and fifth finger are hom(
logons with the fibula and fifth toe, whk
are in like manner arranged in relation
the posterior (post-axial) border of theii
respective limbs. Up to this time the liml
are directed obliquely ventralwards. During
the third month a change in the position
of the limbs takes place, associated with
the assumption of the foetal position.
Owing to the elongation of the limbs,
they become necessarily bent at the elbow
and knee, the upper arm inclining down-
ward along the thoracic wall, whilst the
thigh is directed upwards in contact with
the abdominal parietes. At the same time a
rotation of each of these segments of the limb
takes place in an inverse direction, so that the
pre-axial border of the humerus is turned
laterally, whilst the pre-axial border of the
femur is turned medially. Assuming that
these borders are homologous, it results from
this, that the lateral condyle of the humerus
corresponds to the medial condyle of the
femur. This torsion of the limb is in part
'effected at the shoulder and hip joints,
and to some extent also in the shafts of the
bones. Some anatomists 'hold that this
rotation is not confined to the limb, but
involves the dorsal part of the limb girdles.
Others maintain that there is no evidence
that such takes place. In the upper limb,
owing to a certain amount of pronation, the
Fio. 284. DIAGRAM TO ILLUSTRATE THE HOMOLOGIES OF
THE BONES OF THE LlMBS.
The two limb buds of an embryo prior to flexion and rotation.
The anterior or pre-axial border is coloured red; the
posterior or post-axial border, blue. B. After the
assumption of the foetal position. Flexion and rotation
have now taken place. The red and blue lines indicate
the altered position of the pre-axial and post-axial
borders. C. The fully developed limbs with the flexor
aspects directed towards the reader. The coloured
lines indicate the effect of the torsion of the upper
segment of the limb through quarters of a circle.
MOEPHOLOGY OF THE LIMBS. 295
pre-axial (radial) side of the forearm is now directed forwards and somewhat laterally, whilst
in the hind limb the pre-axial (tibial) side of the leg is turned backwards and laterally the
pre-axial borders of the hand with thumb, and foot with great toe being in correspondence. ' In
consequence of these changes in the position of the limbs, amounting in all in the upper segments
to a rotation through an angle of 90, the extensor surface of the fore limb is directed backwards
whilst that of the hind limb is directed forwards. In order to homologise the arrangement of
the bones in the extended limb, it is necessary to place them so that their flexor or extensor
surfaces are similarly disposed. It will then be observed (see diagram) that the medial or tibial
side of the leg and foot (primitively pre-axial) corresponds to the lateral or radial side of the
forearm and hand (primitively pre-axial), whilst the fibula and lateral border of the. foot
homologise with the ulnar or medial border of the forearm and hand (primitively post - axial),
the result, as previously explained, of the torsion or twisting in opposite directions through an
angle of 90 of the upper segment of the limb. In accordance with this view, it will be
evident that in the fore limb there is nothing homologous with the patella, whilst in the hind
limb there is no part to represent the olecranon.
In the axial mesoderm of each member, differentiation into cartilaginous segments begins
about the second month ; each of these cartilages becomes invested by a perichondrial layer
which stretches from segment to segment, and 'ultimately forms the ligaments surrounding
the joints, which are subsequently developed between the segments. Chondrification first
begins in the basal part of the limb, and extends towards the digits.
The homodynamy of the carpal and tarsal elements may be tabularly expressed, and compared
i with the more generalised types from which they are evolved.
Type. Hand. Foot.
Radiale (Tibiale) = Navicular (body) = Talus.
Intermedium =0s lunatum = Absent, or Os trigonum (?).
Ulnare (Fibulare) = Os triquetrum = Calcaneus.
Centrale = Absent, or fused with Navicular = Navicular, less its tuberosity.
Carpale (Tarsale), i. = Os multangulum majus = First Cuneiform.
Carpale (Tarsale), ii. = Os multangulum minus = Second Cuneiform.
Carpale (Tarsale), iii. = Capitate = Third Cuneiform.
Carpale (Tarsale), iv.^\ _ ,, = Cuboid, plus the peroneal .
Carpale (Tarsale), v. / ~ sesamoii
The pisiform is omitted from the above table, since it is now generally regarded as being a
vestige of an additional digit placed post-axial to the little finger (digitus post-minimus). Its
homologue in the foot is by some considered as fused with the calcaneus. The tuberosity of the
navicular, formed, as has been stated, of three elements, of which the sesamoid bone in the
tendon of the tibialis posterior may be one, is to be regarded as the homologue of the pre-axial
sesamoid in the hand, which probably fuses with the navicular to form its tuberosity. The
peroneal sesamoid probably corresponds to the hamulus (sometimes an independent ossicle)
of the os hamatum. Similarly, on the pre-axial border of the hand and foot, vestiges of a
suppressed digit (prepollex and prehallux) may occasionally be met with. The frequent occur-
rence of an increase in the number of digits seems to indicate that phylogenetically the number
of digits was greater than at present, and included a prepollex or prehallux, and a digitus post-
minimus. The correspondence of the metacarpus with the metatarsus and the phalanges of the
fingers with those of the toes is so obvious that it is sufficient merely to mention it.
The differences in size, form, and disposition of the skeletal elements of the hand and foot is
easily accounted for by a reference to the functions they subserve.
In the hand, strength is sacrificed to mobility, thus leading to a reduction in the size of the
carpal elements, and a marked increase in the length of the phalanges. The freedom of move-
ment of the thumb, and its opposability to the other digits, greatly enhances the value of
the hand as a grasping organ. In the foot, where stability is the main requirement, the tarsus
is of much greater proportionate size, whilst the phalanges are correspondingly reduced. Since
the foot no longer serves as a grasping organ, the great toe is not free and opposable like the
thumb.
Limb Girdles. The free limbs are linked to the axial skeleton by a chain of bones which
constitute their girdles. The fundamental form of these limb girdles consists each of a pair of
curved cartilages placed at right angles to the axis of the trunk on either side, and embedded
within its musculature. Each cartilage has an articular surface laterally, about the middle, for
the reception of the cartilage of the first segment of the free limb. In this way each pectoral
and pelvic cartilage is divided into an upper or dorsal half and a lower or ventral half. The
dorsal halves constitute the scapula and ilium of the pectoral and pelvic girdles respectively.
With regard to the ventral halves there is more difficulty in establishing their homologies. The
original condition is best displayed in the pelvic girdle ; here the ventral segment divides into
two branches one anterior, which represents the pubis, the other posterior, which ultimately
i forms the ischium. Ventrally, the extremities of these cartilages unite to enclose the obturator
foramen. In the pectoral girdle the disposition of the ventral cartilages is not so clear, consisting
primitively of an anterior branch or precoracoid, and a posterior portion or coracoid ; these, in
higher forms, have undergone great modifications in adaptation to the requirements of the fore
limbs. The posterior or coracoid element, the homologue of the ischial cartilage in the pelvic
girdle, is but feebly represented in man by the coracoid process and the coraco-clavicular ligament.
296
OSTEOLOGY.
With regard to the homologue of the pubic element in the pectoral girdle, there is much difference
of opinion ; in reptiles and amphibia it corresponds most closely- to the precoracoid, but it is
doubtful what represents it in mammals. According to Goette and Hoffman, the clavicle is a
primordial bone, and not, as suggested by Gegenbaur, of secondary or dermic origin. If this be
so, it corresponds to the ventral anterior segment of the pectoral girdle, and is therefore homo-
logous with the ventral anterior (pubic) segment of the pelvic girdle. On the other hand, if
Gegenbaur's view be accepted, the clavicle has no representative in the pelvic girdle. It must,
however, be borne in mind that during its ossification it is intimately associated with cartilage,
and that that cartilage may represent the precoracoid bar ; nor must too great stress be laid upon
the fact that the clavicle begins to ossify before it is preformed in cartilage, since that may be
merely a modification in its histogenetic development.
According to another view (Sabatier), the subcoracoid centre (see Ossification of Scapula) is
derived from the posterior ventral segment, and corresponds to the ischium, whilst the coracoid
process is the remains of the anterior ventral segment (precoracoid), and is homodynamous with
the pubis.
In no part of the skeleton does function react so much on structure as in the arrangement of
the constituent parts of the pectoral or pelvic girdles. In man, owing to the assumption of the
erect position and the bipedal mode of progression, the pelvic girdle acquires those characteristics
which are essentially human, viz., its great relative breadth and the expansion of its iliac
portions, which serve as a support to the abdominal viscera, and also furnish an extensive origin
for the powerful muscles which control the movements of the hip-joint. The stability of the
/Vertebral or internal surfaces
/'I
'
/' !
Vertebral or internal surface/
A C
FlG. 285. DIAGRAM TO ILLUSTRATE THE HOMOLOGOUS PARTS OF THK SCAPULA AND ILIUM
ACCORDING TO FLOWER.
A, ideal type ; three-sided rod. B, scapula rotated forward through quarter of a circle (90), so that the
primitive medial or vertebral surface is now directed anteriorly. C, ilium rotated backwards through
quarter of a circle so that the primitive medial surface is now turned posteriorly. In the diagram the
primitive medial or vertebral surface of each figure is coloured black, the pre -axial surfaces red, and the
post-axial surfaces blue.
pelvic girdle is insured by the nature of its union with the axial skeleton, as well as by the
osseous fusion of its several parts, and their union in front at the symphysis pubis.
Various attempts have been made to homologise the several parts of the ilium and scapula.
All are open to objection ; that by Flower is perhaps the most generally accepted. Assuming
that the primitive type is represented by a prismatic rod, of which the dorsal end represents
either the epiphysial border of the vertebral edge of the scapula or the iliac crest, whilst the
ventral end corresponds to the glenoid or acetabular articular areas respectively, the surfaces of
the three-sided rod are disposed so that one is vertebral or medial, another pre-axial, and the
third post-axial. These surfaces are separated by borders, of which one is lateral, separating
the pre-axial and post-axial surfaces, whilst the antero - medial and postero - medial margins
separate the pre-axial and post-axial surfaces respectively from the vertebral or medial aspect.
It is a necessity of Flower's theory that this part of the girdle undergoes a rotation along with
the rest of the limb. Thus in the fore limb the surfaces of the primitive type are turned so that
the vertebral surface looks forward, whilst in the case of the hind limb the vertebral surface is
turned backward. A study of the accompanying diagram will enable the reader to realise how
the ventral surface of the scapula is thus rendered homologous with the gluteal surface of the
ilium, for by reference to the type, both these surfaces will be seen to correspond to the post-
axial areas of the primitive condition. In accordance with this view the surfaces and borders of
the scapula are homologised by Flower, as shewn in the subjoined table :
Scapula.
Supra-spinous fossa
Infra-spinous fossa
Subscapular fossa
SURFACES
Ideal.
1. Vertebral
2. Pre-axial
3. Post -axial
Pelvis.
Medial surface of ilium behind linea ar-
cuata interna, including the articular
surface for the sacrum and the portion
of the bone above and below this
Iliac fossa
Gluteal surface of ilium
MOEPHOLOGY OF THE LIMBS.
297
BORDERS
Axillary border, posterior on '| 1. Lateral
most animals (attachment of
triceps muscle)
Spine continued into acromion
Superior border, anterior in
most animals, with scapulo-
coracoid notch
2. Antero-medial
3. Postero-medial
Anterior border (attachment of rectus
muscle)
Linea arcuata interna continued into
pubis
Posterior border with greater sciatic notch
Flower's views of this matter were strenuously opposed by Humphry, who maintained that
there is strong presumptive evidence against any rotation of the superior parts of the girdles,
since it is difficult to suppose that the scapula and ilium can undergo a rotation which is not
participated in by the coracoid and ischium. According to this anatomist the homologous parts
of the two bones are as stated below :
Scapula.
Pre -spinal ridge forming the floor of the pre-
spinal fossa
Spine and acromion
Post-spinal part of scapula forming the floor of
the post -spinal fossa
Posterior angle
Posterior border
Medial or ventral surface
Ilium.
Linea ilio-pectinea
Fore part of the blade and crest of the ilium,
with its anterior spine or angle
Hinder part of blade and crest of ilium
Posterior spine or angle
Posterior or sciatic border of ilium
Inner or true pelvic surface of ilium, including
the surface for the articulation of the sacrum
B AC
FIG. 286. DIAGRAM TO ILLUSTRATE THE HOMOLOGOUS PARTS OF THE SCAPULA AND ILIUM,
ACCORDING TO HUMPHRY.
A, primitive rod-like ilium of kangaroo, prismatic on section. B, scapula,
surfaces are similarly coloured.
C, ilium. The corresponding
The difficulty arising in this scheme of attempting to homologise the attachments of the
triceps and rectus femoris, Humphry explains by pointing out that the former muscle also arises
from the lateral surface of the scapula, whilst the rectus overruns the lateral surface of the ilium
above the acetabulum, so that there is a correspondence in the origins of both these muscles from
the lateral surface of their respective bones ; but in consequence of the rotation of the extensor
surfaces of the limbs in opposite directions the triceps has been turned backwards on to the
posterior border of the scapula, whilst the rectus has been turned forwards on to the anterior
border of the ilium. Sufficient has been said to enable the reader to recognise that all attempts
to determine in detail the homologies of these parts are beset with difficulty.. It is wiser, therefore,
in our present state of knowledge to be content with establishing a general correspondence, and
so avoid the error of endeavouring to establish a closer homological relationship than actually
exists.
In man, since the erection of the figure no longer necessitates the use of the fore limb as a
means of support, the shoulder girdle has become modified along lines which enhance its mobility
and determine its utility in association with a prehensile limb. Some of its parts remain
independent (clavicle and scapula), and are united by diarthrodial joints, whilst others have
298 OSTEOLOGY.
become much reduced in size or suppressed (coracoid, precoracoid, see ante). The dorsal part
of the girdle (scapula) is not directly united with the axial skeleton as is the ilium, but is only
indirectly joined to it through the medium of the clavicle, which is linked in front with the
presternum. The same underlying principles determine the differences in mobility and strength
between the shoulder, elbow, and wrist, and the hip, knee, and ankle joints of the fore and hind
limbs respectively, whilst the utility of the hand is further enhanced by the movements of
pronation and supination which occur between the bones of the forearm. In the leg such
movements are absent, as they would interfere with the stability of the limb.
THE ARTICULATIONS OK JOINTS.
SYNDESMOLOGY.
By DAVID HEPBURN.
Syndesmology is that branch of human anatomy which treats of the articulations
or joints.
A junctura ossium (articulation or joint) constitutes a mode of union or con-
nexion subsisting between any two separate segments or parts of the skeleton,
whether osseous or cartilaginous. It has for its primary object either the
preservation of a more or less rigid continuity of the parts joined together, or else
the permission of a variable degree of mobility, subject to the restraints of the
uniting media.
Classification of Joints. In attempting to frame a classification of the
numerous joints in the body, several considerations must be taken into account,
viz., the manner and sequence of their appearance in the embryo ; the nature of the
uniting media in the adult, and also the degree and kind of movement permitted
in those joints where movement is possible.
In this way we obtain two main subdivisions of joints :
(1) Those in which the uniting medium is co-extensive with the opposed sur-
faces of the bones entering into the articulation, and in which a direct
union of these surfaces is thereby effected.
(2) Those in which the uniting medium has undergone more or less of interrup-
tion in its structural continuity, and in which a cavity of greater or less
extent is thus formed in the interior of the joint.
To the first group belong all the immovable joints, many of which are only
of temporary duration ; to the second group belong all joints which possess, as their
outstanding features, mobility and permanence.
SYNARTHROSES.
The general characteristics of this group are partly positive and partly nega-
tive. Thus, there is uninterrupted union between the
opposed surfaces of the bones joined together at the plane
of the articulation, i.e. there is no trace of a joint cavity,
and further, there is an entire absence of movement.
Developmentally, these joints result from the approxi-
mation of ossific processes which have commenced from
separate centres of ossification, and therefore the nature
of the uniting medium varies according as the bones
thus joined together have originally ossified in membrane
or in cartilage. In the former case union is effected by
an interposed fibrous membrane continuous with, and
corresponding to, the periosteum. To such articulations
the term sutura (Fig. 287) is applied. In the latter case Fl - 287 -
the uniting medium is a plate of hyaline cartilage. Such
articulations are called synchondroses (Fig. 288). In all the synchondroses, and in
many of the sutures, the uniting medium tends to disappear in the progress of
299
300
THE ARTICULATIONS OK JOINTS.
Intervening
hyaline
cartilage
Fia.
THE OCCIPITO-SPHENOID SYN-
CHONDROSIS.
ossification, and thus the plane of articulation becomes obliterated, so that direct
structural continuity between the osseous segments takes place. The primary
features common to all synarthroses are (a) continuous
and direct union of the opposing surfaces; (&) no joint
cavity ; (c) no movement.
Sutura. This form of synarthrosis is found only in
connexion with the bones of the skull. In a large
number of cases the bones which articulate by suture
present irregular interlocking margins, between which
there is the interposed fibrous membrane to which refer-
ence has already been made. When these interlocking
margins present well-defined projections they are said to
form a sutura vera (true suture) ; on the other hand, when
288. SECTION THROUGH the opposed surfaces present ill-defined projections, or
even flat areas, they are described as sutura notha
(false suture). In each of these subdivisions the particular
characters of the articulating margins are utilised in framing additional descriptive
terms. Thus true sutures may possess interlocking margins whose projections are
tooth-like (sutura dentata), e.g. in the interparietal suture ; saw-like (sutura serrata)
(Fig. 289), e.g. in the interfrontal suture ; ridge-like, or comparable
to the parallel ridges on the welt of a boot (sutura limbosa).
Similarly false sutures may articulate by margins which are scale-
like (sutura squamosa), e.g. in the squamoso-parietal suture ; or by
rough opposed surfaces, sutura harmonia, e.g. in the suture between
the palatine processes of the maxillary bones. There is one
variety of synarthrosis which, in the adult, can scarcely be called a
suture, although the differences are of minor importance, viz.,
schindylesis, which is an articulation between the edge of a plate-
like bone, such as the rostrum of the sphenoid, and the cleft in I
another, such as the vorner.
Synchondrosis. Illustrations of this group can be found only ]
in the young growing individual, because as age advances and
growth ceases, the process of ossification affects the hyaline cartilage which con-
stitutes the uniting medium, and the plane of articulation disappears. Under this
heading we may include the planes of junction between all epiphyses and the
diaphyses to which they severally belong. The occipito- sphenoid (Fig. 288) and
the petro-jugular articulations in the base of the skull provide other well-marked
examples.
289. SUTURA
SERRATA.
AMPHIARTHROSES DIARTHROSES (MOVABLE JOINTS).
The leading features of this group are capability of movement and permanence.
In very few instances do such joints ever become obliterated under normal con-
ditions. Determining their permanence, and regulating the amount of possible
movement, there is always more or less of interruption in the continuity of the
structures which bind the osseous elements together. That is, there is always some
evidence of a cavum articulare (joint cavity), although as a matter of course such
interruption can never be so extensive as to entirely disassociate the articulating
elements. Therefore in all movable joints a new class of structures is found, viz.,
ligamenta (the ligaments), by means of which continuity is maintained even when
all the other uniting media have given place to an articular cavity. The further
subdivision of this group is founded upon the amount of movement permissible, and
the extent to which the articular cavity takes the place of the original continuous
uniting medium. Thus we obtain the amphiarthroses, or partly movable, and the
diarthroses, or freely movable.
An amphiarthrosis (Fig. 292) presents the following characteristics : (a)
partial movement ; (6) union by ligaments and by an interposed plate or disc of
fibro-cartilage, in the interior of which there is (c) an incomplete or partial joint
cavity, which may be lined by a rudimentary stratum synoviale (synovial membrane)
fcl.KUU.1. UJKJ1.
Cartilage
/ articularis
whose function it is to secrete a lubricating fluid, the synovia or joint-oil ; (d~) a
plate of hyaline cartilage coating each of the opposing surfaces of the bones
concerned. All the joints belonging to this group occur in the median plane of
the body. It includes the symphysis pubis, the joints between the bodies of the
vertebras, and the joint between the manubrium sterni and the body of the sternum.
A diarthrosis (Fig. 291) is the most elaborate as well as the most complete form
of articulation. It is characterised by (a) capability of movement which is more or
less free in its range ; (6) a reduction of the
uniting structures to a series of retaining liga-
ments ; (c) an articular cavity which is limited
only by the surrounding ligaments; (d)
the constant presence of synovial membrane ;
(e) cartilage articularis (hyaline encrusting
cartilage) which clothes the opposed surfaces
of the articulating bones. The majority of the
joints in the adult belongs to this group. This
series of joints has been subdivided into a
number of minor sections, in order to
emphasise the occurrence of certain well-
marked structural features, or because of the
particular nature of the movement by which
they are characterised. Although in all
diarthroses there is a certain amount of
gliding movement between the opposed surfaces of the bones which enter into
their formation, yet, when this gliding movement becomes their prominent feature,
as in most of the joints of the carpus and tarsus, they are termed arthrodia. But
bones may be articulated together so as to permit of movement in one, two, or
more fixed axes of movement, or in modifications of these axes. Thus in uniaxial
joints the axis of movement may lie in the longitudinal axis of the joint, in
which case the trochoid rotatory form of joint results, as in the proximal and
distal radio-ulnar articulations ; or it may correspond with the transverse axis of
the articulation, as in the elbow-joint and knee-joint, when the gmglymus or hinge
iety results. If movement takes place about two principal axes situated at
rht angles to each other, as in the radio-carpal joint, the terms ellipsoid (biaxial
condyloid) are applied. Movements occurring about three principal axes placed
right angles to each other, or in modifications of these positions, constitute
mltiaxial joints, in which the associated structural peculiarities provide the
alternative terms of enarthrosis or ball-and-socket joints.
Stratum
synoviale
Cartilage/
articularis
FIG. 290. DIAGRAM OF A DIARTHRODIAL
JOINT.
STRUCTURES WHICH ENTER INTO THE FORMATION OF JOINTS.
The structures which enter into the formation of joints vary with the nature
of the articulation. In every instance there are two or more skeletal elements,
whether bones or cartilages, and in addition there are the uniting media, which are
either simple or elaborate according to the provision made for rendering the joint
more or less rigid, or capable of movement. We have already seen that the uniting
medium in synarthrodial joints is a remnant of the common matrix, whether fibro-
vascular membrane or hyaline cartilage, in which ossification has extended from
separate centres. Among the amphiarthroses there is still extensive union between
the opposing surfaces of the articulating bones, but the character of the uniting
medium has advanced from the primitive embryonic tissue to fibrous and fibro-
cartilaginous material, as well as hyaline cartilage. These, with very few exceptions,
are permanent non-ossifying substances, such as may be seen between the opposing
osseous surfaces of two vertebral bodies. The joint cavity, more or less rudimentary,
is confined to the centre of the fibro-cartilaginous plate, and may result from the
softening or imperfect cleavage of the central tissue. It may also present rudiments
of a synovial membrane.
In the diarthrodial group the extensive cavity has produced great interruption
in the continuity of the uniting structures which originally existed between the
302
THE AETICULATIONS OR JOINTS.
bones forming such a joint. Ligaments have therefore additional importance in
this group, for not only do they constitute the uniting media which bind the
articulating bones together, but, to a large extent, they form the peripheral
boundary of the joint cavity, although not equally developed in all positions.
Thus, every diarthrodial joint possesses a fibrous or ligamentous envelope con-
stituting the fibrous stratum of the articular capsule, which is attached to the ad-
jacent ends of the articulating bones. For special purposes, particular parts of the
fibrous stratum may undergo enlargement and thickening, and so constitute strong
ligamentous bands, although still forming continuous constituents of the envelope.
The fibrous stratum is lined by a stratum synoviale (O.T. synovial membrane),
the two strata constituting the capsula articularis. The synovial stratum is con-
tinued from the inner surface of the fibrous stratum to the surface of the intra-
articular portion of each articulating bone. The part of the bone included within
the joint consists of a " non-articular " portion covered by the synovial layer and
an " articular " portion covered by encrusting hyaline cartilage. The latter provides
the surface which comes into apposition with the corresponding area of another
bone. In its general disposition the synovial layer may be likened to a cylindrical
tube open at each end. This layer is richly supplied by a close network of
vessels and nerves.
Certain diarthroses present intracapsular structures which may be distinguished
as interarticular ligaments and articular discs and menisci (O.T. interarticular
fibro-cartilages).
Ligamenta Interartidularia. Interarticular ligaments extend between, and are
attached to, non-articular areas of the intracapsular portions of the articulating
bones. They usually occupy the long axis of the joint, and occasionally they
widen sufficiently to form partitions which divide the joint-cavity into two com-
partments, e.g. the articulation of the heads of the ribs with the vertebral column,
and certain of the costo-sternal joints.
Articular discs and menisci (O.T. interarticular fibro-cartilages) (Fig. 291) are
more or less complete partitions situated between and separating opposing articular
surfaces, and when complete they divide the joint cavity into two distinct
compartments. By its periphery, a disc is
rather to be associated with the articular
capsule than with the articulating bones,
although its attachments may extend to
non - articular areas on the latter. Those
found in the knee-joint are called menisci ;
those found in other joints are called articular
discs.
Both interarticular ligaments and articu-
lar discs and menisci have their free surfaces
covered by the synovial stratum.
Adipose tissue, forming pads of varying size,
is usually found in certain localities within
the joint, between the synovial stratum and
the surfaces which it covers. These pads are
FIG. 291. DIAGRAM OF A DIARTHRODIAL JOINT soft and pliable, and act as packing material,
WITH ARTICULAR DISC DIVIDING THE JOINT- filling up gaps or intervals in the joint.
CAVITY INTO TWO COMPARTMENTS. T , . & , J
During movement they adapt themselves to
the changing conditions of the articulation.
In addition to merely binding together two or more articulating bones, ligaments
perform very important functions in connexion with the different movements
taking place at a joint. They do not appreciably lengthen under strains, and thus
ligaments may act as inhibitory structures, and by becoming tense may restrain
or check movement in certain directions.
Synovial strata, in the form of closed sacs termed mucous or synovial bursse, are frequently
found in other situations besides the interior of joints. Such bursae are developed for the
purpose of reducing the friction, (a) between the integument and certain prominent subcutaneous
bony projections, as, for instance, the point of the elbow, or the anterior surface of the patella
Cartilage
articularis
THE DIFFERENT KINDS OF MOVEMENT AT JOINTS. 303
(subcutaneous mucous bursae) ; (6) between a tendon and some surface, bony or cartilaginous, over
which it plays (subtendinous mucous bursae) ; (c) between a tendon or a group of tendons and the
walls of osteo-fascial tunnels, in which they play (vaginae mucosae tendinum or mucous sheaths
of tendons). Subtendinous mucous bursae are often placed in the neighbourhood of joints, and in
such cases it not infrequently happens that there is a direct continuity between the bursa and the
synovial stratum which lines the cavity of the joint through an aperture in the articular capsule.
THE DIFFERENT KINDS OF MOVEMENT AT JOINTS.
Reference has already been made to the existence of fixed axes of movement as
a basis for the classification of certain forms of diarthrodial joints. Hence it is
evident that the movements which are possible at any particular joint depend to a
large extent upon the shape of its articular surfaces as well as upon the nature of
its various ligaments. Therefore the technical terms descriptive of movements
either indicate the directions in which they occur, or else the character of the com-
pleted movement.
In the great majority of articulations between short bones, the amount of move-
ment is so restricted, and the displacement of the opposing articular surfaces so
slight, that the term gliding sufficiently expresses its character.
A gliding movement of an extensive kind, for example that of the patella upon the femur, in
which the movement largely resembles that of the tyre of a wheel revolving in contact with the
ground so that different parts are successively adapted to each other, is called co-aptation.
Articulations between long bones, on the other hand, are usually associated
with a much freer range of movement, with a corresponding variety in its character.
Rotation is a movement around an axis which is longitudinal. Sometimes it is the
only form of movement which a joint possesses ; at other times it is merely one of a
series of movements capable of execution at the same joint. Flexion or bending is
a movement in which the formation of an angle between two parts of the body is
an essential feature. As it is possible to perform this movement in relation to two
axes, viz., a transverse and an antero-posterior axis, it is necessary to introduce
qualifying terms. Thus, when two anterior or ventral surfaces are approximated,
as at the hip-, elbow-, or wrist-joints, the movement is called ventral, anterior, or
palmar flexion ; but if posterior or dorsal surfaces are approximated by the process of
bending, then the flexion becomes posterior or dorsi-flexion, as at the knee- or wrist-
joints. Further, at the wrist-joint, the formation of an angle between the ulnar
border of the hand and the corresponding aspect of the forearm, produces ulnar
flexion, and similarly the bending of the hand towards the radial border of the
forearm is radial flexion.
Extension or straightening consists in obliterating the angle which resulted from
flexion. In the case of certain joints, therefore, such as the elbow, wrist, and knee,
the segments of the limb occupy a straight line as regards each other when
extended.
At the ankle-joint the natural attitude of the foot to the leg is flexion at a right angle. The
diminution of this angle by approximating the dorsum of the foot towards the anterior aspect
of the leg constitutes flexion ; while any effort at placing the foot and leg in a straight line, i.e.
obliteration of the angle, as in pointing the toes towards the ground and raising the heel,
constitutes extension.
Abduction is a term which either expresses movement of an entire limb in a
direction away from the median plane of the body, or of a digit, away from the
plane of the middle finger in the hand, or the plane of the second toe in the case
of the foot.
Adduction is the reverse of abduction, and signifies movement towards the
median plane of the body, or towards the planes indicated for the digits. of the hand
and foot.
Circumduction is a movement peculiarly characteristic of multiaxial or ball-
and-socket joints. It consists in combining such angular movements as flexion,
extension, abduction, and adduction, so as to continue the one into the other,
whereby the joint forms the apex of a cone of movement, and the free end of the
limb travels through a circle which describes the base of this cone.
304 THE AKTICULATIONS OK JOINTS.
THE DEVELOPMENT OF JOINTS.
Just as the question of structure determines to a large extent the presence or absence
of movement in joints, so in tracing their development it will be found that the
manner of their appearance forecasts their ultimate destination as immovable or mov-
able articulations.
All joints arise in mesodermic tissue which has undergone more or less differentiation.
When this differentiation has produced a continuous membranous layer, in which
ossific centres representing separate skeletal segments make their appearance, we get the
primitive form of suture. The plane of the articulation merely indicates the limit of
the ossific process extending from different directions. If, again, the differentiation of
the mesoderm has resulted in the formation of a continuous cartilaginous layer, in which
ossification commences at separate centres, the plane of the articulation is marked
out by the unossified cartilage in other words, the articulation is a synchondrosis. Ulti-
mately this disappears through the extension of the process of ossification.
To some extent sutures also disappear, although their complete obliteration is not
usual even in aged people. Developmentally, therefore, synarthroses or immovable
joints do not present any special structural element, and, speaking generally, they have
only a temporary existence.
The development of all movable joints is in marked contrast to that of synar-
throses. Not only are they permanent arrangements so far as concerns normal conditions,
but they never arise merely as planes which indicate the temporary phase of an ossific
process. From the outset they present distinct skeletal units, from which the special
structures of the joint are derived.
The primitive movable joint is first recognised as a mass of undifferentiated meso-
dermic cells situated between two masses, which have differentiated into primitive cartilage.
The cell-mass which constitutes the joint- unit presents the appearance of a thick
cellular disc, the proximal and distal surfaces of which are in accurate apposition with the
primitive cartilages, while its circumference is defined from the surrounding mesoderm by
a somewhat closer aggregation of the cells of which the disc is composed. From this
cellular disc or joint-unit all the structures characteristic of amphiarthrodial and diar-
throdial joints are ultimately developed.
Thus, by the transformation of the circumferential cells into fibrous tissue the invest-
ing ligaments are produced. Within the substance of the disc itself a transverse cleft,
more or less well-defined and complete, makes its appearance. In this manner the disc is
divided into proximal and distal segments, separated from each other by an interval
which is the primitive articular cavity. This cleft, however, never extends so far as to
interrupt the continuity of the circumferential part of the disc which develops into the
fibrous tissue of the investing ligaments. From the proximal and distal segments
of the articular disc the various structures, distinctive of movable joints, are developed.
Thus, in amphiarthrodial joints the cellular articular disc or primitive joint-unit gives
origin to the following structures : From its circumference, investing ligaments ; from
its interior, the fibro cartilaginous plate in which an imperfect articular cavity with
corresponding imperfect synovial stratum may be found.
In the case of a diarthrodial joint the changes take place on a more extended scale.
The articular cavity becomes a prominent feature, in relation to which the surrounding
fibrous structures form an investing capsule, lined with a synovial stratum.
When a single cleft arises, but does not extend completely across the longitudinal axi
of the articular disc, the undivided portion develops into fibrous interarticular ligaments
On the other hand, when two transverse clefts are formed, that portion of the cellula
disc which remains between them becomes transformed into a fibro-cartilaginous dis
(or in the case of the knee-joint, menisci), which in its turn may either be complete o
incomplete, and thus we may obtain two distinct synovial joint cavities belonging to on
articulation. 1
In considering the development of the synovial layer, and the surfaces on which it i
found in the interior of a joint, it is necessary to keep clearly in mind that a synovia
layer is a special structure, whose function it is to produce a lubricating fluid or synovia
and that, therefore, its position is determined by the essential necessity of proximit;
to a direct blood-supply. In other words, this condition is provided by all parts c
1 From a series of observations upon the development of diarthrodial joints, the writer considers th;
there is evidence to show that the " cellular articular disc " is directly responsible for the production
the epiphyses which adjoin the completed articular cavity, and that, among such amphiarthroses as exi
between the bodies of vertebrae, not only the intervertebral fibro-cartilage, but the proximal and dist
epiphyses which ultimately unite with the vertebral bodies have a common origin in the joint-unit.
LIGAMENTS OF THE VEETEBEAL COLUMN. 305
the interior of an articular cavity except the articular encrusting cartilage. Conse-
quently the synovial stratum is absent only from the free surface of articular cartilage,
although it forms a thicker layer upon the inner surface of the articular capsule than
upon the free surfaces of interarticular ligaments, discs, and menisci.
It is not necessary to suppose that the synovial stratum has disappeared from these
articular cartilages as the result of friction, because, notwithstanding constant friction,
such parts as the interior of articular capsules or the menisci of the knee-joint have not
been denuded of their synovial covering.
As the epiphyses adjoining articular cavities are produced in the joint-units, the
attachments of the capsule should be found upon, and restricted to, the non-articular
surfaces of the articular epiphyses. While this is the case in their earliest stages; yet, as
development advances, considerable variations arise, until, in the adult condition, the
capsule of the larger articulations, more particularly of the extremities, is not always
restricted to the epiphyses for its attachments. The student will readily perceive and
appreciate these variations by comparing the accounts and illustrations of the epiphyses
with those of the articulations, and he should note that in some cases the epiphysial line
is extra-capsular, i.e. the capsular attachment is restricted to the epiphysis ; in some the
line is intra-capsular ; and in some the epiphysial line is partly in tra- capsular and partly
extra-capsular.
MORPHOLOGY OF LIGAMENTS.
From what has been said in connexion with the development of joints, it will be evident
that ligaments are essentially products derived from the cellular articular disc.
Nevertheless, in relation to the fully formed joint, many structures are described as ligaments
which do not take origin in the manner just indicated. Some of these ligamentous structures
remain fairly distinct from the articular capsules with which they are immediately associated ;
others become thoroughly incorporated with the articular capsules and cannot be separated
therefrom, while yet others may be found situated within the capsule of a joint, and thus play
the part of interarticular ligaments.
Instances of each of these forms of adventitious ligaments may be readily given. For
example, we may instance the expansion of the tendon of the semimembranosus muscle to the
oblique ligament of the knee-joint, and the offshoots from the tendon of the tibialis posterior
muscle to the plantar aspects of various tarsal bones, as illustrations of structures which play
an important part as ligaments, but are not indelibly incorporated with the joint capsule.
Of structures which have become indelibly incorporated with the primitive capsule, we may
instance the broad tendinous expansions of the quadriceps extensor muscle around the knee-joint.
The tibial collateral ligament of the same joint is regarded as a detached portion of the
tendon belonging to that part of the adductor magnus muscle which takes origin from the
ischium, while the fibular collateral ligament of the knee is considered by some to be the primi-
tive femoral origin of the peronoeus longus muscle. Another illustration of the same condition
is found in the coraco-humeral ligament, which is regarded by some as representing a detached
portion of the pectoralis minor muscle.
Two illustrations may be given of structures playing the part of ligaments within the
capsule of a joint, although in the first instance they are not developed as ligaments. It is
questionable if the ligamentum teres of the hip-joint is an interarticular ligament in the true
sense of the term ; it has been regarded as the isolated and displaced tendon of the ambiens muscle
found in birds. In the shoulder -joint, many observers look upon the superior gleiio-humeral
ligament as representative of the ligamentum teres.
Such structures as the stylo-hyoid ligament and the spheno-mandibular ligament, although
described as ligaments, are in reality skeletal parts which have not attained their complete
ossific development.
Again, certain portions of the deep or muscular fascia of the body which become specialised
into restraining and supporting bands (e.g. the ilio-tibial tract of the fascia lata ; the stylo-mandi-
bular ligament ; the transverse carpal and dorsal carpal ligaments of the wrist-joint ; the
transverse crural ligament, and lig. laciniatum of the ankle-joint), although called ligaments,
have no direct developmental association with articular ligaments.
Lastly, the inguinal ligament of Poupart and the lacunar ligament of Gimbernat, being
special developments in connexion with an expanded tendon or aponeurosis, are still further
removed from association with an articulation.
LIGAMENTA COLUMNS VEETEBRALIS ET CRANIL
Ligaments of the Vertebral Column and Skull. All vertebrse, with the
exception of those which deviate from the common vertebral type, present two
sets of articulations whose various parts are arranged upon a uniform pattern.
Thus, every pair of typical vertebrae presents an articulation between the bodies
and a pair of articulations between the vertebral arches. With the latter there
20
306
THE AETICULATIONS OE JOINTS.
are associated various important accessory ligaments which bind together laminae,
spinous processes, and transverse processes.
Articulations between Bodies of Vertebrae. These are amphiarthrodial joints.
Singly, they present only a slight degree of mobility, but when this amount of move-
ment is added to that of the whole series, the range of movement of the vertebral
Vertebral body
lutervertebral fibro-
cartilage
Nucleus pulposus
Ligamentum flavum
Ligamentura
interspinale
Ligamentum
supraspinale
Spinous process
FIG. 292. MEDIAN SECTION THROUGH A PORTION OP THE LUMBAR PART OF THE VERTEBRAL COLUMN.
column becomes considerable. The articular surfaces are the flattened surfaces of
adjacent vertebral bodies. They are bound together by the following structures :
Fibrocartilagines Intervertebrales (Fig. 292). Each intervertebral fibro-
cartilage accommodates itself to the space it occupies between the two vertebral
bodies, to both of which it is firmly adherent. The fibro-cartilages, from different
Anterior longitudinal ligament
Rib
Three slips of the
radiate ligament
of the head of the rib
Anterior costo-
transverse
ligament
FIG. 293. ANTERIOR LONGITUDINAL LIGAMENT OF THE VERTEBRAL COLUMN, AND THE COSTO-VERTEBRAL i
JOINTS AS SEEN FROM THE FRONT.
parts of the vertebral column, vary in vertical thickness, being thinnest from the]
third to the seventh thoracic vertebra, and thickest in the lumbar region. In theS
cervical and lumbar regions each fibro- cartilage is thicker anteriorly than
posteriorly, thereby assisting in the production of the anterior convexity which >
characterises the vertebral column in these two regions. In the thoracic region
LIGAMENTS OF THE VEETEBEAL COLUMN.
307
the fibro-cartilages are thinnest on their anterior aspects in correspondence with
the anterior concavity of this section of the vertebral column.
Each fibro-cartilage consists of a circumferential portion, annulus fibrosus, formed
for the most part of oblique parallel fibres running from one vertebra to the
other; horizontal fibres are also found. The axial or central part of the fibro-
cartilage, the nucleus pulposus, is elastic, soft, and pulpy.
The superior and inferior surfaces of the fibro -cartilage are closely adherent
to the adjoining epiphyseal plates of the vertebral bodies, and as ossification
advances, the distinction between epiphyseal plates and vertebral body disappears.
As a rule the transverse diameter of the fibro-cartilage corresponds to that of
the vertebral bodies which it joins together; but in the cervical region, where
the inferior margin of the super-imposed vertebra is overlapped on each side by
the one which bears it, the fibro-cartilage does not extend to the extreme lateral
margin, and in this position a small diarthrosis may be seen at each lateral margin
of the fibro-cartilage.
Lig. Longitudinale Anterius. The anterior longitudinal ligament (O.T.
anterior common ligament) (Fig. 293) consists of a wide stratum of longitudinal
fibres which extends from the front of the epistropheus vertebra to the front of
the superior segment of the sacrum, and becomes gradually wider from above
downwards. It lies on the anterior surfaces of the intervertebral fibro-cartilages, to
which it is firmly attached as it passes from one vertebra to the other. Its fibres
vary in length. Some are attached to contiguous margins of two adjoining
vertebrae ; others pass in front of one vertebra to be attached to the next below,
and yet others find their lower attachment three or four vertebrae below the one
from which they started. None of the fibres are attached to the transverse
depression on the anterior surface of a vertebral body.
Lig. Longitudinale Posterius. The posterior longitudinal ligament (O.T,
posterior common ligament) (Fig. 294) is found within the vertebral canal upon
the posterior aspect of the vertebral bodies. It
consists of longitudinal fibres, and it extends from
the sacrum to the epistropheus vertebra, superior
to which it is continued to the skull as the
mernbrana tectoria. Opposite each interverte-
bral fibro-cartilage it is attached to the entire
width of the adjacent margins of the two vertebral
bodies, its fibres being continued over the posterior
surface of the fibro-cartilage. In the lumbar and
thoracic regions the width of the ligament is con-
siderably reduced opposite the back of each vertebral
body, and thus it forms a series of dentate pro-
jections along both of its margins ; but in the
cervical region the width of the ligament is more
uniform. One or two large thin -walled veins
escape from the body of each vertebra under cover
of this ligament.
Articulations between Vertebral Arches.
The vertebral arch of each typical vertebra carries
two pairs of articular processes, by means of which
it articulates with adjacent vertebral arches. The
articulations between these processes are true
diarthroses of the arthrodial variety.
The distinctive characters of these articular surfaces, as regards their shape
j and direction in the different groups of vertebrae, have been referred to in the
section on osteology.
All these articulations are provided with complete but very thin-walled cap-
; sulae articulares, which are thinnest and loosest in the cervical region, where also
the movements are freest. Each capsule is lined with a stratum synoviale.
Associated with these joints between vertebral arches are certain ligaments* which
are accessory to the articulations, although they are quite distinct from the capsule.
FIG. 294. POSTERIOR LONGITUDINAL
LIGAMENT OF THE VERTEBRAL COLUMN-
308
THE AKTICULATIONS OK JOINTS.
Root of
vertebral arcli
divided
The laminae of adjoining vertebrae are bound together by the ligamenta flava
(O.T. subflava) (Fig. 295), which consist of yellow elastic fibres. The ligamenta
flava close the vertebral canal in the intervals between the laminae. Each ligament
is attached superiorly to the anterior aspect of one lamina at a short distance above
its inferior border, and inferiorly it is attached to the posterior aspect of the
subjacent lamina.
In the thoracic region, where the imbrication of adjoining laminae is a prominent
feature, these ligaments are not so distinctly visible from behind as they are in the
regions where imbrication of the laminae is not so marked.
Laterally they extend as far as the articular capsules, while medially the margins
of the ligaments of opposite sides meet under cover of the root of the spinous
process.
Contiguous spinous processes are also attached to each other by ligamenta
interspinalia (interspinous ligaments) (Fig. 292). These are strongest in the lumbar,
and weakest in the thoracic region. Each consists of layers of obliquely inter-
lacing fibres which spring from near the tips of the two adjacent spinous process
and radiate to their op-
posing margins. In the
antero - posterior direc-
tion they extend from
the base to the tip of
the spinous process.
The ligamenta supra-
spinalia (supra-spinous
ligaments) (Fig. 292)
consist of longitudinal j
bands of fibres of varying I
lengths. They extend]
from spine to spine,]
being attached to their!
tips, and are situated
superficial to, although]
in continuity with, the!
ligamenta interspinalia.
In the cervical region]
this series of ligaments;
is extensively developed. i j
where they project back- 1
wards from the spinoug]
processes between the 3
muscles of the two sides!
of the neck in the form oil
an elastic partition called 5
the ligamentum nuchae.
The antero-posterior extent of the ligamentum nuchae increases as it approaches
the occiput, where it is attached to the external occipital crest from the externa]j
occipital protuberance to the posterior border of the foramen magnum. Its posteriori
margin is free, and extends from the external occipital protuberance to the spine j
of the vertebra prominens.
Between the transverse processes there are ligamenta intertransversaria, which-
consist of vertical fibres extending from the postero-inferior aspect of one transverse! 1
process to the superior margin of that next below. These ligaments are generally I
absent from the cervical and upper thoracic regions.
Sacro-coccygeal Symphysis. The last piece of the sacrum is joined to the!
first piece of the coccyx by an intervertebral fibro-cartilage, and the jimctiorjlJ
is rendered more secure by the presence of certain strong ligaments. A lig. sacro
coccygeum anterius, continuous with the lig. longitudinale anterius, is placed irj!
front. A lig. sacrococcygeum posterius, which stretches downwards from the sharjll
border of the lower opening of the sacral canal, strengthens the joint behind. ^J !
FIG. 295. LIGAMENTA FLAVA AS SEEN FROM THE FRONT AFTER RE-
MOVAL OF THE BODIES OF THE VERTEBR-E BY SAWING THROUGH THE
ROOTS OF THE VERTEBRAL ARCHES.
AKTICULATION OF ATLAS WITH AXIS.
309
lig. sacrococcygeum laterale supports the joint on each side, whilst strong bands pass
between the cornua of the two bones and constitute the interarticular ligaments.
Intercoccygeal Joints. So long as they remain separate, the different pieces
of the coccyx are joined by intervertebral fibre-cartilages and by anterior and
posterior ligaments.
Movements of the Vertebral Column. Although the amount of movement permissible
between any two vertebrae is extremely limited, yet the total range of movement capable of
being attained by the entire vertebral column is very considerable.
Flexion may occur both forwards and backwards at the articulations of vertebral bodies, but
more freely in the lumbar and cervical regions than in the thoracic region, where the limited
amount of intervertebral fibre-cartilage and the imbrication of the laminae and spines restrict
the movement. Backward flexion is most pronounced in the cervical region, and forward flexion
in the lumbar region. Between the articular surfaces of the articulations between vertebral
arches a variety of movements are permitted, dependent upon the directions of these surfaces.
Thus lateral flexion is permitted in the lumbar, but not in the cervical or dorsal regions.
Again, in the lumbar region rotation does not occur, owing to the shape of the articular
processes, while it is possible in the thoracic region. In the cervical region the shape and position
of the articular surfaces prevent the occurrence both of lateral flexion and of rotation as isolated
movements, but a combination of these two movements may take place, whereby rotatory move-
ment in an oblique median axis results. Finally, in the lumbar region, by combining the four
forms of flexion, viz., forward, backward, and lateral, a certain amount of circumduction is possible.
ARTICULATIO ATLANTOEPISTROPHICA.
Between the atlas and epistropheus vertebrae three diarthroses occur. Two of
them are situated laterally, in relation to the articular processes, and are called
Membrana tectoria
Ba.silar part of occipital bone
srior atlanto-occipltal ligament
Ligamentum apicis dentis
Synovial cavity
Dens
Anterior arch of atlas
Transverse ligament of atlas
iferior crus of cruciate ligament
Rudimentary intervertebral
tibro-cartilage
Body of epistropheus
Superior crus of cruciate
ligament of the atlas
Synovial cavity
Posterior atlan to-occipital
membranes
Occipital bone
Posterior longitudinal ligament
Posterior arch of atlas
Root of spine of epistropheus
IG. 296. MEDIAN SECTION THROUGH THE ATLANTO-OCCIPITAL AND ATLANTO-KPISTROPHEAL JOINTS.
rodial diarthroses, because of the flattened nature of the articulating surfaces.
I The third articulation is median in position. It is found between the smooth
anterior surface of the dens of the epistropheus and the articular facet on the
posterior aspect of the anterior arch of the atlas. This joint is a rotatory diarthrosis.
Ligamenta. Each of the joints is furnished with a capsula articularis, whereby
the articular cavity is circumscribed. In the case of the lateral articulations, each
articular capsule presents a distinct band, named the accessory ligament, which is
situated within the vertebral canal (Fig. 297),and passes downwards and medially from
the lateral mass of the atlas to the superior aspect of the body of the epistropheus.
The following additional ligaments constitute the leading bonds of union : -
Lig. Obturatorium Atlantoepistrophica Anterior. The anterior covering
atlanto-epistropheal ligament (O.T. anterior atlo-axoid ligament) (Fig. 296) is a mem-
branous structure which is thin laterally, but strong in the median plane, where it is
thickened by a prolongation of the lig. longitudinale anterius. It extends from
the anterior arch of the atlas to the front of the body of the epistropheus.
310
THE ARTICULATIONS OE JOINTS.
Lig. Obturatorium Atlantoepistrophica Posterior. The posterior covering
atlanto-epistropheal ligament (O.T. posterior atlo-axoid ligament) (Fig. 296) occupies
the position which is elsewhere taken by the ligamenta flava. It extends from
the posterior arch of the atlas to the upper border of the vertebral arch of the
epistropheus.
Lig. Trans versum Atlantis. The transverse ligament of the atlas (Figs. 296
and 297) is a strong band, placed transversely, which arches backwards behind
the neck of the dens of the epistropheus. By its extremities it is attached to
the tubercle on the medial aspect of each lateral mass of the atlas. A thin plate
of fibro-cartilage is developed in its central part.
A stratum synoviale (synovial membrane) lines each of the three articular capsules,
and in addition a synovial sac is developed between the dens and the lig. transversum
atlantis. This is more extensive than the synovial cavity between the dens and the
atlas.
ARTICULATIO ATLANTO-OCCIPITALIS.
There are two articulations between the atlas and the occipital bone. Each
is a diarthrosis in which movement takes place in relation to two axes, viz., the
Membrana tectoria
Crus superius
Occipital bone
Lateral mass of atlas
Atlanto-epistropheal joint
Body of epistropheus
-Ligamentum apicis dentis
Ligamentum alare
Crus superius
Ligamentum crucia-
tum atlantis
Accessory atlanto-
epistropheal ligament
Crus inferius
Membrana tectoria
FIG. 297. DISSECTION FROM BEHIND OF THE LIGAMENTS CONNECTING THE OCCIPITAL BONE, THE ATLAS,
AND THE EPISTROPHEUS WITH EACH OTHER.
transverse and the antero-posterior. The condyle of the occipital bone is bi-
convex, and fits into the bi-concave superior articular surface of the atlas, while the
long axes of the two joints are directed horizontally forwards and medially.
Ligamenta. Each articulation is provided with a capsula articularis which
thin but complete. It is attached to the rough non-articular surfaces surrounding
the articular areas on the atlas and occipital bone.
The following supplementary ligaments are the chief structures which bind the
atlas to the occipital bone :
The membrana atlanto-occipitalis anterior (anterior occipito-atloid membrane'
(Fig. 296) is a strong although thin membrane, attached inferiorly to the anterioi
arch of the atlas, and superiorly to the anterior half of the circumference of tl
foramen magnum. Laterally it is in continuity with the articular capsules, whi]
in the median plane, where it extends from the anterior tubercle of the atlas to tl
basilar parfc of the occipital bone, it presents a specially well-defined thickened bai
which might be regarded as a separate accessory ligament or as the beginning
of the anterior longitudinal ligament of the vertebrae.
The membrana atlanto-occipitalis posterior (posterior occipito-atloid membn
(Fig. 296) is another distinct but still thin membrane which is attached superiorly
to the posterior half of the circumference of the foramen magnum, and inferiorly t(
the upper border of the posterior arch of the atlas. Laterally it also is continuou:
with the articular capsules. On each side of the median plane its inferior borde:
AKTICULATION OF SPINE WITH CKANIUM.
311
is arched in relation to the vertebral groove, and is therefore to some extent free,
in order to permit the passage of the posterior ramus of the first cervical nerve
and the vertebral artery. Not infrequently this arched border becomes ossified,
thus converting the groove on the bone into a foramen.
A synovial stratum lines each of the articular capsules.
There is no direct articulation between the epistropheus and the occipital bone,
but union between them is effected by means of the following accessory ligaments :
The membrana tectoria (Fig. 296) is situated within the vertebral canal, and is
usually regarded as the upward continuation of the posterior longitudinal ligament
of the vertebral bodies. It extends from the posterior surface of the body of the
epistropheus to the basilar groove on the superior surface of the basilar part of the
occipital bone, spreading laterally on the circumference of the foramen magnum.
Some of its deepest fibres are attached to the atlas immediately above the atlanto-
epistropheal articulation.
Subjacent to the membrana tectoria there is the ligamentum cruciatum atlantis
(Fig. 297), a structure which is very closely associated with the lig. transversum
atlantis. It consists of a cms transversum, formed by the superficial fibres of
the transverse ligament of the atlas ; a crus inferius, consisting of median longi-
tudinal fibres which are attached below to the posterior surface of the body of the
epistropheus, and above to the crus transversum ; and a crus superius, also median
and longitudinal, whose fibres extend from the crus transversum upwards to the
posterior surface of the basilar part of occipital bone, immediately subjacent to the
membrana tectoria.
Ligamenta Alaria. The alar ligaments (O.T. check ligaments) (Fig. 29*7) are
two very powerful, short, and somewhat rounded bands. They are attached medially
to the sides of the summit of the dens, and laterally to the tubercle on the medial
aspect of the condylar portions of the occipital bone.
Ligamentum Apicis Dentis. The ligament of the apex of the dens (O.T.
middle odontoid) (Fig. 297) consists of fibres running vertically upwards from the
apex of the dens to the median part of the anterior margin of the foramen magnum.
This ligament to some extent represents an intervertebral fibro-cartilage, in the
centre of which remains of the
notochord may be regarded as
present.
Even in advanced life a
small lenticular mass of cartil-
age, completely surrounded by
bone, persists in the plane of
fusion between the dens and
the body of the epistropheus.
Movements at these Joints.
At the joints between occipital bone
and atlas the movements are very
simple, and consist essentially of
movements whereby the head is
elevated and depressed upon the
vertebral column (nodding move-
ments). In addition a certain
amount of oblique movement is
possible, during which great stabil-
ity is attained by resting the
anterior and posterior parts of
opposite condyles upon correspond-
ing parts of the atlas.
The head and the atlas rotate
together upon the epistropheus, the
pivot of rotation being the dens,
and the amount of rotation is limited
by the ligamenta alaria. No rota-
tion can occur between the occiput
and atlas, and stability between atlas and epistropheus is best attained after a slight amount
of rotation, similar to the oblique movement between occipital bone and atlas.
Temporo-mandibular ligament
(anterior and posterior parts)
Styloid process
Stylo-mandibular ligament
FIG. 298. MANDIBULAR JOINT.
312
THE AETICULATIONS OE JOINTS.
Tubevculum articulare
MANDIBLE
FIG. 299. SECTION THROUGH THE MANDIBULAB
JOINT.
ARTICULATIO MANDIBULARIS.
The mandibular joint (O.T. temporo-mandibular) is an arthrodial diarthrosis. It
occurs between the mandibular fossa of the temporal bone and the condyle of
the mandible. These two articular surfaces are markedly dissimilar both in size
and shape. In its general outline the articular surface of the head of the
mandible is cylindrical, having its long
axis directed from the medial side laterally
and forwards. On the other hand, the
mandibular fossa is concavo-convex from
behind forwards. Its articular surface
includes the tuberculum articulare the
eminence at the base of the anterior root
of the zygoma. The articular surfaces of
the bones are clothed with hyaline en-
crusting cartilage, whilst the articular
cavity is divided into a superior and
inferior part by a disc of fibro-cartilage.
Ligaments. The joint is invested by
an articular capsule which is quite com-
plete, but is very thin on the medial side.
The lateral part of the fibrous stratum of
the capsule the temporo-mandibular liga-
ment (O.T. external lateral) (Fig. 298) is divisible into anterior and posterior
portions which are attached superiorly to the root tubercle and inferior border
of the zygoma tic process of the temporal bone, and inferiorly to the lateral side
and posterior border of the neck of the mandible. The direction of its fibres is
downwards and backwards.
Within the capsule there is a disc of fibro-cartilage, the discus articularis
(Fig. 299), which is moulded upon the condyle of the mandible below, and on the
articular surface of the temporal bone above. It thus compensates for the
incongruity between the articular
surfaces of the two bones. The disc
is attached circumferentially to the
capsule. It is widest in the trans-
verse direction, thicker posteriorly
than anteriorly, and thinnest towards
the centre, where it may be perforated.
Its anterior margin is intimately
associated with the insertion of the
external pterygoid muscle.
A synovial stratum lines each of
the compartments into which the
joint cavity is divided by the disc.
As a rule these membranes are
separate from each other, but they
become continuous when the disc
is perforated. The superior synovial
stratum is larger and more loosely
disposed than the lower.
Situated on the medial aspect of the joint, but at a short distance from it, and
quite distinct from the capsule, there is an accessory band called the lig. spheno-
mandibulare (Fig. 300). Superiorly the spheno-mandibular ligament (O.T. internal
lateral) is attached to the angular spine of the sphenoid bone, and inferiorly to
the inferior as well as the anterior border or lingula of the inferior alveolar
foramen. It is not an articular ligament in the true sense ; for, instead of being
connected with the joint, it is developed in the tissue surrounding part of Meckel's
cartilage.
Spheno-mandibular
ligament
Styloid process
Stylo-mandibular
ligament
FIG. 300. SPHENO-MANDIBULAR LIGAMENT OF THE
MANDIBULAR JOINT.
THE JOINTS OF THE THORAX. 313
Portions of the following structures are found in the interval between the spheno-mandibular
ligament and the ramus of the mandible viz., the external pterygoid muscle; internal
maxillary vessels ; inferior alveolar vessels and nerve ; middle meningeal vessels ; auriculo-
temporal nerve ; and sometimes a deep portion of the parotid gland.
Movements of the Mandible. The nature of the movements which the mandible can
perform is determined partly by the character of the articular surfaces of the mandibular joint,
and partly by the fact that, while the two joints always act simultaneously, they may also,
to some extent, perform the same movement alternately.
When movement takes place through the long or transverse horizontal axis of each joint,
the mandible may be elevated, as in clenching the teeth, or it may be depressed, as in gaping.
In the latter movement the condyle leaves the mandibular fossa, and, along with the disc, it
moves forwards until they rest upon the tuberculum articulare. Meantime the chin describes
the arc of a circle, of which the centre or point of least movement corresponds to the position of
the inferior alveolar foramen, and thus the structures which enter at that foramen are protected
against stretching. Coincidently with the forward movement of the condyle, it glides in a
revolving manner upon the inferior aspect of the disc.
At any stage in the movement of depressing the chin the mandible may be protruded, so
that the inferior incisor teeth are projected in front of the'upper set, a movement which results
from the condyles of the mandible being drawn forwards upon the articular tubercles. A similar
relation of the condyle to the articular tubercle occurs during the exaggerated depression of
the mandible which results from yawning, in which position the articulation is liable to be
dislocated. When the two joints perform the same movement alternately, a certain amount of
lateral motion results, from the fact that the long axis of each joint presents a slight obliquity
to the transverse axis of the skull, and consequently a grinding or oblique movement in the
horizontal plane is produced. Excessive depression, with the risk of dislocation, is resisted by
the fibres of the temporo-mandibular ligament, which becomes tense.
In all movements of the mandible the disc conforms closely to the position of the condyle,
and they move forwards and backwards together, but at the same time the disc does not restrict
the movements of the condyle. Thus while the disc, along with the condyle, is gliding upon
the temporal aspect of the joint, the condyle itself revolves upon the inferior surface of the disc.
CRANIAL LIGAMENTS NOT DIRECTLY ASSOCIATED WITH ARTICULATIONS.
Lig. Stylomandibulare. The stylo-mandibular ligament (Figs. 298 and 300) is a
specialised portion of the deep cervical fascia which extends from the anterior aspect
of the tip of the styloid process of the temporal bone to the- posterior border of the
angle of the mandible, between the insertions of the masseter and internal pterygoid
muscles.
Lig. Pterygospinosum. The pterygo-spinous ligament is a membrane extending
from the upper part of the posterior free margin of the lateral pterygoid lamina,
posteriorly and slightly laterally, to the angular spine of the sphenoid. An
interval is left between its upper border and the floor of the skull for the outward
passage of those branches of the inferior maxillary nerve which supply the
external pterygoid, temporal, and masseter muscles. This ligament has a tendency
to ossify either wholly or partially.
Lig. Stylohyoideum. The stylo-hyoid ligament may be regarded as the down-
ward continuation of the styloid process of the temporal bone. Inferiorly it is
attached to the lesser cornu of the hyoid bone. It is not infrequently ossified, in
which case it constitutes the epihyal bone found in many animals.
THE JOINTS OF THE THORAX.
Articulationes Costovertebrales (Costo - vertebral Articulations). - - The
typical rib articulates with the vertebral column both by its head and by its
tubercle. Thus, two sets of articulations, with their associated ligaments, exist
between the ribs and the vertebrae, but each set is constructed upon a common
plan, with the exception of certain joints situated at the upper and lower ends of
the series, where the ribs themselves deviate from the typical form.
ARTICULATIONES CAPITULORUM.
The articulations of the heads of the ribs with the bodies of the vertebras
(Fig. 293) are all diarthroses, which, from their somewhat hinge-like action, may
be classed as ginglymoid.
314 THE AKTICULATIONS OK JOINTS.
The head of every typical rib is wedge-shaped, and presents two articular
facets, an upper and a lower, separated from each other by an antero-posterior
ridge which abuts against an intervertebral fibro- cartilage, while the articular facets
articulate with similar surfaces on the contiguous margins of the two vertebrae
adjoining tfye fibro-cartilage. These surfaces form a wedge-shaped depression or
cup, the bottom of which is more elastic than the sides, and thus an arrangement
is provided which tends to reduce the shock of blows upon the walls of the chest.
Each of these articulations is provided with an articular capsule which
surrounds and encloses the joint, and is attached to contiguous non-articular
margins on the head of the rib and the two vertebral bodies. On its anterior or
ventral aspect the capsule presents three radiating fasciculi which collectively form
the lig. capituli costse radiatum (radiate ligament of the head of the rib (O.T. stellate))
(Fig. 293). These fasciculi radiate from a centre on the anterior surface of the head
of the rib, so that the middle _ fasciculus becomes attached to the intervertebral
fibro-cartilage while the upper and lower fasciculi proceed to the adjacent margins
of the two vertebrae between which the fibro-cartilage is situated, and with which
the rib articulates. To a slight extent these radiating fasciculi pass under cover of
the lateral margin of the anterior longitudinal ligament of the vertebral bodies.
In those joints in which the head of the rib does not articulate with an inter-
vertebral fibro-cartilage the central fasciculus of the radiate ligament is wanting,
but the other two retain the same general arrangement.
Lig. Capituli Costse Interarticulare. The interarticular ligament of the head
of the rib consists of short transverse fibres within the capsule. These are attached,
on the one hand, to the ridge which intervenes between the two facets on the head
of the rib, and on the other to the lateral aspect of the intervertebral fibro-cartilage.
This ligament is not a disc or meniscus, but merely an interarticular ligament, of
width sufficient to divide the joint cavity into an upper and a lower compartment.
It is absent from those joints which do not articulate with an intervertebral fibro-
cartilage, i.e. from those ribs which articulate with the body of only one vertebra.
The interarticular ligament is supposed to represent the lateral end of a ligament which,
under the name of the lig. conjugale costarum, connects the heads of the ribs of certain mammals
across the posterior aspect of the intervertebral fibro-cartilage, and, in the human subject, until
the seventh month of foetal life, connects the posterior aspects of the necks of a pair of ribs with
each other across the median plane.
A stratum synoviale lines each joint cavity, and therefore, in all cases where the
joint is divided into two compartments, each one has its own synovial lining.
ARTICULATIONES COSTOTRANSVERSARLE.
In the costo-transverse joints the tubercle of each typical rib articulates with
the transverse process of the lower of the two thoracic vertebrae with which the
head of the rib is associated. Near the tip of the transverse process there is
an articular facet, on its anterior aspect, for articulation with the corresponding
facet on the medial articular part of the rib tubercle. The joint so formed is
an arthrodial diarthrosis.
The joint cavity is surrounded by a comparatively feeble capsula articularis,
which is attached immediately beyond the margins of the articular facets, and in
which no special bands can be distinguished.
A simple stratum synoviale lines the capsule in all cases where the latter ii
present.
The following accessory ligaments, in connexion with this joint, strengthen an(
support the articulation :
Ligamentum Costotransversarium Anterius. The anterior costo-transvt
ligament (O.T. superior) (Fig. 293) consists of strong bands of fibres which ai
attached to the superior border of the neck of the rib, extending from the h(
laterally to the non-articular part of the tubercle. All these fibres may be tract
upwards. Those situated nearest to the head of the rib proceed obliquely upw*
and laterally, to be attached to the transverse process immediately above, but witl
STEKNO-COSTAL JOINTS. 315
extensions to the adjoining rib and its costo-transverse articular capsule. Others
proceed almost vertically, upwards to the adjoining transverse process, while those
which ascend from the upper surface of the tubercle pass obliquely upwards and
inwards to reach the postero-inferior aspect of the adjoining transverse process.
Some posterior fibres connected with the transverse process at its junction with
the lamina are called the posterior costo-transverse ligament.
Lig. Tuberculi Costae. The ligament of the tubercle of the rib is a band of
transverse fibres applied to the postero-lateral aspect of the capsule. By one end
these fibres are attached to the tip of the transverse process behind its articular
facet, and by the other to the external rough surface of the tubercle of the rib.
Lig. Colli Costse. The ligament of the neck of the rib (O.T. middle costo-
transverse ligament) consists of short fibres which stretch from the posterior aspect
of the neck of the rib, backwards and medially, to the anterior aspect of the
transverse process, but, in addition, a proportion of the fibres passes to the posterior
aspect of the inferior articular process of the upper of the two vertebrae with which
the head of the rib articulates.
The following exceptions to the general plan of rib-articulation indicated above
must be noted :
II. There is no articulation between the eleventh and twelfth ribs and the
transverse processes of the corresponding vertebrae.
2. The anterior costo-transverse ligament is wanting from the first rib, and is
either rudimentary or wanting in the case of the twelfth rib.
3. The lig. colli costse is rudimentary in the eleventh and twelfth ribs.
The ligamentum lumbocostale extends from the superior surface of the base of the
transverse process of the first lumbar vertebra to the inferior surface of the neck of
the twelfth rib, as well as to the inferior surface of the transverse process of the
twelfth thoracic vertebra.
ARTICULATIONES COSTOCHONDRALES.
Each rib possesses an unossified portion, termed its costal cartilage. As age
advances, this cartilage may undergo a certain amount of superficial ossification,
but it never becomes entirely transformed. The line of demarcation between
bone and cartilage is clear and abrupt, and usually the bone forms an oval cup, in
which the end of the cartilage is retained by means of the continuity which exists
between the periosteum and the perichondrium. There is no articulation in the
proper sense between the rib and its cartilage, although a synovial cavity has
occasionally been found between the first rib and its cartilage.
ARTICULATIONES INTERCHONDRALES.
Interchondral joints are arthrodial diarthroses, and they are found between
adjoining margins of certain of the costal cartilages, viz., from the fifth to the eighth
or ninth. The cartilages which thus articulate develop flattened, somewhat conical,
prolongations of their substance, and thereby the intercostal spaces are interrupted
where these flat articular facets abut against each other. Each joint is closed
by a surrounding articular capsule, the superficial and thoracic aspects of which are
specially strengthened by external and internal interchondral ligaments. These
bands extend obliquely between adjacent cartilages.
A stratum synoviale lines each joint capsule.
The upper seven pairs of costal cartilages, as a rule, extend to the lateral
margins of the sternum to form sterno-costal joints. Of these, the first pair is
implanted directly upon the manubrium sterni. The ossific process ends abruptly
in connexion with the rib, and also ceases as suddenly in connexion with the
sternum, and hence the cartilage does not normally present an articulation at
either end. From the second to the seventh pairs of ribs inclusive, the sterno-costal
joints are constructed upon the type of arthrodial diarthroses, although, in the case
ARTICULATIONES STERNOCOSTALES.
316
THE AETICULATIONS OE JOINTS.
of the sixth and seventh cartilages, the joint cavity is always small, and is frequently
obliterated.
The sternal end of each of these costal cartilages presents a slight antero-pos-
terior ridge which fits into a shallow V-shaped depression upon the lateral margin
of the sternum. With the exception of the sixth cartilage, they articulate opposite
the lines of union between the primary segments of the sternum ; the sixth articu-
lates upon the side of the lowest segment of the body of the sternum.
Each joint is enclosed by a capsula articularis, the fibrous stratum of which is
attached to the adjacent borders of the articulating elements. Specially strong
fibres distinguish the superficial and deep aspects of the capsule.
The lig. sternocostale radiatum (O.T. anterior costo-sternal ligament) (Fig. 301) is
composed of strong fibres which radiate from the anterior surface of the costal
cartilage, near its sternal end, to the front of the sternum. The ligaments of
opposite sides interlace with each other, and so cover the front of the sternum with
a felted membrane the membrana sterni.
Costo-clavicular
ligament
Anterior sterno-clavicular
ligament
Joint capsule
Joint cavity
Interarticular ligament
Joint cavity
sterno-costale radiatum
FIG. 301. STERNO-CLAVICULAR AND STERNO-COSTAL JOINTS.
The lig. sternocostale posterius (posterior costo-sternal ligament) also a part
of the capsule has attachments similar to the foregoing, but the arrangement of
its fibres is not so powerful.
The ligamentum costoxiphoideum passes from the front of the upper part of the
xiphoid process, obliquely upwards and laterally to the front of the seventh, and
sometimes to the front of the sixth costal cartilage.
Within the capsules of these joints ligamenta sternocostalia interarticularia (inter-
articular ligaments) (Fig. 301) may be found. Their disposition is somewhat uncertain,
for whereas, in the case of the second pair of cartilages, they invariably divide the
joint cavity into two distinct compartments an upper and a lower such an
arrangement is very uncertain in the other joints, and they occasionally, especially
in the cases of the sixth and seventh cartilages, entirely obliterate the joint cavity.
These ligaments extend horizontally between the ends of the costal cartilages and
the side of the sternum.
The stratum synoviale is found wherever a joint cavity is developed, and there-
fore there may be one or two synovial strata, according to the presence or absence
of a proper interarticular ligament. When the joint cavity is obliterated by the
fibrous structure which represents the interarticular ligament, a synovial stratum
is also absent.
(ARTICULATIONS OF THE CLAVICLE. 317
ARTICULATIONES STERNI.
Primarily the sternum consists of an elongated plate of hyaline cartilage, which
omes subdivided into segments by the process of ossification.
The four segments of which the body of the sternum is originally composed
unite with each other after the manner of typical synchondroses.
Similarly the xiphoid process and the body ultimately become united. It is
not usual to find the joint between the manubrium and the body obliterated by the
ossification of the two bony segments. Even in advanced life it remains open, and
the joint, which is named the synchondrosis sternalis, partakes of the nature of an
amphiarthrosis (Fig. 301), although a joint cavity is not found under any circum-
stances in the plate of fibro-cartilage which intervenes between the manubrium
and the body of the sternum.
The membrana sterni, to which reference has already been made, assists in
strengthening the union between the different segments of the sternum.
Movements of the Ribs and Sternum. These movements may be considered either
independently of, or as associated with, respiration.
In the former condition the ribs move in connexion with flexion and extension of the
vertebral column, being more or less depressed and approximated in the former, and elevated or
pulled apart in the latter case. Considered in connexion with respiration, it is necessary to
observe that, to all intents and purposes, the vertebral column and the sternum are rigid structures.
Next, we must remember that the heads of all the ribs occupy fixed positions, and similarly
the anterior ends of seven pairs of cartilages are fixed to the lateral margins of the sternum.
The ribs thus form arches, presenting a large amount of obliquity from behind forwards. There-
fore, during inspiration, when the rib is elevated, the arch becomes more horizontal, and the
transverse diameter of the chest is increased. At the same time, the anterior ends of the sternal
ribs tend to thrust the sternum forwards and upwards ; but the nature of the attachment of the
first pair of ribs to the sternum, as well as the attachment of the diaphragm to the xiphoid
process, prevents this movement from becoming excessive, and hence the sternum becomes a line
of resistance to the forward thrust of the ribs. As a consequence, the ribs rotate upon themselves
about an oblique axis which passes downwards, laterally, and posteriorly through the capitular
joint and the neck of the rib anterior to the costo-transverse joint.
In this way increase, both of the antero-posterior and transverse diameters of the thorax, is
provided for, although the amount of increase is not equally pronounced in all planes. Thus at
the level of the first rib very little eversion is possible, because the axis of rotation is nearly
transverse, and therefore any increase in the transverse or antero-posterior thoracic diameters at
this level may be disregarded, although a certain amount of elevation of the manubrium sterni
and anterior end of the first rib is evident.
Below the level of the sixth rib elevation and rotation of the rib during inspiration are
usually said to be complicated by a certain amount of backward movement, due to the character
of the costo-transverse joint, until, in the case of the last two ribs, which are destitute of costo-
transverse joints, a movement backwards is almost entirely substituted for elevation. It is
probable, however, that the movements of the asternal ribs exactly correspond to those of the
sternal series, and that by the contraction of the costal digitations of the diaphragm the
anterior ends of the false ribs are provided with fixed positions comparable to those supplied by
the sternum to the ribs of the sternal series.
We may therefore say that during inspiration the ribs move upwards and laterally between
their fixed ends, while as a whole the rib rotates, and its anterior end is thrust slightly forwards.
During expiration these movements are simply reversed.
THE ARTICULATIONS OF THE SUPERIOR EXTREMITY.
The bony arch formed by the clavicle and scapula articulates directly with the
il skeleton only at one point, viz., the sterno-clavicular joint.
ARTICULATIONS OF THE CLAVICLE.
ARTICULATIO STERNOCLAVICULARIS.
The sterno-clavicular joint is an example of an arthrodial diarthrosis. The
(""""'cular surfaces concerned in its formation present the following appearances:
1. The sternal end of the clavicle is somewhat triangular in outline, having
most prominent angle directed inferiorly and posteriorly. The anterior and
318 THE ARTICULATIONS OE JOINTS.
posterior sides of the triangle are slightly roughened for the attachment of
ligaments, while the base or inferior side is smooth and rounded, owing to the
prolongation of the articular surface to the inferior aspect of the bone. In the
antero-posterior direction the articular surface tends to be concave, while vertically
it is slightly convex.
2. An articular facet, situated on the superior lateral angle of the manubrium
sterni, but in a plane slightly behind the supra-sternal notch, articulates with the
clavicle. This facet is considerably smaller than the clavicular facet with which it
articulates.
3. The superior surface of the first costal cartilage close to the sternum also
participates to a small extent in the articulation.
It should be noted that the articular surfaces of the clavicle and sternum are
covered mainly by fibre-cartilage.
A capsula articularis is well marked on all sides except inferiorly, where it is
very thin. The epiphyseal line of the clavicle is intra-capsnlar.
Lig 1 . Sternoclaviculare Anterius. The anterior sterno-clavicular ligament
(Fig. 301) forms part of the fibrous stratum of the articular capsule, and consists
of short fibres which extend obliquely inferiorly and medially from the anterior
aspect of the sternal end of the clavicle to the adjoining anterior surface of the
sternum and the anterior border of the first costal cartilage.
Lig. Sternoclaviculare Posterius. The posterior sterno-clavicular ligament
also forms part of the fibrous stratum of the capsule, and consists of similarly
disposed, but not so strong as the anterior ligament, oblique fibres situated on the
posterior aspect of the articulation.
Discus Articularis. A fibro-cartilaginous articular disc (Fig. 301) divides the
joint cavity into two compartments. It is nearly circular in shape, and adapts
itself to the articular surfaces between which it lies. It is thickest at the circum-
ference and thinnest at the centre, where it occasionally presents a perforation,
thereby permitting the two synovial cavities to inter-communicate. By its circum-
ference it is in contact with, and adherent to, the surrounding capsule, but its
superior margin is attached to the apex of the articular surface of the clavicle, while
by its inferior margin it is fixed to the sternal end of the first costal cartilage.
Two accessory ligaments are associated with this joint, viz., the interclavicular
and the costo-clavicular.
Lig. Interclaviculare. The interclavicular ligament (Fig. 301) is a structure of
considerable strength, forming a broad band of fibrous tissue which is attached to the
superior rounded angle or apex of the sternal end of the clavicle as well as to the
adjacent margins of the articular surface. Its fibres pass across the interclavicular
notch to become attached to corresponding parts of the opposite clavicle, but in their
course they dip down into the supra-sternal notch, in which many of them are fixed
to the sternum. In this way their presence neither bridges nor obliterates the
notch between the two clavicles, and the ligament really becomes a superior sterno-
clavicular ligament for each joint.
Lig. Costoclaviculare. The costo-clavicular ligament (Fig. 301) consists of
short, strong fibres which are attached inferiorly to the superior surface of the first
costal cartilage. They pass obliquely upwards, laterally and posteriorly, to a rough
impression situated on the inferior aspect of the sternal end of the clavicle, and are
distinct from the articular capsule. Occasionally a bursa is found in the interior
of this ligament.
As a rule there is a synovial stratum lining each of the two joint cavities
(Fig. 301), separated from each other by the articular disc. Sometimes, however,
the two membranes establish continuity through a perforation in the disc.
ARTICULATIO ACEOMIOCLAVICULARIS.
The acromio-clavicular joint is another instance of an arthrodial diarthrosis.
It is situated between the acromial end of the clavicle and the medial aspect of
the acromion. Each articular surface is an oval, flattened facet, covered with
fibro-cartilage.
ACKOMIO-CLAVICULAR JOINT. 319
The ligaments which surround this small joint form a complete articular
capsule, of which the superior and inferior parts are specially strong, and are there-
fore named the superior and inferior acromio -clavicular ligaments (Fig. 303). These
consist of short fibres passing between the adjacent rough margins of the two bones
in the positions indicated by their names.
An articular disc, which is nearly always incomplete, and may occasionally be
wanting, is usually found within the joint cavity, where it lies obliquely, with its
superior margin farther from the median plane than its inferior margin, and having
its borders attached to the surrounding capsule. Frequently the disc is wedge-
shaped, with its base directed upwards and its apex free.
A synovial stratum is found forming either a single or a double sac, according to
the condition of the disc. Complete division of the joint cavity, however, is rare.
Ligamentum Coracoclaviculare. Accessory to this articulation there is the
strong coraco-clavicular ligament which binds the acromial end of the clavicle to
the coracoid process of the scapula. It is readily divisible into two parts, viz., lig.
conoideuni and the lig. trapezoideum.
The conoid ligament (Fig. 303) is situated medial to and slightly posterior to the
trapezoid. It is narrow and pointed at its inferior end, by which it is attached
to the superior aspect of the coracoid process, in close proximity to the scapular
notch. Its superior end widens out in the manner expressed by its name, and is
attached to the coracoid tuberosity of the clavicle.
The trapezoid ligament (Fig. 303) is attached inferiorly to the superior surface of
the posterior half of the coracoid process, lateral and anterior to the attachment of
the conoid ligament. Superiorly it is attached to the ridge on the inferior surface
of the acromial end of the clavicle. Its lateral and medial borders are free. Its
anterior surface is principally directed upwards, and its posterior surface, to a
similar extent, looks downwards.
A mucous or synovial bursa usually occupies the re-entrant angle between these
two ligaments.
Movements at the Clavicular Joints. The movements of the medial end of the clavicle at
the sterno- clavicular joint are limited in their range, owing to the tension of the ligaments.
When the shoulder is raised or depressed the acromial end of the clavicle moves upwards and
downwards, whilst its sternal end glides upon the surface of the articular disc ; when, on the
other hand, the shoulder is carried forwards or backwards, the sternal end of the clavicle along
with the articular disc moves upon the sternal facet. In addition to these movements of elevation,
depression, forward movement and backward movement of the clavicle, there is also allowed
at the sterno-clavicular joint a certain amount of circumduction of the clavicle.
The part which is played by certain of the ligaments in restraining movement requires
careful consideration. The costo-clavicular ligament checks excessive elevation of the clavicle,
and restrains within certain limits both backward and forward movement of the clavicle. When
the clavicle is depressed, as in cases where a heavy weight, such as a bucket of water, is carried in
the hand, it receives support by resting upon the first rib, and the tendency for the medial end
of the bone to start up out of its sternal socket is obviated by the tension of the articular
disc, the interclavicular ligament, and the anterior and posterior sterno-clavicular ligaments.
The articular disc not only acts as a cushion which lessens the shock of blows received
upon the shoulder, but it also acts as a most important bond of union, and prevents the medial
end of the clavicle from being driven upwards upon the top of the sternum when force is applied
to its lateral end.
The movements at the acromio -clavicular joint are of such a kind as to allow the inferior
angle, and to some extent the vertebral border of the scapula, to remain more or less closely
applied to the chest-wall during the various movements of the shoulder. The strong connexion
between the coracoid process and the acromial end of the clavicle, by means of the conoid and
trapezoid ligaments, renders it necessary that the scapula should follow the clavicle in its various
excursions. The presence of the acromio-clavicular joint, however, enables the scapula to change
its position somewhat with reference to the clavicle as the shoulder is moved. Thus, when the
shoulder is raised and depressed, a marked difference takes place in the angle between the two
bones ; again, when the shoulder is thrown forwards or backwards, these movements can be
performed without altering in a material degree the direction of the glenoid cavity of the scapula,
or in other words, the socket of the shoulder-joint.
The conoid and trapezoid ligaments set a limit upon the movements of the scapula at the
acromio-clavicular joint. They both, but more particularly the trapezoid ligament, prevent the
acromion from being carried medially below the lateral end of the clavicle when blows fall upon
the lateral aspect of the shoulder.
320 THE ARTICULATIONS OR JOINTS.
LIGAMENTS OF THE SCAPULA.
These ligaments are not directly connected with any articulation.
Lig. Coracoacromiale. The coraco-acromial ligament (Fig. 302) completes the
arch between the coracoid process and the acromion, and thus provides a secondary
socket for the greater protection and security of the shoulder-joint. It is a flat
triangular structure stretched tightly between its attachments. By its base it is
fixed to a varying amount of the postero-lateral border of the coracoid process,
and by its narrower apical end to the tip of the acromion, immediately lateral to the
acromio-clavicular joint. Its surfaces look upwards and downwards, and its free
borders laterally and medially. It is thinnest in the centre, where it is sometimes
perforated by a prolongation of the tendon of the pectoralis minor muscle.
Lig. Transversum Scapulae Superius. The superior transverse scapular ligament
(O.T. suprascapular ligament) is a distinct but short flat band which bridges the
scapular notch. It may be continuous with the conoid ligament, and it is frequently
ossified. As a rule the foramen completed by this ligament transmits the supra-
scapular nerve, while the transverse scapular vessels pass superior to the ligament
to reach the supraspinous fossa.
A small duplicate of this ligament may often be found bridging the foramen on
its costal aspect, subjacent to which small branches of the transverse scapular artery
return from the supraspinous to the subscapular fossa.
Lig. Transversum Scapulae Inferius. The inferior transverse scapular ligament
(O.T. spino-glenoid ligament) consists of another set of bridging fibres which are
situated on the posterior aspect of the neck of the scapula. By one end they are
attached to the lateral border of the scapular spine, and by the other to the adjacent
part of the posterior aspect of the head of the scapula. The suprascapular nerve
and the transverse scapular vessels pass subjacent to this ligament.
ARTICULATIO HUMERI.
THE SHOULDEK-JOINT.
321
tissue attached to the margin of the glenoid cavity. Many of its fibres are
short, and pass obliquely, from the inner to the outer aspect of the ridge, so
that its attached base is ' broader than its free edge, and therefore in cross
section it appears somewhat triangular. The long tendon of the biceps, which
arises from the apex of the glenoid cavity, becomes to a considerable extent in-
corporated with the labrum glenoidale.
Capsula Articularis. The fibrous stratum (O.T. capsular ligament) (Fig. 302)
of the articular capsule presents the general shape which is characteristic of the
corresponding part in other ball-and-socket joints, viz., a hollow cylinder. By its
proximal end the fibrous stratum is attached to the circumference of the glenoid
cavity, external to the labrum glenoidale, and also, to a considerable extent, to the
labrum glenoidale itself.
By its distal end it is attached to the neck of the humerus, and therefore
beyond the articular area of the head. The fibrous stratum is strongest on its
superior aspect, while interiorly, where the neck of the bone is least defined, it
Coraco-acromial ligament
Acromion
Communication
between subscapular
bursa and joint cavity
Articular capsule
Coraco-humeral
ligament
Subscapularis
muscle
11
I Long
l-tendon
n of biceps
FIG. 302. CAPSULE OF THE SHOULDER- JOINT AND CORACO-ACROMIAL LIGAMENT.
extends distally for a short distance upon the humeral shaft. Its fibres for the most
part run longitudinally, but a certain number of them pursue a circular direction.
The greater part of the epiphyseal line of the proximal end of the humerus is
extra-capsular, but it is intra-capsular on the medial side of the bone.
A prolongation of the fibrous stratum, the transverse humeral ligament presenting
both longitudinal and transverse fibres, bridges that part of the intertubercular
groove which is situated between the tubercles of the humerus. At this point
an interruption in the fibrous stratum, beneath the transverse humeral ligament,
permits the long tendon of the biceps to escape from its interior. In addition to
the opening just referred to, there is another very constant deficiency in the
superior and anterior part of the fibrous stratum, where the narrowing tendon of
the subscapularis muscle is brought into contact with a bursa formed by a protrusion
of the synovial stratum. This defect in the fibrous stratum has its long axis in
the direction of the longitudinal fibres. Occasionally there is a similar but smaller
opening under cover of the tendon of the infraspinatus muscle. Through the two
Latter openings the joint cavity communicates with bursae situated between the
Capsule and the muscles referred to.
The tendons of the subscapularis, supraspinatus, and infraspinatus muscles fuse
with, and so strengthen, the articular capsule as they approach their respective
insertions.
On the superior aspect of the articulation the capsule is augmented by an
21
322
THE AKTICULATIONS OE JOINTS.
accessory structure, the ligamentum coracohumerale (Fig. 302). By its proximal
end, which is situated immediately above the glenoid cavity, but subjacent to the
coraco-acromial ligament, it is attached to the lateral border of the root of the
coracoid process, while its distal end is attached to the humeral neck close to the
greater tubercle. This ligament forms a flattened band, having its posterior and
inferior border fused with the articular capsule, but its anterior and superior margin
presents a free edge, slightly raised above the level of the capsule. This structure
is believed to represent that portion of the pectoralis minor to which reference
has already been made in connexion with the coraco-acromial ligament (p. 320).
The coraco-glenoid ligament is another accessory structure, which is not always present. It
springs from the coracoid process along with the former ligament, and extends to the superior
and posterior margin of the head of the scapula.
Gleno-humeral Ligaments (Fig. 303). If the articular capsule is opened from behind, and the
head of the humerus removed, it will be seen that the longitudinal fibres of the anterior part
of the fibrous stratum are specially developed in the form of thick flattened bands which extend
from the anterior border of the glenoid cavity to the anterior aspect of the neck of the humerus.
These gleno -humeral ligaments are three in number, and occupy the following positions : the
Coraco- ^ Conoid
clavicular ^Trapezoid
ligament J
Coraco-acromial ligament S^""" ^-^
Coracoid process
Superior gleno-
humeral ligament
Acromio-
clavicular
ligament
Bursal perforation in
articular capsule
Inferior gleno-
humeral ligament
Glenoid cavity
Capsule of
' ' ftfff shoulder-joint
m
\ La brum
glenoidale
FIG. 303. CAPSULAR LIGAMENT OP SHOULDER- JOINT CUT ACROSS AND HUMERUS REMOVED.
superior is placed above the aperture in the front of the capsule ; the middle and inferior on th<
antero-inferior aspect of the capsule, and below the aperture mentioned.
The superior gleno-humeral ligament, which some believe to represent the ligamentum tei
of the hip-joint, springs, along with the middle gleno-humeral band, from the superior part <
the cavity. The inferior ligament is the strongest of the three, and springs from the inferio :
part of the anterior margin of the glenoid.
Intra-capsular Structures. 1. The labrum glenoidale, already described.
The long tendon of the biceps passes laterally from its attachment to the apex
the glenoid cavity and the adjoining part of the labrum glenoidale, above the h(
and neck of the humerus, to escape from the interior of the capsule by the openinj
between the tubercles of the humerus, subjacent to the transverse humeral ligament
A synovial stratum (Fig. 304) lines the fibrous stratum of the capsule, and e:
tends from the margin of the glenoid cavity to the humeral attachments of the fibroi
stratum, where it is reflected towards the margin of the articular cartilage. It i
therefore important to note that the inferior aspect of the humeral neck has tl
most extensive clothing of the synovial stratum. Further, the synovial strati
envelops the intra-capsular part of the tendon of the biceps, and although tl
tubular sheath is prolonged upon the tendon into the proximal part of
THE ELBOW-JOINT.
323
Long head
of biceps in
its tubular
sheath
of the
synovial
stratum
Head of
humerns
Cavity of joint
FIG. 304. VERTICAL SECTION THROUGH THE SHOULDER- JOINT.
inter tubercular sulcus, yet the closed character of the synovial cavity is maintained.
Thus, while the tendon is within the capsule, it is not within the synovial cavity.
The synovial stratum is continuous with those bursse which communicate with the
joint cavity through openings in the fibrous stratum of the capsule.
Bursse (a) Communicating with the Joint Cavity. Practically there is only one bursa which
is constant in its position, viz.,
the subscapular, between the
capsule and the tendon of the
subscapularis muscle. It
varies considerably in its
dimensions, but its lining mem-
brane is always continuous with
the synovial stratum of the
capsule (Figs. 301 and 302), and
therefore it may be regarded
merely as a prolongation of
the articular synovial stratum.
Occasionally a similar but
smaller bursa occurs between
the capsule and the tendon of
the infraspinatus muscle.
(6) Not communicating with
the Joint Cavity. The sub-
deltoid or sub-acromial bursa
is situated between the muscles
on the superior aspect of the
shoulder-joint on the one hand
and the deltoid muscle on the
other. It is an extensive bursa,
and is prolonged subjacent to
the acromion and the coraco-
acromial ligament. It does
not communicate with the
shoulder -joint, but it greatly facilitates the movements of the proximal end of the humerus
against the inferior surface of the coraco-acromial arch.
Movements at the Shoulder-Joint. A ball-and-socket joint permits of a great variety of
movements, practically in all directions ; but if these movements are analysed, it will be seen that
they resolve themselves into movements around three primary axes at right angles to each other,
or around axes which are the possible combinations of the primary ones.
Thus, around a transverse axis, the limb may move forwards (flexion) or backwards (extension).
Around an antero-posterior axis it may move laterally, i.e. away from the median plane of the
trunk (abduction), or medially, i.e. towards, and to some extent up to, the median plane
(adduction).
Around a vertical axis, the humerus may rotate upon its axis in a medial or lateral direction
to the extent of a quarter of a circle.
Since these axes all pass through the shoulder-joint, and since each may present varying
degrees of obliquity, it follows that very elaborate combinations are possible until the movement
of circumduction is evolved. In this movement the head of the humerus acts as the apex of a
cone of movement with the distal end of the humerus, describing the base of the cone.
The range of the shoulder-joint movements is still further increased owing to the mobility of
the scapula as a whole, and owing to its association with the movements of the clavicle already
i described.
ARTICULATIO CUBITI.
The elbow-joint 1 provides an instance of a diarthrosis capable of performing the
! movements of flexion and extension around a single axis placed transversely, i.e. a
typical ginglymus diarthrosis or hinge-joint.
The bones which enter into its formation are the humerus, ulna, and radius.
; The trochlea of the humerus articulates with the semilunar notch of the ulna
(articulatio humeroulnaris) ; the capitulum of the humerus articulates with the
shallow depression or cup on the proximal aspect of the head of the radius (articu-
latio humeroradialis). The articular cartilage clothing the trochlea of the humerus
'terminates in a sinuous or concave margin both anteriorly and posteriorly, so that it
loes not line either the coronoid or the olecranon fossa. Medially, it merely rounds
off the medial margin of the trochlea, but laterally it is continuous with the encrust-
1 The articulatio cubiti or elbow-joint includes the humero-radial, humero-ulnar, and the proximal radio-ulnar
oints ; but, for convenience, the description given here is limited to the humero-radial and humero-ulnar joints.
324
THE AKTICULATIONS OE JOINTS.
Humerus
Ulnar collateral
ligament
ing cartilage covering the capitulum, to the margin of which the cartilage extends in
all directions, and thus it presents a convex edge in relation to the radial fossa.
The cartilage which lines the semilunar notch of the ulna presents a transverse in-
terruption, considerably wider on its medial as compared with its lateral aspect.
Thereby the coronoid and olecranon segments of the notch are separated from each
other. The cartilage which clothes the coronoid segment is continuous with that
which clothes the radial notch of the ulna. The shallow cup-shaped depression on
the head of the radius is covered with cartilage which rounds off the margin, and
is prolonged without interruption upon the vertical aspect of the head, extending
to its most distal level on that part opposed to the radial notch of the ulna.
Capsula Articularis.
Taken as a whole, the liga-
ments form a complete
fibrous stratum of the
articular capsule, which is
not defective at any point,
although it is not of equal
thickness throughout, and
certain bands of fibres
stand out distinctly because
of their greater strength.
The common epiphyseal
line for the trochlea, capit-
ulum, and the lateral epi-
condyle of the humerus, is
partly intra-capsular and
partly extra-capsular ; that
for the medial epicondyle
is extra-capsular. The
epiphyseal line of the ole-
cranon is intra - capsular
only anteriorly, and it may i
be altogether extra-cap-!
sular.
Lig. Anterius. The
anterior ligament (Fig. 305
consists of a layer whos
fibres run in several direc
tions obliquely, trans
versely, and longitudinally
and of these the vertica
fibres are of most import
ance. It is attached proxi
mally to the proxima
margins of the coronoid and radial fossse ; distally, to the margins of the coronok
process and to the annular ligament of the proximal radio-ulnar joint, but som
loosely arranged fibres reach as far as the neck of the radius. The marginal portion
of this ligament, which are situated in front of the capitulum and the medial margii
of the trochlea respectively, are much thinner and weaker than the central parl
Fibres of origin of the brachialis muscle are attached to the front of this ligament
Lig 1 . Posterius. The posterior ligament is an extremely thin, almost redundan
layer. Proximally it is attached, in relation to the margin of the olecranon fossa
at a varying distance from the trochlear articular surface, and distally to th
summit and sides of the lip of the olecranon. Laterally some of its fibres pass fron
the posterior aspect of the capitulum to the posterior border of the radial note!
of the ulna. This ligament derives material support from, and participates in th
movements of, the triceps brachii muscle, since they are closely adherent to eac
other in the region of the olecranon.
Lig. Collaterale Ulnare. The ulnar collateral ligament (O.T. internal latera]
Annular
ligament
of radius
Radius
Tendon of insertion of
biceps muscle
Oblique chord
Ulna
FIG. 305. ANTERIOR VIEW OP ELBOW-JOINT.
THE ELBOW-JOINT.
325
(Figs. 305 and 306) is a fan-shaped structure of unequal thickness, but its margins,
which are its strongest bands, are continuous with the adjoining parts of the
anterior and posterior ligaments. By its proximal end it is attached to the
anterior, distal, and posterior aspects of the medial epicondyle of the humerus. By
its broad distal end it is attached to the medial margin of the semilunar notch, so
that the anterior land is associated principally with the medial margin of the
coronoid process, and the posterior land with the medial margin of the olecranon,
while the intermediate weaker portion sends its fibres downwards to join a trans-
verse land, sometimes very strong, which bridges the notch between the adjoining
medial margins of the coronoid process and the olecranon.
Lig. Collaterale Radiale. The radial collateral ligament (O.T. external
lateral) (Fig. 305) is a strong flattened band attached proximally to the distal and
Interosseous membrane Radius
Medial epicondyle
Anterior part of ulnar
collateral ligament
Posterior part of ulnar
collateral ligament
Olecranon
Ulna Transverse part of ulnar collateral ligament
FIG. 306. ELBOW- JOINT (Medial Aspect).
posterior aspects of the lateral epicondyle of the humerus. It completes the con-
tinuity of the articular capsule on the lateral side, and blends distally with the
lig. annulare radii, on the surface of which its fibres may be traced both to the
anterior and posterior ends of the radial notch of the ulna. Both of the collateral
ligaments are intimately associated with the muscles which take origin from the
medial and lateral epicondyles of the humerus.
Synovial Pads of Fat (Fig. 307). Internal to the fibrous stratum of the
articular capsule, there are several pads of fat situated between it and the syiiovial
stratum. Small pads are so placed as to lie immediately in front of the coronoid
and radial fossse, but a larger one projects towards the olecranon fossa.
A stratum synoviale (Fig. 307) lines the entire fibrous stratum and clothes
the pads of fat referred to above, as well as those portions of bone enclosed within
the capsule which are not covered by articular cartilage. By its disposition the
elbow and the proximal radio-ulnar joints possess a common joint cavity. It
should be specially noted that the proximal part of the neck of the radius is
surrounded by this synovial layer.
Movements at the Elbow-Joint. The movements of the radius and ulna upon the humerus
have already been referred to as those characterising a uniaxial joint constructed on the plan of
a hinge. In this case the axis of the joint is obliquely transverse, so that in the extended
position the humerus and ulna form an obtuse angle open towards the radius, whereas in the
326
THE ARTICULATIONS OE JOINTS.
flexed position the hand is carried medially in the direction of the mouth. Extreme flexion
is checked by the soft parts in front of the arm and of the forearm coming into contact,
and extreme extension by the restraining effect of the ligaments and muscles. In each case
the movement is checked before either the coronoid process or the olecranon come into contact
with the humerus.
The anterior and pos-
terior bands of the
ulnar collateral liga-
ment are important
factors in these re-
sults. Lateral move-
ment of the ulna is
not a characteristic
movement, although
it may occur to a
slight extent, owing
to a want of complete
adaptation between
the trochlear surface
of the humerus andi
the semilunar notch
of the ulna. This
incongruence is note-
worthy since the
medial lip of the
trochlea is prominent
in front, and the
lateral lip is promi-
nent behind. Conse-
quently, this lattei
part is associated with
a surface on the
lateral side of the
olecranon which ie
only utilised in com-
plete extension.
The capitulum and
the opposing surface
upon the head of the radius are always in varying degrees of contact. The head of the radium
participates in the movements of flexion and extension, and is most closely and completely in
contact with the humerus during the position of semi-flexion and semi-pronation. In completed
extension a very considerable part of the capitulum is uncovered by the radius.
Humerus
Olecranon pad of fat
Ulna
Coronoid
pad of fat
.Coronoid process
Trochlea
lecranon
FIG. 307. VERTICAL SECTION THROUGH THE HUMERO-ULNAR PART OP THE
ELBOW-JOINT.
THE RADIO-ULNAR JOINTS.
These articulations, which are two in number, are situated at the proximal and]
distal ends of the radius and ulna. They provide an adaptation whereby the radius I
rotates around a longitudinal axis in the movements of pronation and supination.
and hence this form of uniaxial diarthrosis is termed lateral ginglymus.
Articulatio Radioulnaris Proximalis. The proximal radio-ulnar joint forme
a part of the articulatio cubiti or elbow-joint. The articular surfaces which enter
into its formation are the radial notch of the ulna and the lateral aspect of the
head of the radius. In each case the articular cartilage is continuous with an
articular surface entering into the formation of the humero-radial and humero-
ulnar joints, consequently the joint cavity is continuous with the cavities of those
joints, and therefore, in a sense, it lies within the cover of the articular capsule
of the elbow-joint ; but its special feature is the annular ligament of the radius.
Lig. Annulare Radii. The annular ligament of the radius (O.T. orbicular
ligament) (Figs. 305 and 308) has been mentioned above as the distal line oil
attachment of the radial collateral ligament and the ligaments on the front and|
back of the elbow-joint.
It is a strong, well-defined structure, attached by its extremities to the volai
and dorsal margins of the radial notch of the ulna, and thus it forms nearly |s
four-fifths of an osseo- tendinous circle or ring. The circle is somewhat wider at I
the proximal than at the distal margin of the annular ligament of the radius;
which, by encircling the proximal part of the neck of the radius, tends to prevent
THE EADIO-ULNAK JOINTS.
327
Olecranon
Radial notcl
Transverse
portion of
ulnar collateial
ligament
milunar notch
Annular ligament of the radius Coronoid process
FIG. 308. ANNULAR LIGAMENT OF THE RADIUS.
displacement of the head of that bone in a distal direction. The distal margin
of this ligament is not directly attached to the radius.
The synovial stratum is continuous with that which lines the elbow-joint. It
closes the joint cavity at the distal unattached margin of the annular ligament, where
it is somewhat loosely arranged in its reflexion from the ligament to the neck of
the radius. The epiphyseal line at the proximal end of the radius is intra-capsular.
Articulatio Radioulnaris Distalis. The distal radio-ulnar joint is situ-
ated between the lateral aspect of the head of the ulna and the ulnar notch
on the medial side of the distal
end of the radius. In addition, it
includes the distal surface of the
head of the ulna, which articulates
with the proximal surface of a tri-
angular articular disc by means
of which the joint is excluded from
the radio-carpal articulation.
Discus Articularis. The tri-
angular articular disc (Figs. 309 and
311), besides presenting articular
surfaces to two separate joints, is
an important ligament concerned in
i binding together the distal ends of
the radius and ulna. It is attached
by its apex to the depression at the
lateral side of the root of the
styloid process of the ulna, and by its base to the sharp line of demarcation between
the ulnar notch and the carpal articular surface of the radius.
Capsula Articularis. The fibrous stratum is very imperfect, and consists of
scattered fibres, termed the anterior and posterior radio-ulnar ligaments (Fig. 310).
These ligaments pass transversely between adjoining non-articular surfaces on the
radius and ulna, and are of sufficient length to permit of the movements of the
radius in pronation and supination.
The synovial stratum completes the closure of the joint cavity. It forms a
loose bulging projection (recessus sacciformis), passing proximally between the distal
ends of the shafts of the radius and ulna, and it also clothes the proximal surface of
the articular disc (Fig. 311). The cavity of this joint is quite distinct from that of
the radio-carpal articulation, except when the articular disc presents a perforation.
Between the proximal and distal radio-ulnar articulations there are two
accessory ligaments, viz., the chorda obliqua and the interosseous membrane, which
' connect together the shafts of the radius and ulna.
Chorda Obliqua. The oblique chord (Fig. 306) is a slender fibrous band of
very varying strength which springs from the lateral part of the coronoid process
of the ulna, and stretches obliquely distally and laterally to the radius where it is
attached immediately distal to the tuberosity of the radius.
Membrana Interossea Antibrachii. The interosseous membrane of the fore-
arm (Fig. 3 06) is a strong
R^^g^*^ _^ ea ; 1 f ul " a fibrousmembrane which
#^j^, PH stretches across the
ft?T Bfi^k. styloid P rocess of ulna interval between the
\A^ I iBll^/ radius and ulna, and
surface for ^s^ ^ISBp^S ^R^ is fi rm ty attached to
Tr^fortendon^S^SF . Apex of articular disc the interOSSCOUS Crest
of each. Distally it
extends to the distal
limit of the space be-
tween the bones, whilst
proximally it only reaches a point about one inch distal to the tuberosity of the
radius. A gap, called the hiatus interosseus, is thus left between its proximal margin
and the chorda obliqua, and through this the dorsal interosseous vessels pass back-
surface for ^&i
navicular bone ^
Groove for tendon
of extensor longtis
pollicis
Apex of articular disc
Articular disc
Surface for lunate bone
FIG. 309. CARPAL ARTICULAR SURFACE OF THE RADIUS,
AND ARTICULAR Disc OF THE WRIST.
328 THE AETICULATIONS OR JOINTS.
wards between the bones to reach the dorsal aspect of the forearm. The fibres
which compose the interosseous membrane run for the most part dis tally and
medially from the radius to the ulna, although on its dorsal aspect several bands
may be observed stretching in an opposite direction. The interosseous membrane
augments the surface available for the origin of the muscles of the forearm ; it
braces the radius and ulna together ; and when shocks are communicated from
the hand to the radius, owing to the direction of its fibres, the interosseous
membrane transmits them, to a large extent, to the ulna.
Movements of the Radius on the Ulna. The axis around which the radius moves is a
longitudinal one, having one end passing through the centre of the head of the radius and
the other through the styloid process of the ulna and the line of the ring-finger. In this axis
the head of the radius is so secured that it can only rotate upon the radial notch of the
ulna within the annular ligament of the radius, and consequently the radial head remains upon
the same plane as the ulna ; but the distal end of the radius being merely restrained by
the articular disc, is able to describe nearly a half-circle, of which the apex of this ligament is
the centre. In this movement the radius carries the hand from a position in which the palm is
directed forwards, and in which the radius and ulna lie parallel to each other (supination), to
one in which the palm is directed backwards, and the radius lies diagonally across the front of
the ulna (pronation).
The ulna is unable to rotate upon a long axis, but while the radius is travelling through the
arc of a circle from lateral to medial side in front of the ulna, it will usually be seen that the
ulna appears to move through the arc of a smaller circle in the reverse direction, viz., from
medial to lateral side. If the humerus is prevented from moving at the shoulder-joint, a very
large proportion, if not the entire amount, of this apparent movement of the ulna will disappear.
At the same time some observers maintain that it really occurs at the elbow-joint, associated with
lateral movement during slight degrees of flexion and extension at that joint.
ARTICULATIO RADIOCARPEA.
The radio-carpal joint is a bi-axial diarthrosis, frequently called a condyloid
joint.
The articular elements which enter into its formation are : on its proximal side,
the carpal surface of the distal end of the radius, together with the distal surface
of the discus articularis ; on its distal side, the proximal articular surfaces of the
navicular, lunate, and triquetral bones, and the interosseous ligaments between
them. The articular surface of the radius is concave both in its antero-posterior
and transverse diameters, in order to adapt itself to the opposing surfaces of the
navicular and lunate, which are convex in the two axes named. In the ordinary
straight position of the hand the articular disc is in contact with the lunate bone,
and the proximal articular surface of the triquetral bone is in contact with the
capsule of the joint. When, however, the hand is bent towards the ulna the
triquetral bone is carried laterally as well as' the lunate and navicular and the
articular disc comes into contact with the triquetral. The articular surface of the
radius is subdivided by an antero-posterior, slightly elevated ridge, into a lateral
triangular facet which usually articulates with the navicular, and a medial
quadrilateral facet for articulation with a portion of the lunate bone.
In the intervals between the navicular, lunate, and triquetral bones, the con-
tinuity of the distal articular surface is maintained by the presence of interosseous
ligaments which are situated upon the same level as the articular cartilage.
Capsula Articularis. An articular capsule completely surrounds the joint. It
is somewhat loosely arranged, and its fibrous stratum permits of subdivision into
the following four portions :
Lig. Radiocarpeum Laterale. The lateral radio-carpal ligament (0. T. external
lateral) (Fig. 310) is a well-defined band which is attached by one end to the tip
of the styloid process of the radius, and by the other to a rough area at the base
of the tuberosity of the navicular bone, i.e. lateral to its radial articular surface.
Lig. Ulnocarpeum Mediate. The medial ulno-carpal ligament (O.T. internal
lateral) (Fig. 310) is also a distinct rounded structure, having one end attached to
the tip of the styloid process of the ulna, and the other to the rough non-articular
border of the triquetral bone, some of its fibres being prolonged to the pisiform bone.
Lig. Radiocarpeum Volare. The volar radio-carpal ligament (O.T. anterior
ligament) (Fig. 310) is attached proximally to the volar margin of the distal end
CAEPAL JOINTS.
329
.
Anterior radio-
ulnar ligament
Pisiform bone
Capitate bone, with
ligaments radiat-
ing from it
Hamulus of
os hamatum
Collateral radio-carpal
ligament
Tubercle of navicular
bone
Ridge on
greater mult-
angular bone
Greater
multangular
bone
FIG. 310. LIGAMENTS ON VOLAR ASPECT OF RADIO-CARPAL,
CARPAL, AND CARPO-METACARPAL JOINTS.
of the radius, as well as slightly to the base of the styloid process of the ulna.
Some transverse
fibres may be seen,
but the greater num-
ber pass obliquely dis-
tally and medially to
. J . J .
the VOlar nOn-artlC-
ular surfaces of the
navicular, lunate, and Medial
triquetral bones, while-
some of them may
even be continued as
far as the capitate
bone. Those fibres
from the ulna run
obliquely laterally.
On its deeper aspect
this ligament is closely
adherent to the volar
border of the articular
disc of the distal radio-
ulnar articulation.
Lig. Radiocar-
peum Dorsale. The
dorsal radio-carpal
ligament (O.T. poster-
ior ligament) extends
from the dorsal margin
of the distal end of the radius, in an oblique direction distally and medially, to the
dorsal non-articular areas on the proximal row of the carpal bones. The slip to the
latter assists in forming the fibrous sheath through which the tendon of the ex-
tensor carpi ulnaris muscle travels to its insertion. The principal bundle of fibres
is connected with the triquetral bone.
The stratum synoviale (Fig. 311) is simple, and is confined to the articulation,
except in those cases in which the articular disc is perforated, or in which
one of the interosseous ligaments between the carpal bones of the first row is absent.
The epiphyseal lines at the distal ends of radius and ulna are extra-capsular.
Movements at the Radio-carpal Joint. The radio-carpal joint affords an excellent example
of a bi-axial articulation, in which a long transverse axis of movement is situated more or less at
right angles to a short axis placed in the antero-posterior direction. The nature of the move-
ments which are possible around these two axes is essentially the same in both cases, viz., flexion
and extension. The movements around the longer transverse axis are anterior or volar flexion,
extension, and its continuation into dorsi-flexion. Around the shorter antero-posterior axis we get
movements which result from combined action by certain flexor and extensor muscles, whereby
the radial or ulnar borders of the hand may be approximated towards the corresponding borders
of the forearm. Lateral movement also may be possible to a slight extent. The range of move-
ment in connexion with either of the principal axes is largely a matter of individual peculiarity,
for, with the exception of the lateral ligaments, there is no serious obstacle to the cultivation' of
greater mobility at the radio-carpal joint.
ARTICULATIONES INTERCARPE^.
Carpal Joints. The articulations subsisting between the individual carpal
bones are all diarthroses, and although the total amount of movement through-
out the series is considerable, yet the extent of movement which is possible
between the two rows or between any two carpal bones is extremely limited.
For this reason, as well as because of the nature of the movement, these articula-
tions are called gliding joints (arthrodia).
It is advisable to consider, first, the articulations between individual bones of
the proximal row; second, the articulations between the separate bones of the
distal row ; third, the articulation of the proximal and distal rows with each other ;
fourth, the pisiform articulation.
330 THE ARTICULATIONS OE JOINTS.
The proximal row of carpal articulations (Fig. 311) comprises the joints
between the navicular, lunate, and triquetral bones. On their adjacent aspects
these bones are partly articular and partly non-articular.
Three sets of simple but strong, although short, ligamentous bands bind these
three carpal bones together, and form an investment for three sides of their inter-
carpal joints. These are (1) the ligamenta intercarpea volaria (anterior or volar liga-
ments), two in number, which consist of transverse fibres passing between the
adjacent rough volar surfaces of the bones ; (2) the ligamenta intercarpea dorsalia
(posterior or dorsal ligaments), also two in number, and composed of similar short
transverse fibres passing between the adjacent dorsal surfaces ; (3) the ligamenta
intercarpea interossea (interosseous ligaments) (Fig. 310), again two in number, and
transverse in direction, situated on a level with the proximal articular surfaces,
and extending from the volar to the dorsal aspect of the bones while attached to
non-articular areas of the opposing surfaces. The radio-carpal joint is entirely
shut off from the intercarpal joints, and also from the joint between the two rows
of carpal bones, except in rare cases, when an interosseous ligament is wanting.
The distal row of carpal articulations (Fig. 311) includes tlie joints between
the greater multangular, lesser multangular, capitate, and hamate bones. Articular
facets occur on the opposing faces of the individual bones.
Associated with this row there are again simple bands of considerable strength,
and presenting an arrangement similar to that seen in the proximal row. As in
the former case, they invest the intercarpal articulations, except on the proximal
aspect, where they communicate with the transverse carpal joint, and on the distal
aspect, where they communicate with the carpo-metacarpal joint cavity.
The ligamenta intercarpea volaria (anterior or volar ligaments) are three in number.
They extend in a transverse direction between contiguous portions of the rough
volar surfaces of the bones. The ligamenta intercarpea dorsalia (posterior or dorsal
ligaments), also three in number, are similarly disposed on the dorsal aspect. The
ligamenta intercarpea interossea (interosseous ligaments) (Fig. 311) are two or three in
number. That which joins the capitate to the os hamatum is the strongest ; that
between the lesser multangular and the capitate bone is situated towards the dorsal
parts of their opposing surfaces ; the third, situated between contiguous non-articular
surfaces of the greater and lesser multangular bones, is always the feeblest, and is
frequently absent.
The transverse carpal articulation (Fig. 311) is situated between the proximal
and distal rows of the carpus. The bones of the proximal row present the following
characters on their distal aspect. The lateral part of the articular surface is
strongly convex, both in the antero-posterior and in the transverse directions, but
the medial part of the same surface is concavo-convex, more especially in the trans-
verse direction.
Proxirnally, the articular surfaces of the distal row of carpal bones present an
irregular outline. That part pertaining to the greater and lesser multangular bones
is concave in the antero-posterior and transverse directions, and lies at a considerably
more distal level than the portion belonging to the capitate and os hamatum, which
is, moreover, markedly convex in the antero-posterior and transverse directions,
with the exception of the most medial part of the os hamatum, where it is concavo-
convex in both of these directions.
This articulation is invested by a complete short articular capsule (Fig. 310)
which binds the two rows of the carpus together, and sends prolongations to
the investing capsules of the proximal and distal articulations. The ligament, as a
whole, is very strong, and individual bands are not readily defined, although certain
special bands may be described. The lig. carpi radiatum (radiate carpal ligament
(volar ligament)) radiates from the capitate bone to the navicular, triquetral, and
pisiform bones. The* interval between the capitate and lunate is occupied by
oblique fibres, some of which pass from navicular to triquetral, while these are
joined by others, prolonged obliquely distally and medially, from the radial end of
the anterior radio-carpal ligament. By these different bands the volar aspect
of the joint is completely closed.
The ligamenta intercarpea dorsalia (dorsal ligaments) are more feeble than the
CAEPAL JOINTS.
is restricted to the pisi-tri-
quetral articulation, and is
correspondingly simple, al-
though occasionally the joint
cavity may communicate
with that of the radio-carpal
joint.
The other synovial stra-
tum is associated with the
transverse carpal joint which
extends transversely be-
tween the two rows of carpal
bones, with prolongations
into the intervals between
the adjoining bones of each
row, i.e. the intercarpal
articulations. It is, there-
fore, an elaborate cavity,
which may be still further
extended, by the absence of
interosseous ligaments, so as
to reach the radio-carpal and
carpo-metacarpal series of
joints. The first condition' is rare, but the second is not uncommon, and may
result from the absence of the interosseous ligament between the greater and lesser
multangular bones, or of that between the lesser multangular and the capitate
bone, but it may occur when all the interosseous ligaments are present.
FIG. 311. FRONTAL SECTION through the radio-carpal, carpal, carpo-
metacarpal, and intermetacarpal joints, to show joint cavities and
interosseous ligaments (diagrammatic).
332 THE ARTICULATIONS OK JOINTS.
ARTICULATIONES INTERMETACARPEJE.
Intermetacarpal Joints. The four medial metacarpal bones articulate with
each other at their proximal ends or bases, between the opposing surfaces of which
joint cavities are found arthrodial diarthroses. These cavities are continuous
with the carpo-rnetacarpal joint (not yet described), and hence the ligamentous
arrangements only enclose three aspects of each joint.
Three strong transverse ligaments (Figs. 310 and 311) bind adjacent volar,
dorsal, and interosseous areas of the bases of the metacarpal bones, and hence they
are called ligamenta basium (oss. rnetacarp.) volaria, dorsalia et interossea. A
synovial stratum is associated with each of these joints, but it may be regarded as
a prolongation from the carpo-metacarpal articulation.
ARTICULATIONES CARPOMETACARPEA;.
Carpo-metacarpal Joints. The articulation of the metacarpal bone of the
thumb with the greater multangular differs in so many respects from the articula-
tion between the other metacarpal bones and the carpus, that it must be considered
separately.
(A) The articulatio carpometacarpea pollicis (Figs. 310 and 311) is the joint
between the disto-lateral surface of the greater multangular and the proximal
surface of the base of the first metacarpal bone. Both of these surfaces are saddle -
shaped, and they articulate by mutual co-aptation.
The joint cavity is surrounded by an articular capsule, in the fibrous stratum of
which we may recognise volar, dorsal, lateral, and medial bands, the last being
the strongest and most important.
A synovial stratum lines the fibrous stratum, and the joint cavity is isolated
and quite separate from the other carpal and carpo-metacarpal articulations.
At tliis joint movements occur around at least three axes. Thus, around a more or less trans-
verse axis, flexion and extension take place ; in an antero-posterior axis abduction and adduction
(movements which have reference to the middle line of the hand) are found ; while a certain
amount of rotation is possible in the longitudinal axis of the digit. The very characteristic
movement of opposition, in which the tip of the thumb may be applied to the tips of all the
fingers, results from a combination of flexion, adduction, and rotation, and by combining all the
movements possible at the various axes a considerable degree of circumduction may be produced.
(E) The articulationes carpometacarpeae digitorum are the joints between
the bases of the four medial metacarpal bones and the four bones of the distal row
of the carpus. They are all arthrodial diarthroses, and the opposed articular surfaces
present alternate elevations and depressions which form a series of interlocking
joints. The joint cavities between the carpal bones of the distal row, and also the
more extensive intermetacarpal joint cavities, open into this articulation.
This series of joints is invested by a common articular capsule which is weakest
on its radial side, but is otherwise well defined. Its fibres arrange themselves in
small slips, which pass obliquely in different directions, and vary in number for
each metacarpal bone. Thus the ligamenta carpometacarpea volaria (volar carpo-
metacarpal ligaments (O.T. oblique palmar)) (Fig. 310) usually consist of one slip for
each metacarpal bone, but there may be two slips, and the third metacarpal bone
frequently has three, of which one lies obliquely in front of the tendon of the flexor
carpi radialis muscle.
The ligamenta carpometacarpea dorsalia (dorsal carpo-metacarpal ligaments (O.T.
oblique dorsal)) are similar short bands, of greater strength and clearer definition,
by which the index metacarpal is bound to the greater and lesser multangular
bones ; the middle metacarpal to the capitate, and frequently to the lesser mult-
angular ; the ring metacarpal to the capitate and os hamatum, and the metacarpal
of the 5th finger to the os hamatum.
Ligamenta interossea (interosseous ligaments), one or sometimes two in number,
occur within the capsule. They are usually situated in relation to one or both of
the contiguous margins of the bases of the third and fourth metacarpal bones, from
which they extend proximally to adjacent margins of the capitate and os hamatum.
Occasionally they are sufficiently developed to divide the joint cavity into radial
and ulnar sections.
METACARPO-PHALANGEAL JOINTS.
333
The synovial stratum (Fig. 311) is usually single and lines the fibrous stratum,
but, as already explained, it has prolongations into the intermetacarpal and inter-
carpal series of joints. In connexion with the intercarpal series, the frequent
absence of the interosseous ligament between the greater and lesser multangular
bones permits the free communication of this joint cavity with that of the
transverse carpal joint.
ARTICULATIONES METACARPOPHALANGE^E.
Metacarpo-phalangeal Joints. In the case of the pollex this joint is con-
structed on the plan of a ginglymus diarthrosis; the four corresponding joints
of the fingers are also diarthroses of a slightly modified ball-and-socket variety.
With the exception of the metacarpal bone of the pollex,
each metacarpal bone has a somewhat spherical head
articulating with a shallow oval cup upon the base of the
first phalanx. It is important to note that the articular
surface upon the head of each of these metacarpal bones
is wider on the volar aspect and narrower on the dorsal
aspect. The articulation in the thumb presents features
similar to those of an interphalangeal joint.
Each joint possesses a capsula articularis (Fig. 312)
which presents very different degrees of strength in
different aspects of the articulation. Thus, on the dorsal
aspect, it cannot be demonstrated as an independent
structure, but the necessity for dorsal ligaments is to
a large extent obviated by the presence of the strong
flattened expansions of the extensor tendons.
The epiphyseal lines are extra-capsular.
Ligamenta Collateralia. The collateral ligaments
(O.T. internal and external lateral) (Fig. 312) are strong
cord-like bands which pass from the tubercles and adjacent
depressions on the sides of the heads of the metacarpal
bones to the contiguous non-articular areas on the bases
of the proximal phalanges. They are intimately connected
on their volar aspects with the volar ligaments.
Ligamenta Accessoria Volaria. The volar accessory
ligaments (O.T. palmar ligaments) consist of thick plates of
fibro- cartilage loosely connected to the metacarpal bones,
but firmly adherent to the phalanges. They are placed
between the collateral ligaments, to both of which they
are in each case connected. Each plate is grooved on the
volar surface for the long flexor tendons, whilst on its
dorsal or joint surface it supports and glides upon the
head of the metacarpal bone during flexion and extension
of the joint. In the case of the thumb this plate of FlG 312 ._ METACAKPO-PHALAN-
fibro-cartilage is usually replaced by sesamoid bones, and
in the case of the index finger one such sesamoid nodule
is frequently found at the radial side of the plate.
An important accessory ligament is found in connexion with the four medial
metacarpo-phalangeal articulations, viz. :
Ligamenta Capitulorum (Oss. Metacarpalium) Transversa. The transverse
ligament of the heads of the metacarpal bones (or transverse metacarpal ligament)
binds together the distal extremities of the four medial metacarpal bones. The
name is applied to three sets of transverse fibres of great strength which are
situated in front of the three medial interosseous spaces. These fibres are con-
tinuous with the ligamenta accessoria volaria (volar metacarpo-phalangeal ligaments)
at their lateral margins.
A stratum synoviale lines the capsula articularis of each joint.
Capsule
GEAL AND
JOINTS.
Collateral
ligament
INTERPHALANGEAL
334 THE ABTICULATIONS OK JOINTS.
ARTICULATIONES DIGITORUM MANUS.
Interphalangeal Joints. Of these joints there are two for each finger and
one for the thumb. They all correspond, in being ginglymus diarthroses in which
the trochlear character of their articular surfaces is associated with one axis of
movement directed transversely.
In their general arrangement they correspond with each other, and to a large
extent with the metacarpo-phalangeal series already described. Each is provided
with a definite articular capsule (Fig. 312), of which the volar and cord-like lateral
portions are well marked, while on the dorsal aspect the extensor tendons act as the
chief support. The volar portions contain fibrous plates of considerable thickness,
and are attached to the two collateral ligaments and to the intervening rough
surface on the distal phalanges, while their proximal margins are not attached to
bone. Each ligament has its lateral margins prolonged proxirnally to the adjacent
sharply defined lateral ridges on the phalangeal shafts.
The collateral ligaments (Fig. 312) are strong, rounded, short bands, continuous
with the preceding, and attached to the non-articular sides of adjacent heads and
bases of the phalanges.
Each joint possesses a synovial stratum which lines its fibrous stratum, but its
arrangement presents no special peculiarity. The epiphyseal lines of the bases of
the phalanges are extra-capsular.
MOVEMENTS OF THE CARPAL, INTERMETACARPAL, METACARPO-PHALANGEAL
AND INTERPHALANGEAL JOINTS.
The amount of movement which is possible at individual joints of the intercarpal, inter-
metacarpal, and carpo-metacarpal series is extremely limited, both on account of the interlocking
nature of the articular surfaces and the restraining character of the ligamentous bands. Taken
as a whole, however, the movements of the carpus and metacarpus enable the hand to perform
many varied and important functions. This is largely due to the greater mobility of those joints
on the radial and ulnar borders of the hand, as well as to the general elasticity of the arches
formed by the carpus and metacarpus. These conditions particularly favour the movements of
opposition and prehension. In the opposite direction, i.e. when pressure is applied from the
volar aspect, the metacarpal and carpal arches tend to become flattened, but great elasticity is
^mparted by the tension of the various ligaments.
The four medial metacarpo-phalangeal joints are ball-and-socket joints, and movements of
velar-flexion and extension are freely performed about a transverse axis. In exceptional cases
a certain amount of dorsi-flexion is possible. About an antero -posterior axis movements occur
which are usually referred to the middle line of the hand, and hence called abduction and
adduction, but in consequence of the difference in the width of the articular surface on the dorsal
and volar aspects of the heads of the four medial metacarpal bone's it is only possible to .obtain
abduction when the joints are extended, while in the flexed position the joints become locked and
abduction is impossible.
The movements of the index finger are less hampered than in the case of the others, but
each of them can perform a modified kind of circumduction.
The metacarpo-phalangeal joint of the thumb and all the interphalangeal joints are uniaxial
or hinge-joints acting about a transverse axis, which permits of volar-flexion and extension
being freely performed, but dorsi-flexion is, as a rule, entirely prevented by the volar and lateral
ligaments.
AKTICULATIONES ET LIGAMENTA CINGULI
EXTREMITATIS INFERIORIS.
Articulations and Ligaments of the Pelvis. Although we may consider the
pelvis as a separate part of the skeleton, yet it is essential to remember that the
bones which enter into its composition belong to the vertebral column (sacrum,
coccyx) and the lower limb (hip bone). Accordingly, the articulations, with their
corresponding ligaments, may be arranged as follows :
(a) Those by which the segments of the coccyx are joined together (already
described, v. p. 310) ;
(6) That by which the sacrum articulates with the coccyx (already de-
scribed, v. p. 309) ;
SACRO-ILIAC JOINT.
335
(c) Those by which the sacrum articulates with the last lumbar vertebra
(Lumbo-sacral joints) ;
(d) Those by which the hip bones are attached to the vertebral column
(Sacro-iliac joints) ;
(e) That by which the hip bones are attached to each other (Symphysis
pubis).
ARTICULATIONES SACROLUMBALES.
Lumbo-sacral Joints. The articulation of the sacrum with the fifth lumbar
vertebra is constructed precisely on the principle ^of the articulations between two.
typical vertebrse, and the usual ligaments associated with such joints are repeated.
There is, however, an additional accessory ligament, termed the lateral lumbo-sacral
ligament. This extends from the anterior aspect of the inferior border of the
transverse process of the last lumbar vertebra, downwards and slightly laterally,
to the front of the lateral aspect of the ala of the sacrum, close to the sacro-
iliac joint. Further, a variable membranous band extends between the lateral
aspect of the inferior part of the body of the last lumbar vertebra and the front of
the ala of the sacrum. This band lies in front of the anterior ramus of the fifth
lumbar nerve.
ARTICULATIO SACROILIACA.
Each hip bone articulates with the sacral section of the vertebral column on
each side through the intervention of a diarthrosis, termed the sacro-iliac joint.
Ilium
Sacrum
Greater sciatic
foramen
Posterior sacro-iliac
ligament
Sacro-iliac joint
Sacro-tuberous
ligament
Sacro-spinous
ligament
Lesser sciatic foramen
Acetabulum
Sacro-tuberous
ligament
Interpubic fibro-cartilage
FIG. 313. FRONTAL SECTION OF PELVIS.
This joint is formed between the contiguous auricular surfaces of the sacrum
and ilium. Each of these surfaces is more or less completely clothed with hyaline
articular cartilage. The joint cavity, which is little more than a capillary interval,
may be crossed by fibrous bands.
336
THE AKTICULATIONS OK JOINTS.
The cavum articulare (joint cavity) is surrounded by ligaments of varying
thickness and strength, which constitute the fibrous stratum of its articular capsule.
Thus, its anterior part is thin, and consists of short but strong fibres which pass
between adjoining surfaces on the ala of the sacrum and .the iliac fossa of the
hip bone; they form the anterior sacro-iliac ligament. On the posterior aspect
there are three ligaments. The interosseous sacro-iliac ligament (Fig. 313) con-
sists of numerous strong fasciculi, which pass from the rough area on the medial
aspect of the ilium, above and behind its auricular surface, downwards and medially
to the tubercles of the transverse processes and the depressions behind the first and
second segments of the sacrum. This ligament is of great strength, and with its
Ilio-lumbar ligament
Short posterior saci
iliac ligament
Long posterior
sacro-iliac ligament
Reflected head of rectus femoris i
Lesser sciatic
foramen
Sacro-tuberous
ligament
Obturator membrane
FIG. 314. POSTERIOR VIEW OF THE PELVIC LIGAMENTS AND OF THE HIP-JOINT.
fellow it is responsible for suspending the sacrum and the weight of the super-
imposed trunk from the hip bones.
The long posterior sacro-iliac ligament (Fig. 314) is a superficial thickened portion
of the interosseous ligament. It consists of a definite band of fibres passing from
the posterior superior iliac spine to the tubercles of the transverse processes of the
third and fourth segments of the sacrum.
The short posterior sacro-iliac ligament consists of superficial fibres of the
interosseous ligament passing from the posterior superior iliac spine to the tubercles
of the first and second transverse processes of the sacrum.
The articular cavity of this joint is very imperfect and rudimentary.
Several accessory ligaments are associated with the articulation of the hip bone
to the sacral section of the vertebral column.
IS Y Mm Y SIS rUBlJS. 337
Lig. Iliolumbale. The ilio-lumbar ligament (Fig. 314), which is merely the
thickened anterior lamina of the lumbo-dorsal fascia, extends from the tip of the
transverse process of the 'last lumbar vertebra, almost horizontally laterally, to
the inner lip of the iliac crest at a point a short distance behind its highest level.
A proportion of these fibres is attached to the medial rough surface of the ilium
between the iliac crest and the auricular impression. To these the name of the
lig. iliolumbale inferius is applied.
Lig. Sacrotuberosum. The sacro-tuberous ligament (O.T. great sacro-sciatic
lig.) (Fig. 314) is somewhat triangular in outline. It occupies the interval between
the sacrum and the hip bone, and is attached medially to the posterior inferior
spine of the ilium ; to the posterior aspects of the tubercles of the transverse processes
and lateral margins of the third, fourth, and fifth segments of the sacrum, as well as
to the side of the first segment of the coccyx. It passes downwards and laterally,
becoming narrower as it approaches the ischium, near to which, however, it again
expands, to be attached to the medial side of the tuber ischiadicum, immediately
below the groove for the tendon of the obturator internus muscle, i.e. the lesser
sciatic notch. A continuation of the medial border of the ligament the processus
falciformis (Fig. 314) runs upwards and forwards on the medial aspect of the
ramus of the ischium.
The ligamentum sacrotuberosum is believed by many to represent the original
or proximal end of the long or ischial head of the biceps femoris muscle.
Ligamentum Sacrospinosum. The sacro-spinous ligament (O.T. small sacro-
sciatic lig.) (Figs. 314 and 313) is situated in front, and in a measure under cover
of the sacro-tuberous ligament. Triangular in form, it is attached by its base to
the last two segments of the sacrum and the first segment of the coccyx, and by its
[ pointed apex to the tip and superior aspect of the spina ischiadica. This ligament
i is intimately associated with the coccygeus muscle, and by some it is regarded as
; being derived from it by fibrous transformation of the muscle fasciculi.
By the sacro-tuberous and sacro-spinous ligaments the two sciatic notches of
the hip bone .are converted into foramina. Thus the sacro-spinous ligament (lig.
sacrospinosum) completes the boundaries of the greater sciatic foramen (foramen
ischiadicum majus) ; while the sacro - tuberous ligament (lig. sacrotuberosum),
l assisted by the sacro-spinous ligament (lig. sacrospinosum), closes the lesser sciatic
foramen (foramen ischiadicum minus).
SYMPHYSIS OSSIUM PUBIS.
The anterior wall of the osseous pelvis is completed by the articulation of the
bodies of the two pubic bones, which constitutes the symphysis pubis. This joint
\., sonforms in its construction to the general plan of an amphiarthrosis. Thus it is
median in position ; each pubic bone is covered by a layer of hyaline cartilage,
which closely adapts itself to the rough tuberculated surface of the pubic bone ;
while between these two hyaline plates there is an interposed fibro- cartilage
3alled the lamina fibrocartilaginea interpubica, in the interior of which there is
isually a vertical antero-posterior cleft. This cavity, which is placed nearer the
posterior than the anterior aspect of the joint, does not appear until between the
seventh and tenth years, and as it is not lined by a synovial stratum, it is supposed
;o result from the breaking down of the interpubic lamina.
Lig. Pubicum Anterius. The anterior pubic ligament (Fig. 313) is a structure
>f considerable thickness and strength. Its superficial fibres, which are derived
^ery largely from the tendons and aponeuroses of adjoining muscles, are oblique,
md form an interlaced decussation. The deeper fibres are short, and extend
ransversely from one pubic bone to the other.
Lig. Pubicum Posterius. The posterior pubic ligament (Fig. 313) is very
veak and consists of scattered fibres which extend transversely between contiguous
>ubic surfaces posterior to the articulation.
Lig. Pubicum Superius. The superior pubic ligament also is weak ; it consists
'f transverse fibres passing between the two pubic crests.
22
338 THE ARTICULATIONS OE JOINTS.
Lig. Arcuatum Pubis. The arcuate ligament of the pubis (O.T. inferior or
subpubic ligament) occupies the arch of the pubis, and is of considerable strength.
It gives roundness to the pubic arch and forms part of the inferior aperture of
the pelvis. It has considerable vertical thickness immediately below the interpubic
nbro-cartilage; to which it is attached. Laterally it is attached to adjacent sides
of the inferior rami of the pubis. Its inferior border is free, and separated from the
upper border of the fascia of the urogenital diaphragm by a transverse oval
interval, through which the dorsal vein of the penis passes backwards to the
interior of the pelvis.
FASCIA DlAPHRAGMATIS UROGENITALIS INFERIOR.
The inferior fascia of the urogenital diaphragm (O.T. superficial layer of the
triangular ligament) is a membranous structure which occupies the pubic arch below
and distinct from the arcuate ligament of the pubis. It assists in completing the
pelvic walls anteriorly in the same manner that the obturator membrane does
laterally. Indeed, these two structures occupy the same morphological plane. The
fascia presents two surfaces one superficial or perineal, the other deep or pelvic
and both of these surfaces are associated with muscles. Its lateral borders are
attached to the sides of the pubic arch, while its base is somewhat ill-defined, by
reason of its fusion with the fascia of Colles in the urethral region of the perineum.
The apex of the fascia is truncated, free, and well defined, constituting the
transverse perineal ligament, above which there is the interval for the dorsal vein of
the penis. It is pierced by a number of vessels and nerves, but the principal
opening is situated in the median plane one inch below the pubic arch, and trans-
mits the urethra.
MEMBRANA OBTURATORIA.
The obturator membrane (Fig. 316) occupies the obturator foramen. It ig
attached to the pelvic aspect of the circumference of this foramen. It consists
of fibres irregularly arranged and of varying strength, so that sometimes it almost
appears fenestrated. At the highest part of the foramen it is incomplete and forms
a U-shaped border, between which and the bony circumference of the foramen
the obturator canal is formed. In this position the membrane is continuous with
the parietal pelvic fascia which clothes the medial side of the obturator internus
muscle, above the superior free margin of the muscle. From the lateral or femoral
aspect of the membrane some of its fibres are prolonged to the antero-inferioi
aspect of the capsule of the hip-joint.
Mechanism and Movements of the Pelvis. The human pelvis presents a mechanism tin
principal requirement of which is stability and not movement, for, through the pelvis, the weigh j
of the trunk, superimposed upon the sacrum, is transmitted to the lower limbs. Moreover, it I
stability is largely concerned in the maintenance of the erect attitude. The movements of it
various parts are therefore merely such as are consistent with stability, without producing absolutl
rigidity.
The two hip bones, being bound together by powerful ligaments at the pubic articulatior
constitute an inverted arch, of which the convexity is directed downwards and forwards, whil
its piers are turned upwards and backwards, and considerably expanded in relation to th
posterior parts of the iliac bones. Between the piers of this inverted arch the sacrum is situatec
This bone is in no sense a key -stone to an arch, because, as may readily be seen in antero-postericl
transverse section, the sacrum is wider in front than behind, and the superposed weight naturall j
tends to make the sacrum fall towards the pelvic cavity, and so fit less closely between tt|
hip bones. The sacrum is in reality an oblique platform, in contact with each hip bone througji
its articular auricular surfaces, and in this position it is suspended by the interosseous ar|
posterior sacro-iliac ligaments, and kept securely in place by the "grip" due to the irregularilk
of the opposed surfaces of the two sacro-iliac articulations. Since the weight of the trunk li
transmitted to the anterior and superior end of this sacral platform, there is a natural tenden< |
for the sacrum to revolve upon the transverse axis which passes through its sacro-iliac join' I
If this were permitted, the promontory of the sacrum would rotate downwards and forwar <
towards the pelvic cavity, as really does occur in certain deformities. This revolution or tiltii i
downwards of the anterior part of the sacrum is prevented by the action of the sacid
tuberous and sacro-spinous ligaments, extending from the ischial tuberosity to the poster! ::|
and inferior end of the suspended platform of the sacrum. Not only so, but these ligamen "1
acting on a rigid sacrum, tend to hold up the weight upon the sacral promontory.
THE HIP-JOINT.
339
The various ligaments passing between the last lumbar vertebra and the sacrum and ilium
retain the weight of the trunk in. position upon the anterior end of the sacrum, and resist its
tendency to slip forwards and downwards towards the pelvic cavity. The entire weight of the
trunk and pelvis is transmitted to the heads of the thigh bones in the most advantageous
position, both for effectiveness and the strengthening of the inverted back of the hip bones, for it
will be evident that the heads of the femora thrust inwards upon the convex side of the arch,
very much at the place where the arches are weakest, viz., at the springing of the arch from its
piers. The forces which tend to cause movement of the pelvic bones during parturition act from
within the pelvis, and have for their object the increase of the various pelvic diameters, in
order that the foetal head may more readily be transmitted. For this purpose the wedge-like
dorsal surface of the sacrum is driven backwards, and a certain amount of extra space may there-
by be obtained. An important factor, however, in the increase of the pelvic capacity at this
period is found in the relaxation of its various ligaments.
,
ARTICULATIONES EXTKEMITATIS INFERIORS.
ARTICULATIO
Ischial spine
'he Hip- Joint. The human body provides no more perfect example of an
enarthrodial diarthrosis than the hip-joint. Combined with all that variety of
movement which characterises a multi-axial joint, it nevertheless presents great
stability, which has been obtained by simple arrangements, for restricting the range
pf its natural movements. This stability is of paramount importance for the
; maintenance of the erect attitude, and the mechanical adaptations whereby this
result is obtained are such that the erect attitude may be preserved without any
^reat degree qf sustained muscular effort.
Articular Surfaces. The head of the femur is globular in shape, and consider-
ably exceeds a hemisphere.
It is clothed with hyaline
articular cartilage on those
parts which come into direct
contact with the acetabulum.
There is frequently more or
less of extension of the
particular cartilage from the
[head to the adjoining anterior
I part of the neck, an extension
b which is accounted for by the
Islose and constant apposition
jf )f this portion of the neck
Itfith the posterior aspect of
:he ilio - femoral ligament.
Irhe limit of the articular
partilage covering the head
f:.s indicated by a sinuous
l)order. Further, there is an
ftjibsence of articular cartilage
iii'rom the fovea or pit on
he head of the femur.
The acetabulum is a deep
i up-shaped cavity which pre-
^ents a notch on its antero-
nferior margin. The interior
I'f the cup is lined with a
i.ibbon-like band of articular
i iartilage which extends to
rhe brim of the cavity, but
oes not cover its floor. This articular ribbon-shaped band is widest on its supero-
^lOsterior aspect, and narrowest at the anterior margin of the acetabular notch.
Lig. Transversum Acetabuli. The transverse ligament (Fig. 315) bridges the
cetabular notch, and consists of strong transverse fibres which are attached to
Transverse acetabular ligament
Retinacula
FIG. 315. DISSECTION OF THE HIP- JOINT.
Bottom of the acetabulum removed, and capsule of the joint thrown
laterally towards the trochanters.
340 THE AKTICULATIONS OE JOINTS.
both of its margins, but more extensively to the postero-inferior. This ligament
does not entirely fill the notch, but leaves an open interval between its inferior
border and the bottom of the notch through which vessels and nerves enter the
cup. The acetabular aspect of this ligament constitutes an articular surface.
The acetabulum is deepened by the labrum glenoidale (O.T. cotyloid ligament)
(Figs. 315 and 316), which consists of a strong ring of fibre-cartilaginous tissue
attached to the entire rim of the cup. The attached surface of the ring is broader
than its free edge, and, moreover, the latter is somewhat contracted, so that the
ligament grasps the head of the femur which it encircles. Its fibres are partly
oblique and partly circular in their direction. By the former it is firmly implanted
on the rim' of the acetabulum and the lig. transversum acetabuli; by the latter
the depth of the cup is increased through the elevation of its edge, and its
mouth slightly narrowed. By one surface this ligament is also articular.
Capsula Articularis. An articular capsule (Figs. 315 and 316) completely
invests the joint cavity. Its fibrous stratum is of great strength, although it is not
of equal thickness throughout, being considerably thicker on the supero-anterior
aspect than at any other part. Unlike the corresponding structure of the shoulder-
joint, it does not permit of the withdrawal of the head of the femur from contact
with the acetabular articular surfaces, except to a very limited extent. Its fibres
are arranged both in the circular and in the longitudinal direction, the former,
known as the zona orbicularis, being best marked posteriorly, while the longitudinal
fibres stand out more distinctly in front, where they constitute special ligaments.
Looked at as a whole, the fibrous stratum of the capsule has the following
attachments : proximally it surrounds the acetabulum, on the superior-and posterior
aspects of which it is attached directly to the hip bone, while on the anterior and
inferior aspects it is attached to the non- articular surfaces of the labrum j
glenoidale and transverse ligaments of the acetabulum ; distally it encircles the neck j
of the femur, where it is attached in front to the intertrochanteric line ; above, to
the medial aspect of the root of the greater trochanter ; below, to the lower part
of the neck of the femur, in close proximity to the lesser trochanter; behind, to
the line of junction of the lateral and middle thirds of the neck of the femur.
It is a matter of some importance to note that only part of the posterior surface
of the neck of the femur is enclosed within the articular capsule. The femora]
attachments of the fibrous stratum of the capsule vary considerably in their
strength, being particularly firm above and in front, but much weaker below and
posteriorly, where the orbicular fibres are well seen. Many fibres of the fibrous
stratum, are reflected from its deep aspect proximally upon the neck of the femur,
where they form ridges, and to these the term retinacula (Fig. 315) is applied.
The epiphyseal line of the head of the femur is intra-capsular ; the epiphyseal
lines of the two trochanters are extra-capsular.
The longitudinal fibres of the fibrous stratum of the capsule are arranged so as tc
form certain definite bands, viz. :
(1) Lig. Iliofemorale. The ilio- femoral ligament (Fig. 316) consists of
triangular set of fibres attached proximally, by their apex, to the inferior part
the anterior inferior iliac spine and the immediately adjoining part of the rim ol
the acetabulum, and distally, by their base, to the intertrochanteric line of the
femur. This ligament is the thickest part of the fibrous stratum, but its sides are
more pronounced than its centre, especially towards its base. Consequently the
ilio-femoral ligament presents some resemblance to an inverted Y (A), and therefore
was formerly named the Y-shaped ligament of Bigelow.
The lateral or upper limb of the ilio-femoral ligament may be somewhat extended by th<
inclusion of additional longitudinal fibres, and described as the ilio-trochanteric ligament. Thi
band arises from the anterior part of the dorsum of the acetabulum, and extends to the femora
neck, close to the anterior end of the medial surface of the greater trochanter.
(2) Lig. Pubocapsulare. The pubo-capsular ligament (Fig. 316) is composed o i
some bands of fibres of no great strength, which extend from the lateral end of th
superior ramus of the pubis, the ilio-pectineal eminence, the obturator crest and th<
obturator membrane, to lose themselves, for the most part, in the capsule, althougl
THE HIP-JOINT.
341
Anterior inferior
iliac spine
a certain proportion of them may be traced to the inferior aspect of the femoral
neck, where they adjoin the distal attachment of the ilio-femoral ligament.
(3) Lig. Ischiocapsulare. The ischio-capsular ligament consists of a broad
band of short, fairly strong longitudinal fibres, which, by their proximal ends,
are attached to the ischium between the lesser sciatic notch and the obturator
foramen, while their distal ends become merged in the zona orbicularis of the general
capsule.
Within the capsule, and quite distinct from it, there are the ligamentum teres
and the Haver sian gland.
Lig. Teres Femoris. The round ligament (Fig. 315) is a strong, somewhat
flattened band of fibrous tissue, attached by one end to the superior half of the pit
or depression on the
head of the femur.
By its medial end it
is attached to the
lower edge of the
articular surface of
the transverse liga-
ment, with exten-
sions to the opposite
borders of the
acetabular notch,
but chiefly to the
posterior or ischial
border. This liga-
ment varies very
greatly in its
strength and de-
velopment in differ-
ent subjects, and in
certain rare cases it
; is absent.
The so-called
Haversian gland
occupies the bottom
or non-articular area
of the acetabulum.
It consists of a mass
of fat covered by -the
synovial stratum of
' the joint. This pad of fat is continuous with the extra-capsular fat through the
passage subjacent to the transverse ligament of the acetabulum.
A synovial stratum lines the fibrous stratum of the capsule from which it is
reflected to the neck of the femur along a line which corresponds to the femoral
attachments of the fibrous stratum. Thus the synovial stratum. clothes more of the
'femoral neck anteriorly than in any other position. Posteriorly, where the fibrous
: stratum is feebly attached to the neck of the femur, the synovial stratum may be
seen from the outside of the capsule. The synovial stratum extends close up to
'bhe articular margin of the head of the femur, and on the superior and inferior
ispects of the neck it is gathered into loose folds upon the retinacula. These
folds or plicae synoviales are best marked along the line of synovial reflection, and
lo not reach as far as the femoral head. At its acetabular end the synovial
stratum is prolonged from the inside of the capsule to the outer non-articular
surface of the labrum glenoidale and transverse ligament, upon which it is
iontinued as a lining for their acetabular or articular surfaces, and further, it pro-
I rides a covering for the fat at the bottom of the acetabular fossa, as well as a
Complete tubular investment for the ligamentum teres femoris.
Occasionally the synovial bursa, which is subjacent to the tendon of the ilio-
)soas muscle, communicates with the interior of the hip-joint through an opening
Pubo-capsular ligament
FIG. 316. DISSECTION OF THE HIP- JOINT FROM THE FRONT.
342 THE AETICULATIOJSTS OE JOINTS.
in the anterior wall of the capsule (Fig. 316), situated between the pubo-capsular
ligament and the medial or lower limb of the ilio-femoral ligament.
Movements at the Hip-Joint. The movements which occur at the hip-joint are those of
a multiaxial joint. These are flexion, extension, abduction, adduction, rotation, and circumduction.
The range of each of these movements is less extensive than in the case of the shoulder-joint, be-
cause, at the hip, the freedom of movement is subordinated to that stability which is essential alike
for the maintenance of the erect attitude and for locomotion. When standing at rest in the erect
attitude the hip-joint occupies the position of extension, and as the weight of the trunk is trans-
mitted in a perpendicular which falls behind the centres of the hip-joints, both the erect attitude
and the extended position are maintained to a large extent mechanically, by means of the tension
of the ilio-femoral ligament, without sustained muscular action. Moreover, the tension of this
ligament is sustained by the pressure of the front of the head and neck of the femur against its
synovial surface. In this association of parts it is important to note that the articular cartilage
of the femoral head may be, and in certain races is, prolonged to the front of the femoral neck ;
and further, that the constant friction does not destroy the synovial stratum of the capsule.
Again, the same mechanism which preserves the erect attitude prevents an excessive degree oi
extension or dorsiflexion. In movement forwards, i.e. ventral flexion, the front of the thigh
is approximated to the anterior abdominal wall. The amount of this movement depends upon
the position of the knee-joint, because when the latter is flexed the thigh may be brought into
contact with the abdominal wall, whereas when the knee-joint is straightened (i.e. extended)
the tension of the hamstring muscles greatly restricts the amount of flexion at the hip-joint
Abduction and adduction are likewise much more restricted than at the shoulder-joint. Abduc-
tion is brought to a close by the tension of the pubo-capsular band and the lower part of the
capsule, and, in addition, the upper aspect of the neck of the femur locks against the margin
of the acetabulum. Excessive adduction is prevented by the tension of the upper band of the
ilio-femoral ligament and the upper part of the capsule. Rotation or movement in a longi-
tudinal axis may be either medially, i.e. towards the front, or laterally, i.e. toward the back.
In the former the movement is- brought to a close by the tension of the ischio-capsular ligament
and posterior part of the capsule, aided by the muscles on the back of the joint ; in the latter
rotation laterally the chief restraining factor is the lateral or upper limb of the ilio-femoral
ligament. The total amount of rotation is probably less than 60.
Circumduction is only slightly less free than at the shoulder, but it is complicated by the
preservation of the balance upon one foot.
The value and influence of the ligamentum teres femoris are not easily estimated, because it
may be absent without causing a"ny known interference with the usefulness of the joint. In the
erect attitude this ligament lies lax between the lower part of the femoral head and the acetabular
fat. In the act of walking it is rendered tense at the moment when the pelvis is balanced on the
summit of the supporting femur. Analysis of this position shows the femur to be adducted,
with probably, in addition, a small amount of flexion (i.e. bending forwards) and medial
rotation. Again, this ligament is said to be tense when the thigh is rotated laterally. The
equivalent of this movement is doubtless found in the rotation of the pelvis, which occurs in
the act of walking at the moment of transition from the toe of the supporting foot to the heel of
the advancing foot. The interest connected with this ligament is perhaps rather morphological
than physiological. It is believed by some to represent the tendon of a muscle which in birds
occupies a position external to the joint capsule.
ARTICULATIO GENU.
The knee-joint is the largest articulation in the body, and its structure ie
of a very elaborate nature. The part it plays in maintaining the erect attitude
materially influences its construction, and special arrangements are provided for thei
mechanical retention of the joint in the extended position in view of the fact thaij
the line of gravity falls in front of the centre of the articulation. Its principal
axis of movement is in the transverse direction, consequently it belongs to th(j
ginglymus or hinge variety of the diarthroses. At the same time a slight amounij
of rotation of the tibia in its long axis is permitted during flexion ; but while thiij
fact is of considerable importance in the study of certain accidents to which thi]
joint is liable, as well as in the study of its comparative morphology, it is no i
sufficiently pronounced to interfere with its classification as a hinge-joint.
Articular surfaces pertaining to the femur, tibia, and patella enter into th<|
formation of the knee-joint. The articular surface of the femur extends over ti
large part of both condyles, and may be divided into patellar and tibial portion
by faintly -marked, almost transverse grooves, which pass across the articula
surface immediately in front of the intercondylar notch. As a rule marginal
indentations of the articular surface render the positions of these transvers
grooves more distinct.
THE KNEE-JOINT.
343
The patellar portion (Fig. 317) is situated anteriorly, and is common to both
condyles, although developed to a larger extent in association with the lateral condyle,
on which it ascends to a more proximal level than on the medial condyle. This
surface is trochlear, and forms a vertical groove bordered by prominent borders.
The tibial portion of the articular surface of the femur is divided into two
articular areas, in relation to the distal aspects of the two condyl^s, by the wide
non- articular intercondyloid notch. These two surfaces are for the most part
parallel, but in front the medial tibial surface turns obliquely laterally as it
passes into continuity with the patellar trochlea, while posteriorly, under certain
circumstances, e.g. the squatting posture, the articular surface of the medial condyle
may extend to the adjoining portion of the popliteal area of the bone.
Impression of lateral
meniscus
Lateral tibial surface of
femur
Fibular collateral ligament
Cut tendon of biceps femoris
muscle
Anterior proximal tibio-
flbular ligament
Fibular collateral ligament
Opening in interosseous
membrane for anterior tibial
vessels
Patellar surface of femur
Semilunar facet for patella
Medial tibial surface of
fen:ur
Posterior cruciate ligament
Anterior cruciate ligament
Transverse ligament
Medial meniscus
Tibial collateral ligament
Ligamentum patellae
Medial perpendicular facet on
patella
FIG. 317. DISSECTION OF THE KNEE-JOINT FROM THE FRONT : PATELLA THROWN DISTALLT.
When the joint is in the position of extreme flexion, the patella is brought into
direct contact with that part of the articular surface on the medial condyle which
bounds the intercondyloid notch upon its medial and anterior aspects. This relation-
ship is indicated by the presence of a distinct semilunar facet on the cartilage in
that situation (Fig. 317). The articular surface of the femur may therefore be
regarded as presenting femoro-patellar and femoro- tibial areas.
The patella presents on its posterior aspect a transversely elongated oval
articular facet and a distal rough, triangular, non-articular area. The articular
; facet is divided into two principal portions by a prominent rounded vertical ridge.
Of these the lateral is the wider. A less pronounced and nearly vertical ridge
marks off an additional facet called the medial perpendicular facet, close to the
medial margin of the articular surface. Two faint transverse ridges cut off narrow
proximal and distal facets from the general articular surface without encroaching
on the narrow, most medial vertical facet (Goodsir) (Fig. 317).
The head of the tibia presents on its superior aspect two condylar articular
, surfaces, separated from each other by a non-articular antero-posterior area, which
is wider anteriorly and posteriorly than in the middle, where it is elevated to form
a bifid eminentia intercondyloidea.
The lateral condylar facet is slightly concavo-convex from before backwards
344
THE AKTICULATIONS OK JOINTS.
and slightly concave transversely. This surface is almost circular, and extends
to the free lateral border of the tibial condyle, where it is somewhat flattened.
Posteriorly the articular surface is prolonged downwards on the condyle in
relation to the position occupied by the tendon of the popliteus muscle. The
medial condylar facet is oval in outline, and distinctly concave both in its antero-
posterior and transverse diameters.
proximal to the articular cavity, subjacent
to the tendon of the quadriceps extensor muscle. Its specially named bands are not
Tendon of adductor magnus muscle (cut)
Medial head of gastrocnemius (cut)
Oblique popliteal ligament
Bursa beneath tendon of
semi-membranosus
Popliteal surface of femur
Plantaris muscle (cut)
Tendon of semi-membranosus
muscle (cut)
Oblique popliteal ligament
Tibial collateral ligament
Lateral head of gastro-
cnemius muscle (cut)
Fibular collateral
ligament (long)
Fibular collateral
ligament (short)
Popliteus muscle (cut)
Biceps flexor
cruris muscle (cut)
Popliteus fascia
Popliteus | muscle (cut)
Popliteal surface of tibia
Fm. 318. THE KNEE-JOINT. POSTERIOR VIEW.
of themselves sufficient to form a complete investment, and the fibrous stratum,
which largely consists of augmentations from the fascia lata and the tendons of
surrounding muscles, supplies the defective areas. Thus, anteriorly, on each side
of the patella and the ligamentum patellae, expansions of the vasti tendons and
fascia lata, constituting the collateral patellar ligaments, are evident. On the lateral
side of the joint the fibular collateral ligament is hidden within a covering derived
from the ilio-tibial tract of the fascia lata. On the medial side expansions from the
tendons of the sartorius and semi-membranosus muscles augment the articular
capsule, which here becomes continuous with the ligamentum collaterale tibiale.
Posteriorly the articular capsule also receives augmentation from the tendon of
the semi-membranosus muscle, but it is very thin subjacent to the origins of the
gastrocnemius muscle, where it covers the posterior parts of the condyles. Not
unfrequently the articular capsule presents an opening of communication between
THE KNEE-JOINT. 345
the interior of the articular cavity and a bursa which lies under cover of the medial
head of the gastrocnemius muscle.
The epiphyseal line of the distal end of the femur is partly intra-capsular and
partly extra-capsular ; that of the proximal end of the tibia is extra-capsular.
Ligamentum Patellae. The ligamentum patellae or anterior ligament (Fig.
318) is a powerful flattened band, attached proximally to the apex and adjoining
margins of the patella, and distally to the rough anterior tuberosity at the proximal
end of the shaft of the tibia. This ligament also serves as a tendon of insertion for
the quadriceps extensor muscle, and a certain number of the fibres of the tendon
may be observed to run distally as a thin fibrous covering for the anterior surface
of the patella. The deep surface of the tendon is separated from the front of the
head of the tibia by a synovial bursa, and proximal to this it rests upon the
infra-patellar pad of fat, which is placed between the tendon and the synovial
stratum of the joint.
The ligamentum posterius posterior (ligament) (Fig. 318) is a compound structure
of unequal strength, and those portions by which it establishes continuity with
the lateral parts of the articular capsule are remarkably thin. It is attached
proximally to the popliteal surface of the femur, close to the intercondyloid notch,
with lateral extensions to the non-articular areas immediately proximal to the
posterior articular margins of the two condyles, where it is closely associated with
the origins of the gastrocnemius muscle.
Distally it is attached to the rough non-articular posterior border of the head
of the tibia, where, to its fibular side, it presents an opening of exit for the tendon
of the popliteus muscle (Fig. 318).
The tendon of insertion of the semi-membranosus muscle contributes an
important expansion which augments the posterior ligament on its superficial
aspect. This expansion lig. popliteum obliquum passes obliquely proximally and
laterally to Ipse itself in the general ligament, but it is most distinct in the region
between the femoral condyles, where it may present proximal and distal arcuate
borders (lig. popliteum arcuatum). A number of vessels and nerves perforate
this ligament, and hence it presents a number of apertures.
Lig. Collaterale Tibiale. The tibial collateral ligament (O.T. internal lateral)
(Figs. 317 and 318) is a well-defined, strong, flat band which is applied to the*
medial side of the knee-joint, and is rather wider in the middle than at either end.
It is frequently regarded as consisting of two portions an anterior or long portion,
and a posterior or short one. The two parts arise close together from the medial
epicondyle, immediately distal to the adductor tubercle. The short or posterior
portion passes distally and slightly backwards, to be attached to the postero-medial
aspect of the medial part of the tibia proximal to the groove for the semi-
membranosus tendon. The long or anterior portion inclines somewhat forwards,
and extending distally superficial to the tendon of the semi-mernbranosus, it is
attached to the proximal part of the medial surface of the shaft of the tibia distal
to the level of the tuberosity.
On its superficial aspect the tibial collateral ligament is augmented by pro-
longations from the tendons of the semi-membranosus and sartorius muscles,
but is separated by a bursa from the tendons of the gracilis, semi-tendinosus,
and sartorius. Its deep surface is adherent to the convex edge of the meniscus
medialis, but more distally the distal and medial articular vessels intervene
between the ligament and the shaft of the tibia.
Lig. Collaterale Fibulare. The fibular collateral ligament (O.T. external lateral)
(Figs. 317 and 318) is a distinct rounded band which is under cover of the ordinary
capsule, and yet well separated from the articular cavity by intervening objects. It
is attached proximally to the lateral epicondyle, immediately proximal to the
groove occupied by the tendon of the popliteus muscle, superficial to which the
ligament extends distally to be attached to the lateral side of the head of the
fibula, in front of the styloid process. In its course it splits the tendon of
insertion of the biceps femoris (Fig. 317), the portions of which are fixed to the
head of the fibula on either side of the ligament, and a bursa may intervene
between the tendon and the ligament. The distal lateral articular vessels pass
346
THE AKTICULATIONS OE JOINTS.
forwards subjacent to this ligament and proximal to the head of the fibula.
Unlike the tibial collateral ligament, it is not attached to the corresponding
meniscus.
The ligamentum laterale externum breve sen posterius (Fig. 317) is an inconstant structure
which is attached by its proximal end immediately behind the preceding, and subjacent to
the lateral head of the gastrocnemius muscle. It likewise passes superficial to the popliteal
tendon, and is affixed distally to the apex capituli of the fibula.
The intra-articular structures of the knee-joint are more important and more
numerous than in any other joint of the body.
Ligamenta Cruciata Genu. The cruciate ligaments (O.T. crucial ligaments)
are two strong, rounded, tendinous bands, which extend from the non-articular area
Tendon of insertion of
adductor magnus
muscle (cut)
Popliteal surface of femur
Anterior cruciate ligament
Tendon of popliteus muscle
(cut)
Accessory attachment
of lateral meniscus
Medial meniscus
Lateral meniscus
Posterior cruciate __
ligament
Groove on tibia for tendon
of popliteus muscle
Proximal portion of cap-
sule of proximal tibio-
fibular articulation
Fibular collateral liga-
ment of knee-joint
Posterior proximal tibio-
iibular ligament
Head of fibula
Tendon of semi-membranosus
muscle (cut)
Tibial collateral ligament
of knee-joint
Popliteal surface of tibia
FIG. 319. THE KNEE-JOINT OPENED FROM BEHIND BY THE REMOVAL OF THE POSTERIOR LIGAMENT.
on the proximal surface of the head of the tibia to the non-articular sides of the
intercondyloid notch of the femur. These interarticular ligaments are distinguished
from each other as the anterior or lateral and the posterior or medial. They
cross each other like the limbs of an X, yet they remain distinct throughout,
and each has its own partial synovial covering. They lie within the articular
capsule, and extend between non-articular surfaces in relation to the longitudinal
axis of the limb.
The ligamentum cruciatum anterius (Figs. 317, 319, and 320) is attached distally
to the medial part of the rough, depressed area in front of and close to the inter-
condyloid eminence of the tibia. It passes obliquely proximally, laterally, and
backwards to the medial non-articular surface of the lateral condyle, where it
finds attachment far back in the posterior part of the intercondyloid notch. This
THE KNEE-JOINT.
347
Anterior cornu of
Transverse ligament lateral meniscus
Anterior cornu of medial
meniscus
ligament is tense in the position of extension, and therefore it assists in maintaining
the erect attitude.
The ligamentum cruciatum posterius (Figs. 31*7, 319, and 320) is somewhat shorter
than the preceding. It is attached distally to the posterior part of the depressed
surface behind the intercondyloid eminence of the tibia and close to the popliteal
notch. Its fibres pass obliquely proximally, forwards, and medially, to be inserted
into the lateral non-articular surface of the medial condyle, far forwards towards
the anterior margin of the intercondyloid notch. It is rendered tense in the
position of flexion.
The semilunar menisci are two in number a medial and a lateral placed
horizontally between the articular surfaces of the femur and tibia. In general
outline they correspond to the circumferential portions of the tibial facets upon
which they rest. Each has a thick, convex, fixed border in relation to the periphery
of the joint, and a thin, concave, free border directed towards the interior of the
joint. Neither of them is sufficiently large to cover the whole of the tibial articular
surface upon
which it rests.
The proximal
and distal sur-
faces of each
meniscus are
smooth and
free, and each
terminates in
an anterior and
a posterior
fibrous horn or
cornu.
Meniscus
Me di alls.
The medial
meniscus (O.T.
internal semi-
lunar fibro-carti-
lage) (Figs. 319
and 320) forms
very nearly a semicircle. It is attached by its anterior horn to the non-articular
surface on the head of the tibia, in front of the tibial attachment of the anterior
cruciate ligament, and by its posterior horn to the non-articular surface imme-
diately in front of the tibial attachment of the posterior cruciate ligament. The
deep or posterior part of the tibial collateral ligament is attached to its periphery.
Meniscus Lateralis. The lateral meniscus (O.T. external semilunar fibro-
cartilage) (Figs. 319 and 320) is attached by its anterior horn to the non-articular
surface of the tibia in front of the intercondyloid eminence, where it is placed to
the lateral side, and partly under cover of the tibial end of the anterior cruciate
ligament. By its posterior horn it is attached to the interval between the two
tubercles which surmount the intercondyloid eminence, i.e. in front of the attach-
ment of the posterior horn of the meniscus medialis. This fibro-cartilage, with its
two horns, therefore forms almost a complete circle. Posteriorly it is attached by
its periphery to the posterior ligament, but on the lateral side it is separated from
the fibular collateral ligament by the tendon of the popliteus muscle, and on this
aspect its periphery is free.
The two horns of the lateral meniscus are embraced by the -two horns of the
medial meniscus, and, while the anterior cruciate ligament has its tibial attachment
almost between the anterior horns of the two menisci, the tibial attachment of the
posterior cruciate ligament is situated behind the posterior horns of the two menisci.
Both menisci possess certain accessory attachments. Thus the lateral meniscus
sends a large bundle of fibres from its convex posterior border to augment the
posterior aspect of the posterior cruciate ligament by which these fibres are
Medial
meniscus
Posterior cornu
of medial
meniscus
Posterior cornu of
lateral meniscus
Fasciculus from lateral meniscus
to posterior cruciate ligament
Posterior cruciate ligament
FIG. 320. PROXIMAL END OF TIBIA WITH MENISCI AND ATTACHED PORTIONS OP
CRUCIATE LIGAMENTS.
348 THE ARTICULATIONS OR JOINTS.
conducted to the femur. Again, the convex or peripheral margins of each meniscus
possess certain attachments to the deep surface of the fibrous stratum of the capsule
on its medial and posterior aspects, as has already been explained, but, in addition,
they are attached to the non-articular circumference of the tibial head by short
fibrous bands known as the ligamenta coronaria. Lastly, a rounded band which
varies in strength, the lig. transversum genu (transverse ligament) (Figs. 317 and 320),
stretches between the anterior convex margins of the two menisci, crossing the front
part of the non-articular area on the tibial head in its course.
The stratum synoviale of the knee-joint is not only the largest, but the most
elaborately arranged of its kind in the body. It not only lines the fibrous stratum
of the capsule articularis, but it forms a more or less extensive covering for the intra-
capsular -ligaments and the free surface of the infra-patellar pad of fat. This pad
acts as a wedge which fits into the interval between the patella, tibia, and femoral
condyles, and the synovial stratum upon its surface forms a band or fold which
extends from the region distal to the level of the patellar articular surface to the
anterior part of the intercondyloid notch. It is named the plica synovialis patellaris.
At its femoral end it is narrow and attenuated, but at its patellar end it expands
on each side to form wing-like fringes or membranes the plicae alares medial
and lateral. These folds are more or less loaded with fat.
Apart from these special foldings, the synovial stratum lines the deep surface
of the common extensor tendon, and extends for a variable distance proximal to the
patella. This extension of the articular cavity almost always communicates with a
large bursa situated still more proximally on the front of the femur. Tracing the
synovial stratum distally, it will be found to cover both surfaces of the two menisci.
The peripheral or convex margins of these menisci are only covered by this membrane
where they are unattached to the capsule. A prolongation invests the intracapsular
portion of the tendon of the popliteus muscle, and separates this tendon from the
posterior part of the tibial head, besides intervening between the lateral meniscus
and the head of the tibia.
From the posterior part of the articular cavity the synovial stratum extends
forwards, and provides a partial covering for the cruciate ligaments between which a
bursa may be found.
This somewhat complicated arrangement of the synovial stratum may be
readily comprehended if it is borne in mind that it really represents the fusion of
three separate synovial cavities, which in some animals are permanently distinct.
These are indicated in the two femoro-tibial and the single femoro-patellar parts of
the articulation.
The articular cavity may communicate with bursse situated in relation to the
medial head of the gastrocnemius muscle and the tendon of the semi-membranosus
muscle, besides the large supra-patellar bursa already described. Lastly, there
may be intercommunication between this articular cavity and that of the proximal
tibio-fibular articulation.
Movements at the Knee-Joint. In studying the movements which may occur at the
human knee-joint, it is necessary to bear in mind that the lower limb of man is primarily required
for purposes of support and locomotion. The principal requirement of the former function is
stability accompanied by rigidity, whereas in the latter function the special desideratum is regu-
lated and controlled mobility. Thus, in the same joint, two entirely opposite conditions have
to be provided. The stable conditions of support are chiefly concerned in the maintenance
of the erect attitude, and the mechanism associated therewith does not call for the exertion of a
large degree of sustained muscular effort.
In standing erect the attitude of the limb is that of extension, which mainly concerns the
femoro-tibial parts of the joint. In this position the force of gravity acts along a vertical line
which falls in front of the transverse axis of the joint, and therefore any tendency to flexion, i.e.
bending backwards, is mechanically counteracted by the application of a force which tends t<
produce bending forwards (so-called over-extension). This, however, is absolutely prohibited ii
normal states of the joint, by the tension of the posterior and collateral ligaments aided by the
anterior cruciate ligament. The value of this fact may be seen by observing the effect proaucec
by giving the joint a sudden push from behind, which causes an immediate reversal of the
positions of the transverse and vertical axes, whereby the body weight at once produces flexior
of the joint.
The menisci and the infra-patellar pad of fat also assist in maintaining extensioi
by reason of their close adaptation to, and packing round the condyles as these rest upon the tibij
THE TIBIO-FIBULAK JOINTS. 349
The anterior margin of the intercondyloid fossa is also brought into contact with the front of
the anterior cruciate ligament.
In the position of extension the patella is retained at such a proximal level in relation to the
trochlear surface of the femur, that the distal articular facets of the patella are in contact with
the trochlea.
During locomotion the movements of the knee-joint are somewhat intricate, for both the
femoro-tibial and the femoro-patellar sections of the joint are brought into action. The principal
movement which results is flexion, with which there is associated, both at its beginning and
ending, a certain amount of screw movement or rotation. Flexion and rotation occur at the
femoro-tibial sections of the joint, whereas the movement at the femoro-patellar portion produces
a regulating and controlling influence upon flexion.
Taking these factors separately, we observe that each femoral condyle adapts itself to a
shallow cup formed by the corresponding tibial condyle and meniscus, and as the two femoral
condyles move simultaneously and parallel to each other, there is more than the characteristic
hinge-joint action, for each femoral condyle glides and rolls in its cup " like a wheel restrained
by a drag" (Goodsir) when the movement of bending occurs. Thus the different parts of
the condyles are successively brought into relation with the transverse axis of the joint while it
passes from extension to flexion and vice versa. From the fact that the medial femoral condyle
is longer than the lateral, it is believed that extension is completed by a movement of rotation
whereby the joint becomes locked, and the anterior cruciate, the posterior and the collateral
ligaments, become tense. A similar rotation initiates the movement of flexion, and unlocks the
joint by relaxing the ligaments just mentioned.
Since the tibia and foot are fixed in the act of walking, it is the femur which rotates upon
the tibia in passing from extension to flexion and vice versa ; and as relaxation of the ilio-femoral
ligament is essential for this rotation, some observers are of opinion that the body weight falls
behind the transverse axis of the knee-joint, as in the case of the hip-joint, and consequently that
extension of the knee-joint is maintained by the ilio-femoral ligament, as it is not possible to
bend the knee without first having bent the hip -joint.
During flexion and extension the menisci glide along with the condyles, so as to maintain
their close adaptation and preserve their value as packing agents. When the movement of flexion
is completed, the condyles are retained upon the tibia, and prevented from slipping off by the
tension of the posterior cruciate ligament. In this position a small degree of rotation of the
tibia, both medially and laterally, is also permissible.
The regulating and controlling influence of the femoro-patellar portion of the articulation is
brought into play during the movements of flexion and extension. In the latter position the
distal pair of patellar facets is in apposition with the proximal part of the femoral trochlea. As
flexion advances, the middle pair of facets adapt themselves to a deeper area of the trochlea, into
which the patellar keel fits. When flexion is still further advanced, the proximal pair of patellar
facets will be found fitting into that part of the trochlea adjoining the intercondyloid notch ;
and finally, when flexion is complete, the patella lies opposite the intercondyloid notch, while
the forward thrust of the longer medial femoral condyle brings its semilunar facet (Goodsir) into
apposition with the somewhat vertical facet at the medial border of the patella. The wedge-like
influence of the patella is most marked, for it is only in the position of extension that it can be
moved from side to side. The movements of the patella may be described as gliding and
co-aptation, as it slips or rocks from one pair of facets to another in its progress along the trough
of the femoral trochlea.
ARTICULATIONES TIBIOFIBULARES.
The Tibio-Fibular Joints. The proximal and distal ends of the fibula articulate
with the tibia. Primarily, the fibula is required to form a strong lateral support
for the ankle-joint, and therefore its articulations are so arranged as to provide
a certain amount of elasticity without any sacrifice of the rigidity necessary
for security. Hence the amount of movement is very small, but what there is
enables these joints to be classified as arthrodial diarthroses.
Articulatio Tibiofibularis. The proximal tibio-fibular joint is formed, on the
one hand, by a flat oval or circular facet which is situated upon the postero-lateral
aspect of the lateral condyle of the tibia, and is directed distally and posteriorly ;
on the other hand, by a similar facet on the proximal surface of the head of the
fibula in front of the apex capituli.
An articular capsule (Fig. 317) invests the joint, and it may be regarded
as holding the articular surfaces in apposition, although certain special bands
receive separate designations. Occasionally there is an opening in the stratum
fibrosum by which communication is established between the articular cavity and
the knee-joint, through the intermediation of the synovial prolongation, subjacent
to the tendon of the popliteus muscle.
The proximal epiphyseal line of the fibula is extra-capsular.
350
THE AKTICULATIONS OK JOINTS.
Lig. Capituli Fibulae Anterius. The anterior ligament of the head of the fibula
(Fig. 317) is a strong flat band whose fibres extend from the anterior aspect of
the fibular head, proximally and medially, to the adjoining part of the lateral
condyle of the tibia.
Lig. Capituli Fibulae Posterius. The posterior ligament of the head of the fibula
(Fig. 319) is a similar, but weaker band, passing, proximally and medially, from the
posterior aspect of the fibular head to the posterior aspect of the lateral condyle
of the tibia, where it is attached immediately distal to the opening in the
capsule of the knee-joint, from which the tendon of the popliteus muscle escapes.
Equally strong but much shorter bands are found on the lateral and medial
aspects of the joint. The former is intimately associated with the tendon of the
Tibio-fibular interosseous membrane
Distal end of shaft of tibia
Groove on medial malleolus
for tendon of tibialis
posterior tendon
Trochlear surface of
talus
Deltoid ligamen
Fibrous sheath for tendon of flexor
hallvcis longus
Sustentaculum tali
Flexor hallucis longus tendon (cut
Posterior calcaneo-taloid ligament
Distal end of shaft of fibula
Posterior ligament of
lateral malleolus
Distal ligament of
lateral malleolus
Facet on talus for
transverse distal tibio-
fibular ligament
Posterior talo-fibular ligament
Calcaneo-fibular ligament
Calcaneus
FIQ. 321. ANKLE-JOINT DISSECTED FROM BEHIND WITH PART OF THE ARTICULAR CAPSULE REMOVED.
biceps flexor cruris muscle which strengthens the lateral aspect of the joint, and
here also is found the occasional opening by which it communicates with the knee-
joint.
The synovial stratum is in certain cases continuous with that of the knee-
joint in the manner already described.
Membrana Interossea Cruris. The interosseous membrane (Figs. 317 and 321)
plays the part of an accessory ligament both for the proximal and the distal tibio-
fibular joints. It is attached to the interosseous borders on the shafts of the tibia
and fibula, and binds them together. The general direction of its fibres is from the
tibia distally and laterally to the fibula, but many fibres pass in the opposite
direction. The membrane may extend upwards until it comes into contact with
the ligaments of the proximal tibio-fibular joint, but there is always a vertical oval
aperture in its proximal part for the forward passage of the anterior tibial vessels.
THE ANKLE-JOINT. 351
This aperture (Fig. 317), which is about one inch long, adjoins the shaft of the
fibula at a point rather less than one inch distal to its head. Towards the distal
end of the leg the distance between the tibia and the fibula rapidly diminishes, and
consequently the width of the interosseous membrane is correspondingly reduced,
and it is tense throughout its entire length. In the distal part of the membrane
there is a small opening for the passage of the perforating peroneal vessels. There
is no sharply marked demarcation between the interosseous membrane and the
interosseous ligament which connects the distal ends of the tibia and fibula the
one, indeed, may be said to run into the other.
Syndesmosis Tibiofibularis. The distal tibio-fibular joint is not on all occasions
provided with articular cartilage, so that it may either be a separate articulation, or
it may merely present a series of ligaments which are accessory to the (ankle-joint),
because it is clear that, under any circumstances, the object aimed at in this articu-
lation is to obtain additional security for the ankle-joint. The articular surface on
the tibia, when present, constitutes a narrow articular strip on the lateral side of
the distal end of the bone, and the joint-cavity is practically an upward extension
of the ankle-joint. The corresponding fibular facet is continuous with the ex-
tensive articular area, by means of which the fibula articulates with the talus.
By far the greater part of the opposing surfaces of tibia and fibula are, however,
non-articular and rough.
The supporting ligaments are of great strength.
Lig. Malleoli Lateralis Anterius. The anterior ligament of the lateral malleolus
(O.T. anterior inferior tibio-fibular ligament) (Fig. 322) consists of strong fibres which
pass obliquely distally and laterally from the front of the distal end of the tibia to
the front of the lateral malleolus.
Lig. Malleoli Lateralis Postering. The posterior ligament of the lateral
malleolus (O.T. posterior inferior tibio-fibular ligament) (Figs. 321 and 322) is equally
strong, and passes in a similar direction between corresponding posterior surfaces.
Lig. Malleoli Lateralis Distale. The distal ligament of the lateral malleolus
(O.T. transverse inferior tibio-fibular ligament) (Figs. 321 and 322) stretches between
the posterior border of the distal end of the tibia and the proximal end of the
pit on the medial and posterior aspect of the lateral malleolus.
Ligamentum Interosseum. An interosseous ligament, powerful and some-
what extensive, connects the contiguous rough non -articular surfaces. Proximally,
as already mentioned, it is continuous with the interosseous membrane. Anteriorly
and posteriorly it comes into contact with the more superficial ligaments. Distally
it descends until it comes into intimate association with the articular cavity.
A synovial stratum is found lining the small articular cavity, but it is always
a direct prolongation from that which lines the ankle-joint.
AETICULATIONES PEDIS.
ARTICULATIO TALOCRURALIS.
The ankle-joint is a ginglymus variety of a diarthrosis. The bones which enter
into its formation are the distal ends of the tibia and fibula, with the articular
areas on the superior, lateral, and medial surfaces of the talus. The tibia and
fibula, aided by the distal ligament of the lateral malleolus, form a three-sided socket
within which the talus is accommodated. The roof or most proximal part of the
socket, which is wider in front than behind, is formed, chiefly, by the quadri-
lateral articular surface on the distal end of the tibia, but towards its postero-
lateral margin the distal ligament of the lateral malleolus assists in its formation.
There also the tibial articular surface is continuous with the narrow articular
facet already described as forming part of the tibio-fibular syndesmosis. The
medial wall of the socket is formed by the articular facet on the lateral side of the
medial malleolus, and there is no interruption of the articular cartilage between
the roof and medial wall. The lateral wall of the socket is quite separate from
the foregoing parts, and consists of a large triangular facet upon the medial side
352
THE AETICULATIONS OR JOINTS.
Anterior talo-
fibular ligament
Articular facet on N
lateral malleolus
Calcaneo-fibular
ligament
Posterior ligament
of lateral malleolus
Posterior talo-fibular
ligament
Distal ligament of
lateral malleolus
Synovial pad of fat
of the lateral malleolus. This facet is situated immediately in front of the deep
pit which characterises the posterior part of this surface of the fibula.
A small lunated facet is frequently found upon the anterior surface of the distal end of the
tibia, particularly among those races characterised by the adoption of the " squatting " posture.
When this facet exists it is continuous with the anterior margin of the roof of the socket, and it
articulates with a similar facet upon the superior surface of the neck of the talus in the
extreme flexion of the ankle-joint which "squatting" entails.
The articular surface upon the body of the talus adapts itself to the tibio-
fibular socket, and presents articular facets corresponding to the roof and sides of
the socket. Thus the superior surface of the talus possesses a quadrilateral
articular area, wider in front than behind, distinctly convex in the antero-posterior
direction, and slightly concave transversely. In addition, towards its postero-
lateral margin, there is also a narrow antero-posterior facet corresponding to the
distal ligament of the lateral malleolus. The articular cartilage of this superior
surface is continued without interruption to the tibial and fibular sides of the bone,
although the margins of the superior area are sharply denned from the facets on
the sides, the lateral of which
is triangular in outline, while
the medial is piriform, but
in eacn case the surface is
vertical.
Ligaments. The liga-
ments form a complete in-
vestment for the joint, i.e.
a fibrous stratum of an
articular capsule in which
the individual parts vary
considerably in strength,
and are described under
separate names. Their
proximal attachments are
restricted to the epiphyses of the distal ends of the tibia and fibula, and the
epiphyseal lines are therefore extra-capsular.
The anterior ligament is an extremely thin membrane, containing very few
longitudinal fibres. It extends from the distal border of the tibia to the
dorsal border of the head of the talus, passing in front of a pad of fat which
fills up the hollow above the neck of that bone.
The posterior ligament is attached to contiguous non-articular borders of the tibia
and talus. Many of its fibres radiate medially from the lateral malleolus. This
aspect of the joint is strengthened by the strong, well-defined, distal ligament of the
lateral malleolus already described in connexion with the tibio-fibular syndesmosis.
The lateral ligament (Figs. 321, 322, and 324) is very powerful, and is divisible
into three fasciculi, which are distinguished from each other by names, descriptive
of their chief points of attachment.
Lig. Talofibulare Anterius. The anterior fasciculus is the shortest. II
extends from the anterior border of the lateral malleolus to the talus immediately
in front of its lateral articular surface.
Lig. Calcaneofibulare. The middle fasciculus is a strong and rounded core
It is attached by one end to the front of the tip of the lateral malleolus, and by
the other to the lateral side of the calcaneus immediately proximal and posterior
to the groove for the peroneal tendons.
Lig. Talofibulare Posterius. The posterior fasciculus is the strongest. It
runs transversely between the distal part of the fossa on the medial aspect
of the fibular malleolus and the posterior surface of the talus, where it is attached
to the posterior process and the adjoining rough surface. Sometimes this process
is detached from the talus, and represents a separate bone the os trigonum.
Lig. Deltoideum. The deltoid ligament is the medial ligament of the ankle-joint
(Figs. 322 and 323). It has the general shape of a delta, and is even stronger
Fia. 322. ARTICULAR SURFACES OF TIBIA AND FIBULA WHICH
ARE OPPOSED TO THE TALUS.
THE ANKLE-JOINT.
353
than the lateral ligament. It is attached proximally to a marked impression on
the distal part of the medial malleolus, and below, in a continuous layer, to the
navicular, talus and cajcaneus. In it we may recognise the following special
bands (&) the lig. talotibiale anterius, which extends from the front of the medial
malleolus to the neck of the talus; (b) the lig. talotibiale posterius, stretching
between the back of the medial malleolus and the postero-medial rough surface
of the talus ; (c) the lig. tibionaviculare, which extends from the tip of the medial
malleolus to the medial side of the navicular body; (cT) the lig. calcaneotibiale,
which extends between the tip of the medial malleolus and the medial side of
the sustentaculum tali ; (0) lig. talotibiale profundum, which consists of deeper
fibres extending from the tip of the medial malleolus to the medial side of the
talus.
A synovial stratum lines the fibrous stratum of the articular capsule and, as
Medial surface of tibia
Deltoid ligament of the ankle
Trochlear surface of talus
Groove for tendon of tibialis
posterior muscle on plantar
calcaneo-navicular ligament
Groove and tunnel for the
tendon of flexor hallucis
longus muscle
Calcaneus
Long plantar ligament
Tendon of tibialis posterior muscle (cut)
Sustentaculum tali
FIG. 323. ANKLE AND TARSAL-JOINTS FROM THE TIBIAL ASPECT.
already described, the articular cavity extends into the interval between the tibia
and fibula distal to the tibio-fibular interosseous ligament. Both at the front
and back of the ankle-joint, as well as proximally in the angle formed by the
three bones, the synovial membrane covers pads of fat.
Movements at the Ankle-Joint. In the erect attitude the foot is placed at right angles to
the leg ; in other words, the normal position of the ankle-joint is flexion. Those movements
which tend to diminish the angle so formed by the dorsum of the foot and the front of the
leg are called dorsiflexion, while those which tend to increase the angle, i.e. to straighten the
foot upon the leg, are called extension. As a matter of fact neither dorsiflexion nor extension
is ever completely carried out, and the range of movement of which the foot is capable is limited
to about 90. These movements occur about an obliquely transverse axis, as is indicated by the
natural lateral pointing of the toes. The weight of the body falls slightly anterior to the ankle-
joint, so that a certain amount of muscular action is necessitated in order to maintain the foot at
right angles to the leg ; but additional stability is obtained from the obliquity above mentioned.
When the foot is raised from the ground, muscular action tends naturally to produce a certain
amount of extension. When the foot is extended, as in standing on the toes, the posterior narrow
part of the talus moves forwards into the wider part of the interval between the tibia and
fibula, whereas in dorsiflexion, as in raising the anterior part of the foot from the ground, the
widest part of the talus is forced back between the tibia and fibula ; but notwithstanding the
difference between these two movements, the fibula remains in close contact with the talus by
reason of the action of the ligamentum malleoli lateralis distale and the posterior talo-fibular
ligament, so that lateral movement is prevented.
23
354
THE AKTICULATIONS OE JOINTS.
It is doubtful whether lateral movement at the ankle-joint can be obtained by any natural
movement of the foot, although it is generally believed that in the position of partial extension
a small amount of side-to-side movement may be produced by the application of external force.
This apparent play" of the ankle-joint during extension "is really due to oscillation . of the
small bones of the foot on each other, largely of the navicular on the talus, but also of the
cuboid on the calcaneus. Excessive mobility of these latter is restrained by an important
function of the posterior tubercle of the cuboid which locks into a notch in the caleaneus "
(Blake).
ARTICULATIONES INTERTARSE.E.
The intertarsal joints are all diarthroses in which the gliding movement is
characteristic, as in the carpus. With the view of obtaining a proper conception
of the many beautiful mechanical principles involved in the construction of the foot,
it is necessary to study these articulations with considerable attention to detail.
Fibula
Posterior ligament
of lateral malleolus
Articular surface of talus
Posterior talo-fibular
ligament of ankle
Calcaneo-fibular
ligament of ankle
Posterior talo-calcaneal
ligament
Calcaneus
Tibia
Anterior ligament of lateral malleolus
Articular surface of talus
Anterior talo-fibular ligament of ankle
Dorsal talo-navicular ligament
Talo-navicular joint
Lateral calcaneo-navicular ligament
Dorsal cuneo-navicular
& naviculo-cuboid ligaments
? iv^X* 211 ' 1 cuneiform
3rd cuneiform
Cuboid
Dorsal calcaneo-cuboid ligament
Calcaneo-cuboid joint
Tendon of peronseus longus
Interosseous talo-calcaneal ligament
Talo-calcaneal joint
Lateral talo-calcaneal ligament
FIG. 324. LIGAMENTS ON THE LATERAL ASPECT OP THE ANKLE-JOINT AND ON THE DORSUM OF THE TARSUS.
Articulatio Talocalcanea. The talus and calcaneus articulate with each
other in the talo-calcaneal joint.
This joint is situated between the inferior facet on the body of the talus and
a corresponding facet on the superior aspect of the posterior part of the calcaneus.
On each bone the articulation is limited in front by a wide, deep groove which
runs obliquely across each bone from the medial to the lateral side and forwards.
The supporting and investing ligaments form the fibrous stratum of an articular
capsule, consisting for the most part of short fibres, but the joint derives additional
strength from the calcaneo-fibular ligaments of the ankle-joint. The fibrous
stratum of the capsule is subdivided into, the following talo-calcaneal bands :
The ligamentum talocalcaneum anterius consists of a band of short fibres
placed immediately in relation to the anterior end of the deep groove which
bounds the articular facets. They are attached to the an tero- lateral aspect of
the neck of the talus, from which they extend downwards to the adjacent superior
surface of the calcaneus.
The ligamentum talocalcaneum laterale (Fig. 324) is in continuity with the
posterior border of the preceding ligament, and it is placed parallel to, but on
INTEKTAKSAL JOINTS.
355
Plantar cal- (
caneo-navicular-J
ligament V.
Tendon of tibialis
posterior muscle
(cut)
a deeper plane than, the calcaneo-fibular ligament of the ankle-joint. It con-
sists of short fibres passing between the adjacent rough lateral margins of the two
bones.
The ligamentum talocalcaneum posterius (Fig. 324) closes the joint-cavity on
its posterior aspect. It consists of fibres which radiate from the posterior aspect
of the posterior process of the talus to the superior surface of the calcaneus,
immediately behind the articular facet.
The ligamentum talocalcaneum mediale lies obliquely on the medial side of the
joint, and consists of fibres which extend from the medial posterior tubercle of the
talus to the posterior roughened border of the sustentaculum tali. Some of its
fibres become continuous with the plantar calcaneo-navicular ligament.
The ligamentum talocalcaneum interosseum (Fig. 325) closes the antero-medial
aspect of the joint. It is the strongest of the series of ligaments entering into the
capsule. Compared with it the other bands are, comparatively speaking, insigni-
ficant. Its attachments
are to the bottom of each
groove, so that it occupies
the tarsal canal formed by Navicular bone
these opposing grooves.
A synovial stratum lines
the fibrous stratum, and it
is distinct from other tarsal
synovial membranes.
Articulatio Talocal-
caneonavicularis. This
is one of the most import-
ant of the joints of the
foot, not only because the Sustentaculun ^ce for talus
talus is here situated in
relation to the summit of
the an tero- posterior arch
of the foot, but because the
head of the talus is received
into a composite socket
made up of the susten-
taculum tali, the navicular,
and the plantar calcaneo-
navicular ligament.
The articular surface
on the head of the talus presents anteriorly a convex rounded facet for articulation
with the navicular, inferiorly a convex facet which rests upon the sustentaculum
tali, and intermediate between these two there is a triangular facet which
articulates with the plantar calcaneo-navicular ligament. All these facets are
in continuity with each other, and are in front of the tarsal groove on the inferior
surface of the talus. Occasionally a fourth narrow facet is found along the lateral
and posterior part of the articular surface of the head of the talus, whereby it
articulates with the calcaneo-navicular part of the bifurcate ligament.
The navicular bone presents a shallow, cup-shaped, articular cavity towards the
head of the talus.
The articular surface of the sustentaculum tali is concave, and is usually marked
off into two facets.
Two ligaments play an important part in binding together the calcaneus and
the navicular, although these bones do not directly articulate ; and further, these
ligaments provide additional articular surfaces for the head of the talus. These
are the two following :
(a) The ligamentum calcaneonaviculare plantare (Figs. 325 and 326) is an
extremely powerful fibro- cartilaginous band. It extends between the anterior
margin of the sustentaculum tali and the plantar surface of the navicular. Certain
of its upper fibres radiate upwards on the medial surface of the navicular, and
Articular surface on
navicular for head of
talus
\ Calcaneo-navicular part
of bifurcate ligament
Interosseous talo-
calcaneal
ligament
Articular surface
on calcaneus for
body of talus
Calcaneus
FIG. 325. THE COMPOSITE ARTICULAR SOCKET FOR THE HEAD OP
THE TALUS.
356
THE AKTICULATIONS OE JOINTS.
become continuous with the tibio-navicular portion of the deltoid ligament of
the ankle-joint. The plantar aspect of this ligament is in contact with the tendon
of the tibialis posterior muscle, through which the head of the talus receives great
support. Superiorly it contributes an articular surface which forms a triangular
portion of the floor of the composite socket in which the head of the talus is
received.
(&) The calcaneo-navicular part of the bifurcate ligament (Fig. 325) lies deeply in
the front part of the sinus tarsi, i.e. the interval between the talus and calcaneus.
Its fibres are short, and extend from the dorsal surface of the front part of the
Tendon of insertion of
peronseus longus muscle
Base of metatarsal bone of
hallux
Plantar inter-metatarsal __
ligaments
Plantar cuboid ridge
Plantar cubo-cuneiform ligament
Plantar calcaneo-cuboid ligament
Tendon of peroneus longus muscle
Long plantar ligament
Tendon of insertion of
tibialis anterior muscle
First cuneiform bone
Plantar naviculo-cuneiform
ligament
Tendon of tibialis posterior
muscle
Groove for tendon of tibialis
posterior muscle
Plantar calcaneo-navicular
ligament
Deltoid ligament of ankle
\ Medial malleolus
Groove for tendon of flexor hallucis
longus muscle
Calcaneus
FIG. 326. PLANTAR ASPECT OF TARSAL AND TARSO-METATARSAL JOINTS.
calcaneus, immediately to the lateral side of the sustentacular facet, forwards to
the lateral side of the navicular bone. Frequently the ligament presents a surface
which articulates with the head of the talus, and in these cases it forms a part of
the composite socket.
The cavity of the talo-calcaneo-navicular joint is closed posteriorly by the
interosseous talo-calcaneal ligament already described. On its medial and lateral
inferior aspects it is closed by the calcaneo-navicular ligaments.
The superior and lateral aspects are covered by the ligamentum talonaviculare
dorsale. This ligament is thin, and extends from the proximal non-articular area
on the head of the talus to the dorsal surface of the navicular bone. It may be
subdivided into dorsal, lateral, and medial talo-navicular bands (Fig. 324), which,
with the calcaneo-navicular and interosseous talo-calcaneal ligaments, complete
the capsular investment of the joint.
INTEETAESAL JOINTS. 357
A distinct synovial stratum lines all parts of the capsule of the joint.
Articulatio Calcaneocuboidea. This is situated between the anterior con-
cavo-convex surface of the calcaneus and the posterior similar surface of the
cuboid.
The ligaments which invest this joint constitute a calcaneo- cuboid capsule, whose
parts are arranged in relation to the four non-articular sides of the cuboid bone,
and are especially strong upon the plantar aspect, in relation to their great import-
ance in resisting strains.
The medial calcaneo - cuboid ligament occupies part of the interval between
the talus and calcaneus the sinus tarsi. It is the calcaneo -cuboid part of the lig.
bifurcatum, and is a V-shaped structure, of which the single end is attached to
the calcaneus, and the double ends separate to reach contiguous areas on the
navicular and cuboid respectively.
The dorsal calcaneo-cuboid ligament (Fig. 324) is a broad portion of the fibrous
stratum of the capsule extending from the dorsal and lateral surfaces of the
calcaneus to the dorsal surface of cuboid.
The lateral calcaneo-cuboid ligament is another but narrower part of the
capsule which extends from the lateral aspect of the calcaneus to the lateral side
of the cuboid, immediately behind the facet on the tuberosity.
The inferior calcaneo-cuboid ligament consists of two parts a superficial and
a deep. The superficial series of fibres, the long plantar ligament (Fig. 326), is
attached to the plantar surface of the calcaneus in front of the processes of the tuber
calcanei. It forms a long powerful structure which runs forwards to be fixed to
the plantar surface of the cuboid ridge, but many of its fibres pass superficial to the
tendon of the peronseus longus, and extend to the bases of the third, fourth, and
fifth metatarsal bones.
The deep series of fibres, the plantar calcaneo-cuboid ligament (O.T. short plantar
ligament) (Fig. 326), is distinctly separated from the long plantar ligament by a layer
of areolar tissue. It forms a broad but short band of great strength, which is
attached to the plantar surface of the distal end of the calcaneus, and extends
to the plantar surface of the cuboid just behind the ridge. Both of these ligaments
are of great importance in maintaining the longitudinal arch of the foot, and in this
respect are only second to the plantar calcaneo-navicular ligament.
A synovial stratum lines the capsule.
Articulatio Tarsi Transversa (Choparti). This is a term sometimes applied
to the talo-navicular and calcaneo-cuboid joints. These articulations do not
communicate with each other ; and although there is an occasional direct articula-
tion between the navicular and cuboid, it does not constitute an extension of
the transverse tarsal joint, but is a prolongation from the series of cuneo-navicular
and cuneo-cuboid articulations.
Nevertheless there is always a set of ligaments which bind the navicular and
cuboid bones together, and these may be regarded as accessory to the various
transverse tarsal joints.
The dorsal cuboideo - navicular ligament (Fig. 324) consists of short oblique
fibres which attach the contiguous dorsal surfaces of the cuboid and navicular
bones.
The plantar cuboideo -navicular ligament is transverse in direction, and extends
between adjacent plantar areas of the cuboid and navicular bones.
The interosseous cuboideo - navicular ligament intervenes between contiguous
surfaces of the same bones. When there is an extension of the cuneo-navicular joint
backwards between the navicular and cuboid, it is situated in front of the last-
mentioned ligament, and is called the articulatio cuboideonavicularis. Around
this joint the preceding ligaments are grouped. Since, however, the joint is
inconstant while the ligaments are always present, it is preferable to consider them
as above indicated.
Articulatio Cuneonavicularis. The cuneo - navicular articulation joint is
situated between the navicular and the three cuneiform bones. The anterior surface
of the navicular presents a facet for each of the cuneiform bones, but its articular
surface is not interrupted. These facets form a somewhat convex anterior surface
358 THE ARTICULATIONS OR JOINTS.
which fits into the shallow articular concavity presented by the proximal ends of
the three cuneiform bones. This joint may be extended by the occasional
cuboideo-navicular articulation already referred to.
The fibrous stratum of the articular capsule is composed of short strong
bands which ' are distinctly visible on all sides except towards the cuboid bone,
where the joint may communicate with the cuneo-cuboid and cuboideo-navicular
joints. Anteriorly the joint communicates with the intercuneiform articulations.
The dorsal parts of the capsule are short longitudinal bands termed dorsal
cuneo-navicular ligaments (Figs. 323 and 324). These extend without interrup-
tion to the medial aspect of the joint. Inferiorly there are similar bands,
known as plantar cuneo - navicular ligaments, also longitudinal in direction,
but intimately associated with offsets from the tendon of the tibialis posterior
muscle.
The synovial stratum which lines the fibrous stratum sends prolongations
forwards on each side of the second cuneiform bone, and in addition it often
communicates with the cuneo-cuboid joint cavity, and it always communicates
with the cuboideo-navicular cavity when that joint exists.
Articulationes Intercuneiformese. These are two in number, and exist
between adjacent contiguous surfaces of the three cuneiform bones. These surfaces
are partly articular and partly non-articular. The small size of the second
cuneiform bone allows the first cuneiform as well as the third cuneiform to project
forwards beyond it, one on each side, and therefore the articular surfaces turned
towards the second cuneiform are not entirely occupied by that bone. They form
a recess facing the metatarsus, into which the base of the second metatarsal bone
is thrust.
Ligamenta intercuneiformea dorsalia constitute fairly strong transverse bands
which extend between adjacent dorsal surfaces and invest the joint cavities in this
direction.
The ligamenta intercuneiformea plantaria are two strong bands which pass
from the rough non-articular areas on opposite sides of the second cuneiform
to the opposing surfaces of the first and third cuneiform bones. These ligaments
shut in the joint cavities inferiorly, and also anteriorly in the case of the lateral
of the two joints.
The ligamenta intercuneiformea interossea are bonds which bind together adjacent
cuneiform bones.
The synovial stratum is an extension of that which lines the cuneo-navicular
joint ; but while it is restricted to the lateral of the two joints, in the case of the
medial one it is prolonged still farther forward to the tarso-metatarsal series of
joints.
Articulatio Cuneocuboidea. This occurs between the rounded or oval facets
on the opposing surfaces of the cuboid and third cuneiform.
The ligamentum cuneocuboideum dorsale is a flat, somewhat transverse band
which closes the joint on its dorsal aspect, and extends between the dorsal
surfaces of the two bones.
The ligamentum cuneocuboideum plantare is difficult to determine. It is
situated deep to the long plantar ligament, and extends between adjacent rough
surfaces of the two bones.
The ligamentum cuneocuboideum interosseum is the strongest. It closes the
joint cavity anteriorly, and is attached to the contiguous non-articular surfaces
of the two bones.
The synovial stratum is frequently distinct, but at other times the joint
cavity communicates with those of the cuneo-navicular and cuboideo-navicular
articulations.
Synovial Strata of the Intertarsal Joints. Four and sometimes five distinct
and separate synovial strata may thus be enumerated in connexion with
the tarsal articulations, viz. : (1) talo-calcaneal ; (2) talo-calcaneo-navicular ; (3)
calcaneo-cuboid ; (4) cuneo-navicular and its extensions ; (5) occasionally cuneo-
cuboid.
TAKSO-METATAESAL JOINTS. 359
ARTICULATIONES TARSOMETATARSE.E.
The tarso-metatarsal joints are found between certain articular facets on the
cuboid and three cuneiform bones on the one hand, and others on the bases of the
five metatarsal bones. These articulations are associated with three distinct
synovial cavities namely, a medial, lateral, and intermediate.
(1) The medial tarso-metatarsal articulation occurs between the anterior
convex reniform surface of the first cuneiform bone and the concavo-reniform surface
on the posterior aspect of the base of the first metatarsal bone.
Ligaments which form the fibrous stratum of the articular capsule surround the
articulation. In the capsule the ligamenta tarsometatarsea dorsalia et plantaria
are its strongest parts, but it is not deficient either on the medial or on the lateral
aspects.
A separate synovial stratum lines the fibrous stratum.
(2) The intermediate tarso-metatarsal articulation is an elaborate joint. It
involves the three cuneiform bones and the bases of the second, third, and part of
the fourth metatarsal bones.
The articulation presents the outline of an indented parapet both on its tarsal
and its metatarsal aspects. Thus, on its tarsal side, the first and the third cunei-
form bones project in front of the second cuneiform, so that the latter only presents
a distal surface to the articulation ; while the first cuneiform presents a portion of
its lateral surface, and the third cuneiform presents both its distal and portions of
its lateral and medial surfaces, since it projects in front of the cuboid bone. On its
metatarsal side the base of the second metatarsal bone fits into the indentation
between the third and first cuneiforms, to which it presents lateral and medial
articular facets, but its posterior facet rests upon the anterior facet of the second
cuneiform. The base of the third metatarsal bone rests its posterior facet upon the
third cuneiform. The fourth metatarsal base presents part of its medial facet to the
lateral side of the third cuneiform. In this way the indentations alternate on the
two sides of the articulation, and an extremely powerful interlocking of parts is
provided, which places any marked independent movement of these metatarsal bones
entirely out of the question.
The ligamenta tarsometatarsea dorsalia are broad, flat bands which represent the
most distinct part of the fibrous stratum of an investing articular capsule. They
pass from behind forwards, and while the second metatarsal bone receives three,
i.e. one from each cuneiform, the third metatarsal only receives one from the third
cuneiform.
The ligamenta tarsometatarsea plantaria correspond with the foregoing in their
general arrangement, but they are weaker. That for the second metatarsal is the
strongest. Oblique bands extend from the first cuneiform bone to the second and
third metatarsals.
The ligamenta cuneometatarsea interossea are three in number. The medial
connects the lateral side of the first cuneiform with the medial side of the base of
the second metatarsal bone. The middle connects the medial side of the third
cuneiform with the lateral side of the base of the second metatarsal. The lateral
connects the adjacent lateral sides of the third cuneiform and third metatarsal.
The stratum synoviale, which lines this articulation, sends a prolongation back-
wards between the first and second cuneiform bones, where it opens into the cuneo-
navicular joint. It is likewise prolonged forwards upon both sides of each of the
bases of the second and third metatarsal bones.
(3) The lateral tarso-metatarsal articulation is found between the proximal
surfaces of the bases of the fourth and fifth metatarsal bones and the distal surface
of the cuboid.
The fibrous stratum of the investing articular capsule may be resolved into the
following ligaments :
The ligamenta tarsometatarsea dorsalia resemble those already described. The
base of the fourth metatarsal receives one from the third cuneiform and one from
the cuboid. The base of the fifth metatarsal receives one from the cuboid.
360 THE ARTICULATIONS OK JOINTS.
The ligamenta tarsometatarsea plantaria are the weakest bands of the series, and
consist of scattered fibres passing from the cuboid to the bases of the two metatarsals.
Some fibres, which are almost transverse, extend from the third cuneiform to the
fifth metatarsal, and additional fibres reach the fifth metatarsals from the long
plantar ligament.
Occasionally the tarsal end of the ligamentum cuneometatarseum interosseum
laterale is attached to the medial margin of the cuboid.
The synovial stratum is restricted to this articulation, and merely sends a pro-
longation forwards between the opposing articular surfaces of the fourth and fifth
metatarsal bases.
ARTICULATIONES INTERMETATARSE.E.
The intermetatarsal articulations are found between adjacent lateral aspects
of the bases of the four lateral metatarsal bones. The articular facets are small,
oval, or rounded surfaces which occupy only a limited portion of the flattened con-
tiguous surfaces of the bones. Each joint is provided with an articular capsule,
which, however, is not a complete investment, because the three joint cavities are in
free communication on their proximal aspects with the tarso-metatarsal joint cavities
one with the lateral and two with the intermediate. The definite fibres of each
fibrous stratum are situated chiefly in the transverse direction
The ligamenta basium dorsalia are short bands which extend from one base to
the other.
The ligamenta basium plantaria and the ligamenta basium interossea are similarly
arranged, but the interosseous ligaments are the strongest and most important
members of this series.
The synovial stratum of each capsule is an extension from the lateral and inter-
mediate tarso-metatarsal joints.
Frequently a bursa is found between the bases of the first and second metatarsal bones. It
produces an appearance of indistinct facetting upon these bones, and it may communicate with
the first cuneo -metatarsal joint.
The ligamentum metatarsale trans versum (transverse metatarsal ligament) lies upon,
and is attached to, the non-articular plantar aspects of the heads of all the meta-
tarsal bones. It differs from the corresponding ligament in the palm in the fact
that it binds all the metatarsal bones together, whereas in the palm the thumb is
left free. It is closely associated with the plantar fibrous plates of the metatarso-
phalangeal joints, to the plantar surfaces of which it contributes prolongations.
ARTICULATIONES METATARSOPHALANGE^.
Metatarso-phalangeal Joints. Each of these joints is a modified ball-and-
socket in which a shallow cup upon the bases of the first phalanges receives the
somewhat globular head of a metatarsal bone.
Each joint retains a modified articular capsule which invests the joint. Its
only distinct bands of the fibrous stratum are the ligamenta collateralia. These are
strong cord-like bands which are situated on the medial and lateral sides of each
joint, where they extend between adjacent rough surfaces.
On the dorsal aspect, ligaments distinct from the dorsal expansion of the ex-
tensor tendons can hardly be said to exist. The plantar aspect of the capsule
consists of a thick fibrous plate strengthened by transverse fibres to form the plantar
accessory ligament, which in the case of the great toe presents developed within it
two large sesamoid bones. In the other toes this plate remains fibrous throughout,
and is grooved on its plantar aspect for the accommodation of the long flexor
tendons. It will thus be seen that the metatarso-phalangeal joints are constructed
upon a plan very similar to that of the corresponding joints in the hand.
A synovial stratum lines the capsule of each articulation ; and the epiphyseal
lines of the metatarsals and phalanges are extra-capsular.
INTERPHALANGEAL JOINTS. 351
ARTICULATIONES DIGITORUM PEDIS.
Interphalangeal Joints. Each toe possesses two interphalangeal joints except
the great toe, which has only one. Not infrequently in the little toe the distal
joint is obliterated through ankylosis. All the joints of this series are uniaxial or
hinge joints. The nature of the articular surfaces closely resembles the correspond-
ing joints in the fingers.
Each joint possesses an articular capsule which is either very thin or limited to
the synovial stratum on the dorsal aspect. The plantar surface of the capsule is
strengthened by a fibrous plate. The ligamenta collateralia are well-defined bands
similar to those already described in connexion with the metatarso-phalangeal
joints.
A synovial stratum lines each capsule in the series. The epiphyseal lines are
extra-capsular.
Mechanism of the Foot. The bones of the foot are arranged in the form of a longitudinal
and a transverse arch. The longitudinal arch is built on a very remarkable plan. Posteriorly
the mass of the calcaneus constitutes a rigid and stable pier of support, while anteriorly, by in-
creasing the number of component parts, the anterior pier acquires great flexibility and elasticity
without sacrificing strength or stability. The summit of the arch is formed by the talus, which
receives the weight of the body from the tibia, and the resilience of the arch is assured by the
calcaneo - navicular, calcaneo-cuboid, and long plantar ligaments, together with the plantar
aponeurosis, which act as powerful braces or tie-bands, preventing undue separation of the piers
of the arch, and consequent flattening of the foot. The weight of the body is distributed over
all the five digits, owing to the arrangement of the bones of the foot in two parallel columns, a
medial and a lateral. The former, consisting of the talus, navicular, and the three cuneiforms,
with the three medial metatarsal bones, distributes weight through the talo-navicular joint,
while the latter (i.e. the lateral column), comprising the calcaneus, cuboid, and the two lateral
metatarsal bones, acts in a similar manner through the talo-calcanean joint. The main line of
immobility of this arch passes from the heel forwards through the middle toe, but its anterior
section, which is slender, is supported on either side by two metatarsal bones, with their proximal
tarsal associations, in all of which greater freedom of movement is found. The transverse arch
is most marked at the level of tarso-metatarsal articulations. The intersection of these two
arches at right angles to each other introduces an architectural feature of great importance in
connexion with the support of heavy weights. These longitudinal and transverse arches of the
foot are in effect " vaults " intersecting each other at right angles, and in relation to the area
which is common to both "vaults" the body weight is superposed exactly as the dome of a
cathedral is carried upon two intersecting vaults.
Movements at the Joints of the Tarsus, Metatarsus, and Phalanges. Considered in
detail, the amount of movement which takes place between any two of these bones is extremely
small, and, so far as the tarsus and metatarsus are concerned, it is mostly of the nature of a
gliding motion.
At the metatarso-phalangeal and interphalangeal joints movement is much more free, and
is of the nature of flexion (bending of the toes towards the sole of the foot, i.e. plantar flexion)
and extension. The latter movement when continued so as to raise the toes from the ground,
and bend or approximate them towards the front of the leg, is termed dorsiflexion. Coincident
with dorsiflexion there is always associated a certain amount of spreading of the toes, which is
called abduction, and similarly with prolonged flexion there follows a diminution or narrowing
of the transverse diameter of the anterior part of the foot by drawing the toes together a move-
ment termed adduction. In the foot the movements of abduction and adduction take place in
regard to a plane which bisects the foot antero-posteriorly through the second toe, for this toe
carries the first and second dorsal interosseous muscles.
Notwithstanding the small amount of possible movement in connexion with individual
tarsal and metatarsal joints, yet the sum total of these movements is considerable as regards the
entire foot. In this way the movements of inversion and eversion of the foot result. By
inversion we mean the raising of the medial border of the foot so that the sole looks medially,
while the toes are depressed towards the ground, and the lateral border of the foot remains down-
wards. This takes place chiefly at the talo-calcanean joint, but the transverse tarsal joints also
participate.
: Eversion is chiefly the opposite of inversion, and the return of the foot to the normal position
of the erect attitude ; but under certain conditions it may be carried further, so that the lateral
border of the foot is raised from the ground, while the medial border is depressed. In both of these
movements there is rotation between the talus and calcaneus about an oblique axis which
'passes from the medial side of the neck of the talus to the lateral and inferior part of the
calcaneus.
Of course, all the movements of the foot are subordinated to its primary functions as an organ
Df support and progression. For these purposes its longitudinal and transverse arches are of
extreme importance. The longitudinal arch resting on the calcaneus behind and the heads of
24
362 THE ABTICULATIONS OK JOINTS.
the metatarsal bones in front receives the weight of the body, as already explained, on the summit
of the talus in the line of the third toe. Hence it is that the medial malleolus appears to be
unduly prominent on the medial side of the ankle. The transverse arch buttresses the longitudinal
one, and therefore, whether the body weight fall to the lateral or the medial side of the longitudinal
arch, it is supported by a mechanism at once stable, flexible, and elastic, or resilient, and capable
of reducing to a minimum all jars that may be received by the -fore part of the foot. As the heel
is raised in the act of walking, the weight is gradually transferred from the lateral to the medial
side of the foot, until the foot finally leaves the ground with a propulsive movement, which
results from flexion of the phalanges of the great toe. In this connexion it is worthy of note
that the longitudinal line of greatest strength is on the medial side of the longitudinal arch, i.e.
in relation to the great toe.
THE MUSCULAR SYSTEM.
IVIYOLOGY.
By A. M. PATERSON.
THE movements of the various parts and organs of the body are brought about by
the agency of muscle-cells, which are characterised by a special histological structure
and by the special function of contracting in length under the influence of a proper
stimulus.
There are three classes of muscle-cells : (1) the striated, and usually voluntary
muscle-cells, out of which the skeletal muscular system is constructed ; (2) the non-
striated, involuntary muscle-cells, occurring in the walls of vessels and hollow
viscera, etc. ; and (3) the cardiac muscle-cells, striated but involuntary, of which the
substance of the heart is composed.
The following section deals solely with the skeletal muscles, the structure,
arrangement, and mechanical action of which are based, upon a common plan.
The cells of which the skeletal muscles are composed are long, narrow, and
characterised by a peculiar striation, which is different from the striation of
the muscle-cells of the heart ; they also differ both in structure and function
from the non-striated muscle-cells which occur in viscera and vessels.
A typical skeletal muscle consists of a fleshy mass enveloped in a membranous
aponeurosis or fascia, and provided at its extremities or borders with membranous
or tendinous attachments to bone, cartilage, or fascia.
Each muscle is made up of a number of fasciculi or bundles, arranged together
in different muscles in different ways, so as to give rise to the particular form of
the muscle in question. The fasciculi are clothed and connected together by a
delicate connective tissue, the perimysium externum, continuous externally with the
fascia enclosing the muscle.
Each muscular bundle or fasciculus is composed of a number of narrow, elon-
gated muscle-cells or fibres, held together by a still more delicate connective tissue,
the perimysium internum. This tissue is connected on the one hand with the sarco-
lemma or cell- wall of the muscle-cell, and on the other hand with the coarser
tissue of the perimysium externum enclosing the muscular bundles.
By -means of these connective tissue envelopes the muscle-cells, the essential
agents of motor activity, are brought into firm and intimate relation with the
osseous or other attachments of the muscle. Through the agency of sarcolemma,
perimysium internum, perimysium externum, fascia, and tendon, the muscle-
cell when it contracts can produce a precise and definite effect upon the structure
to be moved.
Each muscle is supplied by one or more nerves, which, in their course
through the muscle, separate into smaller and smaller branches, ultimately, by
their terminal filaments (axons), forming special end-organs in relation to each
muscle-cell.
While a muscle may thus be looked upon as an organ endowed with particular
properties, and executing a definite movement in response to a stimulus by the
simultaneous contraction of its constituent cells, the various muscles may further
be considered in groups, associated together by mode of development, nerve-supply,
and co-ordination of action. For example, we speak of the hamstring muscles of
363
364 THE MUSCULAE SYSTEM.
the thigh, the muscles of the back, and the prevertebral muscles, groups in whicl
separate muscles are associated together by development, nerve-supply, and action
In their development the separate muscles arise from the subdivision of a large:
stratum, as in the limbs, or from the fusion of segmental elements (myotomes), as ii
the case of the axial muscles. The peripheral nerves supplying skeletal muscles art
distributed, through the plexuses or directly, so as to associate particular musclei
morphologically and physiologically, and to secure a co-ordinated movement by th<
simultaneous contraction of several muscles.
FASCIJE.
Beneath the skin there are two (or in some regions three) layers of tissue whicl
require consideration in relation to the muscular system: the superficial fascia
(panniculus adiposus), the deep fascia, and, in animals, the panniculus carnosu!
(rudimentary in man, and represented chiefly by the platysma in the neck).
Fascia Superficialis (Superficial Fascia). The superficial fascia is a continuous
sheet of areolar tissue which underlies the skin of the whole body. It is closely
adherent to the cutis vera, and is sometimes termed panniculus adiposus, from th(
fact that, except beneath the skin of the eyelids, penis, and scrotum it is usuall]
more or less impregnated with fat. The cutaneous vessels and nerves ramify ii
this fascia ; and its deep surface, membranous in character, is in loose connexioi
with the subjacent deep fascia. It is in this layer that dropsical effusions chiefly
occur.
Fascia Profunda (Deep Fascia). Underneath the skin and superficial fascia
is a fibrous membrane, bluish white in colour, devoid of fat, and in closest relatior
to skeleton, ligaments, and muscles. This is the deep fascia. It covers, invests
and in some cases forms the means of attachment of the various muscles. It has
special tendency to become attached to all subcutaneous bony prominences, anc
to be continuous with the connecting ligaments. It forms septal laminae, whicl:
separate groups of muscles and individual muscles; enclose glands and viscera
and form sheaths for vessels and nerves. Around joints it gives rise to bands
which strengthen the capsule or limit the mobility of the joint, or, as in the region
of the wrist and ankle, bind down the tendons passing over the joint. It not onlj
ensheathes vessels and nerves, but is perforated by those which pass between super-
ficial and deeper parts.
The term aponeurosis is used in relation to muscles. It is synonymous with deep
fascia, either as an investing fascia, or as a membranous layer which (e.g. vertebra]
aponeurosis) performs at one and the same time the purpose of a deep fascia and
the expanded membranous attachment of a muscle.
The panniculus carnosus is a thin muscular layer enveloping the trunk oi
animals with a hairy or furry coat. It is strongly developed in the hedgehog. In
man it is represented mainly by the (rudimentary) platysma. It is placed between
the superficial and the deep fascia.
Bursae. Where a tendon passes over a bony surface, or where the superficial
fascia and skin cover a bony prominence, there is generally formed a mucous
(synovial) sac, or bursa, containing fluid, for the purpose of lubricating the surface
over which the tendon or fascia glides. Allied to these are the mucous or synovial
sheaths which envelop the tendons passing over the wrist and the ankle joints.
Description of Muscles. In studying the muscular system it is necessary to
note the following characters in reference to each individual muscle : (1) The shape
of the muscle flat, cylindrical, triangular, rhomboidal, etc. ; and the character oi
its extremities membranous, tendinous, or fleshy. (2) The attachments of thei
muscle. The origin is the more fixed or central attachment : the insertion is the
more movable or peripheral attachment. (3) The relations of the surfaces anc<
borders of the muscle to bones, joints, muscles, and other important structures
(4) Its vascular and nervous supply ; and (5) its action. It must be borne in mine
that hardly any single muscle acts alone. Each muscle, as a rule, forms on
FASCIA AND SUPEKFICIAL MUSCLES OF THE BACK. 365
of a group acting more or less in harmony with, and antagonised by, other and
opposite groups.
DESCRIPTION OF THE MUSCLES.
The skeletal muscles may be divided into two series : axial and appendicular.
The axial muscles comprise the muscles of the trunk, head, and face, including
the panniculus carnosus (platysma). These muscles are more or less segmental
in arrangement, and are grouped around the axial skeleton. The appendicular
muscles, the muscles of the limbs, are grouped around the appendicular skeleton.
They are not segmental in arrangement, they are morphologically separate from
the axial muscles, and they are arranged in definite strata in relation to the bones
of the limbs.
APPENDICULAR MUSCLES.
THE UPPER LIMB.
FASCIAE AND SUPERFICIAL MUSCLES OF THE BACK.
Fasciae.
The superficial fascia of the back presents no peculiarity. It is usually
of considerable thickness, and contains a quantity of fat.
The deep fascia closely invests the muscles. It is attached in the median
plane of the back to the ligamentum nuchae, supraspinous ligaments, and vertebral
spines ; laterally it is attached to the spine of the scapula and to the clavicle, and
is continued over the deltoid region to the arm. In the neck it is attached,
above, to the superior nuchal line of the occipital bone, and is continuous, laterally,
with the deep cervical fascia. Below the level of the shoulder it is continuous,
round the border of the latissimus dorsi muscle, with the fascia of the axilla and
of the abdominal wall. In the back and loin it constitutes the fascia lumbodorsalis
or aponeurosis of the latissimus dorsi. This layer conceals the sacrospinalis
muscle, and is attached medially to the vertebral spines, and laterally to the angles
of the ribs, and to the iliac crest.
The Superficial Muscles of the Back.
The muscles of the back are arranged in four series according to their attach-
ments: (1) vertebro-scapular and vertebro-humeral; (2) vertebro-costal; (3) vertebro-
cranial ; and (4) vertebral. The first of this series consists of the posterior muscles
connecting the superior extremity to the trunk, and comprises the first two layers
of the muscles of the back (1) trapezius and latissimus dorsi, and (2) levator
scapulae and rhomboidei (major and minor). The deeper (axial) muscles of the
back are dealt with later (p. 437).
M. Trapezius. The trapezius is a large triangular muscle which lies in the
upper part of the back. It arises from the superior nuchal line of the occipital
bone in its medial third, from the external occipital protuberance (Fig. 396,
p. 444), from the ligamentum nuchse, from the spines of the seventh cervical and
all the thoracic vertebras, and the intervening supraspinous ligaments. The origin
is by direct fleshy attachment, except in relation to the occipital bone, the lower
part of the neck, and the lower thoracic vertebrae, in which places the origins are
tendinous.
From their origins the muscular fibres converge towards the bones of the
shoulder, to be inserted continuously from before backwards as follows : (1) The
I occipital and upper cervical fibres into the posterior aspect of the clavicle in its
lateral third (Figs. 327, p. 366, and 329, p. 368); (2) the lower cervical and
Kper thoracic fibres into the medial border of the acromion, and the upper
rder of the spine of the scapula; and (3) the lower thoracic fibres, by a
366 THE MUSCULAE SYSTEM.
triangular flat tendon, beneath which a bursa is placed into a rough tuberosity
at the base of the spine of the scapula (Fig. 328, p. 367). The fibres inserted
into the clavicle, acromion, and the upper border of the spine of the scapula spread
over the adjacent subcutaneous surfaces of those bones for a variable distance.
The occipital portion of the muscle may be in the form of a separate slip, or may
be entirely absent.
The trapezius is superficial in its whole extent. Its upper lateral border forms
the posterior limit of the posterior triangle of the neck. The inferior lateral border,
passes over the upper edge of the latissimus dorsi and the vertebral margin of the
scapula, and forms a boundary of the so-called triangle of auscultation, which is
completed, below, by the latissimus dorsi, and, laterally, by the vertebral margin of the
scapula. This space is partly filled up by the rhomboideus major. The muscle
overlaps the latissimus dorsi, and covers the levator scapulae, rhomboidei, and the
deeper axial muscles of the back, along with the ascending and the descending
branch of the transverse artery of the neck, the accessory nerve, and muscular
branches from the cervical plexus.
Nerve-Supply. The trapezius has a double nerve-supply : (1) from the terminal fibres of
the accessory nerve, and (2) from the cervical plexus (C. 3. and 4.). The cervical nerves communi-
cate with the accessory nerve in the posterior triangle of the neck and beneath the trapezius.
Action. The main action of the trapezius is to draw the scapula backwards and upwards.
The upper fibres of the muscle elevate the shoulder-girdle, while the lower fibres, pulling on the
base of the spine of the scapula, depress the vertebral margin ; the two movements result in a
rotation of the scapula, by which the glenoid cavity is tilted upwards, as in the movement of
raising the arm above the head in a forward direction.
M, Latissimus Dorsi. The latissimus dorsi is a large triangular muscle
occupying the lower part of the back. It has a triple origin. The greater part
Pectoralis major (origin)
Sterno-cleido-mastoid
(clavicular origin)
Sterno-hyoid (origin)
Trapexius (insertiou)-
FIQ. 327. MUSCLE- ATTACHMENTS TO THE RIGHT CLAVICLE (Upper Surface).
of the muscle arises (1) from the posterior layer of the lumbo-dorsal fascia. This
is a thick membrane which conceals the sacrospinalis muscle in the lower part oi
the back. Through it the latissimus dorsi gains attachment to the spines of thf
lower six thoracic vertebrse, the spines of the lumbar vertebrae, and the tendon
the sacrospinalis, with which the fascia blends below. It also arises laterally
from the posterior part of the lateral lip of the iliac crest.
From its origin the muscle is directed upwards and laterally, its fibi
converging to the inferior angle of the scapula. In relation to its lateral am
upper borders additional fibres arise. (2) Along the lateral border muscular sli]
arise from the lower three or four ribs, interdigitating with the slips of
of the obliquus abdominis externus. (3) As the superior "border of tKe musck
passes, horizontally, over the inferior angle of the scapula, an additional flesh]
slip usually takes origin from that part of the bone and joins the muscle on its dee]
surface (Fig. 329, p. 368).
Beyond the inferior angle of the scapula the latissimus dorsi, greatly narrowed
curves spirally round the teres major muscle, and forms the prominence of th(
posterior axillary fold. It ends in a ribbon-like tendon, which is closely adherent
at first, to the teres major, and is inserted into the floor of the intertubercular sulci
of the humerus, extending for about three inches distal to the distal and later*
part of the lesser tubercle (Fig. 336, p. 376). It is placed behind the axilla]
vessels and nerves, and in front of the insertion of the teres major, from whk
it is separated by a bursa.
THE SUPEKFICIAL MUSCLES OF THE BACK.
367
In the back the latissimus dorsi is superficial, except in its upper part,
which is concealed by the trapezius. It covers the lumbo-dorsal fascia, serratus
POSTERIOR TRIANGLE
SEMISPINALIS CAPITIS
STERNO-CLEIDO-MASTOID
Wwti **&*J**A
jEVATOR SCAPULA \ /
RHOMBOIDEUS MINOR . -u'
V \jovi.
RHOMBOIDEUS MAJOR
SUPRASPINATUS
ON
SERRATUS ANTERIOR /- j -i
gap for circumflex scapular part 01 the flOOr OI the
posterior triangle. In
its lower third it is
again hidden from view
by the trapezius. It
conceals the splenius
cervicis and iliocostalis
Deltoid (origin)
Triceps brachii
(origin of long head)
cervicis.
Teres major (origin)
Latissimus dorsi (origin)
FIG. 329. MUSCLE- ATTACHMENTS TO THE RIGHT SCAPULA
(Dorsal Surface).
Nerve - Supply. - The
levator scapulae has a double
nerve-supply : (1) from the
dorsal scapular nerve from
the brachial plexus (C. 5.),
which either pierces or goes
beneath the muscle, and (2)
from the cervical plexus.
Small branches from the
anterior rami of the third
and fourth cervical nerves enter the muscle on its superficial surface near its origin.
Action. The levator scapulae raises the superior angle and vertebral margin of the scapula,
as in shrugging the shoulders.
M. Rhomboideus Minor. The rhomboideus minor may be regarded as a
separated slip of the rhomboideus major, with which it is often continuous. It
arises from the ligamentum nuchce and the spines of the seventh cervical and first
thoracic vertebrae.
Passing obliquely downwards and laterally it is inserted into the vertebral
margin of the scapula below the levator scapulae muscle, and opposite to the
base of the spine (Fig. 329).
M. Rhomboideus Major. The rhomboideus major arises from the spinous
processes of the thoracic vertebrae from the second to the fifth inclusive, and
from the corresponding supraspinous ligaments.
It also passes downwards and laterally and is inserted, below the rhomboideus
minor, into the vertebral margin of the scapula, between the spine and the inferior
angle (Fig. 329). The muscle is only inserted directly into the scapula by means
of its inferior fibres. Its superior part is attached to a membranous band, which,
FASCIAE AND MUSCLES OF THE PECTOEAL REGION. 369
connected to the vertebral margin of the scapula, for the most part, by loose
areolar tissue, and is fixed to the bone at its extremities, above near the base of
the spine, and below at the inferior angle.
The rhomboid muscles are concealed to a large extent by the trapezius. The
lower part of the rhomboideus major is superficial in the triangle of auscultation.
The muscles cover the serratus posterior superior and vertebral aponeurosis.
Nerve-Supply. The rhomboid muscles are supplied- by the dorsal scapular nerve from the
brachial plexus (C. 5.), which supplies branches in the deep surface of the muscles.
Action. The rhomboid muscles elevate and draw backwards the vertebral margin of the
scapula.
THE FASCI/E AND MUSCLES OF THE
PECTORAL REGION.
FASCLE.
The superficial fascia of the chest usually contains a quantity of fat, in which
the mamma is embedded. The origin of the platysma muscle lies beneath its
superior part.
The deep fascia is attached above to the clavicle, and in the median plane to
the sternum. Below it is continuous with the fascia of the abdominal wall. It
gives origin to the platysma and invests the pectoralis major. At the lateral
border of the great pectoral muscle it is thickened, and forms the floor of the
axillary space (axillary fascia), continued posteriorly on to the posterior fold of
the axilla and laterally into connexion with the deep fascia of the arm.
Costo-Coracoid Membrane. Beneath the pectoralis major a deeper stratum of
fascia invests the pectoralis minor muscle. At the superior border of this muscle
it forms the costo-coracoid membrane, which passes upwards to the inferior border
of the subclavius muscle, where it splits into two layers, attached in front of and
behind that muscle to the borders of the inferior surface of the clavicle. The
membrane traced medially along the subclavius muscle is attached to the first
costal cartilage ; passing laterally along the upper border of the pectoralis
minor it reaches the coracoid process. The part of the membrane extending
directly between the first costal cartilage and the coracoid process is thickened
and forms the costo-coracoid ligament. The costo-coracoid membrane is otherwise
thin and of comparatively small importance. It is pierced by the cephalic vein,
thoraco-acromial artery and vein, and branches of the lateral anterior thoracic
nerve. By its deep surface it is connected to the sheath of the axillary vessels.
At the inferior border of the pectoralis minor there is a further extension of the
deep fascia beneath the pectoralis major. It passes downwards to join the fascia
forming the floor of the axilla, and is continued laterally into the fascia covering
the biceps and coracobrachialis muscles.
MUSCLES OF THE PECTORAL REGION.
The anterior muscles connecting the upper limb to the axial skeleton comprise
the pectoralis major, pectoralis minor, subclavius, serratus anterior, and sterno-
cleido-mastoid. The last is described in a later section (p. 458).
M. Pectoralis Major. The pectoralis major is a large fan-shaped muscle
arising in three parts : (1) a pars clavicularis arising from the anterior aspect
of the clavicle in its medial half or two-thirds (Figs. 327, p. 366, and 331, p. 371) ;
(2) a pars sternocostalis, the largest part of the muscle, arising from the anterior
surface of the manubrium and body of the sternum by tendinous fibres decussat-
ing with those of the opposite muscle (Fig. 330, p. 370), and, more deeply, from
: the cartilages of the first six ribs; (3) a pars abdominalis, a small and separate
slip, arising from the aponeurosis of the obliquus abdominis externus muscle. The
; abdominal slip, at first separate, soon merges with the sterno-costal portion, but a
distinct interval usually remains between the two first-named parts of the muscle.
25
370
THE MUSCULAB SYSTEM.
Sterno-cleido-mastoid (origin)
The fibres converge towards the proximal part of the arm, and are inseparably
blended at a point half an inch from their insertion into the humerus. The
muscle is inserted into (1) the lateral border of the sulcus intertubercularis of
the humerus, extending proximally to the greater tubercle and blending, laterally,
with the insertion of the deltoid, and medially, with the insertion of the latissimus
dorsi (Fig. 336, p. 376); (2) from the proximal border of the insertion a
membranous band extends proximally to the capsule of the shoulder- joint, en-
veloping at the same time the tendon of the biceps ; and (3) from the distal border
a band of fascia passes distally to join the fascia of the arm.
The arrangement of the fibres of the muscle at its insertion is peculiar. The
muscle is twisted on itself, so that the lower (sterno-costal) fibres are directed
upwards and laterally behind the upper (clavicular)
part of the muscle ; in consequence the clavicular part
is attached to the humerus more distally than the
sterno-costal portion, and is inserted also into the
fascia of the arm. The twisting of the fibres is specially
found in the inferior sterno-costal fibres of the muscle
and the abdominal fibres. These curve upwards
behind the superior sterno-costal fibres, and have the
highest attachment to the shaft of the humerus,
helping to form the fascial expansion which extends
upwards over the biceps tendon to the capsule of
the shoulder-joint. In this way a bilaminar tendon
is produced united along its inferior border; consisting
of a superficial lamina formed by the superior sterno-
costal fibres, blending for the most part with the-
tendon of the clavicular portion ; and a deep lamina,
composed of the twisted lower sterno-costal and
abdominal fibres. The disposition of the muscular
fibres at their insertions is the reason for the applica-
tion of the terms " portio attollens " to the clavicular
portion, and "portio deprimens" to the sterno-costa
and abdominal portions of the muscle.
Placed superficially, the pectoralis major forms
the anterior wall and anterior fold of the axilla. Its
superior border is separated from the edge of the
deltoid muscle by an interval in which lie the cephalic
vein and deltoid branches of the a. thoracoacromialis
Its deep surface is in relation with the ribs and inter
costal muscles, the costo-coracoid membrane and the
structures piercing it, the pectoralis minor, the
axillary vessels, and the nerves of the brachial plexus
Nerve-Supply. The pectoralis major has a double nerve
supply, from both anterior thoracic nerves. The lateral anterioi
thoracic nerve, derived from the lateral cord of the brachia
plexus (C. 5. 6. 7.), divides into two trunks. One pierces the costo-coracoid membrane, and supplie.
the clavicular part, and superior portion of the sterno-costal part of the muscle. The other branch
communicates over the axillary artery with the medial anterior thoracic nerve, a derivative o
the medial cord of the brachial plexus (C. 8. T. 1.). They then supply the pectoralis minor and
piercing that muscle, terminate in the lower part of the pectoralis major.
Action. The pectoralis major draws the arm to the side. The clavicular fibres flex th<
shoulder-joint and raise the arm besides drawing it forwards. The sterno-costal and abdomina
portions, on the other hand, depress the arm, while drawing it forwards.
Sternalis Muscle. The sternalis is an occasional muscle placed, when present, parallel t(
the sternum upon the sterno-costal origin of the pectoralis major. It has attachments whicl:
are very variable both above and below, to the costal cartilages, sternum, rectus sheath, sterno
mastoid, and pectoralis major. Its nerve-supply is from one or both of the anterior thoraci<
nerves. In certain rare cases it has been said to be innervated by intercostal nerves. It ii
present in 4 -4 cases out of 100, and it is slightly more frequent in the male than in the female
It has been regarded by different observers as (1) a vestige of the panniculus carnosus, (2)
homologue of the sterno-mastoid, or (3) a displaced slip of the pectoralis major.
Chondroepitrochlearis, Dorsoepitrochlearis, Axillary Arches, Costocoracoideus. On
Rectus
abdominis
(insertion)
FIG. 330. MUSCLE- ATTACHMENTS TO
THE FRONT OF THE STERNUM.
MUSCLES OF THE PECTOKAL EEGION.
371
or other of the above-named slips is occasionally present, crossing the floor of the axilla in the
interval between the latissimus dorsi and the pectoralis major. They take origin from the costal
cartilages, ribs, or borders of the" pectoralis major (chondroepitrochlearis, axillary arches, costo-
coracoideus), or from the border of the latissimus dorsi (dorsoepitrochlearis, axillary arches, costo-
coracoideus). Their insertion is variable. The chondroepitrochlearis and dorsoepitrochlearis are
inserted into the fascia of the arm, the medial intermuscular septum, or the medial epicondyle
of the humerus. The axillary arches are inserted into the border of the pectoralis major, the
fascia of the arm, or the coracobrachialis or biceps muscle. The costocoracoideus, arising
from the ribs or the aponeurosis of the obliquus externus, or detaching itself from the border
of the pectoralis major or latissimus dorsi, is attached to the coracoid process, alone or along
with one of the muscles attached to that bone. These variable slips of muscle are supplied
by the medial anterior thoracic nerve, the medial cutaneous nerve of the arm, or the intercosto-
brachial.
M. Pectoralis Minor. The pectoralis minor is a narrow, flat, triangular
muscle. It arises, under cover of the pectoralis major, from (1) the surfaces
and superior borders of the third, fourth, and fifth ribs near their anterior ends,
and (2) from the fascia covering the third and fourth intercostal spaces between
those ribs. It may have an additional origin from the second rib (Fig. 414, p. 468) ;
and that from the fifth rib is often absent.
Directed obliquely upwards and laterally, it is inserted by a short, flat tendon
into the lateral half of the anterior border and upper surface of the coracoid
process (Fig. 333, p. 372), and usually also into the conjoint origin of the biceps
brachii and coracobrachialis.
It enters into the formation of the anterior wall of the axilla, and gives attach-
ment along its superior border to the costo-coracoid membrane. It crosses the
axillary vessels and the cords of the brachial plexus, and is pierced by the medial
anterior thoracic nerve.
Either in part or wholly the pectoralis minor may pass over the coracoid process of the
scapula, separated from it by a bursa, to be inserted into the coraco-acromial ligament, or the
acromion process ; or piercing the coraco-acromial ligament, it may be attached to the capsule of
the shoulder-joint (coraco-humeral ligament).
Pectoralis Minimus. This is a slender slip, rarely present, which extends between the first
costal cartilage and the coracoid process.
I Nerve-Supply. The pectoralis minor is innervated like the pectoralis major by both anterior
thoracic nerves. The lower division of the lateral nerve (0. 5. 6. 7.) communicates with the
medial anterior thoracic nerve (C. 8. T. 1.) over the axillary artery. Both nerves pierce and
supply the pectoralis minor, and end in the pectoralis major.
Action. The main use of the pectoralis minor is to draw the shoulder forwards. It is thus
a chief assistant of the serratus anterior muscle.
M. Subclavius. The subclavius muscle arises from the superior surface of the
Coraco-clavic-
ular ligament
(trapezoid
part)
Pectoralis major (origin)
isertion) __
Subclavius (insertion)
Conoid ligament
FIG. 331. MUSCLE-ATTACHMENTS TO THE RIGHT CLAVICLE (Inferior Surface).
costal cartilage in front of the costo-clavicular ligament, and from the upper
surface of the sternal end of the first rib (Fig. 414, p. 468).
It is inserted into a groove in the middle third of the inferior surface of the
clavicle (Fig. 331).
The muscle is invested by the fascia which forms the costo-coracoid membrane,
and is concealed by the clavicle and the clavicular origin of the pectoralis major.
Nerve-Supply. The nerve to the subclavius is a fine branch of the brachial plexus
(C. 5. 6.), which arises above the clavicle, and passes anterior to the subclavian artery to reach
the muscle.
Action. It acts as a depressor of the clavicle; or, the shoulder girdle being fixed, it is
i I capable of raising and fixing the first rib, in inspiration.
372
THE MUSCULAE SYSTEM.
FIG. 332. THE LEFT SERRATUS ANTERIOR
MUSCLE.
The sternoclavicularis is a small separate
slip, rarely present, extending beneath the pector-
alis major from the upper part of the sternum to
the clavicle.
M. Serratus Anterior. The serratus
anterior (O.T. serratus magnus) is a large
curved quadrilateral muscle occupying the
side of the chest and medial wall of the
axilla. It arises by fleshy slips from the
lateral aspect of the upper eight and occa-
sionally (as in the figure) from nine ribs.
The first slip is a double one, arising from
the first two ribs and the fascia covering
the intervening space (Fig. 332).
The insertion of the muscle is threefold.
(1) The first portion of the muscle (from
the first and second ribs) is directed pos-
teriorly to be inserted into the costal aspect
of the medial angle of the scapula. (2) The
next three slips of the muscle (from the
second, third, and fourth ribs) are inserted
into the vertebral margin of the scapula.
(3) The last four slips (from the fifth, sixth,
seventh, and eighth ribs) are directed ob-
liquely upwards and posteriorly, to be in-
serted on the costal aspect of the inferior
angle of the scapula (Fig. 333).
Triceps brachii
(origin of long
head)
The lateral surface of the
muscle is partly superficial below
the axillary space, on the side wall
of the chest, where its slips of
origin are seen inter-digitating
with those of the obliquus externus
abdominis. Higher up it forms
the medial wall of the axilla, and
is in contact with the pectoral
muscles anteriorly and the sub-
scapularis posteriorly. Its superior
border appears in the floor of the
posterior 'triangle, and over it the
axillary artery and the cords of
the brachial plexus pass in their
course through the axilla. The
inferior border is oblique, and is
in contact with the latissimus dorsi muscle.
The muscle may extend higher than usual, so
as to be continuous in the neck with the
levator scapulae.
Nerve - Supply. The serratus anterior muscle
receives its nerve from the long thoracic nerve, a branch
from the anterior trunks of the fifth, sixth, and seventh
cervical nerves. After piercing the scalenus medius,
the nerve enters the axilla, and supplies branches to the
several digitations of the muscle on their superficial
surface. The highest fibres of the muscle are supplied
by the fifth, the lowest fibres by the seventh, and the
intermediate part of the muscle by the sixth cervical
nerve.
Action. The primary action of the muscle is to
draw the base of the scapula forwards. This causes
Deltoid (origin)
Biceps and coracobrachialis (origin)
I Pectoralis minor (insertion)
Omo-liyoid (origin)
FIG. 333. MUSCLE-ATTACHMENTS TO THE
EIGHT SCAPULA (Anterior Aspect).
FASCIAE AND MUSCLES OF THE SHOULDER 373
the whole shoulder to be brought forward by a movement at the steriio-clavicular joint. The
movement of stretching forward the arm as in fencing is due to this action of the muscle.
Further, by its relation to the inferior angle of the scapula, the serratus anterior causes (along
with the trapezius) a rotation of the scapula, resulting in a tilting upwards of the glenoid
cavity, and so facilitating the upward movement of the arm above the head. Acting from the
shoulder on the ribs the serratus becomes a powerful muscle of inspiration.
Action of Muscles on the Sterno -Clavicular and Acromio -Clavicular Joints. The
muscles just considered (along with the sterno-cleido-mastoid and omo-hyoid muscles) act for
the most part in the sterno-clavicular and acromio-clavicular joints.
A. Sterno- Clavicular Joint. The movements at this articulation are vertical, horizontal,
and rotatory, and the muscles concerned may be tabulated as follows :
Sterno-Clavicular Joint.
a. Movement in a Vertical Plane.
b. Movement in a Horizontal Plane.
Elevation.
Depression.
Forwards.
Backwards.
Trapezius (superior
fibres)
Levator scapulae
Rhomboidei
Sterno-mastoid
Omo-hyoid
Trapezius (inferior
fibres)
Subclavius
Pectoralis minor
Latissimus dorsi
Pectoralis major
(lower fibres)
Serratus anterior
Pectoralis major
Pectoralis minor
Trapezius
Rhomboidei
Latissimus dorsi
c. Rotation a combination of these
muscles.
B. Acromio- Clavicular Joint. Movements at this joint are associated with rotation of the
scapula. By the combined action of such muscles or the trapezius and serratus anterior (inferior
fibres), the inferior angle of the scapula is drawn or thrust forwards, the body of the scapula
is rotated, and the glenoid cavity is tilted upwards, so facilitating the upward movement of
the arm above the horizontal level.
In forced inspiration, the sterno-mastoid, trapezius, levator scapulae, rhomboidei, sub-
clavius, omo-hyoid, serratus anterior, pectoral muscles, and latissimus dorsi, acting together, raise
and fix the shoulder girdle ; while those of them which have costal attachments subclavius,
pectoral muscles, serratus anterior, and latissimus dorsi simultaneously elevate the ribs and
expand the thorax.
Lateral flexion and rotation of the vertebral column in the neck is effected partly by
the action of the trapezius, levator scapulae, and rhomboid muscles (with the shoulder fixed).
The latissimus dorsi and pectoralis major act in climbing in a similar way, raising up the
trunk towards the shoulder.
Action on the Upper Limb. By reason of their insertion into the humerus the pectoralis
major and latissimus dorsi muscles assist the movements of the upper limb. Acting together, the
two muscles depress the shoulder, and draw the arm to the side of the body, at the same time
rotating the humerus medially. The two parts of the pectoralis major have slightly different
actions on the humerus. The clavicular part of the muscle (portio attollens) draws the arm
medially and upwards ; the sterno-costal part of the muscle (portio deprimens) draws it medially
and downwards. The latissimus dorsi acting alone, besides rotating the limb, draws it medially
and backwards, as in the act of swimming.
FASCIAE AND MUSCLES OF THE SHOULDER.
The deep fascia covering the scapular muscles presents no feature of special
importance. Attached to the clavicle, acrornion, and scapular spine, it is thin over
the deltoid muscle. Below the deltoid it is thicker ; it encases and gives origin to
the infraspinatus muscle, and is continuous with the fasciae of the axilla and the
back.
Muscles.
The muscles proper to the shoulder comprise the deltoid, supraspinatus, infra-
spinatus, teres minor, teres major, and subscapularis.
M. Deltoideus. The deltoid, a coarsely fasciculated multipennate muscle, has
an extensive origin from (1) the front of the clavicle in its lateral third (Figs. 327,
p. 366, and 331, p. 371) ; (2) the lateral border of the acromion ; (3) the inferior edge
the free border of the spine of the scapula (Figs. 329, p. 368, and 333, p. 372) ;
and (4) from the deep fascia covering the infraspinatus muscle. Its origin
embraces the insertion of the trapezius.
The fibres of the muscle converge to the lateral aspect of the body of the
374
THE MUSCULAK SYSTEM.
humerus, to be inserted into a well-marked V-shaped impression above the radis
groove (Fig. 336, p. 376). The insertion is partly united with the tendon of th
pectoralis major.
The most anterior part of the deltoid muscle is formed of parallel fibres, nc
LEVATOR BCAPU^ uncommonly sepai
ate from the rest c
the muscle at thei
origin from the cla
vicle. These fibre
may be continuou
with the trapeziu
over the clavicle
Spine of scapula -^P|
RHOMBOIDEUS MINOR
SUPRASPINATUS
INFRA-
SPINATUS
The most posterio
part arises by
fascial origin fror
the spine of th
scapula and th
fascia over the in
fraspinatus muscle
These portions ar
attached respect
ively to the fron
and back of th
main tendon of in
sertion. The inter
mediate fibres ar
multi-pennate, attached above am
below to three or four septal tendon*
which extend for a variable distanc
downwards and upwards from th
origin and insertion of the muscle
The deltoid is superficial in it
whole extent, and forms the pro
minence of the shoulder. Its an
terior border is separated from th
pectoralis major by a narrow in
terval, in which the cephalic vei]
and deltoid branch of the thoraco
acromial artery are placed. The dee;
surface of the muscle, separated frorj
the capsule of the shoulder-join
by a large bursa, is related to - (l
the cor acoid process, associated wit!
which are the coraco-acromial liga
(tendon of insertion) men t, and the attachments of th
pectoralis minor, the coracobrachi
alis, and the short head of th'
biceps brachii ; (2) the capsule o
the shoulder -joint covering th'
head of the humerus, associated wit]
which are the long head of th<
biceps, and the attachments of th'
subscapularis, supraspinatus, infra
spinatus, and teres minor ; and (3
the proximal part of the lateral surface of the body of the humerus, associated wit!
which are the posterior circumflex vessels of the humerus and the axillary nerve.
Nerve-Supply, The deltoid muscle is supplied by the terminal branches of the axillar
(O.T. circumflex) nerve from the fifth and sixth cervical nerves.
Action. The main action of the deltoid is to abduct the arm, and bring the humerus int
TRICEPS BRACHII
EXTENSOR CARPI
ADIALIS BREVIS
Olecranon
PIG. 334. LEFT SCAPULAR MUSCLES AND TRICEPS.
MUSCLES OF THE SHOULDER
375
Nerve - Supply. The
muscle is supplied by the
supra-scapular nerve (C. 5. 6.).
Action. The supraspin-
atus assists the deltoid in ab-
ducting the arm from the side.
... SERRATUS ANTERIOR
.SUBSCAPULARIS
SUPRASPINATUS
I PECTORALIS
/MINOR
Coracoid
process
Triceps brachii
(long head)
the horizontal position. In this movement it is aided by the supraspinatus and infraspinatus.
The anterior (clavicular) portion of the muscle assists the pectoralis major in drawing the arm
forwards, while the posterior portion draws it backwards.
M. Supraspinatus. the supraspinatus arises by fleshy fibres from the supra-
spinous fossa (except near
the neck of the bone) and
from the deep fascia over
it (Fig. 329, p. 368).
It is directed laterally
under the trapezius muscle,
the acromion and coraco-
acromial ligament, to be
inserted by a broad thick
tendon into the most
proximal facet on the
larger tubercle of the
humerus, and into the
capsule of the shoulder-
joint (Fig. 336, p. 376).
SER-'
RATUS ANTERIOR
LATISSIMUS DORSI
TERES MAJOR ^.*"^j
CORACOBRACHTALIS* ^*'~
BICEPS (short head)
TERES MAJOR
BICEPS (long head) >'
PECTORALIS MAJOR--'
M. Infraspinatus. The infraspin-
atus arises from the infra-spinous fossa
of the scapula (excepting near the neck
of the bone and the flat surface along
the axillary margin) and from the thick
fascia over it (Fig. 337, p. 376).
The fibres of the muscle converge to
the neck of the scapula ; and are inserted
by tendon into the middle facet on the
larger tubercle of the humerus, and into
the capsule of the shoulder-joint (Fig.
336, p. 376). A bursa separates the
muscle from the neck of the scapula, and
in a minority of cases communicates with
the synovial cavity of the shoulder-joint.
The supraspinatus and the upper part
of the infraspinatus muscles are concealed
by the trapezius, acromion, and deltoid.
They cover the neck of the scapula, the
transverse scapular artery, and supra-
scapular nerve, and the capsule of the
shoulder-joint.
Nerve-Supply. Supra-scapular nerve.
Action. The muscle assists the deltoid in
abducting and drawing back the arm at the
shoulder-joint.
DELTOID--
TRICEPS
BRACHII
BICEPS
BRACHII"
Medial inter-
muscular septum
BRACHIALIS
Biceps tendon.. J
SUPINATOR
MUSCLE'
fclil
BRACHIORADIALIS.
FLEXOR CARPI
RADIALIS'
PRONATOR TERES --!
FIG. 335. MUSCLES OF POSTERIOR WALL OF
LEFT AXILLA AND FRONT OF ARM.
M. Teres Minor. The teres minor
is a small muscle, arising by fleshy fibres
from the proximal two-thirds of the flat
surface on the dorsal aspect of the
axillary margin of the scapula, and from fascial septa separating it from the infra-
spinatus and teres major muscles (Fig. 337, p. 3*76).
Lying alongside the lateral border of the infraspinatus, it is inserted, under cover
of the deltoid, by a thick flat tendon, into the most distal of the three facets on the
376
THE MUSCULAK SYSTEM.
larger tubercle of the humerus and into the capsule of the shoulder-joint, and, by
fleshy fibres, into the posterior aspect of the surgical neck and body of the humerus
distal to the tubercle for about an inch (Fig. 341, p. 380).
It is separated from the teres major by the long or scapular head of the triceps
brachii, and by the posterior circumflex vessels of the humerus and the axillary
nerve. Its origin is pierced by the circumflex
scapular artery. The muscle is invested by the
deep fascia enclosing the infraspinatus, and is
OnsertTn) aris sometimes inseparable from that muscle.
Nerve-Supply. The teres minor is supplied by a branch
of the axillary nerve (C. 5. 6.). The nerve has a pseudo-
ganglion, a fibrous swelling on it in its course to the muscle.
Action. The muscle is a lateral rotator of the humerus.
Supraspinatus
(insertion)
Pectoralis major
" (insertion)
Latissimus dorsi
(insertion)
Teres major
(iiisertion)
Deltoid
(insertion)
Coracobrachialis
(insertion)
M. Teres Major. The teres major is much
larger than the preceding muscle. It arises by
fleshy fibres from the lower third of the flat surface
on the dorsum of the scapula along its axillary
Brachioradialif
(origin)'
Extensor carpi
radialis longus
(origin)
Common tendon
for origin of
pronator
teres and flexor
muscles of
forearm
Common tendon for origin of
extensor muscles of forearm
FIG. 336. MUSCLE - ATTACHMENTS TO
THE ANTERIOR ASPECT OF THE RIGHT
HUMERUS.
Deltoid
(origin)
Triceps
brachii
(origin of
long head)
Teres minor
(origin) with gap
for circumflex
scapular artery
Teres major (origin)
Latissimus dorsi (origin)
FIG. 337. MUSCLE- ATTACHMENTS TO THE RIGHT SCAPULA
(Dorsal Surface).
margin (except for a small area at the inferior angle), and from fascial septa, which
separate it on the one side from the subscapularis, and on the other from the
infraspinatus and teres minor (Fig. 337).
The muscle is directed along the axillary margin of the scapula to the front
of the body of the humerus, where it is inserted, by a broad flat tendon, into the
medial border of the sulcus intertubercularis medial to the latissimus dorsi muscle
(Fig. 337). Just before its insertion it is closely adherent to the tendon of the
latissimus dorsi.
The teres major lies below the subscapularis muscle in the posterior wall of
MUSCLES OF THE SHOULDER.
the axilla. The latissimus dorsi muscle, sweeping round from the back, covers
its axillary surface on its way to its insertion. The muscle forms the inferior
boundary of a triangular space in the posterior wall of the axilla, of which the other
boundaries are, above, the borders of the subscapularis and teres minor . muscles,
and laterally the surgical neck of the humerus. This space is subdivided by the
long head of the triceps brachii, which passes behind the teres major muscle, into
(a) a quadrilateral space above, for the passage of the axillary nerve and posterior
circumflex artery of the humerus ; and (6) a smaller triangular space below, for
the circumflex scapulae artery.
Nerve-Supply. The teres major is supplied, along with part of the subscapularis muscle,
by the lower subscapular nerve (C. 5. 6.),
Action. A medial rotator of the humerus.
M. Subscapularis. The subscapularis is a large triangular muscle which
covers the. costal surface of the scapula. It arises by fleshy fibres from the whole
of the subscapular fossa and the groove along the axillary margin, excepting the
surfaces at the angles of the bone (Fig. 333, p. 372). Springing from several
ridges in the fossa are fibrous septa projecting into the substance of the muscle,
which increase the extent of its attachment.
Converging to the head of the humerus, the muscular fibres are inserted by a
broad, thick tendon into the smaller tubercle of the humerus and into the capsule
of the shoulder-joint, and by fleshy fibres into the surgical neck and the body of
the humerus distal to the tubercle for about an inch, under cover of the coraco-
brachialis and short head of the biceps (Fig. 336, p. 376).
This muscle forms the greater part of the posterior wall of the axilla. Its
medial or anterior surface is in contact with the serratus anterior and the axillary
vessels and nerves. It is separated from the neck of the scapula by a bursa,
which is in direct communication with the synovial cavity of the shoulder-joint.
The subscapularis minor is an occasional muscle situated below the capsule of the shoulder-
joint. It arises from the axillary border of the scapula below the subscapularis, and is inserted
into the capsule of the joint or the proximal part of the body of the humerus.
Nerve-Supply. There are two and often three nerves supplying the subscapularis, viz.,
the short subscapular (C. 5. 6.), which is often double ; and the lower subscapular (C. 5. 6.), which,
after supplying its lateral (lower) portion, ends in the teres major.
Actions. The muscle aids in drawing the arm forward and medially rotating the humerus.
The principal action of the above group of muscles is on the shoulder-joint,
secondary actions in relation to movements of the trunk and limbs.
1. Movements at the Shoulder -Joint.
They have also
a. Abduction.
Adduction.
b. Flexion (Forwards).
Extension (Backwards).
Deltoid
Supraspinatus
Teres major
Teres minor
Pectoralis major
Latissimus dorsi
Coracobrachialis
Biceps (short head)
Triceps brachii (long
head)
Weight of limb
Deltoid (anterior fibres)
Subscapularis
Pectoralis major
Coracobrachialis
Biceps brachii
Deltoid (posterior fibres)
Teres major
Infraspinatus
Latissimus dorsi
Triceps brachii
c. Rotation Laterally.
Rotation Medially.
Deltoid (posterior fibres)
Infraspinatus
Teres minor
Deltoid (anterior fibres)
Teres major
Pectoralis major
Latissimus dorsi
d. Circumduction combination of previous muscles.
The various movements at the shoulder-joint are greatly aided by the muscles acting on the
shoulder girdle. In raising the arm above the head, for instance, the humerus is brought to the
horizontal position by the deltoid and supraspinatus, and the movement is continued by the
378 THE MUSCULAK SYSTEM.
elevators of the shoulder girdle. Again, in forward and backward movements at the shoulder-
joint, great assistance is derived from muscles acting directly on the shoulder girdle pectoralis
minor and serratus anterior ; trapezius and rhomboidei.
2. In relation to the trunk and limbs, the shoulder muscles, by fixing the humerus, have
auxiliary .power on the one hand in movements of the trunk, such as forced inspiration ; on the
other hand, acting along with muscles fixing the elbow-joint, they stiffen the limb so as to
permit of the more refined movements of the wrist and fingers.
FASCI/E AND MUSCLES OF THE ARM.
FASCIAE.
.The superficial fascia presents no features of importance. There is a bursa
beneath it over the olecranon, and occasionally another over the medial epicondyle
of the humerus.
The deep fascia forms a strong tubular investment for the muscles on the
anterior and posterior aspects of the humerus. It is continuous above with the
deep fascia of the shoulder and axilla, and is further strengthened by fibres derived
from the insertions of the pectoralis major, latissimus dorsi, and deltoid muscles.
At the elbow it becomes continuous with the deep fascia of the forearm, and
gains attachment to the epicondyles of the humerus and the olecranon of the ulna ;
it is strengthened also by important bands associated with the insertions of the
biceps anteriorly and the triceps posteriorly, to which reference will be made in
the account of these muscles.
About the middle of the arm on the medial side, the deep fascia is per-
forated for the passage of the basilic vein and the medial cutaneous nerve of the
forearm.
The intermuscular septa are processes of the deep fascia attached to the
epicondylic ridges of the humerus. The medial and stronger septum is placed
between the brachialis muscle anteriorly and the medial head of the triceps
posteriorly, and gives origin to both. It extends proximally to the insertion
of the coracobrachialis (which is often continued into it), and the ulnar nerve
and superior ulnar collateral vessels pass distally over its medial edge. The lateral
septum is thinner. It separates the brachialis muscle and brachioradialis in front
from the medial and lateral heads of the triceps behind, and gives origin to
those muscles. It extends proximally to the insertion of the deltoid, and is
pierced by the radial nerve and profunda brachii vessels. .
MUSCLES OF THE ARM.
The muscles of the arm comprise the biceps, coracobrachialis, and brachialis
on the anterior aspect, and the triceps brachii on the posterior aspect of the
humerus. Except at its extremities, the biceps brachii is superficial, and forms a
rounded fleshy mass on the anterior aspect of the arm. The coracobrachialis is
visible on its medial side in the proximal half of the arm, particularly when the
arm is raised. The brachialis is concealed by the biceps. The triceps brachii forms
the thick mass of muscle covering the posterior surface of the humerus.
M. Coracobrachialis. The coracobrachialis is a rudimentary muscle. It
arises under cover of the deltoid from the tip of the coracoid process, by fleshy
fibres, in common with the short head of the biceps, and also frequently from
the tendon of insertion of the pectoralis minor muscle.
The fleshy belly is pierced by the musculo-cutaneous nerve, and ends in a flat
tendon which is inserted into a faint linear impression about an inch in length on
the middle of the medial border of the body of the humerus (Fig. 336, p. 376). It
is often continued into the medial intermuscular septum.
The coracobrachialis is the remains of a threefold muscle, of which only two elements are
usually present in man, but of which in anomalous cases all the parts may be more or less fully
developed. The passage of the musculo-cutaneous nerve through the muscle is an indication of
its. natural separation into two parts, which represent the persistent middle and distal elements.
MUSCLES OF THE AEM.
379
The commonest variety is one in which the more superficial (distal) part of the muscle extends
more distally than usual, so as to be inserted into the medial intermuseular septum, or even into
the medial epicondyle of the humerus. A third slip (coracobrachialis superior or brevis,
INSERTION
iiK I'KCTOR-
i.LIS MAJOR
yORACOBRACHIALIS
SHORT HEAD OF
B.ICEPS
LONG HEAD OF
BICEPS
BICEPS (medial head)
-.vY-^Al,**
;
INSERTION OF
PECTORALIS
MINOR
DELTOID
illary artery
Musculo-
cutaueous nerve
Median nerve
(lateral head)
Median nerve
(medial head)
Ulnar nerve
PRONATOR TERES T^O^lu^ [N/,
Deep fascia of forearm
FLEXOR CARPI RADIALIS
PALMARIS LONGUS
FLEXOR CARPI ULNARIS
FLEXOR DIGITORUM SUBLIMIS
FLEXOR POLLICIS LONGUS
PRONATOR QUADRATUS
Ulnar artery
Ulnar nerve
aus
Jr^j^JL
TRAPEZIUS
LATISSIMUS
DO RSI
EXTENSOR CARPI RADIALIS
LONGUS
EXTENSOR CARPI RADIALTS
BREVIS
Deep fascia of forearm
EXTENSOR DIGITORUM
COMMUNIS
EXTENSOR CARPI ULNARIS
__ ABDUCTOR POLLICIS LONGUS
EXTENSOR POLLIOIS BREVIS
EXTENSOR DIGITI
QUINTI PROPRIUS
TENDONS OF RADIAL IEXTENS<
OF CARPUS
Dorsal carpal ligament
EXTENSOR POLLICIS LONGUS
EXTENSOR INDICIS PROPRIUS
3. SUPERFICIAL MUSCLES ON THE ANTERIOR ASPECT OF
THE RIGHT ARM AND FOREARM.
FIG. 339. THE MUSCLES ON THE POSTERIOR Si]
OF THE LEFT ARM, FOREARM, AND HAND.
rotator humeri) may more rarely be present, forming a short muscle arising from the root of the
coracoid process, and inserted into the medial side of the humerus just distal to the capsule of
the shoulder-joint.
380
THE MUSCULAR SYSTEM.
Infraspinatus
(insertion)
Nerve-Supply. The nerve to the coracobrachialis comes from the 7th or 6th and 7th
cervical nerves. Incorporated with the musculo-cutaneous, the nerve separates to supply the
muscle before the latter nerve pierces it.
Action. The muscle assists the biceps to raise the arm and draw it medially.
M. Biceps Brachii. The biceps brachii arises by two tendinous heads. (1)
The short head (caput breve) is attached in common with the coracobrachialis to
the tip of the cora-
coid process of the
scapula (Fig. 333,
p. 372). Concealed
by the deltoid and
tendinous at first,
this head forms a
separate fleshy
belly, which is
united to the long
hea d by an invest-
ment of the deep
fascia. (2) The
long head (caput
longum) arises by
a round tendon
from the supra-
glenoidal tuberos-
ity at the root of
the coracoid pro-
cess and from the
Supraspinatus
(insertion)
.Subscapularis
(insertion)
Pectoralis major
(insertion)
Latissimus dorsi
(insertion)
Teres major
"(insertion)
Deltoid (insertion)
Brachioradialis
"(origin)
Extensor carpi
-radialis longus
k (origin)
Common tendon
for origin of
pronator teres
and flexor
muscles of
forearm
Common tendon for origin of
extensor muscles of forearm
FIG. 340. MUSCLE - ATTACHMENTS TO
THE ANTERIOR ASPECT OF THE
EIGHT HUMERUS.
: lateral h
Triceps : medial
head (origin)
Coracobrachialis
(insertion)
labrum glenoidale
on each side.
Its tendon passes
through the cavity
of the shoulder -
joint, and, emerg-
ing from the cap-
sule beneath the
transverse humeral
ligament (invested
by a prolongation
of the synovial
membrane), it
occupies the inter-
tubercular groove
of the humerus
by a fascial pro-
longation of the
tendon of the pec-
FIG. 341. MUSCLE - ATTACHMENTS TO toralis major. In
THE POSTERIOR SURFACE OF THE fche arm it formg
EIGHT HUMERUS.
fleshy belly united
to that derived from the short head by an envelope of deep fascia.
The insertion of the muscle is likewise twofold. (1) The two bellies become
connected to a strong tendon, attached deeply in the hollow of the elbow
to the rough dorsal portion of the tubercle of the radius (Figs. 335, p. 375,
and 348, p. 389). A bursa separates the tendon from the volar portion of the
tuberosity. (2) From the medial and anterior part of the tendon, and partly
in continuity with the fleshy fibres of the muscle, a strong membranous "band
(the lacertus fibrosus) extends, distally and medially, over the hollow of the elbow
to join the deep fascia covering the origins of the flexor and pronator muscles
Common tendon
for origin of
xtensormuscles
of forearm
Anconseus
(origin)
MUSCLES OF THE ARM. 381
of the forearm. Its proximal part is thickened and can be felt subcutaneously as
a crescentic border.
In the arm the biceps conceals the brachialis muscle and the musculo-cutaneous
nerve. Its medial border is the guide to the position of the brachial artery and
median nerve.
The biceps is an extremely variable muscle. Its chief anomalies are due to an increase
or diminution in the number of origins. A third head of origin is common (10 per cent), and
usually arises from the humerus, between the insertions of the deltoid and coracobrachialis.
Two or even three additional heads may be present at the same time. The long head of the
muscle may be absent, or may take origin from the intertubercular groove. The muscle may
have an additional insertion into the medial epicondyle of the humerus, or into the fascia of
the forearm.
Nerve-Supply. The biceps is supplied by the musculo-cutaneous nerve (C. 5. 6.).
Actions. The actions of the biceps are complex, in that they affect three articulations
the shoulder, humero-radial, and radio-ulnar joint. The muscle raises and draws forward the
humerus at the shoulder-joint, it flexes the elbow-joint, and it supinates the forearm. The
combination of these actions results in a simple movement like that of raising the hand to
the mouth.
M. Brachialis. The brachialis (O.T. brachialis anticus) is a large muscle
arising from the distal two-thirds of the anterior aspect of the body of the
humerus and from the intermuscular septum on each side (Figs. 340 and 341,
p. 380).
Clasping the insertion of the deltoid proximally, it ends dis tally in a strong
tendon, which is inserted, deep in the hollow of the elbow, into the anterior ligament
of the elbow-joint, the distal surface of the coronoid process, and slightly into the
immediately adjacent part of the volar surface of the body of the ulna (Fig. 348,
p. 389). The lateral part of the muscle arising from the lateral epicondylic ridge
and lateral intermuscular septum forms a slip more or less separate, which may
be partially fused with the brachioradialis muscle.
It is concealed for the most part by the biceps muscle in the arm. It forms
the floor of the cubital fossa, and covers the anterior aspect of the elbow-joint.
Nerve-Supply. It is supplied by the musculo-cutaneous nerve (C. 5. 6.) ; and also (in most
instances) at its lateral border by a fine branch of the radial nerve (C. (5.) 6.).
Action. This muscle is a flexor of the elbow-joint.
M. Triceps Brachii. The triceps brachii is the only muscle on the posterior
aspect of the arm. It arises by three heads : a lateral and a medial head, from
the hurnerus, and a long or middle head, from, the scapula. (1) The long head
(caput longum) begins as a strong tendon attached to a rough triangular surface
on the axillary border of the scapula just below the glenoid cavity (infra-glenoidal
tuberosity) (Figs. 333, p. 372, and 337, p. 376). This gives rise to a fleshy belly
which, after passing between the teres major and teres minor muscles, occupies the
middle of the back of the arm. (2) The lateral head is attached by fibres, partly
tendinous and partly fleshy, to the curved lateral border of the humerus from the
insertion of the teres minor proximally to the radial groove distally, and receives
additional fibres from the posterior surface of the lateral intermuscular septum
(Fig. 341, p. 380). Its fibres are directed distally and medially over the radial
groove, concealing the radial (musculo-spiral) nerve, the profunda brachii artery,
and the medial head of the muscle, to the tendon of insertion. (3) The medial
head arises by fleshy fibres from an elongated triangular area on the posterior
surface of the humerus, extending proximally to the level of the insertion of the
teres major, and distally nearly to the margin of the olecranon fossa (Fig. 341,
p. 380). It also arises, on each side, from the intermuscular septum, from the
whole length of the medial septum, and from the part of the lateral septum which
is below the passage of the radial nerve.
The three heads of origin are inserted, by a broad and membranous common
tendon, into an impression occupying the posterior part of the proximal end
of the olecranon of the ulna (Fig. 355, p. 397), and into the deep fascia of the
forearm on each side of it. The long and lateral heads join the borders of the
tendon of insertion, and the medial head is attached to its deep surface. A small
382
THE MUSCULAK SYSTEM.
thick-walled bursa separates the tendon of the triceps from the posterior ligament
of the elbow-joint and the proximal end of the olecranon.
The muscle is superficial in almost its whole extent. The long (scapular) head is concealed
at its origin by its relation to the teres muscles, between which it passes.
The subanconaeus is a small muscle occasionally present. It consists of scattered fibres
arising from the distal end of the posterior surface of the humerus, deep to the triceps, and
it is inserted into the posterior ligament of the elbow-joint.
Nerve-Supply. The several heads of the muscle are supplied separately by branches of the
radial nerve. The lateral head receives fibres from C. (6.) 7. 8. ; the long and medial head from
C. 7. 8. The medial head has a double supply. One nerve enters its proximal part, another (ulnar
collateral nerve of Krause) enters the distal part of the muscle.
Actions. The triceps is the extensor muscle of the elbow -joint. The long head also acts as
an adductor of the humerus at the shoulder-joint.
The chief action of these muscles (excepting the coracobrachialis) is on the elbow -joint,
producing along with other muscles flexion and extension. The flexor muscles are much more
powerful than the extensors.
Table of Muscles acting on the Elbow-Joint.
Flexors.
Extensors.
Biceps brachii
Brachialis
Brachioradialis
Pronator teres
Flexors of wrist and fingers
Extensors of wrist (in pronation)
Triceps brachii
Anconseus
Extensors of wrist and fingers
(in supination)
FASCI/E AND MUSCLES OF THE FOREARM
AND HAND.
Fasciae.
The superficial fascia in the forearm presents no exceptional features. On
the dorsum of the hand it is loose and thin ; in the palm it is generally well
furnished with fat, forming pads for the protection of the vessels and nerves. It is
closely adherent to the palmar aponeurosis and to the skin, especially along the
lines of flexure.
M. Palmaris Brevis. The palmaris brevis is a quadrilateral subcutaneous
muscle which lies in the medial side of the hand, under the superficial fascia. It
arises from the medial border of the thick central portion of the palmar aponeurosis
and from the volar surface of the transverse carpal ligament of the wrist, and is
inserted into the skin of the medial border of the hand for a variable distance. It
covers the ulnar artery and nerve, branches of which supply it. Its action is to
wrinkle the skin of the medial border of the hand, and by raising up the skin and
superficial fascia, to deepen the hollow of the hand.
The deep fascia of the forearm and hand is continuous above with the deep
fascia of the arm. In the proximal part of the forearm it is strengthened by
additional fibres around the elbow ; in front, by fibres from the lacertus fibrosus
(semilunar fascia) of the biceps ; behind, by the fascial insertions of the triceps ; and
laterally, by fibres derived from the humeral epicondyles in relation to the common
tendons of origin of the flexor and extensor muscles of the forearm which in part
take their origin from them. It is attached to the dorsal margin of the ulna, and
affords increased attachment to the flexor and extensor carpi ulnaris and the flexor
digitorum profundus muscles. Above the wrist the volar part of the fascia is
pierced by the tendon of the palmaris longus, and by the ulnar artery and nerve.
At the wrist it gains attachment to the bones of the forearm and carpus, is
greatly strengthened by addition of transverse fibres, and constitutes the transverse
carpal and dorsal carpal ligaments.
Ligamentum Carpi Transversum. The transverse carpal ligament (O.T.
anterior annular ligament) is a band about an inch and a half in depth, continuous,
proxirnally and distally, with the deep fascia of the forearm and the palm of the
FASCIAE AND MUSCLES OF THE FOEEAEM AND HAND. 383
hand. It is attached laterally to the navicular and large multangular; medially
to the pisiform and os hamatum; and it forms a membranous arch binding down,
in the hollow of the carpus, the flexor tendons of the fingers, and the median nerve.
It is divided into two compartments, the larger accommodating the tendons of the
flexors of the digits and the median nerve, the smaller (placed laterally) containing
the tendon of the flexor carpi radialis. There are three synovial membranes in
these compartments : one for the flexor carpi radialis tendon, and two others,
which often communicate together, enveloping the tendon of the flexor pollicis
longus and the flexor
tendons of the fingers
respectively. The
surface of the liga-
ment is crossed by
the palmar branches
of the median and
ulnar nerves ; by the
tendon of the palmaris
longus muscle, which
is attached to its sur-
face ; and by the ulnar
artery and nerve,
which are again
bridged over and pro-
tected by a band of
fibrous tissue, called
the volar carpal liga-
ment, which passes
from the pisiform
bone and the super-
ficial fascia to the
surface of the trans-
verse carpal ligament.
To the distal border
of the ligament are
attached the palmar
aponeurosis in the
centre, and the super-
ficial muscles of the
thumb and the mus-
cles of the little
finger on each side.
Ligamentum
Carpi Dorsale.
The dorsal carpal
ligament (O.T. pos-
terior annular liga-
ment) is placed at a
more proximal level than the transverse carpal ligament. It consists of an
oblique band of fibres about an^inch broad, continuous proximally and distally
with the deep fascia of the forearm and hand. It is attached laterally to the
lateral side of the distal end of the radius, and medially to the distal end of the
ulna (styloid process), the carpus, and the ulnar collateral ligament of the wrist.
It is crossed by veins, by the superficial ramus of the radial nerve, and by the
dorsal branch of the ulnar nerve. Six compartments are formed deep to it by
the attachment of septal bands to the distal ends of the radius and ulna. Each
compartment is provided with a mucous sheath, and they serve to transmit
the extensor tendons of the wrist and fingers in the following order from lateral
to medial side :
(1) Abductor pollicis longus and extensor pollicis brevis, (2) Extensores carpi
Palmar
aponeurosis "
Thenar
eminence
Hypothenar .
eminence
PALMARIS BREVIS _
Transverse carpal
ligament
ABDUCTOR .
POLLICIS LONGUS
FLEXOR CARPI RADIALIS ._
PALMARIS LONGDS
FLEXOR DIGITORUM /
SUBLIMIS 1
FLEXOR CARPI ULNARIS- .-
FIG. 342. THE PALMAR APONEUROSIS.
384
THE MUSCULAE SYSTEM.
"FLEXOR CARPI ULNARIS
-FLEXOR DIGITORUM SUBLIMIS
FLEXOR CARPI RADIALIS
;_PALMARIS LONGUS
-Pisiform bone
-ABDUCTOR POLLICIS LONGUS
TRANSVERSE CARPAL
LIGAMENT
ABDUCTOR DICUTI QUINTI
ABDUCTOR POLLICIS BREVIS
FLEXOR DIGITI
"QUINTI BREVIS
^FLEXOR POLLICIS
'BREVIS
ADDUCTOR
POLLICIS
_ FLEXOR POLLICIS
" LONGUS
radiales, longus and brevis, (3) Extensor pollicis longus, (4) Extensor digitorum
communis and extensor indicis proprius, (5) Extensor digiti quinti proprius,
(6) Extensor carpi ulnaris.
The thin deep fascia of the dorsum of the hand is lost over the expansions of
the extensor tendons on the fingers. Between the metacarpal bones a strong layer
of fascia covers and gives attachment to the interossei muscles.
Aponeurosis Palmaris. The palmar aponeurosis is of considerable import-
ance. In the centre of the palm it forms a thick triangular membrane, the apex
of which joins
the distal edge
of the trans-
verse carpal
ligament, and,
more superfici-
ally, receives the
insertion of the
tendon of the
palmaris longus
muscle. The
fascia separates
below into four
slips, one for
each finger. The
slips are con-
nected together
by transverse
fibres, which
form, beneath
the webs of the
fingers, the
superficial trans-
verse metacarpal
ligament (fasci-
culi transversi).
More distally
each slip separ-
ates into two
parts, to be con-
nected to the
sides of the
metacarpo-
phalangeal
joints and the
first phalanx of
the medial four
FIG. 343. SUPERFICIAL MUSCLES AND TENDONS IN THE PALM OF THE LEFT HAND, digits. In the
cleft between
the two halves of each slip the digital sheath is attached and extends distally on
to the finger. The lateral borders of this triangular central portion of the palmar
aponeurosis are continuous with thin layers of deep fascia, which cover and
envelop the muscles of the thenar and hypothenar eminences. The medial border
gives origin to the palmaris brevis muscle (p. 382).
The digital sheaths (vaginae mucosae) are tubular envelopes extending along
the palmar aspect of the digits and enclosing the flexor tendons. Each consists of
a fibrous sheath attached to the lateral borders of the phalanges and inter-phalan-
geal joints, and continuous proximally with the palmar aponeurosis. Opposite each
inter- phalangeal articulation the digital sheath is loose and thin ; opposite the first
two phalanges (the first only in the case of the thumb) it becomes extremely thick,
and gives rise to the ligamenta vaginalia, which serve to keep the tendons closely
LUMBRICAL MUSCLES
x TENDONS OF FLEXOR DIGITORUM
^SUBLIMIS
FLEXOR DIGITORUM SUBLIMIS
FLEXOR DIGITORUM PROFUNDUS
MUSCLES ON ANTEEIOK AND MEDIAL ASPECTS OF FOBEAKM. 385
applied to the bones during flexion of the fingers. Within each digital sheath are
the flexor tendons, enveloped in a mucous sheath which envelops the tendon
and lines the interior of the sheath. The mucous linings of the digital
sheaths extend a short distance proximally in the palm, and in some cases com-
municate with the large mucous sheaths enclosing the flexor tendons beneath
the transverse carpal ligament. There may be a separate distinct mucous
sheath for each digit; but most commonly only the sheaths for the three
middle digits are separate ; those of the flexor pollicis longus and the flexor
tendons of the little finger usually communicate with the mucous sheaths placed
beneath the transverse carpal ligament.
THE MUSCLES ON THE ANTERIOR AND MEDIAL ASPECTS
OF THE FOREARM.
The muscles on the anterior and medial aspects of the forearm comprise the
pronators and the flexors of the wrist and fingers. In the forearm they are
arranged in three strata : (1) a superficial layer consisting of four muscles which
radiate from the medial epicondyle of the humerus, from which they take origin
by a common tendon. They are named, from radial to ulnar side, pronator teres,
flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. These muscles
conceal the muscle which by itself constitutes (2) the intermediate stratum the
flexor digitorum sublimis, and this again conceals, for the most part, (3) the deep
layer of muscles, including the flexor digitorum profundus covering the ulna, the
flexor pollicis longus on the radius, and the pronator quadratus, which is more
deeply placed than the previous muscles, and stretches across the forearm between
the distal portions of the radius and ulna.
I. Superficial Muscles.
M. Pronator Teres. The pronator teres is the shortest muscle of this group.
It has a double origin: (1) a superficial head (caput humerale), the main origin, partly
fleshy, partly tendinous, from the most distal part of the medial epicondylic ridge
of the humerus and from the medial intermuscular septum, from the medial epi-
condyle of the humerus, from the fascia over it, and from an intermuscular septum
between it and the flexor carpi radialis (Fig. 346, p. 387) ; (2) a deep head (caput
ulnare), a slender tendinous slip from the medial side of the coronoid process of the
ulna, which joins the superficial origin of the muscle on its deep surface (Fig. 348,
p. 389). The median nerve separates the two heads from one another.
The muscle passes distally and laterally to be inserted by tendon into an
oval impression on the middle of the lateral surface of the body of the radius
(Figs. 346, p. 387, and 348, p. 389). The fibres of the muscle are twisted on them-
selves, so that the most proximal humeral fibres form the most distal fibres of the
tendon of insertion, and the most distal humeral fibres and those arising from the
coronoid process are most proximal at the insertion.
The pronator teres forms the medial boundary of the hollow of the elbow. It is
superficially placed, except near its insertion, where it is covered by the brachio-
radialis muscle and by the radial vessels and superficial branch of the radial
nerve.
Nerve-Supply. Median nerve (C. 6.).
Action. The muscle is a flexor of the elbow-joint and a pronator of the forearm.
M. Flexor Carpi Radialis. The flexor carpi radialis muscle takes its origin
from the common tendon from the medial epicondyle of the humerus, from the
fascia over it, and from the intermuscular septa on either side.
Its fleshy belly gives place, in the distal half of the forearm, to a strong round
tendon which, at the wrist, enters the hand in a special compartment under cover
of the transverse carpal ligament, and after occupying the groove on the large mult-
angular bone, is inserted into the proximal ends of the second and third metacarpal
26
386
THE MUSCULAR SYSTEM.
A 1
bones on their volar surfaces (Fig. 351, p. 392). The chief tendon is that to the
second metacarpal bone.
The muscle is superficial except near its insertion. Its tendon, in the distal
half of the forearm, is an important guide to the radial vessels, which are placed
to its radial side. After passing beneath the transverse carpal ligament the
tendon is concealed by the origins of the short muscles of the thumb, and is crossed,
from medial to lateral side, by the tendon of the flexor pollicis longus. Besides the
mucous sheath enveloping the tendon beneath the ligament, a mucous bursa is
placed beneath the insertion of the tendon.
Nerve-Supply. Median nerve (C. 6.).
Actions. This muscle has a threefold action. It is mainly a flexor of , the elbow and wrist,
but it also acts as an accessory pronator of the forearm.
M. Palmaris Longus. The palmaris longus arises also from the common
flexor tendon from the medial epicondyle of the humerus, from the fascia over it,
and from intermuscular septa
on each side.
It forms a short fusiform
muscle, which ends, in the
middle of the forearm, in a
7 long flat tendon. This pierces
the deep fascia, near the wrist,
E and passing over the trans-
F verse carpal ligament, is in-
serted (1) into the surface of
the transverse carpal ligament,
and (2) into the apex of the
thick central portion of the
palmar aponeurosis. A ten-
dinous slip is frequently sent
to the shorb muscles of the
thumb and the fascia covering
them.
The palmaris longus is the
A, PRONATOR TERES (insertion); B, FLEXOR CARPI RADIALIS; C, FLEXOR sma ll es t muscle of the forearm.
DIOITORUM SUBLIMIS J D, PALMARIS LONGUS ; E, FLEXOR CARPI ULNARIS J _ , , . - , . -
F, FLEXOR DIOITORUM PROFUNDUS ; G, EXTENSOR CARPI ULNARIS ; In til 6 QlStal tillm 01 the
H, EXTENSOR POLLICIS LONGUS ; I, EXTENSOR DIGITORUM COMMUNIS AND forearm its tendon is placed
EXTENSOR DIGITI QUINTI PROPRIUS J J, ABDUCTOR POLLICIS LONGUS ; K, dirPCtlv Qvpr 4-1^ TTlPfHlTl
EXTENSOR CARPI RADIALIS BREVIS ; L, EXTENSOR CARPI RADIALIS LONGUS ; L ' U V
M, BRACHIORADIALIS. a, Radius ; b, Interosseous membrane ; c, Ulna, nerve, along the radial border
1, Superficial ramus of radial nerve ; 2, Radial artery ; 3, Volar inter- Q ^g tendons of the fleXOr
osseous artery; 4, Volar interosseous nerve (underneath flexor pollicis -, , VT "
longus) ; 5, Median nerve ; 6, Ulnar artery ; 7, Ulnar nerve ; 8, Dorsal dlgl imiS.
interosseous artery ; 9, Dorsal interosseous nerve.
The palmaris longus is the
most variable muscle in the body, and is often absent (10 per cent).
Nerve-Supply. Median nerve (C. 6.).
Actions. The muscle assists in flexion of the elbow and wrist. It also by tightening the
palmar aponeurosis deepens the hollow of the hand and helps to flex the fingers.
M. Flexor Carpi Ulnaris. The flexor carpi ulnaris muscle has a double
origin, from the humerus and from the ulna. (1) It arises from the common tendon
attached to the medial epicondyle of the humerus, from the fascia over it, and from
a lateral intermuscular septum. (2) By means of the deep fascia of the forearm it
obtains an attachment to the medial border of the olecranon and the dorsal margin
of the ulna in its proximal three-fifths.
The fleshy fibres join a tendon which lies on the anterior border of the muscle
and is inserted into the pisiform bone, and in the form of two ligamentous ban del
(piso-hamate and piso-metacarpal) into the hamulus of the os hamatum, and thel
proximal end of the fifth metacarpal bone (Fig. 351, p. 392).
The muscle is superficially placed along the medial border of the forearm. It
conceals the flexor digitorum profundus muscle, the ulnar nerve (which enters!
PIG. 344. DISTAL SURFACE OF A SECTION ACROSS THE EIGHT
FOREARM IN THE MIDDLE THIRD.
MUSCLES ON ANTEEIOE AND MEDIAL ASPECTS OF FOEEAEM. 387
the forearm between the two heads of origin of the muscle), and the ulnar
artery. The tendon serves as a guide to the artery in the distal half of
the forearm.
BICEPS BRACHII ^
MKDIAL INTER-
MUSCULAR SEPTUM
BRACHIALIS
DIAL EPICONDYLE
NATOR MUSCLE
iONATOR TERES
LEXOR CARPI
.RADIALIS
uEXOR CARPI
ULNARIS-
FLEXOR DIOI-
BUM SUBLIMIS
FLEXOR POLLICIS..!^
T.n'wnTTa
,EXOR CARPI ULNARIS
(tendon)
Pisiform bone
.BDUCTOR POLLICIS
LONGUS-
IAR APONEUROSIS.J
BICEPS BRACHII ..
BRACHIALIS,
MEDIAL INTERMUSCULAR
SEPTUM
LACERTUS FIBROSUS-
BICEPS TENDON-.
PRONATOR
TERES (humeral
origin)
PRONATOR
TERESx
(ulnar origin) "
FLEXOR
CARPI
RA.DIALIS
SUPINATOR MUSCLE '
BRACHIORADIALIS
PRONATOR TERES
(insertion)
FLEXOR DIGITORUM
SUBLIMIS (radial ..
origin)
FLEXOR CARPI ULNARIS
FLEXOR DIGITORUM < -.
SUBLIMIS *
BRACHIORADIALIS TENDON
FLEXOR POLLICIS LONGUS"
PRONATOR QUADRATUS
FLEXOR DIGITORUM
PROFUNDUS
Pisiform bone
FLEXOR CARPI RADIALIS
ABDUCTOR POLLICIS LONGUS
FIG. 3-45. THE SUPERFICIAL MUSCLES OF
THE LEFT FOREARM.
FIG. 346. DEEPER MUSCLES OF
THE LEFT FOREARM.
Nerve-Supply. Ulnar nerve (C. 8. T.
Actions. The flexor carpi ulnaris is
flexor of the elbow -joint.
a flexor and adductor of the wrist, and an accessory
26 a
388
THE MUSCULAK SYSTEM.
Vinculum breve
FLEXOR DIGITORUM SUBLIMIS
FLEXOR DIGITORUM
PROFUNDUS
J 1 1 FIRST LUMBRICAL MUSCLE
FIRST DORSAL INTER-
OSSEOUS MUSCLE
EXTENSOR INDICIS
PROPRIUS TENDON
EXTENSOR DIGITORUM
COMMUNIS TENDON
2. Intermediate Layer.
M. Flexor Digitorum Sublimis. The flexor digitorum sublimis occupies a
deeper plane than the four previous muscles. It has a threefold origin, from the
humerus, radius, and ulna. (1) The chief or humeral head of origin is from the
medial epicondyle of the humerus by the common tendon, from the ulnar collateral
ligament of the elbow, and from adjacent intermuscular septa. (2) The ulnar head
of origin is by a slender fasciculus from the medial border of the coronoid process of
the ulna, proximal and medial to the origin of the pronator teres (Fig. 348, p. 389).
(3) The radial head of origin is from
the proximal two-thirds of the volar
margin of the radius by a thin fibro-
muscular attachment (Fig. 348, p. 389).
The muscle divides in the distal
third of the forearm into four parts,
each provided with a separate tendon
which goes beneath the transverse car-
Expansion of extensor tendon p al ligament, passes through the palm
of the hand, and enters the correspond-
ing digital sheath of a finger. At
the wrist the four tendons are arranged
in pairs, those for the middle and ring
fingers in front, and those for the fore
and little fingers behind, and are sur-
rounded by a mucous sheath, along
with the tendons of the flexor digi-
torum profundus, beneath the trans-
verse carpal ligament. In the palm
of the hand the tendons separate, and
conceal the deep flexor tendons and
lumbrical muscles.
Within the digital sheath each
tendon is split into two parts by the
tendon of the flexor digitorum pro-
fundus ; after surrounding that tendon
the two parts are partially re-united on its deep surface, and are inserted, after
partial decussation, in two portions into the sides of the second phalanx.
The vincula tendinum form additional insertions of the muscle. They consist
of delicate bands of connective tissue enveloped in folds of the mucous sheath, and are
known as the vincula longa and brevia. The vinculum breve is a triangular band
of fibres containing yellow elastic tissue (ligamentum subflavum), occupying the
interval between the tendon and the digit for a short distance close to the insertion.
It is attached to the front of the inter -phalangeal articulation and the head
of the first phalanx. The ligamentum longum is a long narrow band extending
from the back of the tendon to the proximal part of the palmar surface of the
first phalanx.
Nerve-Supply. Median nerve (C. 6.).
Actions. The muscle is a flexor of the elbow, wrist, metacarpo-phalangeal and firs
(proximal) interphalangeal joints.
3. Deep Layer.
M. Flexor Digitorum Profundus. The flexor digitorum profundus is e
large muscle arising from the ulna, the interosseous membrane, and the deep fascia
of the forearm, under cover of the flexor digitorum sublimis and the flexor carp
ulnaris. Its ulnar origin is from the volar and medial surfaces of the bone in itoi
proximal two-thirds, extending proximally so as to include the medial side of th<
olecranon, and to embrace the insertion of the brachialis muscle into the coronoicfl
'
FIG. 347. THE TENDONS ATTACHED TO THE
INDEX FINGER.
MUSCLES ON ANTEKIOK AND MEDIAL ASPECTS OF FOKEABM. 389
Bracliialis muscle (insertion)
Supinator nmscle
(ulnar origin)
Flexor digitorum sub-
limis (ulnar origin)
Pronator teres
(ulnar origin)
Flexor pollicislongus
(occasional origin)
Biceps brachii
(insertion)
Flexor digi
torum sublimis
(radial origin)
Pronator teres
(insertion)
Flexor pollicis
longus (origin
Flexor digitorum
profundus (origin)
process. It arises laterally from the medial half of the interosseous membrane in
its middle third (Figs. 348, p. 389, and 349, p. 390), and medially from the deep
fascia of the forearm dorsal to the origin of the flexor carpi ulnaris.
The muscle forms a broad thick tendon which passes beneath the transverse
carpal ligament, covered by the tendons of the flexor digitorum sublimis, and
enveloped in the same mucous sheath, and divides, in the palm, into four tendons
for insertion into the terminal phalanges of the fingers. The tendon associated with
the forefinger is usually separate
from the rest of the tendons in
its whole length.
Each tendon enters the
digital sheath of the finger
deep to the tendon of the flexor
digitorum sublimis, which it
pierces opposite the first phalanx,
and is finally inserted into the
base of the terminal phalanx.
Like the tendons of the flexor
sublimis, those of the deep flexor
are provided with vincula, viz.,
vincula brevia attached to the
capsule of the second inter -
phalangeal articulation, and
vincula longa, which are in this
case connected to the tendons
of the subjacent flexor digitorum
sublimis.
Mm. Lumbricales. The
lumbricales are four small
cylindrical muscles associated
with the tendons of the flexor
digitorum profundus in the palm
of the hand. The two lateral
muscles arise, each by a single
head, from the radial sides of the
tendons of the flexor digitorum
profundus destined respectively
for the fore and middle fingers.
The two medial muscles arise, each
by two heads, from the adjacent
sides of the second and third, and
third and fourth tendons.
From their origins the mus-
cles are directed distally to
the lateral side of each of the
metacarpo-phalangeal joints, to
be inserted into the capsules of
these articulations, the lateral
border of the first phalanx, and
chiefly into the lateral side of the
extensor tendon on the dorsum of the phalanx. The lumbricales vary considerably
in number, and may be increased to six or diminished to two.
Nerve-Supply. The flexor digitorum profundus is supplied in its lateral part by the volar
interosseous branch of the median nerve (C. 7. 8. T. 1.); and in its medial part by the ulnar
nerve (C. 8. T. 1.). The lateral two lumbricales are supplied by the median nerve (C. 6. 7.), and
the -medial two muscles by the ulnar nerve (C. 8. (T. 1.)).
Actions. The flexor digitorum profundus is a powerful flexor of the wrist. It also flexes
the fingers at the metacarpo-phalangeal joint, and acts in a similar way at both the inter-
phalangeal joints.
The lumbrical muscles act as flexors of the fingers at the metacarpo-phalangeal joints, and
Pronator quad-
ratus (insertion)
Brachioradialis
(insertion)
Pronator quadratus
(origin)
FIG. 348.-
-MUSCLE-ATTACHMENTS TO THE RIGHT RADIUS
AND ULNA (Volar Aspects).
390
THE MUSCULAR SYSTEM.
BICEPS BBACHII
LACERTUS FIBROSUS
(by their attachment to the extensor tendons) as extensors of the fingers, acting on both inter-
phalangeal joints.
M. Flexor Pollicis Longus. The flexor pollicis longus arises, beneath the
flexor digitorum sublimis, by fleshy fibres, from the volar surface of the body of
the radius in its middle two-
fourths, and from a corresponding
portion of the interosseous mem-
brane. It has an additional origin,
occasionally, from the medial border
of the coronoid process of the ulna
(Fig. 348, p. 389). Its radial origin
is limited proxirnally by the oblique
proximal part of the volar margin
of the radius and the origin of the
flexor digitorum sublimis, and
distally by the insertion of the
pronator quadratus muscle.
The muscle ends, proximal to
the wrist, in a tendon, which passes
over the pronator quadratus into
the hand beneath the transverse
carpal ligament, and is enveloped
in a special mucous sheath.
In the palm the tendon is
directed distally along the medial
side of the thenar eminence, be-
tween the flexor brevis and ad-
ductor muscles of the thumb, to
be inserted into the base of the
terminal phalanx of the thumb
on its volar surface.
The muscle is placed deeply in
the forearm, being concealed by the
superficial layer of muscles and by
the flexor digitorum sublimis.
Nerve - Supply. Volar interosseous
branch of the median (C. 7. 8. T. 1.).
Actions. The muscle is a flexor of
the wrist and thumb, acting in the latter
movement on the metacarpal bone and
both phalanges.
M. Pronator Quadratus. The
pronator quadratus is a quadri-
lateral fleshy muscle, occupying
the distal fourth of the forearm.
It is placed beneath the deep flexor
tendons, and arises from the distal
fourth of the volar margin and
surface of the ulna (Fig. 348,
p. 389).
It is directed transversely later-
ally to be inserted into the distal
fourth of the volar surface of the
PRONATOR
TERES
SUPERFICIAL
FLEXOR ORIGIN
BICEPS TENDON
TUBERCLE
OF RADIUS
SUPINATOR MUSCLE
BRACHIORADIALIS
PRONATOR TERES
FLEXOR DIGITORUM..
PROFUNDUS
FLEXOR CARPI
ULNARIS
FLEXOR DIGITORUM
PROFUNDUS (fl
index finger)
FLEXOR POLLICIS LONGUS
BRACHIORADIALIS .
FLEXOR DIGITORUM,
SUBLIMIS
PRONATOR QUADRATUS--^
FLEXOR DIGITORUM
SUBLIMIS
Pisiform bone
FLEXOR CARPI RADIALIS
ABDUCTOR POLLICIS
LONGUS
radius, and into the narrow tri-
FIG. 349. THE DEEPEST MUSCLES ON THE VOLAR ASPECT
OF THE LEFT FOREAKM.
angular area on its medial side, in
front of the attachment of the interosseous membrane (Fig. 348, p. 389).
The pronator quadratus is subject to considerable variations. It may even be
absent ; or it may have an origin from radius or ulna, or from both bones, and an
insertion into the carpus.
SHOKT MUSCLES OF THE HAND.
391
The muscle is placed deeply in the distal part of the forearm, and is wholly
concealed by the tendons, of the muscles which descend, under cover of the
transverse carpal ligament, to the wrist and fingers. The radial artery and its
accompanying veins pass over it at its insertion into the radius.
ABDUCTOR POLLICIS LONGUS
EXTENSOR POLLICIS BREVIS'
ABDUCTOR POLLICIS BREVIS ^
OPP,ONENS POLLICIS
FLEXOR POLLICIS BREVIS
(superficial part)
ADDUCTOR POLLICIS (obliq
hes
\DDUCTOR POLLICIS (trans- ,
verse head)
ABDUCTOR
POLLICIS
FIRST
DORSAL
INTER-
OSSEOUS'
FIRST VOLAR
INTEROSSEOUS
SECOND DORSAL
INTEROSSEOUS
FIRST AND SECOND LUMBRICALS{
FIRST PHALANX
EXOR DIGITORUM SUBLIMIS TENDON
DIGITAL SHEATH --
PLEXOR DIGITORUM PROFUNDUS
TENDON
FLEXOR DIGITORUM PROFUNDUS
PRONATOR QUADRATUS
.. FLEXOR CARPI ULNARIS
PISIFORM BONE
HOOK OF OS HAMATUM
ABDUCTOR DIGITI QUINTI (cut)
- FLEXOR DIGITI QUINTI BREVIS (cut)
OPPONENS DIGITI QUINTI
THIRD VOLAR INTEROSSEOUS MUSCLE
-- FOURTH DORSAL INTEROSSEOUS MUSCLE
SECOND VOLAR INTEROSSEOUS MUSCLE
THIRD DORSAL INTEROSSEOUS MUSCLE
FLEXOR DIGITI QUINTI
BREVIS and ABDUCTOR
DIGITI QUINTI INSERTION
TENDONS OF THIRD AND
FOURTH LUMBRICALS
FIG. 350. THE PALMAR MUSCLES (Eight Side).
Nerve-Supply. Volar interosseous branch of the median nerve (C. 7. 8. T. 1.).
Action. The muscle acts along with the pronator teres in producing pronation of the
forearm.
SHORT MUSCLES OF THE HAND.
The short muscles belonging to the hand, in addition to the palmaris brevis
and the lumbrical muscles, already described, include the six muscles of the
392
THE MUSCULAE SYSTEM.
thumb which produce the thenar eminence, the three muscles of the little finger,
which form the hypothenar eminence, and the interossei muscles, which are
deeply placed between the metacarpal bones.
Muscles of the Thumb.
The short muscles of the thumb are the abductor, opponens, and flexor brevis
(with its deep portion, interosseus primus volaris), and the adductor muscle, sub-
divided into two heads oblique and transverse.
M. Abductor Pollicis Brevis. The abductor pollicis brevis (O.T. abductor
pollicis) arises by fleshy fibres from the tubercle of the navicular, the ridge of the
greater multangular, the volar surface of the transverse carpal ligament, and from
Capitate bone
Navicular bone
Abductor pollicis brevis (origin)
Opponens pollicis (origin)
Greater multangular bone
Abductor pollicis longus
(insertion)
Lesser multangular bone
Opponens pollicis (insertion)
Flexor carpi radialis
(insertion)
Adductor pollicis
(origin of oblique
9 head)
First dorsal interosseous muscle
(one origin)
First volar interosseous muscle
(origin)
Second dorsal interosseous
muscle (one origin)
Os lunatum
Os hamatum
Os triquetrum
Pisiform bone
Abductor digiti quinti (origin)
Flexor carpi ulnaris (insertion)
Flexor brevis digiti quinti
(origin)
Flexor carpi ulnaris (insertion)
Opponens digiti quinti
(origin and insertion)
Third volar inter-
osseous muscle
(origin)
Fourth dorsal interosseous
muscle (one origin)
Second volar interosseous
muscle (origin)
Adductor pollicis (origin
of transverse head)
Third dorsal interosseous
muscle (one origin)
FIG. 351. MUSCLE-ATTACHMENTS TO THE VOLAR ASPECT OF THE CARPUS AND METACARPUS.
tendinous slips derived from the insertions of the palmaris longus and abductor
pollicis longus muscles (Fig. 350, p. 391). Strap-like in form, and superficial in
position, it is inserted by a short tendon into the radial side of the first phalanx of
the thumb at its proximal end, and into the capsule of the metacarpo-phalangeal
joint.
Nerve-Supply. Median nerve (C. 6. 7.).
Actions. The muscle acts on the thumb at both the carpo-metacarpal and metacarpo-
phalangeal joints. It abducts and draws forward the thumb.
M. Opponens Pollicis. The opponens pollicis arises by fleshy and tendinous
fibres from the volar surface of the transverse carpal ligament and from the ridge
on the greater multangular bone. It is partially concealed by the preceding
muscle.
Extending distally and laterally it is inserted into the whole length of the
lateral border and the radial half of the volar surface of the first metacarpal bone i
(Fig. 351, p. 392).
SHOET MUSCLES OF THE HAND. 393
Nerve-Supply. Median nerve (C. 6. 7.).
Action. It acts solely on the first metacarpal bone, in the movement of opposition of the
thumb.
M. Flexor Pollicis Brevis. The flexor pollicis brevis consists of two parts.
a. The superficial part of the muscle, partly concealed by the abductor pollicis
brevis, arises, by fleshy and tendinous fibres, from the distal border of the transverse
carpal ligament, and sometimes from the ridge of the greater multangular.
It is inserted into the radial side of the base of the first phalanx of the
thumb, a sesamoid bone being present in the tendon of insertion.
b. The deep part of the muscle (interosseus primus volaris) arises from the
medial side of the base of the first metacarpal bone.
It is inserted into the medial side of the base of the first phalanx of the thumb
along with the adductor pollicis.
This little muscle is deeply situated in the first interosseous space, in the
interval between the adductor pollicis obliquus and the first dorsal interosseous
muscle. It may be regarded as homologous with the volar interossei muscles,
with which it is in series.
Nerve-Supply. Median nerve (C. 6. 7.).
Actions. It is a flexor of the thumb and assists also in the movement of opposition of the
thumb to the fingers.
M. Adductor Pollicis. The adductor pollicis is separated into two parts by
the radial artery.
(1) The oblique head lies deeply in the palm, covered by the tendons of the long
flexors of the thumb and fingers. It arises by fleshy fibres from the volar surfaces
of the greater and lesser multangular and capitate bones, from the sheath of the
tendon of the flexor carpi radialis, from the volar surfaces of the bases of the
second, third, and fourth metacarpal bones, and from the volar ligaments con-
necting these bones together (Fig. 351, p. 392).
It is inserted by a tendon, in which a sesamoid bone is developed, into the
medial side of the base of the first phalanx of the thumb. At its lateral border
a slender slip separates from the rest of the muscle, and passing obliquely, deep to
the tendon of the flexor pollicis longus, is inserted into the lateral side of the base
of the first phalanx along with the superficial part of the flexor pollicis brevis.
(2) The transverse head, lying deeply in the palm beneath the flexor tendons,
.arises by fleshy fibres from the medial ridge on the volar aspect of the body of the
third metacarpal bone, in its distal two-thirds (Fig. 351, p. 392), and from the fascia
covering the interosseous muscles in the second and third spaces.
Triangular in form, it is directed laterally, over the interossei muscles of the
first two spaces, to be inserted by tendon into the medial side of the base of the
first phalanx of the thumb along with the oblique head.
Nerve-Supply. Deep branch of the ulnar nerve (C. 8. (T. 1.)).
Actions. Adduction and opposition of the thumb.
Muscles of the Little Finger.
The short muscles of the little finger are the adductor, opponens. and flexor
brevis digiti quinti.
M. Abductor Digiti Quinti. The abductor digiti quinti is most superficial.
It arises from the pisiform bone and from the tendon of the flexor carpi ulnaris
and its ligamentous continuations (Fig. 351, p. 392).
It is inserted by tendon into the medial side of the base of the first phalanx of
the little finger.
Nerve-Supply. Deep branch of the ulnar nerve (C. 8. (T. 1.)).
Actions. The muscle separates the little finger from the ring finger, and assists in flexion of
the finger at the metacarpo-phalangeal joint.
M. Opponens Digiti Quinti. The opponens digiti quinti arises under cover
394
THE MUSCULAR SYSTEM.
of the preceding muscle, by tendinous fibres, from the transverse carpal ligament
and from the hamulus of the os hamatum.
It is inserted into the medial margin and medial half of the volar surface of the
fifth metacarpal bone in its distal
three-fourths (Fig. 351, p. 392).
Nerve -Supply. Deep branch of the
ulnar nerve (C. 8. (T. 1.)).
Action. The muscle acts only on the
metacarpal bone, drawing it forward, so as
to deepen the hollow of the hand.
M. Flexor Digit! Quinti Brevis.
The flexor digit! quint! brevis
may be absent or incorporated with
either the opponens or abductor digiti
quinti. It arises, by tendinous fibres,
from the transverse carpal ligament
and from the hamulus of the os
hamatum (Fig. 351, p. 392).
It is inserted along with the ab-
ductor into the medial side of the
first phalanx of the little finger.
Nerve -Supply. The deep branch of
the ulnar nerve (C. 8. (T. 1.)).
Actions. Flexion of the little finger
at the carpo-metacarpal and metacarpo-
phalangeal joints.
FIG. 352. THE VOLAR INTEROSSEOUS MUSCLES
(Right Side).
V 1 , first ; V 2 , second ; and V 3 , third volar interosseous
muscles.
The Interosseous Muscles.
The interosseous muscles of the hand occupy the spaces between the metacarpal
bones. They are arranged in two sets, volar and dorsal.
Mm. Interossei Volares. The volar (O.T. palmar) interossei are three in
Extensor carpi ulnaris (insertion)
Fourth dorsal interosseous
muscle (origin)
Third dorsal inter-
osseous muscle
(origin)
Extensor carpi radialis
brevis (insertion)
Extensor carpi radialis
/longus (insertion)
First dorsal inter-
osseous muscle
(origin)'
Second dorsal interosseous
muscle (origin)
FIG. 353. MUSCLE -ATTACHMENTS TO THE DORSAL ASPECT OF THE RIGHT METACARPUS.
number, occupying the medial three interosseous spaces. Each arises by a single head ;
the first from the medial side of the body of the second metacarpal bone ; the second
and third from the lateral sides of the bodies of the fourth and fifth metacarpal
MUSCLES ON THE DOBSAL SUBFACE OF THE FOBEABM. 395
bones respectively (Fig. 352, p. 394). Each ends in a tendon which is directed
distally behind the deep transverse metacarpal ligament, to be inserted into the
dorsal expansion of the extensor tendon, the capsule of the metacarpo-phalangeal
articulation, and the side of the first phalanx of the finger ; the first is inserted
into the medial side of the second finger ; the second and third into the lateral sides
of the fourth and fifth fingers. The deep part of the flexor pollicis brevis (inter -
osseus primus volaris) is to be regarded as the homologous muscle of the first
interosseous space.
Mm. Interossei Dorsales. The dorsal interossei are four in number. Each
arises by two heads from the sides of the metacarpal bones bounding each in-
terosseous space (Figs. 353, p. 394, and 354, p. 395).
Each forms a fleshy mass, ending in a membranous tendon which, passing
distally, behind the deep transverse metacarpal ligament, is inserted exactly like
the volar muscles into the dorsal aspect of each of the four fingers. The insertion
of the first dorsal interosseous muscle is into the lateral side of the index finger ;
the second muscle is attached to the lateral side of the middle finger ; the third
INSERTION OF FLEXOR
CARPI ULNARIS
ORIGINS OF
VOLAR INTER-
OSSEOUS MUSCLES
INSERTION OF
OPPONENS DIGITI
QUINTI
INSERTION OF
- ABDUCTOR DIGITI
QUINTI
ABDUCTOR POLLICIS BREVIS : origin (cut)
INSERTION OF FLEXOR CARPI RADIALIS
INSERTION OF OPPONENS POLLICIS
Lateral head of FIRST DORSAL
INTEROSSEOUS crossed by
INTEROSSECJS PRIMUS VOLARIS
ABDUCTOR POLLICIS BREVIS :
insertion (cut)
ADDUCTOR POLLICIS OBLIQUUS
(insertion)
ADDUCTOR POLLICIS TRANSVERSUS
(insertion)
FIRST DORSAL INTEROSSEOUS MUSCLE
SECOND DORSAL INTEROSSEOUS MUSCLE
THIRD DORSAL INTEROSSEOUS MUSCLE
FOURTH DORSAL INTEROSSEOUS MUSCLE
FIG. 354. DORSAL INTEROSSEOUS MUSCLES OF THE HAND (seen from the Volar Aspect).
muscle to the medial side of the same finger; and the fourth muscle to the medial
side of the ring finger.
The interosseous muscles of the hand in some cases have a disposition similar to
that of the corresponding muscles of the foot (p. 435).
Nerve-Supply. The deep branch of the ulnar nerve (C. 8. (T. 1.)).
Actions. -The interossei muscles act in a similar way to, and along with, the lumbricales,
flexing the fingers at the metacarpo-phalangeal joints, and extending them at the inter-
phalangeal joints. In addition, the dorsal interossei serve to abduct the fingers into which they
are inserted (fore, middle, and ring fingers) from the middle line of the middle finger ; the volar
muscles on the other hand are adductors of the fingers into which they are inserted (fore, ring,
and little finger) towards the middle line of the middle finger.
THE MUSCLES ON THE DORSAL SURFACE OF THE FOREARM.
The group of muscles occupying the lateral side of the elbow and the dorsal
surface of the forearm and hand include the supinator muscles of the forearm and
the extensors of the wrist and digits. They are divisible into a superficial and a
deep layer.
The superficial layer comprises seven muscles, which are in order, from the
radial to the ulnar side of the forearm, the brachioradialis, the two radial extensors
of the carpus, the extensor digitoruin communis and extensor digiti quinti proprius,
the extensor carpi ulnaris, and the anconseus.
396 THE MUSCULAE SYSTEM.
The deep muscles are five in number : one, the supinator, extends between
the proximal parts of the ulna and radius ; the others are the special extensors
of the thumb and forefinger, viz., the abductor pollicis longus, extensor pollicis longus
and extensor pollicis brevis, and extensor indicis proprius. They cover the dorsal
surface of the bones of the forearm and the interosseous membrane, and are almost
wholly concealed by the superficial muscles. Only the abductor pollicis longus and
the extensor pollicis brevis become superficial in the distal part of the forearm,
where they emerge between the radial extensors of the carpus and the extensor
digitorum communis.
Superficial Muscles.
M. Brachioradialis. The brachioradialis arises, by fleshy fibres, from the
anterior aspect of the proximal two-thirds of the lateral epicondylic ridge of the
humerus, and from the anterior surface of the lateral intermuscular septum
(Fig. 340, p. 380).
The muscle lies in the lateral side of the hollow of the elbow, passes distally
along the lateral border of the forearm, and ends about the middle of the forearm
in a narrow, flat tendon which is inserted, under cover of the tendons of the abductor
pollicis longus and extensor pollicis brevis, by a transverse linear attachment, into
the proximal limit of the groove for the above-named muscles on the lateral side
of the distal extremity of the radius. Some of its fibres gain an attachment
to the ridge on- the volar margin of the groove, and others spread over the surface
of the groove for a variable distance (Figs. 355, p. 397, and 348, p. 389).
Nerve-Supply. The muscle is supplied by a branch of the radial nerve (C. 5. 6.) in the
hollow of the elbow.
Actions. The muscle is primarily a flexor of the elbow-joint. It is also a semi -prona tor and
semi-supinator of the forearm, bringing the limb from the supine or prone position, into a
position in which the radius is uppermost. It thus assists both the pronator and supinator muscles.
M. Extensor Carpi Radialis Longus. The extensor carpi radialis longus
arises, by fleshy fibres, from the anterior aspect of the distal third of the lateral
epicondylic ridge of the humerus, from the anterior surface of the lateral inter-
muscular septum, and from the common tendon of origin of succeeding muscles,
attached to the lateral epicondyle (Figs. 356 and 357, p. 399).
In the distal half of the forearm, it ends in a tendon which passes beneath the
dorsal carpal ligament, to be inserted into the dorsal surface of the base of the
second metacarpal bone on its radial side (Fig. 353, p. 394).
The muscle is concealed in its proximal part by the brachioradialis, and its
tendon, in the distal half of the forearm, is crossed, obliquely, by the abductor pollicis
and by the extensor pollicis brevis.
Nerve-Supply. The muscle is supplied by a branch of the radial nerve in the hollow of the
elbow (C. (5.) 6. 7. 8.).
Actions. The muscle is an extensor of the wrist, and also an accessory flexor of the elbow-
joint.
M. Extensor Carpi Radialis Brevis. The extensor carpi radialis brevis
arises from the common tendon, from the radial collateral ligament of the elbow,
from the fascia over it, and from intermuscular septa on either side.
It passes distally, in the dorsal surface of the forearm and under the dorsal
carpal ligament, in close relation to the previous muscle, to be inserted, by a tendon,
into the bases of the second and third metacarpal bones (Fig. 353, p. 394). A
bursa is placed beneath the two radial extensor tendons close to their insertion.
It is practically concealed, in the forearm, by the extensor carpi radialis longus,
and in the distal half is crossed obliquely by the abductor pollicis longus and the
extensor pollicis brevis. The tendons of the two muscles are crossed, on the dorsum j
of the wrist, by the tendon of the extensor pollicis longus.
Nerve-Supply. The deep branch of the radial nerve (C. (5.) 6. 7. (8.)).
Actions. Like the long extensor, this muscle extends the hand at the wrist; and is a
subsidiary flexor of the elbow- joint.
MUSCLES ON THE DORSAL SURFACE OF THE FOREARM. 39'
Triceps braehii (insertion)
Biceps braehii (insertion)
Supinator muscle
(insertion)
Abductor pollicis longus
(origin)
Pronator teres
(insertion)
M. Extensor Digitorum Communis. The extensor digitorum communis
arises from the common tendon, from the lateral epicondyle of the hurnerus, from
the fascia over it, and fro,m -intermuscular septa on either side. Extending along
the dorsum of the forearm it ends, proximal to the wrist, in four tendons, of which
the most lateral often has a separate fleshy belly. After passing under the
dorsal carpal ligament, in a compartment along with the extensor indicis
proprius, the tendons separate on
the dorsum of the hand, where
the three most medial tendons are
joined together by two obliquely
placed bands. One passes distally
and laterally, and connects to-
gether the third and second ten-
dons ; the other is a broader and
shorter band, which passes also
distally and laterally, and joins
the fourth to the third tendon.
In some cases a third band is
present which passes distally and
medially from the first to the
second tendon ; and, frequently,
the tendon for the little finger is
joined to the tendon for the ring
finger, and separates from it only
a short distance above the distal
end of the metacarpal bone.
The tendons are inserted in
the following manner: On the
finger each tendon spreads out so
as to form a membranous expan-
sion over the knuckle and on the
dorsum of the first phalanx. The
border of the tendon is indefinite
over the metacarpo - phalangeal
articulation, of which it replaces
the dorsal ligament. On the dorsum
of the first phalanx the tendon
receives at its sides the insertions
of the interosseous and lumbrical
muscles. At the distal end of the
first phalanx it splits into ill-de-
fined median and collateral slips,
which pass over the dorsum of the
first inter-phalangeal articulation,
where they replace the dorsal
ligament. The median slip is
inserted into the dorsum of the carpi uin
base of the second phalanx, while
the two lateral pieces become
united to form a membranous
tendon on the dorsum of the
second phalanx, which, after passing over the second inter-phalangeal articula-
tion, is inserted into the base of the terminal phalanx.
The muscle is placed superficially in the forearm, between the extensors of the
carpus and the proper extensor of the little finger.
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. The muscle extends the elbow, wrist, and fingers. On account of the attachment
together of the tendons to the third, fourth, and fifth fingers by accessory bands in the dorsum of
the hand, these three fingers can only be fully extended together, while extension of the first finger
Flexor
digitorum
profundu
(origin)
Extensor pollicis brevis
(origin)
Brachioradialis
/(insertion)
Groove for tendons of
radial extensors of
carpus
Groove for extensor
pollicis longus
Groove for extensor digitorum com-
munis and extensor indicis proprius
FIG. 355. MUSCLE- ATTACHMENTS TO THE RIGHT RADIUS
AND ULNA (Dorsal Aspect).
398 THE MUSCULAK SYSTEM.
can take place separately. In extension of the inter-phalangeal joints, the muscle is aided by
the interossei and lumbrical muscles.
M. Extensor Digit! Quinti Proprius. The extensor digiti quinti proprius
has an origin, similar to and closely connected with that of the preceding muscle,
from the common tendon, the fascia over it, and from interrnuscular septa.
It passes along the dorsum of the forearm, as a narrow fleshy slip, between the
extensor digitoruin communis and the extensor carpi ulnaris, and ends in a tendon,
which occupies a groove between the radius and ulna in a special compartment
of the dorsal carpal ligament. On the dorsum of the hand the tendon, usually
split into two parts, lies on the medial side of the tendons of the extensor
digitorum communis, and is finally inserted into the expansion of the extensor
tendon on the dorsum of the first phalanx of the little finger.
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. The muscle extends the elbow, wrist, and little finger.
M. Extensor Carpi Ulnaris. The extensor carpi ulnaris has a double origin :
(1) from the common tendon from the lateral epicondyle of the humerus, from the
fascia over it, and from the inter muscular septa ; and (2), through the medium of
the deep fascia, from the dorsal margin of the ulna in its middle two-fourths.
Lying in the forearm upon the dorsal surface of the ulna, it ends in a tendon
which occupies a groove on the dorsal surface of the ulna in a special compartment
of the dorsal carpal ligament, and is inserted into the medial side of the base of
the fifth metacarpal bone (Fig. 353, p. 394).
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. The muscle is an extensor of the wrist, and at the same time, acting with the
flexor carpi ulnaris it is a powerful adductor of the wrist. Its humeral attachment makes it also
a subordinate extensor of the elbow-joint.
M. Anconseus. The anconaeus is a small triangular muscle. It arises, by a
separate tendon, from the distal part of the dorsal surface of the lateral epicondyle
of the humerus (Fig. 341, p. 380), and from the dorsal part of the capsule of
the elbow-joint.
It covers part of the dorsal surface of the elbow- joint and proximal part of
the ulna, and is inserted, by fleshy fibres, into a triangular surface on the lateral
aspect of the olecranon and dorsaLsurface of the ulna, as far distally as the oblique
line (Fig. 355, p. 397). It is also inserted into the fascia which covers it.
The epitrochleoanconseus is an occasional small muscle which arises from the dorsal surface
of the medial epicondyle of the humerus, and is inserted into the medial side of the olecranon.
It covers the ulnar nerve in its passage to the forearm.
Nerve-Supply. The muscle is supplied by the terminal branch of the nerve to the medial
head of the triceps muscle from the radial (C. 7. 8.).
Actions. The anconaeus is an extensor of the elbow.
Deep Muscles.
M. Supinator. The supinator muscle (O.T. supinator radii brevis) is the
most proximal of the deeper muscles. It is almost wholly concealed by the
superficial muscles, and has a complex origin, (1) from the lateral epicondyle
of the humerus ; (2) from the radial collateral, and annular ligaments of the
elbow-joint ; (3) from the triangular surface on the shaft of the ulna just distal
to the radial notch ; and (4) from the fascia over it.
From this origin the muscle spreads laterally and distally, enveloping the
proximal part of the radius, and is inserted into the volar and lateral surfaces of
the bone, as far forwards as the tubercle of the radius, as far proximally as the
neck, and as far distally as the oblique line and the insertion of the pronator teres
(Figs. 348, p. 389, and 355, p. 397).
The muscle is divisible into superficial and deep parts with humeral and ulnar
origins, between which the deep branch of the radial nerve passes in its course
to the dorsal part of the forearm.
MUSCLES ON THE DOKSAL SUKFACE OF THE FOKEAKM. .399
Nerve-Supply. The supinator is supplied by a branch from the deep branch of the radial
nerve, which arises from the nerve before the main trunk enters the muscle (C. 5. 6.).
Action. The muscle is an ex-tensor of the elbow, and the main supinator of the forearm.
In the latter action it is assisted by the biceps.
RICEPS
IACHII evr-r-
ENDON I
VCHIO-
DIALIS
LATERAL
ICONDYLE
)eep fascia of
the forearm
ANCON^EUS *.
ENSOR CARPI
RADIALTS
LONGUS
orsal margin
of ulna
ENSOR CARPI
RADIALIS
BREVIS
TENSOR DIOITORUM
COMMUNIS
EXTENSOR DIGITI
QUINT! PROPRIUS
EXTENSOR CARPI
TJLNARIS
SOR CARPI XJLNARIS ---
A.BDUCTOR POLLICIS
LONGUS
EXTENSOR INDICIS
PROPRIUS
SXTENSOR POLLICIS
BREVIS
3XTENSOR POLLICIS
LONGUS
tal carpal ligament -"tfi--
EXTENSOR CARPI )
RADIALIS LONGUS f
EXTENSOR CARPI \
RADIALIS BREVIS/
EXTENSOR CARPI )
ULNARIS /
TRICEPS
BRACHII
TENDON
BRACHIO- ,
RADIALIS
ORIGIN OF
SUPERFICIAL.
EXTENSOR
MUSCLES
ANNULAR LIGA-
MENT OK RADIUS
ANCON^EUS
EXTENSOR CARPI
RADIALIS LONGUS
Dorsal margin
of ulna
EXTENSOR CARPI Jr.
RADIALIS BREVIS 1
SUPINATOR. ,.M
MUSCLE
ABDUCTOR POLLICIS
LONGUS
DORSAL MARGIN OF ULNA
3. 356. SUPERFICIAL MUSCLES ON THE DORSUM
OP THE LEFT FOREARM.
EXTENSOR POLLICIS
LONGUS"
EXTENSOR INDICIS PROPRIUS- ---i^if
EXTENSOR POLLICIS BREVIS 1JL
Dorsal carpal ligament -ISp*
EXTENSOR CARPI \
RADIALIS LONGUS f "~
EXTENSOR CARPI \ ...
RADIALIS BREVIS /
EXTENSOR CARPI \ ..
ULNARIS/
EXTENSOR DIGITI )
QUINTI PROPRIUS /
EXTENSOR
POLLICIS LONGUS
EXTENSOR INDICIS
PROPRIUS"'
FIG. 357. DEEP MUSCLES ON THE DORSUM
OF THE LEFT FOREARM.
M. Abductor Pollicis Longus. The abductor pollicis longus (O.T. extensor
ossis metacarpi pollicis) arises by fleshy fibres, distal to the supinator muscle,
from the most proximal of the narrow impressions on the lateral half of the
dorsal surface of the ulna; from the middle third of the dorsal surface of
400 THE MUSCULAK SYSTEM.
the radius; and from the intervening portion of the interosseous membrane
(Fig. 355, p. 397).
Becoming superficial in the distal part of the forearm, along with the extensor
pollicis brevis, between the extensors of the wrist and the common extensor of the
fingers, its tendon passes, with the latter muscle, under cover of the dorsal carpal
ligament, to be inserted into the lateral side of the base of the first metacarpal bone
(Fig. 356, p. 399). From the tendon, close to its insertion, a tendinous slip passes
to the abductor pollicis brevis and the fascia over the thenar eminence, and
another is frequently attached to the greater multangular bone.
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. The muscle abducts the metacarpal bone of the thumb, and assists in abduction
and extension of the wrist
M. Extensor Pollicis Brevis. The extensor pollicis brevis (O.T. extensor
primi internodii pollicis), an essentially human muscle, is a specialised portion of
the previous muscle. It arises from a rhomboid impression on the dorsal surface of
the radius, and from the interosseous membrane, distal to the abductor pollicis
longus (Fig. 355, p. 397). It is closely adherent to that muscle, and accompanies it
deep to the dorsal carpal ligament and over the radial artery to the thumb.
Its tendon is then continued along the dorsal surface of the first metacarpal
bone, to be inserted into the dorsal surface of the base of the first phalanx of the
thumb. Before reaching its insertion the tendon helps to form the capsule of the
metacarpo-phalangeal joint.
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. The muscle extends the wrist and thumb (or the metacarpo-phalangeal joint),
and assists in abduction of the wrist and thumb.
3VL Extensor Pollicis Longus. The extensor pollicis longus (O.T. extensor
secundi internodii pollicis) arises from the lateral part of the dorsal surface of
the ulna, in its middle third, and from the interosseous membrane, distal to the
abductor pollicis longus (Fig. 355, p. 397). Its tendon grooves the dorsal surface
of the radius, and occupies a special compartment under cover of the dorsal carpal
ligament.
Extending obliquely across the dorsal surface of the hand, the tendon crosses
the radial artery, helps to form the capsule of the first metacarpo-phalangeal
articulation, and is inserted into the dorsal surface of the base of the second phalanx
of the thumb.
At the wrist the tendons of the muscles of the thumb, the abductor pollicis longus
and extensor pollicis brevis laterally, and the extensor pollicis longus medially,
bound a hollow (the " anatomical snuff-box ") best seen in extension and abduction
of the thumb, which corresponds to the position of the radial artery as it winds
round the wrist to reach the palm of the hand.
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. This muscle is an extensor and an abductor of the thumb, and of the wrist.
M. Extensor Indicis Proprius. The extensor indicis proprius (O.T. extensor
indicis) arises, distal to the extensor pollicis longus, from the most distal impression!
on the dorsal surface of the ulna, extending distally from the middle of the body!
to within two inches of its distal end, and sometimes also from the interosseoufl
membrane (Fig. 355, p. 397). Its tendon passes through a compartment of thel
dorsal carpal ligament along with the tendons of the extensor digitorum communis i
On the dorsum of the hand the 'tendon lies on the medial side of the tendon o:
the common extensor destined for the forefinger, and is inserted into the forefinger |
joining the membranous expansion of the tendon of the extensor digitorunn
communis on the dorsum of the first phalanx.
Nerve-Supply. The dorsal interosseous nerve (C. (5.) 6. 7. 8.).
Actions. The muscle is an extensor of the wrist and forefinger.
MUSCLES ON THE DOKSAL SUKFACE OF THE FOEEARM. 401
Actions of the Muscles of the Forearm and Hand.
These muscles are concerned 'in the movements of the elbow, wrist, and digits.
In the majority of cases the muscles act upon more than one joint.
1. Action on the Elbow-Joint. It has been shown already that flexion and extension
of the elbow are assisted by certain of these muscles. The flexor muscles are the pronator
teres, and the flexor muscles of the wrist and fingers. In the position of pronation, the move-
ment of flexion is aided by the brachioradialis and extensor muscles of the wrist and fingers.
The extensors are the supinator muscle and anconaeus, and the extensor muscles of the wrist and
fingers.
2. Pronation and supination of the hand are performed by special muscles, aided by muscles
which act also upon other joints. The brachioradialis assists in flexion and pronation on the one
hand, and in extension and supination on the other hand. In the supine position it assists
pronation, and in the prone position it assists supination, in each case bringing the hand into
the position intermediate between pronation and supination.
Pronation.
Supination.
Pronator teres
Pronator quadratus
Brachioradialis.
Flexor carpi radialis
Weight of the limb
Supinator
Biceps brachii
B rachioradialis
Extensors of thumb and fingers *
Weight of the limb
3. Action on the Wrist- Joint. The movements at the wrist-joint are flexion and extension,
abduction and adduction. Flexion and adduction are much more extensive movements than
extension and abduction, on account of the form of the wrist-joint. The following muscles pro-
duce these movements :
Flexion.
Extension.
Adduction.
Abduction.
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Long flexors of
thumb and fingers
Extensors of the wrist
Extensors of thumb
and fingers
Flexor carpi ulnaris
Extensor carpi ulnaris
Flexor carpi radialis
Extensors of wrist
Extensors of thumb
4. Movements of the Fingers. Two separate series of movements occur in relation to the
articulations of the fingers : flexion and extension (at the metacarpo-phalangeal and inter-
phalangeal joints), and abduction and adduction (only at the metacarpo-phalangeal joints). The
movements and the muscles concerned are given in the following tables :
Flexion.
Extension.
Flexor digitorum sublimis
Flexor digitorum profundus
Lumbricales \(acting on the metacarpo-
Interossei / phalangeal articulations)
Flexor digiti quinti brevis
Extensor digitorum communis
Extensor indicis proprius
Extensor digiti quinti proprius
Lumbricales \(acting on the inter -pha-
Interossei / langeal articulations)
Abduction.
Adduction.
Lumbricales ~\
Flexor brevis and 1 (from the medial side
Opponens, digiti | of the hand)
quinti J
( (from the middle
Dorsal interossei j line of the middle
[ finger)
/(to the middle line
Palmar interossei J of the middle
{ finger)
Flexion is more powerful and complete than extension of the fingers. The flexor digitorum
profundus alone acts on the terminal phalanges ; the flexor sublimis and flexor profundus together
flex the proximal inter-phalangeal joint ; and flexion of the metacarpo-phalangeal articulation is
effected by these muscles, assisted by the interossei, lumbricales, and flexor digiti quinti brevis.
Extension of the phalanges is effected by the united action of the extensors of the digits, the
interossei and lumbricales ; extension of the fingers at the metacarpo-phalangeal joints is produced
solely by the long extensor muscles. Separate extension of the index finger only is possible ; the
three inner fingers can only be flexed and extended together, on account of the connecting bands
joining the extensor tendons together on the back of the hand.
5. Movements of the Thumb. The movements of which the thumb is capable are flexion
27
402
THE MUSCULAK SYSTEM.
and extension (occurring at the carpo-metacarpal, metacarpo-phalangeal, and inter-phalangeal
joints) ; abduction and adduction, together with circumduction (occurring at the carpo-metacarpal
joint).
The muscles and their respective actions are given in the following table :
Flexion.
Extension.
Opponens pollicis { (carpo-metacarpal
Flexor brevis 1 (carpo-metacarpal and
Adductor r metacarpo-phalangeal
Abductor brevis J joint)
Flexor pollicis longus (all joints)
Abductor pollicis j (carpo-metacarpal
longus I joint)
^!^{<-S 5L
I geal joint)
Extensor pollicis longus (all joints)
Adduction.
Abduction.
Adductor of the thumb
Flexor pollicis brevis
Opponens pollicis
First dorsal interosseous
Abductor pollicis brevis
Extensors of the thumb
Circumduction a combination of the above muscles.
The characteristic features of the movements of the upper limb are their range and
refinement. The hand, in addition to its intrinsic powers, can be moved through a
wide range and in several planes by the muscles acting on the wrist and radio-ulnar
joints ; this range is increased by the fore and aft movements at the elbow- joint, and the
extensive movements of which the shoulder and clavicular joints are capable. The
result is that the hand can be brought into a position to cover and guard any portion
of the body. The precision and refinement of movement is made possible by the co-
ordinate movements of the various muscles acting upon the several joints, so that
actions can be performed (as raising the food to the mouth) in which all the articulations of
the limb are brought into play ; while others (such as writing) are possible by movements
at the joints of the wrist and ringers along with fixation of the elbow- joint.
THE LOWER LIMB.
FASCI/E AND MUSCLES OF THE THIGH
AND BUTTOCK.
FASCLffi.
The superficial fascia of the thigh and buttock is continuous above with the
fascia of the abdomen and back, medially with that of the perineum, and distally
with that of the leg. It presents noticeable features in the buttock and groin.
In the buttock the superficial fascia is of considerable thickness, and is usually
loaded with fat, whereby it assists in forming the contour of the buttock and the
fold of the nates.
In the groin it is divisible into two layers : a superficial fatty layer, continuous
with a similar layer on the anterior surface of the abdominal wall above, and over
the perineum medially, and a deeper membranous layer, which is attached above to
the medial half of the inguinal ligament, and to the deep fascia of the thigh just
distal to the lateral half of that ligament. Medially it is attached to the pubic
arch, and below the level of the femoral triangle it blends inseparably with the
superficial fatty layer. The separation of these two layers of the superficial fascia
is occasioned by the presence between them of the inguinal and superficial
subinguinal lymph glands, the great saphenous vein and its tributaries, and some
small arteries. The attachment of the deeper layer of the fascia to the pubic arch
and the inguinal ligament 'cuts off the superficial tissues of the thigh from the
perineum and the abdominal wall, and prevents the passage into the thigh of fluid
collected in the perineum or beneath the fascia of the abdominal wall.
FASCIA AND MUSCLES OF THE THIGH AND BUTTOCK. 403
The deep fascia or fascia lata forms a tubular investment for the muscles and
vessels of the thigh and buttock. It is firmly attached above to the iliac crest, the
sacro-tuberous ligament, the ischium, the pubic arch, the pubic symphysis and crest,
and the inguinal ligament. In the distal part of the thigh it forms the inter-
muscular septa ; and in relation to the knee, it is continuous with the deep fascia
of the leg, gains attachment to the patella, the condyles of the tibia and the head
of the fibula, and forms the collateral ligaments of the patella.
On the front of the thigh the deep fascia is thick and strong. It is pierced by
numerous openings for vessels and nerves, the most important of which is the fossa
ovalis (O.T. saphenous opening) for the passage of the great saphenous vein. A femoral
Linea alba ?
Lig. fundiforme pen
Subcutaneous
inguinal ring
Superior crus
Inferior crus
Spermatic funiculus
Internal spermati c
fascia
Dorsal vein of penis
Dorsal artery
Dorsal nervi
OBLIQUUS ABDOMINIS
EXTERNUS
Anterior superior
iliac spine
External oblique
aponeurosis
Superficial circum-
flex iliac artery
Intercrural fibres
( Attachment of mem-
< branous layer of
( superficial fascia
Poupart's inguinal
ligament
Superficial epigastric
artery
Superficial external
pudendal artery
Superficial sub-
inguinal lymph gland
Great saphenous
vein
FIG. 358. SUPERFICIAL ANATOMY OF THE LEFT GROIN.
hernia passes through this opening to reach the groin and anterior abdominal wall.
It is an oval opening, of variable size, situated just distal to the medial half of the
inguinal ligament, and immediately anterior to the femoral vessels. It is covered
by the superficial fascia, and by a special layer of fascia, the fascia cribrosa, a thin
perforated lamina attached to the margins of the opening. The lateral edge of the
opening (margo falciformis) is formed by the margin of the iliac portion of the
fascia lata, which is attached above to the iliac crest and the inguinal ligament ;
the medial edge is formed by the fascia pectinea which is continued proximally,
behind the femoral sheath, over the adductor longus and pectineus muscles to the
ilio-pectineal line and the capsule of the hip-joint. These two layers of the fascia
lata are continuous at the distal concave margin of the fossa ovalis, forming its
inferior cornu. As they pass proximally towards the pelvis they occupy different
27 a
404
THE MUSCULAE SYSTEM.
planes, the iliac portion being in front of the sheath of the femoral vessels, while
the pectineal fascia is behind it. The superior cornu of the fossa ovalis, placed
in front of the sheath, is derived solely from the iliac portion of the fascia lata. It
forms a strong triangular band of fascia known as the falciform margin, attached
above to the medial half of the inguinal ligament. It has an important share in
directing the course of a femoral hernia upwards on to the abdominal wall.
On the medial side of the thigh the fascia lata is thin where it covers the
adductor muscles. At the knee it is associated with the tendons of the vasti
muscles, and forms the collateral ligaments of the patella, attached to the borders of
the patella and to the condyles of the tibia. On the lateral side of the thigh it
OBLIQUUS ABDOMINIS
EXTERNUS (reflected)
Spermatic funiculi
Intercolumiiar fasc
OBLIQUUS ABDOMINIS
EXTERNUS
OBLIQUUS ABDOMINIS
INTERNUS
Superior anterior
iliac spine
TRANSVERSUS
ABDOMINIS
OBLIQUUS ABDOMINIS
INTERNUS (reflected)
Aponeurosis of obliquus
externus (reflected)
Abdominal inguinal ring
Spermatic funiculus and
infundibuliform fascia
Fascia transversalis
Inguinal aponeurotic
falx
-Fossa ovalb
Great saphenous vein
FIG. 359. THE DISSECTION OF THE LEFT INGUINAL CANAL.
forms the tractus iliotibialis a broad thick layer of fascia which is attached above
to the iliac crest, and receives the insertions of the tensor fasciae latse, and part of
the glutseus maximus muscles ; its distal attachment is to the capsule of the knee-
joint and the lateral condyle of the tibia. A strong band of fascia continued
proximally from the ilio-tibial tract, beneath the tensor fascise latse muscle, joins
the tendon of origin of the rectus femoris and the capsule of the hip-joint.
On either side of the thigh above the knee an intermuscular septum is formed.
The lateral intermuscular septum extends medially from the ilio-tibial tract to the
lateral epicondylic line and linea aspera of the femur, and gives attachment to
the vastus lateralis and vastus interrnedius anteriorly, and the short head of
the biceps posteriorly. The medial intermuscular septum in the distal third of the
thigh is associated with, and to a large extent represented by, the tendon of insertion
of the adductor magnus muscle. It is also related to the fascia which envelops the
MUSCLES OK THE ANTERIOE ASPECT OF THE THIGH. 405
adductor muscles, and forms the sheaths for the sartorius and gracilis muscles. In
the middle third of the thigh the fascia under the sartorius is greatly thickened by
transverse fibres and binds together the vastus medialis and adductor longus and
adductor inagnus muscles. This layer of fascia roofs over the femoral vessels in
their course through adductor canal (Hunter's).
The fascia lata of the buttock is thick anteriorly where it covers and gives
origin to the glutssus medius, thinner posteriorly over the glutseus maximus, at
the upper border of which it splits to enclose the muscle. It is thickened over
the greater trochanter, where it forms the insertion of the greater part of the
latter muscle.
On the posterior surface of the thigh and over the popliteal fossa the fascia is
strengthened by transverse fibres derived from the hamstring muscles. The
popliteal fascia forming the roof of the popliteal fossa is specially thick, and is
usually pierced by the small saphenous vein.
Femoral Sheath. This is a conical membranous investment, derived from
the fascial lining of the abdominal cavity, the fascia transversalis in front and the
fascia iliaca behind, prolonged along the femoral vessels in their passage behind
the inguinal ligament into the femoral triangle. The sheath is about an inch and
a half in length, and is divided into three compartments a lateral space for the
artery, an intermediate space for the vein, and a medial channel containing lymph
vessels and fat, and named the femoral canal. This canal is the passage through
which a femoral hernia enters the thigh. Its proximal limit is the femoral ring,
bounded anteriorly by the inguinal ligament, posteriorly by the origin of the
pectineus muscle from the pubis, medially by the ligamentum lacunare (Gimbernati)>
and laterally by the femoral vein. In front of it the fascia transversalis
forming the sheath is thickened to form the deep femoral arch. The part of
the inguinal ligament in front of the ring is called the superficial femoral arch.
The inferior epigastric artery separates the ring from the abdominal inguinal
ring. The canal ordinarily contains fat which is continuous above with the
extra -peritoneal tissue. The ring is filled by a plug of fat or a lymph gland,
constituting the femoral septum.
The femoral canal ends behind the fossa ovalis, covered by the fascia cribrosa,
while the falciform margin crosses over it and conceals its proximal portion.
The course of a femoral hernia is determined by this band. The hernia descends
through the femoral ring, pushing the femoral septum before it ; after passing through
the femoral canal, it is directed forwards through the fossa ovalis. The anterior
part of the hernia being pressed upon and retarded by the femoral arches, and by
the falciform margin, the posterior part pushes onwards, hooks round the falciform
margin, and is directed upwards over the inguinal ligament. The coverings of a
femoral hernia, in addition to peritoneum and extra-peritoneal tissue (femoral
septum), are femoral sheath, fascia cribrosa, superficial faspia, and skin.
MUSCLES OF THE THIGH AND BUTTOCK.
The muscles of the thigh and buttock are divisible into four main groups by
their situation, action, and nerve-supply. On the anterior surface of the thigh are
the quadriceps femoris, the sartorius, ilio-psoas, and pectineus muscles ; on the
medial side of the thigh are the adductor muscles; in the region of the buttock
are the glutaei and rotators of the hip-joint ; and on the posterior aspect of the
thigh are the hamstring muscles.
THE MUSCLES ON THE ANTERIOR ASPECT OF THE THIGH.
The chief muscle on the anterior aspect of the thigh is the quadriceps femoris,
which occupies the space between the tensor fascise latae and ilio-tibial tract
laterally, and the sartorius medially. The sartorius crosses the thigh obliquely ;
it separates the quadriceps femoris from the adductor muscles ; it forms in the
proximal third of the thigh the lateral boundary of the femoral triangle, and in
406
THE MUSCULAK SYSTEM.
the middle third of the thigh, the
roof of adductor canal (Hunter's).
The ilio-psoas, passing into the
thigh beneath the inguinal liga-
ment, assists, along with the
pectineus and adductor muscles,
in forming the floor of the femoral
triangle.
M. Sartorius. The sartor-
ius, a long strap-like muscle, arises
from the superior anterior spine
of the ilium and half of the margin
of the notch below it (Fig. 360).
It passes distally in the thigh,
across the medial side of the knee,
and is inserted, by aponeurotic
fibres, into the medial surface of
the body of the tibia just distal
to the medial condyle, and by
its borders into fascial expansions
which join the capsule and the
tibial collateral ligament of the
knee-joint, and the fascia lata of
the leg (Fig. 363, p. 408).
The sartorius is superficial in
its whole extent. Its proximal
third forms the lateral boundary
of the femoral triangle ; its middle
third forms the roof of the ad-
ductor canal ; and its distal third,
in contact with the medial side of
the knee, is separated from the
tendon of the gracilis muscle by
the saphenous nerve and the
saphenous branch of the arteria
genu suprema. A bursa lies be-
neath the tendon at its insertion.
Nerve -Supply. The sartorius is
supplied by two sets of nerves associated
with the two intermediate cutaneous
branches of the femoral nerve (L. 2. 3.).
Actions. The sartorius, " the
tailor's muscle," is a flexor of the hip
RECTUS FEMORIS and knee joints. It also everts the
thigh and assists in medial rotation of
the tibia.
M. Quadriceps Femoris.
The quadriceps femoris is com-
posed of four muscles the rectus
femoris, vastus lateralis, vastus
intermedius, and vastus medialis.
The rectus femoris is super-
ficial except at its origin, which
is covered by the glutsei, sartorius,
and tensor fasciae latse muscles.
The vasti lie on either side of
the rectus muscle, the vastus
lateralis being partially concealed
by the tensor fascise latse and ilio-tibial tract, the vastus medialis by the sartorius
ILIACUS
PSOAS MAJOR
TENSOR FASCIA
LAT^E
PECTINEUS
ADDUCTOR
LONGUS .
SARTORIUS
-Ilio-tibial tract
.GRACILIS
ADDUCTOR
MAGNUS
VASTUS
LATERALIS
RECTUS FEMORIS
VASTUS
MEDIALIS
TENDON OF
LlGAMENTUM
PATELLAE
FIG. 360. THE MUSCLES OF THE ANTERIOR ASPECT OF
THE EIGHT THIGH.
MUSCLES ON THE ANTERIOR ASPECT OF THE THIGH. 407
muscle. The vastus intermedius envelops the femur, and is concealed by the other
muscles.
M. Rectus Femoris. The rectus
femoris has a double tendinous origin. (1)
The straight head arises from the inferior
anterior spine of the ilium (Fig. 366, p. 412) ;
(2) the reflected head springs from a rough
groove on the dorsum ilii just above the
highest part of the acetabulum (Fig. 366,
p. 412). A bursa lies beneath this head of
origin. The two heads, bound together and
connected to the capsule of the hip-joint by
a band of fascia derived from the deep
surface of the tensor fasciae latse (ilio-tibial
tract), give rise to a single tendon which
extends, for some distance, on the anterior
surface of the muscle, and from which the
muscular fibres arise. The muscular fibres
springing from this tendon, and also from
a median septal tendon, present a bipennate
arrangement, and end below in a broad
tendon which passes proximally, for some
distance, along the posterior surface of the
muscle. This tendon gradually narrows
towards the knee, and spreading out again,
is inserted into the proximal border of the
patella. It receives laterally and medially
parts of the insertions of the lateral and
medial vasti muscles, and on its deep surface
is joined by the insertion of the vastus intermedius. A bursa, which communi-
cates with the synovial membrane of the knee-joint, lies between the tendon and the
front of the distal end of the shaft of the femur.
Vastus lateralis
(origin)
FIG. 361. MUSCLE-ATTACHMENTS TO THE AN-
TERIOR SURFACE OF THE PROXIMAL PART OF
THE LEFT FEMUR.
VASTUS MEDIALIS
Saplienous nerv
Femoral vessels
SARTORIUS
ADDUCTOR LONG
ADDUCTOR MAGNUS
GRACIL
RECTUS FEMORIS
VASTUS LATERALIS
VASTUS
INTERMEDIUS
Femur
BICEPS FEMORIS (short head)
SEMIMEMBRANOSU
BICEPS FEMORIS (long head)
SEMITENDINOSUS
Sciatic nerve
FIG. 362. TRANSVERSE SECTION OF THE THIGH (HUNTER'S ADDUCTOR CANAL).
M. Vastus Lateralis. The vastus lateralis has an origin, partly fleshy, partly
membranous, from (1) the capsule of the hip-joint, (2) the tubercle of the femur,
(3) a concave area On the anterior surface of the shaft of the bone medial to the
408
THE MUSCULAK SYSTEM.
(insertion)
Ligamentum patellae
rtion)
greater trochanter, (4) the distal border of the greater trochanter, (5) the lateral
margin of the gluteal tuberosity of the femur and the tendon of the glutseus
maximus, (6) the proximal half of the linea aspera, and (7) the fascia lata and
lateral intermuscular septum (Fig. 360, p. 406).
It forms a thick, broad muscle directed distally and forwards, and is inserted
by a broad membranous tendon into (1) the lateral border of the tendon of the
rectus femoris, (2) the proximal and lateral border of the patella, and (3) the
capsule of the knee-joint and the fibular collateral ligament of the patella.
A bursa intervenes between it and the membranous insertion of the glutaeus
maximus.
M. Vastus Medialis. The vastus medialis is larger than the vastus lateralis
and has a more extensive origin, from (1) the distal two- thirds or more of the spiral
line, the linea aspera, and the proximal
two -thirds of the line leading from
the linea aspera to the medial condyle
of the femur ; (2) the membranous ex-
pansion of the fascia lata which lies
beneath the sartorius and forms the
roof of the adductor canal ; and (3) the
Semi-membranosus , . , . ,
medial intermuscular septum and the
tendon of the adductor magnus (Figs.
359, p. 404, and 365, p. 410).
popiiteus (insertion) From its origin the muscle is
Attachment of tibiai coi- directed dis tally and laterally towards
lateral ligament of the knee the knee . ifc ig inserted by a gtrong
Graciiis (insertion) aponeurotic tendon into (1) the medial
border of the rectus tendon; (2) into
the proximal and medial border of
semi-tendinosus (insertion) the patella; and (3) the capsule of
the knee-joint and the collateral liga-
ment of the patella. The muscle con-
ceals the medial side of the body of
the femur and the vastus intermedius,
with which it is closely incorporated in
its distal two-thirds.
M. Vastus Intermedius. -- The
vastus intermedius muscle (O.T.
crureus) arises by fleshy fibres from
(1) the proximal two-thirds of the body
of the femur on the anterior and lateral
FIG. 363. MUSCLE- ATTACHMENTS TO THE MEDIAL SIDE surfaces but not the medial surface '
OF THE PROXIMAL PART OF THE RIGHT TlBIA. x O x ,-, -j , i v lr f ,v i ,
(2) the distal half of the lateral lip
of the linea aspera and the proximal part of the line leading therefrom to the
lateral condyle; and (3) a corresponding portion of the lateral intermuscular
septum (Fig. 359, p. 404).
For the most part deeply placed, the muscle is directed distally to an
insertion into the deep surface of the tendons of the rectus and vasti muscles by
means of fibres which join a membranous expansion on its surface. It is
closely adherent to the vastus lateralis muscle in the middle third of the
thigh ; it is inseparable from the vastus medialis below the proximal third.
In the distal third of the thigh it conceals the articularis genu muscle, a bursa,
and the proximal prolongation of the synovial membrane of the knee-joint.
M. Articularis Genu. The articularis genu (O.T. subcrureus) muscle consists
of a number of separate bundles of muscular fibres arising deep to the vastus
intermedius from the distal fourth of the anterior surface of the femur, and
inserted into the synovial membrane of the knee-joint.
The four elements composing the quadriceps femoris muscle have been traced
in their convergence to the patella. Their ultimate insertion is into the tubercle
of the tibia (Fig. 363), by means of the ligamentmn patellae, and the vasti
MUSCLES ON THE ANTEKIOK ASPECT OF THE THIGH. 409
muscles are in addition connected with the collateral ligaments of the patella. The
patella, indeed, is in one sense a sesamoid bone formed in the tendon of the muscle,
the ligamentum patellae 'being the real tendon of insertion, and the collateral
ligaments fascial expansions from its borders. The insertion of the muscle forms
the anterior part of the capsule of the knee-joint.
Middle arcuate ligament
Vena caval opening
OZsophageal opening in diaphragm
Aortic opening ^
Anterior ramus
of twelfth
thoracic nerve
Quadratus
lumborum
lio-hypogastric_
nerve
Ilio-inguinal-
Lateral
ataneous nerve-
of thigh
Femoral nerve
3enito-femoral
nerve 5
bturator nerve-
I lending branch
fourth lumbar'"
nerve
interior ram
)f fifth lumbar
nerve.
. ( Medial and
! lateral lumbo-
. I. costal arches
Ant. ramus of twelfth
ic nerve
.Quadratus
lumborum
-Ilio-hypogastric
nerve
-Ilio-inguinal
Psoas major
Gen ito- femoral
Lateral
.cutaneous nerve
of thigh
Obturator nerve
FIG. 364. THE VESSELS AND NERVES ON THE POSTERIOR ABDOMINAL WALL.
Nerve-Supply. The parts of the quadriceps extensor are supplied by separate branches of
the femoral nerve (L. 3. 4.).
Actions. The quadriceps muscle is the great extensor of the leg at the knee-joint. The
articularis genu draws proximally the synovial sheath of the joint during this movement.
The rectus femoris is in addition a flexor of the hip-joint. The straight head acts when
the movement begins ; the reflected 'head is tightened when the thigh becomes bent.
The ilio-psoas muscle is a compound muscle, consisting of two elements,
psoas (major and minor), connecting the femur and pelvic girdle to the axial
410
THE MUSCULAK SYSTEM.
Piriformis
(insertion)
Glutseus medius
(insertion)
obturator intemus and
skeleton; and another element, the iliacus, extending between the hip bone
and the femur. The. muscles chiefly occupy the posterior wall of the abdomen
and pelvis major, only their lower parts appear in the thigh below the inguinal
ligament, in the lateral part of the femoral triangle.
M. Psoas Major. The psoas major is a large piriform muscle, which has an
extensive origin, by fleshy fibres, from the vertebral column in the lumbar region.
It arises from (1) the intervertebral fibro-cartilages above each lumbar vertebra,
and the adjacent margins of the vertebrae from the inferior border of the 12th
thoracic to the superior border of the 5th lumbar vertebra ; (2) it arises also
from four aponeurotic arches which pass over the sides of the bodies of the
first four lumbar vertebrae ; and (3) it has an additional origin posteriorly from the
transverse processes of all the
lumbar vertebrae. The fibres form
a fusiform muscle which projects
over the superior aperture of the
pelvis and passes behind the
inguinal ligament, to end in a
tendon which is inserted into the
apex of the lesser trochanter of
the femur (-Fig. 365). A bursa,
which may be continuous with
the synovial cavity of the hip-
joint, separates the tendon from
the pubis and the capsule of the
hip-joint.
M. Psoas Minor. The psoas
minor (O.T. parvus) is often
absent (40 per cent). It arises
from the intervertebral fibro-car-
tilage between the last thoracic
and first lumbar vertebras, and
vastus medians (origin) from the contiguous margins of
those vertebras. The muscle is
closely apposed to the anterior
surface of the psoas major.
It forms a slender fleshy belly,
and is inserted, by a narrow tendon,
into the middle of the linea
terminalis and the ilio-pectineal
eminence, its margins blending
with the fascia covering the psoas
major.
M. . Iliacus. -- The iliacus
muscle arises in the pelvis major
by fleshy fibres, mainly from a horseshoe-shaped origin around the margin of the
iliac fossa ; it has additional origins also from the ala of the sacrum, the anterior
sacro-iliac, lumbo-sacral, and ilio-lumbar ligaments, and outside the pelvis, from
the proximal part of the capsule of the hip-joint (ilio-femoral ligament). It is
a fan-shaped muscle, and its fibres pass distally over the hip-joint towards the lesser
trochanter of the femur.
Lying lateral to the psoas muscle, it passes through the femoral triangle,
and is inserted by fleshy fibres (1) into the lateral side of the tendon of the psoas
major ; (2) into the concave anterior and upper surfaces of the lesser trochanter ;
and (3) into the body of the femur distal to the lesser trochanter for about an inch
(Fig. 365); and (4) by its most lateral fibres into the capsule of the hip-joint.
These fibres are often separate, forming the iliacus minor, or iliocapsularis.
Nerve-Supply. The psoas major is supplied directly by branches from the anterior rami of
the second and third lumbar nerves with additional branches in some cases from the first and fourth.
Glutseus maximus
(insertion)
Adductor niagnus
(insertion)
Adductor brevis
(insertion)
FIG. 365: MUSCLE- ATTACHMENTS TO THE POSTERIOR ASPECT
OF THE PROXIMAL PART OF THE LEFT FEMUR,
THE MUSCLES ON THE MEDIAL SIDE OF THE THIGH. 411
The psoas minor receives a nerve from the first or second lumbar nerve. The iliacus is
supplied by branches from the femoral nerve (L. 2. 3. 4.) within the abdomen.
Actions. The psoas minor assists the psoas major in flexing forwards and laterally the
vertebral column.
Besides this action the psoas major acts with the iliacus muscle as a flexor of the hip-joint.
With the thighs fixed the two muscles can draw the trunk downwards.
M. Pectineus. The pectineus muscle arises by fleshy fibres from, (1) the
sharp anterior portion of the linea terminalis of the pubis, and the triangular
surface of the pubic bone in front of the linea terminalis (Fig. 366, p. 412),
(2) the femoral surface of the ligamentum lacunare, and (3) the pectineal portion
of the fascia lata which covers it.
Forming a broad muscular band, which lies in the floor of the femoral triangle,
medial to the ilio-psoas, it is inserted by a thin flat tendon, about two inches in
length, into the proximal half of the pectineal line, leading from the back of
the lesser trochanter of the femur towards the linea aspera ; its distal attachment
being placed in front of the insertion of the adductor brevis muscle (Fig. 365,
p. 410). The muscle may be occasionally divided into medial and lateral parts,
the former innervated by the obturator, the latter by the femoral nerve.
Nerve-Supply. The pectineus is always supplied by a branch of the femoral nerve (L. 2. 3.)
which passes medially behind the femoral vessels to enter its lateral border. It receives in
some instances an additional nerve from the obturator, or when that is present, the accessory
obturator nerve.
Actions. The muscle is mainly an adductor of the hip-joint. It is also a flexor of the hip.
THE MUSCLES ON THE MEDIAL SIDE OF THE THIGH.
The muscles on the medial side of the thigh include the adductors of the femur
the adductor longus, adductor brevis, and adductor magnus ; the gracilis, and the
obturator externus.
The gracilis is superficially placed along the medial side of the thigh. The
adductor muscles are placed in the medial part of the thigh between the hip bone
and the femur, and in different vertical planes. The adductor longus is in the
same plane as the pectineus and lies superficially in the femoral triangle; the
adductor brevis, on a more posterior plane, is in contact with the obturator externus,
and along with it is largely concealed by the pectineus and adductor longus ; the
adductor magnus, the largest and most posterior of these muscles, is in contact
with the other adductors and the sartorius anteriorly, while its posterior surface
is in relation to the hamstring muscles on the back of the thigh.
M. Gracilis. The gracilis muscle is a long flat band placed on the medial
side of the thigh and knee. It arises by a tendon from the lower half of the edge
of the symphysis pubis, and for a similar distance along the border of the pubic
arch (Fig. 366, p. 412).
Its flattened belly passes distally, on the medial side of the thigh to the knee,
to end in a tendon, placed between the sartorius and semitendinosus, which expands
to be inserted into the medial surface of the body of the tibia just distal to the
medial condyle, behind the sartorius, and proximal to and in front of the
semitendinosus (Fig. 376, p. 420). It is separated from the sartorius tendon by
a bursa, and deep to its tendon is another bursa, common to it and the semi-
tendinosus. It is superficial in its whole extent.
Nerve-Supply. Obturator nerve (L. 2. 3.).
Actions. The gracilis has a threefold action. It adducts the thigh, and it flexes and rotates
medially the tibia.
M. Adductor Longus. The adductor longus is a triangular muscle which lies
in the floor of the femoral triangle and the floor of adductor canal (Hunter's). It
arises from the anterior surface of the body of the pubis in the angle between the
crest and symphysis (Fig. 366, p. 412).
It extends distally and laterally, it is inserted into the middle two-fourths
of the medial lip of the linea aspera in front of the adductor magnus.
412
THE MUSCULAR SYSTEM.
Nerve-Supply. Obturator nerve (L. 2. 3.).
Actions. The muscle adducts and assists in flexing the thigh.
M. Adductor Brevis. The adductor brevis is a large muscle which arises
from an elongated oval surface on the front of the body and upper part of the
inferior ramus of the pubic bone, surrounded by the other muscles of this group
(Fig. 366).
Directed distally and laterally the muscle expands, to be inserted, by a short
appneurotio tendon, behind the insertion of the pectineus, into the distal two-
thirds of the line leading from the lesser trochanter of the femur to the linea
aspera, and to the proximal fourth of the linea aspera itself (Fig. 365, p. 410).
Nerve-Supply. Obturator nerve (L. 2. 3. 4.).
Actions. The muscle adducts and flexes the thigh.
Kectus femoris (straight head of origin)
Rectus femoris (reflected head of origin)
Attachment of ilio-femoral ligament
Pyramidalis abdominis (origin)
\Rectus abdominis (origin)
Gracilis (origin)
Adductor brevis
(origin)
Semimembranosus
(origin)
Quadratus femoris
(origin)
Biceps and semitendin-
osus (origin)
FIG. 366. MUSCLE- ATTACHMENTS TO THE OUTER SURFACE OF THE EIGHT PUBIS AND ISCHIUM.
M. Adductor Magnus. The adductor magnus, the largest of the adductor
group, is a roughly triangular muscle. It arises, mainly by fleshy fibres, by a curved
origin from the lower part of the lateral border and a large portion of the adjoin-
ing inferior surface of the sciatic tuberosity, from the edge of the inferior ramus i
of the ischium, and from the anterior surface of the inferior ramus of the pubic i
bone, its most anterior fibres arising between the obturator externus and adductor
brevis (Fig. 366). Its upper fibres are directed horizontally and laterally froni'
the pubic bone towards the proximal part of the femur; the lowest fibres are,
directed distally from the sciatic tuberosity to the medial condyle of the femur j
while the intermediate, fibres radiate obliquely laterally and distally.
The muscle is inserted by tendinous fibres (1) into the space distal to the
insertion of the quadratus femoris, proximal to the linea aspera; (2) into thffi
THE MUSCLES ON THE MEDIAL SIDE OF THE THIGH. 413
whole length of the linea aspera; (3) into the medial epicondylic line of the
femur ; (4) into the adductor tubercle on the medial condyle of the femur :
and (5) into the medial ' intermuscular septum (Fig. 365, p. 410). The part of
the muscle attached to the space proximal to the linea aspera is often separated
from the rest as the adductor minimus. The attachment of the muscle to the
epicondylic ridge is interrupted for the passage of the femoral vessels into the
popliteal fossa. The attachment to the medial condyle is by means of a strong
tendon which receives the fibres arising from the ischium (the part of the muscle
associated with the hamstring group). This tendon is closely connected with the
tibial collateral ligament of the knee-joint.
The muscle is covered, anteriorly, by the other adductors and by the sartorius
muscle. The profunda femoris artery separates it from the adductor longus muscle,
Obturator nerve
Pubis
PSOAS MAJOR
Branch to hip-joint
Deep branch
Superficial branch
Descending muscular branches
PECTINEUS
Ascending branch to obturator
extern us
Medial circumflex artery
ADDUCTOR LONGUS
ADDUCTOR BREVIS
Cutaneous brand
PlRIFORMIS
GLUT^EUS MAXIMUS
Pelvic fascia
OBTURATOR INTERNUS
OBTURATOR EXTERNUS
Ischium
Deep branch of medial circum-
flex artery of femur
QUADRATUS FEMORIS
Superficial branch of medial
circumflex artery
Descending muscular branches
ADDUCTOR MAGNUS
Branch to knee-joint
Branch to femoral artery GRACILIS
FIG. 367. SCHEME OP THE COURSE AND DISTRIBUTION OF THE RIGHT OBTURATOR NERVE.
while the femoral artery is in contact with the muscle as it pursues its course
through the adductor canal. The posterior surface of the muscle is in relation
with the hamstring muscles.
Nerve-Supply. The adductor magmis is a double muscle, and has a double nerve-supply.
The medial part of the muscle extending between the tuber ischiadicum and the medial condyle
of the femur, associated with the hamstring group of muscles, derives its nerve from the nerve
to the hamstring muscles, from the tibial nerve (L, 4. 5. S. 1.). This enters the muscle on its
posterior surface.
The adductor portion of the muscle is supplied on its anterior surface by the deep branch of
the obturator nerve (L. 3. 4.).
Actions. The adductor magnus is an adductor and extensor of the thigh.
M. Obturator Externus. The obturator externus is placed deeply, under
cover of the previous muscles. It is a fan-shaped muscle lying horizontally in the
angle between the hip bone and the neck of the femur.
It arises from the surfaces of the pubic bone and ischium, which form the
inferior half of the margin of the obturator foramen, and from the corresponding
414
THE MUSCULAE SYSTEM.
portion of the superficial surface of the obturator membrane (Figs. 366 p 412
and 367, p. 413).
Its fibres converge towards the greater trochanter, and end in a stout tendon
which, after passing distal to
and posterior to the hip-joint,
sacro-tuber- is inserted into the trochan-
ment ga " teric fossa of the greater tro-
^Axmus 8 chanter of the femur (Figs.
OBTURATOR 365, p. 410, and 373, p. 417).
"INTERN us
BICEPS AND
...-SEMITENDIN-
SEMIMEM-
BRANOSUS
QUADRATUS
FEMORIS
Nerve-Supply. The deep part
of the obturator nerve (L. 3. 4.).
Actions. This muscle is mainly
a lateral rotator of the thigh ; it
also flexes and addticts it.
ADDUCTOR
MAGNUS
Trigonum Femorale.
The femoral triangle (O.T.
Scarpa's triangle) is a large
triangular space on the front
of the thigh in its proximal
third, which contains the
femoral vessels in the proximal
part of their course and the
femoral nerve. It is bounded
above by the inguinal liga-
ment, laterally by the sartorius,
Fascia lata and medially by the medial border of
the adductor longus muscle. Its floor
is formed laterally by the ilio-psoas, and
medially by the pectineus, adductor
longus, and a small part of the adductor
brevis.
Canalis Adductorius Hunteri.
The adductor canal (O.T. Hunter's
BICEPS canal) lies in the middle third of the
-(short head) me( ji a i g^e of the thigh, and contains the
femoral vessels in the distal part of their
course. It is bounded superficially by the
sartorius, under which is a dense fascia
-(longhead) derived from the fascia lata, binding to-
gether the vastus medialis, which forms
the lateral wall of the canal, and the
adductors, longus and magnus, which form
the medial wall or floor of the canal. Be-
sides the femoral vessels and their sheath,
the canal contains the saphenous nerve.
-GRACILIS
SEMIMEM-
BRANOSUS
THE MUSCLES OF THE
BUTTOCK.
This group includes the three glutaei
muscles, the tensor fasciae latse, piriformis,
obturator internus and gemelli, and quad- 1
ratus femoris.
The glutseus maxinius and tensor fasciae
latse muscles are in the same plane, invested by envelopes of the fascia lata.
The glutaeus medius, partially covered' by the glutseus maximus, conceals the glutasusl
minimus ; while the piriformis, obturator internus, gemelli, and quadratus femoris I
intervene between the glutaeus maximus and the posterior surface of the hip-joint, j
FIG. 368. DEEP MUSCLES ON THE POSTERIOR
ASPECT OF THE RIGHT THIGH.
THE MUSCLES OF THE BUTTOCK.
415
M. Glutaeus Maximus. The glutaeus maximus is a large quadrilateral muscle,
i with a crescentic origin. It arises from, (1) a portion of the area on the dorsum
ilii above the posterior gluteal line (Fig. 369); (2) the tendon of the sacro-
I spinalis muscle ; (3) the dorsal surface of the sacrum and coccyx (Fig. 395,
p. 443); and (4) the posterior surface of the sacro-tuberous ligament. The fibres
which form its superior and lateral border take origin directly from the fascia lata
which envelops the muscle.
The muscle forms a large fleshy mass, whose fibres are directed obliquely over
the buttock, invested by the fascia lata, and are inserted, by short tendinous fibres,
partly into the fascia lata over the greater trochanter of the femur (joining the
ilio-tibial tract), and partly into the gluteal tuberosity (Fig. 3*70, p. 416). The
fascia lata receives the insertion of the whole of the superficial fibres of the muscle
j and the superior half of the deep fibres. The inferior half of the deep portion of
Obliquus externus abdominis
(insertion)
Glutseus maximus
(origin)
Tensor fasciae latse
(origin)
Sartorius (origin)
Rectus femoris (reflected^head
of origin)
Gemellus superior (origin)
Gemellus inferior (origin)
Semimembranosus (origin)
Biceps and semitendinosus (origin)
Quadratus femoris (origin)
Obturator externus (origin)
Adductor magnus (origin)
^H^ -.
Adductor magnus (origin) .
FIG. 369. MUSCLE-ATTACHMENTS TO THE RIGHT DORSUM ILII AND TUBER ISCHIADICUM.
he muscle is inserted, for the most part, into the gluteal tuberosity ; but the most
nferior fibres of all are inserted into fascia lata, and are thereby connected with
he lateral intermuscular septum and the origin of the short head of the biceps.
The glutseus maximus is the coarsest and heaviest muscle in the body. By its
weight it helps to form the fold of the nates. It is superficial in its whole extent,
ihe glutaeus medius is visible at its superior border, covered by the fascia lata ; at
ts lower border the hamstring muscles and sciatic nerve appear on their way to
he thigh. Three bursse are deep to it : one (not always present) over the sciatic
uberosity, a second over the lateral side of the greater trochanter, and a third
ver the vastus lateralis. The fibres of the glutseus maximus arising from the
occyx may form a separate muscle (agitator caudse).
Nerve-Supply. Inferior gluteal nerve, from the sacral plexus (L. 5. S. 1. 2.).
Actions. The glutaeus maximus is mainly an extensor of the thigh, and has a powerful
ction in straightening the lower limb, as in climbing or running. Its lower fibres also adduct
he thigh and rotate it laterally.
M. Tensor Fasciae Latse. The tensor fasciae latae arises from the iliac crest
416
THE MUSCULAE SYSTEM.
Piriformis (insertion)
Glutseus inedius
(insertion)
Obturator interims and
gemelli (insertion)
Obturator externus
(insertion)
Quadratus feraoris
(insertion)
Ilio-psoas (insertion)
Glutaeus raaximus
(insertion)
Adductor magnus
(insertion)
Adductor brevis
(insertion)
Pectineus (insertion)
Vastus medialis
(origin)
and the dorsum ilii just lateral to
the superior anterior spine, and
from the fascia covering its lateral
surface (Fig. 369, p. 415).
Invested, like the glutaeus
maximus, by the fascia lata, it is
inserted, distal to the level of the
greater trochanter of the femur,
into the fascia, which forms the
ilio-tibial tract (p. 404). The
muscle is placed along the an-
terior borders of the glutaeus
medius and gluteeus minimus.
Nerve - Supply. The superior
gluteal nerve from the sacral plexus
(L. 4. 5. S. 1.) ends in this muscle after
passing between the glutseus medius and
glutaeus minimus.
Actions. It assists in the abduction
and rotation of the thigh ; and along
with the glutseus maximus, by its in-
sertion into the ilio-tibial tract, it helps
to support the knee-joint in the extended position.
M. Glutaeus Medius. The glutaeus
medius arises from (1) the dorsum ilii, be-
tween the iliac crest and posterior gluteal
line above and the anterior gluteal line
below (Fig. 369, p. 415), and (2) the strong
fascia lata covering its surface anteriorly.
It is a fan-shaped muscle, its fibres con-
FIQ. 370. MUSCLE - ATTACHMENTS TO THE
POSTERIOR ASPECT OF THE PROXIMAL
PART OF THE LEFT FEMUR.
verging to the greater tro-
chanter, to be inserted by a
strong, short tendon into the
postero-superior angle of the
greater trochanter, and into
a well-marked diagonal line
on its lateral surface (Fig.
370, and Fig. 372, p. 417).
A bursa is placed deep to the
tendon at its insertion.
The muscle is partly super-
ficial, partly concealed by the
glutseus maximus. It covers
the glutseus minimus, and the
superior gluteal nerve and the
deep branches of the superior
gluteal artery.
Nerve -Supply. The superior
gluteal nerve from the sacral plexus
(L. 4. 5. S. L).
Actions. This muscle is a
powerful abductor and medial
rotator of the thigh.
M. Glutaeus Minimus.
The glutaeus minimus arises,
under cover of the glutseus
THE LUMBAB
TRIANGLE
OF PETIT
Fascia lata
GLUT^EUS MAXIMUS
GRACILIS
ADDUCTOR MAGNUS
SEMIMEMBRANOSUS
SEMITENDINOSUS Bt
Sciatic nerve
BICEPS (long
head)
FIG. 371. THE RIGHT GLUTAEUS MAXIMUS MUSCLE.
THE MUSCLES OF THE BUTTOCK.
417
medius, by fleshy fibres, from the dorsum ilii between the
gluteal lines (Fig. 369, p. 415).
This muscle is fan-shaped and its fibres converge to the
of the greater tro-
chanter, to be inserted
into the anterior sur-
face of the trochanter,
and sometimes also
into the front part of
the superior border
(Figs. 361, p. 407,
and 373). It is also
inserted into the cap-
sule of the hip-joint.
A bursa is placed
deep to the tendon in
Prrmf nf fVio (TY-onfov Pudendal nerve
ront oi tne greater Nerve to obturator
trochanter. interims
Nerve -Supply.
The superior gluteal
nerve from the sacral
plexus (L. 4. 5. S. 1.).
Actions. The mus-
cle is primarily an ab-
ductor of the thigh. Its
anterior fibres in addition
produce medial rotation
and its posterior fibres
lateral rotation of the
limb.
anterior and inferior
antero-superior angle
GRACILIS
ADDUCTOR MAGNUS
HAMSTRING MUSCLES
(biceps)
Superior gluteal nerve
GLUT.EUS MEDIUS (cut)
__ Inferior gluteal nerve
PlRIFORMIS
OBTURATOR INTERNUS
AND GEMELLI
OBTURATOR EXTERXUS
UADRATUS FEMORI3
Sciatic nerve
(and subdivisions)
Posterior cutaneous
'nerve of thigh
GLUT^US MAXIMUS
(insertion)
ADDUCTOR MAGNUS
FIG. 372. THE MUSCLES AND NERVES OF THE RIGHT BUTTOCK.
The glutseus maximus is reflected ; and the glutaeus medius is cut, in part, to
show the glutaeus minimus.
Glutseus minimus
(insertion)
Piriformis
(insertion)
M. Piriformis.
The piriformis is
one of the few mus-
cles connecting the
lower limb to the
axial skeleton. It arises (1) within the pelvis from the roots of the vertebral
arches of the second, third, and fourth sacral vertebrae, and from the adjacent
part of the bone lateral to the anterior sacral foramina. Passing out through
the greater sciatic foramen, it receives an origin from (2) the upper margin of the
greater sciatic notch
Obturator internus and gemelli (insertion) ^s^tf^B^^^ of the ilium, and (3)
the pelvic surface of
the sacro-tuberous
ligament.
In the buttock it
forms a rounded ten-
don, which is inserted
into a facet on the
superior border and
medial aspect- of the
greater trochanter of
the femur (Figs. 370,
p. 416, and 373).
FIG. 373. MUSCLE-ATTACHMENTS TO THE PROXIMAL ASPECT OF THE GREATER T-L _ wlVv,-YYiia af
TROCHANTER OF THE LEFT FEMUR. lhe . P mloimls >
its origin, covers part
of the inner surface of the posterior wall of the pelvis minor. In the buttock
it is covered by the glutseus maximus, and lies behind the capsule of the hip-joint,
between the glutseus medius and superior gemellus.
Nerve -Supply. Branches direct from the anterior rami of the first and second sacral
nerves.
28
Obturator externus
(insertion)
418 THE MUSCULAK SYSTEM.
Actions. The muscle is an abductor and lateral rotator of the hip.
M. Obturator Interims. The obturator internus arises on the pelvic aspect
of the hip bone, from (1) the whole of the margin of the obturator foramen
(except the obturator notch) ; (2) the surface of the obturator membrane ; (3)
the whole of the pelvic surface of the hip bone behind and above the obturator
foramen ; and (4) the parietal pelvic fascia covering it medially.
It is a fan-shaped muscle. Its fibres converge to the lesser sciatic foramen,
and end in several tendons, united together, which hook round the margin of the
foramen (a bursa intervening), and after passing over the posterior surface of the
hip-joint, are inserted into a facet on the medial surface of the greater trochanter of
the femur above the trochanteric fossa (Figs. 370, p. 416, and 373, p. 417).
In the pelvis minor the muscle occupies the side wall, covered by the parietal
pelvic fascia, which separates it from the pelvic cavity above and the ischio-rectal
fossa below. In the buttock the tendon is embraced by the gemelli muscles which
are attached to its superior and inferior margins.
The gemelli muscles form accessory portions of the obturator internus.
M. Gemellus Superior. The superior gemellus arises from the gluteal surface
of the ischial spine (Fig. 369, p. 415).
It is inserted into the upper margin and superficial surface of the tendon of the
obturator internus muscle.
M. Gemellus Inferior. The gemellus inferior arises from the superior part of
the gluteal surface of the ischial tuberosity (Fig. 369, p. 415).
It is inserted into the inferior margin and superficial aspect of the tendon of
the obturator internus.
Nerve-Supply. The obturator internus and superior gemellus receive branches from a special
nerve, the nerve to the obturator internus from the anterior aspect of the sacral plexus (S. 1. 2. 3.).
The inferior gemellus is supplied by the nerve to the quadratus femoris, a branch derived also
from the anterior aspect of the sacral plexus (L. 4. 5. S. 1.).
Actions. The obturator internus and gemelli are abductors and lateral rotators of the hip.
M. Quadratus Femoris. The quadratus femoris arises from the lateral
margin of the tuber ischiadicum (Figs. 366, p. 412, and 369, p. 415). It is inserted
into the quadrate tubercle and quadrate line of the femur (Fig. 370, p. 416).
The muscle is concealed by the glutaeus maximus and the hamstring muscles.
Its anterior surface is in contact with the obturator externus muscle and the lesser
trochanter of the femur, a bursa intervening. The muscle is not infrequently
fused with the adductor magnus.
Nerve-Supply. A special nerve from the sacral plexus (L. 4. 5. S. 1.) which enters its
deep (anterior) surface.
Actions. The muscle is an adductor and lateral rotator of the thigh.
THE MUSCLES ON THE POSTERIOR ASPECT OF THE THIGH.
The Hamstring Muscles.
The muscles comprised in this series include the biceps, semitendinosus, am
semimembranosus. A part of the adductor magnus, already described, also belongs,
morphologically, to this group. They lie in the buttock and posterior aspect of
the thigh, and diverge at the knee to bound the popliteal fossa. The origins of
the muscles are concealed by the glutseus maximus. In the back of the thigh,
enveloped by the fascia lata, they are placed behind the adductor magnus th<
semitendinosus and semimembranosus medially, the biceps laterally. The forme]
two muscles help to form the medial boundary of the popliteal fossa, of which the
biceps is a lateral boundary.
M. Biceps Femoris. The biceps femoris has a double origin. (1) Its loi
head arises, by means of a tendon, in common with the semitendinosus, froi
the inferior and medial facet upon the sciatic tuberosity (Figs. 366, p. 41!
and 369, p. 415) and from the sacro-tuberous ligament. This head, united for
THE MUSCLES ON THE POSTEEIOK ASPECT OF THE THIGH. 419
distance of two or three inches with the semitendinosus, forms a separate fleshy
mass, which extends to the distal third of the thigh, to end in a tendon joined by
the short head of the muscle. (2) The short head arises separately from, (1) the
whole length of the lateral lip of the linea aspera and the proximal two-thirds
of the lateral epicondylic line of the femur, and (2) the lateral intermuscular
septum. The proximal limit of its origin is sometimes blended with the insertion
of the lowest fibres of the glutseus maximus.
The fibres of the short head, directed distally, join the tendon of the long
head, and the muscle is inserted (1) into the head of the fibula by a strong tendon,
which is split into two parts by the fibular collateral ligament of the knee-joint ;
(2) by a slip attached to the lateral condyle of the tibia ; and (3) along its posterior
border by a fascial expansion which connects the tendon with the popliteal fascia.
, Obliquus externus abdominis
(insertion)
Glutteus maximus
(origin)
Rectus femoris (reflected
head of origin)
Gemellus superior (origin)
Gemellus inferior (origin)
Semimembranosus (origin)
Biceps and semitendinosus (origin)
Quadratus femoris (origin)
Obturator externus (origin)
Adductor magnus (origin)
Adductor magnus (origin)
FIG. 374. MUSCLE- ATTACHMENTS TO THE RIGHT DORSUM ILII AND TUBER ISCHIADICUM.
There is a bursa between the tendon and the fibular collateral ligament of the
knee-joint.
The short head may be absent : there may be an additional origin from the
ischium or femur ; and the long head may send a slip to the gastrocnemius or tendo
calcaneus (Achillis) (tensor fasciae suralis).
M. Semitendinosus. The semitendinosus arises, in common with the long
head of the biceps, from the inferior and medial facet upon the ischial tuberosity
(Fig. 374, p. 419). Separating from the common tendon, two or three inches
from its origin, the muscle forms a long, narrow band which becomes tendinous
in the middle third of the thigh.
Passing over the medial side of the knee it spreads out and becomes membranous,
and is inserted (1) into the medial side of the body of the tibia just distal to
the medial condyle, distal to the gracilis and behind the sartorius (Fig. 3*76,
p. 420), and (2) into the deep fascia of the leg. A bursa separates it from the
sartorius superficially, and another, common to it and the gracilis, lies deep to its
insertion. The belly of the muscle is marked by an oblique septal tendinous
intersection about its middle.
420
THE MUSCULAE SYSTEM.
OBTURATOR
INTERNUS
Nerve-Supply. The semitendinosus is supplied by two branches from the nerve to the
hamstring muscles (L. 5. S. 1. 2.)
Actions. A flexor of the knee, a medial rotator of the tibia, and an extensor of the hip.
M. Semimembranosus. The semimembranosus arises by a tendon from the
superior and lateral facet on the ischial
tuberosity (Figs. 366, p. 412, and 374,
p. 419). In the proximal third of the
thigh the tendon gives place to a
rounded fleshy belly, which lies an-
terior to the ischial portions of the
biceps and semitendinosus muscles.
Becoming tendinous, at the back
of the knee, it is inserted into the
QUADRATUS horizontal groove on the postero-
medial aspect of the medial condyle
sciatic nerve f the tibia (Figs. 376, below, and
384, p. 428). A bursa lies deep to
the tendon at its insertion. It has
three additional membranous inser-
tions : (1) a fascial band extends
distally and medially to join the
posterior border of the tibial collateral
ligament of the knee-joint; (2) an-
other fascial band extends distally
GRACILISI
ADDUCTOR MAGNUS
SEMITENDINOSUS.
EXTERNUS
GLUT x. us
MAXIMUS
ADDUCTOR
MAGNUS
BICEPS (long
head)
SEYIIMEMBRANOSUf
SARTORIUS TENDON
BICEPS (short
head)
Tibial nerve
BICEPS TENDON
(with common
peroneal
nerve)
PLANTARIS
GASTRO-
CNEMIUS
FIG. 375. THE MUSCLES ON THE POSTERIOR
ASPECT OF THE RIGHT THIGH.
imembran-
i (insertion
Ligamentum
patellae (insertion)
Popliteua (insertion)
Attachment of
tibial collateral
ligament
Gracilis (insertion)
Semitendinosus
(insertion)
FIG. 376. MUSCLE- ATTACHMENTS TO THE MEDIAL
SURFACE OF THE PROXIMAL PART OF THE
RIGHT TIBIA.
and laterally, forms the fascia covering the popliteus muscle (popliteus fascia), and
is attached to the oblique line of the tibia ; and (3) a third strong band extends
proximally and laterally to the back of the lateral condyle of the femur, forming
the oblique popliteal ligament of the knee-joint.
THE MUSCLES ON THE POSTEEIOE ASPECT OF THE THIGH. 421
The membranous origin of the muscle is concealed by the proximal parts of the
semitendinosus and long, head of the biceps. The insertion covers the origin of
the inner head of the gastrocnemius.
Nerve- Supply. It is innervated by the nerve to the hamstring muscles (L. 5. S. 1. 2.).
Actions. A flexor of the knee, a medial rotator of the tibia, and an extensor of the hip.
Actions of the Muscles of the Thigh and Buttock.
Most of the above muscles act on the pelvis and on the hip- and knee-joints. The psoas
major muscle in addition assists in the movements of the vertebral column (p. 411).
1. Movements at the Hip- Joint. The movements of the thigh at the hip-joint are flexion
and extension, adduction and abduction, medial and lateral rotation. The following table
gives the muscles producing these movements :
a. Flexion and Extension.
Sartorius
Iliacus
major
Rectus femoris
Pectineus
Adductor longus
Gracilis
Obturator externus
Glutaeus maximus
medius
minimus
Biceps femoris
S emitendinosus
S emimembranosus
Adductor magnus
b. Adduction and Abduction.
Pectineus
Adductor longus
brevis
,, magnus
Gracilis
Quadratus femoris
Glutseus maximus
(lower fibres)
Tensor fasciae latae
Glutaeus medius
minimus
Obturator externus
Piriformis
Obturator internus
Gemelli
Sartorius
Glutaeus maximus
(upper fibres)
during
flexion
i
c. Medial Rotation and Lateral Rotation.
Tensor fasciae latse
Glutseus medius (anterior fibres)
minimus
Obturator externus
Glutaeus maximus (lower fibres)
Quadratus femoris
Glutaeus medius \ (posterior
minimus /fibres)
Piriformis ] -,
Otorator interne | e S on
Sartorius
Ilio-psoas
Pectineus
Adductor longus
brevis
magnus
Biceps femoris
2. Movements of the Pelvis on the Thigh. It is to be noted that the several movements
tabulated above refer to the movements of the femur at the hip-joint. The contraction of the
same groups of muscles produces similar movements of the pelvis on the femur, exemplified in
the various changes in the attitude of the pelvis in relation to the thigh and the vertebral
column, which occur in locomotion.
3. Movements at the Knee-Joint. The movements at the knee-joint are mainly flexion
and extension. Flexion is much more powerful than extension. There is also a limited amount
of rotation of the tibia. The movements are produced by certain of the muscles described above,
associated with certain of the muscles of the leg.
422
THE MUSCULAK SYSTEM.
a. Flexion and Extension.
b. Rotation medially
and Rotation laterally.
Sartorius
Gracilis
Quadriceps femoris
Sartorius
Gracilis
Biceps femoris
Semitendinosus
Semitendinosus
Semimembranosus
Semimembranosus
Biceps femoris
Gastrocnemius
Popliteus
Plantaris
Popliteus
_
THE FASCIAE AND IVIUSCLES OF THE LEG
AND FOOT.
FASCIJE.
The superficial. fascia of the leg and foot presents no special features except
in the sole, where it is greatly thickened by pads of fat, particularly under the
tuberosity of the calcaneus, and under the balls of the toes.
The deep fascia has numerous important attachments about the knee.
Posteriorly it forms the popliteal fascia, and is joined by expansions from the tendons
of the sartorius, gracilis, Semitendinosus, and biceps femoris muscles. In front of the
knee it is attached to the patella, the ligamentum patellse, and the tubercle of the tibia;
medially and laterally it is connected to the condyles of the tibia and the head of the
fibula, and helps to form the collateral patellar ligaments broad fascial bands which
pass obliquely from the sides of the patella to the condyles of the tibia, and are joined
by fibres of the vasti muscles. Passing into the leg, the fascia blends, over the
medial surface of the tibia, with the periosteum of the bone. It extends round
the lateral side of the leg from the anterior crest to the medial border of the tibia,
binding together and giving origin to the muscles, and gaining an attachment to
the distal part of the body of the fibula. Two septa pass from its deep surface ;
one septum (anterior peroneal septum), attached to the anterior crest of the fibula,
encloses the superficial peroneal nerve, and separates the extensor from the
peronaei muscles. The other septum (posterior peroneal septum) is attached to
the lateral crest of the fibula, and separates the peronsei from the flexor muscles.
From the last-named septum another extends across the back of the leg ; it forms a
partition between the superficial and deep flexor muscles, and encloses the posterior
tibial vessels and the tibial nerve. It gives rise to subordinate septa attached to
the vertical line of the tibia and the medial crest of the fibula, which separate
the tibialis posterior from the flexors of the toes on either side.
At the ankle the deep fascia is strengthened by additional transverse fibres,
which give rise to thickened bands named the ligamentum laciniatum, lig. trans-
versurn cruris, lig. cruciaturn cruris and the retinaculum of the peroneal muscles.
They were formerly known as the annular ligaments.
The ligamentum laciniatum (O.T. internal annular ligament) stretches
between the medial malleolus and the tuberosity of the calcaneus. While it is
continuous, at its proximal border, with the general investment of the deep fascia,
it is chiefly formed by the septal layer covering the deep muscles on the back of
the leg. It sometimes gives insertion to the plantaris muscle. It is continuous,
distally, with the plantar aponeurosis, and gives origin to the abductor hallucis
muscle. It is pierced by the calcanean vessels and nerve. Along with the
posterior tibial vessels and the tibial nerve, the tendons of the tibialis posterior,
flexor digitorum longus, and flexor hallucis longus, pass beneath it, each enclosed
in a separate mucous sheath.
The superior peroneal retinaculum (O.T. external annular ligament) is a
thickened band of the deep fascia stretching between the lateral malleolus and
the calcaneus. It binds down the tendons of the peronsei, which occupy a space
beneath the ligament, lined by a single mucous sheath ; while the inferior
THE FASCIA AND MUSCLES OF THE LEG AND FOOT. 423
peroneal retinaculum binds them down separately on the lateral surfaces of the
calcaneus.
The ligamentum transversum cruris (O.T. anterior annular ligament,
upper band), broad and undefined at its proximal and distal borders, stretches
across the front of the ankle between the two malleoli. This band binds down, to
the distal end of the tibia, the tendons of the tibialis anterior and extensor
muscles of the toes. One mucous sheath is found deep to it, surrounding the
tendon of the tibialis anterior.
Ligamentum Cruciatum Cruris. On the dorsum of the foot, where the
general covering of deep fascia is much thinner, a special well-defined band, named
the ligamentum cruciatum cruris (O.T. anterior annular ligament, lower band),
stretches over the extensor tendons. It has an attachment laterally to the lateral
border of the dorsal surface of the calcaneus. It divides into two bands as it
passes medially over the dorsum of the foot a proximal part, which joins the
Kg. transversum cruris and is attached to the medial malleolus, and a distal part,
which passes across the dorsum of the foot, and joins the fascia of the sole at its
medial border.
Deep to this liga-
ment are three
special compart-
ments with separ-
ate mucous sheaths,
one for the tibialis
anterior tendon, a
second for that of
the extensor hal-
lucis longus, and a
third for the ex-
tensor digitorum
longus and per-
onseus tertius ten-
dons. There are
occasionally other
additional bands
of the deep fascia
passing, like the
straps of a sandal,
across the dorsum
of the foot.
The plantar
aponeurosis is of great importance. In the centre of the sole it forms a thick
triangular band, attached posteriorly to the tuberosity of the calcaneus. It
spreads out anteriorly and separates intone slips, which are directed forwards to
the bases of the toes. These slips as they separate are joined together by ill-defined
bands of transverse fibres, which constitute the superficial transverse metatarsal
ligament (fasciculi transversi aponeurosis plantse). The slip for each toe joins the
tissue of the web of the toe and is continuous with the digital sheath. It splits
to form a band of fibres directed forwards on each side of the toe to be attached to
the sides of the metatarso-phalangeal articulation and the base of the first phalanx.
This central portion of the plantar aponeurosis assists in preserving the arch of
the foot, by drawing the toes and the calcaneus together.
On each side it is continuous with a much thinner layer, which covers the lateral
and medial muscles of the sole and joins the fascia of the dorsum of the foot at
each border. It also gives rise to intermuscular septa, which pass deeply on each
side of the flexor digitorum brevis, enclosing that muscle in a separate sheath, and
giving investments on either side to the abductor muscles of the great and little
toes. At the lateral border of the foot the calcaneo-metatarsal ligament, a thickened
band of the fascia, connects the tuberosity of the calcaneus with the base of the
fifth metatarsal bone.
EXTENSOR HALLUCIS LONGUS
Deep peroneal nerve and
dorsalis pedis artery
EXTENSOR DIGITORUM LONGU
PERON^US TERTIU
Fibula
Interosseous talo-
calcaneal ligament
Calcaneus
PERON^EUS BREVIS
Peroneal retinaculum
PERON^US LONGUS
ABDUCTOR DIGITI QUINTI
Plantar aponeurosi
.Lig. transversum cruris.
fes TIBIALIS ANTERIOR
Tibia
Talus
TIBIALIS POSTERIOR
Ligamentum
laciniatum
/_FLEXOR DIGITORUM
LONGUS
Medial plantar artery
Medial plantar nerve
FLEXOR HALLUCIS LONGUS
ABDUCTOR HALLUCIS
Lateral plantar nerve
Lateral plantar artery
FLEXOR DIGITORUM BREVIS
QUADRATUS PLANTS
FIG. 1 377. FRONTAL SECTION THROUGH THE LEFT ANKLE-JOINT, TALUS,
AND CALCANEUS.
424
THE MUSCULAK SYSTEM.
The digital sheaths, though smaller, are the same in arrangement as those of
the fingers (p. 389). Vaginal ligaments are present in relation to the first and
second phalanges.
THE MUSCLES OF THE LEG AND FOOT.
The muscles of the leg and foot are divisible into three series : (1) the extensor
muscles on the front of the leg and
dorsuni of the foot ; (2) the peronaei
on the lateral aspect of the leg ; and
(3) the flexor muscles on the back of
the leg and in the sole of the foot.
Vaginal
ligament
The IVIuscIesonthe Front
of the Leg and Dorsum
of the Foot.
The muscles on the front of the
leg and dorsum of the foot include
two groups: (1) on the front of the
leg, the tibialis anterior, long extensors
of the toes and peronseus tertius ; and
(2) on the dorsum of the foot, the
extensor digitorum brevis, and ex-
tensor hallucis brevis.
On the front of the leg the tibialis i
anterior and the extensor digitorum
longus and peronseus tertius are
superficially placed, and conceal the
extensor hallucis longus muscle. On
the dorsum of the foot the extensor
digitorum brevis muscle lies beneath
the tendons of the long extensor oi
the toes.
M. Tibialis Anterior. The
tibialis anterior arises from the
lateral condyle and the proximal
two -thirds of the lateral surface of
the body of the tibia, from the inter-
osseous membrane from the fascia
over it, and from an inter muscular
septum laterally. The muscle ends
in a strong tendon which pass
over the dorsum of the foot, to be
inserted into a facet on the medial
surface of the first cuneiform and
the medial side of the base of the
first metatarsal bone (Fig. 379, p.
425). Its tendon occupies special
compartments beneath both liga-
mentum transversum and lig.
cruciatum cruris, enclosed in a
separate, single, mucous sheath.
The tibio-fascialis anterior is a separated portion of the muscle occasionally present, inserted
into the fascia on the dorsum of the foot.
Nerve-Supply. Deep peroneal nerve (L. 4. 5. S. 1.).
Actions. The muscle is a dorsi-flexor of the ankle, and (in combination with the tibialis
posterior) it invests the foot.
Calcaueo-
metatarsal
band
FIG. 378. THE LEFT PLANTAK FASCIA.
THE MUSCLES OF THE LEG AND FOOT.
425
M. Extensor Digitorum Longus. The extensor digitorum longus arises, by
fleshy fibres, from the lateral side of the lateral condyle of the tibia, from the
proximal two-thirds or more of the anterior part of the medial surface of the body
of the fibula, from the fascia over it, and from intermuscular septa on either side.
It gives rise to a tendon which passes deep to the ligamentum transversum
and cruciatum, and in front of the ankle subdivides into four tendons, inserted
into the four lateral toes, exactly in the same way as the corresponding tendons
in the hand (see p. 397). They form membranous expansions on the dorsum of the
first phalanx, joined by the tendons of the extensor digitorum brevis, lumbricales,
Abductor digiti quinti
(origin)
Quadratus plantse (origin)
Long plantar ligament
Plantar calcaneo-cuboid
ligament
Tibialis posterior (part of
insertion)
Peronseus brevis
(insertion)
Flexor digiti quinti
brevis (origin)
Adductor hallucis
(origin of oblique
head)
Flexor digitorum brevis (origin)
Abductor hallucis (origin)
Attachments of
plantar calcaneo-
navicular ligament
Flexor hallucis brevis
(origin)
Tibialis posterior
(main part of insertion)
Peronseus longus
(insertion)
Tibialis anterior
(insertion)
FIG. 379. MUSCLE- ATTACHMENTS TO LEFT TARSUS AND METATARSUS (Plantar Aspect).
and interossei, each of which separates into one central and two collateral slips,
attached respectively to the middle and terminal phalanges. The tendon occupies
a separate compartment, along with the peronaeus tertius, deep to the ligamentum
cruciatum cruris, invested by a special mucous sheath.
Nerve-Supply. Deep peroneal nerve (L. 4. 5. S. 1.).
Actions. A dorsi-flexor of the ankle and an extensor of the four lateral toes.
M. Peronseus Tertius. The peronseus tertius is a separated portion of the
extensor digitorum longus. It is an essentially human muscle. It arises (insepar-
ably from the extensor digitorum longus) from the anterior part of the medial
surface of the fibula, and from the inter-muscular septum lateral to it.
426
THE MUSCULAR SYSTEM.
The tendon of the muscle is inserted into the dorsal aspect of the base of the
fifth metatarsal bone.
Nerve-Supply. Deep peroneal nerve (L. 4. 5. S. 1.).
Actions. The muscle dorsi-flexes the ankle and raises the lateral border of the foot (as in
skating or dancing).
M. Extensor Hallucis Longus. The extensor hallucis longus arises from
the anterior part of the medial surface of the
fibula in its middle three -fifths, medial to
the origin of the extensor digitorum lougus,
and for a corresponding extent from the
interosseous membrane. Its tendon passes
over the dorsum of the foot, to be inserted
into the base of the terminal phalanx of the
great toe.
The extensor primi internodii longus and
extensor ossis metatarsi hallucis are occasional
separate slips of this muscle inserted into the proximal
phalanx and the metatarsal bone.
Nerve-Supply. Deep peroneal nerve (L.4. 5. S. 1.).
Actions. This muscle dorsi-flexes the ankle, and
extends the great toe. t
M. Extensor Digitorum Brevis. The
extensor digitorum brevis arises, on the
dorsum of the foot, from a special impression
on the dorsal surface of the calcaneus, and
from the deep surface of the ligamentum
cruciatum cruris.
It usually gives rise to four fleshy bellies,
from which narrow tendons are directed for-
wards and medially, to be inserted into the
four medial toes. The three lateral tendons
join those of the long extensor muscle to form
the membranous expansions on the dorsum
of the toes. The most medial tendon (ex-
tensor hallucis brevis) is inserted separately
into the base of the first phalanx of the great
toe.
Nerve -Supply. Deep peroneal nerve (L. 4. 5.
S. L).
Actions. Extension of the four medial toes.
The Muscles on the Lateral
Side of the Leg.
These muscles comprise the peronsei,
longus and brevis. They are placed on the
lateral side of the leg between the extensor
digitorum longus in front, and the soleus and
flexor hallucis longus behind, enclosed in a
special compartment of the deep fascia.
M. Peronseus Longus. The peronseus
longus arises from the head and the proximal
two-thirds of the lateral surface of. the body
of the fibula, from intermuscular septa on either side, and from the fascia over it.
It forms a stout tendon, which lies superficial to the peronseus brevis, hooks
round the lateral malleolus deep to the peroneal retinaculum, crosses the lateral side
of the calcaneus, and, passing through a groove on the cuboid bone, is directed across
the sole of the foot to be inserted into the lateral sides of the first cuneiform and the
PEBON^US BREVIS
Ligamentum cruci-
atum cruris
TENDON OF PERON^US
TERTIUS
MOST MEDIAL SLIP OF
EXTENSOR DIGITORUM
BREVIS (EXTENSOR
HALLUOIS BREVIS)
FIG 380 MU OF TH
RIGHT LEG AND DOM OF
bas<
THE MUSCLES ON THE LATERAL SIDE OF THE LEG.
427
e of the first metatarsal bones (Fig. 379, p. 425). As it enters the sole of the foot
a fibro- cartilage is formed in the
tendon, which plays over a 1 smooth
tubercle on the cuboid bone, a bursa
intervening. In its passage across
the foot the tendon is enclosed in a
sheath derived from the long plantar
(long calcaneo-cuboid) ligaments and
the tibialis posterior tendon.
Nerve - Supply. Superficial peroneal
nerve (L. 4. 5. S. 1.).
Actions. An extensor of tne ankle ;
this muscle also everts the foot. It
trengthens the arch of the foot* by its
passage across the sole to its insertion.
SEMIMEMBKANOSUS
TENDON (CUt)
Tibial nerve and
~ popliteal vessels
PLANTAKIS TENDON
(cut)
FIG. 381. THE INSERTIONS -OF THE TIBIALIS
\ POSTERIOR AND PERON/EDS LONGUS IN THE SOLE
IF THE LEFT FOOT.
M. Peronseus Brevis. The
peronaeus brevis arises by fleshy
fibres from the distal two-thirds of
the lateral surface of the body of the
fibula, and from an intermuscular
septum along its anterior border.
Its tendon grooves the back of
the lateral malleolus and the lateral
side of the calcaneus, invested by a
mucous sheath common to it and
the peronseus longus, and is inserted
into the tuberosity and dorsal surface
of the base of the fifth metatarsal
bone.
The peronneus longus and brevis may be
fused together, Or additional slips may be
present, as peronseus accessorius, peronaeus
digiti quinti, peronaeocalcaneus externus,
and peronseocuboideus.
TENDO CALCANEUS
Ligamentuni
laciniatum
PERON^US LONGUS
Superior retina-
culum of
peroueal muscles
Nerve - Supply. Superficial peroneal
e (L. 4. 5. S. 1.).
>ns. An extensor of the ankle and an evertor of the foot.
ei Actio
FIG. 382. THE RIGHT SOLEUS MUSCLE.
428
THE MUSCULAR SYSTEM.
GASTROCNEMHJS
SKMIMKM-
BRANOSUS
SOLEUS (flbular
origin)
SOLEUS (tibial
origin)
Popliteus '
(insertion)
Soleus
(origin) '
Tibialis
posterior
(origin)
The Muscles on the Posterior Aspect of the Leg.
The muscles on the back of the leg are divisible into two groups, superfick
and deep.
The superficial group comprises th
gastrocnemius and soleus (constituting tc
gether the triceps surse) and the plantarii
They form the prominence of the calf of th
MEDIAL HEAD OF leg. The gastrocnemius
pllTA C Ris MIUS i 8 superficial except at
LATERAL HEAD OF its Origin, where the
two bellies, forming the
boundaries of the pop-
liteal foSSa, are OVer- Semimem
lapped by the tendons (i jE3SJ
of the hamstring mus-
cles. The soleus muscle
is partially concealed
by the gastrocnemius
and plantaris, and be-
comes superficial in
the distal part of the
leg on each side of the
common tendon (tendo
calcaneus).
M. Gastrocnemius.
-The gastrocnemius
arises by two heads,
medial and lateral, by
means of strong ten-
dons which are pro-
longed over the surface
of the muscle. The
lateral head arises from
an impression on the
proximal and posterior
part of the lateral sur-
face of the lateral con-
dyle of the femur, and
from the distal end of
the lateral epicondylic
line ; while the medial
head arises from a
prominent rough mark
on the popliteal surface
of the femur, proximal
to the medial epicondyle
and posterior to the
adductor tubercle.
Each head has an ad-
ditional origin from
the back of the capsule
of the knee-joint. A
bursa lies deep to each FlG -
tendon of origin.
Each fleshy belly
of the muscle is inserted, separately, into a broad membranous tendon, prolongec
proximally on its deep surface for some distance. The medial head is the larger.
The tendo calcaneus is formed by the union of the two membranous insertion;
FLEXOR DIGITORUM
LONG us
FLEXOR HALLUCIS
LONG US
Flexor
digitorni
longus
(origin)
PERON^US BREVIS
Ligamentum lacini-
'"" atum
TENDO CALCANEUS
Peroneal retinaculum
PIG. 383. THE DBEP MUSCLES ON THE
BACK OF THE RIGHT LEG.
384. MUSCLE - ATTACI
MENTS TO THE POSTERIC
SURFACE OF THE RIGHT TIBL
THE MUSCLES ON THE POSTERIOK ASPECT OF THE LEG. 429
of the bellies of the gastrociiemius. Prolonged proximally beneath the separate
bellies, the tendon forms a broad membranous band connecting together the distal
parts of the two bellies.
Narrowing gradually, and becoming thicker in the distal half of the leg, the
tendon is finally inserted into the posterior aspect of the calcaneus. A bursa lies
deep to the tendon at its insertion. The tendo calcaneus also affords insertion to
the soleus and (sometimes) the plantaris muscles.
Nerve-Supply. Each head of the muscle is innervated by a branch from the tibial nerve
(S. 1. 2.).
Actions. The muscle is a powerful flexor of the knee and extensor of the ankle.
M. Plantaris. The plantaris arises by fleshy fibres from the lateral epicondylic
line of the femur for about an inch at its distal end, from the adjacent part of the
popliteal surface of the femur, and from the oblique ligament of the knee-joint.
It forms a narrow fleshy slip which ends in a tendon that extends distally in the
back of the leg, to be inserted into, the medial side of the tuberosity of the cal-
caneus, or the tendo calcaneus, or the ligameutum laciniatum. The tendon of the
muscle is capable of considerable lateral extension.
The plantaris lies between the lateral head of the gastrocnemius and the soleus.
In the distal half of the leg its tendon lies along the medial border of the tendo
calcaneus. The muscle is not always present.
Nerve-Supply. Tibial nerve (L. 4. 5. S. 1.).
Actions. The muscle is an accessory flexor of the knee and extensor of the ankle.
M. Soleus. The soleus has a triple origin from (1) the posterior surfaces of
the head and the proximal third of the body of the fibula; (2) a fibrous arch
(arcus tendinous m. solei) stretching, over the popliteal vessels and tifrial nerve,
between the tibia and fibula ; and (3) the oblique line, and the middle third of
the medial border of the tibia (Fig. 384, p. 428).
From their origin the proximal muscular fibres are directed distally to join a
tendon, placed on the superficial aspect of the muscle, which is inserted into the
tendo calcaneus ; the more distal fibres are inserted directly into the tendo calcaneus
to within one or two inches of the calcaneus.
Nerve-Supply. Two nerves supply this muscle. One from the tibial nerve in the popliteal
space enters its superficial surface (S. 1. 2.) ; the other from the tibial nerve in the back of the
leg supplies the deep surface of the muscle (L. 5. S. 1. 2.).
Actions. The soleus is a powerful extensor of the ankle.
The deep muscles of the back of the leg comprise the popliteus, flexor digitorum
longus, flexor hallucis longus, and tibialis posterior.
The popliteus muscle is deeply placed behind the knee-joint, in the floor of the
popliteal fossa, and is covered by the popliteal vessels and tibial nerve. The flexor
digitorum longus lies behind the tibia, the flexor hallucis longus behind the fibula,
and the tibialis posterior, lying between them, is related to the interosseous mem-
brane and both bones of the leg. All these muscles are concealed by the superficial
group, and are bound down to the bones of the leg by layers of the deep fascia.
M. Popliteus. The popliteus arises, by a stout tendon, from a rough impression
in front of a groove on the lateral aspect of the lateral epicondyle of the femur.
The tendon passes between the lateral meniscus and the capsule of the knee-joint,
and pierces the posterior ligament, from which it takes an additional fleshy origin.
A bursa is placed on the medial side of the tendon, and it usually communicates
with the synovial cavity of the knee-joint.
The muscle is inserted, by fleshy fibres, (1) into a triangular surface on the back
of the tibia above the oblique line (Fig. 384, p. 428), and (2) into the fascia over it
(the popliteus fascia, derived from the tendon of the semimembranosus muscle).
The popliteus minor is a small occasional muscle attached to the popliteal surface of the
femur and the posterior ligament of the knee-joint.
Nerve-Supply. The popliteus is supplied by a branch of the tibial nerve (L. 4. 5. S. 1.),
which winds round the distal border of the muscle and enters it in its deep surface.
Actions. A medial rotator of the tibia and flexor of the knee.
430
THE MUSCULAE SYSTEM.
FLEXOR HALLUCIS
- BREVIS
FLEXOR
. DIGITORUM
LONGUS
FLEXOR DIGITI.
-QUINTl BREVIS
QUADRATUS
PLANTS
ABDUCTOR
HALLUCIS
ABDUCTOR DIGITI
QUINTI
PERON^EUS
LONGUS
FLEXOR
DIGITORUM
LONGUS
M. Flexor Digitorum Longus. The flexor digitorum longus lies in both
the back of the leg and the sole of the foot. Its origin is, by fleshy fibres, from the
posterior surface of the body of the tibia in its middle three-fifths, distal to
the oblique line, and medial to the vertical line and the origin of the tibialis
posterior from the fascia over it, and from an intermuscular septum on each side
(Fig. 384, p. 428).
Its tendon, after crossing
obliquely over the tendon of the
tibialis posterior, passes deep to
the ligamentum laciniatum, in-
vested in a special mucous sheath,
and enters the sole of the foot.
There it crosses superficially, the
tendon of the flexor hallucis longus,
and finally divides into four sub-
ordinate tendons, which are inserted
into the four lateral toes in pre-
cisely the same manner as the
flexor digitorum profundus is in-
serted in the hand (p. 389). Each
tendon enters the digital sheath
of the toe, perforates the tendon of
the flexor digitorum brevis, and is
inserted into the base of the ter-
minal phalanx. Vincula accessoria
(longa and brevia) are present as in
the hand.
The tendon of the flexor hallucis
longus sends a fibrous band to the
tendon of the flexor digitorum
longus as it crosses it in the sole
of the foot; the band usually passes
to the tendons destined for the
second and third toes. Associated
with this muscle in the sole of the
foot are the lumbricales and quad-
ratus plantse muscles.
Mm. Lumbricales. The lum-
bricales are four small muscles
which arise in association with the
Long plantar tendons of the flexor digitorum
longus in the sole. The first muscle
arises by a single origin from the
tibial side of the tendon of the
flexor digitorum longus for the
second toe ; each of the other three
arises by two heads from the ad-
jacent sides of two tendons.
Each muscle is inserted into the
dorsal expansion of the extensor
FIG. 385. THE MUSCLES OF THE EIGHT FOOT (Second Layer), tendon, the metatarso-phalangeal
capsule, and the base of the first
phalanx, precisely as in the case of the lumbrical muscles of the hand. Each
muscle passes forwards on the tibial side of the corresponding toe, superficial to the
transverse metatarsal ligament.
Nerve-Supply. The flexor digitorum longus is supplied by the tibial nerve (L. 5. S. 1.). The
first lumbrical is supplied by the medial plantar nerve (L. 4/5. S. 1.) ; the other three, by the
lateral plantar nerve (S. 1. 2.).
Actions. The flexor digitorum longus extends the ankles and flexes the four lateral toes.
THE MUSCLES ON THE POSTEKIOK ASPECT OF THE LEG. 431
The lumbrical muscles have a similar action to those of the hand ; they flex the metatarso-
phalangeal, and extend the interphalangeal joints of the four lateral toes.
M. Quadratus Plantae. The quadratus plantae (O.T. accessorial) arises by two
heads : (1) the lateral tendinous head springs from the lateral border of the plantar
surface of the calcaneus and from the lateral border of the long plantar ligament ;
(2) the medial head, which is fleshy, arises from the concave medial surface of the
calcaneus in its whole extent, and from the medial border of the long plantar
ligament (Fig. 379, p. 425). The long plantar ligament separates the two origins.
The two heads unite to form a flattened band, which is inserted into the dorsal
aspects of the tendons of the flexor digitorum longus, and usually into those
destined for the second, third, and fourth toes.
In the sole of the foot the tendons of the flexor digitorum longus, along with the
lumbricales and quadratus plantse, and the flexor hallucis longus muscles, constitute
the second layer of muscles, lying between the abductors of the great and little toes
and the flexor digitorum brevis superficially, and the flexor brevis and adductor of
the great toe more deeply.
Nerve-Supply. Lateral plantar nerve (S. 1. 2.).
Actions. The muscle is an accessory flexor of the toes, assisting the long flexor of the toes.
It tends to draw the tendons into which it is inserted into the middle of the sole of the foot.
M. Flexor Hallucis Longus. The flexor hallucis longus arises, on the back
of the leg, between the tibialis posterior and the peronsei muscles, from the distal
two-thirds of the posterior surface of the body of the fibula, from the fascia over
it, and from intermuscular septa on either side.
Its tendon passes deep to the ligamentum laciniatum, enclosed in a special
mucous sheath, and after grooving the posterior surface of the distal end of the
* tibia, the talus, and the plantar surface of the sustentaculum tali of the calcaneus,
it is directed forwards in the sole of the foot, to be inserted into the base of the
terminal phalanx of the great toe.
In the foot it crosses over the deep aspect of the tendon of the flexor digitorum
longus, and gives to it a strong fibrous slip, which is prolonged into the tendons for
the second and third toes.
Nerve-Supply. Tibial nerve (L. 5. S. 1. 2.).
Actions. The muscle is one of the most important in the leg and foot. It is an extensor of
the ankle and a flexor of the great toe. By its position in relation to the tarsus and inferior
ft calcaneo-navicular ligament, it has an important share in maintaining and supporting the arch
1 of the foot.
M. Tibialis Posterior. The tibialis posterior has a fourfold fleshy origin in
I the leg. It arises (1) from the proximal four-fifths of the medial surface of the
I body of the fibula between the medial crest and the interosseous crest ; (2) from
> the distal part of the lateral condyle, and from the proximal two-thirds of the
body of the tibia, distal to the oblique line and between the vertical line and the
interosseous border (Fig. 384, p. 428) ; (3) from the interosseous membrane ; and
(4) from the fascia over it and the septa on either side. The muscle gives rise to
a strong tendon which passes deep to the ligamentum laciniatum, invested by a
special mucous sheath, and grooves the back of the medial malleolus, on its way
to the medial border of the foot.
After crossing over the plantar calcaneo-navicular ligament between the
sustentaculurn tali and the navicular bone, the tendon spreads out and is inserted
by three bands into (1) the tubercle of the navicular bone and the plantar surfaces
of the first and second cuneiform bones, (2) the plantar aspects of the bases of the
second, third, fourth, and sometimes the fifth metatarsal bones, the second and
third cuneiform bones, and the groove on the cuboid, and (3) into the medial
border of the sustentaculum tali of the calcaneus (Fig. 379, p. 425).
The peronaeo-calcaneus muscle, when present, arises from the fibula, and is inserted into the
calcaneus.
Nerve-Supply. Tibial nerve (L. 5. S. 1.).
Actions. The muscle extends the ankle and inverts the foot.
432
THE MUSCULAK SYSTEM.
The Muscles in the Sole of the Foot.
The muscles in the sole of the foot are divisible into four layers placed deep to
the plantar aponeurosis.
The first layer includes the abductor hallucis, flexor digitorum brevis, and
abductor digiti quinti. The second layer consists of the lumbricales and quadratus
plantse, together with the tendons of the flexor hallucis longus and flexor digitorum
longus. The third layer comprises the flexor hallucis brevis, adductor hallucis, and
Abductor digiti quinti
(origin)
Quadratus plantse (origin}
Long plantar ligament
Plantar calcaneo-cuboid
ligament'
Tibialis posterior (part of
insertion
Peronaeus brevis
(insertion)
Flexor digiti quinti
brevis (origin)
Adductor hall'.icis
(origin of oblique
head)
Flexor digitorum brevis (origin)
Abductor hallucis (origin)
Attachments of
plantar calcaneo-
navicular ligament
Flexor hallucis brevis
(origin)
Tibialis posterior
v main partof insertion)
Peronseus longus
(insertion)
Tibialis anterior
insertion)
FIG. 386. MUSCLE- ATTACHMENTS TO LEFT TARSUS AND METATARSUS (Plantar Aspect).
flexor digiti quinti brevis. The fourth layer consists of the interossei (plantar and
dorsal), placed between the metatarsal bones : and the tendons of insertion of the
tibialis posterior and peronseus longus.
FIRST LAYER.
M. Abductor Hallucis. The abductor hallucis has a double origin: (1) by a
short tendon from the medial side of the medial process of the tuberosity of the
calcaneus (Fig. 386), and (2) by fleshy fibres from the ligamentum laciniatum,
the plantar aponeurosis which covers it, and the intermuscular septum between it
and the flexor digitorum brevis.
The muscle lies superficially, along the medial border of the sole ; its tendon is
THE MUSCLES IN THE SOLE OF THE FOOT.
433
inserted, along with part of the flexor hallucis brevis into the medial side of the
base of the first phalanx of the great toe.
Nerve-Supply. Medial plantar nerve (L. 4. 5. S. 1.).
Actions. A flexor and abductor of the great toe.
M. Flexor Digitorum Brevis. The flexor digitorum brevis has likewise a
double origin : (1) from the an-
terior part of the medial process
of the tuberosity of the calcaneus
(Fig. 386, p. 432), and (2) from
the thick central part of the
plantar aponeurosis which covers
it, and from the inter muscular
septa on either side.
It passes forwards, and gives
rise to four slender tendons, which
are inserted into the second
phalanges of the four lateral
toes, after having been perforated
by the long flexor tendons, just
as in the case of the tendons of
the flexor digitorum sublirais of
the hand (p. 389).
Nerve - Supply. Medial plantar
nerve (L. 4. 5. S. 1.).
Actions. The muscle is a flexor
of the toes, acting on the metatarso-
phalangeal and first inter-phalangeal
articulations of the four lateral toes.
Plantar
aponeurosis
ABDUCTOR DIGITI
QUINTI
QUADRATUS
PLANTS
FLEXOR .
DIGITORUM BREVIS
ABDUCTOR
HALLUCIS
FLEXOR DIGITI
QUINTI BREVIS
FLEXOR HALLUCIS
BREVIS
FOURTH
LUMBRIOAL
THIRD
LUMBRICAL
SECOND...
LUMBRICAL
FIRST
LUMBRICAL
FLEXOR
M. Abductor Digiti Quinti.
The abductor digit! quinti
also has a double origin: (1) by
fleshy and tendinous fibres from
the anterior part of both pro-
cesses of the tuberosity of the
calcaneus, partly concealed by the
flexor digitorum brevis (Fig. 386,
p. 432), and (2) by fleshy fibres
from the lateral portion of the
plantar aponeurosis and the cal-
caneo-metatarsal ligament, and *
from the intermuscular septum
between it and the flexor digi-
torum brevis.
Its tendon lies along the fifth
metatarsal bone, and is inserted
into the lateral side of the pos-
terior end of the first phalanx of
the little toe. The most lateral
fibres usually obtain an ad-
ditional insertion into the lateral
side of the plantar surface of the
fifth metatarsal bone.
Nerve-Supply. Lateral plantar nerve (S. 1. 2.).
Actions. Flexion and abduction of the little toe.
FIG. 387. SUPERFICIAL MUSCLES OF THE RIGHT FOOT.
SECOND LAYER.
The tendons of the long flexors of the toes, the lumbricales and quadratus
plant* muscles, constituting the second layer of muscles, have already been described
29
434
THE MUSCULAK SYSTEM.
(p. 430). They lie deep to the abductor hallucis and the flexor digitorum brevis,
and occupy the hollow of the tarsus and the space between the first and fifth
metatarsal bones; their deep surfaces are in contact with the adductor of the
great toe and the interossei muscles.
THIRD LAYER.
M. Flexor Hallucis Brevis. The
flexor hallucis brevis arises by tendinous
fibres from (1) the medial part of the
plantar surface of the cuboid bone (Fig.
386, p. 432), and (2) the tendon of the
tibialis posterior. Directed forwards, over
the first metatarsal bone, the muscle
separates into two parts, between which
is the tendon of the flexor hallucis longus.
Each portion gives rise to a tendon
which is inserted into the corresponding
side of the base of the first phalanx
of the great toe ; in each tendon,
under the metatarso-phalangeal
articulation, a sesamoid bone is
developed. The medial tendon is
united with the insertion of the
abductor, the lateral tendon with
the insertions of the adductor
muscle of the great toe.
Long plantar
ligament
FLEXOR HAL-
LUCIS LONGUS
FLEXOR DIGI-
TORUM LONGUS
QUADRATUS -
PLANTS I
(origins) *
PERON^EUS
LONGUS
FLEXOR DIGITI
QUINTI BREVIS
FLEXOR HAL- -
LUCIS BREVIS
INTEROSSEOUS-"
MUSCLES
ADDUCTOR
HALLUCIS
(oblique head)
ADDUCTOR
HALLUCIS
(transverse head)
Nerve - Supply. Medial plantar
nerve (L. 4. 5. S. 1.).
Actions. A flexor of the metatarso-
phalangeal joint of the great toe.
M. Adductor Hallucis. The
adductor hallucis consists of two
parts. The oblique head of the
muscle arises (1) from the sheath
of the peronseus longus, and (2)
from the plantar surfaces of the
bases of the second, third, and
fourth metatarsal bones (Fig. 386,
p. 432). It lies in the hollow of
the foot, on a deeper plane than
the long flexor tendons and lum-
bricales, and on the lateral side
of the flexor hallucis brevis, and
it runs obliquely medially and
forwards, to be inserted on the
lateral side of the base of the first
phalanx of the great toe between
and along with the flexor brevis
and the transverse head of the adductor hallucis.
The transverse head arises from (1) the capsules of the lateral four metatarso-
phalangeal articulations and (2) the transverse metatarsal ligament.
It runs transversely medially under cover of the flexor tendons and
lumbricales, the muscle is inserted, along with the oblique head, into the lateral
side of the base of the first phalanx of the great toe.
FIG. 388. DEEP MUSCLES OF THE SOLE OP THE FOOT.
Nerve-Supply. Lateral plantar nerve (S. 1. 2.).
Actions. Flexion and adduction of the great toe towards the middle line of the toot.
THE MUSCLES IN THE SOLE OF THE FOOT.
435
M, Flexor Digiti Quinti Brevis. The flexor digiti quinti brevis arises from
(1) the sheath of the peronseus longus and (2) the base of the fifth metatarsal
bone (Fig. 386, p. 432).
Partially concealed by the abductor digiti quinti, the muscle passes along the
fifth metatarsal bone, to be inserted, in common with that muscle, into the lateral
dde of the base of the first phalanx of the little toe.
Nerve-Supply. Lateral plantar nerve (S. 1. 2.).
Actions. Flexion of the little toe.
FOURTH LAYER.
Mm. Interossei, The interossei muscles of the foot resemble those of the
and except in one respect. In the hand the line of action of the muscles is the
iddle line of the
iddle finger. In
e foot the second
is the digit
>und which the
uscles are
>uped, and their
ittachrnents and
heir actions
liffer accordingly.
There are four
>rsal and three
intar muscles,
rhich occupy to-
ither the four in-
jeous spaces,
id project into
hollow of the
The four
>rsal muscles,
in each interosseous space, arise by two heads each from the shafts of adjacent
letatarsal bones.
Each gives rise to a tendon, which, after passing dorsal to the transverse
letatarsal ligament, is inserted on the dorsum of the foot, into the side of the first
)halanx, the metatarso-phalangeal capsule, and the dorsal expansion of the
:tensor tendon. The first and second muscles are inserted respectively into the
tedial and lateral sides of the proximal end of the first phalanx of the second toe.
third and fourth muscles are inserted into the lateral sides of the third and
mrth toes.
The three plantar muscles occupy the three lateral interosseous spaces. Each
rises, by a single head, from the medial side of the third, fourth, and fifth metatarsal
>nes respectively.
Each ends in a tendon which passes dorsal to the transverse metatarsal ligament,
id is inserted, in the same manner as the dorsal muscles, into the medial sides of
the third, fourth, and fifth toes.
Nerve-Supply. Lateral plantar nerve (S. 1. 2.).
Actions. The muscles are flexors of the metatarso-phalangeal joints, and extensors of the
inter-pbalangeal joints of the four lateral toes. The dorsal interossei abduct the toes into which
"ley are inserted from the middle line of the second toe. The plantar interossei adduct the
iree lateral toes towards the second toe.
Actions of the Muscles of the Leg and Foot.
The muscles of the leg and foot act chiefly in the movements of the ankle-joint (assisted by
FIG. 389. INTEROSSEOUS MUSCLES OF THE RIGHT FOOT.
proximal
of
436
THE MUSCULAK SYSTEM.
slight gliding movement, occasioned by the action of the biceps and popliteus and the muscles
arising from the fibula.
II. Movements at the Ankle-Joint. The movements at the ankle-joint are movements of
flexion and extension of the foot on the leg, along with inversion and eversion (only during
extension). These movements are produced at the ankle, aided by movements in the intertarsal
joints, and are occasioned by the following muscles :
a. Flexion.
Extension.
b. Inversion.
Eversion.
Tibialis anterior
Extensor digitorum longus
Extensor hallucis longus
Peronaeus tertius
Gastrocnemius
Plantaris
Soleua
Tibialis posterior
Peronaeus longus
Peronaeus brevis
Flexor digitorum longus
Flexor hallucis longus
Tibialis anterior
Tibialis posterior
Peronaeus tertius
Peronaeus longus
Peronaeus brevis
III. Movements of the Toes. A. At the Metatarso-Phalangeal Joints (assisted by move-
ments at the tarso-metatarsal and inter-metatarsal joints). These movements are flexion and
extension, abduction and adduction (in a line corresponding to the axis of the second toe).
a. Flexion.
Flexor digitorum longus
Quadratus plantae
Lumbricales
Flexor hallucis longus
Flexor hallucis brevis
Flexor digitorum brevis
Flexor digiti quinti brevis
Interossei
Extension.
Extensor digitorum longus
Extensor digitorum brevis
Extensor hallucis longus
Extensor hallucis brevis
b. Abduction. Adduction.
(From and to the midd
Abductor hallucis
Dorsal interossei
Abductor digiti quinti
le line of the second toe.}
Adductor hallucis
Plantar interossei
B. At the inter-phalangeal joints the movements are limited to flexion and extension.
Flexion.
Extension.
Flexor digitorum brevis (acting on the first
joint)
Flexor digitorum longus (acting on both
joints)
Flexor hallucis longus (acting on the hallux)
Extensor digitorum longus ^
Extensor digitorum brevis
Interossei
Lumbricales
Extensor hallucis longus
(acting on both
joints)
Movements of the Lower Limb generally.
The characteristic features of the lower limb are stability and strength, and its muscles and
joints are both subservient to the functions of transmission of weight and of locomotion. In the
standing position the centre of gravity of the trunk falls between the heads of the femora,
and is located about the middle of the body of the last lumbar vertebra. It is transmitted
from the sacrum through the posterior sacro-iliac ligaments to the hip bone, and through the
bones of the lower limb to the arch of the foot, where the talus distributes it backwards
through the calcaneus to the heel, and forwards through the tarsus and metatarsus to the balls
of the toes.
Locomotion. The three chief means of progression are walking, running, and leaping. In
walking, the body and its centre of gravity are inclined forwards, the trunk oscillates from side to
side as it is supported alternately by each foot, the arms swing alternately with the corresponding
leg, and one foot is always on the ground. The act of progression is performed by the leg, aided in
two ways by gravity. The movements of the leg occur in the following way. At the beginning
of a step, one leg, so to speak, " shoves off " ; the heel is raised and the limb is extended. By the
action of the muscles flexing the hip and knee-joints, and extending the ankle-joint and toes, this
limb is raised from the ground sufficiently to clear it, and passes forwards by the action of
gravity, aided by the force given to the movement by the extensor muscles. After passing the
line
AXIAL MUSCLES.
437
.e of the centre of gravity the flexion of the joints ceases, the muscles relax, and the limb
gradually returns to the ground. The other limb then passes through the same cycle, the weight
of the body now resting on the limb which is in contact with the ground. As the foot reaches
the ground it, as it were, rolls over it ; the heel touches it first, then the sole, and lastly, as the
. foot leaves the ground again, only the toes. In running, the previous events are all exaggerated.
The time of the event is diminished, while the force and distance are increased. Both feet are off
the ground at one time ; the action of flexors and extensors alternately is much more powerful, so
that on the one hand the knees are drawn upwards to a greater extent in the forward movement,
and not the whole foot, but only the toes reach the ground in the extension of the limb. The
attempt is made to bring the foot to the ground in front of the line of the centre of gravity. At
the same time the trunk is sloped forwards much more than in walking. In leaping, the actions
of the limbs are still more exaggerated. The movements of flexion of the limb are still more
marked, and the foot reaches the ground still farther in front of the line of the centre of gravity.
RECTUS ABDOMINIS
AXIAL MUSCLES.
THE FASCIAE AND MUSCLES OF THE BACK.
THE FASCIAE OF THE BACK.
The general fascial investments of the back have been described along with the
superficial muscles associated with the shoulder -girdle (p. 365). The latissimus
dorsi muscle has been described as arising in large part from the posterior layer of
the lumbo-dorsal fascia. This is a strong fibrous lamina which conceals the sacro-
spinalis muscle.
In the loin it
extends from the
spines of the
lumbar vertebrae,
laterally, to the
interval between
the last rib and
the iliac crest,
where it joins the
middle layer.
Below the loin
the posterior layer
of the lumbo-
dorsal fascia is
attached to the
iliac crest, and
more medially
blends with the
subjacent tendin-
ous origin of the
sacrospinalis.
The layer can be
followed upwards
Middle layer of lumbar fascia
the Sacro- ILIOOOOTALIS
spinalis in the
region of the
thorax, where it
is attached later-
ally to the ribs and is continuous with the intercostal aponeuroses. In the lower
part of the thorax it is replaced by the muscular slips of the serratus posterior
inferior ; in the upper part of the thorax it passes beneath the serratus posterior
superior and blends with the deep cervical fascia.
Fascia Lumbodorsalis. The lumbo-dorsal fascia consists of three fascial
strata, called respectively the posterior layer, just described ; the middle, and the
anterior layers. They unite at the lateral margin of the sacrospinalis muscle to
29 a
OBLIQUUS EXTERNUS
ABDOMINIS
OBLIQUUS INTEKNUS
ABDOMINIS
TRANSVERSUS
ABDOMINIS
Fascia transversalis
Peritoneum
Colon
Extraperitoneal
tissue
Kidney
Lumbo-dorsal fascia
LATISSIMUS DORSI
QUADRATUS LUMBORUM
Psoas fascia
Second lumbar
vertebra
: PSOAS MAJOR
Anterior layer of
lumbar fascia
MULTIFIDUS
SEMISPINALIS
DORSI
Vertebral aponeurosis
LONGISSIMUS DORSI
FIG. 390. TRANSVERSE SECTION THROUGH THE ABDOMEN, OPPOSITE THE
SECOND LUMBAR VERTEBRA.
438
THE MUSCULAE SYSTEM.
SEMI-
SPINALIS
CAPITIS
LONGISSIMUS
form a narrow ligamentous band which connects the last rib to the iliac crest
between the muscles of the back on the one hand and those of the abdominal wall
on the other. The middle layer is a fascia which stretches laterally from the ends
of the transverse processes of the lumbar vertebrae, between the sacrospinalis behind
and the quadratus lumborum muscle in front. The anterior layer is attached to the
lumbar vertebrae near the bases of
their transverse processes. It covers
the anterior surface of the quadratus
lumborum muscle, and separates it from
the psoas major. The psoas fascia is
continuous at the lateral border of the
psoas major muscle with the anterior
layer of the lumbo-dorsal fascia. At
the lateral borders of the quadratus
lumborum and sacrospinalis muscles
the three layers blend together, and
give partial origin to the obliquus
internus and transversus abdominis
muscles.
THE MUSCLES OF THE BACK.
The muscles of the back are ar-
ranged in four series according to their
attachments : (1) vertebro - scapular
and vertebro -humeral, (2) vertebro-
costal, (3) vertebro -cranial, and (4)
vertebral. They are in irregular
strata, the most superficial muscles
having the most widely spread attach-
ments.
The first series of muscles of the
back, connecting the axial skeleton to
the upper limb, have already been
described. They are arranged in two
layers: (1) trapezius and latissimus
dorsi superficially ; (2) levator scapulae,
and rhomboidei, deep to the trapezius
(p. 368).
The remaining muscles are almost
entirely axial, and may be divided into
four groups : (1) serrati posteriores,
superior and inferior ; splenius capitis
and splenius cervipis ; (2) sacrospinalis
and semispinalis capitis ; (3) semi-
spinalis dorsi and cervicis (transverso-
spinales) ; and (4) the small deep
muscles (rotatores, interspinales, inter-
transversarii, and suboccipital mus-
cles). They extend from the sacrum
to the head, forming a cylindrical
column in the loin, filling up the
vertebral groove in the thorax, and giving rise to the muscular mass at the back
of the neck.
First Group.
M. Serratus Posterior Superior. The serratus posterior superior has a
membranous origin from the ligamentum nuchse and the spines of the last cervical
ILIOCOSTALIS
LUMBORUM
FIG. 391. SCHEMATIC EEPBESENTATION OF THE PARTS
OF THE LEFT SACROSPINALIS MUSCLE.
and
THE MUSCLES OF THE BACK. 439
upper three or four thoracic vertebrae. It is directed obliquely downwards
and laterally, to be inserted, by separate slips, into the second, third, fourth, and
fifth ribs. The muscle is -concealed by the vertebro-scapular muscles, and crosses
obliquely over the splenius, sacrospinalis and semispinalis capitis. It lies super-
ficial to the lumbo-dorsal fascia.
Nerve-Supply. Posterior rami of upper thoracic nerves.
Actions. It is an accessory muscle of inspiration and an extensor of the vertebral column.
Acting on the vertebral column, from the costal attachment, it assists in lateral movement of the
column.
M. Serratus Posterior Inferior. The serratus posterior inferior has a
membranous origin, through the medium of the lumbo-dorsal fascia, from the last
two thoracic and first two lumbar spinous processes.
It forms four muscular bands which pass almost horizontally to an insertion
into the last four ribs. The muscular slips overlap one another from below
upwards. The muscle is on the same plane as the posterior layer of the lumbo-
dorsal fascia, and is concealed by the latissimus dorsi.
Nerve-Supply. Posterior rami of the lower thoracic nerves.
Actions. The muscle is an extensor of the vertebral column and an accessory muscle of
inspiration, raising, everting, and fixing the lower four ribs.
M. Splenius. The splenius muscle is a broad, flattened band which occupies
the back of the neck and the upper part of the thoracic region. It arises from the
ligamentum nuchae (from the level of the fourth cervical vertebra downwards) and
from the spinous processes of the last cervical and higher (four to six) thoracic
vertebras.
Its fibres extend upwards and laterally into the neck, separating in their course
into an upper and a lower part. The upper part forms the splenius capitis,
which is inserted into the rnastoid portion of the temporal bone and the lateral
part of the superior nuchal line of the occipital bone (Fig. 396, p. 444). The
lower part forms the splenius cervicis, which is inserted into the posterior
tubercles of the transverse processes of the upper three or four cervical vertebrae,
behind the origin of the levator scapulae.
The muscle is partially concealed by the trapezius and sterno-mastoid, and
appears between them in the floor of the posterior triangle of the neck (splenius
capitis). It is covered by the rhomboid muscles, levator scapulae, and serratus
posterior superior.
Nerve-Supply. Posterior rami of cervical and upper thoracic nerves.
Actions. The splenius cervicis extends the spine, and assists in lateral movement and
rotation. The splenius capitis helps in the movements of raising the head, and also of lateral
flexion and rotation.
Second Group.
M. Sacrospinalis. The sacrospinalis (O.T. erector spinae) possesses vertebral,
vertebro-cranial, and vertebro-costal attachments. It consists of an elongated mass
composed of separated slips extending from the sacrum to the skull. Simple at its
origin, it becomes more and more complex as it is traced upwards towards the head.
It arises (1) by fleshy fibres from the iliac crest ; (2) from the posterior sacro-
iliac ligament ; and (3) by tendinous fibres continuous with the former from the
iliac crest, the dorsurn of the sacrum, and the spines of the upper sacral and all
the lumbar vertebrae. -Its fibres extend upwards through the loin, enclosed between
the posterior and middle layers of the lumbo-dorsal fascia, and separate into two
columns a lateral portion derived from the lateral fleshy origin, the iliocostalis,
and a medial portion comprising the remaining larger part of the muscle, the
longissimus.
M. Iliocostalis. The iliocostalis lumborum is inserted by six slender slips
into the lower six ribs.
Medial to the insertion of each of these slips is the origin of the iliocostalis
dorsi (O.T. accessorius), which, arising from the lower six ribs medial to the
29 &
440
THE MUSCULAR SYSTEM.
iliocostalis lumborum, is inserted in line with it by similar slips into the upper
six ribs.
The iliocostalis cervicis (O.T. cervicalis ascendens) arises in the same way by
six slips from the upper six ribs, medial to the insertions of the previous muscle.
It forms a narrow band, which, extending into the neck, is inserted into the posterior
tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae,
behind the scalenus posterior. The iliocostales, lumborum, dorsi, and cervicis form
together a continuous muscular column, and constitute the most lateral group of the
component elements of the sacrospinalis.
M. Longissimus. The longissimus is the largest element in the sacrospinalis
muscle. The longissimus dorsi forms the middle column of the muscle. It is
continued up into the neck as the longissimus cervicis and longissimus capitis.
Mostly tendinous, on the surface, at its origin, it becomes fleshy in the upper part
of the loin. It is thickest in the loin, and becomes thinner as it passes upwards in
Posterior
tubercles of
transverse
processes
Articular^
processes"
SCALENUS MEDIUS
LEVATOR SCAPULAE
SPLENIUS CERVICIS
SCALENUS POSTERIOR
ILIOCOSTALIS CERVICIS
LONQISSIMUS CERVICIS
LONGISSIMUS CAPITIS
SEMISPINALIS CAPITIS
SEMISPINALIS CERVICIS"
MULTIFIDU
LONG us CAPITIS
LONGUS COLL1
Anterior
tubercles of
^transverse
processes
FIG. 392. SCHEME OF MUSCULAR-ATTACHMENTS TO THE TRANSVERSE AND ARTICULAR
PROCESSES OF THE CERVICAL VERTEBRAE.
the back between the column formed by the iliocostalis and its upward continua-
tions laterally, and the spinalis dorsi medially.
It is inserted by two series of slips, medial and lateral, laterally into nearly
all the ribs, and medially into the transverse processes of the thoracic and the
accessory processes of the upper lumbar vertebrae. It is prolonged upwards into
the neck by its association with the common origin of the longissimus cervicis and
the longissimus capitis.
The longissimus cervicis (transversalis cervicis) has an origin from the
transverse processes of the upper six thoracic vertebrae, medial to the insertions of
the longissimus dorsi.
Extending upwards into the neck, it is inserted into the posterior tubercles
of the transverse processes of the second, third, fourth, fifth, and sixth cervical
vertebrae. It is concealed in the neck by the iliocostalis cervicis and splenius
cervicis muscles.
The longissimus capitis (trachelo-mastoid) arises, partly by an origin common
to it and the previous muscle, from the transverse processes of the upper six thoracic
vertebrae, and partly by an additional origin from the articular processes of the
lower four cervical vertebrae.
Separating from the longissimus cervicis, the muscle ascends through the neck
as a narrow band which is inserted into the mastoid portion of the temporal bone,
THE MUSCLES OF THE BACK.
441
RECTUS CAPITIS POSTERIOR MINOR
RECTUS CAPITIS POSTERIOR MAJOR ^
OBLIQUUS CAPITIS SUPERIOR gg
OBLIQUUS CAPITIS INFERIOR
SPLENIUS CAPITIS
SPLENIUS CERVICIS
STERNO-CLEIDO-MASTOID ^
SEMISPINALIS CERVICIS .
LONGISSIMUS CERVICIS
SEMISPINALIS DORSI
LEVATORES COSTA RUM
QUADRATUS LUMBORUM ..
MULTIFIUUS
LlOAMENTUM NUCH^E
SEMISPINALIS CAPITIS
LONGISSIMUS CAPITIS
SPLENIUS CAPITIS ET CERVICIS
LEVATOR SCAPULAE
- ILIOCOSTALIS CERVICIS
LONGISSIMUS CERVICIS
ILIOCOSTALIS DORSI
SPINALIS DORSI
LONGISSIMUS DORSI
. ILIOCOSTALIS LUMBORUM
ACROSPINALIS
FIG. 393. THE DEEP MUSCLES OF THE BACK.
442 THE MUSCULAE SYSTEM.
deep to the splenius capitis muscle. In the neck the muscle is placed between
the splenius capitis and semispinalis capitis.
M. Spinalis Dorsi. The spinalis dorsi forms the medial column of the sacro-
spinalis. It lies in the thoracic region, and arises by tendinous fibres from the
lower two thoracic and upper two lumbar spinous processes, and also directly from
the tendon of the longissimus dorsi.
It is a narrow muscle which, lying close to the thoracic spinous processes
medial to the longissimus dorsi, and it is inserted into the upper (four to eight)
thoracic spines. It is not prolonged into the neck.
The semispinalis capitis (O.T. complexus) closely resembles in position and
attachments the longissimus capitis.
It takes origin from the transverse processes of the upper six thoracic and the
articular processes of the lower four cervical vertebrae, medial to the longissimus
cervicis and longissimus capitis. It has an additional origin also from the spinous
process of the last cervical vertebra.
It forms a broad muscular sheet which extends upwards in the neck, to be inserted
into the medial impression between the superior and inferior nuchal lines of the
occipital bone (Fig. 396, p. 444). The medial portion of the muscle is separate,
and forms the biventer cervicis, consisting of two fleshy bellies with an intervening
tendon, placed vertically in contact with the ligamentum nuchae. The muscle
is covered mainly by the splenius and longissimus capitis muscles. It conceals the
semispinalis cervicis and the muscles of the suboccipital triangle.
Nerve-Supply. Posterior rami of spinal nerves.
Actions. The several parts of the sacrospinalis muscle have a complex action, on the vertebral
column, head, ribs, and pelvis. The muscle serves as an extensor of the vertebral column, and
assists in lateral movement and rotation. The longissimus capitis and semispinalis capitis assist
in extension, lateral movement and rotation of the head. The iliocostales and longissimus are
accessory muscles of inspiration. The whole muscle helps in extension and lateral movement of
the pelvis in the act of walking.
Third Group.
This group comprises the semispinales (dorsi and cervicis) and multifidus. They
occupy the vertebral furrow, under cover of the sacrospinalis and semispinalis
capitis muscles. They are only incompletely separate from one another. The
semispinales, dorsi and cervicis, form a superficial stratum, the multifidus being
more deeply placed. The more superficial muscles have the longer fibres ; the
fibres of the multifidus pass over fewer vertebrae. Both muscles extend obliquely
upwards from transverse to spinous processes.
M. Semispinalis. The semispinalis muscle extends from the loin to the
second cervical vertebra. Its fibres are artificially separated into an inferior
part, the semispinalis dorsi, and a superior part, the semispinalis cervicis.
The semispinalis dorsi arises from the transverse processes of the lower six
thoracic vertebrae.
It is inserted into the spinous processes of the last two cervical and first four
thoracic vertebras.
The semispinalis cervicis arises from the transverse processes of the upper
six thoracic, and the articular processes of the lower four cervical vertebrae.
It is inserted into the spines of the cervical vertebrae from the second to the
fifth.
M. Multifidus. The multifidus (O.T. multifidus spinae) differs from the
previous muscle in extending from the sacrum to the second cervical vertebra,
and in the shortness of its fasciculi, which pass over fewer vertebrae to reach their
insertion.
It arises from the sacrum, from. the posterior sacro-iliac ligament (Fig. 395,
p. 443), from the mamillary processes of the lumbar vertebrae, from the transverse
processes of the thoracic vertebrae, and from the articular processes of the lower
four cervical vertebrae.
It is inserted into the spines of the vertebrae up to and including the second
cervical.
THE MUSCLES OF THE BACK.
443
INSERTION OF STERNO-
MASTOID
SPLENIUS CAPITIS
LONGISSIMUS CAPITIS
SEMISPINALIS CAPITIS
(thrown laterally)
Third occipital nerv
SPLENIUS CAPITIS
LONGISSIMUS CAPITIS
TRAPEZIUS
SEMISPINALIS CAPITIS
Greater occipital nerve
OBLIQUUS CAPITIS SUPERIOR
RECTUS CAPITIS POSTERIOR MAJOR
RECTUS CAPITIS POSTERIOR MINOR
Vertebral artery
Suboccipital nerve
Posterior arch of atlas
OBLIQUUS CAPITIS INFERIOR
Posterior ramus of second cervical nerve
Posterior ramus of third cervical nerve
Deep cervical artery
Posterior ramus of fourth cervical nerve
SEMISPINALIS CERVICIS
FIG. 394. THE SUBOCCIPITAL TRIANGLE OF THE LEFT SIDE.
Lying in contact with the vertebral laminae, the muscle is covered in the neck
and back by the semispinalis, and in the loin by the sacrospinalis muscle.
Attachment of
interosseous
sacro-iliac
ligaments
Glutseus maximus (origin)
FIG. 395. MUSCLE -ATTACHMENTS TO THE SACRUM (Dorsal Aspect).
444 THE MUSCULAE SYSTEM.
Nerve-Supply. Posterior rami of the spinal nerves.
Actions. These muscles are concerned in extension, lateral movement and rotation of the
spine.
Fourth Group.
This group includes several sets of small muscles, which are vertebro-cranial or
intervertebral in their attachments.
The muscles bounding the suboccipital triangle are four in number obliqui
capitis, inferior and superior, and recti capitis posteriores, major and minor.
These muscles are concealed by the semispinalis capitis and splenius capitis ;
ihey enclose a triangular space (the suboccipital triangle) in which the vertebral
ry, the posterior ramus of the suboccipital nerve, and the posterior arch of the
atlas are contained.
Semispinalis capitis (insertion)
Rectus capitis posterior minor \^^~ ~-~-^Trapezius (origin)
(insertion)
Rectus capitis posterior major
(insertion)
Sterno-cleido-mastoid
^(insertion)
Splenius capitis
(insertion)
Obliquus capitis superior
(insertion)
Rectus capitis lateralis (insertion)
Rectus capitis anterior (insertion)
-Superior constrictor of pharynx (insertion)
Longus capitis (insertion)
FIG. 396. MUSCLE- ATTACHMENTS TO THE OCCIPITAL BONE.
The obliquus capitis inferior arises from the spine of the epistropheus, and
is inserted into the transverse process of the atlas.
Nerve- Supply. Posterior ramus of the first cervical (suboccipital) nerve.
Actions. Extension, lateral flexion and rotation of the atlas in the axis.
M. Obliquus Capitis Superior. The obliquus capitis superior arises from
the transverse process of the atlas, and is inserted into the occipital bone deep
and lateral to the semispinalis capitis and above the inferior nuchal line (Fig. 396).
Nerve -Supply. Posterior ramus of the first cervical (suboccipital) nerve.
Actions. Elevation, lateral movement and rotation of the head on the atlas.
M. Rectus Capitis Posterior Major. The rectus capitis posterior major
arises from the spine of the second cervical vertebra, and is inserted into the
occipital bone deep to the obliquus capitis superior and semispinalis capitis and
below the inferior nuchal line (Fig. 396).
Nerve-Supply. Posterior ramus of the first cervical (suboccipital) nerve.
Actions. Elevation, lateral movement and rotation of the head.
M. Rectus Capitis Posterior Minor. The rectus capitis posterior minor
arises deep to the preceding muscle from the posterior tubercle of the atlas, and is
THE MUSCLES OF THE BACK. 445
inserted into the occipital bone below the inferior nuchal line medial to and beneath
the rectus capitis posterior major (Fig. 396, p. 444).
Nerve-Supply. Posterior ramus of the first cervical (suboccipital) nerve.
Actions. Elevation, lateral movement and rotation of the head.
Mm. Rotatores. The rotatores are eleven pairs of small muscles occupying
the vertebral groove in the thoracic region, deep to the semispinalis dorsi, of which
they form the deepest fibres. Each consists of a small slip arising from the
transverse process and inserted into the lamina of the vertebra directly above.
Nerve -Supply. Posterior rami of the thoracic nerves.
Actions. Extension and rotation of the vertebral column.
Mm. Interspinales. The interspinales are bands of muscular fibres connect-
ing together the spinous processes of the vertebrae.
Nerve-Supply. Posterior rami of the spinal nerves.
Action. Extension of the vertebral column.
Mm. Intertransversarii. The intertransversarii are slender slips extending
between the transverse processes. They are double in the neck, the anterior
branches of the spinal nerves passing between them. In the loin the inter- transverse
muscles are usually double, but they are often absent, or are replaced by membrane.
Nerve-Supply. Anterior rami of the spinal nerves.
Actions. Lateral movement and rotation of the vertebral column.
Mm. Rectus Capitis Lateralis. The rectus capitis lateralis, extending from
the transverse process of the atlas to the jugular process of the occipital bone (Fig.
396, p. 444), is homologous with the posterior of the two inter- transverse muscles.
Nerve-Supply. Anterior ramus of the first cervical (suboccipital) nerve.
Action. Lateral movement and rotation of the head. The action of these muscles is
extremely complex. Not only do they act on the vertebral column, ribs, head, and pelvis,
in conjunction with other muscles, but some of them act also in relation to the movements of
the limbs as well. In this section will be given an analysis of their movements in relation to
the vertebral column, head, and pelvis. The movements of the limbs and of the ribs (respiration)
are dealt with in other sections. The chief muscles are engaged in preserving the erect position,
and in the movements of the trunk they are assisted in large measure by muscles whose chief
actions are referred to elsewhere.
1. Movements of the Vertebral Column. The movements of the vertebral column are
flexion, extension, and lateral movement or rotation. These movements occur in all regions
neck, thorax, and loin ; flexion and extension and lateral movement are most limited in the
region of the thorax ; while rotation is most limited in the region of the loin.
a. Flexion.
Extension.
Longus colli
Longus capitis
Scaleni anteriores (together)
Psoas major and minor
Levator ani
Coccygeus
Sphincter aiii externus
Rectus abdominis
Pyramidalis
Obliquus abdominis externus
Obliquus internus
Transversus
Serrati posteriores
Splenius capitis
Splenius cervicis
Sacrospinalis
Semispinalis dorsi
Semispinalis cervicis
Semispinalis capitis
Multifidus
Interspinales
Intercostal muscles
Diaphragm
Transversus thoracis
b. Lateral Movement (Rotation).
Levator scapulae
Serrati posteriores
Splenius cervicis
Sacrospinalis
Semispinalis capitis
Semispinalis (dorsi and cervicis)
Multifidus
Rotatores
Intertransversarii
Longus colli
Longus capitis
Scaleni, anterior, inedius, posterior
Psoas (major and minor)
Quadratus lumborum
Obliquus abdominis externus
Obliquus internus
Transversus
Rectus
Pyramidalis ,,
446
THE MUSCULAE SYSTEM.
2. Movements of the Head. The movements of the head are flexion and extension, at the
occipito-atlaiitoid articulation ; lateral movement and rotation at the atlanto-epistropheal joint.
a. Flexion.
Extension.
Digastric
Stylo-hyoid
Stylo-pharyngeus
Mylo-hyoid
Hyo-glossus
Sterno-hyoid
Sterno-thyreoid
Omo-hyoid
Longus capitis
Rectus capitis anterior
(the muscles of both
Sterno-mastoid
Splenius capitis
Longissimus capitis
Semispinalis capitis
Obliquus capitis inferior
Recti capitis posteriores (major and minor)
rides acting together)
b. Lateral Movement.
c. Rotation.
Sterno-mastoid
Splenius capitis
Longissimus capitis
Semispinalis capitis
Obliquus capitis superior
Rectus capitis lateralis
Sterno-mastoid
Splenius capitis
Longissimus capitis
Semispinalis capitis
Obliquus capitis inferior
superior
Recti capitis posteriores (major and minor)
Movements of the Pelvis. The movements of the pelvis (as in locomotion) are partly
caused by certain of the muscles of the back. Those muscles, which are attached to the vertebral
column or the ribs on the one hand, and to the hip bone on the other, produce the movements
(flexion, extension, and lateral movement) of the whole pelvis. In addition, the muscles passing
between the hip bone and femur, in certain positions of the lower limb, assist in these
movements.
a. Extension.
Flexion.
Latissimus dorsi
Sacrospinalis
Multifidus (acting on both sides)
Psoas major and minor
Rectus abdominis
Pyramidalis abdominis
Obliquus abdominis externus
Obliquus internus
Transversus abdominis (acting on both
sides)
Piriformis
Glutaei
Obturator (externus and internus)
Sartorius
Tensor fasciae latse
Iliacus
Rectus femoris
Adductors (in the erect position)
b. Lateral Movement.
Flexors and extensors of one side only | Quadratus lumborum
THE FASCIAE AND MUSCLES OF THE HEAD
AND NECK.
FASCLE.
The superficial fascia of the head and neck possesses certain features of special
interest. Over the scalp it is closely adherent to the skin and subjacent gales
aponeurotica and contains the superficial vessels and nerves. Beneath the skin o
the eyelids it is loose and thin and contains no fat. Over the face and at the sid*
of the neck it is separated from the deep fascia by the facial muscles and the
platysma. Between the buccinator and the masseter it is continuous with a pa(
of fat (corpus adiposum buccce} occupying the interval between those muscles.
FASCIAE AND MUSCLES OF THE HEAD AND NECK.
447
The deep fascia of the head and neck presents many remarkable characters.
Over the scalp it is represented by the galea aponeurotica (O.T. epicranial aponeurosis),
the tendon of the epicraneus muscle. This is a tough membrane, tightly stretched
over the calvaria, from which it is separated by loose areolar tissue. It is attached
posteriorly, partly through the agency of the occipitalis muscle, to the superior
nuchal line of the occipital bone ; anteriorly it joins the frontalis muscle and the
orbicularis oculi, and
2 4 6 8 9a 10 12 14 16 18
nas no bony attachment ; i \ 3 \ 5 \ 7 \ 95 9c > 11 13 / 15 / 17/19
laterally it is attached Ov^a^V v \ ,
to the temporal line and
the mastoid process.
Below the temporal line
it is continuous with the
temporal fascia, a stout
layer of fascia attached
to the temporal line and
zygomatic arch, which
covers and gives origin
to the temporal muscle.
This fascia separates into
two layers above the
zygomatic arch, to en-
close a quantity of fat
along with branches of
the temporal and zygo-
matico- orbital arteries.
On the face the fascia is
practically non-existent
anteriorly in relation to
the facial muscles. Pos-
teriorly it forms the thin
parotideo - masseteric
fascia, and is much thicker
in relation to the parotid
gland, for which it forms
a capsule.
In the neck the deep
fascia invests the mus-
cles, and forms fascial
coverings for the
pharynx, trachea, oeso-
phagus, glands, and large
vessels. It encloses the
sterno - mastoid muscle,
and can be traced back- 18 . Internal jugular vein .
wards over the posterior - vagus nerve.
20. Sympathetic trunk.
triangle to the trapezius 21. carotid sheath.
and deeper muscles, 23'.
which it surrounds; it ^
can be traced forwards
over the anterior triangle to the median plane of the neck, where it forms a continu-
ous membrane. Above the sternum the fascia, after enclosing the sterno- mastoid
muscles, is attached in the form of two layers to the front and back of the jugular
notch. The layer enclosing the infra-hyoid muscles passes across the median plane
of the neck anterior to the trachea, and is attached above to the hyoid bone, below
to the sternum, clavicle, and first rib. A third layer of fascia passes medially
anterior to the trachea, enclosing the thyreoid gland. Deep to the steruo-mastoid
the fascia helps to form the carotid sheath, which is completed by septal processes
stretching medially across the neck in relation to the infra-hyoid muscles, trachea,
45 44
FIG. 397. TRANSVERSE SECTION IN THE CERVICAL REGION
(between the fourth and fifth cervical vertebrae).
1. CRICO-ARYT/ENOIDEUS POSTERIOR
MUSCLE.
2. INFERIOR CONSTRICTOR MUSCLE.
3. Pharynx.
4. Cricoid cartilage.
5. Vocal fold.
26. Vertebral vein.
27. SCALENUS MEDIUS. '
28. Posterior triangle.
29. SCALENUS POSTERIOR.
30. LEVATOR SCAPULA.
31. Accessory nerve.
6. VOCALIS AND THYREOARYT.SNOIDEUS 32. SPLENIUS CERVICIS.
MUSCLES.
7. Thyreoid cartilage.
8. Rima Glottidis.
9. Layers of deep cervical fascia.
10. STERNO-HYOID MUSCLE.
11. OMO-HYOID MUSCLE.
12. STERNO-THYREOID MUSCLE.
13. Cervical fascia.
14. Thyreoid gland.
15. Common carotid artery.
16. Descendens hypoglossi nerve.
17. STERNO-MASTOID MUSCLE.
33. LONGISSIMUS CERVICIS.
34. LONGISSIMUS CAPITIS.
35. Fifth cervical nerve.
36. Vertebral artery.
37. Profunda cervicis vein.
38. Profunda cervicis artery.
39. MULTIFIDUS.
40. SEMISPINALIS CERVICIS.
41. SEMISPINALIS CAPITIS
42. SPLENIUS CAPITIS.
43. TRAPEZICS.
44. Ligamentum nuchse.
45. Spine of fourth cervical vertebra.
46. Lamina of fifth cervical vertebra.
47. Dura mater.
48. Spinal medulla.
49. Transverse process.
50. Fibro - cartilage between fourth and
fifth cervical vertebrae.
448 THE MUSCULAE SYSTEM.
oesophagus, and pharynx, and the praevertebral muscles. The trachea, oesophagus,
and pharynx are likewise encapsuled in cervical fascia, a septal layer passing across
the median plane of the neck between the trachea and oesophagus. Lastly, a
strong prsevertebral fascia passes across the neck anterior to the praevertebral
muscles, and posterior to the oesophagus and pharynx.
The cervical fascia is attached above to the bones of the skull : superficially to
the superior nuchal line of the occipital bone, the mastoid process, the zygoma
(over the parotid gland), and the inferior 'border of the mandible ; more deeply to
the styloid and vaginal processes of the temporal bone, the great wing of the
sphenoid and the basilar part of the occipital bone. This deeper attachment
(prcevertebral fascia) is posterior to the parotid gland and pharynx, and is
associated with the formation of three ligaments : stylo-mandibular ligament, spheno-
mandibular ligament, and pterygo-spinous ligament. The fascia is attached below,
through its muscular connexions, to the sternum, first rib, clavicle, and scapula.
By means of its connexion with the trachea and the common carotid artery it is
carried down behind the first rib into the superior mediastinum, and so becomes
continuous with the pericardium. By means of its connexion with the subclavian
vessels and brachial nerves it is carried down to the axilla, as the axillary sheath,
which becomes connected with the costo-coracoid membrane.
THE MUSCLES OF THE HEAD.
The muscles of the head are divisible into three separate groups : the super-
ficial muscles, muscles of the orbit, and muscles of mastication.
Superficial Muscles.
-^The superficial muscles comprise a large group, including the muscles of the
scalp and face, and the platysma in the neck.
The platysma is a thin quadrilateral sheet extending from chest to face
over the side of the neck, between the superficial and deep fasciae. It arises
from the deep fascia of the pectoral region.
It is directed upwards and forwards, and is partly inserted (by its intermediate
fibres) into the inferior border of the mandible, becoming connected with the
quadrat us labii inferioris and triangularis muscles (Fig. 398, p. 449). The more
anterior fibres pass across the median plane of the neck and decussate for a
variable distance below the chin with those of the opposite side. The posterior
fibres sweep over the angle of the jaw and become continuous with the risorius
muscle. The platysma is the rudiment of the cervical portion of the panniculus
carnosus of lower animals, in which it has a much more intimate connexion
with the muscles of the face than is usually the case in man.
Nerve-Supply. Cervical branch of the facial nerve.
Actions. It depresses the mandible and laterally flexes the head. It also throws into folds
the skin of the side of the neck.
The Muscles of the ScaXp.
The muscles of the scalp comprise the epicranius muscle and the muscles of
the auricle.
M. Epicranius. The epicranius (O.T. occipitofrontalis) is a muscle with four
bellies, two posterior and two anterior, and an intervening tendon (the galea
aponeurotica) which stretches uninterruptedly across the median plane of the
cranium. Each posterior belly (occipitalis) arises as a broad flat band from the
lateral two-thirds of the superior nuchal line of the occipital bone. Each anterior
belly (frontalis) has no bony attachments; arising from the galea aponeurotica
about the level of the coronal suture, it passes downwards to the supra-orbital
arch, where it blends with the orbicularis oculi and corrugator supercilii muscles.
It extends across the full width of the forehead, and blends in the median plane
with the muscle of the opposite side.
THE MUSCLES OF THE SCALP.
449
The galea aponeurotica (O.T. epicranial aponeurosis), extending between the
two anterior and the two posterior fleshy bellies, is a continuous membrane which
glides over the calvaria, and has attachments laterally to the temporal ridge, and
behind, between the posterior bellies, to the superior nuchal lines of the occipital
bone. It has no osseous attachment anteriorly.
Nerve-Supply. The occipitalis is supplied by the posterior auricular branch of the facial
nerve. The frontalis is supplied by the temporal branches of the same nerve.
Actions. The epicraneus is usually rudimentary. By the contraction of the fibres of the
frontalis muscle the skin of the forehead is thrown into horizontal parallel folds.
l*v
FRONTALIS
_.ORBICULARIS OCULI
M. PROCERUS
l" h w
s
J or
CAPUT ANGULARE
M. NASALIS
CAPUT ANGULARE j
! *
CAPUT INFRAORBITALE
CAPUT ZYGOMATICUM
CANINUS
ZYGOMATICUS
ORBICULARIS ORIS
BUCCINATOR
B RISORIUS
M. TRIANGULARIS
-- ]\f. QOADRATUS LABII INFERIORI3I
MASSETER ^^mppp-
PLATYSMA
FIG. 398. THE MUSCLES OF THE FACE AND SCALP (Muscles of Expression).
The extrinsic muscles of the ear are three in number : posterior, superior, and
anterior. They are rudimentary and usually functionless.
The m. auricularis posterior (O.T. retrahens aurem) is a narrow fleshy slip
which arises from the surface of the mastoid process and is inserted into the cranial
surface of the auricle. It bridges across the groove between the mastoid process
and the auricle, and conceals the posterior auricular vessels and nerve.
The m. auricularis superior (O.T. attollens aurem) 'is a small fan-shaped
muscle which arises from the temporal fascia, and descends to be inserted into
the top of the root of the auricle.
The m. auricularis anterior (O.T. attrahens aurem) is a similar small muscle,
placed in front of the auricularis superior, and stretching obliquely between the
temporal fascia and the top of the root of the auricle.
*i
30
452 THE MUSCULAE SYSTEM.
Nerve-Supply. The facial and scalp muscles are all innervated by the facial nerve. The
posterior auricular branch supplies the posterior auricular muscle and occipitalis ; the branches
into which it breaks up in the parotid gland supply the frontalis, superior and anterior auricular
muscles, the several muscles associated with the apertures of the eye, nose, and mouth (including
the buccinator), and the platysma.
Actions. The almost infinite variety of facial expression is produced partly by the action
of these muscles, partly by their inactivity, or by the action of antagonising muscles (antithesis).
On the one hand joy, for example, is betrayed by the action of one set of muscles, while grief is
accompanied by the contraction of another (opposing) set. Determination or eagerness is accom-
panied by a fixed expression due to a combination of muscles acting together ; despair, on the
other hand, is expressed by a relaxation of muscular action. For a philosophical account of the
action of the facial muscles, the student should consult Darwin's Expression of the Emotions in
Man and Animals, and Duchenne's Mecanisme de la Physiologic humaine.
The platysma retracts and depresses the angle of the mouth, and depresses the mandible.
The epicranius, by its anterior belly, raises the eyebrows ; both bellies acting together
tighten the skin of the scalp ; acting along with the orbicularis oculi, it shifts the scalp back-
wards and forwards. The corrugator supercilii draws the eyebrow medially and wrinkles the
skin of the forehead vertically. The procerus draws downwards the skin between the eyebrows,
as in frowning. The upper eyelid is raised by the levator palpebrse superioris. The closure of
the lids is effected by the orbicularis oculi, whose fibres also assist in the lowering of the
eyebrows, in the protection of the eyeball, and, by pressure on the lacrimal gland, in the
secretion of tears. The tarsal part, acting along with the orbicularis oculi, compresses the
lacrimal sac and aids in the passage of its contents into the naso-lacrimal duct. The muscles of
the ear and nose have quite rudimentary actions. Of the muscles of the mouth, the orbicularis
oris has a complex action, depending on the degree of contraction of its component parts. It
causes compression and closure of the lips in various ways, tightening the lips over the teeth,
contracting them as in osculation, or causing pouting or protrusion of one or the other. The
accessory muscles of the lips draw them upwards (zygomaticus, quadratus labii superioris),
laterally (zygomaticus, risorius, platysma, triangularis, buccinator), and downwards (triangularis,
quadratus labii inferioris, platysma). The mentalis muscle elevates the skin of the chin and
protrudes the lower lip. The buccinator retracts the angles of the mouth, flattens the cheeks,
and brings them in contact with the teeth.
The Fasciae and Muscles of the Orbit.
The eyeball, with its muscles, vessels, and nerves, is lodged in a mass of soft
and yielding fat which entirely fills up the cavity of the orbit. Surrounding the
posterior part of the eyeball
LEVATOR PALPEBR.E SUPERIORIS ,-, -. -. / r\ m
RECTUS SUPERIOR is the fascia bulbi (O.T. cap-
OBLIQUUS SUPERIOR sl Q e O f Tenon), which COn-
^ RECTUS MEDIALIS
or synovial bursa in relation
to the posterior part of the
eyeball Anteriorly the cap-
t.
suie 1S m contact Wlth t ^ ie
conjunctiva, and intervenes
between the latter and the
eyeball ; posteriorly it is
pierced by and prolonged
along the optic nerve. It is a,
smooth membrane connected
FIG. 399. TRANSVERSE VERTICAL SECTION THROUGH THE LEFT ORBIT ^ ^-u e o-lobe of the eve bv
BEHIND THE EYEBALL TO SHOW THE ARRANGEMENT OF MUSCLES.
loose areolar tissue. It is
pierced by the tendons of the ocular muscles, along which it sends prolongations
continuous with the muscular sheaths.
The muscles of the orbit are seven in number: one, the levator palpebrse
superioris, belongs to the upper eyelid ; the other six are muscles of the eyeball.
M. Levator Palpebrse Superioris. The levator palpebrae superioris lies
immediately beneath the orbital periosteum and covers the superior rectus muscle
It has a narrow origin above that muscle from the margin of the optic foramen.
It expands as it passes forwards, to end, in relation to the upper lid, in a i
membranous expansion which is inserted in a fourfold manner : (1) into the I
orbicularis oculi and skin of the upper lid, (2) mainly into the superior border o:
the superior tarsus, (3) into the conjunctiva, and (4) by its edges into the uppe] ij
border of the margin of the orbital opening.
THE FASCIAE AND MUSCLES OF THE OEBIT.
453
Nerve-Supply. The muscle is supplied by the superior division of the oculo-motor nerve.
Actions. It elevates the upper eyelid and antagonises the action of the orbicularis oculi
muscle.
ORBICULARIS OCULI
\
RECTUS
SUPERIOR
LEVATOR PALPEBR.E
SUPERIORIS
Mm. Recti. The recti muscles are four in number superior, inferior, medial,
and lateral. They all arise from a
membranous ring surrounding the
optic foramen, which is separable into
two parts a superior common tendon,
giving origin to the superior and
medial recti and the superior head of
the lateral rectus ; and an inferior
common tendon, giving origin to the OBLIQUUS
medial and inferior recti and the in- SUPERIOR
ferior head of the lateral rectus. The
two origins of the lateral rectus muscle
are separated by the passage into the
orbit of the oculo-motor, naso-ciliary,
and abducent nerves. Forming flat-
tened bands which lie in the fat of the
orbit around the optic nerve and eye-
ball, the four muscles end in tendons
which pierce the fascia bulbi, and are
inserted into the sclera about eight
millimetres (three to four lines) behind
the margin of the cornea.
The superior and inferior recti are
inserted in the vertical plane slightly
medial to the axis of the eyeball ; the
lateral and medial recti in the trans-
verse plane of the eyeball ; and all are attached in front of the equator of the
eyeball.
M. Obliquus Superior. The obliquus superior arises from the margin of the
optic foramen between the rectus superior and rectus medialis. It passes forwards,
as a narrow muscular band, medial to the rectus superior, and at the anterior
margin of the orbit
forms a narrow ten-
don which passes
through a special
fibrous , pulley
(trochlea) attached
to the roof of the
orbit.
Its olirection is
then altered, and
passing laterally,
between the tendon
of the superior
rectus and the eye-
ball, it is inserted
into the sclera be-
tween the superior
and lateral recti,
midway between
FIG. 400. MUSCLES OF THE EIGHT ORBIT (from above).
OBLIQUUS SUPERIOR
LEVATOR PALPEBR.E SUPERIORIS (cut)
V RECTUS SUPERIOR
RECTUS LATERALIS
Oculo-motor
nerve
Naso-ciliary
nerve
Abducent nerve
OBLIQUUS INFERIOR
RECTUS INFERIOR
the
FIG. 401. MUSCLES OF THE LEFT ORBIT (from lateral aspect).
margin of the cornea and the entrance of the optic nerve.
Obliquus Inferior. The obliquus inferior arises from the medial side of
' of the orbit just behind its anterior margin, and lateral to the naso-
lacrimal groove.
t forms a slender rounded slip, which curls round the inferior rectus tendon.
30 &
452 THE MUSCULAR SYSTEM.
Nerve-Supply. The facial and scalp muscles are all innervated by the facial nerve. The
posterior auricular branch supplies the posterior auricular muscle and occipitalis ; the branches
into which it breaks up in the parotid gland supply the frontalis, superior and anterior auricular
muscles, the several muscles associated with the apertures of the eye, nose, and mouth (including
the buccinator), and the platysma.
Actions. The almost infinite variety of facial expression is produced partly by the action
of these muscles, partly by their inactivity, or by the action of antagonising muscles (antithesis).
On the one hand joy, for example, is betrayed by the action of one set of muscles, while grief is
accompanied by the contraction of another (opposing) set. Determination or eagerness is accom-
panied by a fixed expression due to a combination of muscles acting together ; despair, on the
other hand, is expressed by a relaxation of muscular action. For a philosophical account of the
action of the facial muscles, the student should consult Darwin's Expression of the Emotions in
Man and Animals, and Duchenne's Mecanisme de la Physiologie humaine.
The platysma retracts and depresses the angle of the mouth, and depresses the mandible.
The epicranius, by its anterior belly, raises the eyebrows ; both bellies acting together
tighten the skin of the scalp ; acting along with the orbicularis oculi, it shifts the scalp back-
wards and forwards. The corrugator supercilii draws the eyebrow medially and wrinkles the
skin of the forehead vertically. The procerus draws downwards the skin between the eyebrows,
as in frowning. The upper eyelid is raised by the levator palpebrse superioris. The closure of
the lids is effected by the orbicularis oculi, whose fibres also assist in the lowering of the
eyebrows, in the protection of the eyeball, and, by pressure on the lacrimal gland, in the
secretion of tears. The tarsal part, acting along with the orbicularis oculi, compresses the
lacrimal sac and aids in the passage of its contents into the naso-lacrimal duct. The muscles of
the ear and nose have quite rudimentary actions. Of the muscles of the mouth, the orbicularis
oris has a complex action, depending on the degree of contraction of its component parts. It
causes compression and closure of the lips in various ways, tightening the lips over the teeth,
contracting them as in osculation, or causing pouting or protrusion of one or the other. The
accessory muscles of the lips draw them upwards (zygomaticus, quadratus labii superioris),
laterally (zygomaticus, risorius, platysma, triangularis, buccinator), and downwards (triangularis,
quadratus labii inferioris, platysma). The mentalis muscle elevates the skin of the chin and
protrudes the lower lip. The buccinator retracts the angles of the mouth, flattens the cheeks,
and brings them in contact with the teeth.
The Fasciae and Muscles of the Orbit.
The eyeball, with its muscles, vessels, and nerves, is lodged in a mass of soft
and yielding fat which entirely fills up the cavity of the orbit. Surrounding the
posterior part of the eyeball
LEVATOR PALPEBRSE SUPERIORIS ,, ... , ., . /^ m
RECTUS SUPERIOR is the fascia bulbi (O.T. cap-
OBLIQUUS SUPERIOR su l e O f Tenon), which COU-
RECTUS MEDIALIS
or synovial bursa in relation
to the posterior part of the
eyeball Anteriorly the cap-
conjunctiva, and intervenes
between the latter and the
eyeball ; posteriorly it is
pierced by and prolonged
along the optic nerve. It is a
smooth membrane connected
FIG. 399. TRANSVERSE VERTICAL SECTION THROUGH THE LEFT ORBIT ^ ^ o-lobe of the eve bv
BEHIND THE EYEBALL TO SHOW THE ARRANGEMENT OF MUSCLES. ,
loose areolar tissue. It is
pierced by the tendons of the ocular muscles, along which it sends prolongations
continuous with the muscular sheaths.
The muscles of the orbit are seven in number: one, the levator palpebra?
superioris, belongs to the upper eyelid ; the other six are muscles of the eyeball.
M. Levator Palpebrse Superioris. The levator palpebrae superioris lies
immediately beneath the orbital periosteum and covers the superior rectus muscle.
It has a narrow origin above that muscle from the margin of the optic foramen.
It expands as it passes forwards, to end, in relation to the upper lid, in a
membranous expansion which is inserted in a fourfold manner: (1) into the
orbicularis oculi and skin of the upper lid, (2) mainly into the superior border of
the superior tarsus, (3) into the conjunctiva, and (4) by its edges into the upper
border of the margin of the orbital opening.
THE FASCIJE AND MUSCLES OF THE OEBIT.
453
Nerve-Supply. The muscle is supplied by the superior division of the oculo-motor nerve.
Actions. It elevates the upper eyelid and antagonises the action of the orbicular! s oculi
muscle.
ORBICULAKIS OCULI
\
RECTUS
SUPERIOR
LEVATOR PALPEBR^E
SUPERIORIS
Mm. Recti. The recti muscles are four in number superior, inferior, medial,
and lateral. They all arise from a
membranous ring surrounding the
optic foramen, which is separable into
two parts a superior common tendon,
giving origin to the superior and
medial recti and the superior head of
the lateral rectus; and an inferior
common tendon, giving origin to the
medial and inferior recti and the in-
ferior head of the lateral rectus. The
two origins of the lateral rectus muscle
are separated by the passage into the
orbit of the oculo-motor, naso-ciliary,
and abducent nerves. Forming flat-
tened bands which lie in the fat of the
orbit around the optic nerve and eye-
ball, the four muscles end in tendons
which pierce the fascia bulbi, and are
inserted into the sclera about eight
millimetres (three to four lines) behind
the margin of the cornea.
The superior and inferior recti are
inserted in the vertical plane slightly
medial to the axis of the eyeball ; the
lateral and medial recti in the trans-
verse plane of the eyeball; and all are attached in front of the equator of the
eyeball.
M. Obliquus Superior. The obliquus superior arises from the margin of the
optic foramen between the rectus superior and rectus medialis. It passes forwards,
as a narrow muscular band, medial to the rectus superior, and at the anterior
margin of the orbit
forms a narrow ten-
don which passes
through a special
fibrous , pulley
(trochlea) attached
to the roof of the
orbit.
Its direction is
then altered, and
passing laterally,
between the tendon
of the superior
rectus and the eye-
ball, it is inserted
into the sclera be-
tween the superior
and lateral recti,
midway between
FIG. 400. MUSCLES OF THE EIGHT ORBIT (from above).
OBLIQUUS SUPERIOR
LEVATOR PALPEBRA SUPERIORIS (cut)
RECTUS SUPERIOR
RECTUS LATERALIS
Oculo-motor
nerve
Naso-ciliary
nerve
Abducent nerve
OBLIQUUS INFERIOR
RECTUS INFERIOR
FIG. 401. MUSCLES OF THE LEFT ORBIT (from lateral aspect).
jm
a. of the cornea and the entrance of the optic nerve.
Obliquus Inferior. The obliquus inferior arises from the medial side of
' of the orbit just behind its anterior margin, and lateral to the naso-
lacrimal groove.
forms a slender rounded slip, which curls round the inferior rectus tendon.
306
454
THE MUSCULAR SYSTEM.
and passes between ' the lateral rectus and the eyeball, to be inserted into the
sclera between the superior and lateral recti, and farther back than the superior
oblique muscle.
M. Orbitalis (O.T. Miiller's muscle) is a rudimentary bundle of non-striated muscular fibres
bridging across the inferior orbital fissure and infra-orbital groove. It is supplied by fibres from
the sympathetic, and may have a slight influence in the protrusion of the eyeball.
Lacrimal gland
Frontal nerve
Supra-orbital nerve
Lacrimal nerve
Nerves to rectus superior and
leva tor palpebrae superioris,
from oeulo-motor nerve
Trochlear ner
RECTUS LATERALI
Abducent nerv
Oculo-motor nerve (inferior
division)
Ciliary ganglion
Nerve to rectus inferior, from
oculo-motor nerve
Nerve to obliquus inferior,
from oculo-motor nerve
Supra-trochlear nerve
LEVATOR PALPEBR.E
SUPERIORIS
RECTUS SUPERIOR
OBLIQUUS SUPERIOR
Anterior ethmoidal branch
of naso-ciliary nerve
Infra-trochlear branch
RECTUS MEDIALIS
Nerve to rectus medialis, from
oculo-motor
.Ophthalmic artery
Optic nerve
Long ciliary nerves
RECTUS INFERIOR
OBLIQUUS INFERIOR
FIG. 402. SCHEMATIC REPRESENTATION OF THE NERVES WHICH TRAVERSE THE CAVITY OF THE RIGHT ORBIT.
Nerve-Supply. The muscles of the eyeball are supplied by the third, fourth, and sixth
cerebral nerves. The trochlear (fourth nerve) supplies the obliquus superior; the abducent
(sixth) supplies the rectus lateralis ; the oculo-motor (third nerve) supplies the others recti,
superior, inferior, and medialis, and obliquus inferior.
Actions. The six muscles inserted into the eyeball serve to move the longitudinal axis .J
of the eyeball upwards, downwards, medially, and laterally, besides causing a rotation of the
eyeball on its own axis. The following table expresses the action of individual muscles. It must
be remembered that, while similar movements occur simultaneously in the two eyeballs, the ,j
horizontal movements may, by adduction of the muscles of both sides, cause convergence of the
axes of the two eyeballs for the purposes of near vision.
a. Adduction.
Abduction.
Rectus medialis
Rectus superior
Rectus inferior
Rectus lateralis
Obliquus superior \(correcting
Obliquus inferior ) adductors)
b. Elevation.
Depression.
Rectus superior
Obliquus inferior
Rectus inferior
Obliquus superior
c. Rotation laterally.
Rotation medially.
Obliquus inferior
Obliquus superior
Rectus superior),. ,-, . N
Rectus inferior }( adduction)
Muscles of Mastication.
The muscles of mastication comprise the masseter, temporal, external an(
internal pterygoids, and buccinator (described above).
M. Masseter. The masseter is the most superficial. Covered by the paroti-
gland on the side of the face, it has an origin which is partly tendinous an'
partly fleshy. It arises in two parts : (1) superficially from the inferior border c
the zygomatic arch in its anterior two-thirds, and (2) more deeply from the dee
surface of the zygomatic arch in its whole length. The superficial fibres ai
MUSCLES OF MASTICATION.
455
External ptei-y-
goid (insertion)
M. triangularis
(origin)
M. quadratus
labii inferioris
(origin)
M. mentalis
(origin)
Platysma
(insertion)
FIG. 403. MUSCLE- ATTACHMENTS TO THE LATERAL ASPECT OF THE MANDIBLE.
directed downwards and backwards towards the angle of the mandible ; the deeper
fibres are directed vertically downwards.
The muscle is inserted- by fleshy and tendinous fibres into the lateral surface
of the ramus and angle of the mandible and the coronoid process (Fig. 403).
The deepest fibres
blend with the
fibres of the sub-
jacent temporal
muscle.
The muscle is
partially concealed
on the face by the
parotid gland, ac-
cessory parotid
gland, and parotid
duct; by the ex-
ternal maxillary
artery; the branches
of the facial nerve ;
and by the- zygo-
matic and platysma
muscles. It conceals
the ramus of the
mandible, and, at its
anterior border, is
separated from the buccinator muscle by the corpus adiposum luccce.
M. Temporalis. The temporal muscle is a fan-shaped muscle arising from
the whole area of the temporal fossa, as well as from the temporal fascia which
covers it. Its converging fibres pass medial to the zygomatic arch.
The muscle is in-
serted into the deep
surface and apex of the
coronoid process, and
into the anterior border
of the ramus of the
mandible (Figs. 403
and 404).
The origin of the
muscle is concealed by
the temporal fascia.
As it passes to its in-
sertion the muscle is
concealed by the zygo-
matic arch, the masseter
muscle, and the coronoid
process of the mandible.
It is separated from the
external pterygoid in a
majority of cases by the
internal maxillary
artery. The masseteric
nerve and vessels appear at its posterior border ; the buccinator nerve and vessels
at its anterior border.
M. Pterygoideus Externus. The external pterygoid muscle is deeply placed
under cover of the temporal muscle, in the infra-temporal fossa. It arises by two
heads, superior and inferior. The superior head is attached to the infra-temporal
surface of the great wing of the sphenoid ; the inferior head takes origin from the
lateral surface of the lateral pterygoid lamina of the pterygoid process.
The muscle is directed laterally and backwards, to be inserted into (1) the
30 c
External ptery-
goid (insertion)
Genio-
glossus
(origin)
Genio-liyoid
(origin)
FIG. 404. MUSCLE-ATTACHMENTS ON THE MEDIAL SIDE OF THE
MANDIBLE.
456
THE MUSCULAE SYSTEM.
Galea aponeurotica
Temporal fascia
Temporal fascia (deep
layer)
OCCIPITALIS MUSCLE
TEMPORAL MUSCLE
Auriculo-temporal nerve
Superficial temporal
artery
MASSETEE (deep fibres
Parotid gland
(drawn backwards
and downwards)
-ORBICULARIS OCULI
_CAPUT ZYGOMATICUM
OF QUADRATUS
LABII SUPERIORIS
MASSETER (superficial
^fibres)
Parotid duct
BUCCINATOR
TRIANGULARIS MUSCLE
External maxillary
artery
FIG. 405. MUSCLES OP MASTICATION (superficial view).
TEMPORAL MUSCLE
BUCCINATOR
FIG. 406. THE RIGHT TEMPORAL MUSCLE. (The Zygomatic Arch and the Masseter Muscle have been removec
MUSCLES OF MASTICATION.
457
fovea pterygoidea on the anterior aspect of the neck of the mandible (Figs. 403
and 404, p. 455), and (2) the articular disc and capsule of the mandibular
articulation.
This muscle is covered by the insertion of the temporal muscle and the coronoid
process of the mandible, and is usually crossed by the internal maxillary artery.
It conceals the mandibular branch of the trigeminal nerve, and the pterygoid origin
of the internal pterygoid muscle.
M. Pterygoideus Internus. The internal pterygoid muscle, placed beneath
the external pterygoid muscle and the ramus of the mandible, has likewise a
double origin (1) from the medial surface of the lateral pterygoid lamina and the
Tamidal process of the palate bone, and (2) by a stout tendon from the tuberosity
TEMPORAL MUSCLE (reflected
EXTERNAL PTERYGOID
INTERNAL PTERYGOID
Pterygo-mandibiilar raphc
BUCCINATOR
FIG. 407. THE PTERYGOID MUSCLES OF THE RIGHT SIDE.
the maxilla. Its two heads of origin embrace the inferior fibres of the external
pterygoid muscle.
It is quadrilateral in form, and is directed downwards, laterally, and backwards
lateral to the auditory tube and the tensor and levator muscles of the palate,
to be inserted into a triangular impression on the medial surface of the mandible,
between the mylo-hyoid groove and the angle of the bone (Fig. 404, p. 455).
This muscle is covered by the ramus of the mandible and temporal muscle,
and partially by the external pterygoid muscle. In contact with its superficial
surface are the spheno-mandibular ligament, and the inferior alveolar and lingual
nerves and their accompanying vessels. The muscle conceals the tensor veli
palatini and the wall of the pharynx (superior constrictor).
Nerve-Supply. The mandibular division of the trigeminal nerve supplies all the muscles of
mastication except the buccinator, which is supplied by the facial nerve. The internal pterygoid
1vi uscle 13 supplied by the nerve before its division into anterior and posterior parts ; the other
les are innervated by the anterior trunk.
muse
mus :
Actions. The above muscles, assisted by others in the neck, produce the various move-
ments of the mandible as follows :
458
THE MUSCULAK SYSTEM.
a. Opening of the Mouth.
Weight of the mandible
Digastric
Mylo-hyoid
Genio-hyoid
Genioglossus
Infra-hyoid
muscles
b. Protrusion of the Mandible.
External pterygoid
Internal pterygoid
Temporal (anterior fibres)
Closure of the Mouth.
Masseter
Temporal
Internal pterygoid
Retraction of the Mandible.
Temporal (posterior fibres)
c. Lateral Movement of the Mandible.
External pter
Internal
one side)
THE MUSCLES OF THE NECK.
In addition to those included among the muscles of the back (p. 438), the
following series of muscles occur in the neck : (1) sterno-cleido-mastoid ; (2) the
muscles of the hyoid bone (supra-hyoid and infra-hyoid) ; (3) the muscles of the
tongue (extrinsic and intrinsic) ; (4) the muscles of the pharynx and soft palate ;
and (5) the prse vertebral muscles.
M. Sternocleidomastoideus. The sterno-mastoid muscle is the prominent
muscle projecting on the side of the neck, and separating the anterior from the
posterior triangle. It arises by two heads (1) a narrow, tendinous, sternal head,
from the anterior surface of the manubrium sterni (Fig. 330, p. 370), and (2) a
broader clavicular origin, partly tendinous, partly fleshy, from the superior surface
of the clavicle in its medial third (Fig. 327, p. 366). The muscle is inserted into
the lateral surface of the mastoid portion of the temporal bone and into the
superior nuchal line of the occipital bone (Fig. 396, p. 444).
The muscle passes obliquely over the side of the neck, separating the anterior
from the posterior triangle. It is almost superficial in its whole extent, but is
overlapped superiorly by the parotid gland and is covered in its inferior part by the
platysma. It is crossed by the external jugular vein, and by superficial branches
of the cervical plexus. Its deep surface is in contact with: (a) in its lower third, the
infra-hyoid muscles, which separate it from the common carotid artery, and the
subclavian artery and the internal jugular vein ; (&) in its middle third, with th*
cervical nerves which emerge between the transverse processes of the cervic*
vertebrae to form the cervical plexus ; and (c) in its superior third, with the splenii
capitis muscle, and the accessory nerve, which there pierces the deep surface of tl
muscle. Near its insertion the muscle is related to the splenius capitis, longissimu*
capitis, the posterior belly of the digastric, and the occipital artery.
The sterno-cleido-mastoid muscle is properly divisible into three parts : (1) sterno-mastoii
placed superficially, and passing obliquely from the sternum to the mastoid process ; (2) cleido-
mastoid, placed more deeply, and directed vertically upwards from the clavicle to the mastoic
process ; and (3) cleido-occipitalis, passing obliquely upwards and backwards behind the cleido
mastoid to the superior nuchal line of the occipital bone.
Nerve-Supply. The sterno-mastoid muscle is innervated by the accessory nerve, joined
a branch from the cervical plexus (C. 2.).
Actions. When one muscle acts alone, it flexes the head laterally, and rotates it to th
opposite side. The two muscles acting together (1) flex the head in a forward direction, and
act as extraordinary muscles of inspiration, by raising the sternum and clavicles.
The Muscles of the Hyoid Bone.
The muscles attached to the hyoid bone are in three series : (1) infra-hyoi'
muscles, connecting the hyoid bone to the scapula, the wall of the thorax, an
THE MUSCLES OF THE HYOID BONE.
459
thyreoid cartilage ; (2) supra-hyoid muscles, connecting it to the mandible, cranium,
and tongue ; and (3) the middle constrictor muscle of the pharynx (p. 464).
The infra-hyoid muscles, comprise the omo-hyoid, sterno-hyoid, sterno- thyreoid,
and thyreo-hyoid muscles.
M. Omohyoideus. The omo-hyoid is a muscle with two bellies, anterior and
posterior. The posterior belly arises from the superior margin of the scapula and
the superior transverse scapular ligament (Fig. 333, p. 372). It forms a narrow
muscular band, which passes obliquely forwards and upwards, and ends in an
intermediate tendon beneath the sterno-mastoid muscle.
From this tendon the anterior belly proceeds upwards, to be inserted into the
lateral part of the inferior border of the body of the hyoid bone.
The posterior belly of the muscle separates the posterior .triangle into occipital
and subclavian parts ; the anterior belly crosses the common carotid artery at the
STYLOGLOSSUS
V \ GEN 10-
GLOSSUS
-A- HYOGLOSSUS
GENIO-HYOID
MYLO-HYOID
' DIGASTRIC (anterior belly)
.STERNO-THYREOID
STERNO-HYOID
FIG. 408. THE MUSCLES OF THE TONGUE AND HYOID BONE (right side).
level of the cricoid cartilage, and in the anterior triangle forms the boundary
between the muscular and carotid triangles. A process of the deep cervical fascia
binds down the tendon and the posterior belly to the clavicle and the first rib.
M. Sternohyoideus. The sterno-hyoid muscle arises from the posterior
surface of the manubrium, from the back of the first costal cartilage, and from the
clavicle (Fig. 327, p. 366).
It passes vertically upwards in the neck, medial to the omo-hyoid and anterior
the sterno-thyreoid muscle, to be inserted into the medial part of the body of
the hyoid bone. " Except near its origin, which is covered by the sternum, clavicle,
and sternal head of the sterno-mastoid, the muscle is superficially placed.
M. Sternothyreoideus. The sterno-thyreoid muscle arises beneath the
sterno-hyoid from the back of the manubrium and first costal cartilage.
Broader than the preceding muscle, it passes upwards, and slightly in a lateral
.rection in the neck, in front of the trachea and thyreoid gland, and deep to the
rno-mastoid, omo-hyoid, and sterno-hyoid muscles. It is inserted into the oblique
sterno
460
THE MUSCULAK SYSTEM.
line of the thyreoid cartilage. The muscle is marked by an oblique tendinous
intersection in the middle of its length.
M. Thyreohyoideus. The thyreo-hyoid muscle continues the line of the
preceding muscle to the hyoid bone. Short and quadrilateral, it arises from the
oblique line of the thyreoid cartilage.
Passing over the thyreo-hyoid membrane, deep to the omo-hyoid and sterno-
hyoid, it is inserted into the body and great cornu of the hyoid bone.
The levator glandulae thyreoideae is an occasional slip stretching between the hyoid bone
and the isthmus or pyramid of the thyreoid gland.
STERNO-CLEIDO-
MASTOID
SEMISPINALIS CAPITIS
SPLENIUS CAPITIS
LEVATOR SCAPULAE
SCALENUS MED1US
SCALENUS ANTERIOR
OMO-HYOID
TRAPEZIUS
MYLO-HYOID
j- DIGASTRIC
HYOGLOSSUS
STYLO-HYOID
MIDDLE CONSTRICTO:
THYREO-HYOID
INFERIOR
CONSTRICTOR
^OMO-HYOID
INFERIOR
CONSTRICTOR
STERNO-HYOID
STERNO-THYREOII .
FIG. 409. THE MUSCLES OF THE SIDE OF THE NECK (anterior and posterior triangles).
Nerve-Supply. TJae sterno-hyoid, sterno- thyreoid, and omo-hyoid are supplied by the ansa
hypoglossi ; the thyreo-hyoid, by a special branch from the hypoglossal nerve. Through the ansajM
hypoglossi the muscles are innervated by nerves which are ultimately derived from the first
three cervical nerves. The descendens hypoglossi is derived from the first two cervical nerves,
the descendens cervicis by the second and third ; and these two trunks combine to form the '
ansa. The thyreo-hyoid muscle is innervated (through the hypoglossal) from the loop between if
the first and second cervical nerves.
Actions. The sterno-hyoid, sterno-thyreoid, and omo-hyoid are depressors of the hyoid bone
The two former muscles are also accessory muscles of inspiration. The omo-hyoid is a feeble
elevator of the scapula. The thyreo-hyoid is, on the one hand, an elevator of the thyreoid cartilage
and acting with the previous muscles, on the other hand, it is a depressor of the hyoid bone.
The supra-hyoid muscles comprise the digastric, stylo-hyoid, mylo-hyoid, anc
THE MUSCLES OF THE HYOID BONE.
461
( gejiio- hyoid muscles; and also two muscles, the genioglossus and hyoglossus,
which will be described along with the extrinsic muscles of the tongue.
M. Digastricus. The ' digastric muscle, as its name implies, possesses two
bellies anterior and posterior.
The posterior ~belly arises, under cover of the sterno-mastoid muscle, from the
mastoid notch medial to the mastoid process. It is directed forwards and down-
wards, in company with the stylo-hyoid muscle, to end in an intermediate tendon,
which is connected by a pulley-like band of cervical fascia to the body of the hyoid
bone.
The anterior belly of the muscle is directed forwards and upwards, over the
rnylo-hyoid muscle, to the chin, and is inserted into the oval digastric fossa on the
inferior border of the mandible close to the symphysis (Fig. 410).
The muscle forms the inferior boundary of the submaxillary division of the
anterior triangle, containing the submaxillary gland. The posterior belly in
company with the stylo-hyoid crosses the carotid arteries and internal jugular vein.
The occipital artery ex-
tends posteriorly along
its inferior margin, and
the parotid gland covers
its superior border.
Thp- hypoglossal nerve
emerges from under
cover of the muscle.
The anterior belly, as it
passes to its insertion,
lies upon the mylo-
hyoid muscle.-
Nerve - Supply. The
rterior belly is supplied
the facial nerve ; the
anterior belly by the nerve
to the mylo-hyoid, a branch
of the inferior alveolar
nerve.
External ptery-
goid (insertion)
Genio-
glossus
(origin)
Genio-hyoid
(origin)
FIG. 410. MUSCLE-ATTACHMENTS ON THE MEDIAL SIDE OF THE
MANDIBLE.
M. Stylohyoideus.
-The stylo-hyoid
muscle arises from the
posterior border of the styloid process of the temporal bone.
Crossing the anterior triangle obliquely, along with the posterior belly of the
digastric muscle, it is inserted into the body of the hyoid bone, by two slips which
enclose the tendon of the digastric muscle.
Nerve-Supply. Facial nerve.
M. Mylohyoideus. The mylo-hyoid muscle forms with its fellow a
diaphragm in the floor of the mouth. It arises from the inferior three-fourths of
the mylo-hyoid ridge of the mandible (Fig. 410).
t is directed downwards and medially, to be inserted into (1) the superior border
the body of the hyoid bone, and more anteriorly (along with the opposite muscle)
into (2) a median raphe extending from the hyoid bone nearly to the chin.
The muscle is in contact, on its superficial or lateral surface, with the digastric
muscle and the submaxillary gland. Its deep or medial surface is partially
ered by the mucous membrane of the floor of the' mouth, and is separated from
B muscles of the tongue by the deep part of the submaxillary gland, the sub-
;ual gland, the submaxillary duct, and the lingual and hypoglossal nerves.
Nerve-Supply. The muscle is supplied by the nerve to the mylo-hyoid, a branch of the
inferior alveolar nerve.
M. G-eniohyoideus. The genio-hyoid muscle arises from the inferior of the
) mental spines on the posterior surface of the symphysis of the mandible
(Fig. 410).
462
THE MUSCULAR SYSTEM.
It is directed downwards and somewhat posteriorly, along the inferior border of
the genioglossus, to be inserted into the anterior surface of the body of the hyoid
bone. The muscles of opposite sides are often fused together.
The muscle is placed deeper than the anterior belly of the digastric muscle and
the mylo-hyoid, and is in contact with the inferior border of the genioglossus
muscle.
Nerve-Supply. It is supplied by the hypoglossal nerve, but its nerve can be traced back
to an origin from the communication between that nerve and the first and second cervical
nerves.
Actions. The digastric, stylo-hyoid, mylo-hyoid, and genio-hyoid muscles are all elevators
of the hyoid bone. The posterior belly of the digastric and stylo-hyoid also retract, while the
anterior belly of the digastric and the genio-hyoid protract it. The anterior belly of the digastric,
mylo-hyoid, and genio-hyoid also assist in opening the mouth.
M. trans versus M. verticalis
linguae linguae
M>
The Muscles of the Tongue.
The muscular substance of the tongue consists of two symmetrical series of
muscles placed on either side of a membranous raphe in the median plane. The
series comprise (1) extrinsic
muscles arising from the soft
palate, styloid process, hyoid
bone and mandible, and
(2) intrinsic muscles proper
to the tongue itself. Each
set consists of four series of
muscles.
A. The extrinsic mus-
cles are four in number:;
(1) genioglossus, (2) hyo-
glossus, (3) styloglossus, and?
(4) glossopalatinus.
Profmrta^^lf^^vmimmimm JfllUlf M - G-enioglossus.-
lingute'
artery .V^j
Septum
M. longitudffife
Fat
FIG. 411. A, TRANSVERSE, AND B, LONGITUDINAL VERTICAL
SECTIONS THROUGH THE TONGUE (Krause).
The genioglossus muscle
(O.T. geniohyoglossus
M. transversus (Fig. 408, p. 459) is an ex
trinsic muscle of the tongu<
as well as a supra -hyoi<
muscle.
It is a fan-shaped muscl
arising by its apex froi
the superior of the two mental spines, behind the symphysis of the mandibl
(Fig. 410, p. 461).
From that origin the muscular fibres diverge ; the lowest fibres are directe
downwards and backwards, to be inserted into the body of the hyoid bone ; th
highest fibres curve forwards, to be attached to the tip of the tongue ; the intei
mediate fibres are attached to the substance of the tongue in its whole lengt
between the base and tip.
The muscles of opposite sides are separated by the median raphe of the tongu :
On the lateral aspect, of each, are the hyoglossus and mylo-hyoid muscles.
M. Hyoglossus. The hyoglossus muscle is also an extrinsic muscle of tl
tongue as well as a supra-hyoid muscle.
It arises from the body and great cornu of the hyoid bone.
It is directed upwards and forwards, to be inserted into the side of the tongi
its fibres interlacing with the fibres of the styloglossus.
The muscle is quadrilateral, and lies between the genioglossus and mylo-hyc
muscles, separated from the latter by the mucous membrane of the floor of t
mouth, the sublingual and part of the submaxillary glands, the lingual and hyj
glossal nerves, and the submaxillary duct.
The chondroglossus is a small separated slip of the hyoglossus, not always present.
THE MUSCLES OF THE TONGUE.
463
M. Styloglossus. The styloglossus muscle arises from the anterior border
of the styloid process near its tip, and from the stylo-hyoid ligament.
It sweeps forwards and medially, and is inserted into the side and inferior
surface of the. tongue, its fibres spreading out to decussate with those of the
i glossopalatinus and hyoglossus muscles beneath the submaxillary gland and the
mucous membrane of the tongue.
M. Glossopalatinus. The glossopalatinus (O.T. palatoglossus) is a thin
sheet of muscular fibres arising from the inferior surface of the soft palate, where
it is continuous with fibres of the opposite muscle.
It passes downwards, in the glosso-palatine arch, and spreads out, to be inserted
into the sides of the tongue, blending with the styloglossus and the deep transverse
fibres of the tongue.
The muscle is placed directly beneath the mucous membrane of the soft palate
and tongue.
B. Intrinsic Muscles of the Tongue. Besides receiving the fibres of insertion
of the extrinsic muscles, the substance of the tongue is composed of four intrinsic
muscles on either side two in the sagittal plane, the superior and inferior longi-
tudinal muscles ; two in the frontal plane, the transverse and vertical muscles.
M. Longitudinalis Superior. The superior longitudinal muscle extends from
base to tip of the tongue. It is placed on its dorsum immediately under the
mucous membrane, into which many of its fibres are inserted.
M. Longitudinalis Inferior. The inferior longitudinal muscle is a cylindrical
band of muscular fibres occupying the inferior part of the organ on each side, in the
interval between the genioglossus and the hyoglossus muscles. Posteriorly some
of its fibres extend to the hyoid bone.
M. Transversus Linguae. The transversus linguae (O.T. transverse fibres) arises
from the median raphe, and radiates outwards to the dorsum and sides of the
tongue, intermingling with the extrinsic muscles and the fibres of the vertical
muscle. It occupies the substance of the tongue between the superior and inferior
longitudinal muscles.
M. Verticalis Linguae. The verticalis linguae (O.T. vertical fibres) arises from
the dorsal surface of the tongue, and sweeps downwards and laterally to its sides,
; intermingled with the fibres of the preceding muscle and the insertions of the
extrinsic muscles. The transverse and vertical muscles form a very considerable
part of the total muscular substance of the organ.
Nerve-Supply. All these muscles except the glossopalatinus are supplied by the hypo-
glossal nerve. The glossopalatinus is supplied by the accessory nerve through the pharyngeal
, plexus.
Actions. The genioglossus and the hyoglossus are both elevators of the hyoid bone
besides having actions in relation, to the tongue. The tongue is protruded by the action of the
I posterior fibres of the genioglossus, retracted by the anterior fibres aided by the styloglossus.
The styloglossus and glossopalatinus are elevators, while the genioglossus and hyoglossus are
, depressors of the tongue.
Actions of the Infra -hyoid and Supra -hyoid Muscles, and the Muscles of the
Tongue. These muscles have a complexity of action, owing to their numerous attachments to
more or less movable points. The movements for which they are responsible in whole or part are :
L) movements of the hyoid bone in mastication and deglutition, (2) movements of the thyreoid
cartilage, (3) movements of the tongue, (4) movements of the head, (5) movements of the shoulder,
. and (6) respiration.
) Movements of the Hyoid Bone. The hyoid bone is elevated or depressed, and moved for-
wards or backwards along with the mandible and tongue, in speech, mastication, and swallowing.
a. Elevation.
Depression.
b. Protraction.
Retraction.
Digastric
Stylo-hyoid
Mylo-hyoid
Genio-hyoid
Thyreo-hyoid
Sterno-hyoid
Omo-hyoid
Sterno -thyreoid
Genio-hyoid
Genioglossus.
Stylo-hyoid
Middle constrictor
Genioglossus
Hyoglossus
Muscles closing the
mouth
.
464 THE MUSCULAR SYSTEM.
(2) Movements of the Thyreoid Cartilage. The thyreoid cartilage is raised and lowered
during speech and deglutition.
Elevation.
Depression.
Thyreo-hyoid
Stylopharyngeus
Pharyngopalatinus
Elevators of hyoid bone
Muscles closing mouth
Sterno-thyreoid
Crico-thyreoid
Depressors of hyoid bone
(3) Movements of the Tongue. The chief movements of the tongue in speech and de-
glutition are elevation and depression, protrusion and retraction, and lateral movements.
a. Elevation.
Depression.
Styloglossus (base)
Glossopalatinus
Muscles elevating hyoid bone
Muscles closing mouth
Genioglossus
Hyoglossus
Chondroglossus
Muscles depressing the hyoid bone
b. Protrusion.
Retraction.
Genioglossus (posterior fibres)
Genioglossus (anterior fibres)
Styloglossus
c. Lateral Movements. The muscles of one side only.
(4) Movements of the Head. The sterno-mastoid muscles, acting together, flex the head on
the vertebral column, assisted by the supra-hyoid and infra-hyoid muscles. The sterno-mastoid
muscle of one side, acting alone, bends the head to the same side, and simultaneously rotates it
to the opposite side, as seen in torticollis (wryneck).
(5) Movements of the Shoulder Girdle. The omo-hyoid and sterno-mastoid muscles have
already been included among the elevators of the shoulder girdle.
(6) Respiration. The muscles in the front of the neck are auxiliary muscles in extraordinary
or difficult inspiration. The masseter and temporal muscles fix the mandible ; the hyoid bone
is raised and fixed by the supra-hyoid muscles ; and the sternum is raised by the sterno-mastoid
and infra-hyoid muscles.
The Muscles of the Pharynx.
The muscular envelope of the pharynx is composed of two strata. The externa
or circular layer consists of the three fan-shaped constrictor muscles ; the inter na
or longitudinal layer consists of the fibres of the Stylopharyngeus and pharyngo
palatinus muscles.
M. Constrictor Pharyngis Superior. The superior constrictor muscle
arises successively from the inferior half of the posterior border of the media
lamina of the pterygoid process (pterygopharyngeus), from the pterygo
mandibular raphe (buccopharyngeus), from the mylo-hyoid line of the mandible
(mylopharyngeus) (Fig. 410, p. 461), and from the mucous membrane of the
floor of the mouth (glossopharyngeus).
The muscular fibres radiate backwards, and are inserted, for the most part, intc
a raphe extending down the posterior wall of the pharynx in the median plane
The highest fibres are attached to the pharyngeal tubercle of the occipital bon<
(Fig. 396, p. 444), and the lowest fibres are overlapped by the middle constrictor
A crescentic interval occurs above the muscle, below the base of the skull, in whicl
the auditory tube and the levator and tensor veli palatini muscles appear. It
lower border is separated from the middle constrictor by the stylopharyngeu
muscle.
M. Constrictor Pharyngis Medius. The middle constrictor muscle arise
from the stylo -hyoid ligament and from both cornua of the hyoid bone (chondrc
pharyngeus, ceratopharyngeus).
From its origin the muscular fibres radiate backwards, to be inserted into th
median raphe on the posterior aspect of the pharynx.
THE MUSCLES OF THE PHAKYNX.
465
The superior fibres overlap the inferior part of the superior constrictor ; the
j inferior fibres are concealed from view by the inferior constrictor muscle. In the
(interval between the middle" and inferior constrictors are found the superior
laryngeal artery and internal laryngeal nerve.
M. Constrictor Pharyngis Inferior. The inferior constrictor muscle arises
from the oblique line of the thyreoid cartilage (thyreopharyngeus), and from
the side of the cricoid cartilage (cricopharyngeus).
Its fibres radiate backwards, to be inserted into the median raplie on the
posterior wall of the pharynx, the superior fibres overlapping the inferior part of
the middle constrictor, the inferior fibres blending with the muscular fibres of the
O3sophagus. Below the inferior border of the muscle the inferior laryngeal artery
and nerve enter into relation with the larynx.
Nerve-Supply. The constrictors of the pharynx receive their nerve-supply through the
pharyngeal plexus from the accessory nerve.
The inferior constrictor is supplied also Pharyngo-basiiar fascia
by the external laryngeal and recurrent
branches of the vagus nerve.
The deeper longitudinal stratum
of muscles in the pharyngeal wall
is composed of the insertions of the
stylopharyngeus and pharyngopala-
tinus muscles.
M. Stylopharyngeus. The stylo-
pharyngeus arises from the root of
the styloid process on its medial side,
and passes downwards between the
external and internal carotid arteries.
It enters the wall of the pharynx in
the interval between the superior
and middle constrictor muscles.
Spreading out beneath the middle
I constrictor muscle, it is inserted into
the superior and posterior borders of
the thyreoid cartilage and into the
wall of the pharynx itself, becoming
continuous posteriorly with the palato-
pharyngeus. In the neck the glosso-
pharyngeal nerve winds round it on
its way to the tongue.
Nerve-Supply. Glossopharyngeal
nerve. (Esophagus (with posterior
ends of tracheal rings
showing at the sides)
Auditory tube
LEVATOR VELI
PALATINI
MUSCLE (CUt)
TENSOR VELI
PALATINI
SUPERIOR
CONSTRICTOR
BUCCINATOR
Pterygo-mandi-
bular raphe
STYLO-
PHARYNGEUS
MIDDLE
CONSTRICTOR
Greater cprnu of
hyoid bone
INFERIOR CONSTRICTOR
FIG. 412. POSTERIOR VIEW OF THE PHARYNX AND
CONSTRICTOR MUSCLES.
M. Pharyngopalatinus. The
pharyngopalatinus (O.T. palato-
pharyngeus) occupies the soft palate
and the pharyngeal wall. In the
substance of the soft palate it consists of two layers, a postero-superior layer, thin,
and continuous across the median plane with the corresponding layer on the
opposite side, and an antero-inferior layer, which is thicker, and is attached to
the posterior border of the hard palate. The levator veli palatini and the musculus
uvulae are enclosed between the two layers, which unite at the posterior edge of
the palate, receiving at the same time additional fibres arising from the auditory
tube (salpingopharyngeus). The muscle descends to the pharynx in the
pharyngo-palatine arch.
Its fibres spread out in the form of a thin sheet in the wall of the pharynx,
continuity anteriorly with the stylopharyngeus, and are inserted into the
terior border of the thyreoid cartilage, and behind that into the aponeurosis of
the pharynx, reaching down as far as the inferior border of the inferior constrictor.
The muscle is placed beneath the middle and inferior constrictors, and the fibres
31
466
THE MUSCULAR SYSTEM.
of the muscles of opposite sides decussate in the median plane, in the inferior part
of the pharyngeal wall.
Nerve-Supply. The muscle is innervated through the pharyngeal plexus, by the accessory
nerve.
The Muscles of the Soft Palate.
The soft palate and uvula form a muscular fold, covered on each surface by
mucous membrane, projecting backwards into the pharynx, and forming the posterior
parts of the floor of the nasal
cavities and the roof of the mouth.
The muscular fold is composed
of five pairs of muscles the
pharyngopalatinus, m. uvulse,
levator veli palatini, tensor veli
palatini, and glossopalatinus.
The pharyngopalatinus
muscle has been already described
(p. 465).
The m. uvulae
BUCCINATOR-
MYLO-HYOID
HYOGLOSSUS
DIGASTRIC
STYLO-HYOID
OMO-HYOID
STERNO-HYOID
THYREO-HYOID
CRICO-THYREOID
TENSOR VELI PALATINI
MUSCLE
Auditory tube
LEVATOR VELI PALATINI Q f
Pterygo-mandibular
raphe
SUPERIOR CONSTRICTOR
STYLOPHARYNGEUS
YLOGLOSSUS
Glosso-pharyngeal
nerve
Stylo-hyoid ligament
Hypo-glossal nerve
(0. T.
azygos
consists
two narrow
bundles enclosed,
along with the
insertion of the
levator veli pala-
tini, between the
layers of the
pharyngopala-
tinus. The slips
arise from the
External laryngeal
nerve
FIG. 413. LATERAL VIEW OF THE WALL OF THE PHARYNX.
MIDDLE CONSTRICTOR
DIGASTRIC
Superior laryngeal
nerve
INFERIOR CONSTRICTOR posterior
spine and the
aponeurosis of the
soft palate, and
unite as they pro-
ceed backwards to
end in the uvula.
M. Levator
Veli Palatini.
The levator veli
palatini has a
double origin : (1)
from the inferior
surface of the apex
of the petrous por-
tion of the tern-
(Esophagus
Recurrent nerve
poral bone, and (2) from the inferior part of the cartilaginous part of the
auditory tube. It passes obliquely downwards and medially, across the superior
border of the superior constrictor muscle, and enters the soft palate between the
two layers of the pharyngopalatinus muscle.
It is inserted into the aponeurosis of the soft palate, and some of its fibres
become continuous with those of the opposite muscle.
It is separated from the tensor veli palatini muscle by the auditory tub(
and the deeper layer of the pharyngopalatinus muscle.
M. Tensor Veli Palatini. The tensor veli palatini arises (1) from th<
scaphoid fossa and the angular spine of the sphenoid bone, and (2) from the latera
side of the cartilaginous part of the auditory tube.
LATERAL AND PK^EVEETEBEAL MUSCLES OF THE NECK. 467
It descends, between the internal pterygoid muscle and the medial pterygoid
lamina, and ends in a tendon which hooks round the pterygoid hamulus. The
tendon is inserted, beneath - the levator veli palatini, into the posterior border of
the hard palate, and into the aponeurosis of the soft palate.
M. Glossopalatinus. The glossopalatinus (O.T. palatoglossus), occupying
the inferior surface of the soft palate and the glosso-palatine arch, has already been
described with the muscles of the tongue (p. 463).
Nerve-Supply. The muscles of the soft palate (except the tensor veli palatini, which is
innervated through the otic ganglion by the trigeminal nerve) are supplied through the pharyn-
geal plexus by the accessory nerve.
Actions of the Muscles of the Pharynx and Soft Palate. The muscles of the pharynx
and soft palate are chiefly brought into action in the act of swallowing. This act is divided into
a voluntary stage, in which the bolus lies anterior to the arches of the fauces, and an involuntary
stage, during which the food passes from the mouth through the pharynx. The movements
occurring during the passage of food through the mouth are'as follows : the cheeks are compressed
by the action of the buccinator muscles; the tongue, hyoid bone, and thyreoid cartilage are
successively raised upwards by the action of the muscles which close the mouth and elevate the
hyoid bone. By these means the food is pushed backwards between the palatine arches.
At the same time, by the contraction of the glosso-palatinus and pharyngo-palatinus, the
palatine arches of the fauces are narrowed, while the muscles of the soft palate, contracting,
tighten the soft palate, and by bringing it in contact with the posterior wall of the pharynx,
shut off the nasal portion of the cavity. The elevation of the tongue, hyoid bone, and larynx
simultaneously causes the elevation of the epiglottis and the superior aperture of the larynx,
which is closed by the approximation of the aryteenoid cartilages and the combined action of
laryngeal muscles (aryteenoideus, thyreoarytsenoideus, and thyreoepiglotticus). The food thus
slips over the anterior surface of the epiglottis and the closed superior aperture of the larynx,
and between the palatine arches on either side, into the pharynx. It is now clasped by
the constrictor muscles, which, by their contractions, force it down into the 03sophagus. The
contraction of the constrictor muscles results in a flattening of the pharynx and elevation of its
anterior attachments.
During the act of swallowing, it is generally thought that the auditory tube is opened by
the contraction of the tensor veli palatini muscle, which arises from it. It has been held, on
the other hand, that the auditory tube is closed during swallowing by the compression of ita
wall by the contraction of the levator veli palatini.
Deep Lateral and Prsevertebral Muscles of the Neck.
Three series of muscles are comprised in this group : (1) vert ebro- costal (scaleni,
anterior, medius, and posterior), (2) vertebro- cranial (longus capitis and rectus
capitis anterior, and lateralis), and (3) vertebral (longus colli). They clothe the
anterior surface of the cervical portion of the vertebral column for the most part,
and are in relation anteriorly with the pharynx and oesophagus, and the large
vessels and nerves of the neck.
M. Scalenus Anterior. The scalenus anterior (O.T. anticus) arises from the
anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth
cervical vertebrae.
. It descends, posterior -to the carotid sheath and subclavian vein, to be inserted
into the scalene tubercle and ridge on the first rib (Fig. 414, p. 468).
It is separated posteriorly from the scalenus medius by the roots of the brachial
plexus, the subclavian artery, and the pleura, and it is concealed by the sterno-
mastoid muscle.
M. Scalenus Medius. The scalenus medius arises from the posterior tubercles
of the transverse processes of the cervical vertebras, from the second to the sixth
inclusive.
It descends in the posterior triangle, behind the subclavian artery and the
roots of the brachial plexus, to be inserted into the rough impression on the first
rib behind the subclavian groove (Fig. 414, p. 468). The muscle is pierced by the
dorsal scapular and long thoracic nerves.
It is separated from the scalenus anterior by the subclavian artery and the
roots of the brachial plexus.
M. Scalenus Posterior. The scalenus posterior arises, behind the scalenus
medius, from the posterior tubercles of the fourth, fifth, and sixth cervical transverse
processes. It is inserted into an impression on the outer side of the second rib.
468
THE MUSCULAE SYSTEM.
Serratus posterior
superior (insertion)
Serratus anterior
(origin)
Pectoralis minor (occasional origin)
FIG. 414. MUSCLE- ATTACHMENTS TO THE SUPERIOR SURFACE OF THE
FIRST RIB, AND THE EXTERNAL SURFACE OF THE SECOND KIB
(EIGHT SIDE).
A, First rib ; B, Second rib.
Nerve-Supply. The mus-
cle receives nerves directly from
the anterior rami of the first
four cervical nerves.
Action. Flexion of the
head and cervical vertebrse.
M. Rectus Capitis
Anterior. The rectus
capitis anterior (O.T.
rectus capitis anticus
minor) arises, under cover
of the preceding muscle,
from the lateral mass of
the atlas. It is inserted
into the basilar part of
occipital bone between the
preceding muscle and the
occipital condyle (Fig. 417,
p. 469).
Nerve -Supply. The scalene
muscles are supplied by branches
which arise directly from the
anterior rami of the lowest four
or fiv6 cervical nerves.
Actions. The actions of those
muscles are twofold. They are
lateral flexors of the vertebral
column, and are also important
Scalenus medius (insertion) mugcles of reS piration, as elevators
of the first and second ribs.
M. Longus Capitis.
The longus capitis (O.T.
rectus capitis anticus
major) arises from the an-
terior tubercles of the trans-
verse processes of the third,
fourth, fifth, and sixth cervi-
cal vertebrse.
It forms a fiat triangular
muscle, which is directed up-
wards, alongside the longus
colli muscle and behind the
carotid sheath, to be inserted
into an impression on the
inferior surface of the basilar
part of the occipital bone,
anterior and lateral to the
pharyngeal tubercle (Fig.
417, p. 469).
RECTUS CAPITIS
ANTERIOR
RECTUS CAPITIS
LATERALIS
RECTUS CAPITIS
ANTERIOR
LONGUS CAPITIS
Nerve -Supply. The mus-
cle is innervated by the loop
between the first two cervical
nerves (anterior rami).
Action. Flexion of the
head on the vertebral column.
M. Longus Colli. The
longus colli is a flattened
muscular band extending
from the third thoracic
vertebra to the atlas. It
LONGUS COLLI
FIG. 415. THE PR^EVERTEBRAL MUSCLES OF THE NECK.
LATEEAL AND PK^VEETEBEAL MUSCLES OF THE NECK. 469
is divisible into three portions a vertical, an inferior oblique, and a superior
oblique portion.
Attached to
posterior
tubercles of
transverse
processes
SCALENUS MEDIUS -
LEVATOR SCAPULAE
SPLENIUS CERVICIS
SCALENUS POSTERIOR
ILIOCOSTALIS CERVICIS
LONOISSIMUS CERVICIS
processes
LONGISSIMUS CAPITIS
SEMISPINALIS CERVICIS
MULTIFIDUS
Attached to SEMISPINALIS CAPITIS
articula- '
TV^
NGUS CAPITIS
ILONGUS COLLI
Attached
to anterior
-tubercles of
FIG. 416. SCHEME OF MUSCULAR ATTACHMENTS TO CERVICAL VERTEBRA,
The vertical portion of the muscle arises from the bodies of the first three
thoracic and the last three cervical vertebrae.
Passing vertically upwards, it is inserted into the bodies of the second, third,
d fourth cervical vertebrae.
Semispinalis capitis (insertion)
3tus capitis posterior minor
(insertion)
\
Rectus capitis posterior major
(insertion)
Trapezius (origin)
capitis superior
(insertion)
3tus capitis lateralis (insertion)
Rectus capitis anterior (insertion)
Sterno-cleido-mastoid
(insertion)
Splenius capitis
(insertion)
Superior constrictor of pharynx (insertion)
Longus capitis (insertion)
FIG. 417. MUSCLE- ATTACHMENTS TO THE OCCIPITAL BONE.
The inferior oblique portion arises from the bodies of the first three thoracic
vertebrae.
t is inserted into the anterior tubercles of the fifth and sixth cervical vertebras.
31 a
470 THE MUSCULAR SYSTEM.
The superior oblique portion arises from the anterior tubercles of the transverse
processes of the third, fourth, and fifth cervical vertebrae.
It is directed upwards, to be inserted into the anterior tubercle of the atlas.
Nerve-Supply. It is supplied by nerves from the anterior rami of the second, third, and
fourth cervical nerves.
Action. A flexor of the vertebral column.
M. Rectus Capitis Lateralis. The rectus capitis lateralis, in series with
the posterior inter-transverse muscles in the neck, arises from the transverse
process of the atlas.
It is inserted into the inferior surface of the jugular process of the occipital
bone. It is placed alongside the rectus capitis anterior, separated from it by the
anterior ramus of the first cervical nerve.
Nerve-Supply. The loop between the anterior rami of the first two cervical nerves.
Actions. A lateral flexor of the head and vertebral column. The movements produced by
these muscles are considered along with those of other muscles acting on the head, vertebral
column, and thorax (pp. 445, 446).
THE MUSCLES OF THE THORAX.
Muscles of Respiration.
The muscles which complete the boundaries of the thorax are the diaphragm
and intercostal muscles (external and internal), along with three series of smaller
muscles the transversus thoracis, the levatores costarum, and the subcostal
muscles.
Mm. Intercostales. The intercostal muscles are arranged in eleven pairs,
which occupy the intercostal spaces.
Each external muscle arises from the sharp lower border of a rib, and
is directed inferiorly and anteriorly, to be inserted into the external edge of the
superior border of the rib below. It extends from the tubercle of the rib posteriorly
nearly to the costal cartilage anteriorly. The anterior intercostal aponeurosis is
continuous with it anteriorly, and extends forwards to the side of the sternum.
Each internal muscle arises from the costal cartilage and the internal or
superior edge of the costal groove, and is directed inferiorly and posteriorly, to be
inserted into the internal edge of the superior border of the rib and costal cartilage
below. It extends from the side of the sternum anteriorly to the angle of the rib
posteriorly, where it is replaced by the posterior intercostal aponeurosis extending
to the tubercle of the rib.
The superficial surface of the external muscle is covered by the muscles of
the chest, axilla, abdomen, and back. The deep surface of the internal muscle is in
contact with the pleura.
Mm. Levatores Costarum. The levatores costarum are in series with the
external intercostal muscles. They are twelve small slips arising from the trans-
verse processes of the seventh cervical and upper eleven thoracic vertebrae. Each
spreads out in a fan-like manner as it descends to the lateral surface of the rib
immediately below where it is inserted posterior to the angle.
Mm. Subcostales. The subcostal muscles are slips of muscles found on the
internal surface of the lower ribs near their angles. They are in series with the
internal intercostal muscles, but pass over the deep surface of several ribs.
M. Transversus Thoracis. The transversus thoracis (O.T. triangularis
sterni) occupies the posterior aspect of the anterior thoracic wall, and is separated
from the costal cartilages by the internal mammary vessels. It arises from the
posterior surface of the xiphoid process and body of the sternum as high as the
level of the third costal cartilage.
From that origin its fibres radiate laterally, the lower horizontally, the upper
fibres obliquely upwards, to be inserted into the second, third, fourth, fifth, and
sixth costal cartilages. The muscle is continuous below with the transversus
abdominis.
THE MUSCLES OF THE THOEAX.
471
Diaphragma. The diaphragm is the great membranous and muscular parti-
tion separating the cavities of the thorax and abdomen. It forms a thin lamella
arching over the abdominal cavity, and clothed on that surface, for the most part,
by peritoneum. It is related, on its inferior concave surface, to the liver, stomach,
and spleen, the kidneys and suprarenal glands, and the duodenum and pancreas.
Its superior convex surface projects into the thoracic cavity, rising higher on the
right than on the left side, and is related to the pericardium and pleurse, and along
its margin to the chest wall. The oesophagus and thoracic aorta are in contact
with it posteriorly.
It possesses a peripheral origin from the sternum, ribs, and vertebral column,
EXTERNAL INTERCOSTAL
MUSCLE
^IQUUS EXTERNUS.
ABDOMINIS (reflected)
Anterior intercostal
membrane removed,
exposing the internal
intercostal muscle
INTERNAL INTER-
COSTAL MUSCLE
RECTUS ABDOMINIS
(insertion)
Sheath of the rectus
abdominis
FIG. 418. THE MUSCLES OF THE RIGHT SIDE OP THE THORACIC WALL.
and an insertion into a central tendon. It arises (1) anteriorly (pars sternalis) from
B posterior surface of the xiphoid process by two slender fleshy slips, directed
backwards ; (2) laterally (pars costalis), from the deep surface of the lower six costal
cartilages on each side by fleshy bands which interdigitate with those of the trans-
TSUS abdominis; (3) posteriorly (pars lumbalis), from the lumbar vertebrae, by
the crura, and the medial and lateral lumbo-costal arches. The crura are two
elongated nbro-muscular bundles which arise, on each side of the aorta, from the
anterior surface of the bodies of the lumbar vertebrae, on the right side from
the first three, on the left side from the first two lumbar vertebras. They are
rected upwards and decussate across the median plane in front of the aorta, the
58 of the right crus passing anterior to those of the left crus. The fibres then
encircle the oesophagus, forming an elliptical opening for its passage, and finally
join the central tendon, after a second decussation anterior to the gullet.
31
472
THE MUSCULAR SYSTEM.
The medial part of each crus is wholly tendinous and is sometimes called the cms mediate ;
it is connected with its fellow of the opposite side by a tendinous band called the middle arcuate
ligament, which arches between them, in front of the aorta, and gives origin to fibres which
join the crura as they decussate to encircle the gullet. The most outlying part of the crus is
sometimes called the crus laterale ; its infero-lateral margin is continuous with the medial
lumbo-costal arch. The intermediate part of the crus is the crus intermedium ; the splanchnic
nerves pierce the diaphragm between it and the medial crus. The sympathetic trunk sometimes
pierces the diaphragm between the intermediate and lateral crura.
The arcus lumbocostalis medialis (O.T. internal arcuate ligament) is a thickening
formed by the attachment of the psoas fascia to the body of the first lumbar
vertebra medially and its transverse process laterally. Stretching across the
superior end of the psoas muscle, the ligament gives origin to muscular fibres
which join the fibres of the crus.
The arcus lumbocostalis lateralis (O.T. external arcuate ligament) is the
thickened superior border of the fascia over the quadratus lumber um muscle
(Esophagus and its
opening
Foramen quadratum
(for inferior vena cava)
Middle arcuate
ligament (in front of
aortic opening)
Medial lumbo-c<
Lateral lumbo-costal
QUADRATUS LUMBORUM
MUSCLE
PSOAS MAJOR MUSCLE
Left crus of diaphragm
Right crus of diaphragm
FIG. 419. THE DIAPHRAGM (from below).
and is attached medially to the transverse process of the first lumbar vertebra,
and laterally to the last rib. It gives origin to a broad band of muscular
fibres, separated by an interval from the fibres arising from the medial lumbo-
costal arch which sweep upwards to the central tendon.
From this extensive origin the muscular fibres of the diaphragm converge to
an insertion into a large trilobed central tendon called the centrum tendineum. Of
its lobes the right one is the largest, the middle or anterior is intermediate in
size, and the left is the smallest. It does not occupy the centre of the muscle,
being placed nearer the front than the back. The fibres of the crura are con-
sequently the longest ; those from the xiphoid process are the shortest.
The diaphragm is pierced by numerous structures. The superior epigastric
artery enters the sheath of the rectus abdominis between its sternal and costal
origins ; the musculo-phrenic artery passes between its attachments to the seventh
and eighth ribs. The sympathetic trunk and the splanchnic nerves pierce, or pass
posterior to the diaphragm ; the last thoracic nerve passes behind the lateral
lumbo-costal arch ; and the aorta, the azygos vein, and thoracic duct pass between
the crura, underneath the middle arcuate ligament (hiatus aorticus or aortic opening}.
The special foramina are two in number. The foramen vence cavce (O.T. foramen
THE MUSCLES OF THE THOEAX.
473
quadratum) in the right lobe of the central tendon transmits the inferior vena
cava, and small branches of the right phrenic nerve. The hiatus cesophageus
(wsophageal opening} is in' the muscular substance of the diaphragm, posterior to
the central tendon, and is surrounded by a sphincter -like arrangement of the
crural fibres. Besides the oesophagus, this opening transmits the two vagi nerves.
Middle arcuate ligament
Vena caval
opening
(Esophageal opening in diaphragm
i irior ramus
rth lumbar
nerve
^ irior ramus
c fth lumbar
( Medial and
\ lateral lumbo :
. I. costal arches
Ant. ramus of twelfth
thoracic nerve
Quadratus
lumborum
Ilio-hypogastric
nerve
Ilio-inguinal nerve
Psoas major
Genito-femoral
nerve
Lateral
...cutaneous nerve
of thigh
- Iliacus
Lumbo-sacral
trunk
Femoral nerve
Obturator nerve
FIQ. 420. THE DIAPHRAGM AND POSTERIOR ABDOMINAL WALL.
The diaphragm is found as a complete septum between the thorax and abdomen only in
amals. It is occasionally deficient in the human subject, producing hernia of the diaphragm,
.nto the pericardial cavity through the central tendon, or into the pleural cavity through
Lateral portions of the muscle. A rare condition is congenital deficiency of a part of the
1 half of the muscle, generally placed posteriorly, and on the left side. This produces, by
continuity of the pleural and peritoneal cavities behind the diaphragm, a congenital diaphragmatic
474 THE MUSCULAK SYSTEM.
Nerve-Supply. The intercostal muscles, levatores costarum, subcostal muscles, and traus-
versus thoracis, are all supplied by the anterior rami of the thoracic nerves. The diaphragm
receives its chief, if not its entire, motor supply from the phrenic nerves (C. 3. 4. 5.). It is
innervated also by the diaphragmatic plexus of the sympathetic, and is sometimes said to
receive fibres from the lower thoracic nerves.
Actions. The act of respiration consists of two opposite movements inspiration and ex-
piration.
1. The movement of expiration is performed by (1) the elasticity of the lungs, (2) the weight
of the chest walls, (3) the elevation of the diaphragm, (4) the action of muscles trans versus
thoracis and muscles of the abdominal wall. It is sometimes stated that the interosseous fibres of
the internal intercostal muscles are depressors of the ribs.
2. The movement of inspiration results in the enlargement of the thoracic cavity in all
its diameters. Its antero-posterior and transverse diameters are increased by the elevation and
forward movement of the sternum, and by the elevation and eversion of the ribs, while its
vertical diameter is increased by the descent of the diaphragm.
The muscles of inspiration are divided into two series ordinary and accessory.
a. Ordinary Muscles.
Diaphragm
Intercostals
Scaleni
Serrati posteriores
Levatores costarum
Subcostales
b. Extraordinary and Accessory Muscles.
Quadratus lumborum
Pectorales
Serratus anterior
Sterno-mastoid
Latissimus dorsi
Infra-hyoid muscles
Extensors of the vertebral column
Of the ordinary muscles the diaphragm is the most important. Its action is twofold
centrifugal, elevating the ribs and increasing the transverse and antero-posterior diameters of
the thorax, and centripetal, drawing downwards the central tendon and increasing the vertical
diameter of the thorax. Of the two movements the former is the more important. There has
been considerable diversity of opinion regarding the action of the intercostal muscles. It is
generally agreed that the external muscles elevate the ribs ; it is probable that the whole of each
internal muscle acts in the same way, although it has been stated by different observers that the
whole internal muscle is a depressor; or that the interosseous part is a depressor, the inter-
chondral portion of the muscle an elevator of the ribs.
FASCIAE AND MUSCLES OF THE ABDOMINAL WALL.
The space between the base of the bony thorax and the pelvis is filled up by
a series of muscular sheets, covered externally and internally by fasciae.
FASCIAE.
The fasciae of the abdominal wall are externally, the superficial and deep fasciae
internally, the fascia transversalis, which clothes the interior of the abdominal
cavity, and is continuous with the diaphragmatic, luinbo-dorsal, psoas, iliac, anc
pelvic fasciae, and is lined within by the subserous coat of extra-peritoneal tissue.
The superficial fascia of the abdomen is liable to contain a large quantify
of fat. In the groin it is separated into two layers : a superficial fatty layer con
tinuous over the inguinal ligament with the fascia of the anterior surface o
the thigh (p. 402), and a deeper membranous layer attached to the medial half o
the inguinal ligament, and more laterally to the fascia lata of the thigh distal to tib
inguinal ligament. The two layers are separated by the lymph glands and th
superficial vessels of the groin. Higher up in the abdominal wall the two layer
blend together. As they pass downwards over the spermatic funiculus, they unit
to form the fascia and dartos muscle of the scrotum. The attachment of th
fascia to the groin prevents the passage into the thigh of fluid extravasated in th
abdominal wall.
The deep fascia of the abdominal wall resembles similar fasciae in other situf
tions. It forms an investment for the obliquus externus muscle, and becomes thi
and almost imperceptible in relation to the aponeurosis of that muscle.
FASCIA AND MUSCLES OF ABDOMINAL WALL.
475
Fascia Trans versalis. The fascial lining of the abdominal cavity (fascia
transversalis) consists of a continuous layer of membrane which receives different
names in different parts of its extent. .It covers the deep surface of the transversus
muscle, and is continuous medially with the fascise of the quadratus lumborum
and the psoas muscles. It is continuous above with the diaphragmatic fascia,
and below the iliac crest and the inguinal ligament with the fascia iliaca. Along
with the last-named fascia it forms the femoral sheath, enclosing the femoral vessels
and the femoral canal in their passage to the thigh behind the medial part
of the inguinal ligament (p. 405). It is pierced by the spermatic funiculus or
OBLIQUUS EXTBRNUS
ABDOMINIS
Anterior superior
iliac spine
Aponeurosis of
obliquus externus
Superficial circum-
flex iliac artery
Intercrural fibres
( Attachment^ mem-
j branous layer of
( superficial fascia
Poupart's inguinal
ligament
uperficial epigastric
artery
External pudendal
artery
Superficial sub-inguinal
lymph gland
Great saphenous vein
FIG. 421. SUPERFICIAL ANATOMY OF THE GROIN.
round ligament of the uterus at the abdominal inguinal ring, and its prolongation
into the inguinal canal around the funiculus forms the internal spermatic or in-
fundibuliform fascia. It is lined internally by the peritoneum, from which it, is
separated by a layer of extraperitoneal tissue.
The subserous coat or extraperitoneal tissue is usually loaded with fat ; it envelops
the kidneys, ureters, suprarenal glands, abdominal aorta and inferior vena cava
and their branches, and forms sheaths for the vessels and ducts (ureter, ductus
leferens, etc.). It is continued upwards into the posterior mediastinum of the
thorax through the aortic opening in the diaphragm, and below is in continuity
ith the extraperitoneal tissue in the pelvis. It not only completely invests
kidneys and suprarenal glands, but it also becomes interpolated between the
layers of peritoneum upholding and enveloping the intestines. This tissue is
absent in relation to the diaphragm, on the under surface of which there is no fat.
476
THE MUSCULAK SYSTEM.
THE MUSCLES OF THE ABDOMINAL WALL.
The muscles of the abdominal wall are in three series lateral, anterior, and posterior.
The lateral muscles of the abdominal wall comprise the obliquus externus
abdominis, obliquus internus abdominis, and transversus abdominis.
M. Obliquus Externus Abdominis. The obliquus externus abdominis is a
broad thin sheet of muscle, with an origin from the lateral surfaces of the lower
eight ribs, by slips which interdigitate with the serratus anterior and latissimus
OBLIQUUS EXTERNUS
ABDOMINIS'
(reflected)
Spermatic funiculus--
Bxternal spermatic
fascia'
.OBLIQUOS EXTERNUS
ABDOMINIS
^
* ABDOMINIS
Anterior superior
/'iliac spine
._ TRANSVERSUS
'ABDOMINIS
\OBLIQUUS INTERNUS
ABDOMINIS (reflected)
Aponeurosis of obliquus
"externus (reflected)
Abdominal inguinal ring
Spermatic fnniculus and
infundibuliform fascia
Fascia transversalis
Falx apolfeurotica iu-
guinalis
Fossa ovalis (O.T. saphen-
ous opening)
Great saphenous vein
FIG. 422. THE DISSECTION OF THE INGUINAL CANAL.
dorsi muscles. The muscular fibres radiate downwards and forwards, the lowest
fibres passing vertically downwards.
The muscle fibres of the lower and posterior part of the muscle are inserted,
directly, into the external lip of the iliac crest in its anterior half or two-thirds
(Fig. 369, p. 415). The rest of the muscle fibres are inserted into an extensive
triangular aponeurosis which forms part of the anterior abdominal wall. This
aponeurosis is broader 'below than above ; it is united with part of the aponeurosis
of the obliquus internus in the superior three-fourths of its extent, to form the
anterior layer of the sheath of the rectus muscle. It thus gains an attachment,
above to the xiphoid process, below to the symphysis pubis, and by its intermediate
fibres to the linea alba.
The linea alba is a band of interlacing fibres, about half an inch in width at its
widest part. It occupies the median plane of the anterior abdominal wall in its
whole extent, is pierced by the umbilicus (annulus umbilicalis), and forms the
greater part of the ultimate insertion of all the lateral abdominal muscles.
THE MUSCLES OF THE ABDOMINAL WALL.
477
RECTUS ABDOMINIS
The superior part of the aponeurosis covers the insertion of the rectus abdominis
muscle on the chest wall, and gives origin to fibres of the pectoralis major. In-
teriorly, in the groin, the lower part of the aponeurosis gives rise to the inguinal
ligament, the ligamentum lacunare, the two crura of the subcutaneous inguinal
ring, the external spermatic fascia and the intercrural fibres, and the ligamentum
inguinale reflexum of Colles.
Lig. Inguinale [Pouparti]. The inguinal ligamentum (O.T. Poupart's ligament)
is an aponeurotic band which extends from the anterior superior iliac spine to the
tubercle of the pubis, arching over the iliacus, psoas, and pectineus muscles. It repre-
sents the inferior margin of the aponeurosis of the obliquus externus abdominis, and
it gives attachment below to the iliac portion of the fascia lata of the thigh. Its
lateral part affords partial origin to the obliquus internus and transversus muscles,
and receives the attachment of the fascia transversalis and fascia iliaca ; the medial
part forms the gutter-like floor of the inguinal canal. At its medial end a triangular
band of fibres is
reflected horizon-
tally backwards to
the ilio-pectineal
line, forming the
lig. lacunare [Gim-
bernati] (O.T. Gim-
bernat's ligament),
the lateral edge
of which forms
the medial bound-
ary of the femoral
ring. The femoral
vessels, enclosed in
the femoral sheath,
enter the thigh
posterior to the
inguinal ligament,
On the anterior Posterior aponeurosis
surface of the psoas
major muscle, and
the term super-
ficial femoral arch
is given to the
part of the liga-
ment which covers
the vessels.
Annulus In-
guinalis Subcu-
taneus. The subcutaneus inguinal ring (O.T. external abdominal ring), the place of
exit of an inguinal hernia, is a split in the aponeurosis of the obliquus externus,
just above the tubercle of the pubis. It transmits the spermatic funiculus, or
(in the female) the round ligament of the uterus, covered by the cremaster
muscle or cremasteric fascia. The opening is of considerable extent, and its
edges are drawn together by a thin fascia, strengthened superficially by a number
of arched and horizontal fibres, called the intercrural fibres, which arise from the
inguinal ligament and sweep medially across the cleft in the aponeurosis.
The margins of the ring constitute its crura. The inferior eras is narrow, and
is formed from that part of the aponeurosis which joins the pubic tubercle, and is
continuous with the medial end of the inguinal ligament. The superior eras is the
part of the aponeurosis medial to the ring which is attached to the crest and
symphysis of the pubis. It is flat and broad.
The intercrural fibres and the crura of the subcutaneous inguinal ring are
continuous with a thin tubular sheath, the intercolumnar or external spermatic fascia,
which is attached to the margins of the " ring," and forms an envelope for the
OBLIQUUS EXTERNUS
OBLIQUUS INTERNUS
TRANSVERSUS
ABDOMINIS
Fascia transversalis
Peritoneum
Colon
Extra peritoneal
tissue
Kidney
of transversu
LATISSIMUS DORSI
QUADRATUS LUMBORUM
Psoas fascia %
Second lumbar
vertebra
PSOAS MAJOR
Anterior layer of
lumbo-dorsal
fascia
MULTIFIDUS
SEMISPINALIS
DORSI
Middle layer of lumbo-dorsal fascia
ILIOCOSTALIS
Posterior layer of lumbo-dorsal fascia
LONGISSIMUS DORSI
FIG. 423. TRANSVERSE SECTION THROUGH THE ABDOMEN, OPPOSITE THE
SECOND LUMBAR VERTEBRA.
478
THE MUSCULAK SYSTEM.
spermatic funiculus or round ligament after they have passed beyond the abdominal
wall.
Lig. Inguinale Reflexum Collesi. The reflexed inguinal ligament of Colles
(O.T. triangular fascia), is a triangular band of fibres placed behind the medial
superior crus of the subcutaneous inguinal ring. It consists of fibres from the
OBLIQUUS EXTERNUS
ABDOMINIS
PECTORALIS MAJOR
SERRATUS ANTERIOR
LATISSIMUS DORSI
Sheath of rectus
abdominis'
Anterior superior
iliac spine
The inguinal ligamer
Subcutaneous inguinal
Suspensory ligament
of penis
Spermatic funiculus
FIG. 424. THE LEFT OBLIQUUS EXTERNUS ABDOMINIS
opposite external oblique aponeurosis, which, having traversed the linea alba, to gain
an insertion into the crest and tubercle of the pubis.
The obliquus externus muscle is superficial in almost its whole extent. It ie
overlapped posteriorly by the latissimus dorsi muscle, but may be separated from
it just above the iliac crest by an angular interval (trigonum lumbale or triangle ol
Petit).
M. Obliquus Internus Abdominis. The obliquus internus abdominis is i
broad thin sheet of muscle which lies between the obliquus externus and th<
THE MUSCLES OF THE ABDOMINAL WALL.
479
transversus. It arises from, (1) the lumbo-dorsal fascia, (2) the anterior two-
thirds of the iliac crest, and (3) the lateral half of the inguinal ligament.
It runs for the most part, upwards and forwards, and its highest fibres are
inserted directly into the last three ribs. The rest of the fibres end in an extensive
aponeurosis, broader above than below, which splits along the linea semilunaris,
to form, along with the aponeuroses of the obliquus externus and transversus muscles,
FIG. 425. THE EIGHT OBLIQUUS INTERNUS ABDOMINIS.
the sheath of the rectus abdominis, and is inserted into the seventh, eighth, and ninth
costal cartilages, and into the linea alba from the xiphoid process to the symphysis
pubis. The fibres arising from the inguinal ligament join with those of the
transversus muscle having a similar origin to form the falx aponeurotica inguinalis
(O.T. conjoined tendon), which passes altogether anterior to the rectus muscle, to
be attached to the pubic crest and tubercle, and to the ilio-pectineal line.
The obliquus internus is limited above by the inferior margin of the thorax
480
THE MUSCULAR SYSTEM.
Its lower fibres, arching over the spermatic funiculus, assist in forming, laterally,
the anterior wall of the inguinal canal ; medially, by means of the falx inguinalis,
it helps to form the posterior wall of the canal.
Its lowest fibres are continued into the cremaster muscle, which is prolonged
along the spermatic cord through the inguinal canal.
M. Cremaster. The cremaster muscle forms an investment for the testis and sper-
matic funiculus deep to the external spermatic fascia. In the female it is more largely
represented by fascia than muscular fibres, and constitutes the cremasteric fascia. It
may be said to have an origin from the inferior edge of the obliquus internus and the
Aponeurosis of
obliquus externus
(reflected)
Linea alba
Subcutaneous
inguinal ring
Lig. reflexum inguinale
Inferior crus of
ring
Pubic fascia and
suspensory liga-
ment of penis
OBLIQUUS EXTERNUS
ABDOMINIS
Anterior superior
"iliac spine
OBLIQUUS INTERNUS
ABDOMINIS
Aponeurosis of
.obliquus externus
(reflected)
Spermatic funiculus
-Inguinal canal
.Falx aponeurotica
inguinalis
Lig. reflexum iiiguinale
Inferior crus of sub-
cutaneous inguinal ring
(the inguinal ligament)
Spermatic funiculus
(cut)
FIG. 426. THE LEFT INGUINAL CANAL. STKTJCTTJRES SEEN ON REFLECTION OF THE OBLIQUUS EXTERNUS.
adjacent part of the inguinal ligament. Its fibres form loops over the spermatic funiculus
and testis, the highest fibres getting an insertion into the pubic tubercle.
M. Transversus Abdominis. The transversus abdominis muscle arises (1)
from the deep surface of the costal cartilages of the lower six ribs, interdigitating
with the origins of the diaphragm ; (2) from the lumbo-dorsal fascia ; (3) from the
anterior half of the medial lip of the iliac crest ; and (4) from the lateral third
of the inguinal ligament.'
The muscular fibres run, for the most part, horizontally forwards, and end
in an aponeurosis which has a twofold insertion. (1) After forming (along
with the aponeurosis of the obliquus internus) the posterior layer of the sheath oi
the rectus, the aponeurosis is attached to the xiphoid process and linea alba
(2) The inferior fibres of the muscle arising from the inguinal ligament are joinec
by the inferior part of the obliquus internus to form the larger part of the fab
THE MUSCLES OF THE ABDOMINAL WALL.
481
aponeurotica inguinalis (O.T. conjoined tendon), which passes anterior to the inferior
part of the rectus muscle, to be inserted into the crest and tubercle of the pubis
and the ilio-pectineal line. -
The transversus muscle is separated by the lower intercostal nerves from the
obliquus internus muscle, and is lined on its deep surface by the fascia transversal] s.
Its inferior border forms a concave edge, separated from the inguinal ligament by
a lunular interval in which the fascia transversalis appears, and through which the
spermatic funiculus emerges at the abdominal inguinal ring, under cover of the
obliquus internus muscle and the aponeurosis of the obliquus externus.
OBLIQUUS EXTERNUS
ABDOMINIS
^OBLIQUUS INTERNUS
''ABDOMINIS
Anterior superior
iliac spine
TRANSVERSUS
ABDOMINIS
, OBLIQUUS INTERNUS
ABDOMINIS (reflected)
Aponeurosis of obliquus
"externus (reflected)
Abdominal inguinal ring
.^Spermatic funiculus and
infundibuliform fascia
Fascia transversalis
_.Falx aponeurotica in-
guinalis
.Fossa ovalis (O.T. saphen-
ous opening) '
Great saphenous vein
FIG. 427. THE DISSECTION OF THE INGUINAL CANAL.
The anterior muscles of the abdominal wall include the pyramidalis and rectus
abdominis, enveloped by the sheath of the rectus, on either side of the linea alba.
M. Pyramidalis Abdominis. The pyramidalis abdominis is a small
triangular muscle arising from the pubic crest, anterior to the rectus muscle
(Fig. 428, p. 482).
It is directed obliquely upwards, to be inserted, for a variable distance, into the
linea alba. The muscle is often absent.
M. Rectus Abdominis. The rectus abdominis muscle is broad and strap-
like, and arises, by a medial and a lateral head, from the symphysis and crest of
the pubis (Fig. 428, p. 482).
The muscle expands as it passes upwards, and is inserted, from medial to lateral
side, into the anterior surface of the xiphoid process (Fig. 428, p. 482), and into the
superficial surface of the seventh, sixth, and fifth costal cartilages. On its anterior
32
482
THE MUSCULAR SYSTEM.
surface, but nob extending through the entire substance of the muscle, are three or
more transverse tendinous intersections (inscriptiones tendinese). adherent to the
sheath of the muscle ; the lowest opposite the umbilicus, and the highest about
the level of the xiphoid process. The medial border of the muscle lies alongside
the linea alba ; its lateral border is convex, and corresponds to the linea semilunaris.
The muscle is pierced by the terminal branches of the lower thoracic nerves.
Aponeurosis of
obliquus externus
abdominis (reflected)
RECTUS ABDOMINIS
Anterior lamella of
sheath of rectus
Linea alba
OBLIQUUS EX-
TERNUS ABDOMINIS
OBLIQUUS IN-
TERNUS ABDOMINIS
Aponeurosis of
obliquus externus
Inguinal ligament
Aponeurosis of
obliquus externus
(reflected)
CREMASTER MUSCLE
Spermatic funiculus
OBLIQUUS EXTI
ABDOMINIS
RECTUS ABDOM
(cut)
Posterior lame
' rectal sheath
Anterior lamel
sheath of rectv
Aponeurosis o1
obliquus exter
OBLIQUT'S INTI
ABDOMINIS
TRANSVERSUS
ABDOMINIS
. Linea semicir i
of Douglas
.. "Fascia transv k
RECTUS ABDO 1
-. (cut)
Inguinal liga -t
Obliquus exl '<
aponeurosis
jpT (reflected)
PYRAMIDALI^
ABDOMINIS
Suspensory
of penis
FIG. 428. DEEP DISSECTION OF THE ABDOMINAL WALL. THE RECTUS MUSCLE AND ITS SHEATH.
Vagina M. Recti Abdominis. The sheath of the rectus muscle is derived
from the aponeuroses of the lateral muscles of the abdominal wall, which, aftei
enclosing the muscle, give rise, in the median plane, to the linea alba. At the line*
semilunaris along the lateral border of the rectus muscle, the aponeurosis of th<
obliquus internus splits into anterior and posterior layers. The anterior layer
joined by the aponeurosis of the obliquus externus, passes in front of the rectus
and constitutes the anterior lamina of the sheath. The posterior layer, joined b;
THE MUSCLES OF THE ABDOMINAL WALL.
483
the aponeurosis of the transversus muscle, passes behind the rectus, and constitutes
the posterior lamina of its sheath. This arrangement obtains in the superior three-
fourths of the abdominal wall; Below the level of the iliac crest the sheath of the
muscle is deficient posteriorly, and a crescentic border, the linea semicircularis
(semilunar fold of Douglas), marks the inferior limit of the posterior lamina. In
consequence, the rectus in the lower fourth of the abdominal wall rests directly
upon the fascia transversalis. Close examination, however, usually reveals a thin
layer behind the muscle in continuity with the fold of Douglas, and merging below
with the fascia transversalis. In this region the rectus is covered anteriorly by the
falx aponeurotica inguinalis of the obliquus internus and transversus, and by the
aponeurosis of the obliquus externus,
which gradually separates from the
subjacent aponeurosis. The superior
part of the rectus, lying on the chest
wall, is only covered anteriorly by a
single layer of aponeurosis derived
from the obliquus externus, which in
this situation is giving origin to the
pectoralis major muscle.
Canalis Inguinalis. Inguinal
canal. The spermatic funiculus in
the male, and the round ligament in
the female, in their passage through
the inferior part of the abdominal wall,
pass through the inguinal canal, which
is bounded by these abdominal mus-
cles. The canal begins at the abdominal
inguinal ring, placed half an inch above
the inguinal ligament, and midway
between the anterior superior iliac
spine and the symphysis pubis. It
ends at the subcutaneous inguinal ring,
placed above the tubercle and crest of
the pubis. The anterior wall of the
canal is formed by the aponeurosis of
the obliquus externus, and in its lateral
part by the muscular fibres of the
obliquus internus ; the posterior wall
T . ,.' , , . (I*) In the thoracic wall; II.) In the superior three-
the Canal IS tormed by the taSCia quarters of the abdominal wall ; (III.) In the inferior
transversalis, and in its medial part by fourth of the abdominal wall,
the falx aponeurotica inguinalis ; while A ' RECTUS MUSCLE; B, OBLIQUUS EXTERNUS; c, DIA
the floor of the canal is formed by the
inguinal ligament, and in its medial
part by the lacunar ligament. The
spermatic funiculus, piercing the trans-
versalis fascia, enters the inguinal canal
at the abdominal inguinal ring, and is there invested by its first envelope, the
infundibulifonn or internal spermatic fascia, a sheath of fascia derived from the
margins of the ring and continuous with the fascia transversalis. It then passes
obliquely medially, downwards, and forwards, and escapes below the inferior border
of the obliquus internus muscle, from which it carries off a second investment,
partly fascial, partly muscular, the cremaster muscle or cremasteric fascia. Con-
tinuing its course, in front of the falx inguinalis, it emerges through the sub-
cutaneous inguinal ring, from the edges of which the intercolumnar fascia is
derived, the tJiird or external investment for the funiculus.
Hesselbach's triangle, bounded below by the line of the inguinal ligament,
i medially by the rectus abdominis muscle, and laterally by the inferior epigastric
i artery, coursing upwards and medially beneath the fascia transversalis on the medial
side of the abdominal inguinal ring, is the site of one form of inguinal hernia.
32 a
FIG. 429. THE SHEATH OF THE RECTUS ABDOMINIS
MUSCLE.
PHRAGM ; D, OBLIQUUS INTERNUS ; E, TRANSVER-
SUS ABDOMINIS. a, Anterior layer of rectus sheath ;
b, Fifth costal cartilage ; c, Sixth costal cartilage ;
d, Xiphoid process; e, Posterior layer of rectus
sheath ; /, Fascia transversalis
Linea alba.
Peritoneum ; h,
1, Inferior epigastric artery
484
THE MUSCULAE SYSTEM.
The spermatic funiculus passes over the base of the triangle, covered over by the
aponeurosis of the obliquus externus. Behind the funiculus, and forming the floor
of the triangle, is the fascia transversalis partially covered, in the medial portion of
the triangle, by the falx inguinalis of the obliquus internus and transversus muscles.
Middle arcuate ligament
Vena caval opening
Aortic opening >.__
(Esophageal opening in diaphragn
Anterior ramus
of twelfth
thoracic nerve
Quaclratus_
lumborum
Ilio-hypogastric_
nerve
Ilio-inguinal
Lateral
cutaneous nerve
of thigh
Femoral nerve 3
Genito-femoral
nerve 1
Obturator ne^
Descending branch
of fourth lumbar 1 "
nerve
Anterior ramus
of fifth lumbar
nerve
Medial and
I lateral lunibo-
. I costal arches
Ant. ramus of tw
thoracic nerve
..Quadratus
lumborum
-Ilio-hypogastrie
nerve
ilio-inguinal
-Psoas major
Genito-feinoral
nerve
Lateral
.cutaneous nerve
of thigh
Iliacus
Lumbo-sacral
trunk
Femoral nerve
Obturator nerva
FIG. 430. THE DIAPHRAGM AND POSTERIOR ABDOMINAL WALL.
Inguinal Hernia. For an account of the anatomical relations of the inguinal cana
to the various forms of inguinal hernia, see the section on " Applied Anatomy.""
Nerve-Supply. The nerve-supply of the majority of the foregoing muscles is derived fron
the anterior rami of the lower six thoracic nerves. The pyramidalis muscle is innervated b;
the last thoracic nerve. The cremaster muscle receives its supply from the genito-femora
nerve (L. 1. 2.).
Actions. (1) The chief action of these muscles is to retract the abdominal walls. B
compressing the contents of the abdomen, they are powerful agents in vomiting, defaecatioi
FASCLE OF THE PEKINEUM. 485
micturition, parturition, and laboured expiration. (2) They are also flexors of the vertebral
column and pelvis the muscles of both sides acting together ; the vertebral column and pelvis
are laterally flexed, when one set of muscles acts alone.
The posterior muscles of the abdominal wall and pelvis major include the
psoas (major and minor) and iliacus, described already (p. 410), and the quadratus
lumborum.
M. Quadratus Lumborum. The quadratus lumborum lies in the posterior
wall of the abdomen, lateral to the psoas, and extends between the iliac crest and
the last rib. It arises from the posterior part of the iliac crest, from the ilio-
lumbar ligament, and from the transverse processes of the lower lumbar vertebrae.
It is inserted, above, into the medial part of the inferior border of the last rib
and the transverse processes of the lumbar vertebrae. Its lateral border is directed
obliquely upwards and medially.
It is enclosed between the anterior and middle layers of the lumbo-dorsal
aponeurosis (p. 437^ between the psoas major muscle, in front, and the sacro-
spinalis behind.
Nerve-Supply. The quadratus lumborum is supplied directly by branches from the anterior
rami of the first three or four lumbar nerves.
Actions. The muscle is a lateral flexor of the vertebral column, an extensor of the column
and a muscle of inspiration.
FASCIAE AND MUSCLES OF THE PERINEUM
AND PELVIS.
FASCIAE OF THE PERINEUM.
The superficial fascia of the perineum possesses certain special features. It
is continuous with the superficial fascia of the abdominal wall, thigh, and buttock,
and is prolonged on to the penis and scrotum. In the penis, it is devoid of fat
and consists only of areolar tissue. In the scrotum, it is intermingled with in-
voluntary muscular fibres, and constitutes the dartos muscle, which assists in
suspending the testes and corrugating the skin of the scrotum. This fascia
also forms the septum of the scrotum, which, extending upwards, incompletely
separates the two testes and their coverings. In the female the superficial
fascia, in which there is a considerable quantity of fat, takes a large share in
the formation of the mons Veneris and labia majora pudendi.
The fascia over the posterior part of the perineum fills up the ischio-rectal fossae,
in the form of two pads of adipose tissue, on either side of the rectum and anal
canal. Over the tuberosities of the ischium the fat is intermingled with bands of
fibrous tissue closely adherent to the subjacent deep fascia.
The fascia in the anterior part of the perineum closely resembles the same
fascia in the groin. It is divisible into a superficial fatty and a deeper membranous
layer ; the former continuous with the same layer in the thigh, and with the fat
of the ischio-rectal fossa posteriorly. The deeper membranous layer is attached
laterally to the pubic arch, posteriorly to the base of the fascia inferior of the
urogenital diaphragm and in the median plane to the root of the penis (bulb
and corpus cavernosum urethra) by a median raphe continuous, farther forwards, with
the septum of the scrotum mentioned above. Anteriorly the fascia is continued
over the spermatic funiculi to the anterior abdominal wall. The importance of
this fascia lies in relation to the extravasation of urine from a rupture of the
urethra in the perineum. By the fascial attachments the fluid is prevented from
; passing posteriorly into the ischio-rectal fossa, or laterally into the thigh. It is
directed forwards into relation with the scrotum and penis, and along the
spermatic funiculus to the anterior abdominal wall. The septum of the scrotum
being incomplete, fluid extravasated on one side can pass across the median plane
1 to the opposite half of the perineum and scrotum.
The deep fascia of the perineum exists only in the form of the delicate
fasciae of the muscles.
486
THE MUSCULAE SYSTEM.
THE MUSCLES OF THE PERINEUM.
The perineal muscles are naturally separated into a superficial and a deep set
by the fascia inferior of the urogenital diaphragm. Superficial to it are the
sphincter ani externus, transversus perinei superficialis, bulbocavernosus, and
ischiocavernosus ; deep to it are the sphincter muscle of the membranous urethra
and the transversus perinei profundus.
M. Sphincter Ani Externus. This muscle is fusiform in outline, flattened,
and obliquely placed around the anus and anal canal. It can be separated into
three layers, subcutaneous, superficial, and deep. (1) The most superficial lamina
Posterior scrotal (
nerves \
Perineal branch of
posterior cutaneous
nerve of tliigh
Superficial branch of
perineal nerve
Deep branch of
perineal nerve
Nervus perinei
Inferior hsemorrhoidal
branches
Dorsal nerve of penis
- (displaced)
- Nerve to corpus
cavernosum penis
__ Nerve to corpus
cavernosum urethra
Perineal nerve
Pudeiidal nerve
Inferior hpemorrhoida
branches
Pudendal nerve
FIG. 431. THE MUSCLES AND NERVES OF THE MALE PERINEUM.
consists of subcutaneous fibres decussating posterior and anterior to the anus,
without bony attachments. (2) The sphincter ani superficialis constitutes the
portion of the muscle. It is attached posteriorly to the coccyx, and, anterioi
the anus, it reaches the central point of the perineum. (3) The deep fibres of
muscle form, for the most part, a complete sphincter for the anal canal. They
continuous with the fibres of the leva tor ani ; they encircle the anal canal, i
blend anteriorly with the central point of the perineum and the transvei
perinei superficialis muscle.
M. Corrugator Cutis Ani. The corrugator cutis ani consists of bundles
unstriped muscular fibres which radiate from the margin of the anal openii
superficial to the external sphincter.
THE MUSCLES OF THE PERINEUM.
487
Nerve-Supply. The external sphincter is supplied by the inferior haemorrhoidal branch of
I the pudendal nerve (S. 3. 4), by the perineal branch of the fourth sacral nerve, and by the deep
perineal branch of the pudendal' nerve (S. 3. 4.).
Actions. The muscle closes the anal aperture. It is a voluntary muscle.
M. Transversus Perinei Superficialis. The transversus perinei superficial
is not always present. It consists of a more or less feeble bundle of fibres, which
arises from the inferior rarnus of the ischium and the fascia over it, and from the
base of the fascia inferior of the urogenital diaphragm.
It passes obliquely over the base of the fascia inferior to be inserted into the
central point of the perineum.
i Nerve -Supply. Deep perineal branch of pudendal nerve (S. 3. 4.).
Action. The two muscles acting together draw backwards and fix the central point of
the perineum.
M. Bulbocavernosus. The bulbocavernosus (O.T. ejaculator urinse), in the
male, surrounds the bulb, corpus cavern osum urethrae, and root of the penis.
It is sometimes separ-
ated into two parts
posterior (compressor
bulbi), and anterior
(compressor radicis
penis). It arises from
the central point of
the perineum, and from
a median raphe on the
under surface of the
bulb and corpus cav-
ernosum urethrse.
The muscular fibres
pass laterally and
forwards and have a
triple insertion : from
behind forwards, (1)
into the inferior sur-
face of the fascia in-
ferior of the urogenital
diaphragm ; (2) into
the dorsal aspect of
the corpus cavernosum
urethrae ; and (3), after
encircling the corpora
cavernosa penis, into
the fascia covering the
dorsum of the penis.
The ischiobulbo-
SUS, not always present,
arises from the ischium,
and passes obliquely medially and forwards over the bulbocavernosus, to be inserted into
'the raphe superficial to that muscle. It belongs to the same stratum as the transversus
'perinei superficialis and ischiocavernosus.
The compressor hemispheriorum bulbi is frequently absent. It consists of a thin
cap-like layer of muscular fibres surrounding the extremity of the bulb under cover of the
bulbocavernosus.
ISCHIO-
CAVERNOSUS
BULBO-
CAVERNOSUS
ISCHIO-
CAVERNOSUS
TRANSVERSUS
PERINEI
SUPER-
FICIALIS
LEVATOR ANI
SPHINCTER ANI EXTERNUS
Fia. 432. THE MUSCLES OF THE FEMALE PERINEUM
(after Peter Thompson).
M. Bulbocavernosus. The bulbocavernosus, in the female (O.T. sphincter
jinse), is separated into lateral halves by the vaginal and urethral openings. It
>rms two thin lateral layers covering the bulb of the vestibule, and arises behind
: the vaginal orifice from the central point of the perineum.
Anteriorly it is inserted into the root of the clitoris, some of its fibres em-
bracing the corpora cavernosa clitoridis so as to reach the dorsum of the clitoris.
488
THE MUSCULAK SYSTEM.
Nerve-Supply. Deep branch of the perinea! nerve (pudendal, S. 3. 4.).
Actions. In the male. The bulbocavernosus contracts the urethra in the emission of
urine and semen, and is an accessory muscle in erection of the penis.
In the Female. The muscle contracts the vaginal orifice, and compresses the bulb of the
vestibule of the vagina.
M. Ischiocavernosus. The ischiocavernosus (O.T. erector penis), in the
male, covers the crus penis. It arises from the ischial tuberosity and the sacro-
tuberous ligament.
Passing forwards, it is inserted by a fascial attachment into the inferior surface
of the crus penis, and into the lateral and dorsal aspects of the corpus caver-
nosum penis.
The ischiocavernosus (O.T. erector clitoridis), in the female, has a similar dis-
position, but is of much smaller size than in the male.
The pubocavernosus is an occasional slip arising from the pubic ramus, and inserted into
the dorsum of the penis. It corresponds to the levator penis of lower animals.
Nerve-Supply. Deep branch of the perineal nerve (pudendal, S. 3. 4.).
Action. The muscle assists in erection of the penis (or clitoris).
Corpus cavernosum penis
(cut)
Nerve to corpus
cavernosum penis
Nerve to dorsum of penis
SPHINCTER URETHRA
MEMBRANACEA:
Nerve to bulb
Fascia superior of uro-
genital urophragm
Pudendal nerve
Bulb of penis
Fascia inferior of
urogenital diaphragm
Crus penis
LEVATOR ANI
FIG. 433. THE FASCLE OF THE UROGENITAL DIAPHRAGM OF THE PERINEUM,
AND THE TERMINATION OF THE PUDENDAL NERVE.
Diaphragma Urogenitale. The sphincter urethrse membranacese and tb
transversus perinei profundus constitute the deeper muscular stratum of th
perineum and form the urogenital diaphragm. They lie between two layers c
fascia called the fascia inferior, and fascia superior of the urogenital diaphragm
(O.T. superficial and deep layers of the triangular ligament).
M. Sphincter Urethras Membranacese. The sphincter of the membranoi
urethras (O.T. compressor urethrse) arises from the inferior part of the pubic ramu
and is directed medially, its fibres radiating so as to enclose the membranous urethr
It is inserted into a median raphe, partly anterior to the urethra, but for tl
most part posterior to it. The fibres most intimately related to the urethra for
a muscular sheath for the canal, and have no bony attachments.
M. Transversus Perinei Profundus. The transversus perinei profundi
consists of a bundle of fibres on each side which arises from the inferior ramus of t.
ischium just below the sphincter urethrse membranacese. It is inserted into
median raphe continuous with that of the sphincter urethrse membranacese. T.
muscle, in fact, constitutes a separate bundle below and behind the sphincter.
The ischiopubicus is a term applied to a feeble bundle of fibres which, wl:
present, lies above and in front of the sphincter urethrse membranacese. It arises fr i
PELVIC FASCIA. 489
the pubic ramus, and is inserted into a median raphe on the dorsum of the membranous
urethra. This muscle is homologous with the compressor venae dorsalis penis of lower
animals.
The sphincter urethrse in the female is smaller than in the male. Its
insertion is modified by the relations of the urethra to the vagina. The anterior
fibres are continuous with those of the opposite side above the urethra ; the
intermediate fibres pass between the urethra and vagina, and the posterior fibres
are attached, along with the transversus perinei profundus (transversus vaginae), into
the side of the vagina.
Nerve-Supply. Deep branch of the perineal nerve (pudendal, S. 3. 4.).
Action. It is a feeble compressor of the membranous urethra, and by no means a sphincter.
In the female it has an accessory influence in constricting the vagina.
THE FASCIAE OF THE PELVIS.
The extra-peritoneal tissue in the pelvic cavity is of great importance. The
hypogastric vessels and their branches, the visceral nerves and plexuses, the
ureters, and ductus deferentes, take their course in this tissue outside the peri-
toneum. It forms in relation to the rectum a thick sheath, for the most part
devoid of fat, which encloses the lower part of the rectum completely, down to its
termination in the anal canal. It forms a kind of packing for the parts of the
bladder uncovered by peritoneum, and is present under the organ in relation to the
symphysis pubis and pubo-prostatic ligaments. In the female it forms, in addition,
the basis or matrix of the broad ligament, and also occurs as a layer devoid of fat,
which loosely connects the anterior surface of the cervix uteri with the base of the
bladder.
FASCIA PELVINA.
The cavity of the pelvis minor, in the erect position, resembles a basin tilted
forward, with its margin formed by the superior aperture of the pelvis, with a
cylindrical wall, and a concave floor, formed by bones, ligaments, and muscles.
The deficiencies in the bony walls of the cavity are filled up laterally by the
obturator membrane and the sacro- tuberous and sacro-spinous ligaments. Tn-
feriorly and anteriorly, behind the symphysis pubis, the fascia diaphragmatis
urogenitalis inferior fills up the pubic arch, and separates the anterior part of the
pelvic cavity from the perineum. The inner surface of this osseo-ligamentous
chamber is lined by a series of muscles ; the piriformis and coccygeus posteriorly,
the obturator internus on each side, and the sphincter urethras membranacese and
transversus perinei profundus, inferiorly and anteriorly, on the pelvic surface of
the inferior fascia of the urogenital diaphragm.
The pelvic fascia, continuous above with the fascial lining of the abdominal
cavity, forms a continuous cylindrical investment for these muscles. On the pelvic
surface of the pubis, where muscles are absent, it is merged with the periosteum,
[t gains an attachment to the spine of the ischium as that projects between the
piriformis and obturator internus muscles. Perforations occur in it for the trans-
mission of the obturator nerve and the parietal branches of the hypogastric
artery. At the inferior aperture of the pelvis, it is attached to the posterior
border or base of the fascia inferior of the urogenital diaphragm, to the ischial
ramus and tuberosity, and to the lower edge of the sacro-tuberous ligament.
Different names are applied to the fascia in relation to the several muscles which
; covers. Posteriorly it constitutes the piriformis fascia: laterally it is the
obturator fascia, while that part of the sheet of fascia which covers the pelvic
surface of the sphincter urethras membranacese and transversus perinei profundus
known as the fascia diaphragmatis urogenitalis superior.
The disposition of the pelvic fascia is complicated by its relations to (1) the
structures which constitute the pelvic floor, and (2) the genito-urinary passages
and the rectum.
490
THE MUSCULAE SYSTEM.
The pelvic floor, tense in its anterior part and flexible posteriorly, is formed
behind the symphysis pubis by, successively, (1) the fasciae of the urogenital
diaphragm and the transversus perinei profundus and sphincter muscle of the
membranous urethra between them, the latter enclosing the urethra; and the
vagina in the female. (2) The perineal body. (3) The levator ani and external
sphincter of the anus on each side of the anal canal; (4) the ano-coccygeal body,
between the anal canal and the coccyx, containing the main insertions of the
levatores ani and external sphincter.
Hypogastric vessels
Vesieula seminalis
Rectal channel '
Recto-vesical layer of pelvic fascia
Ductus deferens
; Anal canal
Obturator foramen
Suspensory ligament
of prostate
Lateral pubo-prostatic ligament
Tendinous arch of pelvic fascia
Prostate
Median pubo-prostatic ligament
Cavum Retzii Urethra
FIG. 434. RELATIONS OF THE PELVIC FASCIA TO THE RECTUM AND PROSTATE.
The levator ani muscle completes the concave floor of the pelvic cavil
sweeping downwards and backwards from its lateral wall, so as to form
muscular diaphragm, with an intra-pelvic and a perineal surface. Its superic
concave pelvic surface occupies the lateral part of the pelvic floor. Its inferi(
convex surface forms the oblique medial wall of the ischio-rectal fossathe, lat
wall of which is formed by the obturator fascia covering the pelvic surfa
of the obturator internus. In this wall is a fascial sheath containing tl
pudendal vessels and nerve. The levator ani is covered on both surfaces by pel 1
fascia. The anal fascia clothing its perineal surface is thin and unimportant
The fascia covering its intra-pelvic surface is thick and strong. At the orij "
PELVIC FASCIA.
491
of the muscle it is continuous with the general fascial lining of the pelvic cavity,
and gives rise to a conspicuous thickening, the tendinous arch (arcus tendineus)
of the pelvic fascia, which stretches like a bow-string from the back of the
symphysis pubis to the ischial spine. This band is related not so much to the
origin of the levator ani muscle, which often extends higher up external to the
pelvic fascia, as to the attachments of the fascial investments of the genito-urinary
passages, to be described below. There are sometimes additional thickenings of
the fascia, branching upwards from the tendinous arch towards the superior aperture
of the pelvis. At the insertion of the levator ani, the fascia clothing its pelvic
surface is attached to the perineal body, the margin of the anal canal, and the
ano-coccygeal body, over which it passes to be continuous, above the raphe of in-
sertion of the levatores ani, with the layer of the opposite side. At the antero-
Posterior (recto-vesical) layer
Superior layer : lateral true ligament of the bladder ,
Suspensory ligament of the prostate gland
Rectal channel
SPHINCTER URETHRA MEMBRANACE^E MTTSCLE Anal canal
Sheath of the prostate gland
FIG. 435. RELATIONS OP PELVIC FASCIA TO THE RECTUM AND PROSTATE
(Median Section of the Pelvis).
inferior border of the muscle the fasciae enclosing it become continuous with the
superior fascia of the urogenital diaphragm ; at its postero-superior border they join
the fascia enclosing the coccygeus muscle.
Within the pelvic basin, the walls and floor of which are thus continuously
invested by the pelvic fascia, are contained the rectum and bladder, and in the female
the uterus, suspended and maintained in position by the peritoneum, extra-peritoneal
tissue, and the pelvic vessels and nerves. They are essentially free to distend or
collapse, and are not bound down by the pelvic fascia. The rectum in both sexes
extends down to the floor of the pelvis, where the anal canal takes its origin. It
s invested by the peritoneum and extra-peritoneal tissue, and occupies a special
rectal channel ; this is lined by pelvic fascia, which gains an attachment to the
floor of the pelvis at the margin of the anal canal.
The arrangement of the fascia in relation to the genito-urinary passages is
essentially different.
Just as from the perineal aspect the inferior aperture of the pelvis is divisible
into two different parts, a posterior or dorsal part, comprising the ischio-rectal
492
THE MUSCULAK SYSTEM.
fossse for the passage of the anal canal, and characterised by looseness and dis-
tensibility ; and an anterior or ventral part, the urethral triangle for the genito-
urinary passages, and characterised by firm fixation to the pubic bones ; so also
from the abdominal aspect it is found that, while in the posterior part of the pelvis
a rectal channel exists, in which the rectum is free to collapse and distend, in the
ventral part of the basin the genito-urinary passages are firmly fixed by means of
PSOAS MAJOR MUSCLE
Suspensory ligament of \ j
the vagina and urethra >
Obturator foramen
Arcus tendineus
Recto- vaginal layer
Lateral pubo-prostatic
ligament
Urethro- vaginal layer
Lig. puboprostati-
cum medium
Cavum Retzii -,
I
Clitoris
Bulb of the /'
vestibule
Pubo-urethral fascia (pubo-vesical .' ;
ligament)
Urethral .layer of pelvic fascia j
Urethra
Vagina
Bulb of the vagina
BULBOCAVERNOSUS
Sciatic
spine
Rectal channel
: . \ EXTERNAL SPHINCTER ANI
', '- t \ LEVATOR ANI
; ' \ INTERNAL SPHINCTER ANI
! : '. Anal canal
I Junction of rectum and anal canal
INTERNAL SPHINCTER ANI
EXTERNAL SPHINCTER ANI
FIG. 436. RELATIONS OF THE PELVIC FASCIA TO THE RECTUM, URETHRA, AND VAGINA (Median Section).
the pelvic, fascia, which gives rise to a special suspensory ligament for the prostate
gland and the prostatic urethra in the male, and for the urethra and vagina in the
female.
A crescentic fold of pelvic fascia (suspensory ligament) arises in the neighbour-
hood of the sciatic spine from the general fascia covering the pelvic wall. It has
a posterior free edge, through which the ductus deferens, vesical vessels, and nerve*
pass. Sweeping across the median plane, this border is continuous with the folc
of the opposite side, the two together constituting the anterior limit of the recta
MUSCLES OF THE PELVIS. 493
ichannel. The fascial fold is composed of two layers, posterior and superior,
! between which is a large plexus of veins. They have separate attachments
laterally to the general pelvic fascia. The posterior (recto-vesical) layer passes
across the pelvis between the prostate gland and the rectum. Its inferior edge
is attached to the perineal body between the base of the fascia of the urogenital
diaphragm and the beginning of the anal canal. It forms a sheath for the
vesiculse seminales and ductus deferentes. This is rather in the form of a septum
| than a complete sheath ; it effectually separates the vesiculse seminales and the
bladder from the rectum, forming the anterior wall of the rectal channel, but it
allows the vesiculse seminales to rest directly against the bladder. The superior
layer extends forwards to the symphysis pubis. It has a lateral origin from the
arcus tendineus in its whole length, and sweeping over the prostate gland, it is
inserted along its line of junction with the bladder, and constitutes the so-called
lig. puboprostaticum laterale (lateral true ligament of the bladder). It contains
numerous bundles of muscular fibres in its anterior part, and forms a sheath
for the passage of the inferior vesical vein along the lateral surface of the
prostate gland. In front the fascia stretches from the back of the symphysis
pubis, the arcuate ligament of the pelvis, and the superior fascia of the uro-
genital diaphragm to the neck of the bladder and the prostate gland, forming the
lig. puboprostaticum medium. It is continuous across the median plane with the
ligament of the opposite side. In the median line, where the two ligaments
unite, a hollow occurs behind the symphysis pubis, known as the cavum Betzii.
This ligament is composed of several layers separated by large veins (the pudendal
plexus), which connect the inferior vesical vein with the dorsal vein of the penis
and the hypogastric vein.
The sheath of the prostate gland (fascia prostatae) is formed by (1) the superior
fascia of the urogenital diaphragm on which it lies, (2) by the general pelvic fascia
covering the intra-pelvic surfaces of the levatores aid on each side, and (3) it is
completed above and behind by the two special layers of pelvic fascia just
described. By these means the prostate gland and prostatic urethra are given a
firm attachment to the anterior part of the pelvic walls and floor.
In the female an essentially similar arrangement of the pelvic fascia occurs in
relation to the vagina and urethra. A crescentic fold of the fascia springs from
the pelvic wall in the neighbourhood of the spina ischiadica, and sweeping medially
to the lateral fornix of the vagina and in front of the rectum, separates into two
| layers, posterior and superior. Between the layers are numerous vessels, which,
I along with the visceral nerves, pierce 'its free edge. The posterior (recto-vaginal)
layer passes medially behind the vagina, and gaining the median plane between
the vagina and rectum, gives rise to the anterior wall of the rectal channel, and
is attached below to the perineal body in the floor of the pelvis. The superior
layer, taking origin from the arcus tendineus, is attached medially to the neck of
the bladder, and constitutes the lateral pubo-vesical ligament. It is continuous in
front with the anterior pubo-vesical ligament, which, as in the male, is divisible into
several layers separated by veins. An intermediate (urethro-vaginal) layer of the
, fascia passes between and separates the urethra and vagina.
The urethra and vagina are by means of these layers of fascia firmly bound to
the pelvic walls and floor, while the uterus and bladder are free to distend in the
pelvic cavity.
MUSCLES OF THE PELVIS.
Diaphragma Pelvis. The pelvic diaphragm is formed by the levator ani
and coccygeus muscles, which serve to uphold the pelvic floor, and are related to
the rectum and the prostate gland or vagina.
M. Levator Ani. The levator ani arises from (1) the inferior part of the
>sterior surface of the body of the pubis, (2) the general pelvic fascia above or
-ong the arcus tendineus, and (3) the pelvic surface of the spine of the ischium.
Us fibres are directed downwards and backwards, to be inserted into (1) the
tral point of the perineum (perineal body), (2) the external sphincter around
494
THE MUSCULAE SYSTEM.
the origin of the anal canal, (3) the ano-coccygeal raphe behind the anus, and (4)
into the sides of the lower coccygeal vertebrae.
The levator ani muscle fills up and completes the pelvic floor on each side of
the median plane. Enclosed in a sheath derived from the general pelvic fascia
along the arcus tendineus, the muscle presents an upper concave surface in
relation to the pelvic cavity, prostate gland (or vagina), and rectum, and an
Sacro-tuberous
ligament (cut)
Extra-
peritoneal
tissue
Spina ischia
dica (cut)
ISCHIO-
CAVERNOSUS
Transversus perinei
superh'cialis
Superior fascia of the
urogenital diaphragm
SPHINCTER URETHRA
MEMBRANACE.E
Inferior fascia of the urogenital
diaphragm
The arcus
tendineus of the
pelvic fascia
Pubic bone
(cut)
SPHINCTER ANI
EXTERNUS
FIG. 437. THE FASCIAL AND MUSCULAR WALL OF THE PELVIS AFTER REMOVAL OF PART OF THE
LEFT HIP BONE.
inferior convex surface which appears in the perineum and forms the medial wal
of the ischio-rectal fossa.
The levator ani is divisible into four parts puborectalis, pubococcygeus, ilk
coccygeus, and iliosacralis. The puborectalis (levator prostatae) is the part inserted int
the central point of the perineum. The pubococcygeus is the part inserted into the ami
and the ano-coccygeal raphe, and the iliococcygeus and ischiococcygeus are represents
by the fibres attached to the sacrum and coccyx. The first two are best developed ; th
last two series of fibres are the most rudimentary. These several parts of the muscl
represent the remains of the flexor caudae of tailed animals.
Nerve-Supply. The levator ani is supplied from two sources : by the perineal (muscula
branch of the pudendal nerve, and, on its pelvic surface, by special branches from the thil
and fourth sacral nerves.
MORPHOLOGY OF THE SKELETAL MUSCLES. 495
Actions. (1) Tli_levator ani. muscle serves to uphold and slightly raise the pelvic floor.
2) It^is likewise capable of producing slight flexion of the coccyx^ (3) The anterior fibres
f theTevator ani, in tlie female, sweeping round The vagina, compress its walls laterally, and
I long with the sphincter vaginae, help to voluntarily diminish the lumen of the tube. (4) The
ame part of the muscle in the male elevates the prostate gland (levator prostatse). (5) Thp p."hiqf
i ction of the levator, ani is in defalcation. Along with the external sphincter it acts as a sphincter
Ffn rectum,"closmg the anal caSiF During defecation the muscle draws upwards the anus
ver the faecal mass, and so assists in its expulsion. (6) 'In parturition, in the same way, the
auscle, contracting below the descending foetal head, retards delivery. Contracting on the foetal
lead, it draws upwards the pelvic floor over the foetus, and so assists delivery.
M. Coccygeus. The coccygeus is a rudimentary muscle overlapping the
josterior border of the levator ani. It arises from the ischial spine and the sacro-
pinous ligament.
It is inserted into the sides of the lower two sacral and upper two coccygeal
ertebrse. The muscle is in contact by its anterior border with the levator ani.
it is enclosed in pelvic fascia, assists in forming the pelvic floor, and is in
ontact laterally with the sacro-tuberous and sacro-spinous ligaments.
Nerve-Supply. The coccygeus is supplied on its pelvic surface by the third and fourth
acral nerves.
Actions. The muscle is a feeble lateral flexor of the coccyx, and assists the levator ani to
.phold the pelvic floor.
[E DEVELOPMENT AND MORPHOLOGY OF THE SKELETAL
MUSCLES.
The mesoderm on either side of the embryonic medullary tube separates into three
iiain parts the myotome, nephrotome, and sclerotome or lateral plates (somatopleure
nd splanchnopleure).
The myotomes are probably directly or indirectly the source of the striated muscles
f the whole body. Each consists at first of a quadrilateral bilaminar mass, resting
.gainst the medullary tube and notochord on either side. The cleft between its two layers
epresents the remains of the ccelomic cavity. In the early stages of embryonic life the
;rowth of the myotome is rapid. On its medial side masses of cells arise, which grow
aedially and surround the medullary tube and notochord to form the foundation of the
ertebral column. On its lateral side cells appear to be given off which participate in the
ormatioii of the cutis vera. At the same time the dorsal and ventral borders of the
ayotome continue to extend, and present extremities (growing points) with an epithelial
tructure for a considerable period. On the dorsal side it overlies the medullary tube, and
, ives rise to the muscles of the back ; while by its ventral extension, which traverses the
omato-pleuric mesoderm in the body wall, it produces the lateral and ventral muscles of
he trunk. By a medial extension it probably gives rise also to the hypaxial muscles of
he neck and loin. The cells of the medial layer of the myotome are responsible for the
ormation of the muscle fibres. The cells elongate in a direction parallel to the
ong axis of the embryo, and give rise, by fusion with the cells of neighbouring myotomes,
o the columns and sheets of muscles of the back and trunk. For the most part (e.g. back
nd abdomen) the originally segmental character of the muscular elements is lost by the
acre or less complete fusion of adjacent myotomes. The intercostal muscles, however,
re the direct derivatives of individual myotomes.
Muscles of the Limbs. In fishes and (doubtfully) reptiles there is evidence that
he myotomes are concerned in the formation of the limb-muscles by their extension into
he limb-bud in a manner similar to that described for the trunk. In birds and mammals,
lowever, in which the limb -bud arises as an undifferentiated, unsegmented mass of
aesodermic tissue, partly from the mesoderm surrounding the notochord, and partly from
'he somato-pleuric mesoblast, the myotomes stop short at the root of each limb, and
3 not penetrate into its substance. Instead, the muscular elements of the limb take
rigin independently as double dorsal and ventral strata of fusiform cells on the dorsal and
entral surfaces of the limb-bud. These strata .are unsegmented ; they are grouped around
he skeletal elements of the limb, and they gradually become differentiated into the muscle
Basses and individual muscles of the limb.
Muscles of the Head. Notwithstanding the obscurity and complexity of this
496
THE MUSCULAR SYSTEM.
subject, it appears certain that at least two series of elementary structures are concerned
in the formation of the muscles of the head and face the cephalic myotomes and the
muscular structure of the branchial arches.
The number of myotomes originally existing in the region of the head is not known,
although it is stated with some authority that nine is the complete number. The first three
are described as persisting in the form of the ocular muscles, the last three in relation to
the muscles of the tongue, while the three intervening myotomes disappear.
FIG. 438. SCHEME TO ILLUSTRATE THE DISPOSITION OF THE MYOTOMES IN THE EMBRYO IN RELATK
THE HEAD, TRUNK, AND LIMBS.
A, B, C, First three cephalic myotomes ; N, 1, 2, 3, 4, Last persisting cephalic myotomes ; C., T., L., S., Co
The myotomes of the cervical, thoracic, lumbar, sacral, and caudal regions ; I., II., III., IV., V., VI
VII., VIII., IX., X., XL, XII. , refer to the cerebral nerves and the structures with which they may T
embryologically associated. ^
The following table shows the possible fate of the cephalic myotomes :
First, Superior, medial and inferior recti, obliquus inferior, levator palpebrse superioris.
Second, Obliquus superior.
Third, Rectus lateralis.
Fourth, Fifth and Sixth, Absent.
Seventh, \
Eighth, ^Muscles of the tongue.
Ninth, i Muscles connecting the cranium and shoulder girdle.
Tenth (first cervical) J
The mesoblastic tissue of the branchial arches is probably concerned in the production
the following muscles of the face and neck :
First (mandibular) arch . . . Muscles of mastication.
[Platysma and facial muscles.
Second (hyoid) arch -j Muscles of the soft palate.
I Stapedius, stylo-hyoid, and digastric.
Tk M (tkyreo-kyoid) arcH
Four* on* FiftK M Z) a rc hes
THE NERVOUS SYSTEM.
I. THE CENTRAL NERVOUS SYSTEM.
ORIGINALLY WRITTEN BY D. J. CUNNINGHAM, F.E.S.,
Late Professor of Anatomy, University of Edinburgh ;
EEVISED AND PARTLY REWRITTEN BY G. ELLIOT SMITH, F.B.S.,
Professor of Anatomy, University of Manchester.
In its original form this chapter represented perhaps the most characteristic work of the late Editor
of this Text-book, which continues to bear his name, and is a lasting memorial of his personality
d scientific attainments. By his lamented death the difficult task has fallen upon the reviser
making such considerable alterations as the rapid changes in the state of our knowledge of the
ervous system have rendered unavoidable, while endeavouring at the same time to
naltered the general character of his friend's work.]
ELEMENTS OF THE CENTEAL NEEVOUS SYSTEM.
tegumentary
peripheral process
--sensory nerve cell
central
process
IY type of nervous system with which we are acquainted, from the simplest
ind most primitive, such as that of Hydra, to the most complex and highly
daborated mechanism p A
, . . >" * rpniim*>nrnr\/ -f^~
ound in man, is com-
)osed essentially of
-hree categories of
Cements. These are
1) sensory cells, so
ituated and so special-
:sed in structure as to
')e capable of being
Affected by changes in
he animal's environ-
ment, and of transmit-
ing the effects of such
Simulation, directly or
ndirectly, to (2) effer-
ent nerve-cells, which
nfluence the muscles
>r other active tissues,
o that the stimulation
'nay find expression in
ome appropriate action;
nd (3) intercalated
lerve-cells, which regu-
ate such responsive be-
laviour by bringing it
mder the influence of other sensory impressions and of the state and activities of
he body as a whole.
497 33
i nte real ate di
nerve cells
muscle
FIG. 439. A DIAGRAM REPRESENTING THE ESSENTIAL FEATURES IN THE
ARRANGEMENT OF THE MOST PRIMITIVE TYPE OF NERVOUS SYSTEM.
498 THE NEEVOUS SYSTEM.
The study of a simple scheme representing the relationship that obtains between
these three classes of elements in the extremely primitive animal, Hydra (Fig. 439),
will make these fundamental facts plain. Changes in the animal's environment
affect the extremities of the peripheral processes of the sensory cells (A, B, and
(7), which in Hydra are situated amongst the ordinary tegumentary cells: the
effect is transmitted by the central processes of such cells (A, for example), either
directly to the efferent cell, represented in the diagram by a motor nerve-cell, or
more usually to an intercalated nerve-cell (a, b, or e). Into this (a) impulses
stream from other intercalated cells (b and c), bringing the impulse from the
sensory cell A under the influence of those coming from B and from more distant
parts of the body through the intermediation of the intercalated cell c. The cells
a, c, and d are connected with the motor nerve-cell. Thus, there is provided a
mechanism whereby the conditions affecting other regions of the body, B and (7,
may influence the nature of the response which the stimulation of A evokes
either increasing or diminishing its effect or perhaps altering its character.
In this way the intercalated nerve-cells form a great co-ordinating mechanism,
linking together all parts of the body in such a way that the activity of any part
of the organism may be influenced by the rest, and thus be enabled to act in the
interest of the whole.
Hence the nervous system becomes the chief means whereby the various parts
of the body are brought into functional relationship one with the other, and co-
ordinated into one harmonious whole.
Throughout the whole course of its subsequent evolution the nervous system is
formed of these three kinds of elements ; and the essential feature in its elaboration
and increasing complexity is the multiplication of the intercalated cells, and their
concentration, together with the motor nerve-cells, to form a definite organ, which
we call the central nervous system.
During this process of development of the more complex forms of nervous
system, most of the sensory cells migrate from their primitive positions in the
skin (Fig. 439) ; and, as the free extremity of the peripheral process retains its
primitive relationship to the skin, such migration of the cell bodies necessitates
a great elongation of their peripheral processes. Although these sensory cells thus
move inwards into the deeper tissues of the body, the great majority of them do
not become incorporated in the central nervous system, but become collected into
groups, which form the ganglia of the sensory nerves.
In addition to its primary functions of (a) providing the means whereby the
organism can be brought under the influence of its surroundings, and (b) co-
ordinating the activities of the whole body, the nervous system also comes tc
perform other functions of wider significance.
In the course of its evolution the co-ordinating mechanism formed by the
intercalated cells becomes so disposed in each animal that an appropriate stimulus
applied to the sensory nerves can evoke a definite response, often of great com
plexity and apparent purposiveness. In other words, the nervous system become;
the repository of those inherited dispositions of its constituent parts whicl
determine the instincts : and in the course of time it eventually provides also th
apparatus by which individual experience and the effects of education can b
brought to bear upon and modify such instinctive behaviour. In other word;
from the nervous system is formed the instrument of intelligence ; and th
relatively great bulk and extreme complexity of that instrument the brain i
man are in a sense the physical expression of human intellectual pre-eminence.
In conformity with its primary function of affording a means of communicatio
with the outside world, almost the whole nervous system in the human embryo, '<
in other animals, is developed from the ectoderm, as has already been explained i
the chapter dealing with General Embryology (p. 30 et seq.}. In the most primiti 1
Metazoa the sensory cells remain in the ectoderm (Fig. 439), but other ectoderm
cells become converted into motor nerve-cells and intercalated nerve-cells, whi<
wander into the underlying tissues (Fig. 439). In the human embryo there is <'
analogous process of development, but with the important difference that t
various nervous elements do not wander into the mesoderin individually.
ELEMENTS OF THE CENTKAL NERVOUS SYSTEM.
499
skin
sensory
cell 7
intercalated
nerve cell
median groove
jiefinite patch of ectoderm is set apart to produce the greater part of the nervous
j issues for the whole body ; and all except the margins of this area sinks into the
|)ody, en masse.
In one area of ectoderm all the motor nerve-cells develop (Fig. 440, d), in another
c) only intercalated nerve-cells, in yet another (6) the sensory cells originate ; and
jrhe rest forms the epidermis of
,he skin (a). With our know-
edge of the fact that the sensory
ells were originally distributed
,hroughout the skin (Fig. 439),
,he idea naturally suggests itself
,hat in man also the units of
,he sensory ganglia might be
formed in situ in the ectoderm,
ind that the collection of
sensory cells in the ganglia
night possibly be brought
ibout by the migration of such
sensory cells inwards, while their
peripheral processes elongate FIG. 440. DIAGRAM REPRESENTING (IN BLACK) THE LEFT HALF
,0 permit such migration of the F A TRANSVERSE SECTION OF A 2 MM. HUMAN EMBRYO.
jell bodies without disturbing Superimposed upon it there is sho*n (in colours) the hypo-
. . , . thetical primitive arrangement of the nervous elements derived
iheir Original endings m the from each part of the ectoderm.
jkin. But there is no evidence
;.o show, or even to suggest, that such a process takes place in the human embryo.
Che facts at our disposal seem to indicate that the sensory cells are derived from
iharply circumscribed patches of ectoderm, and that the peripheral processes of
/hese cells are distributed to the outlying area of ectoderm beyond them, from
vhich the epidermis is eventually formed (Fig. 440).
At the beginning of the second week the nervous system of the human embryo
resented by two thickened plates of ectoderm lying parallel the one to the
Yolk-sac,
Neural groove ._
Neurenteric canal
Primitive streak
Body stalk
FIG. 441. THE DORSAL ASPECT OF A VERY EARLY HUMAN EMBRYO (after von Spec).
other, alongside the median axis of the embryo (Fig. 441), which is occupied by a
^hallow furrow.
Upon a diagram (Fig. 440), representing a transverse section through one-half of
i an embryo (the uncoloured part), colours corresponding to those employed in
500 THE JS T EEVOUS SYSTEM.
Fig. 439 have been placed to indicate the nature of the elements that are known to
develop in relation with each area of the ectoderm at a later period in the history of
the embryo : 6 represents an area which later will form the crista neuralis, from
which the sensory cells will be developed. The peripheral processes of these cells
will pass into the skin (a) and their central processes into the area cd, which will
become part of the neural tube. In the area c intercalated cells will develop to
receive the incoming sensory nerves ; and in the area d the motor nerve-cells (as
well as other intercalated cells) will be formed.
When it is recalled that all the elements of the primitive nervous system of
Hydra are modified ectodermal cells, and, moreover, that when the intercalated
and motor nerve-cells wander into the deeper tissues the protoplasm of the whole
nervous network remains in uninterrupted continuity (Fig. 439), it is instructive to
note that in the primitive human nervous system the rudiment of the epidermis
of the skin is linked to the medullary plate by the patch of ectoderm from which
the sensory ganglia will be formed.
In the discussion of the inter-relationships of the various constituent elements
of the nervous system, there will be occasion to refer to this matter again.
But while we are studying Fig. 440 it is important to emphasise the fact that in
accordance with the commonly accepted ideas it is taught that the area & becomes
completely severed from a and c, and shortly afterwards fibres are budded off from
the cells in the area I to form the sensory nerves linking a to c, thus re-establish-
ing a connexion which existed a few days earlier. This suggests the possibility
that the connexions between these three series of elements may not have been
completely sundered during the intermediate phase of development. Early in the
second week in the human embryo the axial groove separating the two bands of
thickened ectoderm (Fig. 441) that form the medullary plate becomes deepened by
the tilting-up of the lateral margins of the two bands. This process becomes
accentuated during the next day or two until a deep cleft is formed, the walls of
which consist of the thickened ectoderm and the floor of the thinner ectoderm
(floor-plate) joining them together. Before the end of the week the dorsal edges
of these thickened plates become joined in the region which will develop into the
neck; and during the third week the sealing of the lips of the neural groove
extends upwards (headwards) and downwards (tailwards), so that the neural tube
becomes completely closed by the end of that week. The extreme anterior (head-)
end and the dorsal aspect of the caudal extremity of the tube are the last parts to
close, the latter being, as a rule, a little later than the former. When the tube is
in the stage of being patent only at its two ends, the openings are known as the
neuroporus anterior and neuroporus posterior, respectively.
In the process of closing, the extreme dorsal edge of the medullary plate
becomes excluded, in the greater part of its extent, from participation in the
constitution either of the neural tube or of the skin, and forms a column of celle
lying between the two. This is the neural crest (Fig. 442, A, B, and C ; x and y
represent the places where the apparent sundering occurs).
It is commonly supposed that the neural crests do not extend the whole lengtl
of the neural tube. Nevertheless, peculiar ectodermal areas, which ultimately giv<
origin to sensory nerves, are found at the junction of the medullary plate with th
skin in those regions where the neural crest is supposed to be lacking. At th'
extreme anterior end of the neural tube the margins of the anterior neuropor
become thickened to form crest-like patches ; but when the tube closes these area
do not separate from the skin (at x, Fig. 442, D), as the rest of the neural crest doe;
They remain part of the skin and become the olfactory areas, in which sensor
cells, precisely like those found in Hydra (Fig. 439), develop.
A little farther on the caudal side of the olfactory region a very large cresf
like mass of ectoderm fails to separate from the medullary plate as it closes, an
becomes a constituent part of the neural tube (Fig. 442, E). It develops into tl:
optic diverticulum from which the cells of origin of the optic nerve are formed.
In several other regions sensory nerves originate from cells of ectodermal, ar
possibly even entodermal, areas which do not form parts of the neural crest,
that term is usually understood. The nerves of hearing and taste are developi
ELEMENTS OF THE CENTRAL NERVOUS SYSTEM.
501
neural plate
crista neuralis
x skin
/ganglion
r^
n a way that seems at first sight utterly abnormal, until it is remembered that
j[ .hey afford examples of very
.Primitive methods of nerve-
Ibrmation.
The essential part of the
>rgan of hearing is an ecto-
lermal sac (otic vesicle) that
ievelops as a diverticulum on
,,he side of the head, from a
,hickened patch of ectoderm,
vhich in the lower vertebrates
brms part of a more exten-
dve area, known as the dorso-
ateral placode. Some of the
;ells of this area seem to be-
iome transformed into nerve-
jells, which migrate into the
space between the otic vesicle
ind the neural tube (Fig. 443)
ind form the acoustic ganglion.
At the upper margins of
}he branchial clefts a series of
:ictodermal (and possibly also
mtodermal) thickenings develop,
,, vhich are known as the epi-
oranchial placodes. Com-
oarison with the process of
levelopment in fish embryos,
;vhich has been elucidated by
Landacre (Journal of Compara-
tive Neurology and Psychology,
L910-1912), suggests that the
lerve-cells may arise from these placodes, from which the nerves of taste originate
peripheral sensory nerve
sensory nerve root
vesicula o
'ptica
FIG. 442. DIAGRAMS OF TRANSVERSE SECTIONS REPRESENTING
THREE STAGES (A, B, AND C) IN THE DEVELOPMENT OF A
SENSORY GANGLION FROM THE NEURAL CREST ; AND Two
DIAGRAMS (D AND E) SUGGESTING A POSSIBLE HOMOLOGY
OF THE OLFACTORY (D) AND VISUAL (E) EPITHELIUM WITH
THE NEURAL CREST.
Ganglion geniculi
Nervus facialis
Ganglion acusticum
Vesicula otica
,.- Ganglion petrosum
Epibranchial placode
,. of glosso-pharyngeal
nerve
Ganglion
nodosum
Epibranchial
placode of
vagus nerve
Area olfactoria
443. RECONSTRUCTION OF THE GANGLIA OF THE FACIAL, ACOUSTIC, GLOSSO-PHARYNGEAL, AND VAGUS
NERVES OF A HUMAN EMBRYO 5 MILLIMETRES LONG (ABOUT THREE WEEKS OLD).
'he epithelium of three branchial clefts and the otic vesicle is represented diagrammatically ; and the supposed mode of
rigm of the gustatory nerve-cells (and their fibres) from the epibranchial placodes is indicated in blue, and of the
istic nerve-cells from the otic vesicle in purple.
502
THE NEKVOUS SYSTEM.
Such fibres are constituent elements of the facial, glosso-pharyngeal, and in some
animals also the vagus cerebral nerves (Fig. 443), in connexion with the ganglia
of which these epibranchial placodes are formed (Froriep and Streeter). The
observations of Professor J. P. Hill upon embryos of Echidna seem to suggest that
in mammals these gustatory neuroblasts are derived from the entoderm.
When first formed, the neural tube is compressed from side to side and presents
an elliptical outline in transverse section (Fig. 444). The two side walls
are very thick, whilst the narrow dorsal and ventral portions of the wall are thin,
and are termed the roof-plate and floor-plate respectively (Fig. 444). The cavity
of the tube in transverse section appears as a narrow slit. The wall of the neural
tube consists at first of low columnar epithelium arranged in a fairly regular
series, but with a certain number of large spherical so-called germinal cells
scattered between the columns. But this regular disposition as a single layer
Funiculus posteno
Sensory
ganglion
Marqinal
\ayer--
Commissural fibre
-Anterior nerve root
FIG. 444. DIAGRAM OF TRANSVERSE SECTION OF EARLY NEURAL TUBE.
of cells does not last long. For even by the second week the rapid proliferation
of the cells has led to a marked increase in the thickness of the side wall and
a scattering of the more numerous nuclei, apparently irregularly, throughout its'
substance (Fig. 444). The latter consists of a network of protoplasm in whicl
definite outlines of cells cannot be detected. As growth proceeds the innermosl
part of this nucleated protoplasmic syncytium becomes condensed to form e
delicate membrane termed the internal limiting membrane, which lines th
lumen of the tube, whilst its outermost part presents a similar relation to ai
external limiting membrane, which invests the outer surface of the tube. To
ward the end of the first month the side walls of the tube show signs of ;
differentiation into three layers. Next to the central canal there is an epithelial
like arrangement of the innermost cells of the syncytium, forming the ependyms
Then there is an intermediate layer crowded with nuclei, hence known as th
nuclear or mantle layer. On the surface is a layer singularly free from nucle
which is called the non-nuclear or marginal layer. The germinal cells ar
ELEMENTS OF THE CENTEAL NERVOUS SYSTEM. 503
j placed in the ependymal layer between its radially arranged cells as they pass
1 in towards the internal limiting membrane ; and the protoplasm of the germinal
cells forms part of the syncytium.
At one time it was imagined that the germinal cells were embryonic nerve-cells,
[the parent-cells of the real neuroblasts, and that the whole of the rest of the
i syncytium represented the supporting tissues, which in the adult form the neuroglia.
But "it is now known that from the proliferation of the germinal cells, in which
c mitotic figures can usually be seen, some cells are formed which become ependymal
epithelium, and others which migrate peripherally into the mantle layer. There,
?'' while forming part of the mantle syncytium, they undergo further proliferation
i! and some of the resulting cells develop into spongioblasts, which constitute the
i. supporting framework, the embryonic neuroglia; others become rudimentary nerve-
cells or neuroblasts, and others again are known as indifferent cells. The latter
are destined to undergo further subdivision, and become the parents of more
spongioblasts and neuroblasts.
From this it is clear that the greater part all except the germinal cells
of the syncytium, which is known as the myelospongium, is not merely supporting
neuroglial tissue, as was once supposed, but is the rudiment of both neuroglia and
true nervous tissues.
The details of the process by which the neuroblasts become dissociated from
the neuroglial network are quite unknown. It is commonly supposed that a
spherical cell in the mantle layer that is to be transformed into a neuroblast
frees itself from the syncytium, and remains for a time independent and wholly
unattached amidst the meshes of the neuroglial network : it is supposed further
that its true nature as a neuroblast becomes revealed when it takes on a pear-
shape, and a protoplasmic process, the stalk of the pear, pushes its way into some
other part of the nervous system, or out of it into the mesoderm to reach some
muscular or glandular tissue, and becomes the axis cylinder process or axon of
the nerve-cell.
Such an interpretation of the appearances exhibited in the walls of the neural
tube at the end of the first month is adduced in support of a view concerning the
constitution of the nervous system known as the neurone theory. "Neurone" is the
term applied to a nerve-cell and all its processes ; and the neurone doctrine assumes
that there is no continuity whatever between the substance of one neurone and that
of another, such as occurs in Hydra (Fig. 439), and that the functional connexions
between them are brought about merely by the contact of the processes of one
element with the processes, or the cell-body itself, of another element. In accord-
ance with this conception the facts of embryology are supposed (by His) to demon-
strate that when the axon grows out from a previously spherical and unattached cell
it is able to push into the surrounding tissues, and, as it were guided by some instinct,
eventually finds its way to that particular area of skin, muscle, gland, or other part
of the body where nature intends it to go.
This is the current teaching in regard to the neurone-theory ; and it is supposed
to have been conclusively demonstrated by the facts revealed not only by embryo-
, logy and the study of the minute structure of the nervous system, but also by the
. phenomena of degeneration and regeneration. Harrison has shown that the out-
growth of processes can be witnessed in the living nerve-cells of the frog. There
; are certain facts, however, which have always led some anatomists to refuse to
believe in the validity of the neurone doctrine as a true expression of the real
constitution of the nervous system. It has been clearly demonstrated by Graham
Kerr that at a very early stage of development the neural syncytium of the spinal
medulla (of the mud-fish Lepidosiren) is in free and uninterrupted continuity with
the protoplasm of the muscle-plart>e, which lies in contact with the neural tube ; and
no stage is known in which these connexions do not exist. When, in the course of
the subsequent growth of the embryo, the muscle-plate becomes removed further
, and further away from the central nervous system the protoplasmic strand, which
links them the one to the other, gradually becomes stretched and elongated. As
the neuroblast matures its chemical constitution becomes modified; it becomes
specialised in structure to fit it for the peculiar functions it has to perform. These
504 THE NERVOUS SYSTEM.
changes manifest themselves first in the body of the neurone itself and thence
spread along its processes. With the knowledge that protoplasmic bridges exist
long before the time His supposed the axon of his neuroblast to push its way
outward, it seems not unreasonable to suppose that it is the chemical modification
of these existing bridges which has been revealed in stained specimens, as it spreads
from the cell body outwards into its processes.
It is now a well-recognised fact that soon after the neural tube becomes closed
the outlines of its constituent cells become blurred and then disappear, and a
continuous protoplasmic network or syncytium is formed. No one has ever been
able to detect the process of detachment of embryonic nerve-cells (neuroblasts) from
this syncytium ; and it is at least a possibility that the free anastomosis of the
protoplasmic processes of many of the cells is not destroyed in the way demanded
by the neurone doctrine. The known facts might be interpreted, at least as
reasonably, by supposing that when nerve currents begin to traverse the syncytium
(Fig. 444) structural modifications occur around the nuclei of the cells affected, and
gradually spread along their processes, so as to give the appearance (in sections
stained by special methods) of processes growing out from each neurone.
Impulses brought from the skin by the sensory nerves, the nutrition of which is
controlled by the cells in the sensory ganglion (Fig. 443), are carried into the wall
of the neural tube, where they are received by processes of intercalated cells, which
in turn transmit their effects directly or indirectly to (a) motor nerve-cells (or
other kind of efferent nerve-cells), which stimulate a muscle, a viscus, or other
active tissue to perform some work, or (b) to intercalated cells, the axons of which
proceed to some other part of the nervous system, perhaps above or below the place
where the sensory nerve enters (Fig. 444, funicular cells). As the walls of the neural
tube increase in size the various neurones gradually become drawn apart, and the
protoplasmic links uniting them become stretched and extended to form processes
of varying length.
It is right to explain that most writers give an explanation of the process of
development which is at variance with that just sketched. The neuroblast is
supposed to originate as a free-lying spherical cell, which is stimulated by some
unknown force, sometimes assumed to be of the nature of a chemical attraction
(chemotaxis), to protrude a process, which gradually elongates and pushes its way
through the tissues, perhaps to some particular patch of skin, muscle, gland, or
some other nerve-cell. The difficulty involved in such a conception is not only
that it is opposed to all that is known of the early stages in the evolution of the
nervous system, but also that it is difficult to conceive that every one of the
millions of nerve-cells, muscle-cells, visceral and cutaneous elements can each have
some specific attractive power which leads every individual nerve fibril to its
appropriate and predestined place in the body.
The Efferent Nerves. The efferent cells of the neural tube are distinguished
by the fact that their axons leave the central nervous system and traverse the
mesoderm for a longer or shorter distance to end in relation to some muscle, gland,
or other tissue outside the nervous axis. At an early stage of development (Fig. 445)
such efferent fibres pass not only to muscles but also to viscera and other kinds of
tissues. In the course of the growth of the body these various structures supplied
by efferent fibres become removed progressively further and further from the central
nervous system ; and in this process a distinction can be detected in the behaviour
of the efferent fibres proceeding (a) to the striped or voluntary muscles, (c) and the
viscera and unstriped muscle, respectively. The efferent cells (a) which innervate
voluntary muscles retain their positions in the central nervous system, their axis-
cylinder processes (motor nerves) becoming elongated in proportion to the migration
of the muscle from its original situation. But thecells (c) innervating non-striped
muscles and viscera behave in a different manner. As the viscus or muscle
migrates (Fig. 445, B), the nerve-cell (c) follows it more or less closely, being as it
were dragged out of the wall of the neural tube by its axon into a peripheral
position, where it becomes a constituent element of one of the so-called sympathetic
or autonomic ganglia. As these sympathetic cells migrate from the central
nervous system, each of them appears to draw out with it the axon of an inter-
ELEMENTS OF THE CENTEAL NEKVOUS SYSTEM.
505
- - Splanchnic
efferent cell
gf ---Somatic
wij&k!.. efferent
;alated cell (rf); and it is customary to distinguish these latter elements (within
;he central nervous system) as splanchnic efferent cells. It is, however, a matter
f fundamental importance- to recognise clearly that the real splanchnic efferent
;ells, the homo-
A B
Roof Plate
ogues of the
jomatic efferent
jells, are found in
;he sympathetic
ganglia, and that
he elements to
.vhich this term is
isually applied are
n reality inter-
calated cells.
Floor Plate NX ^.- ; :\Yf-v/. : //v! ; .v nucleus
This account is
it variance with the
;ustomary descrip-
lon of the develop-
nent of the sym-
aathetic system,
iccording to which
he cells of the sym-
oathetic ganglia are
>aid to be wholly
lerived from the sen-
sory ganglia ; but it
)ffers a reasonable
explanation of the
; acts (i.) that the cells FIG. 445. DIAGRAM OF A TRANSVERSE SECTION THROUGH THE LEFT HALF OP THE
NEURAL TUBE REPRESENTING Two STAGES IN THE DEVELOPMENT ov THE
EFFERENT NERVES, TO SUGGEST THE POSSIBLE ORIGIN OF THE CELLS OF THE
SYMPATHETIC GANGLIA BY MIGRATION FROM THE NEURAL TUBE.
n the sympathetic
ganglia are of the
Afferent, and not of
;he sensory, type,
md (ii.) that the fibres from the central nervous system establishing relations with them emerge
; dong the motor nerves. Moreover, the information brought to light by recent research in
embryology (Froriep, Kuntz, and others) affords positive evidence in support of this view.
Elliott, however, opposes this interpretation (Journal of Physiology, 1907, p. 438).
Many, if not all, of the sympathetic cells are derived from the walls of the
neural tube, and they migrate along the pathways formed by the motor, rather
'ohan the sensory, nerves. In the case of the spinal medulla they pass out chiefly
'ilong the anterior roots, and from the brain along the motor nerves the oculo-
motor, and the motor divisions of the facial and vagus nerves.
Nerve Components. From the statements in the preceding paragraphs it must
->e evident that there are several varieties of afferent and efferent nerves respectively
' 3ntering and leaving the central nervous system. The cells of origin of the efferent
aerves are all placed in the ventral part of the side wall of the neural tube ; and
for this reason this part of the wall becomes swollen at an early stage of develop-
ment (Figs. 445 and 446). It is called the basal lamina. Most of the cells that emit
ifferent fibres are situated in the sensory ganglia outside the central nervous system,
}o that their growth can have no direct influence upon the form of the neural tube ;
r>ut their central processes become inserted into the dorsal part of the side wall
3f the tube, which is called the alar lamina; and groups of intercalated cells
3ollect around the entering fibres to form receptive or terminal nuclei. The
^owth of these terminal nuclei leads to an expansion of the alar lamina which is
inalogous to, but much less extensive than, that seen in the basal lamina. This
unequal swelling of the dorsal and ventral parts of each side wall of the neural
^ube leads to the development of a longitudinal groove, sulcus limitans, as a
lemarcation between the alar and basal laminae.
The nuclei of origin of the efferent fibres, which are found in the basal laminae,
may be divided into two (and, in some regions of the nervous axis, three) main
groups. There is first the group of large multipolar nerve-cells which emit fibres
30 innervate the ordinary striped voluntary muscles. This is commonly called
506
THE NERVOUS SYSTEM.
the somatic efferent nucleus. Then there is a group of small multipolar cells,
the axons of which pass out into sympathetic ganglia, and indirectly control the
involuntary unstriped muscles and other active parts of viscera. These cells
form the splanchnic efferent nucleus.
In the upper cervical and lower cranial region a portion of the somatic efferent
nucleus is set apart to innervate the striped muscles developed in the branchial
arches. This is the lateral somatic or intermediate efferent nucleus. Many recent
writers are of the opinion that this nucleus is splanchnic ; but its fibres directly
innervate striped voluntary muscles, which are developed from the same material
ROOF-PLATE
Splanchnic Terminal Nucleus.
' Gustatory Nucleus.
,Acousti'co-Lateral
Terminal Nucleus.
Somatic Terminal
Nucleus.
--- Ear Vesicle.
LAMINA)
BASALISJ
Somatic --
Efferent Nucleus
Floor
Plate"
Sensory Ganglion.
Skin.
Striped
Muscle
Sympathetic Ganglion -
Unstriped ;
Muscle
Visceral
Mucous Membrane.
--Branchial
Striped
Muscle.
FIG. 446. DIAGRAM OF A TRANSVERSE SECTION THROUGH THE EIGHT HALF OF THE FCETAL EHOMBEN
CEPHALON AND EPITHELIAL AREAS ASSOCIATED WITH IT TO ILLUSTRATE THE DIFFERENT CATEGORIES
OF NERVE COMPONENTS AND THEIR CENTRAL NUCLEI.
(myotomes) from which the other striped muscles are formed (Agar and Grahan
Kerr).
The alar lamina also can be subdivided into a series of functional area;
(Fig. 446).
At the dorsal edge is the somatic afferent terminal nucleus, which receives im
pulses coming from the skin. In one region a part of this nucleus is specialise'
for the reception of impulses coming from the internal ear (acoustico-latera
terminal nucleus). Then there is a group of cells collected around the incomin
visceral sensory nerves the splanchnic afferent terminal nucleus. A part of this :
specialised to receive taste impressions the gustatory nucleus but this has IK
yet been clearly demarcated from the rest of the nucleus.
This analysis of the various functional elements that may enter into tt
constitution of the various cerebral and spinal nerves is made use of in elaboratir
the theory of nerve components, which will help us to understand many featur*
of the structure of the nervous system that otherwise would be unintelligible.
Nerve -cells. We have already noticed that there is a broad distinctk
between the nerve-cells which are found in the ganglia of sensory nerves and tho
NEKVE-CELLS.
507
Axon
j found in the rest of the nervous system. They differ not only in their mode of
prigin and in their subsequent development, but also in the connexions of their
! nerve-fibre processes.
Nerve-cells of the Brain and Spinal Medulla. The cells in the cerebro-
1 spinal axis are variable both in size and form. Some are relatively large, as, for
example, certain of the pyramidal cells of the cerebral cortex and the motor cells
[in the spinal medulla, which almost come within the range of unaided vision;
1 others are exceedingly minute, and require a high power of the microscope to bring
them into view. The cell consists of a protoplasmic nucleated body, from which
>the axon proceeds, and the protoplasmic processes of Deiters, or the dendrites
j Tig. 447).
The axon presents a uniform diameter and a smooth and even outline. It gives
off in its course fine
collateral branches,
but does not suffer
thereby any marked
diminution in its
girth. The most
important point to
note in connexion
with the axon, how- flE '%. frreaggHlfc-. _ +
ever, is the fact that
it becomes continu-
ous with the axis-
cylinder of a nerve -
fibre. The axon
then is simply a
nerve-fibre, and in
certain circum-
stances it assumes
one or two invest-
ing sheaths, of which
more will be said
later. The axon
may run its entire
course within the
substance of the
brain or spinal
: medulla, either for a
short or a long dis-
tance (intercalated
cells), or it may
emerge from the
brain or spinal
: medulla in one of
the cerebral or spinal
! nerves as the essential part of an efferent nerve-fibre, and run a variable distance
: before it finally reaches the peripheral* structure in relation to which it ends
(efferent nerve-cells). The axon and the collaterals which spring from it appear to
terminate either in small button-like swellings or knobs, or more frequently in
; terminal arborisations, the extremities of which seem to be furnished with ex-
ceedingly small terminal varicosities. In those cases where the axon or its
^laterals end within the brain or spinal medulla, some of the terminal arborisa-
tions interlace with the dendrites of nerve-cells, whilst others are twined around
the bodies of other cells. In the latter case the interlacement may be so close
and complete that it almost presents the appearance of an enclosing basket-work.
In cases where the axon emerges from the cerebro-spinal axis its terminal arborisa-
tion ends in relation to a muscle-fibre or some other tissue in the manner described
below.
FIG. 447. THREE NERVE-CELLS FROM THE ANTERIOR COLUMN OF GRAY
MATTER OF THE HUMAN SPINAL MEDULLA.
508
THE NEKVOUS SYSTEM.
FIG. 448. Two MULTIPOLAR NERVE-
CELLS (from a specimen prepared by
the Golgi method).
view, therefore, four different
forms of nerve-fibre may be
recognised :
Non-med ullated
1. Naked axis-cylinders.
2. Axis -cylinders with primi-
tive sheaths.
Medullated
3. Primitive sheath absent.
4. Primitive sheath present.
Every nerve -fibre near its
origin and as it approaches its
termination is unprovided with
sheaths of any kind, and is
simply represented by a non-
medullated, naked axis-
cylinder. The fibres of the
olfactory nerves afford us an
example of non - medullated
fibres furnished with a primi-
tive sheath.
Medullated fibres are
present in greater quantity in
the cerebro-spinal system than
non -medullated fibres. Inus,
all the nerves attached to the
Nerve - fibres. Nerve - fibres, ar-
ranged in bundles of greater or less bulk,
form the nerves which pervade every
part of the body. They also constitute
the greater part of the brain and spinal
medulla. Nerve-fibres are the conduct-
ing elements of the nervous system ; they
serve to bring the nerve -cells into
relation both with each other and with
the various tissues of the body.
There are different varieties of nerve-
fibres, but in all the leading and essential
constituent is a delicate thread-like axon.
The most obvious difference between
individual fibres depends upon the nature
of the covering of the axon. When it
is coated on the outside by a more or
less thick sheath of a fatty substance,
termed myelin, it is said to be a myelinated
or medullated fibre. When the coating
of myelin is absent, the fibre is termed
a non-myelinated or a non- medullated
fibre. A second sheath thin, delicate,
and membranous, and placed externally
may also be present in both cases. It
is termed the primitive sheath or the
neurolemma. From a structural point of
Axon
4 ^ _ NBRVE . CELL FROM CEREBBLLUM (C ELL OK PO,*
SHOWING THE BRANCHING OF THE DENDRITIC PROCESSES
photograph by Professor Symington).
NERVE-FIBKES.
509
,
'cylinder
Myelin
Primitive
sheath
orain and spinal medulla, with the exception of the olfactory and optic, are formed
3f medullated fibres provided with a primitive sheath; whilst the entire mass of
the white substance of the brain and spinal medulla, and also the optic nerves,
4v . a are formed of medullated fibres devoid of a primitive sheath.
It is important to note that the distinction between the
medullated and non- medullated fibres is not one which exists
throughout all stages of development. As will be presently pointed
out, every fibre is the prolongation of a cell, and in the first instance
it is not provided with a medullary sheath. Indeed, it is not
until about the fifth month of foetal life that those fibres which
are to form the white substance of the cerebro- spinal axis begin to
acquire their coating of myelin. Further, this coating appears in
the fibres of different fasciculi or tracts at different periods, and a
knowledge of this fact has enabled anatomists to follow out the
connexions of the tracts of fibres which compose the white matter
of the brain and spinal medulla.
Every nerve-fibre is directly continuous by one extremity with a
nerve-cell, whilst its opposite extremity breaks up into a number of
ramifications, all of which end in relation to another nerve-cell, or
in relation to certain tissues of the body, as, for example, muscle-
fibres or the epithelial cells of the epidermis. The length of nerve-
fibres, therefore, varies very greatly. Some fibres are short and
merely bring two neighbouring nerve-cells into relation with each
other ; others travel long distances. Thus, a fibre arising from one
of the motor cells of the lower end of the spinal medulla may, after
leaving the spinal medulla, extend to the most outlying muscle in
the sole of the foot, before it reaches
its destination. But even when a fibre
does not leave the central axis, a great
length may be attained, and cells situated
in the uppermost part of the brain give
origin to fibres which pass down to the
lower end of the spinal medulla.
It has already been explained that
fibres which form the nerves may be
classified into two sets, afferent and
efferent. Afferent nerve -fibres conduct
impressions from the peripheral organs into the central
nervous system ; and as a change of consciousness, or,
in other words, a sensation is a frequent result, these
fibres are often called sensory. Efferent nerve -fibres
carry impulses out from the brain and spinal medulla to
peripheral organs. The majority of these fibres go to
muscles and are termed motor ; others, however, go to
glands and are called secretory ; whilst some are in-
hibitory and serve to carry impulses which restrain or
check movement or secretion.
The dendrites, or protoplasmic processes of the nerve-
cell, are thicker than the axon, and present a rough-
edged irregular contour. They divide into numerous
branches, and these gradually, as they pass from the
cell-body, become more and more attenuated until finally
they appear to end in free extremities. The branching
of the dendritic processes sometimes attains a marvellous degree of complexity
'Fig. 449), but it is commonly supposed that there is no anastomosis between
the dendrites of neighbouring cells, or between the dendrites of the same cell.
It is commonly believed that the neuroblast passes through stages analogous to
those shown in the diagram (Fig. -451) ; that just as a seed gives off a root which
strikes downward, and leaves which grow upward, so the neuroblast sprouts out an
FIG. 450.
NERVE-FIBRE
MENTAL STAGES EXHIBITED BY A
PYRAMIDAL CELL OF THE BRAIN.
a, Neuroblast with rudimentary
axon, but no dendrites ; b and c,
The dendrites beginning to sprout
out ; d and e, Further develop-
ment of the dendrites and appear-
ance of collateral branches on
the axon.
510
THE NEKVOUS SYSTEM.
axon (a) and subsequently develops a bunch of dendritic processes (6). In the
case of the axon reasons have already been given for not accepting this view as the
whole explanation ; and in the case of the dendrites, although the appearance of
microscopic sections seems to favour the view expressed in the diagrams, the fact
that the neuroblasts are united into a continuous network or syncytium at an
early stage of development (see p. 503) raises the possibility that the dendrites
may be formed by the gradually drawing out of the existing bridges as the linked
cell-bodies become moved apart.
The Ganglia of the Sensory Nerves. The cells found in the ganglia of the
cerebral nerves and on the posterior or dorsal roots of the spinal nerves have a
different origin, and present many points of contrast with neurones in the gray matter
of the brain and spinal medulla. As already indicated, the ganglia in question are
derived from the neural crest. The cells forming these ganglionic masses are some-
what oval in form, and each extremity or pole becomes drawn out into a process, so
that the neurones become bipolar. These processes are distinguished as central and
peripheral, according to the direction which they take. The central processes
penetrate the wall of the neural tube. In
the region of the spinal medulla they form
almost the whole of the fibres which enter
into .the composition of the posterior roots of
the spinal nerves. In the substance of the
cerebro- spinal axis they give off numerous
collaterals, and after a course of varying ex-
tent they end, after the manner of an axon,
in terminal arborisations, which enter into
relationships with certain nerve-cells in the
cerebro-spinal axis. The peripheral processes
proceed along the path of the particular
nerve with which they are associated, and
they finally reach the skin or other sensory
surface. Thus, to take one example : the
majority of the fibres which go to the skin
break up into fine terminal filaments, which
end freely between the epithelial cells of
the epidermis. The two processes of a
ganglion cell, therefore, form the afferent
fibres of the cerebro-spinal nerves, and con-
stitute the path along which the influence
of peripheral impressions is conducted to-
wards the brain and spinal medulla. The
body of the cell is, as it were, interposed in the path of such impulses.
But the original bipolar character of these cells, with very few exceptions
(ganglia in connexion with the acoustic nerve and the bipolar nerve-cells in the
olfactory mucous membrane), gradually undergoes a change which ultimately leads
to their transformation into unipolar cells. This is brought about by the tendency
which the cell-body has to grow to one side, viz., the side towards the. surface of the
ganglion (v. Lenhossek). This unilateral growth leads to a gradual approxima-
tion of the attached ends of the processes, and finally to a condition in which they
appear to arise from the extremity of a short common stalk in a T-shaped manner
(Fig. 452). It is interesting to note that in fishes the original bipolar condition
of these cells is retained throughout life, without change.
Both" the central and peripheral processes of these ganglionic cells become the
axis-cylinders of nerve-fibres, which, acquiring a medullary sheath, belong there-
fore to the medulla ted variety. From this it might very naturally be thought that
the ganglionic neurone, with its two axons and no typical dendrites, is a nervoue
unit very different from a neurone in the gray matter of the cerebro-spinal axis. It
is believed by some, however (van Gehuchten and Cajal), that the periphera
process, in spite of its enclosure within a medullary sheath, and though presenting
all the characters of a true axon, is in reality a dendrite If this is the case, th<
FIG. 452. THREE STAGES IN THE DEVELOPMENT
OF A CELL IN A SPINAL GANGLION.
NEUKOGLIA.
511
j norphological difference between a dendrite and an axon disappears, and van
Tehuchten's functional distinction alone remains characteristic, viz., that the axon
s cellulifugal and conducts 'impulses away from the cell, whilst the dendrites are
j ellulipetal and conduct impulses towards the cell.
It is, however, more in accordance with the facts to regard the sensory neurones
. is genetically quite distinct from the rest of the nervous system (see p. 498).
Neuroglia. The neuroglia is the supporting tissue of the cerebro -spinal axis.
!t may be considered to include two different forms of tissue, viz., the lining
jpendymal cells and the neuroglia proper. We place these under the one heading,
seeing that they have a common developmental origin.
The ependymal cells are the columnar epithelial cells which line the central
ianal of the spinal medulla and the ventricles of the brain. In the embryonic con-
lition a process from the deep extremity of each cell, traverses the entire thickness
>f the neural wall, and reaches the surface. It is not known whether this process
!3xists in the adult.
The neuroglia proper is present in both the white and the gray matter of the
ierebro-spinal axis. It constitutes an all- j
3ervading basis substance, in which the
/arious nerve elements are embedded in such
ii way that they are all bound together into
i consistent mass, and are yet all severally
, isolated from each other. Neuroglia consists
of cells and fine filaments. The fibrils are
present in enormous numbers, and by their
interlacements they constitute what appears
bo be a fine feltwork. At the points where
:t)he fibrils intercross may be seen the flattened
jlial cells. Whilst the neuroglia is for the
i most part intimately intermixed with the
nerve elements, there are, in both brain and
spinal medulla, certain localities where it is
i spread out in more or less pure layers. Thus,
upon the surface of the brain and of the
spinal medulla there is such a layer ; likewise
beneath the epithelial lining of the central
3 analandof the cavities of the brain there
is a thin stratum of neuroglia.
The ependymal cells are derived from
*'*
EMBRYO, SHOWING EPENDYMAL AND NEUK-
OGLIAL CELLS (after v. Lenhossek).
the original neuro-epithelial cells of the early . A > ^J, 1 ce "; B> f euroglial f)' _
, . r , , .,., ,, J [Note that the dorsal (posterior) aspect is below.]
neural tube, and in all probability the neur- L
oglia proper has a similar origin. They both, therefore, are products of the ectoderm.
Summary. 1. The cerebro-spinal nervous system is composed of two parts, viz.,
. (a) a central part, consisting of the brain and spinal medulla, with the efferent nerve-
1 fibres which pass out from them; (6) the ganglionic part, with the afferent nerve-fibres.
2. Each of these parts has a different origin, and is composed of neurones which
I possess characteristic features.
3. The ganglionic neurones are derived from the primitive cells of the neural
crest, and have each one process, which divides into two. Of these the central
division enters the cerebro-spinal axis, whilst the peripheral division becomes con-
' nected with a peripheral part. The central fibres from the ganglionic cells in
the region of the spinal medulla form the dorsal or posterior roots of the spinal
nerves. The cells of origin of these posterior roots are outside the spinal medulla,
i and carry impulses into its substance.
. The cerebro-spinal neurones are derived from the neuroblasts in the wall
of the early neural tube. Certain of these furnish efferent nerve-fibres, which
issue from the spinal medulla in separate bundles termed the anterior or ventral
roots of the spinal nerves. In the case of the cerebral nerves, however, with the
i exception of the trigeminal and facial nerves, the efferent fibres are not thus
i separated from the afferent fibres at their attachment to the brain.
512 THE NERVOUS SYSTEM.
5. The brain and spinal medulla, when studied by the naked eye, are seen to be
composed of white matter and gray matter. The white matter forms very nearly two-
thirds of the entire cerebro-spinal axis. It is composed of medullated nerve-fibres
embedded in neuroglial tissue. The gray matter is composed of nerve-cells with
their dendrites and axons. Some of the axons are in the form of naked axis
cylinders, whilst others have a coating of myelin. Intimately intermixed with
these parts is the neuroglia, which isolates them more or less completely from
each other.
THE NATURE OF THE BRAIN.
In the foregoing account it has been explained that the nervous system is
composed of a series of afferent nerves bringing information from every part of the
body into the central nervous system, from which efferent nerves pass out to the
muscular and other active parts of the body, providing the means for translating
such information into appropriate action. But it has been seen that the essential
part of the central nervous system is the intercalated cells, which provide the
means whereby the information brought in by any sensory nerve may be placed
at the service of the whole body, and the response which it excites may be controlled
and regulated by the condition of the rest of the body. The system of intercalated
cells links together into one co-ordinated mechanism the whole nervous system,
and, through it, every part of the body itself.
In some very primitive and remote ancestor of man (and in fact of the vast
majority of animals) the front end of the nervous system became enhanced
in importance to form a brain, which assumed a dominant influence over the rest.
This was brought about in the first place by the fact that in an elongated prone
animal moving forwards, the front end would naturally come first into relation-
ship with any change in environment ; and this earlier acquisition of information
concerning the outside world would necessarily give the head end of the nervous
system exceptional opportunities for influencing the rest of the nervous system.
This predominance is further accentuated by the development in the head
region of the organs of special sense, which provide mechanisms specially adapted
to be influenced by light, sound, and such delicate chemical forms of stimulation
as excite in ourselves sensations of smell and taste. As the information conveyed
by these special senses, such as the scent of food or the visual impression of some
enemy, must be able immediately to influence the movements of the whole body,
it follows that a specially abundant system of intercalated elements link the
central ends of these nerves of the special senses with the rest of the central
nervous system. Moreover the predominant influence of the head end of the
central nervous system implies that it must be provided with a specially large
series of nerve-fibres, not only for the purpose of bringing this influence to beai
upon the rest of the nervous system, but also of being itself brought into intimate
relationship with the nervous system as a whole, seeing that sensory impulses art
constantly pouring into every part of it.
Thus the head end of the central nervous system becomes the brain, whid
is characterised by a series of large irregular swellings, due to (a) the develop
ment around the insertion of each special sensory nerve of a mass, or group o
masses, of intercalated cells which will enable the effects of the visual, acoustic
olfactory, gustatory or other sensations to influence the whole nervous system
and (6) the evolution of complicated systems of intercalated cells, which receive
and in a sense blend, impressions coming from all parts of the nervous system
and emit fibres which pass, directly or indirectly, to the various groups of moto
nerve-cells and control their activities and, through them, the behaviour of th
animal.
In the development of the human embryo this distinction between the hea<
end and the rest of the central nervous system is indicated even before th
medullary plate is completely folded up to form the neural tube. The widene<
THE NATUEE OF THE BKAIN.
513
part represents the rudiment of the encephalon or brain ; and the rest of the tube
will become converted into the medulla spinalis.
If the attempt is made to analyse the meaning of the early broadening of the
brain rudiment it will be' found to be due in great measure to the fact that there
is added to the margins of the medullary plate (see Fig. 442, E, p. 501) the material
from which the sensitive part of the eye and the optic nerve will be developed ; but
soon after the neural tube is closed irregular swellings will make their appearance
around the attachments of the nerves of smell, vision, hearing, and taste (Fig. 454),
Optic tract
Tectum mesencephali
I
I Red nucleus
Tecto- spinal tract
Ik. ^ Rubro-spinal tract
^^.Brachium conjunctivum
.-- Leraniscus medialis
'Lemniscus lateralis
Cerebellum
Vestibulo-spinal tract
Nucleus gracilis
i- spinal ^
tract -
Olfactory nerve
icates the place where a tract crosses the median plane.
Medulla oblongata
Fibres of
- posterior
funiculus
)4. DIAGRAM REPRESENTING THE CONNEXIONS OP .SOME IMPORTANT SKNSORY AND MOTOR TRACTS
IN THE BRAIN to which references are made in pages 513 to 517. Motor paths in red ; sensory in other
colours.
( and also the great vagus nerve that is widely distributed to the viscera of the neck,
thorax, and abdomen.
But there are other factors besides these irregularities of growth of its walls
which add complexity to the form of the encephalon in the embryo. In the
course of their growth both parts (encephalon and medulla spinalis) of the neural
ube undergo great extensions in length, breadth, and thickness ; but in the case
the spinal medulla it is the increase in length that is most distinctive, whereas
,in the encephalon, the irregular expansion in breadth and thickness is more
obtrusive. Nevertheless, the brain elongates more rapidly than that part of its
,mesodermal capsule which ultimately becomes the brain-case or cranium; and
lence it becomes bent to permit of its being packed in the limited length of the
Cranial cavity. But if it is admitted that these mechanical considerations are
in a measure responsible for the three bends which develop in the embryonic
^ncephalon, their situation and the forms they assume are determined by the
^regularities of growth inherent in the brain itself.
34
514
THE NEEVOUS SYSTEM.
TELENCEPHALON
Anterior limit of mesencephalon
PROSENCEPHALON
Anteri(
nenrophore M
Skin
Recessus mamillaris'
Upper limit of
dp* ^rhombencephalon
Even at a time, during the second week, when the anterior (oral) end of the
neural tube is still open (neuroponis anterior), a right-angled bend has already
developed in the rudiment of the brain (cerebral vesicle). Slightly less than half
of the length of the vesicle had projected beyond the upper (anterior) end of the
no fcochord and became flexed
ventrally round it (Fig.
455).
This bend is known as
the cephalic flexure. The
region of the brain vesicle
in which it develops will
later on become the mesen-
cephalon or mid-brain; and
even at the early stage of
development now under
consideration (Fig. 455)
there is a slight narrowing
of the tube (isthmus) that
marks the boundary be-
tween the mid-brain and
the rhombencephalon or
hind -brain. Just beyond
the end of the notochord
there is an even fainter
trace of a constriction in-
dicating the line of de-
marcation between the
mid-brain and the prosen-
cephalon or fore-brain.
Shortly after the appearance of the cephalic flexure a similar bending occurs
in the region where the encephalon becomes continuous with the medulla spinalis
(Fig. 456, A). This is the cervical flexure.
But at this stage, or even earlier (Fig. 456), there has been developing a third
bend which produces effects differing from those just mentioned. At the end of
the second week a slight bulging can be detected on the ventral side of the hind-
Upper limit of
spinal medulla
FIG. 455. LEFT LATERAL ASPECT OF AN EARLY HUMAN EMBRYO
(after His's model, reversed).
CEREBRAL
HEMISPHERE:
OPTIC VESICLE:
A B
FIG. 456. Two STAGES IN THE DEVELOPMENT OF THE HUMAN BRAIN (after His).
A, Brain of an embryo of the third week. B, Brain of an embryo of five weeks.
brain (Fig. 455) : during the next four weeks this steadily becomes accentuated anc
forms the pontine flexure. The convexity of the bend is directed ventrally
differing in this respect from both of the other flexures. This difference ii
direction has a profound influence upon the form which the hind-brain assumes
If a plastic tube is bent a strain is thrown upon the wall in the concavity
THE NATUBE OF THE BKAIN.
515
CEPHALIC
FLEXURE
of the flexure. If this wall is strong and resisting, like the floor-plate of the
neural tube (in the cases of the cephalic and cervical flexures) the bending does
not affect the outline of the tube (in section) very materially. But when the
strain is thrown upon the thin roof-plate during the development of the pontine
flexure it is not strong enough to resist; it becomes stretched and allows the
side walls of the neural tube to splay laterally in precisely the same manner as
occurs when a rubber tube is bent towards a side which has been split (or
weakened) longitudinally (Fig. 457). This mechanical factor determines the form
assumed by the hind-brain at the end of the first month ; and gives its cavity,
the fourth ventricle, a lozenge or rhomboid form, when seen from its dorsal aspect
through the thin translucent roof. For this reason the hind-brain is known as
the rhombencephalon.
The rhombencephalon forms at first more than half of the encephalon, and as
it expands it appears to become marked off from the rest by a constriction (the
isthmus rhombencephali).
The development of the pontine
flexure subdivides the rhomben-
3ephalon into two parts, one joined
to the spinal medulla, the myelen-
3ephalon, and the other, joined to the
:est of the brain, the metencephalon.
In the myelencephalon develop
jhe nuclei of the nerves that regulate
ihe activities of the heart, lungs, and
i considerable part of the alimentary
3anal, and also the receptive nuclei
)f the nerves of taste. It is known
is the medulla oblongata.
The insertion of the nervus
r icusticus in the neighbourhood of
;he outsplayed lateral angle of the
hombencephalon leads to the pro-
found transformation of the meten-
iephalon. The nervus acusticus
conveys into the hind-brain impulses
/vhich are stimulated by movements
)f fluid in the closed sac developed
rom the otic vesicle (Fig. 443, p. 501).
Che truly acoustic function of this
ipparatus is called into activity
vhen the movements of this fluid
ire caused by waves of sound transmitted to it from the outside world. But
t is obvious that motion may also be set up in this fluid by changes in position
>f the body itself; in other words, movements in the fluid of the otic vesicle
nay stimulate nerves to convey to the brain information concerning the position
md movements of the body itself. A great mass of nerve-cells develops around
he insertion of the nervus acusticus (that part of it, however, which is called
r estibular and is not concerned with the function of hearing) to make use of
his information for the regulation of the movements of the body in balancing
>r equilibration. To enable this terminal vestibular nucleus the better to
>erform this function of equilibration, depending as it does upon the co-operation
nd adjustment of the movements of vast numbers of widely separated muscles,
lerye tracts coming from muscles and skin areas of all parts of the body make
heir way into this vestibular nucleus; and it expands and forms a great
xcrescence which is known as the cerebellum. And as this cerebellum has to
djust the activities of all the muscles of the body it necessarily becomes the
- 'reat organ of muscular co-ordination, and as such it is made use of by those
s of the brain which have to initiate and control complex actions such as
killed movements. It will be shown in the subsequent account how the
34 a
FIG. 457. PROFILE VIEW OF THE BRAIN OF A HUMAN
EMBRYO OF TEN WEEKS (His).
The various cerebral nerves are indicated by numerals.
A, Cerebral diverticulum of hypophysis cerebri.
B, Buccal diverticulum of hypophysis cerebri.
516
THE NERVOUS SYSTEM.
cerebellum becomes linked to the mesencephalon to co-ordinate the movements
of the body which are excited by this part of the encephalon ; and later ho\\
it becomes associated with the prosencephalon, when the latter becomes respons-
ible for the acquisition and control of the most highly skilled actions. Foi
the latter purpose a great pathway of nerve -fibres is laid down to conned
the fore-brain with the cerebellum : the terminal stage of this connexion ii
situated upon the ventral (anterior) aspect of the metencephalon in the fora
of a great mass of transverse fibres. At one time these strands of nerve-fibrei
were looked upon as a bridge between the two hemispheres of the cerebellum
hence the name pons was applied to them. This term is now applied not onlj
to the fibres themselves
^* but also to the upwarc
prolongation of the medulla
oblongata, to the surface oi
which they are applied.
The subdivision of the
rest of the encephalon ink
mesencephalon and prosen-
cephalon develops later anc
is less fundamental thai
the primary demarcation
between them and the
rhombencephalon.
The visual apparatus is
connected with both the
mid- brain and the fore-
brain, but at first more
intimately with the former
to which nerve pathways
are established to convey
from the spinal medulla
|~ and medulla oblongata sen-
sory impressions of touch
and hearing. From the
alar laminse of the mesen-
cephalon there are developed
four little hillocks (col-
liculi) corpora quadri
gemina to receive thest
FIG. 458. THE BRAIN OF A HUMAN EMBRYO IN THE FIFTH WEEK varied impressions and t<
(from His). enable them to influenci
A, Brain as seen in profile. B, Median section through the same brain, the actions of the whoL
M, Mamillary eminence ; Tc, Tuber cmereum ; Hp, Hypophysis ^odv. Special nerve path
(hypophyseal diverticulum from buccal cavity) ; Opt, Optic stalk ; i j j f
TH, Thalamus; Tg, Tegmental part of mesencephalon; Ps, are laid down tr0m
Hypothalamus ; Cs, Corpus striatum ; FM, Foramen inter- Corpora quadrigemina (Fl
ventriculare ; L, Lamina terminalis ; RO, Recessus options ; Ri, 454") to the Spinal medull
Recessus infundibuli. . , , .
to enable the mid-brain t
control the motor nuclei of the muscles of the trunk and limbs. These are calle
the fasciculi tectospinales (tectum being a synonym for corpora quadrigemina). *
group of intercalated cells known as the nucleus ruber develops upon each side of th
mesencephalon for the purpose of establishing connexions between the cerebellui.
and the mid-brain. When an impulse passes out of the mid-brain by the tectc
spinal bundle to excite some movement of the body, the red nucleus provide
the link by which the cerebellum can co-ordinate the actions of the muscL
involved. By means of a fasciculus rubrospinalis it can bring its influence to be*
directly upon the nuclei of motor nerves in the brain and spinal medulla (Fig. 45 J
The prosencephalon is at first, and in some of the lower fishes remains, tl
most insignificant of the three brain vesicles, but in the human brain (as also :
that of most other vertebrates, though in varying degrees) a pair of enormo
Ri.
THE SPINAL MEDULLA.
517
excrescences the cerebral hemispheres are budded off from it ; and they become
the dominant part of the nervous system (Fig. 458).
Each hemisphere is formed, however, from a relatively small part of the
side wall of the prosencephalon, the rest of which goes to form the optic
I diverticula, the thalamus, and the hypothalamus, among other structures. The
cerebral hemisphere is at first pre-eminently olfactory in function, the nerves
of smell being inserted directly into it. But impressions of the associated sense
: of taste make their way into the cerebral hemisphere in the most primitive
vertebrates : the gustatory nerves are inserted into the medulla oblongata, but
fibre-paths are laid down to establish connexions with the hypothalamus, which in
turn emits fibres to the cerebral hemisphere (Fig. 454). The thalamus is a greatly
swollen part of the prosencephalic wall adjoining the mesencephalon. Its main
part receives sensory impressions brought up from the spinal medulla and the
terminal nuclei of the sensory cerebral nerves and transmits them to the cerebral
hemisphere. Its caudal portion becomes specialised as a special receptive nucleus
for visual and acoustic impressions for transmission to the cerebral hemisphere.
It is called the metathalamus or corpora geniculata. Thus the cerebral hemi-
sphere from being essentially a receptive organ for smell impressions ultimately
becomes the terminus of all the sensory paths, and the structure that is concerned
with the consciousness of all kinds of sensations. It also controls the voluntary
movements of one-half of the body and emits a great strand of fibres pedunculus
cerebri to establish relations with the cerebellum and all the motor nuclei on
the other side of the encephalon and spinal medulla (Fig. 454, p. 513).
MEDULLA SPINALIS.
The spinal medulla is that part of the central nervous system which
occupies the upper two-thirds of the vertebral canal. It is an elongated
cylindrical structure, slightly flattened in front
and behind, which extends from the margin of
the foramen magnum to the level of the inferior
.border of the body of the first lumbar vertebra or
to the superior border of the body of the second
lumbar vertebra. Its average length in the male
is 45 cm. and in the female 43 cm.
Lumbar swellipg
of the spinal
medulla
A considerable amount of variation within certain
'limits (viz., the mid-point of the body of the last
thoracic vertebra and the superior border of the body
: )f the third lumbar vertebra) is observed in different
individuals as to the precise level at which the spinal
:oied ulla ends inferiorly, and in the female there
,^ould appear to be a tendency for the medulla to
i reach a slightly lower point in the canal than in the
tmle. Further, the relation presented by the spinal
medulla to the vertebral column differs in a marked
, legree in the foetus and infant at different periods of
ievelopment. Up to the third month of intra-uterine
( .ife the spinal medulla occupies the entire length of
:he vertebral canal ; it extends downwards to the
Lowest limit of the vertebral canal. But from this time
>n wards, as growth proceeds, the vertebral column
.engthens at a more rapid rate than the medulla. The
spinal medulla, therefore, has the appearance of shrink-
; in an upward direction within its canal, and at
rth its inferior end is usually found to be opposite FIG. 459. HUMAN F(ETUS IN THE THIRD
:he body of the third lumbar vertebra. MONTH OF DEVELOPMENT, WITH THE
The attitude assumed by the individual affects to BRAIN AND SPINAL ME DULLA EXPOSED
small degree the position of the inferior end of the
spinal medulla. Thus, when the trunk is bent well forwards, the terminal part of the
pmal medulla rises slightly within its bony canal.
Cerebral
hemisphere
Mesencephalon
Cerebellum
Fourth ventricle
Medulla
oblongata
Cervical swelling
of the spinal
medulla
518
THE NEKVOUS SYSTEM.
At the margin of the foramen magnum the spinal medulla becomes continuous
with the medulla oblongata of the brain, whilst below, it tapers rapidly to a
point and forms a conical extremity termed the conus medullaris. From the end
of the conus medullaris a slender glistening thread is prolonged downwards within
the vertebral canal, and finally anchors the spinal medulla to the back of the coccyx.
This prolongation receives the name of the filum terminale.
The diameter of the spinal medulla is very much shorter than that of the
vertebral canal within which it lies. A wide interval is left between its surface
and the walls of its canal, and this excess of space is clearly a provision for
allowing free movement of the vertebral column without producing any jarring
contact between the delicate spinal medulla and the surrounding bones.
Three protective membranes are wrapped around the spinal medulla. From
within outwards these are termed (1) the pia mater, (2) the arachnoid, and (3) the
dura mater. The pia mater is a fibrous
membrane which forms the immediate
investment. It is closely applied to
the spinal medulla, and from its deep
Conus medullaris
Posterior lateral
groove
Anterior nerve-root
Posterior nerve -root
FIG. 460. THE CONUS MEDULLARIS AND THE
FILUM TERMINALE EXPOSED WITHIN THE
VERTEBRAL CANAL.
Spinal ganglion
Anterior ramus
of spinal nerve
Posterior raimis
of spinal nerve
FIG. 461. THE ROOTS OF ORIGIN OF THE
SEVENTH THORACIC NERVE (semi- diagram-
matic).
surface numerous fine septa penetrate into the substance of the spinal medulla
The arachnoid is an exceedingly delicate transparent membrane which is loosel)
wrapped around the spinal medulla so as to leave a considerable interval, betweer
itself and the pia mater, termed the subarachnoid space, in which there is always *
varying amount of cerebro-spinal fluid. Outside the arachnoid, the dura mater form
a wide, dense, fibrous, tubular sheath, which extends downwards within the vertebra
canal for a considerable distance beyond the conical extremity of the spinal medulk
The spinal medulla is suspended within its sheath or theca of dura mater by tw
lateral wing- like ligaments, termed the ligamenta denticulata. These extend lateral!
from the sides of the spinal medulla and are attached by a series of pointed c
tooth-like processes to the inner surface of the theca of dura mater. Betwee
the wall of the vertebral canal and the dura mater there is a narrow interval, whic
is filled up by soft areolo- fatty tissue and numerous thin-walled veins arrange
in a plexiform manner.
Thirty-one pairs of spinal nerves arise from the sides of the spinal medull
THE SPINAL MEDULLA.
519
These are classified into eight cervical, twelve thoracic, five lumbar, five sacral, and
one coccygeal; and according to the attachments of these groups of nerves the
spinal medulla is arbitrarily subdivided into cervical, thoracic, lumbar, and sacral
regions. In employing these terms, therefore, for different districts of the spinal
medulla, it must be understood that the regions are determined by the . nerve
attachments and not by any direct relationship between these parts of the spinal
medulla and the sections of the vertebral column which bear the same names.
Each spinal nerve is attached to the spinal medulla by an anterior or ventral
and a posterior or dorsal root, and as these are traced to their central attachments
they are seen to break up into a number of separate nerve fascicles or bundles, which
spread out, in some cases very widely from each other, as they approach the side of the
spinal medulla (Fig. 461). Each pair of nerves is therefore attached to a portion of
spinal medulla of some length, and such a portion, with its pair of nerves, receives the
name of a " segment of the spinal medulla." It must be clearly understood, how-
ever, that, in so far as the surface of the spinal medulla is concerned, there is no means
of marking off one segment from another except by the nerve attachments.
In the cervical and lumbar regions of the spinal medulla the nerve-roots are somewhat crowded
together, so that little or no interval is left between the adjoining root fila or fascicles of neigh-
bouring nerves. In the thoracic region, however, distinct intervals may be observed, and the root
fila are more loosely arranged. From
this, it will be evident that the seg-
ments in different parts of the spinal
medulla are not of equal length. In the ,,, .
cervical region the segments measure about JfflKt~ vertebra
12 mm. in length, in the thoracic region
from 20 to 24 mm., and in the lumbar
region about 10 mm. The number of fila ^^mzZ&t&'SSi&ffim'&ftL Dura mater
which attach the different nerve -roots to
the spinal medulla is very different in dif-
ferent nerves, and is not necessarily the
same in the same nerve -root in different
individuals.
Arachnoid
Conus medullaris
Roots of first
lumbar nerve
Cauda equina
FIG. 462. SECTION THROUGH THE CONUS MEDULLARIS AND
THE CAUDA EQUINA AS THEY LIE IN THE VERTEBRAL CANAL.
Owing to the great difference
which exists between the length of
the spinal medulla and the length
of the vertebral column, the farther
we pass down the greater the dis-
tance becomes between the attach-
ment of the various nerve-roots to
the spinal medulla and the intervertebral foramina through which the corresponding
nerves leave the vertebral canal. The lower nerve-roots, therefore, have to traverse
the vertebral canal for .a considerable distance before they reach their apertures of
emergence. It thus happens that the nerve-roots which spring from the lumbar and
sacral regions of the spinal medulla attain a very great length and descend vertically
in the lower part of the vertebral canal in a bunch or leash, in the midst of which
lie the conus medullaris and the filum terminale. This great bundle of nerve-roots
receives the appropriate name of the cauda equina.
Enlargements of the Spinal Medulla. Throughout the greater part of the
thoracic region, the spinal medulla presents a uniform girth and a very nearly
circular outline when seen in transverse section. In the cervical and lumbar
regions, however, it shows marked swellings. The intumescentia cervicalis or
cervical enlargement is the more evident of the two. It begins very gradually at
the upper end of the spinal medulla, attains its greatest breadth (12 to 14 mm.)
opposite the fifth or sixth cervical vertebra, and finally subsides opposite the
lecond thoracic vertebra. To this portion of the spinal medulla are attached the
reat nerves which supply the upper limbs. The intumescentia lumbalis or lumbar
enlargement begins at the level of the tenth thoracic vertebra, and acquires its
cimum transverse diameter (11 to 13 mm.) opposite the last thoracic vertebra.
Below, it rapidly tapers away into the conus medullaris. To the lumbar enlarge-
ment are attached the great nerves of the lower limbs.
34 c
520
THE NEEYOUS SYSTEM.
These enlargements of the spinal medulla are associated with the outgrowth of the
limbs. In the earlier developmental stages of the spinal medulla they are not present,
and they take form only as the limbs become developed. In different animals their size
corresponds with the degree of development of the limbs. Thus, in the long-armed orang
and gibbon the cervical swelling stands out with a remarkable degree of prominence.
Development of the Spinal Medulla. The early stages of the process by
which the originally simple epithelial neural tube becomes converted into the
central nervous system have already been considered. It remains to be explained
how the features specially distinctive of the spinal medulla are produced.
In the early stages of the development of the spinal medulla (Fig. 463), the
neuroblasts are found to be scattered in the intermediate of the three bands of
Funiculus posterior
Sensory
ganglion
Marqinal
lo-ye?--
Floor
plaCe
Commissural fibre
-Anterior nerve root
FIG. 463. DIAGRAM OF TRANSVERSE SECTION OF THE LEFT HALF OF EARLY NEURAL TUBE.
which the thick side wall of the neural tube is composed the mantle layer.
These primitive nerve-cells soon congregate in much larger numbers in the ventral
part of the basal lamina (Fig. 464), so that the mantle layer expands there intc
a broad excrescence, which is the rudiment of the columna anterior or anterioi
cornu of gray matter. This anterior column contains the efferent or motor nerve
cells, the axons of which emerge as the anterior root of a spinal nerve. At this
stage the rest of the mantle layer consists of a thin stratum of neuroblasts (Fig. 463^
mainly intercalated cells, which receive the sensory impressions entering th>
spinal medulla through the radix posterior, and transmit impulses into axon
passing (a) to the motor nuclei, (&) to the other side of the spinal medull;
through the floor-plate (Fig. 463), or (c) into the superficial stratum (periphera
layer) of the spinal medulla where they bend upwards or downwards as constituen
elements of the funiculi (or white columns). As development proceeds (Fig. 462
the substantia grisea (gray substance) formed of these intercalated cells become
much more abundant and forms a broad blunt boss (Figs. 464, B and C), which :'
the rudiment of the columna posterior (O.T. posterior cornu).
The surfaces of these gray columns become coated with a layer of white sul
THE SPINAL MEDULLA.
521
stance, composed at first mainly of the axons
intercalated cells in the spinal medulla; and
as these funiculi increase in size they help
to mould the form of the gray columns.
This is displayed best in the case of the
posterior column (O.T. posterior cornu). The
major portion of the white substance, funiculus
posterior, which accumulates behind (and after-
wards lies on the medial side of) the posterior
column, does not consist of fibres springing
from intercalated cells, either of the spinal
medulla or any other part of the central
nervous system, but of the direct continua-
tions of the central processes of the cells in the
spinal ganglion on the posterior root (Figs. 463
and 464). A large proportion of the fibres of
the posterior root do not enter the gray
columns immediately after their insertion into
the alar lamina, but bifurcate to form two
vertical nerve-fibres, one passing upwards, and
the other downwards, in the funiculus posterior
before they end in the gray column, some
distance above or below the place where they
gained admission to the medulla spinalis. As
the spinal medulla grows, the originally blunt
posterior column becomes drawn backwards
into an increasingly attenuated process, and the
funiculus posterior, which was placed originally
upon its lateral surface (Fig. 464, A), and then
upon its posterior surface (Fig.464,B), gradually
issumes a wedge-shaped form (Figs. 464, C, and
166), upon the medial side of the gray matter.
Development of the Anterior Median
Fissure, Posterior Median Septum, and of
:he Central Canal. As the anterior columns
)f gray matter and the anterior fuuiculi of
vhite matter increase in size, the anterior
.urface of the spinal medulla, on each side
>f the median plane, bulges forwards, and the
issura mediana anterior (Fig. 464, A, B, and C)
s produced as the natural result.
There has been considerable discussion as
o the mode of formation of the posterior median
eptum ; but there is now no doubt as to the
issential facts. Early in the third month the
vails of the posterior three - fourths (of the
agittal extent) of the central canal of the spinal
nedulla become approximated (Fig. 464), and
ater they fuse to obliterate that part of the
anal. But the part of the septum thus formed
3 only an insignificant portion of the whole.
?or most of the septum is produced by the
gradual elongation of the epithelial cells lining
he remnant of the central canal as the fibre-
lasses of the posterior funiculi expand and
leparate the posterior surface of the spinal
nedulla further and further from the situation
f the canal (see Fig. 453, p. 511).
Furrows of the Spinal Medulla. When
of cells in the root ganglia and
Roof-plate
ir lamina
Early posterior
funiculus
Anterior
nerve-root
'Anterior
Mid-ventral lamina funiculus
A
Fasciculus gracilis
Fasciculus cuneatus
Posterior median
septum
Posterior
column
Posterior
nerve-root
Ependyma
Anterior nerve-root
Anterior funiculus
B
Fasciculus gracilis
Fasciculus cuneatus
Posterior median septum
Posterior column
Posterior root
Ependyma
Anterior
column
Anterior median
fissure
Anterior root
Anterior funiculus
FIG. 464. THREE STAGES IN THE DEVELOP-
MENT OF THE SPINAL MEDULLA (His).
cross-sections of the adult spinal
522
THE NEEVOUS SYSTEM.
CVi
Posterior median
septum
Cervical swelling
Sulcus inter-
medius posterior
Posterior lateral
sulcus
-THVn
medulla are made, it is seen to be a bilateral structure which is partially subdivided
into a right and a left half by a median cleft (fissura
mediana anterior) in front and a septum (septum medianum
posterius) behind. The anterior median fissure penetrates
only for a distance corresponding to somewhat less than
a third of the antero-posterior diameter of the spinal
medulla. The pia mater dips down into it and forms a
fold or reduplication within it. The posterior median
septum in the cervical and thoracic regions penetrates into
the spinal medulla until it reaches a point somewhat
beyond its centre. It is extremely narrow, and consists oi
ependymal and neuroglial elements, and is intimately con-
nected with the adjacent sides of the two halves of the
spinal medulla, between which it intervenes. The pia
mater, which invests the surface of the spinal medulla
passes continuously over the posterior median septum
and sends no prolongation of any kind into it. In the
lumbar region of the spinal medulla the septum becomes
shallower, whilst the anterior median fissure deepens, and
ultimately in the inferior part of the spinal medulla the
fissure and septum present a very nearly equal depth.
The two halves of the spinal medulla may show
trifling differences in the arrangement of the parts which
compose them ; but to all intents and purposes they are
symmetrical. They are joined together by a more or less
broad band or commissure, which intervenes between the
median fissure and the septum.
An inspection of the surface of each half of the spinal
medulla brings into view a longitudinal groove or furrow
at some little distance from the posterior median septum
which extends along the whole length of the spinal medulla
Along the bottom of this groove the fila of the posterioi
nerve-roots enter the spinal medulla in accurate linea;
order. It is called the sulcus lateralis posterior. Therr
is no corresponding furrow on the anterior part of eacl
half of the spinal medulla in connexion with the emergcnc
of the fila of the anterior nerve-roots. These fila emerg
irregularly over a broad strip of the surface of the spina
medulla, which corresponds in its width to the thicknes
of the subjacent anterior surface of the anterior column c
gray matter.
The sulcus lateralis posterior subdivides each half (
the spinal medulla into a small funiculus posterior and
much larger antero-lateral funiculus, and it is customai
to map the latter arbitrarily off into a funiculus lateral
and a funiculus anterior by a line corresponding to tl
emergence of the most lateral of the fila or fascicles of tl
anterior nerve-roots.
In the cervical region a distinct longitudinal grocr
may be observed on the surface of the posterior funicuh
It is placed rather nearer to the posterior median septu
than to the posterior lateral sulcus, and as it is trac
down into the thoracic region it gradually becomes i
distinct and finally disappears. This is called the sulc
mtermedius posterior, and it marks on the surface t
position of a septum of pia mater which dips into t !
spinal medulla and subdivides the posterior funiculus into a lateral part, term
the fasciculus cuneatus (O.T. column of Burdach), and a medial portion, which recer '
the name of the fasciculus gracilis (O.T. column of Goll).
Lumbar swelling-
-THVx
-THVxu
LVn
FIG. 465. DIAGRAM OF THE
SPINAL MBDULLA AS SEEN
FROM BEHIND.
CVi shows the level of the 1st
cervical vertebra ; CVv of the
5th cervical vertebra ; THVn
of the 2nd thoracic vertebra ;
THVx of the 10th thoracic
vertebra ; THVxn of the 12th
thoracic vertebra ; LVn of the
2nd lumbar vertebra.
THE SPINAL MEDULLA.
523
Fasciculus gracilis
Posterior funiculus ^=-^^ Fasciculus cuneatus
Anterior
nerve-root
INTERNAL STRUCTURE OF THE SPINAL MEDULLA.
The spinal medulla is composed of a central core of gray matter thickly coated
m the outside by white matter. At only one spot does the gray matter come close
;o the surface, viz., at the bottom of the sulcus lateralis posterior.
Gray Matter of the Spinal Medulla. The gray matter in the interior of the
spinal medulla has the form of a fluted column, but it is customary to describe it
is it appears in transverse sections. It then presents the appearance of the
'iapital letter H. In each half of the spinal medulla there is a semilunar or
.irescen-tic mass, shaped somewhat like a comma, the concavity of which is directed
laterally and the convexity medially. The two crescents of opposite sides are con-
lected across the median plane by a transverse band, which receives the name of
;he commissura grisea (gray commissure). The posterior median septum extends
brwards in the spinal medulla until it reaches the gray commissure. The bottom
>f the anterior median fissure, however, is separated from it by an intervening
.trip of -tthite matter, which is termed the commissura anterior alba, or anterior
vhite commissure. In the gray commissure may be seen the central canal of
he spinal medulla (canalis centralis), which tunnels the entire length of the
.pinal medulla and is just
dsible to the naked eye as
, minute speck. The por-
ion of the gray commis-
ure which lies behind the
entral canal is called Formatio reticularis
.he commissura posterior; Lateral funicu i us
Whilst the portion in front Central canal
eceives the name of the Accessory root
ommissura anterior grisea. Origin of accessory
Each crescentic mass of
(ray matter presents cer-
i ain well - defined parts.
^he projecting portions Anterior funiculus
rilich extend behind and FIG. 466. TRANSVERSE SECTION THROUGH THE SUPERIOR PART OF THE
1 front of the connecting CERVICAL REGION OF THE SPINAL MEDULLA OF AN ORANG.
VPTXP o-rnvrnm -nrp (From a s P ecimeu prepared by the Weigert-Pal method, by which
gray C < the white matter . g rendered dark whilst the ^^ matter is bleached. )
re termed respectively the
osterior and the anterior columns of gray matter (columnae grisese). These stand
ut in marked contrast to each other. In section the columna anterior is short,
hick, and very blunt at its extremity. Further, its extremity falls considerably
hort of the surface of the spinal medulla and is separated from it by a moderately
hick coating of white matter. Through this the fila of the anterior nerve-roots,
s they emerge from the gray matter of the anterior column, pass on their way to
he surface. Throughout the greater part of the spinal medulla the columna posterior
3.T. posterior cornu) is elongated and narrow, and is drawn out to a fine point, which
ilmost reaches the bottom of the posterior lateral sulcus. This pointed extremity
iceives the name of the apex columnse posterioris ; the slightly swollen part which
icceeds it is the caput columnse; whilst the slightly constricted part adjoining
ie gray commissure goes under the name of the cervix columnae posterioris.
The apex or tip of the posterior column differs considerably in appearance from
ie general mass of the gray matter. It is composed of a material which presents
lighter hue and has a somewhat translucent look. It is called the substantia
,3latinosa [Rolandi], and, when seen in transverse section, it exhibits a V-shaped
itline and fits on the posterior column like a cap.
A pointed and prominent triangular projection juts out from the lateral
5pect of the gray matter nearly opposite the gray commissure. This is the columna
.teralis (O.T. lateral cornu), and it is best marked in the upper thoracic region
?ig. 467, B). Traced upwards it becomes absorbed in the greatly expanded anterior
)lumn of the cervical swelling, but it reappears again in the upper part of the
)inal medulla, and is particularly noticeable in the second and third cervical
524 THE NEEVOUS SYSTEM.
segments ; followed in a downward direction it blends with the anterior column in
the lumbar swelling and contributes to the thickening of that column.
The gray matter is for the most part mapped off from the surrounding white matter
with a considerable degree of sharpness ; but in the cervical region, on the lateral
aspect of the crescentic mass and in the angle between the anterior and posterior
columns, fine bands of gray matter penetrate the white matter, and, joining with each
other, form a network, the meshes of which enclose small islands of white matter.
This constitutes what is called the formatio reticularis. Although best marked
in the cervical region, traces of the same reticular formation may be detected
in lower segments of the spinal medulla.
Characters presented by the Gray Matter in Different Regions of the
Spinal Medulla. The gray matter is not present in equal quantity nor does it
exhibit the same form in all regions of the spinal medulla. Indeed, each segment
presents its own special characters in both of these respects. It is not necessary,
however, in the present instance, to enter into this matter with any degree of
minute detail. It will be sufficient if the broad distinctions which are evident in
the different regions are pointed out.
It may be regarded as a general law that, wherever there is an increase in the
size of the nerves- attached to a particular part of the spinal medulla, a correspond-
ing increase in the amount of gray matter will be observed. It follows from this
that the regions where the gray matter bulks most largely are the lumbar and
the cervical swellings. The great nerve-roots which go to form the nerves of the
large limb-plexuses enter and pass out from those portions of the spinal medulla.
In the thoracic region there is a reduction in the quantity of gray matter in
correspondence with the smaller size of the thoracic nerves.
In the thoracic region (Fig. 467, B) both columns of gray matter are narrow,
although the distinction between the anterior column and the- still more attenuated
posterior column is sufficiently manifest. In this region the lateral column of
gray matter also is characteristic, and the substantia gelatinosa in transverse
section is pointed and spear-shaped.
In the upper three segments of the cervical region the anterior columns of gray
matter are not large and they resemble the corresponding columns in the thoracic
region. A lateral column also is present. But in these segments (and more especi-
ally in the first and second) there is a marked attenuation of the neck of the
posterior column, and the posterior commissure is very broad.
In the cervical swelling the contrast between the two columns is most striking ;
the anterior column is of great size and presents a very broad surface towards the
anterior aspect of the spinal medulla, whilst the posterior column remains narrow.
This great increase in the bulk of the anterior column is due to a marked addition
of gray matter on the lateral side of the column, and seeing that this additional
matter is traversed by a greater number of fibres, it stands out, in well-prepared
specimens, more or less distinctly from the part of the column which lies to the
medial side, and which may be considered to represent the entire anterior column
in the thoracic and upper cervical segments. Within this lateral addition to the
anterior column are placed those collections of cells which constitute the nuclei of
origin of the motor nerves of the muscles of the upper limb. The characteristic
thickening of the anterior column of gray matter is evident, therefore, in those
segments of the spinal medulla to which the nerves which enter the brachial plexus
are attached, viz., the lower five cervical segments and the first thoracic segment.
In the lumbar swelling the anterior columns again broaden out, and for the same
reason as in the case of the corresponding columns in the cervical swelling. The
nuclear masses which contain the cells from which the motor fibres which supply
the muscles of the lower limbs take origin are added to the lateral aspect of the
columns and give them a very characteristic appearance. In this region of the
spinal medulla, however, the posterior columns also are broad and are capped
by substantia gelatinosa which in transverse section presents a semilunar outline.
There is consequently no difficulty in distinguishing, from an inspection of the
gray matter alone, between transverse sections of the spinal medulla taken from
the cervical and lumbar swellings of the spinal medulla.
THE SPINAL MEDULLA.
525
In the lower part of the conus medullaris the gray matter in each half of
the spinal medulla assumes the form of an oval mass joined to its fellow of the
opposite side by a thick gray commissure. Here, almost the entire bulk of the
spinal medulla consists of 'gray matter, seeing that the white matter is reduced to
such an extent that it forms only a thin coating on the outside.
White Matter of the Spinal Medulla. In transverse sections of the spinal
medulla the three funiculi into which the white matter is subdivided become very
Posterior median septum
Septum
p. erior lateral groove
'osterior nerve-root
ubstantia
jelatinosa
,oot-tibres
e iring gray
matter
Processus
eticularis
sntral
canal
l ;erior nerve-root
Interior median
fissure-^
Posterior median
septum
Posterior lateral
groove
Posterior colu
Dorsal nucleui
Lateral colum
Central canal
Anterior colui
nterior median
fissure
B. Through the mid -thoracic region.
L. Cervical region at the level of the fifth cervical nerve.
(From a specimen prepared by Dr. A. Bruce.)
median
septum
Substantia
gelatinosa
Root-fibres enter-
ing gray matter
Central \X>,
canal ./$
Anterior whitei
commissure n
Nuclei of origin
T'nnu which the
motor-fibres
for muscles of
the lower limb
arise
Anterior nerve -
root
median
'fissure
Through the lumbar region at the level of the
fourth lumbar nerve.
FIG. 467. SECTION THROUGH EACH OF THE FOUR REGIONS OF
prepared by the Weigert-Pal method ; therefore the white
gray matter is bleached. )
Posterior median
septum
Posterior
nerve-root.
Substantia
gelatinosa
Posterior gray
commissure
Anterior white
commissure
Anterior median
fissure
D. Through the sacral region at the level of the
third sacral nerve. (From a specimen pre-
pared by Dr. A. Bruce. )
THE MEDULLA SPINALIS. (From specimens
matter is rendered dark in colour whilst the
apparent. The posterior funiculus is wedge-shaped, and lies between the posterior
median septum and the posterior column of gray matter. The lateral funiculus
occupies the concavity of the gray crescent. Behind, it is bounded by the posterior
column of gray matter and the sulcus lateralis posterior, whilst in front it extends
as far as the most lateral fasciculi of the anterior nerve-roots as they pass out from
the anterior column. The anterior funiculus includes the white matter between the
anterior median fissure and the anterior column of gray matter, and also the white
526 THE NEKVOUS SYSTEM.
matter which separates the broad extremity of the anterior column from the sur- |
face of the spinal medulla. This latter portion of the anterior funiculus is
traversed by the emerging fila of the anterior nerve-roots.
In cross-sections of the spinal medulla the partition of pia mater, which dips in
at the sulcus intermedius posterior and divides the posterior funiculus into the
medial fasciculus gracilis and the lateral fasciculus cuneatus, is very strongly marked
in the cervical regions, but as it is traced downwards into the thoracic region it
becomes shorter and fainter, and finally disappears altogether at the level of the
eighth thoracic nerve. Below this point there is no visible demarcation of the
posterior funiculus into two parts.
The white matter is not present in equal quantity throughout the entire length
of the spinal medulla. It increases steadily from below upwards, and this increase is
most noticeable in the lateral and posterior funiculi. In the lower part of the conus
medullaris the amount of gray matter is actually greater than that of the white
matter : but very soon this state of affairs is changed, and in the lumbar region the
proportion of gray to white matter is approximately as 1 : 2*1 ; in the thoracic region
as 1:5; and in the cervical region as 1 : 5'1. When it is remembered how the gray
matter expands in the lumbar and cervical regions, and how greatly it becomes reduced
in the thoracic region, the significance of these figures will become more apparent.
Canalis Centralis. As previously stated, the central canal is found in the
gray commissure. It is a very minute tunnel, barely visible to the naked eye
when seen in transverse section, and it traverses the entire length of the spinal
medulla. Above, it passes into the medulla oblongata, and finally opens into the
fourth ventricle of the brain ; below, it is continued for a variable distance into
the filum terminale, and in this it ends blindly. Only in the lumbar region does
the centra] canal occupy the centre of the spinal medulla. Above this level,
in the thoracic and cervical regions, it lies much nearer the anterior than
the posterior aspect of the spinal medulla; whilst below the lumbar region, as
it is traced down into the conus medullaris, it inclines backwards and approaches
the posterior aspect of the spinal medulla. The calibre of the canal also varies
somewhat in different parts of the spinal medulla. It is narrowest in the thoracic
region ; and in the lower part of the conus medullaris it expands into a distinct
fusiform dilatation (very nearly 1 mm. in transverse diameter), which is termed
the ventriculus terminalis (Krause).
The central canal is lined with a layer of ciliated columnar cells, the deep taper-
ing ends of which are prolonged into slender processes which penetrate into the
substance of the spinal medulla. These cells constitute the lining ependymal cells
of the canal. The cilia of the epithelial cells are very early lost, and it is not un-
common to find the canal blocked up by epithelial debris.
The central canal is of interest because it represents in the adult the relatively
wide lumen of the early ectoderrnal neural tube from which the spinal medulla
is developed.
Filum Terminale. The delicate thread to which this name is applied is con-
tinuous with the inferior tapered end of the conus medullaris. It is easily distin-
guished, by its silvery and glistening appearance, from the numerous long nerve-roots
(cauda equina) amidst which it lies. It is about six inches long, and down to the
level of the second sacral vertebra it is enclosed with the surrounding nerve-roots
within the dura mater. Below this point the dura mater is applied directly to
the surface of the filum terminale and is called filum dura matris spinalis. The filum
terminale proceeds downwards in the sacral canal, and finally receives attachment to
the periosteum on the posterior aspect of thecoccyx (Fig. 460, p. 518). It is customary
to speak of the filurn as consisting of two parts, viz., the filum terminale internum and
the filum terminale externum, or the part inside and the part outside the tube of
dura mater.
The filum terminale externum is simply a fibrous thread, strengthened by the pro-
longation it receives from the dura mater. The filum terminale internum is composed
largely of pia mater; but in its superior half it encloses the terminal part of the central
canal, and around this a variable amount of the gray substance of the spinal medulla
is prolonged downwards into the filum. When transverse sections are made through
THE GKAY MATTER OF THE SPINAL MEDULLA.
527
he superior part of the filurn terminale internum some bundles of medullated
erve-fibres are observed clinging to its sides, and with these are associated some
1 erve-cells identical with those in the spinal ganglia. These represent rudimentary
r aborted caudal nerves (Rauber).
SUMMARY OF THE CHIEF CHARACTERS PRESENTED BY THE SPINAL MEDULLA
IN ITS DIFFERENT REGIONS.
Cervical Region.
Thoracic Region.
Lumbar Region.
Sacral Region.
In transverse section, out-
line of spinal medulla
transversely oval ; in
the middle of the
cervical swelling the
transverse diameter
being nearly one- third
longer than the antero-
posterior diameter.
In transverse section,
outline of spinal
medulla more nearly
circular ; but still the
transverse diameter is
greater than the
antero - posterior dia-
meter.
'
In transverse section,
outline of spinal
medulla more nearly
circular than in
thoracic region.
In transverse section,
outline of spinal
medulla, nearly circu-
lar, but still some-
what compressed from
before backwards.
Postero - median sep-
tum very deep, extend-
ing beyond the centre
of the spinal medulla ;
antero - median fis-
sure shallow.
Fostero - median sep-
tum very deep, extend-
ing beyond centre of
the spinal medulla :
antero - median fis-
sure shallow.
Postero - median sep-
tum not nearly so deep
as in regions above :
antero - median fis-
sure, on the other
hand, much deeper.
Postero - median sep-
tum and antero-
median fissure of
equal depth.
Gray matter greatly in-
creased in quantity in
the cervical swelling :
anterior column thick
and massive ; posterior
column slender in
comparison. Lateral
column evident only
above the level of the
fourth cervical nerve.
Processus reticularis
strongly marked.
Gray matter greatly
reduced in quantity.
Both columns slender.
Lateral column well
marked. Processus
reticularis scarcely ap-
parent.
Gray matter greatly in-
creased in the lumbar
swelling. Both
columns very thick
and massive. Lateral
column absorbed in
anterior column. Pro-
cessus reticularis ab-
sent.
Both columns of gray
matter very thick and
massive. Lateral
column apparent. No
processus reticularis.
White matter in great
quantity, and especi-
ally massed in the
lateral and posterior
funiculi.
White matter less
in quantity than in
cervical region, but
bulking largely in
comparison with the
quantity of gray
matter.
White matter small in
quantity compared
with higher regions,
and very small in
amount in relation to
increased quantity of
gray matter.
White matter very
small in quantity in
comparison with the
gray matter.
Sulcus intermedius
posterior and corre-
sponding septum well
marked.
Sulcus intermedius
posterior absent ; but
the corresponding sep-
tum can be traced as
low down as the eighth
thoracic nerve.
No sulcus intermedius
posterior or corre-
sponding septum.
No sulcus intermedius
posterior and no
corresponding septum.
Central canal consider-
ably nearer the anterior
surface than the pos-
terior surface of the
spinal medulla.
Central canal consider-
ably nearer the anterior
surface than the pos-
terior surface of the
spinal medulla.
Central canal in the
centre of the spinal
medulla.
Central canal in the
centre of the spinal
medulla.
COMPONENT PARTS OF THE GRAY MATTER OF THE SPINAL MEDULLA.
Neuroglia enters largely into the constitution of the gray matter of the spinal
medulla. It forms a bed within which the nervous elements are distributed.
tese nervous elements consist of (1) nerve -cells and (2) nerve -fibres both
medullated and non - medullated. The nerve -cells lie in small spaces in the
528 THE NEKVOUS SYSTEM.
neuroglia, whilst the nerve -fibres traverse fine passages the walls of which ar
formed of the same substance. The neuroglia is thus an all-pervading basis sub
stance which isolates the nervous elements one from the other more or less com
pletely, and at the same time binds them together into a consistent solid mass
In two situations the gray matter presents peculiar features, viz., the apex of th<
posterior column and the tissue surrounding the central canal. In both situation
the gray matter stains more deeply with carmine and presents a more translucen
appearance; in other respects the substantia grisea centralis and the substanti,
gelatinosa are very different.
The substantia grisea centralis forms a thick ring around the central cana
It is traversed by the fine processes which proceed from the deep ends of th
ependymal cells which line the canal. It is composed almost entirely of neuroglie
In transverse sections of the spinal medulla the substantia gelatinosa, in th
cervical and thoracic regions, presents the appearance of a V-shaped mast
embracing the extremity of the posterior column of gray matter ; in the lumba
region this cap assumes a semilunar outline.
In the substantia gelatinosa the neuroglia is present in small quantity, an
small nerve-cells are developed within it in considBrable numbers.
Nerve-Cells. The nerve-cells are scattered plentifully throughout the gra
matter, but perhaps not in such great numbers as might be expected when we not
the enormous number of nerve-fibres with which they stand in relation. They ar
all, without exception, multipolar, and send off from their various aspects severe
branching protoplasmic processes or dendrites, and one axon, which becomes th.
axis-cylinder of a nerve- fibre. In size they vary considerably, and as a rule (t
which, however, there are many exceptions) the bulk of a nerve-cell has a mor
or less definite relation to the length of the axis-cylinder which proceeds from it.
When the nerve-cells are studied in a series of transverse sections of the spine
medulla, it will be noticed that a large proportion of them are grouped in clusters i
certain districts of the gray matter ; and as these groups are seen in very much th^
same position in successive sections, it is clear that these cells are arranged in long:
tudinal columns of greater or less length. Thus we recognise (1) a ventral grou
'or column of cells in the anterior column of gray matter ; (2) an intermedio-laten
group or column in the lateral column of gray matter, where this exists ; and (3)
posterior vesicular column of cells (nucleus dorsalis), forming a most conspicuou
group in the medial part of the neck of the posterior column in the thoraci
region of the spiual medulla.
Other cells, besides those forming these columns, are scattered somewhat irregi
larly throughout the gray matter of the posterior column and the part of the gra
crescent which lies between the two columns; and although these also in som
measure may be classified into groups, the arrangement thus effected is not of s
definite a character as to justify us in dwelling upon it in the present instance.
Ventral Cell-Column and the Origin of the Fibres of the Anterior Nerv*
roots. The ventral cell-group occupies the anterior column of gray matter, and i
it are found the largest and most conspicuous cells in the spinal medulla. ]
extends from one end of the spinal medulla to the other. These ventral nerve-ceL
have numerous wide-spreading dendritic processes, and it is to be noticed tha
certain of these dendrites do not confine their ramifications to the gray matte
Thus, some of the cells along the medial border of the anterior column of gra
matter send dendrites across the median plane in the anterior commissure to en
in the anterior gray column of the opposite side; whilst others, lying along th
lateral margin of the anterior column of gray matter, send dendrites in among?
the nerve- fibres of the adjoining white matter.
The axons or axis-cylinder processes of a large proportion of the ventral cells coi
verge together ; and, becoming medullated, they form bundles which pass out froi
the gray matter, and through the white matter which separates the thick end <
the anterior column from the surface of the spinal medulla, to emerge finally i
the fila of the anterior nerve-roots. These cells, then, are the sources from whic
the nerve- fibres of the anterior nerve-roots proceed, and in consequence they ai
frequently spoken of as the " motor cells " of the spinal medulla. Whilst this
THE GKAY MATTEE OF THE SPINAL MEDULLA.
529
he arrangement of the axons of the great majority of the motor cells, it should be
oted that a few cross the median plane in the anterior white commissure and
merge in the fila of origin of the opposite anterior nerve-root.
The ventral cells are not scattered uniformly throughout the anterior column of gray
latter. They are aggregated more closely together in certain parts of the anterior column,
, nd thus form sub-groups or columns more or less perfectly marked off from each other.
Thus, one sub-group or column of ventral cells occupies the medial part of the anterior
olutnn of gray matter throughout almost its whole length. In only two segments of the
aedulla is it absent, viz., the fifth lumbar and the first sacral ; at this level in the spinal
aedulla alone is its continuity broken (Bruce). It is termed the antero-median column or
roup of ventral cells. Behind this cell-column there is another classed with it to which
'he name of postero-median column or group is given, but this column of cells is not con-
! inuous throughout the entire length of the medulla. It is present in the thoracic region of
he spinal medulla, where the motor nuclei for the muscles of the limbs are absent; and
t is seen also in two or three of the segments of the cervical region and in the first
umbar segment (Bruce) ; elsewhere it is not represented.
In the cervical and lumbar swellings of the medulla, where the marked lateral out-
Posterior lateral furrow
Posterior column of
gray matter
Posterior median septum
*ray commissure
Postero-lateral
motor cells
Anterior median
fissure
Antero-median group
of motor cells
Antero-lateral
group of motor cells
FIG. 468.-
-SECTION THROUGH THE FIFTH CERVICAL SEGMENT OF THE SPINAL MEDULLA.
(To a large extent founded on Plates in Dr. Bruce's Atlas.}
growth is added to the lateral side of the anterior column of gray matter, certain groups of
large multipolar cells are visible. These are the nuclei of origin of the motor-fibres which
supply the muscles of the limbs, and consequently they are riot represented in the upper
three cervical segments of the spinal medulla ; nor in any of the thoracic segments, with
the exception of the first thoracic segment ; nor in the lowest two sacral segments.
These lateral cells are arranged in several columns, which extend for varying distances
in the superadded lateral parts of the anterior column of gray matter. The two main
Columns are an antero-lateral and a postero-lateral column; in certain segments there is
likewise a retro-postero-lateral column, and in a number of segments in the lumbar and sacral
: regions a central column of cells (Bruce).
There cannot be a doubt that the grouping of the motor cells in the anterior column of
?ay matter of the medulla stands in relation to the muscle groups to which their axis-cylinder
Jsses are distributed ; but from what has been said it will be apparent that sharply
efined cell -clusters associated with particular muscles do not exist. Still, much can be
iarned regarding the localisation of the motor nuclei in the anterior column of gray
;ter of the medulla from the study of the changes which occur in the cell-columns after
;rophy of isolated muscles or groups of muscles, and after complete or partial amputa-
is of limbs. It has been pointed out that the long muscles of the trunk (as, for
example, the different parts of the sacro-spinalis muscle) receive nerve-fibres from all the
35
530
THE NEEVOUS SYSTEM.
Posterior columi
of gray matter
segments of the spinal medulla. Now, we have noted that there is only one cell-column,
the ventro-median column, which pursues an almost uninterrupted course throughout the
entire length of the medulla.
Posterior lateral furrow It may be assumed,' therefore,
that the nerve-fibres which go
to these long trunk -muscles
take origin in these medial
cells.
Edinger states that in the
anterior column of gray matter
the nuclei of origin of the nerves
which supply the proximal mus-
cles are medially placed ; that
those for the distal muscles are
in general situated laterally.
If this is the case, the cells
connected with the shouldei
muscles will lie nearer the
middle of the anterior columr
of gray matter than those whicl
are connected with the hand
muscles. In cases where the;
forearm and hand, or the le
and the foot, are amputated, i
would appear that it is the pos
tero-lateral column of cells that shows changes in consequence of its separation from th<
muscles to which its fibres are distributed. 1
Posterior median
septum
Nucleus dorsalis
Gray commissure
Anterior median
fissure
Antero-medial group
of motor cells
Intermedio-lateral
column of cells
Postero-medial group
of motor cells
FIG. 469. SECTION THROUGH THE EIGHTH THORACIC SEGMENT OF THE
SPINAL MEDULLA. (To a large extent founded on Plates in
Dr. Bruce' s Atlas.)
Posterior lateral furro
Posterior column i
gray matter
\
Intermedio-lateral Cell-column. The intermedio-lateral cells form a long slende
column which extends throughout the entire thoracic region of the medulla in th
lateral column of gray
matter. It is also pro- ^\
longed downwards into ^
the first and second lum-
bar segments, where it dis-
appears. In transverse sec-
f c t i j i i Posterior median
tions through the spinal septum
medulla this cell -group
presents a very character-
istic appearance, because
the cells which compose
it are small and are closely
packed together. Al-
though these cells, as a
continuous column, are
restricted to the region
indicated, it should be
noted that the same group
of cells reappears above,
in certain of the cervical
segments, and also in the
third and fourth sacral
segments. From these
cells very fine fibres arise
and leave .the spinal
medulla, intermingled
with the motor fibres of
the anterior nerve-roots ; they pass into the sympathetic ganglia, of which th<
Gray
commissure
Anterior median
fissure
Postero-lateral group
of cells
Antero-medial
group of cells
Central group
of cells
An tero-lateral
group of cells
FIG. 470. SECTION THROUGH THE THIRD LUMBAR SEGMENT OF T:
SPINAL MEDULLA TO SHOW THE GROUPING OF THE MOTOR CELI
(To a large extent founded on Plates in Dr. Bruce's Atlas.)
1 Those who seek further information regarding the grouping of the ventral cells of the medulla n
with advantage study Dr. Alexander Bruce's Atlas of the Spinal Cord.
THE WHITE MATTEE OF THE SPINAL MEDULLA.
531
Posterior-
median septum
Gray commis-
sure
Anterior median
fissure
Posterior-lateral furrow
Posterior column of
gray matter
Retro-postero-
lateral group
of cells
institute the white rami communicantes. ' They represent the splanchnic efferent
ibres of the medulla spinalis.
Nucleus Dorsalis (O.T. Clarke's Column). This occupies the posterior column
')f gray matter and is the niost conspicuous of all the cell-groups in the medulla.
:!t does not, however, extend along the whole length of the medulla; indeed it is
ilmost entirely confined to the " dorsal " region, which is the reason for the
tesignation "nucleus dorsalis." (When, in the recent revision of nomenclature,
he term " thoracic " was substituted for " dorsal " the revisers omitted to change
':he name of this structure to " thoracic "). Above, it begins opposite the seventh or
'eighth cervical nerve, whilst below, it may be traced to the level of the second
.umbar nerve, where it disappears. In transverse section of the medulla it presents
in oval outline, and is seen in the median part of the cervix of the posterior column
pf gray matter, immediately behind the gray commissure (Fig. 469, p. 530). On
the lateral side it is circumscribed by numerous curved fibres from the entering
posterior nerve-root, and in the lower thoracic region of the spinal medulla
^opposite the eleventh and
twelfth thoracic nerves)
it becomes so marked that
it forms a bulging on the
median aspect of the pos-
terior gray column.
The cells of the nucleus
dorsalis are large, and pos-
sess several dendritic pro-
cesses. The axons enter
the lateral funiculus of
white matter and there
form a strand of fibres,
which will be described
later under -the name
of the fasciculus spino-
cerebellaris (wrongly called
" cerebellospinalis " in the
B.N.A.).
Nerve -fibres in the
Gray Matter of the
Medulla Spinalis.
Nerve-fibres of both the
medullated and the non- FIG.
medullated variety per-
vade every part of the
gray matter. They are of three kinds, viz., (1) collaterals, (2) terminations of nerve-
fibres, (3) axons given off by the cells. Many of the nerve-fibres which compose
the funiculi of the medulla give off numerous fine collateral branches, which pass
into the gray matter from all sides and finally end in relation with the nerve-
cells. The majority of the nerve-fibres themselves, which thus give off collaterals,
finally enter the gray matter, and end similarly. The axons of the majority of
the cells leave the gray matter and emerge either for the purpose of entering a
peripheral nerve or for the purpose of entering a strand of fibres in the white
matter of the spinal medulla.
The nerve-fibres thus derived are interwoven together in the gray matter in a
dense inextricable interlacement.
Postero-lateral group
of cells
Central group of cells Antero-lateral group of cells
471. SECTION THROUGH THE FIRST SACRAL SEGMENT OF THE
SPINAL MEDULLA TO SHOW THE GROUPING OF THE MOTOR NERVE-
CELLS. (To a large extent founded on Plates in Dr. Bruce's Atlas. )
COMPONENT PARTS OF THE WHITE MATTER OF THE SPINAL MEDULLA.
The white matter of the spinal medulla is composed of medullated nerve-fibres,
embedded in neuroglia. The fibres, for the most part, pursue a longitudinal course ;
and, from the deep surface of the pia mater which surrounds the medulla, fibrous
septa or partitions are carried in along vertical planes between the fibres so as
532
THE NEEVOUS SYSTEM.
to form an irregular and very imperfect fibrous framework of support. The
neuroglia is disposed in a layer of varying thickness around the medulla, subjacent
to the pia mater, and is carried into the medulla so as to give a coating to both
sides of the various pial septa. The neuroglia is disposed also around the various
nerve- fibres, so that each of these may be said to lie in a canal or tunnel of this
substance. The nerve-fibres are all medullated, but they are not provided with
primitive sheaths. It is the medullary substance of the nerve-fibres which gives
to the white matter its opaque, milky-white appearance. When a thin transverse
section of the medulla is stained in carmine and examined under the microscope
the white matter presents the appearance of a series of closely applied circles
each with a dot in the centre. The dot is the transversely divided axis-cylinde]
of a nerve-fibre, and the dark ring which forms the circumference of the circl<
represents the wall of the neuroglial canal which is occupied by the fibre. Thi
medullary substance is very faintly seen. It presents a filmy or cloudy appearanci
between the axis-cylinder and the neuroglial ring.
Arrangement of the Nerve -fibres of the Whiti
Matter in Fasciculi or Tracts. When the whit*
matter of a healthy adult spinal medulla is examinee
the fibres which compose it are seen to vary consider
ably in point of size ; and although there are specia
places where large fibres or it may be small fibre
are present in greater numbers than elsewhere, yel
as a rule, both great and small fibres are mixed up tc'
gether. No conclusive evidence can be obtained in sue"
a spinal medulla, by any means at our disposal, of th
fact that the longitudinally arranged fibres are groupe
together in more or less definite tracts or fascicul
the fibres of which run a definite course and preser
definite connexions. Yet this is known to be tt
case, and the existence of these separate tracts hf
been proved both by embryological investigation, f{i
well as by the examination of the effects of injuri*
produced experimentally or accidentally on tl
nervous system in living beings.
By the experimental method it has been shown th
when a nerve-fibre is severed the part which is detached fro
the nerve-cell from which it is an offshoot degenerates, whil
the part which remains connected with the nerve-cell unde
FlG 472. TRANSVERSE SECTION g es little or no change. This is called the law of " Walleriar
THROUGH THE WHITE MATTER OP degeneration. Thus, if in a living animal one-half of t!
THE MEDULLA SPINALIS, as seen spinal medulla is cut across, and after a few weeks the anim
through the microscope. is killed and the medulla examined, it will be seen that the
are degenerated tracts of fibres in the white matter, both abo
and below the plane of division ; but, still further, it will also be manifest that the tracts whi
are degenerated above the plane of division are not the same as those which are degenerated in t
part of the medulla which lies below this level The interpretation of this is obvious,
nerve-tracts which have degenerated above the plane of section are the offshoots of nerve-ce
which lie in lower segments of the medulla or in spinal ganglia below the plane of sectic
Severed from these nerve-cells, they undergo what is called ascending degeneration. The nen
tracts, on the other hand, which have degenerated in the portion of the medulla below the pla
of division are the axons of cells which lie at a higher level than the plane of section, either
higher segments of the spinal medulla or in the brain itself. Cut off from the nerve-cells fix
which they proceed, they present an example of descending degeneration.
The embryological method was first employed by Flechsig, and it is often referred to
Flechsig's method. It is based upon the fact that nerve-fibres in the earliest stages of th;
development consist of naked axis-cylinders, and are not provided with medullary sheat
Further, the nerve-fibres of different strands assume the medullary sheaths at different peric.
If the foetal central nervous system is examined at different stages of its development, it is
comparatively easy matter to locate the different tracts of fibres by evidence of this kind. Spec-
ing broadly, the tracts which myelinate first are those which bring the central nervous system ii >
relation with the peripheral parts (skin, muscles, etc.) ; then those fibres which bind the vari(
segments of the central nervous system together ; next, those which connect the spinal medu -
with the cerebellum ; and, lastly, the tracts which connect the spinal medulla with the cereb I
hemispheres. The nervous apparatus for the performance of automatic movements is fu f
THE WHITE MATTEE OF THE SPINAL MEDULLA. 533
!-ovided, therefore, before this is put under the control and direction of the higher centres. It
: T no means follows that in all the higher animals corresponding strands myelinate at relatively
rresponding periods. Take the case of a young animal which from the time of its birth is able
move about and perform voluntary movements of various kinds in a more or less perfect
anner, and compare it with the helpless new-born infant which is capable of exhibiting auto-
atic movements only. In the former, the cerebro-spinal tracts, or motor tracts, which descend
i om the cerebrum into the spinal medulla, and which are the paths along which the mandates
' the will travel, myelinate at an early period ; whilst in the infant the corresponding fibres
) not obtain their medullary sheaths until after birth. The study of the dates, therefore, at
hich the various strands of nerve-fibres myelinate not only gives the anatomist a means of
mating their position in the white matter of the central nervous system, but it also affords the
Physiologist most important information regarding their functions, and also the periods at which
lese functions are called into play.
It is a matter of interest to note that influences which either accelerate or retard the periods
. b which nerve-fibres are brought into functional activity have also an effect in determining the
ates at which these fibres assume their sheaths of myelin. Thus, when a child is prematurely
3rn the whole process of myelinisation is, as it were, hurried up ; and further, when in new-
orn animals light is freely admitted to one eye whilst it is carefully excluded from the other,
, le fibres of the optic nerve of the former myelinate more rapidly than those of the opposite nerve.
Study of the minute structure (Anatomical method) of the central nervous system, especially
f material that has been stained by the methods of Golgi and Ramon y Cajal or by the use of
lethylene blue, completes the results attained by these other methods, by demonstrating the
recise mode of origin and termination of the various fasciculi.
Posterior Funiculus and the Posterior Roots of the Spinal Nerves. In
he cervical and upper thoracic regions of the spinal medulla the posterior
uniculus is divided by the posterior intermediate sulcus and septum into the
asciculus cuneatus, which lies laterally and next to the posterior column of gray
natter, and the fasciculus gracilis, which lies medially and next to the posterior-
nedian septum. The fasciculus cuneatus is composed of nerve-fibres which are for
'he most part larger than those entering into the formation of the fasciculus gracilis,
md both tracts have a most intimate relation to the posterior nerve -roots; indeed,
/hey are both composed almost entirely of fibres which enter the medulla by these
.oo ts, and then pursue a longitudinal course.
The nerve-fibres which form the posterior nerve-roots, on entering the medulla along the
wlcus lateralis posterior, divide within the fasciculus cuneatus into ascending and descend-
,ng branches which diverge abruptly as they pass respectively upwards and downwards.
The descending fibres are, as a rule, short, and soon end in the gray matter of the spinal
medulla. These descending fibres occupy an area in the posterior funiculus along the
line of separation of the fasciculus gracilis and the fasciculus cuneatus, and, hence, may
be called the fasciculus interfascicularis (comma tract of Schultze). This area, when
the spinal medulla is divided, undergoes descending degeneration and then presents a
comma-shaped outline. (Fig. 473).
The ascending fibres vary greatly in length, and at differing distances from the point
where the parent fibres enter the medulla they end in the gray matter. A small contribu-
tion, however, of ascending fibres, from each posterior nerve-root, extends upwards to the
upper end of the spinal medulla, to end in the medulla oblongata (Figs. 474 and 475).
As each posterior nerve-root enters, its fibres range themselves in the lateral part of
the posterior funiculus close up against the posterior column of gray matter. The nerve-
fibres of the nerve-root next above take the same position, and consequently those which
entered from the nerve immediately below are displaced medially, and come to lie in the
posterior funiculus nearer to the median plane. This process goes on as each nerve-
root enters, and the result is that the fibres of the lower nerves are gradually pushed
learer and nearer to the posterior median septum in a successive series of lamellar tracts,
f course, the greater proportion of the fibres which are thus carried upwards from
the posterior nerve-roots sooner or later leave the posterior funiculus and enter the gray
matter, to end there in relation to some of its cells ; but, as we have said, every posterior
nerve-root sends a few fibres up the whole length of that portion of the spinal medulla
which lies above, and thus the posterior funiculus gradually increases in bulk as it is traced
upwards, and in all except the lowest part of the spinal medulla, the posterior funiculus
separable into a fasciculus gracilis and a fasciculus cuneatus. The fasciculus gracilis
composed of the long ascending fibres of the posterior nerve-roots, which have entered
Dwer segments of the spinal medulla. To put the matter differently, the fibres
the sacral roots are displaced medially by the entering lumbar fibres, while the fibres
the lumbar roots are 4n their turn pushed medially by the entering thoracic fibres,
35 a
534
THE NEKVOUS SYSTEM.
and, lastly, the fibres of the cervical roots displace the thoracic fibres. The difference
between the fasciculus gracilis and the fasciculus cuneatus consists simply in this, that
the former is composed of the fibres of posterior nerve-roots which have entered the
medulla at a lower level than those which enter into the formation of the fasciculus
cuneatus. The fibres of the fasciculus gracilis, taking them as a whole, must therefore
necessarily run a very much longer course.
Our kiiQwledge of the constitution of the posterior columns of the spinal medulla is
derived largely from the study of the course of degeneration in monkeys, after the medulla
has been cut across either partially or completely. But we have also a direct knowledge
of the lamination of the posterior columns of the human spinal medulla (Fig. 473) that
has been acquired from the examination of cases in which the medulla or its nerve-roots .
had been injured during life.
Numerous collateral fibrils stream into the gray matter of the posterior column
both from the ascending and descending branches of the entering fibres of the
posterior nerve-roots. These are classified into long and short collaterals. The long
Fasciculus gracili
Fasciculus septomarginalis
Fasciculus gracilis
Fasciculus cuneatus
Fasciculus posterolateralis-
Fasciculus spino-
cerebellari^ (posterior)-
Fasciculus
interfascicularis _
(comma tract)
Fasciculus posterior
fcproprius"
Fasciculus later-
alis proprius
Fasciculus
anterolateralis
superficialis'
(Gowers)
Fasciculus
jspinothalamicus' 'A'/-;
(posterior)
Fasciculus/
.spinotectalis
' Fasciculus
anterior proprius
I
Fasciculus spinothalamicus anterior |
Fasciculus cerebrospinalis anterior
Fasck s
Fascii
spinal is (<
olivospina
^.^ Fasciculus
"" ^ vestibulospinalis
ANTERIOR NERVE ROOT
Fasciculus vestibulospinalis
Area sulcomarginalis
FIG. 473. A DIAGRAM TO ILLUSTRATE THE GROUPING OF THE VARIOUS FASCICULI IN THE SPINAL
MEDULLA (in transverse section).
collaterals extend forwards into the anterior column of gray matter and end in relatio
to the ventral nerve-cells. The short collaterals end in relation to the nerve-cells in th
substantia gelatinosa, and other nerve-cells of the posterior column of gray matter.
The majority of the fibres of the posterior nerve-root enter the spinal medulla o
the medial side of the apex of the posterior column of gray matter. The manner in whic
these are related to the fasciculus cuneatus and the fasciculus gracilis has been noticed ; bu
a certain number of those fibres which lie most laterally take a curved course forward
on the medial side of the posterior column of gray matter and then pass into it. I
the thoracic region these curved fibres end in connexion with the cells of the nuclei
dorsalis (Fig. 467, B, p. 525, and Fig. 473).
Fasciculus Posterolateralis (O.T. Tract of Lissauer). The postero-laten
fasciculus is a small tract of nerve-fibres of minute calibre which assume their medullar
sheaths at a comparatively late period. It is placed at the surface of the medulla clos
to the sulcus lateralis posterior. It is formed by some of the lateral fibres of the posteric
nerve-roots which do not enter the fasciculus cuneatus, but pass upwards in the medul
close to the substantia gelatinosa, in which they ultimately end.
It must now be evident that the fibres which enter the medulla spinalis through eac
THE WHITE MATTEE OF THE SPINAL MEDULLA.
535
osterior nerve-root have three main modes of distribution : (1) the majority take part in
ie formation of the fasciculus cuneatus, and pass upwards or downwards to end in the
:ray matter at some other level in the central nervous system ; (2) some fibres, and many
ollaterals of fibres in the fasciculus cuneatus, lie close to the posterior column and
escribe a series of graceful curves as they pass forwards, prior to turning laterally into
11 regions of the gray matter to end at the same level as they enter the medulla spinalis ;
3) a third series form the pos'tero-lateral fasciculus and end in connexion with the cells of
he substantia gelatinosa and other cells in the posterior and anterior columns of gray
latter (Fig. 473).
The fibres derived from the posterior nerve-roots which ascend in the posterior
uniculi of the medulla spinalis to the medulla
blongata of the brain constitute a direct sensory
: ract ; other fibres are described which give rise to a
rossed sensory tract termed the fasciculus spino-
halamicus. These latter fibres arise as the axons of
ertain of the cells in the posterior column in con-
lexion with which fibres from the posterior nerve-
oots have ended, and crossing to the opposite side
)f the medulla spinalis through the anterior commis-
,ure they ascend in the antero-lateral funiculus to
,he brain, where they ultimately reach the thalamus.
Vs the spino-thalamic tract ascends in the spinal
nedulla its fibres are not gathered into a compact
strand, but are more or less loosely scattered in the
.ateral funiculus.
Association Fibres in the Posterior Funiculus. But
;he whole of the fibres of the posterior funiculus are not
lerived from the posterior nerve-roots. A few fibres exist
in this funiculus which have a different origin. They are
derived from certain of the cells of the gray matter, and,
entering the posterior funiculus, they divide into ascend-
ing and descending branches which pass upwards and
downwards in the funiculus for a varying distance, before
they finally turn in to end in the gray matter at higher
and lower levels. These fibres, therefore, constitute
links of connexion between different segments of the
spinal medulla, and they constitute the fasciculus posterior
proprius. Our information regarding these fibres at
present is somewhat defective ; but it is believed that the
deepest part of the funiculus, i.e. the part next the
posterior gray commissure, and the fasciculus septo-
marginalis of Bruce, placed in apposition with the
posterior-median septum and in the adjoining part of the Fm
surface, belong mainly to this category.
TO SHOW THE
MANNER IN WHICH THE FIBRES OF
THE POSTERIOR NERVE-ROOTS ENTER
AND ASCEND IN THE POSTERIOR
FUNICULUS OP THE SPINAL
MEDULLA. (From Edinger. )
Funiculus Lateralis and Funiculus Anterior.
-It is convenient to consider the anterior along
with the lateral funiculus and to call the whole mass
white substance that is left, after eliminating the posterior funiculus, the antero-
lateral funiculus. In contact with the surface of the gray columns there is a broad
band of white matter the parts of which are known respectively as the fasciculus
proprius anterior and lateralis (O.T. the ground bundles of the antero-lateral
iuniculus). It is composed wholly of fibres which spring from nerve-cells in the
gray columns, and, after passing for varying distances upwards or downwards, end
in the gray matter of the spinal medulla. Thus they constitute an intrinsic
tern of fibres linking together different levels of the spinal medulla. They
>ecome medullated before any other fibres, except the root-fibres and their con-
tuations in the posterior funiculus. When cut across some of the fibres degenerate
ove, others below, the injury, and the degeneration extends for varying distances
upwards and downwards respectively.
536
THE NEEVOUS SYSTEM.
The best -known long or extrinsic systems of fibres in the antero- lateral
funiculus are those known as the fasciculus cerebrospinalis lateralis (O.T. crossed
pyramidal tract), the fasciculus cerebrospinalis anterior (O.T. direct pyramidal tract),
the fasciculus cerebellospinalis (O.T. direct cerebellar tract) (which goes from the
spinal medulla to the cerebellum, and ought therefore to be called spinocerebellaris,
as it will le subsequently named in this account), and the fasciculus anterolateralis
superficial (O.T. Gowers' tract).
There are, however, many other fasciculi at least as important as these, but
there is as yet no close agreement as to their precise limits or connexions. One
reason for this is that some of the elements of one tract may become intermingled
with those of another ; moreover, the position and relations of certain of them
Optic tract
Te'ctum mesencephali
I Red nucleus
Tecto-spinal tract
;,, ^'Rubro-spinal tract
Metathalamus
Thalamusx,
^ Brachium conjunctivum
.-* Lemniscus medialis
" Lemniscus lateralis
Cerebellum
Corpus striatum ^
Cerebral hemispl
Cerebro-spinal ^
tract--"
Olfactory ner^e
Olfactory
epithelium
Vestibulo-spinal tract
Nucleus gracilis
Retina of the eye
X indicates the place where a tract crosses the median plane.
FIG. 475. DIAGRAM REPRESENTING THE CONNEXIONS OP SOME IMPORTANT SENSORY AND MOTOR TRACT.-
IN THE BRAIN.
vary considerably at different levels of the spinal medulla. In Fig. 473 a
attempt has been made to present the present state of our knowledge of thee
great strands of white fibres. This diagram is not intended to represent any definit
level of the spinal medulla, though certain features are shown which occur onl
in the cervical region ; and in respect of other features, the arrangement foun
in lower regions of the spinal medulla has been introduced to render the diagrai
more serviceable.
Much of the apparent complexity of this chart will disappear if the readf
recalls some general statements (p. 512) made with regard to the outstandin
features of the brain. It was then explained that when sensory nerves, comic
from the skin and muscles, enter the spinal medulla, they not only establis
relations with the motor nuclei and other spinal structures in the neighbourhoc
of their insertion, but also give rise, directly or indirectly (see Fig. 475) to man
THE WHITE MATTER OF THE SPINAL MEDULLA. 537
:isciculi which pass upwards in the spinal medulla to reach the medulla
blongata, the pons and cerebellum, the mesencephalon (corpora quadrigemina),
rie thalanius, and the cerebral hemisphere. In the neighbourhood of each level
here these ascending sensory tracts end, such as for example the region of the
estibular nucleus and cerebellum, the tectum mesencephali, the corpus striatum,
nd the cerebral hemisphere, great descending tracts originate and pass downwards
i the spinal medulla (Fig. 475 the red lines). Thus we have cerebro-spinal,
ubro-spinal, tecto-spinal, vestibulo-spinal, and bulbo-spinal fasciculi passing down
he spinal medulla ; and each system eventually ends around the series of motor
.uclei (Fig. 475), many of them in the spinal medulla.
In the anterolateral funiculus the various fasciculi will be found to be
rouped roughly into three bands : Next to the gray columns is the fasciculus
>roprius ; then comes a band of descending (motor) fasciculi ; and then, upon the
urface, a series of ascending (sensory) fasciculi. This arrangement, however, is not
naintained with any degree of exactitude in the anterior funiculus, where the
harp demarcation between ascending and descending fasciculi is in great part
lestroyed by the intermingling of fibres passing in opposite directions.
The fibres of the posterior nerve-root have already been studied so far as their
elation to the posterior funiculus is concerned. No clear conception of the nature
ind significance of the ascending fasciculi in the anterolateral funiculus can be ob-
,ained unless they also are studied in relationship with the fibres of the posterior root.
It has already been explained that of the fibres which enter the spinal
nedulla in the posterior root the great majority enter the posterior funiculus,
.vhere they bifurcate (Fig. 473, a) ; one branch of each fibre passes upwards either
n the funiculus gracilis or in the funiculus cuneatus, or it may pass from the
Latter into the former ; the other descends in the fasciculus interfascicularis (O.T.
3omma tract). Other fibres perhaps enter the posterolateral fasciculus (O.T.
Lissauer's bundle). But all the other fibres of the posterior root, together with
the majority of the fibres of the fasciculus cuneatus, sooner or later enter the gray
matter (Fig. 473, ~b to Ji) of the spinal medulla.
Some of them (&) pass directly to end in the nucleus dorsalis of their own side,
and from its cells fresh fibres arise, which pass laterally through the posterior
column and lateral funiculus to reach the surface, where they bend upwards as
constituent fibres of the spino-cerebellar fasciculus. These pass upwards throughout
the whole length of the spinal medulla (above their place of origin), into the
medulla oblongata, thence into the cerebellum through the restiform body.
Other fibres on the same side (e), and perhaps also on the other side (d), end
| amidst cells of the gray matter, the axis-cylinder processes of which' pass into the
antero-lateral superficial fasciculus (O.T. Gowers' tract). In this tract they ascend
throughout the spinal medulla, medulla oblongata, and pons, to enter the cere-
bellum alongside the brachium conjunctivum (superior peduncle). This element
in the antero-lateral fasciculus is sometimes designated the fasciculus spinocere-
bellaris anterior, to distinguish it both from the non-cerebellar fibres of the parent
fasciculus and from the fasciculus spinocerebellaris [posterior] (O.T. the direct cere-
bellar tract). These two spino-cerebellar tracts convey to the cerebellum informa-
tion from the muscles and overlying skin which assists it to co-ordinate the
muscles for carrying on precisely adjusted movements.
Other fibres of the posterior nerve-root (e,f, g, and A) terminate in relation-
ship with cells in the gray columns of their own side of the spinal medulla, the
axons of which cross the median plane in the anterior commissure to pass respectively
j () into the anterolateral superficial fasciculus [not to be confused with the
cerebellar constituents of this bundle] ; (/) into the real fasciculus spinothalamicus
[posterior], of which the last-mentioned fibres are merely outlying members;
( (g) into the fasciculus spinotectalis, to ascend to the mesencephalon ; and (h) into
the marginal area of the anterior funiculus to form a group which may be called
the fasciculus spinothalamicus anterior.
The careful investigations of the late Dr. Page May led him to attach a definite
physiological significance to this grouping of the ascending paths. The fasciculus
spinothalamicus [posterior] is supposed to convey upwards to the thalamus (for
538 THE NEKVOUS SYSTEM.
transmission to the cerebral cortex, which is concerned with the conscious apprecia-
tion of sensations) all impulses of pain, heat, and cold coming from the skin upon
the opposite side of the body. The fasciculus spinothalamicus anterior conveys
impulses of touch and pressure from the opposite side.
The spino-cerebellar fasciculi [anterior and posterior] convey to the cerebellum
respectively homolateral and bilateral unconscious afferent impulses underlying
muscular co-ordination and reflex tone.
Among the descending tracts that establish connexions between various parts
of the brain (see Fig. 475) and the motor nerve-cells in the anterior column may be
mentioned the cerebrospinal, the rubro-spinal (from the red nucleus), the tecto-
spinal (from the corpora quadrigemina), the vestibule -spinal (from the terminal
nucleus of the vestibular nerve), and the bulbo-spinal tracts. The last-mentioned
forms a peculiar triangular area upon the surface immediately to the lateral side of
the anterior nerve-roots (Fig. 473), but there is great uncertainty as to its mode of
origin : it is often called the fasciculus olivospinalis, from the fact that its discoverer.
Helweg, believed it to originate from the olivary nucleus in the bulb or medulla
oblongata. It may be regarded as an outlying part of the vestibular (or cerebellar^
tract to the motor nuclei of the spinal medulla.
The fasciculus cerebrospinalis lateralis (O.T. crossed pyramidal tract) is a large
well-defined descending tract which lies immediately in front of the posterior column
of gray matter, and subjacent to the posterior spino-cerebellar fasciculus, which shut 6
it out from the surface. Below the point where the posterior spino-cerebellai
fasciculus begins the cerebrospinal fasciculus becomes superficial, and in this
position it can be traced as low as the fourth sacral nerve, at which level it ceases t(
exist as a distinct strand. The cerebro-spinal fasciculus is composed of an admixture
of both large and small fibres. These arise in the brain from the large pyramida
cells of the motor or precentral area of the cerebral cortex, and pass downward
through various subdivisions of the brain to gain the spinal medulla. As the;
enter the spinal medulla they cross the median plane from one side to the othei
and it thus happens that the cerebro-spinal tract in the right lateral funiculus of th
spinal medulla has its origin in the cortex of the left cerebral hemisphere, and vie
versa. As the tract descends in the spinal medulla it gradually diminishes in size
and 'this is due to the fact that, as it traverses each spinal segment, numerous fibre
leave it to enter the anterior column of gray matter, and end in connexion with th
anterior motor cells from which the fibres of the anterior nerve-roots arise. Th
entire strand is ultimately exhausted in this way. Numerous collateral fibrils sprin
from the cerebro-spinal fibres, and, entering the gray matter, end in a simila
manner. In this way a single cerebro-spinal fibre may be connected with severe
spinal segments before it finally ends. The lateral cerebro-spinal fasciculus must t
regarded as a great motor strand which brings the spinal motor apparatus unde
the control of the will.
Schafer believes that many of the fibres of the cerebro-spinal fasciculus end i
connexion with the cells of the nucleus dorsalis.
In many marsupials, rodents, and ungulates the lateral cerebro-spinal fasciculus li<
in the posterior funiculus of the spinal medulla.
The fasciculus lateralis proprius represents the remainder of the later
funiculus. Its fibres are largely derived from the cells situated in all parts <
the gray matter, and also from the nerve-cells of the opposite side of the spin
medulla. After a course of very varying length in the fasciculus lateralis, the
fibres turn medially and re-enter the gray matter. Such fibres may thus 1.
regarded as inter-segmental association fibres binding two or more segments of tl
spinal medulla together. It may be mentioned that the association fibres whit
link together segments of the spinal medulla which are near to each other lie close
the gray matter, whilst those which connect the more distant segments are situat-
further out in the lateral funiculus.
Funiculus Anterior. One well-defined tract is situated in the funicul
anterior. This is termed the fasciculus cerebrospinalis anterior. The remaind
of the funiculus receives the name ,of the fasciculus anterior proprius.
THE ENCEPHALON OK BKAIN. . 539
The fasciculus cerebrospinalis anterior (O.T. direct pyramidal tract) is usually a
j rve-strand of small size which lies near the anterior median fissure. As a rule it
( >inot be traced lower than the middle of the thoracic region of the spinal medulla.
is a descending tract and must be associated with the lateral cerebro-spinal
: sciculus of the opposite side, seeing that both of these strands arise from the motor
j3a of the cortex of the same cerebral hemisphere. From this it must be clear
at the anterior cerebro-spinal fasciculus does not cross the median plane as it
- ters the spinal medulla, but descends on the side of the spinal medulla corre-
onding to the cerebral hemisphere in which it arises. Nevertheless, its fibres do
>t end in the same side of the spinal medulla, but at every step along the path of
e strand they make use of the anterior commissure, and cross to the opposite side
the spinal medulla, to terminate in relation to the opposite ventral motor cells
the same manner as the lateral cerebro-spinal fibres.
From this crossing of the cerebro-spinal fasciculi, it follows that the destruction of the fibres
:iich compose them as they descend in one side of the brain must result in paralysis of the
uscles supplied by the efferent nerves of the opposite side of the spinal medulla.
In cases of old brain lesion it is sometimes possible to detect some degenerated fibres in the
teral cerebro-spinal fasciculus of the sound side of the spinal medulla, and from this it is
pposed that this tract contains a few uncrossed fibres. If this is the case, each side of the
inal medulla stands in connexion with the motor area of both cerebral hemispheres.
It is well to note that the fibres of both lateral cerebro-spinal fasciculi are not medullated
itil the time of birth. They are the latest of all the fasciculi of the spinal medulla to myelinate.
Commissura Anterior Alba. The anterior white commissure is composed of
ledullated nerve-fibres passing from one side of the spinal medulla to the other
nd entering the anterior column of gray matter, and also the anterior funiculus of
r hite matter. It is to be regarded more as a decussation than as a commissure,
nd its width, which varies somewhat in different regions, fluctuates in correspond-
Qce with the diameter of the spinal medulla.
Amongst the fibres which .cross in the anterior commissure may be mentioned : (1) The fibres
f the fasciculus cerebrospinalis anterior ; (2) collaterals from both the anterior and lateral
miculi ; (3) axons of many of the cells of the gray matter ; (4) the dendritic processes of some
f the medial anterior cells.
Commissura Grisea. Although this is composed of gray matter with a large
Admixture of neuroglia, numerous nerve-fibres pass transversely through it, so as
o establish relations between the cells in the gray matter on the two sides of the
pinal medulla.
THE ENCEPHALON OR BRAIN.
The brain is the enlarged and greatly modified upper part of the cerebro-spinal
nervous axis. It is surrounded by the same membranes that envelop the medulla
spinalis (viz., the dura mater, the arachnoid, and the pia mater), and it almost
Completely fills up the cavity of the cranium. So closely, indeed, is the skull
! capsule moulded upon the brain that the impress of the latter is almost everywhere
evident upon the inner surface of the cranial wall. The relations, therefore, of
cranium to brain are totally different from those presented by the vertebral canal
the spinal medulla. As we have noted, the medulla spinalis occupies only a
part of its bony case ; and there is not only a wide and roomy space between the
ichnoid and the pia mater, but also an interval of some width between the
dura mater and the walls of the vertebral canal.
General Appearance of the Brain. When viewed from above the brain
'Sents an ovoid figure, the broad end of which is directed backwards. Its
t transverse diameter is usually found in the neighbourhood of that part
lies between the two parietal tuberosities of the cranium. The only parts
i are visible when the brain is inspected from this point of view are the two
avoluted cerebral hemispheres. These present an extensive convex surface, which
540
THE NEBVOUS SYSTEM.
is closely applied to the internal aspect of the cranial vault, and are separated from
each other by a deep median cleft, termed the fissura longitudinalis cerebri, which
extends from the front to the back of the brain.
The inferior aspect of the brain is usually termed the basis cerebri. It presents
an uneven and irregular surface, which is more or less accurately adapted to the
inequalities on the floor of the cranial cavity. Upon this aspect of the brain some
of its main subdivisions may be recognised. Thus, posteriorly, is seen the short
cylindrical portion, called the medulla oblongata, through which, at the foramen
magnum, the brain becomes continuous with the medulla spinalis. The medulla
oblongata lies on the ventral aspect of the cerebellum, and occupies the vallecule
or hollow which intervenes between the two cerebellar hemispheres. The cerebellun
Optic chiasma
Infundibulur
Olfactory bulb
Left corpus mamillare
Substantia perforata
posterior
Pedunculus cerebri
Abducens nerve
Hypoglossal nerve
Olfactory tract
Optic nerve,
Substantia perforata
anterior
Optic tract
Tuber cinereum
Oculomotor nerve
Trochlear nerve
Trigeminal nerve
Facial nerve
Acoustic nerve
' Nervus intermedius
Glosso-pharyngeal nerve
Vagus nerve
MEDULLA OBLONGATA "^^BB^^^" "^^^^^^^^^ Accessory nerve
Medulla spinalis (cut) Hypoglossal nerve
FIG. 476. THE BASE OF THE BRAIN WITH THE CEREBRAL NERVES ATTACHED.
is a mass of considerable size which is placed below the posterior portions of tt
two cerebral hemispheres. It is easily recognised on account of the closely se
curved, and parallel fissures which traverse its surface and give it a foliate
appearance. Above the medulla oblongata, and in close connexion with it, is
prominent white elevation called the pons. Immediately in front of the pons thei
is a deep hollow or recess. This is bounded behind by the pons, on each side b
the projecting temporal lobe of the cerebral hemisphere, and in front by the orbit*
portions of the frontal lobes of the cerebral hemispheres. Passing out from eac
side of the anterior part of this recess is the deep lateral fissure of the brain whic
intervenes between the pointed and projecting extremity of the temporal lot
and the frontal lobe of the cerebrum, whilst, in the median plane in front, tt
longitudinal fissure, which separates the frontal portions of the cerebral hemisphere
opens into it.
Within the limits of this deep hollow, on the base of the brain, two large rop<
THE ENCEPHALON OE BKAIN. 541
; ce strands, the pedunculi cerebri, may be seen issuing from the inferior surface
the cerebral hemispheres. As they pass downwards these peduncles are inclined
diquely towards the median plane, so that when they plunge into the pons they
e situated in close apposition the one to the other (Fig. 478). Turning round
.e lateral side of each peduncle, where it emerges from the cerebrum, a flattened
,nd termed the optic tract may be observed. These bands come from the anterior
irt of the hollow, where they are joined together by a short connecting piece
rmed the optic chiasma. The optic nerve is inserted, on each side, into the
itero-lateral angle of the chiasma.
The pedunculi cerebri, the optic tracts, and the optic chiasma enclose a deep
lomboidal or lozenge-shaped interval on the base of the brain, which is termed
>e fossa interpeduncularis. Within the limits of this area the following parts may
j seen as we pass from behind forwards : (1) the substantia perforata posterior ;
!) the corpora mamillaria : (3) the tuber cinereum and the stalk of the hypo-
lysis cerebri (O.T. pituitary body).
At its posterior angle, immediately in front of the pons, the interpeduncular
ssa is very deep and is floored by a layer of gray matter, in which are
nmerous small apertures. This is the substantia perforata posterior. Through
le apertures which are dotted over its surface the small postero-medial basal
ranches of the posterior cerebral artery enter the brain.
The corpora mamillaria are two small white pea-like eminences placed side by
de in front of the substantia perforata posterior. .
The tuber cinereum is a slightly-raised field of gray matter, which occupies the
iterval between the anterior portions of the optic tracts in front of the corpora
tamillaria. Springing from the anterior part .of the tuber cinereum, immediately
ihind the optic chiasma, is the mfundibulum, or the stalk which connects the
ypophysis cerebri with the base of the brain (Fig. 478).
Lateral to the limits of the anterior part of the interpeduncular space there is, on
ich side, a small depressed triangular field of gray matter, which leads laterally
ito the lateral cerebral fissure. It is perforated by the antero-medial and the
atero-lateral groups of basal arteries, and receives the name of the substantia
erforata anterior.
General Connexions of the Several Parts of the Brain. The medulla
blongata, the pons, and the cerebellum occupy the posterior cranial fossa, and
ley are separated from the cerebral hemispheres, which lie above them, by a
artition of dura mater, termed the tentorium cerebelli. Further, they surround
cavity, a portion of the primitive cavity of the early neural tube, which is termed
ne fourth ventricle of the brain, and they all stand in intimate connexion, one
"ith the other. The medulla oblongata is for the most part carried upwards into
he pons ; but at the same time two large strands from its dorsal- aspect, termed
he restiform bodies, are prolonged into the cerebellum, and constitute its
iferior peduncles, or the chief bonds of union between the medulla (oblongata and
pinalis) and the cerebellum. The pons has large numbers of transverse fibres
ntering into its composition, and the great majority of these are gathered together
n each side in the form of a large rope -like strand. This plunges into the
orresponding hemisphere of the cerebellum, and constitutes its middle peduncle,
iriiich is known as the brachium pontis.
The cerebrum, which forms the great mass of the brain, occupies the anterior
-nd middle cranial fossae, and extends backwards into the occipital region above
i he tentorium and the cerebellum. The greater part of the cerebrum is formed by
he cerebral hemispheres, which are separated from each other in the median
)lane by the longitudinal fissure. At the bottom of this fissure is the corpus
;allosum, a broad commissural band which connects the two hemispheres with
>ach other. Each hemisphere is hollow, the cavity in its interior being termed
he lateral ventricle of the brain. Between and below the cerebral hemispheres,
md almost completely concealed by them, is the inter-brain or diencephalon. The
rincipal parts forming this portion of the brain are two large masses of gray
i-tter, termed the thalami. Between these is the third ventricle of the brain a
leep narrow cavity occupying the median plane. The third ventricle communicates
542
THE NERVOUS SYSTEM.
with the lateral ventricles by two small apertures, called the foramina inter
ventricularia.
The cerebrum is connected with the parts in the posterior cranial fossa (pons
cerebellum, and medulla oblongata) by a narrow stalk called the mesencephalon o:
mid-brain. The mid-brain is built up of (1) the pedunculi cerebri, passing from th<
pons to the cerebrum ; (2) the corpora quadrigemina, forming its dorsal part ; am
(3) the brachia conjunctiva (O.T. superior cerebellar peduncles), proceeding from th<
cerebellum to the cerebrum. It is tunnelled by a narrow passage, the aquseductu
cerebri, which extends between the fourth and third ventricles.
In a view of the intact brain the greater part of the mesencephalon am
diencephalon is hidden by the cerebral hemispheres ; but a precise idea will b
obtained of the inter-relationships of the various parts of the brain, if we stud;
Epithelial roof of third ventricle
Lamina co mm is s u re I^SS&SJSS"* ^ "* ">>
merit nf the enithfilial rnof nf thirrl ventricle > Ttpnia thalami
men
ia commissurte hippocampi at the attach-
nt of the epithelial roof of third ventricle
Corpus callosum
Columna fornicis
Septum pellucidum
AnterioFcommissuie^-
Rostrum corporis callosi^^^""'^ \ \
Germ corporis callosi
! Tsenia thalami
i \ Vena cerebri interna
| i \ Plexus chorioideus ventriculi tertii
\ Commissura habenularum
1 { Recessus suprapinealis
J__ ; ; Pineal body
~""|>^Splenium corporis callos
! / 7^ Lamina quadrigemina
! ; ?-^A Anuaeductus cerebri
Vena magna cerebri
Velum medullare anterius
/ Lobulus centralis cerebelli
Culmen cerebelli
Fissura prima
Fourth ventricle
Attachment
epithelial ro
Paraterminal body
Lamina terminalis
Infundibulum
Hypophysis--
intermedia . .
Sulcus hypothalamicus /
Corpus mamillare / j /
Oculomotor nerve / ,'
Posterior commissure /
Tegmentum (mesencephali) /'
Pons
Pyramid -''
Fourth ventricle''
Central
Decussation of pyramid'
Pyram.
Uvula
Tonsilla
Edge of apertura medialit
Chorioid plexus of fourth v< ide
(the pointing line passes th .'b
the apertura medialis)
FIG. 477. THE PARTS OF THE BRAIN CUT THROUGH IN A MEDIAN SAGITTAL SECTION.
The side walls of the ventricular cavities are also shown .
the relationship of these structures to the series of cavities in the interior of t
brain as they are displayed in a median sagittal section (Fig. 477).
The central canal which tunnels the spinal medulla is seen to extend into t
medulla oblongata for a short distance ; then it expands into the irregular cavity
the fourth ventricle, the floor (anterior wall) of which is formed partly by t
medulla oblongata and partly by its continuation upwards, the pars dorsalis pont
Behind the fourth ventricle lies the cerebellum, but it forms only a small part of t
roof (tegmen). The roof consists mainly of the velum medullare anterius abo
and the thin epithelial lamina (lamina chorioidea epithelialis) below.
The fourth ventricle is continued upwards into the aquseductus cerebri, whi
tunnels the mesencephalon, of which the thick mass of the tegmentum is placed
front of it and the lamina quadrigemina behind.
The aqueduct opens in front into the third ventricle, the major portion
each side wall of which is formed by the thalamus. Near the antero-super '
MEDULLA OBLONGATA.
543
c:ner of each side wall of the third ventricle the small foramen interventriculare
( .T. foramen of Monro) leads into the cavity of the corresponding cerebral hemi-
jhere, which is known as the lateral ventricle.
MEDULLA OBLONGATA.
The medulla oblongata is the continuation upwards of the medulla spinalis.
is a little more than 25 mm. (one inch) in length, and it may be regarded as
Binning immediately above the uppermost root of the first cervical nerve, or,
Optic nerv
Optic chiasma
Optic tract
pedunculi cerebri
Infundibulum (cut)
Tuber cinereum
^ Corpus mamillare
^Sitbstantia perforata po^erior
Oculomotor nerve
Trochlear nerve
Motor root of
trigeminal nerve
Sensory root of
trigeminal nerve*"*"
lusobliquus pontis *--_/
ma intermedius -
Acoustic nerve
Flocculus cerebelli ;
Chorioid plexus in the
apertura lateralis of
: the fourth ventricle
Lateral recess of/
fourth ventricle
Abducens nerve
Facial nerve
Acoustic nerve
?~~Nervus intermedius
- Glossopharyngeal nerve
Facial nerv
Decussation of pyramids
^/ hj """^ Vagus nerve
Accessory nerve
Hypoglossal nerve
^Spinal root of accessory nerve
First spinal nerve
'
FIG. 478. FRONT VIEW OF THE MEDULLA OBLONGATA, PONS, AND MESENCEPHALON OF A
FULL-TIME HUMAN FCETUS.
)ughly, about the level of the foramen magnum. From this it proceeds upwards
i a very nearly vertical direction, and ends at the lower border of the pons.
A first its girth is similar to that of the spinal medulla, but it rapidly expands
3 it approaches the pons, and consequently it presents a more or less conical
i)rm. Its anterior surface lies behind the grooved surface of the basilar portion
f the occipital bone, whilst its posterior surface is sunk into the vallecula of the
arebellum. The medulla oblongata is a bilateral structure, and this is indicated
n the surface by the presence of anterior and posterior median fissures, on the
entral and dorsal surfaces respectively.
The fissura mediana anterior, as it passes from the spinal medulla on to the
ledulla oblongata, is interrupted at the level of the foramen magnum by several
trands of fibres which cross the median plane from one side to the other. This
atercrossing is termed the decussation of the pyramids. Above this level the fissure
544
THE NEEVOUS SYSTEM.
Frenului
Anterior medullary
velum
Brachium con-
junct! vum
Brachium pontis
Striae medullares
Area acustica
Ala cinerea
(trigonum vagi)
Puniculus cuneatus
Funiculus gracilis
Tsenia thalani
Pineal body
Superior quadri-
geininal body
Inferior quadri-
geminal body
Pedunculus cerebri
Pontine part of floor
of 4th ventricle
Colliculus facialis
Fovea superior
Restiform body
Trigonum
n. hypoglossi
Clava
Tuberculum
cihereum
Funiculus cuneatus
is carried upwards to the lower border of the pons, but is often rendered ven
shallow by numerous external arcuate fibres which emerge upon the surfac<
between its lips am
then curve laterally t<
reach the posterior par
of the medulla oblon
gata. At the lowe
margin of the pons i
expands slightly am
ends in a blind pit
which receives the nam
of the foramen caecur
The fissura median
posterior is present onl
on the lower half of th
medulla oblongata. A
it ascends it rapidl
becomes shallowei
Half-way up, where th
central canal opens int
the fourth ventricli
the lips of the posteric
median fissure are thrus
apart from each oth(
and constitute theboui
FIG. 479. POSTERIOR .VIEW OF THE MEDULLA, PONS, AND MESENCEPHALON daries of a trianuulc
OF A FULL-TIME HUMAN FOETUS. c 1 J "U 1.
field, which is seen whe
the epithelial roof of the lower part of the fourth ventricle is removed. This tr
angular field is the lower part of the fossa rhomboidea, or the floor of the fourt
ventricle of the brain. The lower half of the medulla oblongata, containing as it dot
the continuation of the central canal of the spinal medulla, is frequently terme
the closed part of the medulla oblongata ; the upper half, above the opening of tl
canal, which contains the lower part of the fourth ventricle, is called the opt
part of the medulla oblongata.
The examination of the floor of the fourth ventricle will be deferred for tl
present, and the appearance presented by the surface of the medulla oblonga
may now engage our attention. In the spinal medulla the corresponding surfa<
area is divided into three districts or funiculi by the emerging motor roots and tl
entering sensory roots of the spinal nerves. Of these the sensory enter aloi
the bottom of the sulcus lateralis posterior, whilst the motor fila are spre*
over a relatively broad surface area and have no groove in connexion with the
emergence from the spinal medulla. In the case of the medulla oblonga
corresponding rows of fila enter and emerge from the surface of each side. The fi
of the hypoglossal nerve carry up the line of the anterior nerve-roots of the spin
medulla. In one respect, however, they differ : they emerge in linear order ai
along the bottom of a distinct furrow, termed the sulcus lateralis anterior, whi<
proceeds upwards on the surface of the medulla oblongata. The fila which car
up the line of the posterior nerve-roots on the 'surface of the medulla oblonga
are the root-bundles of the accessory, the glosso-pharyngeal, and the vagus nerv-
These are attached along the bottom of a furrow which is the direct continuati
upwards of the sulcus lateralis posterior of the spinal medulla, and therefc
receives the name of the sulcus lateralis posterior of the medulla oblongata. T
root-bundles of these nerves differ, however, in so far that they are not all compos
of afferent fibres which spring from ganglionic cells placed without and enter t
medulla. Certain of them are purely efferent (roots of accessory), whilst oth<
contain a considerable number of efferent as well as afferent fibres, and are the:
fore to be regarded as mixed roots.
By the sulci laterales, and also by the two rows of fila attached along t)
THE MEDULLA OBLONGATA.
545
ottom of these furrows, the surface of the medulla oblongata on each side is
ivided into three districts, viz., an anterior, a lateral, and a posterior, similar to
le surface areas of the three funiculi on the side of the spinal medulla. Indeed,
;, first sight, they appear to be direct continuations upwards of these three portions
[ the spinal medulla ; this, however, is not the case, because the fibres of the
iree funiculi of the spinal medulla undergo a rearrangement as they proceed
pwards into the medulla oblongata.
Anterior Area of the Medulla Oblongata Pyramis. The district between
ie anterior median fissure, and the sulcus lateralis anterior, along the bottom
; f which the root-fila of the hypoglossal nerve issue from the medulla oblongata,
'3ceives the name of the pyramid. An inspection of the surface is sufficient to
! aow that the pyramid is composed of a compact strand of longitudinally directed
erve-fibres. It represents, in fact, the portion of the great cerebro-spinal fasciculus
'hich is destined to carry fibres from the cerebral hemisphere to all the motor
uclei on the other side of the medulla oblongata and medulla spinalis. Somewhat
onstricted at the place where it emerges from the pons (Fig. 478) it swells
nmediately to form a prominent rounded column, which passes vertically down-
ward, separated from the pyramid of the other side by the fissura mediana anterior,
'owards the lower part of the medulla oblongata it gradually tapers.
Although the pyramid at first sight appears to be continuous with the anterior
uniculus of the medulla spinalis, only a very small proportion of the fibres
ontained in the latter are derived from the pyramid. This at once becomes
Manifest when the lips of the anterior median fissure are thrust apart at the place
f junction between the medulla oblongata and spinal medulla. The pyramid is
hen seen to divide at this level into two parts, viz., a small portion composed of
variable number of the most lateral fibres of the pyramid, termed the fasciculus
erebrospinalis anterior (O.T.. direct pyramidal tract), and a much larger portion,
ituated next the median fissure, called the
asciculus cerebrospinalis lateralis (O.T. crossed
tyramidal tract). The anterior cerebro-spinal
; asciculus is continued down into the anterior
uniculus of the medulla spinalis, and in this
t takes up a medial position next the median
issure. The lateral cerebro-spinal fasciculus
s broken up into three or more coarsel)undles,
vhich sink backwards and at the same time
;ross the median plane, to take up a position
n the posterior part of the opposite lateral
uniculus of the spinal medulla. The term
iecussatio pyramidum (decussation of the pyra-
nids) is applied to the intercrossing of the
corresponding bundles of the lateral cerebro-
' spinal fasciculi of opposite sides.
The anterior cerebro-spinal fasciculus is,
therefore, the only part of the pyramid which
'las a place in the anterior f uniculus of the
spinal medulla. The much larger part of this
hmiculus, termed the fasciculus anterior pro-
'prius, as it is traced up into the medulla
oblongata, is seen to be thrust aside by the
'decussating bundles of the lateral cerebro-
spinal fasciculus. It thus comes to occupy
i deep position in the substance of the medulla FlG . 4 80. -DIAGRAM OF THE DECUSSATION OF
oblongata, behind and to the lateral side of THE PYRAMIDS (modified from van Gehuchten).
' the pyramid NH, Nucleus hypoglossi ; NV, Vago-glosso-
Lateral Area of the Medulla Oblongata. 5^C^S ; FS> TraCtUS S mariUS; NA '
This is the district on the surface of the
dulla oblongata which is included between the two rows of nerve-roots, viz., the
hypoglossal roots in front, and the root-bundles of the accessory, the vagus, and the
36
HYPOCLOSSAL
LATERAL CEREBRO-
SPINAL FASCICULUS
ANTERIOR CEREBRO-
SPINAL FASCICULUS
546
THE NEEVOUS SYSTEM.
glossopharyngeal nerves behind. It presents a very different appearance in its
upper and lower parts. In its lower portion it simply appears to be a continuation
upwards of the lateral area of th6 spinal medulla ; in its upper part a striking
oval prominence bulges out on the surface of the medulla, and receives the name
of oliva (O.T. olivary eminence).
The lower part of this district, however, is very far from being an exact counter-
part of the lateral funiculus of the spinal medulla. The large lateral cerebro-
spinal tract is no longer present, seeing that it forms, in the medulla oblongata,
Nucleus lentiformis
Capsula interna (pars lenticulo-thalamica)
Nucleus caudatus
Capsula interna
(pars lenticulo- v
caudata) s
Union of
lentiform and
caudate nuclei
Tractus
olfactorius
Tractus opticus..'''
rhfundibulum-
Hypophysis (anterior lobe -
cerebri | p OS terior lobe ,. ,
Tuber cinereum /
Corpus mamillare ,
Nervus oculomotorius
Basis pedunculi
Pons
Nervus trigeminus (portio major)
Nervus trigeminus (portio minor)
Nervus facialis
Nervus intermedius
Nervus acusticus
Nervus abducens
Nervus glossopharyngeus """
Nervus vagus \
Pyramis
' Oliv
Fasciculus circumolivaris pyramidis
Nucleus amygdalee (cut)
Commissura anterior
Stria terminalis
Capsula interna (pars sublenticularis)
Nucleus caudatus
Thalamus
Corpus geniculatum laterale
Corpus pineale
Corpus geniculatum mediale
Colliculus superior
Brachium quadrigeminum
inferius
Colliculus inferior
Lemniscus lateralis
Nervus trochlearis
Brachium conjunctivum
-.Brachium pontis
Fossa flocculi
. Crus flocculi
Nucleus dentatu
cerebelli
- Corpus ponto-bulbare
.... Fasciculus spinocerebellaris
-- Nervus spinalis
FIG. 481. LEFT LATERAL ASPECT OP A BBAIN FROM WHICH THE CEREBRAL HEMISPHERE (WITH THE i
CEPTION OF THE CORPUS STRIATUM) AND THE CEREBELLUM (EXCEPTING ITS NUCLEUS DENTATUS) HA
BEEN REMOVED
the greater part of the pyramid of the opposite side. Another strand of fibres, vi
the fasciculus spinocerebellaris (posterior), prolonged upwards in the lateral fur
culus of the medulla spinalis, gradually leaves this portion of the medulla oblongal
This tract lies on the surface, and is frequently visible to the naked eye as a whi
band (Fig. 481), which inclines obliquely backwards into the posterior district of t
medulla oblongata to join its upper part, or, in other words, to join the restifor
body. The remainder of the fibres of the lateral funiculus, comprising the fas<
culus lateralis proprius and the fasciculus anterolateralis superficialis, is continu
upwards in the lateral area of the medulla oblongata, and at the inferior border
the olive the majority of these fibres disappear from the surface by dipping irj
THE MEDULLA OBLONGATA. 547
:ie substance of the medulla oblongata under cover of that projection. A small
:oportion of the fibres, however, are retained on the surface and travel upwards
wards the pons in the interval, which exists between the posterior border of the
ive and the roots of the vagus and glossopharyngeal nerves.
The olive is a smooth oval projection which bulges out from the upper part of
ie lateral area of the medulla oblongata. Its long axis is vertical and is about
ilf an inch long. It marks the position of the subjacent nucleus olivaris inferior,
crumpled thin- walled sac of gray matter, which is separated from the surface only
Y a very thin layer of superficial white matter.
Posterior Area of the Medulla Oblongata. In its inferior half, this district is
Dunded behind by the posterior median fissure, and in its superior half by the lateral
targin of the medullary part of the floor of the fourth ventricle of the brain. In
ont it is separated from the lateral area by the row of root-fila belonging
> the accessory, glossopharyngeal and vagus nerves. As in the lateral area, we
^cognise an inferior portion and a superior portion, which appear continuous but
i reality are almost quite distinct the one from the other.
The inferior part of the posterior area corresponds more or less closely with the
osterior funiculus of the spinal medulla. In the cervical region the posterior
iniculus is divided by a septum of pia mater into a medial fasciculus gracilis
nd a lateral fasciculus cuneatus. These are prolonged upwards into the medulla
blongata, and in the lower part of the posterior area they stand out distinctly,
nd are separated one from the other by a continuation upwards from the spinal
ledulla of the sulcus intermedius posterior. In the medulla oblongata the medial
f these strands is called the funiculus gracilis, whilst the lateral one is designated
he funiculus cuneatus. When they reach the level of the inferior part of the floor
f the fourth ventricle, each ends in a slightly expanded bulbous prominence,
"he swollen extremity of the funiculus gracilis is called the clava. This is thrust
,side from its fellow of the opposite side by the opening up of the medulla
'blongata to form the floor of the fourth ventricle, and the central canal opens on
, he surface in the angle between the two clavse.
The elongated prominences formed on the surface of the medulla oblongata by
hese two strands and their enlarged extremities are due to the presence of two
elongated nuclei or collections of gray matter which make their appearance
ubjacent to the strands, and represent the termini of these uppermost extensions
>f the spinal posterior root -fibres. These are termed respectively the nucleus
jracilis and nucleus cuneatus. [As it is the slenderness of the one nucleus and the
,vedge-shape of the other in transverse section which gave rise to the terms gracilis
ind cuneatus respectively, it is clearly wrong to introduce the word funiculi into
l he B.N.A. terminology. The funiculi were named from the nuclei and not the
nuclei from the funiculi. ]
But a third longitudinal elevation is also apparent on the surface of the inferior
part of the posterior area of the medulla oblongata. This is placed on the lateral
side of the funiculus cuneatus between it and the posterior row of nerve-roots
md it has no counterpart in the posterior funiculus of the medulla spinalis. It
is called the tuberculum cinereum. It is produced by a mass of substantia gelatinosa
3oming close to the surface and forming a bulging in this situation. Extremely
uarrow below, it widens as it is traced upwards, and finally ends in an expanded
xtremity. A thin layer of white matter, composed of longitudinally arranged
ibres, is spread over this district, and separates the substantia gelatinosa from the
rface. These fibres constitute the tractus spinalis of the trigeminal nerve, which
. here assumes a superficial position as it descends in the medulla oblongata.
Corpus Restiforme. The restiform body forms the upper part of the posterior
area of the medulla oblongata. It lies between the floor of the fourth ventricle and
; the roots of the vagus and glossopharyngeal nerves. It is a large and prominent
rope -like strand, which inclines upwards and laterally, and then finally takes
turn backwards and enters the cerebellum. It forms the great link of connexion
jween the cerebellum on the one hand and the medulla oblongata and spinal
dulla on the other, and consequently it is also called the inferior cerebellar
peduncle. A study of the surface of the medulla oblongata yields some important
36 a
548 THE NEKVOUS SYSTEM.
information regarding the constitution of the restiform body. Thus, the posterior
spino-cerebellar tract (Fig. 481), from the lateral column of the spinal medulla,
can be traced into it ; and large numbers of fibres which take a curved course on
the surface of the medulla oblongata may likewise be followed into it ; these are
the external arcuate fibres. Numerous other fibres enter the restiform body on its
deep aspect, but these will be studied at a later stage.
Fibrae Arcuatse Externae. The external arcuate fibres enter into the constitu-
tion of the restiform body, after pursuing a longer or shorter course on the
surface of the medulla (Fig. 481).
They are more particularly seen in the neighbourhood of the olive, over the
surface of which they may be observed coursing in the form of a number of fine
curved bundles or as a continuous sheet of fibres. They vary greatly in number
and in distinctness, and they are sometimes so numerous that they cover the
olive almost entirely. An attentive examination will show that the majority of
them come to the surface in the median fissure between the pyramids, and also.
not infrequently, in the groove between the pyramid and olive, or through the
substance of the pyramid itself. The anterior median fissure in its upper part is
often almost completely blocked up by these emerging fibres. The external arcuate
fibres, reaching the surface of the medulla in this manner, turn backwards, and
the great majority enter the restiform body and form a considerable part of its'
outer portion.
Other arcuate fibres arise in the cuneate and gracile nuclei, and enter the
restiform body of the same side. Van Gehuchten, however, denies this.
There is frequently present, especially upon the left side, a bundle of fibres
that is usually mistaken for a group of arcuate fibres. It is the fasciculus circmn
olivaris pyramidis (Fig. 481). It consists of a bundle of varying size which emerge;
from the pyramid, bends backwards, curving round the inferior border of the olive
and then passes obliquely upward and backwards to end in a fusiform ridge of gra]
matter, the corpus ponto-bulbare (Essick), which crosses the restiform body ver
obliquely (Fig. 481, the ridge immediately posterior to the fila of the vagus nerve^
These structures are of great morphological interest, and will be referred I
again in the succeeding pages (see Fig. 499, p. 566).
PONS.
The pons (O.T. pons Varolii) is a marked white prominence on the basal aspec
of the brain which is interposed between the medulla oblongata and the peduncu
cerebri, and lies in front of the cerebellum. It is convex from side to side, and froi
above downwards, and transverse streaks on -its surface show that, superficially e
least, it is composed of bundles of nerve-fibres, most of which 1 course transversel;
On each side these transverse fibres are collected together in the form of a lar
compact strand, which sinks in a backward and lateral direction into the whil
matter of the corresponding hemisphere of the cerebellum. This strand is terme
the brachium pontis, and the term " pons," applied to the entire structure, express*
in an admirable way the arch-like manner in which this portion of the brai
bridges across the interval between the two cerebellar hemispheres.
The ventral surface of the pons is in relation to the basilar part of tl
occipital bone and the dorsum sellse of the sphenoid bone. It presents a medie
groove (sulcus basilaris), which gradually widens as it is traced upwards:
lodges the basilar artery. This median depression is produced by the prominen'
which is caused on each side by the passage of the cerebro- spinal fasciculus dow:
wards through the pons. The trigeminal nerve, with its large entering sensory ro
and its small emerging motor root, is attached to the side of the anterior aspect of t
pons, nearer its superior than its inferior border (Fig. 481). It is usual to restri
the term " pons " to that portion of the structure which lies between the two t
geminal nerves, and to apply the designation of brachium pontis to the part whi
extends beyond the nerve into the hemisphere of the cerebellum. The abduce
nerve, the facial nerve, and the acoustic nerve are attached to the brain at the infer:
border of the pons. The abducens nerve emerges at the inferior border of the pc
THE FOUKTH VENTBICLE. 549
>posite the lateral border of the pyramid ; the facial and acoustic are also attached
i the inferior edge of the pons, but far away from the median plane. The acoustic
?rve is in contact with the cerebellum and the facial is on its medial side, with its
nsory root (the nervus interrnedius) between them (Figs. 478, 481). A large bundle
' fibres upon the front of the pons departs from the transverse course pursued by
.ost of the pontine fibres, and starting at the medial side of the trigeminal nerve,
isses almost vertically downwards between the facial and acoustic nerves (Fig.
26, p. 593) and reaches the lateral aspect of the medulla oblongata, where it passes
Lto the corpus ponto-bulbare (Fig. 481). This bundle is known as the fasciculus
)liquus [pontis]. It is interesting to observe that while the facial nerve lies upon
le medial side of this oblique bundle, its sensory root (the nervus interrnedius) is
aced on its lateral aspect, alongside the acoustic nerve (Fig. 527, p. 594).
Immediately below the insertion of the acoustic nerve at the interior margin of
le pons a little calyx-like appendage of the epithelial roof of the fourth ventricle
ecessus lateralis) projects laterally, partly behind the glossopharyngeal nerve,
hrough an elliptical aperture in this epithelial process (apertura lateralis
jntriculi quarti) a little cauliflower-like mass of chorioid plexus becomes extruded
itween the acoustic and the glossopharyngeal nerves (Fig. 527, p. 594).
The posterior surface of the pons looks backwards towards the cerebellum, and
:esents a triangular area covered with gray matter, which forms the superior part
' the anterior wall or floor of the fourth ventricle. This area is directly continuous
tferiorly with the medullary part of the floor of the fourth ventricle, and is bounded
i each side by a band of white matter termed the brachium conjunct! vum (Fig. 482).
Brachia Conjunctiva (O.T. Superior Peduncles of the Cerebellum). The
rachia conjunctiva are hidden from view by the superior part of the cerebellum,
nder cover of which they lie. They emerge from the hemispheres of the cerebellum,
id, as they proceed upwards on the dorsal aspect of the pons, they converge towards
ich other until, at the inferior level of the corpora quadrigemina, the medial
targins of the two brachia become almost contiguous (Fig. 482, p. 550). At first
ley form the lateral boundaries of the superior part of the fourth ventricle ; but,
,i they ascend and approach closer to each other, they gradually come to overhang
mt cavity, and thus enter into the formation of its roof. They disappear from
le surface of the brain by dipping under cover of the quadrigeminal bodies and
itering the substance of the mesencephalon.
Velum Medullare Anterius. Filling up the triangular interval between the two
rachia conjunctiva, and stretching across from the medial and free margin of the
le to the corresponding margin of the other, is a thin layer of white matter which
)mpletes the roof or dorsal wall of the upper part of the fourth ventricle, and
iceives the name of the anterior medullary velum. When traced downwards, the
^lum is seen to be carried, with the brachia conjunctiva, into the white matter of
.le cerebellum. Spread out on its posterior or superior surface is a small, thin,
>ngue- shaped prolongation of gray matter from the cortex of the cerebellum,
hich is termed the lingula, whilst issuing from its substance close to the inferior
uadrigeminal bodies are the two trochlear nerves.
VENTRICULUS QUARTUS.
Fourth Ventricle. The fourth ventricle of the brain is somewhat rhomboidal in
>rm. Below, it tapers to a point and becomes continuous with the central canal
the lower half of the medulla oblongata ; above, it narrows in a similar manner
nd is continued into the aquseductus cerebri, which tunnels the mesencephalon.
he posterior wall is termed the tegmen or roof and is concealed by the cerebellum,
'he anterior wall is called the floor and is formed by the dorsal surface of the
ons and the corresponding surface of the medulla oblongata. On each side a long,
,urved and narrow prolongation of the ventricular cavity is carried laterally from
i widest part and curves round the upper part of the corresponding restiform
,ody. This is termed the recessus lateralis. The roof of the cavity is very thin
nd is intimately connected with the cerebellum. It is better, therefore, to defer
;s description until that part of the brain has been studied.
365
550
THE NEKVOUS SYSTEM.
Fossa Rhomboidea (floor of the fourth ventricle). In its inferior part the floor
of the fourth ventricle is formed by the dorsal surface of the ventral part of the
medulla oblongata, whilst in its superior part it is formed by the dorsal surface
of the pons (Fig. 482). The area thus constituted is lozenge-shaped, itg
widest part being opposite the superior ends of the restiform bodies or inferior
peduncles of the cerebellum. A thick layer of gray matter, continuous with
that which surrounds the central canal, is spread out like a carpet over the
ventricular floor, and covering this there is the usual ependymal layer which lines
all the ventricles of the brain. The area is circumscribed by definite lateral
boundaries. Thus, below, it is bounded on each side by (1) the clava, (2) tht
expanded upper end of the funiculus cuneatus, and (3) the restiform body ; whilst
above, the lateral limits are formed by the brachia conjunctiva.
The floor of the fourth ventricle is divided into two symmetrical portions b
a median groove. Its lower narrow pointed portion between the two clavae receive
the name of the pars inferior, or, from its resemblance to the point of a pec
Frenulum veli- -\
- Inferior colliculus
- Trochlear nerve
Velum medullare
anterius with
lingula
Colliculus
facialis
Area acustica
crossed by striae -
medul lares
Fovea inferior --
Trigonum
hypoglossi
Brachium conjunc
tivum
Fovea superior
. Brachium
Brachium
junctivum
" Restiform
Stride medullares
--Area acustica
- - Ala cinerea
Funiculus separans
- Area postrema
Obex
-- Clava
Funiculus cuneatus
FIG. 482. FLOOR OF THE FOURTH VENTRICLE. On the right side the right half of the cerebellum has
removed by cutting through its three peduncles and dividing it in the median plane. On the left
the left half of the cerebellum is drawn over to the left so as to expose the floor of the ventricle ful
the calamus scriptorius. Crossing each half of the floor, at its widest part, are seve;
more or less conspicuous bundles of fibres termed the striae medullares. They be
upon the lateral and posterior aspects of the restiform body, where they spri
from the cochlear nuclei, pass transversely medially, and disappear from view in f
median furrow. The striae medullares exhibit a large amount of variation
different specimens, both in their degree of prominence and also in the dii
which they pursue. It is not uncommon to find that no trace of them is visi
upon the surface.
On the inferior (bulbar) district of the ventricular floor a small triangular depr
sion, placed immediately below the striae medullares, catches the eye. This 3
termed the fovea inferior. It is shaped somewhat like an arrow-head. The a] t
or point looks towards the striae, whilst the lateral angles of the base are prolong 1
downwards in the form of diverging grooves (Fig. 482). Of these, the mec 1
groove runs towards the opening of the central canal at the calamus scripte J,
whilst the lateral groove runs towards the lateral boundary of the floor. In t s
ITERNAL STRUCTURE OF MEDULLA OBLONGATA AND PONS. 551
n nner the portion of the floor which lies below the striae medullares is mapped out
i:o three triangular areas. The medial subdivision is slightly elevated and is
t cued the trigonum nervi hypoglossi, because subjacent to the medial part of this
a a is the nucleus of origin of the hypoglossal nerve. The intermediate area,
1; ween the two diverging grooves which proceed from the base of the fovea
i erior, is the ala cinerea. It is sometimes called the trigonum n. vagi because
tj nucleus of the vagus and the glossopharyngeal nerves lies subjacent to it.
Lar the lateral angle is the area acustica. The base of this area is directed
i wards and runs directly into an eminence over which the strise medullares
ps. Subjacent to this district of the floor of the ventricle lies the large terminal
c.ef nucleus of the vestibular division of the acoustic nerve. A more accurate
line for the area acustica would be area vestibularis.
A close inspection of the pars inferior fossae rhomboidese will show that the base of the
t ,'onum vagi is separated from the medial margin of the clava by a narrow lanceolate strip of
t ventricular floor, to which Ketzius has given the name of area postrema. Beneath this area
i ome vascular tissue (Streeter), and marking it off on its superior and medial aspect from the
1 e of the trigonum vagi there is a translucent cord-like ridge called the funiculus separans.
When the floor of the ventricle is examined under water with a magnifying glass, the
t Tontun hypoglossi is seen to consist of a narrow medial strip which corresponds to the hypo-
ssal nucleus, and a wider lateral part which has been shown to be the surface representation
c mother nucleus termed the nucleus intercalatus (Streeter).
On the part of the floor of the ventricle which lies above the striae medul-
]-es, and corresponds to the dorsal surface of the pons, there is also a slight
or. When transverse sections are made through the superior part of the pons,
e substantia ferruginea appears on the cut surface as a small black spot or dot.
XTERNAL STRUCTURE OF MEDULLA OBLONGATA AND PONS.
The structure of the medulla oblongata and pons differs in a marked degree from
iat of the spinal medulla : indeed, in its superior part, it presents very little in
unmon with the latter. Some of the largest fasciculi which come up from the spinal
edulla (such as the funiculus posterior) end in the lower part of the medulla
)longata ; others leave the medulla oblongata and pass into the cerebellum ; and
the bundles of fibres which pass upwards or downwards, from or to the spinal
edulla respectively, most of them come to occupy very different positions in the
-edulla oblongata and pons.
The gray matter instead of being moulded into one compact column, as is the
1 in the spinal medulla, becomes broken up into a series of discrete nuclei.
there are developed from the basal lamina of the rhombencephalon not one
nipact mass like the spinal anterior column, but three distinct broken columns
fferent nuclei (Fig. 526, p. 593) : (1) a medial somatic column, which in turn is
ken up into two parts, a bulbar nucleus (the hypoglossal) which supplies the
fibres to the tongue muscles, and a pontine nucleus (the abducens) which
the lateral rectus muscle of the eye ; (2) a lateral somatic column, broken
p into separate nuclei, viz., accessorius, ambiguus, facial, and trigeminal, supplying
36 c
552 THE NERVOUS SYSTEM.
the sterno-mastoid and trapezius muscles and the striated muscles of the larynx,
pharynx and face and those concerned with mastication ; and (3) a splanchnic
column of nuclei, giving efferent fibres which pass out in the vagus, glosso-
pharyngeal and facial nerves, to be widely distributed to unstriped muscle, glands
and other tissues in the head, neck, thorax and abdomen.
Further, the terminal nuclei of the sensory nerves which are developed in the
alar lamina of the rhombencephalon do not unite to form a definite posterior
column, as happens in the spinal medulla, but form discrete masses ; and as
these act as receptive organs for a much greater variety of sensory nerves than
are represented in the spinal nerves there is a much greater number of nuclei than
would be formed if the various components of the posterior column in the spinal
medulla were dissociated. Thus, there are terminal nuclei in the medulla oblongata
not only for the ordinary cutaneous nerves, but also for nerves coming from the
mucous membranes of the alimentary and respiratory organs, as well as from
other visceral structures ; and there are also special nerves of taste (nervus
intermedius and glossopharyngeal), of hearing (cochlear part of the acoustic) and
of equilibration (vestibular part of the acoustic). But this does not exhaust the
peculiar features of the terminal sensory nuclei of the rhombencephalon. In the
description of the spinal medulla attention was called to the fact that certain of
the fibres of the posterior nerve-root did not end in the gray matter of the spinal
medulla, but passed upwards throughout the whole length (above their points of
entry) of the funiculus posterior to reach the medulla oblongata. Special terminal
nuclei are developed from the alar lamina to receive these fibres. They are the
nucleus gracilis and nucleus cuneatus.
In addition, part of the terminal vestibular nucleus receives accessions of fibre?
from these (gracile and cuneate) nuclei as well as from other sensory terminal
nuclei in the spinal medulla and develops into that great mass of tissue, the
cerebellum, to which vast numbers of other fibres come and go, adding considerably
to the complexity of the region of the pons and medulla oblongata. Moreover
there is developed from the alar lamina a whole series of other masses of gra)
matter the nucleus olivaris inferior, nuclei arcuati, nucleus pontobulbaris and nude
pontis as links in the complex chains that bind all parts of the central nervous
system to the great co-ordinating mechanism of the cerebellum.
Thus it comes about that, instead of having, as in the spinal medulla, a definite
column of gray matter ensheathed in a thick mass of white substance, the rhomb
encephalon is composed of many scattered masses of gray matter; and its white sub
stance is represented partly by great longitudinal strands, but also by man?
great systems of fibres passing transversely through its substance, or upon it
surface, e.g., the superficial fibres of the pons and many of the arcuate fibres.
From what has already been said concerning the external form of the rnedull
oblongata and pons it will be apparent that the distortion of the neura
tube which occurred as the result of the pontine flexure has also been large!
responsible for the distinctive features of this region of the brain.i
As the pontine flexure develops, a strain is thrown upon the thin roof-plat<
which yields and becomes stretched so as to permit the thick lateral walls of th
neural tube to fall laterally (Figs. 483 and 484). One result of this process is th
great lateral expansion of the cavity of the hind-brain, which assumes the charac
teristic rhomboid form. If the thin and greatly attenuated epithelial roof is tor
away from the rhombencephalon of an embryo of the third month the fourt
ventricle will present the appearance (viewed from behind) shown in Fig. 48
The ventricle is seen to be prolonged laterally/on each side, to form a little rece;
upon the lateral aspect of the rhombencephalon. This is called the recessus lateral]
This thin epithelial roof becomes invaginated towards the cavity of the fourt
ventricle, on each side of the median plane, in the whole length of the epitheli
roof, i.e. from the cerebellar attachment, above, almost as far as the closed part
the medulla oblongata below (Fig. 519). The upper end of this invaginated fo
becomes prolonged laterally ag far as the extremity of the recessus lateralis (F
527). Pia mater and blood-vessels extend into these folds, which are then knov
as the chorioid plexuses of the fourth ventricle. At the extremities of these to
:NTERNAL STRUCTURE or MEDULLA OBLONGATA AND PONS. 553
plexuses, which are situated at the three corners of the epithelial roof of the ventricle,
oval or elliptical perforations develop in
the roof at about the fifth month of foetal
life. These are known as the apertura
medialis ventriculi quart! (O.T. foramen of
Magendie), which opens between the clavae
on the posterior surface and the aperturae
laterales upon the anterior faces of the
lateral recesses (Fig. 527), behind the in-
sertion of the glossopharyngeal nerve on
each side. Through each of these lateral
openings the great swollen cauliflower-like
extremity of the chorioid plexus becomes
extruded from the ventricle. The inferior
extremities of the two plexuses lying side
by side present an analogous relationship
to the apertura medialis, but they are
exceedingly attenuated and the epithelial
lamella from which they spring becomes
dragged backwards into contact with the
cerebellum (Fig. 477), so that, when seen
from below, the apertura medialis is a great
funnel-shaped tube leading into the fourth
ventricle and the chorioid plexuses look
like two delicate vascular fringes on the
cerebellum.
These three apertures are the only
means provided for the escape of the fluid
contained in the ventricles of the central
nervous system. The fluid is poured into
a space, enclosed by the arachnoid, which
is called the subarachnoid space.
As a result of the pontine flexure the IG<
side walls of the neural tube in the
neighbourhood of the bend fall away the
one from the other and eventually come
to be placed in the same transverse plane,
B
483. TRANSVERSE SECTIONS ACROSS THE
MEDULLA OBLONGATA IN TWO HUMAN EMBRYOS,
REPRESENTING DIFFERENT STAGES IN THE EX-
PANSION OF THE ROOF AND THE FALLING LATER-
ALLY OF THE SIDE WALLS. (From His, slightly
modified.)
Cerebrum
one with the other and
also with the floor-plate.
At the time this process
is in operation (see Fig.
483) the alar and basal
laminse are particularly
well defined, and the
limiting sulci are ac-
centuated by the bending
of the side wall; but
this sharp distinction is
soon lost as the result of
the great expansion of
the basal lamina (Fig.
485). This is due not
only to growth of its
intrinsic elements, but
even more to its in-
. THE BRAIN OF AN EMBRYO OF ELEVEN WEEKS, viewed from vasion by large numbers
behind. The epithelial roof of the fourth ventricle has been removed. O f neuroblasts which
At this stage the cerebellum is in the form of a simple band or plate f f fV 1
which arches over the posterior aspect of the anterior part of the cavity mi g rare
of the hind-brain. (From His.) into the basal lamina.
Mesencephalon
Early cerebellum
Cavity of
fourth ventricle
Lateral recess
Medulla oblongata
554
THE NEKVOUS SYSTEM.
Later still, the development of the great sensory and motor tracts contributes
largely to the dimensions of the basal lamina.
As the two basal laminae (one on each side of the median plane) increase in
thickness the epithelial cells in the intervening floor-plate become stretched and
lengthened (Fig. 483), so that a definite septum or raphe is formed between the
two halves of the rhombencephalon.
The fate of the extreme posterior edge of the alar lamina is very interesting.
The nervus acusticus is inserted into this edge in the region of the recessus
lateralis, and from it masses of neuroblasts develop to form receptive nuclei for
the two parts of this nerve, these being the cochlear and vestibular. These are the
nucleus cochlearis and nucleus vestibularis respectively. Sensory fasciculi, bringing
impulses from muscles, skin and related structures in all parts of the body, make
their way into the superior part of the vestibular nucleus, and it grows and forms
a large thickening of the posterior edge above the recessus lateralis. Eventually, as
it extends medially (Fig. 484), it reaches and invades the roof-plate and fuses with
the corresponding rudiment of the other side. Thus a semilunar band, the
primitive cerebellum, is formed, arching across the posterior aspect of the meten-
cephalon. The part of the dorsal edge which lies below the vestibular nucleus
becomes bent over (forwards) to form what is known as the rhombic lip (Fig. 483).
It is destined to be transformed into a series of masses of gray matter, the chief
function of which is to emit fibres to carry
impulses into the cerebellum. But most of
these fibres pass not so much to the part of
the cerebellum derived from their own side
as to that of the opposite side. Thus, from
above downwards, the thickened margin of
the fossa rhomboidea on each side develops
into the following structures: cerebellum,
the rest of the vestibular nucleus, the
cochlear nucleus, the nuclei pontis (and
arcuate nuclei), the olivary nucleus, the
nucleu8 acilis a <* th nucleus CUneatUB,
FASC.SOL.
VAGUS
HYPOGLOSSAL
FIG. 485. TRANSVERSE SECTION OP THE HUMAN
EMBRYO AT A LATER STAGK THAN THOSE At an early stage of development most of the
SHOWN IN FIG. 483. (After His.) neuroblasts that form the rudiments of thf
nuclei pontis, nuclei arcuati, and nucleus
olivaris inferior begin a process of migration, the course of which is deter-
mined by the source and direction of the afferent tracts passing into each nucleus
Such migrations are of common occurrence throughout the brain, and attempts t(
explain them have given rise to much discussion. The attractive force which appear;
to lead certain nerve-cells away from the place where they originally developed ha;
been called neurobiotaxis by Ariens-Kappers. But the solution of the problems o
these migrations is quite a simple one. If we take the case of a nerve-cell (A~), a
an early stage of development, which collects afferent impulses through its dendrite
from the cell B, and emits an efferent impulse through its axon to the cell C: a
the whole nervous system is very small at the stage under consideration, the thre
cells necessarily will be comparatively close the one to the other a fact which ma
be represented by the positions of the letters thus :
BAC.
In the course of subsequent growth it must inevitably happen that the points
and C will become removed further and further apart. If we suppose that th
cell B remains constant, the cell A will be faced with two alternatives if it is t
continue to link together the elements B and C: either its dendrites or its axo
must elongate. Now the axon is specially modified in structure for conducti
impulses for long distances, and the dendrites are not so specialised. Therefo
it invariably happens that it is the axon that becomes lengthened. In other wore
the cell-body A, considered in its relations to C, appears to migrate towards t
direction B from which its chief supply of afferent impulses comes. This may 1
represented thus : Tt A * f
INTEKNAL STEUCTUKE OF MEDULLA OBLONGATA AND PONS. 555
In the specific case we are considering the vestibular nucleus and the cerebellum
eceive their chief supply of afferent fibres from the incoming vestibular nerve : hence
here is no reason for migration. Similarly the nucleus gracilis and nucleus cuneatus
eceive the fibres which come up through the funiculus posterior and remain where
,hey are. But the nuclei pontis, the olivary nucleus, and the arcuate nuclei are
fed " with impulses passing downwards (and some perhaps upwards) in the basal
amina, close to the median plane, and they "migrate" towards the direction from
vhich their afferent paths are approaching ; the nuclei pontis towards the peduncles
if the cerebrum bringing cerebro-pontine fibres from the cerebral cortex, and the
ilivary nucleus to the neighbourhood of certain descending tegmental tracts and
,scending spinal sensory tracts that seem to supply the attractive force, which leads
hem to forsake the rhombic lip of the alar lamina and migrate into the basal lamina.
The majority of the cells destined to form the nuclei pontis wander obliquely
ipwards and forwards between the facial and acoustic nerves to reach the basal
Restifonn body
Vago-glossopharyngeal
roots
| Nucleus of the
tractus solitarius
| Trenia
Fasciculus teetospinalis
Vagus nucleus
Tractus solitarius
Descending root of vestibular nerve
Vago-glossopharyngeal roots
sciculus spinocerebellaris
posterior
Fasciculus longitudinalis
medialis
Nucleus tractus spinalis
nervi trigemini [nerve
Tractus spinalis of trigeminal
Nucleus ambiguus
Fasciculus rubrospinalis
Olivo-cerebellar fibres
.sciculus spinothalamicus
Dorsal accessory olivary nucleus
Fasciculus spinocerebellaris anterior
:ternal arcuate fibres
niscus medialis
ial accessory olivary nucleus
;ulus tegmento-dlivaris
Inferior olivary nucleus
Pyramid
mate nucleus <
1 External arcuate fibres
;[Q. 486. TRANSVERSE SECTION THROUGH THE MIDDLE OF THE OLIVARY REGION OF THE HUMAN MEDULLA
OBLONGATA.
L,
The floor of the fourth ventricle is seen, and it will be noticed that the restiform body, on each side, has
now taken definite shape. Some of the descending tracts in red ; ascending tracts in blue.
ina of the metencephalon. But strewn along this pathway from the edge of
ie fossa rhomboidea to the front of the pons are scattered nerve-cells which have,
) to speak, fallen by the way, and remain to indicate in the adult brain the path
ken by the majority of their sister cells. This remnant forms the corpus ponto-
ilbare: the pontine fibres that spring from its cells and are making their way
pwards to fall in line (Fig. 499, p. 566) with the other transverse fibres of the pons
Tin the fasciculus obliquus [pontis], and the cerebro-pontine fibres that pass below
e pons in order to reach this outlying part (corpus ponto-bulbare) of the nuclei
>ntis constitute the fasciculus circumolivaris pyramidis (Fig. 517, p. 583).
But not all of the elements of the nuclei pontis that migrate pass into the
>encephalon; a certain proportion of them invariably pass into the myelen-
'phalon. These collect upon the anterior surface of the pyramids to form small
regular patches of gray matter which have received the name nuclei arcuati.
ferent fibres (probably cerebro-pontine) come from the pyramids ; and their
'ent fibres (which proceed to the cerebellum) form some of the fibrae arcuatae
which are visible upon the surface of the medulla oblongata (Fig. 486).
Dlivary Nuclei. The most conspicuous of the isolated clumps of gray matter
556 THE NEKYOUS SYSTEM.
in the medulla are the inferior olivary nucleus and the two accessory olivar
nuclei. The nucleus olivaris inferior is the mass of gray substance which produce
the swelling known as the olive, and constitutes a very striking object in trans
verse sections through this region. It presents the appearance of a thick wavy c
undulating line of gray matter, folded on itself, so as to enclose a space filled wit
white matter. It is in reality a crumpled lamina arranged in a purse-like manne:
with an open mouth or slit, which is called the hilum (hilus nuclei olivaris), directe
towards the median plane. The hilum does not reach either extremity, so that i
transverse sections through either end of the nucleus the gray lamina is seen in tl
form of a completely closed capsule. Into and out of the open mouth of tt
olivary capsule streams a dense crowd of fibres. These constitute what is calle
the olivary peduncle.
The accessory olivary nuclei are two band-like laminae of gray matter, whic
are respectively placed on the dorsal and medial aspects of the main nucleus. 1
transverse section each of these nuclei presents a rod-like appearance (Fig. 486).
The medial accessory olivary nucleus extends lower down in the medulla oblongal
than the main nucleus, and it is much larger in its lower than in its upper pai
It begins immediately above the decussation of the pyramids, where it is seen lying i
the lateral side of the cerebro-spinal fasciculus and the lemniscus medialis (Fig. 48(
Higher up it lies across the mouth of the main nucleus and on the lateral side of t
medial lemniscus. The dorsal accessory olivary nucleus is placed close to the dorsal aspe :;
of the main nucleus. The two accessory nuclei fuse together before they finally disappe;
The nerve-cells of the inferior olivary nucleus are small and round, and emit a lar
series of short radiating, complexly branched dendrites, so that the cell-body seems to 1
in the centre of a spheri(
mass formed by its own dof
drites and an almost equa
complex mass of intertwin
end branches of the axe
which bring impulses into th<
cells. There is no definite
formation as to the place :
origin of these afferent fibr ; ,
Flechsig and Bechterew, usi ;
different methods of investi ,
tion, have demonstrated i
presence of a large descend j
tract in the mesencephalon j
rhombencephalon, which e) s
amidst the cells of the latf 1
FIG. 487. THE INFERIOR OLIVARY NUCLEUS, as reconstructed and pole of the olivary nuck >.
figured by Florence K. Sabin. This has been called the fa '-
View of the dorso-lateral and lateral surfaces. culus thalamo-olivaris, but il H
not quite certain that it ar 6
in the thalamus, although its origin must be somewhere in the neighbourhood of;.
Flechsig denies that any fibres reach the olivary nucleus from the spinal medulla, .1
the proximity of the spino-thalamic and bulbo-thalamic (lemniscus medialis) fibres i
the demonstration of Ramon y Cajal that fibres enter the nucleus olivaris from adjoir g
fasciculi in these regions suggest that there may be a spinal afferent path.
There seems to be a direct relationship between the size of the inferior olivary nuc 1 IB
and the extent of the cortical area that presides over highly skilled movements.
The axons emitted by the cells of the olivary nucleus cross the median ra ie
and pass through the opposite side of the medulla oblongata as internal arci ;e
fibres, which enter the restiform body and pass into the cerebellum. 1
These fibres are seen only in the superior part of the medulla oblongata. T y
form the deep part of the restiform body and constitute its chief bulk. Strean ig
out from the hilum of the inferior olivary nucleus, they cross the median plane, ic
in the opposite side of the medulla oblongata they either pass through the infe 01
1 These fibres should be called the fasciculus olivocerebellaris, by which designation they will be rel id
to in this account, but in the recognised nomenclature (which most writers do not follow in this instance i& e
tract is called " cerebello-olivaris"
INTERNAL STRUCTURE OF MEDULLA OBLONGATA AND PONS. 557
TxENIA VENTRICULI
QUART!
olivary nucleus of that side or sweep round it. Ultimately, on the dorsal aspect
of the olivary nucleus, they are gathered together in the form of a conspicuous
group of arcuate fibres, which curve backwards to take up a position in the deep
part of the restiform body. In passing back, they traverse the tractus spinalis of
the trigeminal nerve and break it up into several separate bundles. The
olivo-cerebellar fibres thus connect the inferior olivary nucleus of one. side with
the opposite side of the cerebellum. Each part of the inferior olivary nucleus is
connected with a definite part. of the cerebellum.
Decussation of the Pyramids and the Changes produced thereby. As we
examine, under the microscope, a series of successive transverse sections through the
inferior end of the medulla oblongata and the upper end of the spinal medulla, the
most striking change which meets the eye is the decussation of the lateral cerebro-
spinal tracts. From their position alongside the anterior median fissure of the
medulla oblongata most of the fibres of the pyramid cross the median plane
and, after passing
through the anterior
column of gray mat-
ter, bend downwards
in the lateral funi-
culus of the oppo-
site side of the spinal
medulla. Strands
from the right lateral
cerebro-spinal tract
alternate with cor-
responding strands
from the left side,
and the interval be-
tween the bottom of
the anterior median
furrow and the gray
matter surrounding
the central canal be-
comes filled up with
a great mass of inter-
crossing bundles of
fibres.
As a rule the
medial three -fourths
of the pyramid are
composed of fibres
which, lower down in
lateral funiculus of the spinal medulla, form the fasciculus cerebro-
whilst the lateral fourth of the pyramid proceeds downwards in the anterior
iilus of the spinal medulla of the same side, as the fasciculus cerebrospinalis
A considerable amount of variation, however, occurs in the proportion of fibres
s allotted to the formation of these two tracts. Sometimes the lateral cerebro-
tract is much larger than usual, and then the anterior cerebro-spinal tract suffers
esponding diminution in size. Cases, indeed, occur in which the entire pyramid
into the decussation, and in these there is no anterior cerebro-spinal tract.
is not uncommon to meet with variations of an opposite kind which lead to
sase of ^the anterior cerebro-spinal tract at the expense of the lateral cerebro-
Sometimes the decussation is asymmetrical, and the corresponding cerebro-
J on opposite sides of the spinal medulla are then unequal in size. One
: often comes into play and causes asymmetry is the prolongation downwards
pyramid on one side (usually the left) of some of the cerebro-pontine fibres. In
iese fibres soon leave the pyramid and form the fasciculus circumolivaris.
itions indicated above receive an additional interest when viewed in the light
itiye anatomy. It would appear that only in man and the anthropoid apes is
xtion of the pyramids in the inferior part of the medulla oblongata incomplete.
XII.
[HYPOCLOSSAL]
3- DIAGRAM OF THE FASCICULUS OLIVOCEREBELLARIS (CEREBELLO-
OLIVARY FIBRES).
(This diagram has been constructed from the specimen figured on p. 555.)
X., Vago-glossopharyngeal nucleus. N.XIL, Hypoglossal nucleus.
558
THE NEEVOUS SYSTEM.
According to Sherrington, an anterior cerebro-spinal tract in the spinal medulla of th
anthropoid apes stands in connexion with the arm-centre in the cerebral cortex. If this i
the case in man it must have other connexions as well, seeing that it is carried down th
spinal medulla for a considerable distance beyond the level of the spinal segments whicl
give motor fibres to the upper limb. In the lower apes an anterior cerebro-spinal trac
Funiculus gracilis Gracile nucleus d eS n0t , ^ 6m tO ^
the whole pyrami
crosses over to the oj
posite side of the spim
medulla in the shap
of the lateral cerebn
spinal tract.
Funiculus cuneatus
Cuneate nucleus
Tractus spinalis of
trigeminal nerve
Nucleus tractus
-spinalis nervi
trigemini
Central gray matter
Central canal
Lateral cerebro-
'spinal tract
Detached head of anterior
column of gray matter
As we have note<
the decussating pyr;
midal bundles pa;
through the anterii
column of gray ma
ter, and cut it in
two portions (Fig
489 and "490). TI
basal part remains
position on the a
terior and later
aspect of the cent]
canal, and forms ps
of the thick layer
gray matter whi
surrounds it. T
detached head of the anterior column is set free ; and from the large multipo"
cells which lie in its midst some of the fibres of the anterior root of the fi
cervical nerve, and also some of .the root fibres of the accessory nerve, take origin
As we proceed into the medulla oblongata another effect of the decussati
of the pyramids is seen in the submergence from the surface of the strand
fibres which, in the anterior funiculus of the spinal medulla, lies to the lateral s -.
of the anterior cerebro-spinal tract, and which receives the name of the fascicu i
anterior proprius. While the decussation is going on the fasciculus propriusi
thrust aside, and in the medulla oblongata, it takes up its position as a flatter 1
band -like strand on
Funiculus gracilis
^i^y9iMb^.^'' 'SOU f&^WlSiSSS^
Gracile nucleus
Fasciculus anterior proprius Decussation of pyramids
Pyramid Pyramid
FIG. 489. SECTION THROUGH THE INFERIOR END OP THE MEDULLA OBLONGATA
OF A CHIMPANZEE.
Cuneate
nucleus
Gray matter
around canal
the lateral side of the
pyramid (Fig. 489).
When the decussation
is completed, this
strand is seen to lie
close to the median
plane on the dorsal
aspect Of the pyramid, Central canal
where it is separated
from its fellow of the r ^
. , , . , Decussation of.
Opposite Side by the pyramids
median raph'e alone
(Fig. 491). In the
upper part of the
medulla oblongata it
approaches still nearer
Funiculus
cuneatus
Tractus spi
of fifth ner
Nucleus
tractus spi
alls nervi
trigemini
Fasciculus
spino-
cerebellari
Detached 1 i
of auterioi
column
Fasciculus
anterior propr
Fissura medians anterior
FIG. 490. TRANSVERSE SECTION THROUGH THE INFERIOR END OF T
MEDULLA OBLONGATA OF A FULL-TIME FCETUS,
to the dorsal Surface Treated by the Weigert-Pal method. The gray matter is bleached white, '
and appears to form the medullated tracts of fibres are black.
the greater part of a
strand, which is termed the medial longitudinal bundle (Figs.
The detached head of the anterior column of gray matter of the spinal med
INTEKNAL STKUCTUKE OF MEDULLA OBLONGATA AND PONS. 559
3 it is traced upwards, is observed to cling closely to its original relationship
dth the fasciculus anterior proprius. It is applied to the lateral side of this strand,
ad, gradually becoming smaller, finally disappears at the level of the inferior part
f the inferior olivary nucleus.
Cuneate and Gracile Fasciculi, with their Nuclei. As the fasciculus gracilis
ad the fasciculus cuneatus of the posterior funiculus of the spinal medulla are
aced up into the medulla oblongata they seem to increase in bulk, and in trans-
srse sections they assume the form of massive wedge-shaped strands, quite
istinct from each other. They increase in width and lose considerably in depth,
id consequently the transverse diameter of the area which they occupy becomes
reater. As a result of this, and also owing to the removal of the lateral
irebro-spinal tract from the lateral funiculus of the spinal medulla immediately
L front, the posterior column of gray matter is gradually rotated forwards and
>mes to lie transversely and in the same straight line with its fellow of the
Central canal
isciculus anterior
proprius
i Decussation of
inniscus inedialis
Inferior
olivary nucleu
Funiculus gracilis
Gracile nucleus
Funiculus cuneatus
x Cuneate nucleus
Accessory cuneate
nucleus
Tractus spinalis of
fifth nerve
Nucleus tractus
spinalis nervi
trigemini
Fasciculus
anterior proprn
Medial olivary
nucleus
Pyramid
Arcuate nucleus covered
superficially by external
arcuate fibres
FIG. 491. SECTION THROUGH THE CLOSED PART OF THE HUMAN MEDULLA OBLONGATA IMMEDIATELY
ABOVE THE DECUSSATION OP THE PYRAMIDS (Weigert-Pal specimen).
posite side (Figs. 490 and 491). The substantia gelatinosa, at the same time,
, comes increased in quantity and presents a horseshoe-shaped outline in trans-
rse section. It clasps within its concavity the somewhat reduced head of the
isterior column, and forms with it a conspicuous circular mass of gray matter
ich lies close to the surface, and produces upon it the bulging termed the
berculum cinereum. The basal portion of the posterior column of gray matter
Lains upon the dorsal and lateral aspect of the central canal, and forms a
iioii of the central gray mass of the closed part of the medulla oblongata ; but
oon the neck of the column, which at this level is greatly reduced owing to
* absence of entering posterior nerve-roots, is invaded by bundles of fibres
ich traverse it in different directions and convert it into a forma tio reticularis.
is means the rounded head of the posterior column becomes cut off from the
-1 gray matter, and from this point upwards it remains as an isolated gray
uumn intimately associated with the spinal root of the trigeminal nerve. It has,
, become the nucleus tractus spinalis nervi trigemini.
The gracile and cuneate nuclei are seen in their most typical form in sections
the level of the decussation of the pyramids (Figs. 489 and 490). The gracile
560
THE NEKVOUS SYSTEM
Cuneate nucleus
Tractus spinalis of
fifth nerve
Nucleus tractus
spinalis n. trigemini
Fasciculus .spino-
cerebellaris
tract
Detached anterior
column of gray matter
Decussation of
pyramids
Anterior basis-bundle
FIG. 492. SECTION THROUGH THE INFERIOR PART OF THE
MEDULLA OBLONGATA OF THE ORANG.
nucleus appears in the form of a relatively slender mass of gray matter in th
interior of the funiculus gracilis.
The cuneate nucleus is a direct offshoot from that part of the base of th
posterior column of gray matter which is preserved as a portion of the centra
gray mass. In transverse section it is seen to invade the funiculus cuneatus upoi
its deep aspect, and it gradually grows backwards into its substance. It present
Graciie nucleus a very different appearance froi
cuneate nucleus ^^ j the gracile nucleus, becaus
throughout its whole length th
gray nucleus and the fibres d
the strand are separated froii
each other by a sharp line on the dorsal
ipect of the pyra-
ids. Having
i us gained the
)posite side of the
edulla oblongata,
ley immediately
irn upwards and
>rm a conspicuous
rand of longi-
idinal fibres,
hich ascends close
i the median plane
id is separated
om its fellow of
i e opposite side
Y the median
,phe alone. This
rand is termed
ie lemniscus
FIG. 494. TRANSVERSE SECTION THROUGH THE HUMAN MEDULLA OBLONGATA
As we proceed up IN THE INFERIOR OLIVARY REGION.
e medulla oblon-
internal arcuate fibres which first come into sight appear as coarse bundles which
Funiculus cuneatus
Cuneate nucleus
Tractus solitarius
Tractus spinalis of
trigeminal nerve
Nucleus of
tractus spinalis-
of trigeminal nerve
Internal arcuate
fibres
Fila of hypoglossal
nerve
External
arcuate fibres
Inferior olivary
nucleus
Medial accessory
olivary nucleus
Pyramid
External
arcuate fibres
Restiform borly
Vago-glossopharyugeal
roots
I Nucleus of the
Fasciculus tectospinalis
Vagus n ucleus
Tractus sulitarius
Descending root of vestibular nerve
go-glossopharyngeal roots
Fasciculus spinocerebellaris
posterior
Fasciculus longitudinalis
medialis
Nucleus tractus spinalis
nervi trigemini [nerve
tus spiuulis of trigeminal
Nucleus ambiguus
iculus rnbrospmalis
o-cerebellar fibres
Fasciculus spinothalainicua
rsal accessory olivary nucleus
iculus spinocerebellaris anterior
External arcuate fibres
Lemniscus medialis
Medial accessory olivary nucleus
Fasciculus tegmento-olivaris
Inferior olivary nucleus
Pyramid
1 External arcuate fibres
TRANSVERSE SECTION 'THROUGH THE MIDDLE OF THE OLIVARY REGION OF THE HUMAN MEDULLA
OBLONGATA.
The floor of the fourth ventricle is seen, and it will be noticed that the restiform body on each side has
now taken definite shape. Some of the descending tracts in red ; ascending tracts in blue.
fe forwards in a narrow group round the central gray matter (Figs. 494 and 495). Soon,
her finer bundles appear, which describe wider curves on the lateral side of the coarser
37
562 THE NEKVOUS SYSTEM.
group, until a very large part of each half of the medulla is seen to be traversed by the;
arcuate fasciculi (Fig. 495). The internal arcuate fibres decussate in the median plai
with the internal arcuate fibres of the opposite side. They then change their directk
and turn upwards, and the lemniscus, as already stated, takes form and gradual
increases in volume as it ascends. This great and important tract is thus laid do\*
between the pyramid and the fasciculus longitudinalis medialis ; and the consequence
this is that the latter tract is pushed still farther backwards, and, when the lemnisci
is fully established, it comes to lie immediately beneath the gray matter of the floor
the fourth ventricle (Fig. 495). But the lemniscus is not in direct contact with ill
fasciculus longitudinalis, for a bundle of fibres, the continuation of which has ber
seen in the anterior funiculus of the medulla spinalis, the fasciculus tectospinali
separates them, as well as fibres coming from sensory nuclei of the cerebral nerves whi<
are crossing the raphe' to join the medial lemniscus (Fig. 495).
It is important that we should realise at this stage the full significance of tl
decussation of the lemniscus and have a clear conception of the connexions of tK
fibres which take part in it. The funiculus posterior, which ends in the cuneate ai
fracile nuclei, is derived from the posterior roots of the spinal nerves. The lemnisc
bres therefore carry on the continuity of part of the posterior funiculus, fr
gracile and cuneate nuclei, which are thrown across its path in the lower part
the medulla oblongata, constituting merely a nodal interruption. At this point t
lemniscus is transferred to the opposite side of the medulla oblongata. But it w .
be remembered that a large proportion of the fibres of the entering posterior ner\
roots of the spinal nerves end in connexion with the cells of the posterior column
gray matter of the spinal medulla. It must not be supposed that the path repi
sented by these latter fibres comes to a termination thereby ; from these poster:
column cells other fibres arise which cross, in the anterior white commissure, to 1 1
opposite side of the spinal medulla and proceed up the spinal medulla to t
lateral part of the medulla oblongata. These fibres constitute the spino-thalar
tract already referred to. The practical bearing of this is that, owing to the crossi
of the lemniscus medialis and lower down of the spino-thalamic tract, unilate^
lesions of the medulla oblongata are apt to produce complete hemi-ancesthesia ; whv-,
unilateral lesions of 'the spinal medulla produce only partial hemi-ancesthesia.
The pyramid forms a massive tract in front of and quite distinct from i>
lemniscus medialis. The lemniscus medialis, the tecto-spinal bundle, and the rned t
longitudinal bundle are, in the first instance, not marked off from each oth
They appear as a broad flattened band applied to the raphe. One edge of t5
band is directed backwards and reaches the gray matter on the floor of the fou: i
ventricle, while the other edge looks forwards, and is in contact with the pyraii .
In the upper part of the medulla oblongata the lemniscus and the mecl
longitudinal fasciculus begin to draw asunder from each other. The intermedi s
longitudinal fibres become reduced in number and the two strands grow densei -
the one on the dorsal aspect of the pyramid, and the other immediately beneath 3
gray matter of the floor of the fourth ventricle (Fig. 495).
The fasciculus longitudinalis medialis is largely formed of fibres homolog s
with those which in the spinal medulla constitute the fasciculus anterior propr 5.
As they are followed upwards these fibres are thrust back by the two decussatio :
the lower decussation pushing them behind the pyramids, and the upper decussat a
displacing them still farther backwards to a position behind the lemniscus m.edif 3.
Corpus Restiforme. The gracile and cuneate nuclei gradually give plaw o
the restiform body in the superior part of the posterior district of the media
oblongata. Fibres from various quarters converge to form this great strand,
first takes shape as a thin superficial layer of longitudinal fibres, which are gathe d
together on the lateral aspect of the cuneate nucleus ; but after that nucleus has c< .e
to an end, and as the superior part of the medulla oblongata is reached, the restif- a
body is seen to have grown into a massive strand, which presents a kidney-sha n
or oval outline on transverse section (Fig. 495) ; and it ultimately enters the w e
central core of the cerebellum as its inferior peduncle. The fibres which build p
the restiform body are the following : (1) the fasciculus spinocerebellaris [posteri 1 ;
(2) arcuate fibres coming from the nucleus gracilis and nucleus cuneatus of 1 h
INTERNAL STRUCTURE OF MEDULLA OBLONGATA AND PONS. 563
REST! FORM
BODY
.DORSAL EXT.
3CUATE FIB.
RACILENUCL.
CUNEATE NUCL.
des of the medulla oblongata ; (3) external arcuate fibres coming from the arcuate
uclei; and (4) olivo-cerebeUar fibres.
The fasciculus spinocerebellaris [posterior] extends upwards from the lateral funi-
ilus of the medulla spinalis. In the lateral district of the medulla oblongata it
?cupies a similar position ; but before
le olive is reached it inclines back-
ards, crosses the posterior lateral
irrow and passes obliquely upwards
ito the restiform body. As its fibres
iverge backwards, they pass over and
over up the tractus spinalis of the tri- NUCL1
Bminal nerve and its nucleus, thus TRA TU T S R*
mtting them out from the surface,
he fibres of the fasciculus spinocere-
ellaris, in the first instance, enter
ito the lateral or superficial part of
ie restiform body.
Bruce has shown that the fibres of the
)ino-cerebellar tract ultimately lie in the
intre of the restiform body, forming as it
, ere its central core, and that, in the cere-
ilium, they can be traced to the superior FlQ - 496. DIAGRAM,
Tmis. Which shows in part the fibres which enter into the
constitution of the restiform body.
The posterior external arcuate fibres
ike origin from the gracile and cuneate nuclei, and enter the superficial part of
le restiform body of the same side.
The anterior external arcuate fibres proceed from the inferior portions of the
.racile and cuneate nuclei of the opposite side. It can easily be determined that,
fter decussating in the median plane, all the internal arcuate fibres which arise
om these nuclei do not enter the lemniscus medialis. A large proportion of them
rain the surface by sweeping round the medial aspect of the pyramid in the
aterior median fissure. Many of them gain the surface by piercing the pyramid
: by passing out between it and the olive. These fibres constitute the anterior
t.al arcuate group, and on the surface of the medulla oblongata they sweep
Fasciculus graciiis backwards around it, forming a
Graciie nucleus thin i ayer over fa e olive and
luscuneatus^ / ,.. . ', , . . , ..
^^aiMK^L ultimately reaching the restiform
body. The anterior external
arcuate fibres, as well as the
spino - cerebellar tract - fibres,
cover over the tractus spinalis
of the trigeminal nerve, which
thus comes to take up a deeper
position in the substance of the
medulla oblongata (Figs. 495
and 496).
The other elements in the
restiform body, viz., those de-
rived from the nucleus olivaris
inferior and the nuclei arcuati,
Nucleus of tractus
pinalis n. trigemini
us spinalis of
trigeminal nerve
Fasciculus spino-
cerebellaris
cerebro-spinal
fasciculus
Central canal
Decussation of pyramids
tuched anterior column of gray matter
SECTION THROUGH THE JUNCTION BETWEEN THE
SPINAL MEDULLA AND MEDULLA OBLONGATA OF THE ORANG.
apino-cerebellar tract is well seen, especially on the right side, have already been described
Thus, the restiform body
veys to the cerebellum (1) fibres conveying impulses from the posterior spinal
3 of the same and also from the opposite side of the medulla spinalis, the former
P being interrupted in the nucleus dorsalis and the nucleus graciiis and nucleus
s of the same side, the latter in the nucleus graciiis and nucleus cuneatus
ie other side ; and (2) fibres from the olivary and arcuate nuclei, which convey
from the higher regions of the brain, directly or indirectly (probably the
ter) from the motor area of the cerebral cortex.
37 a
564 THE NEKVOUS SYSTEM.
Formatio Reticularis. Behind the olive and the pyramid is the formatic
reticularis. In the medulla oblongata it occupies a position which, to a large
extent, corresponds with that of the lateral funiculus in the spinal medulla. Ir
transverse section it appears as an extensive area, which is divided into a lateral
and a medial field by the fila of the hypoglossal nerve as they traverse the s.ubstanc<
of the medulla oblongata to reach the surface. In the lateral portion, which lies
behind the olive, a considerable quantity of gray matter, continuous with that ii ;
the spinal medulla, is present in the reticular formation ; it is, therefore, called th
formatio reticularis grisea. In the medial part, which lies behind the pyramid
the gray matter is extremely scanty, and the reticular matter here is termed thi
formatio reticularis alba.
The nerve-fibres which traverse the formatio reticularis run both in a transvers<
and in a longitudinal direction. The transverse fibres are the internal arcuate fibres
The longitudinal fibres are derived from different sources in the two fields. In th
formatio grisea they represent to a large extent the fibres of the lateral funiculus o
the spinal medulla, after the removal of the posterior spino-cerebellar and the latera
cerebro-spinal tracts. They consist, therefore, of the fibres of the fasciculi rubro
spinalis, thalamo-olivaris, spinothalamicus, and spinocerebellaris anterior (antero,
lateralis superficialis) of the spinal medulla. In the formatio alba the longitudina
fibres are the tract of the lemniscus medialis, the fasciculus tectospinalis, and th
medial longitudinal bundle, all of which have already been described.
Central Canal and the Gray Matter which surrounds it. The central cana
as it proceeds upwards through the closed part of the medulla, is gradually force
to assume a more dorsal position, owing to the accumulation of fibres on its ventre
aspect. (Moreover, the posterior cleft-like part of the cavity of the foetal neur*
tube, which becomes obliterated in the spinal medulla by the fusion of its wall
remains patent in the medulla oblongata. Hence the central canal in the close
part of the medulla oblongata extends backwards to the roof-plate.) First tl
decussation of the pyramids, and then the decussation of the medial lemniscu
both of which take place in front of the canal, tend to push it backwards; ar
the formation of the longitudinal strands in which these intercrossings result (vi;
the pyramid and the medial lemniscus), together with the continuation upwards \
the funiculus anterior proprius, leads to a great increase in the amount of tissi
which separates it from the anterior surface of the medulla oblongata. In the close
part of the medulla oblongata the canal is surrounded by a thick layer of gre
matter, which is continuous with the basal portions of the 'anterior and posteri'
columns of gray matter of the spinal medulla. This central gray matter is sharp'
defined on each side by the internal arcuate fibres, which curve forwards ar
medially around it. Finally, the central canal opens on the dorsal aspect of tl
medulla oblongata into the cavity of the fourth ventricle. The central mass
gray matter which surrounds the canal in the closed part of the medulla oblonga
is now spread out in a thick layer on the floor of the fourth ventricle, and in su<
a manner that the portion which corresponds to the basal part of the anteri
column of the spinal medulla is situated close to the median plane, whilst the pa
which represents the base of the posterior column occupies a more lateral positic
This is important, because the nucleus of origin of the hypoglossal nerve is plac
in the medial part of the floor, whilst the nuclei of termination of the afiere
fibres of the vagus, glossopharyngeal, and acoustic nerves lie in the lateral part
the floor. The gray matter of the ventricular floor is covered with ependyma.
Three Areas of Flechsig. In transverse sections, through the upper, open part of 1
medulla oblongata, the fila of the hypoglossal and vagus nerves are seen traversing the substai
of the medulla oblongata. The nucleus of origin of the hypoglossal is placed in the gray mat
of the floor of the fourth ventricle close to the median plane ; the nucleus of the vagus is situa
in the gray matter of the ventricular floor immediately to the lateral side of the hypoglos
nucleus. From these nuclei the root-bundles of the two nerves diverge from each other as t
are traced to the surface and subdivide the substance of the medulla, as seen in transverse secti
into the three areas of Flechsig, viz., an anterior, a lateral, and a posterior.
The anterior area, which is bounded medially by the median raphe and laterally by
hypoglossal roots, presents within its limits : (a) the pyramid ; (6) the lemniscus medialis
the fasciculus tecto-spinalis ; (d) the medial longitudinal fasciculus ; () the medial access-
olivary nucleus ; (/) the arcuate nucleus.
INTERNAL STKUCTUEE OF THE PONS.
565
The lateral area lies between the root fibres of the hypoglossal and those of the vagus. It
>ntains : (a) the inferior olivary nucleus ; (6) the dorsal accessory olivary nucleus ; (c) the nucleus
teralis ; (d) the nucleus ambiguus ; (e) the splanchnic efferent nucleus of the vagus and glosso-
liaryngeal nerves ; (/) the formatio reticularis grisea.
The posterior area is situated behind the vagus roots, and within its limits are seen : (1) the
! :stiform body ; (2) the superior part of the cuneate nucleus ; (3) to the medial side of this a crowd
' transversely cut bundles of fibres, loosely arranged and forming the descending root of the
>,stibular part of the acoustic nerve ; (4) close to these, but placed more deeply, a round,
mpact, and very conspicuous bundle of transversely cut fibres, viz., the tractus solitarius, or
Ascending root of the vagus and glossopharyngeal nerves ; (5) the large tractus spinalis of the
1 igeminal nerve close to the lateral side of its nucleus composed of substantia gelatinosa.
w
INTERNAL STRUCTURE OF THE PONS.
hen transverse sections are made through the pons, it is seen to be composed
basilar part and a dorsal or tegmental part. The latter may be regarded as
a) -; r^5
S W)
3 8 : Restiform body
fllli !
Nucleus of
tractus spinalis
of trigeminal
nerve
Tractus spinalis
of trigeminal
nerve
Facial nucleus
Facial nerve
Superior olive
Corpus
trapezoideum
Deep transverse fibres
of pons
Pyramidal bundles
Superficial transverse fibres of pons
-SECTION THROUGH THE LOWER PART OF THE HUMAN PONS IMMEDIATELY ABOVE THE
MEDULLA OBLONGATA.
'upward prolongation of the- medulla oblongata, exclusive of the pyramids
are drawn forward into the basilar part.
*ars Basilaris Pontis. This constitutes the chief bulk of the pons. It is
of: (1) transverse fibres arranged in coarse bundles, called the fibrse
[2) longitudinal fibres, gathered together in massive bundles; and (3) a
amount of gray matter, termed the nuclei pontis, which fills up the interstices
t iween the intersecting bundles of fibres.
fasciculi longitudinales, to a large extent, consist of the same fibres which,
>wn, are gathered together in the two solid pyramidal tracts of the medulla
ita. When the pyramids are traced upwards into the pons they are seen to
376
566
THE NEKVOUS SYSTEM.
trigemf
present the form of two compact bundles. Superiorly, however, they are broken up
into smaller bundles by the transverse fibres of the pons, and are spread out over a
wider area. At the upper border of the pons they again come together and form two
solid strands, each of which is continuous with the central part of the correspond-
ing basis of the cerebral peduncle. Added to these there are twice as many other
fibres entering the pons from the basis pedunculi to terminate in the nuclei pontis
The fibrae pontis at the inferior border of the pons are placed on the superficial
or ventral aspect of the pyramidal bundles. As we proceed upwards they increase
in number, and many are seen breaking through the pyramids and even passing
across upon their dorsal aspect. Laterally, these transverse fibres are collected togethe:
into one compact mass, which enters the white central core of the cerebellum anc
constitutes the brachium pontis (O.T. middle cerebellar peduncle). At the mediai
plane the transverse fibres of the two sides of the basilar portion of the pon
intercross and form a coarse decussation.
The nuclei pontis form a considerable part of the bulk of the basilar portio]
of the pons. The gray matter is packed into the intervals between the intersectm
transverse and longitudinal bundles.
There is some analogy between the pyramidal portions of the medulla oblongata an
the ventral part of the pons. In the medulla oblongata fine arcuate fibres, on their way 1
the surface, pass through the pyramids. Other external arcuate fibres sweep over tl
surface of the pyramids. These present a strong resemblance to the transverse fibres i
the pons. They likewise rea(
the cerebellum, although I
a different route, viz., tl
restiform body. The nucl
pontis are represented also
the pyramidal part of t
medulla oblongata by t
arcuate nuclei, which a
covered over by the exterr
arcuate fibres, and even te:
to penetrate, to a slight <
tent, into the pyramidal trac
VRhomt)ic lip> These arcuate nuclei, as alrea
pointed out, are continue
with the nuclei pontis.
Connexions of t
Longitudinal and Trai
verse Fibres. When
FIG. 499. DIAGRAM OF THE LEFT LATERAL ASPECT OF THE FOSTAL trans verse section through 1
RHOMBENCEPHALON REPRESENTING SOME OF THE CELL GROUPS superior part of the pons
AND FIBRE TRACTS. compared with one close to
inferior border, it becomes
once apparent that the numerous scattered bundles of longitudinal fibres which en '
the ventral part of the pons from above, if brought together into one tract, would fc i
a strand very much larger than the two pyramids which leave its lower aspect and en '
the medulla oblongata. It is clear, therefore, that many of the longitudinal fib
which pass into the pons from above do not pass out from it below into the medi i
oblongata. What becomes of these fibres that are thus absorbed in the pons? 1
known that the pyramidal bundles suffer a small loss by the fibres which they send to -
nuclei of origin of the efferent nerves which arise within the pons (viz., the motor roo f
the trigeminal, abducens, and facial nerve nuclei) ; but this loss is, comparatively speak
trifling. It is clear, therefore, that other longitudinal bundles enter the pons from at e
apart from those which form the pyramidal tracts. These bundles occupy a lateral J
dorsal position in the ventral part of the pons, and may be termed the cerebro-pom e
fibres, seeing that they come from the cerebral cortex and end in fine ramifications aro d
the cells of the nuclei pontis (Fig. 498).
The transverse fibres take origin as axons of the cells of the nuclei pontis. Cros g
the median plane, they enter the brachium pontis of the opposite side, and thus r< h
the cerebellar cortex, where they end in ramifications round certain of the cortical c s.
Some authorities believe that there are also fibres passing in the opposite direction. *
Fasciculus
circumolivaris
pyramidis.
,8rchium
ponfis.
CEREBELLAR
RUDIMENT.
Flocculus.
Recessus laferalis
vcnrriculi quarti.
MEDULLA OBLONCATA.
nl-o -bulbsre.
^m t
INTEKNAL STEUCTUKE OF THE PONS. 567
Dm the cerebellum to the nuclei pontis ; but there is some doubt concerning the
istence of any such fibres. The brachium pontis thus may contain both efferent and
:erent cerebellar fibres ; but no fibres pass continuously through the pons from one
achium pontis into the other.
| Certain of the transverse fibres of the pons turn backwards and enter the dorsal or
;gmental part of the pons, but the precise connexions of these are doubtful.
Corpus Trapezoideum. This name is applied to a group of transverse fibres
,[iich traverse the lower part of the pons (Fig. 498). They are quite distinct from
.ose which have been just described as entering the brachium pontis, and they lie
the boundary between the dorsal and basilar parts of the pons, but encroaching
nsiderably into the ground of the former. They arise from the cells of the
rminal nucleus of the cochlear division of the acoustic nerve, and constitute a
act which establishes certain central connexions for that nerve. They will be
ore fully described when we treat of the cerebral connexions of the acoustic nerve.
Pars Dorsalis Pontis (Dorsal or Tegmental Part of the Pons). On the dorsal
rface of the tegmental part of the pons there is spread a thick layer of gray
atter, covered with ependyma, which forms the floor of the upper or pontine
it of the fourth ventricle. Beneath this the median raphe of the medulla
longata is continued up into the pons, so as to divide its tegmental part into two
i mmetrical halves.
In the inferior part of the pons, immediately beyond the medulla oblongata, the
stiform body is placed on the lateral side of the dorsal part (Fig. 498). In trans-
rse sections through the pons it appears as a large, massive oval strand of fibres
'rich inclines backwards into the cerebellum, and thus leaves the pons.
itween the restiform body and the median raphe the tegmental part of the pons
composed of substantia reticularis, continuous with the same material in the
: idulla oblongata. Thus, arcuate or transverse fibres, curving in towards the raphe,
: d also longitudinal fibres, are seen breaking through a mass of gray matter which
supies the interstices of the intersecting fibres. To the naked eye the formatio
:;,icularis presents a uniform gray appearance, but its constituent parts are
: sealed by low powers., of the microscope in properly stained and prepared
;:3cimens. Embedded in this substantia reticularis are various clumps of compact
jiy matter and certain definite strands of fibres. These we shall describe as we
;'ss from the restiform body medially towards the median raphe.
1 (1) Spinal Root of the Trigeminal Nerve and its Nucleus. Close to the medial side
( the restiform body, but separated from it by the vestibular root of the acoustic
irve as it proceeds backwards through the pons, is seen a large crescentic group
< coarse transversely divided bundles of fibres. This is the tractus spinalis (O.T.
ynal root) of the trigeminal nerve; and applied to its medial concave side is
i, small mass of gray matter, which is the direct continuation upwards of the
f bstantia gelatinosa.
(2) The nucleus of the facial nerve comes next. It is sunk deeply in the
,ween it and the medial longitudinal bundle, and in close relation to the gray
570
THE NEEVOUS SYSTEM.
matter of the floor of the ventricle, is the collection of pigmented cells which con-
stitutes the substantia ferruginea.
The medial longitudinal bundle, as it is traced upwards through the tegmental
part of the pons, maintains the same position throughout, and as it ascends it
becomes more clearly mapped out as a definite and distinct tract. It lies close
to the median raphe, and immediately subjacent to the gray matter of the floor
of the fourth ventricle.
The lemniscus medialis, as it ascends through the tegmental part of the pons,
undergoes striking changes in shape. In the lower portion of the pons its fibres,
which in the medulla oblongata are spread out along the side of the median raphe,
are collected together in the form of a loose bundle, which occupies a wide field,
somewhat triangular in shape, on either side of the median raphe and immediately
behind the basilar portion of the pons. As it proceeds up, the fibres spread out
laterally until a compact ribbon-like layer is formed in the interval between the
tegmental and basilar portions of the pons (Figs. 501 and 502).
Above the level of the trigeminal nuclei another flattened layer of fibres come:
Upper end of fourth ventricle
Trochlear nerve
Mesencephalic root of trigeminal nerve
Fasciculus anterolateralis
superficialis
Medial longitudinal
bundle
Brachium conjunctivum
Lateral lemniscus
Formatio reticularis
Medial lemniscus
A B
FIG. 502. Two SECTIONS THROUGH THE DORSAL PORTION OF THE PONS AT ITS SUPERIOR PART, '.
CLOSE TO THE MESENCEPHALON.
A is at a slightly lower level than B.
into view to the lateral side of the lemniscus medialis. To this the name of lemnisc
lateralis is given. These fibres spread laterally and backwards, and finally ta
up a position on the lateral surface of the brachium conjunctivum. In the an*
between the medial and^ lateral lemnisci a little knot of compact gray matt
termed the nucleus lemnisci lateralis, comes into view (Fig. 501). This appe-
to be in more or less direct continuity with the superior olivary nucleus. Ma
of the fibres of the lemniscus lateralis take origin in this nucleus. Bruce cal I
attention to the continuity between the superior olive and the nucleus of the late I
lemniscus in man, and Cunningham confirmed the observation in so far as
orang brain is concerned. In many other mammals the nuclei are quite distr
THE CEREBELLUM.
istinc
ied fi J
In the foregoing account it has been seen that the cerebellum is formed
two distinct rudiments, each derived from the posterior edge of the alar lair a
immediately above the pontine flexure and the insertion of the vestibular ne -
As development proceeds during the second month there is a rapid prolifera<
of cells in the mantle layer of the cerebellar rudiments, and they become consi'
ably thickened. But at first this thickening manifests itself not so mucl:
a swelling of the superficial aspect of the cerebellum but as a bulging inw*
into the cavity of the fourth ventricle (Fig. 503).
THE CEEEBELLUM.
571
Cerebellar rudiment
Tsenia
The accentuation of the pontine flexure at this stage brings the two cerebellar
idiments into the transverse direction and in line one with the other and with
le roof-plate, which is now being thickened by immigrant neuroblasts from the
icdial extremities of the two cerebellar rudiments. When one organ is thus
rmed by the union in the roof-plate of the originally separate rudiments, it
resents the form of a dumb-bell shaped mass (Fig. 503). Upon the inferior
;pect of this mass there is a slight ridge, to
hich the tela chorioidea ventriculi quart! is
Cached. Opposite the lateral cerebellar rudi-
ients (but not in the median plane) the attach -
ient of the tela becomes thickened to form the
Dsterior medullary velum.
Early in the third month the growth of the
>rebellar rudiment begins to manifest itself by
teral bulgings of its surface.
The rhombic lip, the inferior part of which
is been seen to play an important part in the
ivelopment of the nuclei pontis and nucleus
ivaris inferior, is also continued upwards beyond
le pontine flexure on to the cerebellar rudiment, Fia - 503. DORSAL ASPECT OF THE RHOMB-
here it forms a marginal fringe. Thus/even
L the second month, a groove can be detected upon the cerebellum separating off
band which is continuous with the tuberculum acusticum. The part nearest to
le tuberculum represents the rudiment of the flocculus and the medial extremity the
)dulus (Fig. 503). During the third month the cerebellum appears as a rounded
ir transversely placed across the upper part of the roof of the fourth ventricle,
id as the lateral extremities of this bar expand (Fig. 504), it assumes a dumb-bell
tape not unlike that presented a few weeks earlier (Fig. 503) on its ventricular
,pect. As these lateral bosses (lobi laterales) develop, a mass of transverse fibres
connexion with them also becomes apparent. It represents the fibres trans-
srsae of the pons. They arise from the cells (nuclei pontis) which have wandered
to the basal lamina of the metencephalon from the rhombic lip of the myelen-
phalon (Fig. 499) ; and the fibres which enter each cerebellar boss come mainly
om the nuclei pontis of the other side. Towards the end of the fourth month,
I 1 even a month earlier in some cases, a little bud grows out from the cerebellum
L each side immediately above the flocculus. It is the paraflocculus or flocculus
secundarius. In man it never attains
Fiss.secunda.
Fiss. suprapyramidalis.
' Fiss. prima. / Lobus
Velum
medullare
posl-erius./
lareralis.
^Parafloc.
Floe.
Recessus
lareralis
v venh. quarH.
Tuberculum acusHcum.
Medulla oblongafa.
Modulus. Obex. Taenia venlriculi quarH.
a large size, but in most mammals it
develops into a large lobe, even as big
as one -third the size of a cerebellar
hemisphere (in the manatee), and in
many animals a deep fossa is formed in
the temporal bone to lodge this part of
the cerebellum.
As the cerebellum grows the lateral
hemispheres expand much more rapidly
than the median part the handle of the
dumb-bell. But the superficial area
J. 504. THE POSTERIOR ASPECT OF A FCETAL r. ,-, i , -, . - -, -,
(FOURTH MONTH) CEREBELLUM, MEDULLA OB- of the latter becomes increased by means
LONGATA AND FOSSA RnoMBoiDEA. of transverse folds which begin to make
their appearance at the close of the
ird month. Earlier in that month the median part of the cerebellum presents
sagittal section almost a semicircular outline (Fig. 50*7, A) with a slight notch
its inferior margin (fissura postnodularis) demarcating the nodulus. As
ilopment proceeds during the third month the nodular region becomes bent
wards upon the rest of the cerebellum (Fig. 507, B), thus starting the posterior
< rertieulum of the fourth ventricle, which ultimately assumes a . tent-like outline
ig- 519).
At the close of the third month the irregular growth of the surface of the
572
THE NEKVOUS SYSTEM.
Horizontal fissure of cerebellum
Tuber vermis I Supra-pyramidal fissure
Pyramid \ N ! / Fissura secunda
Postero-inferior
lobule ~
Parapyramidal
sulcus ""
Post-tonsillar
sulcus~
Peduncle of_
flocculus
Paraflocculus
Flocculus
Post-nodular fissure
Uvula
median bridge, which can now be called the vermis, leads to the appearance c
a transverse depressio
upon the superior sui
face. This is the fissur
prima (Fig. 507, B, (
and D), which become
the deepest and mos
Biventral lobule COmpleX of all the mult 1
Tonsil of tude of fissures th^
r cerebellum
--Fioccuiar fissure ultimately cut into tt
cerebellum (Fig. 519
Soon afterwards the fi
sura secunda makes i *
appearance (Fig. 507,0
FIG. 505. INFERIOR SURFACE OF THE CEREBELLUM OF A HUMAN FCETUS and with the fissura prin
WHICH HAS REACHED THE END OF THE FlFTH MONTH OF DEVELOPMENT. Subdivides the Verm
into anterior, media
and posterior lobes. 1
Other transverse fi
sures appear in rap
succession until tl:
vermis becomes cut i
into the following par
named from above (&
the velum medulla
anterius) downward
lingula, lobulus central
Nodule
Clivus monticuli
Culmen
| Fissura prima
Fissura postlunaris
Postero-superior lobule
Supra-pyramidal fissure
Horizontal fissure
Postero-inferior lobule
Infra-pyramidal fissure
FIG. 506. CEREBELLUM OF A HUMAN FCETUS WHICH HAS REACHED THE END culmen declive Dvram
OF THE FIFTH MONTH OF DEVELOPMENT. Viewed from above and behind. ,' ,
uvula, and nodule.
Quite unnecessary importance is usually attached to the subdivisions of the part here cal
i/elu
lobus ant.
velum med. /fiss. prima
- fiss. postnoduk
- nodulus
plx. choroid.
B
..-fiss. postnodul.
nod ulus
plx. chor.oid.
lobus anterior
lobulus centralis
lingula
fiss. praeculminata velum medullare ant.'
fiss. prima
/culmen
s lobus posterior
V
riss. postnodul.
pnma
.-declive
fiss. suprapyr.
_- pyramis
- - fiss. secunda
fiss.postnodularis " uvula
FIG. 507. MEDIAN SAGITTAL SECTIONS OF FCETAL CEREBELLA IN FOUR STAGES OF DEVELOPMENT.
A and B, third month ; C, fourth month ; D, fifth month.
declive, which is described as consisting of three parts (declive, folium vermis, and tuber
1 The term median is used advisedly because, the anterior and posterior lobes having quite insigni
lateral connexions, the rest of the vermis is virtually the medial continuation of (or bridge between]
lateral lobes.
THE CEEEBELLUM.
573
Pons--l-
Fl,
Olivet
ss. pnma
--Ffss. postlunarfs
r . ere is no justification for such a subdivision, nor is any useful purpose served by linking
t ether two parts so distinct, morphologically and physiologically, as the culmen and declive
si giving the name monticulus to the complex.
Only some of the fissures of the vermis become prolonged laterally beyond the
1 lits of the vermis, but as the boss-like lateral lobes begin to expand, their surface
1 iomes folded and a series of independent lateral fissures are formed. [The anterior
I e, however, is prolonged laterally upon each side into tapering wings and all the
jmres in them are merely prolongations of the fissures of the vermis.]
After the limiting fissures of the flocculus and paraflocculus, the first independent
f sure to make its appearance is one which develops behind and almost parallel to
t '. lateral prolonga-
tns of the fissura
jma. Kolliker called
t; intervening strip of
c;ebellum lolulus
I latus posterior and
t fissure may be called
fim'ra postlunaris.
lese postlunar fissures
fy;in far out on the
Ii3ral swelling in the
f( rth monthandgradu-
a, 7 approach the median
pne, where they may
nst and become con-
flmt on the vermis.
It it often happens
tt they do not meet,
ii vvhich case no folium
vtnis is cut off the
d live.
At the end of the
ft rth or beginning of ^^r^iffli^^^^^^^ 3 k develo f7
fissure horrzontdis
line of floor of
fissura horiiontalis
is*, p r i m a
|L--fiss. postlunaris
floe.-
Fiss. para pyramid ali s
FIG.
B
08. THE LEFT LATERAL ASPECT OF THE F(ETAL RHOMBENCEPHALON
AT THE FOURTH (A) AND FIFTH (B) MONTHS.
The cerebellum is stippled.
tl fifth month an oval
selling makes its ap-
p ranee upon each side
o:bhe uvula upon the
iiTior surface of each
laxal lobe (Fig. 505).
T s is called the tonsilla
c< belli or tonsil, and
t fissure which de-
vops behind it and
d< mits it is called post-
tc lillar. Asa rule the
^ post-tonsillar fissures become confluent with the fissura secunda upon the vermis
the whole furrow in the adult may be called fissura secunda. At the middle of the
fiJ i month a lateral fissure, called parapyramidal, makes its appearance some distance
bt ind the post-tonsillar, from which it is separated by an area called the lobulus
bi nter. As a rule, these parapyramidal fissures become confluent with the supra-
Pi imidal fissure. The whole furrow is known in the adult by the latter name,
issure to which most importance is usually attached develops quite late in the
hi lan cerebellum, and not at all in that of the great majority of other animals. It
lied the fissura horizontalis cerebelli. In the adult it begins upon the front, where
i brachium pontis plunges into the cerebellum, and the furrow is formed in a
^3 or less mechanical way by the bulging forwards (above and below the cerebellar
e mcles) of the exuberant mass of the cerebellar hemispheres. The actual infold-
is preceded by the appearance of several irregular depressions (Fig. 508) in the
e where the horizontal fissure will develop. This fissure begins in front and
574
THE NERVOUS SYSTEM.
passes continuously round the circumference of the organ, cutting deeply into it
lateral and posterior margins. In front, its lips diverge to enclose the thre
cerebellar peduncles as they pass into the interior of the cerebellum. Th
horizontal fissure divides the organ into a superior and an inferior part, whic
may be studied separately.
In some cases it meets the corresponding fissure of the other side upon tl
vermis, but very often such a confluence does not occur. The folium vermis
such cases is not distinguished from the tuber vermis.
The cerebellum is subdivided somewhat arbitrarily into a median porti<
termed the vermis, and two much larger lateral portions, called the hemisphen
The demarcation between these main subdivisions of the organ is not ve
evident from every point of view. In front, and also behind, there is a mark
deficiency or notch. The incisura cerebelli posterior (O.T. marsupial notch)
smaller and narrower than the anterior notch. It is bounded at the sides
the hemispheres, whilst its bottom is formed by the axial lobe or vermis.
is occupied by a fold of dura mater called the falx cerebelli. The incisi
cerebelli anterior (O.T. semilunar notch) is wide, and," when viewed from above
is seen to be occupied by the inferior quadrigeminal bodies and by the brad
Pons
Mesencephalon occup-
the incisura anterior '
Lobulus culminis
Lobtilus
Central lobule
Culmen
Declive
Folium vermis
Postero-inferior lobul
Tuber vermis Incisura posterior
FIG. 509. SUPERIOR SURFACE OF THE CEREBELLUM.
conjunctiva. As in the case of the posterior notch, its sides are formed by &
hemispheres, and the bottom by the vermis.
On the superior surface of the cerebellum there is little distinction toe
noted between the median lobe and the superior surface of each hemisphere,
this aspect the median lobe receives the name of superior vermis, and it fon a
high median elevation, from which the surface slopes gradually downwards on J
side to the margin of the hemisphere. The superior vermis is highest in f:
immediately behind the anterior notch, and from this it shows a somewhat
descent towards the posterior notch. This elevation of the superior verm
frequently called the monticulus. The folia on the surface of the sup 01
vermis are thicker and fewer in number than those on the upper surface of ^
hemisphere. It is this which gives it the worm-like appearance from whic ^
derives its name.
On the inferior surface of the cerebellum the distinction between the three ] 1
constituent parts of the organ is much better marked (Fig. 510). On this a, 1 ^
the hemispheres are full, prominent, and convex, and occupy the cereb
fossae in the floor of the cranium. They are separated by a deep median he w
which is continued forwards from the posterior notch. This hollow is termec I
vallecula cerebelli, and in its anterior part the medulla oblongata is lodged. "V eB
the medulla oblongata is raised and the hemispheres are pulled apart, so
expose the bottom of the vallecula, it will be seen that this is formed by the v^ 11
THE CEEEBELLUM. 575
ferior, or inferior aspect of the median lobe, and, further, that the vermis is
para ted on each side from ' the corresponding hemisphere by a distinct furrow,
rmed the sulcus valleculse.
Lobes on the Superior Surface of the Cerebellum. When examined from
fore backwards, the superior vermis presents the following subdivisions: (1) the
; : gula cerebelli; (2) the lobulus centralis ; (3) the culmen; (4) and the declive.
' ith the exception of the lingula, each of these is continuous, on each side, with
i Corresponding district on the upper surface of the hemisphere. Thus, the central
I )ule is prolonged laterally on each side in the form of a small, flattened, wing-
):e expansion called the ala lobuli centralis. The culmen together with its lateral
plongations can be called the lobulus culminis of the hemispheres; the declive
i,nds in the same relation to the lobulus lunatus; and the postero-superior lobules
( the hemispheres may be linked by a folium vermis.
The lingula can be seen only when the part of the cerebellum which forms the
\ ;tom of the anterior notch is pushed backwards. It consists of four or five small
ft folia, continuous with the gray matter of the vermis superior, which are pro-
hged forwards on the superior surface of the anterior medullary velum in the
i ,erval between the two brachia conjunctiva.
The lobulus centralis lies at the bottom of the anterior cerebellar notch, and is
sn only to a very small extent on the superior surface of the organ. It is a
l;le median mass which is prolonged laterally for a short distance round the
a ;erior notch in the form of two expansions, termed the alee lobuli centralis.
The culmen constitutes the highest part or summit of the monticulus of the
v mis superior. It is bounded behind by a deep and strongly marked fissura prima,
a I is prolonged laterally on each side into the hemisphere. This is the most
a erior subdivision on the superior surface of the hemisphere.
The declive lies behind the culmen, from which it is separated by the fissura
pna, and it forms the sloping part or descent of the monticulus of the vermis
si erior. On each side it is continuous with the hemisphere, and the three
pts are included under the one name of lobulus lunatus -(Fig. 509).
Lobes on the Inferior Surface of the Cerebellum. The connexion between
] several parts of the inferior vermis and the corresponding districts on the
ii ;rior surface of the two hemispheres is not so distinct as in the case of the vermis
si erior and the lobules on the superior surface of the hemispheres. A groove,
e; ed the sulcus valleculae, intervenes between the vermis inferior and the hemi-
sj ere on each side.
From behind forwards the following subdivisions of the vermis inferior
be recognised : (1) the tuber vermis ; (2) the pyramis ; (3) the uvula ; (4) the
nonius.
On the inferior surface of the hemisphere there are four main lobules mapped out
b; intervening fissures. From behind forwards these are : (1) the postero-inferior
t> le, a la^ge subdivision which bounds the horizontal fissure on its inferior aspect ;
the biventral lobule, which lies in front of the postero-inferior lobule, and is
* iially divided into two parts by a curved fissure which traverses its surface ; (3)
^ tonsil, a small rounded lobule which bounds the anterior part of the vallecula,
i is lodged in a deep concavity on the medial aspect of the biventral lobule ; (4)
flocculus, a minute lobule situated on the brachium pontis of the cerebellum
n:ront of, and partially overlapped by, the anterior border of the biventral
lo ile.
These lobules, with the corresponding portions of the vermis inferior, constitute
i lobes on the inferior surface of the cerebellum. Still, it should be noted that,
it as in the case of the superior surface of the organ, this subdivision is to some
t artificial, and is not in every particular provided with a sound morphological
The tuber vermis (usually not definitely marked off from the declive) forms
'h most posterior part of the vermis inferior, and is composed of several trans-
^eely arranged folia which, on either side, run directly into the postero-inferior
lot, le.
The postero-inferior lobule, which is wider towards the vallecula than it is more
576
THE NEEVOUS SYSTEM.
laterally, is traversed by two or it may be three curved fissures. The most anterior
of these cuts off a narrow, curved strip of cerebellar surface, which presents a more
or less uniform width throughout its whole length. This is the so-called lobulus
gracilis.
The pyramid is connected with the biventral lobule on each side by an elevated
ridge which crosses the sulcus valleculae. The term lobus pyramidis is applied to
the three lobules, which are thus associated with each other.
The uvula is a triangular elevation of the vermis inferior. It lies between the
two tonsils, and is connected with each of these by a low-lying band-like ridge
of gray matter scored by a few shallow furrows, and in consequence termed the
furrowed band. The two tonsils and the uvula form the lobus uvulae.
.Central lobule Anterior medullary velum
Brachiuru coniunctivum ' Ala lobuh cen
Brachium pontis^
Fourth ventricle
Uvula-
Horizontal fissui
Postero-inferior lobule
Postero-inferior lobule
Lobulus gracilis
Biventral lobute
Pyramid Tuber vermis
FIG. 510. INFERIOR SURFACE OF THE CEREBELLUM.
The right tonsil has been removed so as to display more fully the 'posterior medullary velum and
the furrowed band.
The nodule and the flocculus of each side are linked by a delicate connect-
ing lamina which is formed by the posterior medullary velum.
THE STRUCTURE AND CONNEXIONS OF THE CEREBELLUM.
Arrangement of the Gray and White Matter of the Cerebellum. The white
matter of the cerebellum forms a solid compact mass in the interior, and over
this is spread a continuous and uniform layer of gray matter. In each hemi-
sphere the white central core is more bulky than in the vermis, in which tl
central white matter is reduced to a relatively thin bridge thrown aci
between the two hemispheres. When sagittal sections are made through the
cerebellum, the gray matter on the surface stands out clearly from the white
matter in the interior. Further, from all parts of the surface of the central core
stout stems of white matter are seen projecting into the lobes of the cerebellum.
From the sides of these white stems secondary branches proceed at various angles,
and from these again tertiary branches are given off. Over the various lamellae
of white matter thus formed the gray cortex is spread, and the fissures on the
surface show a corresponding arrangement, dividing up the organ into lobes,
lobules, and folia. When the cerebellum is divided at right angles to the general
direction of its fissures and folia, a highly arborescent appearance is thus presented
by the cut surface. To this the term arbor vitae is applied.
Nucleus Dentatus and other Gray Nuclei in the White Matter of the
Cerebellum. Embedded in the midst of the mass of white matter which forms the
central core of each hemisphere there is an isolated nucleus of gray matter, which
presents a strong resemblance to the inferior olivary nucleus of the medulla.
It is called the nucleus dentatus, and it consists of a corrugated or plicated lamina
THE STEUCTUEE AND CONNEXIONS OF THE CEEEBELLUM. 577
Culmen
of gray matter, which is folded on itself so as to enclose, in a flask-like manner,
a portion of the central white matter (Figs. 511 and 512). This gray capsule
is not completely closed. It presents an open mouth, termed the hilum, which
is directed medially and upwards, and out of this stream the fibres of the
brachium con-
junctivum.
Three small ad-
ditional masses of
gray matter are also
present on each side
of the median plane
in the central white
matter of the cere-
bellum. These are
termed the nucleus
emboliformis, the
nucleus globosus,
and the nucleus
fastigii. The nu-
cleus emboliformis
or embolus is a small
lamina of gray
matter which lies
just medial to the
hilum of the nucleus
dentatus, being thus
related to it some-
inferior olivary nucleus
FIG. 511. SAGITTAL SECTION THROUGH THE LEFT HEMISPHERE
OP THE CEREBELLUM.'
Showing the "arbor vitse" and the nucleus dentatus.
what in the same manner that the medial accessory olivary nucleus is related to the main
inferior olivary nucleus. The nucleus globosus lies medial to the nucleus emboliformis and on a
somewhat deeper horizontal plane. The nucleus fastigii or roof nucleus is placed in the white
substance of the vermis close to the median plane and its fellow of the opposite side. It is,
"lerefore, situated on the medial aspect of the nucleus globosus.
mrm
!
Stria terminalis
Pulvinar of the thalamus
Inferior colliculus
Brachium pontis
j~ Third ventricle
i-Si Tsenia thalami
\ ,
a,----Trigonum habenulse
_ . Pineal body
- Superior colliculus
Inferior brachium
Trochlear nerve
- Velum medullare anterius
- Brachium conjunctivum
Nucleus dentatus
512. From a dissection by Dr. Edward B. Jamieson in the Anatomical Department of the University of
Edinburgh. The nucleus dentatus is displayed from above and the), brachium conjunctivum has
been traced from it to the mesencephalon.
The nucleus dentatus and the emboliform nucleus present a structure very similar to that of
the inferior olivary nucleus. In the nucleus globosus and the nucleus fastigii the cells are some-
what larger in size.
Cerebellar Peduncles. These are three in number on each
side, viz.,
38
the
578 THE NERVOUS SYSTEM.
middle, the inferior, and the superior (Fig. 519, p. 585). The fibres of which
they are composed all enter or emerge from the white medullary centre of the
cerebellum.
The middle peduncle or brachium pontis is much the largest of the three,
and has already been described on pp. 565 and 566. It is formed by the
transverse fibres of the pons, and it enters the cerebellar hemisphere on the
lateral aspect of the other two peduncles. The lips of the anterior part of the
horizontal fissure are separated widely from each other to give it admission
(Fig. 510). Within the cerebellar hemisphere its fibres are distributed in two
great bundles. Of these, one, composed of the superior transverse fibres of the pons,
radiates out in the inferior part of the hemisphere ; whilst the other, consisting of
the inferior transverse fibres of the pons, spreads out in the superior part of the
hemisphere.
The inferior peduncle is simply the restiform body of the medulla oblongata.
After leaving the medulla oblongata it ascends for a short distance on the dorsal
surface of the pons and then turns sharply backwards, to enter the cerebellum
between the other two peduncles.
The superior peduncle or brachium conjunctivum, as it issues from the cerebellum,
lies close to the medial side of the middle peduncle (Fig. 512). Its further course
upwards on the dorsum of the pons to the inferior quadrigeminal body has been
previously described (pp. 548 and 569).
Connexions established by the Peduncular Fibres. The fibres of the brachium
pontis represent the second stage of the connexion between the cerebral hemisphere
of one side and the opposite cerebellar hemisphere. The connexions which they establish
in the pons are described on p. 566.
The restiform body is also composed of afferent fibres (see p. 563) ; only the more
important connexions which these establish in the cerebellum can be touched on here.
The principal afferent strand is the fasciculus spinocerebellaris [posterior]. The fibres of
this strand end in the cortex of the superior vermis on both sides of the median plane, but
chiefly on the opposite side. The olivo-cerebellar tract (fasciculus olivocerebellaris) are also
afferent. It appears that they end in connexion with cells in the cortex of both the
vermis and hemisphere, and also with cells in the nucleus dentatus. The numerous
external arcuate fibres which enter the restiform body establish connexions with cells in
the cortex of the hemisphere and of the vermis.
The brachium conjunctivum is an efferent tract : its fibres come from the cells of the
nucleus dentatus, and pass to the red nucleus and thalamus of the opposite side.
According to Ramon y Cajal collateral branches springing from these fibres descend to
the motor nuclei in the medulla oblongata and spinal medulla.
There is, however, a bundle of fibres passing downwards alongside the brachium
conjunctivum from the tegmentuin of the mesencephalon and possibly from the
thalamus : these fibres cross in the mid-brain and pass inferiorly to the cerebellum,
in contact with the lateral margin of (or intermingled with) the fibres of the
brachium. They probably convey to the cerebellum fibres from the visual centres
of the opposite side.
The fasciculus anterolateralis superficialis of the spinal medulla (O.T. Gowers' tract),
for which the better name fasciculus spinocerebellaris anterior is now in common use, also
enters the cerebellum alongside the emerging brachium conjunctivum. It has been
noticed in connexion with the lateral funiculus of the spinal medulla (p. 537). The
fibres which compose it are carried upwards through the formatio reticularis grisea of
the medulla oblongata and the corresponding part of the tegmental portion of the pons.
In this part of its course the fibres are scattered and do not form a compact strand.
Reaching the superior end of the pons the tract turns backwards across the brachium
conjunctivum, enters the anterior medullary velum, and proceeds downwards in it into
the cerebellum.
Roof of the Fourth Ventricle. In its superior part the roof of the fourth
ventricle is formed by the anterior medullary velum as it stretches across between
the two brachia conjunctiva, and also, to some extent, by these brachia themselves
as they approach the mesencephalon.
HISTOGENESIS AND MINUTE STEUCTUKE OF CEEEBELLUM. 579
Fiss.secunda.
Fiss. suprapyramidalis.
,' Fiss. prima.
Lobus
lareralis.
In its inferior part the roof of the ventricle is exceedingly thin and is not all
formed of nervous matter. The posterior medullary velum is a mere ridge which
can hardly be said to enter into its formation : the epithelial lining of the cavity,
supported by pia mater, is carried downwards towards the inferior boundaries of
the floor of the ventricle. At the lowest
part of the calamus scriptorius, and also
along each lateral boundary of the floor,
the epithelial roof becomes thickened
at its attachment to the parts of the
medulla oblongata. The small semilunar
lamina which stretches across between
the inferior parts of the two clavse at
the calamus scriptorius and overhangs
the opening of the central canal is
termed the obex (Fig. 482, p. 550). A
downwardly directed protrusion of the
epithelial roof is often found behind
the obex.
Velum
medullare.
posl-erius./
/.Parafloc.
'Floe.
Recessus
lareralis
venh.quarrt.
Tuberculum acushcum.
Medulla oblongara.
Modulus. Obex. Taenia ventriculi quarH.
FIG. 513. THE POSTERIOR ASPECT OF A FCETAL
CEREBELLUM AND MEDULLA OBLONGATA.
THE HlSTOGENESIS AND MlNUTE STRUCTURE OF THE CEREBELLUM.
The developmental history of the cerebellum presents certain peculiar features
which seem quite enigmatic unless considered from the point of view of the evolu-
tion of the connexions and functions of the organ. The cerebellum is derived from
part of the alar lamina of the rhombencephalon, and at an early stage of its develop-
ment the rudiment shows the regular lamination into ependyma, mantle layer, and
marginal layer, which has already been de-
scribed as distinctive of the corresponding
place of development in the whole nervous
system. The cells of this mantle layer are to
be looked upon as an outlying (superior) part
of the receptive nucleus , of the vestibular
nerve, the cells to which information con-
cerning the position and movements of the
body as a whole or of the head will be trans-
mitted from the semicircular ducts of the
internal ear. But, if such information is to
be put to any use in influencing behaviour, it
is obvious that the activity of these cerebellar
'ff**J I 1 ffl ^oT \\l '/ I / ce ^ s mus ^' fi rs kty > be correlated with visual
!//*) fe *jO I \ -^L impassions, which also supply information
*"x/VrW >J?vlA/ ^ concerning the position and movements of the
*X/y Jn^ Small cell of the molecular layer.
the cells of Purkinje and GR. Granule cell.
entering into contact associ- GrR 1 . Axons of granule cells in molecular layer cut transversely.
ation with them. When it M '- Basket-cells
:- j J.L A At, ZK. Basket-work around the cells of Purkinje.
i borne in mind that the GL Neuroglial cell>
number of granule cells N. Axon of an association cell.
is very great, and that
each sends an axon into the molecular layer, the important part which these fibres,
with their longitudinal branches, take in building up the molecular layer will be under-
stood. They are found pervading its entire thickness from the surface down to the
bodies of the cells of Purkinje.
THE MESENCEPHALON.
e mesencephalon or mid-brain is the short, narrow part of the brain-stem
which occupies the aperture of the tentorium cerebelli (incisura tentorii), and
connects the cerebrum, which lies above, with the parts which occupy the posterior
cranial fossa. It is about three-quarters of an inch in length, and it consists of a
dorsal part, composed of the corpora quadrigemina, and a much larger ventral part,
which is formed by the two pedunculi cerebri.
The pedunculi cerebri can be seen to some extent on the base of the brain,
where they bound the posterior part of the interpeduncular fossa. Encircling the
upper end of each cerebral peduncle, where it emerges from the cerebrum, is the
optic tract (Fig. 527, p. 594).
The mesencephalon is tunnelled from below upwards by a narrow passage,
called the aquseductus cerebri, which connects the fourth ventricle with the third
386
582
THE NEKVOUS SYSTEM.
ventricle (Fig. 519, p. 585). This channel lies much nearer the dorsal aspect than
the ventral aspect of the mesencephalon.
Corpora Quadrigemina. This name is applied to four rounded eminences or
colliculi on the dorsal aspect of the mesencephalon (Figs. 516 and 517). The
superior pair are larger and broader than the inferior pair, but they are not so
well denned nor are they so prominent. A longitudinal and a transverse groove
separate the colliculi from each other. The longitudinal groove occupies the median
plane and extends upwards to the posterior commissure of the brain. The superior
end of this groove widens out into a shallow depression, in which the pineal body,
a small conical structure which belongs to the diencephalon, rests. From the lower
end of the same groove a short but well-defined and projecting band, the frenulum
veli, passes to the
Non-ventricular
part of thalamus
Groove
corresponding
to for nix
Quadrigeminal
bodies
Trochlear nerv
Brachium
pontis
Brachium
conjunctivum
Lingula
Medulla
oblongata
Genu of corpus
callosum
Corpus callosum
(cut)
Cavum septi
pellucidi
Septum pellucidum
Caudate nucleus
Fornix
Foramen inter-
ventriculare
Anterior commissure ,
Anterior tubercle Separates
of thalamus
Massa intermedia
Third ventricle
FIG. 516. THE CORPORA QUADRIGEMINA AND THE NEIGHBOURING PARTS.
anterior medul-
lary velum,
which lies im-
mediately below
the inferior col-
liculi. The
transverse groove
curves round be-
low each of the
superior pair of
colliculi and
them
from the inferior
pair. It is also
continued in
an upward and
ventral direction
the lateral
aspect of the
stalk of pineal body mesencephalon.
The quadri-
geminal bodies
are not marked
off laterally from
the sides of the
mesencephalon,
but each has in
connexion with
it, on this aspect,
a prominent
strand, which is
Stria terminalis
Tsenia thalami
Trigonum habenulse On
Posterior
commissure
Pulvinar
Pineal body
prolonged superiorly and ventrally towards the thalamic region. These strands
are called the brachia of the corpora CLuadrigemina, and they are separated from
each other by a continuation, on the side of the mesencephalon, of the transverse
groove which intervenes between the two pairs of colliculi.
The corpus geniculatum mediale is closely associated with the brachia, although
it does not form part of the mesencephalon, but belongs to the prosencephalon.
It is a small, sharply defined oval eminence, which lies on the lateral side of the
superior part of the mesencephalon under shelter of the posterior end of the thalamus.
The brachmm CLuadrigeminum informs, proceeding upwards from the colliculus
inferior, advances towards the corpus geniculatum mediale and disappears from
view under cover of this prominence.
The brachium quadrigeminum superius is carried upwards and ventrally between
the overhanging thalamus and the corpus geniculatum mediale. A superficial
examination of the mesencephalon is sufficient to show that, while a large part
of this strand enters the corpus geniculatum laterale, a considerable portion is a
continuation of the lateral root of the optic tract.
THE MESENCEPHALON.
583
Pedunculi Cerebri. The cerebral peduncles (Figs. 517 and 527) appear upon
the ventral or basal aspect of the mesencephalon as two large rope-like strands
which emerge from the cerebral hemispheres and disappear below by plunging
into the pars basilaris of the pons. At the place where each peduncle emerges
from the corresponding side of the cerebrum it is encircled by the optic tract.
Each pedunculus cerebri is composed of two parts, viz., a dorsal tegmentaL part
(tegmentum), which is prolonged upwards into the region below the thalamus
(hypothalamus), and a ventral portion (basis pedunculi), which, when traced
upwards into the cerebrum, is seen to take up a position on the lateral side of
Nucleus lentiformis
Capsula interna (pars lenticulo-thalamica)
Nucleus caudatus
Capsula interna
(pars lenticulo-v
caudata)
Union of
lentiform and
caudate nuclei
Tractub
olfactorius
Tractus opticus^''
Infundibulum
Hypophysis [anterior lobe "
cerebri ^posterior lobe
Tuber cinereum ' ,.
Corpus mainillare /
Nervus oculomotorius (
Basis pedunculi''
Pons
Nervus trigeminus (portio major
Nervus trigeminus (portio minor)'' ^
Nervus facialis-
Nervus intermedius-
Nervus acusticus'' f
Nervus abducens ''
Nervus glossopharyngeus
Nervus vagus
Pyramis'"
' Oliva--''
Fasciculus circumolivaris pyramidis
Nucleus amygdalae (cut)
/
Commissura anterior
Stria terminalis
Capsula interna (pars sublenticularis)
Nucleus caudatus
Thalamus
Corpus geniculatum laterale
Corpus pineale
^Corpus geniculatum mediale
Colliculus superior
Brachium quadrigeminum
inferius
Colliculus inferior
Lemniscus lateralis
Nervus trochlearis
- -Brachium conjunctivum
Brachium pontis
-Fossa flocculi
_.Crus flocculi
Nucleus dentatus
cerebelli
Corpus ponto-bulbare
Fasciculus spinocerebellaris
posterior
Nervus spinalis
FIG. 517. THE LEFT LATERAL ASPECT OF THE BRAIN-STEM AFTER THE CEREBRAL HEMISPHERE
PT THE CORPUS STRIATUM) AND THE CEREBELLUM (EXCEPT THE NUCLEUS DENTATUS) HAVE BEEN REMOVED.
the thalamus and to be continuous with the internal capsule of the brain ; and an
. intermediate part, the substantia nigra. When the base of the brain is examined,
'. it is the basis pedunculi which is seen, and it is observed to be white in colour and
streaked in the longitudinal direction. In the tegmentum the longitudinally-
, arranged fibres are, in large part, corticipetal, or, in other words, fibres which are
ascending towards the cortex of the cerebrum ; the basis pedunculi, on the other
, hand, is composed entirely of longitudinal strands of fibres which are corticifugal,
or fibres which descend from the cerebral hemisphere.
On the surface of the mesencephalon the separation between the tegmental and
basal portions of the pedunculus cerebri is clearly indicated by a medial and a
lateral groove. The medial furrow is the more distinct of the two. It looks
38 c
584 THE NEEVOUS SYSTEM.
into the interpeduncular fossa, and from it emerge the fila of the oculo-motor
nerve. It is termed, therefore, the sulcus n. oculomotor!!. The lateral groove, which
is placed on the lateral aspect of the mesencephalon, is called the sulcus lateralis
[mesencephali]. Its lower end becomes continuous with the furrow between the
brachium pontis and brachium conjunctivum of the cerebellum.
A close inspection of the lateral surface of the tegmental part of the pedunculi
cerebri, below the level of the brachia, will reveal some faintly-marked bundles
of fibres curving obliquely upwards and backwards to reach the inferior colliculus
(Fig. 517, p. 583). These are fibres of the lateral lemniscus, coming to the surface
at the sulcus lateralis and sweeping over the subjacent brachium conjunctivum to
gain the inferior colliculus, inferior brachium, and medial geniculate body.
INTERNAL STRUCTURE OF THE MESENCEPHALON.
"When transverse sections are made through the mesencephalon the aquseductus
cerebri is seen to be surrounded by a thick layer of gray matter, which receives the
name of the stratum griseum centrale or the central gray matter of the aqueduct. On
the dorsal aspect of this gray matter the corpora quadrigemina form a layer which
separates it from the surface, and
to which the term, lamina, quadri-
gemina is applied. On the anterior
and lateral aspects of the central
gray mattQT are the tegmental por-
LATERAL. fr^ Q f ^ Cerebrai pgdundCS J
whilst, intervening between each of
the tegmenta and the corresponding
basis pedunculi, there is a conspicu-
ous mass of dark pigmented matter,
termed the substantia nigra.
OCULOMOTOR Aquaeductus Cerebri and
Stratum Griseum Centrale. The
FIG. 518. DIAGRAMMATIC VIEW OF THE CUT SURFACE OF aqueduct is the canal which leads
A TRANSVERSE SECTION THROUGH THE SUPERIOR PART f ^. n ,1 *. i i ,
OF THE MESENCEPHALON. from the f urth ventricle below, up-
wards through the mesencephalon,
to the third ventricle above. It is not quite three-quarters of an inch in length,
and it lies much nearer the dorsal than the ventral surface of the mesencephalon.
When examined in transverse section, it presents a triangular outline as it passes
into the fourth ventricle and a T-shaped outline close to the third ventricle. In
the intermediate part of its course it assumes different outlines, and not always
the same form at the same level in different specimens.
The aqueduct is lined with ciliated epithelium, and outside this is the thick layer
of central gray matter, which is directly continuous below with the gray matter
spread out on the floor of the fourth ventricle, and above with gray matter on
the floor and sides of the third ventricle. Scattered more or less irregularly
throughout the central gray matter are numerous nerve-cells of varying forms and
sizes, whilst in addition to these there are three definite collections or clusters of-
cells, which constitute the nuclei of origin of the trochlear nerve, the oculomotor
nerve, and the mesencephalic root of the trigeminal nerve. The position and
relations of these will be given at a later stage.
Substantia Nigra. When seen in transverse section, the substantia nigra
presents a semilunar outline. It consists of a mass of gray matter, in the midst of j
which are large numbers of deeply pigmented nerve-cells. It is only when this
substance is examined in bulk that it appears dark; in thin sections it does not-/
differ much in colour from ordinary gray matter, although, under the microscope, jj
the brown -coloured cells stand out very conspicuously, even under low powers.-
The substantia nigra is disposed in the form of a thick layer, interposed between?
the tegmental and basal portions of the cerebral peduncle." It begins below at
the superior border of the pons and extends upwards into the hypothalamus
The margins of this layer of dark-coloured substance come to the surface at the*'
INTEENAL STEUCTUEE OF THE MESENCEPHALON.
585
oculomotor and the lateral sulci of the mesencephalon, and its medial part is
traversed by the emerging fila of the oculomotor nerve. It is not equally
thick throughout. Towards the lateral sulcus it becomes thin, whilst it thickens
considerably near the medial aspect of the pedunculus cerebri. The surface of the
substantia nigra, which is turned towards the tegmentum, is concave and uniform ;
the opposite surface is convex and rendered irregular by the presence of numerous
slender prolongations of the substance into the basis pedunculi.
The morphological and physiological significance of the substantia nigra is not
fully understood, and the connexions established by its cells are imperfectly known.
Bechterew, however, is of the opinion that fibres arising in the motor area of the
cerebral cortex end in relationship with the cells of the substantia nigra, the
axons of which proceed to the motor trigeminal nucleus for the purpose of co-
ordinating the muscles of mastication.
Colliculi Inferiores (or inferior quadrigeminal bodies). Each inferior colliculus
Sulcus cinguli
Gyrus cinguli j
Commissura fornicis
Corpus fornicis
Corpus callosum .'
Septum pellucidum l^^|
Sulcus cinguli x*"*i
Paracentral area
Paracentral sulcus
Sulcus centralis
Hippocampal rudiment
Incisura sulci cinguli
Gyrus frontalis superior
Lamina chorioidea
Olfactory
Corpus paraterminale'' /'
Columna fornicis /'
Olfactory tract
Stria olfactoria lateralis
Nucleus amygdai
Piriform area
Thalamus (cut surface)
Khlnal fissure
Cauda fasciae dentatse
Hippocampus
'Sulcus praecunei
Prsecuneus
^...Sulcus subparietalis
Fossa parieto-
--occipitalis
Sulcus paramedialis
-Area striata
Sulcus
sagittalis cunei
Sulcus
retrocalcarinus
-Area striata
Sulcus polaris inferior
Sulcus calcarinus
Sulcus sagittalis gyri lingualis
\ \ \ Sulcus collateralis
\ I Hippocampus
! Splenium of corpus callosum
Fascia dentata
Crus fornicis
Gyrus paradentatus
mbria
I i
Fimb
FIG. 519. THE MEDIAL ASPECT OF THE RIGHT HALF OF THE BRAIN EXPOSED BY A MEDIAN SAGITTAL SECTION.
is composed largely of a mass of gray matter which, in transverse section, presents
; an oval outline (Fig. 520, p. 587). This central nucleus is, to a large extent,
encapsulated by white matter. Numerous cells of various sizes are scattered
throughout it, and the whole mass is pervaded by an intricate interlacement of
fine fibres, which are derived, to a large extent, from the lateral lemniscus.
In transverse sections through this region, the lateral lemniscus is seen to abut
( against the lateral margin of the central nucleus. Many of the fibres of this tract
enter it at once and become dispersed amongst its cells ; others sweep over its
dorsal surface, so as to give it a superficial covering ; whilst a third group is carried
medially, in the form of a thin layer, on its ventral aspect, so as to mark it off from
the subjacent central gray matter of the aqueduct (Fig. 520, p. 587). In this
: manner, therefore, the inferior colliculus becomes partially circumscribed by the
fibres of the lateral lemniscus. Several of the lateral lemniscus fibres, which
proceed over the superficial or dorsal aspect of the nucleus, reach the median plane
and form a loose decussation with the corresponding fibres of the opposite side.
The intimate connexion which is thus exhibited between the fibres of the lateral lemniscus
586 THE NERVOUS SYSTEM.
and the nucleus of the inferior colliculus is very significant. The lateral lemniscus, to a large
extent, comes from the nuclei of termination of the cochlear nerve of the opposite side. We
must associate, therefore, the inferior colliculus, and also the corpus geniculatum mediale, which
likewise receives fibres from the lateral lemniscus, with the organ of hearing.
This view regarding the inferior colliculi is supported both by experimental and by morpho-
logical evidence. Speaking broadly, it may be stated that the inferior colliculi become prominent
only in mammals, and then they are invariably correlated with a spirally wound, and well-
developed cochlea. That they have nothing to do with sight is shown by the fact that, when the
eye-balls are extirpated in a young animal, the inferior colliculi remain unaffected, whilst the
superior colliculi after a time atrophy (Gudden). When, on the other hand, the cochlear
terminal nuclei are destroyed, fibres which have undergone atrophy may be followed to the
inferior colliculi of both sides, but particularly to that of the opposite side (Baginski, Bumm,
and Ferrier and Turner). A very considerable tract of ascending fibres takes origin within the
inferior colliculus and passes upwards, in the inferior brachium, into the tegmentum subjacent to
the medial geniculate body. Within the tegmentum they proceed up to the thalamus (Ferrier
and Turner).
Colliculi Superiores (or superior quadrigeminal bodies). The superior colli-
culus presents a more complicated structure (Fig. 521). Superficially, it is coated with
a very thin layer of white matter, which is termed the stratum zonale. Underneath
this there is a gray nucleus, called the stratum griseum, which, in transverse section,
exhibits a crescentic outline and rests in a cap- like manner upon the subjacent part
of the eminence. The succeeding two strata, which respectively receive the names
of stratum opticum and the stratum lemnisci, present this feature in common, that
they are composed of gray matter, traversed by numerous fibres. The source from
which the fibres are derived is different, however, in each case.
Nerve- fibres reach the superior colliculus through (1) the lemnisci and (2)
the superior brachium.
The fibres of the lemnisci constitute the stratum lemnisci. The superior brachium
contains fibres of two different kinds, viz., fibres from the optic tract and fibres from
the cortex of the occipital lobe of the cerebrum. By the former it is connected with
both retinae, and by the latter with the visual centre in the occipital region of the
cerebral cortex. The great majority of these fibres pass into the margin of the
colliculus superior and form a layer stratum opticum underneath the stratum
griseum, in which they ultimately terminate.
Tegmentum. The tegmentum of the pedunculus cerebri may be regarded as
the continuation upwards of the formatio reticularis of the medulla oblongata
and the dorsal or tegmental portion of the pons into the mesencephalon. It
consists, therefore, of fine bundles of longitudinal fibres intersected by arching fibres,
which take a transverse and curved course. The interstices between these nerve-
bundles is occupied by gray matter containing irregularly scattered nerve-cells. On
its dorsal aspect the tegmentum is continuous, at the side of the central gray matter,
with the bases of the corpora quadrigemina, whilst, ventrally, it is separated from
the basis pedunculi by the substantia nigra. The tegmenta of opposite sides are,
to some extent, marked off from each other in the median plane by a prolongation
upwards of the median raphe of the pons and medulla oblongata, although, in
the inferior part of the mesencephalon, this is much obscured by the decussation
of the brachia conjunctiva. The two longitudinal strands, termed the medial longi-
tudinal bundle and the medial lemniscus, are prolonged upwards throughout the
entire length of the mesencephalon ; and they present the same relations to the
tegmentum as in the inferior parts of the brain. The medial longitudinal fasci-
culus is placed in relation to its dorsal aspect, whilst the lemniscus is carried up
in its ventral part.
The tegmentum of the mesencephalon may be considered as presenting two
parts : viz., (1) an inferior part, which is placed subjacent to the inferior colliculi
and is largely occupied by the decussation of the brachia conjunctiva (Fig. 520);
and (2) a superior part, subjacent to the superior colliculi which is traversed by
the emerging bundles of the oculomotor nerve. The superior part contains a large
and striking nuclear mass, termed the nucleus ruber or the red tegmental nucleus
(Fig. 521). In the inferior part of the central gray matter of the mesencephalou
is the nucleus of the trochlear nerve; in the superior part, the nucleus of the
oculomotor nerve is situated.
INTERNAL STRUCTURE OF THE MESENCEPHALON. 587
Inferior colliculus
Mesencephalic root of
' trigeminal nerve
^/Nucleus of trochlear nerve
- Brachium inferius
J\ Medial longitudinal
bundle
Medial
lemniscus
Brachia Conjunctiva. As the brachia conjunctiva leave the pons and sink
into the tegmentum of
ithe mesencephalon, they
undergo a complete de-
cussation, subjacent to
i the inferior colliculi and
the central gray matter
(Figs. 520, 521, p. 587;
and 522, p. 588). In this
manner each brachium
is transferred from one
side, across the median
'plane, to the opposite
side. The decussation
is completed at the level
of the superior borders
of the inferior colliculi,
and then each brachium
proceeds upwards into
the superior part of the
tegmentum, where it en-
counters the red nucleus.
Into this a large propor-
tion of its fibres plunge,
and come to an end in
connexion with the
nuclear cells. Many of
the fibres, however, are FJG 52 o. TRANSVERSE SECTION THROUGH THE HUMAN MESENCEPHALON
carried around the nucleus AT THE LEVEL OF THE INFERIOR COLLICULUS.
so as to form for it a
iperior colliculus
Basis
pedunculi
Lateral geniculate '
body~~
Inferior brachium
Medial geniculate
body
Medial lemniscus
Basis pedunculi
Optic tract
Central gray matter
Aqueduct
Tegmentum
Nucleus of oculomotor
nerve
Medial longitudinal
bundle
Red nucleus
Fibres of brachium
conjunctivum
Oculomotor nerve
Substantia nigra
_ i-Corpus mamillare
i. 521. TRANSVERSE SECTION THROUGH THE HUMAN MESENCEPHALON AT THE LEVEL OF THE
SUPERIOR COLLICULUS.
588
THE NEKVOUS SYSTEM.
Decussating
fibres ~~
Inferior
colliculus
Mesencephalic
root of tri-
geminal nerve
Trochlear
nerve
Medial
longitudinal
bundle
Lateral
lemniscus
Decussating
brachia
conjunctiva
Medial
lemniscus
capsule, which is thicker on the medial than on the lateral side (Fig. 521). These
are prolonged into the thalamus, and end ultimately in connexion with the ventral
thalamic cells. The brachium conjunctivum is, therefore, a great efferent tract
which issues from the nucleus dentatus of the cerebellum, crosses the median plane
in the inferior part of the mesencephalon, and ends in the red nucleus and the
ventral part of the thalamus.
Nucleus Ruber. The red nucleus is a rounded nuclear mass, of a reddish tint
in the fresh brain, which lies in the superior part of the tegmentum, and in the
path of the brachium conjunctivum. In transverse section it presents a circular
outline. It begins at the level of the inferior border of the superior colliculus
and it extends upwards into the hypothalamus. At first it is small and is placed
at a little distance from the median plane ; but, as it proceeds upwards, it
increases in bulk and approaches more nearly to the median raphe, and to its
fellow of the opposite side. The
curved emerging bundles of the
oculomotor nerve pass through it
on their way to the surface. The
relation which the fibres of the
opposite brachium conjunctivum
present to it has been described.
These fibres traverse its inferior
part in such numbers that in
Weigert-Pal specimens it presents
a very dark colour ; but higher up,
as the fibres gradually end in
nuclear mass, they become less
numerous in its midst, and the
nucleus assumes a paler tint.
Numerous fibres which descend
from the cerebral cortex, and others
from the corpus striatum, enter the
red nucleus. It also sends out
FIG. 522. SECTION THROUGH THE INFERIOR COLLICULUS , , . , -,.
AND THE TEGMENTUM OF THE MESENCEPHALON BELOW "Dres which proceed in two direc-
THE LEVEL OF THE NUCLEUS OF THE TROCHLEAR tions : (1) upwards into the thala-
NERVE IN THE ORANG. (The decussation of the mus . ( 2 ) downwards to the spinal
bracnia conjunctiva and the course of the trochlear j 11 mi_ A.-L. ^ .ci_
nerve in the central gray matter are seen.) medulla. I he thalamic tlbres may
be regarded as carrying on the
continuity of the path of the brachium conjunctivum after its nodal interruption in
the red nucleus. The fibres to the spinal medulla, called the rubro-spinal tract
and first described by Monakow, cross to the opposite side and then descend in the
tegmentum to reach the lateral funiculus of the spinal medulla (Fig. 473, p. 534).
Fasciculus Longitudinalis Medialis. The medial longitudinal fasciculus is a
very conspicuous tract of longitudinal fibres which extends throughout the whole
length of the medulla oblongata, pons, and mesencephalon, in the formatio reti-
cularis or tegmental part of each. Below, at the level of the decussation of the
pyramids, it becomes continuous with the fasciculus anterior proprius of the spinal
medulla (p. 562), whilst, by its opposite or superior end, it establishes intricate
connexions in the region immediately above the mesencephalon. Throughout its
whole length it lies close to the median plane and its. fellow of the opposite side.
In the mesencephalon it is applied to the ventral aspect of the central gray
matter, whilst in the pons and medulla oblongata it is situated immediately
subjacent to the gray matter of the floor of the fourth ventricle. One of its
most salient features is the intimate association which it presents with the three
motor nuclei from which the nerves for the supply of the muscles of the eyeball
take origin, viz., the oculomotor nucleus, the trochlear nucleus, and the abducent
nucleus. The first two of these are closely applied to its medial and dorsal aspect,
whilst the abducent nucleus is placed on its lateral side. Into each of these nuclei
it sends many collaterals, and probably also some of its constituent fibres, and these
end around the nuclear cells. It would appear, therefore, that one of the most
INTEENAL STEUCTUEE OF THE MESENCEPHALON.
589
Decussating
fibres
Nucleus of
inferior
colliculus
Mesencephalic
root of tri-
geminal nerve
Trochlear
nerve
Medial
longitudinal
bundle
Lateral
lemniscus
Brachium
conjunctivum
Medial
lemniscus
portant functions of this strand is to bind together these nuclei, and thus enable
m to act in harmony one with the other. Fibres also enter the medial
gitudinal fasciculus from the vestibular nucleus of the acoustic nerve system,
e results obtained by degeneration would seem to indicate that, to a large
tent, it is formed of fibres which run a short course within it.
It is evident that it is a brain tract of high importance, from the fact that it
a present in all vertebrates, and, further, that its fibres assume their medullary
Deaths at an extremely early period. In fishes, amphibians, and reptiles, it is one
the largest bundles of the medulla oblongata. In man, its fibres medullate
>etween the sixth and seventh months of foetal life, and at the same time as
,he fibres of the fasciculus anterior proprius of the spinal medulla, with which
t stands in connexion.
According to van Gehuchten and Edinger, it extends upwards beyond the
evel of the oculomotor nucleus,
.nd in the thalamic region its
ibres take origin from a special
mcleus of its own in the gray
natter of the third ventricle, im-
nediately behind the level of the
;orpora mamillaria. Fibres also
mter the medial longitudinal
)undle from a nucleus common to
t and the posterior commissure of
;he brain. This nucleus is placed
n the anterior part of the central
*ray matter of the mid-brain. Held
isserts that numerous fibres, aris-
ng from cells in the superior col-
iculus, curve in an arcuate manner
n the tegmentum outside the cen-
tral gray matter, to take part on
:he ventral aspect of this in what
S called the fountain decussation Fia -523. SECTION THROUGH THE INFERIOR COLLICULUS
. , AND THE TEGMENTUM OF THE MESENCEPHALON, AT A
teaching the opposite Side, these SLIGHTLY LOWER LEVEL THAN FIG. 522.
ibres turn downwards and join the
nedial longitudinal bundle. The same authority considers that fibres from the
central part of the posterior commissure can also be traced downwards into the
medial longitudinal bundle. Edinger, on the other hand, places these fibres as
: i distinct tract on the ventral and lateral aspect of the medial longitudinal bundle,
although in apposition with it.
Mendel believed that fibres from the oculomotor nucleus are carried down in
the medial longitudinal bundle, and, from this, into the facial nerve for the supply
of the orbicularis oculi and the corrugator supercilii, bringing these muscles,
therefore, under the control of the same nucleus as the levator palpebrse superioris
muscle. This view was adopted by many clinicians because this upper group of
facial muscles is often spared in cases of facial paralysis ; but Harman has adduced
reasons in support of the view that there is a superior prolongation of the facial
1 nucleus which innervates these muscles. It has been suggested further that fibres
from the hypoglossal nucleus may, by the medial longitudinal bundle, reach the
facial nerve, and through it the orbicularis oris. In this manner the same nucleus
would hold sway over the tongue and the sphincter muscle of the lips. The close
relation which exists between the ascending part of the intrapontine portion of
the facial nerve and the medial longitudinal bundle would render the passage of
fibres from one to the other a circumstance which could easily be understood.
But the balance of evidence now available inclines us to regard the facial nucleus
as the origin of the fibres innervating all the facial muscles. Another interchange
of fibres through the medial longitudinal bundle has been described by Duval and
Laborde. According to these authorities, fibres from the abducens nucleus ascend
in the medial longitudinal bundle into the mesencephalon, and establish connexions
590
THE NEEVOUS SYSTEM.
with that part of the oculomotor nucleus from which the nerve for the medial
rectus of the opposite side derives its fibres. If this view is correct, it affords
a ready and simple anatomical explanation of the harmonious action of the
lateral and medial recti muscles in producing movements of the two eyeballs
simultaneously to the right and to the left. From the investigations of E. H.
Fraser it would appear that no fibres from the abducens nucleus go directly into
the oculomotor nerve. The same observer has shown that many fibres from
Deiters' nucleus, a part of the vestibular nucleus of the acoustic nerve to be
described later in this account, enter the oculomotor and the trochlear nuclei
through the path afforded by the medial longitudinal bundle.
Optic tract
Posterior commissure
Nucleus
hypoglossi
Nucleus
gracilis
Anterior
column of
spinal
medulla
FIG. 524. DIAGRAM REPRESENTING SOME OF
THE CONSTITUENT ELEMENTS OF THE
FASCICULUS LONGITUDINALIS MEDIALIS.
FIG. 525. DIAGRAM OF THE CONNEXIONS (
THE MEDIAL LEMNISCDS AND ALSO OF CER
TAIN OF THE THALAMO-CORTICAL FIBRES.
Lemniscus Lateralis. The lateral lemniscus is a definite tract of longitudinal
fibres, which extends upwards through the lateral part of the tegmental substance
of the superior portion of the pons and the mesencephalon. It is formed by the
fibres of the corpus trapezoideum and striae medullares in the inferior part of the
pons, turning abruptly upwards and taking a course towards the quadrigemina]
region. But the details of the arrangement and connexions of this important
fasciculus must be left for fuller consideration when we are discussing the central
connexions of the acoustic nerve.
Lemniscus Medialis. The medial lemniscus has already been followed through
the medulla oblongata and pons, and its position in each of these portions of the
brain-stem has been defined (pp. 561 and 562). In the tegmentum of the inferioi
part of the mesencephalon it is carried up in the form of a more or less flattened
INTEKNAL STKUCTUEE OF THE MESENCEPHALON. 591
und on the ventral aspect of the decussating brachia conjunctiva. To its lateral
lie, and forming an angle with it (as seen in transverse section), is the lateral
irnniscus (Figs. 522 and 523), and at this level there is no clear demarcation
i jtween these two tracts. In the superior part of the mesencephalon the appearance
1 the red nucleus in the tegmentum causes the medial lemniscus to take up a
Lore lateral and dorsal position, so that it now comes to lie subjacent to the
;>rpus geniculatum mediale (Fig. 521, p. 587). At this level it exhibits a crescentic
itline in transverse section, and the lateral lemniscus has to a large extent dis-
jpeared from its lateral side.
A part of the medial lemniscus, which is called the fasciculus bulbothalamicus,
:,kes origin in the inferior part of the medulla oblongata from the gracile and
meate nuclei of the opposite side (p. 560). Seeing that the posterior funiculus of
le spinal medulla ends in these nuclei, the medial lemniscus may be considered
continue that funiculus upwards into the brain. Other fibres arise from the
irminal nuclei of the various sensory cerebral nerves of the opposite side. The
jst of the tract consists of the superior part of the fasciculus spinothalamicus
om the spinal medulla. In the mesencephalon a considerable contribution of.
;bres is given by the medial lemniscus to the superior colliculus, and then the
ismainder of the tract proceeds into the lateral (ventro-lateral) nucleus of the
lalamus. Here its fibres end amidst the thalamic cells.
Ganglion Interpedunculare and Fasciculus Retroflexus. Immediately
Dove the pons a small collection of nerve-cells is found in the median plane,
edged in between the two cerebral peduncles. It is all that is found in the
iiman brain to represent a large nucleus projecting into the interpeduncular
>ssa in most other animals, especially those with a highly developed sense of
nell. In this interpeduncular ganglion ends the fasciculus retroflexus, a tract of
bres which comes from the nucleus habenulse of the epithalamus. We shall
;turn to the consideration of this tract later.
Fountain Decussation. If the region ventral to the medial longitudinal
undies is examined in the superior part of the mesencephalon a very close decussa-
.on of fibres in the median plane will be observed in the interval between the two
id nuclei. This is the " fountain decussation." According to Held, the fibres
hich take part in the dorsal portion of the fountain decussation (decussation of
leynert) come from the superior colliculi, and, after they have gained the opposite
.de, they turn downwards in the medial longitudinal fasciculus.
Many of the fibres that cross in this decussation enter a descending tract
fasciculus tecto-bulbaris et spinalis) which connects the corpora quadrigemina with
tie motor nuclei on the other side of the medulla oblongata and spinal medulla.
Basis Pedunculi. The basis pedunculi presents a somewhat crescentic
utline when seen in transverse section, and it stands quite apart from its fellow
: f the opposite side. It is composed of a compact mass of longitudinally directed
bres, all of which, as Dejerine has shown, arise in the cortex of the cerebrum
nd pursue an unbroken corticifugal course into and through the pedunculus
erebri. These fibres may be classified into two distinct sets, viz., cerebro-pontine
nd pyramidal or cerebro-spinal.
The cerebro-pontine fibres possess this leading character : in their course down-
yards they are all arrested in the ventral part of 'the pons, and end amidst the
;ells of the nuclei pontis. These tracts would appear to hold a very definite
osition within the crus. Thus, it has been satisfactorily established that the
ibres coming from the temporal area of the cerebral cortex (temporo-pontine
trand) form the lateral fifth of the basis pedunculi, whilst those coming from
: he frontal area (fronto-pontine strand) hold a similar position in the medial part
>f the basis pedunculi.
The pyramidal fibres constitute the great motor tract from the cerebral cortex.
Chey occupy a position corresponding to the middle three-fifths of the basis.
Che pyramidal tract differs from the cerebro-pontine strands in being carried
lownwards through the ventral part of the pons and on the ventral aspect of the
.aedulla oblongata into the spinal medulla, which it enters in the form of the
'asciculi cerebrospinales lateralis and anterior. On its way through the pons and
592 THE NERVOUS SYSTEM.
medulla oblongata it sends fibres across the median plane to the various moto:
nuclei on the opposite side of those sections of the brain-stem.
DEVELOPMENT OF THE MESENCEPHALON.
Even in the early embryo the mesencephalon constitutes the smallest section of th<
brain-tube, although the disproportion in size between it and the other primitive sub
divisions of the brain is not nearly so marked as in the adult. Owing to the cephalii
flexure, the mid-brain for a time occupies the summit of the head. Later it become!
completely covered over by the expanding cerebral hemispheres.
The corpora quadrigemina are derived from the alar laminae of the side walls of th<
brain-tube, whilst the basal laminae thicken and ultimately form the tegmenta. Th<
original cavity of the mid-brain is retained as the aqueduct.
For a considerable time the cavity of the mesencephalon remains relatively large, anc
the lower part of its dorsal wall is carried downwards in the form of a diverticulum 0]
recess, which overlaps the cerebellar plate. About this time, also, the dorsal wall shows i
median fold or ridge. Both of these conditions are transitory. As the corpora quadri
gemina take shape, the median ridge disappears and is replaced by the median longitudina
groove, which separates the quadrigeminal bodies. Only its inferior part is retained, and thii
is represented by the frenulum veli of the adult brain. The diverticulum of the cavitj
gradually becomes reduced, and finally disappears as the aqueduct assumes form.
The precise mode of origin of the red nucleus is not known.
Later in this account reasons will be given for the belief that the representatives o
the neural crests in the region of the mesencephalon become absorbed and assimilatec
in the walls of the neural tube as it closes in.
THE DEEP CONNEXIONS OF THE CEREBRAL NERVES ATTACHED TO
THE MEDULLA OBLONGATA, PONS, AND MESENCEPHALON.
There are twelve pairs of cerebral nerves, of which the inferior eight are attached
to the medulla oblongata and pons. From above downwards these are named the
trigeminal (fifth), the abducens (sixth), the facial (seventh), the acoustic (eighth), the
glossopharyngeal (ninth), the vagus (tenth),. the accessory (eleventh), and the hypo-
glossal (twelfth). Two others, the trochlear (fourth) and oculomotor (third) spring
from the mesencephalon. The hypoglossal, the accessory, the greater part of the
facial, the abducens, the motor root of the trigeminal, the trochlear and the oculo-
motor are efferent nerves; the acoustic, the nervus intermedius (sensory root oi
the facial) and the sensory root of the trigeminal are purely afferent nerves ; whilst
the vagus and the glossopharyngeal are composed of both efferent and afferent fibres.
In all these cases (with a possible reservation in the case of part of the trigeminal)
afferent fibres arise from ganglionic cells placed outside the brain and penetrate the
brain-stem, to end in connexion with the cells of certain nuclei of termination.
Efferent fibres, on the other hand, take origin within the brain as the axons of
cells which are grouped together in certain places in the form of nuclei of origin.
Nuclei of Origin, or Motor Nuclei. In the spinal medulla the nuclei of
origin are represented by elongated columns of cells which run more or less con-
tinuously in the anterior column of gray matter of successive spinal segments, and
from these the series of efferent anterior nerve-roots take origin. In the medulla
oblongata, pons, and mesencephalon the nuclei of origin, or, in other words, the motor
nuclei of the individual nerves, become, for the most part, discontinuous, and are
represented by certain isolated clumps of compact gray matter, in which are placed
the clusters of cells from which the fibres of the efferent nerves arise. The nucleus
ambiguus, however, which consists of a column of cells from which root- fibres of the
bulbar part of the accessory, of the vagus, and also of the glossopharyngeal are
derived, is an exception to this rule. At the decussation of the pyramids, the anterioi
column of gray matter of the spinal medulla is broken up by the intercrossing bundle,'
into a detached head and a basal part which remains in relation with the ventro
lateral aspect of the central canal. Certain of the efferent nuclei of the medulk
oblongata, pons, and mesencephalon lie in the line of the basal portion of the anterio:
column of gray matter of the spinal medulla, and, thus, close to the median plane
These are termed medial somatic nuclei, and are met with at different levels in th<
THE DEEP CONNEXIONS OF THE CEEEBKAL NERVES. 593
)rain-stem. This group comprises the hypoglossal nucleus, the abducens nucleus and,
'.n the mesencephalon, the trochlear nucleus and part of the oculomotor nucleus.
3ther motor nuclei of origin are present in the form of isolated clumps or columns
)f gray matter, which lie at different levels in the medulla oblongata and pons
n a more lateral and deeper situation. They are the nucleus ambiguus of the
iccessory, vagus and glossopharyngeal, the facial nucleus, and the nucleus of
]he motor root of the trigeminal nerve. From their position in the substantia
>:eticularis of the medulla oblongata and pons they constitute a group to which the
' name of lateral somatic nuclei is applied.
In addition to these two columns of motor nuclei there is a third efferent
3olumn of splanchnic nuclei represented by the dorsal nucleus of the vagus and
glossopharyngeal nerves, and similar nuclei emitting sympathetic fibres into the
ROOF-PLATE
Splanchnic Terminal Nucleus.
' Gustatory Nucleus.
,Acoustico -Lateral
Terminal Nucleus.
Somatic Terminal
Nucleus.
JO, Ear Vesicle.
LAMINA]
BASALISJ
Rssf--
Striped
Muscle
Sympathetic Ganglion -
Sensory Ganglion.
Somatic ----j
Efferent Nuclcus/jjVj
Skin.
ranchial
trtped
udcle.
Visceral
Mucous Membrane.
526. DIAGRAM REPRESENTING THE DIFFERENT KINDS OF COMPONENTS FOUND IN THE CEREBRAL
NERVES AND OF THEIR NUCLEI OF ORIGIN OR TERMINATION.
facial and oculomotor nerves. It is possible some splanchnic efferent fibres may
pass into the trigeminal nerve.
The different nuclei of origin of the efferent fibres which belong to the various
( serebral nerves, both medial and lateral, are connected with the motor area of the
cerebral cortex by fibres of the cerebro-spinal tract of the other side, which enter
the nuclei and end in association with their cells.
Nuclei Terminales. The general scheme of arrangement of the terminal nuclei
.ias already been explained (Fig. 526); its details will be further elucidated as
'^he various nerves are considered seriatim.
The axons of many of the cells of the nuclei of termination enter the substantia
^'eticularis as arcuate fibres, and, crossing the median plane, are carried upwards
in the substantia reticularis of the opposite side, to establish direct connexions
,with the thalamus and, indirectly through it, with the cerebral cortex (Fig. 525).
Others pass to the nuclei of motor nerves, to the cerebellum or other groups of
j aerve-cells, to form connexions necessary for the performance of reflex actions.
39
594
THE NEKVOUS SYSTEM.
Nervus Hypoglossus. The nucleus of origin of the hypoglossal nerve, the
motor nerve of the tongue, lies in the substance of the medulla oblongata. It is
composed of several groups of large multipolar cells, which closely resemble the
cells in the anterior column of gray matter in the spinal medulla, and is
pervaded by an intricate network of fine fibrils. In form it is elongated aiw
rod-like, and in length it is about 18 mm. It extends from a point immediately
above the decussation of the pyramids up to the level of the striae medullares.
The inferior portion of the nucleus is thus placed in the closed part of the medulla
oblongata (Fig. 494, p. 561), whilst its superior part is situated in the open part
(Fig. 495, p. 561). The former lies in that part of the central gray matter which
is continuous with the basal part of the anterior column of gray matter of the
Optic nerve
Optic chiasma
Optic tract
Basislpedunculi cerebri^
xlnfundibulum (cut)
Tuber cinereum "-..
^Corpus mamillare
Substantia perforata posterior
Oculomotor nerve
'Trochlear nerve
Motor root of
trigeininal nerve\
Sensory root of^
trigeminal ~
V-3/
Fasciculus obliquus pontis ~~~jf, "TJf
Nervus intermedius "S.
Acoustic nerve 3
Flocculus cerebelli-
Chorioid plexus in the
apertura lateralis of-j*
the fourth ventricle ' '
Lateral recess of /*- ^f*
fourth ventricle
Facial nerve
'Acoustic nerve
" Nervus intermedius
Glossopharyngeal nerve
Vagus nerve
Olive
Pyramid'
Decussation of pyramidsr-~
Accessory nerve
Hypoglossal nerve
^Spinal root of accessory nerve
^First spinal nerve
FIG. 527.
-THE VENTRAL ASPECT OP THE MEDULLA OBLONGATA,: PONS, AND MESENCEPHALON,
showing the nerve roots.
spinal medulla. It is thus placed on the anterior and lateral aspect of the central
canal, close to the median plane and the corresponding nucleus of the opposite side.
The superior part of the nucleus occupies a position in the gray matter on the floor
of the fourth ventricle, subjacent to the medial part of the surface area, which has
been described under the name of the trigonum hypoglossi. Within the nucleus
the axons of the cells arrange themselves in converging bundles of fine fibres, which
come together and leave the ventral aspect of the nucleus as the fila radicularia of the
nerve. The nerve bundles thus formed traverse the entire antero-posterior thickness
of the medulla oblongata, between the substantia reticularis grisea and the substantia
reticularis alba, and emerge on the surface, in linear order, at the bottom of the
furrow between the olive and the pyramid. After they emerge these fibres collect
to form three definite bundles like the anterior nerve-roots of three spinal nervee
(Fig. 527). In the substance of the medulla oblongata the fila radicularia of the
THE DEEP CONNEXIONS OF THE CEEEBKAL NERVES. 595
hypoglossal pass between the main inferior olivary nucleus and the medial accessory
olivary nucleus, and many of them on their way to the surface pierce the ventral
lamina of the main olivary nucleus.
No decussation between the nerves of opposite sides takes place in the medulla
oblongata, but commissural fibres pass between the two nuclei (Kolliker). Further,
numerous fibres from the opposite pyramidal tract enter the nucleus and end in connexion
with its cells. The nucleus is thus brought into connexion with the motor area of the
opposite side of the cerebral cortex.
Nervus Accessorius. The accessory nerve also is a motor nerve, and it is
generally described as consisting of a spinal and a cerebral or accessory part.
The spinal part of the nerve emerges by a series of roots which issue from the
surface of the lateral column of the superior part of the spinal medulla as low down
as the fifth cervical nerve. These take origin in a column of cells situated in the
anterior column of gray matter of the spinal medulla, close to its lateral margin, and
Fasciculus gracilis Fasciculus cuneatus
_ >
ANT.K
FIG. 528. DIAGRAM OP THE SPINAL
ORIGIN OF THE ACCESSORY NERVE
(after Bruce).
Entering
posterior nerve
root
Substantia
gelatinosa
Emerging
filum of
accessory nerve
Fibres of spinal
rigin of
accessory
Emerging
,nterior nerve-
root
FIG. 529. SECTION THROUGH THE SUPERIOR PART OF THE
CERVICAL REGION OF THE SPINAL MEDULLA (Orang).
Showing the origin of the spinal part of the accessory nerve.
immediately behind the nerve-cells which give rise to the fibres of the anterior
roots of the upper five cervical nerves. The cells of the accessory nucleus are
large, multipolar, and in every respect similar to the motor cells of the spinal
nerves. The axons from these cells leave the dorsal aspect of the nucleus in
converging groups to form the fila radicularia or root-bundles of the nerve. These,
in the first place, proceed straight backwards in the anterior column of gray matter.
Reaching the bay between the two columns of gray matter, they turn sharply
laterally into the white matter and traverse the lateral funiculus to gain their
points of exit from the spinal medulla. At the decussation of the pyramids, fila,
which join the accessory nerve, are seen to proceed from the detached head of the
anterior column of gray matter.
The cerebral part of the accessory nerve has its nucleus of origin in the medulla
oblongata ; and its fila, as they proceed laterally from this, can be distinguished
by the fact that they pursue a course on the ventral side of the tractus spinalis
of the trigeminal nerve, whereas the vagus roots, with which they are apt to be
confused, pass through or lie on the dorsal aspect of the trigeminal root (Kolliker).
The nucleus of origin of the cerebral part of the accessory nerve is formed by the
same column of cells which constitutes the nucleus ambiguus, and which, at a higher
level, gives motor fibres to the vagus and glossopharyngeal nerves.
The part of the accessory nerve which takes origin in the spinal medulla supplies the
sterno-mastoid and trapezius muscles. The cerebral portion joins the vagus, and through the
external laryngeal and recurrent nerves it supplies the muscles of the larynx. The portion of
39 (i
596 THE NEKVOUS SYSTEM.
the nucleus ambiguus from which it arises has thus been termed the laryngeal nucleus (Edinger)
but it is not certain whether it is vagal or accessory.
Collaterals and fibres of the opposite lateral cerebro -spinal tract end in connexion with the
cells of origin of the accessory nerve, and thus bring its nucleus into connexion with the motor
area of the cerebral cortex. Fibres also from the posterior roots of the spinal nerves (afferent or
sensory fibres) end in the nucleus.
Nervus Vagus, Nervus Glossopharyngeus. The vagus and glossopharyngeal
nerves present similar connexions with the brain, and they may therefore be
studied together. The greater part of both nerves is composed of afferent fibres,
which arise outside the brain-stem from ganglionic cells placed in relation to the
nerve-trunks. Both nerves possess efferent fibres also, which spring from two
special nuclei of origin situated within the medulla oblongata and termed re-
spectively the dorsal or splanchnic nucleus and the nucleus ambiguus, which is the
somatic nucleus. The afferent ganglionic fibres of the vagus and glossopharyngeal
enter the brain by a series of roots which penetrate the medulla oblongata along
the ventral side of the restiform body. Within the medulla oblongata they separate
into .two sets, viz., a series of bundles (composed chiefly of vagus fibres, i.e. afferent
splanchnic), which end in the dorsal nucleus of termination of the vagus and glosso-
pharyngeal nerves, and another series of bundles (composed chiefly of glosso-
pharyngeal fibres, i.e. taste fibres), which join a conspicuous longitudinal tract of
fibres called the tractus solitarius.
The dorsal nucleus (Figs. 488, p. 557, and 526, p. 593) of the vagus and glosso-
pharyngeal nerves is mixed, and contains both motor cells which give origin to
efferent fibres, and cells around which afferent fibres of the vagus, and possibly also
of the glossopharyngeal nerve, break up into terminal arborisations. It very nearly
equals in length the nucleus of the hypoglossal nerve, with which it is closely
related. Above, it reaches as high as the striae medullares, whilst, below, its inferior
end falls slightly short of that of the hypoglossal nucleus. In specimens stained by
the Weigert-Pal method the two nuclei offer a marked contrast. The hypoglossal
nucleus presents a dark hue, owing to the enormous numbers of fine fibres which
twine in and out amidst its cells ; the vago-glossopharyngeal dorsal nucleus is pale,
from the scarcity of such fibres within it. Its cells, like those of all splanchnic
efferent nuclei, are much smaller than the somatic cells of the nucleus ambiguus.
In the closed part of the medulla oblongata the dorsal vago-glossopharyngeal nucleus
lies in the central gray matter immediately behind the hypoglossal nucleus, and
upon the lateral aspect of the central canal; in the open part of the medulla oblongata
it lies in the gray matter of the floor of the fourth ventricle, immediately to the
lateral side of the hypoglossal nucleus and subjacent to the surface area termed the
trigonum vagi or ala cinerea.
All the fibres which arise from this dorsal or splanchnic efferent nucleus are
very fine, and in sections of the vagus nerve can readily be distinguished from the
much coarser somatic fibres, which come from the nucleus ambiguus, and also from
the medium-sized sensory fibres, which spring from the ganglia placed upon the nerves.
The fine fibres from the dorsal nucleus are distributed (probably indirectly, i.e. after
being interrupted in a peripheral ganglion), to the involuntary striped muscle of
the oesophagus and heart, and the unstriped muscle of the oesophagus, stomach and
respiratory system (van G-ehuchten and Molhant, La Ntvraxe, June 15, 1912, p. 55).
The nucleus ambiguus (Figs. 488, 530, 526) gives origin to the somatic
motor fibres of the glossopharyngeal and vagus nerves. All the fibres from this
nucleus which pass into the glossopharyngeal nerve end in the stylo-pharyngeus
muscle ; the vagal branches are distributed to the striated muscles of the pharyi
and larynx. The cells of the nucleus ambiguus are large, multipolar, and simil
in every respect to the large cells in the anterior column of the spinal medul
These cells are arranged in a slender column which is fyest developed in the
open part of the medulla oblongata. Here the nucleus can easily be detected, in
transverse sections, as a small area of compact gray matter which lies in the substantia
reticularis grisea, midway between the dorsal accessory olive and the nucleus
tractus spinalis nervi trigemini. It therefore lies more deeply in the substance of
the medulla oblongata than the dorsal vago-glossopharyngeal nucleus. Kolliker
states that it can be traced downwards as low as the level of the decussation of
THE DEEP CONNEXIONS OF THE CEEEBKAL NEEVES. 597
;he medial lemniscus, and upwards as high as the place of entrance of the
jochlear root of the acoustic nerve. From its dorsal aspect the axons of the cells
proceed, and in the first instance they pass backwards towards the floor of the
ourth ventricle; then, bending suddenly laterally and forwards, they join the
ifferent roots of the vagus and the glossopharyngeal nerves, and emerge from the
Drain in company with these.
Sensory or Terminal Nuclei of the Glossopharyngeal and Vagus.
Splanchnic and Gustatory Components. The cells in the portion of the dorsal
lucleus which acts as a nucleus of termination are spindle-shaped in form and
Lemniscus
Mesencephalic root
of triqeminus
Motor root
of tricjeminus
Nucleus vestibul
superior
Nucleus vestibuli
lateralis
N.vestibula
N. facial!
Glossopharyngeal n. ^
Nucleus vestibuli'
medialis
Vagus
Va
FIG. 530. DIAGRAM, showing the brain connexions of the vagus, glossopharyngeal, acoustic,
facial, abducens, and trigeminal nerves.
iimilar to those found in the posterior column of gray matter in the spinal medulla.
[n connexion with these cells, the greater number of the afferent fibres of the
> r agus nerve, and a small proportion of the afferent fibres of the glossopharyngeal
icrve, end in fine terminal arborisations. A small part of the superior portion of
;he nucleus may be said to belong to the glossopharyngeal nerve and the remainder
)f the nucleus to the vagus nerve.
The tractus solitarius (Figs. 494, p. 561; 495, p. 561; and 530) is a round
3undle of longitudinal fibres which forms a very conspicuous object in trans-
verse sections through the medulla oblongata. It begins at the superior limit
rf the medulla oblongata, and can be traced downwards through its whole
length. Its precise point of termination is not known, but some authorities believe
598 THE NERVOUS SYSTEM.
that it is carried for some distance downwards into the superior part of the spinal
medulla, and, according to Kolliker, to the level of the fourth cervical nerve. Most
modern writers, however, limit it to the medulla oblongata. The relations of the
tractus solitarius are not the same in all parts of its course. It lies immediately
to the lateral side of the dorsal vago-glossopharyngeal nucleus; but, whereas in
the superior part of the medulla oblongata it is situated somewhat on the ventral
side of that nucleus, in the inferior, closed part of the medulla oblongata it is
placed on its dorsal aspect. Throughout its entire length it is intimately associated
with a column of gelatinous gray substance called the nucleus tractus solitarii,
which constitutes the nucleus of termination in which its fibres end. When
traced from above downwards, the tractus solitarius is observed to become gradually
smaller owing to the loss of fibres which it thus sustains. The great bulk of the
tractus solitarius is formed of fibres derived from the glossopharyngeal nerve ^ only
a few of the afferent fibres of the vagus enter it, but fibres of the sensory root
(nervus intermedius) of the facial also enter it. As the fibres of the three nerves
join the fasciculus they immediately turn downwards, and at different levels come
to an end in the associated nucleus tractus solitarii.
As the afferent root-bundles of the vagus and the glossopharyngeal nerves traverse
the substance of the medulla oblongata in a backward and medial direction to reach
the tractus solitarius and the dorsal nucleus of termination, they pass through the
tractus spinalis of the trigeminal nerve and the nucleus of that tract. As the
afferent root of the vagus passes through the trigeminal tractus spinalis and its
nucleus, which is somatic sensory in nature, it gives off to this nucleus its own somatic
sensory branches, the peripheral ends of which constitute the auricular branch, dis-
tributed to the skin on the back of the auricle. The other afferent fibres in the
glossopharyngeal and vagus nerves include taste fibres, sensory fibres from the pharynx,
larynx, and other parts of the respiratory and alimentary systems, and other splanchnic
afferent fibres. Although there is no sharp demarcation between the terminal nuclei of
these various components, it is probable that the taste fibres proceed to the nucleus
traetus solitarii, the splanchnic afferent fibres to the dorsal nucleus, and the somatic
afferent fibres to the nucleus of the spinal trigeminal tract.
Nervus Acusticus.^As this is a nerve of special sense it will be left for con-
sideration after the rest of this series.
Nervus Facialis (Figs. 530 and 531). The facial nerve is composed of two
distinct parts, viz., a large efferent (mainly motor) portion, the facial nerve proper,
and a small afferent sensory portion termed the nervus intermedius.
The facial nerve proper emerges from the brain at the inferior border of the pons,
to the medial side of the acoustic nerve, whilst the nervus intermedius sinks into
the superior part of the medulla oblongata between the facial and acoustic nerves,
but alongside the latter, rather than the former, from which it is separated
by the fasciculus obliquus pontis (Fig. 527). The three nerves, therefore, lie in
intimate relation with each other, where they are attached to the surface of the
brain, and they pass in company into the internal acoustic meatus.
The fibres of the nervus intermedius arise from the cells of the ganglion geniculi
of the facial nerve. These, like the cells of a spinal ganglion, are unipolar, the
single process in each case dividing into a peripheral and a central branch. The
group of peripheral fibres represent parts of the greater superficial petrosal nerve
and chorda tympani branch of the facial nerve, whilst the central fibres form the
nervus intermedius. The central fibres penetrate the brain, and, parsing either
through or on the dorsal side of the tractus spinalis of the trigeminal nerve, they
finally reach the superior part of the column of gray matter in connexion with the
tractus solitarius, and in this they end. The nervus intermedius presents, therefore,
the same terminal connexions within the brain as the glossopharyngeal nerve.
The motor nucleus of the facial nerve contains elements serially homologous
with both the somatic (nucleus ambiguus) and splanchnic (nucleus dorsalis)
efferent nuclei of the glossopharyngeal and vagus. It is composed partly of the
larger cells characteristic of the former and the smaller cells distinctive of
the latter. The axons of the somatic cells innervate the striated muscles of
the face, whereas the splanchnic efferent fibres pass to the spheno-palatine, otic
THE DEEP CONNEXIONS OF THE CEEEBKAL NEEVES. 599
ind submaxillary ganglia (as their white rami comraunicantes), and are largely
3oncerned with the regulation of the secretory activity of the large salivary glands
ind other glands around the mouth.
The facial nucleus is situated close to the place where the nerve emerges from
the brain, but the nerve does not at once pass to this point of exit. It pursues
a long and devious path within the pons before it finally reaches the surface.
This intrapontine part of the nerve may be divided into three parts, viz. : (1) a
radicular part, (2) an ascending portion, and (3) an emergent part.
The radicular part of the facial nerve (Fig. 531) is composed of a large number
of fine, loosely arranged bundles of fibres, which issue from the lateral and dorsal
aspect of the nucleus and proceed backwards and slightly medially through the
pons. Beaching the floor of the fourth ventricle they curve medially, and the
bundles which He highest up sweep over the lateral and dorsal aspect of the
inferior part of the nucleus of the sixth nerve. Close to the median plane they
(turn sharply upwards and are collected into a single solid nerve-bundle, which
constitutes the ascending part of the facial nerve (Figs. 530 and 531). This
proceeds upwards immediately beneath the ependyma of the ventricular floor
on the dorsal aspect of the medial longitudinal bundle, and along the medial side
of the abducent nucleus for a distance of about five millimetres. Then the
nerve bends laterally at a right
angle, and curves a second time
over the dorsal aspect of the ab-
ducent nucleus. This gives rise
to a prominent hemispheral pro-
jection in the floor of the fourth
ventricle, the colliculus facialis (Fig.
531 and Fig. 482, p. 550). The
nerve now passes straight to the
place of exit from the brain, and
this part of the intrapontine trunk
may be termed the emergent por-
tion (Figs. 498 and 531). The
facial nerve thug forms a curved
loop over the dorsal aspect of the
abducent nucleus. The emergent
part of the nerve takes an oblique
course through the pons to reach
the surface. It inclines laterally
s and downwards as it proceeds to-
wards the ventral aspect of the pons,
and on its way it passes between
its own nucleus and the tract us
spinalis of the trigeminal nerve.
Entering the facial nucleus,
| and ending in fine terminal arborisa-
1 tions around its cells, are many
fibres from the opposite pyramidal
tract ; fibres from the spinal tract
1 of the fifth nerve ; fibres from the
corpus trapezoideum, etc. The nucleus is thus brought into connexion with the
motor area of the cerebral cortex, with the trigeminal nerve or sensory nerve of
the face, and with the acoustic nerve.
The peculiar course of the efferent fibres of the facial nerve within the pons
is to be explained in accordance with the general principle regulating migrations
of nerve-cells, to which reference has already been made (p. 554). In the embryo
the nucleus facialis develops alongside the nucleus abducens. The latter, con-
trolling one of the eye-muscles, receives most of its afferent impulses from the
medial longitudinal bundle (descending from the optic centres in the superior
colliculus), and therefore it remains alongside the medial longitudinal bundle
39 &
FIG. 531. DIAGRAM OF THE INTRAPONTINE COURSE OF
THE FACIAL NERVE.
Sub. gel. rol. refers to the nucleus of the spinal trigeminal
tract.
600 THE NEKYOUS SYSTEM.
and perhaps moves slightly upwards, i.e. towards the mesencephalon. The facial
nucleus, however, receives most of its stimuli from the nucleus tractus spinalis
nervi trigemini, and therefore, as the walls of the metencephalon thicken during
their growth, this nucleus retains its proximity to the trigeminal nucleus
(Fig. 531), and so migrates along a course which remains mapped out by its
emerging fibres. Streeter, working with human embryos, and Ariens-Kappers,
on comparative and therefore broader lines, have elucidated the meaning of this
peculiar intracentral course of the facial nerve.
Nervus Abducens (Figs. 498 and 531). The abducens nerve is a small
motor nerve which emerges from the brain at the inferior border of the pons
above the lateral side of the pyramid of the medulla oblongata. It is the nerve
of supply to the lateral rectus muscle of the eyeball. Its nucleus of origin is
a small spherical mass of gray matter, containing large multipolar cells, which
lies in the dorsal part of the tegmental portion of the pons, close to the median
plane and immediately subjacent to the gray matter of the floor of the fourth
ventricle. Its position can be easily indicated on the ventricular floor, seeing
that it is placed subjacent to the colliculus facialis and immediately above the
level of the striae medullares. Its peculiar and intimate relation to the intra-
pontine portion of the facial nerve has already been indicated. It lies on the ventral
aspect of, and within the concavity formed by, the two limbs of the loop of that nerve.
The axons of the multipolar cells of this nucleus emerge from the medial aspect
of the nucleus in the form of several bundles, which proceed through the whole
dorso- ventral thickness of the pons towards the place of exit. As they pass
forwards they incline downwards and slightly laterally. In the dorsal part
of the pons they proceed forwards on the medial side of the nucleus olivaris superior,
whilst in the basilar part of the pons they keep for the most part to the lateral
side of the pyramidal bundles, although several of the nerve fila pierce these
on their way to the surface.
.It would appear probable that certain of the axons of the cells of the abducens nucleus enter
the medial longitudinal fasciculus and proceed upwards in it to end in the oculomotor
nucleus of the opposite side. Fibres and collaterals from the basis pedunculi of the opposite
side enter the nucleus, and, ending around the cells, bring the nucleus into connexion with the
motor area of the cerebral cortex. The pedicle of the nucleus olivaris superior ends partly
within the nucleus of the abducent nerve (Fig. 530).
Nervus Trigeminus. The trigeminal nerve strikes its roots deeply into the
brain and establishes a connexion with it which extends from the upper part of
the mesencephalon above to the level of the second cervical nerve below. No
other cerebral nerve presents so extensive a connexion (Fig. 530, p. 597). It
is composed of two roots a large afferent or sensory root and a small efferent
or motor root. Both roots appear close together on the surface of the pons,
rather nearer its superior than its inferior border, and in the same line as the
facial, and glossopharyngeal and vagus nerves (Fig. 527, p. 594).
The sensory root of the trigeminal nerve is composed of fibres which arise outside
the brain from the cells of the semilunar ganglion. They end within the brain in a
somewhat tadpole-shaped terminal nucleus, the swollen body of which is situated
in the pons and is termed the main sensory nucleus of the trigeminal nerve:
the tail is a long column of gray matter which is directly continuous below
with the substantia gelatinosa of the spinal medulla.
The main sensory nucleus (Fig. 532) is an oval mass of gray matter placed
half-way up the pons in the lateral part of its dorsal or tegmental portion. It lies
close to the lateral surface of the pons and immediately subjacent to the ventral
submerged margin of the brachium conjunctivum. It is directly continuous with
the substantia gelatinosa, and may be regarded as being merely the enlarged
superior end of that column of gray matter.
The fibres of the sensory root of the trigeminal nerve, on reaching the sensory
nucleus, divide, in the same way as the fibres of the entering posterior roots of the
spinal nerves, into a system of ascending and descending branches (Fig. 530, p. 597).
The ascending fibres are short, and almost immediately enter the sensory nucleus
and end within it ; the descending fibres turn sharply downwards and form the
THE DEEP CONNEXIONS OF THE CEKEBEAL NERVES. 601
tractus spinalis. This tract descends on the lateral side of the column of gray matter
formed by the substantia gelatinosa, which constitutes its terminal nucleus, nucleus
tractus spinalis nervi trigemini. Fibres constantly leave it to enter the nucleus,
so that the lower it gets the smaller does the spinal tract become until, in the
upper part of the spinal medulla, about the level of the first or second spinal nerve,
it disappears altogether.
The large spinal tract of the trigeminal nerve is a conspicuous object in sections
> through the pons and medulla oblongata. In the pons it traverses the dorsal or
tegmental part, first, between the emergent part of the facial nerve and the
vestibular nerve; and then lower down, between the restiform body and the nucleus of
the facial nerve (Fig. 498, p. 565). In cross sections it presents a well-defined semi-
lunar or curved piriform outline. In the superior part of the medulla oblongata it lies
on the ventral aspect of the restiform body, and therefore nearer the surface than in
Brachium conjunctivum
Anterior medullary velum
Mesencephalic root of the trigeminal nerve
Motor nucleus of the trigeminal nerve
Motor root of the trigeminal nerve
Sensory nucleus of the
trigeminal nerve
Superior olive
Sensory root of
trigeminal nerve
Brachium ponti
FIG. 532. SECTION THROUGH THE PONS OF THE ORANG, AT THE LEVEL OF THE NUCLEI
OF THE TRIGEMINAL NERVE.
the pons (Fig. 495, p. 561). Here it is traversed and broken up into separate bundles
, by the olivo-cerebellar fibres and the roots of the glossopharyngeal and vagus nerves.
Finally, it comes to the surface and its fibres are spread over the area on the side of
t the medulla oblongata known as the tuberculum cinereum of Rolando (Fig. 494, p. 561).
The small motor part of the trigeminal nerve is distributed chiefly to the muscles
of mastication, and derives its fibres from the motor nucleus.
The motor nucleus (Fig. 532) lies in the lateral part of the tegmental portion of
: the pons, close to the medial side of the main sensory terminal nucleus, but some-
what nearer the floor of the fourth ventricle. It is serially homologous with the
: motor nuclei of the lateral somatic group, namely, the facial and nucleus ambiguus.
It does not become displaced so far forwards as these nuclei, because its chief source
of sensory impulses the terminal nucleus of the trigeminal afferent fibres is
placed alongside it, and there is no need for any definite migration (Fig. 532).
The mesencephalic root or radix descendens nervi trigemini takes origin from
602
THE NEEVOUS SYSTEM.
a column of loosely arranged pear-shaped unipolar cells which are placed in the
extreme lateral part of the gray matter surrounding the aquaeductus cerebri. As
this root is traced downwards it gradually increases in size by the accession of new
fibres, and it assumes a crescentic form in transverse section (Figs. 501, p. 569 ;
532, p. 601 ; 533 ; and 534, p. 603). In the inferior part of the mesencephalon it
lies on the medial side of the brachium conjunctivum ; and the trochlear nerve, on its
way to the surface, runs downwards in its concavity and on its medial aspect. In
the superior part of the pons it continues its course downwards on the lateral and deep
aspect of the gray matter in the floor of the fourth ventricle. Finally, reaching the
level of the nuclei of the trigeminal nerve, the fibres of the mesencephalic root turn
forwards and are said to join the sensory part (Johnston) of the trigeminal nerve. Otto
May and Horsley, however, confirm the usual description, viz., that it passes into the
motor root; but, according to them, it cannot be traced beyond the semilunar ganglion.
It is customary to de-
scribe this mesencephalic root
as belonging to the motor
division of the trigeminal
nerve; but Johnston has re-
cently questioned this and
claimed : (1) that its fibres
become associated at their exit
from the central nervous
system with the sensory, and
not with the motor, root ; (2)
that its nucleus develops in
the alar and not in the basal
lamina ; and (3) that the
pear-shaped unipolar cells,
from which its fibres arise,
conform to the sensory and
not to the motor type.
The reason why its sensory
nature has not been suspected
hitherto is no doubt the fact
that its fibres arise not in
FIG. 533. SECTION THROUGH THE INFERIOR COLLICULUS AND THE some ganglion outside the
TEGMENTUM OF THE MESENCEPHALON AT THE LEVEL OF THE central nervous system like
(Sg). PA F ND LEnS * ^^ NEKVE other sensory nerves/ but
from cells in the tectum
mesencephali. If Johnston's view is correct, the neural crest in the mesen-
cephalic region must have been drawn into the neural tube during development
and given rise to this sensory nucleus of origin (not a terminal nucleus) within
the central nervous system.
Otto May and Sir Victor Horsley have shown that the mesencephalic root is
a mixture of ascending and descending fibres, but there is no evidence to show
that the latter may not be sensory like the former. Nothing is known of their
peripheral distribution.
Nervus Trochlearis. The trochlear nerve supplies the superior oblique muscle
of the eyeball. It emerges from the brain, on its dorsal aspect, at the superior
part of the anterior medullary velum, immediately below the lower border of the
inferior colliculus (Fig. 517, p. 583). The nucleus from which it arises is a small
oval mass of gray matter, placed in the ventral part of the central gray matter, at
the level of the superior part of the inferior colliculus. The close association of this
nucleus with the medial longitudinal bundle has already been referred to. It is
sunk deeply in a bay which is hollowed out on the dorsal and medial aspect of
that tract. The nerve has a course of some length within the mesencephalon. The
axons of the cells leave the lateral aspect of the nuclear mass, and curve backwards
and laterally in the central gray matter until they reach the concave medial surface
of the mesencephalic root of the trigeminal nerve. Here they are gathered together
Decussation of lateral lemniscus fibres
Aquseductus cerebri
Central gray matter
Nucleus of inferior
colliculus
Inferior brachium
Mesencephalic root
of trigeminal nerve
Nucleus of trochlear
nerve
Medial longi-
tudinal bundle
Lateral lemniscus
Decussation of the
brachia conjunctiva
Medial lemniscus
THE DEEP CONNEXIONS OF THE CEEEBEAL NEEVES. 603
.nto one or two round bundles, which, bending sharply, turn downwards at a right
ingle and descend on the medial side of the trigeminal root. When the region
Delow the inferior colliculus is reached, the nerve makes another sharp bend. This
ime it turns medially, enters the superior end of the anterior medullary velum, in
vhich it decussates with its fellow of the opposite side. Having thus crossed the
nedian plane, the trochlear nerve emerges at the medial border of the brachium
jonjunctivum. The course pursued by the trochlear nerve within the central
l^ray matter may be traced by examining in succession Fig. 533 ; Fig. 534 ;
Fig. 502, p. 570; and Fig. 512, p. 577.
Nervus Oculomotorius. The oculomotor nerve supplies the levator palpebrse
juperioris, all the ocular muscles, with the exception of the superior oblique and
}he lateral rectus, and also two muscles within the eyeball, viz., the sphincter iridis
ind the musculus ciliaris. The nucleus of origin is placed in the ventral part of
.;he central gray matter subjacent to the superior colliculus (Fig. 521, p. 587). In
.ength it measures from 5 to 6
.nm. Its inferior end is par-
tially continuous with the
lucleus of the trochlear nerve,
whilst its superior end extends
.ipwards for a short distance
Beyond the mesencephalon
.nto the gray matter on the
i|ade wall of the third
/entricle. Its relation to the
,nedial longitudinal bundle is
iven more intimate than that
)f the trochlear nucleus. It
.s closely applied to the
.lorsal and medial aspect of
}his strand ; many of its cells
>ccupy a position in the in-
,-ervals between the nerve-
Bundles of the tract, and some
',ven are seen on its ventral or
negmental aspect. The axons
>f the nuclear cells leave the FIG. 534. SECTION THROUGH THB INFERIOR COLLICULUS AND THE
Central gray
atter
Aquseductus
cerebri
Mesencephalic
root of tri-
geminal nerve
Trochlear
nerve leaving
nucleus
Medial
longitudinal
bundle
Decussation of
the brachia
conjunctiva
TEGMENTUM OF THE MESENCEPHALON AT THE LEVEL OF THE
INFERIOR PART OF THE NUCLEUS OF THE TROCHLEAR NERVE
(Orang).
mcleus in numerous bundles,
i vhich describe a series ' of
I'.urves as they proceed for-
vards through the medial longitudinal bundle, the tegmentum, red nucleus, and
nedial margin of the substantia nigra, to emerge finally from the brain-stem along
he bottom of the sulcus oculo-motorius on the medial aspect of the basis pedunculi.
The cells of the oculomotor nucleus are not uniformly distributed through-
put it. They are grouped into several more or less distinct collections or
slumps, some of which possess cells which differ in size and appearance from the
)thers. These cell-clusters are very generally believed to possess a definite relation
;o the several branches of the nerve and the muscles which they supply. Perlia
ecognises no less than seven such cell-clusters in each nucleus, with a small median
mcleus placed accurately on the median plane, and from which fibres for both nerves
Spring. Whilst the majority of the fibres in the oculomotor nerve arise from the
iell-groups which lie on its own side of the median plane, it has been satisfactorily
i established that a certain proportion of its fibres are derived from the nucleus of
yhe opposite side, thus forming a crossed connexion and giving rise to a median
lecussation. These crossed fibres are supposed by some to supply the medial rectus
nuscle ; and we have seen that there is reason to believe that the part of the nucleus
Tom which these fibres are derived stands in connexion through the medial loiigi-
, -udinal fasciculus with the abducens nucleus from which proceeds the nerve of supply
, or the lateral rectus muscle. The harmonious action of the medial and lateral
ecti in producing the conjugate movements of the eyeballs is thus explained.
604 THE NEKVOUS SYSTEM.
The oculomotor nucleus is connected (1) with the occipital part of th
cerebral cortex by fibres which reach it through the optic radiation ; (2) with th
vestibular, trochlear and abducent nuclei (and probably with other nuclei) b
fibres which come to it through the medial longitudinal bundle ; (3) possibly wit!
the facial nerve by fibres which pass out from it into the medial longitudina
bundle (p. 589) ; (4) with the visual system by fibres which enter it from the cell
of the superior colliculus.
It is important to recognise that although the main part of the oculomoto
nucleus belongs to the medial somatic group, which also includes the trochleai
abducent and hypoglossal nuclei, it also includes a representative (the Edingei
Westphal group of small cells) of the column of splanchnic efferent nuclei in serie
with those of the facial, glossopharyngeal, and vagus nerves. Its axons pass on
along with the other fibres of the oculomotor nerve and enter the ciliar
ganglion, where they end in relationship with the cells that innervate the ciliar
muscle and the circular muscle of the iris.
Nervus Acusticus. This large nerve enters the brain at the inferior borde
of the pons. Its fibres spring from bipolar ganglionic cells in the immediat
neighbourhood of the labyrinth or internal ear (see section dealing with th
Organs of Sense). One group of these forms the spiral ganglion, the periphery
branches of which are distributed to the organ of Corti in the cochlea : anothe
group constitutes the vestibular ganglion (often called Scarpa's), which distribute
fibres to the ampullae of the semicircular ducts, the utricle, and the saccule. Althoug
the central processes of the cells in these two ganglia accompany one another and ai
known collectively as the acoustic nerve they really remain distinct throughout, i
their mode of termination in the brain as well as in their peripheral distributioi
Beaching the brain the acoustic nerve divides into two parts, viz., the nervu
cochlearis and the nervus vestibularis, which present totally different connexion
corresponding to their distinct functions. In their further course these frw
divisions deviate from each other so as to embrace the restiform body th
vestibular part entering the pons on the medial aspect of the restiform bod;
whilst the cochlear part sweeps round its lateral surface. Special nuclei <
termination require to be studied in connexion with each part of the nerve.
The cochlear nerve is composed of finer fibres than the vestibular nerv
and its fibres acquire their medullary sheaths at a later period. It is the true nen
of hearing, and its fibres end in a nucleus which lies in intimate relation to tt
restiform body. It may be described as consisting of two parts. Of the*
one, called the dorsal cochlear nucleus, is a piriform mass which is placed on tl:
dorsal aspect of the restiform body between it and the flocculus of the cer<
bellum. The second part, termed the ventral cochlear nucleus, is placed o
the ventral aspect of the restiform body in the interval between the cochlear au
vestibular divisions of the acoustic nerve, after they have separated from eac
other. The fibres of the cochlear nerve enter these two ganglia and end arouc
the cells in arborisations, which are finer, closer, and more intricate than thos
met with in any other nerve-ending in the brain.
The vestibular nerve enters the brain at a slightly higher level than the cochlea
nerve and on the medial aspect of the ventral cochlear nucleus. It proceec
backwards through the pons between the restiform body, which lies on its later;
side, and the spinal tract of the trigeminal nerve, which is placed on its medial sid
Its fibres end in a series of terminal nuclei (Fig. 530, p. 597), viz. : (1) the nuclei
vestibularis dorsalis, often known as the principal nucleus, (2) its inferior pr<
longation, nucleus tractus descendentis, (3) the nucleus vestibularis lateralis (Deiters
(4) the nucleus vestibularis superior (Becliterews), and (5) the cerebellar cortex.
The principal nucleus (Figs. 498, p. 565, and 535, p. 605) is a large diffui
nuclear mass, which lies in the floor of the fourth ventricle subjacent to the surfa<
district known as the area acustica (Fig. 482, p. 550). It is situated, therefor
in both the pons and the medulla oblongata to the lateral side of the fovea superi<
and the fovea inferior. In transverse section it is prismatic in outline, and cros
ing the surface of its upper or pontine part immediately under the ependyma i
the ventricle are the striae medullares.
THE DEEP CONNEXIONS OF THE CEEEBEAL NERVES. 605
When the nervus vestibularis, as it traverses the brain, reaches the medial aspect
of the dorsal portion of the restiform body, its fibres bifurcate to form ascending
jand descending tracts. The latter pass vertically downwards in separate bundles
and form the descending tract of the vestibular nerve (Figs. 498, p. 565; 495,
p. 561; and 530, p. 597). This proceeds through the inferior part of the
. pons into the medulla oblongata, in which it may be traced as far as the level of
the decussation of the medial lemniscus. Associated with the descending tract
'there is a column of gray matter, with nerve-cells strewn sparsely throughout it.
This is the nucleus of the descending tract, and the fibres end in fine arborisa-
tions around these nerve-cells.
Some of the ascending fibres of the vestibular nerve end in the nucleus lateralis.
This nucleus is composed of a number of large and conspicuous multipolar
nerve-cells,
Nucleus fastigi
Vermis Cerebell ,
which are scat-
tered amidst the
bundles of the
vestibular
nerve. As it is Anterior
j j Cransvers'
traced upwards temporal
Vestibular fibre
passing Co vermis
Insula
into the pons
the nucleus
gradually in-
clines back-
wards, and final-
ly it occupies a
place in the
side wall of
the fourth ven-
tricle. It attains
its greatest de-
velopment at
the level of the
emerging part of
the facial nerve
and this upper
part is some -
times termed
the nucleus
gyr
AUDITORY
RADIATION
LEMNISCUS__
LATERALIS"
Nucleus
lemniscus
lateralis \
Nucleus emboliformis
Ngcleus
de ntatus
ebelli
Corpus
qeniculatum
mediate
Vestibular Fibre
enbro-pontine tracts
in the pons
Nervus acusticus
rpus trapezoideum -
Pyramid
Decussation of pyramids
entral cerebro-spinal tract
FIG. 537. A VERTICAL TRANSVERSE SECTION OF THE BRAIN TO SHOW THE WHOLE OF THE CENTRAL
ACOUSTIC PATH. The left hemisphere (right side of the figure) is cut on a plane posterior to that of
the right. Motor fibres red. Sensory fibres blue. Acoustic fibres yellow.
ganglion emit axons that terminate in the brain ; in' (2) the cochlear nuclei, from the
nerve-cells of which fibres arise and cross to the lateral lemniscus of the opposite side,
proceeding to (3) the medial geniculate body, from which fibres pass to the cerebral cortex.
It must be borne in mind that all the axons of the cells of the superior olive do not
join the trapezoid strand.' Many leave its dorsal aspect and pass backwards in a group
called the pedicle of the superior olive, to end in the nucleus of the abducens nerve,
and, through the medial longitudinal bundle, in the nuclei of the trochlear and oculo-
motor nerves. In this way the organ of hearing is brought into connexion with the
iclei which preside over the movements of the eyeballs (Figs. 531, p. 599, and 536, p.
606).
PEOSENCEPHALON OR FOEE-BRAIN.
The fore-brain vesicle in the embryo has been subdivided, somewhat arbitrarily,
608 THE NEKVOUS SYSTEM.
into two parts an anterior, termed the telencephalon, and a posterior, called th
diencephalon, which forms the greater part of the walls of the third ventricle. Th
extreme anterior part of the third ventricle belongs to the telencephalon, and thi
includes the anterior wall of the neural tube, which is known as the lamiu
terminalis.
DEVELOPMENT OF PARTS DERIVED FROM FORE-BRAIN.
The alar part of each side wall of the telencephalon is pushed out to form
diverticulum, which ultimately constitutes the cerebral hemisphere, and thus, from a vei
early period, the primitive position of this part of the side wall is indicated by tl
wide foramen interventriculare, or aperture of communication between the cavity of tl
cerebral hemisphere and the third ventricle (Fig. 538).
The alar part of the side wall of the diencephalon is utilised for the developmei
of the thalamus, the epithalamus, and the metathalamus. Of these the thalamus
derived from the anterior and by far the greatest part of the alar wall. It arises as
large oval swelling, which gradually approaches its fellow of the opposite side, and thi
diminishes the width of the third ventricle. Finally, the two bodies sometimes come im
contact in the median plane and cohere over an area corresponding to the massa inte
media. This may occur about the end of the second month.
From that section of the side wall to which the name of metathalamus is given tl
two geniculate bodies arise. Each of these shows, in the first place, as a depression c
the inside, and a slight elevation on the outside, of the wall of the diencephalon. As tl
thalamus grows backwards, it encroaches greatly upon the territory occupied by the ger
culate bodies. It thus comes about that in the adult brain the medial geniculate boc
seems to hold a position on the lateral aspect of the mesencephalon, whilst the later
geniculate body, viewed from the surface, appears to be a part of the thalamus.
From the epithalamic region of the wall of the diencephalon are developed tl
pineal body, its peduncle, and the habenular region. These parts are relatively much mo:
evident in the embryonic than in the adult brain. The pineal body appears to 1
developed as a diverticulum of the posterior part of the roof of the diencephalon, but
reality it is a derivative of the alar lamina. Viewed from the dorsal aspect of the brai
tube, this diverticulum shows in the first instance, as a rounded elevation, from eac
side of which a broad ridge runs forwards. This ridge becomes the tsenia thalan
whilst in the region of its junction with the pineal elevation the trigonum habenul
takes shape. The pineal diverticulum ultimately becomes solid, but a small portion <
the original cavity is retained as the recessus pinealis of the third ventricle.
The part of the diencephalon and telencephalon which represents the basal lamina (i.
lies below the level of the sulcus hypothalamicus) retains its primitive form, and undergo<
only slight change. Consequently, when this region in the adult brain is compared with tl
corresponding region in the embryonic brain, the resemblance between the two is verystrikinj
In the fore-brain, therefore, it is the alar lamina which plays the predominant part i
the formation of the cerebrum. The value, also, of the basal part of the wall of th
portion of the neural tube is still further reduced by the fact that it no longer contaii
the nuclei of origin of efferent nerves. The highest of these nuclei (the oculomotor)
placed in the mesencephalon. [Johnston has recently announced the discovery of a sensor
nerve (nervus terminalis) attached to the fore-brain in human embryos ; and of course tl
optic and olfactory nerves enter the fore-brain.]
The region of the fore-brain which lies below the sulcus hypothalamicus is termed tl
hypothalamus. The part of this, which corresponds to the diencephalon is called tl
pars mamillaris hypothalami, whilst the part in front, which belongs to the tele
cephalon, receives the name of pars optica hypothalami. From the pars mamillar
hypothalami are derived the corpus mamillare and a portion of the tuber cinerem
With the pars optica hypothalami are associated the following parts, viz., the tub'
cinereum, with the inf undibulum and the cerebral part of the hypophysis, the opt
chiasma, the optic recess, and the lamina terminalis. The corpora mamillaria fon
in the first instance, a relatively large ventral bulging of the floor of the brain-tut i
As development goes on this bulging becomes relatively small, and about the four
month the single projection becomes divided into the two tubercles. The infundibulu
and posterior or cerebral lobe of the hypophysis are developed as a hollow downwa
diverticulum of the floor of the telencephalon (Fig. 538). A portion of the origii
cavity is retained in the upper part of the infundibulum, and constitutes the infundibul
recess in the floor of the third ventricle.
PAETS DEEIVED FEOM THE DIENCEPHALON.
609
FORE -.
The optic nerve is formed chiefly by the passage of fibres backwards from the retina
i t n the wall of the original optic stalk, whilst the chiasma takes form by the transit of
^fibres across the median plane
n front of the infundibulum
ind behind the optic recess.
To a large extent these fibres
ire derived from the optic
;ierve. The optic recess of
:he third ventricle marks the
spot where the hollow optic
vesicle was originally attached
to the inferior and lateral
part of the fore-brain, and in
the adult it therefore repre-
sents a portion of the primitive
cavity of the tubular stalk of
^he optic vesicle. In the
course of development the
optic nerve fibres, which ap-
pear in the stalk of the optic
vesicle to form the optic nerve,
' seek an attachment much
further back, and through the
optic tract they are even car-
Tied as far as the mesen-
cephalon.
The roof of the fore-
brain remains thin, and does
not proceed to the develop-
; ment of nervous elements,
although its posterior part
becomes invaded by nervous
tissue to form the pineal body
and the posterior commissure.
In front of these structures
the roof of the fore-brain is
epithelial, and remains so dur-
ing life. It constitutes the
: epithelial roof of the third
ventricle, and it becomes in-
volutedalongthe median plane
into the cavity to form the
FIG. 538. Two DRAWINGS OP THE EMBRYONIC BRAIN (by His).
A, Reconstruction of the fore-brain and mid-brain of His's embryo KO ;
profile view. B, Same brain as A, divided along the median plane
and viewed upon its inner aspect.
M, Mamillary eminence ; Tc, Tuber cinereum ; Hp, Hypophysis
(hypophyseal diverticulum from buccal cavity) ; 'Opt, Optic stalk ;
TH, Thalamus ; Tg, Tegmental part of mesencephalon ; Ps, Pars
hypothalamica ; Cs, Corpus striatum ; FM, Foramen* interventricu-
lare ; L, Lamina terminalis ; RO, Recessus opticus ; Ri, Recessus
infundibuli.
chorioid plexuses of the ven-
tricle (Fig. 549, p. 622). The posterior commissure appears as a transverse thickening
at the bottom of a transverse groove which appears in the roof of the early brain- tube,
behind the pineal diverticulum.
PARTS DERIVED FROM THE DIENCEPHALON.
Under this heading we have to consider : (1) the thalamus ; (2) the epithalamus,
which comprises the pineal body and the habenular region ; (3) the metathalamus,
or the corpora geniculata ; and (4) the hypothalamus.
The hypothalamus consists of two portions, viz., the pars mamillaris hypothalami,
which comprises the corpus mamillare and the portion of the central gray matter
which forms the floor of the third ventricle in its immediate vicinity ; and the pars
optica hypothalami, which embraces the tuber cinereum, the infundibulum, the
hypophysis (O.T. pituitary body), and the lamina terminalis. Strictly speaking, the
optic part of the hypothalamus does not belong to the diencephalon, but it is
convenient to study the parts which it represents at this stage.
The original cavity of that part of the brain-tube which forms the diencephalon
is represented by the greater part of the third ventricle of the brain.
Thalamus. The thalamus is the principal object in this section of the brain
40
610
THE NEKVOUS SYSTEM.
(Fig. 538). It is a large ovoid mass of gray matter, which lies obliquely aero
the path of the cerebral peduncle as it descends from the cerebral hemisphei
The smaller anterior end of the thalamus lies close to the median plane, and
separated from the corresponding part of the opposite side only by a very narro
interval. The enlarged posterior ends of the two thalami are placed more wide'
apart, and in the interval between them the corpora quadrigemina are situated.
The two thalami, in their anterior two-thirds, lie close together, one on each si(
of the deep median cleft which receives the name of the third ventricle of tl
brain. The inferior and lateral aspects are in apposition with, and, indeed, direct
connected with, adjacent parts of the brain, and on this account it is customary
study them by means of sections through the brain. The superior and medi
surfaces are free.'
The lateral surface of the thalamus is applied to a thick layer of white matt
interposed b
tween it and t]
lentiform ni
cleus, called tl
internal capsu!
and composed
fibres passir
both upwards t
wards and dow:
wards from tl
cerebral corte
A large propo
tion of these fibr
descend to for
the basis pedu:
culi. From tl
entire extent
the lateral su
face of the thai
mus large nur
bers of fibn
stream out ai
enter the ii
ternal capsule,
reach the cer
bral cortex. Th<
constitute wh
is termed tl
thalamic radi
tion. As tl
fibres leave tl
FIG. 539. THE THALAMI AND THE PARTS OF THE BRAIN SURROUNDING THEM. thalamus OV<
Superior aspect. the whole of tl
lateral surface of the ganglionic mass they form a very distinct reticulated zoi
or stratum, which is termed the external medullary lamina.
The inferior surface of the' thalamus rests on the hypothalamus. From tl
latter region many fibres enter the thalamus on its inferior aspect, whilst oth
fibres leave this surface of the thalamus to take part in the thalamic radiation.
The superior surface of the thalamus is free. Laterally it is bounded by
groove, which traverses the floor of the lateral ventricle of the brain ai
intervenes between the thalamus and the caudate nucleus. In this groo
are placed a slender band of longitudinal fibres, termed the stria terminal
and in its forepart the vena terminalis. Medially, the superior surface of t
thalamus is separated from the medial surface in its anterior half by i
sharp edge or prominent ledge of the ependyma of the third ventricle. This
termed the tsenia thalami, and the ridge which it forms is accentuated by t,J
Non-ventricular
part of thalamus
Groove
corresponding
to fornix
Quadrigeminal
bodies
Trochlear nerve
Brachium
pontis
Brachium
conjuiictivum
Lingula
Medulla
oblongata
Genu of corpus
callosum
Corpus callosum
(cut)
Cavum septi
pellucidi
Septum pellucid urn
Caudate nucleus
Fornix
Foramen inter-
ventriculare
Anterior commissure
Anterior tubercle
of thalamus
Massa intermedia
Third ventricle
Stria terminalis
Tsenia thalami
Trigonum habenulse
Posterior
commissure
Stalk of pineal body
Pulvinar
Pineal body
PAETS DERIVED FROM THE DIENCEPHALON. 611
. presence of a subjacent longitudinal strand of fibres called the stria medullaris.
, When these two structures, viz., the ependynial ridge and the subjacent stria, are
, traced backwards, they are seen to turn medially and become continuous with
i the stalk or peduncle of the pineal body. Behind the portion of the tsenia
thalami which turns medially towards the pineal body a small depressed triangular
area, the trigonum habenulae, situated in front of the superior colliculus, forms a very
definite medial boundary for the posterior part of the superior surface of the thalaruus.
The superior surface of the thalamus is slightly bulging or convex, and is of a
whitish colour, owing to the presence of a thin superficial covering of nerve-fibres,
termed the stratum zonale. It is divided into two areas by a faint oblique groove,
which begins in front at the medial border, a short distance behind the anterior
extremity of the thalamus, and extends laterally and backwards to the lateral
part of the posterior extremity. This groove corresponds to the edge of the
fornix. The two areas which are thus mapped out are very differently related to
the ventricles of the brain, and also to the parts which lie above the thalamus.
The lateral area, which includes the anterior extremity of the thalamus, forms a
part of the floor of the lateral ventricle. It is covered with ependyma, overlapped
by the chorioid plexus of this ventricle, and lies immediately subjacent to the
corpus callosum. Along the line of the groove the epithelial lining of the lateral
ventricle is reflected over the chorioid plexus of this cavity. The medial area,
which includes the posterior end of the thalamus, intervenes between the lateral
and third ventricles of the brain, and takes no part in the formation of the walls
of either. It is covered by a fold of pia mater, termed the tela chorioidea of the
third ventricle, above which is the fornix, and these two structures intervene
between the thalamus and the corpus callosum.
The anterior extremity of the thalamus, called the tuberculum anterius thalami,
forms a marked bulging. It projects into the lateral ventricle, behind and to the
lateral side of the free portion of the column of the fornix. The foramen
interventriculare, a narrow aperture of communication between the lateral and
third ventricles of the brain, is bounded in front by the column of the fornix and
behind by the anterior tubercle of the thalamus.
The posterior extremity of the thalamus is very prominent and forms a cushion -
like projection, which overhangs the brachia of the corpora quadrigemina. This
prominence is called the pulvinar. Another oval bulging on the posterior part of
the thalamus receives the name of the corpus geniculatum laterale. It is situated
below, and to the lateral side of, the pulvinar, and presents a very intimate connexion
with the optic tract.
The medial surfaces of the two thalami are placed close together, and are
covered not only by the lining ependyma of the third ventricle, but also by a
moderately thick layer of gray matter, continuous below with the central gray
substance which surrounds the aquseductus cerebri in the mesencephalon. A band
of gray matter, termed the massa intermedia, crosses the third ventricle and joins
the medial surfaces of the two thalami together.
Intimate Structure and Connexions of the Thalamus. The upper surface
of the thalamus is covered by the stratum zonale, a thin coating of white
fibres derived to some extent from the optic tract, and probably also from the
optic radiation. The medial surface has a thick coating of central gray matter,
whilst intervening between the internal capsule and the lateral surface is the lamina
medullaris externa. The lower surface merges into the hypothalamus.
The gray matter of the thalamus is marked off into three very apparent parts
-termed the anterior, the medial, and the lateral thalamic nuclei by a thin
vertical sheet of white matter, continuous with the stratum zonale, termed the
lamina medullaris interna. The lateral nucleus (nucleus lateralis thalami) is by far
the largest of the three. It is placed between the medial and the lateral
medullary laminse, and it stretches backwards beyond the medial nucleus, and thus
includes the whole of the pulvinar (Fig. 541). The medial nucleus (nucleus medialis
thalami) reaches only as far back as the habenular region. It is placed between
the central gray matter of the third ventricle and the internal medullary lamina.
The lateral nucleus is more extensively pervaded by fibres than the medial nucleus.
40 a
612
THE NEKVOUS SYSTEM.
From the lateral nucleus by far the greatest number of the fibres which form the
radiatio thalami pass, and these are seen crossing it in various directions towards
the lamina medullaris externa. The anterior nucleus (nucleus anterior thalami) is
the smallest of the three thalamic nuclei. It forms the prominent anterior tubercle,
and is prolonged in a wedge-shaped manner, for a short distance, downwards and
backwards between the anterior parts of the medial and lateral nuclei. The internal
medullary lamina splits into two parts and partially encloses the anterior nucleus.
In connexion with its large cells a very conspicuous bundle of fibres, the fasciculus
thalamomamillaris, comes to an end. [As this bundle arises in the corpus
inamillare, it ought to be called "fasciculus marnillo-thalamicus."]
A diffuse gray mass, imperfectly marked off from the inferior surface of the lateral nucleus,
receives the name of the ventral nucleus. Its inferior part is composed of the central nucleus oi
Luys and the nucleus arcuatus. In section the former appears as a circular mass of gray matter,
which comes into view immediately behind the point where the internal medullary lamina
disappears. It would seem to be intimately connected with fibres which reach it from the red
nucleus and from the posterior commissure. These fibres pass round it so as to mark it off from
the rest of the thalamus, and in front of the nucleus many of them enter the internal medullas
lamina. The nucleus arcuatus is a small semilunar mass of gray matter placed below and to the
lateral side of the central nucleus of Luys.
The connexions of the thalamus are of an extremely intricate kind. It would
appear to be a ganglionic mass interposed between the tegmental corticipetal tracts
and the cerebral cortex. In its posterior part, and through its stratum zonale, it alsc
has important connexions with the optic tract. The corticipetal tegmental tracts
which enter it from below, will be noticed in connexion with the hypothalamic
region. Suffice it to say, for the
present, that these fibres end in the
midst of the thalamus in connexion
with the thalamic cells. In additior
to these, enormous numbers of fibres
arising within the thalamus as th(
axons of its cells, stream out from it:
lateral and inferior surfaces to forn
the thalamic radiation. Thes<
thalamo-cortical fibres pass to ever
part of the cortex ; and althougl
there is no separation of them int
distinct groups as they leave th
thalamus, it is customary to regari;
them as constituting a frontal stall
a parietal stalk, an occipital stall
and a ventral stalk. But fibres fror j
the cortex, cortico- thalamic fibre
likewise stream into the thalamu
in large numbers, and end in fir
arborisations around its cells,
double connexion with the cerebrr
cortex is thus established by tl
thalamus.
The frontal stalk of the thalanr
radiation emerges from the anterior pa
of the lateral surface of the thalamus ai
passes through the anterior limb of t '
FIG. 540. -SCHEMA. Founded on the observations of internal capsule to reach the cortex of 1 1
CORP. CALLOSUM
ANT9 LIMB
NTtCAPSUUr
CORP:GEN:MED
SUP QUADV BODY
ME.6t4PEPHALON
TEMPORO-PONTINE
TRACT
Flechsig, and Ferrier and Turner.
frontal lobe. Many of these hbres end
the caudate and lentiform nuclei, betwej
which they proceed. The parietal stalk issues from the lateral surface of the thalamus, ai
passing through the internal capsule (and to some extent, also, through the lentiform nucl(
and the external capsule), gains the cortex of the posterior part of the frontal lobe and of 1 '
parietal lobe. The occipital stalk emerges from the lateral aspect of the pulvinar and constitu i
the so-called optic radiation. These fibres sweep laterally and backwards round the lateral s
of the posterior horn of the lateral ventricle to gain the cortex of the occipital lobe, ijf
PAKTS DERIVED FBOM THE DIENCEPHALON.
613
ventral Stalk streams out from .the under aspect of the anterior part of the. thalamus, in front
of the hypothalamic tegmental region and the corpus mamillare. Its fibres arise in both the
medial and lateral nuclei, and sweep downwards and laterally to reach the region below the
lentiform nucleus. One very distinct band which lies dorsal to the other fibres (ansa lenticu-
laris) comes from the lentiform nucleus to the thalamus, whilst the remainder (ansa peduncularis)
proceed in a lateral direction from the thalamus below the lentiform nucleus and gain the cortex
of the temporal lobe and of the insula.
Flechsig divides the thalamo -cortical fibres of ordinary sensation into three sensory systems.
These he has been able to distinguish by studying the order in which they assume their sheaths
of myelin in the foetus and infant.
Ferrier and Turner, by the degenerative method of investigation, corroborate Flechsig's
results. They confirm the observation of Flechsig that, while thalamic fibres are distributed to
the several regions of the cerebral cortex to an almost equal extent, there is one district, viz., the
frontal pole, to which the supply is scanty. Another very important result has been obtained
by these authors. They have established the fact that many of the thalamic fibres cross the
median plane in the corpus callosum, and thus gain the cortex of the opposite cerebral
hemisphere. Hamilton's crossed callosal tract thus receives confirmation.
Intimate Structure of the Corpus Geniculatum Laterale. Sections through the
lateral geniculate body reveal the fact that it is composed of a series of alternately
placed gray and
white curved
laminae. This
gives it a very
characteristic ap-
pearance. The
white laminae are
composed of fibres
which enter the
body from the
optic tract. The
connexions of the
geniculate bodies
will be studied
with the optic
tract.
Hypothala-
mic Region.
The tegmental
part of the pedun-
culus cerebri is
prolonged up-
wards and assumes
a position below
the posterior part
of the thalamus.
The red nucleus is
a conspicuous ob-
ject in sections
through the lower
part of this region
(Fig. 541). It presents the same appearance as lower down in the mesen-
cephalon, and, gradually diminishing, it disappears before the level of the corpus
mamillare is reached. Carried up around it are the same longitudinal tracts
of fibres which have been studied in relation to it in the tegmental part of the
mesencephalon. Certain of these fibres, placed in immediate relation to the red
nucleus, form a coating or capsule for it. This coating is partly derived from
those fibres of the brachium conjunctivum which pass directly up into the thalamus
and also partly from fibres which issue from the nucleus itself. The medial
lemniscus also, which in the superior part of the mesencephalon is observed to take
up a position on the lateral and dorsal aspect of the red nucleus, maintains a similar
position in the hypothalamic region. When the red nucleus comes to an end these
various fibres are continued onwards and form, in the position previously occupied
40 I
Intersection of
the corona
radiata and
callosal systems
of fibres
Caudate nucleus
Corpus callosum
For nix
Anterior nucleus
of thalamus
Stria medullaris
Internal capsule
Medial nucleus
of thalam
Lateral nucleus
of thalamus
Red nucleus
Nucleus hypo-
thalamicus
Substantia nigra
Basis pedunculi
External capsule
Putamen
Fronto-parietal
operculum
f operculum
Globus pallidus
Caudate nucleus
-Optic tract
Hippocampus
FIG. 541. FRONTAL SECTION THROUGH THE CEREBRUM OF AN ORANG PASSING
THROUGH THE HYPOTHALAMIC TEGMENTAL REGION.
614 THE NEKVOUS SYSTEM.
by the nucleus, a very evident and dense mass of fibres. The fibres of the medial
lemniscus, of the brachium conjunctivum, and of the red nucleus are prolonged
upwards into the ventral part of the thalamus, where they end in connexion with
the thalamic cells (ventro-lateral nucleus).
The substantia nigra is likewise carried into the hypothalamic region, where
it maintains its original position on the dorsal aspect of the basis pedunculi.
As it is traced upwards, it is seen gradually to diminish in amount. It shrinks
from the medial to the lateral side, and finally disappears when the posterior part
of the corpus mamillare is reached.
In frontal sections through the hypothalamic region, the most conspicuous object
which comes into view is the nucleus hypothalamicus or the nucleus of Luys (Fig. 541).
It is a small mass of gray matter, shaped like a biconvex lens, which makes its appear-
ance on the dorsal aspect of the basis pedunculi immediately to the lateral side of
the substantia nigra. At first it lies in an angle which is formed by the meeting
of the cerebral peduncle and the internal capsule; but, rapidly enlarging in a
medial direction, it takes the place of the diminishing substantia nigra on the dorsal
surface of the basis pedunculi at the level of the inferior part of the corpus mamillare.
The nucleus hypothalamicus is rendered all the more evident by the fact that it is
sharply defined by a thin capsule of white fibres. On its medial aspect these fibres
proceed medially and form a very evident decussation across the median plane in the
floor of the third ventricle, immediately above the posterior ends of the corpora
mamillaria.
The nucleus hypothalamicus, in the fresh condition, presents a brownish colour,
partly from the fact that its cells are pigmented, and partly also on account of
the numerous capillary blood-vessels which pervade its substance.
Corpus Pineale. This is a small, dark, reddish body, about the size of a cherry
stone and shaped after the fashion of a fir-cone. Placed between the posterio
ends of the two thalami, it occupies the depression on the dorsal aspect of th
mesencephalon, which intervenes between the two superior colliculi. Its base
which is directed upwards, is attached by a hollow stalk or peduncle. Thi
stalk is separated into a dorsal and a ventral part by the prolongation back
wards into it of a small pointed recess of the cavity of the -third ventricle. Th
dorsal part of the stalk curves laterally and forwards, and, on each thalamus
becomes continuous with the tsenia thalami ; the ventral part is folded round
narrow but conspicuous cord-like band of white matter, which crosses the medial
plane immediately below the base of the pineal body and receives the name of th
posterior commissure of the cerebrum (Fig. 519, p. 585).
The pineal body is not composed of nervous elements. The only nerves in its midst are th
sympathetic filaments which enter it, with its blood-vessels. It is composed of spherical an
tubular follicles, filled with epithelial cells, and containing a variable amount of gritty, calcareou
matter.
The pineal body is a rudimentary structure, but in certain vertebrates it attains a inuc
higher degree of development than in man. In the lamprey, lizard, etc., it is present in th
form of the so-called pineal eye. In structure it resembles, in these animals, an invertebrate ey(
and it possesses a long stalk, in which nerve-fibres are developed. Further, it is carried throng
an aperture in the cranial wall, and consequently lies close to the surface on the dorsum of tn
head between the parietal bones.
Trigonum Habenulae. The small, triangular, depressed area which receive
this name is placed immediately in front of the superior colliculus in the intern
between the peduncle of the pineal body and the posterior end of the thalami
(Fig. 539, p. 610). It marks the position of an important collection of nerve-cell
which constitute the ganglion habenulae. The axons of these cells are collected o
the ventral aspect of the ganglion into a bundle, called the fasciculus retroflexu
which takes a curved course downwards and forwards in the tegmentum of tl
mesencephalon. The fasciculus retroflexus lies close to the medial side of tl
red nucleus, and finally comes to an end in a group of cells termed the gangli(
interpedunculare, situated in the inferior part of the substantia perforata poster!
(see p. 591).
The ganglion habenulee is likewise intimately connected with the stria medullai
(tsenia thalami) and the dorsal part of the stalk of the pineal body.
PAKTS DEEIVED FKOM THE DIENCEPHALON. 615
As previously stated, -the stria medullaris a very evident band of white
matter lies on the thalamus, subjacent to the ependymal ridge termed the tsenia
thalami. When traced backwards, many of the fibres of the stria medullaris
are observed to end amongst the cells of the ganglion habenulse, whilst others are
continued past the ganglion to enter the peduncle of the pineal body, and, through
it, to reach the ganglion habenulae of the opposite side, in connexion with the cells
of which they terminate. The stria medullaris, therefore, ends partly in the
ganglion habenulas of their own side and partly in the corresponding ganglion of the
opposite side. The decussation of fibres across the median plane forms the dorsal
part of the pineal stalk or peduncle, and is termed the commissura habenularum.
When the stria medullaris is traced in the opposite direction, it is noticed
to split into dorsal and ventral parts near the column of the fornix. The dorsal
part arises from cells in the hippocampus : these fibres pass into the fornix and
when they reach its column they turn abruptly backwards to enter the stria
medullaris. The ventral part springs from a collection of cells in the gray matter
on the base of the brain close to the optic chiasma. The striae medullares are
believed to form a part of the olfactory apparatus.
Gommissura Posterior. The posterior commissure is a slender band of white
matter, which crosses the median plane under cover of the stalk of the pineal body
and overlies the entrance of the aqueduct of the brain into the third ventricle. The
fibres which enter into the formation of the posterior commissure are believed to
arise in a special nucleus, which is placed in the central gray matter immediately
above the oculo-motor nucleus. They decussate with each other across the median
plane and thus the commissure is formed. The other connexions of this little
band are not satisfactorily established, but Held believes that some of its ventral
fibres pass downwards into the medial longitudinal bundle.
Substantia Perforata Posterior. This has already been described on p. 542.
Some delicate bands of white matter, termed the tsenia pontis, may frequently be
seen emerging from the gray matter of this region ; they then curve round the
pedunculus cerebri in close relation to the superior border of the pons, with which
they enter the cerebellum to end in the nucleus dentatus (Horsley).
Corpora Mamillaria. The corpora mamillaria are two round white bodies,
each about the size of a pea, which lie side by side in the interpeduncular fossa on
base of the brain, immediately in front of the substantia perforata posterior.
Each corpus mamillare is coated on the outside by white matter derived
the column of the fornix, and contains, in its interior, a composite gray
ileus with numerous nerve-cells. Several important strands of fibres are con-
nected with the corpus mamillare: (1) The column of the fornix curves' down-
wards in the side wall of the third ventricle to reach the corpus mamillare,
and their fibres end amidst the cells of that body. (2) A bundle of fibres, the
fasciculus mamillo-thalamicus, takes origin in the midst of each corpus mamillare
and extends upwards into the thalamus, to end in fine arborisations around the
large cells in the anterior thalamic nucleus. (3) Another bundle of fibres, the
pedunculus corporis mamillaris, takes form within the corpus mamillare and extends
downwards in the gray matter of the floor of the third ventricle, to reach the
tegmentum of the mesencephalon. These tracts, together with the strise medullares
(thalami) and the fasciculi retroflexi, are amongst the most ancient fibre-systems in
the brain. They represent the paths by which olfactory impulses may reach the
brain-stem, and perhaps the spinal medulla also, and so influence the muscles of
the body.
Tuber Cinereum and Infundibulum. The tuber cinereum is a small, slightly
prominent field of gray matter, which occupies the anterior part of the inter-
peduncular fossa between the corpora mamillaria behind and the optic chiasma
in front. From its anterior part the infundibulum, or stalk of the hypophysis,
projects downwards and connects the hypophysis with the base of the brain. In its
upper part the infundibulum is hollow, a small, funnel-shaped diverticulum of the
a-vity of the third ventricle being prolonged downwards into it.
Hypophysis (O.T. Pituitary Body). This is a small oval structure, flattened
above downwards, and with its long axis directed transversely, which
40 c
616
THE NERVOUS SYSTEM.
occupies the fossa hypophyseos in the floor of the cranium. It is composed of two
lobes a large anterior lobe and a smaller posterior lobe, which are closely applied
the one to the other. The in-
f undibulum, which ( extends down-
wards from the tuber cinereuni,
is attached to the posterior lobe.
Foramen inter-
ventriculare
Anterior
commissure
Third ventricle
Corpus,
mamillare
Optic nerve
Infundibulum
Hypophysis
The infundibulum and posterior
lobe of the hypophysis are developed
in the form of a hollow diverticulum,
which grows downwards from the
floor of that part of the embryonic
brain which afterwards forms the
third ventricle. The original cavity
of this diverticulum becomes ob-
literated, except in the superior part
of the infundibulum. In structure^
the posterior lobe of the hypophysis
shows little trace of its origin from
the wall of the brain -tube. It is
chiefly composed of connective tissue
and blood-vessels, with branched cells
scattered throughout it.
The anterior lobe has quite a
different origin, and may be regarded
as the functional part of the hypophysis. It is derived from a tubular diverticulum
which grows upwards from the primitive buccal cavity or stomodseum. Its connexion
with the latter (canalis craniopharyngeus) is in the course of time cut off, and the
diverticulum becomes encased within the cranial cavity in intimate association with the
cerebral portion of the organ. Structurally, it consists of tubules or alveoli, lined with
epithelial cells and surrounded by capillary vessels. Its structure is in some respects
not unlike that of the parathyreoid
bodies. In the disease known as
acromegaly, the hypophysis is usually
greatly enlarged.
FIG. 542. MEDIAN SECTION THROUGH THE HYPOPHYSEAL
REGION IN A CHILD TWELVE MONTHS OLD.
(From a photograph by Professor Symington.)
Foramen inter-
ventriculare
Lamina Terminalis. This is
a thin, delicate lamina which may
be seen on the basal aspect of the
brain, 'stretching from the upper
aspect of the optic chiasma in an
upward direction to become con-
nected with the anterior end of the
corpus callosum.
Anterior Commissure of the
Cerebrum. In the anterior part
of the cleft between the two
thalami, and immediately in front
of the columns of the fornix, a
round bundle of fibres crosses the
median plane. This is the anterior
commissure.
Ventriculus Tertius. The
third ventricle is the narrow cleft
which separates the two thalami.
Its depth rapidly increases from
behind forwards, and it may be said to extend from the pineal body behind to tl
lamina terminalis in front. Its floor is formed by the tuber cinereum and th
corpora mamillaria : the gray matter of the substantia perforata posterior, an
the tegmenta of the cerebral peduncles may also be looked upon as forming pai
of the floor (Figs. 542 and 543). It is interesting to note that the central gra ,
Anterior commissure
Third ventricle
Corpus mamillare
Subarachnoid tissue
in cisterna basalis
Infundibulum
Hypophysis
Posterior part of
subarachnoid space
Basilar part of the
occipital bone
Sphenoidal sinus
FIG. 543. MEDIAN SECTION THROUGH THE HYPOPHYSEAL
REGION IN THE ADULT.
PAETS DEEIVED FKOM THE DIENCEPHALON.
617
matter which surrounds the aqueduct is directly continuous with the gray matter
3f the substantia perforata posterior and tuber cinereum, and in this way it comes
. bo the surface in the base of the brain. The optic chiasma crosses the floor in front
ind marks the place where the latter becomes continuous with the anterior wall
sf the cavity. The anterior wall of the third ventricle is formed by the lamina
fcerminalis, which extends upwards from the optic chiasma. The anterior com-
missure, as it crosses from one side to the other, projects into the ventricle, but, of
bourse, it is excluded from the cavity by the ventricular epithelial lining. It may
be taken as indicating the place where the roof joins the anterior wall. The roof
rf the third ventricle is formed by a thin epithelial layer which stretches across the
median plane from one tsenia thalami to the other, and is part of the thin epithelial
lining of the cavity. Applied to the superior surface of the epithelial roof
Epithelial roof of third ventricle
Foramen in terventriculare | Lamma commissune hi pp O campi
oina commissure hippocampi at the attach- | } .
uent of the epithelial roof of third ventricle i j Ta?nia thalami
Corpus callosum ,' j
Columna fornicis 1 ;
Septum pellucidum \ '.''.
Anterior commissure^ -\- - J T\~ j ~-J
-rnuii oorporis callosi^^-^""^ ' i i / j i
on "iris callosi
Vena cerebri interna
\ Plexus chorioideus ventriculi tertii
\ } Commissura habenulae
\ I Recessus suprapinealis
i-^J i Pineal body
l f I i """]>J^Splenium corporis callosi
I ;xNk Lamina quadrigemina
'-^ / ^quaeductus cerebri
Vena magna cerebri
*.. Velum medullare anterius
Lobulus centralis cerebelli
/ Culmen cerebelli
Ik./
Paraterminal body--
Lamina terminalis-
Optic chiasma
Infundibulum
Fissura prima cerebelli
/Fourth ventricle
.Attachment of
''epithelial roof
iNodulus
cerebelli
Hypophysis
Massa intermnd
Sulcus hypothalamicus ;
Corpus mamillare / /
Oculomotor nerve/
Posterior commissure ,
Tegmentum (mesencephali) ;
Pons
Pyramid--''
Fourth ventricle'
Central canal-' 3
Decussation of pyramid*"'
.Pyramis
cerebelli
Uvula cerebelli
'%) Tonsilla cerebelli
Edge of apertura medialis
Chorioid plexus of fourth ventricle
(the pointing ]ine passes through
the apertura medialis)
FIG. 544. THE PARTS OP THE BRAIN CUT THROUGH IN A MEDIAN SAGITTAL SECTION.
The side walls of the ventricular cavities are also shown.
the fold of pia mater, termed the tela chorioidea, and the roof is invaginated
into the cavity along its whole length by two delicate chorioid plexuses, which
hang down from the under surface of this fold. When the pia mater is removed
the thin epithelial roof is torn away with it, leaving only the lines of attach-
ment in the shape of the taenia thalami (Fig. 549).
The side wall of the third ventricle is formed for the greater part of its
extent by the medial surface of the thalamus, covered by a thick layer of central
Y matter continuous with the central gray matter of the mesencephalon. A
little in front of the middle of the ventricle the cavity is often crossed by the
massa intermedia, which connects the thalami one with the other, and in front of
this the columna fornicis is seen curving downwards and backwards in the side
At first the bulging which it forms is distinctly prominent, but it gradu-
ally subsides as the strand, on its way to end in the corpus mamillare, becomes
more and more sunk in the gray matter on the side of the ventricle.
618
THE NERVOUS SYSTEM.
The third ventricle communicates with both of the lateral ventricles, and also
with the fourth ventricle. The aquseductus cerebri, the narrow channel which
tunnels the mesencepbalon, brings it into communication with the fourth ventricle.
The opening of this aqueduct is placed at the posterior part of the floor of the third
ventricle, immediately below the posterior commissure. The foramina inter-
ventricularia bring it into communication with the lateral ventricles. These
apertures are placed at the upper and anterior parts of the side walls, and lead
laterally and slightly upwards between the most prominent parts of the columns
of the fornix and the anterior tubercles of the thalami. They are just large
enough to admit a crow-quill, and through these passages the epithelial lining of
the three ventricles becomes continuous. From the foramen a distinct groove on
--OPTIC RECESS
^INFUNDIBULAR
RECESS
'FOURTH
VENTRICLE
FIG. 545. PROFILE VIEW OF A CAST OF THE VENTRICLES OF THE BRAIN (from Retzius).
This figure faces in the direction opposite to that of Fig. 544.
R.SP. Recessus suprapinealis.
R.P. Recessus pinealis.
A.S. Aqiueductus cerebri.
F.M. Foramen interventriculare.
the side wall of the ventricle leads backwards towards the mouth of th
aqueduct. It is termed the sulcus hypothalamicus, and is of interest, inasmuch t
it is considered by His to represent in the adult brain the furrow which dividii
the side wall of the embryonic brain-tube into an alar and a basal lamina.
The outline of the third ventricle, when viewed from the side in a median secti(
through the brain (Fig. 544), or as it is exhibited in a plaster cast of the ventricular syste
of the brain (Fig. 545), is seen to be very irregular. It presents several diverticula jj
recesses. Thus, in the anterior part of the floor there is a funnel-shaped pit or recess, leadrii
down through the tuber cinereum into the infundibulum of the hypophysis. Anotb *
recess, the recessus opticus, leads forwards immediately in front of this, above the op*':
chiasma. Posteriorly two diverticula are present. One, the recessus pinealis, passes ba(|
wards above the posterior commissure and the mouth of the aquseductus cerebri foi
short distance into the stalk of the pineal body. The second is placed above this and <
carried backwards for a greater distance. It is a diverticulum of the epithelial roof, ai
therefore, is difficult to demonstrate. It is termed the recessus suprapinealis.
CEEEBKAL CONNEXIONS OF THE OPTIC TRACT.
619
CEREBRAL CONNEXIONS OF THE OPTIC TRACT.
The optic nerve is connected with the hypothalamus. At the optic
jhiasma the optic nerves of the two sides are joined together and a partial
lecussation of fibres takes place. The fibres which arise in the medial half of each
.-etina cross the median plane and join the optic tract of the opposite side. The
')ptic tract proceeds backwards round the cerebral peduncle, and in the neighbour-
lood of the geniculate bodies appears to divide into two roots, viz., a lateral and
i medial (Fig. 546), but only the former is really part of the tract.
Commissure of Gudden. The so-called medial root disappears under cover of
Tuberculum olfactorium
Olfactory tract
Optic tract | /'
Substantia perforata anterior |
tria olfactoria lateralis upon anterior |
part of piriform area
fucleus amygdalae (cut surface) i
'iriform area (cut surface) j
iimen insulae !
Optic nerve
Optic chiasma
/ / Infundibulum
Corpus mamillare
( / Substantia perforata posterior
Oculomotor nerve
Internal capsule
)ptic radiation / / ; /
Stria terminalis / / /
Caudate nucleus / ; ,'
Lateral geniculate body / /
Brachium colliculi superioris [
Thalamus (pulvinar)
Medial geniculate body \ i
Basis pedunculi cerebri \
Red nucleus
Optic radiation
Caudate nucleus
y Stria terminalis
Radiatio thalamo-temporalis (acoustic
radiation) passing from the medial
geniculate body into the anterior
transverse temporal gyrus
Substantia nigra
546. THE VENTRAL ASPECT OF PART OF THE PROSENCEPHALON, SHOWING THE EIGHT OPTIC TRACT.
The mesencephalon has been cut across. Olfactory area, dull yellow ; optic fibres, blue ; motor fibres,
red ; acoustic fibres, bright yellow.
the medial geniculate body an _ Two DRAWINQS OP THE - EMBRYONIC BRAIN (by His).
A. Reconstruction of the fore-brain and mid-brain of His's embryo KO;
profile view. B, Same brain as A, divided along the median plane
and viewed upon its inner aspect.
two fnlrU hp M ' Mamillary eminence ; Tc, Tuber cinereum ; Hp, Hypophysis
JTT" (hypophyseal diverticulum from buccal cavity) ; Opt, Optic stalk ;
Come invagmated trom this TH> Thalamus ; Tg, Tegmental part of mesencephalon ; Ps, Pars
epithelial roof in the whole hypothalamica ; Cs, Corpus striatum ; FM, Foramen interventricu-
ov f OT1 f rt f fVo TKvnaoi lare ; L, Lamina terminalis ; RO, Recessus optic us ; Ri, Recessus
infundibuli, Met, Metathalamus.
cephalon, both its telen-
cephalic and diencephalic parts. In the greater part of their length these
folds project into the third ventricle, and form its chorioid plexus (Fig. 549);
but the anterior parts of the two chorioidal folds, namely, those parts formed
from the roof of the inter ventricular foramina (F.M.), become greatly enlarged
and project each into the corresponding lateral ventricle. The furrow cor-
responding to this invagination of the roof is called the fissura chorioidea.
When the hemisphere vesicle first begins to expand, the thinner part of the
hemisphere wall, which is called the pallium, is freely continuous around the
vertical caudal margin of the foramen interventriculare (Fig. 548, Y) with the
thalamus (TH).
But as development proceeds the wall of the prosencephalon becomes attenuated
along the line of this pallio-thalamic junction, and eventually the edge of the
pallium fringing this attachment to the thalamus becomes reduced to a thin layer
of epithelium which is continuous at its superior end with the lamina chorioidea of
Ri.
union between them. At
a somewhat later Stage in
622
THE KEKVOUS SYSTEM.
the roof. Into this secondarily formed caudal extension of the chorioid lamina the
invagination that commenced in the roof of the foramen interventriculare extends
untif it reaches the inferior extremity of the deep cleft separating the cerebral
hemisphere from the thalamus (Fig. 548, A). Below this point the thalamus
remains in uninterrupted continuity with the floor of the cerebral hemisphere (Cs),
which is becoming thickened to form the corpus striatum.
At a very early stage in the development of the embryo, long before there is any
sign of the hemisphere vesicles, the ectoderm upon each side of the anterior neuro-
pore (see p. 500) becomes
( Fissura chorioidea. thickened to form the area
olfactoria (see Fig. 440, D, p.
501). Certain of the epithelial
cells in this area become con-
verted into bipolar sensory cells,
which become specially adapted
to be affected byicertain kinds of
air-borne chemical stimuli that
awaken a consciousness of smell.
These cells always remain in situ
in the olfactory epithelium, just
as the most primitive sensory
cells do in Hydra (Fig. 439, p.
497). But other nerve -cells
FIG. 549. DIAGRAM OF A TRANSVERSE SECTION THROUGH A , , . ,
FCETAL BRAIN TO SHOW THE INVAGINATION OF THE ROOF seem to be derived trom the
THROUGH EACH iNTERVENTRicoLAR FORAMEN. area olfactoria which do not
remain in the parent epithelium,
but become attached to the adjoining part of the neural tube. These cells form
the olfactory ganglion, which acts as the receptive organ for the impressions brought
into it by the processes of the sensory cells in the olfactory epithelium; and the
--Pallium.
.-i-\ -Venfriculus lareralis.
_ Lamina chorioidea
venhriculi la^ralis.
-Foramen inrervenrriculare.
Lamina chorioidea
venrriculi rerrii.
Corpus srriafum.
-Third ventricle.
Floor plafe.
HYPOPHYSEAL DIVERTICULUM
RECESS CHIASMA
FIG. 550. Two DRAWINGS BY His, ILLUSTRATING THE DEVELOPMENT OF THE HUMAN BRAIN.
A, Median section through a foetal human brain in the third month of development.
B, Schema showing the directions in which the cerebral hemisphere expands during its growth
P.M.H. Pars mamillaris hypothalami. M. Mamillary region. 0. Occipital lobe.
P.O.H. Pars optica hypothalami. F. Frontal lobe. T. Temporal lobe.
P. Parietal lobe.
area of the neural tube to which it bscomes attached is destined to become part of
the cerebral hemisphere. At the end of the first month this portion of the hemi-
sphere becomes drawn out as a hollow protrusion, the distal end of which is
coated with a layer of olfactory ganglion and is known as the bulbus olfactorius ;
the rest forms a peduncle. In the course of its subsequent development in the
human brain (though not in those of most mammals) the cavity in the bulb and
peduncle becomes completely obliterated. The peduncle becomes so greatly
elongated and attenuated that, to the unaided eye, it appears to be wholly formed
THE CONNEXIONS OF THE OLFACTOKY NEKVES.
623
of white nerve-fibres passing to and fro between the olfactory bulb and the
hemisphere ; hence it is called the tractus olfactorius.
The cerebral hemisphere first appears in the form of a slight bulging upon each
side of the fore-brain, but it soon assumes large dimensions. At first it grows
forwards and upwards (Fig. 550), and a distinct cleft, the floor of which is the
roof-plate and lamina terminalis, appears between the two hemispheres : this is known
as the fissura longitudinalis cerebri. The separation of the two cerebral vesicles
by the longitudinal fissure begins at the end of the first month. This fissure
becomes occupied by mesodermic tissue, which later on forms the falx cerebri.
The cerebral hemisphere, in its further growth, is carried progressively backwards
over the posterior parts of the developing brain. At the end of the third month it
has covered the thalamus. A month later it reaches the corpora quadrigemina,
and by the seventh month it has not only covered these, but also the entire upper
surface of the cerebellum.
In the earlier stages of its development the cerebral hemisphere is a thin-walled
vesicle with a relatively large cavity, which represents the primitive condition of
the lateral ventricle. At first the vesicle is bean-shaped and the cavity is curved.
As development proceeds the posterior portion of the hemisphere grows backwards
over the cerebellum in the shape of a hollow protrusion, and a distinct occipital
lobe enclosing the posterior horn of the lateral ventricle is the result. This
developmental stage begins about the fourth month.
THE CONNEXIONS OF THE OLFACTORY NERVES.
The olfactory nerves are the axons of the spindle-shaped bipolar cells situated
in the olfactory mucous membrane (Fig. 551). These
axons collect in the submucous layer to form small
bundles, which enter the cranial cavity through the
foramina in the lamina cribrosa .of the ethmoid
bone. They at once enter the inferior surface of
the bulbus olfactorius, and each fibre breaks up into
a tuft of terminal filaments. Towards these tufts
dendrites proceed from large mitral cells placed in a
deeper plane within the bulb, and each dendrite also
breaks up into numerous terminal branches inter-
twined with those of the olfactory nerves. In this
way are formed a large number of globular bodies,
each consisting of the arborescent terminations of
a mitral dendrite and of certain olfactory nerve-
fibres. These are the olfactory glomeruli of the bulb.
Each mitral cell gives otf several dendrites and one
axon. Only one dendrite enters into the formation
of a glomerulus, but several nerve- fibres may be
connected with such a body. It thus happens that,
through its dendrite, a mitral cell may stand in
connexion with several olfactory nerve-fibres. The
axon of the mitral cell passes upwards to the white
matter of the bulb, enters this, and, bending back-
wards, is conducted through the tract towards the
cerebral cortex.
The olfactory bulb is a small, flattened, elliptical mass of gray substance placed
upon the upper surface of the lamina cribrosa of the ethmoid. Its posterior
xtremity is attached to the rest of the cerebral hemisphere by the long tractus
olfactorius (Fig. 476), a prismatic band of white substance placed in a furrow
(sulcus olfactorius) on the under surface of the frontal region of the cerebral
hemisphere. A short distance in front of the optic chiasma each olfactory tract
becomes inserted into the hemisphere (Fig. 552). The swollen pyramidal-shaped
OLFACTORY MUCOUS
JJlimill!! MEMBRANE
624
THE NEKVOUS SYSTEM.
attached end of the peduncle is called the trigonum olfactorium. Immediately
behind the trigone a small obliquely placed ovoid area of gray matter, the
tuberculum olfactorium, can sometimes be detected in the human brain ; but in the
brains of most mammals with a greater development of the organs of smell this
swollen area is much more prominent and constant. In most human brains,
however, it is difficult to distinguish it from a much more extensive area, which is
situated behind it and to its lateral side, and is named the substantia perforata
anterior (Fig. 552). Along the anterior margin of this perforated substance there
can sometimes be detected a small, rounded, rope-like strand of gray matter, the
medial end of which passes into the trigonum olfactorium. This is the anterior
Tuberculum olfactorium
Olfactory tract , |
Optic tract
Substantia perforata anterior I 5 /
Stria olfactoria lateralis upon anterior | \
part of piriform area
Nucleus amygdal* (cut surface)
Piriform area (cut surface)
Limen insulae
Optic nerve
1 Optic chiasma
i i Infundibulum
Corpus mamillare
Substantia perforata posterior
/ Oculomotor nerve
Internal capsule
Optic radiation / / /
Stria terminalis / /. /
Caudate nucleus / / '
Lateral geniculate body ; '
Brachium colliculi superioris [
Thalamus (pulvinar)
Medial geniculate body i -
Basis pedunculi cerebri 1
Red nucleus
/ Optic radiation
/ / Caudate nucleus
/ i
; Stria terminalis
Radiatio tlialamo-temporalis (acoustic
radiation) passing from the medial
geniculate body into the anterior
transverse temporal gyrus
Substantia nigra
FIG. 552. PART OF THE VENTRAL SURFACE OF THE PROSENCEPHALON, SHOWING THE ATTACH-
MENT OF THE OLFACTORY TRACT.
Olfactory area, dull yellow ; optic, blue ; motor fibres, red ; acoustic fibres, bright yellow.
part of the area piriformis the stalk of the pear-shaped lobe and upon its surface
is placed a very well-defined narrow band of nerve-fibres, the stria olfactoria
lateralis, which is composed of axons of mitral cells (in the olfactory bulb) pro-
ceeding to the piriform area. Even when the anterior part of the piriform area
is not distinguishable, the stria lateralis is always a prominent feature.
The piriform area extends transversely laterally in the deep valley between
the orbital and temporal regions of the hemisphere (fossa cerebri lateralis) :
becoming slightly broader, and reaching what is known as the insula (of which it
forms the limen insulse), it becomes sharply bent upon itself (Figs. 552, and 553, C)
It then passes medially and backwards, and emerges from the fossa as a broad
area upon the under surface of the temporal region (Fig. 553, C). This greatly j
expanded caudal extremity of the pear is the area piriformis in the strict senst j
of the term.
THE CONNEXIONS OF THE OLFACTOKY NEEVES.
625
If the brain of almost any other mammal is examined (take the rabbit's as
an example), the area piriformis will be found to constitute relatively an enormously
larger proportion of the cerebral hemisphere than it does in the human brain ;
and it is separated from the part of the hemisphere (neopallium) that lies above
it by a longitudinal furrow called the fissura rhinalis. The enormous expansion
of the neopallium in the human brain accentuates the flexure of the piriform
area at the point x (Fig. 553), and at the point y the exuberant growth of
neopallium relegates the swollen posterior part of the piriform area on to the
medial surface (Fig. 554), where the posterior part of the rhinal fissure persists to
separate it from the neopallium.
The surface of the piriform area often presents numerous small wart -like
Olfactory peduncle
Olfactory bulb -.
/\
Olfactory tract ' ' VjJ, .._
/ x \-*&^ f- ^ Rhinal fissure
Olfactory tubercle ' v
Nucleus amygdalae Piriform area
Olfactory bulb^
Olfactory tract
Piriform area
(anterior part)
x -
Rhinal fissure -
y
Neopallium
Piriform area
(posterior
part)
Piriform area
(anterior part)
Olfactory tubercle
Optic chiasma
Nucleus
amygdalae
y-
Rhinal fissure --
Neopallium ^V -
FIG. 553.
Olfactory l bulb
- Olfactory-tubercle
-Optic chiasma
Nucleus
amygdalae
Piriform area
(posterior part)
A, The lateral aspect of the left cerebral hemisphere of a rabbit. B, The inferior aspect of the right half of
a rabbit's brain. C, The corresponding view of a human foetal brain at the fifth month.
Olfactory areas, green ; neopallium, blue.
excrescences ; and it is whitened by a thin layer of fibres (substantia reticularis
alba) prolonged backwards from the stria olfactoria lateralis. By these fibres
olfactory impulses are poured directly from . the mitral cells of the bulb into the
piriform area. If we call the olfactory nerves the primary olfactory neurones, the
fibres which pass from the bulb to the piriform area would then be secondary
olfactory neurones.
Formatio Hippocampalis. From all parts of the area piriformis, as well as
the trigonum and tuberculum olfactorium, fibres arise (tertiary olfactory neurones),
and proceed on to the medial aspect of the hemisphere, where they terminate in
the edge of the pallium, alongside the lamina chorioidea. In the human brain the
vast majority of these tertiary neurones proceed from the posterior extremity of
the piriform area, but a certain number arise in the neighbourhood of the
substantia perforata anterior and proceed at once on to the medial surface of the
hemisphere. The large number of small nerve-cells that collect in the medial
edge of the pallium become specially modified in structure to form a receptive
organ for impressions of smell, known as the fascia dentata; and the axons of
these cells pass into the part of the pallium which immediately surrounds the
peripheral edge of the fascia dentata and is known as the hippocampus (Fig. 556).
41
626
THE NEKVOUS SYSTEM.
In" the hippocampus impressions of smell are brought into relation with those of
other senses (probably taste) ; and from the hippocampal cells fibres are emitted
to form a system known as the fornix, which establishes connexions with the
hippocampus of the other hemisphere and with the hypothalamus, thalamus, and
more distant parts of the brain.
The rudiment of the hippocampal formation that develops on the medial surface
begins in front, alongside the place where the stalk of the olfactory peduncle (which
becomes the trigonum olfactorium) is inserted ; it passes upwards to the superior
end of the lamina terminalis, from the rest of which it is separated by a triangular
mass of gray matter called the corpus paraterminale (Fig. 555) ; and then it proceeds
backwards, fringing the fissura chorioidea in the whole of its extent, ending below
in the temporal region alongside the posterior part of the area piriformis. The
anterior part of this great hippocampal fringe of the pallium does not attain its full
development in the human brain and remains as a more or less vestigial aborted
Gyrus cinguli
Commissura fornicis j
Corpus fornicis
Corpus callosum
Septum pellucidum
Sulcus cinguli
Sulcus cinguli
Paracentral area
! Paracentral sulcus
' Sulcus centralis
Gyrus frontalis superior
Lamina chorioidea
Foramen
interventriculare
Hippocampal rudiment
Incisura sulci cinguli
Olfactory bulb ,.
Corpus paraterminale' /
Columna fornicis
Olfactory tract
Stria olfactoria lateralis /
Nucleus amygdalae
Piriform area
Thalamus (cut surface) ',
Rhinal fissure
Cauda fasciae dentatte
'Sulcus praecunei
., Praecuneus
.. Sulcus subparietalis
Fossa parieto-
-'occipitalis
-Sulcus paramedu
Area striata
.Sulcus
sagittalis ct
.Sulcus
retrocalcari:
Area striata
\ \ Sulcus polaris inferior
\ \ Sulcus calcarinus
\ iSulcus sagittalis gyri linguali
\ Sulcus collaterals
, Hippocampus
', , Splenium of corpus callosum
\ Fascia dentata
, Crus fornicis
Gyrus paradentatus
Hippocampus Fimbria
FIG. 554. MEDIAL ASPECT OF THE RIGHT CEREBRAL HEMISPHERE, WITH THE OLFACTORY PARTS COLOURED.
structure ; but the posterior part undergoes a peculiar transformation. The tertiary
olfactory neurones, coming mainly from the posterior part of the area piriformis, enter
the. margin of the hippocampal formation, and the small cells which receive these
incoming fibres multiply rapidly during the third month, and arrange themselves
in a densely packed row of granules, which represent the distinctive feature of the
fascia dentata (Fig. 556). At first this cell-column is continuous at its peripheral
margin with a much more loosely packed column of larger and less numerous cells,
which represent the hippocampus ; and these in turn give place to the more
diffusely arranged and laminated cells of the typical cortex cerebri, which we
the neopallium. As development proceeds both the dentate and hippocam]
columns of cells rapidly increase in length, and both appear to push their w
towards the ventricle (Fig. 556, B) into the substance of the wall, which becom<
correspondingly thickened. The ventricular swelling thus formed is the hip
campus ; and it is important to recognise that this swelling is not produced
any invagination of the surface, such as is usually described under the name of tl
THE CONNEXIONS OF THE OLFACTOKY NERVES.
627
fissura hippocampi. There is no fissura hippocampi in the human brain. What is
usually described under, this name is an artificial cleft made by pushing the
handle of a scalpel into the hippocampal formation at the edge of the exposed
part of the fascia dentata (Fig. 556, B and C, at x) and separating the morpho-
logical surface of the hippocampus from that of the buried part of the fascia
dentata. Cleavage readily occurs along this line because there are numerous
nerve-fibres, hippocampal and dentate respectively, upon each side of it.
As development proceeds a break occurs in the cell-column at the junction
of its hippocampal and dentate parts, and the two columns (Fig. 556, C) become
partially interlocked.
The axons of the hippo-
campal cells collect upon
its ventricular surface to
form the alveus, the fibres
of which converge towards
the margin of the fascia
dentata, where they bend
into the longitudinal direc-
tion (i.e. parallel to the
edge of the pallium and
the lamina chorioidea) to
form a prominent white
marginal fringe, the fimbria.
Corpus callosum-^.
commissure-
Anterior commissure -
Paraterminal body "'
Lamina terminalis
Fascia dentata
Olfactory bulb /
Optic chiasma
Column of fornix
The fibres of the fimbria
FIG. 555. MEDIAL ASPECT OF THE RIGHT CEREBRAL HEMISPHERE
OF 'A HUMAN FCETUS OF THE FOURTH MONTH.
The broken red lines indicate the paths taken by callosal fibres in the
S Upwards and forwards neopallium to reach the upper end of the lamina terminalis.
(Fig. 555), and ultimately
reach the upper end of the lamina terminalis, which provides a bridge to
conduct a certain number of them across the median plane into the fornix or
I ' P
Hippocampus. i ; i V
Fascia
denfafa
Fimbria:
Alveus.
Hippocampus.
Plexus chorioideus.
FIG. 556. DIAGRAMS REPRESENTING THREE STAGES IN THE DEVELOPMENT OF THE HIPPOCAMPAL
FORMATION.
fimbria of the other hemisphere, so as to link together in functional associa-
tion the two hippocampi. These crossing fibres are known as the commissura
hippocampi.
Most of the fibres that go up in the fimbria from the hippocampus do
not pass into the hippocampal commissure, but bend downwards in the anterior
lip of the foramen interventriculare to. enter the thalamic region. They are
collected into a vertical rounded column, which is called the cohimna fornicis ;
when it reaches the hypothalamus it bends backward to end in the corpus
mamillare.
The olfactory bulb and tract, the area piriformis, tuberculum olfactorium,
corpus paraterminale, and the formatio hippocarnpalis together form a part of
the hemisphere, which is concerned mainly with the function of smell. Hence
they may be grouped together as the rhinencephalon ; but this term has been used
in so many different ways that it is of doubtful utility.
628 THE NEKVOUS SYSTEM.
In the lowest vertebrates the whole hemisphere is practically rhinencephalon.
Nevertheless, fibres coming from other parts of the nervous system and conveying
impressions from other sense organs than those of smell make their way into the
cerebral hemisphere and influence the state of its activities. In other words, the
hemisphere is primarily an olfactory receptive nucleus, but is also the place where
impressions of smell are brought under the modifying influences of other sensory
impressions before they make their effects manifest in behaviour.
But it is only in the most highly organised types of brain, more especially
those of mammals and birds, that the non-olfactory senses acquire a representation
in the hemisphere which is relatively independent of, or at any rate not wholly
subservient to, the influence of the sense of smell. In the mammalian brain a
definite area of pallium is set apart to receive impressions of the tactile, visual,
acoustic, and other senses. This area is the neopallium. In the human brain it
has grown to such an extent that it forms almost the whole of the hemispheres
a mass far greater than the whole of the rest of the central nervous system.
THE CEEEBEAL COMMISSUEES AND THE SEPTUM PELLUCIDUM.
We have seen that certain fibres from the hippocampi cross from one hemisphere
to the other, using the upper part of the lamina terminalis as a bridge across the
median plane. But at an earlier stage of development other fibres can be detected
at a slightly lower level in the lamina terminalis forming a bundle, of oval outline
in sagittal section, called the commissura anterior. Its fibres come from the
olfactory bulb, area piriformis, tuberculum olfactorium, and a small temporal area
of neopallium. If the composition of the hippocampal commissure is analysed
in a foetus of the third month, it will be found that there are intermingled with
the truly hippocampal fibres some which come from the neopallium. During the
fourth month the bulk of the neopallial element in this dorsal commissure
outgrows the hippocampal element. The latter fibres become crowded into the
postero-inferior corner of the commissure and the neopallial fibres come to form a
flattened transverse bridge the corpus callosum above them. These fibres are en-
closed in a neuroglial matrix derived from the lamina terminalis and the adjoining
paraterminal bodies. Some nerve-cells also may make their way into this matrix.
As it elongates, the corpus callosum pushes its way forwards in the upper part of
the paraterminal body of each hemisphere, and as development proceeds a small area
of this body becomes almost completely circumscribed by the corpus callosum and
commissura hippocampi. As these commissural bands increase in size this small
circumscribed patch of paraterminal body becomes greatly stretched and ex-
panded to form a thin translucent leaf. The two leaves thus formed in the medial
walls of the two hemispheres are known as the septum pellucidum ; and the narrow
cleft that separates them the one from the other in the median plane is called the
cavum septi pellucidi.
There is still an element of uncertainty concerning the precise manner in which
these changes are brought about, and especially as to the precise mode of closure
of the cavum septi. As the cerebral hemisphere expands, some parts of it grow
forwards, others upwards, and others again backwards. Such growth in each
part will naturally tend to exert traction upon its commissural fibres that pass
through the corpus callosum. Hence the anterior part of this great commissure
becomes drawn forwards, its posterior part backwards, and the greater intermediate
part upwards; so that it comes to assume the form shown in Fig. 557, C.
As the posterior part of the corpus callosum pushes its way backwards, it exerts
traction upon the fibres of the hippocampal commissure and their matrix, which
becomes enormously stretched so as to form a thin lamella (the floor of the cavum
septi) stretching from a point just above the anterior commissure to the under
surface of the swollen posterior end of the corpus callosum, which is called the
splenium (Fig. 558). The hippocampal commissural fibres are scattered through-
out this lamella. The backward growth of the splenium also thrusts back th(
THE CEEEBEAL COMMISSUEES AND SEPTUM PELLUCIDUM. 629
upper end of the hippocampal formation so that it becomes removed far from the
lamina terminalis. The, fibres of the fimbria which are prolonged forwards under
the corpus callosum and septum pellucidum to bridge this great gap form the cms
fornicis on each side. As a rule in the human "adult brain the crura fornicis of the
two hemispheres become crowded together at the median plane so as to obscure
the connecting lamella which serves as a matrix for the commissura hippocampi
(Fig. 557, C) ; but the true arrangement can be seen in the brains of foetuses of
the sixth, seventh, and eighth months, and is at once revealed in the adult if
the corpus callosum is raised up by an accumulation of fluid in the lateral
ventricles (hydrocephalus), so as to put a strain upon the septum pellucidum.
The mass formed by the crura fornicis and their commissure is called the corpus
fornicis.
The fascia dentata appears as a notched band behind and below the fimbria ;
its upper end passes on to the under surface of the splenium of the corpus
callosum, where it tapers and ends (fasciola cinerea) ; but as it dwindles the upper
end of the hippocampus emerges upon the surface below and behind it and passes
into a thin film of gray matter indusium griseum which is prolonged on to the
upper surface of the corpus callosum. It proceeds forwards, becoming as a rule still
Nfestiges of the supracallosal
hippocampus
Riratermmal \,
B
Vestiges of the supracallosal
x x hippocampus
\ Septum pellucidum
/ Olfactory bulb
Vestiges of the precallosal
hippocampus
Epithelial
roof of third
ventricle
Septu
pellucidum
Paraterminal body
Roof
terminalis
Commissura
hippocampi
I
Paraterminaf body ( .
Commissura
hippocampi
FIG. 557. THREE STAGES IN THE DEVELOPMENT OP THE CORPUS CALLOSUM.
more attenuated, and after surrounding the anterior end (genu) of the corpus
callosum it passes downwards towards the trigonum olfactorium along the line that
separates the corpus paraterminale from the neopalliuin. The indusium represents
the atrophied remains of the anterior part of the hippocampal arc of the foetal brain
Tig. 555), from which the fascia dentata has entirely disappeared. It is accom-
panied by longitudinal fibres homologous to the fornix system : in other words, the
fornix fibres of the atrophied supracallosal hippocampus; they form the striae
longitudinales of the corpus callosum (Fig. 558; Fig. 564, p. 635; Fig. 559,
p. 631).
The inferior (or anterior) extremity of the fascia dentata dips into a deep furrow,
around which the area piriformis is bent in a hook-like manner (uncus) ; in this
becomes considerably reduced in diameter and then emerges (at right angles
its previous direction) to form Giacomini's " banderella," which we may call
the cauda fasciae dentatae. Behind this the inferior end of the hippocampus
'mes to the surface, but is turned inside out, hippocampus inversus. Just in
ont of the upper ending of the cauda fasciae dentatae a little knob of solid gray
matter appears upon the surface, surrounded by area piriformis. It is the nucleus
amygdalae (Fig. 558).
Corpus Callosum. The corpus callosum is the great transverse commissure
.ch passes between the two cerebral hemispheres. It is placed nearer the
r than the posterior aspect of the brain, and it unites the medial sur-
>s of the hemispheres throughout very nearly a half of their antero-posterior
630
THE NEKVOUS SYSTEM.
length. The corpus callosum is highly arched from before backwards, and
presents a convex superior surface and a concave inferior surface when viewed from
the side (Fig. 558).
The superior surface of the corpus callosum forms the bottom of the longi-
tudinal fissure, and on each side of this it is covered by the gyrus cinguli. Only
in its posterior part is it approached by the falx cerebri ; in front, this process of
dura mater falls considerably short of it. The superior surface of the corpus callosum
is covered by a thin layer of indusium continuous at the bottom of the sulcus
corporis callosi with the gray cortex on the surface of the hemisphere. In this there
are embedded, on each side of the median plane, two delicate longitudinal bands
of fibres, called respectively the stria longitudinalis medialis and lateralis. The
stria longitudinalis medialis is the more strongly marked of the two, and it is
separated from its fellow of the opposite side by a faint median furrow. The
stria longitudinalis lateralis is placed farther out, under cover of the gyrus
Sulcus cinguli
Gyrus cinguli
Commissura fornicis
Corpus fornicis j
Corpus callosum
Septum pellucidum
Sulcus cinguli * ^
Paracentral area
j Paracentral sulcus
I Sulcus centralis
Hippocampal rudiment
Incisura sulci cinguli
'Sulcus prsecunei
.Prsecuneus
.Sulcus subparietalis
Fossa parieto-
''occipitalis
Sulcus paramedia
-A.rea striata
Gyrus frontalis superior
Lamina chorioidea
Foramen
interventriculareX
Genu of
corpus
callosum
Rostrum of
corpus
callosum
Sulcus.^^Sj
genualis jj^j
AnteriorjSjffl
commissure VT
Olfactory bulb
Corpus paraterminalfc"
Columna fornicis /
Olfactory tract
Stria olfactoria lateralis /
Nucleus amygdalae /
Piriform area
Thalamus (cut surface) ',
Rhinal fissure \ |
Cauda fasciae dentatse |
\ \ Sulcus polaris inferior
'* v Sulcus calcarinus
Sulcus sagittalis gyri lingualis
Sulcus col lateralis
, \ i Hippocampus
\ l Splenium of corpus callosum
\ Fascia dentata
Crus fornicis
Gyrus paradentatus
Hippocampus Fimbria
FIG. 558. THE MEDIAL ASPECT OF THE RIGHT CEREBRAL HEMISPHERE.
cinguli. The thin coating of gray matter, with the two striee, represents the
aborted remains of the hippocampus (see p. 627). So thin is this gray coating that
the transverse direction pursued by the callosal fibres proper can be easily perceived
through it.
The two extremities of the corpus callosum are much thickened, whilst the
intermediate part or body is considerably thinner. The massive posterior end,
which is full and rounded, lies over the mesencephalon and extends backwards as
far as the highest point of the cerebellum. It is called the splenium, and it consists
of a superior and inferior part. The latter is bent forwards under the upper part,
to the inferior surface of which it is closely applied. The anterior end of the corpus
callosum is not quite so massive, and it is folded downwards and backwards on
itself. It is termed the genu. The recurved inferior part of the genu is separated
from the part of the corpus callosum which lies above, by an interval. It rapidly
thins as it passes backwards and receives the name of the rostrum. The fine
terminal ~edge of the rostrum becomes connected by means of a band of neuroglial
THE CEEEBEAL COMMISSUEES AND SEPTUM PELLUCIDUM. 631
tissue with the lamina terminalis on the antero-superior aspect of the anterior
commissure (Fig. 558). ,
The inferior surface of the corpus callosum, on each side of the median plane, is
coated with ependyma (Fig. 564, p. 635), and forms the roof of the anterior horn
and the central part of the lateral ventricle. In the median plane, however, it is
attached to subjacent parts, viz., to the septum pellucidum in front and directly
or indirectly (Fig. 564) to the body of the fornix behind (Fig. 558, p. 630).
The transverse fibres of the corpus callosum, as they enter the white medullary
centre of the cerebral hemisphere, separate from each other so as to reach most parts
of the cerebral cortex. These diverging fibres are termed the radiatio corporis
Genu
Cingulum
Frontal fibres
Cut surface
Fibres of corona radiata
Intersection of i
callosal and corona I
radiata systems of i
fibres
Corpus callosum
Cingulum (cut)
Transverse fibres
of corpus
callosum
Tapetuni
Inferior longi-
'tudinal bundle
Occipital part of
radiation of
corpus callosum
Tapetum
Stria longitudinalis medialis
Splenium
FIG. 559. THE CORPUS CALLOSUM, exposed from above and the right half dissected,
to show the course taken by its fibres.
The lateral longitudinal stria (which lies near the cingulum) is not shown.
callosi, and they intersect those which form the corona radiata or, in other
words, the fibres which extend between the internal capsule and the cerebral
cortex (Figs. 570, p. 640, and 576, p. 649). The more anterior of the fibres which
compose the genu of the corpus callosum sweep forwards in a series of curves into
the anterior frontal region of the hemisphere. A large part of the splenium,
forming a solid bundle termed the occipital part of the radiation of the corpus
callosum (O.T. forceps major), bends suddenly and abruptly backwards into the
occipital lobe (Fig. 559). Fibres from the body and superior part of the splenium,
curving round the lateral ventricle, form a very definite stratum, called the
tapetum. This is a thin layer in the medullary centre of the hemisphere, which
constitutes the immediate roof and lateral wall of the posterior horn arid the
lateral wall of the posterior part of the inferior horn of the lateral ventricle
632
THE NEEVOUS SYSTEM.
In frontal sections through the occipital and posterior temporal regions the tapetum
stands out very distinctly (Fig. 559, p. 631 ; see also Figs. 565, p. 636, and 567,
p. 638).
Septum Pellucidum. The septum pellucidum is a thin vertical partition which
intervenes between the two lateral ventricles. It is triangular in shape, and
posteriorly it is prolonged backwards for a variable distance between the body of
the corpus callosum and the fornix, to both of which it is attached. In front it
occupies the gap behind the genu of the corpus callosum, whilst below, in
the narrow interval between the posterior edge of the rostrum of the corpus
callosum and the fornix, it is prolonged downwards in the paraterminal body
towards the base of the brain. The septum pellucidum is composed of two
thin laminae in apposition with each other in the median plane (Fig. 562 ; Fig.
564, p. 635).
Cavum Septi Pellucidi. This name is applied to the median cleft between the
Sulcus cinguli
Gyrus cinguli paracentral area
Commissura fornicis
Corpus fornicis
Corpus callosum
Septum pellucidum
Sulcus cinguli
Paracentral sulcus
! Sulcus centralis
Hippocampal rudiment
Incisura sulci cinguli
Gyrus frontalis superior
Lamina chorioidea
Foramen
interventriculare's
Rostrum of
corpu
callosum
Sulcus_^3H
genuali
Anterior
commissure"
Olfactory bulb
Corpus paraterminale' /
Columna fornicis .,/
Olfactory tract
Stria olfactoria lateralis -
Nucleus amygdalae
Piriform area
Thalamus (cut surface)
Rhinal fissure
Cauda fasciae dentatse
Hippocampus
'Sulcus prsecunei
.Praecuneus
^..Sulcus subparietalis
parieto-
''occipitalis
Sulcus paramediali
.,-A.rea striata
iV J3ulcus
"sagittalis cunj
Sulcus
retrocalcarim
Area striata
Sulcus polaris inferior
Sulcus calcarinus
> Sulcus sagittalis gyri lingualis
\ JSulcus collateralis
Hippocampus
j Splenium of corpus callosum
Fascia dentata
| Cms fornicis
Gyrus paradentatus
mbria
FIG. 560. THE MEDIAL ASPECT OF THE RIGHT HALF OF THE BKAIN EXPOSED BY A MEDIAN SAGITTAL SECTION.
two laminae of the septum pellucidum.
brains.
It varies greatly in size in different
VENTRICULUS LATERALIS.
The cavity in the interior of the cerebral hemisphere is called the lateral
ventricle. It is lined throughout by ependyma continuous with the ependymal
lining of the third ventricle. In some places the walls of the cavity are in
apposition, whilst in other localities spaces of varying capacity, and containing
cerebro- spinal fluid, are left between the bounding walls.
The lateral ventricle communicates with the third ventricle of the brain by
means of a small foramen, just large enough to admit a crow-quill, which is
termed the foramen interventriculare. This aperture is placed in front of the
anterior end of the thalamus and behind the column of the fornix.
The highly-irregular shape of the lateral ventricle can be best understood by the
stu
THE LATERAL VENTRICLE.
633
study of a cast of its interior
(Figs. 561 and 545, p. 618).
It is usual to describe it as
being composed of a body and
three horns, viz. an anterior, a
posterior, and an inferior horn.
The cornu anterius is that part
of the cavity which lies in
front of the interventricular
foramen. The body or pars
centralis is the portion of the
ventricle which extends from
the interventricular foramen
to the splenium of the corpus
callosum. At this point the
posterior and inferior horns
diverge from the posterior
part of the body. The cornu
posterius curves backwards and
. medially into the occipital
lobe. It is very variable in
its length and capacity: the
chief reason for this variability
is that adhesions between the
walls of this part of the ven-
tricle 'are of common occur-
rence. The cornu inferius
proceeds with a bold sweep
round the posterior end of the Fra. 561. DRAWING TAKEN FROM A CAST OF THE VENTRICULAR
thalamus, and then tunnels in SYSTEM OF THE BRAIN, as seen from above. (After Ketzius.)
a forward and medial direction Vent. III. Third ventricle. Vent. IV. Fourth ventricle.
the temporal lobe KSP -
through
Longitudinal
fissure
Corpus callosum
Lateral ventricle
Column of fornix
Chorioid plexus.
Foramen inter-
ventriculare
Septum pellucidum
towards the tem-
poral pole.
The early
foetal lateral ven-
tricle is very
capacious and
presents an
arched or semi-
lunar form. It is
composed of parts
which correspond
to the anterior
horn, the central
part and the in-
ferior horn, and
there is little or
no demarcation
between them.
The posterior
horn is a later
"tSTS-/ lllvtfuP^ production. It
Nucleus lentiformis / COmeS into CXlst-
ciaustrum ence as a diver-
FIG. 562. FRONTAL SECTION THROUGH THE CEREBRAL HEMISPHERES so as to cut ticulum or elon-
through the anterior horns of the lateral ventricles, through which the central CTn t fir q pouch
part of the ventricles, the columns of the fornix, and the interventricular
foramina can be seen.
which grows
634
THE NEKVOUS SYSTEM.
backwards from the superior and posterior part (i.e. the convexity) of the primitive
cavity.
Cornu Anterius. The anterior horn forms the foremost part of the cavity, and
extends in a forward and lateral direction in the frontal lobe. When seen in
frontal section (Fig. 562) it presents a triangular outline, tKe floor sloping upwards
and laterally to meet the roof at an acute angle. It is bounded in front by the
posterior surface of the genu of the corpus callosum ; the roof also is formed by the
Corpus callosum
Cavum septi pellucidi
Foramen interventriculare
Caudate nucleus
Thalamus
Chorioid plexus
Stria terminalis
Trigonum collateral
Hippocampus
Fimbria ;
Occipital part of the radiation of the corpus callosum
Calcar avis
Bulb of the cornu
Hippocampus
Crus of the fornix
Body of the fornix
FIG. 563. DISSECTION, to show the fornix and lateral ventricles ; the body of 'the corpus callosum
has been turned over to the left.
corpus callosum. The medial wall, which is vertical, is formed by the septum
pellucidum; whilst the sloping floor presents a marked elevation or bulging,
viz., the smooth, rounded, and prominent extremity of the pear-shaped caudate
nucleus.
Pars Centralis. The central part or body of the cavity is likewise roofed by the
corpus callosum. On the medial side it is bounded by the posterior part 'of the
septum pellucidum which attaches the fornix to the inferior surface of the corpus
callosum. On the lateral side it is closed, as in the case of the anterior horn, by the
meeting of the floor and the roof of the cavity. On the/oor a number of important
Corpus callosum-- -~~
THE LATEEAL VENTKICLE. 635
objects may be recognised. From the lateral to the medial side these are met
in the following order : , (1) the caudate nucleus ; (2) a groove which extends
obliquely from before backwards and laterally between the caudate nucleus
and the thalamus, in which are placed the vena terminalis and a white band
called the stria terminalis ; (3) a portion of the superior surface of the thalamus ;
(4) the chorioid plexus; (5) the thin, sharp edge of the fornix (Fig. 564).
The caudate nucleus narrows rapidly as it proceeds backwards on the lateral part
of the floor of the lateral ventricle. The vena terminalis (O.T. vein of the corpus
striatum) is covered over by ependyma. It joins the vena cerebri interna close to
the foramen interventriculare. The connexions of the stria terminalis will be dealt
with later. The portion of the superior surface of the thalamus which appears
in the floor of the ventricle is in great part hidden by the chorioid plexus, which
lies upon it. The lamina chorioidea is an epithelial fringe which is attached to
the sharp edge of the fornix superiorly and after surrounding a rich vascular
fold of pia mater becomes fixed to the superior surface of the thalamus.
The vascular fold is the chorioid plexus. In front it is continuous, in the inter-
ventricular foramen, with the corresponding chorioid plexus of the third ventricle
(Fig. 560), whilst behind, it is carried into the inferior horn of the ventricle.
Although the chorioid plexus has all the appearance of lying free within the
ventricle, it must be borne in mind that it is invested by the epithelial
Gyrus cinguli Indusium Stria longitudinalis medialis
Commissura hippocampi^ { ^ ,/ m| ^xCavum septi pellucidi
^/Septum pellucidum
5 ^.--Ventriculus lateralis
. -Grus fornicis
^ _ J Plexus chorioideus
Nucleus caudatus ^H ZYfjfcl 2$S2^I
- - - - Stria terminalis
Tela chorioidea' "~ ~ ""^J^^Mf WfflJ^^HB^^T "^Attachment of lamina chorioidea
-Thalamus (free surface)
Thalamus / ; Tamia thalami
Plexus chorioideus vent, tertii Ventriculus tertius
FIG. 564. DIAGRAM OF TRANSVERSE SECTION ACROSS THE CENTRAL PARTS OF
THE LATERAL VENTRICLES.
chorioidal lamina which represents a portion of the hemisphere wall and excludes
it from the cavity.
Cornu Posterius. The posterior horn is an elongated diverticulum carried
backwards into the occipital lobe from the posterior end of the ventricle. It tapers
to a point and describes a gentle curve, the convexity of which is directed
laterally. The roof and lateral watt of this portion of the ventricular cavity are
formed by the tapetum of the corpus callosum. In frontal sections through the
occipital lobe this is seen as a thin but distinct layer of white fibres, which lies
immediately lateral to the ependyma and to the medial side of a much larger
strand of fibres in the medullary substance of the occipital lobe, viz., the optic
radiation.
On the medial wall two elongated curved elevations may be observed. The
uppermost of these is termed the bulb of the cornu (bulbus cornu posterioris), and is
produced by the fibres of the radiation of the corpus callosum as they curve
abruptly backwards from the lower part of the splenium of the corpus callosum into
the occipital lobe. Below this is the elevation known as the calcar. It varies
;reatly in size in different brains, and is caused by an infolding of the ventricular
in correspondence with the anterior part of the calcarine sulcus on the
irior of the hemisphere. It may come into contact with and adhere to the
3ral wall of the ventricle in a part or even the whole of its extent.
Cornu Inferius. The inferior horn is the continuation of the cavity into the
smporal region. At first directed backwards and laterally, the inferior horn
suddenly sinks downwards behind the thalamus into the temporal region, in the
636 THE NEKVOUS SYSTEM.
centre of which it takes a curved course forwards and medially to a point about an
inch behind the extremity of the temporal pole.
In the angle between the diverging posterior and descending horns the cavity
of the ventricle presents an expansion of a somewhat triangular shape. To this
the name of trigonum collaterale is sometimes given.
The roof of the inferior horn is formed for the most part by the tapetum of
the corpus callosum. At the extremity of the horn the roof presents a bulging
into the cavity. This is produced by a collection of gray matter termed the
amygdaloid nucleus. The stria terminalis and the attenuated tail of the caudate
nucleus are both prolonged into the inferior horn and are carried forwards, in
its roof, to the amygdaloid nucleus.
On the, floor of the inferior horn the following structures are seen : (1)
hippocampus; (2) the chorioid plexus; (3) the fimbria; and (4) the eminentia
collaterals.
The hippocampus is for the most part covered by the chorioid plexus of the
lateral ventricle. If this is detached a fissure appears between the fimbria and the
roof of the ventricular horn. This is the chorioid fissure. It appears at a very
Splenium of corpus callosum
Bulb of the posterior cornu Bulb of the posterior cornu
', Fibres of corpus callosum (tape-
tum)
'. Optic radiations
Inferior occipito-frontal fasciculus.
FIG. 565. FRONTAL SECTION THROUGH THE POSTERIOR HORNS OF THE LATERAL VENTRICLES,
VIEWED FROM THE FRONT.
early date in the development of the cerebral hemisphere, and takes an arcuate
course round the posterior end of the thalamus. In the region of the pars
centralis of the lateral ventricle it extends as far forwards as the foramen inter-
ventriculare and is formed by the involution of an epithelial part of the wall of
the ventricle over the chorioid plexus (p. 622). In the region of the inferior horn,
when the chorioid plexus, with the involuted epithelial layer which covers it, is
withdrawn, the chorioid fissure is converted into an artificial gap which leads
directly into this part of the ventricular cavity.
The chorioid plexus is a convoluted system of blood-vessels in connexion with a
fold of pia mater, which is prolonged into the inferior horn of the lateral
ventricle. It lies on the surface of the hippocampus and is continuous, behind
the posterior part of the thalamus, with the chorioid plexus in the pars centralis
of the lateral ventricle. But it must not be supposed that the chorioid plexus lies
free in the ventricular cavity. It is clothed in the most intimate manner by an i
epithelial layer, which represents the medial wall of the inferior horn involuted
into the cavity over the chorioid plexus. The ventricle, therefore, opens on the
surface only through the chorioid fissure when this thin epithelial layer is torn
away by the withdrawal of the chorioid plexus. From the above, it will be under-
BASAL GANGLIA OF THE CEEEBEAL HEMISPHEEE.
637
(viz., from
the lateral
Digitationes
hippocampi
Hippocampus
Collateral
eminence
Trigonum
collaterale
Posterior horn of
lateral ventricle
Calcar avis
Bulb of the cornu
stood that the arcuate chorioid fissure, throughout its whole length
the interveutricular foramen to the extremity of the inferior horn of
ventricle), is formed by the
involution of the roof and a
portion of the wall of the
hemisphere which remains
epithelial. In the central
part of the ventricle this layer
is attached, on the one hand,
to the sharp margin of the
fornix, and on the other to
the superior surface of the
thalamus ; in the inferior horn
it is attached, in like manner,
to the edge of the fimbria hip-
pocampi or crus of the fornix,
whilst, above, it joins the roof
of this portion of the ventricle
along the line of the stria
terminalis (Fig. 564).
The eminentia collateralis
shows very great differences
in its degree of development.
The trigonum collaterale is
a smooth elevation in the floor
of the ventricle, in the interval
which is left between the
calcar avis and the hippo-
campus as they diverge one
from the other.
BASAL GANGLIA OF THE
CEREBRAL HEMISPHERE. FlG 555. DISSECTION from above, to show the posterior and
, , . inferior cornua of the lateral ventricle,
heading are B . G . Cauda fascia; dentat{e> F .D. Fascia dentata hippocampi.
3luded Certain masses Ot F . Fimbria hippocampi. H.C. Gyrus hippocampi.
gray matter more or less com-
pletely embedded in the white medullary substance of the hemisphere, and which
are developed in its wall. They compose the caudate and lentiform nuclei, which
together form the corpus striatum, and the amygdaloid nucleus.
The nucleus caudatus bulges into the lateral ventricle. It is a piriform,
highly arched mass of gray matter, which presents a thick, swollen head, or anterior
extremity, and a long, attenuated tail. The head projects into the anterior horn of
the lateral ventricle, whilst its narrower part is prolonged laterally and posteriorly
in the floor of the ventricle, where it is separated from the thalamus by the stria
terminalis. Finally, its tail curves downwards with a bold sweep and enters the
inferior horn of the lateral ventricle. In the roof of this horn it is prolonged
forwards to the amygdaloid nucleus, the lower part of which it joins. The caudate
nucleus thus presents a free ventricular surface, covered with ependyma, and a deep
surface embedded in the white substance of the cerebral hemisphere, and for the
most part related to the internal capsule.
Owing to its arched form it follows that, in' horizontal sections through the
cerebral hemisphere below a particular level, it is cut at two points, and both the
head and the tail appear on the field of the section (Fig. 567). In frontal sections
behind the amygdaloid nucleus, it is also divided at two places.
The anterior extremity of the head of the caudate nucleus coincides very nearly
with that of the anterior horn of the lateral ventricle. In the region of the sub-
stantia perforata anterior, the head of th'e caudate nucleus gains the surface and its
gray matter becomes continuous with that of the cerebral cortex.
638
THE NEKVOUS SYSTEM.
The nucleus lentiformis lies on the lateral side of the caudate nucleus and
thalamus, and is for the most part embedded within the white medullary sub-
stance of the cerebral hemisphere. It does not extend either so far forwards or
so far backwards as the caudate nucleus. Indeed, it presents a very close corre-
spondence in point of extent with the insula on the surface. When seen in hori-
zontal section, it presents a shape similar to that of a biconvex lens. Its medial
surface bulges
more than the
lateral surface, and
its point of highest
convexity is placed
opposite the stria
terminalis and the
interval between
the caudate nuc-
leus and the thala-
mus. In frontal
section the appear-
ance presented by
the lentiform nuc-
leus differs very
much in different
planes of section.
Fig. 568 represents
a section through
its anterior por-
tion. Here it is
semilunar or cres-
centic in outline
and is directly
continuous below
with the head of
the caudate nuc-
leus ; above, also,
it is intimately
connected with the
caudate nucleus
by bands of gray
matter, which pass
between the two
nuclei and break
up the white
matter of the an-
terior part of the
intervening in-
ternal capsule. It
is due to the ribbed
or barred appearance, which is presented by such a section as this, that the term
corpus striatum is applied to the two nuclei. In the region of the substantia
perforata anterior both nuclei reach the surface and become continuous with the
cortex.
When a section is made in a plane further back (e.g. immediately posterior to
the anterior commissure, as in Fig. 569) the divided lentiform nucleus assumes an
altogether different shape, and is seen to be completely cut off from the caudate
nucleus by the internal capsule. It is now triangular or wedge-shaped. Its lase
is turned towards the insula and is in direct relation to a thin lamina of white
matter, termed the external capsule. Its medial surface is oblique and is applied
to the internal capsule, whilst its inferior surface is horizontal and is directed
downwards towards the base of the brain. But, further, two white laminae, the
Genu of corpus callosum =_
Anterior horn of lateral
ventricle
Caudate nucleus
Anterior limb of internal
capsule
Cavum septi pellucidi
Genu of internal capsule
Columns of fornix
Globus pallidus (of
nucleus lentiformis)
Fasciculus mamillo-
t-halamicus
Posterior limb of internal
capsule
Thalamus
Retrolenticular part of
internal capsule
Hippocampus
Splenium
Chorioid plexus
Gyrus cingul:
Calcarine sulcus
Optic
radiation
Tapetum
Optic radia-
tion passing
back to
white line in
the area
striata
FIG. 567. HORIZONTAL SECTION THROUGH THE RIGHT CEREBRAL HEMISPHERE
AT THE LEVEL OF THE WIDEST PART OF THE LENTIFORM NUCLEUS.
BASAL GANGLIA OF THE CEREBEAL HEMISPHERE.
639
external and internal medullary laminae, are now evident, which traverse its sub-
stance in a vertical direction and divide it into three masses. The lateral, basal,
and larger mass is termed the putamen ; the two medial portions together constitute
the globus pallidus.
The putamen forms much the largest part of the lentiform nucleus. It is
darker in colour than the globus pallidus, and in this respect resembles the caudate
nucleus. It is traversed by fine radiating bundles of fibres, which enter it from the
external medul-
lary lamina.
Both in point of
structure and in
mode of develop-
ment it is closely
associated with
the caudate nuc-
leus, and it is the
only part of the corpus caiiosum
lentiform nucleus
which is con-
nected by inter-
vening bands of
gray matter with
the caudate nuc-
leus. Theantero-
pOSteriOr length, Septum pellucidum
as well as the
vertical depth of
the putamen, is
Caudate nucleus
much greater Internal capsule
than in the Case Nucleus lentiformis
Claustrum
Longitudinal
fissure
Lateral ventricle
Column of fornix
Chorioid plexu
Foramen inter-
ventriculare
of the globus
pallidus ; conse-
quently, in both
frontal and hori-
zontal sections
through the cerebrum it is encountered before the plane of the globus pallidus is
reached.
FIG. 568. FRONTAL SECTION THROUGH THE CEREBRAL HEMISPHERES so as to cut
through the anterior part (putamen) of the lentiform nucleus in front of the
globus pallidus. Viewed from in front ; looking through the anterior horn into
the central part of the ventricle.
The external capsule is loosely connected with the lateral surface of the putamen, and it can be
readily stripped off. This accounts for the tendency, exhibited in haemorrhages in this locality,
for the effused blood to spread out in the interval between these structures.
The globus pallidus is composed of the two smaller and medial masses of the
lentiform nucleus. They present a faint yellowish tint, and are paler and more
abundantly traversed by fibres than the putamen. The mass next the putamen
(i.e. the intermediate part) is much larger than the medial subdivision. It extends
forwards to a point a little in front of the plane of the anterior commissure. When
the lentiform nucleus is cut in a frontal direction, and in its widest part, the
medial mass shows an indication of a separation into two parts, so that 'here the
globus pallidus appears to consist of three subdivisions.
Connexions of the Corpus Striatum. Recent clinical investigation has demon-
strated the importance of the functions of the corpus striatum, which seems to exercise a
"steadying influence" (Kinnier Wilson) upon the muscles which perform voluntary
movements that call for delicate co-ordination. Hence it is desirable to study the
connexions of these large masses of gray matter. Fibres of the internal capsule coming
from the motor cortex (as well as from all other cortical areas) end in the corpus striatum
(Fig. 571), so that when a voluntary movement is initiated this structure is called into
activity. Fibres coming from the nucleus caudatus break through the anterior limb of
the internal capsule (Fig. 572), some of them to reach the putamen, others to pass
through the external medullary lamina to the globus pallidus. Other tracts pass from
640
Lateral ventricle
Claustrum
Fasciculus
mamillothalamicus
Putamen
Insu
Globus pallidus
Column of fornix
Amygdaloid
nucleus
THE NEEVOUS SYSTEM.
Chorioid plexus
Longitudinal fissure
orpus callosum
Fornix
udate nucleus
Vena terminalis
Tela chorioidea
ventriculi tertii
Thalamtis
Third ventricle
Chorioid plexus
Internal capsule
'nterventricnlar
foramen
Column of fornix
Anterior commissure
Optic tract
Infundibulum
ptic chiasma
Optic nerve
Substantia perforata anterior
Olfactory peduncle
FIG. 569. FRONTAL SECTION THROUGH THE CEREBRUM so as to cut through the three divisions of the
lentiform nucleus ; posterior surface of the section shown here.
Intersection of corona radiata
and callosal systems of fibres
Corpus callosum
Caudate nucleus
Fornix
Internal capsule
Ansa lenticularis
Globus pallidus
Optic tract
Anterior commissure
Nucleus amygdalae
Superior occipito-frontal
association bundle
Putamen
External capsule
Claustrum
Frontoparietal operculum
Insula
Temporal operculum
FIG. 570. FRONTAL SECTION THROUGH THE LEFT SIDE OF THE CEREBRUM OF, AN ORANG
(Weigert-Pal specimen).
The section passes through the middle of the lentiform nucleus.
BASAL GANGLIA OF THE CEREBKAL HEMISPHEEE.
641
the lentiform nucleus into the caudate nucleus (fibrse lenticulocaudatse). From the
globus pallidus fibres arise which proceed into the internal capsule in the region of the
genu and the neighbouring part
of the posterior limb (Fig. 572).
Many of these fibres become
collected on the inferior aspect
of the lentiform nucleus, where
they form a transversely directed
bundle (Fig. 570), known as the
ansa lenticularis, which is dis-
tributed to the thalamus (Fig.
571, fasciculus striothalamicus)
and hypothalamus, the red
nucleus (fasciculus striorubricus)
and substantia niger (fasciculus
Red nucleus
Thalamus
Substantia
nigra
Rubrospinal
tract
FIG. 571.
Internal capsule
-Claustrum
Insula
__- Putamen
Globus
pallidus
Motor
trigeminal
Ansa peduncular^
Nucleus amyadalae
nucleus
AGRAM OP A FRONTAL SECTION TO ILLUSTRATE THE
FIBRE CONNEXIONS OF THE CORPUS STRIATUM.
strionigricus). These connexions
afford some explanation of the
difficulties of articulation and
swallowing and in the perform-
ance of delicate voluntary move-
ments that result from damage
to the corpus striatum or to this
system of fibres.
This system of fibres is phylo-
genetically very old, being the
most primitive efferent tract from the cerebral hemisphere.
Claustrum. This is a thin plate of gray substance embedded in the white
matter which intervenes between the lentiform nucleus and the gray cortex of
the insula. Followed in an upward direction, it becomes gradually thinner and
ultimately disappears. As it is traced downwards, however, it thickens consider-
ably, and at the base
of the brain it comes
to the surface at the
anterior perforated
y^v.-/.-v\A - substance and becomes
Flbrae corricosfriarae
, -Fasciculus fronroponhcus.
Fibrae
f. \\Vlenriculocaudarae.
(V Anterior thalamic
radiarion
-7
Cenu
capsulte
inrernae
To oculomotor iiuc
To facial, trigeminal, vagal,
and hypoglossal nuclei
continuous with
gray matter of
the
the
cortex. Its extent
corresponds very
closely with the area
occupied by the insula,
and its surface towards
this portion of the
cerebral cortex shows
ridges and depressions
corresponding to the
Auditory radiarion, ^sular gyri and sulci.
Nucleus Amyg-
dalae. In the anterior
p ar O f ^ e temporal
region, above the piri-
form area a fusiform
mass of gray matter
appears upon the sur-
face (Fig. 558, p. 630),
at the lateral extremity of the substantia perforata anterior (Fig. 584, p. 657). It
is part of a large rounded mass, called the amygdaloid nucleus, which occupies a
position in front of, and to some extent above the extremity of the inferior
horn of the lateral ventricle. The tail of the caudate nucleus joins its inferior part
(Fig. 573, p. 643), whilst above it is carried up into the putamen (Fig. 570).
42
Thalamo-cerebral tract to
posterior central gyms
Thalamo-cerebral tract to supra -
marginal and angular gyri
Opric radiarion.
caudate nucleus
FIG. 572. DIAGRAMMATIC REPRESENTATION OP THE INTERNAL CAPSULE
(AS SEEN IN HORIZONTAL SECTION).
642 THE NEKVOUS SYSTEM.
Inferiorly it is continuous with the gray cortex of the piriform area, to which it is
functionally related, probably in the same way that the major part of the corpus
striatum is associated with the neopallium.
Stria Terminalis. This is a band of fibres which, for the most part, arise in the
amygdaloid nucleus. From this it runs backwards in the roof of the inferior
horn of the lateral ventricle (Fig. 584, p. 657, and Fig. 573, p. 643), and then
arches upwards and forwards, so as to gain the floor of the pars centralis of the
lateral ventricle. In both situations it lies close to the medial side of the nucleus
caudatus, and finally, at the interventricular foramen, it bends downwards towards
the anterior commissure. Some of its fibres pass in front and others behind the
commissure, and ultimately they end in the neighbourhood of the substantia
perforata anterior (Kolliker).
Internal Capsule. This term is applied to the broad band of white matter which
intervenes between the lentiform nucleus, on the lateral side, and the thalamus
and caudate nucleus on the medial side. It presents many different appearances,
according to the plane in which the brain is cut. A frontal section through the
brain which passes through the cerebral peduncles shows that, in great part, the
internal capsule is directly continuous with the basal part of the cerebral peduncle
(Fig. 580, p. 652). Viewed from the lateral aspect after removing all else of the
cerebral hemisphere excepting the corpus striatum (Fig. 573), the cut ends of the
fasciculi of the internal capsule form three-fourths of an ellipse, the other fourth
of which is occupied by the bridge of union between the lentiform and caudate
nuclei, the substantia perforata anterior, the amygdaloid nucleus and the anterior
commissure. It may be divided into an anterior (lenticulo-caudate) part, a superior
(lenticulo-thalamic) part, a retrolenticular part (not labelled in the figure), and a
postero-inferior (sublenticular) part. The last three parts are usually grouped
together as the posterior limb. In horizontal section the internal capsule is
observed to be bent upon itself opposite the stria terminalis, or the interval
between the caudate nucleus and the thalamus. This bend, which points medially,
is called the genu. About one-third of the internal capsule lies in .front of the
genu, and is termed the anterior limb ; the remaining two-thirds, which lie behind
the genu, constitute the posterior limb (Fig. 572).
The anterior limb of the internal capsule intervenes between the lentiform
nucleus and the caudate nucleus. In its inferior and anterior* part it is much
broken up by the connecting bands of gray matter which pass between the anterior
part of the putamen and the caudate nucleus.
The anterior limb of the internal capsule is composed largely of corticipetal fibres
belonging to the anterior thalamic radiation. It contains corticifugal fibres also.
The corticipetal fibres arise in the median and anterior part of the lateral nucleus of the
thalamus, and go through the anterior limb of the internal capsule to reach the cortex
of the frontal lobe.
The corticifugal fibres are represented by the fronto-pontine tract.
The fronto-pontine tract arises in the cortex of the frontal region, traverses the
anterior limb of the internal capsule, forms the medial fifth of the basis of the cerebral
peduncle, and finally ends in the nuclei pontis.
The posterior limb of the internal capsule is placed between the thalamus and
the lentiform nucleus, and it extends backwards for a short distance beyond
the posterior end of the putamen on the lateral side of the posterior part of the
thalamus and of the tail of the caudate nucleus. The posterior limb, therefore, is
spoken of as consisting of a lenticular, a retrolenticular, and a sublenticular part.
The lenticular or more properly lenticulo-thalamic part of the posterior limb is com-
posed of both corticipetal and corticifugal fibres. The corticipetal fibres enter the internal
capsule from the lateral aspect of the thalamus, and are composed of fibres which arise
within the thalamus from the ventral (ventro-lateral) nucleus, and proceed upwards to the
cerebral cortex.
The corticifugal fibres consist of the cerebro-spinal tract and the cortico-thalamic fibres
The great motor or cerebro-spinal tract, descending from the cerebral cortex
occupies the anterior half of the lenticular part of the internal capsule. The fibres, that g<
BASAL GANGLIA OF THE CEREBRAL HEMISPHERE.
643
to the nuclei of the oculomotor, trigeminal, and facial nerves, lie close to the genu, and
behind these are the fibres which go to the hypoglossal nucleus ; still further back are
cerebro-spinal fibres which enter the spinal medulla and end around the motor cells of
the anterior column of gray matter. This cerebro-spinal tract has been observed occupying
the middle part of the pedunculus cerebri, into which it passes directly -from the internal
capsule.
According to Monakow the posterior limb contains also an important tract of fibres
passing from the motor cortex to the red nucleus (fasciculus cerebrorubricus).
The retrolenticular part of the posterior limb contains : (1) the fibres of the optic
radiation as they pass from the lateral geniculate body to establish their connexions with
Nucleus lentiformis
Capsula intfrnu (pars lenticulo-thalamica)
Nucleus cauclatus
Capsula interna
(pars lenticulos
caudate)
Union of
lentiform and
caudate nuclei
Hypophysis f an
cerebri ^posterior lobe--
Tuber cinereum ' / /I
Corpus mamillare .' / 1
Nervus oculomotorius / KT \'.A
Basis pedunculi'' / N "/ -*
Pons' ,
Nervus trigeminus (portio major) (
Nervus trigeminus (portio minor)''
Nervus facialis -
Nervus intermedius-'
Nervus acusticus'''
Nervus abducens **
Nervus glossopharyngeus-
Nervus vagiu
Pyramiss
Oliva
Fasciculus circumolivaris pyramidis-
Nucleus amygdalae (cut)
Commissura anterior
Stria terminalis
Capsula interna (pars sublenticularis)
-Nucleus caudatus
'Tlialamus
Corpus geniculatum laterals
-Corpus pineale
-Corpus geniculatum mediale
-Colliculus superior
Brachium quadrigeminum
'"inferius
-Colliculus inferior
Lemniscus lateralis
Nervus trochlearis
Brachium conjunctivurn
... .Brachium pontls
-Fossa flocculi
.__Crus flocculi
Nucleus dentatu?
"cerebelli
Corpus ponto-bulbare
Fasciculus spinocerebellarh
-Nervus spinalis
FIG. 573. DISSECTION EXPOSING THE LATERAL ASPECT OF THE LENTIFORM NUCLEUS OF THE
LEFT HEMISPHERE.
the occipital cerebral cortex; (2) the fibres of the acoustic radiation, or those which
connect the medial geniculate body with the acoustic cortical field in the temporal lobe
Fig. 572, p. 641, and Fig. 578, p. 650) ; (3) the temporo-pontine tract, which is com-
osed of fibres which take origin in the middle and inferior gyri of the temporal
lobe and pass through the sublenticular section of the internal capsule to reach the
lateral part of the pedunculus cerebri. Through this they reach the basilar part of the
xms, in the gray matter of which they end. This tract is accompanied by the fasciculus
temporothalamicus, which has a widespread origin from the temporal and occipital regions
and passes through the sublenticular part of the internal capsule.
f the fibres -of the internal capsule are traced upwards they are found to
spread out widely from each other in a radiating or fan-shaped manner, as they
42 a
644 THE NERVOUS SYSTEM.
are followed to the various gyri of the cerebral hemisphere. This arrangement
is termed the corona radiata. The callosal system of fibres, as they proceed into
the hemisphere, also radiate, and they intersect the fibres of the corona radiata
(Fig. 576, p. 649).
External Capsule. The thin lamina of white matter between the lateral aspect
of the putamen and the claustrum is called the external capsule. This joins with
the internal capsule in front of and behind the putamen, and in this manner the
nucleus lentiformis is encapsuled by white matter.
INTIMATE STRUCTURE OF THE CEREBRAL HEMISPHERE.
The cerebral hemisphere is composed of an external coating of gray matter,
termed the cortex, spread over an internal mass of white matter, which is called the
medullary centre. The cortex is of peculiar interest, seeing that there is good reason
for believing that in it the higher functions of the brain, or those which may be
classed under the general designation of the intellectual functions, take place. It
is within the same layer of gray matter that the influence of those external impres-
sions, which gain access to the cerebro-spinal axis through the senses, finally take
shape as consciousness ; and in it are placed also the centres which carry on the
psycho-motor functions. The white medullary centre is composed of nerve-fibres
which constitute the paths along which the influence of impressions is carried to
and from the cortex, and from one part of the cortex to another.
THE CEREBRAL CORTEX.
The gray cortex is spread over the entire surface of the cerebral hemisphere, but
it does not form a layer of equal thickness in all localities. At the summit of a
gyrus it is apt to be thicker than at the bottom of a furrow. The maximum
thickness of cortex (about 4 mm.) is attained in the superior parts of the motor
area, whilst the minimum (about 1/25* mm.) may be observed in the region
of the occipital pole. The amount of gray cortex differs considerably in different
individuals, and appreciably diminishes in old age. It is also stated, but upon
imperfect evidence, that it is relatively more abundant in the male than in the
female.
In structure, likewise, marked differences may be noted in the gray cortex of
different regions, and much has been recently done in the direction of pointing out
the connexion of these structural peculiarities with the functional characteristics of
particular areas and applying them to the determination of the significance of the
furrows that subdivide the cerebral cortex into a series of ridges or gyri. This
structural difference is quite apparent to the najjed eye when sections are made
through the cortex in a fresh brain, and sharp transitions in structure occur at the
place where one area joins another. It is only to those general structural feature
which more or less characterise the entire cortical layer that we shall be able to refer.
When sections are made through the fresh brain, and the cut surface is closeb
inspected, it will usually be apparent that the cortex is distinctly stratified,
the outside there is a thin, whitish layer, and beneath this the gray matter presenl
two strata of very nearly equal thickness, viz., a middle, gray-coloured stratum ai
an inner, yellowish-red stratum. Between the two latter layers a narrow whit
band is, in many places, visible. This is termed the outer band of Baillarger. Whe
the layers indicated above are present, four strata, superimposed one upon the othe
are recognised ; but in certain regions a second white streak traverses the deep
inner gray layer and divides it into further stratifications. This is termed the i]
white band of Baillarger, and, when it is present, the gray cortex becomes divide
obscurely into six alternating white and gray layers.
The outer band of Baillarger is strongly marked in the region behind
calcarine sulcus and gives a characteristic appearance to this portion of the corte:
In this locality it receives the name of the stria of Gennari (Fig. 567, p. 638).
White Medullary Centre of the Cerebral Hemisphere. The white matter of tl
,
THE NEOPALLIUM.
645
misphere which lies subjacent to the gray cortex is composed of medulla ted nerve-
fibres, arranged in a very intricate manner. But the arrangement of these fibres
cannot be properly understood until the configuration of the surface of the hemi-
sphere has been considered.
FIG. 574. DIAGRAM TO ILLUSTRATE THE MINUTE STRUCTURE OP THE CEREBRAL CORTEX AND
EXPLAIN HOW IT INFLUENCES THE MACROSCOPIC APPEARANCE.
VNeuroglia cells.
A
B
C. Cell with short axon (N) which breaks
up in a free arborisation.
D. Spindle-shaped cell in stratum zonale.
E. Small pyramidal cell.
F. Large pyramidal cell.
G. Cell of Martinotti.
H. Polymorphic cell.
K. Cprticipetal fibres.
THE JSTEOPALLIUM.
Fibre-tracts proceed into different districts of the neopallium from the various
nuclei of the thalamus to serve as the channels through which tactile, visual,
acoustic, and other kinds of sensory impressions are poured into it. These districts
may be regarded as the receptive sensory areas, tactile, visual, acoustic, etc. ; but
around each sensory area there is differentiated a series of more or less concentric
bands of neopallium, which are related to an incoming sensory path only through the
intermediation of the sensory area which it fringes. Finally, there are interposed
between the sensory area and its fringing bands of one sense and those of
another, certain association areas, which cannot be regarded as the territory of
425
646 THE NEEVOUS SYSTEM.
any one sense, but as the place of meeting (and the physical counterpart of the
blending in consciousness) of the impressions of different senses. In the human
brain the neopallium becomes mapped out into a large series (more than forty) of
areas, which differ one from the other in structure and in their connexions, and
presumably therefore in their functions ; and many of these areas may be further
subdivided into a series of less obtrusively differentiated territories (Figs. 553
and 581).
The gray matter of the neopallium is spread over the surface of the white
matter as a thin film (cortex cerebri), which is nowhere more than 4 millimetres,
and may be only T25 millimetres thick. In different regions it presents every
gradation of thickness between these two extremes. As the cortex increases in
volume it does so not by any addition to its depth, but solely by an expansion of
its superficial area. Thus it happens that in all larger mammalian brains, as the
cerebral hemisphere expands and there is an increasing disproportion between the
bulk of the hemisphere and the area of its surface, the cortex must become folded
to accommodate itself to the limited area of surface upon which it has to be packed.
But this process of folding does not take place in any haphazard or purely
mechanical way. The situations of the furrows or sulci which make their
appearance are determined, for the most part, by the arrangement and the
relative rates of expansion of the various areas into which the neopallium becomes
differentiated.
The great majority of the furrows belong to a group, which we may call (1)
sulci terminales, i.e. they make their appearance along the boundary lines between
areas of different structure. The fissura rhinalis and sulcus centralis are examples
of this group. Another group, which may be called (2) sulci axiales, develop by
the folding of areas of uniform structure, i.e. along the axis of certain territories.
The retro-calcarine sulcus and the sulcus occipitalis lateralis belong to this
group. There is a third group of (3) sulci operculati, where the edge of one area
becomes pushed over an adjoining territory, so that a trough is formed (Fig. 575, C),
which is neither a limiting nor an axial sulcus. The sulcus lunatus is an example.
And finally there is a fourth group, in which some more definitely mechanical
factor comes into play to complicate the operation of these other factors, or even
to determine the development of a furrow. The sulcus parieto-occipitalis and
the fissura lateralis are examples of the fourth group.
[It is the custom to call certain furrows sulci and others fissures, and to call
some of them complete, because they indent the whole thickness of the wall of the
ventricle, and to call the rest incomplete. There is no justification whatever for any
such distinctions.
It is usual also to subdivide the surface of the hemisphere in a purely arbitrary
manner into "lobes" and to speak of interlolar fissures, but this is an artificial and
misleading terminology which we shall avoid as far as possible.]
Fissura Longitudinalis Cerebri. The longitudinal fissure is not a fissure
of the cortex but is the great cleft between the two cerebral hemispheres. In
front and behind it separates the cerebral hemispheres completely the one from
the other. In its middle part, however, the fissure is interrupted and floored
by the corpus callosum, a white commissural band, which passes between the
hemispheres and connects them together. The superior surface of the corpus
callosum is displayed when the contiguous medial surfaces of the cerebral
hemispheres are drawn asunder. The longitudinal fissure is occupied by a median
fold of dura mater, termed the falx cerebri, which partially subdivides the part
of the cranial cavity allotted to the cerebrum into a right and left chamber.
External Configuration of each Cerebral Hemisphere. Each cerebral hemi-
sphere presents a lateral, a medial, and an inferior surface. The lateral surface is
convex and is adapted accurately to the internal surface of the cranial vault. The
medial surface is flat and perpendicular, and bounds the longitudinal fissure. In
great part it is separated from the corresponding surface of the opposite hemisphere
by the falx cerebri. The inferior surface is irregular and is adapted to the
anterior and middle cranial fossae of the cranial floor and, behind these, to the
superior surface of the tentorium cerebelli. Traversing this surface in a transverse
THE WHITE MATTER OF THE CEEEBRAL HEMISPHERES. 647
direction, nearer the anterior end of the hemisphere than the posterior end, is
the stem of the lateral fissure. This deep cleft divides the inferior surface into an
anterior or orbital area, which rests on the orbital part of the frontal bone and is
consequently concave from side to side, and a more extensive posterior or tentorial
area, which lies on the floor of the lateral part of the middle cranial fossa and upon
the superior surface of the tentorium cerebelli. This surface is arched from before
backwards, and looks medially as well as downwards. In its posterior two-thirds it
lies above the cerebellum, from which it is separated by the tentorium cerebelli.
The borders which intervene between these surfaces are the supero-medial, the
superciliary, the infero-lateral, the medial occipital and medial orbital. The supero-
medial border, convex from before backwards, intervenes between the convex lateral
surface and the flat medial surface of the hemisphere. The superciliary border is
highly arched and separates the orbital surface from the lateral surface. The
infero-lateral border marks off the tentorial surface from the lateral surface. The
medial occipital border can be seen only in cases where the brain has been hardened
in situ and faithfully retains the natural form. It extends from the posterior end
of the hemisphere towards the posterior extremity of the corpus callosum, and inter-
venes between the medial and tentorial surfaces. It is the border which lies along
the straight blood sinus, and it therefore occupies the angle which is formed by the
attachment of the posterior part of the falx cerebri to the superior surface of the
tentorium cerebelli. The medial orbital border separates the medial surface from
the orbital surface.
The most projecting part of the anterior end of the cerebral hemisphere is called
limiting sulcus
area x ; area y
limiting slllcus axiai sulcus
area x I area y ! area y area
operculated sulcus
area z area y area x
FIG. 575. DIAGRAMS TO EXPLAIN THREE TYPES OP CEREBRAL FURROWS.
the frontal pole, whilst the most projecting part of the posterior end is termed the
occipital pole. On the inferior surface of the hemisphere the prominent point of.
cerebral substance which extends forwards below the lateral fissure receives the
name of the temporal pole. In a well-hardened brain a broad groove is usually
present on the medial and inferior aspect of the occipital pole of the. right hemisphere.
This corresponds to the commencement of the right transverse venous sinus. A less
distinct groove on the occipital pole of the left hemisphere frequently indicates the
commencement of the left transverse sinus. On the tentorial surface, a short
distance behind the temporal pole, a well-marked depression, impressio petrosa, is
always visible. This corresponds to the elevation on the anterior surface of the
petrous portion of the temporal bone over the superior semicircular canal.
THE WHITE MATTEK OF THE CEREBRAL HEMISPHERES.
According to the connexions which they establish the fibres forming the white
medullary matter of the hemispheres may be classified into three distinct groups,
iz., (1) commissural fibres; (2) association fibres; and (3) projection fibres.
Commissural Fibres. These are fibres which link together portions of the
pay cortex of opposite cerebral hemispheres. They are arranged in three groups
>rming three definite structures, viz., the corpus callosum, the anterior commissure,
and the hippocampal commissure.
The corpus callosum has in a great measure been already studied (p. 628). As
it enters each hemisphere, its fibres spread out in an extensive radiation (the radia-
648 THE NEKVOUS SYSTEM.
fcion of the corpus callosum). It thus comes about that every part of the cerebral
cortex, with the exception of the bulbi olfactorii, the olfactory parts of the hemi-
sphere, and the inferior and anterior part of the temporal lobe, is reached by the
callosal fibres. But it should be clearly understood that all the regions of the cortex
do not receive an equal proportion of fibres ; in other words, some cortical areas
would appear to be more plentifully supplied than others. Another point of some
importance consists in the fact that the callosal fibres do not, as a rule, connect
together symmetrical portions of the gray cortex. As the fibres cross the median
plane they become greatly scattered, so that dissimilar parts of the cortex of
opposite hemispheres come to be associated with each other.
The commissura anterior is a structure supplemental to the corpus callosum,
although originally it was the principal cerebral commissure long before the corpus
callosum was evolved. It connects together the two olfactory bulbs, and also
portions of the opposite temporal lobes. It presents a cord-like appearance and
in median section appears as a small oval bundle in the lamina terminalis
(Fig. 544, p. 617). The middle free portion is placed immediately in front of the
columns of the fornix as they curve downwards, and also in intimate relation to the
anterior end of the third ventricle. Posteriorly, the small portion of the anterior
commissure which appears in the ventricle between the two columns of the fornix is
clothed with the ventricular ependyma ; anteriorly, the commissure is connected
with the lamina terminalis as it stretches from the optic chiasma upwards towards
the inferior (anterior) end of the hippocampal commissure.
The lateral part of the anterior commissure penetrates the cerebral hemisphere,
and, gaining the inferior part of the anterior end of the internal capsule, divides into
two portions, viz., a small inferior olfactory part and a much larger temporal part.
The olfactory portion of the anterior commissure is an exceedingly small fasci-
culus. It passes downwards and forwards, and finally enters the olfactory tract.
It is composed (1) of true commissural fibres, which bind one olfactory bulb to the
other ; and (2) of other fibres, which connect the olfactory bulb of one side with
the piriform area of the other side.
The temporal portion is formed of almost the whole of the fibres of the
commissure. It is carried laterally under the lentiform nucleus, until it gains
the interval between the globus pallidus and the putamen. At this point it
changes its direction and sweeps backwards. In frontal sections through the
brain, posterior to this bend, the temporal portion of the anterior commissure
appears as an oval bundle of fibres cut transversely and placed in close contact
with the inferior surface of the lentiform nucleus (Fig. 576). Finally, it turns
sharply downwards on the lateral aspect of the amygdaloid nucleus, and its fibres
are lost in the white medullary centre of the temporal lobe. When the lateral
part of the anterior commissure is displayed by dissection, it is seen to be twisted
like a rope.
The hippocampal commissure is composed of fibres which connect the hippo-
campus of one side with the corresponding structure of the opposite side. It is
described on p. 629.
Association Fibres. The association fibres bind together different portions of
the cortex of the same hemisphere. They are grouped into long and short associa-
tion bundles.
The greater number of the short association fibres pass between adjacent
gyri. They curve round the bottoms of the sulci in U-shaped loops. Some of
these occupy the deepest part of the gray cortex itself, and are termed intracortical
association fibres (Figs. 577 and 578) ; others lie immediately subjacent to the gray
matter between it and the general mass of the white matter and receive the
name of subcortical fibres. Many groups of short association fibres, instead of linking
together contiguous gyri, pass between gyri more or less remote. It is only
after birth, when intellectual effort and education have stimulated different portions
of the cortex to act in harmony and in conjunction with each other, that these
association fibres assume their sheaths of myelin and become functional.
The long association fibres are arranged in bundles which run for considerable
distances within the white medullary centre of the cerebral hemisphere, and unite
THE WHITE MATTEE OF THE CEEEBEAL HEMISPHEEES. 649
districts of gray cortex which may be far removed from each other. The better
known of these fasciculi are the following: (1) the uncinate bundle; (-2) the
cingulum; (3) the superior longitudinal bundle; (4) the inferior longitudinal; and
(5) the occipito-frontal.
The fasciculus uncinatus is composed of fibres which arch over the stem of the
Cavum septi pellucid i
Corpus callosum
Cingulum
Corpus callosum
Lateral ventricle
Lateral ventricle
Internal
capsule
3 ('Temporal
part
R-
Olfactory
part
Caudate nucleus
Fasciculus occipito-
frontalis [superior]
Internal
capsule
Putamen
Fasciculus longi-
tudinalis superior
Globus
pallidus
Claustrum
Superior
*" operculum
Insula
Fasciculus occipito
frontalis [inferior]
Temporal
operculum
Anterior
commissure
Fasciculus uncinatus
FIG. 576. Two FRONTAL SECTIONS THROUGH THE CEREBRAL HEMISPHERES OF AN ORANG,
IN THE PLANE OF THE ANTERIOR COMMISSURE.
A, Section through the left hemisphere in a plane a short distance behind B, which is a section through the
right hemisphere. The positions of the great longitudinal association tracts are indicated in red.
lateral cerebral fissure and connect the frontal pole, and the orbital gyri of the
frontal lobe, with the anterior portion of the temporal lobe.
The cingulum is a very well-marked and distinct band, which is closely associated
with the medial edge of the neopallium. Beginning in front, in the region of the
anterior perforated substance, it arches round the genu of the corpus callosum and
FIG. 577. DIAGRAMS OF THE LEADING ASSOCIATION BUNDLES OF THE CEREBRAL HEMISPHERE.
(Founded on the drawings of Dejerine).
A, Lateral aspect of hemisphere. B, Medial aspect of hemisphere.
is carried backwards on the superior surface of this structure at the place where
its fibres pass into the callosal radiation. The cingulum, therefore, lies under
cover of the gyrus cinguli and stands in intimate relation to the white centre
of this gyrus (Fig. 559, p. 631). At the posterior end of the corpus callosum
the cingulum turns round the splenium and is carried forwards, in relation to
650 THE NEKVOUS SYSTEM.
the hippocampal gyrus, to the uncus and the temporal pole. The cingulum
is composed of several systems of fibres which run only for short distances
within it.
The fasciculus longitudinalis superior is an arcuate bundle which is placed on the
lateral aspect of the foot or basal part of the corona radiata and connects the
frontal, occipital, and temporal regions of the hemisphere. It lies in the base of the
superior operculurn and sweeps backwards over the insular region to the posterior
end of the lateral cerebral fissure. Here it bends downwards round the posterior
end of the putamen and proceeds forwards in the temporal lobe, to reach its anterior
extremity. As it turns downwards to reach the temporal lobe numerous fibres
radiate from it into the occipital lobe.
The fasciculus longitudinalis inferior is a very conspicuous bundle which extends
along the whole length of the occipital and temporal regions (Fig. 577, B). Curran
has recently demonstrated that the fasciculus uncinatus and the inferior longi-
Acoustic radiation
Transverse temporal gyrus | Fasciculus longitudinalis superior passing
Short association fibres over the lateral side of the
^^BMfc^ViBAfefeiiiBli^fei^ Fasciculus occipito-frontalis infe:
Fasciculus longitudinalis
superior
Fasciculus occipito-frontalis inferior
Fasciculus unciuatus
Fissura lateralis
Optic radiation seen in a gap cut put of
the inferior occipito-frontal fasciculus
FIG. 578. DISSECTION TO DISPLAY SOME OF THE PRINCIPAL ASSOCIATION BUNDLES OF THE CEREBRAL
HEMISPHERE.
The occipito-temporal extremity of the superior longitudinal bundle has been cut away in order to expose the
subjacent inferior occipito-frontal bundle, parts of which in turn have been removed to expose the origin
and termination of the still deeper optic radiation (coloured blue) ; (acoustic fibres, yellow).
tudinal bundle are merely the shorter inferior fibres of a much bigger and longer
tract (Fig. 578), to which he has applied the name occipito-frontalis inferior. The
arrangement of these longitudinal tracts may be put concisely by saying that fibre
connexions of differing lengths link together the various cortical areas in the
longitudinal direction, the deeper fibres (i.e. those furthest removed from the
cortex, medial, lateral, superior or inferior) being progressively longer than the
superficial. The deepest fibres extend the whole length of the hemisphere and
are pushed aside by the insula (Fig. 578) and collected into two great bundles, a
superior longitudinal and an inferior occipito-frontal bundle. In the occipital
lobe the inferior occipito-frontal bundle is placed on the lateral aspect of the
optic radiation, which takes a similar direction and from which it is distinguished
by the greater coarseness of its fibres (Figs. 576, p. 649 ; 578 ; 559, p. 631).
It is not present in the macaque monkey (Ferrier and Turner), but is well
developed in the orang and the chimpanzee.
THE WHITE MATTER OF THE CEKEBEAL HEMISPHERES. 651
The fasciculus occipito-frontalis superior is a bundle of fibres which runs in a
sagittal direction in intimate relation to the lateral ventricle (Fig. 576, p. 649). It may
be regarded as the medial edge of the superior longitudinal bundle. It has been pointed
out (Forel, Onufrowicz, and others) that, in cases where the corpus callosum fails to
develop, the tapetum remains apparently unaffected, and Dejerine has endeavoured to
prove that the fibres of this layer really belong to the fasciculus occipito-frontalis. The
fasciculus occipito-frontalis lies on the medial aspect of the corona radiata in intimate
relation to the caudate nucleus, and posteriorly it spreads out over the superior and
lateral aspect of the lateral ventricle, immediately outside the ependyma, where,
according to Dejerine, it constitutes the tapetum (see p. 632).
Projection Fibres. We have already seen that every part of the cerebral
cortex is linked to other cortical areas, not only in its own neighbourhood (short
association fibres) (Fig. 578), but also
in the most distant parts of the hemi-
sphere (long association fibres), as well
as to the cortex of the other hemi-
sphere (commissural fibres). In
addition there are two large series of
fibres : (i.) an ascending group which
conveys to the cerebral cortex im-
pulses coming from the thalamus and
metathalamus, the corpora quadri-
gemina and the red nucleus, and the
various other sensory nuclei scattered
throughout the brain stem and spinal
medulla ; and (ii.) a descending group
connecting the cerebral hemisphere
with the corpus striatum, various parts
of the diencephalon, mesencephalon
and cerebellum, as well as with all the
motor nuclei scattered throughout the
central nervous system. These two
groups of tracts, respectively passing
r , , J . &
to and from the cerebral cortex, are
known collectively as its projection
fibres.
While examining the general ar-
rangement of these projection fibres
of the cerebral hemisphere it is con-
venient to refer incidentally to certain
other fibre -tracts which do not fall
strictly within this group.
The Sensory Tracts. A certain
proportion of the fibres that enter the
spinal medulla by its posterior root, which are supposed to be the sensory nerves^ of
muscles, tendons, and joints, pass upwards without interruption in the posterior
funiculi throughout the whole length of the spinal medulla until they reach the
medulla oblongata, where they end in the nucleus gracilis and nucleus cuneatus.
From these nuclei, arcuate fibres (fasciculus bulbothalamicus) arise and, after crossing
the median plane, proceed upwards in the medial lemniscus of the other side to end
in the ventro-lateral nucleus of the thalamus, from which a third group of neurones
arises and proceeds upwards through the internal capsule to the cerebral cortex,
where the impulses conveyed by it excite a consciousness of position and movement.
But other sensory fibres end in the spinal medulla near their place of entry into
it, and from the cells related to the endings of these fibres a new tract (fasciculus
spinothalamicus) arises, crosses the median plane to reach the antero-lateral funiculus
of the opposite side, in which it proceeds upwards throughout the whole length of
the spinal medulla (that lies above its origin), the rhombencephalon and mesen-
cephalon to the thalamus, where it ends alongside the bulbo-thalamic tract in
FIG. 579. DIAGRAM OF THE SENSORY TRACTS FROM THE
SPINAL MEDULLA TO THE CEREBRAL CORTEX.
652
THE NEEVOUS SYSTEM.
relationship with cells of the ventro-lateral nucleus. The fibres arising from this
nucleus proceed to the gyrus centralis posterior, and convey impulses to it, which
may excite a consciousness of touch, pressure, pain, heat, or cold. Some of these
spino-thalamic fibres enter the medial lemniscus in the medulla oblongata, but
others remain separate from it (Fig. 580) until they reach the level of the pons,
where they become added to the lateral margin of the bulbo-thalamic tract.
[In Fig. 580 the line from the label "lemniscus medialis" points to the place
of junction of the spino- and bulbo-thalamic tracts.]
Other groups of fibres, serially homologous to both the spino-thalamic and the
bulbo-thalamic tracts, come from the various sensory cerebral nerves trigeminal,
Lateral ventricle
Nucleus caudatus
Corona radiata \
Corpus callosum
Internal capsule
Claustrunu
Yhalamo-cortical (sensory)
radiation in internal capsule
Tnsula
Acoustic
, radiation enter-
' ing transverse
temporal gyri
Ventro-lateral thalamic i
receiving the medial leu
nd emitting sensory
fibres to the cortex
Acoustic radiation
Lateral geniculate body
receiving lateral lemnist
emitting acoustic radial
Lateral ventricle inferio
Medial geniculate body
'Fimbria
cerebri
Substantia -"'^"^JBBSSF^" """^SB^l "'"-.'Lateral lemniscus
Cere n b?o*pinaland--' > " " P^K""^ Medial lemniscus at the part wh<
cerebro-pontine tracts /4R^LSjBaj|^3 -^ffiM & ^the spino-thalamic and bulbo-
inthepons jKliHBffl? Btt^ I thalamic tracts join
Nervus acusticus-
Corpus trapezoideum -
Pyramid
Decussation of pyramids
Ventral cerebro-spinal tract
FIG. 580. FRONTAL SECTION OF BRAIN, PASSING IN THE LINE OP THE CEREBRO-SPINAL TRACT (marked
in red] IN THE RIGHT HEMISPHERE (left side of Fig.), and on a more posterior plane in the left
hemisphere, where the sensory paths (tactile in blue, and acoustic in yellow) have been represented.
facial, glossopharyngeal, and vagus and become added to the great strands that are
proceeding upwards to the thalamus (Figs. 5*79 and 494, p. 561).
Of the other great ascending tracts in the spinal medulla, such as the two
pairs of fasciculi spinocerebellares, nothing further need be said ; nor is it necessary
to do more than remind the reader that from the nucleus dentatus of the cerebellum
a great tract (brachium conjunctivum) ascends to the opposite red nucleus and
thalamus, and through them establishes an indirect connexion with the cerebral
cortex in the precentral and frontal regions.
The other sensory pathways to the cerebrum, auditory, vestibular, visual,
gustatory, and olfactory, are described elsewhere.
The Corticifugal Projection Strands. The fasciculus cerebrospinalis, the great
motor or pyramidal tract, is composed of fibres which arise from giant pyramidal
THE SULCI AND GYEI OF THE CEREBRAL HEMISPHERES. 653
cells of Betz in the posterior part of the precentral cortex (p. 663) in the district
immediately in front of the sulcus centralis. The fibres descend through the
corona radiata into the posterior limb of the internal capsule. From this point the
further course of the pyramidal tract has been traced, viz., through the central part
of the basal region of the cerebral peduncle and pons, and the pyramid of the
medulla oblongata. At the level of the foramen magnum it decussates in the
manner already described, and enters the spinal medulla as the lateral cerebro-
spinal and anterior cerebro-spinal tracts. The fibres composing these end in
connexion with the ventral or motor column of cells, from which the fibres of the
anterior roots of the spinal nerves arise.
Similar fibres arise from the inferior part of the precentral area and proceed
through the internal capsule and cerebral peduncle to all the motor nuclei upon
the opposite side of the brain stem (fasciculi cerebronucleares). Hence the cerebral
cortex of one hemisphere can control all the muscles of the opposite side of the body.
The fronto-pontine strand is composed of fibres which arise as the axons of
the cells in the cortex which covers the frontal region that lies in front of the
precentral furrows. It descends in the anterior limb of the internal capsule,
enters the medial part of the base of the cerebral peduncle, through which it
gains the basilar part of the pons. In this its fibres end amongst the cells of the
nuclei pontis, from which axons arise and establish relations with the cortex of
the opposite cerebellar hemisphere.
The temporo-pontine tract consists of fibres which spring from the cells, of that
part of the cortex which covers the middle portions of the lower two temporal
gyri. The temporo-pontine tract passes medially under the nucleus lenti-
formis, enters the retrolenticular part of the posterior limb of the internal capsule,
and thus gains the lateral part of the cerebral peduncle. From this it descends
into the basilar part of the pons, in which it ends in the nuclei pontis.
Cortico-striate and other Descending Fibres. From the fibres of the internal
capsule numerous collateral branches are given off to the nucleus caudatus and
nucleus lentiformis, and from these basal ganglia fibres arise which enter the
cerebral peduncle as constituent elements of the great cerebro-spinal tract.
Some of the fibres from the corpus striatum, especially the nucleus lentiformis,
as well as others descending from the frontal cortex, pass into the red nucleus
(Fig. 571), which also receives afferent tracts from the tectum mesencephali and
from the cerebellum : it emits an important efferent tract (fasciculus rubrospinalis),
which crosses the median plane and descends in the brain stem and spinal medulla
to the various motor nuclei (see Figs. 454 and 475).
THE SULCI AND GYRI OF THE CEREBRAL HEMISPHERES.
Fissura Cerebri Lateralis (O.T. Fissure of Sylvius). This is the most con-
spicuous furrow on the surface of the cerebral hemisphere. In reality it is formed,
not as a furrow upon the surface of the hemisphere, but as a great fossa, the
margins of which develop into large lip-like folds that bulge over the fossa and
meet to form the superficial pattern of the lateral fissure. It is composed of a
short main stem, from the lateral extremity of which two or three branches or
limbs radiate. The stem of the lateral fissure is placed on the inferior surface of
the hemisphere. It begins at the substantia perforata anterior and passes
laterally, forming a deep cleft between the temporal pole and the orbital surface of
the frontal region. Appearing on the lateral surface of the hemisphere, the fissure
immediately divides into two or three radiating rami. These are : (1) the ramus
posterior ; (2) the ramus anterior horizontalis ; (3) the ramus anterior ascendens,
of which the last is inconstant.
The posterior ramus is the longest and most constant of the three limbs. It
extends backwards, with a slight inclination upwards, on the lateral surface of the
hemisphere for a distance which may vary from about two to three inches. It
intervenes between the frontal and parietal regions, which lie above it, and the
temporal region which lies below it ; and it finally ends in the region subjacent to
654
THE NERVOUS SYSTEM.
the parietal tuberosity of the cranial wall by turning upwards* into the parietal
region in the form of an ascending terminal piece.
The anterior horizontal ramus extends horizontally forwards in the frontal region
for a distance of not more, as a rule, than three-quarters of an inch, immediately
above and parallel to the posterior part of the superciliary margin of the hemisphere.
The anterior ascending ramus proceeds upwards and slightly forwards, into
the inferior part of the lateral surface of the frontal region for a variable distance
(an inch or less). In many cases the two anterior limbs spring from a common stem
of greater or less length, and not infrequently there is only a single anterior limb.
Sulcus Circularis. If the lips of the posterior ramus of the lateral fissure are
pulled widely asunder from each other, the insula (island of Eeil) will be seen at the
Inferior frontal gyrus (posterior part)
Superior frontal
gyrus (inter-
itermediate part of inferior frontal gyrus mediate part)
3yrus frontalis superior (anterior part) \ Snlcus '
.r ascending ramus of lateral fissure v . diagonals I
ior part of inferior frontal gyrus
Middle frontal area
horizontal
is of lateral
ibral fissure
r frontal
area
Inferior precentral sulcus Middle frontal gyrus (posterior part)
Gyrus frontalis superior
| Superior precentral sulcus
j | Area supramarginalis ;
MOTOR CORTEX
Sulcus postcentndis
Sulcus centralis
KNSORY
ORTEK
Anterior part "|
Intermediate part [ Gyrus centralis posterioi
Posterior part J
Superior parietal lobule (anterior
part)
upramarginal gyrus
Icus parietalis superior
ulcus intermedius
Gyrus angularis ipui
~uperior parietal lobule (pos
ulcus iuterparietalis propri
Lat. fis. (ascend, term, piei
Sulcus angularis
Sulcus paroccipitalis
Area peristriata
ncisura parieto-
/ occipitalis
^rea fron
polaris
Sulcus orbitalis ,
(anterior ramus) '
irea frontomarginalis
Area prjefrontalis
\ orbitalis (transverse limb)
Orbital area
Area temporal! s polari
Sulcus temporalis anterior
Middle temporal gyrus |
Middle temporal sulcus
Inferior temporal gyrus
Pars eirenmambiens (superior temporal gyrus)
ulcus retrocalcarinus
AREA STRIATA
^ulcus lunatus (sulcus simialis)
I Sulcus occipitalis lateralis
Area praeoccipitalis
occipitotemporalis
I Sulcus temporalis superior
AREA ACUSTICA
I Area subcentralis
Pars intermedia (superior temporal gyrus)
FIG. 581. A DIAGRAM OF THE LATERAL ASPECT OF THE LEFT CEREBRAL HEMISPHERE.
The inferior frontal sulcus (the superior boundary of the inferior frontal gyrus), the middle frontal sulcus
(separating the anterior and middle frontal areas), and the superior frontal sulcus (bounding the superior
frontal gyrus) are not labelled.
bottom. The insular district of the cortex is completely hidden from view, when
the lateral fissure is closed, by overlapping portions of the cerebral hemisphere,
and, when brought into view in the manner indicated, it is observed to present a
triangular outline and to be surrounded by a limiting sulcus, of which three parts
may be recognised, viz., a superior part, bounding it above and separating it from the
parietal and frontal regions ; an inferior part, marking it off below from the temporal
region ; and an anterior part, separating it in front from the frontal region.
The insula consists of three areas of different structure. At the antero-inferior
corner (where the sulcus circularis is deficient) the knee-like bend of the area
piriformis (see Figs. 582 and 584) appears at the limen insulse. The rest is subdivided
by an oblique furrow (sulcus centralis insulse) into a posterior part divided into
gyri longi and an anterior part divided into gyri breves.
THE SULCI AND GYEI OF THE CEREBEAL HEMISPHERES. 655
Opercula Insulae. The overlapping portions of the cerebral substance which
cover over the insula are termed the insular opercula, and they form, by the apposi-
tion of their margins, the three rami of the lateral fissure. The rami of the
fissure extend from the exposed surface of the hemisphere to the submerged surface
of the insula, and, in this manner, separate the opercula from each other.
The temporal opercuhim (pars temporalis) extends upwards over the insula from
the temporal region, and its superior margin forms the inferior lip of the posterior
ramus of the lateral fissure.
The superior opercuhim is carried downwards from the parietal (pars parietalis)
and frontal (pars frontalis) regions over the insula, and its inferior margin, meeting
the temporal operculum, forms the superior lip of the posterior ramus of the lateral
fissure.
The small triangular piece of cerebral substance which sometimes intervenes
between the ascending and horizontal anterior rami of the lateral fissure is
formed by the bending downwards of the front part of the upper operculum. It
Superior opercuhim
Gyri breves insulte
Sulcus centralis insulse
Gyrus longus insulse
Gyrus temporalis transversus
anterior
Tractus olfactorius
Area piriformis | Limen insulse
Line of obliterated rhinal fissure
Area acustica extending on to
the superior temporal gyrus
FIG. 582. PART OF A LEFT CEREBRAL HEMISPHERE WITH THE OPERCULA OF THE INSULA WIDELY
SEPA HATED TO EXPOSE THE INSULA AND THE SUPERIOR SURFACE OF THE TEMPORAL OPERCULUM.
The area acustica is coloured a uniform blue, the area intermedia with large blue spots and the
area circumambiens with fine blue dots.
covers over a small part of the anterior portion of the insula, and is sometimes
termed the pars triangularis.
The orbital operculum is, for the most part, on the inferior surface of the hemi-
sphere. It lies below and to the medial side of the horizontal anterior ramus of the
lateral fissure, and proceeds backwards from the orbital aspect of the frontal lobe
over the anterior part of the insula.
Development of the Lateral Fissure and of the Insular District of the Cerebral Hemi-
sphere. It is only during the latter half of the intra-uterine period of development that the
opercula take shape and grow over the insula, so as to shut it out from the surface. In its
early condition the insula presents the form of a depressed area on the side of the cerebral
hemisphere, surrounded by a distinct boundary wall formed by the surrounding more elevated
surface of the hemisphere (Fig. 583, A). After a time this depressed area, which is called the
fossa lateralis, assumes a triangular outline, and then the bounding wall is observed to be com-
posed of three distinct parts, viz., a superior or fronto- parietal, an inferior or temporal, and
an anterior or orbital part (Fig. 583, B). The angle formed by the meeting of the superior
and anterior portions of the boundary, may become flattened, and a short oblique part of the
limiting wall develop into a small triangular frontal operculum (Fig. 583, F). Each of these
portions of the bounding wall of the fossa becomes a line of growth, from which an operculum
656 THE NERVOUS SYSTEM.
takes origin, and by the approximation of these opercula, as they grow over the surface of the
fossa, the insula becomes closed in and the rami of the lateral fissure are formed (Fig. 583, C).
The lateral fissure is an example of the fourth category of furrows enumerated
above. It is largely the result of the operation of the mechanical factors incidental
to the bending downwards of the pallium in front of and behind the place where
the hemisphere-wall is supported and held in position by the corpus striatum.
The cortical area roughly corresponding to the surface of the corpus striatum is the
insula ; the temporal region extends downwards behind it, and to a less extent
the frontal region
in front of it (Fig.
583, A). Then
towards the end of
the fifth month of
foetal life the ex-
uberant growth of
the free fronto -
^^^ parietal pallium
v v^. /""%/ T ^^ I above the insula
^PHHMBB^^ ^-^:-: ~m*^F ( Fi g- 5S3 > B ) aiid
c ^^^ B the temporal pal-
FIG. 583. RIGHT HEMISPHERES OF HUMAN FCETUSES SHOWING THREE STAGES l lum below and
IN THE DEVELOPMENT OF THE INSULA AND THE INSULAR OPERCULA. behind it leads to
A, Right cerebral hemisphere from a foetus in the latter part of the fourth month the development of
of development ; B, Right cerebral hemisphere from a foetus in the fifth lip-like folds of n60-
month of development ; C, Right cerebral hemisphere from a foetus in the |i
latter part of the eighth month of development.
In C the temporal operculum has been removed, and thus a large part of the CUla which gradu-
insula is exposed. The outline of the temporal operculum is indicated by a ally approach One
F.P, Superior operculum. F, Frontal operculum. 0, Orbital opejculum. another (Fig. 583,0)
and eventually
cover up the insula. Other factors come into play in determining the form and
topographical relations of the fissura lateralis. For example, the posterior part
of the fissure is the morphological boundary between the acoustic and tactile terri-
tories of the neopallium.
THE ACOUSTIC AEEA AND FIBEE-TKACTS.
In the embryo of the fifth month (Fig. 583, B), as well as in every later stage,
even up to the adult condition (Fig. 582), an area upon the superior surface of
the temporal operculum can be seen to slope medially towards the upper limb of
the sulcus circularis, behind the insula. This area constitutes the receptive centre
for acoustic impressions the gyrus temporalis transversus or Heschl's convolution
although the extent of this acoustico-sensory area does not coincide exactly
with that of the transverse temporal gyrus. The area formed by the upper surface
of the temporal operculum immediately behind this prominent transverse gyrus
is also called by the same name, so that there are anterior and posterior transverse
temporal gyri (Fig. 582; the posterior transverse temporal gyrus is not labelled in
the figure).
In studying the brain-stem we have seen that a tract of fibres originating in
the cochlear terminal nuclei (in the medulla oblongata) crosses the median plane
(corpus trapezoideum) and bends upwards in the lateral lemniscus of the other
side (Fig. 580) to end in the medial genie ulate body of the metathalamus.
From the medial geniculate body a new tract arises (composed of tertiary
acoustic neurones), which passes laterally (Figs. 580 and 584) to end in the
transverse temporal gyri. This tract may be called the radiatio thalamotemporalis.
The area into which this acoustic radiation is inserted occupies not only the
region of the anterior transverse temporal gyrus (Fig. 582) hidden within the lateral
fissure, but also extends over its inferior lip, on to the exposed surface of the superior
temporal gyrus (Fig. 581). Surrounding this area there are two concentric bands,
THE ACOUSTIC AEEA AND FIBKE-TKACTS.
657
which are also concerned with acoustic functions, but are related to the acoustic
radiation only through t^e intermediation of the area acustica of the transverse
gyrus (Figs. 581 and 582).
These areas may be distinguished as the pars intermedia and pars circumambiens,
respectively, of the gyrus temporalis superior. During the sixth month of foetal life a
furrow makes its appearance along the line of the inferior boundary of the superior
temporal area (Fig. 590). It is called the sulcus temporalis superior.
At a much later stage of development another furrow (sulcus temporalis
anterior) makes its appearance further forwards in the temporal region, as the
posterior boundary of the area temporalis polaris;~it often becomes confluent with
Tuberculum olfactorium
Olfactory tract | Optic nerve
Optic tract [ / ( ' Optic chiasma
Substantia perforata anterior | / i i Infundibulum
i / / / / Corpus inamillare
\ ; / / / f Substantia perforata posterior
/ / / Oculomotor nerve
/ / / / Internal capsule
Jtria olfactoria lateralis upon anterior j
'
part of piriform area
Nucleus amygdalae (cut surface) [
triform area (cut surface) j
jimen insulae
Optic radiation / /
Stria terminalis . * / ,'
Caudate nucleus ' / '
Lateral geniculate body /
Brachium coliiculi superioris J
Thalamus (pulvinar)
Medial geniculate body i !
Basis pedunculi cerebri |
Red nucleus
/ / Optic radiation
/ Caudate nucleus
Stria terminalis
Radiatio thalamo-temporalis (acoustic
radiation) passing from the medial
genicnlate body into the anterior
transverse temporal gyrus
Substantia nigra
FIG. 584. INFERIOR ASPECT OP PART OF THE BRAIN. The mesencephalon has been cut across and a great
part of the cerebral hemisphere dissected away to expose the acoustic radiation (right side of figure
in yellow) passing laterally from the medial geniculate body to the deep surface of the transverse
temporal gyri, of which a small part is shown in section. Motor fibres in red ; optic fibres, blue :
olfactory, dull yellow.
the real sulcus temporalis superior, and is usually described as part of it. But it is
genetically quite distinct from it (Fig. 581).
If the area acustica is cut across in a perfectly fresh brain it 'will be found to
be composed of a thin layer (1'75 mm.) of cortical gray matter, in which two
very dense and fairly broad bands of white matter are visible (Fig. 584). These
bands are composed largely of fibres of the acoustic radiation, which have entered
the cortex to terminate in it. The superior temporal area is composed of somewhat
thicker cortex with two bands which are not so densely white as those of the
area acustica. The cortex of the temporal polar area is composed of moderately
thick, clear, gray matter in which there is a single, narrow, sharply defined white
line.
43
658
THE NEEVOUS SYSTEM.
r Olfactory bulb
The remainder of the true temporal region is composed of an extensive district
below the superior temporal sulcus. It is composed of thicker cortex than the
superior temporal area, ranging from 3 mm. just below the superior temporal
sulcus to 2-5 mm. at the inferior border of the hemisphere. It is composed of
three bands of different texture, the middle temporal gyrus, the inferior temporal
gyrus, and the pararhinal gyrus, which fringes the area piriformis on the tentorial
surface. Upon the lateral aspect of the temporal region a series of irregular
furrows are situated along the line of demarcation between the gyrus temporalis
medius and the gyrus temporalis inferior ; they are considered to represent a sulcus
temporalis medius, but
they are subject to much
irregularity, especially in
highly developed brains.
The sulcus temporalis in-
ferior, which forms the
line of demarcation be-
tween the gyrus tempor-
alis inferior and the gyrus
suicus orbitaiis fusiformis, is placed upon
the inferior aspect of the
temporal region.
The great extent of
the middle and inferior
temporal gyri constitutes
- - Area piriformis one of the outstanding
features distinctive of the
pararhinai gyrus human brain. Flechsig
has shown that the fibres
passing to and from these
two gyri are the last to
become medullated, later
even than the important
parietal and frontal areas.
- - optic chiasma
temporal sulcus
(posterior part)
*:*&
Fronto-marginal area
Orbital area
Pronto-marginal area
Inferior frontal gyrus
Area temporalis polaris
Inferior
temporal gyrus
Inferior
temporal sulcus
(anterior part)
k Sulcus cal-
'carinus
Area temporo-
occipitalis
Sulcus collateralis trans-
versus
Area parastriata
Area striata
Area peristriata
^.
Sulcus col-
lateralis
THE VISUAL AEEAS
AND FIBEE-TEACTS.
Area peristriata -
Sulcus lunatu
Sulcus calcarinus lateralis _
Sulcus polaris
inferior
Sulcus calcar-
inus posterior
- Area striata
FIG. 585. CORTICAL AREAS on the tentorial and orbital aspects of the
cerebral hemispheres.
We have already seen
(Figs. 578 and 584) that
each optic tract ends in
the lateral geniculate
body, the pulvinar of
the thalamus, and the
superior colliculus. From
the lateral geniculate
body (and according
to most writers the thalamus also, though this is not admitted by all) a tract
arises which conveys visual impulses back to the occipital pole of the hemi-
sphere. This radiatio thalamo-occipitalis (Gratiolet's optic radiation) is seen from
various points of view in the figures mentioned, but it is possible (see Fig.
587) to expose it in a section which will display it in its relationship to the
rest of the visual path (Fig. 586).
From this it will be seen that the fibres of the optic radiation, after emerging
from the lateral geniculate body, bend backwards in the lateral wall of the ventricle
and proceed to an extensive district of thin cortex (1/5 mm. or less in thickness),
occupying an area of about 3000 sq. mm. of the medial surface and pole of
the occipital area. The cortex in this area is distinguished by the presence of'
THE VISUAL AEEAS AND FIBKE-TKACTS.
659
a very distinct white line or stria, which was first noticed by Gennari in the
year 1776.
If this visual receptive area striata of the occipital cortex is excised and spread
out in one plane, it will be found to present an elongated ovoid form and a super-
ficial extent of about 3000 sq. mm. (varying in different brains from about
2700 to 4000). The narrow extremity of the oval is placed a short distance
behind and below the splenium of the corpus callosum ; and from this point the
area extends horizontally backwards to the occipital pole, or even beyond it on to
the lateral aspect of the hemisphere. In the course of development this area
striata becomes folded along its axis during the sixth month, and the furrow thus
formed is called the sulcus calcarinus. This name was applied to the furrow by
Huxley because its deep anterior part indents the whole thickness of the medial
4 Hubstantia
perforata
i~~ anterior
r ,m|| Optic tract
- - (cut)
__ jj _J| Basis pedun-
* culi cerebri
-$-. -~,^~ Optic tract
Corpus
geniculatun
laterale
^~ - Fascia dentata
_ Isthmus gyri
cinguli
-Area striata
Lunate sulcus
FIG. 586. DIAGRAM OF THE CENTRAL CONNEXIONS
OF THE OPTIC NERVE AND OPTIC TRACT.
FIG. 587. A SLIGHTLY OBLIQUE (ALMOST HORI-
ZONTAL) SECTION THROUGH A CEREBRAL HEMI-
SPHERE IN THE PLANE OF THE OPTIC TRACT
AND RADIATION.
wall of the hemisphere, and the swelling so produced in the posterior cornu of the
lateral ventricle was supposed by the older .'anatomists to resemble a cock's spur,
and was hence called calcar avis (see Fig. 566, p. 637).
The anterior part of this furrow is much deeper, more constant in form and
position, more precocious in development, and phylogenetically much older than
the posterior part. As it is the part of the sulcus which gives rise to the calcar avis,
it is the true calcarine ; while the newer, shallower posterior part is wholly on the
caudal side of the calcar avis, and is called, sulcus calcarinus posterior. If the
area striata is prolonged on to the lateral surface, it also may become folded in the
line of its axis, and so give rise to a sulcus calcarinus lateralis.
There is a fundamental distinction between the calcarine sulcus and the posterior
calcarine in their t relations to the area striata. For the stria of Gennari is
found only in the inferior wall of the sulcus calcarinus, which is therefore a sulcus
43 a
660
THE NEKVOUS SYSTEM.
limitans ; whereas the stria extends throughout both walls of the posterior calcarine
sulcus, and in most cases beyond its lips on to the surface of the cuneus and the
gyms lingualis (Figs. 588 and 589), i.e. the exposed cortical areas placed upon the
superior and inferior aspects respectively of the sulcus calcarinus posterior.
Along the superior and inferior boundary lines of this area shallow limiting
sulci usually develop (Fig. 589), and these furrows often pass backwards into
little arched sulci polar es, which are furrows of the operculated variety (see
p. 646), called into existence by the broadening out of the area striata (not
an actual broadening, but an unfolding) as it passes round the edge of the
hemisphere.
At the point of transition from the deep sulcus calcarinus into the shallower
sulcus calcarinus posterior (Fig. 588) a submerged ridge is usually found the gyrus
cuneolingualis anterior; and other similar ridges, which may be exposed on the
Praecuneus
Parieto-occipital fossa
Inctf urai paneio-occipitalis
Cunei
Anterior cuneo- Jp;
lingual gyrus
Sulcus calcarinus fc|
posterior
Posterior cuneo- 3^
lingual gyrus
I Gyrus cinguli
j
Corpus callosum
Thalamus
Gyrus cunei
Sulcus calcarinus
Gyrus lingualis
Sulcus lingualis
inferior
Fia. 588. THE PARIETO-OCCIPITAL AND THE CALCARINE SULCI FULLY OPENED UP, so as to show the
deep transitional gyri marking off the several elements of the -<-shaped system.
Area striata, uniform blue ; area parastriata, large blue spots ; area peristriata, fine blue dots.
surface or may be submerged, are often found interrupting the posterior and lateral
calcarine sulci themselves (Fig. 588).
The posterior and lateral calcarine sulci are subject to a very wide range of
variation in form, but they are always axial foldings of the area striata.
When the area striata crosses on to the lateral surface of the hemisphere a small
semilunar furrow develops a short distance in front of its anterior edge. This is
the sulcus lunatus. The larger the lateral extension the closer does the edge of the
area striata approximate to the caudal lip of the sulcus, which under such circum-
stances assumes a definitely operculated form. Such cases occur most often in the
left hemisphere and in the brains of primitive people ; and they represent a perfect
realisation of a furrow once supposed not to occur in the human brain, but to be
distinctive of the ape. Hence it used to be called the " Affenspalte " or sulcus
simialis.
The area striata is surrounded by two peripheral concentric bands an inner,
which may be called area parastriata, and an outer, the area peristriata. Sulci
develop along the boundary lines of each of these areas ; and those which indicate
the superior and inferior limits of the peripheral band (i.e. peristriate area"
THE VISUAL AEEAS AND FIBKE-TKACTS.
661
make their appearance relatively early in development and become very deep
furrows.
The inferior of these is placed upon the tentorial surface, and is known as the
sulcus collateralis ; the superior limiting furrow of the visual territory (its peristriate
part) is upon the superior surface of the hemisphere, and is usually regarded as the
ramus occipitalis of the sulcus interparietalis. But it is genetically independent of
the latter furrow, and may be distinguished as the sulcus paroccipitalis.
Near the super o- medial margin of the hemisphere there is a furrow, which
indicates the line of demarcation between the para- and the peristriate areas the
sulcus occipitalis paramedialis. It may be situated upon either the medial or the
superior surface of the hemisphere. In some cases it belongs to the category of
limiting sulci, in others to the group of operculated sulci (see p. 646).
Lobulus paracentralis
Sulcus cinguli |
Superi
Gyrus cingul
frontal gyrus (posterior part) \
Corpus callosum \ \
Superior frontal gyrus (intermediate part;
perior frontal gyrus (anterior part)
Gyrus cinguli
Sulcus cinguli
Area paracingularis
Icus paracingularis
ior frontal area
Sulcus paracentralis
I Sulcus subparietalis
Parasplenial area
Sulcus ceiitralis
Incisura sulci cinguli
Praecuueus (anterior part)
Sulcus prsecunei
Praecuneus (posterior part)
Sulcus parieto-occipitalis
Incisura parieto-occipits
rea peristriata
i Sulcus polaris su
Area frontopolar
Sulcus rostrali
Area praefrontalis i
Sulcus subrostralis
Area temporalis polaris*
Gyrus cinguli
Fissura rhlnalis
Piriform area
Gyrus temporalis inferior
Junction of
| / ,| | Sulci limitantes areee striatse
tategyri, I Sulcus collateralis
which form Area occipito temporalis
one area I Area parastriata
Sulcus calcarinus'
Icus calcari
lateralis
| Sulcus polaris inferior
Area striatu
ileus calcarinus posterior
Area peristriata
FIG. 589. THE CORTICAL AREAS ON THE MEDIAL ASPECT OF THE CEREBRAL HEMISPHERE.
Passing horizontally forwards upon the lateral surface of the hemisphere there
is a constant furrow formed by the axial folding of part of the peristriate area,
approximately in line with the axial folding of the striate area (sulcus cal-
carinus lateralis) ; it is the sulcus occipitalis lateralis. When there is a fully
developed sulcus lunatus the lateral occipital sulcus joins it near its midpoint
(Fig. 581, p. 654).
The sulcus (or fossa) parieto-occipitalis (Fig. 554) is usually a deep furrow upon
the medial aspect of the hemisphere which passes vertically downwards from the
supero-medial border and appears to join the calcarine sulcus near its union with
the posterior calcarine, forming upon the surface a Y-shaped pattern, the stem of
which is calcarine, the limbs posterior calcarine and parieto-occipital respectively,
and the wedge-shaped area between the limbs the cuneus (Fig. 588 ; compare with
the pattern shown in Fig. 589, where the parieto-occipital sulcus is not labelled).
If, however, the lips of these three furrows are divaricated (Fig. 588), the parieto-
occipital depression will be found to be separated from the calcarine by a prominent
43 &
662
THE NERVOUS SYSTEM.
submerged cortical ridge, the gyrus cunei ; and the parieto-occipital will be found
to be something more than a mere sulcus. It is, in fact, a great fossa in which are
submerged the anterior parts of the area parastriata and area peristriata, and the
posterior part of the parietal area known as the prascuneus, as well as the sulci
which separate these territories one from the other. It is a great trough formed
by the splenium of the corpus callosurn as in the course of its development it
thrusts itself backwards and crumples up the cortex. When the corpus callosum
fails to develop, no parieto-occipital fossa makes its appearance. The part of the
sulcus that notches the supero-medial border (Figs. 589 and 593) forms a distinct
element, which Retzius has called the incisura parieto-occipitalis.
Sulcus Collateralis. The collateral sulcus is a strongly marked furrow on the
tentorial face of the cerebral hemisphere. It begins near the occipital pole and
extends forwards towards the posterior end of the rhinal fissure, with which it
sometimes becomes confluent. In its posterior part it is placed below, and parallel
to, the calcarine fissure, from which it is separated by the lingual gyrus. From
the posterior extremity a sulcus proceeds forwards and then laterally across the
inferior surface of the occipital region, forming a V-shaped pattern with the
collateral sulcus (Fig. 585). As it is serially homologous with the latter, being, like
it, an inferior boundary of the area peristriata, it may be called the sulcus collateralis
trans versus. The lingual gyrus is sometimes subdivided by a furrow (sulcus
sagittalis gyri lingualis) midway between the collateral sulcus and the inferior
margin of the area striata. It is the line of demarcation between the parastriate
and peristriate areas, and when deep is often mistaken for the collateral sulcus.
THE PAEIETAL REGION.
We have seen that the acoustic pathway leads into the temporal region and
the visual pathway into the occipital region. The facts of clinical medicine show
that large areas in these two regions
beyond the limits of the cortex in
which the acoustic and op tic radiations
end are concerned with the functions
of hearing and vision. A large part
of the parietal area is interposed be-
tween these temporal and occipital
territories, and its integrity and
normal functioning is a necessary
condition for the proper performance
of many acts, such as reading written
or printed documents, in the apprecia-
tion of which both hearing and vision
have played some part. But the
parietal region also includes the
cortical area in which a part, at
least, of the chief thalamo- cerebral
tract ends the bundle of fibres that
represents the third stage of the great
sensory pathway, the first stage of
which is formed by the spinal and
cerebral sensory nerves and their
FIG. 590. LEFT CEREBRAL HEMISPHERE, from a foetus in
the early part of the seventh month of development.
p.c.s. Sulcus prsecentralis superior.
p.c.i. Sulcus praecentralis inferior.
r 1 . Inferior part of central sulcus.
r 2 . Superior part of central sulcus.
p 1 . Inferior postcentral sulcus.
p 3 . Sulcus interparietalis proprius.
p 4 . Sulcus paroccipitalis.
t 1 . Superior temporal sulcus.
S. Lateral fossa.
F.P. Fronto-parietal wall.
F. Frontal wall.
0. Orbital wall.
central prolongations, and the second
stage by the spino-thalamic, bulbo-
thalamic, and ponto-thalamic fasciculi, which pass upwards in the medial lemniscus
and end in the ventral nucleus of the thalamus (Figs. 579 and 580).
The sensory area in question forms part of the gyrus centralis posterior, whic
intervenes between two oblique furrows, the sulcus centralis and the sulcus posl
centralis, which extend across the whole breadth of the hemisphere above tl
sulcus lateralis (Fig. 581).
Sulcus Centralis. During the sixth and seventh months of foetal life the expand-
THE PAEIETAL KEGION.
663
ing posterior central area becomes raised up into a prominent ridge, and a similar
ridge is formed immediately in front of it (Fig. 590) from the area which emits
the great efferent or motor tract to control all the motor nuclei upon the other
side of the brain and spinal medulla. As these ridges become raised up a
depression is left between them : this is the sulcus centralis. At first it consists
of two parts, a superior and an inferior (Fig. 590, r 2 and r 1 ) ; but as a rule these
become confluent later.
The sulcus centralis in the adult takes an oblique course across the lateral
convex surface of the cerebral hemisphere, and intervening between the frontal
and parietal regions it forms the immediate posterior boundary of the motor area of
the cortex. Its upper end cuts the supero-medial border of the hemisphere a short
distance behind the mid-point between the frontal and occipital poles, whilst its
inferior end terminates above the middle of the posterior ramus of the lateral fissure.
Its superior extremity, as a rule, turns round the supero-medial border of the hemi-
sphere, and is then continued backwards for a short distance on the medial surface.
Although, in its general direction, the
sulcus is oblique, it is very far from being
straight. It takes a sinuous course
across the hemisphere. This is largely
due to the varying breadth of the motor
areas representing the lower limb, trunk,
upper limb, and head, respectively, which
are placed immediately in front of it. Ik interlocking
When the sulcus centralis is widely opened
up, so that its bottom and its opposed sides
may be fully inspected, it will be seen that the
two bounding gyri are dovetailed into each
other by a number of interlocking gyri, which
do not appear on the surface (Fig. 591). Further,
two of these, placed on opposite sides of the
fissure, are frequently joined across the bottom
of the sulcus in the form of a sunken bridge of
connexion, which constitutes what is termed a
deep transitional gyrus. The continuity of the
sulcus is thus, to some extent, interrupted.
This condition is rendered interesting when
considered in connexion with the development
of the sulcus. The deep interlocking gyri in-
dicate a great exuberance of cortical growth in
this situation in the early stages of the develop-
ment of the sulcus ; and the presence of the deep
transitional gyrus is explained by the fact that the sulcus generally develops in two pieces, which
run into each other to form the continuous sulcus of the adult, viz., a part corresponding to the
inferior two-thirds, and a superior part, which represents the superior third and which appears
at a slightly later date. In certain very rare cases the sulcus centralis is found to remain double
throughout life, through a failure of its two pieces to unite. In such cases the deep transitional
gyrus, which is frequently seen at the bottom of the furrow, remains on the surface. Heschl,
who examined 2174 cerebral hemispheres, found this anomaly only six times ; Eberstaller met
with it twice in 200 brains.
If a section is made at right angles to this sulcus in a fresh brain (Fig. 592), it
will be seen that its anterior (gyrus centralis anterior) and posterior (gyrus centralis
posterior) walls present a marked contrast the one to the other, and that the transi-
tion from the one type of cortex to the other takes place precisely at, or near to,
the bottom of the sulcus. The anterior wall is composed of thick (3 '5 to 4 mm.)
motor cortex thickly laden with medullary matter arranged in the form of three
or four pale bands with blurred edges and multitudes of fine pencils of fibres
passing to and fro between it and the white matter of the hemisphere. The
posterior wall is composed of thin (1-5 mm.) cortex containing two narrow and
sharply denned white lines.
This sensory area forms little more than the posterior wall of the sulcus
centralis, and barely emerges upon the surface to form the posterior lip of the
sulcus (Fig. 581). Here it becomes continuous with a slightly thicker cortex with
FIG. 591. SULCUS CENTRALIS FULLY OPENED UP,
so as to exhibit the interlocking gyri and deep
transitional gyrus within it.
Motor cortex coloured red, sensory cortex blue.
664
THE NERVOUS SYSTEM.
doubled lines which are less dense than those of the sensory cortex ; this area forms
the crest of the gyms centralis posterior, and then gives place to another slightly
modified type of cortex which forms the anterior wall of the sulcus postcentralis.
Thus the sensory cortex has two fringing bands analogous to those already noticed
alongside the visual and acoustic areas.
The motor and sensory areas cross on to the medial aspect of the hemisphere,
into a region known as the lobulus paracentralis.
Sulcus centralis T j_i p i
Gyrus centralis anterior | Gyrus centralis posterior In thlS region a lUrrOW (SUlcUS paracentrallS)
is sometimes found along the line of demarca-
tion of the medial parts of the motor and
sensory areas (Fig. 589).
That portion of the parietal region which
intervenes between the gyrus centralis pos-
terior and the occipital region is usually
subdivided into two distinct parts (lobulus
parietalis superior and lobulus parietalis in-
ferior) by a horizontal furrow, called the
sulcus interparietalis proprius. The term
sulcus interparietalis is usually applied in a
purely arbitrary and artificial manner to a
complex of four genetically distinct and in-
dependent furrows (Fig. 593, p 1 , p 2 , p*, and p*\
the Sulcus Postcentralis inferior (^ ), the sulcus
postcentralis superior (p*), the sulcus inter-
parietalis proprius (ramus horizontalis) (p 3 \
and the sulcus paroccipitalis (ramus occipitalis) (p*\ which ends in the sulcus
occipitalis transversus.
These four furrows develop quite independently one of the other, the postcentral
sulci as the posterior boundary of the sensory territory, the paroccipital sulcus as
the supero-lateral boundary of the visual territory, and the more variable horizontal
ramus (the sulcus interparietalis, in the strict sense of the term) as a demarcation
Transitional gyrus Par ie to-occipital sulcus (incisura)
Posterior central gyru
Transitional /
gyri I
Boundary line between motor and sensory cortex
FIG. 592. SECTION ACROSS THE SUPERIOR PART
OF THE SULCUS CENTRALIS IN A FRESH BRAIN.
Termination of lateral fissure
FIG. 593. THE FOUR SULCI OF THE INTERPARIETAL COMPLEX OPENED UP, so as to show the deep
transitional gyri intervening between them.
p 1 . Sulcus' postcentralis inferior.
p 2 . Sulcus' postcentralis superior.
p 3 . Ramus horizontalis (sulcus interparietalis proprius).
p 4 . Ramus occipitalis (sulcus paroccipitalis).
between the two parietal lobules. The four furrows may unite to form any possible
combination.
The superior parietal lobule is composed of moderately thick cortex (2'5 to
3 mm.) placed between the interparietal sulcus (ramus horizontalis) and the superior
border of the hemisphere,, where it becomes continuous on the medial surface with
the precuneus. Each of these parts is' subdivided by a transverse sulcus, the
THE FKONTAL EEGION. 665
superior lobule by the sulcus parietalis superior and the precuneus by the sulcus
prascunei (Fig. 589).
The latter sulcus usually joins a small inverted U-shaped furrow (sulcus sub-
parietalis), which encloses a cortical territory of distinctive structure the area
parasplenalis [praecunei].
The inferior parietal lobule, which from its position is the natural meeting- place
for impressions coming from the visual, acoustic, and tactile territories, is naturally
a region of great functional significance. It is composed of a series of areas differ-
ing in thickness and texture. The anterior region forms a convolution (gyrus
supramarginalis) surrounding the upturned extremity of the lateral fissure ; behind
it there is a second convolution called the gyrus angularis, which surrounds a
vertical sulcus angularis, often described as the extremity of the sulcus temporalis
superior ; but in reality it is quite independent of the latter furrow, but it often
becomes confluent with it. Behind the gyrus angularis and separated from it by a
transverse furrow (sulcus occipitalis anterior) there is a cortical territory (area parieto-
occipitalis) which may perhaps be looked upon as a specialised and outlying part
of the peristriate area of the visual cortex.
THE FKONTAL EEGION.
The frontal region is the biggest of the main cortical areas the so-called "lobes."
On the lateral surface of the hemisphere, it is bounded behind by the sulcus centralis
and below, in part, by the lateral fissure. It presents a lateral surface, a medial
surface, and an inferior or orbital surface.
On its lateral aspect the surface is broken up by a large series of furrows,
which exhibit considerable variability.
The inferior precentral sulcus consists of a vertical and an oblique part. The
vertical portion lies in front of the inferior part of the sulcus centralis, whilst
the oblique part extends forwards and upwards (Fig. 594).
The superior precentral sulcus is a short vertical sulcus which lies at a higher
level than the inferior precentral sulcus, in front of the upper part of the sulcus
centralis. It is almost invariably connected with the posterior end of the superior
frontal sulcus.
The anterior central gyrus is a long continuous gyrus, which is limited in front
by the two precentral furrows and behind by the sulcus centralis. Inferiorly it is
continuous with the area subcentralis which links it to the posterior central gyrus.
The area subcentralis is limited in front and behind by the anterior and posterior
sulcentral sulci (not labelled in Fig. 594).
The superior frontal sulcus extends forwards in a more or less horizontal direc-
tion from the sulcus praecentralis superior.
The gyrus frontalis superior is the narrow convolution between the supero-medial
border of the hemisphere and the superior frontal sulcus and the continuation of
this convolution into a broad area upon the medial surface.
The inferior frontal sulcus occupies a lower level than the superior frontal sulcus.
Its posterior end is placed in the angle between the vertical and horizontal parts of
the inferior precentral sulcus, and is not infrequently confluent with one or other
of these. It proceeds forwards towards the superciliary margin of the hemisphere
and ends a short distance from this in a terminal bifurcation (Fig. 594).
The gyrus frontalis medius is the name given to the broad convolution which
lies between the superior and inferior frontal sulci.
The gyrus frontalis inferior is that portion of the lateral surface of the frontal
region which is placed in front of the inferior precentral sulcus and below the
inferior frontal sulcus. The inferior frontal convolution includes three cortical
areas (Fig. 594) differing in structure the one from the other. The sulcus diagonalis
separates the intermediate of these from the posterior.
The sulcus frontalis medius begins midway between the anterior ends of the
superior and inferior frontal sulci and proceeds obliquely forwards towards the
frontal pole. When the furrow reaches the superciliary margin of the hemisphere
it ends near a transverse furrow, called the fronto-marginal sulcus.
666
THE NEKVOUS SYSTEM.
On the medial aspect of the frontal lobe there are two convolutions, the larger
peripheral area which forms part of the gyms frontalis superior and a smaller inner
part encircling the corpus callosum, which is called the gyrus cinguli. These gyri
are separated by the sulcus cinguli (Fig. 589).
The posterior part of the sulcus cinguli is genetically distinct from the anterior
part and it circumscribes a broader area, the lobulus paracentralis, which is con-
tinuous with the gyri centrales of the lateral surface of the hemisphere.
Inferior precentral sulcus
Inferior frontal gyrus (posterior part) I
Superior frontal j
gyrus (inter-
Intermediate part of inferior frontal gyrus mediate part)
Gyrus frontalis superior (anterior part) \ Sulcus
;rior ascending ramus of lateral fissure x n diagonal!
nterior part of inferior frontal gyrus
Middle frontal area
rior horizontal
unus of lateral
:erebral fissure
Middle frontal gyrus (posterior part)
Gyrus frontalis superior
| Superior preoentral sulcus
| Area suprainargiualis anterior
I I | MOTOR CORTEX
I l I Sulcus postcentralis
Sulcus centralis
. SENSORY CORTEX
' , 'Anterior part "j
Intermediate part \ Gyrus centralis postei
Posterior part J
^ Superior parietal lobule (anterior
xSupramarginal gyrus
^ Sulcus parietalis superior
Icus intermeuius
Gyrus angularis
ior parietal lobule
I
Superi
. Sulcus iiiterparietalis pro
Lat. fis. (ascend, term. ]
Sulcus angulaiis
Sulcus paroccipitalis
Area peristriata
Tncisura parieto-
' cipitalis
Anterior occipital
sulcus
Area praeoceipitali
Area parastriat
ulmis occipiti
parauiedial
Area fronto-
polaris
Sulcus orbitalis
anterior ramus /
Area frontomarginalis
Area proefrontalis
ssura orbitalis transverse limb
Orbital area
Area temporalis polaris
Sulcus temporalis anterior
Middle temporal gyrus |
Middle temporal sulcus
\ Inferior temporal gyrus
Pars circuinambiens (superior temporal gyrus)
Sulcus retrocalcarinut
AREA BTRIATA
Sulcus lunatus (sulcus simialis)
Sulcus occipitalis lateralis
Area praeoccipitalis
Area occipitotemporalis
ulcus temporalis superior
AREA ACUSTICA
I Area subcentralis
Pars intermedia (superior temporal gyrus)
FIG. 594. AREAS ON LATERAL ASPECT OF LEFT CEREBRAL HEMISPHERE.
The superior, middle, and inferior frontal sulci are not labelled. The middle is in the midst of the green
area, the superior and inferior respectively at its superior and inferior boundaries.
On the orbital aspect of the frontal region there are two sulci, viz., the olfactory
and the orbital.
The olfactory sulcus is a straight furrow which runs parallel to the medial orbital
border of the hemisphere. It is occupied by the olfactory tract and bulb, and it
cuts off a narrow strip of the orbital surface close to the medial border, which
receives the name of gyms rectus.
The orbital sulcus is a composite furrow which assumes many different forms.
It consists essentially of a U-shaped furrow, the convexity of which is directed
anteriorly (Fig. 585), and one or two variable branches passing forwards from it.
The conventional manner of subdividing the cortical territory anterior to the
sulcus centralis into gyri, which -has just been sketched, is apt to convey a mis-
leading idea of the distribution of the anatomical areas of differentiated cortex.
The gyrus centralis anterior together with the major portion of the paracentral
lobule and the posterior part of the middle and superior frontal gyri form a natural
subdivision of the cortex, which Brodmann calls the regio prsecentralis. It is com-
posed of a series of areas of different structure, which may be grouped as the area
prsecentralis posterior (the true motor area), the area prsecentralis intermedius, and
DUKA MATER 667
the area praecentralis anterior (Fig. 594). Most of the motor area is hidden in the
sulcus centralis, but towards the supero-medial margin of the hemisphere a con-
siderable area emerges upon the surface of both the gyrus centralis anterior and
the paracentral lobule.
Brodmann calls the rest of the frontal territory the regio frontalis ; but in the
colour scheme adopted in Figs. 585, 589, and 594 the inferior frontal gyrus and
the orbital area posterior to the orbital sulcus have been associated with the
" precentral " rather than the " frontal " regions.
WEIGHT OF THE BRAIN.
The average weight of the adult male brain may be said to be about 1360
grammes. The female brain weighs rather less, but this is to be expected from the
smaller bulk of the female body. Probably the relative weight of the brain in the
two sexes is very much the same. The variations met with in brain-weight are
very great, but it is doubtful if normal intellectual functions could be carried on in
a brain which weighs less than 960 grammes. In microcephalic idiots brains of
extremely small size are met with.
THE MENING-ES OF THE ENCEPHALON AND
MEDULLA SPINALIS.
The brain and spinal medulla are enclosed within three membranes, which are
termed the meninges or meningeal membranes. From without inwards these
are: (1) the dura mater, (2) the arachnoid, and (3) the pia mater. The space
between the dura mater and the arachnoid receives the name of subdural space,
while the much more roomy interval between the arachnoid and the pia mater is
called the subarachnoid space.
DURA MATER.
The dura mater is a dense and thick fibrous membrane which possesses a very
considerable degree of strength. Its arrangement within the cranial cavity is so
different from that within the vertebral canal that it is customary to speak of it as
consisting of two parts, viz., a cranial and a vertebral, although in adopting this sub-
division it must be clearly understood that both portions are continuous with each
other at the foramen magnum.
Dura Mater Encephali. The cranial dura mater is adherent to the inner
surface of the cranial wall, and performs a double office. It serves as an internal
periosteum for the bones which it lines and it constitutes an envelope for the brain.
Its inner surface, which bounds the subdural space, is smooth and glistening, and
is covered with a layer of endothelial cells. The outer surface when separated from
the cranial wall, is rough, this being due to numerous fine fibrous processes and
blood-vessels which pass between it and the bones. Its degree of adhesion to
the cranial wall differs considerably in different regions. To the vault of the
cranium, except along the lines of the sutures, the connexion is by no means
strong, and in the intervals between the fibrous processes which pass into the bone
there are small lymph spaces (epidural spaces) where the outer surface of the
membrane is covered by endothelial cells. So long as the sutures are open the
dura mater is connected with the periosteum on the exterior of the skull, along the
sutural lines, by a thin layer of fibrous tissue which intervenes between the bony
margins. Around the foramen magnum, and on the floor of the cranium, the dura
mater is very firmly adherent to the bone. This is more particularly marked in the
case of the projecting parts of the cranial floor, as, for example, the petrous portions
of the temporal bones, the clinoid processes, and so on. This firm adhesion in
these regions is still further strengthened because the nerves, as they leave the
cranium through the various foramina, are followed by sheaths of the fibrous dura
668
THE NEKVOUS SYSTEM.
mater. Outside the cranium these prolongations of the membrane blend with the
fibrous sheaths of the nerves, and likewise become connected with the periosteum on
the exterior of the skull. In the child, during the growth of the cranial bones, and
also in old age, the dura mater is more adherent to the cranial wall than during the
intermediate portion of life.
The cranial dura mater is composed of two layers intimately connected with
each other, but yet capable of being demonstrated in most regions of the cranium.
Along certain lines these two layers separate from each other so as to form channels
lined with endothelium. These channels are the venous blood-sinuses which receive
the blood from veins which come from various parts of the brain. They are described
in the section dealing with the Vascular System.
Strong fibrous partitions or septa are given off along certain lines from the deep
Internal carotid artery
Basilar venous plexus
Inferior petrosal sinus |
Superior petrosal sinus
Sigmoid part of
transverse sinus
FIG. 595. SAGITTAL SECTION THROUGH THE SKULL, A LITTLE TO THE LEFT OF THE MEDIAN PLANE
to show the arrangement of the chira mater.
The cerebral nerves are indicated by numerals.
surface of the dura mater. These project into the cranial cavity, and subdivide
it partially into compartments which all freely communicate with each other,
and each of which contains a definite subdivision of the brain. These septa are : (1)
the falx cerebri ; (2) the tentorium cerebelli ; (3) the falx cerebelli ; and (4) the
diaphragma sellae.
The falx cerebri is a sickle-shaped partition which descends in the great longi-
tudinal fissure between the two hemispheres of the cerebrum. In front it is narrow,
and attached to the crista galli of the ethmoid bone. As it is followed backwards
it increases in breadth, and posteriorly it is attached, along the median plane, to the
upper surface of the tentorium. The anterior narrow part of the falx is frequently
cribriform, and is sometimes perforated by apertures to such an extent that it almost
resembles lace-work. Along each border it splits into two layers, so as to enclose a
blood-sinus. Along its superior convex attached border runs the superior sagittal
sinus ; along its concave free border sometimes courses the much smaller inferior
DUKA MATER. 669
sagittal sinus ; whilst along its attachment to the tentorium is enclosed the straight
sinus.
The tentorium cerebelli is a large crescentic partition of dura mater, which forms
a membranous tent-like roof for the posterior cranial fossa, and thus intervenes
between the posterior portions of the cerebral hemispheres and the cerebellum. It
is accurately applied to the superior surface of the cerebellum. Thus, its highest point
is in front and in the median plane, and from this it slopes downwards towards its
attached border. It is kept at a high degree of tension, and this depends on the
integrity of the falx cerebri, which is attached to its superior aspect in the median
plane.
The posterior border of the tentorium is convex, and is attached to the hori-
zontal ridge which marks the deep surface of the occipital bone. Beyond this, on
each side, it is fixed to the postero-inferior angle of the parietal bone, and then
forwards and medially along the superior border of the petrous portion of the
temporal bone. From the internal occipital protuberance to the postero-inferior
angle of the parietal bone this border encloses the sinus transversus, whilst along
the superior border of the petrous bone it encloses the superior petrosal sinus. The
anterior border of the tentorium is sharp, free, and concave, and forms with the
dorsum sellse an oval opening shaped posteriorly like a pointed arch. This opening
receives the name of the incisura tentorii, and within it is placed the mesencephalon,
or the stalk of connexion between the parts which lie in the posterior cranial fossa
and the cerebrum. Beyond the apex of the petrous part of the temporal bone the
two margins of the tentorium cross each other like the limbs of the letter X ; the
free margin is continued forwards, to be attached to the anterior clinoid process,
whilst the attached border proceeds medially, to be fixed to the posterior clinoid
process.
The falx cerebelli is a small, sickle-shaped process of dura mater placed below
the tentorium, which projects forwards in the median plane from the internal occi-
pital crest. It occupies the notch which separates the two hemispheres of the
cerebellum posteriorly. Inferiorly it bifurcates into two small diverging ridges
which gradually fade away as they are traced forwards on each side of the foramen
magnum.
The diaphragma sellse is a small circular fold of dura mater which forms a roof
for the fossa hypophyseos. A small opening is left in its centre for the trans-
mission of the infundibulum.
Dura Mater Spinalis. In the vertebral canal the dura mater forms a tube which
encloses the spinal medulla, and which extends from the foramen magnum above
to the level of the second or third piece of the sacrum below. It is very loosely
applied to the spinal medulla and the nerve-roots which form the cauda equina ; in
other words, it is very capacious in comparison with the volume of its contents.
Moreover, its calibre is not uniform. In the cervical and lumbar regions it is
considerably wider than in the thoracic region, whilst in the sacral canal it rapidly
contracts, and finally ends by blending with the filum terminale externum, the
chief bulk of which it forms. At the superior end of the vertebral canal the spinal
dura mater is firmly fixed to the third cervical vertebra, to the epistropheus vertebra,
and around the margin of the foramen magnum. In the sacral canal the filum
terminale externum, with which it blends, extends downwards to the back of the
coccyx, to the periosteum of which it is fixed. The inferior end of the tube is thus
securely anchored and held in its place.
Within the cranial cavity the dura mater is closely adherent to the bones, and
forms for them an internal periosteum. As it is followed into the vertebral canal its
two constituent layers separate. The inner layer is carried downwards as the long
cylindrical tube which encloses the spinal medulla. The outer layer, which is much
thinner, becomes continuous behind and on each side of the foramen magnum with
the periosteum on the exterior of the cranium, whilst in front it is prolonged
downwards into the vertebral canal in connexion with the periosteum and ligaments
on the anterior wall of the canal. The spinal dura mater, therefore, corresponds to
the inner layer of the cranial dura mater, and to it alone. It is separated from the
walls of the vertebral canal by an interval, the cavum epidurale, which is occupied by
670 THE NERVOUS SYSTEM.
soft fat and a plexus of thin-walled veins. In connexion with the spinal dura
mater there are no blood-sinuses such as are present in the cranial cavity, but it
should be noted that the veins in the epidural space, placed as they are between
the periosteum of the vertebral canal and tube of dura mater, occupy the same
morphological plane as the cranial blood-sinuses. Another feature which serves to
distinguish the spinal dura mater from the cranial dura mater consists in the fact
that it gives off from its deep surface no partitions or septa.
The cylindrical tube of spinal dura mater does not lie quite free within the
vertebral canal. Its attachments, however, are of such a character that they
in no way interfere with the free movement of the vertebral column. On each
side the spinal nerve-roots, as they pierce the dura mater, carry with them into the
intervertebral foramina tubular sheaths of the membrane, whilst in front loose fibrous
prolongations more numerous above and below than in the thoracic region
connect the tube of dura mater to the posterior longitudinal ligament of the vertebral
column. No connexion of any kind exists between the dura mater and the posterior
wall of the vertebral canal.
When the interior of the tube of spinal dura mater is inspected, the series of
apertures of exit for the roots of the spinal nerves is seen. These are ranged in
pairs opposite each intervertebral foramen.
Viewed from the inside of the tube of dura mater, each of the two roots of a
spinal nerve is seen to carry with it a special and distinct sheath. When examined
on the outside, however, the appearance is such that one might be led to conclude
that both roots are enveloped in one sheath of dura mater. This is due to the fact
that the two sheaths are firmly held together by intervening connective tissue.
The two tubular sheaths remain distinct as far as the ganglion on the posterior
root, and then blend with each other.
Cavum Subdurale. The dura mater and the arachnoid are closely applied
to each other, and the capillary interval between them is termed the subdural
space. It contains a minute quantity of fluid, which is just sufficient in amount to
moisten the opposed surfaces of the two bounding membranes.
The subdural space in no way communicates with the subarachnoid space.
The fluid which it contains is led into the venous blood-sinuses around the arach-
noideal granulations (O.T. Pacchionian bodies), and thus gains exit. The subdural
space is carried outwards for a very short distance on the various nerves which are
connected with the brain and the spinal medulla, and it has a free communication
with the lymph-paths present in these nerves. In the case of the optic nerve the
sheath of dura mater is carried along its whole length, and with it the subdural
space is likewise prolonged to the back of the eyeball. .'
ARACHNOIDEA.
The arachnoid is a very thin membrane, remarkable for its delicacy and trans-
parency, which envelops both the brain and the spinal medulla between the dura
mater and the pia mater. The cranial part of the arachnoid or the arachnoidea
encephali, except in the case of the longitudinal and the lateral fissures, does not
dip into the sulci on the surface of the brain. In this respect it differs from the
pia mater. It bridges over the inequalities on the surface of the brain. Conse-
quently, on the basal aspect of the encephalon it is spread out in the form of a very
distinct sheet over the medulla oblongata, the pons, and the hollow which lies
in front of the pons, and in certain of these regions it is separated from the brain-
surface by wide intervals.
The spinal part of the arachnoid or arachnoidea spinalis, which is directly
continuous with the cranial arachnoidea, forms a loose wide investment for the
spinal medulla. This arachnoideal sac is most capacious towards its inferior part,
where it envelopes the inferior end of the spinal medulla and the collection of long
nerve-roots which constitute the cauda equina.
As the nerves, both from the brain and the spinal medulla, pass outwards they
receive an investment from the arachnoid, which runs for a short distance upon
them and then comes to an end.
THE AKACHNOIDEA.
671
Cavum Subarachnoideale. The interval between the arachnoidea and the
pia mater receives the. name of the subarachnoid space. It contains the
cerebro-spinal fluid, and communicates freely, through certain well-defined
apertures, with the ventricular cavities in the interior of the brain (aperturse
ventriculi quarti).
Within the cranium the subarachnoid space is broken up by a meshwork of fine
filaments and trabeculae, which connects the two bounding membranes (viz., the
arachnoidea and the pia mater) in the most intimate manner, and forms a delicate
sponge-like interlacement between them. Where the arachnoidea passes over the
summit of a cerebral gyrus, and is consequently closely applied to the sub-
jacent pia mater, the meshwork is so dense and the trabeculse so short that it is
hardly possible to discriminate between the two membranes. To all intents and
purposes they form in these localities one lamina. In the intervals between the
rounded margins of adjoining gyri, however, distinct angular spaces exist, where
the subarachnoid trabecular tissue can be studied to great advantage. These
Granulatio arachnoidealis
Lacuna lateral
Dura mater -
Subdural space -
Arachnoidea
ibarach-
id space-
" tissue
mater
1. 596. DIAGRAM to show the relations of the membranes of the brain to the cranial wall and the cerebral
gyri, and also of the arachnoideal granulations to the superior sagittal sinus and the lateral lacunae.
intervals on the surface of the cerebrum constitute numerous communicating
channels which serve for the free passage of the subarachnoid fluid from one part of
the brain to another. The larger branches of the arteries and veins of the brain
traverse the subarachnoid space ; their walls are directly connected with the sub-
arachnoid trabeculse, and are bathed by subarachnoid fluid.
In certain situations within the cranium the arachnoidea is separated from the
pia mater by intervals of considerable width and extent. These expanded portions
of the subarachnoid space are termed cisternse subarachnoideales. In these the sub-
arachnoid tissue is much reduced. There is no longer a close meshwork; the
trabeculse connecting the two bounding membranes take the form of long fila-
mentous intersecting threads which traverse the spaces. All the subarachnoid
cisterns communicate in the freest manner with each other and also with the
narrow channels on the surface of the cerebrum.
Certain of these cisterns require special mention. The largest and most con-
spicuous is the cisterna cerebellomedullaris. It is formed by the arachnoid
membrane bridging over the wide interval between the posterior part of the
inferior surface of the cerebellum and the medulla oblongata. It is continuous
672
THE NEEVOUS SYSTEM
Arachnoid
Posterior nerve-root
Spinal ganglion
Anterior rainus
of nerve^
Posterior rainus
of nerve
Dura mater
Arachnoid
Ligamentuiu denticulatum
Dura mater
Anterior nerve-
root (cut)
Posterior nerve-
root
Anterior nerve-
root (cut)
Ligarnentum
denticulatum
Pia mater
Anterior nerve-root
through the foramen magnum with the posterior part of the wide subarachnoid
space of the spinal medulla.
The cisterna pontis is the continuation upwards on the floor of the cranium of
the anterior part of the subarachnoid space of the spinal medulla. In the region
of the medulla oblongata it is continuous behind with the cisterna cerebello-
medullaris, so that this subdivision of the brain, like the spinal medulla, is
surrounded by a wide sub-
arachnoid space.
In front of the pons the
arachnoidea bridges across
between the projecting
temporal lobes, and covers
in the deep hollow in this
region of the brain. This
space is called the cisterna
interpeduncularis, and with-
in it are placed the large
arteries which take part in
the formation of the arterial
circle (of Willis). Leading
out from the interpedun-
cular cistern there are
certain wide subarachnoid
channels. Two of these are
prolonged into the lateral
fissures, and in these are
accommodated the middle
cerebral arteries. Anteriorlv
FIG. 597. MEMBRANES OF THE SPINAL MEDULLA, AND THE MODE OF
ORIGIN OF THE SPINAL NERVES. tne mterpeduncular cistern
passes into a space in front
of the optic chiasma (cisterna chiasmatis), and from this it is continued into the
longitudinal fissure above the corpus callosum. In this subarachnoid passage the
anterior cerebral arteries are lodged.
The spinal part of the subarachnoid space is a very wide interval which is
partially subdivided into compartments by three incomplete septa. One of these
is a median partition called the septum posterius, which connects the pia mater
covering the posterior aspect of the spinal medulla with the arachnoid. In the upper
part of the cervical region the septum posterius is imperfect, and is represented
merely by some strands passing between the two membranes; in the inferior
part of the cervical region and in the thoracic region it becomes more com-
plete. The other two septa are formed by the ligamenta denticulata which spread
laterally one from each side of the spinal medulla. These will be described with
the pia mater.
Granulationes Arachnoideales. When the surface of the dura mater is i
inspected after the removal of the calvaria, a number of small fleshy -looking ;
excrescences, purplish-red in colour, are seen ranged in clusters on each side of the
superior sagittal sinus, and when this sinus is opened they are also observed protrud-
ing in considerable numbers into its interior. These are the arachnoideal granu-
lations (O.T. Pacchionian bodies), and they are found also, in smaller numbers and
distinctly smaller size, in connexion with other blood-sinuses, such as the transverse
sinus, the straight sinus, and the cavernous sinus. At first sight they appear to
belong to the dura mater, but in reality they are projections from the arachnoid, i
In the child they are exceedingly small and rudimentary, and it is only as life
advances that they become large and conspicuous.
Each granulation is a bulbous protrusion of the arachnoid. It is attached to
the arachnoid by a narrow pedicle, and into its interior there is prolonged, through ;j;
this pedicle, a continuation of the subarachnoid space and its characteristic mesh-
work. The granulations do not pierce the dura mater. As they push their way jf
into a blood-sinus they carry before them a thin covering continuous with the
THE PIA MATER 673
sinus wall. On each side of the superior sagittal sinus there is a number of
irregular spaces in the clura mater which communicate with the sinus either by
a small aperture or a narrow channel. These spaces are called the lacunas laterales,
and certain of the meningeal veins and some of the diploic veins open into them.
Granulations push themselves into the lateral lacunae from below in such a manner
that they receive a complete covering from the layer of dura mater which forms
the sinus floor. Nor does the bone escape. As the granulations enlarge they
cause absorption of the cranial wall, and small pits are hollowed out on its internal
surface for their reception. It must be clearly understood, however, that in such
cases the granulation is separated from the bone by the following : (1) A con-
tinuation round the granulation of the subdural space ; (2) the thinned floor of
the lateral lacuna ; (3) the lumen of the sinus ; and (4) the greatly thinned upper
wall of the sinus.
The granulations have a special function to perform. Through them fluid can
pass from the subarachnoid space into the venous sinuses with which they stand
in connexion. Wheaever the pressure of blood in the sinuses is lower than that
of the fluid in the subarachnoid space and the ventricles of the brain, the cerebro-
Granulationes araclmoideales Mouth of a vein
^--saigas Bone
FIG. 598. MEDIAN SECTION THROUGH THE CRANIAL VAULT IN THE FRONTAL REGION. ENLARGED.
Displays a portion of the superior sagittal sinus and the arachnoideal granulations protruding into it.
spinal fluid filtrates through the granulations into the blood-sinuses. This is not
the only way that subarachnoid fluid may obtain exit. The subarachnoid space
is carried outwards for a short distance on the nerves in connexion with their
arachnoideal sheaths, and communicates with the lymph channels of the nerves.
This connexion is more complete in the case of the olfactory, the optic, and
the acoustic nerves than in other nerves. A very free communication is said to
exist between the subarachnoid space and the lymph-vessels of the nasal mucous
membrane.
THE PIA MATER.
The pia mater forms the immediate investment of the brain and spinal
medulla. It is a delicate and very vascular membrane.
Pia Mater Encephali. The pia mater which covers the brain is finer and
more delicate than that which clothes the spinal medulla. It follows closely all
the inequalities on the surface of the brain, and in the case of the hemisphere
it dips into each sulcus in the form of a fold which lines it completely. On the
cerebellum the relation is not so intimate ; it is only into the larger fissures that it
penetrates in the form of folds.
The larger blood-vessels of the brain lie in the subarachnoid space. The finer
twigs ramify in the pia mater before they proceed into the substance of the brain.
As they enter they carry with them sheaths derived from the pia mater. When
a portion of the membrane is raised from the surface of the encephalon, numerous
fine processes are withdrawn from the cerebral surface. These are the blood-vessels
with their sheaths, and they give the deep surface of the pia mater a rough and
flocculent appearance.
As the pia mater is carried over the inferior part of the roof or posterior wall
the fourth ventricle of the brain it receives the name of the tela chorioidea
44
-
674
THE NEEVOUS SYSTEM.
Genu of corpus
callosum
Cavura septi pellucidi
Septum pellucidum
-Caudate nucleus
Fornix
Column of fornix
Vena terminalis
Thalamus
Chbripid tela of third
ventricle
Vena interna cerebri
ventriculi quarti, and it is in connexion with this portion of the pia mater that the
chorioid plexuses of that cavity are developed. The tela chorioidea ventriculi tertii
(O.T. velum interpositum) is a fold of pia mater which is invaginated into the brain,
so that it comes to lie over the third ventricle and to project, in the shape of chorioid
plexuses, into the lateral ventricles. This invagination requires special notice.
The tela chorioidea ventriculi tertii (O.T. velum interpositum) is a double layer
or fold of pia mater which intervenes between the body of the fornix, which lies
above it, and the epithelial roof of the third ventricle and the two thalami,
which lie below it. Between its two layers are blood-vessels, and some subarachnoid
-^r-^-. trabecular tissue. In shape the
chorioid tela of the third
ventricle is triangular, and the
narrow anterior end or apex
reaches forwards as far as the
interventricular foramina. The
base lies under the splenium of
the corpus callosum, and here
the two layers of the tela separate
and become continuous with the
investing pia mater on the sur-
face of the brain by passing out
through a cleft called the trans-
verse fissure.
Along each margin the tela
chorioidea of the third ventricle
chorioid plexus of is bordered by the chorioid
lateral ventricle plexus of the central part of
the lateral ventricle, which pro-
jects into the ventricular cavity
from under cover of the free
margin of the fornix. It
should be borne in mind that
the epithelial lining of the ven-
tricle gives a complete covering
to the chorioid plexus. Pos-
teriorly the chorioid plexus is
FIG. 599.-DISSECTION TO SHOW THE CHORIOID TELA OF THE cont inuous with the similar
THIRD VENTRICLE, AND THE PARTS IN IMMEDIATE RELA- ., . P . ,
TION TO IT. structure in the interior horn 01
the ventricle, whilst in front it
narrows greatly, and becomes continuous across the median plane with the corre-
sponding plexus of the opposite side, behind the epithelial layer which lines
the interventricular foramen. From this median junction two much smaller
chorioid plexuses run backwards on the under surface of the tela chorioidea,
and project downwards into the third ventricle. These are the chorioid plexuses
of the third ventricle.
The most conspicuous blood-vessels in the tela chorioidea are the two internal
cerebral veins, which run backwards, one on each side of the median plane. In
front, each is formed at the apex of the fold by the union of the vena terminalis
and a large vein issuing from the chorioid plexus ; behind, they unite to form
the vena cerebri magna [Galeni], and this pours its blood into the anterior end of
the straight sinus (Fig. 599, p. 674).
The continuous cleft in the brain through which the chorioid tela of the
third ventricle and the chorioid plexuses of the inferior horns of the two
lateral ventricles are introduced into the interior of the brain is sometimes
called the transverse fissure. It consists of a superior intermediate part and
two lateral parts. The former passes forwards between the corpus callosum and
the fornix above and the roof of the third ventricle and the thalami below.
It is limited on each side by the epithelial covering of the chorioid plexuses,
which shuts out these structures from the cavity of the lateral ventricles. The
Hippocampal
commissure
Crura of fornix
(under surface)
Body of fornix (thrown
backwards)
THE PIA MATEE.
675
lateral part is the chorioidal fissure. This is continuous with the intermediate
part, and has already been described in connexion with the inferior horn of the
lateral ventricle (p. 636).
Pia Mater Spinalis. The pia mater of the spinal medulla is thicker and
denser than that of the brain. This is largely due to the addition of an outside
fibrous layer, in which the fibres run chiefly in the longitudinal direction. The
pia mater is very firmly adherent to the surface of the spinal medulla, and in
front it sends a fold into the anterior-median fissure of the spinal medulla. The
posterior median septum is likewise firmly attached to its deep surface. In front
of the anterior-median fissure of the spinal medulla the pia mater is thickened in
the form of a longitudinal glistening band, termed the linea splendens, which runs
along the whole length of the spinal medulla, and blends with the filum terminale
below. The blood-vessels of the spinal medulla lie between the two layers of the
pia mater.
The nerves which leave both the brain and spinal medulla receive closely
Commissura hippocampi
Corpus callosum ~~
Nucleus caudatus
Gyrus cinguli Indusium Stria longitudinalis medialis
urn septi pellucidi
Septum pellucidum
, - Ventriculus lateralis
, Crus fornicis
Plexus chorioideus
lateralis
~-.~ Stria terminalis
- Attachment of lamina chorioidea
Tela chorioidea
;Q /\ P "^Thalamus (free surface)
Thalamus / \ Tsenia thalami
Plexus chorioideus vent, tertii Ventriculus tertius
G. 600. DIAGRAM OF A FRONTAL SECTION ACROSS THE CHORIOID TELA OP THE THIRD VENTRICLE.
lied sheaths from the pia mater. These blend with the connective- tissue sheaths
of the nerves.
The ligamentum denticulatum is a strong fibrous band which stretches out like
a wing from the pia mater on each side of the spinal medulla, so as to connect
the pia mater with the dura mater. The pial or medial attachment of the ligament
extends in a continuous line between the anterior and posterior nerve-roots, from
the level of the foramen magnum above to the level of the first lumbar vertebra
below. Its lateral margin is serrated or denticulated, and for the most part free.
From twenty to twenty-two denticulations may be recognised. They occur in the
intervals between the spinal nerves, and, pushing the arachnoid before them, they
are attached by their pointed ends to the inner surface of the dura mater. The
ligamenta denticulata partially subdivide the wide subarachnoid space in the
vertebral canal into an anterior and a posterior compartment. The anterior
nerve -roots traverse the anterior compartment, whilst the posterior nerve-
roots traverse the posterior compartment. Further, the posterior compartment
is imperfectly subdivided into a right and a left half by the septum posterius.
By means of the ligamenta denticulata the spinal medulla is suspended in the
iddle of the tube of dura mater.
THE PERIPHERAL NERVES AND THE SYMPATHETIC
SYSTEM.
By A. MELVILLE PATERSON, M.D., F.B.C.S.
Professor of Anatomy in the University of Liverpool.
THE nervous mechanism comprised under this title is responsible for the trans-
mission of peripheral impulses to the brain and spinal medulla, through afferent
nerves, and for the distribution of central impulses to peripheral structures through
efferent nerves. The peripheral nerves are at the outset divisible into two series :
Posterior root
Ligamentum denticulatum
Anterior root
Posterior root
Anterior root
Fila radicularia of anterior root
Ligamentum denticulatum
Arachnoid
_ Pia mater
Posterior root
Spinal ganglion
Posterior ramus
Posterior ramus
Anterior ramus
Anterior ramus
Anterior root
Spinal medulla
FIG. 601. SCHEME OF THE ARRANGEMENT OP THE MEMBRANES OF THE SPINAL MEDULLA AND
THE ROOTS OF THE SPINAL NERVES.
cerebral nerves, derived from or associated with the brain; and spinal nerves,
in relation to the spinal medulla. Associated with the cerebro-spinal nerves is the
sympathetic system. The animal body is naturally divided into two different
areas or regions, the somatic area, forming the body wall and the associated limbs,
innervated by the larger (somatic) parts of the spinal nerves ; and the splanchnic
677
678
THE NERVOUS SYSTEM.
area, comprising the chief viscera ; this area is governed by the sympathetic system,
subordinate to and controlled by its connexions with the splanchnic or visceral
branches of the spinal nerves.
The cerebral nerves are twelve in number (see note, p. 798), arranged in
pairs ; they present striking differences in origin, in distribution, and in functions.
Number.
Name.
Function.
Superficial Attachment
to Brain.
I.
Olfactory .
Smell
Olfactory bulb.
II.
Optic . . . Sight
Optic chiasma.
III.
Oculomotor . Motor to most of the muscles of Cerebral peduncle.
eyeball and orbit
IV.
Trochlear . . Motor to superior oblique muscle of
Anterior medullary
eyeball
velum.
V.
Trigeminal . . Sensory to face, tongue, and teeth ; Pons.
motor to muscles of mastication
VI.
Abducent .
Motor to lateral rectus muscle of
Junction of pons and
eyeball
medulla oblongata.
VII.
Facial . . . Motor to muscles of scalp and face, Lower border of pons.
sensory to tongue
VIII.
Acoustic . . Hearing" and equilibrium
Lower border of pons.
IX.
Glossopharyngeal Sensory to tongue and pharynx ;
Medulla oblongata.
motor to stylo-pharyngeus
X.
Vagus . . . Sensory to pharynx, oesophagus and
Medulla oblongata.
stomach, and respiratory organs
XL
Accessory .
(a) Accessory to vagus. Motor to
Medulla oblongata.
muscles of palate, pharynx, oeso-
phagus, stomach and intestines,
and respiratory organs ; inhibitory
for heart
(6) Spinal part : motor to trapezius
Spinal medulla.
and sterno-mastoid muscles
XII.
Hypoglossal
Motor to muscles of the tongue
Medulla oblongata.
The spinal nerves are usually thirty-one in number, also arranged in pairs.
Each nerve arises by two roots from the spinal medulla, one posterior and gangliated,
the other anterior and not gangliated. After each root has pierced separately the
dura mater, the two roots become enclosed in a common sheath, and unite to form
the spinal nerve in the intervertebral foramen ; emerging from this, the nerve is
distributed to the trunk and limbs in a manner to be described later.
The nerves are designated cervical, thoracic, lumbar, sacral, and coccygeal, in rela-
tion to the vertebrae between which they emerge from the vertebral canal. Each
nerve appears above the corresponding vertebra, in the cervical region, except the
eighth, and below the corresponding vertebra in all other regions. There are thus
eight cervical nerves (the last appearing between the seventh cervical and first
thoracic vertebrae) ; there are twelve thoracic, Jive lumbar, five sacral, and one
coccygeal nerve, all appearing below the corresponding vertebrae.
The thirty-first nerve is occasionally absent; and there are sometimes one or two
additional pairs of minute filaments below the thirty -first, which, however, do not
emerge from the vertebral canal. These are rudimentary caudal nerves.
The size of the spinal nerves varies. The largest are those which take part in the
formation of the great nerve -trunks of the limbs (lower cervical and first thoracic,
and lower lumbar and upper sacral nerves) ; and of these the nerves destined for the
lower limbs are the larger. The coccygeal nerve is the smallest of the spinal nerves;
tbe thoracic nerves (except the first) are more slender than the limb nerves ; and
the cervical nerves diminish in size from below upwards.
Systema Sympathicum. The sympathetic system consists of a pair of gangliated
trunks, connected, on the one hand, in. certain regions to the spinal nervous system by a
series of white rami communicantes splanchnic or visceral branches of the spinal nerves ;
and, on the other hand, distributing branches (a) to the spinal nerves (gray rami com-
municantes), and (b) to the viscera and vessels occupying the splanchnic area. The
DEVELOPMENT OF THE SPINAL NEEVES.
679
splanchnic system serves to) collect and transmit to the spinal medulla impulses from the
viscera, and to distribute efferent fibres to vessels in the splanchnic area, and to glands
and involuntary muscle-fibres.
DEVELOPMENT OF THE PERIPHEKAL NERVES AND
SYMPATHETIC SYSTEM.
DEVELOPMENT OF THE SPINAL NERVES.
I. Origin of the Spinal Nerve Roots. The process of development of the spinal
nerves commences by means of the outgrowth of posterior and anterior roots from the
medullary tube. The two roots take origin in pairs in quite different ways.
FIG. 602. DEVELOPMENT OF THE SPINAL NERVES.
A, Formation of nerve roots.
D.R, Posterior root.
V.R, Anterior root.
N.T, Neural tube.
No, Notochord.
C, Formation of nerves.
So, Somatic division.
Vi, Visceral branch.
P, Posterior ramus.
Al.C, Alimentary canal.
Ao, Aorta.
V, Cardinal vein.
M.P, Muscle plate.
D, E, Formation of subordinate
branches.
Lat, Lateral, and
Ant, Anterior, branches.
B, Formation of nerve trunk (N).
D.G, Spinal ganglion.
Sy, Sympathetic trunk.
W.D, Wolffian duct.
Co, Coelom.
Formation of nerve trunks in relation
to the limb : dorsal and ventral
trunks corresponding to lateral and
anterior trunks in D and E.
The posterior root is the first to appear, before, during, or after the union of the
medullary plates and the formation of the neural tube.
It takes origin as a ganglionic crest, forming a continuous lateral unsegmented
band, on the dorsal surface of the medullary tube. It may arise in one of three ways :
(1) from the junction of the medullary plate and surface epiblast, before the closure of
the medullary groove ; (2) from a neural crest, a median ridge on the dorsum of the
completed tube ; or (3) as a direct outgrowth from the dorsal surface of the medullary
tube. The ganglionic crest becomes completely separated from the medullary tube, and
secondarily its cells (neuroblasts) rapidly become spindle-shaped, and by the end of the
fourth week give rise to two sets of processes : (1) a central series, which grow centrally
44 I
680 THE NEKVOUS SYSTEM.
and are secondarily connected with the dorso-lateral aspect of the medullary tube as the
fibres of the posterior root ; and (2) a peripheral series, which constitute "the posterior
root-fibres of the spinal nerve and join the anterior root, to form the spinal nerve proper.
It is only after the appearance of these nerve-fibres that the ganglionic crest becomes
notched along its peripheral border, and it is gradually divided up to form the individual
segmental spinal ganglia.
The anterior root of a spinal nerve arises in quite a different way, from cells (neuro-
blasts) in the substance of the medullary tube. In the account of the development of the
spinal medulla it has been shown how the cellular constituents of the medullary tube
are converted into two classes of cells : (1) spongioblasts, which produce the matrix
(neuroglia) of the spinal medulla; and (2) neuroblasts, which produce the nerve-cells
of the gray matter of the spinal medulla. The neuroblasts give rise to the axis-
cylinder processes or axons, which, penetrating the spongy tissue of the medullary tube
and the outer limiting membrane, find their way into the mesodermic tissue on the
ventro-lateral surface of the tube. Fibrillar from their earliest origin and derived from
nerve-cells which remain within the medullary tube, the axons of the anterior root become
surrounded by mesodermic cells immediately on their emergence, which give rise to the
sheaths of the nerve. The anterior root is a little later in its date of appearance than
the posterior root. It begins to be evident at the twenty-fourth day and is completely
formed by the twenty-eighth day.
II. Formation of the Spinal Nerve. The fibres of the posterior root ganglion and
the anterior root grow by extension from the cells with which they are respectively con-
nected, and meet in the space between the myotome and the side of the medullary tube
to form the spinal nerve. In the adult there is a fundamental division of the spinal
nerve into posterior and anterior rami. In the process of development this separation is
even more obvious. As the fibres of the posterior and anterior roots approximate, they
separate at the same time each into two unequal portions : the smaller parts of the
two roots unite together to form the posterior ramus, and the larger parts unite to form
the anterior ramus of the spinal nerve.
The posterior ramus, curving laterally and dorsally, passes through the myotome
and is connected with it. In the substance of the myotome it separates into branches
as it proceeds towards the dorsal wall of the embryo. At a later stage, the branches
are definitely arranged into a lateral and a medial series.
The anterior ramus grows gradually in a ventral direction to reach the somato-
splanchnopleuric angle, under cover of the growing myotome. It spreads out at its
distal end and eventually separates into two portions : a smaller, splanchnic, or visceral ;
and a larger, somatic, or parietal portion. (1) The smaller, splanchnic, or visceral portion
grows inwards, dorsal to the Wolman ridge, to be connected through the sympathetic trunk
with the innervation of organs in the splanchnic area. This branch of the spinal nerve
becomes the white ramus communicans of the sympathetic. It is not present in the case
of all the spinal nerves, but only in relation to the thoracic and upper lumbar and the
third and second or fourth sacral nerves. It will be referred to again in connexion with
the sympathetic system. (2) The larger, somatic, or parietal portion becomes the
main part of the anterior ramus of the nerve. It continues the original ventral
course of the nerve, and, reaching the body wall, subdivides into two terminal branches
a lateral branch, which grows laterally and downwards and reaches the lateral aspect
of the trunk, after piercing the myotome ; and a ventral or anterior branch, which grows
onwards in the body wall to reach the ventral axis. This arrangement is met with in
the trunk between the limbs and in the neck.
III. Formation of Limb-plexuses. The method of growth of the spinal nerves,
just described, is modified in the regions where the limbs are developed. In relation to
the limbs, which exist in the form of buds of undifferentiated cellular mesoblast before
the spinal nerves have any connexion with them, the development of the anterior ramus
of the nerve proceeds exactly in the way described, up to the point of formation of
somatic and splanchnic branches. The somatic branches then stream out into the
limb bud, passing into it below the ends of the myotomes and spreading out into a
bundle of fibres at the basal attachment of the limb. Later, the nerves separate, each
into a pair of definite trunks, which are named posterior or dorsal and anterior or ventral,
and which, dividing round a central core of mesoderm, proceed to the dorsal and ventral
surfaces respectively of the limb bud. While this process is going on, a secondary wiion
takes place between parts of adjacent dorsal and ventral trunks. Dorsal trunks unite
with dorsal trunks, ventral trunks unite with ventral trunks, to form the nerves distri-
buted ultimately to the surfaces and periphery of the limb. These dorsal and ventral
DEVELOPMENT OF THE SYMPATHETIC SYSTEM.
681
trunks are homologous with the lateral and ventral branches of the somatic nerves in
other regions.
DEVELOPMENT OF THE SYMPATHETIC SYSTEM.
There are two conflicting views of the mode of development of the sympathetic
system.
In birds and mammals the first rudiment of the sympathetic trunk occurs in the
formation of a longitudinal unsegmented column of mesodermic cells (which stain more
deeply than the mesoderm in which they lie) on each side of the aorta, and coterminous
with it. This column of cells becomes joined at an early stage by the visceral branches
of the spinal nerves which grow inwards from the main nerve trunks into the splanchnic area,
and result from the division of the nerve into
somatic and visceral parts. These visceral
branches constitute the white rami communi-
cantes. They receive contributions usually from
both posterior and anterior roots, and gradually
approaching the above-mentioned column of
mesodermic cells, they become intimately associ-
ated with the cells. In some cases fibres of the
visceral nerves pass over the cellular column
into the splanchnic area without connexion with
it (Fig. 603). By the junction of these visceral
nerves with the cells of the column, certain
cells persist and produce the ganglia. The in-
tervening portions of the column, by changes in
the cells, and by the addition of fibres belonging
to the visceral nerves, give rise to the con-
necting cords. The cellular column, besides
producing the gangliated trunk, by the further
growth of its cells and their extension centrally
and peripherally, produces the gray rami com-
municantes, parts of the peripheral branches,
and the peripheral (collateral and terminal)
ganglia, as well as the medullary portion of the
suprarenal gland. The cervical, lower lumbar,
and sacral portions of the sympathetic gangliated
trunk are secondary extensions from the primitive
trunk, gradually growing upwards and downwards
along the main vessels. These portions of the
system are not provided with white rami com-
municantes. The ganglia of the sympathetic
assume their segmented appearance (1) from the
persistence of the primitive cells and their con-
nexion with the spinal nerves by means of the
white and gray rami communicantes, and (2)
from the way in which the primitive column is Sy, Sympathetic trunk ; Spl, Splanchnic branchy
, , , , J , , . of spinal nerves (white rami communi-
moulded by the surrounding structures (bones, cantes) ; V.S, Vertebral segments; D.G,
segmental arteries, etc.). Spinal ganglia.
In another account of the development of
the sympathetic system (Onodi), the gangliated trunk is described as an outgrowth of
the thoracic spinal ganglia of the spinal nerves. It is said that each ganglion gives off
a bud at its inferior end, which, growing inwards into the splanchnic area, becomes
attached to the trunk of the spinal nerve just beyond the union of the posterior and
anterior roots. The bud still extending inwards into the splanchnic area, remains
associated with the nerve by an attenuated stalk. These buds, it is said, become the
ganglia, which, after reaching their permanent place in the splanchnic area, are sup-
posed to grow upwards and downwards so as to coalesce and form a beaded chain of
ganglia. The stalks connecting the ganglia with the spinal nerves become the white
rami communicantes. This mode of development does not satisfactorily account for
several important features of the sympathetic system the development of those parts
of the gangliated trunk which possess no white rami, the absence of a truly segmental
character in the trunk, and the constancy of its continuity. No instance is recorded
FIG. 603. THE DEVELOPMENT OF THE
SYMPATHETIC GANGLIATED TRUNK.
682 THE NERVOUS SYSTEM.
of a hiatus between two ganglia. It is, on the other hand, an attractive view, as it
ascribes to one germinal layer (ectoderm) the formation of all the elements of the nervous
system, and it brings the sympathetic ganglia into serial homology with the isolated
ganglia ciliary, spheno-palatine, and otic associated with the trunks of the trigeminal
cerebral nerve.
THE DEVELOPMENT OF THE CEREBRAL NERVES.
The cerebral nerves are divisible morphologically into three series : (1) those
associated with sense organs the first or olfactory, second or optic, and eighth or
acoustic; (2) those connected with the embryonic branchial arches the fifth
or trigeminal, seventh or facial, ninth, tenth, and eleventh, glossopharyngeal,
vagus, and accessory ; and (3) motor nerves distributed to muscles derived from
cephalic myotomes the third or oculomotor, fourth or trochlear, sixth or abducent,
and twelfth or hypoglossal.
Omitting the olfactory and optic nerves, which are special vesicular outgrowths
of the brain itself, it is possible to trace a distinct homology in the process of
development of the other cerebral and the spinal nerves. In the primitive brain the
gray matter is arranged into Alar and Basal Laminas (His), comparable to the
postero-lateral and anterior areas of gray matter (columns) of the spinal medulla.
Further, the basal lamina may be split up into lateral and medial areas.
The origin of the third, fourth, sixth, and twelfth cerebral nerves all motor
efferent nerves is from the medial part of the basal lamina of the primitive brain,
in serial homology with the anterior efferent roots of the spinal nerves.
The efferent motor roots of the fifth, seventh, ninth, tenth, and eleventh nerves
arise from the lateral part of the basal lamina, and so may be differentiated from
the preceding series.
The afferent sensory roots of the fifth, seventh (nervus intermedius), eighth,
ninth, and tenth nerves are homologous with the posterior roots of the spinal nerves.
They are all gangliated, and are connected with the alar lamina of the brain.
I. The olfactory nerves are associated in their development with the formation of
the olfactory pit and the olfactory bulb.
The olfactory pits appear on each side of the front of the head at a little later period
than the formation of the lens and the auditory vesicle. They become converted into the
nasal cavities by the formation of the pre-oral visceral clefts and arches, fronto-nasal
and ethmo-vomerine in the median plane, and lateral ethmoid and maxillary processes at
the sides (p. 49).
The Rhinencephalon or olfactory bulb is a hollow outgrowth from each telencephalon
or cerebral hemisphere, and appears in the first month. It grows forwards into relation
with the deep surface of the nasal pit. In many animals (as in the horse) the olfactory
bulb remains hollow ; but in the human subject it loses its lumen and becomes a solid
bulb (olfactory bulb) connected to the brain by a narrow stalk, the olfactory tract.
The epithelium of the olfactory pit is responsible for the formation of the olfactory nerves.
There are two views as to the mode of their development from the epithelial cells. Both
views admit the proliferation of the epithelium of the nasal pit so as to produce neuroblasts.
According to the one view these neuroblasts detach themselves from the epithelial surface,
and constitute an olfactory ganglion which becomes applied to and incorporated with the
olfactory bulb. The cells of the ganglion become bi-polar, and the peripheral axons
constitute the olfactory nerves, while the central axons (in the second month) proceed back-
wards to the brain along the olfactory tract. According to the other view (based on Disse's
investigations), the proliferating cells of the nasal epithelium remain in the wall of the
nasal pit, and become the olfactory cells of the nasal cavity, with peripheral processes
projecting to the surface of the epithelium. Their central axons become the olfactory
nerve fibres which end in the olfactory bulb, forming dendrites associated with the dendritic
processes of the nerve-cells of the bulb. The central axons of these latter cells develop
into the fibres of the olfactory tract (see p. 622).
II. The optic nerve is developed wholly from the brain. Its formation begins with
the outgrowth of the optic vesicle, a paired hollow outgrowth from the ventral surface of
the diencephalon. The ectodermic invagination of the lens, growing inwards from the
surface of the head, causes the collapse of the vesicle and its conversion into the optic
THE DEVELOPMENT OF THE CEEEBEAL NEEVES. 683
cup, the narrow tube connecting the vesicle to the brain becoming the optic stalk. This
stalk becomes solid, and forms the basis of the optic tract, optic chiasma, and optic
nerve. The optic cup, bilaminar in form, and by its edge clasping the lens, is imbedded
in mesodermic tissue, which gives rise to the envelopes of the eyeball, etc. The outer
layer of the optic cup produces the layer of hexagonal pigment cells of the retina. The
cells of the inner layer produce the tissues of the retina proper. They form neuroblasts
with peripheral and central processes. The peripheral processes are converted into retinal
nerve tissues ; the central processes extend backwards along the optic stalk, and give rise
to the optic nerve, optic chiasma, and optic tract. Spongioblasts in the inner lamina
of the optic cup produce the sustentacular tissue of the retina (Mtiller's fibres). The
mesodermic tissue surrounding the optic cup and lens gives rise to the rest of the structure
of tlie eyeball, the formation of which is described in the section which deals with the
organs of sense.
III. The oculomotor nerve arises, like the ventral root of a spinal nerve, from a
group of neuroblasts in the medial part of the basal lamina of the mid -brain. The
peripheral fibres extend forwards, to end around the optic cup in the mesodermic tissue,
from which the eye muscles are derived. Numerous cells are carried along with the cell
processes in their course, and these have been described as being concerned in the
formation of the ciliary ganglion.
IV. The trochlear nerve also arises from a group of neuroblasts occupying the
medial part of the basal lamina of the mid-brain, close to its junction with the hind-brain.
The peripheral processes do not emerge directly from the brain, but extend dorsally from
their origin along the side of the brain to its dorsal aspect, where they appear, after
decussating with the fibres of the opposite nerve, just behind the quadrigeminal lamina.
V. The trigeminal nerve is developed by means of a large posterior and a small
anterior root. Their origin to a large extent resembles the mode of formation of the
roots of a spinal nerve.
The large posterior (afferent) root is formed by means of a cellular bud from the alar
lamina of the hind -brain. This bud separates from the brain, and forms the semi-
lunar ganglion. Its cells becoming bipolar, like the cells of a spinal ganglion, are
secondarily connected with the brain by means of their central processes; while the
peripheral processes, separating into three groups, proceed along the fronto-nasal and
maxillary processes, and along' the mandibular arch, to form the three main divisions of
the nerve. Numerous cells accompany each main division in its course from the ganglion,
and form eventually the subordinate ganglia the ciliary on the ophthalmic nerve, the'
spheno-palatine on the maxillary nerve, and the otic ganglion on the mandibular nerve.
The small anterior (efferent) root of the trigeminal nerve, like the motor anterior root
of a spinal nerve, is later in its appearance than the sensory root. It arises as the peri-
pheral fibres of a group of neuroblasts occupying the lateral part of the basal lamina of
the hind-brain, which proceed directly to the surface to join the mandibular division of
the nerve.
VI. The abducens nerve resembles in its mode of development the oculomotor
and trochlear nerves with which in its origin it is in series. It is formed by the peripheral
processes of a group of neuroblasts in the medial part of the basal lamina in the upper
part of the hind-brain. These processes pierce the part of the brain in which, at a later
stage, the fibres of the pyramid are developed. They then proceed to the mesodermic
tissue round the optic cup, which is destined to form the eye muscles.
VII. The facial nerve has developmen tally a double origin. (1) In connexion with
the formation of the acoustic nerve a group of cells becomes separated from the alar
lamina of the hind-brain opposite the auditory vesicle. This group becomes separated
into three parts, of which the middle portion is the rudiment of the genicular ganglion
which becomes incorporated with the efferent part of the facial nerve, and is connected to
the brain by a slender root, known as the nervus intermedius (O.T. pars intermedia).
(2) The efferent root of the nerve arises from a group of neuroblasts in the lateral part
of the basal lamina of the hind-brain, in series with efferent fibres of the vago-glosso-
pharyngeal nerves ; after a tortuous course within the brain its fibres emerge beneath
the above-mentioned cellular mass, opposite the auditory vesicle. They are joined by the
ganglionic root, and in their course round the auditory vesicle become imbedded in the
auditory capsule (canalis facialis). The chorda tympani nerve appears early as a branch
of the facial nerve. It is probable that the nervus intermedius, the genicular ganglion,
and the chorda tympani nerve together represent the posterior afferent element in
the constitution of this nerve.
VIII. The acoustic nerve arises as a cellular bud from the alar lamina of the hind-
684
THE NEKVOUS SYSTEM.
brain, dorsal to the efferent portion of the facial nerve, opposite to the auditory vesicle,
and in close association with it.
Becoming separated from the brain, the cellular mass separates into three portions, of
which the intermediate part is associated with the facial nerve and intermediate nerve (as
the genicular ganglion), while the medial and lateral parts are converted into the medial
(vestibular) and lateral (cochlear) ganglia and the roots of the acoustic nerve. The cells
becoming bipolar, their central processes are secondarily connected with the brain on
the dorsal (lateral) aspect of the facial nerve ; the peripheral processes proceed to the
auditory vesicle, to which they are distributed as the vestibular and cochlear nerves.
Numerous cells are carried along with the nerve trunks into relation with the auditory
capsule, and constitute the vestibular and cochlear ganglia.
IX. and X. The glossopharyngeal and vagus nerves are developed from 'the
side of the hind-brain, both in the same way, and each by two roots. A collection of
cells separates itself from the alar lamina of the hind-brain behind the auditory vesicle to
form the ganglionic afferent root. The ganglion of the vagus is much larger than that
of the glossopharyngeal. Each ganglion becomes divided into two parts, a proximal and a
distal portion, connected together by a commissural band of fibres. The proximal ganglion
(superior ganglion of the glossopharyngeal ; j ugular ganglion of the vagus) is secondarily
connected by centripetal fibres to the hind-brain. From the distal ganglion (petrous
LATERAL AREA
MEDIAL AREA
(BASAL
LAMINA
f ANTERIOR ROOT
POSTERIOR ROOT
. IX.X.XI. _.
A JD
FIG. 604. COMPARISON OF ORIGINS OF NERVE ROOTS FROM SPINAL MEDULLA AND HIND-BRAIN (after His).
A. Spinal medulla ; B. Hind-brain.
ganglion of the glossopharyngeal ; ganglion nodosum of the vagus) peripheral fibres
grow outwards to form the nerve trunk.
Each nerve is also provided with a small efferent root, consisting of nerve fibres,
arising from a collection of neuroblasts in the lateral part of the basal lamina of the hind-
brain, and emerging beneath the ganglionic root at the junction of the alar and basal
laminae (in series with the fibres of the efferent root of the facial nerve above and of the
accessory nerve below).
XL The accessory nerve arises in two parts one medullary, the other spinal.
The medullary (accessory) portion develops as the processes of a series of neuroblasts in
the lateral portion of the basal lamina of the hind-brain, which emerge in series with the
efferent roots of the glossopharyngeal and vagus nerves. The spinal portion arises
as the processes of a group of neuroblasts in the anterior part of the medullary tube
(anterior column), which, turning outwards, emerge as a series of roots on the lateral aspect
of the spinal medulla.
XII. The hypoglossal nerve is developed, not in series with the nerves above
mentioned, but like the third, fourth, and sixth nerves, from the medial part of the basal
lamina of the hind-brain, in the space between the glossopharyngeal and other nerves
above, and the first cervical nerve below. It is formed as a series of peripheral processes
from a collection of neuroblasts occupying the hind -brain. Froriep's ganglion is a
transitory collection of nerve cells developed from the alar lamina of the hind-brain on
the dorsal aspect of the nerve, and represents in a rudimentary condition its posterior
ganglionic root. The ganglion gives off no branches and soon disappears.
THE SPINAL NEKVES.
685
DESCRIPTION OF THE PERIPHEEAL NEKVES AND
SYMPATHETIC SYSTEM.
I. THE SPINAL NERVES.
Origin of the Spinal Nerves. Each spinal nerve is attached to the
medulla by two roots, called respectively posterior
(dorsal, afferent) and anterior (ventral, efferent).
The posterior root is larger than the anterior
root ; it contains a larger number of radicular fibres,
and the individual fibres are of larger size than in
the anterior root. It has a vertical linear attach-
ment to the postero- lateral sulcus of the spinal
medulla. The fibres of contiguous posterior roots are
in close relation, and, in some instances, overlap.
The posterior root separates, as it passes away from
the spinal medulla, into two bundles, both of which
become connected with the proximal end of a spinal
ganglion. From the distal end of this ganglion the
posterior root proceeds to its junction with the
anterior root in the intervertebral foramen.
The spinal ganglia are found on the posterior
roots of all the spinal nerves. (In the case of the
first cervical or sub-occipital nerve, the spinal ganglion
may be rudimentary or absent ; and the posterior root
itself may be wanting, or derived from the accessory
nerve.) They occupy the intervertebral foramina,
except in the case of the sacral and coccygeal nerves,
the ganglia of which lie within the vertebral canal ;
and the first and second cervical nerves, the ganglia
of which lie upon the vertebral arches of the atlas
and epistropheus respectively. With the exception
of the coccygeal ganglia they are outside the cavity
of the dura mater, but are invested by the mem-
brane. The ganglia are of ovoid form, bifurcated in
some cases at their proximal ends. They consist of
unipolar nerve-cells, whose axons, after a very short
course, divide into central (root) and peripheral
(trunk) fibres. The central fibres form the portion
of the root entering the spinal medulla ; the peri-
pheral fibres are continued in a lateral direction
from the ganglion into the spinal nerve.
Ganglia Aberrantia (aberrant spinal ganglia). Between
spinal
the spinal ganglion and the spinal medulla small collections
of cells are occasionally found on the posterior roots, either as
scattered cells or distinct ganglia. They are most frequently
met with on the posterior roots of the lumbar and sacral
nerves.
The anterior root is smaller than the posterior
root. It arises from the anterior surface of the spinal
medulla (anterior root zone} by means of scattered
bundles of nerve-fibres, which occupy a greater hori-
zontal area and are more irregular in their arrange-
ment than the radicular fibres of the posterior root.
It possesses no ganglion in its course. The rootlets
sometimes overlap, and are not infrequently con-
nected with neighbouring radicular fibres above and
below.
The dorsal and ventral roots, from their attachment to the spinal medulla, proceed
Co
FIG. 605. DIAGRAMMATIC REPRE-
SENTATION OF THE ORIGIN OF THE
SPINAL NERVES, showing the posi-
tion of their roots and ganglia re-
spectively in relation to the vertebral
column. The nerves are shown as
thick black lines on the left side.
686
THE NERVOUS SYSTEM.
laterally in the vertebral canal towards the intervertebral foramina, where they
unite to form the spinal nerve. The direction of the roots of the first two nerves
is upwards and laterally ; the roots of the remaining nerves course obliquely
downwards and laterally, the obliquity gradually increasing until, in the case of
the lower lumbar, the sacral and coccygeal nerve-roots, their course is vertically
downwards in the vertebral canal. The collection of nerve -roots which occupies
the lower part of the canal, below the first lumbar vertebra, and comprises all the
nerve-roots below those of the first lumbar nerve, is designated the cauda equina.
They arise from the lumbar enlargement and conns medullaris, and surround the
tilum terminale of the spinal medulla.
Within the vertebral canal the nerve-roots are in relation with the meninges of
the spinal medulla, and are separated from one another by the ligamentum denticu-
latum, and, in the neck, by the spinal part of the accessory nerve. Each receives a
covering of pia mater, continuous with the neurilemma; the arachnoid invests
Posterior column of spinal medulla
Posterior nerve-root
Anterior nerve-root |
Anterior column of spinal medulln
Spinal ganglio
Posterior ramus (medial branch >
Posterior rani
Posterior ramus (lateral branch;
Recurrent meniiigeal branch (uniting with a sympathetic branch
Gray ramus cominunicans
Splanchnic branch (white ramus
cominunicans)
Anterior raiuu
Lateral branch (posterior
subdivision)
Lateral branch
Anterior branch
Lateral branch (anterior^*
subdivision) ~"1
Gangliated sympathetic trunk
Efferent (vaso-motor) branch
Aorta
Cardinal vein
Afferent viscero-iuhibitory
branch
FIG. 606. THE ORIGIN AND DISTRIBUTION OF A TYPICAL SPINAL NERVE.
each root as far as the point where it meets with the dura mater ; and each root
pierces the dura mater separately. The two roots are thereafter enclosed in a
single tubular sheath of dura mater, in which is included the spinal ganglion of
the posterior root. The spinal nerve thus ensheathed occupies the intervertebral
foramen (except the first two cervical and the sacral and coccygeal nerves).
Divisions of a Spinal Nerve. After emerging from the intervertebral foramen
the nerve immediately divides into two primary divisions, named respectively
the posterior and anterior rami (O.T. posterior and anterior primary divisions). Just
before its division each nerve gives off a minute rneningeal (recurrent) branch,
which re-enters the vertebral canal after effecting a junction with a branch from
the sympathetic trunk, and is distributed to the spinal medulla and its membranes.
The posterior and anterior rami of the spinal nerves are mainly somatic in their
distribution, and are responsible for the innervation of the skeletal muscles and
of the skin covering the trunk and limbs.
POSTERIOR EAMI OF THE SPINAL NERVES. 687
The posterior and anterior rami of the nerves contain fibres from both posterior
and anterior roots. Indeed, each root can be seen, on removal of its sheath, to
divide into two portions, of which one portion enters into the formation of the
posterior ramns, the other into the formation of the anterior ramus. The posterior
rami, with the exception of the first two, are smaller than the anterior rami. They
are responsible for the innervation of the skin and axial muscles of the back. They
do not supply the muscles of the limbs, although in their cutaneous; distribution
they are prolonged on to the back of the head, the shoulder, and the buttock.
They form two small plexuses the posterior cervical and the posterior sacral
plexuses. The anterior rami are, with the exception of the first two cervical
nerves, much larger than the posterior rami. They supply the sides and anterior
parts of the body, the limbs, and the perineum. For the most part they have a
complicated arrangement. The thoracic or intercostal nerves alone have a simple
mode of distribution; the other nerves give rise to the three great plexuses
cervical, brachial, and lumbo-sacral.
White Rami Communicantes. From the anterior rami of certain nerves
(second thoracic to second lumbar inclusive) a series of fine nerves arises,
which serves to connect the spinal with the sympathetic system. These visceral
or splanchnic branches, or white rami communicantes, through the medium of the
gangliated trunk of the sympathetic, serve to innervate the vessels and viscera in
the splanchnic area. A second stream of pelvic splanchnic nerves, associated with
the second and third, or third and fourth sacral nerves, connects these spinal
nerves with the pelvic sympathetic plexuses (p. 766).
Distribution of the Spinal Nerves. Although the distribution, like the origin
of the spinal nerves, presents primarily and essentially a segmental arrangement, this is
masked, and in some instances obliterated, by developmental changes in the parts supplied.
In no region can an isolated nerve be traced to a complete segment. The nearest
approach to a complete girdle of innervation is found in the thoracic region, in such a
nerve as the sixth thoracic nerve. Yet even such a nerve is not distributed to any part
entirely alone. In its cutaneous distribution it supplies a complete belt of skin, a
distinctly segmental area from the median plane posteriorly to the median plane
anteriorly; yet at the same time the adjacent nerves overstep, so to speak, the
boundaries of the area and assist in the cutaneous nerve supply. Its muscular distribu-
tion, also, is segmental ; the anterior ramus supplies the intercostal muscles of the space
in which it lies ; but in this it forms communications with adjacent nerves. The posterior
ramus supplies axial muscles of the back, not, however, in an obviously segmental
manner, on account of the fusion of the segmental myotomes in the formation of complex
longitudinal muscles, which are together supplied by the series of muscular branches
derived from the posterior rami of contiguous nerves. In other regions still greater
changes of structure are accompanied by deviations from a segmental type of distribu-
tion, causing the foundation of the nerve-plexuses by which the trunk and limbs are
innervated.
POSTERIOE RAMI OF THE SPINAL NERVES.
The posterior rami (O.T. posterior primary divisions) of the spinal nerves
innervate both skin and muscles ; the skin of the trunk posteriorly, the back of
the head, the shoulder and the buttock, and the longitudinal muscles of the back,
but not the muscles of the limbs.
Each posterior ramus divides as a rule anto two parts, a medial and a lateral
trunk (Fig. 606, p. 686). In the upper half of the body the medial trunks
generally supply .the cutaneous branches, while the lateral trunks are purely
muscular nerves. In the lower part of the body the opposite is the case: the
lateral trunks provide the cutaneous nerves and the medial trunks are distributed
entirely to muscles. The cutaneous branches have a different course in the two
cases. In the upper half of the back they course backwards beneath and among
the muscles to within a short distance of the spinous processes of the vertebrae, close
to which they become superficial. They then extend laterally in the superficial
fascia. In the lower half of the back the cutaneous nerves are directed downwards
688
THE NEEVOUS SYSTEM.
and laterally among the muscles, and become superficial at a greater distance from
the median plane. In both regions the nerves pursue a sinuous course to the
surface, and the lower series emerge and
become superficial a considerable distance
below the level of their spinal origin.
There are considerable individual differ-
ences in the origin, course, and distribu-
tion of the several nerves.
CERVICAL NERVES.
First Cervical Nerve (N. sub-occip-
italis). It has already been pointed out
that the posterior root of this nerve may
be very small,
or even absent
altogether. Its
posterior ramus
is larger than
the anterior
ramus ; it does
not divide into
medial or lat-
eral branches,
and it does not
directly supply
any cutaneous
branch.
Passing
backwards, in
the space be-
tween the oc-
cipital bone and
the posterior
arch of the atlas,
the nerve occu-
pies the sub-oc-
cipital triangle,
and is placed
below and be-
hind the ver-
tebral artery,
and under cover
of the semi-
spinalis capitis
muscle. It sup-
plies the follow-
ing branches:
(a) Muscular
branches to the
semispinalis
FIG. 607. THE DISTRIBUTION OP CUTANEOUS NERVES ON THE BACK OF THE TRUNK.
On one side the distribution of the several nerves is represented, the letters indicating their nomenclature.
G.O (C.2), Greater occipital ; C.3, Third occipital ; T.I et seq., Posterior rami of thoracic nerves ; L.I et seq.,
Posterior rami of first three lumbar nerves ; S.I et seq., Posterior rami of sacral nerves ; Acr, Posterior
supra-clavicular branches from cervical plexus ; T.2-12, Lateral branches of thoracic nerves ; Circ.
Cutaneous branches of axillary nerve ; L.I, Iliac or lateral cutaneous branch of ilio-hypogastric nerve
E.C, Lateral cutaneous nerve of thigh ; S.Sc, Posterior cutaneous nerve of thigh.
On the other side a schematic representation is given of the areas supplied by the above nerves, the numeral
indicating the spinal origin of the branches of distribution to each area.
CEEVICAL NEKVES.
689
capitis (O.T. complexus), rectus capitis posterior major and minor, and obliqui
capitis, superior and inferior.
(&) A communicating branch descends to join the second cervical nerve.
The communicating branch may arise in common with the nerve to^the obliquus inferior,
and reach the second cervical nerve by piercing or passing superficial or deep to that muscle ;
or it may accompany the nerve to the semispinalis capitis and communicate with the greater
occipital nerve, under or over that muscle.
Second Cervical Nerve. The posterior ramus of this nerve is larger than
the corresponding anterior ramus. It passes backwards between the atlas and
epistropheus, and in the interval between the obliquus inferior and the semispinalis
cervicis muscles, under cover of the semispinalis capitis muscle. In this situa-
Insertion of sternp-.
mastoid
Splenius capiti
Longissimus capitis
Semispinalis capitis
OCCIPITAL NERV
Splenius capit
Longissimus capitis<
-Attachment of trapezius
Insertion of semispinalis capitis
REATER OCCIPITAL NERVE
Obliquus superior
Rectus capitis posterior major
Rectus capitis posterior minor
Vertebral artery
* POSTERIOR RAMUS OF
SUBOCCIPITAL NERVE
Posterior arch of atlas
POSTERIOR RAMUS OF SECOND CERVICAL
NERVE
POSTERIOR RAMUS OF THIRD CERVICAL
NERVE
Profunda cervicis artery
POSTERIOR RAMUS OF FOURTH CERVICAL
NERVE
Semispinalis cervicis
FIG. 608. POSTERIOR CERVICAL PLEXUS.
tion the nerve gives off several small muscular and communicating branches.
The main trunk, after piercing the semispinalis capitis and trapezius muscles,
accompanies the occipital artery to the scalp as the greater occipital nerve. This
is the chief cutaneous nerve for the posterior part of the scalp. It enters the
superficial fascia at the level of the superior nuchal line of the occipital bone and
about an inch from the external occipital protuberance. Bamifying over the
surface, it supplies the skin of the scalp as far as the vertex. It communicates on
the scalp with the following nerves : great auricular, lesser occipital, posterior
auricular, and third occipital.
The muscular branches of the second cervical nerve are destined for the semi-
spinalis capitis, obliquus inferior, semispinalis cervicis, and multifidus.
Its communicating branches form the posterior cervical plexus. Descending over
the posterior arch of the atlas is a branch from the sub-occipital nerve which forms a loop
or network with a branch of the second nerve. From this loop twigs are supplied to the
surrounding muscles. A similar loop is formed by a communication between branches
of the second and third nerves, from which muscles are also supplied. Occasionally an
additional loop is formed between branches of the third and fourth nerves.
45
690 THE NERVOUS SYSTEM.
Third Cervical Nerve. This is much smaller than the second nerve. Near
its origin it forms a loop of communication with the second, and it may give off
a similar communicating branch to the fourth nerve. The main trunk divides
into medial cutaneous and lateral muscular branches. The lateral muscular
branch enters contiguous muscles ; the medial cutaneous branch passes backwards
and medially, and becomes superficial as the third occipital nerve (O.T. n. occipitalis
minimus), close to the median plane of the neck. It supplies fine branches to
the neck and scalp, and communicates with the greater occipital nerve.
The fourth, fifth, and sixth cervical nerves are still smaller. Beneath the
semispinalis capitis each divides into lateral muscular and medial cutaneous
branches. The muscular branches supply neighbouring muscles ; the cutaneous
branches are small nerves, which, passing backwards, become superficial close to the
median plane. They supply the skin of the back of the neck. The sixth is the
smallest, and the cutaneous branches of the fifth and sixth nerves may be absent
altogether. In certain cases the fourth nerve forms, with the third, a loop of com-
munication from which muscles are supplied.
Seventh and Eighth Cervical Nerves. These are the smallest of the posterior
rami of the cervical nerves. They give off ordinarily no cutaneous branches,
and end in the deep muscles of the back. There is occasionally a small cutaneous
offset from the eighth nerve.
THORACIC NERVES.
The posterior ramus of each thoracic nerve divides into a medial and a lateral
branch. In the case of the upper six or seven thoracic nerves the medial
branches are distributed chiefly as cutaneous nerves, only giving off small muscular
branches while the lateral branches are wholly muscular in their distribution ;
in the case of the lower five or six thoracic nerves the opposite is the case. In all
cases the muscular branches serve to innervate the longitudinal muscles of the
back. The distribution of the cutaneous branches is different in the upper and
lower part of the back. The upper six or seven thoracic nerves innervate the skin
of the scapular region. The medial cutaneous branches, after a sinuous backward
course from their origin, among the dorsal muscles, reach the surface near the
spines of the vertebrse and are directed almost horizontally laterally over the
trapezius muscle. The first is small ; the second is very large and reaches to the
acromion. The rest diminish in size, from above downwards, and become more
and more oblique in direction. The lateral cutaneous branches of the lower five or
six thoracic nerves are directed from their origin obliquely downwards and laterally
among the parts of the sacro-spinalis muscle. Becoming cutaneous by piercing
the latissimus dorsi at some distance from the median plane, they supply the skin
of the back in the lower part of the chest and loin, the lowest nerves (eleventh
and twelfth) reaching over the iliac crest on to the buttock. The lower nerves
often subdivide into two branches before or after their emergence from the latis-
simus dorsi muscle.
LUMBAR NERVES.
First three Lumbar Nerves. The posterior rami of the first three lumbar j
nerves subdivide into medial and lateral branches, in the same way as the lowers
thoracic nerves. The medial branches are muscular and innervate the deep!
muscles of the back. The lateral branches are chiefly cutaneous. They are|
directed obliquely downwards and laterally among the fibres of the sacro-spinalie|
and become superficial by piercing the lumbo-dorsal fascia, just above the iliac crest
and a short distance in front of the posterior superior iliac spine. They are ther
directed downwards in the superficial fascia of the buttock, and supply a length}!
strip of skin, extending from the median plane above the iliac crest to a pom i
distal to and behind the greater trochanter of the femur. There may be onbjji
two cutaneous branches, derived from the first two lumbar nerves; in other case
the three nerves are the branches of the twelfth thoracic and first two lumbaf'j
nerves.
SACRAL AND COCCYGEAL NERVES. 691
The fourth and fifth lumbar nerves (like the last two cervical nerves) usually
supply only muscular branches to the longitudinal muscles of the back. The fifth
i nerve in many cases sends a branch to form a loop of connexion with the posterior
: ramus of the first sacral nerve (posterior sacral plexus).
SACRAL AND COCCYGEAL NERVES.
The posterior rami of the sacral nerves issue from the posterior sacral foramina.
As in the case of the thoracic and lumbar nerves, the upper sacral nerves differ
from the lower in their distribution.
The first three sacral nerves supply medial muscular branches for the
multifidus, and lateral cutaneous branches which pierce the fibres of the sacro-
1 tuberous ligament and the glutseus maximus muscle, and supply the skin over
J the back of the sacrum and contiguous part of the buttock, giving rise to the
posterior sacral plexus.
The posterior sacral plexus consists, like the posterior cervical plexus, of loops
or plexiform communications over the back of the sacrum between the posterior rami of
the first three sacral nerves, to which are frequently joined branches of the last lumbar
j nerve and fourth and even the fifth sacral nerve. From these loops branches proceed to
supply the multifidus muscle ; others, piercing the sacro-tuberous ligament, form secondary
loops beneath the glutseus maximus muscle. From the secondary loops, two or more
I cutaneous branches arise, which, after traversing the muscle, supply the skin over the
\ sacrum and medial part of the buttock.
Posterior Ano-coccygeal Nerve. The posterior rami of the fourth and fifth
sacral nerves do not divide into medial and lateral branches. They unite together
to form a loop which is joined by the minute posterior ramus of the coccygeal
nerve. The union of the three nerves constitutes the posterior ano-coccygeal nerve,
which, after perforating the sacro-tuberous ligament, is distributed to the skin in
the neighbourhood of the coccyx. It supplies no muscles. This nerve is the
representative of the superior caudal trunk of tailed animals.
MORPHOLOGY OF THE POSTERIOR RAMI.
There are several points of morphological interest in relation to the posterior rami of
i the spinal nerves.
1. Muscular Distribution. In their muscular distribution they are strictly limited to the
longitudinal muscles of the back : namely, those associated with the axial skeleton alone.
2. Cutaneous Distribution. Their cutaneous distribution represents two points of interest.
A. In the first place, while the skin of the back is supplied in a regularly segmental manner
by the several nerves, certain of them fail to reach the surface at alL The absence of a cutaneous
branch from the sub-occipital nerve may be due either to the absence of a perfect posterior root, or
to its communication with the second nerve. The other nerves which do not usually supply the
skin are the last two, three, or four cervical, and the fourth and fifth lumbar nerves. These nerves
are placed in the centre of regions in which the upper and lower limbs are developed. They are
minute nerves, while the corresponding anterior rami are among the largest of the spinal
nerves. Thus, opposite the centre of each limb, posteriorly, there is a hiatus in the
segmental distribution of the posterior rami of the spinal nerves to the skin of the shoulder
and buttock, attributable to the formation of the limbs, and the extension into them of the
greater part of the nerves of the region. This gap, in the case of the upper limb, commences at
the level of the vertebra prominens ; in the case of the lower limb it commences opposite the
level of the posterior superior iliac spine. It can be continued on to each limb as a hypothetical
area (the dorsal axial line), which indicates the area of contact (and overlapping) of cutaneous
nerves not in strictly numerical sequence. Thus, in the region of the shoulder, the sixth (or
fifth) cervical nerve innervates an area of skin adjoining that supplied by the eighth cervical
or first thoracic nerve ; in the region of the buttock the third, lumbar nerve supplies an area
i contiguous with that supplied by the fifth lumbar or first sacral nerve.
. The cutaneous- branches of the posterior rami of the spinal nerves differ from the muscular
r i branches in respect of their penetration into regions beyond those supplied by their motor
' roots. The cutaneous branches, in regions where outgrowths or extensions from the trunk have
occurred, follow these extensions ; and, in consequence, supply skin covering parts which do not
belong to segments represented by the nerves in question. Thus, the second and third cervical
nerves (greater and third occipital) are drawn upwards so as to supply the posterior part of the
scalp ; the upper thoracic nerves are drawn laterally over the scapular region ; the upper lumbar
and sacral nerves supply the skin of the buttock ; and the ano-coccygeal nerve forms a rudi-
mentary caudal nerve.
692 THE NERVOUS SYSTEM.
3. Plexuses. The plexuses formed by the posterior rami of the upper cervical and upper
sacral nerves are the simplest met with in the human body. The posterior cervical plexus is
one from which muscular branches are supplied ; the posterior sacral plexus is mainly concerned
in producing cutaneous offsets. In the case of the posterior cervical plexus the loops of com-
munication between the first three or four cervical nerves result in the formation of a series of
nerves for the supply of the semispinales and other muscles, which bring into contact with
these muscles, simultaneously, a considerable area of the spinal medulla, and provide a combined
and simultaneous innervation for the -several parts of each muscle. In the case of the posterior
sacral plexus, the formation of loops between the nerves results in the innervation of any given
spot in the cutaneous area supplied from these loops by more than one spinal nerve. As has
been said already, the cutaneous nerves, even without the formation of plexuses, overlap in their
cutaneous distribution. The formation of a plexus causes a more intimate union of neighbouring
spinal nerves, so that stimulation of the surface affects a wider area in the spinal medulla than if
the nerves passed separately to it from the surface. While segmentation becomes less obvious,
increased co-ordination of both movement and sensation is effected.
ANTERIOE RAMI OF THE SPINAL NERVES.
The anterior rami (O.T. anterior primary divisions) of the spinal nerves, are, with
the exception of the first two cervical nerves, much larger than the correspond-
ing posterior -rami. Composed of elements of both posterior and anterior roots, each
nerve separates from the posterior ramus on emerging from the intervertebral
foramen, and, proceeding laterally, is distributed to structures on the lateral and
anterior aspects of the body, including the limbs.
Each nerve is joined near its origin by a gray ramus communicans from the
corresponding sympathetic gangliated trunk ; and in the case of certain thoracic,
lumbar, and sacral nerves, the anterior ramus gives off a delicate bundle of fibres,
which forms the white ramus communicans to the sympathetic trunk. That part of
the spinal nerve which is distributed to the body wall and limbs may be termed
somatic ; the small white ramus communicans, innervating structures in the
splanchnic area, may be termed the visceral or splanchnic part of the spinal nerve.
The anterior rami of the spinal nerves are distributed in a regular segmental
manner only in certain cases. Except in the case of the thoracic nerves, the j
anterior rami combine to form the three great plexuses cervical, brachial, and j
lumbo-sacral and their arrangement and distribution is rendered exceedingly j
complex.
A thoracic nerve, such as the fifth or sixth, may be regarded as a type to I
illustrate the mode of distribution of the anterior rami of the spinal nerves I
(Fig. 606, p. 686). It occupies an intercostal space; near its origin it possesses jj
gray and white rami communicantes ; it courses through the interval between the
intercostal muscles; it supplies branches to those muscles and gives off, when it
reaches the side of the chest, a lateral branch, which, after supplying small muscular i
branches, pierces the external intercostal muscle, and is distributed to an area off.
skin over the lateral part of the trunk, contiguous dorsally with a similar area,
innervated by the cutaneous branches of the posterior ramus of the same nerve, n
The lateral branch generally subdivides into a smaller posterior and a larger
anterior ramus, as it pierces the muscles clothing the wall of the chest. The :
main trunk of the nerve, having given off its lateral branch, then pursues itsjj
course obliquely forwards to the side of the sternum, where, after piercing thef.
pectoral muscles, it appears superficially as the terminal anterior cutaneous branch.
This supplies an area of skin continuous with that supplied by the anterior part off,
the lateral branch of the same nerve. Such a nerve thus supplies, by means oi
its lateral and anterior branches, an area of skin which (with the area supplied;
by the cutaneous branch of its posterior ramus) forms a continuous and unin-i
terrupted belt, extending from the median plane behind to the median plane ir
front. The lateral and anterior branches of the nerve innervate in their cours<
the intercostal and other muscles, to be afterwards mentioned in detail.
NERVI CERVICALES.
The anterior rami of the cervical nerves, together with parts of the first an>
second thoracic nerves, are distributed to the head, neck, and upper extremity
CEKVICAL NEKVES. 693
The first four cervical nerves, by means of the cervical plexus, innervate the neck ;
FIG. 609. THE DISTRIBUTION OF CUTANEOUS NERVES ON THE FRONT OF THE TRUNK.
On one side the distribution of the several nerves is represented, the letters indicating their nomenclature.
Gr.A, Great auricular nerve ; S.C, N. cutaneus colli ; S.CL, Supra- clavicular nerves ; ACR, Posterior ; CL, Middle ;
ST, Anterior ; T.2-12, Lateral and anterior branches of thoracic nerves ; I.H, Ilio-hypogastric nerve ;
I.I, Ilio-inguinal nerve ; CIRC, Cutaneous branch of axillary nerve ; L.I.C, Medial cutaneous nerve of the
arm (lesser internal cutaneous nerve) ; I.H, Intercosto-brachial ; I.C, Medial cutaneous nerve of the fore-
arm (internal cutaneous) ; M.S, Cutaneous branch of radial nerve ; E.C, Lateral cutaneous nerves ; G.C,
Lumbo-inguinal nerve ; M.C 1 2 , Intermediate cutaneous nerves ; I.C 1 , Branch of medial cutaneous nerve ;
P, Branches of pudendal nerve ; S.Sc, Branches of posterior cutaneous nerve of the thigh.
On the other side a schematic representation is given of the areas supplied by the above nerves, the numerals
indicating the spinal origin of the branches of distribution to each area.
the last four cervical nerves, together with a large part of the first thoracic nerve,
694
THE NEKYOUS SYSTEM.
through the brachial plexus, supply the upper limb. The second thoracic nerve
may contribute a trunk to this plexus, and always assists in the innervation of
the arm.
PLEXUS CERYICALTS.
The anterior rami of the first four cervical nerves are concerned in forming the
cervical plexus. Each nerve emerges from the vertebral canal posterior to the
STERNO-TMVKEOID
SUPRA-CUAV1CUUAR NERVES
FIG. 610. THE LEFT CERVICAL PLEXUS.
vertebral artery. Each is joined on its emergence from the intervertebral foramen,
at the side of the vertebral column, by a gray ramus communicans from the superior
cervical ganglion of the sympathetic. In the neck the cervical nerves are
concealed by the sterno-mastoid muscle ; in front lies the longus capitis muscle,
and behind are the scalenus medius, and (behind the first or sub-occipital nerve)
the rectus capitis lateralis. The cervical plexus is constituted by the combination
of the four nerves in an irregular series of loops under cover of the sterno-mastoid
muscle, and overlapped, in part, by the internal jugular vein.
From the loops of the plexus the branches of distribution arise, as (a) cutaneous
branches to the head, neck, and shoulder ; (&) muscular branches to muscles of the
CERVICAL PLEXUS. 695
neck and to the diaphragm ; and (c) communicating branches to the vagus, accessory,
hypoglossal, and sympathetic nerves.
For convenience of description, the nerves derived from the plexus may be
classified as follows :
I. Superficial (cutaneous) Branches
A. Ascending Branches (C. 2, 3). B. Descending (supra-clavicular) Branches (C. 3, 4).
N. occipitalis minor (lesser Nn. supraclaviculares anteriores (O.T. supra
occipital), sternal),
N. auricularis magnus (great Nn. supraclaviculares medii (O.T. supra-clavi-
auricular), cular),
N. cutaneus colli (O.T. trans- Nn. supraclaviculares posteriores (O.T. supra-
verse superficial cervical). acromial).
II. Deep (muscular and communicating) Branches
A. Lateral Branches. B. Medial Branches.
1. Muscular branches to 1. Muscular to
Sterno-mastoid (C. 2), Pre vertebral muscles (C. 1, 2, 3, 4),
Trapezius (C. 3, 4), Infra-hyoid muscles (C. 1, 2, 3)
Levator scapulae (C. 3, 4), (ansa hypoglossi),
Scaleni (medius and posterior) (C. 3, 4). Diaphragm (C. 3, 4, 5) (phrenic
2. Communicating branches to nerve).
Accessory nerve (C. 2, 3, 4). 2. Communicating branches to
Vagus nerve (C. 1, 2),
Hypoglossal nerve (C. 1, 2),
Ansa hypoglossi (C. 2, 3),
Sympathetic (C. 1, 2, 3, 4).
The second, third, and fourth cervical nerves are the chief nerves engaged in
forming the plexus. The first cervical nerve only enters into the formation of a
small part the medial portion of the deep part of the plexus.
Superficial Cutaneous Branches. These nerves, six in number, are entirely
cutaneous. They radiate from the plexus, and appear in the posterior triangle of
the neck at the posterior border -of the sterno-mastoid muscle. They are divisible
into two series the one ascending: lesser occipital, great auricular, and nervus
cutaneus colli; the other descending (supra -clavicular): posterior, middle, and
anterior.
Ascending Branches. The lesser occipital nerve is variable in size and is
sometimes double. Its origin is from the second and third cervical nerves (more
rarely from the second only). It extends backwards under cover of the sterno-
mastoid, and then upwards along its posterior border. Piercing the deep fascia near
the apex of the posterior triangle, it divides into auricular, mastoid, and occipital
branches, and supplies small cervical branches to the upper part of the neck. The
auricular branch supplies the skin of the cranial surface of the auricle ; the
mastoid and occipital branches supply the scalp. The nerve communicates on
the scalp with the greater occipital and great auricular nerves, and with the posterior
auricular branch of the facial nerve.
The great auricular nerve is the largest of the cutaneous branches. It arises
from the second and third cervical nerves (or, more rarely, from the third alone).
Winding round the posterior border of the sterno-mastoid muscle, it courses
vertically upwards towards the ear. In this course it crosses the sterno-mastoid
muscle obliquely and is covered by the platysma muscle. Before arriving at the
ear it subdivides into mastoid, auricular, and facial branches. The mastoid branches
ascend over the mastoid process and supply the skin of the scalp behind the ear,
communicating with, the lesser occipital and posterior auricular nerves. The
auricular branches ascend to the ear and supply the lower part of the auricle on
both aspects ; they communicate with the same nerves. The facial branches,
passing over the angle of the mandible and through the substance of the parotid
696
THE NEKVOUS SYSTEM.
gland, supply the skin of the cheek over the inferior part of the masseter muscle
and the parotid gland. They communicate with branches of the facial nerve in
the parotid gland.
The nervus cutaneus colli arises from the second and third cervical nerves.
It winds round the posterior border of the sterno-mastoid muscle, and crosses
the muscle to reach the anterior triangle, under cover of the platysma muscle and
the external jugular vein. It divides near the anterior edge of the sterno-mastoid
muscle into superior and inferior branches, which are distributed through the
platysma to the skin covering the anterior triangle of the neck. The upper
branches communicate freely beneath the platysma with the cervical branch of
the facial nerve.
Descending (supra-clavicular) Branches. By the union of two roots derived
from the third and fourth
cervical nerves a considerable
trunk is formed, which emerges
from under cover of the sterno-
mastoid muscle and extends
obliquely downwards through
the inferior part of the posterior
triangle of the neck. It sub-
divides into radiating branches
anterior, middle, and posterior
which pierce the deep fascia
of the neck above the clavicle,
and are distributed to the skin
of the inferior part of the side
of the neck, to the front of the
chest, and the shoulder. The
anterior (O.T. supra - sternal)
branches are the smallest. Pass-
ing over the medial end of the
clavicle, they supply the skin
of the neck and chest as far
down as the synchondrosis
sternalis. The middle (O.T.
supra-clavicular) branches pass
over the intermediate third
of the clavicle, beneath the
platysma, and can be traced
as low as the third rib. The
posterior (O.T. supra-acromial]
branches pass over or through
the insertion of the trapezius
muscle, and over the lateral
third of the clavicle, to the
shoulder, where they supply the skin as far down as the distal third of the deltoid
muscle.
Deep Branches. The deep branches of the cervical plexus are separated
into a lateral and a medial set by their relation to the sterno-mastoid muscle.
Beneath the muscle, the lateral branches are directed laterally towards the posterior
triangle, and the medial branches pass medially towards the anterior triangle.
The lateral branches consist of muscular and communicating nerves, which
for the most part occupy the posterior triangle.
The muscular branches are the following : (1) To the sterno-mastoid, from the
second cervical nerve. This enters the muscle on its deep surface and communicates
with the accessory nerve. (2) To the trapezius, from the third and fourth cervical
nerves. These nerves cross the posterior triangle and end in the trapezius, after
having communicated with the accessory nerve, both in the posterior triangle, and
under cover of the muscle. (3) To the levator scapulce, from the third and fourth
FIG. 611. DISTRIBUTION OF CUTANEOUS NERVES TO THE HEAD
AND NECK.
CEKYICAL PLEXUS.
697
vical nerves. Two independent branches enter the lateral surface of the muscle
in the posterior triangle. , (4) To the scaleni (medius and posterior), from the third
and fourth cervical nerves.
The communicating branches are three in number. They join the accessory
nerve in three situations: (a) A branch from the second cervical nerve to the
sterno-mastoid joins the accessory nerve under cover of that muscle. (&) Branches to
the trapezius from the third and fourth nerves are connected with the accessory
nerve in the posterior triangle, (c) Branches from the same nerves join the nerve
under cover of the trapezius muscle.
r vical branch of facia ,--
ferves to levator scapulae-
Anterior supra-
clavicular nerve
- Greater occipital
Lesser occipital
Third occipital
Great auricular
N. cutaneus colli
Nerves to levator scapulae
Accessory nerve
Communicating branch to accessory
> Nerve to trapezius
. Posterior supra-clavicular
nerve
Middle supra-clavicular nerve
Supra-scapular
FIG. 612. THE NERVES OF THE SIDE OF THE NECK.
The medial branches of the plexus also comprise muscular and communi-
branches. The first cervical nerve assists in the formation of this series of
jrse
, forming a slender loop with part of the second nerve in front of the trans-
process of the atlas.
Communicating Branches. (a) With the sympathetic. Gray rami communi-
ntes pass to each of the first four cervical nerves, near their origins, from the
.perior cervical ganglion or from the trunk below the ganglion. (&) With the
vagus nerve. The ganglion nodosum of the vagus nerve may be connected by a
slender nerve with the loop between the first two cervical nerves. This communica-
tion is not constant, (c) With the hypoglossal. An important communication
occurs between the hypoglossal nerve and the loop between the first and second
698
THE NEEVOUS SYSTEM.
cervical nerves (Fig. 613). A trunk from the loop joins the hypoglossal just beyond
its exit from the skull. One fine branch from this trunk passes upwards along
the hypoglossal nerve to the cranium (meningeal branch'). The main part of the
trunk accompanies the hypoglossal and separates from it to form successively three
nerves the descendens hypoglossi, and the nerves to the thyreo-hyoid and genio-hyoid
muscles. The portion of the nerve which remains accompanies the hypoglossal to
the muscles of the tongue. It is probable that no part of the hypoglossal nerve
itself is concerned in the formation of these three branches. The descending
branch of the hypoglossal descends in front of the internal and common carotid
C2
SCENOINO CERVICAL
FIG. 613. THE MUSCLES OP THE HYOID BONE AND STYLOID PROCESS, AND THE EXTRINSIC MUSCLES OF
THE TONGUE, WITH THEIR NERVES.
arteries, and is joined in the anterior triangle of the neck by the descending
cervical nerve, to form the ansa hypoglossi, from which the infra-hyoid muscles
are innervated. . (The descending branch of the hypoglossal, in some cases, arises
from the vagus nerve. ^
Muscular Branches. The muscles supplied by the medial branches of the
plexus are the prevertebral muscles, the genio-hyoid and the infra-hyoid muscles,
and the diaphragm.
(a) Prevertebral Muscles. 1. From the loop between the first and second
cervical nerves a small branch arises, for the surmlv of the rectus capitis lateralis,
u
;
i
PHEENIC NEEVE. 699
ngus capitis, and the rectus capitis anterior. 2. From the second, third, and
urth nerves small branches supply the inter- transverse, longus colli, and longus
pitis muscles. 3. From the fourth nerve a branch arises for the upper part of the
enus anterior.
(&) Genio-hyoid and Infra-hyoid Muscles. The descending cervical nerve is formed
in front of the internal jugular vein by the union of two slender trunks from the
cond and third cervical nerves (communicantes hypoglossi). It forms a loop
' communication in front of the carotid sheath with the descending branch of the
ypoglossal nerve (derived ultimately from the first two cervical nerves). This
>p of communication is called the ansa hypoglossi. It is often plexiform ; and
rom it branches are given to the sterno-hyoid and sterno-thyreoid muscles, and
both bellies of the omo-hyoid muscle. The nerve to the sterno-hyoid muscle is
often continued behind the sternum, to join, in the thorax, with the phrenic nerve
>r the cardiac plexus.
The thyreo-hyoid and genio-hyoid muscles are supplied by branches of the hypo-
lossal nerve, which are also traceable back to the communication between the
ypoglossal and the first two cervical nerves.
The anterior muscles in immediate relation to the median plane of the neck,
tween the chin and the sternum, are thus continuously supplied by the first
three cervical nerves. The hypoglossal is the nerve of the muscles of the tongue,
d it is not certain that it contributes any fibres to the above-named muscles,
(c) Diaphragm. The phrenic nerve supplies the diaphragm.
jSTERvus PHRENICUS.
The phrenic nerve is derived mainly from the fourth cervical nerve, reinforced
y roots from the third (either directly or through the nerve to the sterno-hyoid)
and fifth (either directly or through the nerve to the subclavius muscle). It runs
downwards in the neck upon the scalenus anterior muscle ; at the root of the neck
passes between the subclavian artery and vein, enters the thorax and traverses
mediastinum to reach the diaphragm, lying in the middle mediastinum
tween the pericardium and pleura, and anterior to the root of the lung. In its
urse it presents certain differences on the two sides. In the neck, on the left
.de, it crosses the first part of the subclavian artery ; on the right side it crosses
e second part. In the superior mediastinum, on the left side, it lies between
left subclavian and carotid arteries, and crosses the vagus nerve and the
>rtic arch. On the right side it accompanies the innominate vein and superior
vena cava, and is entirely separate from the vagus nerve. The left nerve is longer
than the right, owing to the position of the heart and the left half of the
diaphragm. The right nerve sends fibres along the inferior vena cava through
the foramen vense cavse. Eeaching the diaphragm the nerve separates into
umerous branches for the supply of the muscle ; some enter its thoracic surface
ub-pleural branches), but most of the fibres supply it after piercing the muscle
ub-peritoneal branches).
The branches of the phrenic nerve are 1. Muscular (to the diaphragm); 2.
pleural ; 3. pericardiac ; 4. inferior vena-caval ; 5. suprarenal ; and 6. hepatic.
The branches to the pleura and pericardium arise as the phrenic nerve
traverses the mediastinum. The branches to the inferior vena cava, suprarenal
gland, and liver arise after communication of the phrenic nerve with the
diaphragmatic plexus of the sympathetic on the abdominal surface of the
diaphragm.
Communications of the Phrenic Nerve. 1. The phrenic nerve may communicate
ith the nerve to the subclavius muscle. 2. It may communicate with the ansa
ylossi, or a branch from it (the nerve to the sterno-hyoid). 3. It frequently com-
unicates with the cervical part of the sympathetic. 4. It communicates with the
eliac plexus by a junction upon the abdominal surface of the diaphragm with the
diaphragmatic plexus on the inferior phrenic artery, in which a small diaphragmatic
ganglion is found on the right side. From this junction branches are given off to the
inferior vena cava, suprarenal gland, and hepatic plexus.
700 THE NEEVOUS SYSTEM.
MORPHOLOGY OF THE CERVICAL PLEXUS.
The characteristic feature of the cervical plexus is the combination of parts of adjacent nerves
into compound nerve-trunks by the formation of series of loops. The result of the formation of
these loops is that parts (particularly cutaneous areas) are supplied by branches of more than one
spinal nerve.
A. Cutaneous Distribution. By the combinations of the nerves into loops the discrimination
of the elements in the upper cervical nerves, corresponding to the lateral and anterior rami
of a typical thoracic nerve, is made a matter of some difficulty. The second, third, and
fourth nerves, through the cervical plexus, supply an area of skin extending, laterally, from the
side of the head to the shoulder ; anteriorly, from the face to the level of the third rib. The higher
nerves supply the upper region (second and third) ; the lower nerves supply the lower region
(third and fourth). It is not possible to compare the individual nerves strictly with the lateral
and anterior rami of a thoracic nerve. A line drawn from the ear to the middle of the
clavicle separates, however, a lateral from an anterior cutaneous area ; and certain of the
cutaneous nerves fall naturally into one of these two categories. The nerves homologous with
anterior rami of intercostal nerves are the n. cutaneus colli and the anterior branches of the
supra-clavicular series ; those homologous with lateral branches are the smaller occipital and
posterior supra -clavicular branches. The great auricular and middle supra-clavicular branches
are mixed nerves, comprising elements belonging to both sets.
B. Muscular Distribution. The nerves from the cervical plexus supplying muscles are
simpler in their arrangement. They are not generally in the form of loops, and they are easily
separated into lateral and anterior series. The lateral nerves comprise the branches to the
rectus capitis lateralis, sterno-mastoid, trapezius, levator scapulae. The nerves in the anterior
series are those to the longus capitis, rectus capitis anterior, the hyoid muscles, and the
diaphragm.
It is noteworthy that the last-named muscles genio-hyoid, thyreo-hyoid, sterno-hyoid, omo-
hyoid, sterno-thyreoid, and diaphragm are continuously supplied by branches from the first five
cervical nerves : the higher muscles by the higher nerves ; the lower muscles by the lower nerves.
PLEXUS BRACHIALIS.
The [Brachial Plexus is formed by the anterior rami of the fifth, sixth, seventh,
and eighth cervical nerves, along with the greater part of the first thoracic nerve.
In some cases a slender branch of the fourth cervical nerve is also engaged ; and
the second thoracic nerve also, in all cases, contributes to the innervation of
the arm, through the intercosto-brachial (O.T. intercosto-humeral) nerve. In many
cases it contributes also directly to the plexus, by an intra-thoracic communication
with the first thoracic nerve.
Position of the Plexus. The nerves forming the brachial plexus appear in
the posterior triangle of the neck between the scalenus anterior and scalenus
medius muscles; the^ plexus is formpri in .close relation to the subclavian and
axHHry"ar leri.es ; the nerves emanating from it accompany h&_a^^tojfa^xtta,,
whence they aredistributed to the shoulder-aa4~upfier limb.
Communications with the Sympathetic. The lower four cervical nerves communicate
with the cervical portion of the sympathetic by means of gray rami communicantes.
Two branches arise from the middle cervical ganglion, and join the anterior rami
of the fifth and sixth nerves. Two arising from the inferior cervical ganglion join the
seventh and eighth nerves. They reach the nerves either by piercing the prevertebral
muscles or by passing round the border of the scalenus anterior muscle.
Composition of the Brachial Plexus. In an analysis of the brachial plexus
four stages may be always seen :
(1) The undivided nerves.
(2) The separation of the nerves into anterior and posterior trunks ; ancj^k^
formation of three primary cords.
(3) The formation of three secondary cords lateral, medial, and posterior.
(4) The origin of the nerves of distribution.
(1) The undivided nerves have only a very short independent course at the side
of the neck, after passing between the scalene muscles.
(2) Three primary cords are formed almost immediately after the undivided j
nerves enter the posterior triangle : the first cord is formed by the union of the
fifth and sixth nerves ; the second, by the seventh nerve alone ; and the third, j
by the union of the eighth cervical and first thoracic nerves. While these cords
are being formed, a division occurs in each of the nerves, into anterior and j
posterior trunks. The anterior and posterior trunks of the fifth, sixth, and seventh
BEACHIAL PLEXUS.
'01
nerves are nearly equal in size. The posterior trunk of the eighth cervical nerve
is much smaller. The 'posterior trunk of the first thoracic nerve is very minute,
and may not be present at all.
(3) The secondary cords of the plexus are formed by combinations of these
anterior and posterior trunks, in relation to the axillary artery. They are three
in number. The lateral cord is formed by a combination of the anterior trunks
of the fifth, sixth, and seventh nerves, and lies on the lateral side of the axillary
artery. The medial cord is formed by a combination of the anterior trunk of the
eighth cervical with the part of the first thoracic nerve engaged in the formation
of the plexus; it lies on the medial side of the axillary artery. The posterior
cord is made up of all the posterior trunks from the fifth, sixth, seventh, and
eighth cervical and first thoracic nerves, and lies behind the axillary artery.
N. INTERCOSTAL.S
FIG. 614. THE NERVES OF THE BRACHIAL PLEXUS.
ie first" thoracic nerve may not contribute to the posterior cord, and the branch,
rhen present, is a very small nerve.
(4) The nerves of distribution for the shoulder and arm are derived from these
secondary cords, and receive in this way various contributions from the constituent
spinal nerves. From the lateral cord arise the lateral anterj r>r t.hnrapjn and muscuJQ-
cutaneous nerves, and the lateral head of the median nerve. From the, medial cord
e the medial head of the median nerve, the ulnar nerve, medial cutaneous
iiftt tfpHfttG forearm, medial cutaneous nerve of the arm, and the medial anterior
icic nerve. From the posterior cord arise the axillary nerve, the two sub-
ilar nerves, the thoraco-dorsal nerve, and the radial nerve.
I to be remembered that, although derived from a secondary cord formed by a certain
it of spinal nerves, any given nerve does not necessarily contain fibres from all the constituent
B^jrres ; e.g., both the musculo-cutaneous and axillary nerves, from the lateral and posterior cords
respectively, are ultimately derived only from the fifth and sixth cervical nerves. In other
* words, the secondary cords are merely collections of nerves of distribution bound together in a
common sheath in their passage through the axilla.
5 THE BRANCHES OF THE BRACHIAL PLEXUS.
It is customary to separate artificially the nerves of distribution of the brachial
xus into two sets : (1) supra-clavicular and (2) infra-clavicular. Clinically it is
y
702
THE NEEVOUS SYSTEM.
important to realise the position of origin of certain nerves. The nerves to the
prevertebral muscles, the communication with the phrenic, the dorsal scapular, and
long thoracic nerves, arise from the anterior rami of the nerves involved in the
plexus. The supra-scapular and the nerve to the subclavius arise at the level of
formation of the secondary cords; and the anterior thoracic, subscapular, and
thoraco - dorsal nerves arise from the secondary cords, prior to their ultimate
subdivision into the nerves of distribution for the upper limb.
Pars Supraclavicularis. The nerves derived from the plexus above the
level of the clavicle are, like the main trunks, divisible into two series : anterior
branches, arising from the front of the plexus ; posterior branches, arising from the
back of the plexus (Fig. 614, p. 701).
Anterior Branches.
1. Nerves to scalenus anterior and
longus colli.
2. Communicating nerve to join
the phrenic nerve.
3. Nerve to the subclavius muscle.
Posterior Branches.
1. Nerves to scalenus medius and
scalenus posterior.
2. Dorsal (posterior) scapular nerve.
3. Long thoracic nerve.
4. Supra-scapular nerve.
INNER
CORD
The muscular twigs to the anterior scalene and longus colli muscles arise from
the lower four cervical nerves, as they emerge from the intervertebral foramina.
The communicating branch to the phrenic nerve arises usually from the fifth
cervical nerve at the lateral border of the anterior scalene muscle. It is sometimes
absent, and occasionally an additional root is
present from the sixth cervical nerve. In some
instances the nerve is replaced by a branch which
springs from, the nerve to the subclavius, and
passes medially behind the sterno-mastoid muscle
to join the phrenic at the inlet of the thorax.
N. Subclavius. The nerve to the subclavius
is a slender nerve, which arises from the front
of the cord formed by the fifth and sixth cervical
nerves. It descends in the posterior triangle of
the neck over the third part of the subclavian
artery. It often communicates with the phrenic
nerve.
The branches to the scalenus medius and scalenus
posterior, are small trunks which arise from the
lower four cervical nerves as they emerge from the
intervertebral foramina.
N. Dorsalis Scapulae. The dorsal scapular
FIG. BISDIAGRAM OF THE ORIGIN AND nerve (- T posterior scapular or nerve to the
DISTRIBUTION OP THE NERVES TO THE rhomboids) arises from the back of the fifth
PECTORAL MUSCLES. cervical nerve, as it emerges from the interver-
L.A.T, Lateral anterior thoracic nerve; tebral foramen. It appears in the posterior
^ft$&5%ZMSti trian gk of the neok > afto pg fche scalen s
plexus; ART, Axillary artery; CL, medius muscle. It is directed downwards,
Clavicle ; SCL, Subclavius muscle ; under cover of the levator scapulae and rhomboid
$^8$ muscles > and alM >g the vertebral mar s in of the
P.MA, Pectoralis major. scapula, to be distributed to the levator scapulae,
rhomboideus minor, and rhomboideus major
muscles. It occasionally pierces the levator scapulae.
N. Thoracalis Longus. The long thoracic nerve (O.T. posterior thoracic or
external respiratory nerve of Bell) arises by three roots, of which the middle one
is usually the largest, from the back of the fifth, sixth, and seventh nerves, as they
emerge from the intervertebral foramina. The nerve pierces the scalenus medius
as two trunks, of which the lower represents the contribution from the seventh
cervical nerve, and, descending along the. side of the neck behind the cords of the
brachial plexus, it enters the axilla between the superior edge of the serratus
ANTERIOK THOKACIC NEEVES. 703
anterior muscle and the axillary artery. It continues its downward course over
the axillary surface of the serratus, to the slips of which it is distributed.
There is a more or less definite relation between the roots of this nerve and the parts of the
serratus muscle. The first part of the muscle is innervated by the fifth nerve alone ; the second
part by the fifth and sixth, or the sixth alone; the third part by the sixth and seventh,
or the seventh nerve alone.
N. Suprascapularis. The supra -scapular nerve arises from the back of the
cord formed by the fifth and sixth cervical nerves in the posterior triangle of the
neck. It occupies a position above the main cords of the brachial plexus, and
courses downwards and laterally parallel to them towards the superior margin of
the scapula. It passes through the scapular notch to reach the dorsum of the
scapula. After supplying the supra-spinatus muscle it winds round the great
scapular notch in company with the transverse scapular artery and terminates in
the infra-spinatus muscle. It also supplies articular branches to the back of the
shoulder-joint.
Pars Infraclavicularis. The so-called infra-clavicular branches of the brachial
plexus are distributed to the chest, shoulder, arm and forearm. According to
their origin they are divisible into two sets an anterior set, derived from the
lateral and medial cords, and a posterior set, derived from the posterior cord. In
their distribution the same arrangement is maintained. The anterior nerves of
distribution, springing from the lateral and medial cords, supply the chest
and the front of the limb ; the posterior nerves, springing from the posterior cord,
supply the shoulder and the back of the limb.
Anterior Branches.
From the Lateral Cord. , From the Medial Cord
Lateral anterior thoracic. Medial anterior thoracic.
Median (lateral head). Median (medial head).
Musculo-cutaneous. . Ulnar.
Medial cutaneous nerve of forearm (O.T.
internal cutaneous).
Medial cutaneous nerve of arm (O.T. lesser
internal cutaneous).
Posterior Branches. ^
Axillary nerve.
Radial nerve.
Two subscapular nerves.
Thoraco-dorsal nerve.
NERVI THOKACALES ANTERIORES.
The anterior thoracic nerves are two in number, lateral and medial. The
lateral anterior thoracic nerve arises from the lateral cord of the brachial plexus by
three roots from the fifth, sixth, and seventh cervical nerves. The medial
anterior thoracic nerve arises from the medial cord of the plexus, from the eighth
cervical and first thoracic nerves. They course downwards and forwards, one on
each side of the axillary artery, and a loop of communication is formed between them
in front of the artery. They are finally distributed to the pectoralis major and
minor muscles (Fig. 615).
The nerves are distributed to the pectoral muscles in the following way. Two sets of
branches from the lateral anterior thoracic nerve pierce the costo-coracoid membrane. The
superior branches supply the clavicular part of the pectoralis major ; the inferior branches
are distributed to the superior fibres of the sternal portion of the muscle. The superior
branches come from the fifth and sixth cervical nerves ; the inferior branches, from the fifth,
sixth, and seventh nerves. The pectoralis minor is pierced by two sets of nerves the
superior set is derived from the loop of communication between the two anterior thoracic
nerves over the axillary artery ; the inferior set is derived from the medial anterior
704
THE NEKVOUS SYSTEM.
' Short subscapular
Lower subscapular
Axillary nerve
thoracic nerve alone. These nerves supply the pectoralis minor muscle, and, after
piercing it, supply the sternal part of the pectoralis major. The inferior nerve, in many
cases, sends its branches to the pectoralis major round the inferior border of the
pectoralis minor, and on its
Thoraco-dorsai nerve wav it may supply the axillary
arches, if present. These two
branches are derived the
superior from the seventh and
eighth cervical, and first thoracic
nerves; the inferior from the
eighth cervical and first thoracic
nerves. The pectoral muscles are
thus both supplied by the two
anterior thoracic nerves. The
clavicular fibres of the pectoralis
major are innervated by the fifth
and sixth nerves; the sternal
fibres, from above downwards,
by the fifth, sixth, seventh, and
eighth cervical, and first thoracic
nerves ; and the pectoralis minor
is supplied by the seventh and
eighth cervical, and first thoracic
nerves.
NERVUS MUSCULOCUTANEUS.
The musculo - cutaneous
nerve takes origin from the
lateral cord of the plexus, from
the fifth and sixth cervical
nerves (Fig. 614). The nerve
to the coracobrachialis muscle,
arising from the seventh or
sixth and seventh nerves, is
usually associated with it.
Separating from the lateral
head of the median nerve, the
musculo -cutaneous nerve lies
at first between the coraco-
brachialis muscle and the
axillary artery. It is then
directed distally between the
two parts of the coracobrachi-
alis, and passes between the
biceps and brachialis muscles,
to the bend of the elbow. It
pierces the deep fascia over the
front of the elbow, between
the biceps and brachioradialis,
and terminates as the lateral
cutaneous nerve for the supply
of the lateral aspect of the
forearm. In its course it
may send a branch under the biceps to join the median nerve.
The branches of the nerve are muscular and cutaneous. The muscular branches
are supplied to the two heads of the biceps and the brachialis, as the nerve lies
between the muscles. The nerve to the coracobrachialis (usually incorporated
with the trunk of the musculo-cutaneous nerve) has an independent origin from
Musculo-cutaneous nerve
Radial nerve
Post. cut. nerve of upper arm
Nerve to coracobrachialis
Nerve to long head of triceps
Nerve to medial head of triceps
(collateral ulnar)
Nerve to brachialis ...
Nerve to brachialis muscle
Nerve to brachioradialis muscle-
Nerve to extensor carpi
radialis longus
Superficial ramus of radial....
Deep ramus of radial~- _
Branch to supinator muscle___
Branch to extensor carpi
radialis brevis
FIG. 616. THE DEEPER NERVES OF THE ARM.
MEDIAN NEKVE. 705
the seventh or sixth and seventh nerves. It is usually double, one branch entering
each portion of the muscle. The lateral cutaneous nerve of the forearm divides into
volar and dorsal branches (Fig. 616, p. 704). The volar branch runs distally along
the front of the lateral aspect of the forearm to the wrist, and supplies an area
extending medially to the middle line of the forearm anteriorly, and distally so
as to include the ball of the thumb. It communicates, proximal to the wrist,
with the superficial ramus of the radial nerve, and supplies branches to the
radial artery. The dorsal branch passes backwards and distally over the extensor
muscles and supplies the skin on the lateral aspect of the forearm posteriorly in
its proximal three-fourths, communicating with the cutaneous branches of the
radial nerve.
In addition to the above branches, the musculo-cutaneous nerve supplies in many
cases the following small twigs in the arm : (1) a medullary branch to the humerus ; (2)
a periosteal branch to the distal erid of the humerus on its anterior surface ; and (3) a
branch to the brachial artery.
NERVUS MEDIANUS.
The median nerve arises by two heads one from the lateral cord, the other
from the medial cord of the brachial plexus. The lateral head, from the (fifth),
sixth, and seventh nerves, descends along the lateral side of the axillary artery ;
the medial head, from the eighth cervical and first thoracic nerves, crosses the
end of the axillary artery or the beginning of the brachial artery, to join the other
head in the proximal part of the arm. Descending along the lateral aspect of the
brachial artery, the nerve crosses over it obliquely in the distal half of the arm. In
the hollow of the elbow, it lies on the medial side of the brachial artery, behind the
lacertus fibrosus and the median basilic vein. It passes into the forearm between
the two heads of the pronator teres muscle, separated from the ulnar artery by the
deep origin of that muscle. Extending distally along the middle of the forearm,
between the superficial and deep muscles, to the wrist, it enters the palm of the hand
on the lateral side of the flexor tendons of the fingers, and deep to the transverse
carpal ligament. In the hand, it spreads out at the distal border of the transverse
carpal ligament, under cover of the palmar aponeurosis and superficial volar arch,
and separates into its six terminal branches. In the forearm a small artery accom-
panies it, the median branch of the volar interosseous artery. Immediately
proximal to the wrist it is comparatively superficial, lying on the lateral side of the
superficial flexor tendons and directly behind the tendon of the palmaris longus.
Branches. The median nerve usually gives off no branches in the (upper)
arm.
Branches in the Forearm. (1) Articular Branches. Minute articular filaments
are distributed to the front of the elbow-joint.
(2) Muscular Branches. Just below the elbow a bundle of nerves arises to be
distributed to the following muscles : pronator teres, flexor carpi radian's, palmaris
longus, flexor digitorum sublimis. Nerves are also generally traceable from this
bundle to the upper fibres of the flexor pollicis longus and flexor digitorum
profundus. The nerve to the pronator teres often arises independently in the
hollow of the elbow.
(3) The volar interosseous nerve of the forearm (O.T. anterior interosseous) arises
from the posterior surface of the median nerve in the forearm. It passes distally on
the volar aspect of the interosseous membrane along with the volar interosseous
artery, lies dorsal to the pronator quadratus muscle, and terminates by supplying
articular filaments to the radio-carpal articulation. In its course the nerve supplies
muscular branches to the flexor pollicis longus, the lateral half of the flexor
digitorum profundus, and the pronator quadratus, minute medullary branches to
the radius and ulna, and twigs to the periosteum and interosseous membrane.
(4) Palmar Eamus. In the distal third of the forearm a small cutaneous
branch arises, which pierces the deep fascia and crosses the transverse carpal
ligament to reach the palm of the hand. It supplies the skin of the palm and com-
46
706
THE NEEVOUS SYSTEM.
municates with a similar branch of the ulnar nerve. This branch is not always
present.
Branches in the Hand. In the hand the median nerve gives off its terminal
branches. These are muscular and cutaneous.
The main muscular branch arises just distal to the transverse carpal ligament and
passes to the base of the thenar eminence ; entering the ball of the thumb super-
ficially on the medial side, it supplies branches to the abductor pollicis brevis,
opponens pollicis, and the flexor pollicis brevis.
RADIAL
(R. SUPERFICIALIs)
MEDIAN "
OSTERIOR ] 1
UTANE.OUS }
FARM J \ / \
(MEDIAL
CUTANEOUS
OF ARM
f INTERCOSTO-
\BRACHIAL
MUSCULO-
CUTANEOUS)
(MEDIAL
/ < CUTANEOUS
I OF FOREARM
VOLAR BR. (MEDIAN)
VOLAR BR. (ULNAR)
ULNAR
FIG. 617. THE DISTRIBUTION OF CUTANEOUS NERVES ON THE FRONT OF THE ARM AND HAND.
(B) is a schematic representation of the areas supplied by the above nerves, the lettering indicating the spinal
oTigin of the branches of distribution to each area. V. A.L., Ventral axial line.
The cutaneous branches are five in number. Three separate branches supply each
side of the thumb and the lateral side of the index finger. The two remaining
branches (nn. digitales volares communes) subdivide at the cleft between the
second and third, and the third and fourth fingers respectively, into branches
(nn. digitales volares proprii) which supply the adjacent sides of the second and
third, and the third and fourth fingers. From the nerves which supply j
respectively the lateral side of the index finger, and the contiguous sides of the;
index and third fingers, fine muscular branches arise for the first two lumbrical;
muscles. The cutaneous branches of the median nerve are placed in the palni!
between the superficial palmar arch and the flexor tendons. They become super- i
MEDIAN NERVE.
707
ficiai at the roots of the fingers between the slips of the palmar aponeurosis, or, in
the case of the nerves to the thumb and lateral side of the index finger, at the lateral
edge of the central portion of the palmar aponeurosis. In the fingers they are placed
superficial to the digital arteries, and are distributed to the sides and volar aspects
of the fingers. Each nerve supplies one or more dorsal branches, distributed to the
skin on the dorsal aspect of the terminal phalanx of the thumb and the distal two
INTERCOSTO- \
BRACHIAL
POSTERIOR )
CUTANEOUS f
OF ARM )
MEDIAL
CUTANEOUS
OF FOR
AXILLARY
- - MEDIAL CUTANEOUS
(RADIAL)
DORSAL CUTANEOUS
OF FOREARM
ROXIMAL BRANCH)
( DORSAL CUTANEOUS
4 OF FOREARM
((DISTAL BRANCH)
-V -MUSCULO-CUTANEOUS
RADIAL
(R.SUPERFICIALIS)
A B
FIG. 618. THE DISTRIBUTION OF CUTANEOUS NERVES ON THE BACK OF THE ABM AND HAND.
a schematic representation of the areas supplied by the above nerves, the lettering indicating the spinal
. origin of the branches of distribution to each area. D.A.L., Dorsal axial line.
phalanges of the first two and a half fingers, thus making up for the deficiency of
the superficial branch of the radial nerve in those situations.
Communications. (1) The median nerve, in some cases, receives a communicating
branch from the musculo-cutaneous nerve in the arm. (2) It communicates in some
sases, in the proximal part of the forearm, with the ulnar nerve beneath the flexor muscles.
) It communicates by means of its cutaneous branches with the ulnar nerve in the
palm of the hand (ramus anastomoticus cum nervo ulnari).
708
THE NEKVOUS SYSTEM.
Nerve to teres minor
Axillary nerve
Branches to deltoid
Lateral cutaneous
nerve of the arm
Nerve to long
head of triceps
NERVUS ULNARIS.
The ulnar nerve arises from the medial cord of the brachial plexus, from
the eighth cervical and first thoracic nerves. It also occasionally has a root from
the lateral cord of the
plexus (seventh cervical
nerve). In the axilla it
lies between the axillary
artery and vein, and behind
^^gg^g55^^3j|gj^ the medial cutaneous nerve
of the forearm (O.T. in-
ternal cutaneous); in the
proximal half of the arm
it lies on the medial side
of the brachial artery
anterior to the triceps
muscle. In the distal
half of the arm it is separ-
ated from the brachial
artery ; and passing behind
the intermuscular septum,
and in front of the medial
head of the triceps in com-
pany with the superior
ulnar collateral (O.T. in-
ferior profunda) artery, it
reaches the interval be-
tween the medial epicon-
dyle of the humerus and
the olecranon. It is there
protected by an arch of
deep fascia stretching be-
tween the epicondyle and
the olecranon. It enters
the forearm between the
humeral and ulnar origins
of the flexor carpi ulnaris,
and courses distally be-
tween the flexor carpi
ulnaris and flexor digi-
torum profundus. In the
distal half of the forearm
it becomes comparatively
superficial, lying on the
medial side of the ulnar
artery, overlapped by the
tendon of the flexor carpi
ulnaris. Just proximal to
the transverse carpal liga-
ment, and lateral to the
pisiform bone, it pierces the
deep fascia, in company
with the artery, and passes
into the hand over the
transverse carpal ligament. Reaching the palm it divides, under cover of thej
palmaris brevis muscle, into its two terminal branches, superficial and deep.
Branches. The ulnar nerve gives off no branches till it reaches the forearm.
In the forearm it gives off articular, muscular, and cutaneous branches.
---Radial nerve
Posterior cu-
""taneous nerve
of the arm
Proximal branch of dorsal
cutaneous nerve of --
forearm
Distal branch of dorsal
cutaneous nerve ...
of forearm
Ulnar nerve
FIG. 619. THE AXILLARY AND RADIAL NERVES.
MEDIAL CUTANEOUS NEKVE OF THE FOBEAKM. 709
The articular branch is .distributed to the elbow-joint and arises as the nerve
passes behind the medial epicondyl6 of the humerus.
The muscular branches arise as soon as the nerve enters the forearm. They are
distributed to the muscles between which the ulnar nerve lies the flexor carpi
ulnaris and the medial half of the flexor digitorum profundus.
The cutaneous branches are two in number, palmar and dorsal.
The palmar cutaneous ramus is variable in size and position. It pierces the
deep fascia in the distal third of the forearm and passes to the hypothenar
eminence and palm of the hand, to the skin over which it is distributed. It gives
branches to the ulnar artery, and communicates often with the medial cutaneous
nerve of the forearm and the palmar branch of the median nerve.
The dorsal ramus of the hand is much larger (Fig. 618). It arises from the
ulnar nerve in the middle third of the forearm ; and, directed obliquely distally and
backwards, beneath the tendon of the flexor carpi ulnaris, it becomes cutaneous on
the medial side of the forearm in its distal fourth. It passes on to the back of
the hand, and, after giving off branches to the skin of the wrist and hand which
communicate with the superficial ramus of the radial nerve, it terminates in two
dorsal digital nerves, to supply the little finger and half the ring-finger, in the
following way : the medial branch courses along the medial side of the dorsum
of the hand and little finger : the lateral branch subdivides at the cleft between
the ring and little fingers to supply the adjacent sides of these fingers ; this
branch communicates with the superficial ramus of the radial nerve. The nerve
may supply two and a half fingers on the dorsum of the hand.
Ramus Volaris Manus. In the palm the ulnar nerve supplies a small muscular
branch to the palmaris brevis, and then subdivides into its terminal branches,
which are named superficial and deep.
Ramus Superficialis. The superficial branch is purely cutaneous ; it passes
distally deep to the palmar aponeurosis, and subdivides into a medial and a lateral
branch. The medial branch courses along the medial border of the little finger,
which it supplies on its palmar aspect. The lateral branch (common volar digital
nerve} becomes superficial at the cleft between the fourth and fifth fingers, between
the slips of the palmar aponeurosis, and subdivides into two branches (proper volar
digital nerves) which supply the adjacent sides of these fingers on their palmar
aspect. It communicates with the adjacent digital branch of the median nerve.
Ramus Profundus. The deep branch is purely muscular. It separates from the
superficial branch, and passes deeply between the flexor brevis and abductor digiti
quinti muscles ; it supplies those muscles and the opponens digiti quinti, and,
turning laterally along the line of the deep palmar arch and under cover of the
deep flexor tendons, it supplies branches to the following muscles : interossei, third
and fourth lumbricales (on their deep surfaces), the adductor pollicis (oblique and
transverse parts), and the interosseus primus volaris (deep part of the flexor pollicis
brevis).
Communications. The ulnar nerve communicates (1), in some cases, with the median
nerve in the forearm ; (2) with the medial cutaneous nerve of the forearm, and sometimes
with the median nerve, by its palmar branch ; (3) with the cutaneous part of the median
nerve in the palm, by means of its terminal cutaneous branches ; (4) with the superficial
ramus of the radial nerve on the dorsum of the hand, by means of its dorsal branch.
NERVUS CUTANEUS ANTIBRACHII MEDIALIS.
The medial cutaneous nerve of the forearm (O.T. internal cutaneous nerve)
arises from the medial cord of the brachial plexus, from the eighth cervical and first
thoracic nerves (Figs. 614 and 617). In the axilla and proximal half of the arm it
lies superficial to the main artery. It becomes cutaneous by piercing the deep fascia
about the middle of the arm on its medial side, and accompanying the basilic vein
through the distal half of the arm, it divides at the front of the elbow into its two
terminal branches.
Branches. In the arm, as soon as it becomes superficial, the nerve gives off a
branch which supplies the skin of the distal half of the anterior surface of the
46 a
710 THE NEKVOUS SYSTEM.
arm on its medial side. At the elbow it divides into two terminal branches
volar and ulnar, which, crossing superficial or deep to the median basilic vein, are
distributed to the medial side of the forearm.
The volar branch can be followed to the wrist and supplies the whole of the
volar surface of the forearm in the medial half; the ulnar branch is not so large,
and, passing obliquely backwards and distally over the origins of the pronator
and flexor muscles, it is distributed to the proximal two-thirds or three-fourths of
the dorsal aspect of the forearm on the medial side.
Communication. The medial cutaneous nerve of the forearm communicates
with the volar branch of the ulnar nerve in the distal part of the forearm.
NERVUS CUTANEUS BEACHII MEDIALIS.
The medial cutaneous nerve of the arm (O.T. lesser internal cutaneous nerve)
arises from the medial cord of the brachial plexus, and ultimately from the first
thoracic nerve (Fig. 614, p. 701). It lies at first between the axillary artery and
vein ; and after descending over, under, or even, in some cases, through the axillary
vein, it perforates .the deep fascia and is distributed to the skin of the arm for the
proximal half or 'more on its medial side.
The nerve varies considerably in size. It may be absent, its place being taken by branches
of the intercosto-brachial or by branches from the posterior cutaneous branch of the radial nerve.
It generally bears a distinct relation in size to the intercosto-brachial, due to the fact that the size
of the latter depends upon the size of the part of the second thoracic nerve connected with 'the
first in the thorax. If an intra- thoracic connexion occurs between the first and second thoracic
nerves, the intercosto-brachial may be deprived of a certain number of its fibres, which in
that case reach the upper limb through the medial cutaneous nerve of the arm. When traced
up to the plexus the medial cutaneous nerve of the arm is found to have an origin from the
posterior part of the cord formed by the eighth cervical and first thoracic nerves, and usually
receives fibres from the first thoracic nerve only. In cases where " axillary arches " are present
they may be supplied by this nerve.
NERVUS AXILLARIS.
The axillary nerve (O.T. circumflex) at its origin is just below the supra-
scapular and comes from the same spinal nerves the fifth and sixth cervical
nerves (Fig. 614, p. 701). Extending distally and laterally behind the axillary
artery, it leaves the axilla by passing round the lateral border of the subscapularis
muscle, in company with the posterior circumflex artery of the humerus, in a quadri-
lateral space bounded by the humerus, subscapularis, triceps (long head), and teres
major. Winding round the surgical neck of the humerus from medial to lateral
side, it terminates by supplying the deltoid muscle (Fig. 619, p. 708).
Branches. Muscular branches are supplied to the teres minor and deltoid
muscles. The nerve to the teres minor enters the lateral aspect of the muscle. It
possesses a pseudo-ganglion, a thickening of fibrous tissue, on its trunk.
Articular branches enter the posterior part of the capsule of the shoulder-joint.
A cutaneous branch of considerable size the lateral cutaneous nerve of the arm
passes obliquely distally and forwards from beneath the deltoid muscle, becoming
superficial at its posterior border. Sometimes branches pierce the muscle. It
supplies the skin over the insertion of the deltoid and the proximal half of the arm
on its lateral aspect (Figs. 617, p. 706, and 618, p. 707).
NERVUS EADIALIS.
The radial nerve (O.T. musculo-spiral) appears to be the continuation into the
upper limb of the posterior cord of the brachial plexus. It usually takes origin
from all the nerves which form the posterior cord the fifth, sixth, seventh, and
eighth cervical and first thoracic nerves (Fig. 614, p. 701). In some cases the first
thoracic contributes no fibres, and often the fifth cervical nerve is excluded
from it. It extends from the axilla, round the back of the humerus, to the bend of
the elbow, where it ends by dividing into its superficial and deep terminal branches.
THE EADIAL NERVE.
711
RADIAL NERVE.
In the axilla it lies behind the axillary artery, and in front of the subscapularis,
teres major, and latissimus dorsi muscles.
In the arm, in the proximal third, it lies to the medial side of the humerus, behind
the brachial artery, and upon the long head of the triceps. In the middle third of
the arm it courses obliquely laterally and distally in the radial groove of the
humerus, along with the profunda brachii artery, separating the long, lateral, and
medial heads of the triceps muscle (Fig. 619, p. 708). In the distal third of the arm,
piercing the proximal part of the intermuscular septum at the lateral border of the
triceps muscle, it passes to the bend of the elbow in front of the lateral epicondyle
of the humerus, in the interval between the brachio-radialis and brachialis muscles.
Under cover of the former muscle, in the hollow of the elbow, it divides into its
two terminal branches, the superficial and deep rami.
The collateral branches are in three sets, arising (a) on the medial side, (6)
on the back, and (c) on the lateral side of the humerus
(Fig. 620).
1. Branches arising medial to the Humerus.
1. N. cutaneus brachii posterior (O.T. upper internal
cutaneous branch of musculo-spiral). The posterior
cutaneous nerve of the arm, arising in common with
one of the following, or independently, pierces the
fascia on the medial side of the arm near the axilla.
It supplies the skin of the posterior surface of the arm
in the proximal third, proximal and posterior to the
area supplied by the medial nerve of the arm (O.T.
lesser internal cutaneous) (Fig. 618, p. 707). This
nerve varies in size, according to the bulk of the last-
named and the intercosto-brachial nerves.
2. Rami Musculares. The muscular branches are
in two sets. One series supplies the long head
of the triceps muscle near its origin ; the other series
enters the medial head of the muscle. One of the
latter, separating itself from the rest, accompanies the
ulnar nerve in the middle third of the arm, and sup-
plies the distal part of the muscle. This is sometimes
called the collateral ulnar nerve.
II. Branches arising on the Posterior Surface
of the Humerus. Muscular branches arise from the
nerve in the radial groove for the supply of all
three heads of the triceps muscle. The branch
which enters the medial head of the muscle, besides
supplying it, passes through the muscle and behind
the lateral epicondyle of the humerus, to terminate in
the anconseus.
III. Branches arising at the Lateral Side of the
Humerus. 1. The dorsal cutaneous nerve of the forearm
consists of two branches, proximal and distal. Arising
from the radial nerve before it pierces the lateral intermuscular septum, these
branches pierce the deep fascia close together on the lateral side of the arm in
its distal half. Passing distally over the back of the lateral epicondyle, the
proximal branch supplies the skin of the lateral side and posterior surface of the
arm in its distal third, and the dorsal surface of the forearm in its proximal half.
The distal branch supplies an area of skin on the dorsal surface of the forearm
in the proximal two-thirds, medial to the area innervated by the inusculo-cutaneous
nerve (Fig. 618, p. 707).
'. Muscular Branches. The radial nerve, as it lies in the interval between
the brachialis and brachio-radialis muscles, supplies a small branch to the brachialis
(which in some cases is not present) and nerves to the brachio - radialis and
extensor carpi radialis longus. It may also provide the nerve to the extensor
carpi radialis brevis.
46 &
DORSAL
CUTANEOUS N.
OF FOREARM
JOINT
TO ANCONAEUS
THE RADIAL NERVE.
712
THE NEKVOUS SYSTEM.
KAMUS SUPERFICIALIS NERVI EADIALIS.
The superficial ramus (O.T. radial nerve) is entirely cutaneous in its dis-
tribution. Arising in the hollow of the elbow beneath the brachio-radialis, it courses
distally under cover of that
muscle through the proximal
two -thirds of the forearm,
and accompanies the radial
artery in the middle third of
the forearm. It then passes
backwards, under cover of the
tendon of the brachio-radialis,
and pierces the deep fascia on
the lateral aspect of the fore-
arm in the distal third. It is
distributed to the skin of the
dorsum of the wrist, the lateral
side and the dorsum of the
hand, and the dorsum of the
thumb and lateral two and a
half fingers (Fig. 618, p. 707).
Its branches communicate, on
the ball of the thumb, with
the musculo-cutaneous nerve,
and, on the dorsum of the
hand, with the dorsal branch
of the ulnar nerve (ramus
anastomoticus ulnaris). The
digital nerves are small, and
are five in number. Two
pass to the back of the thumb
and reach the level of the
inter-phalangeal articulation.
One supplies the lateral side
of the index finger as far as
the second phalanx. The re-
maining two branches divide
at the clefts between the
second and third, and third
and fourth fingers respect-
ively, and innervate the ad-
jacent sides of those fingers
as far as the second phalanx.
The rest of the skin of those
digits to the tips is supplie
by digital branches of tl
median nerve. The nerve mai
only supply the thumb am
one and a half fingers, beinj
replaced by branches from tl
ulnar nerve.
Radial nerv
Superficial ramus r
Deep ramus-
Deep ramus ^~"
Muscular branches to superficial muscles^-"
Dorsal interosseous artery'''
Dorsal interosseous nerve
Muscular branch to abductor pollicis longus.
Muscular branch to extensor pollicis longus,-
Muscular branch to extensor indicis propri
Muscular branch to extensor pollicis brevis *~
Terminal branch to carpal joints *~-
FIG. 621. DISTRIBUTION OF THE DEEP BRANCH OF THE
RADIAL NERVE.
KAMUS PROFUNDUS NERVI EADIALIS.
The deep ramus (O.T. posterior interosseous nerve) is entirely muscular am
articular in its distribution. It arises, like the superficial ramus, under cover of th<
brachio-radialis muscle. Directed obliquely distally and backwards, it reactu
the back of the forearm, after passing round the lateral aspect of the radius,
piercing the fibres of the supinator muscle (Fig. 621). On the dorsal surface of th
THOEACIC NEEVES. 713
forearm it is called the dorsal interosseous nerve, and is placed in the proximal part
of its course beneath the superficial extensor muscles, and upon the supinator and
abductor pollicis longus, along with the dorsal interosseous artery. In the distal
half of the forearm it passes under cover of the extensor pollicis longus, and lies
upon the interosseous membrane. At the wrist it passes deep to the extensor
tendons, on to the back of the carpus, where it terminates in a gangliform enlarge-
ment of small size, from which branches pass to the inter-carpal articulations. The
nerve supplies the following branches :
(1) Terminal articular branches to the carpal joints.
(2) Muscular branches, in its course through the forearm. Thus, on the lateral
side of the radius, it supplies the extensor carpi radialis brevis and the supinator
muscles before it enters the fibres of the last-named muscle. After emerging from
the supinator it supplies a large bundle of nerves which enter the extensor
digitorum communis, extensor digiti quinti proprius, and extensor carpi ulnaris, near
their origins. At a more distal level the nerve gives off branches to^ the abductor
pollicis longus, extensor pollicis longus and extensor pollicis brevis, and extensor
indicis proprius.
NERVI SUBSCAPULARES.
There are two subscapular nerves (Figs. 614 and 616).
The first or short subscapular nerve is generally double, and there may be
three trunks present. It arises from the posterior cord of the plexus behind the
axillary nerve, and comes from the fifth and sixth cervical nerves. It passes
distally behind the axillary artery and enters the subscapularis muscle.
The second or lower subscapular nerve also arises behind the axillary nerve
from the posterior cord of the plexus (from the fifth and sixth cervical nerves).
Its origin is distal and lateral to that of the first nerve. It courses distally
behind the axillary artery and the axillary and radial nerves, to the teres
major muscle. It supplies branches to the lateral part of the subscapularis
muscle and ends in the teres major.
NERVUS THORACODORSALIS.
The thoraco-dorsal nerve (O.T. long subscapular) arises from the back of the
posterior cord of the plexus, behind the radial nerve, and from the sixth, seventh,
and eighth cervical nerves, or from the seventh and eighth nerves only. It is
directed distally and laterally between the two preceding nerves, behind the axillary
artery and over the posterior wall of the axilla, in company with the subscapular
artery, to the latissimus dorsi muscle, which it supplies on its anterior (deep)
surface.
NEEVI THOEACALES.
The anterior rami of the thoracic nerves are twelve in number, each nerve
emerging below the corresponding vertebra and rib. Eleven of the series are
intercostal, the twelfth lying below the last rib. The first, second, third, and
twelfth nerves present peculiarities in their course and distribution. The other
thoracic nerves, as already stated, are simple, and may be regarded as types
both in course and distribution.
The anterior ramus of the first thoracic nerve is the largest of the series.
It emerges from the vertebral canal below the neck of the first rib, and divides
in the first intercostal space into two very unequal, superior and inferior, parts.
The superior and larger part ascends obliquely over the neck of the first rib, lying
lateral to the arteria intercostalis suprema, and enters the neck behind the sub-
clavian artery and the pleura. It proceeds laterally upon the scalenus
medius muscle and enters into the formation of the brachial plexus, as already
described.
The inferior, intercostal part of the nerve is much smaller in size. It courses
714
THE NERVOUS SYSTEM.
forwards in the first intercostal space and supplies the intercostal muscles. It
usually gives off no anterior branch to the skin of the chest and no lateral
cutaneous branch.
In some cases a lateral cutaneous branch emerges from the side of the first intercostal space.
This may be derived from the first nerve, or it may be the intercosto-brachial nerve, i.e. the lateral
branch of the second thoracic nerve. In many cases an anterior cutaneous branch perforates
the first intercostal space and supplies the skin on the front of the chest. This branch, similarly,
is sometimes traceable to the second thoracic nerve.
Communications. Besides its junction with the eighth cervical to form the
brachial plexus, the first thpracic nerve effects the following communications : (a) The
last cervical or first thoracic ganglion of the sympathetic sends a gray ramus communi-
cans to join the nerve on its appearance in the thorax. (6) The second thoracic nerve in
a majority of cases communicates with the first. This communication varies considerably
in size and distribution. It may reinforce the intercostal branch of the nerve, it may
send one branch to the intercostal portion and another to the part of the nerve joining the
Posterior column of spinal medulla
Posterior nerve-root
Anterior nerve-root | |
Spinal ganglion .[,.
Posterior ramus (medial branch) ^^vgtfK&MlB
of spinal medulla
Posterior ramus
Posterior ramus (lateral branch)^
Recurrent uieningeal branch (uniting with a sympathe
Gray ramus communican
Splanchnic branch (white ram
Anterior
Lateral branch (posterio
subdivisi
Lateral branch
Anterior ramus
Lateral branch (anterior
subdivision)
O.-j nsrl i.ited sympathetic trunk
Efferent I vaso-motor) branch
Cardinal vein
Afferent viscero-iiihibitury
branch
Mesentery
-i-Intestina
l canal
FIG. 622. SCHEME OF THE DISTRIBUTION OF A TYPICAL SPINAL NERVE.
brachial plexus, or it may consist of a nerve proceeding solely to join the brachial plexus by
a junction in the first intercostal space with the part of the first thoracic nerve, which is
engaged in forming the plexus, (c) It is possible that the first white ramus communicans
in the thoracic region connects the first thoracic nerve with the sympathetic trunk, but
this is not known with certainty.
The anterior ramus of the second thoracic nerve is of large size, though much
smaller than the first. It passes forwards in the second intercostal space, lying
at first in the costal groove, between the external and internal intercostal
muscles. At the level of the mid-axillary line it gives off a large lateral branch ;
continuing its course, it pierces the internal intercostal muscle and lies upon the
pleura; finally, at the lateral border of the sternum, it passes forwards in front of|
the internal mammary artery and through the internal intercostal muscle, and
THOKACIC NEEVES. 715
the aponeurosis of the external intercostal muscle and pectoralis major, and ends
FIG. 623. THE DISTRIBUTION OF CUTANEOUS NERVES ON THE FRONT OF THE TRUNK.
On one side the distribution of the several nerves is represented, the letters indicating their nomenclature.
G.A, Great auricular nerve ; S.C, N. cutaneus colli ; S.CL, Supra-clavicular nerves ; ACR, Posterior ; CL, Middle ;
ST, Anterior ; T.2-12, Lateral and anterior branches of thoracic nerves ; I.H, Ilio-hypogastric nerve ;
I.I, Ilio-inguinal nerve ; CIRC, Cutaneous branch of axillary nerve ; L.I.C, Medial cutaneous nerve of the
I arm (O.T. lesser internal cutaneous nerve) ; I.H, Intercosto-brachial ; I.C, Medial cutaneous nerve of the
forearm (O.T. internal cutaneous) ; M.S, Cutaneous branch of radial nerve; E.C, Lateral cutaneous nerves ;
G.C, Lumbo-inguinal nerve ; M.C 12 , Intermediate cutaneous nerves ; I.C 1 , Branch of medial cutaneous
nerve ; P, Branches of pudendal nerve ; S.Sc, Branches of posterior cutaneous nerve of the thigh,
the other side a schematic representation is given of the areas supplied by the above nerves, the numerals
indicating the spinal origin of the branches of distribution to each area.
by supplying the skin of the front of the chest over the second intercostal space.
716 THE NEEVOUS SYSTEM.
The nerve supplies the following branches :
1. Muscular branches to the muscles of the second intercostal space.
2. Cutaneous branches, (a) Anterior terminal branches to the skin over the
second intercostal space (Fig. 623). (6) A large lateral cutaneous branch, the intercosto-
brachial (O.T. intercosto-humeral) nerve (Fig. 614, p. 701). This nerve pierces the
intercostal and serratus anterior muscles, and, crossing the axilla, extends to the arm.
It pierces the deep fascia just beyond the posterior fold of the axilla, and can be traced
as far as the interval between the medial epicondyle of the humerus and the olecranon.
It supplies an area of skin stretching across the axilla and along the posterior surface of
the arm on the medial side as far as the elbow (Fig. 617, p. 706). It may supply the
axillary arches, when present.
The intercosto-brachial nerve varies in size. It may pierce the first intercostal space, and it
is often divisible into anterior and posterior branches, like the lateral branch of an ordinary
intercostal nerve.
Communications. (1) The intercosto-brachial nerve communicates with two adjacent
nerves. Either before or after piercing the fascia of the axilla it is joined by the medial
cutaneous nerve of the arm. It also communicates with the posterior part of the lateral
branch of the third intercostal nerve by means of the branches distributed to the floor and
boundaries of the axilla. (2) Besides the branches referred to, the second thoracic nerve
in many cases transmits a nerve to the brachial plexus, which becomes incorporated with
the first thoracic nerve after passing over the neck of the second rib. This branch is
inconstant. As already mentioned, it may join only the intercostal part of the first
thoracic nerve, it may join the brachial plexus only, or it may send branches to both
parts of the first thoracic nerve. (3) Besides the communications effected by branches
of the second thoracic nerve in its course, it also receives a gray ramus communicans
from the second thoracic ganglion of the sympathetic trunk in the thorax. It also sends
to the sympathetic a white ramus communicans, probably the first, though this is not
known with certainty.
The anterior ramus of the third thoracic nerve differs from a typical thoracic
nerve only in one respect. Its lateral branch divides in the usual way into
anterior and posterior parts, of which the latter is carried to the arm and supplies
an area of skin on the medial side near the root of the limb. It effects a junction
with the intercosto-brachial nerve (Fig. 614, p. 701).
The anterior rami of the fourth, fifth, and sixth thoracic nerves have a course
and distribution which is simple and typical. Except for the peculiarities above
mentioned, the second and third thoracic nerves have a similar distribution.
The nerves lie on the posterior wall of the thorax, in the costal groove of the
corresponding rib. They extend forwards between the intercostal muscles as far
as the middle of the chest wall, lying at a lower level than the intercostal vessels.
At the side of the chest each nerve passes obliquely through the internal intercostal
muscle, and comes to lie upon the pleura, transversus thoracis muscle, and
internal mammary artery. Thereafter, piercing the fibres of the internal inter-
costal muscle, the aponeurosis of the external muscle, and the pectoralis major,
each nerve ends by supplying the skin of the front of the chest, over an area
corresponding to the medial or anterior part of the intercostal space to which
it belongs.
Branches. Each intercostal nerve supplies, in addition to the anterior terminal
cutaneous branches, muscular branches to the intercostal muscles and a lateral
cutaneous ramus, which, piercing the intercostal and serratus anterior muscles,
divides into anterior and posterior branches for the innervation of the skin over
the side of the chest. Each area of skin thus innervated is continuous anteriorly
with the area innervated by the anterior rami of the same nerves, and posteriorly
with the areas supplied by their posterior rami.
The upper six intercostal nerves supply the muscles of the first six intercostal
spaces and the transversus thoracis (3, 4, 5, 6). The second, third, fourth, fifth,!
and sixth nerves supply the skin of the front of the chest : the second, opposite
the sternal synchondrosis ; the sixth, opposite the base of the xiphoid process.:
Their lateral branches supply branches to the intercostal muscles and the skin of
THOEACIC NERVES. 717
the side of the chest, the, second (intercosto-brachial) and the third, in part, being
drawn out to the arm. The fourth supplies the nipple (Fig. 623).
Communications. Each of these intercostal nerves communicates with the sympathetic
trunk and ganglia by two branches a white ramus communicans to the corresponding sym-
pathetic ganglion or the adjacent part of the sympathetic trunk ; and a gray ramus com-
municans, which passes to each nerve from the corresponding ganglion.
The anterior rami of the seventh, eighth, ninth, tenth, and eleventh thoracic
nerves differ from the preceding nerves only in regard to a part of their course and
distribution. Each has the same course and communications as the preceding nerves
in the thoracic wall. In addition, these nerves have a further course and distribu-
tion in the abdominal wall. Each nerve traverses an intercostal space in the way
described. At the anterior end of the space, the nerve pierces the attachment of
the diaphragm and the transversus abdominis muscle to the costal cartilages, and
courses forwards in the abdominal wall between the transversus and obliquus
internus muscles. The nerve then passes between the rectus abdominis muscle
and the posterior layer of its sheath, and eventually reaches the anterior abdominal
wall and becomes cutaneous by piercing the rectus abdominis itself and the anterior
layer of its sheath.
Muscular Branches. The lower intercostal nerves supply the intercostal
muscles of the spaces in which they lie ; and in the abdominal wall they innervate
the transversus, obliquus externus and internus, and rectus abdominis. The
branches arise from the main trunk as well as from its lateral and anterior
branches. (The ninth, tenth, and eleventh nerves are described as assisting in the
innervation of the diaphragm by communications with the phrenic nerve.)
Cutaneous Branches. These are lateral and anterior. The lateral branches
divide into anterior and posterior parts, and, becoming superficial along the line of
inter-digitation of the obliquus externus muscle with the serratus anterior and
latissimus dorsi, they are directed more obliquely downwards than the lateral
branches of the higher intercostal nerves, and are distributed to the skin of the
loin as low down as the buttock. The lateral branch of the eleventh nerve can be
traced over the iliac crest (Fig. 625).
The anterior branches are small. That of the seventh nerve innervates the skin
at the level of the xiphoid process. The eighth and ninth appear between the
xiphoid process and the umbilicus; the tenth nerve supplies the region of the
umbilicus ; and the eleventh, the area immediately below the umbilicus.
The cutaneous branches of these nerves, including those of the posterior rami, thus supply
continuous belts of skin, which can be mapped out on the body from the vertebral column
behind to the median plane in front. These areas are not placed horizontally, but tend to be
drawn more downwards anteriorly as the series is followed from the upper to the lower nerves.
The anterior ramus of the twelfth thoracic nerve is peculiar in its course
and distribution. It emerges below the last rib (Fig. 625), and passes laterally
and downwards in the posterior abdominal wall under cover of the psoas muscle,
and between the lateral lumbo-costal arch and the quadratus lumborum muscle ;
it pierces the transversus abdominis muscle, and courses forwards in the interval
between it and the obliquus internus as far as the sheath of the rectus muscle.
After piercing the posterior layer of the sheath, the rectus muscle, and the anterior
layer of the sheath, it terminates by supplying the skin of the anterior abdominal
wall midway between the umbilicus and the os pubis. The branches of the nerve
are muscular to the transversus, obliqui, rectus, and pyramidalis muscles of the
abdominal wall; and cutaneous branches, two in number an anterior terminal
branch, which supplies the skin of the anterior abdominal wall midway between
the umbilicus and the pubis, and a large lateral cutaneous branch, which, passing
obliquely downwards through the lateral muscles of the abdominal wall, becomes
superficial above the iliac crest, a couple of inches behind the anterior superior
spine. It supplies the skin of the buttock as far down as a point below and
anterior to the greater trochanter of the femur (Fig. 623, p. 715).
The twelfth thoracic nerve, in many cases, receives a communicating branch from the eleventh,
near its origin, and still more frequently sends a fine branch to join the origin of the first
718
THE NEKVOUS SYSTEM.
lumbar nerve in the psoas muscle. It may communicate also with the ilio-hypogastric nerve, as
they lie together in the abdominal wall.
Inter-communications of the Thoracic Nerves. It has been noted already that the belts or
areas of skin supplied by the branches of the thoracic nerves are also innervated by adjacent
nerves on either side which invade the area supplied by a given nerve. Communications also
take place between the branches of the nerves supplying the intercostal muscles, whereby the'
muscles of a given space derive their innervation from more than one intercostal nerve.
SYMPATHETIC
LATERAL CUTANEOUS
NEKVE OF THE THI
WHITE RAMUS
S3
WHITE RAMUS
S4
SCIATIC
FIG. 624. NERVES OF THE LUMBO-SACRAL PLEXUS.
PLEXUS LUMBOSACRALIS.
The lumbo-sacral plexus is formed by the union of the anterior rami of th
remaining spinal nerves five lumbar, five sacral, and one coccygeal. Frequently
LUMBAR PLEXUS. 719
a fine communicating branch of the twelfth thoracic nerve joins the first lumbar
nerve near its origin.
Of the nerves in question the first sacral is generally the largest in size, the
nerves diminishing gradually above and rapidly below this nerve. The plexus,
for the most part, forms the nerves destined for the supply of the lower limb. In
addition, however, nerves arise at its superior limit which are distributed to the
trunk above the level of the -limb, and at the inferior end of the plexus nerves
arise for the supply of the perineum.
Partly for convenience of description, and partly on account of the differences
in position and course of some of the nerves emanating from it, the plexus is sub-
divided into three subordinate parts lumbar, sacral, and pudendal plexuses.
There is, however, no strict line of demarcation between the three parts.
Plexus Lumbalis. The lumbar plexus is formed by the first four lumbar
nerves, and is often joined by a branch from the twelfth thoracic nerve as well.
It is limited below by the fourth lumbar nerve (n. furcalis), which enters also
into the composition of the sacral plexus. The nerves of the lumbar plexus are
formed in the loin, and supply that region as well as part of the lower limb.
They are separated from the nerves of the sacral portion of the plexus by the
articulation of the hip bone with the sacrum.
Plexus Sacralis. The sacral plexus is formed by the fourth and fifth lumbar,
and the first two or three sacral nerves. It is generally limited below by the third
sacral nerve (n. bigeminus), which assists also in forming the pudendal plexus. The
nerves of the sacral plexus are placed on the posterior wall of the pelvis, and are
destined almost entirely for the lower limb.
Plexus Pudendus. The pudendal plexus is formed by the second, third,
fourth, and fifth sacral nerves, and the minute coccygeal nerve. It is placed on
the posterior wall of the pelvis and supplies branches mainly to the perineum.
Communications with the Sympathetic. Each of these nerves has communica-
tions with the gangliated trunk of the sympathetic in the abdomen and pelvis.
Gray Kami Communicantes. From the lumbar and sacral ganglia long slender gray
rami Communicantes are directed backwards and laterally over the bodies of the vertebrae,
and (in the lumbar region) beneath the origins of the psoas muscle, to reach the spinal
nerves. These branches are irregular in their arrangement. A given nerve may receive
branches from two ganglia, or one ganglion may send branches to two nerves. The rami
are longer in the loin than in the pelvis, owing to the projection of the lumbar portion of
the vertebral column.
White Rami Communicantes. Certain lumbar and sacral nerves are also connected
with the abdominal and pelvic sympathetic by means of white rami Communicantes. From
the first two, and possibly in some cases also the third and fourth lumbar nerves, white
rami Communicantes are directed forwards, either independently or incorporated with the
corresponding gray rami, to join the upper part of the lumbar sympathetic trunk. The fifth
lumbar nerve and the first sacral nerves are unprovided with white rami Communicantes.
From the anterior rami of the second and third, or third and fourth sacral nerves, white
rami (visceral or splanchnic branches) pass medially, and, crossing over (without joining)
the sympathetic trunk, enter the pelvic plexus of the sympathetic. The fifth sacral and
coccygeal nerves possess no white rami Communicantes.
PLEXUS LUMBALIS.
The lumbar plexus is formed by the anterior rami of the first three and a part
of the fourth lumbar nerves, with the addition, in some cases, of a small branch
from the twelfth thoracic nerve. The nerves increase in size from above down-
wards (Fig. 624).
Position and Constitution. The plexus is formed in the substance of the psoas
muscle, in front of the transverse processes of the lumbar vertebrae. The nerves,
on emerging from the intervertebral foramina, are connected as above described
with the sympathetic system, and then divide in the following manner in the sub-
stance of the psoas major muscle. The first and second nerves divide into superior
720 THE KEKVOUS SYSTEM.
and inferior branches. The superior branch of the first nerve (which may be joined
by the branch from the twelfth thoracic nerve) forms two nerves, the ilio-hypogastric
and ilio-inguinal. The inferior branch of the first joins the superior branch of the
second nerve, to produce the genito -femoral nerve (O.T. genito-crural). The inferior
branch of the second" nerve, the whole of the third, and that part of the fourth
nerve engaged in the constitution of the plexus divide each into two unequal parts
smaller anterior and larger posterior parts. The smaller anterior portions combine
together to form the obturator nerve, which is thus formed by the second, third, and
fourth lumbar nerves. The root from the second nerve is not always present. The
larger posterior portions of the same nerves combine together to form the femoral
nerve (O.T. anterior crural). From the posterior aspect of the posterior parts of the
second and third nerves the lateral cutaneous nerve of the thigh (O.T. external
cutaneous) arises. The nerves also provide, near their origins, irregular muscular
branches for the psoas and quadratus lumborum muscles. The following is a list
of the nerves which spring from the lumbar plexus (Figs. 624 and 625) :
(1) Muscular branches to the quadratus (4) Genito-femoral.
lumborum and psoas muscles. (5) Lateral cutaneous.
(2) Ilio-hypogastric. (6) Obturator.
(3) Ilio-inguinal. (7) Femoral.
Muscular Branches. The nerves to the quadratus lumborum muscle arise
independently from the first three or four lumbar nerves (and sometimes also from
the twelfth thoracic nerve). The nerves to the psoas muscles arise from the second
and third lumbar nerves, with additions, in some cases, from the first or fourth.
They are often associated in their origin with the nerve to the iliacus from the
femoral nerve. The psoas minor, when present, is innervated by the first or
second lumbar nerve.
The ilio-hypogastric and ilio-inguinal nerves closely resemble, in their course
and distribution, the lower thoracic nerves, with which they are in series.
N. Iliohypogastricus. The ilio-hypogastric nerve is the highest branch of
the first lumbar nerve. It receives fibres also from the twelfth thoracic, when
that nerve communicates with the first lumbar nerve. After traversing the psoas
muscle obliquely, it appears at its lateral border, on the surface of the quadratus
lumborum and behind the kidney. It courses through the loin, lying between the
transversus and obliquus abdominis internus muscles, above the crest of the ilium.
About an inch in front of the anterior superior spine it pierces the obliquus internus,
and continues its course in the groin beneath the aponeurosis of the obliquus ex-
ternus. It finally becomes cutaneous in the anterior abdominal wall, by piercing
the aponeurosis of the obliquus externus about an inch and a half above the sub-
cutaneous inguinal ring (Fig. 623, p. 715).
Its branches are (1) muscular to the muscles of the abdominal wall ; and (2)
cutaneous branches, two in number. The lateral cutaneous branch corresponds
with the lateral branch of an . intercostal nerve, and, after piercing the obliquus
internus and obliquus externus, becomes cutaneous just above the iliac crest, below
and behind the iliac branch of the last thoracic nerve. It is small, and may be;
absent. It is distributed to the skin over the superior part of the lateral side of
the buttock, in continuity with the cutaneous branch of the posterior ramus olf
the first lumbar nerve. The anterior cutaneous branch is the anterior terminal
branch of the nerve. It supplies the skin of the anterior abdominal wall belo\v
the level of the last thoracic nerve and above the os pubis.
N. Ilioinguinalis. The ilio-inguinal nerve is the second branch given of
from the first lumbar nerve. It also may receive fibres from the last thoracic
nerve. Not infrequently the ilio-hypogastric and ilio-inguinal nerves are repre
sen ted for a longer or shorter part of their course by a single trunk. Wher
separate the nerve takes a course similar to that of the ilio-hypogastric nerve
but at a lower level, as far as the anterior abdominal wall. It then pierces th<
obliquus internus farther forward and lower down than the ilio-hypogastric
and coursing forwards beneath the aponeurosis of the obliquus externus, jus
LUMBAE PLEXUS.
721
above the inguinal ligament, it becomes superficial after passing through the
subcutaneous inguinal ring and external spermatic fascia (Fig. 623, p. 715).
Its branches are muscular to the muscles of the abdominal wall, among which it
passes, and cutaneous branches (anterior scrotal, or labial nerves), which innervate
Middle arcuate ligament
Vena caval opening
(Esophageal opening in diaphragm
Aortic opening
Anterior ramus
of twelfth
thoracic nerve
Quadratus
lumborum
lio-hypogastric
nerve
Ilio-inguinal
nerve
Lateral
utaneous nerve
of thigh
Femoral nerve ~"
Genito-femoral
nerve
bturator nerve ~~
cending ramus
fourth lumbar
nerve
interior ramus ..--',
of fifth lumbar
nerve
. f Medial and
j lateral lumbo-
. I costal arches
Ant. ramus of twelfth
thoracic nerve
Quadratus
lumborum
Ilio-hypogastric
nerve
Ilio-inguinal nerve
Psoas major
Genito-femoral
Lateral
cutaneous nerve
of thigh
Iliacus
Lumbo-sacral
trunk
" Femoral nerve
Obturator nerve
FIG. 625. THE MUSCLES AND NERVES ON THE POSTERIOR ABDOMINAL WALL.
the skin (1) of the anterior abdominal wall over the symphysis pubis, (2) of the
thigh over the proximal and medial part of the femoral triangle, and (3) of the
superior part of the scrotum, and root and dorsum of the penis (of the mons Veneris
and labium rnajus in the female). These last-named branches are contiguous to
branches of the perineal and pudendal nerves. No lateral cutaneous branch arises
from the ilio- inguinal nerve. It thus corresponds, like the anterior cutaneous
part of the ilio-hypogastrie nerve, to the anterior trunk of a typical thoracic nerve.
47
722 THE NEKVOUS SYSTEM.
N. Genitofemoralis. The genito-femoral nerve (O.T. genito-crural) usually
arises by two independent roots from the front of the first and second lumbar
nerves, which unite in the substance of the psoas major to form a slender trunk.
It appears on the posterior abdominal wall, lying on the psoas major, medial to
the psoas- minor, and, piercing the psoas fascia, it extends downwards on the lateral
aspect of the common and external iliac vessels and behind the ureter, to the
inguinal ligament (Fig. 625, p. 721). At a variable point above that ligament it
divides into two branches. 1. The external spermatic branch is a small nerve.
It crosses the terminations of the external iliac vessels, and, along with the ductus
deferens and testicular and external spermatic vessels, enters the inguinal canal
through the abdominal inguinal ring. It terminates by supplying small branches
to the skin of the scrotum and adjacent part of the thigh. In the female it
accompanies the round ligament to the labium majus. This nerve gives off in its
course the following small branches : (1) to the external iliac artery ; (2) to
the cremaster muscle; (3) to communicate with the spermatic plexus of the
sympathetic. 2. The lumbo- inguinal branch continues the course of the parent
nerve into the thigh, lying on the lateral aspect of the femoral artery. It becomes
cutaneous by passing through the fossa ovalis or through the iliac portion of the
fascia lata, and supplies an area of skin over the femoral triangle, lateral to
that supplied by the ilio-inguinal nerve (Fig. 623, p. 715). It communicates
in the thigh with the intermediate cutaneous branch of the femoral nerve.
Before piercing the deep fascia it gives a minute branch to the femoral artery.
N. Cutaneus Femoris Lateralis. The lateral cutaneous nerve of the thigh
is distributed only to the skin (Fig. 625). It arises from the back of the lumbar
plexus, and usually from the second and third lumbar nerves. Emerging from the
lateral border of the psoas major muscle, the nerve crosses the iliacus muscle, beneath
the fascia iliaca, to reach the anterior superior iliac spine. It enters the thigh beneath
the lateral end of the inguinal ligament, and either over, under, or through the
origin of the sartorius muscle. It extends distally along the front of the thigh for
a few inches, lying at first beneath the fascia lata, and afterwards in a tubular
investment of the fascia. It gives off small branches in this part of its course, and
finally, piercing the fascia about four inches distal to the anterior superior iliac
spine, it separates into anterior and posterior terminal branches. The anterior branch
is the larger, and is distributed on the lateral aspect of the front of the thigh almost
to the knee. The smaller posterior branch supplies the skin of the lateral side of
the buttock, distal to the greater trochanter, and the skin of the proximal two-
thirds of the lateral aspect of the thigh (Fig. 625, p. 721).
OBTURATORIUS.
The obturator nerve supplies the muscles and skin on the medial side of
the thigh. It arises in the substance of the psoas major muscle by three roots
placed in front of those of the femoral nerve, and derived from the second, third,
and fourth lumbar nerves (Fig. 624, p. 718). Sometimes the root from the second
nerve is absent. Passing vertically downwards, the nerve emerges from the psoas
major at its medial border, behind the common iliac, and on the lateral side
of the hypogastric vessels. It passes forwards below the pelvic brim in company
with the obturator artery to the obturator groove of the obturator foramen, through
which it reaches the thigh. While in the obturator groove it separates into its
two main branches, named anterior and posterior (Fig. 626, p. 723).
The anterior (O.T. superficial) branch enters the thigh in front of the obturator
externus and adductor brevis muscles, and behind the pectineus and adductor
longus. In the middle third of the thigh it is found coursing along the medial
border of the adductor longus, anterior to the gracilis ; and it finally divides into
two slender terminal filaments, of which one enters the adductor canal and ends on
the femoral artery, while the other supplies the skin for a variable distance on the
medial side of the thigh and joins in the obturator plexus.
The branches of the anterior part of the nerve are :
OBTUEATOE NEEVE.
723
1. An articular branch to the hip-joint, which arises from the nerve as soon as
it enters the thigh, and supplies the joint through the acetabular notch.
2. Muscular branches to the adductor longus, gracilis, adductor brevis (usually),
pectineus (occasionally). The last-named muscle is not usually supplied from the
obturator nerve.
3. A cutaneous branch of very variable size forms one of the terminal branches
(Fig. 626). It becomes superficial between the gracilis and adductor longus, in the
middle third of the thigh, and may supply the skin of the distal two- thirds of the
thigh on its medial side. It is generally of small size, and is connected with
branches of the medial cutaneous and saphenous nerves behind the sartorius muscle
to form the obturator (O.T. sub -sartorial) plexus. The branch from the saphenous
nerve to the plexus passes medially behind the sartorius after piercing the
Obturator nerve
Os pubis
Cut edge of psoas major
Nerve to pectineus
Posterior ramus of obturator nerv
Anterior ramus of obturator nerve
Descending muscular branches
Pectineus -~
Ascending branch to
obturator externus
Medial circumflex artery
Adductor longus-
Adductor brevis
Cutaneous branch
Second sacral vertebra
Piriformis
Glutseus maximus
Peritoneum
Obturator interims
Obturator externus
Ramus of ischium
Ascending branch of medial
circumflex artery
Quadratus femoris
Medial circumflex artery
Descending muscular branch
Adductor magnus
Branch to knee-joint
Branch to femoral artery Gracilis
FIG. 626. SCHEME OP THE COURSE AND DISTRIBUTION OF THE OBTURATOR NERVE.
aponeurotic covering of the adductor canal. The branch from the medial cutaneous
nerve is generally superficial at the point of formation of the plexus.
4. The branch to the femoral artery is the other terminal branch of the
nerve. It enters the adductor canal along the medial border of the adductor
longus, and ramifies over the distal part of the artery.
5. A fine communicating branch sometimes joins the femoral nerve in front
of the hip-joint.
The posterior (O.T. deep) branch of the obturator nerve reaches the thigh
by piercing the obturator externus muscle. It passes distally between the adductor
brevis and adductor magnus muscles. After passing obliquely through the
adductor magnus, it appears in the popliteal fossa on the popliteal vessels, and
terminates by piercing the oblique ligament of the knee and supplying the knee-
joint.
Its branches are : (1) muscular branches to the obturator externus, adductor
magnus, and (when the muscle is not supplied by the superficial part of the nerve)
724 THE NEKVOUS SYSTEM.
the adductor brevis. The branch to the obturator externus arises before the nerve
enters the muscle, in the obturator groove. The nerve to the adductor magnus
is given off as the obturator nerve passes through the substance of the muscle.
(2) An articular terminal branch is supplied to the posterior aspect of the knee-joint.
NERVUS FEMORALIS.
The femoral nerve (O.T. anterior crural) is the large nerve for the muscles
and skin of the front of the thigh. It arises in the substance of the psoas major
muscle, from the back of the second, third, and fourth lumbar nerves, posterior to
the obturator nerve. Passing obliquely through the psoas major muscle, it emerges
from its lateral border in the pelvis major (Fig. 625, p. 721). Passing downwards
in the groove between the psoas and iliacus, it enters the thigh beneath the inguinal
ligament, lateral to the femoral sheath and femoral vessels. In the femoral triangle
it breaks up into a large number of branches, among which the lateral circumflex
artery of the thigh passes in a lateral direction.
The branches of the femoral nerve, which are (1) muscular, (2) articular, and
(3) cutaneous, arise in the following way :
In the abdomen a muscular branch arises from the lateral aspect of the nerve
and enters the iliacus muscle.
In the femoral triangle the terminal muscular, articular, and cutaneous branches
arise in the form of a large bundle of nerves.
1. Rami Musculares. The muscular branches supply the pectineus, sartorius,
and quadriceps. The nerve to the pectineus arises close to the inguinal ligament,
and, coursing obliquely distally and medially behind the femoral vessels, enters the
muscle at its lateral border. It is not infrequently double. It sometimes gives off
a fine communicating branch to the anterior part of the obturator nerve. The
nerves to the sartorius are in two sets : a lateral, short set of nerves, associated with
the lateral part of the intermediate cutaneous nerve, which supply the proximal
part of the muscle ; and a medial, longer set, which are associated with the medial
part of the intermediate cutaneous nerve, and enter the middle of the muscle.
The parts of the quadriceps are supplied by several branches. The vastus lateralis
and rectus femoris are supplied on their deep surface by separate nerves which are
accompanied by branches of the lateral circumflex artery of the thigh. The vastus
intermedius muscle is supplied superficially by a nerve which passes through the
muscle, and innervates also the muscle of the knee-joint (subcrureus). It also
receives fibres from one of the nerves to the vastus medialis. The vastus medialis
muscle is supplied by two nerves : a proximal trunk, which supplies the proximal
part of the muscle, and sends fibres to the vastus intermedius as well ; and a distal
trunk, which descends on the lateral side of the femoral artery along with the
saphenous nerve, and passing beneath the sartorius, over or under the aponeurotic
covering of the adductor canal, enters the medial side of the muscle. This nerve
gives off a small branch which enters the medullary canal of the femur.
2. The articular branches supply the hip and knee-joints. The articular branch
to the hip-joint arises from the nerve to the rectus femoris, and is accompanied by
branches from the lateral circumflex artery of the thigh. The articular branches
to the knee-joint are four in number. Three of them arise from the nerves to the
vastus lateralis, vastus intermedius, and vastus medialis, which, after the muscular
nerves are given off, are continued downwards to the knee-joint along the front of
the femur. A fourth articular branch arises (sometimes) from the saphenous nerve.
3. Rami Cutanei Anteriores. The cutaneous branches are the intermediate
and medial cutaneous, and the saphenous nerves (Fig. 627).
The intermediate cutaneous nerve arises in two parts, a lateral and a medial
branch, in the proximal part of the femoral triangle. The two branches descend
vertically and become cutaneous by piercing the fascia lata over the proximal third
of the sartorius muscle. They carry muscular branches to the sartorius, and the
lateral branch in many cases pierces the muscle. These two nerves supply the skin
of the distal three-fourths of the front of the thigh, between the lateral cutaneous
nerve of the thigh laterally and the medial cutaneous on the medial side. They
THE FEMOKAL NERVE.
725
reach to the front of the patella, and there assist in the formation of the patellar
plexus. The lateral branch communicates, in the proximal third of the thigh, with
twigs from the lumbo-inguinal branch of the genito-femoral nerve.
The medial cutaneous nerve lies at first in the femoral triangle on the lateral
side of the femoral vessels. At the apex of the triangle it crosses over the femoral
vessels, and is directed distally over or through the sartorius muscle, and beneath
TH THORACIC - { j - - HT9 THORACIC
, N ^_ - 1 2T" THORACIC
\ ^BB tLIO-HYPOGASTRIC
Sir
- -I lUO-INGUINAL
I2T M THORACIC
GENITO-FEMORAL
LATERAL CUTANEOUS N.\
/
OF THE THIGH
L.I
V^LsU. ^ f POSTERIOR CUTANEOUS N.
VJI- - "\OF THE T.HIftM
INTERMEDIATE CUTANEOUS RAMI
LATERAL CUTANEOUS
OF THE LEG
SUPERFICIAL PERONEAL N.
SURAU N.
"4 \ OBTURATOR
-MEDIAL CUTANEOUS RAMI
' INFRAPATELLAR BR.
SAPHENOUS N.
] L2Z
L.2.3
L.3.4
L.3.4
DEEP PCRONEAL N.
A B
FIG. 627. DISTBIBUTION OF CUTANEOUS NERVES ON THE FRONT OF THE LOWER LIMB.
On the left side the distribution of the several nerves is represented in colour.
On the right side a schematic representation is given of the areas supplied by the above nerves, the figures
indicating the spinal origin of the branches of distribution to each area.
the fascia lata, to the distal third of the thigh. It is distributed to the skin of
the distal two-thirds of the thigh on the medial side by means of three branches
proximal, middle, and distal.
The proximal branch may be represented by two or more twigs. It arises
from the main nerve near its origin, and pierces the fascia lata near the apex of
the femoral triangle. It is distributed to the skin of the proximal part of the
thigh, along the line of the great saphenous vein. The middle or anterior branch is
a larger nerve. It separates from the distal branch at the apex of the femoral
triangle, and passing over the sartorius muscle becomes cutaneous in the middle
47 a
726 THE NEKVOUS SYSTEM.
third of the thigh on the medial side. It supplies the skin of the distal half of
the thigh, extending as far as the knee, where it joins in the formation of the
patellar plexus.
The distal branch represents the termination of the nerve. It passes along the
medial side of the thigh over the sartorius muscle, and communicates in the
middle third of the thigh with the saphenous and obturator nerves to form the
obturator plexus. Piercing the fascia lata on the medial side of the thigh in the
distal third, it ramifies over the side of the knee, and assists in the formation of
the patellar plexus.
The size of the medial cutaneous nerve varies with the size of the cutaneous
part of the obturator, and of the saphenous nerve.
N. Saphenus. The saphenous nerve may be regarded as the terminal branch
of the femoral nerve. It is destined for the skin of the leg and foot. From its
origin in the femoral triangle it extends distally alongside the femoral vessels to
the adductor canal. In the canal it crosses obliquely over the femoral sheath
from lateral to medial side. At the distal end of the canal, accompanied by the
saphenous branch of the arteria genu suprema, it passes over the tendon of the
adductor magnus, and opposite the medial side of the knee-joint becomes cutaneous
by passing between the sartorius and gracilis muscles. The nerve then extends
distally in the leg along with the great saphenous vein, and coursing over the front
of the medial malleolus it terminates at the middle of the medial border of the foot.
Branches. 1. A communicating branch arises in the adductor canal, and,
passing medially behind the sartorius, joins with branches of the obturator nerve
in forming the obturator plexus.
2. Ramus Infrapatellaris. The infra-patellar branch arises at the distal end of
the adductor canal, and piercing the sartorius muscle is directed distally and
forwards below the patella, and over the medial condyle of the tibia to the front
of the knee and proximal part of the leg. It enters into the formation of the
patellar plexus.
3. An articular branch sometimes arises from the nerve at the medial side of
the knee.
4. Rami Cutanei Cruris Mediales. The terminal branches of the saphenous nerve
are distributed to the skin of the front and medial side of the leg and the
posterior half of the dorsum and medial side of the foot.
Plexus Patellaris. The patellar plexus consists of fine communications
beneath the skin in front of the knee, between the branches of the cutaneous
nerves supplying that region. The nerves which enter into its formation are
the infra-patellar branch of the saphenous, medial and intermediate cutaneous
nerves, and sometimes the lateral cutaneous nerve of the thigh.
The accessory obturator nerve (n. obturatorius accessorius) is only occasionally present (29
per cent., Eisler). It arises from the third, or third and fourth lumbar nerves, between the roots
of the obturator and femoral nerves. Associating itself with the obturator, from which, however,
it is quite separable, it appears in the abdomen at the medial side of the psoas muscle, and
coursing over the pelvic brim behind the external iliac vessels, it leaves the obturator nerve, and
enters the thigh in front of the os pubis.
In the thigh, behind the femoral vessels, it usually ends in three branches : a nerve which
replaces the branch from the femoral nerve to the pectineus, a nerve to the hip-joint, and a
nerve which communicates with the superficial part of the obturator nerve. In some cases it
only supplies the nerve to the pectineus ; more rarely it is of considerable size, and reinforces the
obturator nerve in the inner vation of the adductor muscles.
The accessory obturator nerve was first described by Winslow as the n. accessorius anterioris
cruralis. Schmidt later described it in great detail, and gave it the name it now bears. It is
more closely associated with the femoral than with the obturator. Its origin is behind the roots
of the obturator : it is separated, like the femoral, from the obturator by the pubic bone, and
its chief branch, to the pectineus muscle, replaces the normal branch from the femoral nerve.
On the other hand, for a part of its course it accompanies the obturator, and in rare cases it
may replace branches of that nerve.
SACEAL PLEXUS/ 727
PLEXUS SACRAL1S.
The sacral portion of the luinbo-sacral plexus is destined almost entirely
for the lower limb. It is usually formed by the anterior rami of a part of the
fourth lumbar nerve (n. furcalis), the fifth lumbar, the first, and parts of the
second, and third sacral nerves (n. bigeminus).
Communications with the Sympathetic. Each of the nerves named is connected
to the lumbar or pelvic sympathetic by gray rami communicantes, as already described ;
and ivhite rami communicantes pass from the third and usually also from the second
or fourth sacral nerves to join the pelvic plexus of the sympathetic.
Position and Constitution. The plexus is placed on the posterior wall of the
pelvis between the parietal pelvic fascia and the piriformis muscle. In front of it
are the pelvic colon, the hypogastric vessels, and the ureter.
The plexus is constituted by the convergence of the nerves concerned towards
the inferior part of the greater sciatic foramen, and their union to form a broad
triangular band, the apex of which is continued through the greater sciatic
foramen below the piriformis muscle into the buttock, as the sciatic nerve.
From the anterior and posterior surfaces of this triangular band numerous small
branches arise, which are distributed to the parts in the neighbourhood of the
origin of the nerve.
The sciatic nerve ends in the thigh by dividing into two large nerves, the tibial
(O.T. internal popliteal), and common peroneal (O.T. external popliteal). In many
cases these two nerves are distinct at their origin, and are separated sometimes by
fibres of the piriformis muscle. In all cases, on removal of the sheath investing
the sciatic nerve, the tibial and peroneal nerves can be traced up to the plexus, from
which they invariably take origin by distinct and separate roots.
Formation. The descending branch of the fourth lumbar nerve (n. furcalis)
after emerging from the border of the psoas major muscle, medial to the obturator
nerve, divides behind the iliac vessels into anterior and posterior (ventral and dorsal)
parts, each of which joins a corresponding part of the fifth lumbar nerve. The
anterior ramus of the fifth lumbar nerve descends over the ala of the sacrum, and
divides into anterior and posterior parts, which are joined by the corresponding parts
of the fourth lumbar nerve. The two resulting trunks are sometimes called the
truncus lumbosacralis or lumbo- sacral trunk. The first and second sacral nerves pass
almost horizontally laterally from the anterior sacral foramina, and divide in
front of the piriformis into similar anterior and posterior parts. The third sacral
nerve (n. bigeminus) divides into superior and inferior parts. The inferior part is
concerned in forming the pudendal plexus. The superior part is directed laterally,
and slightly upwards, towards the second nerve, and does not separate into two
parts, but remains undivided.
These trunks combine to form the sacral plexus, and its main subdivisions,
in the following way. Lying in apposition, and converging to the lower part
of the greater sciatic foramen, the posterior (dorsal) trunks of the fourth and fifth
lumbar nerves (lum bo-sacral trunk), and of the first and second sacral nerves,
combine to form the common peroneal nerve and the subordinate nerves which arise
from the posterior aspect of the plexus. The anterior (ventral) trunks of the fourth
and fifth lumbar nerves (lumbo-sacral trunk), and of the first and second sacral
nerves, together with that part of the third sacral nerve which is contributed to the
plexus, unite to form the tibial nerve and the subordinate nerves arising from the
front of the plexus.
Of these nerves the fifth lumbar and first sacral are the largest; the others
diminishing in size as they are traced upwards and downwards. There is no
distinct demarcation between the sacral and pudendal plexuses. The second and
third sacral nerves (and in some cases the first sacral also) are concerned in the
formation of both plexuses.
Branches. The nerves of distribution derived from the sacral plexus are
divided according to their origin into an anterior (ventral) and a posterior (dorsal)
47 &
728
THE NEKVOUS SYSTEM.
series. Each set comprises one of the two essential terminal parts of the sciatic
peroneal and tibial nerves and numerous smaller collateral branches.
Anterior (Ventral) Branches.
Tibial nerve
Muscular branches
Nerves to hamstring muscles
quadratus femoris
gemelli
obturator internus
Articular branches (to hip-joint)
Posterior (Dorsal) Branches.
Common peroneal nerve
Muscular branches
Nerves to short head of biceps
piriformis
Superior gluteal nerve
Inferior gluteal nerve
Articular branches (to knee-joint)
NERVUS ISCHIADICUS.
It has already been shown how the sciatic nerve is formed. It comprises the
two main nerves of the sacral plexus, bound together by an investing sheath, which
contains, in addition to the common peroneal and tibial nerves, a subordinate
branch of each, the nerve to the hamstring muscles, from the tibial, and the
nerve to the short head of the biceps femoris, from the peroneal nerve. A thick
band about half an inch in breadth is formed, consisting, from medial to lateral
side, of (1) nerves to the hamstring muscles, (2) tibial, (3) common peroneal,
(4) nerve to the short head of the biceps muscle. The sciatic nerve extends
through the buttock into the back of the thigh. Forming a continuation of the
sacral plexus, it enters the buttock by passing through the greater sciatic foramen,
in the interval between the piriformis and superior gemellus. Concealed by the
glutseus maximus muscle, it passes distally to the thigh, accompanied by the inferior
gluteal artery, and the arteria comitans nervi ischiadici. It lies in the hollow
between the greater trochanter of the femur and the tuberosity of the ischium, and
enters the thigh beneath the fold of the nates at the lower border of the glutseus
maximus. At that spot it is comparatively superficial, lying in the angle between
the edge of the glutseus maximus above and laterally, and the origins of the ham-
string muscles medially. In the thigh it is placed upon the adductor magnus,
anterior to the hamstring muscles, and it terminates at a variable point by dividing
into the tibial and common peroneal nerves. As already stated, these two nerves
may be separate from their origins, and their separation may occur at any point
between the greater sciatic foramen and the proximal part of the popliteal fossa.
THE NERVES OF DISTRIBUTION FROM THE SACRAL PLEXUS.
These are divisible into two series collateral and terminal branches. Each
subdivision consists of a series of anterior and posterior trunks.
1. Collateral Branches. The anterior branches are (a) muscular branches (to
the quadratus femoris, gemelli, obturator internus, and hamstring muscles); and
(6) articular branches (to the hip-joint). These nerves all arise from the anterior
aspect of the sacral plexus.
The nerve to the quadratus femoris (and inferior gemellus) arises from the
front of the fourth and fifth lumbar and first sacral nerves. It passes downwards
over the back of the capsule of the hip-joint (to which it sends a fine branch) beneath
the sacral plexus, gemelli, and obturator internus muscles. It supplies a nerve to
the inferior gemellus, and terminates in the deep surface of the quadratus femoris.
The nerve to the obturator internus (and superior gemellus) arises from the
anterior aspect of the fifth lumbar and first two sacral nerves. In the buttock it
lies medial to the sciatic nerve on the lateral side of the pudendal vessels ; crossing
the ischial spine, it enters the ischio-rectal fossa through the lesser sciatic foramen.
The nerve supplies, in the buttock, a branch to the superior gemellus, and terminatee
by entering the pelvic surface of the obturator internus.
The nerve to the hamstring muscles forms the most* medial part of the
sciatic trunk in the lower part of the buttock. It arises from all the roots of the
tibial nerve on their anterior aspect, viz., from the fourth and fifth lumbar anc
NEEVES OF DISTRIBUTION FROM THE SACKAL PLEXUS. 729
the first three sacral nerves. These roots unite to form a cord which is closely
associated with the tibia! nerve and is placed in front of it and afterwards on its
medial side. Extending into the thigh, the trunk is distributed to the hamstring
muscles by means of two sets of branches. Just distal to the ischial tuberosity
a proximal set of nerves enters the proximal part of the semitendinosus and the
ischial head of the biceps. More distally in the thigh the remaining portion of
the nerve separates off from the tibial part of the sciatic trunk and supplies
branches to the seminiembranosus, the distal part of the semitendinosus, and
the adductor magnus.
Articular branches for the hip-joint arise from the nerve to the quadrat us
femoris, and often directly from the anterior surface of the tibial part of the
sciatic nerve near its origin. They enter the back of the capsule of the joint in
the region of the buttock.
The posterior branches are : (a) muscular branches a nerve to the piriformis,
the superior gluteal nerve, the inferior gluteal nerve, and a nerve to the short head
of the biceps ; (6) articular branches (to the knee-joint).
These nerves all arise from the posterior aspect of those roots of the sacral
plexus, which are associated with the origin of the common peroneal nerve.
The nerve to the piriformis muscle may be double. It arises from the back
of the second, or first and second sacral nerves, and at once enters the anterior
surface of the muscle.
N. Glutaeus Superior. The superior gluteal rierve arises from the posterior
surface of the fourth and fifth lumbar and first sacral nerves, and is directed
backwards and laterally into the buttock, above the piriformis muscle, along with
the superior gluteal artery. Under cover of the glutseus maximus and glutseus
medius, it passes over the glutseus minimus, along with the inferior branch of the
deep division of the superior gluteal artery, to the deep surface of the tensor fasciae
latse, in which it ends. On its way it supplies branches to the glutseus medius
and glutseus minimus muscles.
N. Glutaeus Inferior. The inferior gluteal nerve arises from the posterior
surface of the fifth lumbar and first two sacral nerves. It appears in the buttock
at the lower border of the piriformis muscle, superficial to the sciatic nerve, and at
once breaks up into a number of branches for the supply of the glutseus maximus.
In its course in the buttock it is closely associated with the posterior cutaneous
nerve of the thigh. Its origin is sometimes combined with that of the following
nerve.
The nerve to the short head of the biceps springs from the lateral side of the
common peroneal trunk in the proximal part of the thigh. When traced to its
origin, it is found to arise (sometimes in combination with the inferior gluteal nerve)
from the fifth lumbar and first two sacral nerves. In its course it is closely
applied to the common peroneal nerve, from which it separates in the middle third of
the thigh, usually in combination with the articular branches of that nerve for the
knee-joint. In some cases it has an independent course in the thigh, and it may
be associated in the buttock with the inferior gluteal nerve.
An articular branch for the lateral and anterior aspects of the knee-joint
generally arises from the common peroneal nerve in common with the nerve to the
short head of the biceps. When traced up to the plexus, it is found to arise from
the posterior surface of the fourth and fifth lumbar and first sacral nerves. It passes
through the proximal part of the popliteal fossa concealed by the biceps muscle,
and separates into proximal and distal branches, which accompany the superior
and inferior lateral articular arteries to the knee-joint.
Terminal Branches. The common peroneal (O.T. external popliteal) and tibial
(O.T. internal popliteal) nerves are the two main trunks resulting from the com-
bination of the posterior and anterior cords of the sacral plexus respectively. The
common peroneal nerve is homologous with the radial nerve of the upper limb ;
the tibial nerve represents a medio-ulnar trunk ; and, as already stated, the two
nerves, constituting the sciatic nerve, are enveloped in a common sheath for a
variable distance before pursuing an independent course in the leg.
730 THE NERVOUS SYSTEM.
NERVUS PERON.EUS COMMUNIS.
The common peroneal (O.T. external popliteal) nerve arises from the posterior
part of the sacral plexus from the fourth and fifth lumbar and first two sacral
nerves. Incorporated with the sciatic nerve in the buttock and proximal part of
the thigh, it passes distally from the bifurcation of that nerve through the popliteal
fossa, to its termination at a point about an inch distal to the head of the fibula. It
is concealed at first by the biceps muscle. Following the tendon of that muscle, it
passes obliquely through the proximal and lateral part of the popliteal fossa and
over the lateral head of the gastrocnemius muscle to the posterior aspect of the
head of the fibula. In the distal part of its course it is quite superficial, but at
its termination it is covered by the peronseus longus muscle.
Collateral Branches. These are divided into two sets : (a) Nerves arising from
the roots or trunk of the nerve while it is in combination with the tibial nerve in
the sciatic trunk. These have been already described, as a muscular branch to the
short head of the biceps, and an articular branch to the knee-joint. (6) Nerves
arising in the popliteal fossa. These are cutaneous branches, viz., the lateral sural
nerve or lateral cutaneous nerve of the calf and the peroneal anastomotic ramus.
N. Cutaneus Surae Lateralis. The lateral sural branch is irregular in size
and distribution, and may be represented by two or more branches (Fig. 628, p. 731).
Arising from the common peroneal nerve in the popliteal fossa, often in common
with the succeeding nerve, it pierces the deep fascia over the lateral head of the
gastrocnemius, and is distributed to the skin on the lateral aspect of the back of
the leg in the proximal two-thirds. The extent of its distribution varies with
that of the posterior cutaneous nerve of the thigh and the nervus suralis.
Ramus Anastomoticus Peronseus. The peroneal anastomotic nerve (O.T. com-
municans fibularis), arising in the popliteal fossa, passes over the lateral head of
the gastrocnemius beneath the deep fascia to the middle third of the leg, where
it assists in forming the nervus suralis by its union with an anastomotic (communi-
cating) branch of the tibial nerve called the medial sural nerve or medial cutaneous
nerve of the calf. In many cases the two branches do not unite. In such cases
the peroneal anastomotic nerve may be limited in its distribution to the skin of
the lateral side of the leg, heel, and ankle, or it may be distributed to the area
usually supplied by the nervus suralis.
Terminal Branches. The terminal branches of the common peroneal nerve
are three in number : recurrent tibial, deep peroneal (O.T. anterior tibial), and
superficial peroneal (O.T. musculo-cutaneous). They arise just distal to the head of
the fibula, and are directed forwards, diverging in their course, beneath the peroneus
longus muscle.
The recurrent tibial nerve is the smallest branch. Passing forwards under cover
of the origin of the peronseus longus and the extensor digitorum longus muscles, it
divides, distal to the lateral condyle of the tibia, into branches which supply the
proximal fibres of the tibialis anterior muscle, the proximal tibio-fibular articula-
tion, and the knee-joint.
NERVUS PERONSEUS PROFUNDUS.
The deep peroneal nerve (O.T. anterior tibial) passes obliquely distally,
under cover of the peronseus longus, extensor digitorum longus, and extensor hallucis
longus muscles, to the front of the leg. In its course it is deeply placed upon the
interosseous membrane and the distal part of the tibia, in company with the
anterior tibial artery. At the ankle it lies under cover of the transverse ligament
of the leg and the tendon of the extensor hallucis longus, and, crossing the ankle-
joint, it divides on the dorsum of the foot into its terminal branches.
1. Collateral Branches (in the leg). These are given off to the muscles between
which the deep peroneal nerve passes, namely : tibialis anterior, extensor hallucis
longus, extensor digitorum longus, and peronseus tertius. A fine articular branch
surmlies the ankle-ioint.
SUPEKFICIAL PEKONEAL NEKVE.
731
2. Terminal Branches (on the foot). The terminal branches are medial and
lateral. The medial branch passes along the dorsum of the foot, on the lateral
side of the dorsalis pedis artery, to the first interosseous space, where it divides
into two dorsal digital branches for the supply of the skin of the lateral side of
the great toe and the medial side of the second toe (nervi digitales dorsales,
hallucis lateralis et digiti secundi medialis). Each of these branches communicates
with branches of the superficial peroneal (O.T. musculo-cutaneous) nerve. It
gives off one or two dorsal interosseous branches, which supply the medial tarso-
metatarsal and metatarso-phalangeal articulations, and enter the first dorsal
interosseous muscle.
The lateral branch, passes obliquely over the tarsus under cover of the extensor
digitorum brevis, and ends in a gangliforin enlargement (similar to the gangliform
enlargement on the dorsal interosseous nerve of the forearm at the back of the
wrist). From this enlargement muscular branches arise for the supply of the
extensor digitorum brevis, along with branches for the tarsal, tarso-metatarsal,
and metatarso-phalangeal articulations. Its dorsal interosseous branches may be
as many as four in number. Of these the lateral two, extremely small, may only
reach the tarso-metatarsal articulations. The medial two are fine branches, which,
besides supplying the articulations, may give branches to
the second and third dorsal interosseous muscles.
The branches from the nerve to the interosseous
muscles are probably sensory, the motor supply of these
muscles being certainly derived from the lateral plantar
nerve.
NERVUS PERON^IUS SUPERFICIALIS.
The superficial peroneal nerve (O.T. musculo-
cutaneous), the last of the branches of the common
peroneal nerve, passes distal to the head of the fibula and
under cover of the proximal fibres of the peronseus longus
muscle. Lying in a sheath in the intermuscular septum,
between the peronsei and the extensor digitorum longus,
it proceeds distally in front of the fibula to the distal
third of the leg, where it pierces the deep fascia in two
branches, medial and lateral.
Its branches are : (1) collateral muscular branches dis-
tributed to the peronaeus longus and peronseus brevis, as
the nerve lies in relation to these muscles ; (2) terminal
cutaneous branches, medial and lateral.
Nn. Cutanei Dorsales Medialis et Intermedius.
The medial terminal branch (n. cutaneus dorsalis medialis)
courses distally over the transverse ligament of the leg, and
after supplying offsets to the distal third of the leg and to the
dorsum of the foot, divides into three branches. (1) The
most medial branch supplies the skin of the dorsum of the
foot and the medial side of the great toe, and communicates
with the saphenous nerve. (2) The intermediate branch
passes to the interval between the great toe and the second,
and divides into two branches which communicate with
the medial branch of the deep peroneal nerve. (3) The
lateral branch passes to the interval between the second
and third toes, and divides into dorsal digital branches to
supply the adjacent sides of these toes.
The lateral terminal branch (n. cutaneus dorsalis intermedius) of the nerve passes
over the transverse ligament of the leg, and after supplying branches to the distal
part of the leg and to the dorsum of the foot, divides into two parts, which, passing
to the intervals between the third and fourth, and fourth and fifth toes respectively,
divide into dorsal digital branches for the adjacent sides of these toes. These
branches communicate with offsets of the nervus suralis (nerve of the calf).
E.P
FIG. 628. DISTRIBUTION OF
CUTANEOUS NERVES ON THE
DORSUM OF THE FOOT.
I.S, Saphenous nerve ; M.C,
Superficial peroneal nerve ;
A.T, Deep peroneal nerve ;
E.S, Nervus suralis. The
extremities of the toes are
supplied by the medial
and lateral plantar nerves
(I.P, E.P).
732 THE NEEVOUS SYSTEM.
The arrangement of the cutaneous branches of the superficial peroneal nerve is liable
to considerable variation. The lateral division of the nerve may be increased in size, and
may supply the nerve to the adjacent sides of the second and third toes ; or it may be reduced
in size, in which case the nervus suralis takes its place on the dorsum of the foot, often supply-
ing as many as two and a half toes on the lateral side.
The cutaneous nerves on the dorsum of the toes are much smaller than the corresponding
plantar digital nerves. They are reinforced on the dorsum of the terminal phalanges by twigs
from the plantar nerves, which supply the tips of the toes and the nails.
NERVUS TIBIALIS.
The tibial nerve (O.T. internal popliteal) arises from the anterior surface
of the sacral plexus, usually from the fourth and fifth lumbar and first three
sacral nerves (Fig. 631, p. 736). It is incorporated in the sciatic trunk in the
buttock and proximal part of the thigh. At the bifurcation of the sciatic nerve
it passes onwards through the popliteal fossa and the back of the leg. The part
of the nerve from its origin from the plexus or the bifurcation of the sciatic nerve
to the distal border of the popliteus muscle, was formerly called internal popliteal;
the part of the nerve in the back of the leg being then designated posterior tibial.
The course of the nerve through the buttock and thigh has already been described
(p. 728). In the popliteal fossa it is concealed at first by the semimembranosus and
the other hamstring muscles. It passes to the medial side of the popliteal vessels,
and is thereafter found upon the popliteus muscle, under cover of the gastrocnemius
and plantaris. In the back of the leg, from the distal border of the popliteus
muscle to the ankle, the tibial (O.T. posterior tibial) nerve lies on the tibialis
posterior muscle and the tibia, and, along with the posterior tibial vessels, occupies
a sheath in the intermuscular septum separating the superficial and deep muscles
of the back of the leg. In the proximal part of the leg the nerve is medial to
the vessels, but, crossing behind them, it lies on their lateral side in the distal
portion of its course. It terminates under cover of the ligamentum laciniatum by
dividing into the lateral and medial plantar nerves.
The collateral branches may be divided into three series, arising respectively
in the region of the thigh, the popliteal fossa, and -the back of the leg :
(a) Branches arising from the Hoots or Trunk of the Nerve while it is incor-
porated with the Sciatic Nerve. These have been already described as muscular
branches to the quadra tus femoris, gemelli, obturator internus, and the hamstring
muscles, and an articular branch to the hip-joint (Fig. 631, p. 736).
(b) Branches arising in the Popliteal Fossa proximal to the Knee-Joint,
These are in three sets articular, muscular, cutaneous.
1. The articular branches are slender nerves, variable in number. There are
usually two, an azygos branch which pierces the oblique ligament of the knee-
joint, and a medial branch, a long fine nerve which, crossing the popliteal vessels,
runs distally on the medial side of the fossa to accompany the distal medial articular
artery to the knee-joint. In its course it gives off a branch, often absent, which
accompanies the proximal medial articular artery.
2. The muscular branches are five in number. Nerves for the two heads of
the gastrocnemius, and for the plantaris enter those muscles at the borders of the
popliteal fossa. A nerve for the soleus enters the superficial surface of the
muscle. A nerve for the popliteus muscle passes over the surface of that muscle,
and after winding round its distal border, supplies it on its deep (anterior) surface.
As this nerve passes below the popliteus it supplies branches to the tibialis
posterior, an inter osseous branch for the interosseous membrane, which can be
traced as far as the tibio-fibular syndesmosis, an articular branch for the
proximal tibio-fibular joint, and a medullary branch for the shaft of the tibia.
3. N. Cutaneous Surae Medialis (O.T. N. Communicans Tibialis). The
cutaneous branch is the medial cutaneous nerve of the leg. This nerve passes
from the popliteal fossa in the groove between the two heads of the gastrocnemius
muscle, and afterwards lies upon the tendo calcaneus. It pierces the deep fascia
in the middle third of the back of the leg, and is joined immediately afterwards
by the peroneal anastomotic ramus from the common peroneal nerve. From
TIBIAL NEEVE.
733
their union the nervus suralis results, which reaches the foot, winding round
the back of the lateral malleolus, along with the small saphenous vein. - The
nervus surah's supplies cutaneous branches to the lateral side and back of the
distal third of the leg, the ankle and heel, and the side of the foot and little toe,
as well as articular branches to the ankle and tarsal joints.
ILIO-HYPOGASTRIC
- /POSTERIOR CUTANEOUS N.
THE THIGH
[LATERAL CUTANEOUS N.
I OF THE THIGH
S.1.23
S.l.2.3
MEDIAL CUTANEOUS
SAPHENOUS N.
S12.3
f LATERAL CUTANEOUS N.
\Qf THE LEG
-SUPERFICIAL PERONEAL N.
..4.S.S.I '
134
-H SUHAL N
CALCANEAN N. 1
MEDIAL PLANTAR N. 1
\ LATERAL PLANTAR N.
LAS
A B
FIG. 629. DISTRIBUTION OF CUTANEOUS NERVES ON THE BACK OF THE LOWER LIMB.
In A the distribution of the several nerves is represented, their names being given.
a schematic representation is given of the areas supplied by the above nerves, the figures indicating
the spinal origin of the branches of distribution to each centre.
nervus suralis communicates on the foot with the superficial peroneal nerve, and its
size varies with the size of that nerve. It may extend on to the dorsum of the foot for
a considerable distance, and may either reinforce or replace the branches of the above-
named nerve to the intervals between the fourth and fifth and the third and fourth
toes. The mode of formation of the nervus suralis is very variable. The usual arrange-
ment is that described. Frequently the peroneal anastomotic nerve and the medial sural
nerve (medial cutaneous nerve of the leg) do not unite, and in such cases the more usual
arrangement is for the tibial trunk alone to form the nervus suralis (nerve of the calf),
734 THE NEEVOUS SYSTEM.
the peroneal anastomotic ramus extending only to the ankle and heel. It is less usual
for the peroneal anastomotic ramus alone to form the nervus suralis, the medial sural
nerve in these cases ending at the heel.
(c) Branches arising in the Back of the Leg distal to the Knee- Joint. These
branches are mainly muscular and cutaneous.
The muscular branches are four in number, comprising nerves to the soleus
(entering its deep surface) and tibialis posterior, often arising by a common trunk,
and nerves to the flexor digitorum longus and flexor hallucis longus, the latter
generally accompanying the peroneal artery for some distance.
Rami Calcanei Mediales. The cutaneous branches are the medial calcanean
rami, which pierce the ligamentum laciniatum, and is distributed to the skin
of the heel and posterior part of the sole of .the foot.
In addition, a medullary nerve to the fibula, and a small articular branch to
the ankle-joint, are supplied by the tibial nerve.
The terminal branches of the tibial nerve are the medial and lateral
plantar nerves.
NERVUS PLANTARIS MEDIALIS.
The medial plantar nerve is homologous with the median nerve in the hand
(Fig. 629, p. 733). It is rather larger than the lateral plantar. It courses
forwards in the sole of the foot, under cover of the ligamentum lanciniatum
and abductor hallucis, to the interval between that muscle and the flexor digitorum
brevis, in company with the medial plantar artery.
The collateral branches are muscular, cutaneous, and articular. The muscular
branches supply the abductor hallucis and the flexor digitorum brevis. The plantar
cutaneous branches are small twigs which pierce the plantar aponeurosis in the
interval between these muscles to supply the medial part of the sole of the foot.
The articular branches are minute twigs which supply the tarsal and tarso-
metatarsal articulations.
Nn. Digitales Plantares Communes. The terminal branches are four in
number, the common plantar digital nerves, and. may be designated first, second,
third, and fourth, from medial to lateral side.
The first (most medial) branch separates from the nerve before the others,
and pierces the plantar aponeurosis behind the ball of the great toe. It supplies
a muscular branch to the flexor hallucis brevis, and cutaneous branches to the
medial side of the foot and ball of the great toe. It terminates as the plantar
digital nerve for the medial side of the great toe.
The second branch arises along with the third and fourth; after supplying ai
branch to the first lumbrical muscle, it becomes superficial in the interval between
the first and second toes, and terminates by dividing into two proper digital
nerves for the supply of the adjacent sides of these toes.
The third and fourth branches are entirely cutaneous in their distribution. They j
become superficial in the intervals between the second and third and the third
and fourth toes, respectively, and there divide into proper digital branches for
the supply of the adjacent sides of these toes.
Nn. Digitales Plantares Proprii. The plantar proper digital nerves supply
the whole length of the toes on the plantar aspect, and, in relation to the terminalj
phalanges, 'furnish minute dorsal offsets for the supply of the nails and tips oi|
the toes on their dorsal surface.
The medial plantar nerve thus supplies the skin of the three and a half medial j
toes in the sole of the foot; and four muscles: the abductor hallucis and flexor:
digitorum brevis, the flexor hallucis brevis, and the first lumbrical muscle.
NERVUS PLANTARIS LATERALIS.
The lateral plantar nerve is homologous with the ulnar nerve in the hand
From its origin, under cover of the ligamentum laciniatum, it extends forward f
PUDENDAL PLEXUS.
735
and laterally in the sole^ in company with the lateral plantar artery, between
the flexor digitorum brevis and the quadratus plantse, towards the base of the
fifth metatarsal bone. There it terminates by dividing
into superficial and deep branches.
Collateral Branches. Muscular branches are given off
from the undivided nerve to the quadratus plantse and
abductor digiti quinti muscles. Cutaneous branches pierce
the plantar fascia at intervals along the line of the inter-
muscular septum, between the flexor digitorum brevis and
abductor digiti quinti.
Terminal Branches Ramus Superficialis. The super-
ficial branch is mainly cutaneous. Passing forwards be-
tween the flexor digitorum brevis and abductor digiti
quinti, it divides into lateral and medial parts.
The- lateral branch, after supplying the flexor quinti
digiti brevis muscle, and sometimes one or both interossei
of the fourth space, becomes superficial behind the ball
of the little toe, and supplies cutaneous twigs to the sole of
the foot and ball of the toe. It terminates as the proper
digital branch for the lateral side of the little toe.
The medial branch passes forwards to the interval
between the fourth and fifth toes, where it becomes
cutaneous, and divides into two proper digital branches
for the supply of the adjacent sides of these toes. It
communicates with the fourth terminal branch of the FlG - 630. SCHEME OF DISTRI-
j- 1 T BUTION OP THE PLANTAR
medial plantar nerve. NERVES
Ramus Profundus. The deep branch of the lateral In brown ^ medial plantar nerve>
plantar nerve, passing deeply along with the lateral and its cutaneous and mus-
plantar artery, extends medially towards the great toe,
under cover of (i.e. dorsal to) the quadratus plantse and
oblique head of the adductor hallucis. It gives off
articular branches to the tarsal and tarso-metatarsal joints,
and muscular branches to the interossei of each space
(except in some cases the muscles of the fourth space) :
to the adductor hallucis, and the lateral three lumbrical
muscles. These nerves enter the deep surface of the
muscles, that to the second lumbrical reaching its muscle
after passing forwards dorsal to, the transverse head of the adductor hallucis.
cular branches ; F.B.D,
Flexor digitorum brevis; A.H,
Abductor hallucis ; F.B.H,
Flexor hallucis brevis ; L.I,
First lumbrical. In green,
lateral plantar nerve, and its
cutaneous and muscular
branches ; Quad. P, Quadratus
plantse ; A.D.Q, Abductor
digiti quinti; F.B.D.Q, Flexor
brevis digiti quinti.
,
PLEXUS PUDENDUS.
The pudendal plexus constitutes the third and last subdivision of the lumbo-
sacral plexus. It is composed, for the most part, of the spinal nerves below
those which form the sacral plexus; but, as already stated, there is no distinct
point of separation between the two plexuses. On the contrary, there is con-
siderable overlapping, so that two and sometimes three of the principal nerves
derived from the pudendal plexus have their origin in common with nerves of the
sacral plexus.
The plexus is formed by fibres from the anterior rami of the first three
sacral nerves, and by the whole of the anterior rami of the fourth and fifth sacral
( and coccygeal nerves. The size of the nerves diminishes rapidly from the first
sacral to the coccygeal, which is extremely slender.
Position and Constitution. The plexus is formed on the posterior wall of
the pelvis. Of the nerves forming it, the upper ones emerge from the anterior
sacral foramina ; the fifth sacral nerve appears between the last sacral and first
coccygeal vertebra; and the coccygeal nerve appears below the transverse pro-
cess of that vertebra. The nerves of distribution derived from the plexus are the
following :
736
THE NEKVOUS SYSTEM.
1. Visceral branches. 4. Pudendal nerve.
2. Posterior cutaneous nerve of the thigh. 5. Muscular branches.
3. Perforating cutaneous nerve. 6. Ano-coccygeal nerve.
All the nerves, except the visceral branches, are distributed to the perineum.
LATERAL CUTANEOUS
NERVE OF THE THKH
WHITE RAMUS
84
SCIATIC
FIG. 631. NERVES OF THE LUMBO-SACRAL PLEXUS.
Only two, the posterior cutaneous nerve of the thigh and the perforating cutaneous
nerve, send branches to the lower limb.
Visceral Branches. Like the other spinal nerves, the fourth and fifth sacra
and coccygeal nerves are provided with fine gray rami communicantes fronc
the sacral sympathetic trunk, which join them after a short course on the front o
PUDENDAL PLEXUS. 737
the sacrum. The third (along with the second or fourth) sacral nerve, in addition,
sends a considerable white ramus communicans or visceral branch direct to the
pelvic plexus and viscera.
N. Cutaneus Femoris Posterior Posterior Cutaneous Nerve of the Thigh
(O.T. Small Sciatic). This nerve is complex both in origin and distribution
(Fig. 631, p. 736). Springing from the junction of the sacral and pudendal
plexuses, it is derived from the first three or second and third sacral nerves. It
is distributed to the lower limb and perineum, and is associated with other nerves
belonging to both regions. It arises from the back of the roots of the sacral
plexus in the pelvis. Its higher roots from the first and second sacral nerves
are intimately associated with the origin of the inferior gluteal nerve-; its lowest
root from the third sacral nerve is associated with the origins of the perforating
cutaneous or of the pudendal nerve. It enters the buttock through the greater
sciatic notch, below the piriformis, along with the inferior gluteal artery and nerve.
Proceeding distally, posterior to the sciatic nerve, it enters the thigh at the
lower border of the glutseus maximus muscle, where it gives off considerable
branches. Becoming gradually smaller as it courses distally over the hamstring
muscles to the popliteal fossa, it finally pierces the popliteal fascia in one or more
cutaneous branches, which supply the skin over the calf of the leg for a variable
distance (Fig. 629, p. 733).
Branches. The nerve is purely cutaneous. It supplies branches to the
perineum, buttock, thigh, and leg.
Kami Perineales. The perineal branch arises at the lower border of the
gluteeus maximus muscle (Fig. 631, p. 736). It sweeps in a medial direction to
the perineum, lying on the origin of the hamstring muscles, distal to the ischial
tuberosity; and becoming subcutaneous after passing over the pubic arch, its
terminal branches supply the skin of the scrotum and root of the penis, or, in the
female, the labium inajus and clitoris, some of them being directed backwards
towards the anus and central point of the perineum. They communicate with
the inferior hsemorrhoidal and perineal branches of the pudendal nerve, and with
the ilio-inguinal nerve. In its course to the perineum the nerve gives off
collateral branches to the skin of the proximal and medial part of the thigh.
Nn. Clunium Inferiores. The inferior gluteal branches are large and numerous
(Fig. 631, p. 736). They arise from the nerve beneath the glutaeus maximus,
and become subcutaneous by piercing the fascia lata at different points along its
lower border. They supply the skin of the lower half of the buttock. The most
lateral branches, reaching to the back of the greater trochanter, overlap the terminal
filaments of the gluteal branches of the lateral cutaneous nerve of the thigh,
and the posterior rami of the first three lumbar nerves. The most medial branches,
which may pierce the sacro-tuberous ligament, reach nearly to the coccyx, and
are co-extensive in their distribution with the branches of the perforating cutaneous
nerve, which they reinforce and not infrequently replace.
The femoral branches are divisible into two sets medial and lateral. They
pierce the fascia lata of the thigh at intervals, and supply the skin of the back of
ihe thigh.
The sural branches are two or more slender nerves which pierce the fascia
)ver the popliteal fossa, and are distributed for a variable extent to the skin of
;he back of the leg. They may stop short over the popliteal fossa, or may extend
is far as the ankle. Usually they innervate the skin as far as the middle of the
ialf. They communicate with the nervus suralis.
In cases where the sciatic nerve is naturally divided at its origin into tibial and common
>eroneal nerves (e.g. by the piriformis muscle), the posterior cutaneous nerve also is separated into
wo parts : a posterior part, associated with the common peroneal nerve and arising in common
ath the lower roots of the inferior gluteal nerve (usually from the first and second sacral nerves),
, nd comprising the gluteal and lateral femoral branches ; and an anterior part, associated with
lie tibial nerve and arising usually from the second and third sacral nerves, along with the
erforating cutaneous and pudendal nerves, and comprising the perineal and medial femoral
ranches.
Perforating Cutaneous Nerve (n. perforans ligamenti tuberoso - sacri
Schwalbe), n. cutaneus clunium inferior medialis (Eisler)). This nerve arises
48
738 THE NEK VOUS SYSTEM.
from the back of the second and third sacral nerves (Fig. 631, p. 736). At
its origin it is associated with the lower roots of the posterior cutaneous nerve
of the thigh. Passing dis tally it pierces the sacro - tuberous ligament,
along with the coccygeal branch of the inferior gluteal artery ; and after winding
round the lower border of the glutseus maximus muscle, or in some cases piercing
its lower fibres, it becomes cutaneous a little distance from the coccyx, and supplies
the skin over the lower part of the buttock and the medial part of the fold of the
nates.
The perforating cutaneous nerve is not always present. In a minority of cases it is associated
at its origin with the pudendal nerve. When absent as a separate nerve, its place is taken by (1)
gluteal branches of the posterior cutaneous nerve of the thigh, or (2) a branch from the pudendal
nerve, or (3) a small nerve (n. perforans coccygeus major, Eisler), arising separately from the
posterior part of the third and fourth sacral nerves.
Muscular Branches. Between the third and fourth sacral nerves (occasion-
ally reinforced by the second, Eisler) a plexiform loop is formed, from which
muscular nerves are given off to the levator ani (supplying the muscle on its pelvic
surface), coccygeus, and external sphincter. The nerve to the external sphincter
(perineal branch of fourth sacral) pierces the sacro-tuberous ligament and the
coccygeus muscle, to which it gives offsets, and appears in the ischio-rectal fossa
between the glutseus maximus and the external sphincter. Besides supplying the
posterior fibres of the external sphincter, it distributes cutaneous offsets to the skin
of the ischio-rectal fossa and the fold of the nates behind the anus. This nerve,
in some instances, replaces the perforating cutaneous nerve.
Nn. Anococcygei (Ano-coccygeal Nerve). By the union of the remaining
part of the fourth with the fifth sacral and coccygeal nerves, the so-called
plexus coccygeus (coccygeal plexus) is formed. A fine descending branch of the
fourth sacral nerve passes over or through the sacro-tuberous ligament, to join the
fifth sacral nerve. This fifth sacral nerve, joined by the descending branch of the
fourth, descends alongside the coccyx and is again joined by the coccygeal nerve,
so that a plexiform cord, the ano-coccygeal nerve results, homologous with the inferior
caudal trunk of tailed animals. Fine twigs arise from it, which pierce the sacro-
tuberous ligament and supply the skin in the neighbourhood of the coccyx, medial
to the branches of the perforating cutaneous nerve and behind the anus.
NERVUS PUDENDUS.
The pudendal nerve (O.T. pudic) is the principal nerve for the supply of the
perineum. It arises in the pelvis usually by three roots from the second, third, and
fourth sacral nerves (Fig. 631, p. 736). (Frequently one of its branches, the inferior
hsemorrhoidal nerve, arises independently from the third and fourth sacral nerves.}
The nerve passes to the buttock through the greater sciatic foramen, below the
sciatic nerve, and lies on the sacro-spinous ligament, or the spine of the ischium
medial to the internal pudendal artery. It enters the perineum along with thf
artery through the lesser sciatic foramen. In the perineum it is deeply placed ir
the lateral wall of the ischio-rectal fossa, enclosed in a special sheath derivec
from the parietal pelvic fascia covering the medial surface of the obturator in
ternus muscle. At the anterior limit of the ischio-rectal fossa, the nerve approache
the surface and divides at the base of the urogenital diaphragm into it
terminal branches, the perineal nerve and the dorsal nerve of the penis.
The branches of the nerve are essentially the same in the two sexes. As ;
rule no branches are given off till it enters the perineum, but sometimes th
inferior hsemorrhoidal nerve has an independent origin from the plexus, rnerel
accompanying the pudendal nerve in the first part of its course ; and in exceptions
cases the perforating cutaneous nerve of the buttock is a branch of the pudenda
nerve.
Nn. Haemorrhoidales Inferiores. The inferior hsemorrhoidal nerve aris<
from the pudendal nerve under cover of the glutaeus maximus, at the posterior part <
the ischio-rectal fossa. In cases in which it has an independent origin from the plexu
it arises from the third and fourth sacral nerves. It crosses the ischio-rectal fos^
PUDENDAL NEKVE.
739
in company with the inferior haemorrhoidal vessels, and separates into numerous
branches muscular, cutaneous, and communicating.
The muscular branches end in the external sphincter ani muscle. The cutaneous
branches supply the skin around the anus. The communicating branches connect
the inferior hsemorrhoidal with three other nerves the perineal branches of the
posterior cutaneous nerve of the thigh, pudendal, and fourth sacral nerves.
Nervus Perinei. The perineal nerve, one of the two terminal branches of
the pudendal nerve, arises near the base of the urogenital diaphragm. It almost
immediately divides into two parts, superficial and deep.
The superficial part is purely cutaneous and consists of two nerves, the posterior
sterior scrotalj
nerves \
Perineal branch of
sterior cutaneous
nerve of thigh "
iperficial branch of
perineal nerve
Deep branch of"
perineal nerve""
Nervus perinei --
haemorrhoidal
branches
Dorsal nerve of penis
(displaced)
Nerve to corpus
cavernosum penis
Nerve to corpus
cavernosum urethra}
ir Superficial)
branches
of perineal
ne:
Perineal nerve
- Pudendal nerve
Inferior hsemorrhoidal
branches
--Pudendal nerve
FIG. 632. DISTRIBUTION OF THE PUDENDAL NERVE.
lateral and the anterior or medial superficial perineal nerves (nn. scrotales
posteriores or nn. labiales posteriores), which pass, along with the superficial perineal
vessels, to the anterior part of the perineum. The posterior or lateral superficial
perineal nerve, at the anterior limit of the ischio-rectal fossa, usually passes over the
base of the urogenital diaphragm and over the (superficial) trans versus perinei
muscle. The anterior or medial superficial perineal nerve, lying more deeply, pierces
the base of the fascia inferior of the urogenital diaphragm and goes underneath
or through the transversus perinei muscle. Becoming superficial in the anterior
(urethral) triangle of the perineum, they are distributed to the skin of the scrotum
(or labium majus), and communicate with the perineal rami of the posterior
cutaneous nerve of the thigh and with the inferior haemorrhoidal nerve.
The deep part of the perineal nerve is mainly but not entirely muscular
48 a
740
THE NEEVOUS SYSTEM.
Coursing forwards through the anterior part of the ischio-rectal fossa, it passes
between the two layers of fascia of the urogenital diaphragm towards the urethra.
It supplies muscular branches to the anterior parts of the levator ani and external
sphincter, to the transversus perinei superficialis and profundus, ischio-cavernosus,
bulbo-cavernosus (or sphincter vaginse), and sphincter urethrse membranacese. It
terminates as the nerve to the bulb, which, piercing the urogenital diaphragm,
enters the bulb of the urethra and supplies the erectile tissue of the bulb and
corpus cavernosum urethrae, as well as the mucous membrane of the urethra as far
as the glans penis.
N. Dorsalis Penis vel Clitoridis. The dorsal nerve of the penis or clitoris,
the other terminal branch of the pudendal nerve, accompanies the internal pudendal
artery above the fascia inferior of the urogenital diaphragm. It passes forward
close to the pubic arch, lying under cover of the crus and ischio-cavernosus and
fascia inferior of the urogenital diaphragm, and upon the sphincter urethrae mem-
branacese muscle ; piercing the fascia inferior of the urogenital diaphragm near
Nerve to obturator interims --T-
Puclendal nerve
Lumbo-sacral trunk
_ The anterior rami
^of the first four
sacral nerves
TTT-- Pudendal nerve
Perineal branch of
the fourth sacral
nerve
.Inferior
haemorrhoidal
Perineal branch
of pudendal nerve
Deep perineal nerve
Superficial perineal nerve
FIG. 633. THE ORIGIN AND COURSE OF THE PUDENDAL NERVE.
its apex, at the lateral side of the dorsal artery of the penis (or clitoris), it passes
on to the dorsum of the penis or clitoris, to which it is distributed in its distal
two-thirds, sending branches round the sides of the organ to reach its under surface.
In the female the nerve is much smaller than in the male. The dorsal nerve of
the penis supplies one branch, the nerve to the corpus cavernosum penis, as it lies
between the fasciae of the urogenital diaphragm. This is a slender nerve, which,
piercing the fascia inferior of the urogenital diaphragm, supplies the erectile tissue
of the crus and corpus cavernosum penis.
Morphology of the Pudendal Plexus. The structures occupying the perineum are placed
in the ventral axis of the body, and comprise, from before backwards, the penis and scrotum, or
mons Yeneris and vulva, the central point of the perineum, the anus and ischio-rectal fossa, and
the coccyx. They are placed on the medial side of the attachment of the lower limbs the penis
or mons Veneris in relation to the preaxial border ; the coccyx in relation to the postaxial border
of the limb.
The nerves of the perineum, thus reaching the ventral axis of the trunk, are homologous with
the anterior (ventral) terminations of other nerves. They are separable into two series. The
perineum is supplied mainly through the pudendal plexus by the last four sacral and the coccygeal
nerves, but it is also innervated to a minor extent by the first lumbar nerve through the ilio-
inguinal nerve, which reaches the root of the penis and the scrotum. The region is thus
supplied by two series of widely separated nerves, which have their meeting-place on the
dorsum and side of the penis and scrotum. This junction of the ilio-inguinal and pudendal
nerves constitutes the beginning of the ventral axial line, which extends peripherally along
MOEPHOLOGY OF THE LIMB-PLEXUSES.
741
the medial side of the lower limb. Apart from this break in their distribution, a definite
numerical order may be followed in the arrangement of the perineal nerves. The higher parts of
the perineum are innervated by the higher spinal nerves ; the lower parts, by the lower nerves.
This is best exemplified in the distribution of the cutaneous nerves. The base of the penis and
scrotum (or mons Veneris) is supplied by the first lumbar nerve (ilio-inguinal). The dorsal nerve
of the penis (or clitoris), when
traced back to the pudendal plexus,
is found to come from the second,
and to a less extent from the third
sacral nerves ; the scrotal nerves
(perineal branches of the pudendal
and posterior cutaneous nerve of
the thigh) similarly arise from the
third, and to a less extent from
the second sacral nerves ; the skin
of the ischio-rectal fossa and anus
is innervated by the inferior
hsemorrhoidal (third and fourth
sacral nerves), and the perineal
branch of the fourth sacral nerve.
The ano-coccygeal nerve (coccygeal
plexus), lastly, supplies the skin
round the coccyx (fourth and fifth
sacral and coccygeal nerves).
Judged from its nerve supply the
perineum is to be regarded as FIQ. 634. SCHEME of the ianervation of the hinder portion of the
occupying, for the most part, a trunk and of the perineum, and the interruption of the segmental
position behind or more caudal arrangement of the nerves associated with the formation of the
than that of the lower limb in re- limb.
lation to the trunk. There is here
a remarkable gap in the numerical sequence of the nerves supplying the ventral axis of the
body. All the nerves between the first lumbar and the second sacral fail to reach the mid ventral
line of the trunk and are wholly concerned in the innervation of the lower limb.
At the preaxial border of the limb (groin) the first lumbar nerve, the highest nerve supplying
the perineum, is concerned also in innervating the skin of the limb. At the postaxial border of
the limb (fold of the nates and back of the thigh), the nerves which are the highest of those con-
stituting the pudendal plexus (the second and third sacral nerves) are also implicated in inner-
vating that border of the limb. The fourth sacral nerve is concerned only to a very slight
extent in the innervation of the limb by means of the perineal branch, which reaches the
beginning of its postaxial border ; the last two spinal nerves are wholly unrepresented in the
limb proper and end entirely in the trunk behind the limb.
The arrangement of the limb nerves is rendered complex and the significance of the plexuses
is obscured by the changes through which, coincidently, the nerves, on the one hand, and the
parts supplied by them, on the other hand, have passed in the course of development
Nature of the Limbs. As already described, the mammalian limbs arise as flattened buds
from the extremities of the "Wolffian ridge. Each bud possesses a preaxial and a postaxial border,
and a dorsal and a ventral surface, continuous with the dorsal and ventral aspects of the trunk
and homologous with its lateral and ventral surfaces. Each bud consists at first of a mass of
I undifferentiated, unsegmented mesoderm, covered with epithelium. Around the central core of
mesoderm which produces the skeletal axis, the vessels and muscles of the limb are formed
in situ, the muscles as double dorsal and ventral strata, beneath the corresponding surfaces of
the bud.
Each limb bud is connected to the lateral and ventral aspects of the trunk, and is associated
with a number of body segments, varying in the two extremities and in different animals.
Although the mesodermal material of which the limb bud is composed exhibits in itself no
segmental divisions at any period of its development, a clear indication of the segmental relations
of the limbs is obtained from the arrangement of the limb nerves. Taking the nerves which
supply the limbs in man as a guide, the segments engaged in the formation of the upper ex-
tremity are the last five cervical and first two thoracic. The lower extremity is related by its
nerves to all the lumbar and the first three sacral segments. In each limb, the segments at the
preaxial and postaxial borders are only partially concerned in limb formation.
It has been already shown that the somatic branches of the nerves enter the substance of the
embryonic limb and divide in their course into dorsal and ventral trunks, which supply the
)rsal and ventral surfaces of the limb bud. The higher nerves supply the preaxial border, the
lower nerves supply the postaxial border, while the nerves most centrally situated extend furthest
towards the periphery of the limb.
In order to understand properly the constitution of the limb-plexuses, it is necessary, further,
to make a comparison of the surfaces and borders of the embryonic and adult limbs.
Upper Limb. (A) Borders. The preaxial border of the upper extremity extends from the
48 &
MORPHOLOGY OF THE LIMB-PLEXUSES.
742
THE NEEVOUS SYSTEM.
middle of the clavicle, in the line of the cephalic vein, distally along the front of the shoulder, the
lateral border of the arm, forearm and hand, to the lateral border of the thumb. The postaxial
border extends from the middle of the axilla along the medial side of the arm (in the line of
the basilic vein), the medial side of the forearm and hand, to the medial border of the little
finger.
(B) Surfaces. The areas of the limb between these lines, anteriorly and posteriorly, correspond
to the ventral and dorsal surfaces of the embryonic limb bud. The ventral surface is represented
by the front of the chest, arm, and forearm, and the palm of the hand. The dorsal surface is
represented by the scapular and deltoid regions, the back of the arm, forearm, and hand.
Lower Limb. (A) Borders. The preaxial border of the lower limb extends from the
middle of the inguinal ligament distally along the medial side of the thigh and leg in the
line of the great saphenous vein, to the medial side of the great toe. The postaxial border,
beginning at the coccyx, extends along the fold of the nates and the lateral border and back
of the thigh and leg (in the line of the small saphenous vein) to the lateral border of the foot
and little toe.
(B) Surfaces. The areas between these lines correspond to the primitive dorsal and ventral
surfaces of the embryonic limb bud. The unequal amount of rotation in the parts of the lower
limb obscures the relation of foetal and adult surfaces, which are most easily made out in the
infantile position of the limbs, with the thighs and knees flexed and the soles of the feet
inverted. The ventral surface of the embryonic limb is represented by the medial side and
posterior part of the thigh, the back of the leg, and the sole of the foot. The dorsal surface
is represented by the front of the thigh and buttock, the front of the leg, and the dorsum of
the foot.
Composition of the Limb-plexuses. In all mammals the same definite plan underlies the
constitution of the limb -plexuses. The nerves concerned are the anterior rami of certain
segmental spinal nerves, which (with certain exceptions at the preaxial and postaxial borders)
are destined wholly and solely for the innervation of the limb. Each of the anterior rami
engaged divides into a pair of secondary trunks, named dorsal or posterior, ventral or anterior.
The dorsal and ventral trunks again subdivide into tertiary trunks, which combine with the
corresponding subdivisions of neighbouring dorsal and ventral trunks to form the nerves of
distribution. The combinations of dorsal trunks provide a series of nerves for the supply of that
part of the limb which is derived from the dorsal surface of the embryonic limb bud ; the
combinations of ventral trunks give rise to nerves of distribution to the regions corresponding
to its ventral surface. The relation of the nerves derived from the limb-plexuses to the areas
of the limbs is given in the accompanying tables :
I. Upper Limb.
Origin.
Nerves.
Distribution.
/ Dorsal scapular .
1
Long thoracic
Suprascapular
Subscapular (2) .
Scapular region and
shoulder
Dorsal trunks
(Posterior cord)
Thoraco -dorsal
Axillary
Medial cutaneous nerve of the)
arm /
Arm, medial side
Dorsal
surface
Intercosto-brachial
Brachial
^Radial .
Back of arm, fore-
arm, and hand
Plexus
/Nerve to subclavius "i
Anterior thoracic (2) / '
Front of chest
Ventral trunks
(Lateral and
medial cords)
Musculo-cutaneous . . /
Medial cutaneous nerve of the \
arm . . . . . /
Medial cutaneous nerve of the j
Front of arm and
forearm
Medial side of arm
Front of arm and
Ventral
surface
forearm . . . . /
forearm
Median . . . . . \
Front of forearm and
v Ulnar ....
hand
MORPHOLOGY OF THE LIMB-PLEXUSES.
743
II. Lower Limb.
Origin.
Nerves.
Distribution.
Ilio-hypogastric (lateral
branch) ....
-
Superior gluteal ,
Inferior gluteal .
Buttock
Nerve to piriformis
Posterior cutaneous nerve of
Dorsal
Dorsal
trunks
the thigh ....
'Lateral cutaneous nerve of the^
Buttock and thigh, lateral side
surface
thigh . /
and front
/i
Genito-femoral (lumbo-|
inguinal branch) . . i
Front of thigh
Femoral . . . . |
Front and medial side of thigh,
leg, and foot
Peroneal ....
Front of leg and foot
Lumbo-
, /
sacral (
Plexus
^Ilio-hypogastric (anterior
branch)
Abdominal wall (ventral sur-^
face)
'
(
Ilio-inguinal . . . -j
Abdominal wall, thigh, and
perineum
Genito-femoral (external^
spermatic branch) . . J
(jrom
Ventral
Obturator . . . . |
Thigh (medial side) and knee
(back)
Ventra]
trunks
- Nerve to obturator internusA
and superior gemellus
surface
Nerve to quadra tus femoris t
and inferior gemellus
Buttock and back of thigh
Nerve to hamstrings
Posterior cutaneous nerve oH
the thigh J
Back of thigh and perineum
Tibial . . . . . |
Back of knee, leg, and sole of
foot J
norn<
thei
bord
the regions of the limbs no anterior cutaneous branches, derived from the limb nerves,
ply the trunk. The whole of the nerve is carried into the limb and is absorbed in its
ervation, and the dorsal and ventral trunks forming the limb-plexuses are to be looked upon
as homologous with the lateral and anterior trunks of an intercostal nerve. Two series of
anomalies in relation to the formation and distribution of the nerves to the limbs must, however,
be considered, because it has been suggested (Goodsir) that the nerves of the limbs are serially
homologous not with the whole, but only with the lateral branches of the anterior rami of
" e intercostal nerves.
(1) Nerves in connexion with the primitive borders of the Limbs. At the preaxial
er of the upper limb, at its root, the fourth cervical nerve, which supplies the anterior and
lateral surfaces of the neck, is also distributed through the supraclavicular nerves to the skin of
both ventral and dorsal surfaces of the limb. The nerves and surfaces are here not merely
homologous, but in actual continuity.
At the preaxial border of the lower limb, similarly, the first lumbar nerve, by means of the
ilio-hypogastric and ilio-inguinal branches, supplies on the one hand the buttock, in series with
the lateral branches of the lower thoracic nerves, and, on the other hand, the lower part of the
abdominal wall and the adjacent medial side of the thigh, in series with the anterior terminal
branches of the lower thoracic nerves.
At the postaxial border of the upper limb the first and second thoracic nerves are concerned
in supplying trunk segments as well as parts of the limb. The first thoracic nerve, besides
supplying the limb through the medial cord of the plexus, also innervates at least the muscles of
the first intercostal space ; the second thoracic nerve is concerned in the innervation of the limb,
principally by means of its lateral branch only, which, as the intercosto-brachial nerve, supplies
the skin along the postaxial border of the limb and on its dorsal side. At the postaxial border of
the lower limb, in the same way, the third and fourth sacral nerves, partially implicated in the
innervation of the limb (through the tibial, posterior cutaneous nerve of the thigh, perforating
cutaneous nerve, and perineal branch of the fourth sacral nerve), are also engaged in supplying
the trunk (perineum) through the pudendal nerve. These peculiarities of arrangement of the
nerves at the borders of the limbs may be explained on the supposition that the segment corre-
sponding to the nerve named is only partially concerned in limb formation, and is, at the same
time, implicated to a greater or less extent in the formation of structures belonging to the trunk.
(2) The origin and distribution of the nerves at the postaxial border of the limbs present
48 c
744
THE NERVOUS SYSTEM.
a special difficulty. In the composition of the brachial plexus the first thoracic nerve is almost
wholly engaged in forming the ventral series of nerves. It only gives a minute nerve to join
the posterior cord, and this is not always present. In the case of the lumbo-sacral plexus
the third sacral nerve does not as a rule divide into ventral and dorsal trunks, but contributes
only to the formation of the ventral series of nerves. A solution of this difficulty may be found
in the examination of the areas of distribution of the nerves derived from the first thoracic
and third sacral nerves respectively. In the case of the brachial plexus (the medial cord of which
receives normally the whole contribution of the first thoracic nerve) the medial cutaneous nerve
of the arm, the ulnar branch of the medial cutaneous nerve of the forearm, and the dorsal branch
of the ulnar nerve supply the dorsal aspect of the limb on its postaxial border. These nerves
are in serial homology with the intercosto-brachial and lateral trunks of intercostal nerves. In
the case of the lumbo-sacral plexus similarly, in which the third sacral nerve does not divide into
ventral and dorsal trunks, the posterior cutaneous nerve of the thigh and tibial nerves containing
the contribution from the third sacral nerves innervate, by means of the gluteal and lateral
femoral branches of the former and the medial sural nerve (medial cutaneous nerve of the calf)
of the latter, the dorsal surface of the limb along the postaxial border, in series with the
perforating cutaneous nerve and the perineal branch of the fourth sacral.
These apparent anomalies appear to indicate that, instead of dividing into its proper dorsal
and ventral trunks, the entire contribution of the spinal nerve concerned, is in these instances
carried undivided along the postaxial border of the limb in association with the ventral trunks,
and that the dorsal subdivisions are thrown off successively as the plexus cords approach the
periphery. Indeed, in the case of the posterior cutaneous nerve of the thigh, Eisler has
shown that, when the common peroneal and tibial nerves are separated at their origin, its
gluteal and lateral femoral branches arise from and are connected with the dorsal trunk, and
the perineal and medial femoral branches with the ventral trunk.
THE DISTRIBUTION OF THE SPINAL NERVES TO THE MUSCLES AND SKIN
OF THE LIMBS.
By dissection, experiment, and clinical observation, it is conclusively proved that,
as a rule, each nerve of distribution in the limb, whether to muscle or skin, is made up of
fibres derived from more than one spinal nerve ; and, further, that in cutaneous distribution
a considerable overlapping occurs in the course of the several peripheral nerves. Moreover,
the arrangement of the distribution of the nerves to skin and to muscles is not identical.
In the case of the skin of the limbs, by the covering of the limb being drawn on to it from
adjacent parts in the process of growth, cutaneous nerves are engaged which are derived
from sources not represented in the muscular innervation of the limbs. Again, among the
muscles, some have undergone fusion, others have become rudimentary, and others again
have altered their position in the limb. Bearing these qualifications in mind, it is
possible to formulate a definite plan for the innervation of the skin and muscles of the
upper and lower limb. The accompanying tables give an analysis of the distribution of
the spinal nerves to the skin and muscles of the upper and lower limb respectively :
I. Upper Limb. A. Cutaneous Nerves.
1. Dorsal (Posterior) Surface.
Regions.
Nerves.
Spinal Origins.
Preaxial. Postaxial.
{Upper part
(preaxial)
{
Posterior cervical rami
Cervical plexus, posterior supra-
clavicular ....
C. 4. 5. 6.
C. 3. 4.
Lower part
f
Posterior thoracic rami .
T. 1.-7.
(postaxial)
{
Intercostal nerves, lateral branches
T. 2. 3. 4.
1 Upper part
1
Cervical plexus, posterior supra-
clavicular ....
C. 3. 4.
(preaxiaT)
(
Axillary . . .
C. 5. 6.
Lower part
f
Intercostal nerves, lateral
(postaxial}
{
branches .....
T. 2. 3.
f
Axillary .....
C. 5. 6.
{Lateral side
(preaxial)
\
Radial, proximal branch of dorsal
cutaneous of forearm
C. (5). 6.
Medial side
1
Radial, posterior cutaneous of arm
Medial cutaneous nerve of arm
C. 8.
T. 1.
(postaxial)
I
Intercosto-brachial
T. 2.
THE DISTRIBUTION OF THE SPINAL NERVES.
1. Dorsal (Posterior) Surface continued.
745
Lateral side
(preaxial)
XVittUiai, u.istai uraiiuii ui uuieai
cutaneous nerve of forearm
Musculo - cutaneous, posterior
C. 6. 7. 8.
branch .....
P 5 6
Forearm-
Superficial branch of radial .
C. 6. 7.
I 1
Medial side j
(postaxial) j
Medial cutaneous nerve of fore-
arm (ulnar branch) .
Ulnar, dorsal branch
C. 8. T. 1.
C. 8.
{Lateral side
Superficial branch of radial .
C. 6. 7.
M&fd]
Ulnar
C. 8.
(postaxial)
2. Ventral (Anterior) Surface.
Regions.
Nerves.
Spinal Origins.
'
Preaxial. Postaxial.
/Upper part
(preaxial)
Cervical plexus, supraclavicular
branches .....
C. 3. 4.
Chest '{Lower part f
1 (postaxial) j
Intercostal nerves, anterior
branches
Intercostal nerves, lateral branches
T. 2. -7.
Lateral part j
(preaxial) |
Axillary .....
Radial, proximal branch of dorsal
cutaneous nerve of forearm
C. 5. 6.
C. 5. 6.
Upper arm -
(
Medial cutaneous nerve of the
Medial part J
forearm .....
C. 8. T. 1.
(postaxial) I
Medial cutaneous nerve of the arm
T. 1.
t. :. I
Intercosto-brachial . .
T. 2.
( Lateral part
Musculo - cutaneous, anterior
(preaxial)
branch . . . . .
C. 5. 6.
K orearm . -^ j^ e( ^j a j p ar ^
Medial cutaneous nerve of the
v (postaxial)
forearm, volar branch
C. 8. T. 1.
'Lateral part
Musculo-cutaneous, ball of thumb
C. 5. 6.
(preaxial}
Median, palmar branch
C. 6. 7.
digital branches
C. 6. 7. 8. T. 1.
thumb, lateral side .
C. 6. (7).
,, medial side )
index, lateral side/ '
C. 6. 7.
. <
medial side)
middle, lateral side/
C. (6). 7. 8. (T. 1).
medial side t
ring, lateral side /
C. 8. T. 1.
Medial part
Ulnar, palmar branch .
T. 1.
!
^ (postaxial)
digital branches
T. 1.
B. Muscular Nerves.
1. Dorsal (Posterior) Surface.
Spinal Origins.
Regions. Muscles. Nerves.
Preaxial. Postaxial.
rUpper part Trapezius .... Cervical plexus . C. 3. 4.
(preaxial r (Cervical plexus . C. 3. 4.
onouiaer-' Levator scapulae . . . { -r^ T ^ n K
| muscles) I .Dorsal scapular . \*>. o.
Rhomboidei . . . . Dorsal scapular . C. 5.
746
THE NEKVOUS SYSTEM.
1. Dorsal (Posterior) Surface continued
Regions.
Muscles.
Nerves.
Spinal Origins.
Preaxial. PostaxiaL
r
Serratus anterior .
Long thoracic
C. 5. 6. 7.
Supraspinatus \
Infraspinatus /
Suprascapular
Shoulder^
Subscapularis
/Short subscapular
\Lower
C. 5. 6.
Teres major ....
Lower subscapular
Lower part
(postaxial
Teres minor \
Deltoid /
Axillary
(. muscles)
Latissimus dorsi .
Thoraco-dorsal
C. 6. 7. 8.
Triceps .....
f
Lateral head
C. (6). 7. 8.
Upper arm . . \
Long head ....
Radial.
)
Medial head . .
C. 7. 8.
I
Anconseus ....
J
Brachio-radialis
}
C. 5. 6.
Extensor carpi radialis
\ Radial.
longus ....
J
C. (5). 6. 7. 8.
Forearm
Extensor carpi radialis
brevis ....
Supinator ....
Extensor digitorum communis
1 Deep branch of
j radial
1C. (5). 6. 7. (8).
JC. (5). 6.
digiti quinti .
carpi ulnaris .
Abductor pollicis longus
Extensor pollicis longus
Dorsal inter-
osseous .
C. (5). 6. 7. 8.
pollicis brevis
s
indicis .
2. Ventral (Anterior) Surface.
Regions.
Muscles.
Nerves.
Spinal Origins.
Preaxial. Postaxial.
f Upper part
S terno - mas toid
Cervical plexus
C. 2.
(preaxial
muscles}
Omo-hyoid \
S terno -hyoid J
Ansa hypoglossi .
C. 1. 2. 3.
Pectoral
Subclavius . . . .
Brachial plexus
C. 5. 6.
Region
Pectoralis major .
^
C. 5. 6. 7. 8. T. 1.
Lower part
Clavicular part
[Anterior thoracic
C. 5. 6.
(postaxial
Sternal part
f nerves
C. 5. 6. 7. 8. T. 1.
> muscles}
Pectoralis minor .
J
C. 7. 8. T. 1.
f Lateral part
Biceps
Musculo-cutaneous
}p n fi
(preaxial)
E V T
/ Musculo-cutaneous
\j _/ D.
-bracmaiis ....
I Radial
C. (5). 6.
Coracobrachialis .
Musculo-cutaneous
C. 7.
Upper
fMedial anterior
arm
thoracic, or medial
Medial part
Axillary arches .
-< cutaneous nerve
C. 8. T. 1. (2). '
(postaxial}
of thearm,orinter-
>
l costo-brachial
Lateral part
Pronator teres
\
C. 6.
(preaxial)
Flexor carpi radialis .
Palmaris longus .
VMedian
C. 6.
Flexor digitorum sublimis .
J
Forearm^
Flexor digitorum profundus
fVolar interosseous :
\ Ulnar
C. 7. 8. T. 1.
C. 8. T. 1.
Flexor carpi ulnaris
Ulnar .
C. 8. T. 1.
Medial part
> (postaxial)
Flexor pollicis longus .
Pronator quadratus
JYolar interosseous
JC. 7. 8. T. 1.
THE DISTBIBUTION OF THE SPINAL NEKVES.
2. Ventral (Anterior) Surface continued.
747
Regions.
Muscles.
Nerves.
Spinal Origins.
Preaxial. Postaxial.
r Lateral part
(preaxial)
Abductor pollicis brevis
Opponens pollicis
Flexor pollicis brevis .
r Median .
-C. 6. 7.
Lateral two lumbricales
J
Medial two lumbricales
Hand ,
Interossei ....
Adductor pollicis (transverse
and oblique parts) .
-Ulnar .
|C. 8. (T. 1).
I
Medial part
^ (postaxial)
Abductor digiti quinti .
Opponens digiti quinti
Flexor digiti quinti brevis .
II. Lower Limb. A. Cutaneous Nerves.
1. Dorsal Surface.
(Front and lateral part of thigh, buttock, front of leg, dor sum of foot.)
Regions.
Nerves.
Spinal Origins.
Preaxial. Postaxial.
(
Geni to -femoral (lumbo - inguinal
branch)
L. 1. 2.
Thigh]
Femoral, medial cutaneous .
)
*ont of thigh and
Femoral, intermediate cutaneous .
[ L. 2. 3.
front part of but-
I
Lateral cutaneous ....
J
tock
Twelfth thoracic, lateral branch .
T. 12.
(preaxial nerves)
Ilio-hypogastric, lateral branch .
L. 1.
Posterior lumbar rami .
L. 1. 2. 3.
teral part of thigh'
Buttock
Posterior sacral rami .
S. 1.-5.
and buttock, back |
Posterior coccygeal rarnus
Co.
and lower part
Posterior cutaneous of thigh :
ostaxial nerves)
gluteal, and femoral branches
S. 1. 2. 3.
r Medial side /
g. | (preaxial) \
Saphenous
Infrapatellar branch
}L. 3. 4.
' 1 Lateral side /
Superficial peroneal
L 4. 5. S. 1.
1 (postaxial) \
Peroneal, sural branches
L. (4). 5. S. 1.
C Medial side /
>rsum of 1 (preaxial) \
Saphenous
Deep peroneal ....
L. 3. 4.
L. 4. 5. (S. 1).
foot ^| Lateral side /
Superficial peroneal
L. 4. 5. S. 1.
I (postaxial) \_
N. suralis . .
S. 1. (2).
2. Ventral Surface.
(Medial side and back of thigh, back of leg, and sole of foot.)
Regions.
Nerves.
Medial side
and back
thigh
Jk of leg
Medial side of j Ilio-inguinal
thigh I /Obturator
(preaxial)
Back of thigh
(postaxial)
Posterior cutaneous of thigh
Common peroneal, sural branches
Common peroneal, anastomotic
branch
Posterior cutaneous of thigh
N. suralis
Spinal Origins.
Preaxial. Postaxial.
L. 1.
L. 2. 3. (4).
S. 1. 2. 3.
L. (4). 5. S. 1.
S. 1. 2. 3.
S. 1. (2).
748
THE NEEVOUS SYSTEM.
2. Ventral Surface continued.
Regions.
Sole of foot
f Medial side
(preaxial)
Lateral side
(postaxial)
Nerves.
Saphenous
Tibial, calcanean rami
Medial plantar
Great toe, medial side
lateral side
Second toe, medial side
lateral side
Third toe, medial side
lateral side
Fourth toe, medial side
Lateral plantar
Fourth toe, lateral side
Fifth toe, medial side
lateral side
N. suralis
Spinal Origins.
Preaxial. Postaxial.
L. 3. 4.
L. 4. 5. S. 1.
L. 4. 5.
JL. 4. 5. S. 1.
S. 1. 2.
L. 5. S. 1.
L. 4. 5. S. 1 2.
S. 1. 2.
S. 1. (2).
B. Muscular Nerves.
1. Dorsal Surface.
(Front and lateral part of thigh, buttock, front and lateral part of leg,
dor sum of foot.)
Regions.
Muscles.
Nerves.
Spinal Origins.
Preaxial. Postaxial.
,
Pectineus
Sartorius .
|L. 2. 3.
Front of thigh
(preaxial)
Iliacus .
Psoas
Quadriceps
Vastus medialis .
Femoral
JL. 2. 3. 4.
Rectus femoris
L. 3. 4.
Vastus intermedius
V
Vastus lateralis .
>
1-
f
Tensor fasciae latae .
Glutaeus minimus .
medius
\- Superior gluteal
\ L. 4. 5. S. 1.
maximus .
Biceps, short head .
Piriformis
Inferior gluteal . 1 L 5 S 1 2
Common peroneal /
Sacral plexus
f Medial side . Tibialis anterior
\
(preaxial)
; Extensor hallucis
Front of leg -
longus .
Extensor digitorum
longus .
Peronaeus tertius
^Deep peroneal
L. 4. 5. S. 1.
Lateral side
Peronaeus longus . ) Superficial pero-
^ (postaxial} ,
Peronaeus brevis
/ neal
Dorsum of foot
Extensor digitorum
Deep peroneal
brevis .
THE DISTBIBUTION OF THE SPINAL NEKVES.
749
2. Ventral Surface.
(Medial side and lack of thigh, lack of leg, and sole of foot.)
Regions.
Muscles.
Nerves.
Spinal Origins.
Preaxial. Postaxial.
Thigh, medial 1
side
'Adductor longus
Gracilis .
Adductor brevis
j- Obturator .
} L. 2. 3.
L. 2. 3. 4.
(preaxial} ' Obturator externus .
[}. Adductor magnus .
}L.3.4.
Thigh and
buttock
Thigh, lateral I
side
(postaxial) \
Adductor magnus .
Semimembranosus .
Semitendinosus
Biceps, long head .
! Nerve to ham-
1 strings .
} L. 4. 5. S. 1.
I L. 5. S. 1. 2.
j S. 1. 2. 3.
Quadratus femoris
}
and inferior gem-
[ L. 4. 5. S. 1.
Buttock,
ellus .
Superior gemellus
- Sacral ple*xus .
J
)
and obturator in-
[ S. 1. 2. 3.
ternus .
J
Plantaris .
Popliteus .
} Tibial
} L. 4. 5. S. 1.
Flexor digitorum
>>
}
longus
[ L. 5. S. 1.
Back of leg .
Tibialis posterior .
Flexor hallucis
- Tibial
I
^
longus .
[ L. 5. S. 1. 2.
Soleus
J
Soleus
)
Gastrocnemius (both
Y Tibial
S. 1. 2.
heads) .
J
' c
Abductor hallucis .
Flexor digitorum
Medial side 1
(preaxial) \
brevis .
Flexor hallucis
Medial plantar
L. 4. 5. S. 1.
brevis .
I
First lumbrical
Snip nf fnnt
,
Second, third, and
QUlc Ul iUUt
fourth lumbricals
Quadratus plantae .
Lateral side
(postaxial)'
Adductor hallucis .
Interossei
Flexor digiti quint i
Lateral plantar
S. 1. 2.
brevis .
Abductor digiti
quinti .
A Innervation of the Muscles of the Limbs. The following laws appear to be applicable
to the upper and lower limbs alike :
No limb-muscle receives its nerve-supply from posterior rami.
2. The dorsal and ventral strata of muscles are always supplied by the corresponding dorsal and
ventral branches of the nerves concerned. The ventral muscular stratum is more extensive than the
dorsal ; the ventral nerves are the more numerous, and the additional nerves are postaxially placed.
The spinal nerves supplying muscles of the upper limb are C. 5, 6, 7, 8 (dorsal), and C. 5, 6, 7, 8,
1 (ventral) ; the nerves for the muscles of the lower limb are L. 2, 3, 4, 5, S. 1, 2 (dorsal), and
L 2, 3, 4, 5, S. 1, 2, 3 (ventral).
. The dorsal and ventral trunks of the nerves are distributed in the limb in a continuous,
segmental manner ; so that, " of two muscles, that nearer the head end of the body tends to be
supplied by the higher nerve, and that nearer the tail end by the lower nerve " (Herringham).
4. ^ The nerves placed most centrally in the plexus extend furthest into the limb, and the more
oreaxial nerves terminate sooner in the limb than the more postaxial nerves.
750
THE NEKVOUS SYSTEM.
Upper Limb.
Dorsal
Surface.
Ventral
Surface.
Muscles of shoulder
. C.
3,
4, 5, 6, 7, 8.
Muscles of chest
C.
5,
6,
7,
8,
T. 1.
arm .
. C.
6,
7,8.
arm
C.
5,
6,
7.
,, forearm
. C.
6,
forearm .
C.
6,
7,
8,
T.
1.
hand
C.
6,
7,
8
(T
1).
Lower Limb.
Dorsal Surface.
Ventral
Surface.
Muscles of thigh and
buttock . . L. 2, 3, 4, 5, S. 1, 2.
Muscles of leg and foot L. 4, 5, S. 1.
Muscles of thigh .
le g
foot
L. 2, 3 4, 5, S.
L. 4, 5, S. 1. 2
L. 5, S. 1, 2.
1, 2, 3.
The only exception to this rule is on the ventral (anterior) surface of the arm, where a sup-
pression of the muscle elements leads to an absence of the regular series of segmental nerves
(C. 8, T. 1) on its postaxial border. These nerves reappear in the forearm, and the occasional
L/AfB
DORSAL SURFACE
Shoulder Arm Forearm Hand
Chest
VENTRAL SURFACE
Arm. forearm JFand
C.3
"1
4
J
5
I A
8
'
7
8
!
:
j
L.2
3
4
5
S.I
2
LOWER L/MB
DORSAL SURFACE VENTRAL SURFACE
Thigh & ButtocJc. Ley foot Thigh JLep Fnof
ID L.2
)
) i j 3
\ i
i ! j 4
i i s
i \ S.I
2
3
i
DIAGRAM of the segmental distribution of the muscular nerves of the upper and lower limbs.
" axillary arches " may be regarded as the muscular elements usually suppressed, and, when
present, supplied by these nerves.
Muscles with a Double Nerve-supply. The existence of more than one nerve to a muscle
indicates usually that the muscle is composite and is the representative of originally separate
elements, belonging to more than one segment or to both surfaces of the limb. In the case of
the pectoralis major, subscapularis and flexor digitorum profundus, adductor magnus, and soleus,
parts of the same (ventral or dorsal) stratum have fused, to form muscles innervated from the
corresponding ventral or dorsal nerves. The other muscles having a double nerve-supply
brachialis, biceps femoris, and (sometimes) pectineus are examples of fusion at the preaxial or
postaxial border of muscular elements derived from the dorsal and ventral surfaces of the limb,
which are correspondingly innervated by branches from both dorsal and ventral series : e.g. the
brachialis is innervated by the musculo-cutaneous and radial nerves ; the biceps femoris by the
peroneal (short head) and tibial nerves (long head) ; and the pectineus, by the femoral and
(sometimes) obturator nerves.
B. Innervation of the Skin of the Limbs. While the scheme of cutaneous inner-ration of
the limbs is fundamentally segmental, yet the arrangement is confused and complicated by
various causes. The growth of the limb from the trunk has caused the skin to be drawn out
over it like a stretched sheet of india-rubber (Herringham), and at the same time the extent of
the dorsal area of the limb is increased at the expense of the ventral area. The central nerves of
the plexus remain buried deeply in the substance of the limb, only coming to the surface towards
the periphery. The proximal parts of both surfaces of the limb thus become innervated by
cutaneous nerves otherwise not necessarily concerned in the innervation of the limbs. Herring-
ham has shown that (A) Of two spots on the skin, that nearer the preaxial border tends to b(
supplied by the higher nerve. (B) Of two spots in the preaxial area, the lower tends to be supplied fa
THE DISTRIBUTION OF THE SPINAL NEEVES.
751
the lower nerve; and of two spots in the postaxial area, the lower tends to be supplied by the higher
nerve. In other words, from the. root of the limb along the preaxial border to its distal extremity,
and along the postaxial border to the root of the limb again, there is a definite numerical sequence
of spinal nerves supplying skin areas through nerves of the limb -plexuses. A similar numerical
sequence in the arrangement of the nerves is also found extending over the dorsal and ventral
surfaces of the limbs from preaxial to postaxial border, except in certain situations.
On the dorsal and ventral surfaces of both upper and lower limbs there is a hiatus, for a
certain distance, in the numerical sequence of the spinal nerves in their cutaneous distribution,
explicable on the ground that the central nerves of the plexus, which fail to reach the surface in
these situations, are replaced by cutaneous branches from neighbouring nerves. This hiatus has
been named the axial area or line.
In the upper limb, the dorsal axial area or line extends from the median line of the back,
' opposite the vertebra prominens, to the insertion of the deltoid.
The ventral axial area or line extends anteriorly from the median plane of the trunk, at the
sternal synchondrosis, across the chest, distally along the front of the arm and forearm to the
wrist.
In the lower limb, the dorsal axial area or line may be traced from the median plane of the
back over the posterior superior iliac spine, across the buttock and thigh, to the head of the
fibula.
A ventral axial area or line can also be traced from the root of the penis along the medial side
of the thigh and knee, and along the back of the leg to the heel.
These areas or lines represent the meeting-place and overlapping of nerves, which are not in
numerical sequence ; and it is only at the peripheral parts of the limbs, on the dorsal and ventral
surfaces, that the nerves appear in numerical sequence from the preaxial to the postaxial border.
In the case of the upper limb the hiatus is caused, in both surfaces of the limb, by the absence of
cutaneous branches of the seventh cervical nerve ; in the case of the lower limb the hiatus is due
to the absence of branches from the fifth lumbar nerve on both surfaces of the limb, and the
absence of branches from the fourth lumbar nerve, in addition, on the dorsal surface.
Understanding the significance of these dorsal and ventral axial areas or lines, and at the
same time bearing in mind the overlapping which occurs in the cutaneous distribution of each
spinal nerve, the areas of skin supplied through the limb-plexuses can be mapped out with con-
siderable precision, as indicated in the following tables :
A. Cutaneous Distribution. Upper Limb.
Nerves.
Spinal Origin.
Distribution.
Supraclavicular nerves
C. 3. 4.
Chest, shoulder, deltoid, and
Axillary
C. 5. 6.
scapular regions.
Deltoid region, lateral side of arm.
Radial (proximal
C. (5). 6.
Lateral part and back of arm and
Preaxial border
branch of dorsal
forearm.
from neck to '
cutaneous of forearm)
hand
Radial (distal branch
C. 6. 7. 8.
Lateral part and back of elbow
i
of dorsal cutaneous
and forearm.
of forearm)
Musculo-cutaneous
C. 5. 6.
Lateral part of forearm, volar
V
and dorsal aspects.
rDorsum f
TTanrl V
Superficial branch of
radial
C. 6. 7.
Lateral part j
j- of dorsum of hand.
Hand, (
Ulnar ....
C. 8.
Medial part J
IPalm
Musculo-cutaneous
C. 5. 6.
Ball of thumb.
1
Median
C. 6. 7.
Lateral part ) f -,
I
Ulnar ....
T. 1.
Medial part / P aim ol nand>
Thumb C. 6. 7.
f
First finger, C. 6. 7. 8.
Digits
Median
Second C. 7. 8. T. 1.
\
Ulnar
Third C. 8. T. 1.
Fourth 1m T
(
Fifth J 1 - 1 '
Medial cutaneous of
C. 8. T. 1.
Medial side of forearm, volar
forearm
and dorsal aspects.
Radial (posterior cu-
C. 8.
taneous of arm)
Postaxial border
Medial cutaneous of
T. 1.
Medial side of arm.
from hand to
arm
chest
Intercosto-brachial
T. 2.
A
Intercosto-brachial
T. 2.
Third intercostal
T. 3.
Axillary folds.
Fourth
T. 4.
752 THE NEBVOUS SYSTEM.
B. Cutaneous Distribution. Lower Limb.
Nerves.
Spinal Origin.
Distribution.
Lateral branch of
T. 12.
Lateral part of buttock.
twelfth thoracic
Lateral branch of ilio-
L. 1.
Lateral part of buttock.
hypogastric
Preaxial border
Ilio-inguinal
Genito-femoral .
L. 1.
L. 1. 2.
Groin and over femoral triangle.
Front of thigh, proximal third.
from trunk to
Lateral cutaneous
L. 2. 3.
Front and lateral part of thigh.
foot
^
Femoral (intermediate
and medial)
L. 2. 3.
Front and medial part of thigh,
distal two-thirds.
Obturator .
L. 2. 3. (4).
Medial part of thigh, middle
third.
Femoral (saphenous
L. 3. 4.
Knee and leg, medial part and
nerve)
front.
Saphenous nerve
L. 3. 4.
Medial side of foot.
Deep peroneal
L. 4. 5. S. (1).
Interval between first and
r Dorsum .
second toes.
f
Superficial peroneal .
L. 4. 5. S. 1.
Dorsum of foot and toes.
*
N. suralis .
S. 1. (2).
Lateral side of foot.
1 oot-
Medial plantar .
L. 4. 5. S. 1.
Medial part "|
I Q -I
Lateral plantar .
S. 1. 2.
Lateral part j- of sole.
Vbole 1
Tibial (calcanean rami)
S. 1. 2.
Heel and back part J
Digits . . \
Medial and lateral
plantar .
L. 4. 5. S. 1.
S. 1. 2.
Great toe, L. 4. 5. S. 1.
Second toe, L. 4. 5. S. 1.
Third L. 5. S. 1.
Fourth L. 5. S. 1. 2.
\
N. suralis .
S. 1. (2).
Fifth S. 1. 2.
V
Lateral part of foot and leg,
Postaxial border
Posterior cutaneous of
distal third.
from foot to
thigh . .
S. 1. 2. 3.
Back of leg, thigh, and buttock.
coccyx
Perforating cutaneous .
S. 2. 3.
Buttock (fold of nates, medial
t
half).
Ano-coccygeal
S. 4. 5. Co. 1.
Anal fold.
VARIATIONS IN THE POSITION OF THE LIMB-PLEXUSES.
Two different kinds of variations occur in relation to the limb -nerves.
(1) Individual variations, both in the extent of origin and in the area of distribution of a
given nerve, are not uncommon ; these variations are usually concomitant with compensatory
variations in adjacent nerves, and are due to the fibres of a given spinal nerve taking an
abnormal course in the trunk of another nerve of distribution and effecting a communication
with the proper nerve peripherally. In this way the variations in the origin and distribution
of the intercosto-brachial nerve may be explained ; and, similarly, the ulnar nerve may have
some of its fibres carried as far as the forearm, incorporated with the median and transferred to
it by a communication between the two nerves in that region.
(2) Variations in the limb-plexus, in relation to the vertebral column, are the chief cause of
variations in the constitution of the limb-nerves. These variations affect more or less the whole
series of nerves in the plexus.
The brachial plexus is subject only to very slight variation in position and arrangement.
It may be reinforced at the upper end by a slender trunk from the fourth cervical nerve, and,
more frequently, by an intra - thoracic communication between the second and first thoracic
nerves. The presence of one or other of these nerves is an indication of a slight tendency
towards a cephalic or caudal shifting of the whole plexus in relation to the spinal medulla. It is,
however, never sunicient to cause the exclusion to any extent of the nerves normally implicated.
The presence of a cervical rib may coincide with little or no change in the relation of the nerves.
Indeed, the inclusion of the second thoracic nerve in the plexus may be, as already stated,
merely an individual variation, a change in the path to the limb of the intercosto-brachial
nerve. Concomitant variations occur among groups of nerves, however, which indicate a certain
tendency to variation in the position of the whole plexus. At one end, the suprascapular and
niusculo-cutaneous nerves may arise from the fourth and fifth, fifth alone, or fifth and sixth
cervical nerves. At the other end of the plexus, the radial may or may not receive a root
from the first thoracic nerve, and this addition is rather more likely to occur when the second
thoracic nerve is implicated in the plexus.
The lumbo-sacral plexus shows a very considerable variability in position and constitution.
Eisler records concomitant variations in the plexus in 18 per cent, of the cases examined by him.
The variations occur within wide limits. The plexus may begin at the eleventh or twelfth
SYMPATHETIC SYSTEM. 753
thoracic or first lumbar nerve. The last nerve in the sciatic cord may be the second, third,
or fourth sacral nerve. The. position of the n. furcalis is a guide to the arrangement of the
plexus. It may be formed by the third, third and fourth, fourth, fourth and fifth, or fifth
lumbar nerves. The resulting variations are illustrated by the following extreme cases :
(1) Prefixed Variety. (2) Postfixed Variety.
Nervus furcalis . . . L. 3 and 4 (double). L. 5.
Obturator . . . . L. 1, 2, 3. L. 2, 3, 4, 5.
Femoral . . . . T. 12, L. 1, 2, 3, 4. L. 2, 3, 4, 5.
Tibial L. 3, 4, 5, S. 1, 2. L. 5, S. 1, 2, 3, 4.
Common peroneal . . L. 3, 4, 5, S. 1. L. 5, S. 1, 2, 3.
Those variations in the constitution of the lumbo-sacral plexus are most numerous which
are due to the inclusion of nerves more caudally placed. Thus, out of twenty -two variations
in the position of the n. furcalis, in nineteen Eisler found it formed by the fifth lumbar nerve ;
in two cases only, by the third lumbar nerve. There is further evidence that variations in the
position of the plexus are accompanied by variations in the vertebral column itself. Out of the
twenty -two abnormal plexuses examined by Eisler, sixteen were coincident with abnormal
arrangement of the associated vertebrae.
SIGNIFICANCE OF THE LIMB-PLEXUSES.
From the above considerations, it is obvious that something more than convenience of transit
for the spinal nerves to skin and muscles is secured by the formation of the limb -plexuses. It
has been shown that by their combinations in the plexuses, every spot or area of skin in the
limbs is innervated by more than one spinal nerve ; and generally, also, each limb-muscle is
supplied by more than one spinal nerve. Each cutaneous area and each limb -muscle is thus
brought into relationship with a wider area of the spinal medulla than would occur if the
plexuses were non-existent. A simultaneous record of sensation is thus transmitted from any
given point on the surface of the limb through more than one posterior root ; and a more ready
co-ordination of muscular movement is brought about by the transmission of motor impulses
from the anterior root of a given spinal nerve to more than one muscle at the same time. In a
word, a plexus exists to supply the whole limb and the limb as a whole, as an organ which has
its different active parts connected with the central nervous system by means of the limb-plexus.
SYSTEMA NERVORUM SYMPATHICUM.
The sympathetic nervous system comprises a pair of elongated gangliated
trunks, extending through the whole length of the body from the base of the skull
to the coccyx, connected to the peripheral spinal nerves by one series of nerves,
and to the viscera by another series. At its cephalic end each sympathetic trunk
passes into the cranial cavity along with the internal carotid artery, on which it
forms plexuses, and thereby forms complex relations with certain cerebral nerves.
At their caudal ends the two sympathetic trunks are joined together by fine
filaments and unite with the coccygeal ganglion (g. impar).
The sympathetic system is essentially dependent on and subservient to the spinal
nervous system. It distributes efferent fibres from the peripheral spinal nerves to
(a) the viscera and vessels of the splanchnic area, and (&) through recurrent (gray)
rami to vessels, glands, and involuntary muscles in the course of the somatic
divisions of the spinal nerves. It further collects and transmits to the cerebro-
spinal system afferent fibres from the viscera (Fig. 635).
General Structure of the Sympathetic System. The sympathetic system is
composed of two elements ganglia and nerve fibres.
Ganglia Trunci Sympathici. The ganglia are variable in number, form, size,
and position. They are not definitely segmental in position, but they are always
connected together by a system of narrow cords of nerve fibres. A ganglion
(Fig. 635) consists of a larger or smaller number of multipolar nerve cells,
enclosed in a capsule of connective tissue. Each cell is provided with one axon and
a number of dendrites. The axon may enter into the composition of (a) the con-
necting cord ; (6) a central branch (gray ramus communicans) ; or (c) a peripheral
branch from the sympathetic trunk. These axons are commonly medullated at
their origin, but become non-medullated in their course from the parent cell.
Besides these ganglia, two other series of ganglia are present in connexion with
the peripheral branches of the sympathetic : ganglia plexuum sympatMcorum,
49
754
THE NERVOUS SYSTEM.
intermediate or collateral ganglia, on the branches or in the sympathetic plexuses ;
and terminal ganglia, in close relation to the endings of the nerves in the viscera.
The nerve-fibres in the sympathetic system are of two classes, medullated and
non-medullated. The distinction is not absolute. The medullated fibres may lose
their medullary sheaths before reaching their terminations ; and the non-medullated
fibres may at their origin possess a medullary sheath. The medullated fibres form
the series of white rami communicantes (the visceral branches of the spinal nerves).
They take origin from the anterior rarni of certain spinal nerves in two streams:
thoracico-lumbar from the second thoracic to the second lumbar nerve inclusive, and
pelvic, or sacral, from the second and third, or third and fourth sacral nerves. The
roots of these rami arise from both posterior and anterior roots of the spinal nerves,
but in largest numbers from the anterior root.
The fibres from the anterior root are of very
small size. They are the axons of nerve cells
within the spinal medulla, which enter the
sympathetic trunk through the white ramus,
and end by. forming arborisations around the
cells of a sympathetic ganglion. There are
three known courses for such a fibre to take in
relation to the sympathetic system (a) It
may end in the ganglion with which the ramus
is immediately related; (b) it may course up-
wards or downwards in the connecting cord to
reach a neighbouring ganglion ; (c) it may pass
beyond the sympathetic trunk to end in relation
to cells of the peripheral (collateral) ganglia
along with fibres of distribution from the sym-
pathetic ganglia. These fibres are splanchnic
efferent fibres ; motor fibres for the unstriped
muscular tissue of the vessels and viscera, and
secretory fibres for the glands in the splanchnic
area. The fibres from the posterior root of the
spinal nerve entering into the composition of
the white ramus communicans are the axons
FIG. 635. SCHEME OF THE CONSTITUTION OF of spinal ganglion cells. They constitute the
THE WHITE RAMUS COMMUNICANS OF THE splanchnic afferent fibres, and probably traverse
the sympathetic gangliated trunk, passing up-
The roots and trunks of a spinal nerve are war ds, downwards, and peripherally, without
tw^JespiLSrer^Sd'rj^^fhetid bein g connected with its cells. They are the
ganglion (Sy). The splanchnic efferent sensory fibres from the viscera, with which
fibres (in red) are shown, partly ending in they are associated along with the peripheral
branches arising from the sympathetic trunk
(in blue) are itself. It is not certain that fibres from the
spinal ganglia are only found in connexion
with nerves provided with distinct white rami.
Similar medullated fibres are found also in the
gray rami communicantes.
The non-medullated fibres in the sympathetic system are derived from the axons
of the sympathetic ganglion cells. They have different destinations, (a) Some
fibres appear to contribute to the formation of the cord connecting the
ganglia together, and to end in arborisations round the cells of a neighbouring
ganglion, (b) Non-medullated fibres form a large part of the system of peripheral
(splanchnic efferent) branches, streaming into the splanchnic area in an irregular
manner, both from the ganglia and the connecting cords. (c) The gray rami
communicantes form a series of non-medullated fibres (with a small number
of medullated fibres intermingled) proceeding centrally from the ganglia to the
spinal nerves. These gray rami are found in connexion with each and all of the
spinal nerves. Their origin from the gangliated trunk is quite irregular : they may
come from the ganglia or the commissure; they may divide after their origin, so
SPLANCHNIC
EFFERENT
splanchnic afferent fibres n ue are
shown, partly entering the ganglion, and
cord into peripheral branches.
SYMPATHETIC SYSTEM.
755
that two spinal nerves are supplied from one ganglion ; or two ganglia may supply
branches to a single spinal nerve. The gray ramus is distributed along the somatic
divisions of the spinal nerves, supplying branches to unstriped muscular fibres
(vase-motor, pilo-motor) and glands (secretory). They also provide small recurrent
branches, ending in the membranes enveloping the spinal nerve-roots. Mingled
with the non-medullated fibres of the gray rami are a small number of medullated
fibres, regarded as
afferent fibres
axons passing to the
spinal ganglia which
are incorporated with
the gray rami.
The connect-
ing cords of the
sympathetic system
are composed of white
and gray fibres. The
white fibres are : (1)
splanchnic efferent
fibres, passing to a
ganglion above or
below the point of
entrance into the
sympathetic system ;
(2) splanchnic affer-
ent fibres, guided \\/ SPLANCHNIC
along the connect-
ing cord and over or
through the ganglia.
The gray fibres are
the axons of sympa-
thetic ganglion cells:
(1) true association
fibres passing into
connexion with the
cells of a neighbour-
ing ganglion; (2)
fibres passing along
the connecting cord
for a certain distance
upwards or down-
wards before entering
the splanchnic area as
peripheral branches.
The peripheral
branches of the
sympathetic trunk
consist of (1) white
fibres, which may be
either splanchnic afferent fibres on their way from the viscera through the
gangliated trunk to the spinal ganglia, or splanchnic efferent fibres which, after
traversing the gangliated trunk, proceed to join and end in collateral or terminal
ganglia in relation to viscera; (2) gray fibres, efferent branches, the axons of
the ganglion cells, distributed on the one hand peripherally to the vessels and
viscera of the splanchnic area, and on the other hand centrally through the gray
rami communicantes and the somatic divisions of the spinal nerves, to the glands
and involuntary muscles in the somatic area, as secretory, and vaso-motor and
pilo-motor fibres.
Although forming always one continuous cord, the sympathetic system may
49 a
FIG. 636. SCHEME OF THE CONSTITUTION AND CONNEXIONS OF THE
GANGLIATED TRUNK OF THE SYMPATHETIC.
The gangliated trunk is indicated on the right, with the arrangement of the fibres
arising from the ganglion cells. On the left the roots and trunks of
spinal nerves are shown, with the arrangement of the white ramus com-
municans above and of the gray ramus below.
756 THE NEKVOUS SYSTEM.
for convenience of description be dealt with in four parts cephalic and cervical,
thoracic, lumbar, and pelvic.
I. PAES CEPHALICA ET CEEVICALIS SYSTEMATIS SYMPATHICL
The cephalic and cervical part of each sympathetic trunk is to be regarded
as an upward prolongation of the primitive sympathetic system along the great
vessels of the neck. It is characterised by the absence of segmental ganglia and by
the absence of white rami communicantes joining it to the spinal nerves. Its con-
nexion with the spinal nervous system is through the white rami communicantes
of the upper thoracic nerves, which join the gangliated trunk in the thorax, and
stream upwards into the cervical portion of the trunk. The trunk possesses two
or three ganglia, from which branches are distributed to structures belonging to
head, neck, and thorax : (1) motor fibres to involuntary muscles (e.g. dilator of the
pupil) ; (2) vaso-motor fibres for arteries of the head, neck, and upper limbs ; (3)
pilo-motor fibres (along the cervical spinal nerves) to the skin of the head and
neck ; (4) cardio-motor fibres ; and (5) secretory fibres (e.g., submaxillary gland).
Each gangliated trunk in the neck is placed upon the prevertebral muscles and
behind the carotid vessels of the corresponding side. It extends from the root of
the neck, where it is continuous, in front of the neck of the first rib. with the
thoracic portion of the trunk, to the base of the skull, where it ends in the
formation of plexiform branches upon the internal carotid artery. It consists
of a narrow cord composed of inedullated and non-medullated fibres, with two
or three ganglia a superior ganglion at the upper end, an inferior ganglion at
the point of junction with the thoracic portion of the trunk, and a middle
ganglion, varying in position and often absent.
Ganglion Cervicale Superius. The superior cervical ganglion, situated at the
base of the skull, lies between the internal jugular vein and the internal carotid
artery. It is the largest of the sympathetic ganglia, measuring an inch or more in
length.
Ganglion Cervicale Medius. The middle cervical ganglion is of small size,
is frequently absent, and may be divided into two parts. It is usually placed in
front of the inferior thyreoid artery as it passes behind the carotid sheath.
Ganglion Cervicale Inferius. The inferior ganglion is joined by the con-
necting cord to the middle (or superior) ganglion above, and is only imperfectly
separated from the first thoracic ganglion below. It is of considerable size,
irregular in shape, and is placed behind the first part of the vertebral artery in
the interval between the last cervical transverse process and the neck of the first rib.
The branches from the cervical sympathetic ganglia and connecting cords are
divisible into two sets (A) Central communicating branches for other nerves ;
(B) Peripheral branches of distribution, which alone, or along with other nerves,
form plexuses, accompanying and supplying vessels and viscera of thei head, neck,
and thorax. Although this distinction is made, it is to be borne in mind that
the branches of communication are as much nerves of distribution as the others.
GANGLION CERVICALE SUPERIUS.
Central Communicating Branches. 1. Gray rami communicantes pass from
the ganglion to the anterior rami of the first four cervical nerves.
2. Communications with Cerebral Nerves. Just outside the skull, in the deep
part of the neck, communicating branches pass to the following cerebral nerves : (a]
to the petrous ganglion of the glossopharyngeal and the jugular ganglion of the
vagus ; (&) to the ganglion nodosum of the vagus ; (c) to the hypoglossal nerve.
Peripheral Branches of Distribution. 1. Pharynx. Plexus Pharyngeus
Ascendens. A pharyngeal branch passes behind the carotid sheath to reach the
wall of the pharynx, where it joins (along with the pharyngeal branches of th(
glossopharyngeal and vagus nerves) in the formation of the ascending pharyngea.
plexus, and assists in supplying the muscles and mucous membrane of the pharynx
SUPEEIOE CEEVICAL GANGLION.
757
2. Heart. N. Cardiacus Superior. The superior cardiac branch is a slender
nerve which, on the right side, descends behind the large vessels into the thorax
to join the deep cardiac plexus. On the left side the course of the nerve is similar
in the neck, but in the superior mediastinum it passes between the left common
carotid and subclavian arteries, and across the aortic arch, to join with the inferior
cervical cardiac branch of the vagus in the formation of the superficial cardiac
plexus. In their course both nerves form connexions with the other cardiac
nerves of the sympathetic, and with cardiac and other branches of the vagus
(recurrent and external laryngeal).
3. Vessels. (a) Nn. Carotici Extern!. The external carotid branches pass
Internal carotid artery Internal carotid plexus
Cavernous plexus
Emergence of first cervical nerve v
Anterior ramus of first cervical nerve --
Pharyngeal branch of vagus
/ Glossopharyngeal nerve
/ / Stylopharyngeus
iray ramus communicans from superior
- ganglion to first cervical nerve'
Pharyngeal branches----. .--
Superior cervical ganglion
iray ramus communicans from superior
rvical ganglion to second cervical nerve
Anterior ramus of second cervical nerve*
iray ramus communicans from superior
i-rviciil ganglion to third cervical nerve"
iray ramus communicans from superior
rvical ganglion to fourth cervical nerve"
Anterior ramus of third cervical nerve-
Ulterior ramus of fourth cervical nerve---
Anterior ramus of fifth cervical nerve
: iac branches from cervical sympathetic -'^j.
i: mus communicans from middle cervical f Jr I
ganglion to 5th cervical nerve
Anterior rain us of 6th cervical nerve
i; mus coinmunicans from middle cervical _
ganglion to 6th cervical nerve
Vertebral plexus- -
iterior ramus of seventh cervical nerve -,
iray ramus communicans from inferior
cervical ganglion to 7th nerve'"'
ray rami communicantes from inferior
cervical ganglion to 8th cervical nerve""
interior ramus of 8th cervical nerve/
Anterior ramus of first thoracic 11
" "Pharyngeal plexus
External carotid plexus
Superior laryngeal
'branch of vagus
-Internal laryngeal
"'External laryngeal
- Common carotid artery
-'Thyreoid gland
. Plexus on inferior
thyreoid artery
Middle cervical ganglion
Ansa subclavia
Cardiac branches froi
cervical sympathetic
_ .Inferior cervical
ganglion
Subclavian artery
Cardiac branches from
cervical sympathetic
Superior thoracic ganglic
FIG. 637. DISTRIBUTION OF THE SYMPATHETIC IN THE NECK.
wards to the external carotid artery, and form the plexus caroticus externus
xternal carotid plexus), which supplies offsets to that artery and its branches,
11 as to the glomus caroticum (O.T. inter-carotid body). From the subordinate
xuses on the external maxillary and middle meningeal branches of the
-rtery sympathetic fibres are supplied to the submaxillary ganglion and otic
1 ganglion, respectively.
(V) N. Caroticus Interims. The internal carotid branches form an upward pro-
ition of the ganglion which applies itself in the form of bundles of nerve-fibres
internal carotid artery as it enters the carotid canal in the temporal bone.
Branches separate into lateral and medial parts, which form plexuses investing
Artery in the cranium. The lateral division forms the inferior or internal
)tid plexus (pi. caroticus internus) ; the medial division gives rise to the superior
496
758
THE NEKVOUS SYSTEM.
or cavernous plexus (pi. cavernosus). Both plexuses supply offsets to the artery and
its branches, and form communications with certain cerebral nerves.
PI. Carotids Interims. The internal carotid plexus communicates by fine
Kami communicantes
Greater splanchnic nerve - -.
Lesser splanchnic nerve _ JS
Coeliac ganglion --*--:
Lowest splanchnic nerve --
Aortico-renal ganglion
Superior mesenteric plexus
Aortic plexus
Spermatic plexus
Branches to aortic arch
- Kami communicantes
Kami communicantes
| Left vagus
} Right vagus
-- Thoracic sympathetic trunk
-- (Esophageal plexus
Branches to oesophagus
Blanches to descending aorta
v Splanchnic ganglion
| Lesser splanchnic nerve
Lowest splanchnic nerve
--- Coeliac plexus
-- Suprarenal plexus
- Lowest splanchnic nerve
Lesser splanchnic nerve
Renal plexus
Fir. 638. THE SYMPATHETIC TRUNK IN THE THORAX.
branches with (a) the abducens nerve, and (6) the semilunar ganglion, and give*
off (c) the great deep petrosal and (d) the carotico-tympanic nerves. The deei
petrosal nerve joins the greater superficial petrosal nerve from the genicular ganglior
THOEACIC PAET OF THE SYMPATHETIC SYSTEM. 759
of the facial, in the foramen lacerum. By their union the pterygoid nerve is
formed, which, after traversing the pterygoid canal, ends in the spheno-palatine
ganglion. The carotico-tympanic nerves pass to the tympanic plexus. This plexus,
formed by the carotico-tympanic nerves, the tympanic branch of the glosso-
pharyngeal, and a twig from the genicular ganglion of the facial nerve, is placed
on the labyrinthic wall of the tympanum. It supplies the mucous lining of the
tympanum and auditory tube; and the lesser superficial petrosal nerve passes
from it to the otic ganglion.
Plexus Cavernosus. The cavernous plexus communicates with (a) the oculo-motor,
(6) the trochlear nerve, and (c) the ophthalmic division of the trigeminal nerve ;
it also (d) supplies twigs to the hypophysis (pituitary body), and (e) forms the
sympathetic root of the ciliary ganglion. This may pass to the ganglion inde-
pendently, or it may be incorporated in the long root of the ganglion from the
naso-ciliary branch of the ophthalmic nerve.
GANGLION CERVICALE MEDIUS.
Central Communicating Branches. 1. Gray rami commuiiicantes arise from
the ganglion or from the connecting cord, and join the anterior rami of the fifth
and sixth cervical nerves. 2. The ansa subclavia (Vieussenii) is a loop of com-
munication from this ganglion, which, after passing in front of and supplying offsets
to the subclavian artery and its branches, joins the inferior cervical ganglion.
Peripheral Branches of Distribution. 1. Heart. A slender middle cardiac
branch descends, either separately or in company with other cardiac nerves, behind
the large vessels into the thorax, where it ends in the deep part of the cardiac
plexus on each side.
2. Thyreoid Gland. Branches extend medially along the inferior thyreoid
artery to supply the thyreoid gland.
When the middle ganglion is absent the branches described arise from the
necting cord.
GANGLION CERVICALE INFERIUS.
Central Communicating Branches. 1. Gray rami communicantes arise from
this ganglion for the anterior rami of the seventh and eighth cervical nerves.
2. The ansa subclavia already mentioned connects the middle and inferior ganglia
over the front of the subclavian artery. 3. A communication frequently occurs
with the recurrent nerve.
Peripheral Branches of Distribution. 1. Heart. An inferior cardiac branch
is given off on each side to enter the deep cardiac plexus.
2. Vessels. (a) The vertebral plexus is a dense plexus of fibres surrounding
the vertebral artery and accompanying its branches in the neck and the cranial
cavity. (6) The subclavian plexus is derived from the ansa subclavia (subclavian
loop), and supplies small offsets to the subclavian artery. It gives branches to the
internal mammary artery, and communicates with the phrenic nerve.
II. PAES THOEACALIS SYSTEMATIS SYMPATHICI.
The thoracic part of the sympathetic trunk lies behind the pleura, in front
of the necks of the ribs, and the intercostal vessels and nerves. It consists of a
number of ganglia of an irregularly angular or fusiform shape, joined together by
connecting bands of considerable thickness. The number of ganglia is usually
ten or eleven; but the first and sometimes others may be so fused with the
neighbouring ganglia as to reduce the number still further.
This part of the sympathetic trunk is characterised by its union with the thoracic
spinal nerves. Each thoracic nerve, with the probable exception of the first, sends
a visceral branch (white ramus communicans) to join the gangliated trunk in the
thorax. These white rami separate into two main streams in relation to the
sympathetic trunk. Those of the upper five nerves are for the most part directed
upwards to be distributed through the cervical part of the sympathetic trunk
49 c
760
THE NERVOUS SYSTEM.
in the manner already described. The white rami of the lower thoracic nerves are
for the most part directed downwards in the inferior part of the sympathetic trunk
and its branches, to be distributed in the abdomen ; at the same time some of
their fibres are directly supplied to certain thoracic viscera, lungs, aorta, oesophagus.
These white rami are composed of (1) splanchnic afferent fibres passing from
its peripheral branches through the sympathetic trunk into the ganglia of the
Nervus caroticus in tern us
-Nervus caroticus interims
Superior cervical ganglion
of the sympathetic
Superior cardiac branch-
Middle cervical ganglion -
Superior cardiac branch -
Middle cardiac branch -
Inferior cervical ganglion'
Inferior cardiac branch'
Recurrent nerve -
Inferior cardiac branch
Cardiac branch from right recurrent nerve
Thoracic cardiac branch of vagus
Trachea
Deep cardiac plexus - -
Nerves to posterior
pulmonary plexus
Branches to right anterior
pulmonary plexus
Anterior pulmonary plexus
Superior vena cava
Branches to right coronary pie
Right coronary plexus
Superior cervical ganglior
'of the sympathetic
" 'Superior cardiac branch
Vagus
^Middle cervical ganglion
Superior cardiac branch
Middle cardiac branch
Inferior cardiac branch
Inferior cervical ganglion
Inferior cardiac branch
Recurrent nerve
-Cardiac branch from left recurrent nerve
-Middle cardiac branch
Inferior cardiac branch
Superior cardiac braiu-h
-Cardiac branch from left recurrent nerve
-Deep cardiac plexus
_ Superficial cardiac plexus
-Nerves to posterior pulmonary plexus
-Branches to left anterior pulmonary plea
Branches to left vagus
.Pulmonary artery
Branches to right coronary plexus
Anterior pulmonary plexus
Aorta
Branches to right coronary plexus
Branches to left coronary plexus
" * ..Left coronary plexus
FIG. 639. THE CARDIAC PLEXUSES.
spinal nerves medulla ted nerve-fibres unconnected with sympathetic ganglion
cells; and (2) somatic and splanchnic efferent fibres, small medullated nerves
which, after a longer or shorter course in the gangliated trunk or its peripheral
branches, become connected with the sympathetic ganglion cells, or with the
cells of peripheral (collateral or terminal) ganglia, from which again (non-medullated)
axons proceed to supply branches to viscera and vessels. The ultimate destination
of the upper stream of white rami from the thoracic nerves has been mentioned
in the description of the cervical sympathetic.
ABDOMINAL PAET OF THE SYMPATHETIC SYSTEM. 761
The peripheral branches supplying thoracic organs contain vaso-motor fibres
for the lungs and aorta.' The peripheral branches from the lower part of the
sympathetic trunk in the thorax, receiving white rami from the lower thoracic
nerves, are distributed mainly to structures below the diaphragm. They comprise
(a) viscero-inhibitory fibres for the stomach and intestines ; (b) motor fibres for
part of the rectum ; (c) pilo-motor fibres for the lower part of the body ; (d) vaso-
motor fibres for the abdominal aorta and its branches, and for the lower limbs ;
(e) secretory, and (/) sensory fibres for the abdominal viscera.
The branches from the gangliated trunk are, as in the neck, divisible into two
sets (A) Central branches, communicating with other nerves, and (2?) peripheral
branches, distributed in a plexiform manner to the thoracic and abdominal viscera.
(A) Central Communicating Branches. The white rami communicantes from
the thoracic nerves have already been described. Passing forwards from the
anterior rami of the nerves, they become connected with the ganglia or the con-
necting cord of the sympathetic.
The gray rami communicantes are branches arising irregularly from each thoracic
ganglion ; passing backwards along with the white rami, they join the anterior
rami of the thoracic nerves, and are distributed in a manner already described
(p. 754).
(B) Peripheral Branches of Distribution. These branches arise irregularly
from the ganglia and the connecting cord. They are composed of non-medullated
(splanchnic efferent) fibres derived from the ganglion cells, and medulla ted fibres
(splanchnic efferent and afferent) derived directly from the white rami, without
the intervention of the cells of the ganglia.
1. Rami Pulmonales. Pulmonary Branches. From the gangliated trunk
opposite the second, third, and fourth ganglia fine filaments arise which join the
posterior pulmonary plexus.
2. Rami Aortici. Aortic Branches. The upper part of the thoracic aorta
receives fine branches from the upper five thoracic ganglia.
3. Nn. Splanchnici. Splanchnic Nerves. Three nerves arise from the inferior
part of the gangliated trunk, partly from the ganglia themselves, and partly from
the connecting cord between the ganglia. Passing downwards over the bodies
of the thoracic vertebrae they pierce the diaphragm, to end in the abdomen.
(a) N. Splanchnicus Major. The greater splanchnic nerve arises from the gangli-
ated trunk between the fifth and ninth ganglia. By the union of several irregular
strands a nerve of considerable size is formed, which descends in the posterior
mediastinum, and piercing the crus of the diaphragm, joins at once the anterior
end of the cceliac ganglion. In its course in the thorax the splanchnic ganglion
is formed upon the nerve. It is more prominent in the foetus than in the adult.
From both nerve and ganglion branches arise in the thorax, for the supply of
the oesophagus and descending thoracic aorta (Fig. 638).
(6) N. Splanchnicus Minor. The lesser splanchnic nerve arises from the gangli-
ated trunk opposite to the ninth and tenth ganglia. It passes over the bodies of
the lower thoracic vertebrae, pierces the diaphragm near or along with the greater
splanchnic nerve, and ends in the coeliac plexus (aortico-renal ganglion).
(c) N. Splanchnicus Imus. The lowest splanchnic nerve arises from the
last thoracic ganglion of the sympathetic, or it may be a branch of the lesser
)lanchnic nerve. It pierces the diaphragm, and ends in the renal plexus.
III. PAES ABDOMINALIS SYSTEMATIS SYMPATHICI.
The abdominal part of the sympathetic trunk is placed upon the bodies of
the lumbar vertebrae, medial to the origins of the psoas major muscle, and in front
of the lumbar vessels. It is connected with the thoracic portion of the trunk by
an attenuated cord which either pierces or passes behind the diaphragm. It is
continuous below with the pelvic portion of the trunk by means of a connecting cord,
which passes behind the common iliac artery.
It is joined by medullated fibres (white rami communicantes) from the first two
762
THE NERVOUS SYSTEM.
lumbar spinal nerves, and it contains, as well, inedullated fibres continued down
from the lower part of the thoracic sympathetic trunk, and derived from the
visceral branches (white rami communicantes) of the lower thoracic nerves.
This part of the trunk is characterised by great irregularity in the number of
the ganglia. They are usually four in number, but there are frequently more
(up to eight) ; and in extreme cases fusion may occur to such an extent that the
separation of individual ganglia
s - becomes impossible.
1. Central Communicating
Branches. White rami communi-
cantes. Only the first two (or
three) lumbar spinal nerves send
visceral branches (white rami
communicantes) to the upper
lumbar ganglia or to the sym-
pathetic trunk. These nerves form
the lower limit of the thoracic-
lumbar visceral branches of the
2 spinal nerves. They comprise vaso-
motor fibres (for the genital organs),
and motor fibres for the bladder
and uterus.
Gray rami communicantes pass
from the gangliated trunk to the
anterior rami of the lumbar nerves
in an irregular manner. One
ramus may divide so as to supply
branches to two adjacent spinal
nerves ; or one spinal nerve may
be joined by several (two to five)
gray rami from the sympathetic
trunk.
The rami course deep to the
origin of the psoas major muscle
and over the bodies of the vertebras.
Gray rami sometimes pierce the
fibres of the psoas muscle.
2. Peripheral Branches of
no. 640.-THE LUMBAR PORTION OF THE SYMPATHETIC Distribution. -From the lumbar
GANGLIATED TRUNK AND LUMBAR PLEXUS. (From a dissection.) Sympathetic trunk numbers
T.n, T.12, L.I, L.2, L.3, L.4, L.5, Anterior rami of spinal small branches arise irregularly,
nerves, with white and gray rami communicantes. and Supply the abdominal aorta,
Sy, Sympathetic trunk ; Va, Vagus nerve ; G.S, Greater reinforcing the aortic plexus (de-
splanchnic nerve, joining coeliac ganglion ; S.R.C, Supra- r i v ed from the CCeliaC plexus),
renal gland and plexus ; R.P1, Renal plexus ; Ao.Pl,
Aortic plexus ; S. M, Superior mesenteric plexus ; I.M,
Inferior mesenteric plexus ; Hy.Pl, Hypogastric plexus ;
Q, Nerves to quadratus lumborum ; I.H, Ilio-hypogastric
nerve ; I.I, Ilio - inguinal nerve ; G.C, Genito - femoral
nerve ; E.C, Lateral cutaneous nerve ; A.C, Femoral
nerve ; Ace. Obt, Accessory obturator nerve ; Obt,
Obturator nerve ; 4, 5, Lumbo-sacral trunk.
r . PARS PELVINA SYS-
TEMATIS SYMPATHICI.
The pelvic part of the sym-
pathetic trunk, like the cervical
and lower abdominal portions of
this system, receives no white rami communicantes from the spinal nerves. The
visceral branches (pelvic splanchnic} of the third sacral nerve, and usually, also,
the second or fourth sacral nerve, enter the plevic plexus without being directly
connected with the sympathetic trunk. These nerves, however, are to be regarded
as homologous with the white rami communicantes of the thoracico- lumbar
nerves (abdominal splanchnic}. They convey to the pelvic viscera (1) motor
and inhibitory fibres for rectum, uterus, and bladder, (2) vaso-dilator fibres for the
genital organs, and (3) secretory fibres for the prostate gland.
CCELIAC PLEXUS. 763
This portion of the sympathetic trunk is placed on the pelvic surface of the
sacrum, medial to the anterior sacral foramina. It is connected above by a
cord with the abdominal portion of the sympathetic, and below it ends in
a plexiform union over the coccyx with the trunk of the other side, the two
being frequently connected by the ganglion impar or coccygeal ganglion. The
number of ganglia is variable ; there are commonly four. They are of small size,
gradually diminishing from above downwards.
Central communicating branches arise irregularly in the form of gray rami
communicantes from the sacral ganglia, which join the anterior rami of the sacral
and coccygeal nerves.
Peripheral Branches of Distribution. (1) Visceral branches of small size arise
from the upper part of the pelvic sympathetic trunk, and join the pelvic plexus
(see below).
(2) Parietal branches, also of small size, ramify over the front of the sacrum, and
form, in relation to the middle sacral artery, a plexiform union with branches from
the sympathetic trunk of the other side.
PLEXUS SYMPATHICI.
Sympathetic Plexuses. It has already been seen that the peripheral branches
the sympathetic trunk, throughout its length, are characterised by forming or
joining plexuses in their neighbourhood.
The cervical sympathetic ganglia and nerves give rise to the carotid and
cavernous plexuses ; the external carotid, pharyngeal, thyreoid, vertebral, and
subclavian plexuses; and they send important branches to the cardiac plexuses
(described with the vagus nerve).
The thoracic ganglia send branches to join the pulmonary and cesophageal
plexuses (described with the vagus nerve). They form plexuses on the thoracic
aorta, and by means of the splanchnic nerves they form the chief source of
the coeliac plexus.
THE CCELIAC AND PELVIC PLEXUSES.
These great plexuses serve to distribute nerves to the viscera and vessels of the
abdominal and pelvic cavities. Taken together they include three plexuses the
coeliac plexus, the hypogastric plexus, and the pelvic plexus. They are constituted
by peripheral branches of the lower thoracic, abdominal, and upper pelvic parts
of the sympathetic trunk ; and they are related to the central nervous system
by means of the visceral branches (white rami communicantes) of the lower
thoracic and upper lumbar nerves on the one hand, and by the visceral branches
of the second and third, or third and fourth sacral nerves, on the other hand. The
thoracico-lumbar series join the sympathetic trunk, and reach the coeliac plexus
mainly through the splanchnic nerves, and to a lesser extent through the abdominal
part of the sympathetic trunk. The sacral series enter the pelvic plexus without
connexion with the sympathetic trunk. The hypogastric plexus serves as a con-
necting link between the coeliac and pelvic plexuses.
PLEXUS CCELIACUS.
The coeliac plexus lies on the posterior abdominal wall in relation to the
abdominal aorta and behind the stomach. It is composed of three elements : the
coeliac plexus surrounding the origin of the coeliac artery, between the crura of
the diaphragm ; and two cceliac ganglia, each lying on the corresponding or us of
the diaphragm, and overlapped by the suprarenal gland, and on the right side
by the inferior vena cava. The plexus is continuous with subordinate plexuses,
diaphragmatic, suprarenal, renal, superior mesenteric and aortic; and by means
of the hypogastric nerves the aortic plexus is continued into the hypogastric
plexus, which again forms the chief origin of the pelvic plexuses.
The coeliac ganglia constitute the chief ganglionic centres in the cceliac
plexus. They are irregular in form. They are often partially subdivided, and one
764
THE NEKVOUS SYSTEM.
detached portion at the lower end is named the aortico-renal ganglion. Other small
scattered masses of cells are present in the cceliac plexus. At the upper end the
coeliac ganglion receives the greater splanchnic nerve. The aortico-renal ganglion
Coeliac plexus '-*^l
Lesser splanchnic nerve ----&&
Superior mesenteric plexus /j^
Aortic plexus .-
Spermatic plexus --
Abdominal sympathetic chain-
Inferior mesenteric plex
Hypogastric nerves -j
v 1
Greater splanchnic nerve
Abdominal sympathetic chain
- -Coeliac ganglion
-Suprarenal plexus
Lowest splanchnic nerve
Aortico-renal ganglion
Renal plexus
White ram us communicans from
-- second lumbar nerve to
sympathetic trunk
- Second lumbar nerve
Hypogastric plexus _
Right pelvic plexus .
Cord connecting
abdominal and pelvic
sympathetic
Left pelvic plexus
Visceral branch of
second sacral, nerve
Pelvic sympathetic
trunk
- Visceral branch of
third sacral nerve
Branch from pelvic
'- sympathetic trunk to
pelvic plexus
Left pelvic plexus
Hfemorrhoidal plexus
Branch from pelvic sympathetic
trunk to pelvic plexus
Nerves to corpus
cavernosum penis
Vesical p
Cavernous plexus
Nerves to corpus cavernosum urethrse
FIG. 641. THE SYMPATHETIC IN THE ABDOMEN AND PELVIS.
at its lower end receives the lesser splanchnic nerve. Branches from the
ganglion radiate in all directions medially to join the cceliac plexus, upwards
to form the diaphragmatic plexus, laterally to the suprarenal plexus, downward
to the renal, superior mesenteric, and aortic plexuses.
CCELIAC PLEXUS. 765
The coeliac plexus forms a considerable plexiibrrn mass surrounding the
coeliac artery. It consists of a dense meshwork of fibres with ganglia inter-
mingled, joined by numerous branches from the coeliac ganglion on each side,
and by branches from the right vagus nerve. It is continuous below with the
superior mesenteric and aortic plexuses. Investing the coeliac artery, it forms
subsidiary plexuses which are distributed along the branches of the artery. The
left gastric plexus supplies branches to the oesophagus and stomach ; the hepatic
plexus supplies branches to the liver and gall-bladder, stomach, duodenum, and
pancreas ; and the splenic plexus sends offsets to the spleen, pancreas, and stomach.
Subordinate plexuses are formed on the aorta and its branches by nerves
derived from the coeliac ganglia and coeliac plexus.
a. Plexus Phrenicus. The phrenic plexus consists of fibres arising from the
coeliac ganglion, and it accompanies the inferior phrenic artery. Besides supplying
the diaphragm, it gives branches to the suprarenal plexus, and on the right side
to the inferior vena cava on the left side to the oesophagus. It communicates on
each side with the phrenic nerve. At the junction of the plexus and the phrenic
nerve of the right side a ganglion is formed (phrenic ganglion).
1. Plexus Suprarenalis. The suprarenal plexus is of considerable size. It is
mainly derived from branches of the coeliac ganglion, reinforced by nerves from
the inferior part of the coeliac plexus which stream laterally on the suprarenal
arteries. It is joined by branches from the phrenic plexus above and from the
renal plexus below. The nerves enter the substance of the suprarenal gland.
c. Plexus Renalis. The renal plexus is derived from (1) branches of the coeliac
ganglion, and (2) fibres from the aortic plexus, extending laterally along the renal
artery to the hilum of the kidney. . It receives also the lowest splanchnic
nerve, and is connected by numerous branches to the suprarenal plexus.
d. Plexus Mesentericus Superior. The superior mesenteric plexus is inseparable
above from the coeliac plexus, and is joined on each side by fibres from the coeliac
and aortico-renal ganglia. It is continuous below with the aortic plexus. A
separate detached ganglionic mass (superior mesenteric ganglion) is present in the
plexus. Accompanying the superior mesenteric artery it forms subordinate
plexuses around the branches of the vessel. The plexuses at first surround
the intestinal arteries, but near the intestine they form fine plexuses between
the layers of the mesentery, from which branches pass to the wall of the gut.
This plexus supplies the small intestine, caecum, vermiform process, ascending
and transverse portions of the colon.
e. Plexus Aorticus Abdominalis. The aortic plexus is the continuation down-
wards of the coeliac plexus around the abdominal aorta. It is continuous above
with the coeliac and superior mesenteric plexuses ; it is reinforced by the peripheral
branches of the lumbar sympathetic trunk ; and it is connected with the hypo-
gastric plexus below by the hypogastric nerves. Besides investing and supplying
the aorta, the plexus is connected with various subordinate plexuses on the branches
of the artery. It contributes to the suprarenal and renal plexuses, and it gives
rise to the spermatic or ovarian, and the inferior mesenteric plexuses.
Plexus Spermaticus. The spermatic plexus invests and accompanies the sper-
matic artery. It is derived from the aortic plexus, and receives a contribution
from the renal plexus. It supplies the spermatic cord and testis.
Plexus Arterise Ovaricse. The plexus of the ovarian artery in the female arises
like the spermatic plexus. It accompanies the ovarian artery to the pelvis, and
supplies the ovary, broad ligament, and uterine tube. It forms communications in
the broad ligament with the uterine plexus (from the pelvic plexus), and sends
fibres to the uterus.
Plexus Mesentericus Inferior. The inferior mesenteric plexus is a derivative from
the aortic plexus, prolonged along the inferior mesenteric artery. It forms sub-
ordinate plexuses on the branches of the artery (colic, sigmoid, and superior
hsemorrhoidal), and is distributed to the descending colon, iliac colon, pelvic colon,
and upper part of the rectum.
766
THE NEKVOUS SYSTEM.
PLEXUS PELVINI.
The hypogastric nerves form the continuation of the aortic plexus into the
pelvic cavity. They consist of numerous plexiform bundles of nerve-fibres which
descend along the front and back of the bifurcation of the aorta and the origin of
the common iliac arteries, and over the sacral promontory, where, becoming in-
extricably mingled, they constitute the hypogastric plexus.
The hypogastric plexus is continued downwards in front of the sacrum on each
side of the rectum, and ends in the pelvic plexuses.
The pelvic plexuses are formed by the separation of the hypogastric plexus
into two halves at the sides of the rectum. Each is joined by fibres from the
upper portion of the pelvic part of the sympathetic trunk, and by the visceral
branches (white rami communicantes) from the second and third or third and
fourth sacral nerves. Accompanying the hypogastric artery and its branches,
each pelvic plexus gives off subordinate plexuses for the pelvic viscera.
a. Plexus Hsemorrhoidalis The haemorrhoidal plexus supplies the rectum, and
joins the superior hsemorrhoidal plexus from the inferior mesenteric plexus.
&. Plexus Vesicalis. The vesical plexus accompanies the vesical arteries to the
bladder-wall. Besides supplying the muscular wall and mucous membrane of the
bladder, it forms subordinate plexuses for the lower part of the ureter, the vesicula
seminalis, and the ductus deferens.
c. Plexus Prostaticus. The prostatic plexus is of considerable size. It is placed
on both sides of the gland, and, in addition to supplying its substance and the
prostatic urethra, it sends offsets to the neck of the bladder and the vesicula
seminalis. It is continued forwards on each side to form the plexus cavernosus penis
(cavernous plexus of the penis). Bundles of nerves pierce the layers of the fascia
of the urogenital diaphragm, and, after supplying the membranous urethra,
give off branches which enter and supply the corpus cavernosum penis. The
cavernous nerves communicate with branches of the pudendal nerve and give
offsets to the corpus cavernosum urethrae and the penile portion of the urethra.
d. Plexus Uterovaginalis. The uterine plexus passes upwards with the uterine
artery between the layers of the
broad ligament, and is dis-
tributed to the surfaces and
substance of the organ. It com-
municates between the layers of
the broad ligament with the
plexus of the ovarian artery.
The vaginal plexus is formed
mainly by the visceral branches
of the sacral nerves entering
the pelvic plexus. It supplies
the wall and mucous membrane
of the vagina and urethra, and
provides a cavernous plexus for
the clitoris. The uterine and
vaginal plexuses of the female
correspond to the prostatic plexus
of the male.
THE MORPHOLOGY OF THE
SYMPATHETIC SYSTEM
S P I. I
Sy.
From a consideration of its struc-
Fio. 642. SECTION THROUGH THE SYMPATHETIC TRUNK
OF AN EMBRYO.
Showing the connexion with the ganglion (Sy) of the white ture > functions, and development, there
ramus communicans (Spl) ; (a) a portion of the ramus joining appear to be two separate structures
the ganglion ; (|8) fibres passing over the trunk, accompanied represented in the sympathetic nerve
by a stream of cells ; (7) continuous with those of the gan- system the spinal and the sym-
glion ; (Ao) Aorta. pathetic elements. The structure of
the system presents a union of two
distinct elements fibres of cerebro - spinal origin and "sympathetic" cells and fibres. While
the function of the sympathetic trunk and its branches seems to be dependent upon the
OLFACTOKY NEKVES.
767
cerebro -spinal nervous system, it is certain that the cells and fibres of the sympathetic system
possess a vital activity apart from their connexion with the central nervous system. In the
development of the sympathetic it is at least highly probable that a mesoblastic rudiment or
precursor forms the basis of the sympathetic system, which is secondarily joined by nerve-
fibres from the roots of the spinal nerves.
Morphologically this part of the nervous system is essentially a longitudinal cord or column,
associated with involuntary muscles and glandular tissues, and particularly related to the organs
in the splanchnic area. Like other longitudinal structures in the body, and especially like the
organs of the splanchnic area, the sympathetic system is not truly segmental. The sympathetic
trunk is only quasi-segmental, the segmentation being attributable to its junction with the
visceral branches of the spinal nerves. The peripheral branches from the sympathetic trunk are
by no means segmental ; even the gray rami are not properly metameric, but, like the ganglia,
assume a segmental character in consequence of their connexions with the spinal nerves.
The phylogenetic relation of the sympathetic and the cerebro-spinal elements in the system
it is impossible to determine. It may be that the sympathetic system is the representative of
an ancient architecture independent of the cerebro-spinal nervous system, the materials of which
are utilised for a more modern nervous system ; or it may be that the correlation of spinal
nerves and sympathetic are both the consequences of the formation of new organs and structures
in the splanchnic area. Examined in every light, it possesses features which effectually differ-
entiate it from the cerebro-spinal system, although it has become inextricably united with it
and subservient to it.
THE CEEEBEAL NERVES.
Number.
Name.
Function.
Superficial Attachment
to Brain.
I.
Olfactory
Smell .
Olfactory bulb.
II.
Optic .
Sight . . . . .
Optic chiasma.
III.
Oculo-motor .
Motor to most of the muscles of
Cerebral peduncle.
eyeball and orbit
IV.
Trochlear
Motor to superior oblique muscle of
Anterior medullary
eyeball
velum.
V.
Trigeminal .
Sensory to face, tongue, and teeth ;
Pons.
motor to muscles of mastication
VI.
Abducent
Motor to lateral rectus muscle of
Junction of pons and
eyeball
medulla oblongata.
VII.
Facial .
Motor to muscles of scalp and face,
Medulla oblongata.
sensory to tongue
VIII.
Acoustic
Hearing and equilibrium
Medulla oblongata.
IX.
Glossopharyngeal
Sensory to tongue and pharynx ;
Medulla oblongata.
motor to stylo-pharyngeus
X.
Vagus .
Sensory to pharynx, oesophagus and
Medulla oblongata.
stomach, and respiratory organs
XI.
Accessory
(a) Accessory to vagus. Motor to
Medulla oblongata.
muscles of palate, pharynx, oaso-
phagus, stomach and intestines,
and respiratory organs ; inhibitory
for the heart
(b) Spinal part. Motor to trapezius
Spinal medulla.
and sterno-mastoid
XII.
Hypoglossal .
Motor to muscles of the tongue
Medulla oblongata.
See note, p. 798.
'he deep connexions of the cerebral nerves are dealt with in the section
( which treats of the Brain (pp. 592 to 607). Certain general points in connexion
with these nerves are also touched upon in the chapter introductory to the
Nervous System (p. 500). Their development is given on p. 501 et seq.
NERVI OLFACTORII.
In the older accounts, the first or olfactory nerve is described as consisting
of several parts : (1) a series of fine nerves, which arise from (2) the olfactory
bulb. This again is connected by (3) the olfactory tract with the brain, to which
lit is attached by (4) two striae or roots (Fig. 643).
The anatomy of the olfactory bulb, the olfactory tract and its roots is described
elsewhere (pp. 623 to 628).
The olfactory nerve consists of about twenty separate filaments which arise in
768
THE NEEVOUS SYSTEM.
the olfactory mucous membrane and terminate in the olfactory bulb. The fibres
are non-medullated. After their origins from the olfactory cells of the olfactory
region on the upper part of the nasal septum and the corresponding part of the
lateral wall of the nasal cavity, the nerve fibres form fine plexuses from which the
terminal filaments pass through the cribriform plates of the ethmoid on their way
to the olfactory bulb. Each filament has a sheath of dura mater.
Olfactory bulb
Olfactory trac
Olfactory tubercl
Optic n
Optic chiasma
Oculo-motor nerve
Trochlear nerve
Trigeminal nerv
Abducens nerv
Facial ner
N. intermediu
Acoustic nerv
Glossopharyngeal nerv
Vagus nerve
Accessory nerve (accessory)
Accessory nerve (spinal) j
Hypoglossal nerve
Olfactory bulb
Olfactory tract
Area parolfactoria
Olfactory tubercle
Medial stria of olfactory
nerve
Lateral stria
Optic chiasma
Ant. perforated sub-
stance
e?nporal lobe (cut)
ptic tract
ulo-motor nerve
1-Trochlear nerve
Stria terminalis
Trigeminal nerve
-Lat. geniculate body
Abducens nerve
-Med. geniculate bod)
Pulvinar
Facial nerve
N. intermedius
, ^Acoustic nerve
Lateral ventricle
.Mid. cerebellar peduncli
Glossopharyngeal nerve
Vagus nerve
Accessory nerve
vAccessory nerve (spina!
ipital lobe (cut)
ypoglossal nerve
Spinal medulla
Vermis of cerebellum (cut)
FIG. 643. VIEW OP THE INFERIOR SURFACE OF THE BRAIN,
With the lower portion of the temporal and occipital lobes, and the cerebellum on the left side removed,
to show the origins of the cerebral nerves.
NERVUS OPTICUS.
The second or optic nerve consists of nerve fibres which spring from the
ganglion cells of the retina, and converge to the optic papilla, where they are grouped
together to form the optic nerve. The nerve pierces the outer layers of the retina,
the chorioid, and the sclera. It pierces the sclera 3 mm. (one-eighth of an inch),
to the medial side of the posterior pole of the eyeball, and enters the orbital fat,
through which it runs backwards and medially surrounded by the ocular muscles.
At the posterior part of the orbit it enters the optic foramen of the sphenoid bone,
through which it passes to the middle fossa of the skull, where it ends in the optic
chiasma, which lies at the base of the brain, anterior to the interpeduncular area
and between the right and the left anterior perforated substance.
From each of the two postero-lateral angles of the optic chiasma an optic tract
sweeps round to the back of the thalamus and to the mid-brain, between the pedun-
culus cerebri and the hippocampal gyrus of the corresponding side, and each tract
OCULO-MOTOE NEEVE.
769
terminates in connection with the pulvinar, the lateral geniculate body the superior
brachium, and the medial geniculate body all of the same side.
When the optic nerve reaches the optic chiasma some of its fibres pass to the optic
tract of the same side and some to the optic tract of the opposite side. Therefore,
each optic nerve is connected with both sides of the brain. But each optic tract, in
addition to some fibres of both optic nerves, contains also fibres passing from the
medial geniculate body of one side to the medial geniculate body of the opposite side.
FIG. 644. CENTRAL CONNEXIONS OF THE OPTIC NERVE AND OPTIC TRACTS.
In the orbital portion of its course the optic nerve is surrounded by sheaths of
the membranes of the brain, and by a sheath of fascia bulbi, as well as by the fat and
muscles ; and it is crossed by the ophthalmic artery and the naso-ciliary nerve. It
3 pierced on its inferior surface by the central artery of the retina, and as it
approaches the eyeball it is surrounded by the ciliary vessels and nerves.
NERVUS OCULOMOTORIUS.
The third or oculo-motor nerve arises from the brain, in the region of the
terior perforated substance, by several fila radicularia (radicles) emerging from
i oculo-motor sulcus, on the medial side of the cerebral peduncle, just in front
of the pons (Fig. 643). Passing forwards between the posterior cerebral and
50
770
THE NEKVOUS SYSTEM.
superior cerebellar arteries, the nerve pierces the dura mater beside the posterior
clinoid process, in a small triangular space between the free and attached borders
of the tentorium cerebelli. Beneath the dura mater the nerve courses through the
Diaphragma sellae
Fossa hypophyse
Sphenoidal sinus
Sphenoid bone
Internal carotid artery
Internal carotid artery
Trochlear nerve
Oculo-motor nerve ,'
Optic nerve
I Ophthalmic artery
Anterior clinoid process
Trochlear nerve
Frontal nerve
Lacrimal nerve
Oculo-motor nerve
(superior division)
Naso-ciliary nerve
Oculo-motor nerve
(inferior division)
Abducens nerve
Maxillary nerve
Abducens nerve
Cavernous sinus
Ophthalmic nerve
Maxillary nerve |
Mandibular nerve
Foramen ovale
' Mandibular nerve
Motor root of trigeminal nerve
FIG. 645. DELATIONS OF STRUCTURES IN THE CAVERNOUS SINUS AND SUPERIOR ORBITAL FISSURE.
lateral wall of the cavernous sinus, and enters the orbit through the superior
orbital fissure and between the two heads of the lateral rectus muscle. As it
enters the orbit it divides into upper and lower branches, separated by the naso-
ciliary nerve.
Branches. The
superior branch of the nerve
supplies two muscles of
the orbit the superior
rectus and the levator
palpebrse superioris.
The inferior branch
passes forwards, and after quadr ? g eS
giving branches to the
medial and inferior recti,
ends in the inferior oblique
muscle. The short root of
the ciliary ganglion arises
from the terminal branch
which goes to the inferior
oblique muscle.
Frenulum veli
Anterior medullary velum
Thalamus
Brachium
quadrigeminum
Trochlear nerve
Lateral lemniscus
Brachium
conjunctivum
Pedunculus cerebri
Lingula
FlG. 646.-
-DORSAL SURFACE OF THE MID-BRAIN, to show the origin
of the trochlear (fourth) nerve.
Communications. 1. In the cavernous sinus the oculo-motor nerve communicates with
the cavernous plexus on the internal carotid artery. 2. In the cavernous sinus it also
receives a slender communication from the ophthalmic division of the trigeminal nerve.
3. The short root of the ciliary ganglion passes upwards from the branch of the nerve
which supplies the inferior oblique muscle.
NERVUS TROCHLEARIS.
brain. It arises at tne side 01 the Jrenuium veil irom tne anterior end 01 tne
anterior medullary velum, just behind the corpora quadrigemina. It is extremely
slender, and of considerable length. Passing round the cerebral peduncle, the
nerve appears at the base of the brain behind the optic tract, in the interval
between the cerebral peduncle and the temporal lobe of the brain. Continued
forwards to the base of the skull, it pierces the free border of the tentorium cerebelli
postero-lateral to the oculo-motor nerve, and proceeds forwards in the lateral wal)
of the cavernous sinus, to the superior orbital fissure, lying between the oculo-
TEOCHLEAE NERVE.
motor nerve and the ophthalmic division of the trigeminal nerve. It enters the
orbit above the muscles of the eyeball, and terminates in the orbital (superior)
surface of the superior oblique muscle.
Communications. In the cavernous sinus the nerve receives (1) a communicating
Olfactory bulb
Optic nerve
Optic chiasma
terior cerebral
artery
[iddle cerebral
artery
Posterior
:ominuni-
i ng artery
alo-motor
nerve
: 'rior cere-
ral artery
i 'rior cere-
lar artery
Trochlear
nerve
i ucens
nerve
G sopharyn-
geal nerve
Vagus nerve
Accessory nerve
Hypoglossal nerve
Transverse sinus/
Vertebral artery
Spinal medul
Openings of occipital sinus
Infra-trochlear nerve
Supra-trochlear nerve
Oculo-motor nerve
Spheno-parietal sinus
Ophthalmic vein
Anterior clinoid
process
Trochlear nerve
Oculo-motor
nerve
Abducens nerve
Circular sinus
Ophthalmic nerve
Maxillary nerve
Mandibular nerve
Cavernous sinus
Basilar plexus
Semilunar
ganglion
Basilar
artery
Inferior
petrosal
sinus
Vertebral
artery
Sigmoid
sinus (part
of trans-
verse sinus)
Transverse sinus
Tentorium cerebelli
(cut)
Occipital sinuses
Inferior sagittal sinus
Confluens sinuum
Superior sagittal sinus
Falx cerebri (cut)
FIG. 647. THE BASE OF THE SKULL, to show the dura mater, sinuses, arteries, and nerves.
)h from the cavernous or carotid plexus on the internal carotid artery, and (2) a
slender filament from the ophthalmic division of the trigeminal nerve.
NERVUS TRIGEMINUS.
The fifth or trigeminal nerve arises from the inferior surface of the pons
n its lateral part by two roots, a large sensory root and a small motor root
Fig. 643, p. 768). The two roots proceed forwards in the posterior fossa of the
>kull, and piercing the dura mater beneath the attachment of the tentorium
Cerebelli to the superior angle of the petrous part of the temporal bone, enter
i cavity in the dura mater (cavum Meckelii) over the apex of the petrous bone.
772
THE NEKVOUS SYSTEM.
The large sensory root gradually conceals the small motor root in its course
forwards, and expands beneath the dura mater into a large flattened ganglion
the semilunar ganglion. This ganglion occupies an impression on the apex of the
petrous portion of the temporal bone, and from it three large trunks arise the
ophthalmic or first, the maxillary or second, and the mandibular or third divisions
of the nerve. The small motor root of the nerve passes forward beneath the
ganglion, and is incorporated wholly with the mandibular division of the nerve.
NERVUS OPHTHALMICUS.
The ophthalmic nerve passes forwards to the
of the skull, in the dura mater. It lies in the
orbit through the middle fossa
lateral wall of the cavernous
sinus, at a lower level than the
trochlear nerve, and reaches
the orbit through the superior
orbital fissure (Fig. 645).
In the wall of the cavernous
sinus the ophthalmic nerve gives
off (1) a small recurrent branch
to the dura mater (n. tentorii],
(2) communicating branches to
the cavernous plexus of the sym-
pathetic on the internal carotid
artery, and (3) small communi-
cating twigs to the trunks of
the oculo-motor, trochlear, and
abducent nerves.
In the, superior orbital
fissure the nerve divides into
three main branches lacrimal,
frontal, and naso-ciliary (Fig.
645).
N. Lacrimalis. -- The
lacrimal nerve enters the orbit
through the lateral angle
the superior orbital fissui
above the orbital muscles.
It passes forwards, between
the periosteum and the orbital
contents, to the anterior part
of the orbit, and ends by
supplying branches (a) to the
lacrimal gland, (ft) to the con-
junctiva,and (c) to the skin of the
lateral commissure of the eye.
The lacrimal nerve communicates in the orbit with the zygomatic branch of the maxillary
nerve, and on the face, by its terminal branches, with the temporal brandies of the facial
nerve (Fig. 653).
N. Prontalis. The frontal nerve enters the orbital cavity through
superior orbital fissure, courses forwards above the ocular muscles, and divi(
at a variable point into two branches a larger supra-orbital and a smaller supra-
trochlear nerve.
N. Supraorbitalis. The supra - orbital nerve passes directly forwards, anc
leaves the orbit through the supra-orbital groove or foramen to reach the forehead
It gives off the following secondary branches : (1) the principal (frontal) branche!
(rami frontales) are distributed to the forehead and scalp, reaching backwards as
far as the vertex ; (2) small branches supply the upper eyelid ; and (3) twigs ar<
FIG. 648. DISTRIBUTION OF SENSORY NERVES TO
THE HEAD AND NECK.
dis
OPHTHALMIC NEEVK 773
tributed to the frontal sinus. On the forehead the supra-orbital nerve com-
municates with the temporal branches of the facial nerve.
N. Supratrochlearis. The supra-trochlear nerve courses obliquely forwards
and medially above the tendon of the superior oblique muscle to reach the medial
side of the supra - orbital arch, where it leaves the cavity of the orbit; it is
distributed to the skin of the medial part of the forehead, the root of the nose, and
the medial commissure of the eye.
It communicates with the infra -trochlear branch of the naso- ciliary nerve, either
before or after leaving the orbital cavity.
N. Nasociliaris. The naso-ciliary nerve (O.T. nasal) enters the orbit through
the superior orbital fissure, between the heads of the lateral rectus muscle,
and between the two divisions of the oculo-motor nerve (Fig. 652, p. 776). It
crosses the orbital cavity obliquely to reach the anterior ethmoidal foramen, lying
in its course below the superior rectus and superior oblique muscles, and above the
optic nerve and medial rectus muscle. The nerve is transmitted, under the name
of anterior ethmoidal, through the anterior ethmoidal foramen into the cranial
cavity, where it lies embedded in dura mater on the lamina cribrosa of the
ethmoid bone. It enters the nasal cavity through the nasal fissure, and termin-
ates by dividing into medial and lateral branches. The medial division supplies
the mucous membrane over the upper and anterior part of the nasal septum.
The lateral branch, after supplying collateral offsets to the lateral wall of the
nasal cavity, finally appears on the face as the external nasal nerve between the
nasal bone and lateral cartilage, and supplies branches to the skin of the lower part
and tip of the nose.
The branches of the naso-ciliary nerve may be divided into three sets, arising
(a) in the orbit, (&) in the nose, and (c) on the face.
In the orbit the branches are given off in three situations lateral to, above, and
medial to the optic nerve. (a) As the nerve lies on the lateral side of the
optic nerve, it gives off the radix longa ganglii ciliaris (long root of the ciliary
ganglion). (&) As it crosses above the optic nerve, nn. ciliares longi (two long ciliary
branches) arise, and pass forwards alongside the optic nerve to the eyeball, (c) On
the medial side of the optic nerve the n. infratrochlearis (infra -trochlear nerve)
arises, a slender branch which courses forwards below the pulley of the superior
oblique muscle to the front of the orbit. It ends on the face by supplying
the skin of the root of the nose and the eyelids, and communicates either in
. the orbit or on the face with the supra-trochlear nerve. On the face it also
i communicates with zygomatic branches of the facial nerve.
In the nose the rami nasales mediales (medial nasal branches) supply the mucous
, membrane of the anterior part of the nasal septum ; the rami nasales laterales (lateral
nasal branches) supply the anterior part of the lateral wall of the nasal cavity.
On the face the terminal filaments of the nerve are distributed, as the ramus
nasalis externus (external nasal branch), to the skin of the lower half and tip of
the nose. The terminal branch communicates with the zygomatic branches of the
facial nerve (Fig. 653).
Ganglion Ciliare. The ciliary ganglion is associated with the naso-ciliary
branch of the ophthalmic nerve and with the inferior division of the oculo-motor
nerve. It is a small reddish ganglion, placed between the lateral rectus muscle
1 and the optic nerve, and in front of the ophthalmic artery. Its roots are three
in number : (1) sensory or long, derived from the naso-ciliary branch of the
: ophthalmic nerve; (2) motor or short, derived from the inferior division of the
. oculo-motor nerve; and (3) sympathetic, a slender filament from the cavernous
plexus on the internal carotid artery, which may exist as an independent root
or may be incorporated with the long root from the naso-ciliary nerve. The
branches from the ganglion are twelve to fifteen nn. ciliares breves (short ciliary
nerves), which pass to the eyeball in two groups above and below the optic nerve.
They supply the coats of the eyeball, including the iris and ciliary muscles. The
circular fibres of the iris and the ciliary muscle are innervated by the third nerve ;
the radial fibres of the iris by the sympathetic.
774
THE NEKVOUS SYSTEM.
Branches of the olfactory nerves
Right naso-palatine nerve
Medial nasal nerve
Posterior palatine nerve
Middle palatine nerve
Left naso-palatine
nerve
Anterior palatine nerve
FIG. 649. TNNERVATION OF NASAL SEPTUM AND PALATE.
Posterior superior lateral nasal nerve
Spheno-palatine ganglion
Olfactory nerves
Anterior palatine nerve-
Middle palatine nerve-
Posterior palatine nerve-
Posterior inferior nasal nerve
Lateral nasal nerve
Naso-palatine nerv
Posterior palatine nerve
Middle palatine nerve
Anterior palatine nerve
FIG. 650. INNERVATION OF LATERAL WALL OF NASAL CAVITY AND PALATE.
MAXILLAEY NEEYE.
775
NERVUS MAXILLARIS.
The Maxillary Nerve. This large nerve courses forwards from its origin in
the semihmar ganglion through the middle fossa of the skull, in the dura mater,
and in relation to the lower part of the cavernous sinus (Fig. 647, p. 771). It
passes through the foramen rotundum, traverses the pterygo-palatine fossa, and
enters the orbit as the infra-orbital nerve, through the inferior orbital fissure. In
the orbit it occupies successively the infra-orbital groove and canal, and it finally
appears on the face through the infra-orbital foramen (Fig. 653).
The branches and communications of this nerve occur (a) in the cavity of the
cranium, (Z>) in the pterygo-palatine fossa, (c) in the infra-orbital canal, and (d)
on the face.
Supra-trochlear branch
Supra-orbital branch ^-\
Lacrimal gland
Levator palpebrse %'
superioris
Infra-trochlear nerve
Obliquus superior
muscle
Anterior ethmoidal
nerve
superiori
Frontal nerve
Jaso- ciliary nerve
Lacrimal nerve
Bectus lateralis ^^g^ ^MBM V Tr^T" ' '" Troclilear nerve
Superior orbital
fissure ^^ ^ -^MW.,
Naso-ciliary nerve
Ophthalmic division jrfHPlT/ ^^^SS^SS^.- Optic nerve
of trigeminal
Maxillary division
of trigeminal
Mandibular division
of trigeminal
Semilunar ganglion -
In the cavity of the cranium the nerve gives off a minute (n. meningeus medius)
middle meningeal (O.T. recurrent nerve) to the dura mater of the middle fossa of
the skull.
In the pterygo-palatine fossa the nerve gives off (1) two short thick spheno-
palatine nerves, the sensory roots of the spheno-palatine ganglion.
(2) Posterior superior alveolar nerves, which may be double, descend through the
pterygo-maxillary fissure to the lateral side of the maxilla, and proceed forwards
along the alveolar arch, in company with the posterior superior alveolar artery.
They supply the gum and the upper molar teeth by branches which perforate the
bone to reach the alveoli. The nerves form a fine plexus joined by the middle
alveolar nerve before finally reaching the teeth.
(3) A small zygomatic (O.T. orbital) branch enters the orbital cavity through
the inferior orbital fissure, and proceeding along the lateral wall, communicates
Oculo-motor nerve
Trochlear nerve
Trigeminal nerve
FIG. 651. THE NERVES OF THE ORBIT FROM ABOVE.
776
THE NERVOUS SYSTEM.
with the lacriinal nerve, and passes through the zygomatico-orbital foramen in the
zygomatic bone, where it divides into two branches. The zygomatico-facial (O.T.
malar) branch appears on the face, after traversing the zygomatic bone, and supplies
Lacrimal gland
Frontal nerve
Supra-orbital nerve
Lacrimal nerve
Nerves to superior rectus and
levator palpebne from oculo-
motor nerve (superior division)
Trochlear nerve -
Rectus lateral! s
Abducens nerve
Oculo-motor nerve
(inferior division)
Ciliary ganglion
Nerve to rectus inferior from
oculo-motor nerve
Nerve to obliquus inferior
from oculo-motor nerve
Supra-trochlear nerve
Levator palpebrse superioris
Rectus superior
Obliquus superior
Naso-ciliary nerve
Infra-trochlear nerve
Rectus medialis
Nerve to rectus medialis from
'oculo-motor
Ophthalmic artery
Optic nerve
Long ciliary nerves
Rectus inferior
Obliquus inferior
FIG. 652. SCHEMATIC REPRESENTATION OF THE NERVES WHICH TRAVERSE THE CAVITY OF THE ORBIT.
the skin over that bone. It communicates with the zygomatic branches of the
facial nerve. The zygomatico-temporal (O.T. temporal) branch perforates the temporal
surface of the zygomatic bone, and is distributed, after piercing the temporal fascia,
Ophthalmic nerve
Maxillary nerve
Semilunar ganglion ^
Trigeminal nerve |
(afferent root)
Mandibular
nerve
Communication with lacrimal nerve
Frontal nerve |
Lacrimal nerve
Naso-ciliary nerve v
Maxillary nerve
Pharyngeal nerve
Nerve of pterygoid canal
Spheno-palatine ganglion
Palatine nerves
Posterior superior alveolar nerves
Zygomatic nerve 1M
Infra-orbital nerve, entering canal
Supra-orbital nerve
Supra-trochlear nerves
Sensory root from maxillary. nerve
Sensory root from maxillary
nerve
_,-- Zygomatico-temporal branch
Infra-trochlear nerve
Zygomatico-facial branch
Inferior palpebral branch
External nasal nerves
Infra-orbital nerve,
leaving canal
External nasal
branch
Superior labial branches ^
FIG. 653. THE COURSE OF THE OPHTHALMIC AND MAXILLARY NERVES.
to the skin over the anterior part of the temple. It communicates with th(
temporal branches of the facial nerve. It may be very minute, and not
further than the temporal fascia, between the two layers of which it may form s
communication with the facial nerve.
777
MAXILLAEY NEKVE.
(4) The infra-orbital nerve, is the terminal branch of the maxillary nerve, which
enters the orbit through the inferior orbital fissure and traverses the infra-orbital
canal to reach the face.
In the infra-orbital canal the infra-orbital nerve supplies one and sometimes
two branches to the teeth the middle and anterior superior alveolar nerves (ramus
alveolaris superior medius et rami alveolares superiores anteriores). The former may be
only a secondary branch of one of the latter nerves, or it may arise independently
from the infra-orbital nerve. However formed, the nerves descend in bony canals
in the wall of the maxillary sinus (to the lining of which branches are given), and
reach the alveolar arch, where they form minute plex'uses and supply the teeth
(joining posteriorly with the branches of the posterior superior alveolar nerves).
The anterior superior alveolar nerve supplies the incisor and canine teeth; the
middle superior alveolar nerve supplies the premolar teeth.
After emerging on the face from the infra-orbital foramen, the infra-orbital
nerve divides into a number of radiating branches arranged in three sets (a)
Zygomatic branch at inferior orbital fissure
Maxillary nerve at foramen
rotundum
jfra-orbital nerve appearing
the face at the infra-orbital
foramen
Middle and anterior/
alveolar branches \
Spheno-palatine ganglion and nerves
v - Palatine branches
Posterior superior alveolar nerve
FIG. 654. COURSE -AND BRANCHES OF THE MAXILLARY NERVE.
inferior palpebral (rami palpebrales inferiores), for the lower eyelid ; (&) external nasal
(rami nasales externi), for the skin of the side of the nose ; and (c) superior labial
(rami labiales superiores), for the cheek and upper lip. These branches form com-
munications with the zygomatic branches of the facial nerve, and' give rise to the
infra-orbital plexus (Fig. 657, p. 783).
Ganglion Spheno-palatinum. The spheno - palatine ganglion occupies the
upper part of the pterygo- palatine fossa. It is a small reddish-gray ganglion,
suspended from the maxillary nerve by the two spheno-palatine branches which
constitute its sensory roots. The motor and sympathetic roots of the ganglion are
derived from the nerve of the pterygoid canal. This nerve is formed in the cranial
cavity, upon the cartilage filling up the foramen lacerum, by the union of the
greater superficial petrosal nerve from the genicular ganglion of the facial nerve
(emerging from the temporal bone through the hiatus canalis facialis) with the
deep petrosal nerve, a branch of the sympathetic plexus on the internal carotid
artery. The nerve of the pterygoid canal passes through the pterygoid canal
to the pterygo-palatine fossa, where it joins the spheno-palatine ganglion.
778 THE NEKVOUS SYSTEM.
The branches from the ganglion are seven in number.
(a) The pharyngeal branch passes backwards through the pharyngeal canal to
supply the mucous membrane of the roof of the pharynx.
(&) Nervi Palatini. The palatine nerves, three in number, are directed down-
wards to the palate through the palatine canals.
The large anterior palatine nerve emerges on the under surface of the palate
through the greater palatine foramen, and at once separates into numerous branches
for the supply of the mucous membrane of the soft and the hard palate. Its
anterior filaments communicate with branches of the naso-palatine nerve. The
main nerve gives off, as it lies in the palatine canal, a small posterior inferior lateral
nasal nerve (rami nasales posteriores inferiores laterales), which enters the nasal
cavity and supplies the mucous membrane of the lower part of its lateral wall.
The middle palatine nerve descends through a small palatine canal, and, piercing the
pyramidal process of the palate bone, is distributed to the mucous membrane of the
soft palate, uvula, and palatine tonsil. It possibly conveys motor fibres to the levator
veli palatini and uvular muscles. The n. palatinus posterior (posterior palatine
nerve) consists of one or more small twigs which pass through lesser palatine canals,
and supply branches to the mucous membrane of the tonsil, soft palate, and uvula.
(c) The branches directed medially from the spheno-palatine ganglion enter the
nasal cavity through the spheno-palatine foramen. They are two in number the
posterior superior lateral nasal and the naso-palatine. The posterior superior
lateral nasal branch (rami nasales posteriores superiores laterales) is a small nerve
destined for the mucous membrane of the superior and posterior part of the lateral
wall of the nasal cavity. The n. nasopalatinus (naso-palatine nerve), after passing
through the spheno-palatine foramen, crosses the roof of the nasal cavity, and
extends obliquely downwards and forwards along the nasal septum, grooving the
vomer in its course, to reach the incisive foramen near the front of the hard palate.
The nerves pass through the subordinate median foramina (of Scarpa), the lefb
nerve in front of the right. In the incisive foramen the two nerves communicate
together. They then turn backwards and supply the mucous membrane of the
hard palate. They communicate posteriorly with terminal filaments of the anterior
palatine nerves. In its course through the nasal cavity the naso-palatine nerve
furnishes collateral branches to the mucous membrane of the roof and septum of
the nose (posterior superior medial branches') (Fig. 649, p. 774).
(d) Rami Orbitales. The orbital branches, one or more minute branches, pass
upwards to the periosteum of the orbit from the spheno-palatine ganglion.
NERVUS MANDIBULARIS.
The mandibular nerve is formed by the union of two roots ; a large sensory
root, from the semilunar ganglion, and the small motor root of the trigeminal
nerve, which is wholly incorporated with the mandibular trunk. The two roots
pass together in the dura mater of the middle fossa of the base of the skull
to the foramen ovale, through which they emerge into the infra-temporal fossa.
Outside the skull they combine to form a single trunk, which soon separates into
anterior and posterior divisions.
At its emergence from the skull the nerve is deeply placed beneath the middle
of the zygoinatic arch, and is concealed by the ramus of the mandible, and by the
masseter, temporal, and external pterygoid muscles.
The branches of the nerve may be divided into two series (1) those derived
from the undivided nerve, and (2) those derived from its terminal divisions.
The branches of the undivided nerve are two in number, (a) A small nervus
spinosus (O.T. recurrent nerve) arises just outside the skull, and accompanying the
middle meningeal artery through the foramen spinosum, supplies the dura mater.
(6) In the infra-temporal region a small branch arises for the supply of the internal
pterygoid muscle. This nerve forms a connexion with the otic ganglion.
The terminal divisions of the nerve are a small anterior and a large posterior
trunk.
The small anterior trunk (nervus masticatorius or masticator nerve) passes
MANDIBULAR NERVE.
779
downwards and forwards medial to the external pterygoid muscle, and separates into
the following branches : (1) A branch for the external pterygoid muscle, which
supplies it on its deep surface ; (2) a branch to the masseter muscle (h. mas-
setericus), which passes over the superior border of the external pterygoid and
through the mandibular notch of the mandible ; (3) and (4) two deep temporal
branches (nn. temporales profundi), an anterior and a posterior, to the temporal muscle,
which also ascend above the external pterygoid muscle ; and (5) the n. buccinatorius
(buccinator (O.T. buccal) nerve), which passes obliquely forwards between the two
heads of the external pterygoid to reach the buccinator muscle. This nerve is
sensory, and its fibres are, in part, distributed to the skin of the cheek (communi-
cating with buccal branches of the facial nerve) ; they are also, in part, distributed
to the mucous membrane of the inside of the mouth, to reach which they pierce
nerve
' Genicular ganglion
i | Carotico-tyinpanic nerve
| Lesser superficial petrosal nerve
Tympanic plexv
Tympanic branch of
glos
lossopharyngeal
Chorda tympani nerve 1
Auriculo-temporal nerve
Inferior alveolar nerve
Stylogl
Mylo-hyoid branch
Internal carotid artery
I Middle meningeal artery
Sympathetic root from sympathetic plexus on the middle meningeal artery
| Otic ganglion
Nerves to tensor tympani and tensor veli palatini
Nerve to internal pterygoid muscle
Mandibular nerve
-- Anterior division (motor)
^Temporal branch
Lingual nerve
-Masseteric branch
'External pterygoid branch
Temporal branch
Buccinator branch
Communication to hypoglossal
Submaxillary ganglion
Hyoglossus
Genioglossus
Nerve to mylo-hyoid musa
Nerve to digastric (anterior belly)
icisor branch
igastric (anterior belly)
FIG. 655. THE MANDIBULAR NERVE.
fibres of the buccinator muscle. The buccinator nerve usually supplies a
third branch to the temporal muscle, after emerging between the two heads of
1 the external pterygoid muscle (Fig. 655).
The large posterior trunk extends downwards a short way medial to the external
pterygoid muscle. After giving off, by two roots, the auriculo-temporal nerve, it
ends by dividing into two, the lingual and the inferior alveolar nerves.
N. Auriculotemporalis. The auriculo-temporal nerve is formed by the union
i of two roots which embrace the middle meningeal artery. The nerve passes
backwards medial to the external pterygoid muscle and between the spheno-man-
! dibular ligament and the neck of the mandible. After passing through the parotid
1 gland, it is directed upwards to the temple over the zygoma, in company with the
superficial temporal artery. It is finally distributed as a cutaneous nerve of the
1 temple and scalp, and reaches almost to the vertex of the skull.
The auriculo-temporal nerve gives off the following branches: (1) A small
branch to the mandibular articulation. (2) Branches to the parotid gland (rami
780 THE NERVOUS SYSTEM.
parotidei). (3) A twig for the supply of the skin of the external acoustic meatus
and membrana tympani (n. meatus auditor!! extern! et ramus membranae tympani).
(4) Branches to the superior half of the auricle on its lateral aspect. (5) Terminal
branches to the skin of the temple and scalp (ram! temporales superficiales).
It has the -following communications with other nerves : (1) Important communica-
tions are effected by the roots of the nerve, which are separately joined by small branches
from the otic ganglion. (2) The parotid branches of the nerve are connected with branches
of the facial nerve in the substance of the gland (rami anastomotici c. nervo faciali).
(3) The temporal branch of the nerve is in communication superficially with the temporal
branches of the facial nerve.
N. Lingualis. The lingual nerve is the smaller of the two terminal branches
of the posterior division of the mandibular trunk. It proceeds downwards in front
of the inferior alveolar nerve, medial to- the external pterygoid muscle, to its inferior
border. After passing between the internal pterygoid muscle and the ramus of
the mandible, it crosses beneath the mucous membrane of the floor of the mouth
in the interval between the mylo-hyoid and hyoglossus muscles and beneath the
duct of the submaxillary gland. It sweeps forwards and medially to the side of
the tongue, to the mucous membrane over the anterior two-thirds of which it is
distributed.
Two nerves communicate with the lingual nerve in its course to the tongue :
(1) The chorda tympani branch of the facial nerve joins it medial to the external
pterygoid muscle, and is incorporated with it in its distribution to the tongue.
(2) The hypoglossal nerve forms larger or smaller loops of communication with
the lingual nerve as they course forwards together over the hyoglossus muscle (rami
anastomotici cum nervo hypoglosso).
Besides supplying the aforesaid branches to the mucous membrane over the sides
and dorsum of the tongue in its anterior two- thirds, the lingual nerve supplies the
mucous membrane of the side wall and floor of the mouth. It also assists, along
with the chorda tympani nerve, in forming the roots of the submaxillary ganglion.
Ganglion Submaxillare. The submaxillary ganglion is a minute reddish
ganglion placed on the hyoglossus muscle, between the lingual nerve and the duct
of the submaxillary gland. It is suspended from the former by two trunks, con-
sisting for the most part of fibres of the lingual and chorda tympani nerves, which
at that point become separated from the lingual nerve and incorporated with the
ganglion. The roots of the ganglion are (1) an afferent root, derived from the
lingual nerve ; (2) an efferent root, derived from the chorda tympani ; and (3) a
sympathetic root, from the sympathetic plexus upon the external maxillary artery.
The branches from the ganglion are distributed to the submaxillary gland and
duct (rami submaxillares), and by fibres which become reunited with the trunk of
the lingual nerve, to the sublingual gland.
N. Alveolaris Inferior. The inferior alveolar nerve (O.T. inferior dental)
is larger than the lingual nerve. It passes from beneath the inferior border of the
external pterygoid muscle to reach the interval between the ramus of the man-
dible and the spheno- mandibular ligament. Entering the mandibular canal
through the mandibular foramen, it traverses the substance of the ramus and body
of the mandible, distributing branches to the teeth in its course. A fine plexus is
formed by the dental branches before they finally supply the teeth.
Branches and Communications. (1) N. Mylohyoideus. The mylo-hyoid nerve is
a small branch arising just before the inferior alveolar nerve passes through the
mandibular foramen. Grooving the ramus in its course, it descends into the
submaxillary triangle on the superficial aspect of the mylo-hyoid muscle. Concealed
in this situation by the submaxillary gland and the external maxillary artery, it
is distributed to the mylo-hyoid muscle and the anterior belly of the digastric muscle.
(2) N. Mentalis. The mental branch of the inferior alveolar nerve is a trunk of con-
siderable size arising from the main nerve in the mandibular canal. It emerges
from the mandible through the mental foramen, and is distributed by many branches
to the chin and lower lip. It communicates, under cover of the facial muscles, with the
ramus marginalis mandibulse of the facial nerve (Fig. 657, p. 783). (3) The incisor
FACIAL NEEVE. 781
branch is the terminal part of the inferior alveolar nerve remaining after the origin
of the mental branch. It supplies the canine tooth and the incisor teeth.
Ganglion Oticum. The otic ganglion is situated deep to the mandibular
nerve just below the foramen ovale. Like the other ganglia described above, it
possesses three roots : (1) A motor root, derived from the nerve to the internal
pterygoid muscle ; (2) a sensory root, formed by the lesser superficial petrosal nerve
from the tympanic plexus (through which communications are effected with the
tympanic branch of the glossopharyngeal nerve, and a branch from the genicular
ganglion of the facial nerve); (3) a sympathetic root, from the plexus on the
middle meningeal artery (Fig. 656).
Five branches arise from the ganglion three communicating and two motor
branches. The three communicating nerves are fine branches which join respectively
the nerve of the pterygoid canal, the roots of the auriculo-temporal nerve, and the
chorda tympani nerve. The two motor nerves supply the tensor tympani and
tensor veli palatini muscles.
Summary. The trigeminal, the largest and most complex of the cerebral nerves, is (1) the
chief sensory nerve for the face, the anterior half of the scalp, the orbit and eyeball, the nose and
nasal cavity, the lips, teeth, mouth, and anterior two-thirds of the tongue ; (2) the motor fibres
of the nerve supply the muscles of mastication, the mylo-hyoid and anterior belly of the digastric,
possibly the levator veli palatini and uvular muscle (through the spheno-palatine ganglion), and
the tensor tympani and tensor veli palatini muscles (through the otic ganglion) ; (3) through the
ganglia placed on the three divisions of the nerve, not only are important organs, areas, and
muscles innervated, but communications are also effected with the sympathetic system, with the
oculo-motor nerve (ciliary ganglion), facial nerve (spheno-palatine and otic ganglia), and glosso-
pharyngeal nerve (otic ganglion).
In its distribution to the skin of the face the branches of the fifth nerve present two striking
peculiarities : (1) While the branches to the skin reach the surface at many points and in
diverse ways, the three main divisions are severally, by their branches, responsible for the supply
of three clearly demarcated cutaneous areas (Fig. 648, p. 772). (2) By numerous communications
with the facial nerve, sensory fibres are given to the muscles of expression supplied by the*
facial nerve.
NERVUS ABDUCENS.
The sixth or abducens nerve issues from the brain at the inferior border of
the pons, just above the pyramid of the medulla oblongata (for the deep origin, see
p. 600). It is directed forwards, it pierces the dura mater in the posterior
fossa of the base of the skull alongside the dorsum sellse, and enters the cavernous
sinus (Fig. 647, p. 771). In the sinus it is placed close to the lateral side of the
internal carotid artery. After it leaves the sinus it passes through the superior
orbital fissure below the oculo-motor and naso-ciliary nerves and between the two
heads of the lateral rectus muscle (Fig. 652, p. 776). In the cavity of the orbit it
supplies the lateral rectus muscle on its deep (ocular) surface.
Communications. In the wall of the cavernous sinus the sixth nerve receives two
communicating filaments : (1) From the carotid plexus of the sympathetic, and (2) from
the ophthalmic division of the trigeminal nerve.
NERVUS FACIALIS.
The seventh or facial nerve emerges from the brain at the inferior border of
the pons, below the trigeminal nerve and medial to the acoustic nerve (for the deep
origin, see p. 598). Between it and the acoustic nerve is the minute nervus inter -
medius (Fig. 656, p. 782). The facial nerve passes through the internal acoustic
meatus, and through the canalis facialis in the petrous portion of the temporal bone,
emerges at the base of the skull by the stylo-mastoid foramen, and passes forwards
through the parotid gland to supply the muscles of the face. In the internal
acoustic meatus the nerve is placed upon the acoustic nerve, the nervus intermedius
intervening. In the canalis facialis the nerve first passes forwards and laterally
to the hiatus of the canal, then backwards on the medial side of the tympanum,
and finally downwards behind the tympanum, in the medial wall of the tympanic
antrum. In the parotid gland it crosses the external carotid artery and the posterior
facial vein superficially. On the face its branches radiate from the anterior border
of the parotid gland and enter the deep surface of the facial muscles.
782
THE NEKVOUS SYSTEM.
Branches and Communications. (i.) In the internal acoustic meatus the nervus
intermedius, lying between the facial and acoustic nerves, sends communicating
branches to both of them. The branch to the acoustic nerve probably separates
from it again to join the genicular ganglion of the facial nerve.
(ii.) In the canalis facialis the ganglion geniculi is formed at the point where
the facial nerve bends backwards. It is an oval swelling on the -nerve, and is
joined by a branch from the upper (vestibular) trunk of the acoustic nerve, by
which it probably receives fibres of the nervus intermedius. From the ganglion
three small nerves arise : (1) The greater superficial petrosal nerve passes forwards
through the hiatus canalis facialis to the middle fossa of the skull. In the
upper part of the foramen lacerum it is joined by the deep petrosal nerve
from the sympathetic plexus on the internal carotid artery to form the nerve
of the pterygoid canal, which, after traversing the pterygoid canal, ends in the
spheno- palatine ganglion. (2) A minute nerve (ramus anastomoticus cum plexu
tympanico} pierces the temporal bone and joins the tympanic branch of the glosso-
Anastornotic with tympanic plexus
Tympanic plexus v i
Chorda tympaui , \
Nerve to stapedius \ \ \
Genicular ganglion
Facial nerve
I Nervus intermedius
/ | Acoustic nerve
External superficial petrosal nerve
,1 Greater superficial petrosal nerve
Carotico-tyin panic nerve
Smaller superficial petrosal nerve
Sympathetic plexus on internal carotid artery
Spheno-palatine brai
Maxillary nerve
| Spheno-palatii
branches
Posterior auricular nerve / /
rves.to stylo-hyoid and digastric (posterior belly)
Communication with auricular branch of vagus'
Auricular branch
Vagus nerve, jugular ganglioi:
Glossopharyngeal nerve
Tympanic branch
Auriculo-teuiporal nerve
External super-
ficial petrosal nerve .
Sympathetic plexus on Spheno-palatin
middle meningeal artery
"Otic ganglion
"ZirJ }Communication to roots of auriculo-tempo
I Communication to chorda tympani
- Mandibular nerve
Masticator nerve (anterior division of mand
Lingual nerve
Inferior alveolar nem
FIG. 656. THE CONNEXIONS OF THE - FACIAL NERVE IN THE TEMPORAL BONE.
pharyngeal in the substance of the bone. By their union the lesser superficial
petrosal nerve is formed, which pierces the temporal bone and ends in the otic
ganglion. (3) The external superficial petrosal nerve is a minute inconstant branch
which joins the sympathetic plexus on the middle meningeal artery.
In the course of the facial nerve in the lower part of the canalis facialis,
behind the tympanum, three branches arise (1) N. Stapedius. The small nerve
to the stapedius muscle, which passes forwards to the tympanum. (2) Chorda
Tympani. The chorda tympani nerve (probably associated with the nervus inter-
medius), which enters the tympanic cavity through the tympanic aperture of the
canaliculus chordce, passes over the membrana tympani and the handle of the
malleus, and leaves the cavity through the medial end of the petro-tympanic fissure
to reach the infra -temporal fossa. Medial to the external pterygoid muscle it
becomes incorporated with the lingual branch of the mandibular nerve, and in its
further course is inseparable from that nerve. It supplies a root to the submaxillary
ganglion, and is finally distributed to the side and dorsum of the tongue in its
anterior two-thirds. The chorda tympani nerve receives, under cover of the ex-
ternal pterygoid muscle, a fine communication from the otic ganglion. (3) Before
it leaves the canalis facialis a fine communicating branch arises from the facial
nerve to join the auricular branch of the vagus nerve.
(iii.) In the neck the facial nerve gives off three muscular branches : (1) and (2)
FACIAL NEEVE.
783
Eamus Stylohyoideus, Eamus Digastricus. Small branches supply the stylo-hyoid
and the posterior belly of the digastric, the latter nerve sometimes communicating
with the glossopharyngeal. (3) N. Auricularis Posteriori The posterior auricular
nerve bends backwards and upwards over the 'anterior border of the mastoid pro-
cess along with the posterior auricular artery. It divides into two branches an
auricular branch for the posterior auricular muscle and the intrinsic muscles of
the auricle, and an occipital branch for the occipital belly of the epicranius muscle.
Supra-trochlear nerve
Supra-orbital nerve ,
i-trochlear nerve ,/L
matico -facial nerve
External nasal nerve
Infra-orbital nerve
ifra-orbital plexus
Lower zygomatic
inches of temporo-
facial division
Buccinator nerve ~
Mental nerve
_ Zygomatico-temporal
nerve
Auriculo-temporal nerve
Temporal \ branches
Posterior auricular nerve
~~ Facial nerve
Cervico-facial division
- ( Branches to stylo-hyoid
1 and digastric
^(posterior belly)
"" Buccal branch
Marginal mandibular branch
Cervical branch
657. THE DISTRIBUTION OF THE TRIGEMINAL AND FACIAL NERVES ON THE FACE.
The posterior auricular nerve, in its course, communicates with the great auricular,
. lesser occipital, and auricular branch of the vagus nerves.
(iv.) In the parotid gland the facial nerve spreads out in an irregular series of
: branches (plexus parotideus), indefinitely divided into a temporo-facial and a cervico-
! facial division. Communications occur in the substance of the gland between the
main trunks and the great auricular and auriculo-temporal nerves.
The temporo-facial division gives off two series of subordinate branches which
radiate forwards and upwards from the parotid gland.
1. Kami Temporales. The temporal branches are of large size, and, sweeping
3ut of the parotid gland over the zygomatic arch, are distributed to the orbicularis
)culi, frontalis, corrugator supercilii, auriculares anterior and superior. The temporal
pranches communicate in their course with the auriculo-temporal, zygomatico-
' temporal, lacrimal, and supra-orbital branches of the trigeminal nerve.
!. Kami Zygomatici. The upper zygomatic branches are small, and sometimes
ire inseparable from the temporal or lower zygomatic nerves. Extending forwards
784
THE NEEYOUS SYSTEM.
across the zygomatic bone, they supply the orbicularis oculi and zygomatic muscle,
and communicate with the zygomatico-facial branch of the maxillary nerve.
. The lower zygomatic branches are of considerable size. Passing forwards over
the masseter muscle in company with the parotid duct, they supply the orbicularis
oculi, the zygomaticus, buccinator, and the muscles of the nose and upper lip.
The infra-orbital plexus is formed by the union of these nerves with the infra-orbital
branch of the maxillary nerve below the lower eyelid. Smaller communica-
tions occur with the infra-trochlear and nasal nerves on the side of the nose.
The cervico-facial division of the facial nerve supplies three series of secondary
branches.
1. Rami Buccales. The buccal branch (or branches) extends forwards to the
angle of the mouth to supply the muscles converging to the mouth, including the
buccinator. It communicates with the buccinator branch of the mandibular nerve
in front of the anterior border of the masseter muscle.
2. Eamus Marginalis Mandibulse. The marginal branch of the mandible (O.T. supra-
mandibular) passes along the mandible to the interval between the lower lip and
chin, and supplies the triangularis oris, quadratus labii inferioris, and orbicularis
oris. It communicates with the mental branch of the inferior alveolar nerve.
3. Ramus Colli. The cervical branch (O.T. infra-mandibular) emerges from the
parotid gland near its lower end, and sweeps forwards below the angle of the
mandible to the front of the neck. It supplies the platysma, and forms loops of
communication with the nervus cutaneus colli.
NERVUS ACUSTICUS.
The eighth or acoustic nerve (O.T. auditory) arises from the brain by two
roots, medial and lateral. The medial, vestibular root emerges between the olive
and the restiform body. The lateral, cochlear root, continuous through the cochlear
nucleus with the strise medullares of the fourth ventricle, winds round the lateral
side of the restiform body (for the deep connexions, see p. 604). The two roots
unite with one another to form the trunk of the nerve, which is attached to the
Principal
vestibular nucleus
Dorsal cochlear nucleus
Restiform body
Ampulla of lateral semicircula
Corpus trapezoideum
Ampulla of superior semicircular duct
Acoustic nerve
Olive Internal acoustic meatus
Superior division
Inferior division
Cochlear nerve
Ductus cochlearis
, , ' Saccus end<
Ampulla of lymph atici
posterior
Saccule semicircular
duct
FIG. 658. SCHEME OF THE ORIGIN AND DISTRIBUTION OF THE ACOUSTIC NERVE.
brain on the lateral side of the facial nerve and nervus intermedius, at the lower
border of the pons (Fig. 643, p. 768).
The nerve passes laterally through the internal acoustic meatus, lying below
the facial nerve and nervus intermedius (Fig. 647, p. 771). In the meatus the
trunk separates into two divisions, an upper consisting of vestibular fibres only
and a lower which consists mainly of cochlear fibres but contains also some
vestibular fibres. The divisions subdivide, and their branches pass through the
lamina cribrosa, to supply the several parts of the labyrinth.
The superior division in the internal acoustic meatus usually receives fibres
GLOSSOPHARYNGEAL NERVE.
785
i.e.
from the nervus intermedius, and gives off a communicating branch to the
genicular ganglion of the facial nerve. It then separates into three terminal
branches which pierce the lamina cribrosa. (1) N. Utricularis. The utricular
nerve supplies the macula acustica of the utricle. (2) and (3) Nn. Ampullaris Superior
et Lateralis. The superior and lateral ampullary nerves supply the ampullae of the
superior and lateral semicircular ducts.
The inferior division gives off (1) n. saccularis, a saccular nerve to the macula
acustica of the saccule, (2) n. ampullaris inferior, an inferior ampullary nerve to the
ampulla of the posterior semicircular duct, and (3) is continued through the lamina
cribrosa to the labyrinth as the cochlear nerve, which is distributed through the
modiolus and osseous spiral lamina to the organ of Corti in the cochlea.
Both the vestibular and cochlear nerves contain among their fibres collections of nerve
cells, forming in each nerve a distinct ganglion the vestibular ganglion on the vestibular
trunk, and the ganglion spirale or spiral ganglion of the cochlea on the cochlear trunk.
NERVUS G-LOSSOPHARYNGEUS.
The ninth or glossopharyngeal nerve (Fig. 643, p. 768) arises from the brain
by five or six fine fila radicularia (radicles) which emerge from the medulla oblongata,
between the posterior and lateral
columns, close to the facial nerve
above, and in series with the fila
of the vagus nerve below (for the
deep connexions, see p. 596). The
fila combine to form a nerve which
passes through the jugular fora-
men, along with the vagus and
accessory nerves, but enveloped in
a separate sheath of dura mater
(Fig. 647, p. 771). Eeaching the
neck, the nerve arches downwards
and forwards to the interval be-
tween the hyoid bone and the
mandible. In its course to the side
of the pharynx it lies at first- be-
tween the internal carotid artery
and the internal jugular vein, and
then between the internal and ex-
ternal carotid arteries. It sweeps
round the stylopharyngeus muscle
and the stylo-hyoid ligament, and
disappears medial to the hyoglossus
muscle, to reach its termination in
the tongue.
The branches of the nerve mav ,
.,. - *V FIG. 659. SCHEME OF THE DISTRIBUTION OF THE GLOSSO-
Dlassined in three series accord- PHARTOGEAL NERVE.
to their Origin (i.) in the G . Pllj Glossopharyngeal nerve ; J, Superior, and P, Petrous
JUgular foramen ; (ii.) in the nei^k ; ganglia ; Ty, Tympanic nerve ; Ty.Plex., Tympanic plexus;
Fa, Root from genicular ganglion of facial nerve; S.S.P.
Sy.
(iii.) in relation to the tongue.
In the jugular foramen there
are two enlargements upon the
trunk of the nerve the superior
and petrous ganglia. The superior
ganglion (O.T. jugular) is small,
does not implicate the whole width
of the nerve, and may be fused
with the petrous ganglion, or
even absent altogether. No branches arise from it.
G-anglion Petrosum. The petrous ganglion is distinct and constant. It is
placed upon the nerve at the lower part of its course through the jugular foramen.
51
Lesser superficial petrosal nerve to the otic ganglion ; S.D.P,
Carotico-tympanic nerve ; I.C, Internal carotid artery ; Va,
Vagus nerve ; Aur., Auricular branch of vagus ; Sy.,
Superior cervical sympathetic ganglion ; F, Communicating
branch to facial nerve ; Ph, Pharyngeal branch of vagus ;
E.C, External carotid artery ; Ph. PI, Pharyngeal plexus ;
S.Ph, Stylopharyngeus muscle; S.H.L, Stylo-hyoid liga-
ment; H.G, Hyoglossus; S.G, Styloglossus ; Ton, Palatine
tonsil; S. Pal., Soft palate; G.H.G, Genioglossus ; G.H,
Genio-hyoid ; Hy, Hyoid bone.
786 THE NEEYOUS SYSTEM.
Branches and Communications of the Petrous Ganglion. N. Tympanicus. The
tympanic branch is the most important offset from this ganglion. It passes
through a small canal in the bridge of bone between the jugular foramen
and the carotid canal to reach the cavity of the tympanum, where it breaks up into
branches, to form, along with branches from the carotid plexus of the sympathetic
on the internal carotid artery (nn. caroticotympanici superior et inferior, O.T. small
deep petrosal), the plexus tympanicus Jacobsoni (tympanic plexus), for the supply of
the mucous lining of the tympanum, mastoid cells, and auditory tube (Fig. 656,
p. 782). The fibres of the tympanic branch of the glossopharyngeal nerve
become reunited to form, by their union with a small nerve from the genicular
ganglion of the facial nerve (anastomotic with the tympanic plexus), the lesser super-
ficial petrosal nerve in the substance of the temporal bone. This passes forwards
through the temporal bone, and eventually joins the otic ganglion.
Besides forming the tympanic branch, the petrous ganglion of the glossopharyngeal
nerve communicates with three other nerves (1) with the superior cervical ganglion of
the sympathetic ; (2) with the auricular branch of the vagus ; and (3) sometimes with
the jugular ganglion of the vagus.
In the neck the glossopharyngeal nerve gives off two branches. (1) As it crosses
over the stylopharyngeus muscle it supplies the nerve to that muscle (ramus stylo-
pharyngeus), fibres of which pierce the muscle to reach the mucous membrane of
the pharynx. (2) Kami Pharyngei. The pharyngeal branches of the nerve supply
the mucous membrane of the pharynx directly after piercing the superior constrictor
muscle, and indirectly after joining, along with the pharyngeal offsets from the
vagus and the superior cervical ganglion of the sympathetic, in the formation of
the pharyngeal plexus.
The terminal branches of the nerve supply the mucous membrane of the
tongue and adjacent parts. Kami Tonsillares. A tonsillar branch forms a plexus
to supply the mucous membrane covering the palatine tonsil, the adjacent part of
the soft palate, and the palatine arches. Kami Linguales. Lingual branches supply
the mucous membrane of the dorsal third and lateral half of the tongue, extending
backwards to the glosso-epiglottic folds and the front of the epiglottis.
NERVUS VAGUS.
The tenth or vagus nerve (O.T. pneumogastric) arises from the brain by
numerous fila radicularia attached to the floor of the postero-lateral sulcus of the
medulla oblongata, in series with the glossopharyngeal nerve above and the accessory
nerve below it (for the deep connexions, see p. 656). The fila of the nerve unite
to form a single trunk which emerges into the neck through the jugular foramen.
In the jugular foramen the nerve occupies the same sheath of dura mater as the
accessory nerve, it is placed behind the glossopharyngeal nerve, and a small
ganglion the jugular ganglion is developed upon it.
In the neck the vagus nerve pursues a vertical course in~ front of the vertebra]
column. It occupies the carotid sheath, lying between and behind the internal and
common carotid arteries and the internal jugular vein. It enters the thorax behind
the large veins : on the right side, after crossing over the subclavian artery; on the
left side, in the interval between the left common carotid and subclavian arteries.
In the upper part of the neck, immediately below the jugular foramen, a second and
larger ganglion the ganglion nodosum is developed on the trunk of the nerve.
In the thorax the nerves occupy the superior and posterior mediastinal spaces,
and their relations are different on the two sides, (a) In the superior mediastinum
the right nerve continues its course alongside the innominate artery and the trachea,
and behind the right innominate vein and superior vena cava, to the posterior
surface of the root of the lung. The left nerve courses downwards between the
left common carotid and subclavian arteries, and behind the left innominate vein
and the phrenic nerve. It passes over the aortic arch, and then proceeds to the
posterior surface of the root of the left lung. (&) In the posterior mediastinum t
vagi nerves are concerned in the formation of two great plexuses the pulmonar)
and the cesophageal. Behind the root of each lung the nerve breaks up to fonr
THE VAGUS NEKVE.
787
C.i
Va.
A.PP.
FIG. 660. THE DISTRIBUTION OF .THE VAGUS NERVE.
Va, Right and left vagi ; r, Ganglion jugulare and connexions with Sy, Sympathetic, superior cervical ganglion ;
-.Ph, Glossopharyngeal ; Ace, Accessory nerve ; F, Meningeal branch ; Aur, Auricular branch ; Va,
Connexion with ganglion nodosum of vagus ; Sy, Nerve to stylo-hyoid ; Hy, Nerve to hyoglossus ; Cl,
C2, Loop between the first two cervical nerves ; Sy, Sympathetic, superior cervical ganglion ; Ace,
Accessory nerve ; Ph. Pharyngeal branch ; Ph. PI, Pharyngeal plexus ; S.L, Superior laryngeal nerve ;
I.L, Internal laryngeal branch; E.L, External laryngeal branch; I.C, Internal, and E.C, External
carotid arteries ; Cal, Superior cervical cardiac branch ; Ca2, Inferior cervical cardiac branch ; R.L,
Recurrent nerve ; Ca3, Cardiac branches from recurrent nerves ; Ca4, Thoracic cardiac branch (right
vagus); A.P.P, Anterior, and P.P.P, Posterior pulmonary plexuses; Oes.Pl, (Esophageal plexus;
Cort.Pl, Coeliac plexus.
788 THE NERVOUS SYSTEM.
the large posterior pulmonary plexus, from the lower end of which two nerves
emerge on each side. These nerves on the right side pass obliquely over the vena
azygos; on the left side they cross the descending thoracic aorta. Both series
reach the oesophagus, and divide into small anastomosing branches which form the
cesophageal plexus. At the oesophageal opening of the diaphragm the two nerves
become separated from the plexus, and entering the abdomen the left nerve in
front of the oesophagus, the right nerve behind it they terminate by supplying
the stomach and other abdominal organs.
The communications and branches of the vagus nerve may be described as
(i.) ganglionic, (ii.) cervical, (iii.) thoracic, and (iv.) abdominal (Fig. 660).
Ganglion Jugulare. The jugular ganglion (O.T. ganglion of the root) is small
and spherical. It occupies the jugular foramen, and gives off two branches
meningeal and auricular.
Ramus Meningeus. The meningeal branch passes backwards to supply the
dura mater of the posterior fossa of the skull.
Ramus Auricularis. The auricular branch ascends to the ear in a fissure
between the jugular and stylo-mastoid foramina. It receives near its origin a twig
from the tympanic branch of the glossopharyngeal nerve, and usually communi-
cates with the facial nerve by a branch arising from the latter in the canalis
facialis. The nerve is distributed to the back of the auricle and the external
acoustic meatus, and communicates superficially with the posterior auricular nerve.
Communications. Besides supplying the meningeal and auricular branches, this
ganglion receives communications from (1) the superior cervical ganglion of the
sympathetic ; (2) the accessory nerve ; and (3) (sometimes) the petrous ganglion of the
glossopharyngeal nerve {ramus anastomoticus cum nervo glossopharyngeo}.
Ganglion Nodosum. The ganglion node-sum (O.T. ganglion of the trunk),
placed immediately below the preceding, is large and fusiform. Like the jugular
ganglion, it supplies two branches the pharyngeal and superior laryngeal nerves.
Rami Pharyngei. The pharyngeal branch receives its fibres (through the
ganglion) from the accessory nerve. It passes obliquely downwards and medially
to the pharynx between the internal and external carotid arteries, and combines with
the pharyngeal branches from the glossopharyngeal and superior cervical ganglion
of the sympathetic to form the pharyngeal plexus. From this plexus the muscles of
the pharynx and soft palate (except the stylopharyngeus and tensor veli palatini)
are supplied. The lingual branch is a small nerve which separates itself from the
plexus and joins the hypoglossal nerve in the anterior triangle of the neck.
N. Laryngeus Superior. The superior laryngeal nerve passes obliquely down-
wards and medially, medial to the external and internal carotid arteries, towards
the thyreoid cartilage. It divides in its course into two unequal parts a larger
internal and a smaller external laryngeal branch.
Ramus Internus. The internal laryngeal branch passes medially into the
larynx between the middle and inferior constrictor muscles of the pharynx and
through the thyreo-hyoid membrane. It supplies the mucous membrane of the
larynx, reaching upwards to the epiglottis and base of the tongue, and forms com-
munications beneath the lamina of the thyreoid cartilage with the branches of the
inferior laryngeal nerve (ramus anastomoticus cum nervo laryngeo inferiore).
Ramus Externus. The external laryngeal branch passes downwards upon the
inferior constrictor muscle of the pharynx. It supplies branches to that muscle,
and ends in the crico-thyreoid muscle.
Communications. Besides supplying these pharyngeal and laryngeal nerves, this
ganglion has the following communications with other nerves: (1) with the superior
cervical ganglion of the sympathetic ; (2) with the hypoglossal ; (3) with the loop
between the first and second cervical nerves ; and (4) with the accessory nerve. This
nerve applies itself to the ganglion, and thereby supplies to the vagus nerve the inhibitory
fibres for the heart, as well as the motor fibres for the pharynx, oesophagus, stomach
and intestines, larynx and respiratory organs.
Branches of the Vagus in the Neck. In the neck the vagus nerve
THE THOEACIC PLEXUSES. 789
supplies cardiac branches and (on the right side) the recurrent (laryngeal)
nerve (Fig. 661).
Kami Cardiaci Superiores. The cardiac branches are superior and inferior.
On the right side both cardiac branches pass downwards into the thorax behind the
subclavian artery, and proceed alongside the trachea to join the deep cardiac plexus.
On the left side the two nerves separate on reaching the thorax. The superior
nerve passes deeply alongside the trachea to join the deep cardiac plexus. The
inferior nerve accompanies the vagus nerve over the aortic arch, along with the
superior cervical cardiac branch of the sympathetic, to end in the superficial
cardiac plexus.
N. Eecurrens. The right recurrent (laryngeal) .nerve arises at the root of
the neck, as the vagus crosses in front of the first part of the subclavian artery.
It hooks round the artery, and passes obliquely upwards and medially behind the
subclavian, the common carotid, and the inferior thyreoid arteries and the thyreoid
gland. It finally disappears beneath the inferior border of the inferior constrictor
muscle, and, receiving the name of inferior laryngeal nerve, it ends in supplying the
muscles of the larynx. In its course it gives off the following branches :
(1) Cardiac branches (rami cardiaci inferiores) arise as the nerve winds round the
subclavian artery, and course downwards alongside the trachea to end in the deep
cardiac plexus.
(2) Communicating branches to the inferior cervical ganglion of the sympathetic
arise from the nerve behind the subclavian artery.
(3) Muscular branches supply the trachea, oesophagus (rami tracheales et
cesophagei), and the inferior constrictor of the pharynx.
(4) Terminal branches supply the muscles of the larynx (except the crico- thyreoid)
and communicate beneath the lamina of the thyreoid cartilage with branches of
the internal laryngeal nerve.
Branches of the Vagus in the Thorax. In the thorax the vagi form the
great pulmonary and oesophageal plexuses. The right nerve, in addition, furnishes
, cardiac branches ; and the left nerve gives off the recurrent (laryngeal) nerve.
N. Recurrens. The left recurrent (laryngeal) nerve differs from the nerve
of the right side mainly in its point of origin and in the early part of its course.
It springs from the vagus as it crosses the aortic arch, and, after hooking round the
arch, lateral to the ligamentum arteriosum, it passes upwards in the superior medi-
astinum, in the interval between the trachea and oesophagus, to the neck. In the
, neck its course and relations are similar to those of the nerve of the right side.
The branches of the nerve are the same as those of the right nerve. The cardiac
branches are larger, and, arising below the aortic arch, proceed to the deep cardiac
plexus.
Cardiac branches from the right vagus nerve arise in the superior mediastinum,
and pass downwards alongside the trachea to join the deep cardiac plexus. On
the right side thoracic cardiac branches are thus supplied from both the trunk of
the nerve and its recurrent branch ; on the left side the cardiac branches in the
, thorax arise solely from the recurrent branch.
Abdominal Branches. After the formation of the oesophageal plexus the
two vagi nerves resume their course, and passing along with the gullet through
the diaphragm, terminate by supplying the stomach. The right nerve enters
the abdominal cavity behind the gullet, and is distributed to the posterior
surface of the stomach. It sends communicating offsets to the cceliac, splenic, and
renal plexuses. The left nerve applies itself to the anterior surface and small cur-
vature of the stomach, to which it is distributed. It sends communicating offsets
along the small curvature of the stomach to the right vagus, and between the
1 layers of the gastro-hepatic ligament to the hepatic plexus.
PLEXUS THORACALES.
Plexus Cardiaci. The cardiac branches of the vagus nerve (both cervical
md thoracic) combine with the cardiac branches of the sympathetic to form the
.superficial and deep cardiac plexuses.
515
790
THE NERVOUS SYSTEM.
The superficial cardiac plexus is placed in the hollow of the aortic arch,
superficial to the pericardium. It contains a small ganglion (cardiac ganglion of
Wrisberg), and is joined by two small nerves (1) the cardiac branch from the
superior cervical ganglion of the sympathetic, and (2) the inferior cervical cardiac
branch of the vagus both of the left side which reach it after passing over the
arch of the aorta.
Vagu
Nervus caroticus intern us
/
Nervus caroticus interm
Superior cervical ganglion
of the aympatheti
Superior cardiac branch H
Middle cervical gangli
Superior cardiac branch
Middle cardiac branch
Inferior cervical ganglion
Inferior cardiac branch~--
Recurrent nerve"-
Inferior cardiac branch -
Cardiac branch from right recurrent nerve-
Thoracic cardiac branch of vagus
Deep cardiac plexus -jm
Nerves to posterior. ffg[ f
pulmonary plexus
Branches to right anterior ^i^T13
pulmonary plexus
Anterior pulmonary plexus-
Superior vena cava-
Branches to right coronary plexus
Kight coronary plexus**-
Superior cervical ganglion
of the sympathetic
Superior cardiac branch
Vagus
'Middle cervical ganglion
Superior cardiac branch
Middle cardiac branch
"Inferior cardiac branch
Inferior cervical ganglion
" ' Inferior cardiac brunch
' Recurrent nerve
Cardiac branch from left recurrent nerve
Middle cardiac branch
"Inferior cardiac branch
Superior cardiac branch
- Cardiac branch from left recurrent nerve
Deep cardiac plexus
.Superficial cardiac plexus
Nerves to posterior pulmonary plexus
Branches to left anterior pulmonary plexu"
Branches to left vagus
Pulmonary artery
Branches to right coronary plexus
Anterior pulmonary plexus
Aorta
Branches to right coronary plexus
Branches to left coronary plexus
: - Left coronary plexv
FIG. 661. THE INNERVATION OF THE HEART.
Branches and Communications. From the plexus branches of communication
pass (1) to the left half of the deep cardiac plexus, between the aortic arch and the
bifurcation of the pulmonary artery; (2) to the left anterior pulmonary plexus
along the left branch of the pulmonary artery ; (3) the branches of distribution to
the heart extend along the pulmonary artery to join the anterior (right) coronary
plexus, which supplies the substance of the' heart in the course of the right
coronary artery.
Plexus Cardiacus Profundus. The deep cardiac plexus is much larger. It
ACCESSOEY NEEVE. 791
is placed behind the arch ,of the aorta, on the sides of the trachea, just above its
bifurcation. It consists of two lateral parts, joined together by numerous com-
munications around the termination of the trachea. The two portions of the plexus
are different in their constitution and distribution. The right half of the plexus
is joined by both the cervical and thoracic branches of the right vagus and by the
branches of the right recurrent nerve, as well as by branches from the superior,
middle, and inferior cervical ganglia of the sympathetic. The left half of the plexus
is joined by the superior cervical cardiac branch of the left vagus, by branches from
the left recurrent nerve, and by branches from the middle and inferior cervical
ganglia of the left sympathetic ; it also receives a contribution from the superficial
cardiac plexus.
The deep cardiac plexus is distributed to the heart and lungs. The right
half of the plexus for the most part constitutes the anterior coronary plexus,
reaching the heart alongside the ascending aorta, and is distributed to the heart
substance in the course of the right coronary artery. It is reinforced by fibres
from the superficial cardiac plexus, which reach the heart along the pulmonary
artery. Fibres from the right half of the deep cardiac plexus pass also to join
the posterior coronary plexus, and others extend laterally to join the anterior
pulmonary plexus of the right side.
The left half of the deep cardiac plexus, reinforced by fibres from the superficial
cardiac plexus, is distributed to the heart in the form of the posterior coronary
plexus, which is joined by a few fibres behind the pulmonary artery from the right
half of the plexus, and supplies the heart substance in the course of the left coronary
artery. The left half of the plexus contributes also to the left anterior pulmonary
plexus by fibres which extend laterally to the root of the lung along the left
branch of the pulmonary artery.
Plexus Pulmonales (Pulmonary Plexuses). As already stated, the vagus
nerve on each side, on reaching the back of the root of the lung, breaks up
into numerous plexiform branches for the formation of the posterior pulmonary
plexus. From each nerve a few fibres pass to the front of the root of the lung,
above its upper border, to form the much smaller anterior pulmonary plexus.
Plexus Pulmonalis Anterior. The anterior pulmonary plexus on each side
is joined by a few fibres from the corresponding part of the deep cardiac plexus,
and on the left side from the superficial cardiac plexus as well. It surrounds and
supplies the constituents of the root of the lung anteriorly.
Plexus Pulmonalis Posterior. The posterior pulmonary plexus, placed
behind the root of the lung, is formed by the greater part of the vagus nerve,
reinforced by fine branches from the second, third, and fourth thoracic ganglia of
:he sympathetic. Numerous branches proceed from it in a plexiform manner along
:he bronchi and vessels into the substance of the lung.
Plexus CEsophageus Anterior et Posterior (CEsophageal Plexus). The
esophagus in the thorax is supplied by the vagus nerve both in the superior and
Dosterior mediastina. In the superior mediastinum it receives branches from the
/agus nerve on the right side, and from its recurrent branch on the left side.
In the posterior mediastinum the gullet is surrounded by the cesophageal plexus,
brmed from the trunks of the vagi nerves emerging from the posterior pulmonary
)lexuses, which form a large plexus surrounding the gullet. This part of the
esophagus also receives fibres from the greater splanchnic nerve and ganglion.
From the oesophageal plexus branches supply the muscular wall and mucous
nembrane of the oesophagus.
Pericardiac branches are also supplied from the plexus to the posterior surface
)f the pericardium.
NERVUS ACCESSORIUS.
The eleventh or accessory nerve (O.T. spinal accessory) consists of two
ssentially separate parts, different both in origin and in distribution. One
portion is accessory to the vagus nerve, and arises, in series with the fila of that
lerve, from the side of the medulla oblongata. The other, spinal portion, arises from
792
THE NERVOUS SYSTEM.
Va,
A.RP.
FIG. 662. THE DISTRIBUTION OF THE PNEUMOGASTRIC NERVE.
Va, Right and left vagi ; r, Ganglion jugulare and connexions with Sy, Sympathetic, superior cervic
ganglion ; G.Ph, Glossopharyngeal ; Ace, Accessory nerve ; F, Meningeal branch ; Aur, Ainiculi
branch ; Va, Connexion with ganglion nodosum of vagus ; Sy, Nerve to stylo-hyoid ; Hy, Nerve '
hyoglossus ; Cl, C2, Loop between the first two cervical nerves ; Sy, Sympathetic, superior cervic,
ganglion ; Ace, Accessory nerve ; Ph. Pharyngeal branch ; Ph.Pl, Pharyngeal plexus ; S.L, Superi<
laryngeal nerve ; I.L, Internal laryngeal branch ; E.L, External laryngeal branch ; I.C, Internal, an
E.C, External carotid arteries ; Cal, Superior cervical cardiac branch ; Ca2, Inferior cervical cardii
branch; R.L, Recurrent nerve; Ca3, Cardiac branches from recurrent nerves; Ca4, Thoracic eardh
branch (right vagus) ; A.P.P, Anterior, and P.P.P, Posterior pulmonary plexuses ; Oes.Pl, (Esophage;
HYPOGLOSSAL NERVE.
793
G.Ph.
the lateral aspect of the spinal medulla, between the anterior and posterior roots
of the spinal nerves, its origin extending from the level of the accessory portion
as low as the origin of the sixth cervical nerve (for the deep origin, see p. 596).
Successively joining together, the fila radicularia (rootlets) form a trunk which
ascends in the subdural space of the spinal medulla, posterior to the ligamenturn
denticulatum, to the foramen magnum. There the two portions unite into a single
trunk, which leaves the cranial cavity through the jugular foramen in the same
compartment of dura mater as the vagus nerve
(Fig. 647, p. 771).
Ramus Inter mis. In the jugular foramen
the accessory portion of the nerve or internal
ramus (after furnishing a small branch to the
jugular ganglion of the vagus) applies itself to
the ganglion nodosum, and in part joins the
ganglion, in part the trunk of the nerve beyond
the ganglion. By means of these connexions
the vagus receives viscero- motor and cardio-
inhibitory fibres.
Ramus Externus. The spinal portion of the
nerve, or external ramus, extends into the neck,
where at first it lies along with other nerves, in
the interval between the internal carotid artery
and the internal jugular vein. Passing obliquely
downwards and laterally over the vein, it de-
scends close beneath the sterno-mastoid muscle,
which it supplies as it pierces it on its deep
surface. After crossing the posterior triangle
the nerve ends by supplying the trapezius muscle
on its deep surface. This portion of the nerve
communicates in three situations with nerves
from the cervical plexus (1) in or beneath the
sterno-mastoid, with the branch for the muscle
derived from the second cervical nerve ; (2) in Flo> 663 ._s CH EME OF THE ORIGIN, CON-
the posterior triangle, with branches from the NEXIONS, AND DISTRIBUTION OP THE
third and fourth cervical nerves; (3) beneath ACCESSORY NERVE.
the trapezius, with the branches for the muscle Sp. Ace, Accessory nerve ; C.l-4, First lour
derived from the third and fourth cervical nerves. cervical nerves (posterior roots) ; Va,
Vagus nerve ; R, Ganglion jugulare ; T,
Ganglion nodosum ; G.Ph, Glossopharyn-
geal nerve ; S.M, Nerves to sterno-
cleido-mastoid ; Tr, Nerves to trapezius ;
F. M, Foramen magnum ; J. F, Jugular
foramen.
S.M.
NERVUS HYPOGLOSSUS.
The twelfth or hypoglossal nerve arises by
numerous fila radicularia from the front of the
medulla oblongata between the pyramid and the olive (Fig. 643, p. 768) (for the
deep origin, see p. 594). The fila arrange themselves in two bundles which
separately pierce the dura mater, and unite in the hypoglossal canal, or after
emerging from the skull. In the neck the nerve arches downwards and forwards
towards the hyoid bone, and then turns medially among the supra-hyoid muscles
to the tongue. At first it is placed deeply, along with other cerebral nerves,
on the lateral side of the internal carotid artery; it then curves forwards and
downwards over the two carotid arteries, lying medial to the digastric and stylo-hyoid
muscles. As it crosses the external carotid artery it hooks round the occipital artery.
Above the greater cornu of the hyoid bone the nerve conceals the lingual artery ;
and it then disappears between the mylo-hyoid and hyoglossus muscles to reach
the tongue, in the muscular substance of which it terminates.
Communications. In its course the hypoglossal nerve has the following communica-
tions with other nerves : Near the base of the skull it is connected by small branches
with (1) the superior cervical ganglion of the sympathetic ; (2) the ganglion nodosum
of the vagus ; (3) by a larger branch, with the loop between the first two cervical
nerves ; (4) as it crosses the external carotid artery it receives a communication from the
794
THE NERVOUS SYSTEM.
pharyngeal plexus (lingual branch of the vagus) ; and (5) medial to the mylo-hyoid musclt
at the anterior border of the hyoglossus, it forms loops of communication with the lingua
branch of the mandibular nerve.
The branches of the nerve are : (1) Eecurrent ; (2) Descending ; (3) Thyreo
hyoid ; and (4) Lingual.
Ramus Recurrens. The recurrent branch passes from the nerve near its origin t
supply the dura mater of the posterior fossa of the base of the skull. It probabl
derives its fibres from the communication with the first and second cervical nerves
Ci
SCENOINC CERVICAL
FIG. 664. THE MUSCLES OF THE HYOID BONE AND STYLOID PROCESS, AND THE
EXTRINSIC MUSCLES OF THE TONGUE, WITH THEIR NERVES.
Ramus Descendens. The descending branch of the hypoglossal nerve is th<
chief branch given off in the neck. It arises from the hypoglossal nerve as i
crosses the internal carotid artery, and descends in the anterior triangle superncia
to the carotid sheath. It is joined about the middle of the neck by the descendinj
cervical nerve (from the second and third cervical nerves). By their union th<
ansa hypoglossi (hypoglossal loop) is formed, from which branches are distributed t
the majority of the infra-hyoid muscles both bellies of the omo-hyoid, the sterno
hyoid, and the sterno-thyreoid. The descending branch of the hypoglossal nervi
derives its fibres from the communication to the hypoglossal nerve from the loo]
between the first and second cervical nerves ; so that the ansa hypoglossi is madi
up of fibres of the first three cervical nerves.
THE MOKPHOLOGY OF THE CEEEBKAL NEKVES.
795
Ramus Thyreohyoideus. The nerve to the thyreo-hyoid muscle is a small
Branch which arises from the hypoglossal nerve before it passes medial to the mylo-
lyoid muscle. It descends behind the greater cornu of the hyoid bone to reach
;he muscle. When traced backwards this nerve is found associated with the loop
setween the first and second cervical nerves.
Rami Linguales. The lingual branches of the hypoglossal nerve are distributed
bo the hyoglossus, genio-hyoid, and genioglossus, and to all the intrinsic muscles
)f the tongue. The nerve to the genio-hyoid is said to be derived from the loop
oetween the first and second cervical nerves. It is not known if these two cervical
aerves are implicated in the innervation of the proper muscles of the tongue, but
.t appears certain that the muscles named the genio-hyoid, thyreo-hyoid, sterno-
tiyoid, omo-hyoid, and sterno-thyreoid are not supplied by the hypoglossal, but
Dnly by cervical nerves, the genio-hyoid and thyreo-hyoid by the first two, the
Dther muscles by the first three cervical nerves.
THE MORPHOLOGY OF THE CEREBRAL NERVES.
The head and face, possibly the oldest, and from every point of view the most fundamental
md important portion of the body fabric, present in some respects a more conservative type of
LATERAL AREA
MEDIAL AREA
I BASAL
I LAMINA
f ANTERIOR ROOT
'POSTERIOR ROOT
A
ix.x.xr
FIG. 665. COMPARISON OF ORIGINS OF NERVE ROOTS FROM SPINAL MEDULLA AND HIND-BRAIN (after His).
A. Spinal medulla ; B. Hind-brain.
structure, and in other aspects have been subject to more profound alterations than other parts
of the body. Segmentation is characteristic of the trunk, pervading bones, muscles, vessels, and
nerves. An absence of true segmentation is characteristic of the head region omitting for the
moment the cerebral nerves. The head is characterised by the possession of an unsegmented
tubular nervous system, enclosed in a bony capsule not obviously segmental, with which the
capsules of the sense-organs become united. The pre-oral and post-oral visceral arches and clefts
are not truly segmental like the costal arches of the trunk. The branchial clefts are said to be
inter-segmental ; and their muscles (associated with the myoblast surrounding the developing
heart) are described as visceral, and not myotomic, so that the branchial vessels and nerves
(similarly) are not to be regarded as comparable to the segmental vessels and nerves of the trunk.
The truly segmental structures present are certain persistent myotomes or muscle plates, which
give rise to muscles innervated by the third, fourth, sixth, and twelfth cerebral nerves.
Another difficulty in the morphology of the head arises from the absence of body cavity, and
the consequent difficulty of differentiating the somatic and splanchnic mesoderm, and the somatic
and splanchnic distribution of a given nerve.
Under these circumstances there is little help to be derived from head structures other than
the nerves themselves in seeking a solution of the question of the morphological relations of the
cerebral nerves. The spinal nerves are, generally speaking, all alike. The cerebral nerves, on
the other hand, are all different. Scarcely any two nerves are alike ; and no single cerebral nerve
possesses in itself all the characteristic features of a spinal nerve. As seen in the account of its
development (p. 504), the cranial nervous system possesses a series of dorsal ganglia, comparable
n position and development to the spinal ganglia with which afferent nerves are associated ;
and the efferent roots are developed in the same way, and occupy somewhat the same position
796 THE NEKVOUS SYSTEM.
as the anterior roots of the spinal nerves. But there is no single complete segmental nerve i
the head. The very essence of the architecture of the head is a want of segmentation ; and th
character is shared by the cerebral nerves. In addition it must be borne in mind that, in relatic
to the mammalian head, there are organs which have no homologues in the trunk, and c
whose existence the essential arrangement of the cerebral nerves depends e.g. sense-organs an
gill-arches.
Among the cerebral nerves there are several which possess a resemblance to one or other <
the elements of a typical spinal nerve. In the neck the origin of the fibres of the accessor
nerve is from the side of the spinal medulla, and it is in series with the motor roots of the vagi
glossopharyngeal, facial, and fifth nerves. His (as shown in the account of the develoj
ment of the nerves) has described the neuroblastic origin of the motor roots of these nervi
from the lateral part of the basal lamina of the primitive brain. They thus form a seri
apart lateral motor roots separable from the series of motor roots originating from the medi,
part of the basal lamina, comprising those of the third, fourth, sixth, and twelfth nerves ; tl
latter nerve roots being comparable to and in series with the anterior roots of the spinal nerve
The lateral motor roots are not represented in the spinal series except in the neck. It
questionable if there is any fundamental distinction between the lateral and anterior motor roo
of the cerebral nerves. The accessory fibres, for example, when traced into the spinal medull
have an origin from the anterior column of the spinal medulla, and only differ from the motor <
anterior root fibres of a spinal nerve in their different course to the surface. The ganglia in associi
tion with the cerebral nerves are comparable to the spinal ganglia. The trigeminal nerve, wit
the semilunar ganglion, the ganglion of the facial, the ganglia of the acoustic, of the glossi
pharyngeal and the vagus, and the transitory (Froriep's) ganglion of the hypoglossal nerves, ari:
from the brain in a comparable position, and in the same way as the spinal ganglia. But anothi
series of structures the sense organs of the lateral line, and the so-called " epibranchial " orgai
which are highly developed in lower vertebrates (e.g. elasmobranchs), and which appear transitori]
only, or are absent altogether in mammalian development, may possibly have a share in tl
formation of certain of these ganglia or parts of them (e.g. ciliary ganglion, genicular ganglioi
ganglia of the acoustic nerve, petrous ganglion of the glossopharyngeal, and the ganglio
nodosum of the vagus).
Certain of the cerebral nerves are apparently distinctly segmental, supplying muscles derive
from the persisting myotomes of the head. The first three myotomes are said to give rise to tl
muscles of the eyeball. The first produces the superior rectus, inferior rectus, medial rectu
and inferior oblique muscles, and its segmental nerve is the oculo-motor. The second myoton
is said to produce the superior oblique muscle, and its segmental nerve is the trochlear. Tl
third myotome is said to produce the lateral rectus muscle, and its segmental nerve is tl
abducent. It has been asserted that the tongue muscles are derived from the last three or foi
cephalic and first cervical myotomes, and that the hypoglossal nerve is the segmental nerve f(
these myotomes, comprising the motor elements of several (four or five) segmental nerves. Tl
intervening myotomes between the first three and this occipital series disappearing, the corr<
spending elements of segmental nerves are supposed to be absent also (Fig. 666).
Certain of the cerebral nerves are essentially related to the structures derived from and ass(
ciated with the pre-oral and post-oral visceral clefts and arches (Fig. 667). The trigeminal nen
is essentially the nerve of the mandibular arch. By its efferent root it supplies the muscles <
that arch. By its afferent root and branches it is related to (1) the fronto-nasal process (opl
thalmic division and ciliary ganglion) ; (2) the maxillary arch (maxillary nerve) ; and (3) tl
mandibular arch (mandibular nerve). The mandibular is at first the main nerve ; and th
maxillary division is sometimes regarded as a subordinate branch (prse-branchial, prse-tremati<
for the supply of the anterior margin of the cleft (mouth), with which the nerve is in relatioi
The ophthalmic nerve is sometimes regarded as a morphologically separate nerve. The nervt
to these arches have been compared to the anterior rami of spirial nerves, the branches whic
they supply to the forehead and temple (frontal, zygomatic, and auriculo-temporal) representin
the posterior rami. The ganglia on each division of the nerve are formed as extensions froi
the semilunar ganglion.
The facial nerve is essentially the nerve of the second (hyoid) arch and the cleft in front c
that arch (spiracular cleft, auditory tube). Its motor root supplies the muscles of that arc
(stapedius, stylo-hyoid, and digastric), and the epicranial and facial muscles and platysm?
which are developments from 'the hyoid arch (Rabl). The chorda tympani nerve is regarde
as the subordinate (prae -branchial, prae-trematic) branch to supply the anterior margin of th
first post-oral cleft. It is possible that the genicular ganglion, with the nervus intermediu
and the chorda tympani, may, in part at least, represent the ganglionic and afferent element c
the nerve. Or the genicular ganglion, and the nerves in relation to it, may be associated wit'
an " epibranchial " sense-organ.
The acoustic nerve, on the other hand, may be either the sensory element of the branchia
nerve, associated with the hyoid arch and first post-oral cleft, or it may represent the nerve or nerve
belonging to ancestral sense-organs of the lateral line.
The glossopharyngeal is the branchial nerve of the third post-oral (thyreo-hyoid) arch an<
the cleft in front. Its efferent fibres supply the muscle of this arch, the stylopharyngeui
The superior constrictor of the pharynx is also assigned to this arch ; the middle and inferio
muscles to the fourth (first branchial) arch. The afferent portion of the nerve is possibl;
composed of two separate parts ; the petrous ganglion being associated with an epibranchia
or lateral line sense-organ, and the rest of the nerve forming the afferent fibres for the gill-cleJ
THE MOEPHOLOGY OF THE CEEEBEAL NERVES. 797
and arch. The lingual branches -are regarded as the main stem (post-trematic), the pharyngeal
branches as subordinate branches ; the tympanic branch being the> prse-branchial or prse-trematic
branch for the anterior margin of the third gill-cleft.
The vagus nerve is generally regarded as representing the fusion of all the branchial nerves
behind the glossopharyngeal. Its efferent fibres are in series with those of the glossopharyngeal
above and the accessory nerve below, and belong to the lateral series of His. Its afferent fibres,
like those of the glossopharyngeal, represent two elements. The ganglion nodosum has possible
connexions with epibranchial sense-organs the rest of the nerve representing the fused branchial
nerves of fishes. The superior laryngeal nerve is looked upon as the branchial nerve of the
fourth, and the recurrent nerve as the branchial nerve of the fifth arch. While the relation
of the nerve to the hinder gill-arches and clefts makes it possible to understand the innervation
by the vagus of the heart and lungs, no satisfactory explanation is forthcoming of the
L, and its distribution to the stomach and other organs be
of the nerve into the abdomen, and its distribution to the stomach and other organs below the
diaphragm.
666. SCHEME TO ILLUSTRATE THE DISPOSITION OF THE MYOTOMES IN THE EMBRYO IN RELATION
TO THE HEAD, TRUNK, AND LIMBS.
I A, B, C, First three cephalic myotomes ; N, 1, 2, 3, 4, Last persisting cephalic myotomes ; C, T, L, S,
Co, The myotomes of the cervical, thoracic, lumbar, sacral, and caudal regions ; I., II., III., IV., V.,
VI., VII., VIII., IX., X., XL, XII., refer to the cerebral nerves, and the structures with which they
may be embryologically associated.
I
The accessory nerve consists of two parts. The internal ramus (accessory portion) of the nerve
, consists of efferent fibres for the branchial region, in series with the lateral motor roots of the
glossopharyngeal and vagus nerves. The external ramus (spinal portion) of the nerve is also
composed of efferent fibres, and represents the only lateral motor elements arising from the
spinal medulla.
Olfactory Nerve. There is complete uncertainty regarding the morphology of this nerve.
!t consists of three elements : (1) the olfactory bulb, derived from the cerebral hemisphere,
solid in man, but a hollow cerebral diverticulum in certain animals, and forming the
rhinencephalon ; (2) the olfactory ganglion, with its central and peripheral processes, derived
from the ectoderm ; (3) the nasal pit. Attention has been specially fixed on the olfactory
; ganglion, which has been compared to (1) a spinal ganglion, derived from the anterior end of the
medullary groove ; and to (2) a lateral line sense-organ.
The optic nerve also presents an insoluble problem in regard to its morphological position
798
THE NERVOUS SYSTEM.
in the series of cerebral nerves. The optic stalk and optic cup have been regarded as a high
modified spinal ganglion ; but there is insuperable difficulty in accepting this view. T]
peripheral processes do not become connected with either ectodermal or mesodermal structure
but become the tissue of the retina ; while the central processes, growing backwards, envelc
the optic stalk, and obtain connexions with the brain. The retina must be regarded as a high
modified nerve-layer, morphologically in series with the wall of the fore-brain ; and the ectoderm
structure of superficial origin comparable to the olfactory ganglion or the auditory vesicle is tl
lens (which may possibly be homologous with a lateral line sense-organ). The optic nerve, opt
chiasma, and optic tract are then to be looked upon as cerebral commissures, and not as nerv
in the ordinary sense.
The simplest and most primitive condition of the head, in relation to the morpholo^
of the cerebral nerves, is found before the formation of the gill-clefts, when the salient features a
Abducent nerve
Trigeminus
Optic cup and lens I
Trochlearis
Telencephalon
Oculo-motor nerve
Ophthalmic nerve
Diencephal
Hind-brain
Acoustic nerve
I Otic capsule
Second post-oral cleft
Glossopharyngeal nerve
Third post-oral cleft
Auricular branch of vagus
Froriep's ganglion
Root and trunk of
the first cervical
spinal nerve
Accessor ins
Trunk of 2nd cervicj
Hypoglossal nerve
Roots and trunks
cervical spinal
nerves 3-7
Olfactory bulb
Fronto-nasal process \
Nasal pit
Ocular fissure
Lateral nasal process
Maxillary nerve
Maxillary process
Mouth cleft
Mandibular trunk
Mandibular arch
First post-oral cleft
| Fourth post-oral cleft
Vagus nerve
Second branchial arch
First branchial arch
Thyreo-hyoid arch
Facial nerve
Hyoid arch
FIG. 667. THE EMBRYOLOGICAL ARRANGEMENT OF THE CEREBRAL NERVES. (Modified from Mall.)
a tubular and simple brain, and a series of superficial invaginations which pass from the surfa
inwards to become connected with outgrowths corresponding to them from the primitr
brain. On each side of the head three hollow invaginations occur : (1) The nasal pit bearii
the olfactory epithelium becomes connected by the olfactory ganglion with the rhinencephalon,
outgrowth from the fore-brain, and so forms the basis of an olfactory organ and nerve ; (2) a simiL
invagination produces the lens, connected with a protrusion of the optic vesicle from the for
brain, by which the basis of the eye and the optic nerve is formed ; (3) behind the oral cavil
a third invagination forms the auditory vesicle, which is connected with the solid extensic
from the hind-brain of the acoustic ganglia, to form the essentials of the organ of hearir
and acoustic nerve.
The trigeminal nerve is essentially the nerve of the buccal cavity and the subordinai
cavities, nasal and oral, derived from it. The branchial arches and clefts are secondary structure
and their nerves are (1) the trigeminal, for the first (mandibular) arch and the cleft in froi
of it ; (2) the facial, for the second (hyoid) arch and cleft ; (3) the glossopharyngeal, for the thii
(thyreo-hyoid) arch and cleft; and (4) the vagus, for the succeeding arches and clefts. Th
cerebral part of the accessory nerve is inseparable from the motor portion of the vago-gloss<
pharyngeal nerves ; the spinal part is beyond the series of the cerebral nerves.
Lastly, there are certain truly segmental nerve elements, motor fibres which, remainin
associated with certain persistent cephalic myotomes, give rise to the oculo-motor, trochlea:
abducent, and hypoglossal nerves.
NOTE. Since 1913 an additional pair of cerebral nerves, the nervi terminates, has bee
known in man. The nerves were discovered in 1894 in protopterus, and since then they hav
been demonstrated in all groups of vertebrates. In man each nervus terminalis is a ver
small ganglionated nerve which is attached to the inferior surface of the frontal portion of th
brain in the region of the olfactory trigone. In the intracranial part of its course it lies medis
to the olfactory tract and bulb and its peripheral filaments accompany the filaments of th
olfactory nerve. The functions of the nervi terminales, the course of their fibres, and thei
associations in the substance of the brain are not known.
ORGANA SENSUUM ET INTEGU-
MENTUM COMMUNE.
By ROBERT HOWDEN, M.B., F.R.S.E.
Professor of Anatomy in the University of Durham.
ORGANA SENSUUM.
THE organs of the senses are derived from cells of the ectoderm and constitute the
apparatus by which man is made acquainted with his surroundings.
Every sense organ consists of three parts : (a) a peripheral or receptive portion,
capable of responding to external stimuli, (6) an intermediate or conductive part,
along which the impulses are conveyed, and (c) a central or perceptive portion, where
the impulses are collected and transformed into sensations. The intermediate and
central parts have been described in the section on the Nervous System; the
peripheral parts form the subject matter of this chapter, and may be grouped under
two headings : (a) those connected with the special senses of smell, sight, hearing,
and taste, and located in the nose, eye, ear, and mouth, respectively; and (ft)
those of general sensations (pressure, heat, cold, pain, etc.), which are widely dis-
tributed throughout the body.
ORGANON OLFACTUS.
The nose is the peripheral olfactory organ and consists of the nasus externus,
which projects from the face, and the cavum nasi, which is divided by a vertical
septum into right and left cavities.
Nasus Externus. The external nose forms a more or less triangular pyramid,
of which the upper angle is termed the root, and is usually separated from the fore-
head by a depression, while its base, directed downwards, is perforated by the nares
or nostrils. Its free angle is named the apex ; and the anterior border, joining
root and apex, is termed the dorsum ; the upper part of the dorsum is supported by
: the nasal bones, and is named the bridge. Each side of the nose forms an open
angle (naso-facial angle) with the cheek, and ends below in a mobile expanded
( portion, the ala nasi, which forms the lateral boundary of the naris, and is limited
. above by a furrow, the alar sulcus. The skin of the nose is thin and movable
i over the root, but thick and adherent over the apex and alee, where it contains
; numerous large sebaceous glands.
The arterial supply of the external nose is derived from the external maxillary and ophthalmic
arteries, and its veins open into the anterior facial vein and communicate with the ophthalmic
i vein. Its principal lymph vessels follow the course of the anterior facial vein and open into the
submaxillary lymph glands. From the root of the nose one or two vessels run laterally in the
upper eyelid and end in the upper anterior auricular lymph glands, while a third group runs
below the orbit to the lower anterior auricular lymph glands. Its muscles are supplied by the
facial nerve, and the skin covering it is supplied by the infra-trochlear and naso- ciliary branches
of the ophthalmic nerve and the infra-orbital branch of the maxillary nerve.
The external nose presents great variety as to its size and shape, and certain well-defined
I types, such as aquiline, Grecian, etc., are described. The relation which its breadth, measured
across the alae, bears to its length, measured from root to apex, is termed the nasal index, and is
expressed thus :
greatest breadth x 100
greatest length.
799
800
THE ORGANS OF SENSE.
In white races this index is below 70 (leptorhines) ; in yellow races, between 70 and
mesorhines) ; and in black races, above 85 (platyrhines).
CARTILAGINES NASI.
Five chief cartilages are concerned in the formation of the nose ; they are th
lateral and greater alar cartilages, on each side, and the cartilage of the septum.
Cartilage Nasi Later alls. The lateral cartilage (Figs. 669, 670) is triangular i]
shape and is situated immediately below the nasal bone. Its posterior edge is thii
and is attached to the maxilla and the nasal bone ; its anterior edge is thick, am
its superior part is directly continuous with the cartilage of the septum ; its inferio
margin is joined, by fibrous tissue, to the upper edge of the greater alar cartilage.
Cartilago Alaris Major. The greater alar cartilage (Figs. 668, 669, 670
encircles the anterior part of the nostril and assists in keeping it open. It consist
Frontal air-sinus
Nasal bon
Perpendicular lamina of
ethmoid
Cartilage of septum
Medial crus
of left greater
alar cartilage
Palatine bone
FIG. 668. VIEW OF NASAL SEPTUM FROM THE LEFT SIDE.
of a lateral and a medial crus, which are continuous with each other in a rounde<
angle at the apex of the nose. The lateral crus is oval in shape and is attache<
to the lateral cartilage and the maxilla by fibrous tissue. Above and behind it an
two or three lesser alar cartilages, while sometimes a horizontal furrow cuts off >
narrow linear part from its superior margin. The inferior edge of the lateral cru
does not descend as far as the opening of the nostril, the ala being there devoid o
cartilage and composed of fatty and connective tissue covered with skin. The media
crus (Fig. 668) bounds the medial wall of the nostril and lies in the septum mobile
below the anterior part of the cartilage of the septum. The medial crura of tb
two cartilages are separated, in front, by a notch which corresponds with the ape:
of the nose, and the posterior end of each curves slightly lateralwards and ends ii
a rounded extremity.
Cartilago Septi Nasi. The cartilage of the septum (Fig. 668) is of ai
irregularly quadrilateral form. Its postero-superior edge is attached to the perpendi
cular lamina of the ethmoid; its postero-inferior margin to the vomer and the maxillae
Its antero-superior border is thick, and is fixed above to the back of the internasa
NASAL CAVITY.
801
suture ; immediately below the level
of the nasal bones it is continued, on
each side, into the lateral cartilages,
which may be looked upon as its
wing-like expansions. The inferior
part of this border is separated by
a fissure from the , lateral cartilage,
and extends downwards between the
greater alar cartilages, to which it is
attached by fibrous tissue; in this
fibrous tissue a small accessory car-
tilage is usually seen on either side
of the median plane. Its antero-
inferior border is short, and is at-
tached by fibrous tissue to the medial
crura of the greater alar cartilages,
while its anterior angle is rounded
and does not reach as far as the
apex of the nose. The lowest part
of the nasal septum is not formed
by the septal cartilage, but by the
medial crura of the greater alar
cartilages and by the integument,
and, being freely movable, is termed
the septum mobile nasi. The cartilage
of the septum may be prolonged
backwards (especially in children)
as a narrow process, the processus
sphenoidalis, into the angle between
the vomer and ethmoid ; this process
varies from 4 to 6 mm. in width, and sometimes reaches as far as the body of the
sphenoid.
On either side of the inferior
edge of the cartilage of the septum,
and seen best in a frontal section
of the nose, is a narrow band of
cartilage, the vomero-nasal cartil-
age ; it measures from 6 to 12 mm.
bone in length, and is attached to the
vomer.
FIG. 669. PROFILE VIEW OF THE BONY AND CARTI-
LAGINOUS SKELETON OF THE EXTERNAL NOSE.
Frontal pr
of maxilla
CAVUM NASI.
septum
Accessory
cartilage
Greater alar
cartilage
Lateral crus
~ Medial crus
FIG. 670.
FRONT VIEW OF THE BONY AND CARTILAGINOUS
SKELETON OF THE EXTERNAL NOSE.
Lateral cartilage The nasal cavity (Fig. 672) is
cartilage of divided by the nasal septum into
a right and a left nasal cavity,
which extend from the nostrils in
front to the choanse behind, and
open, through the choanse, into the
nasal part of the pharnyx. Their
bony boundaries are described in
the section on Osteology (p. 183).
On the lateral wall of each are
found the orifices of the frontal,
ethmoidal, sphenoidal, and maxil-
lary sinuses, together with that of
the naso-lacrimal duct.
Immediately above the aper-
ture of the nostril is a slightly
52
802
THE ORGANS OF SENSE.
Nares
Crus laterale A of greater
Crus mediate f alai L.
Lower edge of
cartilage of
septum
Fatty tissue of
ala nasi
FIG. 671. CARTILAGES OF NOSE FROM BELOW.
expanded area, the vestibule ; this is bounded laterally by the lateral crus of the
greater alar cartilage, and medially by the lower part of the septum; it is prolonged
as a small recess towards the apex of the nose. The vestibule is partly subdivided
by a curved ridge. It is lined with skin and,
in its lower half, there are hairs and sebace-
ailtl . ous glands; the hairs are curved downwards
j cartilage to g uarc [ the entrance to the nostril. The
superior part of the vestibule is smooth,
and is limited above and posteriorly by a
slightly marked arched prominence, the
limen nasi, beyond which the nasal cavity
is lined with mucous membrane.
Each nasal cavity, above and behind
the vestibule, is divided into a superior or
olfactory, and an inferior or respiratory
region. The olfactory region is a narrow
slit-like space; it comprises the middle of the superior nasal concha and the
corresponding portion of the septum. The respiratory region includes the remaining
part of the cavity.
Septum Nasi (Fig. 668). Where the bony septum of the nose is deficient, below
and in front, the gap is filled by the septal cartilage. Until the seventh year the
nasal septum lies, as a rule, in the median plane, but after this age it is very often
bent to one or other side more frequently to the right the deflection being greatest
usually along the line of junction of the vomer with the perpendicular lamina of
the ethmoid. De-
flection of the
septum is more
common in Euro-
pean than in non-
European skulls
occurring in
about 53 per cent
of the former and
in about 28 per
cent of the latter
(Zuckerkandl).
Associated with,
or apart from, this
deviation, crests
or spurs of bone
are found, project-
ing from the sep-
tum into one or
other nasal cavity,
in about 20 per
cent of skulls. In
the septum, a little
above and in front
of the naso-pala-
tine recess, is a
minute orifice, not
always recognisable, from which a blind pouch extends upwards and backwards for
a distance of from 2 to 9 mm. This is the vomero-nasal organ of Jacobson, and is
supported by the vomero-nasal cartilage. In man this organ is rudimentary, but
in many of the lower animals it is well developed (Fig. 673), and probably plays
a part in the sense of smell, since it is lined with epithelium similar to that
covering the olfactory region, and is supplied by branches of the olfactory nerve.
Lateral Wall (Fig. 674). In the lateral wall of the nasal cavity,above the superior
nasal concha, is a narrow recess, the recessus sphenoethmoidalis, into the posterior
Inferior
concha'
Maxillary
sinus
Inferior
meatus
FIG. 672. FRONTAL "SECTION THROUGH NASAL CAVITIES
SECTION VIEWED FROM BEHIND.
ANTERIOR HALF OF
NASAL CAVITY.
803
part of which the sphenoidal, air- sinus opens. The superior meatus of the nose is a
short oblique fissure, directed downwards and backwards, under cover of the superior
nasal concha ; into it the posterior ethmoidal cells open by one or more orifices.
A small meatus, bounded superiorly by a
concha suprenaa, frequently exists above
the superior meatus. The narrow slit-like
interval between the nasal septum and the
medial surface of the middle nasal concha
is named the olfactory cleft or sulcus.
The middle meatus, situated below and
lateral to the middle nasal concha, is a
roomy passage, and is continued forwards
into a slightly depressed area, termed the
atrium meatus nasi, which lies immediately
above the vestibule. The atrium is limited Vomero . n
superiorly and anteriorly by a low ridge, cartilages
the agger nasi, the representative of the FlG> 673 ._ SECTION THBOUGH NOSE'OF A KITTEN,
naso-turbinal found in many animals. When showing position of the vomero-nasai organs.
the middle nasal concha has been removed
the lateral wall of the meatus is exposed. On it is seen a narrow semilunar
cleft, the hiatus semilunaris, bounded above by a rounded elevation, the bulla
ethmoidalis, and below by the sharp edge of the processus uncinatus of the
Vomero-nasal organs
Frontal air-sinus
Bristle passed
from it into the
middle meatus
Opening of middle ethmoidal cells
Openings of posterior ethmoidal cells
Recessus sphenoethmoidalis
Sphenoidal air-sinus
Cut edge of inferior nasal concha
Bristle in opening of naso-lacrimal duct
FIG. 674. VIEW OF THE LATERAL WALL OP THE NOSE THE NASAL CONCHA HAVING BEEN REMOVED.
1. Vestibule.
2. Opening of maxillary sinus.
3. Hiatus semilunaris.
4. Bulla ethmoidalis. 7. Cut edge of superior nasal concha.
5. Agger nasi. 8. Cut edge of middle nasal concha.
6. Opening of anterior ethmoidal cells. 9. Pharyngeal orifice of auditory tube.
ethmoid. The size of the bulla varies with that of the middle ethmoidal cells,
which are contained within it and which open on or near its upper surface.
Through the hiatus semilunaris the middle meatus opens into the infundibulum,
a curved channel, limited above by the bulla ethmoidalis, and below by the lateral
surface of the processus uncinatus. The anterior end of the infundibulum receives
52 a
804
THE OEGANS OF SENSE.
the openings of the anterior ethmoidal cells, and, in rather more than fifty per cent
of skulls, is continued upwards as the fronto-nasal duct into the frontal air-sinus ;
in the remainder it is shut off from the lower end of the fronto-nasal duct by
the union of the anterior part of the bulla ethmoidalis with the upper end of
the processus uncinatus, and the fronto-nasal duct then opens into the anterior
part of the middle meatus. The ostium maxillare or opening of the maxillary sinus
is placed below the bulla ethmoidalis, and is hidden by the lower end of the
processus uncinatus ; an accessory ostium is frequently seen in the middle meatus,
above the posterior part of the inferior nasal concha.
The inferior meatus lies below the inferior nasal concha, under cover of the
anterior part of which is the slit-like orifice of the naso-lacrimal duct (see p. 825).
The roof is very narrow, except at its posterior part, and is divisible into three
portions, fronto-nasal, ethmoidal, and sphenoidal, in accordance with the bones
which enter into its formation.
The floor is nearly horizontal from before backwards, and is formed by the
palatine process of the maxilla and the horizontal part of the palatine bone. In
it, close to the inferior margin of the septum and immediately over the incisive
foramen, a slight depression, the naso-palatine recess, is sometimes seen ; it is directed
downwards and forwards for a short distance, and indicates the position of a
communication which existed between the nasal and buccal cavities in early
foetal life.
Membrana Mucosa Nasi. The nasal mucous membrane is thick, highly
vascular, and firmly bound to the subjacent periosteum and perichondrium. It
is continuous, through the choanae, with the mucous lining of the nasal part of the
pharynx; through the naso-lacrimal and lacrimal ducts, with the conjunctiva;
and, through the apertures leading into the air-sinuses, with the delicate lining
of these cavities.
Throughout the respiratory region it is covered with columnar, ciliated
epithelium, interspersed amongst which are goblet or mucin cells, whilst between
the bases of the columnar cells smaller pyramidal cells are interpolated. It contains
a freely anastomosing venous plexus, which in some parts, e.g. over the inferior nasal
conchse, forms a cavernous plexus. Many acinous glands, secreting a watery fluid,
are embedded in it, and are especially large and numerous in the posterior halves of
the nasal cavities,
Zone of oval
nuclei
Zone of
round nuclei
Basal cells
Olfactory
glands
I Epithelium
_ tory glands
FIG. 675. SECTION THROUGH THE OLFACTORY Mucous MEMBRANE.
while in children
the mucous
membrane con-
Duct of one , . . i
oftheoifac- tains a consider-
able amount of
adenoid tissue.
In the olfac-
tory region the
mucous mem-
brane is yellow-
ish in colour,
more delicate,
and is covered
with non-ciliated
columnar epi-
thelium (Figs.
675, 676). Em-
bedded in it are
numerous tubu-
lar and branched
glands, the olfactory glands, which are lined with polygonal cells and open by fine
ducts on its free surface. The epithelium of the olfactory region consists of : (1)
supporting cells, (2) olfactory cells, and (3) basal cells.
1. Supporting Cells. The superficial parts of these cells are columnar in shape
and contain fine granules of yellow pigment, whilst the deeper portions are continued
NASAL CAVITY
805
Central
processes of
olfactory
Olfactory
hairs
Peripheral
process
Body of
cell with
nucleus
Central
process
FIG. 676. OLFACTORY AND SUPPORTING CELLS.
for some distance as attenuated or branched processes. These cells contain
elliptical or oval nuclei, which are situated at the deep ends of the columnar
parts of the cells, and' form what is termed the zone of oval nuclei. In many
animals the free surface
of this columnar epithel-
ium is covered byia thin
limiting membrane.
2. Olfactory Cells.
These are bipolar
nerve -cells, the central
processes of which are
continued as the axons
of the olfactory nerve-
fibres. They are homo-
logous with the cells of
the spinal ganglia, but
differ from them in that
they retain their primi-
tive position in the sur-
face epithelium. The
cell bodies are spindle-
shaped and are arranged
in several rows between
the deeper, attenuated
parts of the supporting
cells. Each consists of
a large, spherical nucleus
with a small amount of
enveloping protoplasm ;
the nuclei form a layer of some thickness, termed the zone of round nuclei. The
peripheral process of each cell is rod-like, and extends between the columnar
portions of the supporting cells as far as their free surfaces, where it pierces the
external limiting membrane and divides into a number of fine hair-like processes,
termed olfactory hairs. The central process is a delicate, beaded filament, and is
continued upwards as the axon of an olfactory nerve-fibre.
3. Basal Cells. These cells are branched, and lie on a basement membrane
between the deep extremities of the supporting and olfactory cells.
Olfactory Nerves. The fibres of the olfactory nerves are devoid of medullary
sheaths, and arise, as stated, from the olfactory cells. They are collected into
fasciculi which form a plexiform network under the mucous membrane and ascend
on the medial and lateral walls of the olfactory region of the nasal cavity. They
are lodged, near the base of the skull, in grooves or canals in the ethmoid bone and
pass into the cranial cavity through the foramina in the lamina cribrosa of the
ethmoid. Immediately above the lamina cribrosa they enter the olfactory bulb, in
the glomerular layer of which they subdivide and form synapses with the dendrites
of the mitral cells of the bulb.
The trigeminal nerve supplies branches of ordinary sensation to the nasal mucous membrane
as follows : The septum is chiefly supplied by the naso-palatine nerve, but its posterior part
receives 'some filaments from the spheno-palatine ganglion and from the nerve of the pterygoid
canal, and its anterior portion from the naso-ciliary branch of the ophthalmic. The lateral
wall is supplied (1) by the upper nasal branches of the nerve of the pterygoid canal and from
the spheno-palatine ganglion ; (2) by the lower nasal branches derived from the anterior palatine ;
and in front by (3) the naso-ciliary branch of the ophthalmic. The floor and anterior part of the
inferior meatus are supplied by a nasal branch of the anterior superior alveolar nerve.
Blood-vessels. Arteries. The chief artery of the nose is the spheno-palatine branch of the
internal maxillary artery. This reaches the nasal cavity through the spheno-palatine foramen, and
divides into (a) posterior nasal, which ramifies over the meatuses and conch ae and sends branches
to the maxillary and frontal sinuses and the ethmoidal cells ; and (6) naso-palatine, the artery
' the septum. Twigs are given to the upper portion of the cavity by the anterior and posterior
thmpidal arteries, while its posterior part receives some small branches from the descending
palatine. The nostrils are supplied by the lateral nasal branch of the external maxillary, and by
806
THE ORGANS OF SENSE.
the septal artery from the superior labial. The maxillary sinus is partly supplied by the infra-
orbital artery, whilst the sphenoidal sinus gets its chief supply from the spheno-palatine artery.
The veins form a dense cavernous plexus ; this condition is well seen in the respiratory region,
and especially so over the middle and inferior nasal conch ae and on the lower part of the septum.
The venous blood is carried in three chief directions, viz., anteriorly into the anterior facial
vein, posteriorly into the spheno-palatine vein, and superiorly into the ethmoidal veins. The
ethmoidal veins communicate with the ophthalmic veins and the veins of the dura mater ; further,
an ethmoidal vein passes up through the lamina cribrosa of the ethmoid, and opens either into
the venous plexus of the olfactory bulb or directly into one of the veins on the orbital surface of
the frontal lobe of the brain.. The lymph, vessels form an irregular network in the superficial
part of the mucous membrane, and can be injected from the subdural or subarachnoid cavities.
The larger vessels are directed posteriorly towards the choanae, and are collected into two
trunks, of which the larger passes to a lymph gland in front of the epistropheus, and the
smaller to one or two lymph glands situated near the greater cornu of the hyoid bone.
The development of the nose is described in the section which deals with
" General Embryology " (p. 50).
OEGANON VISUS.
OCULUS.
The bulb of the eye (O.T. eyeball) constitutes the peripheral part of the organ
of sight ; associated with it are certain accessory structures, such as the eyelids
and the lacrimal apparatus.
Cornea
Sinus venosus sclera 1
Suspensory ligament
Len
Tendon of
lateral
rectus
Anterior chamber
Iris
-Posterior chamber
Ciliary process
Spatia zonularia
Tendon 01
medial
rectus
Vitreous body
Fovea centralis
Lamina cribrosa sclerse
Arteria centralis retinae
Optic nerve
FIG. 677. DIAGRAM OF A HORIZONTAL SECTION THROUGH LEFT BULBUS OCDLI AND
OPTIC NERVE ( x 4).
Bulbus Oculi. Situated in the anterior part of the orbital cavity, the bulb of the
eye is protected in front by the eyelids, and is pierced behind by the optic nerve,
which ramifies in its innermost tunic, the retina. The tendons of the ocular
muscles are attached to the outer surface of the bulb, a short distance in front of
FIBKOUS TUNIC OF THE EYE. 807
its equator, while its posterior two-thirds are enveloped by a loose membrane
termed the fascia bulbi (O.T. capsule of Tenon).
The bulb of the eye- is not quite spherical, being composed of the segments of
two spheres, viz., an anterior, transparent, corneal segment, possessing a radius of 7 or
8 mm., and a posterior, opaque, scleral segment, with a radius of about 12 mm.
(Fig. 677). The anterior or corneal segment, in consequence of its shorter radius,
projects forwards, in front of the scleral portion, the union of the two parts
being indicated, externally, by a slight groove, the sulcus sclerse. The central
points of the anterior and posterior curved surfaces of the bulb constitute,
respectively, its anterior and posterior poles, and a straight line joining the two
poles is termed the optic axis ; an imaginary line encircling the bulb, midway
between the poles, is named the equator. The axes of the two bulbs are almost
parallel, diverging only slightly in front ; but the axes of the optic nerves converge
behind, and, if prolonged backwards, would meet in the region of the dorsum
sellse of the sphenoid. The sagittal and transverse diameters of the bulb are
nearly equal about 24 mm.; its vertical diameter is about 23'5 mm. All three
diameters are rather less in the female than in the male, but the size of the bulb
is fairly constant in the same sex. What are popularly described as large eyes
owe their apparent size to a greater prominence of the bulb and to a wider fissure
between the eyelids.
At birth the bulb of the eye is nearly spherical and has a diameter of about
17'5 mm. By the age of puberty this has increased to 20 or 21 mm., after which it
rapidly reaches its adult size.
Fascia Bulbi. The fascia bulbi (O.T. capsule of Tenon) is a fibrous tunic
enveloping the posterior two- thirds of the bulb of the eye, and separating the
posterior part of the bulb from the surrounding orbital fat. It blends posteriorly
with the sheath of the optic nerve and with the sclera around the lamina cribrosa ;
anteriorly it is continued into the ocular conjunctiva, and is also attached to the
ciliary region of the bulb. It is pierced by the tendons, of the ocular muscles, and
is reflected on each as a tubular sheath. The sheath on the tendon of the obliquus
superior surrounds the tendon as far as its pulley, to which it is attached ; that
on the obliquus inferior is prolonged as far as the floor of the orbit. The sheaths
on the recti muscles are continuous posteriorly with the perimysium of those
muscles, and each gives off an expansion. The expansion from the sheath of the
rectus superior blends with the sheath of the levator palpebrse superioris, and that
from the sheath of the rectus inferior is attached to the tarsus of the inferior
eyelid. The expansions from the sheaths of the medial and lateral recti are strong,
especially that from the latter muscle, and are attached to the lacrimal and zygo-
matic bones respectively ; they are named the medial and lateral check ligaments,
because they probably limit the action of the corresponding muscles. The portion
of the fascia bulbi which lieg inferior to the bulb of the eye has been named the
suspensory ligament (Lockwood) ; it is expanded in the centre, and is slung like
a hammock from side to side, its narrow ends being fixed to the lacrimal and
zygomatic bones.
The bulb of the eye (Fig. 677) consists of three concentric tunics or coats, and
contains three transparent refracting media. The three tunics are : (1) an outer
fibrous tunic, consisting of an opaque posterior part, the sclera, and a transparent
anterior portion, the cornea ; (2) an intermediate vascular, pigmented, and partly
muscular tunic, the tunica vasculosa oculi, comprising, from behind forwards, the
chorioid, the ciliary body, and the iris ; (3) an internal nervous tunic, the retina.
The three refracting media are named, from before backwards, the aqueous humour,
the crystalline lens, and the vitreous body.
TUNICA FIBEOSA OCULI.
Sclera. The sclera is a firm, opaque membrane, forming approximately the
posterior five-sixths of the outer tunic. Thickest posteriorly (about 1 mm.), it thins
at the equator to 04 or 0'5 mm., and again increases to 0'6 mm. near the sulcus
526
808
THE OBGANS OF SENSE.
Ligamentum pectinatum iridis
Scleralspur [ Radial muscle of iris
Venous sinus of sclera i e T
Sclera
sclerse. It is thinner in the child than in the adult, and presents a bluish appearance
caused by the pigment of the chorioid shining through it ; in old age it assumes
a yellowish tinge. In front of the equator it gives attachment to the tendons of
the ocular muscles, while its anterior part is covered by the conjunctiva. Its deep
surface presents a brownish colour, and is loosely attached to the chorioid, except
at the entrance of the optic nerve and in the neighbourhood of the sulcus sclerae.
It is pierced, behind, by the optic nerve, the entrance for which is funnel-shaped,
wide behind and narrow in front, and is situated 3 mm. to the nasal side and
slightly below the level of the posterior pole. The fibrous sheath of the nerve blends
with the outer part of the sclera, while the nerve bundles pass through a series of
orifices ; this perforated portion is named the lamina cribrosa sclerae. Around the
entrance of the optic nerve are some fifteen to twenty small apertures for the
passage of the ciliary nerves and short ciliary arteries. The two long posterior
ciliary arteries pierce it, one on each side, some little distance from the entrance of
the optic nerve ; while a little behind the equator are four openings, two above and
two below, for the exit of veins, called venae vorticosae ; near the sulcus sclerse it is
perforated by the anterior ciliary arteries. The deep surface of the sclera is lined
with flattened endothelial
cells; and between it and
the chorioid is an exten-
sive lymph space, the
spatium perichorioideale,
which is traversed by the
ciliary nerves and arteries
just mentioned, and by
an irregular mesh work of
fine, pigmen ted, connective
tissue, the lamina fusca,
which loosely attaches the
sclera to the chorioid. At
the sclero-corneal junction
the fibrous tissue of the
sclera passes continuously
into that of the cornea, and
in the deeper part of this
\ Parts of ciliary processes junction there is a circular
Circular fibres of ciliary muscle ^^ the ginus venogus
FIG. 678. SECTION OF IRIDIAL ANGLE. (Prof. Arthur Thomson.) sclerae (O.T. canal of
Schlemm) (Fig. 678).
When seen in a meridional section of the sclero-corneal junction, the sinus
venosus sclerse appears as a narrow cleft ; its outer wall is formed by the compact
tissue of the sclera, while its inner consists of a triangular mass of trabecular tissue ;
the apex of the triangle is directed forwards and is continuous with the posterior
elastic lamina of the cornea. The sinus is lined with endothelium, and
occasionally contains a few red blood corpuscles. It communicates, on the one
hand, with the anterior ciliary veins, and on the other, through the spatia anguli
iridis in the trabecular tissue, with the anterior chamber of the eye.
Structure. The sclera consists of bundles of white fibrous tissue, together with some fine
elastic fibres, the bundles forming equatorial and meridional layers, which interlace with each
other. Numerous spaces containing connective tissue cells and migratory cells exist between the
fibres. Pigmented cells are plentiful in the lamina fusca, and a few are found also in the tissue
of the sclera, near the entrance of the optic nerve, and in the region of the sclero-corneal junction.
Vascular and Nervous Supply. The sclera receives its blood-supply from the short
posterior ciliary and the anterior ciliary arteries, while its veins open into the venae vorticosae and
anterior ciliary veins. The cell spaces play the part of lymph vessels and communicate with
the pericborioidal and suprascleral lymph spaces. Its nerves are derived from the ciliary
nerves, which, after losing their medullary sheaths, pass between the fibrous bundles ; their exact
mode of ending is not known.
Cornea. The cornea is transparent and forms the anterior sixth of the outer
tunic; its index of refraction is from 1'33 to 1/35 ; the thickness of its central part
Meridional fibres of ciliary muscle
Iridial angle
FIBKOUS TUNIC OF THE EYE.
809
Anterior chamber
Lens
Iris
Cornea
Sulcus circularis corneas.
Posterior chamber
Ciliary muscle--
Ciliary process -
Spatia zonularia
Vitreous^
Ora serrata
Chorioid
Rectus muscle.
Retina
FIG. 679. SECTION OF A PORTION OF THE BULB OF THE EYE SHOWING
THE SULCUS CIRCULARIS CORNER.
is about '95 mm., of its peripheral part, about 119 mm. Its anterior surface is
covered with a stratified epithelium, continuous with that which lines the con-
junctiva ; its posterior surface
is directed towards the an-
terior chamber of the eye and
is in contact with the aqueous
humour. Its degree of curva-
j cc i. J Sinus venosus sclerte
ture varies in different indi-
viduals ; it is greater in youth conjunctiva
than in old age, and is, as a
rule, slightly greater in the
vertical than in the horizontal
plane ; it diminishes from its
centre to its circumference,
and is less on the nasal than
on the temporal side of the
anterior pole. The outline of
the anterior surface of the
cornea is almost circular,
measuring 11 mm. vertically
and 11 '9 mm. transversely ;
that of the posterior surface is circular and has a diameter of 13 mm.
The tissue of the cornea is continuous posteriorly with that of the sclera, the
line of union being known as the sclero-corneal junction. Directly in front of this
junction the inner surface of the cornea projects in the form of a rounded rim ;
behind this rim, in the interval between the sclero-corneal junction and the attach-
ment of the iris, is a groove, the sulcus circularis cornese (Arthur Thomson) 1 (Fig. 679).
The outer wall of this sulcus is composed of a thin stratum of trabecular tissue
placed on the inner side of the sinus venosus sclerae. Between this trabecular tissue
and the front of the circum-
ference of the iris is a narrow
recess which on section ap-
pears as an acute angle ; it is
named the filtration angle or
angle of the iris.
Structure. The cornea con-
sists, from before backwards, of
the following strata, viz., (Fig.
680) :
1. Epithelium corneae.
2. Anterior elastic lamina.
3. Substantia propria.
4. Posterior elastic lamina.
5. Endothelium of anterior
chamber.
1. The epithelium cornese is
continuous with that covering the
free surface of the conjunctiva and
consists of six or eight strata of
nucleated cells. Deepest of all is
a single layer of perpendicularly
arranged columnar cells, the flat-
tened bases of which rest on the
anterior elastic lamina, while their
opposite ends are rounded and
contain the nuclei. Superficial
to this layer are three or four
strata of polygonal cells, the majority of which exhibit finger-like processes joining with the
corresponding processes of neighbouring cells ; the more superficial layers consist of squamous
cells. The thickness of this stratified epithelium is about 45 /* at the centre, and about 80 n at
the periphery of the cornea.
Substantia
propria, in
which the
corneal cor-
puscles are
seen to be
spindle-
shaped on
section
Posterior
elastic lamina
Endothelium of
anterior chamber
FIG. 680. VERTICAL SECTION OF CORNEA (magnified).
1 The Ophthalmoscope, September 1910, and July 1911.
810 THE OEGANS OF SENSE.
2. The anterior elastic lamina is from 19-20 ^ thick, and is regarded merely as a differentia-
tion of the anterior part of the snbstantia propria, from which it is with difficulty separated ; it
is not stained yellow by picrocarmine, thus differing from true elastic tissue. Its degree of
development varies in different animals.
3. The substantia propria presents, in a fresh condition, a homogeneous appearance ; but,
with the assistance of reagents, it is seen to consist of modified connective tissue, with a few
elastic fibres. An amorphous interstitial substance binds the fibres into bundles, and, in turn,
cements the bundles into lamellae which are flattened from before backwards. The fibres of any
one lamella cross those of adjacent lamellae almost at right angles, while the superimposed lamellae
are joined by sutural fibres and by amorphous substance. Between the lamellae are found the
cell spaces or lacunae of the cornea irregularly stellate in shape, and communicating freely
with each other by means of fine canaliculi. The corneal cells or corpuscles are contained in
these lacunae, without, however, completely filling them, the remainder of the cavities being
occupied by lymph. The cells are nucleated, flattened, and star-like, and their branched pro-
cesses join those of neighbouring cells in the canaliculi. Migratory or lymph cells are also found
in cell spaces.
After middle age a grayish opaque ring, 1*5 to 2 mm. in breadth, is frequently seen near the
periphery of the cornea ; it is termed the arcus senilis, and results from a deposit of fat granules
in the lamellae and corneal corpuscles.
4. The posterior elastic lamina is a clear homogeneous membrane, covering the posterior
surface of the substantia propria and possessing a thickness of 6-8 /* at the centre and 10-12 fj, at
the periphery of the cornea. Less firmly attached than the anterior elastic lamina, it may be
stripped off, when it will be found to roll up with its attached surface inwards. Between the
ages of twenty and thirty years small wart-like projections appear on its deep surface, near its
periphery, and these increase in size and number as years advance, so that in old age the
membrane may attain a thickness of 20 /*. At the sclero-corneal junction the posterior elastic
lamina splits into bundles of fine fibres which interlace and form the triangular area of trabecular
tissue already referred to (p. 808), and which is usually spoken of under the name of the
ligamentum pectination iridis. The meshes or spaces between the trabeculse are termed the
spatia anguli iridis (O.T. spaces of Fontana), and are lined with endothelium prolonged from the
endothelium of the anterior chamber. They communicate internally with the filtration angle
and externally with the sinus venosus sclerae, and form important channels through which fluid
may filter from the anterior chamber into the sinus and thence into the anterior ciliary veins.
When the trabecular tissue of the ligamentum pectinatum iridis is followed backwards most of
its fibres are seen to be attached to the anterior surface of an inwardly directed rim of scleral
tissue ; in a meridional section this rim appears as a triangular projection, and is named the scleral
spur. A few fibres of the trabecular tissue are carried past the apex of the scleral spur on to the
inner surface of the origin of the meridional fibres of the ciliary muscle, and, passing behind
the filtration angle, are prolonged into the iris (Fig. 678), where they are directly continuous with
the fibres of the dilatator pupillae muscle (Arthur Thomson). 1
5. The endothelium of the anterior chamber consists of a single stratum of nucleated,
flattened, polygonal cells, which present a fibrillar structure and are continued as a lining to the
spatia anguli iridis ; this layer of endothelium is also reflected on to the anterior surface of the iris.
Vascular and Nervous Supply of the Cornea. In the foetus the cornea is traversed, almost
as far as its centre, by capillaries ; but in the adult it is devoid of blood-vessels, except near its
margin. The capillaries of the conjunctiva and sclera pass into this marginal area for a distance
of about 1 mm., where they terminate in loops. All the remainder of the cornea is nourished by
the lymph which circulates in its cell spaces and canaliculi.
The nerves of the cornea are derived from the ciliary nerves. Around its periphery they
form an annular plexus, from which fibres pass into the cornea, where, after a distance of 1 or
2 mm., they lose their medullary sheaths and ramify in the substantia propria, forming what is
termed the fundamental or stroma plexus. Fibres extend from this plexus through the anterior
elastic lamina and form a subepithelial plexus, from which fine filaments ramify between the
epithelial cells as far as the superficial layers. From the annular and stroma plexuses fibrils
pass to the substantia propria and come into close relation with the corneal corpuscles.
TUNICA VASCULOSA OCULI.
The middle, vascular, and pigmented tunic of the bulb of the eye comprises,
from behind forwards, the chorioid, the ciliary body, and the iris (Fig. 681).
Chorioidea. The chorioid intervenes between the sclera and the retina, reach-
ing as far forwards as the ora serrata of the retina (p. 815). It is dark brown or
black in colour, and is thicker behind than in front ; posteriorly it is pierced by
the optic nerve, and is there firmly attached to the sclera. Its outer surface is
flocculent and is connected to the sclera by the loose lamina fusca; its inner
surface is smooth and is adherent to the outermost or pigmented layer of the retina.
The chorioid consists of a loose connective tissue, embedded in which are blood-
vessels and branched pigment cells; from without inwards it consists of three
1 Op. cit.
VASCULAE TUNIC OE THE EYE.
811
layers, viz. : (a) the lamina suprachorioidea ; (&) the proper tissue of the chorioid ;
and (c) the lamina basalis (Eig. 681).
Lamina basalis
Lamina choriocapillaris
Intermediate stratum
> Lamina vasculosa
=; Lamina suprachorioidea
Sclera
FIG. 681. VERTICAL SECTION OF CHORIOID AND INNER PART OF SCLERA.
resembles the lamina fusca of the
Cornea
Sinus venosus sclerae
Circulus arteriosus
major
Conjunctival vessels
Recurrent artery
of chorioid
Anterior
ciliary
vessels
Sclera
Chorioid
Retina
The lamina suprachorioidea resembles the lamina fusca of the sclera, and
consists of a series of fine non- vascular lamellae, each containing a delicate network
of elastic fibres, amongst
which are stellate, pig-
men ted cells and amoe-
boid cells. The spaces
between the laminse
are lined with endo-
thelium, and together
form the spatium peri-
chorioideale, already
referred to (p. 808).
The proper tissue of
the chorioid consists
of blood - vessels and
numerous pigmented
cells, supported by con-
nective tissue, elastic
fibres, and some non-
striped muscular fibres.
Its outer part contains
the larger blood- vessels,
and is named the lamina
vasculosa, while its
inner portion is com-
posed of a network of
fine capillaries, and is
termed the lamina
choriocapillaris ; these
two laminae are joined
by a thin intermediate
stratum. The arteries
of the chorioid are de-
rived from the short
posterior ciliary vessels
which pierce the sclera
around the entrance of
the optic nerve, and
form a wide-meshed FlG 682 ._ D iAGRA M OF THE CIRCULATION IN THE EYE (Leber).
plexus in the lamina
vasculosa. The circular muscular coats of the arteries are well developed, and
longitudinal muscular fibres also are present in the larger branches. The veins,
Vessels of iris
Vessels of ciliury process
Suprascleral vessels
Vena vorticosa
Long posterior ciliary artery
Short posterior ciliary artery
( Outer and
Dinner vessels of optic sheath
Optic nerve
Central artery and vein of retina
812
THE OKGANS OF SENSE.
destitute of muscular tissue, are superficial to the arteries ; they are surrounded
by perivascular lymph sheaths and converge to form whorls, which open into the
vense vorticosae. In the tissue between the blood-vessels are numerous stellate,
flattened, and pigmented cells.
The lamina choriocapillaris is composed essentially of small capillaries, which
form an exceedingly close network, embedded in a finely granular or almost
homogeneous tissue.
The intermediate stratum between the lamina vasculosa and lamina chorio-
capillaris consists of a network of delicate elastic fibres and contains almost no
pigment cells; it is lined, next the lamina choriocapillaris, with a layer of
endothelium.
The lamina basalis is transparent and nearly structureless. Its outer surface
exhibits a trellis-like network of fibres which unite it to the lamina choriocapillaris,
while its inner surface is smooth and is in contact with the pigmented layer of the
retina.
Tapetum. In many animals a brilliant iridescence is seen on the postero-lateral part of
the chorioid ; to this the name tapetum is applied. Absent in man, it may be due, as in the
horse, to a markedly fibrous condition of the stratum intermedium (tapetum fibrosum), or as
in the seal, to the presence of some five or six layers of flattened iridescent cells lying imme-
diately outside the lamina choriocapillaris (tapetum cellulosum).
Corpus Ciliare. The ciliary body connects the chorioid to the circumference
of the iris (Fig. 683), and comprises three zones, viz. : (a) the orbiculus ciliaris,
(&) the ciliary processes,
and (c) the ciliary muscle,
-ins The orbiculus ciliaris
is a zone of about 4 mm.
in width immediately
adjoining the chorioid ;
it exhibits numerous
radially arranged ridges.
Processus Ciliares.
The ciliary processes,
about seventy in number,
form a circle of radial
, thickenings, each of a
Meridional fibres of
ciliary muscle somewhat triangular
shape ; the base of the
triangle is directed for-
Pars ciliaris retinse Wards, towards the
equator of the lens, while
the apex is continuous
behind with some three
or four ridges of the or-
biculus ciliaris. They
vary in size, the largest
having a length of 2-5
Zonula ciliaris
mm.
The structure of the
orbiculus ciliaris and
ciliary processes is similar
to that of the chorioid,
but the capillaries are
larger and more tortuous,
and there is no lamina
choriocapillaris. The
FIG. 683. SECTION THROUGH CILIARY REGION OF THE BULB OF THE EYE. deep surface of the ciliary
processes is covered by
two strata of columnar epithelium, the anterior layer of which is pigmented ; these
two strata form a direct continuation forwards of the retina and constitute the
Cornea
Anterior chamber
Sinus venosus
sclerse
Spatia angul
iridis
Conjunctiva
Pars iridica retinae
Ciliary process
Ligamentum
pectinatum iridis
.Circular fibres
of ciliary muscle
Sclera
Perichorioidal lymph space
Orbiculus
ciliaris
Retina
VASCULAE TUNIC OF THE EYE. 813
pars ciliaris retinae ; this epithelium is invaginated to form more or less tubular
glands.
M. Ciliaris. The ciliary muscle is triangular on horizontal or vertical section,
and consists of two sets of fibres meridional and circular (Fig. 683). The meridional
fibres arise from the scleral spur, already described, and radiate backwards, to be
attached to the ciliary processes and orbiculus ciliaris. When they contract the
chorioid is drawn forwards and the lens becomes more convex, owing to the
relaxation of its suspensory ligament (see p. 810). The circular fibres form a
triangular zone behind the filtration angle, close to the periphery of the iris.
Considerable individual differences are found as to the degree of development
of these two portions of the ciliary muscle ; the meridional fibres are always more
numerous than the circular fibres, the latter being absent or rudimentary in myopic
eyes, but well developed, as a rule, in hypermetropic eyes.
Iris. The iris forms a contractile diaphragm in front of the lens, and is
pierced, a little to the nasal side of its centre, by an almost circular aperture,
the pupil, which, during life, is continually varying in size in order to regulate
the amount of light admitted into the interior of the eye. It partially divides
the space between the cornea and lens into two portions, which are filled by the
aqueous humour, and are named, respectively, the anterior and posterior chambers
of the eye. It is thinnest at its peripheral or ciliary margin which is directly
continuous with the ciliary body, and, through the medium of the ligamentum
pectinatum iridis, with the posterior elastic lamina of the cornea. Its pupillary
or free margin forms the circumference of the pupil, and rests upon the anterior
surface of the capsule of the lens.
The distinctive colour of the eye, in different individuals, depends on the arrangement
of the pigment in the iris; in the blue eye the pigment is limited to the posterior
surface of the iris, but in the brown or black eye it is also scattered throughout its stroma ;
in the albino the pigment is absent.
The pupil is closed, during the greater part of foetal life, by a thin transparent
vascular membrane, the membrana pupillaris, continuous with the pupillary margin of
the iris. Its vessels are derived partly from the vessels of the iris and partly from those
of the capsule of the lens ; they converge towards the middle of the membrane, near which
they form loops so as to leave the central part non-vascular. About the seventh month
the vessels begin to be obliterated, from the centre towards the circumference ; and this
is followed by a thinning and absorption of the membrane, which becomes perforated by the
aperture of the pupil. This perforation gradually enlarges, and at birth the membrane
has entirely disappeared ; in exceptional cases it persists.
On the anterior surface of the iris is a layer of flattened endothelium, placed
on a basement membrane, and continuous with the endothelium of the anterior
chamber. Depressions or crypts are seen here and there in which the endothelium
and basement membrane are absent, and are, by some, regarded as stomata,
through which the lymph vessels of the iris communicate with the cavity of the
anterior chamber. The posterior surface of the iris is covered with a basement
membrane, on which are placed two layers of columnar, pigmented epithelium,
continuous with the pars ciliaris retinae, and termed the pars iridica retinas. The
stroma iridis, or proper tissue of the iris, consists of delicate connective tissue
and elastic fibres, with pigmented cells, blood-vessels, nerves, and non-striped
muscle.
The blood-vessels of the iris (Fig. 682) are derived from the long ciliary and
the anterior ciliary arteries. The long ciliary arteries, two in number, pierce the
sclera on the medial and lateral sides of the optic nerve respectively, and extend
forwards, between the sclera and chorioid, towards the ciliary margin of the iris.
There each divides into a superior and an inferior branch, and the resulting four
branches anastomose in the form of a circle, termed the circulus arteriosus major.
This circle is joined by a varying number of anterior ciliary arteries, derived from
the lacrimal and muscular branches of the ophthalmic artery, and, after supplying
the ciliary muscle, sends converging branches towards the aperture of the pupil,
where a second circle, the circulus arteriosus minor, is formed. The veins proceed
814
THE OEGANS OF SENSE.
Veins of chorioid
Aperture of
pupil
Long
ciliary
artery
Long
ciliary
artery
towards the ciliary margin of the iris, and communicate with the veins of the
ciliary processes and with the sinus venosus sclerse. The convergence of the blood-
vessels towards the aper-
Auterior ciliary arteries ture Q f t h e pupil gives to
the anterior surface of the
iris a striated appearance.
The non-striped muscular
fibres of the iris are arranged
in two sets : (a) circular,
(6) radial. The circular
fibres form a band, the m.
sphincter pupillse, around
the pupillary aperture ; by
the contraction of these
fibres the size of the pupil
is lessened. The radial fibres
constitute the m. dilatator
pupillae and extend out-
wards from the sphincter to
the ciliary margin. Many
anatomists regard the radial
fibres, in man and most
mammals, as being elastic
-, , , j
animals in which the radial
fibres are muscular, the
degree of their development varies considerably ; they are feebly marked in the
rabbit, but are well developed in the bird, and still more so in the otter.
The nerves of the chorioid and iris (Fig. 685) are derived from the long and
short ciliary nerves. The former, two or three in number, are branches of the naso-
ciliary nerve ; the latter, vary-
ing from eight to fourteen,
are derived from the ciliary
ganglion. Piercing the sclera
around the. entrance of the
optic nerve, the ciliary nerves
traverse the perichorioidal
lymph space, where they form
a plexus, rich in nerve-cells, Vena vorticosa
from which filaments are sup-
plied to the blood-vessels of
the chorioid. In front of the
ciliary muscle a second plexus,
also rich in nerve -cells, is
formed ; this supplies the
ciliary muscle and sends fila-
ments into the iris, as far as
its pupillary margin, for the
supply of its muscular fibres and blood-vessels. The sphincter pupillse is suppliec
by the oculo-motor nerve, the dilatator pupillse by the sympathetic.
Anterior ciliary arteries
FIG. 684. BLOOD-VESSELS OF IRIS AND ANTERIOR PART OF CHORIOID,
viewed from the front (Arnold).
Cornea
Sinus venosus sclerse -
Anterior ciliary
artery
Sclera
Pupil
Anterior ciliar
artery
Ciliary muscle
Long posterior
ciliary artery
Vena vortico
Long posterior
ciliary artery
FIG. 685. DISSECTION OF THE EYEBALL SHOWING THE VASCULAR
TUNIC AND THE ARRANGEMENT OF THE CILIARY NERVES AND
VESSELS.
RETINA.
The retina, or nervous tunic of the eyeball, is a soft, delicate membrane, in
which the fibres of the optic nerve are spread out. It consists of two strata, viz.
(a) an outer, pigmented layer, attached to the chorioid ; and (&) an inner nervous
lamina, the retina proper, in contact with the hyaloid membrane of the vitreous
body, but attached to it only around the entrance of the optic nerve and in the
region of the ciliary processes. Expanding from the entrance of the optic nerve
THE EETINA.
815
Iris
Ciliary process.
Sclera
Chorioid
Retina
- Lens
Ciliary processes
Pars ciliaris
"retinae
Ora serrata
Retina
FIG. 686. A SEGMENT OF THE BULBUS OCULI SHOWING THE ORA
SERRATA.
the retina appears to end, a short distance behind the ciliary body, in a wavy
border, the ora serrata (Fig. 686). There its nervous elements cease and the mem-
brane becomes suddenly 'thinned, but a delicate continuation of it is prolonged
over the posterior aspect
of the ciliary body and Cornea
iris. This continuation
consists of the pig-
niented layer, together
with a layer of columnar
epithelium, and con-
stitutes the pars ciliaris
retinae and pars iridica
retinae, already referred
to (p. 813). The portion
behind the ora serrata
is termed the pars optica
retinae, and its thickness
gradually diminishes
from 04 mm. near the
entrance of the optic nerve, to 0*1 mm. at the ora serrata. It presents, at the
posterior pole of the eye, and therefore directly in the optic axis, a small, oval
yellowish spot, the macula lutea. The greatest or transverse diameter of the
macula measures from 2-3 mm. ; its central part is depressed and is named the
fovea centralis. About 3 mm. to the nasal side and slightly below the level of the
posterior pole is a whitish, circular disc, the optic disc, which corresponds with the
entrance of the op tic -nerve, and has a diameter of about 1-5 mm. The circum-
ference of the optic disc is slightly raised and is named the papilla nervi optici,
while its depressed central portion is termed the excavatio papillae nervi optici
(O.T. optic cup). The optic disc consists merely of nerve-fibres, the other layers
of the retina being absent, and it constitutes the
" blind spot."
The nervous layer of the retina is transparent
during life, but becomes opaque and of a grayish
colour soon after death. If an animal is kept
in the dark before the removal of it's eyeball, the
retina presents a purple tinge, due to the presence
of a colouring matter named rhodopsin or visual
purple, which is rapidly bleached on exposure to
sunlight. This colouring matter is absent from
the macula lutea, and absent also over a narrow
zone, 3-4 mm. in width, near the ora serrata.
(Stratum
/pigmenti
Structure of the Retina (Figs. 687, 688,
689). The nervous elements of the retina are sup-
ported by non-nervous or sustentacular fibres, and
are arranged in seven layers, to which must be added
the stratum pigmenti.
The layers from within outwards, i.e. from
vitreous body to chorioid, are :
1. Stratum opticum or layer of nerve-fibres.
2. Ganglionic or nerve-cell layer.
v. 3. Inner molecular or inner plexifc-rm layer.
4. Inner nuclear layer or layer of inner granules.
5. Outer molecular or outer plexiform layer.
6. Outer nuclear layer or layer of outer granules.
7. Layer of rods and cones.
8. Stratum pigmenti.
1. Stratum opticum or layer of nerve-fibres. Most of the fibres of this
stratum are centripetal, and are direct continuations of the axons of the cells in the
Gangli-
onic
layer
Stratum
f opticum
Membrana limitans interna
FIG. 687. DIAGRAMMATIC SECTION OF THE
HUMAN RETINA (modified from Schultze).
816
THE ORGANS OF SENSE.
ganglionic layer ; a few are centrifugal and end in branched clubbed extremities in the
inner molecular or inner nuclear layers of the retina.
FIG. 688. PERPENDICULAR SECTIONS OF MAMMALIAN RETINA (Cajal).
A. Layer of rods and cones ; B, Outer nuclear layer ; C, Outer molecular layer ; D, Inner nuclear layer ; E,
Inner molecular layer ; F, Ganglionic layer ; G, Stratum opticum ; r, rods ; c, cones, r.g, rod granules ;
c.g, cone granules; r.b, rod bipolars ; c.b, cone bipolars ; c.r, contact of rod bipolars with the
spherules of the rod fibres ; c.c, contact of cone bipolars with the branches of the cone fibres ; ar,
internal arborisation of cone bipolars ; ar', internal arborisation of rod bipolars ; c.n, centrifugal nerve
fibre ; h, horizontal cells ; s.s, stratified spongioblasts ; d.s, diffuse spongioblasts ; s.g, stratified
ganglion cell ; M, Sustentacular fibre.
2. Ganglionic or nerve-Cell layer. The cells of this stratum vary in size, are oval
or piriform in shape, and form a single layer, except at the macula lutea, where several
strata are present. Each cell contains a large nucleus, and
gives off, from its inner surface, an axon which is continued as
a fibre of the stratum opticum. From the outer surface of
each cell numerous dendrites arise, which form arborisations in
the inner molecular layer. The cells may be divided into uni-
stratified, multi-stratified, and diffuse, according as their den-
drites ramify in one or in several strata of the inner molecular
layer, or extend throughout neafly its whole thickness.
3. Inner molecular or inner plexiform layer. This
is constituted chiefly by the interlacement of the dendritic
arborisations of the cells of the ganglionic layer with those of
the inner nuclear layer, and has been divided by Ramon y Cajal
into five strata. It sometimes contains horizontal cells (spongio-
blasts), whose branched processes ramify in it.
4. Inner nuclear layer or layer of inner granules.
This is the most complicated of the retinal strata, and consists
of numerous cells which may be divided into three groups, viz. :
(a) bipolar cells, (6) horizontal cells, and (c) spongioblasts, or
amacrine cells.
(a) The bipolar cells, by far the most numerous, are fusi-
form and nucleated, and each gives off an external and an
internal process. The internal processes terminate in flattened
tufts, at different levels, in the inner molecular layer, while the
external produce an abundant ramification in the external zone
of the outer molecular layer. These bipolar cells are divided
into rod bipolars, cone bipolars, and giant bipolars. The rod
bipolars end peripherally in vertical arborisations around the
button-like ends or spherules of the rod fibres, and, centrally,
j n branched extremities which mostly become applied to the
cells of the ganglionic layer. The cone bipolars end peripher-
^\\j m flattened arborisations in the outer molecular layer,
in contact with the ramifications of the foot-plates of the cone
fibres, and, centrally, ramify in some one of the five strata of
the inner molecular layer. The giant bipolars form, peripher-
ally, an extensive horizontally arranged arborisation in the outer molecular layer ; centrally,
they ramify in one or other of the strata of the inner molecular layer.
FIG. 689.
A, A cone and two rods from the
human retina (modified from
port ot^od'lparSed hrto
THE EETINA.
817
(6) The horizontal cells are of two varieties : (1) small, flattened, star-like cells, lying
immediately internal to the outer molecular layer, and sending a tuft of dendrites outwards,
towards the bases of the cone fibres, while their axons are directed horizontally, for a
variable distance ; (2) large, irregular cells, lying internal to the above and ending in
finger-like ramifications in the outer molecular layer. Their axons run horizontally for
some distance, and end, in extensive varicose arborisations, under the spherules of the
rod fibres.
(c) The spongioblasts are situated in the innermost part of the inner nuclear layer ;
their processes ramify in the inner molecular layer, it may be in one stratum (stratified
spongioblasts) or in several strata (diffuse spongioblasts).
5. Outer molecular or outer plexiform layer. This is constituted by the
interlacement of the dendrites of the bipolar and horizontal cells, just described, with
the spherules of the rod fibres and the ramifications of the foot-plates of the cone fibres.
It is divided into two strata : (a) external, indicating the contact of the rod bipolars with
the spherules of the rod fibres ; (b) internal, the line of contact between the cone bipolars
and the branches of the cone fibres.
6. Outer nuclear layer or layer of outer granules. This is made up of clear
granules which somewhat resemble those of the inner nuclear layer, and are divisible into
two kinds : (a) cone granules, (b) rod granules. The cone granules are the larger, and each
contains an oval nucleus ; they lie immediately inside the outer limiting membrane, through
which they are continuous with the cones of the next layer. Each is prolonged internally
as a straight fibre, which, on reaching the outer molecular layer, expands to form a foot-
plate, from which several horizontal fibrils are given off. The rod granules are far more
numerous than the cone granules, and each contains a small oval nucleus, which is
transversely striated. Their outer processes are continuous, through the outer limiting
membrane, with the rods of the next layer, while their inner processes pass into the outer
molecular layer and end in free, unbranched spherules amongst the arborisations of the
rod bipolars.
7. Layer of rods and cones. This consists of two sets of structures, viz., rods
and cones. Except at the macula lutea the rods are far more numerous than the cones,
and assume the form of elongated cylinders, while the cones are shorter than the rods,
and taper externally to fine points. Each rod and cone consists of two segments inner
and outer. The inner segment of the rod only slightly exceeds in diameter its outer
segment, whereas the inner segment of the cone greatly exceeds its outer part. The inner
segments of both rods and cones have an affinity for staining reagents, and consist of a
basal homogeneous portion and an outer longitudinally striated part, the proportion of the
latter to the former being greater in the cones than in the rods. The outer segments
ive not the same affinity for reagents, but tend to break transversely into numerous discs
689, B). The colouring matter, rhodopsin, already referred to, is found only in the
iter segments of the rods, the terminal parts of which extend into the layer of pigmented
)ithelium.
8. Stratum pigmenti. This consists of a single stratum of cells which, on surface
)\v, are hexagonal (Fig. 690), their outer flattened surfaces being firmly attached to
the chorioid. When seen in profile the outer part of each cell contains
a large oval nucleus and is devoid of
pigment, while the inner portion is
filled with pigment and extends as a
series of thread-like processes amongst
the outer segments of the rods and
cones. ' When the eye is kept in the
dark the pigment accumulates near
the outer part of the cell, but when
exposed to light it streams in between
the rods and cones (Fig. 691).
Sustentacular fibres of the
retina. These form a framework for
RETINA (viewed from the support of the nervous structures
(Fig. 688 M). They begin at the FlG 69L _ SECTION THROUGH OUTBR
inner surface of the nerve-fibre layer
in single or forked expanded bases, by the apposition of
which a delicate membrane, the membrana limitans in-
terna, is formed. In the ganglionic layer they give off a few side branches, and, on
passing through the inner nuclear layer, supply ramifications amongst the inner granules
53
LAYERS OF RETINA (semi-diagram-
matic).
818
THE OKGANS OF SENSE.
for their support; in this part of each fibre there is an oval nucleus. In the outer
nuclear layer they break up into a network of fibrils which surround the rod and cone
granules and fibres, and end externally at the bases of the rods and cones in a delicate
membrane, the membrana limitans externa.
Structure of the macula lutea and fovea centralis. The yellow colour
of the macula is due to the presence of pigment in the inner layers of the retina. At the
circumference of the macula the nerve-fibre layer is greatly thinned and the rods are few
in number; the ganglionic layer, on the other hand, is thickened and may contain
from seven to nine strata of cells, while the outer granular layer also is thicker and its
granules have an oblique direction. At the fovea centralis the retina is much thinned,
since here its nerve-fibre and ganglionic layers are absent and its other strata greatly
attenuated. The stratum pigmenti, on the other hand, is thicker and its pigmentation
more pronounced. The cone nuclei are situated some distance internal to the outer
limiting membrane, and thus the thin inner and outer granular layers are in apposition.
There are no rods, and the cones, closely crowded together, are narrower and their outer
segments more elongated than elsewhere, so that the line of their bases, indicated
by. the membrana limitans externa, presents a convexity directed forwards. The fovea
centralis and macula lutea are spoken of by physiologists as the "region of distinct
vision."
Structure of the ora serrata. Here the nervous layers of the retina suddenly
cease ; the layer of rods and cones ends a little behind the margin of the ora serrata ; the
other nervous strata persist as far as its margin. In front of the ora serrata the retina is
prolonged over the ciliary processes in the form of two layers of cells : (a) an inner layer of
columnar epithelium, and (6) an outer, consisting of the stratum pigmenti, the two
forming the pars ciliaris retinae. The same two layers are prolonged over the back of
the iris, where both are pigmented and form the pars iridica retinae.
Vessels of the retina (Fig. 692). The retina is supplied by the arteria centralis retinae,
a branch of the ophthalmic artery, which pierces the sheath of the optic nerve about
2 c.m. behind the bulb of the eye, and makes its appearance in the centre of the optic
papilla. There it divides into an upper and a lower branch, and each of these again bifur-
cates into a medial or nasal, and a lateral or temporal, branch. The resulting four branches
ramify towards the periphery of the retina, and are named the superior and inferior temporal
Superior nasal branch
Optic disc
Inferior nasal branch
Superior .temporal branch
Superior and inferior macular
arteries
Macula lutea
Inferior temporal branch
FIG. 692. BLOOD-VESSELS OF THE RETINA.
and the superior and inferior nasal arteries. The temporal arteries pass laterally above and
below the macula lutea, to which they give small branches ; these do not, however, extend as
far as the fovea centralis, which is devoid of blood-vessels. The macula also receives two small
arteries (superior and inferior macular) directly from the stem of the arteria centralis. The
larger vessels run in the nerve-fibre layer near the membrana limitans interna and form two
capillary networks an inner, in the nerve-fibre layer, and an outer, in the inner nuclear layer.
The inner network arises directly from the arteries and sends numerous small branches to form
the outer network, from which the veins take origin. The vessels do not penetrate deeper than
the inner granular layer, nor do the arteries anastomose, except through the capillary plexuses.
The veins follow the course of the arteries ; they have no muscular coats, but consist merely
of a layer of endothelial cells, outside which is a perivascular lymph sheath, surrounded by
delicate retiform tissue.
REFRACTING MEDIA OF THE EYE.
819
KEFRACTINO MEDIA.
Corpus Vitreum. The vitreous body is a transparent, jelly-like substance
situated between the crystalline lens and the retina, and occupying the posterior
four-fifths of the bulb of the eye (Fig. 677). In front it presents a deep concavity,
the hyaloid fossa (O.T. fossa patellaris), for the reception of the posterior convexity
of the lens. It is enclosed within a thin transparent membrane, the membrana
hyaloidea, which is in contact with the membrana limitans interna of the retina,
and is adherent to it at the entrance of the optic nerve. The portion of the
membrana hyaloidea in front of the ora serrata is thickened and strengthened
by radial fibres, and is termed the zonula ciliaris. Situated behind the ciliary body,
the zonula is radially folded and presents a series of alternating furrows and
elevations. The ciliary processes are received into, and are firmly adherent to, the
furrows, with the result that, if removed, some of their pigment remains attached
to the zonula. The elevations of the zonula are not attached to the interciliary
depressions, but are separated by a series of lymph spaces named the recessus
cameras posteriores ; these may be regarded as diverticula of the posterior chamber
with which they communicate. As the zonula approaches the equator of the
lens it splits into two chief layers, viz. : (a) a thin posterior lamina, which lines
the hyaloid fossa ; and (&) a thicker anterior layer, termed the suspensory ligament
of the lens (Fig. 677), which blends with the front of the lens capsule a short
distance from the equator of the lens. Scattered fibres of this ligament are also
attached to the equator itself and to the regions immediately anterior and posterior
to it. By this suspensory ligament the lens is retained in position, and its con-
vexity varies inversely with the degree of tension of the ligament. The radial
fibres of the ciliary muscle, by pulling forward the
ciliary processes and the attached zonula ciliaris,
relax the ligament, and thus allow the lens to
become more convex. Behind the suspensory
ligament, a sacculated lymph space surrounds the
equator of the lens; it is named the spatia
zonularia (O.T. canal of Petit), and may be easily
inflated on introducing a fine blow-pipe through
the suspensory ligament (Fig. 677). In the foetus
a blood-vessel, termed the arteria hyaloidea, is con-
tinued from the arteria centralis retinae forwards
through the vitreous body, for the supply of the
T , J ' ... . r f, J , ,, FIG. 693. THE SPATIA ZONULARIA DIS-
capsule of the lens. Its position, m the adult, TENDED AND VIEWED FROM THE
is represented by a lymph channel, termed the FRONT (enlarged).
canalis hyaloideus of Stilling (Fig. 677), the
presence of which may be demonstrated by shaking up the vitreous body in a
solution of picrocarmine, when some of the pigment may be seen to extend along
the canal (Anderson Stuart).
When the vitreous body is treated by a
weak solution of chromic acid it presents a
series of concentric, peripherally arranged
strise, together with numerous radial striae
converging towards its centre. Between
these the more fluid part lies, and it frequently
contains vacuolated amoeboid cells scattered
through it. The vitreous body consists of
98*4 per cent of water, having in solution
about 1-4 per cent of sodium chloride and
traces of extractives and albumen.
Lens Crystallina. The crystalline lens
SHOWITSCONCENTRIC LAM1 lies in front of the vitreous body and behind
the iris, and is a biconvex, transparent body
(Fig. 677). It is enclosed in a thin, transparent, homogeneous capsule, the capsule
of the lens. The central points of its anterior and posterior surfaces are termed
KO ~
Substantia
corticalis
Nucleus
lentis
FIG. 694. LENS HARDENED IN FORMALIN AND
820
THE OKGANS OF SENSE.
FIG. 695. DIAGRAMMATIC REPRESENTATION OF THE RADIAL
LINES OF THE F(ETAL LENS.
A, Seen from the front ; B, From behind.
respectively its anterior and posterior poles, a line joining" which is known as its
axis ; its peripheral circumference is named the equator. Its axial measurement
is 4 mm., and its transverse diameter from 9 to 10 mm. Its anterior surface is less
curved than the posterior and on
it rests the pupillary margin of
the iris ; the central part of the
surface corresponds with the aper-
ture of the pupil and is directed
towards the anterior chamber ; the
peripheral part is separated from
the iris by the aqueous humour of
the posterior chamber. Its pos-
terior surface, more convex than
^ anteriorj QCCUpicS the hyaloid
fossa of the vitreous body. The
curvatures of its surfaces, especi-
ally that of the anterior, are constantly varying, during life, for the purpose of
focussing near or distant objects on the retina.
The substantia lentis consists of a soft outer part, the substantia corticalis, easily
crushed between the finger and thumb, and of a dense central part, the nucleus
lentis. The refractive index of the substantia corticalis is
about 14 ; that of the nucleus lentis about 145. Faint radial
lines run from the anterior and posterior poles of the lens
towards its equator. In the foetus they are three in number, and
form angles of 120 with each other (Fig. 696). From the
anterior pole one ray ascends vertically and the other two
diverge downwards, while from the posterior pole one ray
descends vertically and the other two diverge upwards. In
the adult the rays may be increased to six or more. They
represent the free edges of a corresponding number of septa
which dip into the substance of the lens, and along which
the extremities of the different groups of lens fibres come into
contact, and are attached by a clear, amorphous substance.
The lens, when hardened, exhibits a series of concentrically
arranged laminae (Fig. 694), superimposed like the scales of an
onion and attached to each other by a clear, amorphous sub-
stance. Each lamina is split along the radiating lines, and
consists of a series of hexagonal, riband-like fibres, the fibrse
lentis, which are adherent to each other by their margins ;
those of the deeper laminae are small and serrated, but non-
nucleated ; while those of the superficial coats are large and
nucleated, but non-serrated. The fibres extend in a curved
manner from the rays on the anterior surface to the rays on
the posterior surface, but no fibre extends from pole to pole.
Fibres which start at or near one pole end at or near the
equator on the opposite surface, and vice versa, while the inter-
vening fibres take up intermediate positions. Between the
substantia lentis and the anterior part of the capsule there is
a layer of nucleated columnar epithelial cells, the epithelium
lentis. On being traced towards the equator its cells become SECTION THROUGH THE
gradually elongated and transformed into lens fibres, which,
when fully formed, lose all trace of their nuclei, except in Showing the gradual tean
the more superficial laminae. Each lens fibre represents, there- h^lens ^bres Rafter
fore, a greatly elongated columnar cell (Fig. 696). Babuchiu).
In the foetus the lens is soft, of a pinkish colour, and
nearly spherical ; while in old age it becomes somewhat flattened, and assumes a
yellowish tint.
Cameras Oculi (Fig. 677). As already stated (p. 813), the space between the
cornea and the lens is divided by the iris into two unequal parts, viz., the camera
FIG. 696.
THE EYELIDS.
821
oculi anterior, in front, and the camera oculi posterior, behind. These are filled
with the aqueous humour, and, in the adult, communicate freely through the aperture
of the pupil, but in the -foetus are separated from each other by the membrana
pupillaris. The camera oculi anterior or anterior chamber is bounded in front
by the cornea, behind by the iris and lens, whilst peripherally it communicates
with the spatia anguli iridis. The camera oculi posterior or posterior chamber
is triangular on section, and is bounded in front by the iris, behind by the
circumferential part of the lens and its suspensory ligament; the base of the
triangle corresponds with the thick, anterior extremities of the ciliary processes.
It communicates with the recessus camerae posteriores and spatia zonularia. The
aqueous humour has a refractive index of about T336, and consists of about 98
per cent of water, with 14 per cent of sodium chloride, and traces of albumen.
PALPEBE^E.
The eyelids are two movable curtains situated in front of the bulb of the eye,
and named, from their positions, superior and inferior. The superior is the larger
and more movable,
being provided with a
special elevator muscle,
the m. levator palpebrce
superioris. The inter-
val between the eyelids
is termed the palpebral
fissure, and measures
transversely about 30
mm., but varies con-
siderably in different
individuals and in
different races. When
the eye is open the
fissure is elliptical in
shape, but when closed
it assumes the form of
a transverse slit, which
lies on a level with the
lower margin of the
cornea. The two lids
meet at the extremities
of the fissure, and form
the lateral and medial
commissures. Their FIG. 697. EYELID SLIGHTLY EVERTED TO SHOW THE CONJUNCTIVA
free margins are flat- (enlarged),
tened and are sur-
mounted by eyelashes, from the lateral commissure to a point about 5 mm. from
the medial commissure a point indicated by a small papilla, the papilla lacrimalis.
Medial to this papilla the margins are rounded and destitute of eyelashes, and
form the upper and lower boundaries of a triangular space, termed the lacus lacri-
malis, which is occupied by a small pale red body, the caruncula lacrimalis. The
caruncula consists of a small island of modified skin, and contains sudoriferous and
sebaceous glands, and fine hairs. Posteriorly the lids are lined with mucous
membrane, the conjunctiva, and are in contact with the bulb of the eye, except
near the medial commissure, where, between the bulb of the eye and the caruncula
lacrimalis, there intervenes a vertical fold of conjunctiva, the plica semilunaris con-
junctivse, which in many animals contains a plate of cartilage.
In each eyelid there exists a framework of condensed fibrous tissue, which gives
consistence and shape to the lid, and is termed the tarsus. In front of the tarsus
are the fibres of the orbicularis oculi muscle and the integument, while embedded
in its posterior surface, and covered by the conjunctiva, are numerous modified
53 &
Margin of the upper eye-
,/lid with openings of
ducts of tarsal glands
Papilla lacrimalis with
punctum lacrimale on
the summit
Plica semilunaris
Caruncula lacrimalis
Papilla lacrimalis
Opening of tarsal gland
Tarsal glands
shining through the
conjunctiva
822
THE OKGANS OF SENSE.
sebaceous glands, named the tarsal glands. The superior tarsus is larger than
the inferior, and of a half oval shape, with its greatest vertical diameter measuring
about 10 or 11 mm. Its upper margin is thin and convex, and is continuous with
the tendon of the levator palpebrse superioris muscle, while its lower edge is thick
and straight. The inferior tarsus is a thin, narrow strip, with a nearly uniform
vertical diameter of about 5 mm. The extremities of the two plates are con-
tinuous with the lateral palpebral raphe and the medial palpebral ligament. The
lateral palpebral raphe is a narrow band attached to the zygomatic bone ; it divides,
at the lateral commissure, into superior and inferior pieces which are fixed to the
margins of the respective tarsi. The medial palpebral ligament is a strong band
attached to the frontal process of the maxilla, directly in front of the lacrimal
Tendon of levator palpebrse
superioris
Conjunctiva
Tarsal gland in tarsus
Muscle of Riolan
Skin
Orbicularis oculi
Eyelashes
FIG. 698. SAGITTAL SECTION THROUGH SUPERIOR EYELID.
groove ; it divides at the medial commissure into two slips, one for each tarsus
(Fig. 699).
The eyelids are further strengthened by membranous expansions, termed the
superior and inferior palpebral ligaments, which extend into them from the margin
of the orbit. The superior palpebral ligament is continuous, along the superior
margin of the orbit, with the pericranium and with the periosteal lining of the orbit,
and it blends, below, with the tendon of the levator palpebrse superioris. The inferior
palpebral ligament is prolonged from the lower edge of the inferior tarsus to the
inferior margin of the orbit, where it is continuous with the periosteum of the face
and orbital floor. Laterally the two palpebral ligaments fuse to form the lateral
palpebral raphe, while medially they become thinned, and, separating from the
medial palpebral ligament, are attached to the lacrimal bone, behind the lacrimal
sac. The superior and inferior palpebral ligaments form the septum orbitale, between
the superficial and deep structures of the eyelids ; this septum is perforated by the
vessels and nerves, which extend from the orbital cavity to the face or scalp.
THE CONJUNCTIVA.
823
The skin covering the eyelids is thin and delicate, and is continuous, at their
margins, with their conjunctival lining. It contains numerous small sudoriferous
glands and fine hairs, the' latter being provided with sebaceous follicles. Branched
pigment cells are
present in the _^jjjjjjg^. f
cutis, and
ment exists
Pig-
also
Superior palpebral
ligament
lacrimal nerve
Superior tarsus
Raphe palpebralis
lateralis
Inferior palpebral
ligament
Supra-orbital nerve
Supra-trochlear nerve
Superciliary arch
Infra-trochlear nerve
Lacrimal sac
Ligamentum palpe-
brale mediale
Inferior tarsus
FlG.
Infra-orbital nerv
.DISSECTION OF THE .RIGHT EYELID. The orbicularis oculi has been
completely removed.
Tendon of levator
in the deep layers palpebrse superior!*
of the epidermis.
The subcutaneous
tissue iS loose and M pebl branch of
devoid of fat, and
in it are found
the fibres of the
orbicularis oculi
muscle a small
separate bundle
of which, termed
the muscle of
Riolan, occupies
the margin of the
lids behind the
eyelashes.
The glandulae
tarsales(O.T.Mei-
bomian glands) are
elongated sebaceous glands with numerous lateral offshoots ; they are embedded
in the tarsi and are filled with cubical epithelium. There are from twenty-five to
thirty in the superior eyelid, and from twenty to twenty-five in the inferior ; they
open by small ducts, about 1 mm. in length, along the lid margins, behind the
eyelashes ; the ducts are lined with stratified epithelium, placed on a basement
membrane. Between the eyelashes and the muscle of Eiolan are two or three
rows of modified sudoriferous glands, termed the glands of Moll.
H. Miiller described a layer of non -striped muscle in each lid : in the superior extending from
the tendon of the levator palpebrse superioris to the upper tarsus, and in the inferior connecting
the inferior tarsus with the inferior oblique muscle.
The eyelashes are curved, silky hairs which project from the free margins of
the lids ; in the upper lid they are longer and more numerous than in the lower,
and are curved upwards, while those of the lower lid are bent downwards.
Conjunctiva. The conjunctiva is the mucous membrane which lines the
eyelids, and is continued, from them, on to the front of the bulb of the eye.
The part on the eyelids is termed the tunica conjunctiva palpebrarum, that on the
bulb of the eye the tunica conjunctiva bulbi ; the lines of reflection of fhe membrane
from the eyelids to the bulb are known as the superior and inferior conjunctival
fornices. The conjunctiva palpebrarum is intimately adherent to the tarsi and
presents numerous papillae. It is covered with a layer of columnar epithelial cells,
beneath the bases of which are small flattened cells ; near the fornices a number
of acino-tubular glands, much more plentiful in the upper than in the lower eyelid,
open on its free surface. The conjunctiva bulbi is thinner than the conjunctiva
palpebrarum, and is loosely attached to the sclera by submucous tissue. The
plica semilunaris conjunctive has already been referred to (p. 821). On the cornea
the conjunctiva is represented merely by the epithelium corneae (p. 809).
Vessels and Nerves. The chief arteries of the eyelids are the superior and inferior palpe-
bral branches of the ophthalmic, which pierce the septum orbitale above and below the medial
palpebral ligament, and run laterally in the corresponding lid near its free margin. On reaching
the region of the lateral palpebral commissure they anastomose with each other and with twigs
from the lacrimal, superficial temporal, and transverse facial arteries, and in this way an arch
is formed in each lid. Secondary smaller arches are found, one above the primary arch in the
upper lid, and another below that of the lower lid, while the upper lid receives branches also
53 c
824
THE OKGANS OF SENSE.
from the supra-orbital and frontal arteries. The veins are arranged in two sets : (a) subcon-
junctival or retrotarsal, opening into the muscular tributaries of the ophthalmic veins, and (6)
pretarsal, into the angular and superficial temporal veins. The lymph vessels, like the veins,
form pre- and retrotarsal networks, which communicate with each other through the tarsal
plates. The lymph is drained chiefly into the anterior auricular and parotid lymph glands, but
partly, by vessels which accompany the anterior facial vein, into the submaxillary lymph glands.
The sensory nerves of the eyelids are supplied by the trigeminal nerve the upper lid chiefly
by the supra-orbital and supra-trochlear branches of the ophthalmic ; the lower, by the infra-
orbital branch of the maxillary. The region of the lateral commissure receives some filaments
from the lacrimal nerve, that of the medial from the infra-trochlear. These sensory nerves
form a marginal plexus behind the orbicularis oculi muscle. The levator palpebrae superioris
muscle is supplied by the oculomotor nerve and the non-striped fibres of the eyelids by the
sympathetic.
APPAEATUS LACEIMALIS.
The lacrimal apparatus consists of : (1) the lacrimal gland, which secretes the
tears ; (2) the lacrimal ducts, by which the tears are drained from the front of the
eye ; and (3) the lacrimal sac and naso-lacrimal duct, which convey them into the
nasal cavity.
Lucriinal gland
(superior part)
Temporal muscle -
Temporal fascia
Excretory ducts
of lacrimal gland
Lacrimal gland,
(inferior part)
Infra-orbital
nerve
Maxillary sinus -
Buccinator
Superior fornix
of conjunctiva
Puncta
lacrimalia
Lacrimal ducts
Lacrimal sac
Medial palpebral
ligament
Naso-lacrimal
duct
Middle concha
Muco-
periosteum
Plica lacrimalis
Inferior meatus
Inferior concha
FIG. 700. DISSECTION TO SHOW THE LACRIMAL APPARATUS.
Glandula Lacrimalis. The lacrimal gland is a flattened, oval body situated
in the superior and lateral part of the orbital cavity ; it consists of two portions
superior and inferior imperfectly separated from each other by the expansion of
the tendon of the levator palpebrse superioris muscle. The glandula lacrimalis
superior is firm and much larger than the inferior ; it measures transversely about
20 mm., and sagittally from 12 to 14 mm. It occupies the fossa lacrimalis on the
medial surface of the zygomatic process of the frontal bone, and is fixed by fibrous
bands to its periosteum, while its inferior surface is in contact with the levator
palpebrae superioris and rectus lateralis muscles, which intervene between it and
the bulb of the eye. The glandula lacrimalis inferior consists of small, loosely
aggregated lobules ; it lies below and in front of the orbital portion, and projects
into the posterior part of the upper eyelid, where its deep surface is in contact
with the conjunctiva. The ducts draining the glandula superior are from three
to five in number ; they pass between the lobules of the glandula inferior, and
open at the upper and lateral part of the fornix conjunctivas superior. The ducts
of the glandula inferior number from three to nine ; some of them join those
from the glandula superior, while others open separately at the fornix conjunctive
superior. The lacrimal gland has a structure resembling that of the parotid, and
DEVELOPMENT OF THE EYE. 825
is supplied by the sympathetic and lacrinial nerves and by the lacrimal artery,
while its veins are drained into the ophthalmic vein.
Ductus Lacrimales. The lacrimal ducts, two in number, commence in minute
orifices, termed the puncta lacrimalia, at the apices of the papillae lacrimales
(p. 821), and are directed medial wards, along the medial parts of the margins of the
eyelids, above and below the lacus lacrimalis. The superior duct at first ascends
for a short distance and then inclines downwards ; the inferior duct descends for
a short distance and then runs horizontally; at the angle where it changes its
direction each duct is dilated into an ampulla. The two ducts open close together
into the lateral and front part of the lacrimal sac, a little below its middle ; some-
times they open separately into a pouch-like dilatation of the sac, termed the sinus
of Maier. The ducts are lined with stratified epithelium placed on a tunica propria,
outside which is a layer of striped muscular fibres derived from the lacrimal part
of the orbicularis oculi. These muscular fibres are arranged somewhat spirally
around the ducts, but at the base of each papilla lacrimalis they are circular
in direction and form a species of sphincter. On contraction they serve to
empty the contents of the lacrimal ducts into the lacrimal sac. '
The saccus lacrimalis and ductus nasolacrimalis together form the passage by
which the tears are conveyed from the lacrimal ducts to the nasal cavity.
The lacrimal sac is the upper expanded part of the passage, and measures from
12 to 15 mm. in length, about 7 mm. antero-posteriorly, and from 4 to 5 mm. trans-
versely. It lies in the groove formed by the lacrimal bone and frontal process
of the maxilla, and ends above in a rounded, blind extremity or fundus, while
it narrows below into the naso-lacrimal duct. At the junction with the duct a
fold of mucous membrane, named the valve of Beraud, together with a laterally
directed pouch, the sinus of Arlt, are sometimes present. Near its superior ex-
tremity it is crossed, in front, by the medial palpebral ligament (O.T. tendo oculi),
from the upper and lower edges of which the orbicularis oculi takes origin ; the
lacrimal part of the orbicularis oculi muscle is behind it.
The naso-lacrimal duct averages about 18 mm. in length, and has a diameter of
from 3 to 4 mm. Eather narrower in the middle than at its extremities, it is directed
downwards and slightly backwards, and opens into the inferior meatus of the nose
at the junction of its anterior fourth with its posterior three-fourths, i.e. a distance
of 30 to 35 mm. from the posterior boundary of the nostril. Its lower orifice is
somewhat variable in form and position, and is occasionally duplicated. It is
frequently guarded by a fold of mucous membrane, termed the plica lacrimalis
(Hasneri). Through this orifice the mucous lining of the duct is continuous with
that of the nasal cavity. The mucous membrane of the duct is thrown into
inconstant folds, several of which have been described as valves. Its epithelium
is columnar and in part ciliated ; opening into the lower part of the duct are
numerous glands, similar to those in the nasal mucous membrane.
The nerves of the lacrimal ducts and sac are derived from the infra-trochlear branch of the
naso-ciliary ; their arteries from the inferior palpebral and nasal. The veins of the naso-lacrimal
duct are large and numerous, forming a sort of erectile tissue similar to that in the nasal cavity.
DEVELOPMENT OF THE EYE.
The retina and optic nerve are developed from a hollow outgrowth of the fore-brain, termed
the optic vesicle (see pp. 54 and 33). This extends towards the side of the head, and its
connexion with the brain is gradually elongated to form the optic stalk. The ectoderm
overlying the optic vesicle becomes thickened, invaginated, and finally cut off as a hollow
island of cells, which is named the lens vesicle. This vesicle indents the outer and lower
part of the optic vesicle, converting it into a cup (optic cup), lined by two layers of cells
continuous with each other at the margin of the cup. The inner of these strata, thicker
than the outer, is named the retinal layer, and becomes differentiated into the nervous
and supporting elements of the retina ; while the outer, named the pigmentary layer,
forms the stratum pigmenti. The edge of the optic cup extends in front of the equator
of the lens, and bounds the future aperture of the pupil. In front of the lens, and also
opposite its equator, the retinal layer is thin, and represented only by a stratum of
columnar cells which becomes closely applied to the pigmentary layer, the two forming the
826
THE OEGANS OF SENSE.
pars ciliaris and pars iridica retinae. The indentation of the optic cup extends as a groove
for some distance along the postero-inferior aspect of the optic stalk, forming what is termed
the chorioidal fissure (Fig. 701). Through this fissure mesoderm passes inwards between
the lens and the retina to form a part of the vitreous body, while the arteria centralis retinse
also becomes enclosed in it and so gains its future position in the centre of the optic
Lens rudiment
Optic cup
Optic stalk '
Cavity of
fore-brain
Outer layer of optic cup
Inner layer of optic cup
Lens
Optic
vesicle
becoming
cupped
| Optic stalk
I Chorioidal fissure
Lens
Arteria
centralis
fissure
Lens
FIG. 702. OPTIC CUP AND LENS VIEWED
FIG. 701. SECTIONS THROUGH PORTIONS OF THE HEADS OF FCETAL RABBITS, to illustrate the connexion
of the optic cup with the fore-brain, and the invagination of the ectoderm to form the lens.
nerve. The arteria centralis is prolonged forwards from the porus options through
the vitreous body, as a cone of branches, as far as the back of the lens. By the fifth
or sixth month all these branches have disappeared except one, the arteria hyaloidea,
which persists until the last month of foetal life, when it also atrophies, leaving only the
canalis hyaloideus to indicate its position.
The vitreous body is developed between the optic cup and the lens, and is derived
partly from ectoderm and partly from mesoderm. It consists primarily of a series of
fine protoplasmic fibres which project from the cells
of the retinal layer* of the cup and form a delicate
Optic stalk reticular tissue. At first these fibres are seen in relation
to the whole of the optic cup, but later they are limited
to the ciliary region, where by a process of condensation
.Chorioidal they appear to form the zonula ciliaris. When the
mesoderm reaches the cup through the chorioidal fissure
it unites with this reticular tissue to form the vitreous
body.
The lens, at first in contact with the ectoderm
FROM BEHIND AND BELOW, to show from which it ig derived, is soon separated from it by
"rTo? th cenSsTe" mesoderm, and then consists of a rounded vesicle with
tinse (from model by Ziegler). epithelial walls. The anterior wall remains as a single
layer of cells the anterior lens epithelium of the
adult ; the cells of the posterior wall become elongated into lens fibres, and by the
forward growth of these the cavity of the vesicle is obliterated. This elongation into
lens fibres is greatest at the centre of the lens, while near 'the equator the fibres are
shorter, and here the gradual transition between the anterior epithelium and the lens
fibres is seen (Fig. 696). The lens becomes enveloped in a vascular tunic, which receives
its vessels from the arteria centralis retinse and from the vessels of the iris. The front
part of this tunic forms the membrana pupillaris, and this, like the rest of the tunic,
disappears before birth.
The hollow optic stalk becomes solid by the thickening of its walls and, acquiring
nerve-fibres, is transformed into the optic nerve. These nerve-fibres are mostly centripetal,
and are derived from the nerve-cells of the retina ; but a few are centrifugal and have
their origin in the brain. The further development of the retina resembles, in certain
respects, that of the spinal medulla.
Cameron states (Jeurn. Anat. and PhysioL, vol. xxxix.) that in the early stages of the
development of the inner or retinal layer of the optic cup all the structures, described by His as
being present in the spinal medulla of the human embryo, are to be found, viz., (a) spongioblasts,
(6) germinal cells, and (c) neuroblasts.
THE EXTEKNAL EAE. 827
The spongioblasts undergo ramification and form a network or myelospongium, and also give
rise to the inner and outer limiting membranes ; the latter is next the original cavity of the optic
vesicle, and therefore corresponds to the inner limiting membrane of the spinal medulla. The
spongioblasts also form the groundwork of the inner and outer molecular layers into which the
processes of the neuroblasts grow and arborise.
The germinal cells are always situated beneath the external limiting membrane, and by their
division give rise to the neuroblasts. The first-formed neuroblasts are larger than those of
succeeding generations, and are found in the site of the future ganglionic layer. The germinal
cells in the middle of the convexity of the retinal cup cease to divide at an early stage of
development, and become directly transformed into the rod and cone cells from which the rods
and cones develop as processes ; hence these structures appear first over the middle of the
convexity of the retina, and gradually extend towards the margin of the retinal cup.
The molecular layers make their appearance as plexuses of myelospongium. The internal
molecular layer is first developed at the centre of the retinal cup, and gradually extends towards
the cup margin, and into it the processes from the nuclei on either side grow and ramify. The
rod and cone fibres, and the outer processes of the internal nuclear layer, grow into and arborise
within the external molecular layer.
The condensed mesoderm surrounding the optic cup becomes the sclera and chorioid.
In the portion of the mesoderm which lies in front of the lens a cleft-like fissure appears,
and divides it into a thick anterior and a thin posterior layer. The former becomes the
substantia propria of the cornea ; the latter, the stroma of the iris and anterior part of the
vascular tunic of the lens. The fissure represents the future camera oculi anterior,
and its lining cells form the endothelium of this chamber.
The eyelids arise as two integumentary folds above and below the cornea, each being
covered on both its surfaces by the ectoderm. By the third month the folds meet and
unite with each other at their edges, the eyelids being only permanently opened shortly
before birth; in many animals they are not opened until after birth. The ectoderm
forms the epithelium of the conjunctiva and the epithelium corneee. It is also invaginated
at the lid margins to form the hair follicles and the lining cells of the tarsal glands and
glands of Moll, and, at the fornix conjunctivae superior, to form the lining of the alveoli
and ducts of the lacrimal gland.
The naso-lacrimal duct, lacrimal sac, and ducts represent the remains of the furrow
between the maxillary and lateral nasal processes (p. 49). It is at first filled with a
solid rod of cells, which becomes hollowed out to form the sac and ducts.
ORGANON AUDITUS.
The ear or auditory organ (Fig. 703) consists of three portions external,
middle, and internal the last constituting its essential part, since the peripheral
terminations of the acoustic nerve are distributed within it.
EXTEKNAL EAE.
The external ear l includes (a) the auricula, attached to and projecting from
the side of the head ; and (6) the external acoustic meatus leading inwards from
the most depressed part of the auricula to the tympanic membrane.
AURICULA.
The auricle (O.T. pinna) (Fig. 704) presents two surfaces, lateral and medial,
the latter forming an angle (cephalo-auricular angle) of about 30 with the side of
the head. The lateral surface is irregularly concave, but presents several well-
marked elevations and depressions. The deepest of the depressions is situated near
its middle, and is named the concha auriculae. It is divided by an almost transverse
ridge, the cms helicis, into an upper, smaller, and a lower, larger portion : the
former is termed the cymba conchse ; the latter, which leads into the meatus,
the cavum conchas. Anteriorly, the crus helicis is continuous with the margin of
the auricula or helix, which is incurved in the greater part of its extent, and is
directed at first upwards, and then backwards and downwards, to become gradually
1 Although it is usual to speak of the external, middle, aud internal ear, it would be more correct to use
the terms external, middle, and internal portions of the ear.
828
THE ORGANS OF SENSE.
lost in the upper part of the lobule. Near the point where the helix begins
to descend a small tubercle, the tuberculum auriculae (Darwini), is often seen.
Tympanic cavity, with chain of ossicles In fr0nt f the de ~
scending part of the
helix is a second ele-
Auditory tube
Membrana tympani
Recessus epityrapanicus
External acoustic meatu^
Single below, it
divides superiorly
into two limbs,
termed the crura
antihelicis, between
which is a triangular
Auricula depression, the fossa
triangularis. The
elongated furrow be-
tween the helix and
antihelix is named
the scapha. The con-
cavity of the concha
is overlapped in front
by a tongue-like pro-
cess, the tragus, and
below and behind by a
FIG. 703. DIAGRAMMATIC VIEW OF THE ORGAN OF HEARING. triangular projection,
the antitragus ; the
notch, directed downwards and forwards between these two processes, is named
the incisura intertragica. The tragus consists really of two tubercles, the upper of
which constitutes the tuberculum supratragicum of His, and is separated from the
helix by a groove, the sulcus auris anterior. The lobule is situated below the
incisura intertragica, and is the
most dependent part of the
auricle.
The medial or cranial surface
also is irregular, and presents cms antihelicis superior-
elevations corresponding to the
depressions on its lateral surface,
e.g. eminentia conchas, eminentia
triangularis, etc.
Fossa triangularis
Crus antihelicis inferior
Cymba conchae
Crus helici
Incisura intertragica
Tragus
Antitragus
Lobule
FIG. 704. VIEW OF LATERAL SURFACE OF LEFT AURICULA
(half natural size).
The auricula is usually smaller and
more finely modelled in the female than
in the male, but presents great varia-
tions in size and shape in different indi-
viduals. In the newly born child its
length is about one -third of that of the
adult, while it increases slightly in
length and breadth in old age.
The relation of the width to the
height is termed the auricular index, and is expressed as follows :
width of auricula x 100
; TT- ^ : i = Auricular index.
length of auricula
This index is less in white than in dark races.
The cephalo-auricular angle may be practically absent, as in those cases where the skin of the
head passes directly on to the lateral surface of the auricula, or it may be increased to nearly a
right angle, so that the lateral surface of the auricula looks directly forwards. The tuberculum
auriculae, the significance of which was recognised by Darwin, is a somewhat triangular
prominence which projects forwards in cases where the helix is well rolled over, but backwards and
upwards when the incurving of the helix has been arrested. More frequently present in men
than in women, it is of developmental interest since it has been shown to be well marked at the
sixth month of foetal life, the entire auricula, at this stage, resembling in appearance that of the
adult macaque monkey.
The lobule may be small and sessile or considerably elongated ; it may adhere to the skin of
the cheek (i.e. webbed), or may tend to bifurcate at its lower extremity.
THE AUKICULA.
829
M. helicis major
Spina helicis
M. helicis minor
M. tragicus
Fissure of
Santorini
Isthmus cartila-
ginis auris
Incisura terminalis
auris
M. antitragicus
Fissura antitragohelicina
Cauda helicis
FIG. 705. LATERAL SURFACE OP CARTILAGE OF THE
AURICULA (one-half natural size).
Structure of the Auricula. The greater part of the auricula consists of a
lamella of yellow fibro-cartilage, the cartilage auriculae ; the cartilage is, however,
absent from the lobule, which is composed of fat and connective tissue. When
laid bare, the cartilage (Figs. 705,
706) presents, in an exaggerated
condition, all the inequalities of the
auricula, and is prolonged medially
to form a considerable portion of the
external acoustic meatus. The car-
tilage of the helix projects anteriorly
as a conical eminence, the spina
helicis, and its inferior extremity
extends downwards as a tail -like
process, the cauda helicis, which is
separated from the lower part of the
antitragus by the fissura antitrago-
helicina. The cartilage of the
auricula is continuous with that of
the meatus by a narrow isthmus, the
isthmus cartilaginis auris, measuring from 8 to 9 mm. in breadth. This isthmus corre-
sponds laterally with the deepest part of the incisura intertragica, and medially it
forms the outer boundary of a deep fissure, the incisura terminalis auris, which
separates the cartilage of the meatus from that of the concha. The upper edge of
the tragus fits into an angle below the crus helicis. Two fissures, in addition
to those already described, are usually present, one in the tragus and another
immediately behind the spina helicis.
On the cranial surface of the cartilage (Fig. 706) the eminences produced by
the concha and fossa triangularis are separated by a transverse furrow, the sulcus
antihelicis transversus, corresponding
with the crus antihelicis inferior;
further, the eminentia conchse is
crossed horizontally by a groove, the
sulcus cruris helicis, and almost vertic-
ally by a slight ridge, the ponticulus :
the latter indicates the attachment of
the m. auricularis posterior.
Ligaments of the Auricula. The
cartilage of the auricle is attached
termmalis o _
to the temporal bone by two fibrous
\cartiiageof bands which form its extrinsic liga-
ments, viz. : an anterior, stretching
FIG. 706. MEDIAL SURFACE OF THE CARTILAGE OF from the zygomatic process to the spina
THE AURICULA (one-half natural size). helicis and tragus ; and a posterior,
passing from the eminentia conchae
and upper wall of the meatus to the mastoid portion of the temporal bone. Small
ligamentous bands pass between individual parts of the auricle, and form what are
termed its intrinsic ligaments.
Muscles of the Auricula (Figs. 705, 706). The muscles of the auricle are
divided into two groups, extrinsic and intrinsic. The extrinsic muscles pass to the
auricula from the skull or the scalp, and are described in the section on Myology.
The intrinsic muscles, on the other hand, are confined to the auricula and are six
in number, four on its lateral and two on its cranial or medial surface.
(a) On the lateral surface (Fig. 705)
1. M. helicis major passes upwards from the spina helicis along the ascending
part of the helix. 2. M. helicis minor covers the crus helicis. 3. M. tragicus,
quadrangular in shape, consists of fibres running vertically over the greater
part of the tragus. Some of its fibres are prolonged upwards to the spina helicis
and constitute the m. pyramidalis. 4. M. antitragicus covers the antitragus and
runs obliquely upwards and backwards as far as the antihelix and cauda helicis.
M. transversus
Ponticulus
830 THE ORGANS OF SENSE.
(&) On the medial surface (Fig. 706)
1. M. transversus auriculae consists of scattered fibres, which stretch from the
eminentia conchae to the convexity of the helix. 2. M. obliquus auriculae (Tod)
comprises a few fasciculi, which run obliquely or vertically across the furrow corre-
sponding with the crus antihelicis inferior. A small muscle, the m. stylo-auricu-
laris, sometimes extends from the root of the styloid process to the cartilage of
the meatus.
Skin of the Auricula. The skin covering the auricle is thin and smooth,
and is prolonged, in the form of a tube, as a lining to the external acoustic
meatus. On the lateral surface of the auricula, it adheres firmly to the subjacent
perichondrium. Strong hairs are present on the tragus and antitragus, and also
in the incisura intertragica, forming the barbula hirci, which guard the entrance to
the concha ; soft downy hairs are found over the greater part of the auricula and
point towards the tuberculum auriculae. Sebaceous glands, present on both
surfaces of the auricle, are most numerous in the concha and fossa triangularis.
Sudoriferous glands are found on the medial surface ; few or none on the lateral
surface.
Vessels of the Auricula. The arteries of the auricle are derived (a) from tlie superficial
temporal, which sends two or three branches to the lateral surface ; and (6) from the posterior
auricular, which gives three or four branches to the medial surface. From the posterior auricular
artery two sets of twigs are prolonged to the lateral surface, one turning round the free margin
of the helix, and the other passing through small fissures in the cartilage. The veins from the
lateral surface open into the superficial temporal vein ; those from the medial surface chiefly join
the posterior auricular vein, but some communicate with the mastoid emissary vein. The
lymph vessels take three directions, viz. : (a) forwards to the parotid lymph glands, and
especially to the anterior auricular gland in front of the tragus ; (6) downwards to the lymph
glands which accompany the external jugular vein, and to the lymph glands under the sterno-
cleidomastoideus ; and (c) backwards to the posterior auricular lymph glands.
Nerves of the Auricula. The muscles of the auricle are supplied by the facial nerve.
The skin receives its sensory nerves from (a) the great auricular, which supplies nearly the
whole of the medial surface, and sends filaments in company with the branches of the posterior
auricular artery to the lateral surface ; (b) the auriculo-temporal, which supplies the tragus and
ascending part of the helix ; (c) the lesser occipital, which sends a branch to the upper part of the
medial surface.
MEATUS ACUSTICUS EXTERNUS.
The external acoustic meatus (Figs. 707, 708) is the passage leading from
the concha to the membrana tympani. Its average length, measured from
the bottom of the concha, is about 24 mm., but, if measured from the level
of the tragus, about 35 mm. On account of the obliquity of the membrana
tympani the anterior and inferior walls of the meatus are longer than the posterior
and superior. The meatus consists of two parts, viz. : (a) an external portion,
the pars cartilaginea, about 8 mm. in length ; and (6) an internal portion, the pars
ossea, about 16 mm. in length. The entire meatus forms a somewhat S -shaped
bend (Fig. 708), and may be divided into three portions external, intermediate,
and internal ; each is directed medialwards, but, in addition, the external part is
inclined forwards and slightly upwards; the intermediate, backwards; and the
internal, the longest, forwards and slightly downwards. On transverse section the
canal is seen to be elliptical, its greatest diameter having an inclination downwards
and backwards. Widest at its lateral extremity, it becomes somewhat narrower
at the medial end of the pars cartilaginea; once more expanding in the lateral
portion of the pars ossea, it is again constricted near the medial end of the
latter, where its narrowest part, or isthmus, is found at a distance of about 19 mm.
from the bottom of the concha. The medial extremity of the meatus is nearly
circular and is closed by the membrana tympani.
Bezold gives the diameters of the meatus as follows :
Greatest. Least.
At the commencement of the pars cartilaginea . . 9 '08 mm. 6 '54 mm.
At the end 7 '79 mm. 5-99 mm.
At the commencement of the pars ossea . . . 8'67 mm. 6'07 mm.
At the end 8-13 mm. 4-60 mm.
EXTEENAL ACOUSTIC MEATUS.
831
The lumen of the pars cartilaginea is influenced by the movements of the
mandible, being increased when that bone is depressed. This can be easily verified
by inserting a
finger into
nieatus, and
Pars ossea of external acoustic meatus
Recessus
epitympanicus
Malleus
Cochlea
Cavum tympani
Membrana
tympani
Internal carotid
artery
Crus antihelicis inferior
Cymba conchse
Cms helicis
Pars cartilaginea of
external acoustic meatus
Cavum conchse
Lower boundary of
incisura intertragica
FIG. 707. FRONTAL SECTION OF RIGHT EAR ; ANTERIOR HALF OF SECTION,
viewed from behind (natural size).
Umbo
the
then
alternately opening
and shutting the
mouth.
The condyle of
the mandible lies
in front of the pars
ossea, while between
the condyle and the
pars cartilaginea
a portion of the
parotid gland is
sometimes present.
Behind the pars
ossea, and separated
from it by a thin
plate of bone, are the
mastoid air-cells.
Structure of the Meatus. The cartilage of the meatus, directly continuous
with that of the auricula, is folded on itself to form a groove, opening upwards
and backwards, the margins of which are connected by fibrous tissue. The medial
end of the cartilaginous tube is firmly fixed to the lateral margin of the bony
meatus, whilst its lateral extremity is continuous with the cartilage of the tragus
(p. 829). Two fissures
exist in the anterior
portion of the pars
cartilaginea, and are
filled by fibrous tissue.
.Membrana tympani In the lateral part of
11 of the meatus the cartil-
age forms about three-
fourths of the circum-
ference of the tube ;
but, near the medial
end of the pars cartil-
aginea the cartilage
forms merely a part
of the anterior and
lower boundaries of
the canal.
IG. 708. HORIZONTAL SECTION THROUGH RIGHT EAR; UPPER HALF OF
SECTION, seen from below (natural size). The pars ossea of the
meatus is described on p.
127 ; but it may be well to state here that in the new-born child it is represented only by an
incomplete ring of bone, the annulus tympanicus, together with a small portion of the squama
temporalis, which articulates with, and bridges over the interval between, the extremities of the
ring superiorly. In the concavity of the annulus is a groove, the sulcus tympanicus, in which the
circumference' of the membrana tympani is fixed. On the medial surface of the anterior part of
the annulus, a little below its free extremity, a groove, the sulcus malleolaris, is directed down-
wards and forwards. It transmits the anterior process and the anterior ligament of the malleus,
the tympanic artery, and the chorda tympani nerve. It is limited above by a ridge, the
crista spinarum (Henle), which ends in front and behind in a spinous process (spina tympanica
major and minor). Below the sulcus malleolaris there is a second, less prominent ridge,
the crista tympanica (Gruber), which subsequently unites with a process of the tegmen tympani,
so shuts off the canalis musculotubarius from the petrotympanic fissure. A fibrous
tympanic plate (Symington) intervenes between the annulus tympanicus and the cartilage
of the meatus, and into this plate the bony ring extends. The bony outgrowth does not,
however, proceed uniformly from the whole of circumference of the annulus, but occurs most
rapidly in its anterior and posterior parts. These outgrowths fuse about the end of the second
Dndylo of
mandible
Dtid gland
Tragus
)ncha
tihelix
Helix
um tympani
Mastoid air-cells
Transverse sinus
832 THE ORGANS OF SENSE.
year of life, so as to surround a foramen (foramen of Huschke) in the floor of the meatus ; this
foramen is usually closed by the fifth year, but persists until adult life in some 19 per cent
of skulls (Biirkner).
The lumen of the meatus in the new-born child is extremely small : its outer part is funnel-
shaped ; its inner a mere slit, bounded below by the fibrous tympanic plate and above by the
obliquely placed membrana tympani.
The skin which envelops the auricula lines the entire meatus, and covers also
the outer surface of the membrana tympani. It is thick in the pars cartilaginea,
and contains fine hairs and sebaceous glands, the latter extending for some
distance along the postero-superior wall of the pars ossea. The sudoriferous
glands are enlarged and of a brownish colour; they constitute the glandulse
cemminosae and secrete the ear wax or cerumen.
Vascular and Nervous Supply of the Meatus. The external acoustic meatus receives its
blood-supply from the posterior auricular and superficial temporal arteries, and also from the
deep auricular branch of the internal maxillary artery, the last distributing some minute twigs
to the membrana tympani. The veins open into the external jugular and internal maxillary
veins, and also into the pterygoid plexus, while the lymph vessels have a similar mode of
termination to those of the auricle. Sensory nerves are supplied to the meatus by the
auriculo -temporal branch of the trigeminal and by the auricular branch of the vagus.
CAVUM TYMPANI OB MIDDLE EAR.
The tympanic cavity is a small air chamber in the temporal bone, between
the membrana tympani and the lateral wall of the internal ear or labyrinth (Figs.
707, 708). Lined with mucous membrane, it contains a chain of ossicles, malleus,
incus, and stapes, which reaches from its lateral to its medial wall, and transmits
the vibrations of the membrana tympani across the cavity to the internal ear.
Attached to the ossicles are several ligaments and two small muscles.
The tympanic cavity consists of two portions : (1) The tympanum proper, or
atrium, lying medial to the membrana tympani ; and (2) the recessus epitympanicus,
or attic, lying above the level of the membrane and containing the greater part
of the incus and the upper half of the malleus. Including this recess, the
vertical and antero-posterior diameters of the tympanic cavity each measure
about 15 mm. The distance between its lateral and medial walls is about 6
mm. above and 4 mm. below, while at its central part, owing to the bulging
of the two walls towards the cavity, it measures only from 1-5 to 2 mm.
The tympanic cavity is enclosed by six walls, tegmental, jugular, labyrinthic,
inastoid, carotid, and membranous.
Paries Tegmentalis. The tegmental wall or roof (Fig. 709) is formed by a
thin plate of bone, the tegmen tympani, constituting a portion of the anterior surface
of the petrous part of the temporal. It extends backwards so as to cover in the
tympanic antrum, and forwards, to roof in the semicanal for the tensor tympaui
muscle. It separates the tympanic cavity and antrum from the middle fossa of the
cranial cavity, and may contain a few air-cells, whilst occasionally it is partly
deficient. In the child its lateral edge corresponds with the petro-squamous suture,
traces of which can generally be seen in the adult bone.
Paries Jugularis. The jugular wall or floor is narrower than the tegmental
wall, and consists of a thin plate of bone which separates the tympanic cavity from
the fossa jugularis; anteriorly, it extends upwards and is continuous with the
posterior wall of the carotid canal. The inner orifice of the foramen for the
transmission of the tympanic nerve is seen near the junction of the jugular and
labyrinthic walls.
Paries Labyrinthica. The labyrinthic or medial wall of the tympanic cavity
is formed by the lateral surface of the internal ear (Fig. 709). It presents (1)
a rounded eminence, the promontory, which is caused by the first coil of the cochlea,
and is grooved for the tympanic plexus of nerves. (2) An oval or somewhat
reniforrn opening, the fenestra vestibuli, which is situated above and behind the
promontory, with its long axis directed antero-posteriorly. It measures 3 mm. in
length and 1-5 mm. in width and, in the macerated bone, leads into the vestibule
of the osseous labyrinth, but is closed in the recent state by the base or foot-plate
TYMPANIC CAVITY OK MIDDLE EAR
833
of the stapes, surrounded by its ligamentum annulare. (3) An elevation, the pro-
minentia canalis facialis, which is situated above the fenestra vestibuli, in the
recessus epitympanicus ; this elevation indicates the position of the upper part of
the canalis facialis (O.T. aqueduct of Fallopius), which contains the facial nerve, and
Antrum tympanicum
Recessus epitympanicus
Prominentia canalis facialis
Tegmen tympani
Eminentia
pyramidalis
Sinus tympani
Mastoid air-cells
Fenestra vestibuli
Semicanal for tensor tympani
Septum canalis musculotubarii
Promontory with
grooves for
tympanic plexus
Osseous part of
auditory tube
Bristle introduced into the
foramen for the tympanic nerve
Fenestra cochleae
Course of canalis facialis
FIG. 709. SECTION THROUGH LEFT TEMPORAL BONE, showing labyrinthic wall of tympanic cavity, etc.
is continued backwards and downwards behind the tympanic cavity, to end at the
stylo-mastoid foramen. (4) The septum canalis musculotubarii (O.T. processus
cochleariformis), which extends backwards, above the anterior end of the fenestra
vestibuli, where it makes a sharp lateral curve, and forms a pulley over which the
tendon of the tensor tympani muscle plays. (5) A funnel-shaped recess, situated
behind and below the promontory, and almost hidden by its overhanging edge,
leads to an irregularly oval opening, termed the fenestra cochleae ; in the macerated
bone this fenestra communicates with the cochlea, but in the recent state is closed
by the membrana tympani secundaria ; this membrane is bent angularly along a line
joining its antero-inferior two-thirds with the postero-superior third ; and consists
Of three layers : (a) Recessus epitympanicus
lateral, continuous
with the mucous
lining of the tym-
panum, and con-
taining a network
of capillaries ; (V)
intermediate, or
membrana propria,
the fibres of which
radiate chiefly
towards the peri-
phery of the mem-
brane some
branched, dendritic
fibres are also
present ; (c) medial,
continuous with
the epithelial FIG. 710. LEFT MEMBRANA. TYMPANI AND RECESSUS EPITYMPANICUS,
lining of the
labyrinth. (6) Be-
tween the fenestra vestibuli above and the fenestra cochleae below is a small circular
depression, the sinus tympani, which is perforated by one or two minute foramina
for blood-vessels, and indicates the position of the ampullated end of the posterior
semicircular canal.
54
Pars flaccida
(Shrapnell)
Anterior and posterior
malleolar plicae
Tendon of tensor
tympani muscle (cut)
Manubrium mallei
Pars tensa
Sulcus tympanicus
viewed
from within. The head and neck of the malleus have been removed to
show the pars flaccida and the malleolar plicse. x 3.
834 THE OEGANS OF SENSE.
Paries Mastoidea. The mastoid or posterior wall presents, from above down-
wards : (1) a rounded or triangular opening, extending backwards from the
recessus epitympanicus and leading into the tympanic antrum (Fig. 709) ; (2) a
depression, the fossa incudis, situated in the postero-inferior part of the recessus epi-
tympanicus (Fig. 710), for the reception of the end of the short crus of the incus ;
(3) a minute conical bony projection, the eminentia pyramidalis (Fig. 709), the
summit of which is perforated by a round aperture for the passage of the tendon of
the stapedius muscle. This aperture is continued downwards and backwards as a
canal in front of the facial canal, and frequently opens, by a minute orifice, on the
base of the skull in front of the stylo-mastoid foramen ; it communicates with the
facial canal by one or two small foramina, which transmit the vessels and nerve
to the stapedius muscle ; a minute spicule of bone often extends from the eminentia
pyramidalis to the promontory on the labyrinthic wall of the tympanum ; (4) a small
aperture, the apertura tympanica canaliculi chordae (Fig. 710), which is situated close
to the posterior edge of the membrana tynipani, nearly on a level with the upper
end of the manubriuni mallei ; (5) a rounded eminence, the prominentia styloidea, is
sometimes seen below the last, and is caused by the upward and forward prolongation
of the styloid process.
Paries Carotica. The carotid or anterior wall is narrowed in its transverse
diameter by the approximation of the lateral and medial boundaries of the tympanic
cavity, and in its vertical diameter by the descent of the roof and the ascent of the
carotid canal. It presents (Fig. 709) two parallel semicanals, one above the other
separated by a thin lamella of bone, the septum canalis musculotubarii (O.T.
processus cochleariformis). These run forwards on the lateral wall of the carotid
canal and open in the angle between the squama and the petrous part of the
temporal bone. The higher and smaller of the two is termed the semicanalis m.
tensoris tympani, and lies immediately below the tegmen tympani. It has a diameter
of about 2 mm., and extends on to the medial wall of the tympanic cavity above
the anterior part of the fenestra vestibuli. The lower and larger semicanal gradu-
ally increases in size from before backwards, and is named the semicanalis tubas
auditivse. It forms the bony part of the auditory tube and opens .on the carotid
wall of the tympanic cavity opposite the orifice leading into the tympanic antrum.
Below the orifice of the auditory tube the anterior part of the tympanic cavity
is separated from the ascending portion of the carotid canal by a thin plate of
bone in which there are sometimes gaps or deficiencies. It is perforated by the
carotico- tympanic canal, which transmits the carotico- tympanic nerve from the
sympathetic plexus of the carotid artery to the tympanic plexus. The auditory
tube is described on p. 837.
Paries Membranacea. The membranous or lateral wall is formed almost en-
tirely by the membrana tympani (Fig. 710), which closes the medial end of the
external acoustic meatus, and is fixed throughout the greater part of its circum-
ference in a groove, the sulcus tympanicus. The bony ring containing this sulcus is
deficient superiorly, where it exhibits a distinct notch, the notch of Eivinus. On a
level with the upper edge of the membrane, and in front of the ring of bone in
which it is fixed, is the medial end of the petrotympanic fissure. This transmits the
tympanic branch of the internal maxillary artery, and lodges the anterior process
and anterior ligament of the malleus. Close to the medial end of the fissure is
the iter chordae anterius through which the chorda tympani nerve leaves the
tympanic cavity.
Membrana Tympani. The tympanic membrane is an elliptical disc, its greatest
diameter, 9 to 10 mm., being directed from above, downwards and forwards, whilst
its least diameter is from 8 to 9 mm. It is placed very obliquely, forming an
angle of about 55 with the lower and anterior walls of the external acoustic
meatus ; it is said to be more oblique in cretins and deaf mutes, and more
perpendicular in musicians.
The circumference of that portion of the membrane which is fixed in the sulcus
tympanicus is considerably thickened, and is named the annulus fibrocartilagineus.
It is prolonged from the anterior and posterior extremities of the notch of Kivinus
to the processus lateralis of the malleus, in the form of two ligamentous bands, the
TYMPANIC CAVITY OR MIDDLE EAR
835
anterior and posterior malleolar plicae. The small triangular portion of the membrane
(Fig. 710) situated above these folds is thin and lax, and constitutes the pars flaccida
(O.T. membrane of Shrapriell) ; the main portion of the membrane is, on the other
hand, tightly stretched and termed the pars tensa. A small orifice, sometimes
seen in the pars flaccida, is probably either a pathological condition or has been
produced artificially during manipulation. The manubrium mallei is firmly fixed to
the medial surface of the membrana tympani, the central portion of which is drawn
towards the tympanic cavity so that its lateral surface is concave. The deepest
part of this concavity corresponds with the lower end of the manubrium of the
malleus, and is named the umbo membranae tympani.
The membrana tympani consists of three layers : (1) a lateral, the stratum
cutaneum ; (2) an intermediate, the membrana propria ; (3) a medial, the stratum
mucosum.
The stratum cutaneum is continuous with the skin of the meatus, and consists
of a thin layer of cutis covered with epidermis. The cutis is thickest near the
circumference ; the epidermis, on the other hand, is thickest near the centre of the
membrane.
The membrana propria consists of two sets of fibres : (a) a lateral, the stratum
radiatum, situated immediately under the stratum cutaneum, and radiating from
the manubrium of the malleus to the annulus fibrocartilagineus ; (6) a medial, the
stratum circulare, the fibres of which are numerous near the circumference, but
scattered and few in number near the centre of the membrane (Fig. 710). Both
radial and circular fibres are absent from the pars flaccida, which consists only of
the cutaneous and mucous strata. Gruber pointed out that, in addition to the
radial and circular fibres, there exists, next the stratum mucosum, a series of
dendritic or branched fibres, which are best developed in the posterior part of the
membrane.
The stratum mucosum is continuous with the mucous lining of the tympanic
cavity. It is thicker over the upper part of the membrane than near its centre,
and is covered with pavement epithelium.
Otoscppic Examination of the Membrana Tympani (Fig. 711). The membrana tympani,
in the living, is of a " pearl-gray " colour, but may present a reddish or yellowish tinge, depending
upon the condition of its mucous lining and on the condition of the cutaneous lining of the meatus ;
the posterior segment is usually
clearer than the anterior. At the
an tero- superior part, close to its
periphery, a whitish point appears
as if projecting towards the meatUS ; Membrana flaccida |M -^IM^I^BE malleus
this is the processus lateralis of the Anterior malleolar
malleus. Passing downwards and [_ Postero-superior
backwards from this point to the 9k i quadrant
umbo is a ridge caused by the Manubrium mallei
manubrium mallei, the lower ex-
tremity of which appears rounded.
Two ridges, corresponding with the
malleolar plicae, extend from the
processus lateralis of the malleus,
one forwards and upwards, the other
backwards and upwards. Behind,
and near the lower extremity of the
manubrium mallei, is a reddish or
yellowish spot, due to the promontory of the medial wall of the tympanic cavity shining through.
[f the membrane is very transparent, the long crus of the incus may be visible behind the upper
part of the manubrium mallei, and reaching downwards as far as its middle. From the lower
end of the manubrium mallei, the " cone of light " or " luminous triangle " extends downwards
and forwards, its apex being directed towards the handle ; this triangle varies in size in different
people. A line prolonging the manubrium downwards divides the membrane into two parts,
while another, drawn at right angles to this through the umbo, will subdivide it into quadrants,
viz., postero-superior, postero-inferior, antero-superior, and antero-inferior ; this subdivision is
useful in enabling the otologist to localise and describe accurately the seat of lesions in the
membrane.
Vascular and Nervous Supply of the Membrana Tympani. The arteries are arranged in
two sets, one on the cutaneous and another on the mucous surface ; they anastomose by means
: small branches which pierce the membrane, especially near its periphery. The first set is
derived ehiefly from the deep auricular branch of the internal maxillary, whilst those on the
54 a
Antero-superior
quadrant
Antero-inferior
quadrant
Posterior
malleolar plica
Lateral process of
Postero-inferior
quadrant
Cone of light
FIG. 711. LEFT TYMPANIC MEMBRANE (as viewed from the external
acoustic meatus). x 3.
836
THE OEGANS OF SENSE.
mucous surface are small and proceed from the anterior tympanic branch of the internal maxillary,
and from the stylo-mastoid branch of the posterior auricular. The veins from the cutaneous surface
open into the external jugular ; those from the mucous surface partly into the venous plexus on the
auditory tube, and partly into the transverse sinus and veins of the dura mater. The lymph
vessels, like the blood-vessels, are arranged in two sets, cutaneous and mucous, which, however,
communicate freely with each other. Kessel has described as lymphatics the spaces between the
branches of Gruber's dendritic fibres. The lateral surface of the membrane receives its nerves
from the auriculo-temporal branch of the trigeminal and from the auricular branch of the vagus ;
the medial surface, from the tympanic branch of the glossopharyngeal.
ANTRUM TYMPANICUM ET CELLULJE MASTOIDE.E.
Antrum Tympanicum. The tympanic antrum (O.T. mastoid antrum) is an air-
space situated above and behind the tympanic cavity. It is nearly as large in the
new-born child as in the adult. In the adult its measurements are length from
Tympanic antrum, the medial
wall of which is related to the
lateral semicircular canal
edial part of posterior wall of external
acoustic meatus left in situ
Points to the recessus epitympanicus
Mastoid air-cells
Facial nerve
Facial canal laid open, displaying the facial nerve within
FIG. 712.
Preparation to display the position and relations of the tympanic antrum. The greater part of the posterior
wall of the external acoustic meatus has been removed, leaving only a bridge of bone at its medial ex-
tremity ; under this a bristle is displayed, passing from the tympanic antrum through the iter to the
cavity of the tympanum.
12 to 15 mm., height from 8 to 10 mm., and width from 6 to 8 mm. It is roofed
in by the tegmen tympani, and its floor and medial wall are formed by the pars
petrosa and pars mastoidea of the temporal bone, while laterally it is closed by
the junction of the thin outer part of the squama with the pars mastoidea. It
communicates with the epi tympanic recess by a triangular or rounded opening,
on the medial wall of which, immediately above and behind the canalis facialis, is
a smooth, convex area of bone indicating the position of the arnpullated extremities
of the superior and lateral semicircular canals. At birth the lateral wall of the
antrum has a thickness of only 1-2 mm., but by the ninth year this has increased
to about 10 mm. Coincident with the growth of the mastoid process the mastoid
air-cells are developed downwards and backwards as diverticula from the antrum,
and present the greatest possible variation in different skulls.
Cellulae Mastoidese. The mastoid air-cells may be large, comparatively few
in number, and involve the whole mastoid process, in which case the compact
bone surrounding them is extremely thin, and the innermost cells are separated
AUDITOKY TUBE.
837
from the transverse sinus by a transparent lamella which, in some instances, is
partly deficient. In other eases the cells may be small and numerous, invading
only a portion of the process, the remainder consisting of diploetic tissue ;
occasionally a solid mastoid is met with. No definite conclusion can be formed
as to their condition by external percussion or examination. The air-cells are
not limited to the mastoid portion of the temporal bone, but extend forwards over
the roof of the meatus, upwards towards the squama temporalis, and medially towards
the temporo-occipital suture ; occasionally they invade the pars jugularis of the
occipital bone. The tympanic antrum and the mastoid air-cells are lined with
thin mucous membrane, continuous with that of the tympanic cavity ; the deep
surface of the mucous membrane is fixed to the periosteum ; its free surface is
covered with a layer of flattened, non-ciliated epithelium.
TUBA AUDITIVA.
The auditory tube (O.T. Eustachlan tube) leads from the tympanic cavity to
the nasal part of the pharynx, and transmits air to the former, in order that the
pressures on the medial and lateral surfaces of the membrana tympani may be
equalised ; it may also serve to convey mucous secretion from the tympanic cavity.
Its tympanic orifice (Fig. 709) opens into the anterior part of the tympanic cavity,
below the semicanal for the tensor tympani muscle. Directed downwards and medial-
wards, the tube ends on the upper part of the nasal part of the pharynx by a wide
pharyngeal orifice (Fig. 674, p. 803). It measures about 35 mm. in length, and forms
with the horizontal plane an angle of 30 to 40, with the sagittal plane an angle
of about 45, and with the bony part of the external acoustic meatus an angle of 135
to 140. It consists of two portions: (a) an antero-medial, the pars cartilaginea
tubae auditivae, having a length of about 25 mm. ; and (b) a postero-lateral, the
pars ossea tubae auditivae, measuring about 10 mm. in length. The two portions are
not in the same plane, the cartilaginous part inclining downwards a little more
than the osseous portion, and forming with it a wide angle. The lumen of the tube
is widest at the pharyngeal orifice, narrowest
at the junction of the bony and cartilaginous
portions, forming here the isthmus, and
again expanding towards the tympanic
cavity ; hence it presents, on longitudinal
section, somewhat the appearance of an
hour-glass. The pars ossea occupies the
angle between the tympanic part and the
petrous part of the temporal bone, and is
separated by the septum canalis musculo-
tubarii from the semicanal containing the
tensor tympani muscle ; medial to it is the
carotid canal. The pars cartilaginea con-
sists partly of cartilage and partly of
fibrous membrane. The cartilage of the
auditory tube is an elongated triangular
plate, of which the apex is firmly attached
to the medial end of the pars ossea, while
the base is free, and forms a projection on
the upper and posterior aspects of the
pharyngeal orifice. The upper edge of this
cartilaginous plate is bent laterally in the
form of a hook, and so produces a furrow
open below, the furrow being converted into a complete canal by the membranous
.na of the tube. On transverse section (Fig. 713) the cartilage presents two
.aminae continuous with each other superiorly : (a) lamina medialis, broad and
ik ; and (&) lamina lateralis, thin and hook-shaped. At the pharyngeal orifice
lamina medialis forms the entire medial wall of the tube, but it gradually
liminishes in breadth on approaching the isthmus tubae. Fissures are often seen
54 &
Mucous
glands
FIG. 713. TRANSVERSE SECTION OF THE
CARTILAGINOUS PART OF THE AUDITORY TUBE.
838 THE OKGANS OF SENSE.
in the cartilage; sometimes it is completely separated into several pieces, or
accessory islands may be observed in the roof, floor, or membranous lamina.
The upper and medial surfaces of the medial lamina are firmly fixed to the base
of the skull, where it lies in a groove, the sulcus tubae auditivae, between the great
wing of the sphenoid and the petrous part of the temporal. Extending forwards
on to the root of the pterygoid process this sulcus ends at a projection, the proeessus
tubarius, on the medial pterygoid lamina. The tensor veli palatini muscle lies on
the lateral side of the tube and receives some fibres of origin from its lamina
lateralis; these fibres constitute the dilatator tubas muscle (Elidinger). On the
medial side of the cartilage are the levator veli palatini and the mucous membrane
of the pharynx. The membranous lamina consists of a strong fibrous membrane,
stretching between the two edges of the cartilage, and so completing the lower and
lateral walls of the tube. Thin above, it becomes thickened below and forms the
fascia salpingopharyngea of Troltsch, which gives origin to some of the fibres of the
tensor veli palatini muscle. Between this fascia and the mucous lining of the tube
is a layer of adipose tissue.
The pharyngeal orifice of the auditory tube, triangular or oval in shape, is situated
on the lateral wall of the nasal part of the pharynx, the centre of the opening
being on a level with the posterior end of the inferior nasal concha. It is
bounded above and behind by a pad, the torus tubarius, produced by the base of
the cartilage, which there abuts against the mucous membrane ; the posterior part
of the torus is very prominent and forms the anterior boundary of the pharyngeal
recess. Prolonged downwards from it is an elevation of the mucous membrane,
termed the plica salpingopharyngea, which covers the small salpingopharyngeus
muscle. From the upper part of the torus an indistinct fold, the plica salpingo-
palatina, extends to the palate.
The mucous lining of the tube is continuous behind with that of the tympanic
cavity, and in front with that of the nasal part of the pharynx. It is thin in the
pars 03sea, contains few, if any, mucous glands, and is firmly fixed to the bony wall ;
in the pars cartilaginea it is loose and thrown into longitudinal folds. Numerous
mucous glands open into the tube near its pharyngeal orifice, and here also exists
a considerable amount of adenoid tissue, which constitutes the " tube-tonsil " of
Gerlach. This adenoid tissue is continuous with that of the nasal part of the
pharynx, and, like it, is especially well developed in children. The lumen of the
tube is lined with ciliated columnar epithelium.
The tube is opened, during deglutition, by the dilatator tubse and salpingo-
pharyngeus muscles. The former springs superiorly from the cartilaginous hook of
the tube, and blends inferiorly with the tensor veli palatini. When the dilatator
tubse contracts, the cartilaginous hook and the membranous lamina of the tube are
drawn lateralwards and forwards. Some anatomists believe that the entire tensor veli
palatini acts chiefly as a dilator of the tube, and Kiidinger named it the abductor
tubse. The salpingopharyngeus muscle draws downwards and backwards the
medial lamina, increasing the angle between it and the lateral lamina. Some
difference of opinion exists as to the precise action of the levator veli palatiiii;
probably it assists in opening the tube.
The auditory tube receives its blood-supply from the ascending pharyngeal artery, and from
the middle meningeal artery and the artery of the pterygoid canal, both of which are branches
of the internal maxillary artery. Its veins form a network which drains into the pterygoid
venous plexus. The sensory nerves of the tube are derived from the tympanic plexus and from
the pharyngeal branch of the spheiio-palatine ganglion.
The auditory tube of the child differs considerably from that of the adult; its lumen is
relatively wider, its direction more horizontal, and its pars ossea relatively shorter. Kunkel
states that its pharyngeal orifice is below the level of the hard palate in the foetus ; at birth
it is on the same level as the palate, whilst at the fourth year it is 3 to 4 mm., and in the adult
10 mm., above it. In the child the pharyngeal orifice forms a narrow fissure, and its cartilage
projects less towards the middle line.
OSSICULA AUDITUS.
The auditory ossicles form an articulated column connecting the lateral
with the medial wall of the tympanic cavity; they are named, from without
AUDITORY OSSICLES.
839
inwards, the malleus, incus, and stapes. The first is attached to the medial
surface of the mernbrana timpani ; the last is fixed within the circumference of
the fenestra vestibuli.
The malleus (Fig. 714, B, D), the largest of the three ossicles, has a length of
8 to 9 mm., and consists of a head, a neck, a manubrium, and two processes, viz. :
FIG. 714. AUDITORY OSSICLES OF LEFT EAR (enlarged about three times).
A, Incus, seen from the front ; B, Malleus, viewed from behind ; C, Incus, and D, Malleus, seen from medial
aspect ; E, Stapes.
1. Body of incus, with articular
surface for head of malleus.
2. Crus longum.
3. Processus lenticularis.
4. Articular surface for incus.
5. Head of Malleus.
6. Neck of Malleus.
7. Processus lateralis.
8. Manubrium.
9. Body of incus.
10. Crus breve.
11. Crus longum.
12. Processus anterior.
13. Head of malleus.
14. Facet for incus.
15. Manubrium.
16. Head of stapes.
17. Neck.
18. Crus anterius.
19. Crus posterius.
(a) processus anterior, (5) processus lateralis. The head and neck are situated in
the epityrnpanic recess ; the processus lateralis and manubrium are fixed to the
medial surface of the membrana tympani; while the processus anterior is directed for-
wards, towards the petro-tympanic fissure, to which, in the adult, it is connected by
ligamentous fibres. The head, somewhat rounded, is smooth and convex above and
in front, and presents, on its posterior surface, a facet for articulation with the body
Recessus epitympanicus
Body of incus
Crus breve of incus
Ligament of incus
Chorda tympani nerve
Eminentia pyramid-
alis, with tendon of
in. stapedius issuing
from it
Base of stapes
Superior ligament of malleus
Head of malleus
Anterior ligament of malleus
Manubrium mallei
Fio. 715. LEFT MEMBRANA TYMPANI AND CHAIN OF AUDITORY OSSICLES (seen from the medial aspect), x 3.
of the incus. This facet is directed obliquely downwards and medialwards, and is
more or less elliptical in form. It is constricted near the middle so as to resemble,
somewhat, the figure 8 ; an oblique ridge, corresponding with the constriction,
divides the facet into two parts an upper and larger, directed backwards, and a
lower and lesser, directed medialwards. Opposite the lower part of the constriction
the inferior edge of the facet is very prominent, and is continued upwards into the
oblique ridge just referred to ; it forms a tooth-like process, the spur or cog-tooth of
840 THE ORGANS OF SENSE.
the malleus. On the back of the head, below this spur, is an oblique crest, the crista
mallei, to which is attached the lateral ligament of the malleus. The neck is the
slightly constricted portion immediately below the head. Flattened from before
backwards, its lateral surface is directed towards the membrana flaccida, whilst its
medial surface is crossed by the chorda tympani nerve. The manubrium or handle
is directed downwards, backwards, and medialwards from the neck, forming with the
long axis of the head an angle of 126 to 150. Its upper part is flattened from
before backwards, but towards the lower end it is twisted on itself, so that its
surfaces look laterally and medially ; moreover, the lower end is slightly curved,
the concavity being directed forwards and laterally. It is fixed, along its entire
length, to the membrana propria of the tympanic membrane by its periosteum and
by a layer of cartilage (Gruber). The cartilage intervenes between the manubrium
and the membrane, and must be regarded as a residue of that stage of development
when the entire malleus was cartilaginous. On the medial surface of the manubrium,
near its upper extremity, is a slight projection for the attachment of the tendon of
the tensor tympani muscle. The processus anterior, a slender spicule, springs from
the front of the neck and is directed forwards, towards the petro-tympanic fissure.
In the foetus it is the longest process of the malleus, but in the adult it usually
assumes the form of a small projection, since its anterior part is replaced by
ligamentous tissue. The processus lateralis may be looked upon as the upper
extremity of the manubrium projected laterally ; it is fixed to the upper part of the
membrana tympani by the cartilaginous layer already referred to, and to the
extremities of the notch of Rivinus by the anterior and posterior malleolar plicse.
The incus (Fig. 714, A, C) may be likened to a prsemolar tooth with widely
divergent roots. It consists of a body, a crus longum, and a crus breve ; the crura
form with each other an angle of 90 to 100. The body and crus breve are situated
in the recessus epitympanicus. The body presents a more or less saddle-shaped
surface for articulation with the head of the malleus. This surface is directed
forwards, and its lower part is hollowed out for the accommodation of the cog-tooth
of the malleus; in front of this hollow it is prominent and spur-like. The crus
breve is thick, triangular in shape, and projects horizontally backwards ; its conical
extremity, covered with cartilage, is received into the fossa incudis in the postero-
inferior part of the epitympanic recess. The crus longum projects, almost per-
pendicularly, downwards from the body into the tympanic cavity, where it lies
parallel with, but T25 mm. behind and medial to, the manubrium mallei. Its lower
end is bent medialwards and narrowed to form a short neck, on the end of which
is a small knob of bone, the processus lenticularis, for articulation with the head
of the stapes. Until the sixth month of fcetal life this process exists as a separate
ossicle, termed the os orbiculare.
The stapes (Fig. 714, E) consists of a head, a neck, two crura, and a base.
The head, directed lateralwards, is concave for articulation with the processus
lenticularis of the incus. The neck is slightly constricted, and from it the two
crura spring ; the tendon of the stapedius is inserted into the posterior aspect of
the neck. The crus anterius is shorter and less curved than the crus posterius.
Diverging from each other, the crura are directed medialwards and are attached one
near the anterior, the other near the posterior end of the base. The base almost
completely fills the fenestra vestibule, and, like it, is somewhat oval or reniform,
its anterior end being the more pointed. In the recent condition a membrane fills
the arch formed by the crura and the base, the crura being grooved for its reception.
In the child the crura of the stapes are less curved than in the adult, and the
opening bounded by them and the base is nearly triangular.
Articulations of the Auditory Ossicles. The incudo-malleolar joint between
the head of the malleus and the body of the incus is diarthrodial, and may be
described as one of reciprocal reception. It is surrounded by an articular capsule,
and from the inner surface of the fibrous stratum a wedge-shaped meniscus projects
into the joint cavity and incompletely divides it. The incudo-stapedial articulation
between the processus lenticularis and the head of the stapes is of the nature of
an enarthrosis and is surrounded by an articular capsule. An interarticular
cartilage has been described as occurring in this joint, while some observers deny
AUDITOEY OSSICLES. 841
the presence of a synovial cavity and regard the articulation as a syndesmosis, the
articular surfaces being held together by fibrous tissue.
Ligamenta Ossiculornm Auditus. The malleus is attached to the walls of the
tympanic cavity by three ligaments (Fig. 715), viz. : anterior, superior, and lateral.
The anterior ligament consists of two portions : (a) the band of Meckel, which is
attached to the base of the processus anterior, and passes forwards, through the petro-
tympanic fissure, to reach the spine of the sphenoid ; it represents the remnant
of a portion of Meckel's cartilage, and was formerly described as the laxator tympani
muscle; (&) a firm bundle of fibres, the anterior ligament of Helmholtz, which
extends from the spina tympanica anterior at the anterior boundary of the notch
of Kivinus to the anterior surface of the malleus, above the base of the processus
anterior. The superior ligament stretches, almost vertically, from the head of the
malleus to the roof of the epitympanic recess. The lateral ligament is short and
fan-shaped ; its fibres converge from the posterior half of the notch of Kivinus to
the crista mallei. The posterior part of this ligament is strong and constitutes
the posterior ligament of Helmholtz ; it forms, together with the anterior ligament
of the malleus, the axis around which the malleus rotates, and the two constitute
what Helmholtz termed the " axis-ligament " of the malleus.
The posterior extremity of the crus breve of the incus is tipped with cartilage
and fixed by means of a ligament to the fossa incudis (Fig. 715). Some observers
describe this as a diarthrodial joint. The vestibular surface and the circum-
ference of the base of the stapes are covered with hyaline cartilage, and a similar
layer lines the opening of the fenestra vestibuli; that encircling the base of the
stapes is joined to that lining the fenestra by a dense ring of elastic fibres,
named the ligamentum annulare baseos stapedis. The posterior fibres of this
ligament are thicker and shorter than the anterior, and thus during the movements
of the stapes, the anterior end of its base is free to make greater excursions than
the posterior.
Development of the Auditory Ossicles. It is generally maintained that the
malleus and incus are developed from the upper end of Meckel's cartilage, and that the
stapes arises from the mesoderm in the region of the fenestra vestibuli, where it is developed
around a small artery, the stapedial artery, which atrophies in man, but persists in many
mammals. On the other hand, Gadow (Phil. Trans., London, vol. clxxix.) says "the whole
system of the one to four elements of the middle ear, which have all the same function,
is to be looked upon as one organ, of one common origin, viz., a modification of the hyo-
mandibular, the proximal paramere of the second visceral arch." Ossification commences
in all three bones about the third month of foetal life. The malleus is ossified from two
centres, one for the head and manubrium, and one for the processus anterior ; the incus
from two centres, one for the body including the crura, and a second for the processus
lenticularis ; the stapes from one centre which appears in the base.
Muscles of the Tympanic Cavity. These are two in number, viz., m. tensor
tympani and m. stapedius.
The m. tensor tympani is the larger, and takes origin from the roof of the carti-
laginous part of the auditory tube, from the adjacent part of the great wing of the
sphenoid, and from the bony canal in which the muscle lies. The muscle ends in a
tendon which bends laterally, nearly at a right angle to the belly of the muscle,
round the pulley-like posterior extremity of the septum canalis musculotubarii.
Passing across the tympanic cavity this tendon is inserted into the medial edge
and anterior surface of the manubrium mallei, near its upper end. When the
muscle contracts it draws the manubrium of the malleus towards the tympanic cavity,
and so renders tense the membrana tympani ; it probably also slightly rotates the
malleus around its long axis. It receives its nerve from the motor division of the
trigeminal nerve, through the otic ganglion.
The m. stapedius arises within the eminentia pyramidalis, and from the canal
which prolongs the hollow of the pyramidal eminence downwards. Its tendon
emerges from the apex of the eminence and is inserted into the posterior surface
of the neck of the stapes. On contraction it draws back the head of the stapes,
and so tilts the anterior end of the base towards the tympanic cavity and the
842 THE OEGANS OF SENSE.
posterior end towards the labyrinth, thus rendering tense the ligamentum annulare
the lateral movement of the anterior end of the base being greater than the
medial movement of its posterior end. The muscle is supplied by the facial nerve.
Movements of the Auditory Ossicles. The manubrium mallei follows all the
movements of the membrana tympani, while the malleus and incus move together around
an axis extending forwards through the crus breve of the incus and the anterior
ligament of the malleus. When the membrana tympani moves medialwards it carries with
it the manubrium mallei, while the incus, moving medialwards at the same time, forces the
base of the stapes towards the labyrinth. This movement is communicated to the fluid
(perilymph) in the labyrinth, and causes a lateral bulging of the secondary tympanic
membrane, which closes the fenestra cochleae. These movements are reversed when the
membrana tympani is relaxed, unless the lateral movement of the membrane is excessive.
In such a condition the incus does not follow the full movement of the malleus, but
merely glides on this bone at the incudo-malleolar joint, and thus the forcible dragging
of the base of the stapes out of the fenestra vestibuli is prevented. The cog-tooth
arrangement, already described, on the head of the malleus and body of the incus, causes
the incudo-malleolar joint to become locked during the medial movement of manubrium
mallei, the joint becoming unlocked during its lateral movement.
Tunica Mucosa Tympanica. The mucous lining of the tympanic cavity is
continuous, through the auditory tube, with that of the nasal part of the pharynx ;
it extends backwards also and lines the tympanic antrum and the mastoid air-cells.
Thin, transparent, and closely united with the subjacent periosteum, it covers the
medial surface of the membrana tympani and is reflected over the auditory ossicles
and their ligaments. It also supplies sheaths for the tendons of the tensor tympani
and stapedius muscles, and forms the following folds, viz. : (a) one from the roof of
the recessus epitympanicns to the head of the malleus and body of the incus;
(5) one enveloping the chorda tympani nerve and crus longum of the incus ; (c) two
extending from the processus lateralis mallei one to. the anterior, the other to the
posterior margin of the notch of Kivinns. A recess, the pouch of Prussak, is situated
between the membrana flaccida and the neck of the malleus. Communicating
behind with the tympanic cavity, this pouch may serve as a reservoir to confine
pus or other fluid, since its opening into the tympanic cavity is above the level
of its floor, a condition analogous to the opening from the maxillary sinus into the
nasal cavity. The fold of mncous membrane which extends downwards to envelop
the chorda tympani nerve gives rise to two pouches, one in front of, and the other
behind, the manubrium mallei ; these are named the anterior and posterior recesses
of Troltsch. The epithelium which lines the mucous membrane is flattened over the
membrana tympani, promontory, and auditory ossicles, but ciliated and columnar
over the greater portion of the rest of the cavity.
Vessels and Nerves of the Tympanic Cavity. The arteries supplying the tympanic
cavity are : (1) The anterior tympanic artery, a branch of internal maxillary, which reaches the
cavity by way of the petro-tympanic fissure. (2) The stylo-mastoid branch of posterior auricular,
which passes through the stylo-mastoid foramen and the facial canal ; it supplies branches to the
tympanic antrum and mastoid air-cells, to the stapedius muscle, to the floor and medial wall of
the tympanic cavity, and forms an anastomotic circle, around the membrana tympani, with the
anterior tympanic artery. (3) The middle meningeal artery sends a branch to the tensor tympani
muscle, and, after entering the skull, gives off its petrosal artery, which is conducted to the
tympanic cavity along the hiatus canalis facialis ; some twigs from the posterior division of the
middle meningeal reach the tympanic antrum and epitympanic recess through the petro-
squamous fissure. (4) The internal carotid artery, in its passage through the canal in the
temporal bone, gives off one or two tympanic twigs, while (5) a branch from the ascending
pharyngeal accompanies the tympanic nerve. The veins drain into the pterygoid plexus, and the
superior petrosal sinus. The lymph vessels form a network in the mucous membrane and end
mainly in the retro-pharyngeal and parotid lymph glands. The nerves supplying the muscles
of the tympanic cavity have already been referred to (pp. 832, 834). The mucous membrane
receives its nerves from the tympanic plexus, which is described on p. 786. The chorda tympani
branch of the facial nerve passes from behind, upwards, and forwards through the tympanic
cavity. Its course is described on p. 782.
Early Condition of Tympanic Cavity During the greater part of intra-uterine existence
the tympanic cavity is almost completely filled by a soft, reddish, jelly-like embryonic tissue
in which there is a slit-like space lined with epithelium. Towards the end of foetal life this tissue
disappears and at birth the cavity is filled with fluid which becomes absorbed, after the entrance
of air from the nasal part of the pharynx through the auditory tube.
OSSEOUS LABYRINTH.
843
AUEIS INTEKNA.
The internal ear or essential part of the organ of hearing is situated in the
substance of the petrous part of the temporal bone, and consists of two sets of
structures, viz. : (1) a series of passages hollowed out of the bone and constituting
the osseous labyrinth; these are continuous with each other, and are named
Superior semicircular canal
Ampulla of superior
semicircular canal
Canalis facialis
Recessus ellipticus
Crista vestibuli
Recessus sphsericus
Cochlea
Fenestra cochleae
Fenestra vestibuli
Ampulla of posterior semi-
circular canal
Ampulla of lateral semi- I
circular canal |
Lateral semicircular canal
Posterior semi-
circular canal
Crus commune
Scala tympani
Lamina spiralis ossea
Scala vestibuli
Opening of aquseductus
cochleae
Fenestra cochleae
Recessus cochlearis
Posterior
circular
canal
| Opening of crus commune
Opening of aquseductus vestibuli
FIG. 716. LEFT BONY LABYRINTH
(viewed from the lateral aspect).
FIG. 717. INTERIOR OP LEFT BONY LABYRINTH
(viewed from lateral aspect).
from before backwards the cochlea, vestibule, and semicircular canals (Figs. 716,
717) ; (2) a complex arrangement of membranous channels (Fig. 720), situated
within, but not nearly filling, the bony labyrinth and forming the membranous
labyrinth. These channels are named the ductus cochlearis, the utricle, the saccule,
and the semicircular ducts ; the utricle and saccule are lodged within the vestibule.
LABYKINTHUS OSSEUS.
Vestibulum. The vestibule is the central portion of the osseous labyrinth, and
communicates behind with the semicircular canals and in front with the cochlea. It
is somewhat ovoid in shape, its long axis being directed forwards and lateralwards ;
it measures about 6 mm. antero-posteriorly, 4-5 mm. vertically, and about 3 mm.
transversely. Its lateral wall is directed towards the tympanic cavity, and in it
is the fenestra vestibuli, which is closed by the base of the stapes. Its medial
wall corresponds with the bottom of the internal acoustic meatus, and presents, at
its antero-inferior part, a rounded depression, the recessus sphaericus, which lodges
the saccule. This recess is perforated by twelve or fifteen small foramina (macula
cribrosa media), which transmit the filaments of the acoustic nerve to the saccule.
The recessus sphsericus is limited above and behind by an oblique ridge, the crista
vestibuli, the anterior extremity of which is triangular in shape and named the
pyramis vestibuli. Posteriorly this crista divides into two limbs, between which is
a small depression, the recessus cochlearis, perforated by about eight small fora-
mina, which give passage to the nervous filaments supplying the vestibular end of
the ductus cochlearis. Above and behind the crista vestibuli, in the roof and
medial wall of the vestibule, is an oval depression, the recessus ellipticus, which
lodges the utricle. The pyramis vestibuli and adjacent part of the recessus ellipticus
are perforated by twenty-five or thirty small apertures (macula cribrosa superior).
The foramina in the pyramis vestibuli transmit the nerves to the utricle ; those in
the recessus ellipticus, the nerves to the ampullse of the superior and lateral
semicircular ducts. Behind and below the recessus ellipticus is a furrow, gradually
deepening to form a canal, the aquseductus vestibuli, which passes backwards through
the petrous part of the temporal bone, and opens, as a slit-like fissure, about
midway between the internal acoustic meatus and the groove for the transverse
sinus. This aqueduct measures 8-10 mm. in length, and gives passage to the
844 THE OKGANS OF SENSE.
ductus endolymphaticus and a small vein. The posterior part of the vestibule
receives the five rounded apertures of the semicircular canals ; its anterior part
leads, by an elliptical opening, into the scala vestibuli of the cochlea. This opening
is bounded inferiorly by a thin osseous plate, the lamina spiralis ossea, which
springs from the floor of the vestibule immediately lateral to the recessus
sphsericus, and forms, in the cochlea, the bony part of the septum between the scala
tympani below and the scala vestibuli above. From the anterior part of the floor
of the vestibule a narrow cleft, the fissura vestibuli, extends forwards into the bony
canal of the cochlea. It is bounded internally by the lamina spiralis ossea, and
externally by a second, smaller lamina, the lamina spiralis secundaria, which
projects from the outer wall of the cochlea. These two lamina are continuous
with each other round the posterior extremity of the fissura vestibuli.
Canales Semicirculares Ossei. The osseous semicircular canals (Figs. 716, 71*7),
three in number, are situated above and behind the vestibule. They are dis-
tinguished from each other by their position, and are named superior, posterior,
and lateral. They open into the vestibule by five apertures, since the medial end
of the superior and the upper end of the posterior join to form a common canal
or crus commune. Differing slightly in length, each forms about two-thirds of
a circle, one extremity of which is dilated and termed the osseous ampulla.
They are somewhat compressed from side to side, and their diameter is from 1 to
1*5 mm., whilst that of the ampullae is about 2 mm.
The superior semicircular canal, 15 to 20 mm. in length, is vertical and placed
transversely to the long axis of the petrous part of the temporal bone. Its
convexity is directed upwards, and its position is indicated on the anterior surface
of the petrous part of the temporal bone by the arcuate eminence. Its ampulla is
anterior and lateral, and opens into the vestibule immediately above that of the
lateral canal. Its opposite extremity joins the non-ampullated end of the posterior
canal to form the crus commune, which is about 4 mm. in length, and opens into
the upper and medial part of the vestibule. The posterior semicircular canal is
the longest and measures from 18 to 22 mm. Its ampulla is placed inferiorly, and
opens into the lower and back part of the vestibule, where may be seen about
six or eight small apertures (macula cribrosa inferior), for the transmission of the
nerves to this ampulla. Its upper extremity ends in the crus commune. The
lateral canal is the shortest ; it measures from 12 to 15 mm., and arches nearly
horizontally. Of its two extremities the lateral is ampullated, and opens into the
vestibule immediately above the fenestra vestibuli and in close relationship to
the ampullary end of the superior canal.
Crum Brown (Journ. Anat. and Physiol, London, vol. viii.) pointed out that the lateral
canal of one ear is very nearly in the same plane as that of the other ; while the superior canal
of one ear is nearly parallel to the posterior canal of the other.
Cochlea. 1 When freed from its surroundings the cochlea assumes the form of
a short cone (Fig. 720) ; the central part of its base corresponds with the bottom
of the internal acoustic meatus, whilst its apex or cupula is directed forwards
and laterally, and comes into close relation with the semicanal for the tensor
tympani muscle. It measures about 9 mm. across the base and about 5 mm.
from base to apex, and consists of a spirally arranged tube, which forms from
2 J to 2| coils around a central pillar, termed the modiolus. The length of the tube
is from 28 to 30 mm., and its diameter, near the base of the cochlea, 2 mm. Its
coils are distinguished by the terms basal, central, and apical ; the first, or basal
coil, gives rise to the promontory on the labyrinthic wall of the tympanic cavity.
The modiolus is about 3 mm. in height, and diminishes rapidly in diameter from
base to apex, while its tapered extremity fails to reach the cupula by a distance of
1 mm. Its base corresponds with the area cochlesB on the fundus of the internal
acoustic meatus, and exhibits the tractus spiralis foraminosus, which transmits the
nerves for the basal and central coils of the cochlea and the foramen centrale, which
gives passage to the nerves for the apical coil. The foramina of the tractus spiralis
foraminosus traverse the modiolus, at first parallel to its long axis, but, after a
1 In the following description the cochlea is supposed to be placed on its base.
OSSEOUS LABYRINTH.
845
varying distance, they bend outwards to reach the attached edge of the lamina
spiralis ossea, where they expand and form by their apposition a spiral canal, the
canalis spiralis cochleae, which lodges the ganglion spirale cochleae. From this spiral
canal numerous small foramina, for the transmission of vessels and nerves, pass
outwards to the free edge of the lamina spiralis ossea. The lamina spiralis ossea,
a thin, flat shelf of bone, winds round the modiolus like the thread of a screw, and,
projecting about half-way into the cochlear tube, incompletely divides it into two
passages an upper is named the scala vestibuli ; a lower, the scala tympani. The
lamina spiralis ossea begins at the floor of the vestibule, near the fenestra cochleae,
and ends close to the apex of the cochlea in a sickle-shaped process, the hamulus
laminae spiralis, which assists to bound an aperture named the helicotrema. In the
Section through promontory
Lamina spiralis
ossea secundaria
Fissura vestibuli
Lamina spiralis ossea
Canalis centralis
Canalis spiralis cochleae
Modiolus
Scala vestibuli
Lamina spiralis ossea
Scala tympani
Tractus spiralis
foraminosus
Recessus cochlearis of vestibule Internal acoustic meatus
FIG. 718. SECTION OF BONY COCHLEA.
basal coil the upper surface of the lamina spiralis ossea forms almost a right angle
with the modiolus, but the angle becomes more and more acute on ascending the
tube. In the lower half of the basal coil a second smaller bony plate, the lamina
spiralis secundaria, projects from the outer wall of the cochlea towards the lamina
spiralis ossea, without, however, reaching it. If viewed from the vestibule the
slit-like fissura vestibuli, already referred to (p. 844), is seen between the two
laminae. A membrane, the membrana basilaris, stretches from the free edge of the
lamina spiralis ossea to the outer wall of the cochlea, and completes the septum
between the scala vestibuli and scala tympani, but the two scales communicate
with each other through the opening of the helicotrema at the apex of the cochlea.
The scala tympani begins at the fenestra cochleae, which is closed by the secondary
tympanic membrane (vide p. 833). At the commencement of the scala tympani
a crest, termed the crista semilunaris, stretches
from the attached margin of the lamina Area vestibuiaris superior
spiralis ossea towards the orifice of the fenestra
cochleae. Close to this crest is seen the inner
orifice of the aquaeductus cochleae, a canal
measuring from 10 to 12 mm. in length, and
opening on the under surface of the petrous
part of the temporal bone medial to the
fossa jugularis. Through it a communica-
tion is established between the scala tympani
and the subarachnoid cavity, and through
it, also, a small vein passes to join the inferior
petrosal sinus. The scala vestibuli, the higher
Area n. facialis
Foramen singulare
Tractus spiralis
foraminosus
Foramen centrale
of the two passages, begins in the vestibule ;
its diameter in the basal coil is less than that Area vestibularis infcrior
of the scala tympani, but in the upper coils
it exceeds that of the scala tympani.
Meatus Acusticus Internus. It is
convenient, at this stage, to study the fundus of the internal acoustic meatus,
which has been referred to as forming the medial wall of the vestibule and the
AREAS BY THE CRISTA TRANSVERSA.
846
THE OEGANS OF SENSE.
base of the modiolus. It is divided by a transverse ridge, the crista transversa,
into two parts an upper or fossula superior and a lower or fossula inferior. The
anterior part of the fossula superior is termed the area n. facialis and exhibits a
single large opening, the commencement of the facial canal, for the transmission of
the facial nerve. Its posterior part is named the area vestibularis superior, and is
perforated by the nerves for the utricle and the ampullae of the superior and lateral
semicircular ducts. The anterior part of the fossula inferior is termed the area
cochleae, and consists of the canalis centralis and the surrounding tractus spiralis
foraminosus, for the passage of the nerves to the cochlea. Behind the area cochleae,
and separated from it by a ridge, is the area vestibularis inferior, which is pierced
by the nerves to the saccule ; at the posterior part of the fossula inferior is the
foramen singulare, which gives passage to the nerves for the ampulla of the posterior
semicircular duct.
Recessus utriculi
Saccule
semicircular duct
Ampulla of lateral
duct
Ductus
cochlearis
Ductus reunions
Ductus
endolymphaticus
Ampulla of posterior duct
Saccus endolymphaticus
FIG. 720. DIAGRAMMATIC REPRESENTATION OF THE DIFFERENT
PARTS OF THE MEMBRANOUS LABYRINTH.
Crus commune
Ductus
utriculosaccularis
Sinus inferior
LABYEINTHUS MEMBRANACEUS.
The membranous labyrinth (Fig. 720) is contained within the bony labyrinth,
but does not nearly fill it. It contains a fluid termed endolymph, while the interval
between it and the bony labyrinth is named the perilymphatic space, and is occupied
by a fluid termed perilymph. The perilymphatic space in the vestibule is continuous
behind with the perilymphatic space of the semicircular canals, and opens in front
into the scala vestibuli. At the apex of the cochlea it is continuous, through the
helicotrema, with the scala
tympani, which is shut off
of superior from the tympanic cavity
by the secondary tympanic
membrane. The perilym-
phatic space is prolonged
into the aquseductus coch-
leae, at the extremity of
which it communicates
with the subarachnoid
cavity. The ductus semi-
circulares and the ductus
cochlearis follow the course
and lie along the inner surface of the outer walls of the corresponding bony
tubes. The bony vestibule, on the other hand, contains two chief membranous
structures, the utricle and saccule. The former receives the extremities of the
ductus semicirculares, whilst the latter communicates with the ductus cochlearis.
Moreover, the cavities of the utricle and saccule are indirectly connected, and
thus all parts of the membranous labyrinth communicate with each other, and
the endolymph is free to move from one portion to another. The vestibule
contains also the ductus endolymphaticus and the commencement of the due tut
cochlearis.
Utriculus. The utricle, the larger of the two sacs (Fig. 720), occupies tht
postero-superior portion of the vestibule. Its highest part, or recessus utriculi, lie*
in the recessus ellipticus and receives the ampullae of the superior and latera
semicircular ducts. Its central part receives on its lateral aspect the non
ampullated end of the lateral semicircular duct, and is prolonged upwards anc
backwards as the sinus superior, into which the crus commune of the superior anc
posterior semicircular ducts open. The ampulla of the posterior semicircular due'
opens into the lower and medial part, or sinus inferior. The floor and anterior wal
of the recessus utriculi are thickened to form the macula acustica utriculi, to whicl
the utricular fibres of the acoustic nerve are distributed. Whitish in colour, am
of an oval or nearly rhombic shape, this macula measures 3 mm. in length am
2-3 mm. in its greatest breadth.
Sacculus. The saccule occupies the recessus sphaericus, in the lower and anterio
part of the vestibule (Fig. 717). Smaller than the utricle, it is of an oval shape an<
measures 3 mm. in its longest, and about 2 mm. in its shortest diameter. It present
MEMBEANOUS LABYKINTH.
847
_ Wall of
^T bony canal
anteriorly an oval, whitish thickening, the macula acustica sacculi. This has a
breadth of about 1'5 mm., and to it the saccular fibres of the acoustic nerve are
distributed. The superior extremity of the saccule is directed upwards and back-
wards, and forms the sinus utricularis sacculi, which abuts against, but does not fuse
with, the wall of the utricle. From the lower part of the saccule a short canal,
the ductus reuniens (Henseni), opens into the ductus cochlearis, a short distance
in front of its vestibular extremity. A second small channel, the ductus
endolymphaticus, is continued from the posterior part of the saccule, and, passing
between the utricle and the medial wall of the vestibule, is joined by a small canal,
the ductus utriculosaccularis, which arises from the medial side of the utricle. It
then enters and traverses the aquaeductus vestibuli and ends, under the dura mater
on the posterior surface of the petrous part of the temporal bone, in a dilated
blind extremity, termed the saccus endolymphaticus ; this, according to Riidinger, is
perforated by minute foramina, through which the endolymph may pass into the
meningeal lymphatics.
The vestibule also contains the vestibular extremity of the ductus cochlearis,
which lies immediately below the saccule in the recessus cochlearis.
The walls of the utricle and saccule are composed of connective tissue which
blends with the periosteal lining of the vestibule. It is modified medially to form
a homogeneous membrana propria, which is covered with a layer of pavement
epithelium and is thickened at the maculae acusticae. Towards the periphery
of the maculae the epithelium is cubical, while on them it is columnar.
The structure of the maculae in the utricle and saccule is practically the
same ; two kinds of cells are found, viz., (a) supporting cells, and (&) hair cells. The
supporting cells are some-
what fusiform, each con-
taming, >n ear its middle, a
nucleus. Their branched,
deep extremities are at-
tached to the membrana
propria; their free ends
lie between the hair cells
and form a thin inner
limiting cuticle. The
hair cells are flask-shaped
and do not reach the
membrana propria, but
end in rounded extremi-
ties which lie between
the supporting cells.
Each contains, at its
deepest part, a large
nucleus, the rest of the
cell being granular and
pigmented. From the
free end of each there
projects a stiff, hair-like
process, which, on the
application of reagents,
splits into several finer filaments. The nerve-fibres pierce the membrana propria,
and ramify around the deep extremities of the hair cells (Fig. 722). A collection
of small, rhombic crystals of carbonate of lime, termed otoconia, adheres to each
of the maculae.
Ductus Semicirculares. The semicircular ducts are * elliptical on transverse
section (Fig. 721), and are attached to the walls of the bony canals. The convex
wall of each duct is fixed to the periosteal lining of the canal, whilst the opposite
part is free, except that it is connected by irregular ligamentous bands, which pass
through the perilymphatic space to the bony wall. Like the bony canals, each
of the semicircular ducts is dilated at one extremity into a membranous ampulla,
Lumen of semi-
~v circular duct
Periosteum
FIG. 721. TRANSVERSE. SECTION OF HUMAN SEMICIRCULAR
CANAL AND SEMICIRCULAR DUCT (Riiclinger).
848
THE OKGANS OF SENSE.
which is especially developed towards the concavity of the tube. The membranous
ampullae nearly fill the corresponding portions of the bony tubes, but the diameter
of the semicircular ducts is only about one-fourth of that of the osseous canals.
Each semicircular duct consists of three layers, viz. : (a) an outer vascular
and partly pigmented fibrous stratum which fixes the duct to the bony wall;
Perilymphatic space
Macula acustica
Cuticular wall
Fibres of the ramus recessus utriculi
FIG. 722. VERTICAL SECTION OF THE WALL OF THE RECESSUS UTRICULI WITH THE MACULA ACUSTICA
AND THE BUNDLES OF NERVE FIBRES.
(5) an intermediate, transparent tunica propria, presenting a number of papilliform
elevations which project towards the lumen. The fibrous layer and tunica propria
are thinnest along the attached surface of the duct, and in this region also the
papilliform elevations are absent; (c) an internal epithelial layer, composed of
pavement cells. In the ampullae the tunica propria is much thickened, and projects
into the cavity as a transverse elevation, termed the septum transversum, which,
when seen from above, is somewhat fiddle-shaped; its most prominent part is
covered by acoustic epithelium forming the crista ampullaris, at each end of which
is a half-moon-shaped border of small columnar cells, the planum semilunatum. The
cells covering the crista ampullaris consist of supporting cells and hair cells, and
are similar in their arrangement to those in the maculae of the utricle and saccule ;
the hairs of the hair cells are, however, considerably longer, and project as far as
the middle of the ampullary lumen. In fresh specimens they appear to end free,
but in hardened preparations are seen to terminate in a soft, clear, dome -like
structure, the cupula terminalis, which is striated, the striae converging towards its
concavity. The nerves form arborisations around the bases of the hair cells.
SCALA VESTIBULI
Membrana vestibularis
Membrana tectoria s
Sulcus spiralis
internus
Limbus laminae
spiralis
Stria
vascularis
i llL.j_V/__ Ligamentum
spirale
/ Ma Sulcus spiralis
externus
Crista basilaris
Inner hair cell \
Outer hair cells y, ^
Membrana basilaris
SCALA TYMPANI
FIG. 723. SECTION ACROSS THE DUCTUS COCHLEARIS (Retzius).
Ductus Cochlearis. The ductus cochlearis (O.T. membranous cochlea or seal;
media) is closed at both of its extremities; the lower extremity occupies th<
recessus cochlearis of the vestibule and communicates with the saccule through th
ductus reuniens. It forms a spirally arranged canal inside the cochlea, and a
the
DUCTUS COCHLEAEIS.
849
Outer attachment of
the membrana
vestibularis
Stria vascularis
apex of the latter its upper extremity, the lagena, or caecum capulare, is
fixed to the cupula and partly bounds the helicotrema. As already stated, the
membrana basilaris extends from the free edge of the lamina spiralis ossea to the
outer wall of the cochlea. A second, more delicate membrane, the membrana
vestibularis (O.T. membrane of Reissner), stretches from the thickened periosteum
covering the upper surface of the lamina spiralis ossea to the outer cochlear wall,
some little distance above the external attachment of the membrana basilaris. A
canal is thus enclosed between the underlying scala tympani and the overlying
scala vestibuli, and constitutes the ductus cochlearis. Triangular on transverse
section, the duct possesses a roof, an outer wall, and a floor, and is lined throughout
with epithelium and filled with endolymph. On its floor the epithelium is greatly
modified, and there the endings of the cochlear nerve are found.
The roof or vestibular wall of the ductus cochlearis is formed by the mem-
brana vestibularis, a delicate, nearly homogeneous membrane, covered on each
surface by a layer of epithelium. Its entire thickness is about 3 p.
The outer wall of the ductus cochlearis (Fig. 724) consists of the periosteal
lining of the bony cochlea, which, however, is thickened and greatly modified to
form the ligamentum spirale cochleae. Occupying the whole outer wall, this liga-
ment projects inwards inferiorly as a
triangular prominence, the crista basilaris,
to which the outer edge of the membrana
basilaris is attached. In the upper part
of the ligamentum spirale the periosteum
is of a reddish-yellow colour, and con tains,
immediately under its epithelial lining,
numerous small blood-vessels and capil-
lary loops, forming the stria vascularis.
The lower limit of this stria is bounded
by a prominence, the prominentia spiralis,
in which is seen a vessel, the vas pro-
minens, and between this prominence
and the crista basilaris is a concavity,
the sulcus spiralis externus. The height
of the outer wall diminishes towards the
apex of the cochlea.
The floor or tympanal wall of the
ductus cochlearis is formed by the peri-
osteum covering that portion of the
lamina spiralis ossea which is situated
to the outer side of the membrana ves-
tibularis, and by the membrana basilaris,
which stretches from the free edge of
the lamina spiralis ossea to the crista
basilaris. On the inner part of the
membrana basilaris the complicated
structure termed the organon spirale
(O.T. organ of Corti) is situated. The
lamina spiralis ossea consists of two
plates of bone, between which are placed
the canals for the branches of the cochlear
nerve. On the upper plate the perios-
teum is thickened and modified to form
the limbus laminae spiralis, the outer ex-
tremity of which forms a C-shaped con-
cavity, the sulcus spiralis interims. The
portions of the limbus which project
above and below this concavity are
ermed respectively the labium vestibulare and labium tympanicum. The latter is
perforated by about 4000 small apertures, the foramina nervosa, for the transmission
55
FIG. 724. TRANSVERSE SECTION THROUGH OUTER
WALL OF DUCTUS COCHLEARIS (Schwalbe).
850
THE OKGANS OF SENSE.
of the cochlear nerves, and is continuous with the membrana basilaris. The upper
surface of the labium vestibulare presents a number of furrows crossing each other
nearly at right angles, and intersecting a series of elevations which, at the free
margin of the labium, form a row of tooth-like structures, about 7000 in number,
the auditory teeth of Huschke. Covering the limbus is a layer of apparently
squamous epithelium ; the deeper protoplasmic portions of the cells, however, with
their contained nuclei, lie in the intervals between the elevations and auditory
teeth. This layer of epithelium is continuous above with that covering the under
surface of the membrana vestibularis and below with that which lines the sulcus
spiralis internus.
Membrana Basilaris. The inner part of this membrane is thin, and supports
the organon spirale ; it is named the zona arcuata, and reaches as far as the foot-
plate of the outer rod of Corti. Its outer part, extending from the foot-plate of
the outer rod of Corti to the crista basilaris, is thicker and distinctly striated,
and is termed the zona pectinata. The substantia propria of the membrane is
almost homogeneous, but exhibits, in its deeper part, numerous fibres. These fibres
are most distinct in the zona pectinata, and number, according to Ketzius, about
24,000. Covering the under surface of the membrana basilaris is a layer of con-
nective tissue, containing, in its inner part, small blood-vessels ; one of these is
larger than the others and lies below the tunnel of Corti, and is named the vas
spirale. The width of the membrana basilaris increases from 210 //, in the basal
coil to 360 //. in the apical coil.
Organon Spirale (O.T. Organ of Corti) (Fig. 725). Placed upon the inner
portion of the membrana basilaris, the organon spirale consists of an epithelial eminence
which extends along the entire length of the ductus cochlearis, and comprises the
following structures, viz. : (1) Corti's rods or pillars, (2) hair cells (inner and outer),
(3) supporting cells of Deiters, (4) the cells of Hensen and Claudius, (5) the lamina
retieularis, and (6) the membrana tectoria.
The rods of Corti form two rows, inner and outer, of stiff, pillar-like structures, and
each rod presents a base or foot-plate, an intermediate elongated portion, and an upper
Outer rod of Corti
Inner rod of Corti
Inner hair cell
Hensen's stripe
Membrana tectoria
Sulcus spiralis
Limbus laminaj internus
spiralis
Outer hair cells
Cells of Hensen
Membrana basilaris
Cells of Claudius
*&&#* ^
Cells of Deiters
Vas spirale Space of Nuel
Tunnel of Corti
FIG. 725. TRANSVERSE SECTION OF THE ORGANON SPIRALE FROM THE CENTRAL COIL
OF THE DUCTUS COCHLEARIS (Ketzius).
end or head. The bases of the two rows are planted on the membrana basilaris son:
little distance apart. The intermediate portions of the rods incline towards each oth(
and the heads come into contact, so that, between the two rows above and the membraii
basilaris below, a triangular tunnel, the tunnel of Corti, is enclosed ; this tunnel increas<
both in height and width on passing towards the apex of the cochlea. The inner roc
number nearly 6000, and the head of each resembles somewhat the proximal end of tl
ulna, presenting externally a deep concavity for the reception of a corresponding coi
vexity on the head of the outer rod. The part of the head which overhangs this concavil
is prolonged outwards, under the name of the head-plate, and overlaps the head of tl
SPIKAL OEGAN OF COKTI. 851
i outer rod. The expanded bases of the inner rods are situated on the innermost portion
of the membrana basilaris, immediately to the outer side of the foramina nervosa of the
labium tympanicum. The intermediate parts of the inner rods are sinuously curved, and
. form with the membrana basilaris, an angle of about 60. The outer rods number about
4000, and are longer than the inner, especially in the upper part of the cochlea. They are
! more inclined towards the membrana basilaris, and form with it an angle of about 40. The
head of each is convex internally, to fit the concavity on the head of the inner rod, and is pro-
' longed outwards as a plate, the phalangeal process, which becomes connected with the lamina
reticularis ; in the head is an oval body which has an affinity for certain reagents. The
main part of each rod consists of a nearly homogeneous material, which is finely striated.
At the bases of the rods, on the side next Corti's tunnel, is a nucleated mass of protoplasm
which reaches as far as the heads of the rods, and covers also the greater part of the
tunnel floor ; this protoplasm may be regarded as the undifferentiated part of the cell from
which the rod was developed. Slit-like intervals, for the transmission of nerves, exist
between the intermediate portions of adjacent rods.
Hair Cells. These, like Corti's rods, form two sets, inner and outer. The former
i consists of a single row lying immediately internal to the inner rods the latter of three,
or, it may be, four rows placed to the outer side of the external rods. The inner hair
cells are about 3500 in number ; the diameter of each is greater than that of an inner
rod, and so each inner hair cell is supported by more than one rod. Somewhat oval in
shape, their free extremities are surmounted by about twenty fine hair-like processes,
arranged in the form of a crescent, with its concavity directed inwards. The deep end
of the cell contains a large nucleus and is rounded ; it reaches only about half-way
down the rod, and is in contact with the arborisations of the nerve terminations. To
the inner side of this row of hair cells are two or three rows of elongated columnar cells,
which act as supporting cells, and are continuous with the low columnar cells lining the
sulcus spiralis internus. The outer hair cells number about 12,000, and form three
rows in the basal coil and four rows in the upper two coils, although in the higher
coils the rows are not so regularly arranged. The rounded free ends of the hair cells
support some twenty hairlets arranged in the form of a crescent, opening inwards. Their
deep extremities reach about half-way to the membrana basilaris, and are in contact with
the nerve arborisations.
Alternating with the rows of the outer hair cells are the rows of Deiters' supporting
cells, the lower extremities of which are expanded on the membrana basilaris, whilst their
upper ends are tapered ; the nucleus is placed near the middle of each cell, and, in addition,
each cell contains a bright, thread-like structure called the supporting fibre. This fibre
is attached by a club-shaped base to the membrana basilaris, and expands, at the free
end of the cell, to form a phalangeal process of the membrana reticularis.
The cells of Hensen, or outer supporting cells, consist of about half a dozen rows,
immediately outside Deiters' cells, and form a well-marked elevation on the floor of the
ductus cochlearis. Their deep extremities are narrow and attached to the membrana
basilaris, while their free ends are expanded ; each cell contains a distinct nucleus and
some pigment granules. The columnar cells, situated externally to the cells of Hensen,
cover the outer part of the zona pectinata, and are named the cells of Claudius. A space,
the space of Nuel, exists between the outer rods of Corti and the neighbouring row of
hair cells ; it communicates internally with Corti's tunnel, and extends outwards between
the outer hair cells as far as Hensen's cells.
The lamina reticularis is a thin cuticular structure which lies over the organon
spirale, and extends from the heads of the outer rods as far as Hensen's cells, where it
ends in a row of quadrilateral areas which form its outer border. It consists of two or
three rows of structures, named phalanges, which are elongated cuticular plates resembling
in shape the digital phalanges. The innermost row is formed by the phalangeal processes
of the heads of the outer row of Corti's rods ; the succeeding row, or rows, represent the
expanded upper ends of Deiters' supporting cells. The number of rows of phalanges,
therefore, varies with the number of rows of outer hair cells and the alternating cells of
i Deiters. The free ends of the hair cells occupy the somewhat circular apertures between
, the constricted middle portions of the phalanges.
The membrana tectoria (Fig. 725) is an elastic membrane overlying the sulcus spiralis
nternus and the organon spirale. Attached, by its inner end, to the limbus laminse
spiralis, near the lower edge of the membrana vestibularis, it reaches outwards as far as
the outer row of hair cells. Its inner portion is thin and overlies the auditory teeth of
Huschke. Its outer part is thickened, but becomes attenuated near its external border,
which, according to Retzius, is attached to the outer row of Deiters' cells. Its lower edge
852
THE OKGANS OF SENSE.
presents a firm, homogeneous border, and opposite the inner row of hair cells contains a
clear, spirally arranged band, named Hensen's stripe.
Nervus Acusticus (Fig. 726). The acoustic nerve divides within the internal
acoustic meatus into an anterior or cochlear and a posterior or vestibular nerve.
Sinus superior
Ampulla of lateral duet
Ampulla of superior duct
Macula acustica utriculi
Macula acustica sacculi
Vestibular nerve
Nervus facialis
Cochlear nerve - .
Superior semicircular duct
Lateral semicircular duct
Posterior semicircular duct
Ligamentum
spirale
Membrana basilaris
Brandies of cochlear
nerve to organon spirale
Branch of cochlear
nerve to ampulla of posterior duct
Ampulla of posterior duct
Sinus inferior
Ductus endolymphaticus
Spiral fibres
Ganglion spirale
Nerve-fibres which pass out
between the two layers of the
lamina spiralis ossea
Ductus reunions
FIG. 726. MEMBRANOUS LABYRINTH OF A FIVE MONTHS' FCETUS,
viewed from its postero- medial aspect (Retzius).
N. Cochleae. The cochlear nerve is distributed to the hair cells of the organoc
spirale, the branches for the basal and middle coils entering the foramina in the
tractus spiralis foraminosus, those for the apical coil running in the canalis cen trails
of the modiolus. Extending through the bony canals of the modiolus, the nerve-
fibres radiate outwards between the lamellae of the lamina spiralis ossea. Contained
in the spiral canal of the modiolus, neaj
the attached margin of the lamina, is e
ganglion of bipolar nerve-cells whicl
winds spirally round the modiolus, anc
is named the ganglion spirale (O.T
ganglion of Corti) (Fig. 727) ; the fibre:
of the nerve arise from the cells of thii
ganglion. Beyond the ganglion spiral*
the nerve-fibres extend outwards, at firs
in bundles, and then in a more or les
continuous sheet, from the outer edg'
of which they are again collected int<
bundles, which pass through th
foramina nervosa of the labium tym
panicum. Beyond this they appea
as naked axis -cylinders, and, turning in a spiral manner (inner or first spira
fasciculus), send fibrillae towards the inner row of hair cells. Other fibrils ru:
between the inner rods and form a second spiral fasciculus in Corti's tunne
from which fibrils extend outwards across the tunnel, and, passing betwee
the outer rods, enter Nuel's space. They form a spiral fasciculus on the inne
aspect of each row of Deiters' cells, and fibrillse pass from these fasciculi toward
the bases of the outer hair cells.
The cochlear nerve gives off a vestibular branch, the terminal filaments <
FIG. 727. PART OF COCHLEAR NERVE, highly
magnified (Henle).
whic
DEVELOPMENT OF LABYEINTH.
853
which go through the foramina in the recessus cochlearis and are distributed to the
hair cells of the vestibular part of the ductus cochlearis. On this vestibular branch,
close to its origin from the cochlear nerve, is a minute ganglion (Bcettcher).
N. Vestibuli. The vestibular nerve is distributed to the utricle, the saccule, and
the ampullae of the semicircular ducts. It divides into three branches, superior,
inferior, and posterior, and each of these splits into filaments which pass through
foramina in the fundus of the internal acoustic meatus. The filaments from the
superior branch go through the foramina in the area vestibularis superior and
supply the macula of the utricle and the cristae ampullares of the superior and
lateral semicircular ducts ; those from the inferior branch run through the fora-
mina in the area vestibularis inferior to the macula of the saccule. The posterior
branch passes through the foramen singulare, and its filaments, six to eight in
number, are distributed to the crista ampullaris of the posterior semicircular duct.
Ganglion Vestibular e. On the trunk of the vestibular nerve, within the
internal acoustic meatus, is a ganglion, the vestibular ganglion, of bipolar nerve cells ;
the fibres of the nerve arise from the cells of this ganglion. Sometimes the
vestibular nerve divides on the proximal side of the ganglion and the latter is then
split into three parts, one on each of the three branches of the nerve.
Vessels of the Internal Ear. The internal auditory artery, a branch of the basilar, enters the
internal acoustic meatus and divides into vestibular and cochlear branches. The vestibular branch
supplies the soft tissues in the vestibule and semicircular canals, each canal receiving two arteries,
which, starting from opposite extremities of the canal, anastomose on the summit of the arch.
The cochlear branch divides into numerous twigs, which enter the foramina in the tractus
spiralis foraminosus, and run outwards in the lamina spiralis ossea to reach the soft structures ;
the largest of these arteries runs in the canalis centralis. The stylo-mastoid artery also supplies
some minute branches to the cochlea. Siebenmann describes the internal auditory artery as
dividing into three branches, viz. : (1) anterior vestibular, (2) cochlear proper, and (3) vestibulo-
cochlear. The veins from the cochlea and vestibule unite, at the bottom of the meatus, with the
veins from the semicircular canals to form the internal auditory vein, which may open either into
the posterior part of the inferior petrosal sinus or into the transverse sinus. Small veins also pass
through the aquseductus cochleae and aqueeductus vestibuli, the former opening into the inferior
petrosal sinus or into the internal jugular vein, the latter into the superior petrosal sinus.
DEVELOPMENT OF LABYRINTH.
The epithelial lining of the labyrinth is derived from an invagination of the cephalic
ectoderm, termed
the auditory pit,
which appears Auditory pit
opposite the hind
brain immedi-
ately above the
first visceral cleft.
The mouth of the
pit is closed by
the growing to-
gether of its mar-
gins, and it then
assumes the form
of a hollow
vesicle, the otic
vesicle, which
severs its con-
nexion with the
ectoderm and
sinks into the
subjacent meso-
derm. The vesicle
soon becomes
pear-shaped; and
its dorsal taper-
ing part rapidly
lengthens into a recess, the recessus labyrinth!, which later forms the ductus and saccus
Otic vesicle
Rudiment of ductus cochlearis-
FIG. 728. SECTIONS THROUGH THE EEGION OF THE HIND BRAIN OF FCETAL BABBITS
(to illustrate the development of the labyrinthine epithelium).
In A the ectoderm is invaginated to form the auditory pit ; in B the auditory pit is closed
and detached from the ectoderm, forming the otic vesicle ; while C shows a further
stage in the development of the vesicle.
854
THE OKGANS OF SENSE.
Recess us
labyrinth!
endolymphaticus (see note, p. 79). About the fifth week, the lower part of the vesicle is
prolonged forwards as a diverticulum, the future ductus cochlearis. This is at first straight,
but as it elongates it curves on itself,
so that at the twelfth week all
three coils are differentiated. From
the upper part of the vesicle the
semicircular ducts are developed,
semicircular anc ^ a PP ear as three hollow, disc-like
duct
Posterior
semicircular
duct
Lateral
semicircular
duct
Cochlear
part
Cochlea -
Utricle
Saccule
evaginations ; the central parts of
the walls of each disc coalesce and
disappear, leaving only the peri-
pheral ring or canal. The three
ducts are free about the beginning
of the second month, and are de-
veloped in the following order, viz. :
superior, posterior, and lateral. The
intermediate part of the otic vesicle
represents the vestibule, and is
divided by a constriction into an
anterior part, the saccule, communi-
cating with the ductus cochlearis,
and a posterior portion, the utricle,
receiving the extremities of the
semicircular ducts. The constric-
tion extends for some distance into
the ductus endolymphaticus, and
thus the utricle and saccule are connected by a Y-shaped tube. Another constriction
makes its appearance between the saccule and the vestibular end of the ductus cochlearis
and forms the canalis reuniens. The epithelial lining is at first columnar, but becomes
cubical throughout the whole labyrinth, except opposite the terminations of the acoustic
nerve, where it forms the columnar epithelium of the maculae of the utricle and saccule, of
the cristse ampullae, and of the organon spirale. On the floor of the ductus cochlearis two
ridges appear, of which the inner forms the limbus laminae spiralis, whilst the cells of
the outer become modified to form the rods of Corti, the hair cells, and the supporting
cells of Deiters and Hensen.
The mesoderm surrounding the otic vesicle is differentiated into: (1) a fibrous layer,
the. wall of the membranous labyrinth ; (2) a cartilaginous capsule, the future petrow
bone ; and (3) an intervening layer of gelatinous tissue, which is ultimately absorbed,
leaving the perilymphatic space between the bony and membranous labyrinths.
The development of the external and middle parts of the ear are described or
pp. 50-53.
FIG. 729.
A, Left labyrinth of a human embryo of about four weeks ; B,
Left labyrinth of a human embryo of about five weeks (from
W. His, jun.).
OKGANON GUSTUS.
The peripheral gustatory organ consists of groups of modified epithelial cells
termed calyculi gustatorii or taste buds, found on the tongue and in its immediat<
neighbourhood.
Taste buds are present in large numbers around the circumference of th<
papillae vallatae, while some are found also on their opposing walls (Fig. 730). The;;
are very numerous over the foliate papillae, which correspond with the papilla
foliatae of the tongue of the rabbit, and are found also over the posterior part an<
sides of the tongue, either on the papillae fungiformes or throughout the stratifie<
epithelium. They exist, also, on the oral surface of the velum palatinurn and or
the posterior surface of the epiglottis.
Structure of Taste Buds (Fig. 731). The taste buds are oval or flask-shapec
and occupy nests in the stratified epithelium of the regions mentioned. The dee
extremity of each is expanded and rests upon the corium ; the free end is perfoi
ated by a minute pore, termed the gustatory pore. They consist of two kinds (
epithelial cells (a) supporting cells, and (&) gustatory cells (Fig. 732). Tl:
supporting cells are elongated, nucleated spindles, and are mostly arranged like t]
staves of a cask to form the outer envelope of the bud ; but some are found in tl
OEGANS OF TASTE. 855
jrior of the bud, amongst the gustatory cells. The gustatory cells occupy the centre
^ig^
g^TT-.i > v^r".";
A
FIG. 730.
A, Section through a papilla vallata of human tongue. B, Section through a part of the papilla foliata
of a rabbit.
1. Papilla. 2. Vallum. 3. Taste buds. 4. Papillae. 5. Taste buds. 6. Duct of serous gland.
the bud, and each consists of a nucleated cell-body, prolonged into a peripheral
Gustatory hairs
Supporting
cells
K^
FIG. 731.
quarter surface view of taste bud from the B, Vertical section of taste bud from the papilla
papilla foliata of a rabbit (highly magnified). foliata of a rabbit (highly magnified).
and a central process. The peripheral process is rod-like and almost hyaline, and
terminates at the gustatory pore in a slender
filament, the gustatory hair. The central
process passes towards the deep extremity of
the bud, where it ends free, as a single or
branched varicose filament.
Nerves of Taste. The nerve supplying
the taste buds over the anterior part of the
tongue is the chorda tympani, which is de-
rived from the sensory root of the facial
nerve ; that for the posterior part is the glosso-
pharyngeal. The nerve fibrils, having lost
their medullary sheaths, ramify partly be-
tween the gustatory cells and partly amongst
the supporting cells of the taste buds.
The ducts of Ebner's glands open into the
bottom of the valleys surrounding the papillae
vallatae, and the serous-like secretion of these glands probably washes the free
FIG. 732. ISOLATED CELLS FROM TASTE BUD
OF RABBIT (Engelmann).
a, Supporting cells. b, Gustatory cells.
856
THE SKIN OK INTEGUMENT.
hair-like extremities of the gustatory cells, and so renders them ready to be
stimulated by successive substances. It should be added that there is a close
association between the senses of smell and taste. This can be best appreciated by
considering the defective taste perceptions resulting from inflammatory conditions
of the nasal mucous membrane, or the common practice of holding the nose in
order to minimise the taste of nauseous drugs.
The development of the tongue is described on pp. 45-46.
INTEGUMENTUM COMMUNE.
Duct of
sweat gland
Ha
Hair follicle
Glomerulus
of sweat
gland
The integument or skin covers the body, and is continuous, at the orifices on
its surface, with the mucous lining of its alimentary and other canals. It contains
the peripheral terminations of many of the sensory nerves, and serves as an organ
of protection to the deeper tissues. It is the chief factor in the regulation of the
body temperature, and by means of the sudoriferous and sebaceous glands, which
open on its free
surface, consti-
tutes an important
excretory struc-
ture. Its super-
ficial layers are
modified to form
appendages in the
shape of hairs and
nails.
The skin is
very elastic and
resistant, and its
colour, determined
partly by its own
pigment and
partly by that of
the blood, is deeper
on exposed parts
and in the regions
of the genitals,
axillae, and mam-
mary areolse, than
elsewhere. The
colour varies also
with race and age,
the different races
of the world being
roughly classified,
according to the
colour of their
skin, into the
three groups of white, yellow, and black. Pinkish in colour in childhood, the skin
assumes a yellowish tinge in old age, while in certain diseases (e.g. icterus and
melasma Addisonii) the colour undergoes marked alteration.
The surface of the skin is perforated by the hair follicles and by the ducts of the
sudoriferous and sebaceous glands, and on the palms, soles, and flexor aspect of the
digits it presents numerous permanent ridges, the cristse cutis, which correspond
with rows of underlying papillae. Over the terminal phalanges these ridges form
distinctive patterns, which are retained from youth to old age, and are utilised for
purposes of identification. Ketinacula of the skin are seen in the neighbourhood
Papilla of hair
FIG. 733. VERTICAL SECTION OF THE SKIN (schematic).
Oblique section through
a Pacinian corpuscle
STEUCTURE OF THE SKIN.
857
of the joints, and it can be thrown into wrinkles by the contraction of the sub-
cutaneous muscles, where those exist. Over the greater part of the body it is freely
movable ; but on the scalp and lateral surfaces of the auriculae, as well as on the
palms and soles, it is bound down to the subjacent tissues.
The skin consists of two strata, viz. : a deep, termed the corium, and a superficial,
the epidermis (Fig. 734).
The corium or cutis vera is derived from the embryonic mesoderm, and consists
essentially of a felted interlacement of connective tissue and elastic fibres. In its
deeper part, or stratum reticulare, the fibrous bundles are coarse and form an open
network, in the meshes of which are vessels, nerves, pellets of fat, hair follicles,
and glands. This reticular stratum passes, as a rule, without any line of demarca-
tion, into the panniculus adiposus or subcutaneous fatty tissue, but in some parts it
rests upon a layer of
striped or unstriped
muscular fibres the
latter in the case of the
scrotum. In the super-
ficial layer, or stratum
papillare, of the corium,
the connective tissue-
bundles are finer and
form a close network.
Projecting from its
superficial surface are
numerous finger -like,
single, or branched ele-
vations, termed papillae
(Fig. 734), which are
received into corre-
spending depressions
. on the under surface of
the epidermis. These
papillae vary in size,
being small on the eye-
! lids, but large on the
palms and soles, where
they may attain a
length of 225 u, and
Stratum lucidum
Stratum
granulosum
Blood-vessels
and nerves
EPIDERMIS AND PAPILLA OF CORIUM
Where they produce the Fia ^.-VERTICAL SECTION
permanent curved
ridges already referred' to. Each ridge usually contains two rows of papillae, between
which the ducts of the sudoriferous glands pass to reach the surface. The papillae
consist of fine connective tissue and elastic fibres, mostly arranged parallel to the
long axis of the papillae ; the majority contain capillary loops, but some contain the
terminations of nerves. The superficial surface of the corium is covered with a
thin, homogeneous basement membrane.
The epidermis or cuticle is derived from the embryonic ectoderm and covers
the corium. Its thickness varies in different parts of the body and ranges from
3 mm. to 1 mm. or more ; it is thickest on the palms of the hands and soles of
the feet, and thinnest on the eyelids and penis. It is non-vascular and consists of
stratified epithelium ; its superficial layers are modified to. form the stratum corneum,
which may be separated by maceration or blistering from the deeper, softer portion,
or stratum mucosum (Malpighi). The epidermis consists from within' outwards of
the following five strata (Fig. 734) :
The stratum germinativum is a single stratum of nucleated columnar cells
planted by denticulated extremities on the basement membrane of the corium.
. The stratum mucosum consists of six or eight layers of polygonal, nucleated
" prickle " or " finger " cells, the processes of which join those of adjacent cells.
Between the cells of this layer are minute channels, in which leucocytes or pigment
858
THE SKIN OK INTEGUMENT.
granules may be seen. The cells of the stratum mucosum are characterised by the
presence of numerous epidermic fibrils, which are coloured violet by hsernatoxylin
and red by carmine. These fibrils are unaffected by boiling, but swell up under
the action of acids and alkalies, and form the filaments of union between adjacent
cells. On account of their presence, L. Ranvier has named this layer the stratum
filamentosum. The dark colour of the negro's skin is caused by the presence of
numerous pigment granules in the deeper layers of the stratum mucosum ; the
pigment of which melanin forms an important constituent is absent from the
more superficial layers of the epidermis.
3. The stratum granulosum comprises two or three layers of horizontally
arranged, flattened cells, scattered around the nuclei of which are elliptical or
spherical granules of eleidin, a substance staining deeply with carmine and haema-
toxylin, and probably representing an intermediate stage between the protoplasm
of the deeper cells and the keratin of the superficial layers.
4. The stratum luciduin, an apparently homogeneous layer, is in reality made up
of several strata of flattened or irregular squames, which contain granules or
droplets of keratohyalin, a hyaline substance, staining less deeply than eleidin.
5. The stratum corneum comprises several layers of flattened non-nucleated
squames, the more superficial of which assume the form of horny scales and are
from time to time removed by friction. The deeper cells contain granules of a fatty
material having the consistency and plasticity of beeswax, and staining with osmic
acid. The peripheral parts of the cells consist of keratin, a highly resistant
substance which is unaffected by mineral acids, and is indigestible in pepsin-
hydrochloric acid.
L. Eanvier has pointed out that the stratum lucidum is really double, and has named the
deeper of its two layers the stratum intermedium ; this he describes as consisting of two or three
layers of clear cells with atrophied nuclei, while in the cell-walls the epidermic fibrils " are rolled
up like the threads of a cocoon."
Eegeneration of the epidermis is generally regarded as taking place by cell proliferation in
the stratum germinativum, the young cells gradually passing through the polyhedral and
granular stages, and ultimately
becoming the flattened squames
of the stratum corneum, while
the eleidin granules of the
stratum granulosum are con-
verted into the keratin of the
stratum corneum.
Vessels and Nerves of the
Skin. In the subcutaneous
tissue the arteries form a plexus
from which branches extenc
into the corium, where the)
supply the hair follicles ant
glands, and form a seconc
plexus under the papilla?, t>
which small loops are given
The veins and the lymphati
vessels commence in th
papillae, and, after formin;
subpapillary plexuses, ope:
into their respective subcut
aneous vessels.
The nerves of the skin var
in number in different parl
of the body ; they are extremely numerous where the sense of touch is acute, e.g. on the palms
surfaces of the terminal phalanges, while in the skin of the back, where the sensibility is les
they are fewer in number. Their different modes of ending are described on pp. 863-866.
FIG. 735. TACTILE CORPUSCLES.
A, End bulb (Krause).
B, Corpuscle of Pacini "| , ,,, T, . N
C, Corpuscle of Meissner / < after Ranvier )'
APPENDAGES OF THE SKIN.
The appendages of the skin are the nails, the hairs, the sebaceous glands, ao
the sudoriferous or sweat glands.
Ungues. The nails (Figs. 736, 737) are epidermal structures, and represei
the hoofs and claws of the lower animals. The root of the nail is hidde
APPENDAGES OF THE SKIN.
859
from view and embedded in a fold of skin ; the body, or uncovered part, rests
on the corium and ends in, a free margin. The greater part of the lateral margin
is overlapped by a duplicature of skin, termed the vallum unguis or nail-wall.
The nails are pink in colour, with the exception of a small semilunar area
near the root, which is more opaque than the rest, and is named the lunula. The
lunulse diminish in size from the thumb towards the little finger, while the
thickness of the nail diminishes towards its root and lateral margins. The corium
under the nail is highly vascular and sensitive, and presents, especially under
- Horny part of nail
Stratum mucosum
Nail bed
Vallum
FIG. 736. TRANSVERSE SECTION OF A NAIL.
anterior part of the body, numerous longitudinally arranged ridges. The part
of the corium under the body is termed the nail bed ; that under the root, the nail
matrix. The deep part of the nail consists of the stratum germinativum and
stratum mucosum, while its superficial horny portion is constituted by a greatly
thickened stratum lucidum, and consists of nucleated, keratinised squames. The
stratum corneum is represented by the thin cuticular fold overlapping the lunula,
and termed the eponychium, while the stratum granulosum can be traced only as
far forwards as the nail root.
Root of nail
Nail matrix
FIG. 737. LONGITUDINAL SECTION THROUGH ROOT OF NAIL.
Pili. Hairs are well developed on the external genitals, scalp, and margins of the
eyelids, in the axilla, the vestibule of the nose, and at the entrance to the concha,
and also on the face of the male. Those on the genitals and face appear about
puberty. Eudimentary over the greater part of the body, they are entirely absent
from the flexor surfaces of the hands and feet, the dorsal surfaces of the terminal
phalanges, the glans penis, the inner surface of the prepuce, and medial surfaces
of the labia. Marked variations, individual and racial, exist as to the colour of
the hair, and also as to the manner of its growth; hence the terms straight,
curly, woolly, etc. are used to designate it. Straight hairs are coarser than curly
ones, and have, moreover, a circular or oval outline on transverse section, curly
hairs being flat and riband-like.
The root of the hair is embedded in a depression of the skin, termed the hair
follicle (Fig. 738); the free portion is named the scapus or shaft, and consists
860
THE SKIN OK INTEGUMENT.
from without inwards of three parts, viz., cuticle, cortex, and medulla. The
cuticle is formed by a layer of imbricated scales which overlap one another from
below upwards. The cortex consists of longitudinally arranged fibres made up of
elongated, closely applied, fusiform cells, which contain pigment and sometimes air
spaces, the latter especially in white hairs. The medulla, absent from the fine
hairs of the body generally and from the hairs of young children, forms a central core,
which appears black by transmitted, and white by reflected light, and is composed
of polyhedral nucleated cells containing pigment, fat granules, and air spaces.
The hair follicle consists of an oblique or curved the latter in curly hairs invag-
ination of the epidermis and corium, and in the case of large hairs extends into the
subcutaneous tissue (Fig. 733) ; some little distance below its orifice the ducts of
the sebaceous glands open into it. The dermic coat or portion of the follicle derived
from the corium consists of a fibrous sheath of external longitudinal and internal
circular connective tissue fibres, the latter being lined by a hyaline layer directly
Fibrous sheath | Derived from
/ Basement membrane ) the corium
Stratum germinativum * Outer root
Stratum mucosum /sheath
Henle's layer
Huxley's layer
Cuticle
Section of hair
FIG. 738. TRANSVERSE SECTION OF HAIR FOLLICLE WITH CONTAINED HAIR (highly magnified),
continuous with the basement membrane of the corium. The parts of the follicle
derived from the epidermis are named the inner and outer root sheaths. Below the
orifices of the sebaceous gland ducts the outer root sheath is formed by the stratum
germinativum and stratum mucosum, while above them all the epidermal strata
contribute to it. The inner root sheath surrounds the cuticle of the hair, and
comprises from without inwards (a) Henle's layer, a single stratum L of nucleated
cubical cells ; (6) Huxley's layer, a single or double layer of polyhedral nucleated
cells ; and (c) a delicate cuticle, composed of a single layer of flattened imbricated
cells, with atrophied nuclei. The bottom of the hair follicle is moulded on a
vascular papilla, derived- from the corium and capped by the bulb of the hair or
expanded part of the hair root. The cells of the bulb are continuous with those
of the outer root sheath, and form the different parts of the hair, as well as its
inner root sheath. The vessels form capillary loops in the papilla of the hair, and
send twigs into the outer layer of its fibrous sheath; the inner and outer root
sheaths and the different parts of the hair are non-vascular. The nerves end in
longitudinal and annular fibrils below the level of the sebaceous glands and outside
the hyaline layer of the follicle.
Glandulse Sebaceae. Sebaceous glands exist wherever there are hairs, and their
DEVELOPMENT OF THE SKIN AND ITS APPENDAGES. 861
ducts open into the superficial parts of the hair follicles (Fig. 733) ; the number of
glands associated with each follicle varies from one to four. On the labia minora
and mammary areolse they open on the surface of the skin independently of hair
follicles, and in the latter situations undergo great enlargement during pregnancy.
The deep extremity of each gland expands into a cluster of oval or flask-shaped
alveoli, which are surrounded by a basement membrane, and filled with polyhedral
cells containing oil droplets. By the breaking down of the superficial cells, their
oily contents are liberated as the sebum cutaneum and discharged into the hair
follicle, whilst the deeper cells undergo proliferation. The size of the gland bears
no proportion to that of the hairs, since they are very large in the minute hair
follicles of the foetus and newly born child, and also in the follicles of the rudimen-
tary hairs of the nose and certain parts of the face.
Bundles of non-striped muscular fibre are associated with the hair follicles, and
are named the mm. arrectores pilomm. Attached to the deep part of the hair follicle,
and forming with it an acute angle, they pass outwards close to the sebaceous
glands, and end in the papillary layer of the corium. They are situated on the
side towards which the hair slopes, so that, on contraction, they diminish the
obliquity of the hair follicle and render the hair more erect, and, at the same
time, compress the sebaceous glands and expel their contents. The condition of
" goose-skin " is caused by the contraction of these slender muscles.
Arthur Thomson suggests that the condition of curly hair is produced by the contraction of
the mm. arrectores pilorum. Straight hair is thick and cylindrical ; curly hair is flat and ribbon-
like. When the arrector muscle contracts, the thick rounded hair resists the tendency of the
muscle to bend it, while the flat hair, not sufficiently strong to resist the strain of the muscle,
becomes bent, and this is probably the explanation why the follicle assumes the curved form
characteristic of the scalp of a bushman. The sebaceous gland lies in the concavity of the bend
between the follicle and the muscle, and forms a mass of greater resistance, around which the
follicle may be curved by the contraction of the muscle. The cells at the root of the hair
accommodate themselves to the curved follicle, and, becoming more horny as they advance to
the surface, retain the form of the follicle in which they are moulded.
Glandulae Sudoriferse. Sudoriferous or sweat glands are found in the skin
of nearly every part of the body ; they are relatively few in number on the back
of the trunk, but are very plentiful on the palms and soles, where they open on the
summits of the curved ridges. Each consists of an elongated tube, the deeper portion
of which forms its secretory part, and is coiled in the subcutaneous tissue or deep
part of the corium in the form of an ovoid or spherical ball, termed the corpus
glandulse sudoriferse (O.T. glomerulus) (Fig. 733). The superficial part of the tube, or
ductus sudoriferus, extends through the corium and epidermis, and opens on the
surface by a funnel-shaped orifice, the poms sudoriferus ; where the epidermis is thick
the duct is spirally coiled. The bodies of the glands, as a rule, vary in diameter
from 0*1 to 0'5 mm., but in the axillse they are much larger, and may measure
from 1 to 4 mm. Each is surrounded by a capillary network and by a capsule of
connective tissue, inside which is a homogeneous basement membrane. The lumen
of the tube is lined with a layer of nucleated, granular, and striated, columnar,
or prismatic epithelial cells, between the deep extremities of which and the
basement membrane is a layer of non-striped muscular fibres, the long axis of which
is more or less parallel with that of the tube. The excretory ducts are devoid of
muscular fibres, and consist of a basement membrane lined by two or three layers of
polyhedral cells, which are covered, next the lumen of the duct, with a thin cuticle.
The glandulse ciliares, at the margins of the eyelids, and the glandulse ceruminosse
of the external acoustic meatus, are modified sudoriferous glands ; the former are,
however, not coiled, while the cell protoplasm of the latter contains yellowish
pigment, and their gland ducts, in the foetus, open into hair follicles.
DEVELOPMENT OF THE SKIN AND ITS APPENDAGES.
Skin. The vascular and sensitive corium is developed from the mesoderm, the cells
of which, immediately underlying the ectoderm, have, by the second month of foetal life,
become aggregated together and flattened parallel to the surface of the embryo. By the
third month they are seen to form two layers, the superficial of which becomes the
862 THE SKIN OK INTEGUMENT.
corium, and the deeper the subcutaneous tissue ; the papillae of the corium make their
appearance in the fourth month. The epidermis, nails, hairs, sudoriferous and sebaceous
glands are of ectodermal origin.
The epidermis at first consists of a single layer of cells, but by the end of the second
month it is duplicated, and then exhibits a superficial layer of irregular cells and a deeper
layer of more or less cubical cells. By the third month three strata are seen : (a) a deep
layer, consisting of a single layer of cubical cells the future stratum germinativum ;
(6) a middle layer, comprising two or three strata of irregular cells the future stratum
mucosum ; and (c) an outer layer, a double stratum of large cells. This outer layer
appears to be homologous with a thin membrane, termed the epitrichium^ first described
as covering the embryo of the sloth and overlying its hairs, but since shown to be present
also in birds and mammals. Over the hairy parts of the body it disappears about the
sixth month ; but over the free edge and root of the nails, and on the palms and soles, it
develops into several layers of cells, which, in these parts, probably persist to form the
thick stratum corneum. The part which persists over the root of the nail is termed
the eponychium, and covers the proximal part of the lunula (vide p. 859, Fig. 737).
Nails. The first rudiment of the nails is seen about the beginning of the third month
of embryonic life, and consists of a thickening of the epitrichium over the ends of the
digits. Owing to the greater growth of the volar surfaces of the digits, the nail rudiment
comes to be placed dorsally, and, at its proximal edge, an ingrowth of the stratum
mucosum occurs to form its root, while the future nail is limited behind and at the sides
by a groove. The superficial cells of the stratum mucosum become keratinised to form
a thick stratum lucidum, the future nail proper, over the greater part of which the
epitrichium disappears. The latter persists in the adult as the eponychium across the
root of the nail, and, until fifth month, also forms a thick mass over the extremity of the
nail, and is continued into the stratum corneum over the end of the digit. The future
distal edge of the nail, at this stage, is continuous with the stratum lucidum in front of
it ; but this continuity is lost, and by the seventh month the nail presents a free border.
The nails grow in length, and are renewed, in case of removal, by a proliferation of the
cells of the stratum mucosum at the root of the nail, while an increase in their thickness
takes place from the part of the same stratum which underlies the lunula.
Hairs. The hair rudiments appear about the third month of embryonic life as solid
downgrowths of the stratum mucosum, which pass obliquely into the subjacent corium.
The deep end of this column of cells expands to form the hair bulb, and is moulded on
a papilla derived from the corium ; the epidermis immediately overlying the papilla
becomes differentiated into the hair and its inner root sheath, while the %i peripheral cells
form its outer root sheath. The surrounding corium is condensed to form the fibrous
sheath of the hair follicle, the hyaline layer of which is continuous with the basement
membrane covering the corium. The hair gradually elongates, and, reaching the neck of
the follicle, its extremity lies at first under the epitrichium, but becomes free on the dis-
appearance of the latter. This takes place about the fifth month of foetal life, and the
first crop of hairs constitutes the lanugo, and is well developed by the seventh month.
The lanugo consists of very delicate hairs, some of which are shed before, the remainder
shortly after birth the last to drop out being those of the eyelashes and scalp and are
replaced by stronger hairs. Shedding and renewal of the hairs take place during life ;
prior to the shedding of a hair active growth and proliferation of the cells of the hair bull
cease, and the papilla becomes atrophied, while the hair root, gradually approaching th(
surface, at last drops out. New hairs arise from epidermic buds, which extend downwards
from the follicle, and their development is identical with that of the original hairs.
Sebaceous Glands. These appear about the fifth month as solid outgrowths fron
the sides of the hair follicles, and consist of epidermal offshoots continued from the celL
of the outer root sheath. Their deep ends become enlarged and lobulated, to form the
secreting part of the gland, while the narrow neck connecting this with the follicle forms
its duct. The sebaceous secretion, together with the cast-off epidermal cells, is collectec
on the surface of the body during the last months of intra-uterine life, and forms a laye:
of varying thickness, termed the vernix caseosa or smegma embryonum.
Sudoriferous Glands. These, like the hairs, arise as solid downgrowths of th<
stratum mucosum. They descend, however, perpendicularly, instead of obliquely, an<
are of a yellowish colour ; they appear on the palms and soles early in the fifth month
but much later over the hairy parts of the body. The downgrowths extend through th
corium, and, on reaching the subcutaneous tissue, become coiled up to form the body o
secreting part of the gland. The ducts of the glands do not open on the surface unti
the seventh month.
SPECIAL END OKGANS.
863
ENDINGS OF NERVES OF GENERAL SENSATIONS.
The peripheral endings of the nerves associated with the special senses have
been described in the preceding pages. Under this heading will be considered the
terminations of those sensory nerves which are widely distributed throughout the
body and are associated with the muscular sense and the senses of pressure, heat,
cold, and pain. These nerves may end as fine ramifications of the axis cylinders
lying free amongst the tissues, or in special end organs where the terminations of
the axis cylinders are surrounded by connective tissue capsules.
FKEE NERVE-ENDINGS.
Free nerve -endings are found chiefly in the epithelium covering the skin or
the mucous membranes. The nerve-fibres, after subdividing in the sub-epithelial
connective tissue, lose success-
ively their medullary and primi- c
tive sheaths and are continued
as naked axis cylinders, which,
if stained with gold chloride, are
seen to consist of fine varicose
filaments. The axis cylinders
subdivide and form primary and
secondary plexuses, and from
the latter numerous fibrillse
pierce the sub-epithelial base-
ment membrane and ramify be-
tween the overlying epithelial
cells where they end in minute
knobs of flattened discs. In the Fia 739. VERTICAL SECTION OF CORNEA STAINED WITH
epidermis the nerve fibrillse are CHLORIDE OF GOLD (Ranvier).
limited to the stratum mucosum, a> 6> primary plexus in connective tissue of cornea; Cj branch
but in the cornea they reach the passing to sub-epithelial plexus e ; /, intra-epithelial plexus ;
Surface layers of epithelium d > terminations of fibrils.
(Fig. 739). Free nerve-endings
also occur around the sudoriferous glands, in the papillae and root sheaths of the
hair follicles, in the sub-epithelial and intermuscular connective tissues, and in
serous membranes.
i^^^> rf ^--.~:.-^>r\^v-^-^. S ;M,v.;v./ Modifications of free nerve-endings
J are seen in the tactile discs or cells of
::A-\ Merkel ; here the neuro-fibrillse end in
jy the deeper layers of the epidermis in
crescentic or cup-shaped expansions, in
contact with large, modified epithelial
cells. These tactile discs are well marked
in the pig's snout (Fig. 740).
FIG. 740. ENDING OF NERVE IN TACTILE DISCS OF THE
SNOUT (Ranvier). (From Quain's Anatomy. )
SPECIAL END ORGANS.
The special end organs vary greatly
m ^ ZQ an( j fQ im> Du fc in all of them the ter-
n, medullated fibre ; m, terminal discs in muscle ; e, m i na tion of the axis Cylinder is enclosed
is applied.
within aconnective tissuecapsuleorsheath
of varying thickness. The following are
the more important special end organs.
(1) End Bulbs of Krause (Fig. 742). These are minute cylindrical or oval bodies
which are found in the conjunctiva, in the mucous membrane of the lips, and in
864
ENDINGS OF NERVES OF GENERAL SENSATIONS.
the skin of the glans penis and glans clitoridis. Each consists of a thin connective
tissue capsule enclosing a core of homogeneous or nucleated semifluid substance.
As the nerve-fibre pierces the capsule, it loses its
medullary sheath, and the axis cylinder is con-
tinued into the core of the bulb where it may
pursue a somewhat tortuous course, but more fre-
quently divides into minute varicose fibrils which
form an intricate plexus. The end bulbs of the
glans penis and glans clitoridis are named genital
corpuscles and differ from those just described in
FIG. 741. GBANDRY'S CORPUSCLES FROM that they are larger and possess thicker capsules.
(Zn^in's ^r^.j 1 ^^ ^ Similar endings, termed articular lulbs, are found
A, composed of three cells with two inter- m the synovial membranes of certain joints, e.g.
posed discs, into which the axis those of the fingers.
cylinder of the nerve-cell is observed (2) Corpuscles of Grandly (Fig. 741). These
are *" in * he skin OOTe g thebeaks of aquatic
animals, and in the mucous membrane of the duck s
palate. Each consists of two or more flattened
epithelial cells enclosed within a capsule, and the axis cylinder ends in flattened
" tactile discs " which lie between the cells.
(3) Corpuscles of Pacini (Fig. 742). These are widely distributed and consist of
small oval bodies which measure from 2 to 3 mm. in length and about 1 mm. in
width. They are found on the cutaneous nerves of the hand and foot, on the infn
orbital and intercostal nerves, on the cutaneous nerves of the neck, nipple, am
mamma, and on the nerves of the solar plexus. They are present in the pariei
peritoneum and on the nerves of the joints, and are very plentiful in the mesentery
tactile cells.
FIG. 742.
A, End bulb (Krause).
B, Corpuscle of Pacini x 12 \, . .
C, Corpuscle of Wagner and Meissner/^ atte
FIG. 743. HERBST CORPI
OF DUCK (Sobotta).
medullated nerve-fibre ; a, its a
cylinder ending in an enls
ment ; c, nuclei of cells of cc
t, nuclei of cells of outer tuni
t', inner tunics.
of the cat. The capsule of the corpuscle consists of a number of connective tissu
tunics arranged concentrically around a central core of more or less clear proto
plasm ; the deeper tunics are closely applied to each other, but those towards th
circumference of the corpuscle are here and there separated by" narrow lymphati
spaces. Each corpuscle is attached to a nerve trunk by a narrow pedicle compose'
of a single medullated nerve-fibre which pierces the capsule and, on reaching th
core, loses its medullary sheath. The axis cylinder is continued into the core a
SPECIAL END OEGANS.
865
far as its distal end and there terminates in one or more enlargements in which
the neuro-fibrillse form a dense plexus. The corpuscles of Herbst (Fig. 743), which
are found in the skin of birds, differ from the Pacinian corpuscles in that their
cores consist of nucleated cells, between which the axis cylinder extends as a single
or branched process.
(4) Corpuscles of Golgi and Mazzoni. These are present in the subcutaneous tissue
of the pulp of the fingers and also in other parts of the skin. Their capsules are
thinner and their cores thicker than those of the Pacinian corpuscles, while their
axis cylinders undergo a greater degree of ramification and their terminal filaments
end in somewhat flattened expansions.
(5) Tactile Corpuscles of Wagner and Meissner (Fig. 742). These are plentifully
distributed in the papillae of the corium of the hand, foot, and front of the forearm.
They are found also in the skin of the lips, in the mucous membrane of the tip of
the tongue, in the palpebral conjunctiva and the skin of the nipple. They are
oval in shape, and their length varies from -04 mm. to -15 mm., and their
thickness from -03 mm. to '06 mm. One or more nerve-fibres pierce the capsule
of the corpuscle, losing, at the same time, their medullary sheaths. The axis
cylinders, which are frequently varicose, assume a spiral or convoluted course and
end in terminal enlargements. From the deep surface of the capsule imperfect
membranous septa are continued inwards between the nerve ramifications.
744. AN ORGAN OF RUFFINI FROM THE SUBCUTANEOUS TISSUE (Ruffini). (From Quain's Anatomy.)
a, Entering nerve-fibres ; b, d, endings of their axons ; e, c, capsule of organ ; c', core.
(6) Organs of Ruffini (Fig. 744). These were found by Euffini in the sub-
cutaneous connective tissue of the fingers. They are of considerable size, and their
shape is oval or fusiform. One or more nerve-fibres penetrate the side of the capsule,
within which they pursue a curved course and then lose their medullary sheaths.
Th(
FIG. 745. ORGAN OF GOLGI FROM THE HUMAN TENDO-CALCANEUS, CHLORIDE OF GOLD
PREPARATION (Ciacceo). (From Quain's Anatomy.)
m, Muscular fibres ; t, tendon bundles ; G, Golgi's organ ; n, two nerve- fibres passing into it.
e axis cylinders break up into a close-meshed network which lies between, or
partly encircles, the smaller fasciculi of connective tissue.
(7) Neuro-tendinous Spindles (Fig. 745). These were first described by Golgi in
56
866
ENDINGS OF NEEVES OF GENERAL SENSATIONS.
1878. They consist of long spindle-shaped bodies, and are usually found near the
junctions of the tendons with their muscles. Each is surrounded by a capsule
which encloses a number of intrafusal tendon
fasciculi. The nerve- fibres pierce the side
of the capsule and then lose their medullary
' M1SJ7I!2C/!; H - 1 sheaths; the axis cylinders subdivide, and
mVratyS ^ their terminal branches ramify between, or
^^ partly encircle, the smaller tendon bundles
and end in plate-like expansions.
(8) Neuro-muscular Spindles (Fig. 746).
These are widely distributed throughout the
voluntary muscles but are more numerous in
the muscles of the limbs than in those of the
trunk, and are plentifully found in the
muscles of the hand and foot. They have
not yet been seen in the intrinsic muscles
of the tongue, and only a few are present
in the ocular muscles. They lie in the con-
nective tissue between the muscular bundles,
and each consists of a lamellated capsule en-
closing a fasciculus of striped muscular fibres
(intra/usal fibres), together with minute
blood-vessels and three or four medullated
nerve -fibres. These intrafusal muscular
fibres display many of the characteristics of
embryonic muscle ; they are smaller both in
PIG. 746._ENmG OF NEBVE-HBRES , MUSCLE lf"g th a " d diame t er than ordinary muscular
fibres; they contain numerous nuclei near
the centre of the spindle where their cross
nerve-fibres entering spindle ; a, axis cylinders striation is leSS distinct ; they also pOSSeSS
terminating around and between the intrafusal more pro toplasm than Ordinary niUSCular
fibres. The nerve-fibres pierce the side of
the capsule, inside which they lose their
medullary sheaths and undergo subdivision ; they are then prolonged in a spiral
or annular manner around the individual muscular fibres and end in flattened or
ovoid enlargements.
d J-
SPINDLE (Ruffini). (From Quain's Anatomy.}
Three intrafusal muscle fibres are shown : x,
fibres in b, ring-like ; c, spiral
regularly ramified endings.
and d, ir-
THE VASCULAR SYSTEM.
BY THE LATE ALFRED H. YOUNG,
Professor of Anatomy, Victoria University, Manchester,
AND
ARTHUR EOBINSON,
Professor of Anatomy, University of Birmingham.
EEVISED BY ARTHUR EOBINSON, M.D.,
Professor of Anatomy in the University of Edinburgh.
vascular system consists of a series of tubes, called vessels, which run
through all parts of the body. Some of the vessels contain a coloured fluid
called blood, others are filled with a colourless fluid, called lymph; hence the
distinction between the blood-vascular system and the lymph-vascular system. The
two systems differ, not only as regards their contents, but also in their relations
to the tissues amongst which they lie ; for whilst the vessels of the blood- vascular
system, with the possible exception of the splenic vessels, are closed, those of the
lymph-vascular system communicate with the serous sacs.
The tubes or vessels of the blood-vascular system vary in size and in the
structure of their walls, but all contain blood, which is conveyed, through them,
to and from the tissue elements of the body. The blood is propelled along the
vessels chiefly by a central propulsive organ the heart. The outgoing vessels
from the heart, along which blood is transmitted to the tissues, are termed arteries ;
the vessels which return blood from the tissues to the heart are known as veins ;
whilst the smallest tubes those which connect the arteries and veins together,
constituting at once the terminations of the arteries and the commencements of
the veins are called capillaries.
Blood capillaries are very small (hair-like) vessels, with exceedingly thin walls
which permit of the easy passage of the nutritive materials outwards from the
blood to the tissues, and, of the passage in the opposite direction, of some of the
products of tissue changes and of food material absorbed from the alimentary canal.
Arteries and veins are simply conducting passages; structurally they differ
from capillaries in the greater complexity of their walls. They vary greatly in size,
but are always larger than capillaries. The calibres of the arteries and veins
increase progressively from the periphery up to the heart, where both sets of vessels
reach their greatest size. With the increase in calibre there is a corresponding
increase in the thickness and complexity of the walls of the vessels.
Structure of Blood Capillaries. Blood capillaries measure from 8 p to
12-5 /A in diameter, and about *75 mm. in length. Their walls are simple, and, in
the smallest capillaries, consist of elongated elastic endothelial cells, with sinuous
edges, pointed extremities, and oval nuclei. The cells are cemented to one another,
along their margins, by intercellular cement, which readily stains with nitrate of
silver. Here and there the cement substance appears to accumulate, forming minute
spots indicative of the less perfect apposition of the edges of the cells. Such spots
when small, form the so-called stigmata ; when larger they are known as stomata.
The larger capillaries are invested by a connective tissue sheath consisting of
branched cells which are united together and to the endothelial cells of the capillary
This sheath is termed the tunica externa capillaris.
Capillaries are arranged in networks, the nature and character of which differ
867 56 a
868
THE VASCULAE SYSTEM.
T. media
T. intima
C B A2 A*
FIG. 747. STRUCTURE OF BLOOD-VESSELS (diagrammatic).
U, Capillary with simple endothelial walls. A2, Larger capillary
with connective tissue sheath, "adventitia capillaris." B,
Capillary arteriole showing muscle cells of middle coat, few
and scattered. C, Artery muscular
media forming a continuous layer.
in different tissues. The small arteries which end in them are known as capillary
arterioles, and the venous radicles which commence from them are appropriately
termed capillary veins.
Structure of Arteries and Veins. The delicate elastic endothelial membrane
which forms the wall of the simplest capillaries extends also, as a continuous lining,
throughout the whole of the blood-vascular system. In the arteries the con-
stituent cells are fusiform, narrow, and pointed, whilst in the veins they are some-
what shorter and broader.
The most essential structural difference between capillaries on the one hand and
the arteries and veins which they unite together on the other, is the presence, in
both the arteries and the veins, of
T. externa/^ . ,...,.... . ^^r^^^z^\\ in voluntary muscular fibres which
are interposed between the endo-
thelial lining and the outer con-
nective tissue sheath. In small
vessels, e.g. capillary arterioles, the
muscle cells are few in number and
more or less scattered. In larger
vessels the walls are stronger and
ments of the tunica thicker, muscular fibres are more
numerous and form a continuous
layer, whilst yellow elastic and ordinary white connective tissue are present in
varying proportions. The walls of the larger vessels are, therefore, complex, and
numerous strata may be distinguished ; which, for convenience, are regarded as
forming three layers, known as the tunica intima and the middle and outer tunics.
Superadded to the tunics is the investing fibrous sheath or vagina vasis.
Structure of Arteries. The walls of arteries are stronger and thicker than
those of veins of corresponding size, the tunica intima and middle tunic being
particularly rich in elastic and muscular elements.
Tunica Intima. In the tunica intima the endothelial lining is strengthened
by the addition of yellow elastic tissue, the fibres
of which are arranged in such a manner as to
simulate a fenestrated membrane. In arteries of
medium size the elastic lamina is separated from
the endotheliunl by a layer of connective tissue
consisting of branched cells and numerous fibrils.
In the larger arteries the subendothelial connective
tissue is considerably increased, and delicate elastic
fibres appear which connect it with the more ex-
ternally situated and fenestrated elastic layer.
Tunica Media. In the capillary arterioles the
tunica media consists solely of scattered unstriped
muscle fibres ; the individual fibres are circularly dis-
posed, but do not entirely surround the vessel. In
small arteries the muscle cells are so much increased
in number that they form a continuous though
thin layer. The larger arteries have two or more
layers of muscle cells, and the greater thickness of
their walls is mainly due to the increase of the
muscular elements of the middle coat. In the
larger vessels delicate laminae of elastic tissue
alternate with the layers of muscular fibres, and
in the aorta and the carotid arteries, as well as
in some of the branches of the latter, the elastic
elements largely preponderate. In the first part
of the aorta, in the pulmonary artery, and in the
arteries of the retina, the muscular fibres are entirely replaced by elastic tissue.
Tunica Bxterna. The outer tunic of an artery consists almost entirely c
fibrillated connective tissue, in which lie many connective tissue corpuscles
FIG. 748. TRANSVERSE SECTIOI
THROUGH THE WALL OF A L.ARG)
ARTERY.
A, Tunica intima. B, Tunica media.
C, Tunica externa.
STEUCTUKE OF AETEEIES,
869
FIG. 749. TRANSVERSE SECTION OP
THE WALL OF A VEIN.
A, Tunica intima. B, Tunica media.
C, Tunica externa.
In all but the smallest arteries numerous elastic fibres are also present. The
elastic element is specially strong near the middle coat in small and medium
sized vessels, and is sometimes described as an external elastic membrane. In
some arteries longitudinally arranged unstriped muscular fibres are also found in
the external coat.
Vagina Vasis. In addition to the three tunics above described, arteries
are enclosed in a sheath of the surrounding connective tissue, and are more
or less connected with it by fine strands of fibrillated connective tissue.
Structure of Veins. The walls of veins are similar in structure to those
of arteries; they are, however, thinner, so much so, that, although veins are
cylindrical tubes when full of blood, they collapse
when empty and their luniina almost disappear.
The structural details of the three tunics vary
somewhat in different veins ; in most the innermost
tunic is marked by folds which constitute valves.
Like, the arteries, the veins are enclosed in connec-
tive tissue sheaths.
Tunica Intima. In the majority of the veins
the tunica intima includes an internal endothelial
layer, a middle layer of subendothelial connective
tissue, and an outer layer of elastic tissue. The
innermost tunic of a vein is less brittle than the
inner coat of an artery, and is more easily peeled off
from the middle coat. The subendothelial tissue
is a fine fibrillated connective tissue, less abundant
than in the arteries, and in many cases it is absent.
The elastic layer consists of lamellae of elastic
fibres which are arranged longitudinally ; it rarely
has the appearance of a fenestrated membrane.
One of the chief peculiarities of the tunica
intima is the presence of folds of its substance which constitute valves. The cusps
of the valves are of semilunar shape, and they are usually arranged in pairs.
Their convex borders are continuous with the vessel wall, and their free borders
are turned towards the heart ; whilst, therefore, they do not interfere with the free
flow of blood from the periphery, they prevent any backward flow towards it, and
they help to sustain the column of blood in all vessels in which there is an upward
flow. Each valve cusp consists of a fold of the endothelial layer, strengthened
by a little connective tissue. As a general rule, the wall of the vein is dilated on
the central side of each valve into a shallow pouch or sinus ; consequently, when
the veins are distended they assume a nodulated appearance. The valves are more
numerous in the deep than in the superficial veins, and in the veins of children
than in the veins of adults.
Tunica Media. The middle tunic is much thinner than the corresponding
tunic of an artery, and it contains a smaller amount of muscular and a larger
amount of ordinary connective tissue ; indeed, so much does the latter preponderate
that it separates the muscular fibres into a number of bands, which are isolated from
one another by strands of connective tissue ; therefore the muscle fibres do not form
a continuous layer. In some of the veins the more internal muscular fibres do not
retain the transverse direction which is usually met with both in arteries and
veins ; on the contrary, they run longitudinally. This condition is met with in
the branches of the mesenteric veins, in the femoral and iliac veins, and in the
umbilical veins. The middle tunic is absent in the thoracic part of the inferior
vena cava; it is but slightly developed in many of the larger veins, whilst in
the jugular veins its muscular tissue is very small in amount.
Tunica Externa. This tunic consists of white fibrous and elastic tissue.
In many of the larger veins a considerable amount of muscular tissue is also
present ; this is the case in the iliac and axillary veins, the abdominal part of the
nferior vena cava, the azygos and hemiazygos veins, and in the renal, spermatic,
splenic, superior mesenteric, portal, and hepatic veins. The striped muscle fibres of
870 THE VASCULAE SYSTEM.
the heart are prolonged into it at the terminations of the venae cavse. The external
tunic is frequently thicker than the middle tunic, and the two are not easily
separable from one another.
Vascular and Nervous Supply of Arteries and Veins. Blood-vessels. The
walls of the blood-vessels are supplied by numerous small arteries, called vasa
vasorum, which are distributed to the outer and middle tunics. They arise either
from the vessels they supply or from adjacent arteries, and after a short course
enter the walls of the vessels in which they end. The blood is returned by small
venae vasorum.
Lymphatics. Although the cell spaces in the middle and inner tunics may be
regarded as the commencement of lymphatics, definite lymphatic vessels are limited
to the outer tunic.
Nerves. Arteries and veins are well supplied with nerves, which form a
coarse network in the outer tunic. Branches from this network enter the tunica
media, where they form a finer network which supplies twigs to the muscle fibres
and sends fine filaments into the inner coat.
Divisions of the Blood- Vascular System. Blood-vessels convey blood to or
from the tissues of the body generally, or to and from the lungs. The former
constitute the systemic vessels or general system ; the latter form the pulmonary
system. The two systems are connected together by the heart.
The venous trunks passing to the liver, and their tributaries, form a subsidiary
part of the general systemic group of vessels, which is known as the portal system.
COR.
The heart is a hollow muscular organ, which is enclosed in a fibro-serous
sac known as the pericardium. It receives blood from the veins, and propels it
into and along the arteries. The cavity of the fully developed heart is completely
separated into right and left halves by an obliquely placed longitudinal septum, and
each half is divided into a posterior receiving chamber, the atrium, and an anterior
ejecting chamber, the ventricle. The separation of the atria from the ventricles,
however, is not complete. Externally a comparatively shallow constriction,
running transversely to the long axis of the organ, indicates the distinction
between the atria and ventricles ; internally a wide aperture is left between
the atrium and ventricle of each side. Each atrio - ventricular aperture is pro-
vided with a valve which allows the free passage of blood from the atrium to the
ventricle, but effectually prevents its return.
The delicate walls of the blood capillaries allow the fluid part of the blood blood plasma
to pass outwards to the tissues. In the tissues the plasma enters spaces, or intercellular channels,
in which the tissue elements lie ; thus the latter are directly bathed in blood plasma which
contains nutritive materials and oxygen. The intercellular spaces may be looked upon as the
commencement of the lymph -vascular system. They communicate together, and lymph plasma
passes from them into lymph vessels which carry it to the blood -vascular system. It must
be remembered, in addition, that materials also pass from the tissues into the blood capillaries.
Lymph vessels, in other words, convey material from the tissues. Blood-vessels convey
material both to and from the tissues.
The removal of waste products which have passed from the tissues to the blood is provided
for by special organs, some of which are simply interposed in the course of the general circulation
e.g. the liver, the kidneys, and the skin. The lungs, however, where the impure or venous
blood receives its main supply of oxygen and gives up most of its carbon dioxide, etc., do not
lie in the course of the general or systemic circulation ; for them a secondary or pulmonary
circulation is established, by which venous blood is conveyed from the heart to the lungs by the
pulmonary artery and its branches, and, after passing through the pulmonary capillaries, is
returned again to the heart, as oxygenated or arterial blood, by the pulmonary veins.
The heart, anatomically a single organ, is correspondingly modified, and, as described above,
it is divided by a septum into a right and a left part. The right side receives the blood from
the systemic veins, and ejects it into the pulmonary artery ; whilst the left side receives blood
from the pulmonary veins, and ejects it into the main systemic artery the aorta.
The shape of the heart is that of an irregular and somewhat flattened cone ; and
a base, an apex, two surfaces (inferior or diaphragmatic and antero-superior 01
sterno-costal), and three borders (right, left, and inferior) are distinguishable.
THE HEAET.
871
An oblique groove, the sulcus coronarius, runs transversely to the long axis
of the organ ; it separates the postero-superior or atrial portion from the antero-
inferior or ventricular part. The separation of the atrial portion into right and left
chambers is marked, externally, at the base of the heart only, where an indistinct
interatrial groove exists. The division of the ventricular part into right and left
ventricles is more definitely marked on the surface by anterior and an inferior
longitudinal sulcus which meet at the inferior border to the right of the apex.
The heart lies in the middle mediastinum. It rests below on the diaphragm,
and is enclosed in the pericardium, which intervenes between it and the neighbour-
ing structures. Its long axis, from base to apex, runs obliquely from behind
forwards, downwards, and to the left.
Basis Cordis. The base, which is formed by the atria, and almost entirely by
Ligamentum arteriosum
Aorta
Left pulmonary artery
Vestigial fold
(Marshall)
Left pulmonary veins
Right pulmonary artery
Superior vena cava
Circumflex
branch of left
coronary artery
Left marginal artery
ight pulmonary veins
Sulcus terminalis
Right atrium
Inferior vena cava
Left ventricle ^
Right ventricle
Coronary sinus
7 50. THE BASE AND DIAPHRAGMATIC SURFACE OF THE HEART, showing the openings of the great
vessels and the line of reflection of the serous pericardium in a formalin hardened preparation.
the left atrium, is directed upwards, posteriorly, and to the right. It lies anterior
o the descending thoracic aorta, the oesophagus, and the lower right pulmonary
vein, which separate it from the bodies of the sixth, seventh, and eighth thoracic
vertebrae.
On the whole the base is somewhat flattened. It is irregularly quadrilateral
in outline, and the terminations of the superior and inferior venae cavse and the
four pulmonary veins pass through it. The opening of the superior vena cava is
situated at the upper right angle, that of the inferior cava occupies the lower
angle on the right side ; between and a little to the left of those openings are the
orifices of the two right pulmonary veins, and immediately to the right of the
latter is the indistinct posterior interatrial sulcus, which descends to the left
of the orifice of the inferior vena cava. The openings of the two left pulmonary
eins are situated near the left border of the base. The portion of the surface
which lies between the right and left pulmonary veins forms the anterior boundary
of a section of the pericardial cavity called the great oblique sinus.
872
THE VASCULAE SYSTEM.
The base is limited below by the inferior part of the coronary sulcus, in which
the coronary sinus lies; its upper border is in relation with the pulmonary
arteries. A fold of pericardium, the vestigial fold, descends, near the left border
of the base, from the left branch of the pulmonary artery, above, to the left superior
pulmonary vein below. It contains the ligamentum v. cavse sinistrse, and from
its lower end a small vein, the oblique vein of the left atrium, passes below the
orifice of the lower left pulmonary vein, and descends to the coronary sinus.
Further, it is from the base that the visceral layer of the pericardium, which
elsewhere completely invests the heart, is reflected to the fibrous layer, the lines of
reflection corresponding with the orifices of the great vessels. 1
Left atrium
Pulmonary artery
Superior vena
cava
Right coronary
artery
Right auricle
Right coronary
artery
Anterior ventri-
cular artery
-Left auricle
Right marginal
artery
Circumflex branch of left
coronary artery
Interventricular branch of left
coronary artery
Left ventricle
Left marginal
artery
Right ventricle
FIG. 751. THE STERNO-COSTAL SUEFACE OF FORMALIN-FIXED HEART.
The apex, bluntly rounded, is formed entirely by the left ventricle. It is
directed downwards, anteriorly, and to the left, and is situated, under cover of
the anterior borders of the left lung and pleura, behind the fifth left intercost
space, three and a half inches from the anterior median line.
The diaphragmatic surface is formed by the ventricular part of the heart. It
rests upon the diaphragm, chiefly on the central tendon, but, upon the left side, on
a small portion of the muscular substance also, and it is divided into two
a smaller to the right side and a larger to the left side by an oblique antero-
posterior groove, the inferior interventricular sulcus. It is separated from the base
by the posterior or inferior portion of the coronary sulcus.
The sterno-costal surface is directed upwards, anteriorly, and to the left. II
lies posterior to the body of the sternum and the medial extremities of th<
cartilages of the third, fourth, fifth, and sixth ribs of the right side, and
greater extent of the corresponding cartilages of the left side. This surfa
is separated into upper and lower sections by the anterior portion of th<
1 In the foetus and young child the atrial portion of the heart forms not only the base, but also
posterior part of the inferior or diaphragmatic surface.
THE CHAMBERS OF THE HEAKT.
873
coronary sulcus, which runs obliquely from above downwards, and from left to
right, from . the level of the third left to that of the sixth right costal cartilage.
The upper section of the surface, which is concave anteriorly, is formed by the
atria ; it is separated from the sternum by the ascending aorta and the pulmonary
artery, and is continuous laterally with the auricles of the atria which, projecting
forwards, embrace the great vessels.
The lower section of the sterno-costal
surface is convex ; it is formed by the
ventricular part of the heart, and is
divided, by an anterior interventricn-
lar sulcus, into a smaller left and a
larger right part. At the junction of
the atrial and ventricular parts of
this surface are the orifices of the
pulmonary artery and the aorta, the
former lying anterior to the latter.
The right margin of the heart is
formed by the right atrium. It lies
posterior to the cartilages of the third,
fourth, fifth, and sixth ribs on the
right side, about half an inch from the
margin of the sternum ; it is in re-
lation with the right pleura and lung,
the phrenic nerve with its accompany-
ing vessels intervening, and it is
marked by a shallow groove the
sulcus terminalis which passes from
the front of the superior vena cava to
the front of the inferior vena cava.
The inferior margin of the sterno-costal surface is sharp, thin, and usually concave
corresponding with the curvature of the anterior part of the diaphragm; it is
formed mainly by the right ventricle and only near the apex by the left ventricle
It lies, almost horizontally, in the angle between the diaphragm and the anterior
wall of the thorax, passing from the sixth right costal cartilage, posterior to the
lower part of the body of the sternum, or the xiphoid process, and the cartilages
rf the sixth and seventh ribs on the left side, to the apex of the heart.
The left margin is formed mainly by the left ventricle, and only to a small
3xtent by the left atrium ; it is thick and rounded. It lies in relation with
:he left pleura and lung, the phrenic nerve and its accompanying vessels inter-
vening, and it passes from just above the third left costal cartilage, about an inch
Tom the sternum, to the apex of the heart, descending obliquely and with, a con-
vexity to the left.
Fio/752. THE RELATION OF THE HEART TO THE
ANTERIOR WALL OF THE THORAX.
i, n, in, iv, v, vi, the upper six costal cartilages.
THE CHAMBEKS OF THE HEAKT.
Atria. The atrial or basal portion of the heart is cuboidal in form. Its long
, which lies transversely, is curved, with the concavity of the curve forwards.
s cavity is divided into two chambers the right and left atria by a septum
ich runs from the anterior wall backwards and to the right, so obliquely that
)he right atrium lies anterior and to the right, and the left atrium posterior and
;o the left.
Each atrium is also somewhat cuboidal in form, the long axes of both being
rtical, and each possesses a well-marked ear-shaped, forward prolongation, known
the auricle, which projects from its anterior and upper angle.
Atrium Dextrum. The right atrium receives, posteriorly, the superior vena
i above and the inferior vena cava below. Between them, and a little above
niddle, it is crossed posteriorly by the lower right pulmonary vein. It is coii-
luous below and anteriorly with the right ventricle, at the atrio-ventricular
874
THE VASCULAE SYSTEM.
aperture. Above and anteriorly it is in relation with the ascending aorta, and
from the junction of this aspect with the right lateral boundary the right
auricle is prolonged anteriorly and to the left. Its right side forms the right
margin of the heart, and is in relation with the right phrenic nerve and its accom-
panying vessels, and with the right pleura and lung, the pericardium intervening.
On the left the right atrium is limited by the oblique septum which separates it
from the left atrium. The sulcus terminalis is a shallow groove on the surface of
the right atrium, which passes from the front of the superior vena cava to the
front of the inferior vena cava. It indicates the junction of the primitive sinus
venosus with the atrium proper.
The interior of the right atrium is lined with a glistening membrane, the endo-
Vena cava superior
Upper right
pulmonary vein
Lower right
pulmonary vein
Musculi pectinati
Limbus fossse ovalis
Fossa ovalis
Valve of vena cava JftJ
Aorta
Pulmonary artery
- Right auricle
Conns arteriosus
Vena cava inferior
Anterior cusp of
tricuspid valve
Chordae tendineae
Moderator band
Coronary valve
Musculi papillares
FIG. 753. THE CAVITIES OF THE RIGHT ATRIUM AND EIGHT VENTRICLE OF THE HEART.
From a formalin fixed heart.
cardium; its walls are smooth, except anteriorly and in the auricle whe
muscular bundles, the musculi pectinati, form a series of small vertical columi
The musculi pectinati terminate, above, in a crest, the crista terminalis, which corr
sponds in position with the sulcus terminalis on the external surface.
At the upper and posterior part of the cavity is the opening of the super!
vena cava, devoid of a valve. At the lower and posterior part is the orifice
the inferior vena cava, bounded, anteriorly, by the rudimentary valve of the ve
cava (O.T. Eustachian) ; and immediately anterior and to the left of this val' 1
between it and the atrio-ventricular orifice, is the opening of the coronary sin^
guarded by the unicuspid coronary valve. The atrio-ventricular aperture, guard
by a tricuspid valve, is known as the tricuspid orifice. It is situated in the infer '
part of the anterior boundary, and admits three fingers. A number of small fosf ,
foramina venarum minimarum, are scattered over the walls, and into some i
them the venae cordis minimae open. In the septal wall is an oval depression, 1 J
fossa ovalis, bounded, above and anteriorly, by a raised margin, the limbus fos J
ovalis, which is continuous, inferiorly, with the valve of the vena cava ; the fo i
THE CHAMBERS OF THE HEART. 875
is the remains of an aperture, the foramen ovale. through which the two atria
communicated with one another before birth. Even in the adult a portion of the
1 aperture persists at the upper part of the fossa in about one in five cases. Between
'the apertures of the superior and inferior venae cavae, and posterior to the upper
part of the fossa ovalis, a small eminence may be distinguished, which is called
the tuberculum intervenosum ; it probably directs the blood from the superior vena
cava to the tricuspid orifice, during foetal life.
The valvula venae cavae inferioris is a thin and sometimes fenestrated fold of
endocardium and subendocardial tissue, which extends from the anterior and
lower margin of the orifice of the inferior vena cava to the anterior part of
the limbus ovalis. It varies very much in size, and is usually of falciform shape ;
its apex is attached to the limbus fossae ovalis and its base to the margin of the
inferior caval orifice. It is an important structure in the foetus, directing the
blood from the inferior vena cava through the foramen ovale into the left atrium.
The valvula sinus coronarii is usually a single fold of endocardium which is
Right anterior cusp of pulmonary valve
Left anterior cusp of pulmonary valve Anterior cusp of aortic valve
Pulmonary ^ery^^^JJ^^ Orifice of right coronary artery
Posterior cusp , '^ ' - ' -^ ^ ' Conus arteriosus
Interventricular branch \^^Bfiii^'^^^S^^B^^^^^^B^k.-'^^ coronary artery
Left coronary artery
Orifice of left jC^^P^HIEk^lS ^SP\ \ ^ Anterior cusp of tricuspid valve
coronary artery "
Circumflex branch of _
left coronary artery
Left posterior cusp _
of aortic valve '
Inferior cusp of
tricuspid valve
Posterior cusp of ,1
mitral valve
Medial cusp of tricuspid valve
Right posterior cusp of aortic valve Interventricular branch of right coronary artery
FIG. 754. THE BASES OF THE VENTRICLES OF THE HEART, showing the auriculo-ventricular, aortic,
and pulmonary orifices and their valves.
placed at the right margin of the orifice of the coronary sinus. It is almost
invariably incompetent.
Atrium Sinistmm. The left atrium is in relation posteriorly with the
descending thoracic aorta and the oesophagus, but is separated from them by the
pericardium and the oblique sinus of the pericardium. Below and anteriorly it is
continuous with the left ventricle. Its sterno-costal surface is concave, and lies in
, close relation to the ascending aorta, the pulmonary artery, and the left coronary
artery. Its right side, formed by the interatrial septum, is directed anteriorly and
, to the right. Its left side forms a very small portion of the left margin of the
heart, and from it, at its junction with the antero-superior surface, the long and
.narrow left auricle is prolonged, forwards, round the left side of the ascending
, portion of the aorta and the trunk of the pulmonary artery.
The four pulmonary veins enter the upper part of the posterior surface, two on
each side.
Che interior of the left atrium is lined with endocardium, and its walls are
)th, except in the auricle, where musculi pectinati are present, and on the
im, in a position corresponding with the upper part of the fossa ovalis on
e right side, where there are several musculo-fibrous bundles radiating anteriorly
,and upwards. These septal bundles are separated at their bases by small semi-
lunar depressions, in the largest of which remains of the foramen ovale may
lound. Foramina venarum minimarum, and the apertures of venae cordis
minimse, are scattered irregularly over the inner aspect, whilst in the inferior
876
THE VASCULAR SYSTEM.
part of the anterior boundary is the a trio- ventricular aperture or mitral orifice.
The orifice is oval in form ; its long axis is 'placed obliquely antero-posteriorly, and
from left to right, and is capable of admitting two fingers. It is guarded by a
valve formed of two large cusps, known as the mitral valve.
Ventriculi. The ventricular portion of the heart is conical and somewhat
flattened. The base, directed upwards and posteriorly, is partly continuous with
the atrial portion and partly free. It is perforated by four orifices, the two
atrio-ventricular, the aortic, and the pulmonary. The atrio-ventricular orifices
are placed, one on each side, inferiorly and posteriorly ; anteriorly and between
them is the aortic orifice, whilst the
orifice of the pulmonary artery is still
more anterior, and slightly to the
left of the aortic orifice.
In the triangle between the atrio-
ventricular and the aortic orifices is
embedded a mass of dense fibrous
tissue which is the representative of
the os cordis of the ox. It is con-
tinuous with the upper part of the
interventricular septum, and with
fibrous rings which surround the
apertures at the bases of the ven-
tricles.
The diaphragmatic surfaces and
the sterno-costal surfaces of the two
ventricles constitute respectively the
greater portions of the corresponding
surfaces of the heart ; the former
rest upon the diaphragm, whilst the
latter are directed upwards and
anteriorly towards the sternum and
the costal cartilages of the left side.
The apex of the left ventricle forms
the apex of the heart.
The inferior margin of the ven-
tricular region, which is thin, forms
the inferior margin of the heart ;
and the left margin, which is thick
and rounded, forms the greater part
FIG. 755. THE RELATIONS OF THE HEART AND THE
ATRIO - VENTRICULAR, AORTIC, AND PULMONARY
ORIFICES TO THE ANTERIOR THORACIC WALL.
I to VII, Costal cartilages.
A, Aortic orifice.
Ao, Aorta.
C, Clavicle.
LA, Left atrium.
LV, Left ventricle.
M, Mitral orifice.
P, Pulmonary orifice.
HA, Right atrium,
RV, Right ventricle.
SVc, Superior vena cava.
T, Tricuspid orifice.
the left margin of the heart.
The ventricular portion of the heart is divided into right and left chambei
by the ventricular septum, which is placed obliquely, with one surface directed
anteriorly and to the right, and the other posteriorly and to the left ; it bul
into the right ventricle, and its lower margin lies to the right of the apex of
heart, which is, therefore, formed entirely by the left ventricle. The margins
the septum are indicated on the two surfaces of the ventricular part of the he
by anterior and inferior interventricular sulci.
Ventriculus Dexter. The right ventricle is triangular in form. Its base
directed upwards and to the right, and, in the greater part of its extent, it
continuous with the right atrium, with which it communicates by the atric
ventricular orifice ; but its left and anterior angle is free from the atrium, am
gives origin to the pulmonary artery. Its inferior wall rests upon the diaphragi
The sterno-costal wall lies posterior to the lower part of the left half of tl
sternum and the cartilages of the fourth, fifth, and sixth ribs of the left sid<
The left or septal wall, which is directed posteriorly and to the left, bulges inl
its interior, and on this account the transverse section of the cavity has a semi
lunar outline. The cavity itself is a bent tube consisting of an inferior portion o?
body into which the atrio-ventricular orifice opens, and of an antero-superior
the infundibulum or conus arteriosus, which terminates in the pulmonary arter
THE CHAMBERS OF THE HEART. 877
In the angle between the two limbs is a thick ledge of muscle, the supra-
ventricular crest.
The right atrio-ventricular orifice is guarded by a tricuspid valve. The three
cusps are an anterior, which intervenes between the atrio-ventricular orifice
and the infundibulum, a medial or septal, and an inferior. Each cusp consists
of a fold of endocardium, strengthened by a little intermediate fibrous tissue.
The bases of the cusps are generally continuous with one another at the atrio-
ventricular orifice, where they are attached to a fibrous ring, but they may be
separated by small intermediate cusps which fill the angles between the main
segments. The apices of the cusps project into the ventricle. The margins,
which are thinner than the central portions, are notched and irregular. The
atrial surfaces are smooth. The ventricular surfaces are roughened, and, like the
margins and apices, they give attachment to fine tendinous cords, the chordae
tendinese. The opposite extremities of the chordae tendineae are attached to
muscular bundles, the musculi papillares, which project from the wall into the
cavity of the ventricle.
The pulmonary orifice, which lies anterior and to the left of the tricuspid orifice,
is guarded by a pulmonary valve composed of three semilunar segments, two of
which are placed anteriorly and one posteriorly. The convexity or outer border
of each semilunar segment is attached to the wall of the pulmonary artery. The
inner border is free, and it presents at its centre a small nodule, the nodulus valvulae
semilunaris. On each side of the nodule there is a small, thin marginal segment,
of semilunar form, the lunule. Each segment of the valve is formed by a layer of
endocardium on its 'Ventricular surface, an endothelial layer of the inner coat of
the artery on its arterial surface, and an intermediate stratum of fibrous tissue.
Both the attached and the free margins of the cusps are strengthened by
fibrous bands, and strands of condensed fibrous tissue radiate from the outer
border of each cusp to the nodule, but they do not enter the lunulae. When the
valve closes the noduli are closely apposed, the lunulse of the adjacent segments
of the valve are pressed together, and both noduli and lunulae project vertically
upwards into the interior of the artery.
The cavity of the right ventricle is lined with endocardium; the walls are
smooth in the conus arteriosus, but are rendered rugose and sponge-like in the
body by the inward projection of numerous muscular bundles, the trabeculse carneae.
The fleshy trabeculse are of two kinds : the simpler are merely columns raised
in relief on the wall of the ventricle ; the other class are rounded bundles, free
in the middle, but attached at each end to the wall of the ventricle. One special
bundle of the second group, called the moderator band, is attached by one extremity
; to the septum, and by the other to 'the ster no-costal wall, at the base of the
anterior papillary muscle ; it tends to prevent over-distension of the cavity. In
addition to the trabeculae carneae conical muscular eminences, the musculi papillares,
i project into the cavity of the ventricle. The bases of the papillary muscles are
; continuous with the wall of the ventricle, and their apices 'terminate in numerous
i chordae tendineae which are attached to the apices, the borders, and ventricular
surfaces of the cusps of the tricuspid valve.
The musculi papillares of the right ventricle are (1) a large anterior, muscle,
from which the chordae pass to the anterior and inferior segments of the
valve ; (2) a smaller and more irregular inferior muscle, sometimes represented
by two or more segments, from which chordae pass to the inferior and medial
i cusps; and (3) a group of muscular bundles, varying in size and number,
which spring from the septum and are united by chordae to the anterior and
i medial cusps.
The walls of the right ventricle, the septal excepted, are much thinner than
those of the left, but the trabeculae carneae are coarser and less numerous in the
right than in the left ventricle.
Ventriculus Sinister. The left ventricle is a conical chamber, and its cavity
is oval in transverse section. The base is directed upwards and posteriorly, and in
the greater part of its extent it is continuous with the corresponding atrium,
with which it communicates through the mitral orifice; but anteriorly and to % the
878 THE VASCULAK SYSTEM.
right of its communication with the atrium it is continued into the ascending
aorta.
The mitral orifice is oval; its long axis runs obliquely from above down-
wards and to the right, and -it is guarded by a valve consisting of two cusps,
which is known as the bicuspid or mitral valve. The two cusps of the valve
are triangular and of unequal size. The smaller of the two is placed to the left
and inferiorly; and the larger, placed to the right and anteriorly, between the
mitral and aortic orifices, is known as the aortic cusp. The bases of the cusps
are either continuous with one another, at their attachments to the fibrous ring
around the mitral orifice, or they are separated by small intermediate cusps of
irregular form and size. The apices of the cusps project into the cavity of the
ventricle. The atrial surfaces are smooth ; the ventricular surfaces are roughened
by the attachments of the chordae tendinese, which are connected also with the
irregular and notched margins and with the apices. The structure is the same
as that of the cusps of the tricuspid valve, but the ventricular surface of the
anterior cusp is relatively smooth ; therefore the blood flow into the aorta is
not impeded.
The aortic orifice is circular ; it lies immediately anterior and to the right of
the mitral orifice, from which it is separated by the anterior cusp of the mitral
valve, and it is guarded by the aortic valve, formed of three semilunar segments,
one of which is placed anteriorly and the other two posteriorly. The structure
and attachments of the cusps of the aortic valve are similar to those of the
cusps of the pulmonary valve (see p. 877).
The cavity of the left ventricle is separable, like that of the right, into two
portions, the body and the aortic vestibule ; the latter is a small section placed
immediately below the aortic orifice ; its walls are non-contractile, consisting of
fibrous and fibro - cartilaginous tissue. The wall of the cavity is lined by
endocardium. . The inferior wall and the apex are rendered sponge-like by numerous
fine trabeculse carneae, whilst the upper part of the sterno-costal wall and the
septum are relatively smooth.
There are two papillary muscles of much larger size than those met with in the
right ventricle an anterior and an inferior ; each is connected by chordae tendinese
with both cusps of the mitral valve.
The walls of the left ventricle are three times as thick as those of the right
ventricle, and they are thickest in the region of the widest portion of the cavity,
which is situated about a fourth of its length from the base. The muscular portion
of the wall is thinnest at the apex, but the thinnest portion of the boundary lies at
the upper part of the septum, and it consists entirely of fibrous tissue ; this part
is occasionally deficient, and an aperture is left through which the cavities of the
two ventricles communicate.
The ventricular septum is a musculo-membranous partition. It is placed
obliquely, so that one surface looks anteriorly and to the right, and bulges into the
right ventricle, whilst the other looks posteriorly -and to the left and is concave
towards the left ventricle. Its sterno - costal and inferior margins correspond
respectively with the anterior and the inferior portions of the interventriculai
sulcus, and it extends from the right of the apex to the interval between the
pulmonary, the aortic, and the atrio- ventricular orifices. The main part of ife
extent is muscular, and is developed from the wall of the ventricular part of tht
heart ; but its upper and posterior portion, the pars membranacea, which is developec
from the septum of the truncus arteriosus, is entirely fibrous, and constitutes th<
thinnest portion of the ventricular walls. The pars membranacea lies between th<
aortic vestibule of the left ventricle, on the left, and the upper part of the righ
ventricle and the lower and left part of the right atrium, on the right.
STKUCTUEE OF THE HEAKT.
The walls of the heart consist mainly of peculiar striped muscle, the myocardium, which i
enclosed between the visceral layer of the pericardium, or epicardium, externally, and th
endocardium internally. The muscular fibres differ from those of ordinary voluntary stripe
STKUCTUKE OF THE HEAKT. 879
muscle in several ways : they are shorter, many of them being oblong cells, with forked ex-
tremities which are closely cemented to similar processes of adjacent cells ; they form a reticulum,
and the nuclei lie in the centres of the cells. Moreover, still more peculiar fibres, the fibres of
Purkinje, are found immediately beneath the subendocardial tissue. The fibres of Purkinje
are large cells which unite with one another at their extremities ; their central portions consist
of granular protoplasm, in which sometimes one but more frequently two nuclei are embedded,
and the peripheral portion of each cell is transversely striated. These cells, in short, present, in
a permanent form, a condition which is transitory in all other striped muscle cells.-
The reticulating cardiac muscle cells are grouped in sheets and strands which have a more or
less characteristic and definite arrangement in different parts of the heart ; by careful dis-
section, and after special methods of preparation, it is possible to recognise many layers and
bundles, some of which are, however, probably artificially produced.
In the atria the muscular fasciculi fall naturally into two groups : (a) superficial fibres
common to both atria ; (b) deep fibres special to each atrium.
The superficial fibres are most numerous on the sterno-costal aspect and in the neighbourhood
of the coronary sulcus. They run transversely across the atria and a few of them dip into the
interatrial septum.
The deep fibres are (1) looped fibres. The extremities of the looped fibres are attached to
the fibrous rings around the atrio-ventricular orifices and the fibres pass antero-posteriorly over
the atria. (2) Annular fibres which surround (a) the extremities of the large vessels which open
into the atria ; (b) the auricles ; (c) the fossa ovalis.
In the ventricles the muscular fasciculi form more or less definite V-shaped loops which
, commence from and end at the fibrous rings which surround the large orifices at the bases of the
ventricles. In their courses the loops embrace the cavities of either one or both ventricles, one
stem of each loop lying on the outer surface of the heart and the other in the interior, and some
of the loops possessing very acute whilst others have very open bends.
The superficial fibres on the sterno-costal surface pass towards the left, those on the inferior
surface towards the right. At the apex all are coiled into a whorl or vortex through which they
pass into the interior of the ventricular walls and run towards the base, some in the septum
and others in the papillary muscles. The various bundles which have been described can,
according to Mall, be resolved into two main systems. One system arises from the conus
arteriosus and the root of the aorta, that is from the remains of the primitive aortic trunk :
; it is called the " bulbo-spiral" system. The other springs from the region of the primitive
i venous sinus and is termed the " sino-spiral." Both systems are separable into superficial and
deep portions, and the general plan of more or less spirally curved V -sna P e( i loops is retained
in each, but the details of the arrangement are too complicated for consideration within the
limits of an ordinary text-book (see Amer. Journ. of Anat. vol. ii. 1910-1911).
The Atrio-Ventricular Bundle. It would appear from the preceding description that the
i muscle-fibres of the atria and the ventricles are entirely separated from one another by the fibrous
rings which surround the atrio-ventricular orifices ; that, however, is not the case, for the two
groups are connected together by a bundle of muscle fibres of pale colour and rudimentary
| structure, which lies immediately adjacent to the endocardium and constitutes the atrio-ventricular
. bundle.
The bundle commences in a nodular enlargement which lies in the lower part of the wall
; of the right atrium, close to the base of the medial cusp of the tricuspid valve. From that point
the bundle runs along the posterior and lower borders of the membranous part of the ventricular
septum to the upper and posterior part of the muscular portion of the septum, where it divides
into right and left branches. The right branch runs along the right side of the ventricular
septum to the moderator band, along which it passes into the anterior papillary muscle of the
; right ventricle. The left branch runs along the left side of the septum and both branches give
off numerous ramifications, by means of which the main bundle is associated with all parts of
, the walls of the two ventricles.
Both the function and the origin of the atrio-ventricular bundle are uncertain. After the
scovery of the bundle it was asserted that impulses were conveyed from the atria to the
ventricles by the muscle fibres of the atrio-ventricular bundle and by them alone ; more recently
t has been shown that minute nerve fibrils are intimately intermingled with the muscle fibres of
the bundle, and it has yet to be decided whether the impulses which pass from the atria to
the ventricles, for the purpose of maintaining the proper sequence of the movements of the
chambers, travel by the nerve fibrils or the muscle fibres or by both.
The atrio- ventricular bundle is probably a remnant of the muscular continuity which
sted in the early stages of development between the atrial and ventricular chambers of the
: heart, but it may be, wholly or in part, a new formation.
The epicardium, or visceral portion of the pericardium, consists of white connective and
elastic tissue, the latter forming a distinct reticulum in the deeper part. The surface which
looks towards the pericardial cavity is covered with flat polygonal endothelial plates, which are
partially separated, here and there, by stomata. It has been asserted that the pericardial cavity
communicates with the lymphatics of the epicardium through the stomata.
The endocardium lines the cardiac cavities and is continuous with the inner coats of the
s which enter and leave the heart. It consists, like the epicardium, of white connective
5 and elastic fibres, but it is much thinner than the epicardium, and its elastic fibres are in
some places blended into a fenestrated membrane. Its inner surface is covered with endothelial
Us, and it rests externally upon the subendocardial tissue, in which there are blood-vessels and
nerves ; the endocardium itself is entirely devoid of vessels.
880 THE VASCULAK SYSTEM.
Size of the Heart. The heart is about 125 mm. (five inches) long, 87 mm. (three and a half
inches) broad ; its greatest depth from its sterno-costal to its diaphragmatic surface is 62 mm. (two
and a half inches), and it is roughly estimated as being about the same size as the closed fist. The
size, however, is variable, the volume increasing at first rapidly, and then gradually, with increasing
age, from 22 cc. at birth to 155 cc. at the fifteenth year, and to 250 cc. by the twentieth year.
From that period to the fiftieth year, when the maximum volume (280 cc.) is attained, the in-
crease is much more gradual, and after fifty a slight decrease sets in. The volume is the same
in both sexes up to the period of puberty, but thereafter it preponderates in the male.
Weight. The average weight of the heart in the male adult is 310 grms. (11 ounces), and in
the female adult 255 grms. (9 ounces) ; but the weight varies greatly, always, however, in definite
relation to the weight of the body, the relative proportions changing at different periods of life.
Thus at birth the heart weighs 24 grms. (13|- drachms), and its relation to the body weight
is as 1 to 130, whilst in the adult the relative proportion is as 1 to 205. The heart is said to
increase rapidly in weight up to the seventh year, then more slowly up to the age of puberty,
when a second acceleration sets in ; but after the attainment of adult life the increase, which
continues till the seventieth year, is very gradual.
The above changes affect the whole heart, but the several parts also vary in their relation to
one another at different periods of life. During foetal life the right atrium is heavier than the left ;
in the first month after birth the two become equal ; at the second year the right again begins
to preponderate, and it is heavier than the left during the remainder of life. In the latter part
of foetal life the two ventricles are equal ; after birth the left grows more rapidly than the right,
until, at the end of the second year, a position of stability is gained, when the right is to the left
as 1 to 2, and this proportion is maintained until death.
Capacity. During life the capacity of the ventricles is probably the same, and each is capable
of containing about four ounces of blood, whilst the atria are a little less capacious. After
death the cavity of the right ventricle appears larger than that of the left.
Vascular Supply of the Heart. The walls of the heart are supplied by the coronary arteries
(p. 887), the branches of which pass through the interstitial tissue to all parts of the muscular
substance and to the subendocardial and subepicardial tissues ; the endocardium and the valves
are devoid of vessels. The capillaries, which are numerous, form a close -meshed network around
the muscular fibres. Sometimes the valves contain a few muscular fibres, and in those cases they
also receive some minute vessels. The majority of the veins of the heart end in the coronary
sinus, which opens into the lower part of the right atrium ; some few very small veins, how-
ever, open directly into the right atrium, and others are said to end in the left atrium, and
in the cavities of the ventricles.
Lymphatics of the Heart. Lymphatic vessels are freely distributed throughout the whole
substance of the heart. They all communicate with the superficial network which lies beneath
the epicardium. The efferent vessels from the subepicardial network accompany the coronary
arteries to the coronary sulcus and pass thence to the anterior mediastinal glands (p. 1011).
Nerves of the Heart. The heart receives its nerves from the superficial and deep cardiac
plexuses. The former lies beneath the aortic arch and the latter between the arch and the bifurca-
tion of the trachea. Through the plexuses it is connected with the vagus, the accessory
(through the vagus), and the sympathetic nerves. After leaving the cardiac plexuses many oi
the nerve -fibres enter the walls of the atria and anastomose together in the subepicardial
tissue, forming a plexus in which many ganglion cells are embedded, especially near th(
terminations of the inferior vena cava and the pulmonary veins. From the subepicardia
atrial plexus, nerve filaments, on which nerve ganglion cells have been found, pass into the
substance of the atrial walls.
Other fibres from the cardiac plexuses accompany the coronary arteries to the ventricles, anc
upon those also ganglion cells are found in the region immediately below the coronary sulcus.
The nerve-fibres which issue from the ganglionated plexuses of the heart are non-medullated
They form fine plexuses round the muscle fibres, and they terminate either in fine fibrils on th
surfaces of the muscle fibres, or in nodulated ends which lie in contact with the muscle cells.
PEKICAKDIUM.
The pericardium is a fibro-serous sac which surrounds the heart. It lies i:
the middle mediastinum, and is attached below to the diaphragm, and above an
posteriorly to the roots of the great vessels. Anteriorly and posteriorly it is i
relation with the structures in the corresponding mediastina and laterally it is i
close apposition with the pleural sacs.
The fibrous pericardium is a strong fibrous sac of conical form ; its base
attached to the central tendon and to the adjacent part of the muscular sul
stance of the diaphragm, and it is pierced by the inferior vena cava. At its ape
and posteriorly it is gradually lost upon the great vessels which enter and enier^
from the heart, giving sheaths to the aorta, the two branches of the pulmonai
artery, the superior vena cava, the four pulmonary veins, and the ligamentu
arteriosum. Its anterior surface forms the posterior boundary of the anteri
rnor
PEEICAEDIUM.
881
mediastinum, and it is attached, above and below, by the superior and inferior
sterno-pericardial ligaments, to the sternum. In the greater part of its extent
it is separated from the anterior wall of the thorax by the anterior margins of the
lungs and pleural sacs, but it is in direct relation with the left half of the lower
portion of the body of the sternum and, in many cases, with the medial ends of the
cartilages of the fourth, fifth, and sixth ribs of the left side and the left transversus
thoracis muscle. Its posterior surface forms the anterior boundary of the posterior
Right common carotid
Inferior thyrcoid veins
Left common carotid artery
Right internal jugular vein..
Right subclavian artery
Right subclavian vein j
Left internal mammary vein
Right internal mammary vein---
.it edge of fibrous pericardium
Superior vena cava **
it edge of serous pericardium 1"^
Aorta---
Division of pulmonary artery
Right pulmonary artery-
Superior vena cava-
Ipper right pulmonary vein .-
nver right pulmonary veil
Cut edges of serous
pericardium" " "
Inferior vena cava , .
Left internal jugular vein
-Thoracic duct
-Left subclavian artery
-Left subclavian vein
Left phrenic nerve
Left vagus nerve
Left superior intercostal vein
Left recurrent nerve
Ligamentum arteriosum
Left pulmonary artery
Arrow in great transverse sinus
of pericardium
Left bronchus
Upper left pulmonary vein
--- Lower left pulmonary vein
. Fibrous pericardium
Serous pericardium
} . 756. POSTERIOR WALL OF THE PERICARDIUM AFTER THE REMOVAL OF THE HEART.
Showing the relation of the serous pericardium to the great vessels.
mediastinum ; it is in relation with the oesophagus and the descending aorta,
both of which it separates from the back of the left atrium. Each lateral aspect
is in close contact with the mediastinal portion of the parietal pleura, the phrenic
nerve and its accompanying vessels intervening. The inner surface of the fibrous
sac is lined by the serous pericardium, which is closely attached to it.
The serous pericardium is a closed sac containing a little fluid (liquor peri-
cardii). It is surrounded by the fibrous pericardium and in vagina ted by the heart.
It is, therefore, separable into two portions the parietal, which lines the inner sur-
face of the fibrous sac, and the visceral, which ensheaths, or partially ensheaths, the
heart and the great vessels ; but the two portions are, of course, continuous with
one another where the serous layer is reflected on to the great vessels as they pierce
the fibrous layer. The majority of the great vessels receive only partial coverings
from the visceral layer : thus, the superior vena cava is covered anteriorly and on
57
882 THE VASCULAE SYSTEM.
each side ; the pulmonary veins anteriorly, above, and below ; and the inferior vena
cava anteriorly and on each side. The aorta and the pulmonary artery are enclosed
together in a complete sheath of the visceral layer. Therefore, when the pericardial
sac is opened from the front, it is possible to pass the fingers behind them and
in front of the atria, from the right to the left side, through a passage called the
great transverse sinus of the pericardium (Fig. 756). The spaces or pouches which
intervene between the vessels which receive partial coverings from the serous
pericardium are also called sinuses ; and the largest of them, which is bounded
below and on the right by the inferior vena cava, and above and on the left by
the left inferior pulmonary vein, is known as the great oblique sinus. It passes
upwards and to the right behind the left atrium, and lies anterior to the oesophagus
and the descending thoracic aorta.
A small fold of the serous pericardium, the vestigial fold, passes from the left
pulmonary artery to the left superior pulmonary vein, posterior to the left extremity
of the transverse sinus. It merits special attention because it encloses a fibrous
strand, the ligame^itum vence cavce sinistrce. This is a remnant of the left superior
vena cava or duct of Cuvier, which atrophied at an early period of fcetal life.
Structure. The fibrous pericardium consists of ordinary connective tissue fibres felted
together into a dense, unyielding membrane. The serous pericardium is covered on its inner
aspect by a layer of flat endothelial cells. The endothelium rest upon a basis of mixed white
and elastic fibres in which run numerous blood-vessels, lymphatics, and nerves.
ARTERLE.
AETEEIA PULMONALIS.
The pulmonary artery springs from the anterior and left angle of the base
of the right ventricle, at the termination of the conus arteriosus. It is slightly
larger at its commencement than the aorta, and is dilated, immediately above the
cusps of the valve, into three pouches, the sinuses of the pulmonary artery. It runs
upwards and posteriorly, towards the concavity of the aortic arch, curving from the
front round the left side of the ascending aorta to reach a plane posterior to the
latter ; and it terminates, by dividing into right and left branches, opposite the
fifth thoracic vertebrae. Its length is a little more than two inches.
Relations. The pulmonary artery is enclosed within the fibrous pericardium,
and is enveloped, along with the ascending aorta, in a common sheath of the
visceral layer of the serous pericardium. It lies behind the anterior extremity
of the second left intercostal space, from which it is separated by the anterior
margins of the left lung and pleural sac.
Its posterior relations are the bulb of the aorta, the anterior wall of the left
atrium, and the first part of the left coronary artery. To the right it is in relation
with the right coronary artery, the auricle of the right atrium, and the ascending
aorta, and to the left with the left coronary artery and the auricle of the left
atrium. Immediately above its bifurcation, between it and the aortic arch, is the
superficial cardiac plexus.
The right branch of the pulmonary artery is longer and larger than the
left. It passes to the hilum of the right lung, forming one of the constituents of
the root of the lung, and, after entering the lung, it descends, with the main
bronchus, to the lower extremity of the organ.
Relations. Before it enters the lung the right pulmonary artery passes posterior to
the ascending aorta, the superior vena cava, and the upper right pulmonary vein. At first,
it lies below the arch of the aorta and the right bronchus, anterior to the oesophagus, and
above the left atrium and the lower right pulmonary vein ; then it crosses anterior to the
right bronchus, immediately below the eparterial branch of that bronchus, and reaches the
hilum of the lung. After it has passed through the hilum the artery descends, in the lung,
posterior and lateral to the main bronchus and between its ventral and dorsal branches.
Branches. Before entering the hilum it gives oif a large branch to the upper lob(
of the right lung which accompanies the eparterial bronchus, and in the substance o
THE PULMONAEY AETEEY.
883
the lung it gives off numerous branches which correspond with and accompany the
dorsal, ventral, and accessory branches of the right bronchus (see p. 1097).
The left branch of the pulmonary artery, shorter, smaller, and somewhat
higher in position than the right, passes laterally and posteriorly from the bifurca-
34
IG. 757. THE PULMONARY ARTERIES AND VEINS AND THEIR KELATIONS IN A FORMA LTN-
HARDENED PREPARATION.
The ascending aorta and part of the superior vena cava have been removed.
1. Aorta.
2. Superior vena cava.
3. Upper right pulmonary
vein.
I. Right pulmonary artery.
5. Superior vena cava.
6. Left innominate vein.
7. Innominate artery.
Right innominate vein.
9. Subclavius muscle.
10. Clavicle.
11. Internal mammary artery.
12. Subclavian vein.
13. Transverse scapular artery.
14. Transverse cervical artery.
15. Vertebral artery.
16. Inferior thyreoid artery.
17. Internal jugular vein.
18. Common carotid artery.
19. Superior thyreoid artery.
20. Sterno-thyreoid muscle.
21. Omo-hyoid muscle.
22. Sterno-hyoid muscle.
23. Platysma.
24. Sterno-hyoid muscle.
25. Sterno-thyreoid muscle.
26. Sterno-mastoid muscle.
27. Phrenic nerve.
28. Vagus nerve.
29. Vertebral artery.
30. Inferior thyreoid artery.
31. Thoracic duct.
32. Left subclavian artery.
33. Subclavius muscle.
34. 1st rib.
35. Left common carotid
artery.
36. Aorta.
37. Ligamentum arteriosum.
38. Left pulmonary artery.
39. Upper left pulmonary
vein.
40. Pulmonary artery.
tion of the pulmonary stem, and runs, in the root, to the hilum of the left lung ; it
then descends, in company with the main bronchus, to the lower end of the lung.
Relations. Before it enters the lung it is crossed, anteriorly, by the upper left
pulmonary vein ; posterior to it, are the left bronchus and the descending aorta ; above, are
884 THE VASCULAR SYSTEM.
the aortic arch, to which it is connected by the ligamentum arteriosum, and the left re-
current nerve ; below, it is in relation with the lower left pulmonary vein. After entering
the lung it descends, like the right pulmonary artery, posterior and lateral to the stem
bronchus, and between its ventral and dorsal branches.
Branches. Just before it passes through the hilum it gives off a branch to the
upper lobe of the left lung, and in the substance of the lung its branches correspond
with the ventral, dorsal, and accessory branches of the bronchial tube.
THE SYSTEMIC ARTERIES.
AORTA.
The aorta is the main trunk of the general arterial system. It commences at the
base of the left ventricle and ascends, with an inclination to the right, to the level
of the second right costal cartilage ; then it curves backwards and to the left, until
it reaches the left side of the lower border of the fourth thoracic vertebra ; there
it turns downwards and descends, through the thorax into the abdomen, where it
terminates, on the left of the median plane, at the level of the fourth lumbar
vertebra, by bifurcating into the two common iliac arteries. The portion of the
aorta which is situated in the thorax is, for convenience, termed the thoracic aorta,
and the rest of the vessel is known as the abdominal aorta.
AORTA THORACALIS.
The thoracic aorta is subdivided into aorta ascendens, arcus aortse, and aorta
descendens.
Aorta Ascendens. The ascending aorta lies in the middle mediastinum. It
springs from the base of the left ventricle, posterior to the left margin of the sternum
opposite the lower border of the third left costal cartilage and at the level of thf
body of the sixth thoracic vertebra. From its origin it passes upwards, anteriorly
and to the right, and it terminates in the arch of the aorta, posterior to the righi
margin of the sternum, at the level of the second costal cartilage. Its lengtl
is from 50 to 56 mm. (2 to 2J inches), and its diameter is 28 mm. (1^ inches)
In the adult it is a little narrower at its commencement than the pulmonary
artery is, but in old age it enlarges and exceeds the latter vessel in size. Th<
diameter, however, is not uniform throughout the whole length of the ascending
aorta. Its dilated commencement, the bulbus aortse, has three secondary dilatations
the sinus aortse (Valsalva) in its wall, immediately above the semilunar cusps o
the aortic valve ; one is anterior in position, and two are situated posteriorly. A
a higher level there is a diffuse bulging of the right wall, which is known as th
great sinus of the aorta.
Relations. The ascending aorta is completely enclosed within the fibrous per.
cardium which blends above with the sheath of the vessel, and it is enveloped, togethe
with the stem of the pulmonary artery, in a tubular prolongation of the serous pericai
dium. At its origin it has the pulmonary artery in front, the transverse sinus of th
pericardium and the anterior wall of the left atrium behind, and the right atrium on it
right side. In the upper part of its course the ascending aorta is overlapped by th ,
anterior margins of the right lung and right pleural sac, whilst posterior to it are th
right atrium, the right branch of the pulmonary artery, the right bronchus, and the lei
margin of the superior vena cava. The superior vena cava lies on the right side, an
partly posterior to the upper part of the ascending aorta, whilst the pulmonary artery
at first anterior to it and then, at a higher level, on its left side.
Branches. Two branches arise from the ascending aorta, viz., the right and the le
coronary arteries. The right coronary artery springs from the anterior, and the le
from the left posterior sinus of the aorta (Valsalva) (Fig. 751).
Arcus Aortse. The arch of the aorta lies in the superior mediastinum, posteric
to the lower part of the manubrium sterni, and connects the ascending with tl
descending aorta. It commences posterior to the right margin of the sternum, c
a level with the second costal cartilage, and extends to the left side of the low<
THE ABDOMINAL AOETA. 885
border of the fourth thoracic vertebra. As its name implies, it forms an arch ;
i and the arch makes two curves, one with the convexity upwards, and the other
with the convexity forwards and to the left. From its origin it runs for a short
distance upwards, posteriorly, and to the left, anterior to the trachea ; then it
passes posteriorly, round the left side of the trachea to the left side of the body
of the fourth thoracic vertebra. Finally it turns downwards to become continuous
with the descending aorta.
At its commencement it has the same diameter as the ascending aorta, 28 mm.
(1-J- inches), but after giving off three large branches, the diameter is reduced to
23 mm. (a little less than one inch).
Relations. It is overlapped anteriorly and on the left side by the right and left
lungs and pleural sacs, but much more by the left than the right, and in the interval
between and posterior to the anterior borders of the pleural sacs it is covered by the
remains of the thymus. As it turns backwards it is crossed vertically, on the left side,
by four nerves in the following order from before backwards : the left phrenic, the
inferior cervical cardiac branch of the left vagus, the superior cardiac branch of the left
sympathetic, and the trunk of the left vagus. The left superior intercostal vein passes
1 obliquely upwards and to the right, across it, between the left vagus and left
phrenic nerves.
Posterior to, and to the right side of the arch, are the trachea, the deep cardiac plexus,
the left recurrent nerve, the left border of the oesophagus, and the thoracic duct. Above
are its three large branches the innominate, the left common carotid, and the left
subclavian arteries ; and crossing anterior to their roots is the left innominate vein.
Below is the bifurcation of the pulmonary artery and the root of the left lung ; the
ligamentum arteriosum, which is also below, attaches it to the commencement of the left
pulmonary artery, whilst to the right of the ligament lies the superficial cardiac plexus,
and to its left the left recurrent nerve.
Branches. The three great vessels which supply the head and neck, part of the
thoracic wall, and the upper extremities viz. the innominate, the left common carotid,
and the left subclavian arteries arise from the aortic arch.
Aorta descendens. The thoracic portion of the descending aorta lies in the
posterior mediastinum ; it extends from the termination of the arch, at the lower
border of the left side of the fourth thoracic vertebra, to the aortic opening in the
: diaphragm, where, opposite the twelfth thoracic vertebra, it becomes continuous
with the abdominal portion. Its length is from 1*7*5 to 20 cm. (seven to eight
inches), and its diameter diminishes from 23 mm. at its commencement to 21
i mm. at its termination.
- Relations. Immediately posterior to it are the vertebral column and the anterior
i longitudinal ligament. It rests also on the accessory hemiazygos and the hemiazygos
veins, whilst from its posterior aspect the aortic intercostal branches are given off.
Anteriorly it is in relation, from above downwards, with the root of the left lung, the
pericardium, which separates it from the back of the left atrium, the oesophagus with the
oesophageal plexus of nerves, and the crura of the diaphragm which separate it from the
caudate lobe of the liver. On the left side are the left lung and pleura. On the right side
the thoracic duct and the vena azygos form immediate relations along its whole length.
The oesophagus also lies to the right of the upper part of the descending aorta, whilst the
right lung and pleura are in relation below.
Branches. Nine pairs of aortic intercostal arteries, two left bronchial arteries, four
1 or five oesophageal, some small pericardial, and a few posterior mediastinal and superior
phrenic branches, usually arise from the thoracic part of the descending aorta.
.
AOETA ABDOMINALIS.
The abdominal portion of the descending aorta lies in the epigastric and
umbilical regions of the abdomen. It extends from the middle of the lower border
of the last thoracic vertebra to the body of the fourth lumbar vertebra, where, to the
left of the median plane, it bifurcates into the right and left common iliac arteries.
The point of division is a little below and to the left of the umbilicus, opposite
576
886
THE YASCULAE SYSTEM.
a line drawn transversely across the abdomen on a level with the highest points of
the iliac crests.
At its commencement it is 21 mm. in diameter, but after the origin of two large
branches, the coeliac and the superior mesenteric arteries, it diminishes considerably,
and then retains a fairly uniform diameter to its termination.
Relations. Posteriorly, it is in contact with the upper four lumbar vertebrae and
intervening fibro-cartilages, the anterior longitudinal ligament, and the left lumbar veins ;
Hepatic vein*.
Inferior phrenic artery
Suprarenal glancL
Inferior vena cav
Renal arter
Renal vein
Right ovarian vein
Ovarian artery
Urete
Psoas major muscle
Ascending colo:
Common iliac vein
Common iliac artery
Middle sacral artery
Ileum
Csecu
External iliac
artery
External iliac
vein
Median umbili-
cal ligamen
Oesophagus
Cms of diaphragm
Mi - Inferior phrenic
artery
Suprarenal gland
Coeliac artery
Suprarenal visin
- Superior
mesenteric artery
Renal artery
Renal vein
Lumbar arteries
Left colic artery
Ovarian artery
Inferior mesenteric
artery
Descending colon
s major muscle
Common iliac artery
Sigmoid artery
Common iliac vei
Superior luvmor-
rhoidal artery
Iliac colon
Pelvic colon
External iliac
artery
External iliac ve
terine tube
FIG. 758. THE ABDOMINAL AORTA AND ITS BRANCHES IN A FORMALIN-HARDENED PREPARATION.
the lumbar and the middle sacral arteries spring from the posterior surface of the vessel
Anteriorly, and in close relation with it, there are from above downwards the followin
structures : the coeliac axis and coeliac plexus, the pancreas and splenic vein, the superio
mesenteric artery, the left renal vein, the third part of the duodenum, the root of th
mesentery, the aortic plexus, the inferior mesenteric artery, the peritoneum and coils c
small intestine. More superficially the stomach, the transverse colon, and the greater an
lesser omenta are in front. On the right side, in the upper part of its extent, are tb
thoracic duct and cisterna chyli, the vena azygos, and the right crus of the diaphragn
the latter separating it from the right coeliac ganglion and from the upper part of 1
AKCH OF THE AOETA.
887
inferior vena cava. Its lower part is in direct relation, on the right side, with the inferior
vena cava. On the left side, the left crus of the diaphragm with the left cceliac ganglion,
and the terminal portion of the duodenum, are in close relation with its upper part, whilst
in the lower portion of its extent the peritoneum and some coils of the small intestine
are in contact with it. Lumbar lymph glands lie around it, on all sides.
Branches. The branches form two groups, visceral and parietal, and each group
consists of paired and unpaired vessels, as follows :
Visceral.
Unpaired.
Paired.
Cceliac
Superior mesen-
teric
Inferior mesen-
teric
Suprarenal
Renal
Testicular or
ovarian
Parietal.
Unpaired.
Middle sacral (which
is the original
continuation)
Paired.
Inferior phrenic
Lumbar (four pairs)
Common iliac
BRANCHES OF THE ASCENDING AOKTA.
ARTERLE; CORONARI^E.
The coronary arteries are two in number, a right and a left ; they are distributed
almost entirely to the heart, but give also some small branches to the roots of the
great vessels, and to the pericardium (Figs. 750, 751, and 754).
The right coronary artery springs from the anterior aortic sinus. It runs
forwards, between the root of the pulmonary artery and the auricle of the right
atrium, to the coronary sulcus, in which it passes downwards and to the right to
the junction of the right and inferior margins of the heart. There it turns to the
left, in the inferior part of the coronary sulcus, as far as the posterior end of the
inferior interventricular sulcus, where it gives off its interventricular branch
and then ends by anastomosing with the circumflex branch of the left coronary
artery. It is accompanied by branches from the cardiac plexus and the right
coronary vein.
Branches. The interventricular branch runs forwards in the inferior interventricular
.sulcus ; it supplies both ventricles, and anastomoses, at the apex of the heart, with the inter-
ventricular branch of the left coronary artery.
Aortic and pulmonary twigs are distributed to the roots of the aorta and pulmonary artery
respectively. A right atrial branch passes upwards on the anterior surface of the right atrium,
tween it and the ascending aorta ; one or more anterior ventricular branches, of small size,
descend on -the anterior surface of the right ventricle ; a branch of larger size, the right
marginal artery, runs along the inferior margin of the heart and gives branches to both
surfaces of the right ventricle.
The left coronary artery arises from the left posterior aortic sinus. Its short
trunk runs forwards, between the root of the pulmonary artery and the auricle of the
left atrium, to the coronary sulcus at the upper end of the anterior interventricular
groove, where it divides into a circumflex and an interventricular branch.
Branches. The circumflex branch runs to the left margin of the heart, and there turns to
the inferior surface where it comes into relation with the coronary sinus ; it ends by anastomos-
ith the right coronary artery. It supplies branches to the left atrium, the left margin of
heart, and the posterior part of the inferior surface of the left ventricle. The inter -
icular terminal branch passes down the anterior interventricular sulcus to the apex of
i heart, where it anastomoses with the interventricular branch from the right coronary ; it
s both ventricles, and is accompanied by cardiac nerves and by the great cardiac vein.
A left atrial branch or branches of small size pass to the wall of the left atrium, and small
rtic and pulmonary branches are also given to the roots of the aorta and pulmonary artery.
BRANCHES OF THE ARCH OF THE AORTA.
The branches which arise from the arch of the aorta supply the head and neck,
i upper extremities, and part of the body wall.
57c
888 THE VASCULAR SYSTEM.
They are three in number, viz., the innominate, the left common carotid, and
the left subclavian arteries. The innominate is a short trunk, from the termination
of which the right common carotid and the right subclavian arteries spring (Figs.
756 and 757) ; thus there is, at first, a difference between the stem vessels of opposite
sides, but the subsequent course and the ultimate distribution of those vessels
closely correspond.
ARTERIA ANONYMA.
The innominate artery (Fig. 757) arises, posterior to the middle of the
manubrium sterni, from the convexity of the arch of the aorta near its right
or anterior extremity, and it ends opposite the right sterno- clavicular articulation,
where it divides into the right subclavian and right common carotid arteries.
Course. The trunk measures from 37 to 50 mm. in length ; it runs upwards,
posteriorly, and laterally, in the superior mediastinum, to the root of the neck.
Relations. Posterior. It is in contact behind, with the trachea below and with
the right pleural sac above.
Anterior. The left innominate vein crosses in front of the lower part of the artery,
and above that the sterno-thyreoid muscle separates it from the sterno-hyoid and the
right sterno-clavicular joint. The remains of the thymus, whicfr separate it from the
manubrium sterni, are also in front.
Right Lateral. The right innominate vein and the upper part of the superior vena
cava are on the right side of the artery.
Left Lateral. On its left side is the origin of the left common carotid artery, whilst
at a higher level the trachea is in contact with it.
Branches. As a rule the innominate artery does not give off any branches except
its two terminals, but occasionally it furnishes an additional branch, the thyreoidea ima.
The thyreoidea ima is an inconstant and slender vessel. When present it
may arise from the arch of the aorta, but it springs usually from the lower part of
the innominate. It passes upwards, anterior to the trachea, through the anterior
part of the superior mediastinum and the lower part of the neck, and gives oft
branches to the lateral lobes and isthmus of the thyreoid body and to the trachea.
THE AKTEEIES OF THE HEAD AND NECK.
The vessels distributed to the head and neck are chiefly derived from the
carotid trunks ; there are, however, in addition, other vessels which arise from the
main arterial stems of the upper extremities, and it will be advantageous tc
describe the most important of those, viz., the vertebral arteries, with the carotic
system. The smaller additional branches will be considered along with the
remaining branches of the subclavian arteries.
The carotid system of arteries consists, on each side, of a common carotid trunk
which divides into internal and external carotid arteries, from which numerou
branches are given off (Figs. 759, 760, 761, 764).
The internal carotid arteries are distributed, almost entirely, to the contents o
the cranial cavity, internal to the dura mater, and to the structures in the cavit;
of the orbit. The external carotid arteries, on the other hand, supply structures c
the head and neck more externally situated.
It is to be noted, however, that the vascular supply of the brain is not wholl
derived from the internal carotid vessels, but that it is contributed to, largely, b
the vertebral arteries also.
ARTERIA CAROTIDES COMMUNES.
The right and the left common carotid arteries are of unequal length. Tl
right common carotid commences at the bifurcation of the innominate arte)
posterior to the right sterno-clavicular articulation ; the left arises in the superi
mediastinum, from the arch of the aorta; but each terminates at the level
the upper border of the thyreoid cartilage ; the left artery has thus a short intr
THE COMMON CAEOTID AKTEKIES. 889
thoracic course, and, so far, its relations call for separate consideration ; whilst in
the rest of its course it passes upwards in the neck, like the right common carotid,
and has almost similar relations.
Thoracic Portion of the Left Common Carotid. The thoracic or mediastinal
portion of the left common carotid artery extends from the upper aspect of the
aortic arch, immediately posterior and to the left of the origin of the innominate
artery, to the left sterno-clavicular articulation, where the cervical portion com-
mences. It is from 25 to 37 mm. (1 or 1J inches) in length, and it runs
upwards and slightly laterally through the upper part of the superior mediastinum.
It lies on a more posterior plane than the innominate artery.
Relations. Posterior. The vessel is in contact posteriorly, and from below upwards,
with the trachea, the left recurrent nerve, the oesophagus, and the thoracic duct ; and the
thoracic part of the left subclavian artery is a postero-lateral relation.
Anterior. The left innominate vein runs obliquely across the anterior aspect of the
artery, upon which cardiac branches from the left vagus and sympathetic descend
vertically. These structures, together with the remains of the thymus and the anterior
margins of the left lung and pleura, separate the artery from the manubrium sterni,
and from the origins of the sterno-hyoid and sterno-thyreoid muscles.
Medial. The innominate artery below, and the trachea above, are on the right side.
Lateral. The left pleura, and, on a posterior plane, the left phrenic and vagus nerves
and the left subclavian artery are on its left side.
Cervical Portion of the Left Common Carotid Artery. The cervical part of
the left common carotid artery is about 85 mm. (three and a half inches) long ; it
extends from the left sterno-clavicular articulation to the level of the upper border
of the thyreoid cartilage and the lower border of the third cervical vertebra, where
it ends by dividing into the external and internal carotid arteries.
Course. It runs upwards, laterally, and backwards, through the muscular and
in the lower portion of the carotid divisions of the anterior triangle of the neck.
Below it is separated from its fellow of the opposite side by the trachea and the
oesophagus, and above by the relatively wide pharynx.
Relations. It is enclosed, together with the internal jugular vein and the vagus
nerve, in a sheath of deep cervical fascia the carotid sheath.
Posterior. The longus colli and scalenus anterior, below, and the longus capitis, above,
are separated from the posterior surface of the artery and its sheath by the pre vertebral
fascia and the sympathetic trunk. The vertebral artery arid the thoracic duct are posterior
to it at the level of the seventh cervical vertebra ; the inferior thyreoid artery crosses
behind it, either between it and the vertebral or between it and the transverse process of
the sixth cervical vertebra, and the vagus nerve lies postero-lateral to it.
Superficial. The descendens branch of the hypoglossal nerve lies superficial to the
artery, usually outside the sheath, but sometimes enclosed in it (Fig. 759). Opposite the
sixth cervical vertebra the omo-hyoid muscle and the sterno-mastoid branch of the superior
thyreoid artery cross superficial to the carotid artery, which is overlapped, above the omo-
hyoid muscle, by the anterior border of the sterno-mastoid and by cervical lymph glands.
It is frequently crossed, in that part of its extent, by the superior thyreoid vein (Figs. 759,
36). Below the omo-hyoid the artery is covered by the sterno-thyreoid, the sterno-hyoid,
and the sterno-mastoid muscles, and it may be overlapped by the lateral lobe of the
thyreoid gland ; it is also crossed, deep to the muscles, by the middle thyreoid vein, whilst
occasionally a communication between the common facial and anterior jugular veins
descends anterior to the artery along the anterior border of the sterno-mastoid. Just
above the sternum the anterior jugular vein is in front of the artery, but separated from
it by the sterno-hyoid and sterno-thyreoid muscles.
Medial. The trachea and oesophagus, with the recurrent nerve in the angle between
them, are medial to the lower part of the artery ; the larynx and pharynx are medial
to its upper part. The carotid gland or glomus carOticum lies on the medial side of the
termination of the artery.
Lateral. The internal jugular vein occupies the lateral part of the carotid sheath.
The vein lies not only to the lateral side of the artery, but also slightly in front of it,
especially in the lower part of the neck.
Branches. As a rule no branches are given off from either of the common carotid
890
THE VASCULAE SYSTEM.
arteries, except the terminal branches and some minute twigs from each to the correspond-
ing carotid sheath and glomus caroticum.
The right common carotid artery, as already stated, differs as regards origin
from the left common carotid. In length and general position it corresponds with
the^ cervical portion of the left common carotid, and its relations also are very
similar. Such differences as exist may be briefly summarised as follows: The
A. et V., temporalis superficialis -
A. et V auriculares posteriores .
End of A. carotis externa --
A. et V., oc-cipitalis
N. occipitalis tertius
Mm. digastrious et stylohyoideu
N. oceipitalis minor
Kami sternomastoideoe
N. hypoglossus
A. carotis externa
A. carotis iuterna
A. superftcialis colli
Kamus commuui
A. traiisversa colli -
A. subclavia
M. serratus anterior
A. et V., transversa scapulae
A. thoracoacromia"
ramus acromi
M. deltoideus .
A. thoraco- -^. M
aeromialis, ramus
deltoideus
A. et V, supraorbitalix
. A. et V., frontalis
A. angula
A. labialis superior
A. labialis inferior
A. maxillaris externa
A. etV.,maxillaris externa
_ Gl. .submaxillaris
(deep part)
-- A. lingualis
A. submentalis
. mylohyoideus
hypoglossus, ramus thyreohyoideus
. laiyngeus superior, ramus interims
" V. facialis comimmis
-A. et V., thyreoidea superior
- A. carotis communis
M. sternohyoideus
M. omohyoideus
M sternohyoi mucous membrane of the roof of the mouth. As it descends it gives off the artery of the
pterygeid canal, and several small twigs which pass through the accessory palatine canals
to supply the soft palate, and to anastomose with the ascending palatine and tonsillar
branches of the external maxillary and with the ascending pharyngeal artery. The great
palatine artery, which is the continuation of the descending palatine, runs forwards in the
roof of the mouth, medial to the alveolar process, to terminate in a small branch, which
ascends through the incisive foramen and anastomoses with the posterior artery of the
58 a
900 THE VASCULAK SYSTEM.
septum nasi, which is a branch of the spheno-palatine artery. In its course forwards in
the roof of the mouth the great palatine artery supplies the gums and the mucous
membrane of the hard palate, and also the palatine and maxillary bones.
(d) The artery of the pterygoid canal is a long, slender branch, usually given off
from the descending palatine ; it runs backwards through the pterygoid canal with the
corresponding nerve (Vidian), and supplies branches to the upper part of the pharynx,
to the levator and tensor veli palatini muscles, and to the auditory tube. One of the
latter branches passes along the wall of the auditory tube to the tympanic cavity, where
it anastomoses with the other tympanic arteries.
(e) The pharyngeal branch is a small artery which runs backwards, with the pharyngeal
branch of spheno-palatine ganglion, through the pharyngeal canal 'to the roof of the
pharynx. It supplies the upper and posterior part of the roof of the nose, the roof of the
pharynx, the sphenoidal sinus, and the lower part of the auditory (Eustachian) tube, and
anastomoses with the pterygoid branch of the internal carotid.
(/) The spheno-palatine branch springs from the termination of the internal maxillary
artery. It passes medially, through the spheno-palatine foramen, into the nasal cavity,
where it gives off (a) a branch to the sphenoidal sinus, and (b) a branch which may replace
the pharyngeal artery and which has a similar course and distribution. Then it divides into
lateral and septal posterior nasal branches. The lateral posterior nasal branches supply
the lateral wall of the nasal cavity and the sinuses which open through it, and they
anastomose with the posterior and anterior ethmoidal arteries and* the lateral nasal
branch of the external maxillary. The septal posterior nasal branch accompanies the
posterior septal nerve across the roof of the nasal cavity and then anteriorly and down-
wards in the groove on the vomer. It anastomoses with the great palatine artery and
the septal branch of the superior labial.
ARTERIA CAROTIS INTERNA.
The internal carotid artery (Figs. 759, 761, 764, and 788) commences at the
termination of the common carotid, opposite the upper i border of the thyreoid
cartilage, and terminates in the middle fossa of the skull, close to the commence-
ment of the stem of the lateral fissure (Sylvius), where it divides into the middle
and anterior cerebral arteries.
Course. From its origin in the carotid triangle it ascends to the base of the
skull, lying first in the carotid triangle, medial to the anterior border of the
sterno-mastoid, and then between the areolar tissue behind the lateral border of
the pharynx, medially, and the posterior belly of the digastric and the styloid
process and its muscles laterally. At its commencement it lies postero-lateral to
the external carotid, but as it ascends it gradually passes to the medial side of the
external carotid, from which it is separated by the styloid process, the stylo-
pharyngeus muscle, the glosso-pharyngeal nerve, and the pharyngeal branch of the
vagus.
At the base of the skull it enters the carotid canal, in which it ascends, anterior
to the tympanum and the cochlea ; then it turns antero-medially to the apex of
the bone where it enters the foramen lacerum, through which it ascends, along the
side of the body of the sphenoid, to the middle fossa of the cranium.
In the middle fossa it runs forwards, in the lateral wall of the cavernous sinus,
bo the small wing of the sphenoid ; there it turns backwards along the medial
border of the anterior clinoid process, which it grooves. At the posterioi
extremity of the process it turns upwards to its termination at the medial end oi
the stem of the lateral fissure (Sylvius), below the medial part of the anterioi
perforated substance.
Relations. The relations of the various parts of the artery require separat*
consideration
In the Neck. Posterior. The longus capitis (O.T. rectus capitis anticus major), th<
prevertebral fascia, and the sympathetic trunk separate it from the transverse processes o
the cervical vertebrae, and postero-lateral to it are the internal jugular vein and the vagu
nerve. The accessory and the glossopharyngeal nerves are also postero-lateral to th<
artery for a short distance, in the upper part of the neck, where they intervene betweei
it and the internal jugular vein. Medial or deep to the internal carotid is the externa
THE INTERNAL CAEOTID AETEEY.
901
carotid artery for a short distance below, and afterwards the wall of the pharynx, the
areolar tissue posterior to the wall of the pharynx, the ascending pharyngeal artery, the
pharyngeal plexus of veins, and the external and internal laryngeal nerves. Just before
it enters the temporal bone the levator palati muscle is to its medial side. Lateral or
, superficial to it are the sterno-mastoid, skin, and fasciae, and it is crossed under cover
of the sterno-mastoid, from below upwards, by the hypoglossal nerve, the occipital artery,
, and the posterior auricular artery. It is also crossed superficially, between the last-
: mentioned arteries, by the digastric and stylo-hyoid muscles, which separate it from the
parotid gland, and below the digastric it is covered by the lower part of the postero-medial
surface of the gland. Passing obliquely across its anterior lateral surface, and separating
Vertebral arteries
Internal carotid artery-.
Ascending pharyngeal
artery
Ascending palatine artery
Styloglossus muscle-.
Stylopharyngeus muscle
Posterior auricular artery.
Occipital artery.
External maxillary artery-
Lingual arter;
External carotid artery
Superior thyreoid artery
Frontal artery
Nasal artery
Ciliary arteries
,1 max-
illary artery
W
Common carotid
artery
'ertebral artery
Deep
cervical artery
Superior inter- /
costal artery_/L_
Anastomosis /
with first
aortic inter-
:ostal artery
communicating arteries
"-* cerebral arteries
Thyreo-cervical trunk
Subclavian artery
Internal mammary artery
Innominate artery
FIG. 761. THE CAROTID, SUBCLAVIAN, AND VERTEBRAL ARTERIES AND THEIR MAIN BRANCHES.
it from the external carotid artery, are the following structures, viz., the stylo-pharyngeus,
the styloid process, or the styloglossus muscle, and the glossopharyngeal nerve, the
pharyngeal branch of the vagus, and some sympathetic twigs.
In the Carotid Canal. The artery, as it passes upwards, is an tero -inferior to the cochlea
and the tympanum; postero-medial to the auditory (Eustachian) tube and the canal for
the tensor tympani ; and below the semilunar ganglion. The thin lamina of bone which
separates it from the tympanum is frequently perforated, and that between it and the
semilunar ganglion is frequently absent. In its course through the canal it is accom-
panied by small veins and sympathetic nerves. The veins receive tributaries from
the tympanum, and communicate above with the cavernous sinus and below with the
internal jugular vein. The nerves are branches of the nervus caroticus internus, which
is the upward continuation of the sympathetic trunk ; they form a plexus around the
artery, called the internal carotid plexus.
As it enters the cavity of the cranium the internal carotid artery pierces the external
layer of the dura mater and passes between the lingula and the sixth cerebral nerve
laterally, and the posterior petrosal process of the body of the sphenoid medially.
In the Cranial Cavity. The artery runs forwards, in the lateral wall of the cavernous
* 58 &
902 THE VASCULAR SYSTEM.
sinus, in relation with the oculomotor, trochlear, the ophthalmic division of the trigeminal,
and the abducens nerves laterally, and with the endothelial wall of the sinus medially.
When it reaches the lower root of the small wing of the sphenoid it turns upwards to the
medial side of the anterior clinoid process, pierces the inner layer of the dura mater, and
comes into close relation with the inferior surface of the optic nerve immediately
posterior to the optic foramen. It then turns abruptly backwards below the optic
nerve, and on the medial side of the anterior clinoid process which it frequently grooves ;
inclining laterally, it runs between the optic and oculo-motor nerves, and below the
anterior perforated substance, to the medial end of the stem of the lateral fissure (Sylvius),
where it turns upwards, at some distance from the corresponding lateral border of the
optic chiasma, and, after piercing the arachnoid, divides into its two terminal branches,
the anterior and middle cerebral arteries.
BRANCHES OF THE INTERNAL CAROTID ARTERY.
Branches are given off from the internal carotid in the temporal bone and in
the cranium, but, as a rule, no regular branches are given off in the neck.
In the Temporal Bone. (1) A carotico-tympanic branch, very small, perforates the
posterior wall of the carotid canal, and anastomoses in the tympanum with the stylo-mastoid
artery and with the tympanic branches of the internal maxillary and ascending pharyngeal
arteries.
(2) A small and inconstant branch which accompanies the nerve of the pterygoid
canal (Vidian) ; it anastomoses with a branch of the descending palatine artery.
In the Cranium. (1) Cavernous, small branches to the walls of the cavernous sinus
and to the oculomotor, trochlear, trigeminal, and abducens nerves.
(2) Minute twigs which supply the sernilunar ganglion.
(3) Hypophyseal branches pass to the hypophysis (O.T. pituitary body).
(4) Meningeal branches ramify in the dura mater of the middle cranial fossa, anasto-
mosing with the branches of the middle and accessory meningeal arteries.
(5) Arteria Ophthalmica. The ophthalmic artery (Fig. 761) springs from
Intermediate medial frontal artery Corpus callosum Septum pellucidum
Posterior medial frontal artery
Parieto-occipital
artery
Medial orbital
artery
Anterior cerebral
artery
Lateral orbital arterj
Middle cerebral artery / - jiiBP^^^^X^ Calcarine artery
Temporal branch of middle cerebral Posterior cer- Pedunculus Temporal branches of posterior cerebral
ebral artery cerebri
FIG. 762. DISTRIBUTION OF THE CEREBRAL ARTERIES ON THE MEDIAL AND INFERIOR SURFACES
OF THE CEREBRAL HEMISPHERES.
The anterior cerebral artery is coloured green, the middle cerebral artery red, and the
posterior cerebral artery orange.
the antero-medial side of the internal carotid as it turns upwards on the medi*
side of the anterior clinoid process. It passes forwards and laterally, below th
optic nerve and through the optic foramen into the orbital cavity. In tt
orbit it runs forwards, for a short distance, on the lateral side of the optic nerv
and it is in relation laterally with the ciliary ganglion and the lateral recti
IBEANCHES OF THE INTEENAL CAEOTID AETEEY. 903
scle ; turning upwards and medially, it crosses, between the optic nerve and
the superior rectus, to the medial wall of the orbit, where it turns forwards
to terminate at the anterior boundary of the cavity by dividing into frontal
and dorsal nasal branches. It is accompanied, at first, by the naso-ciliary nerve,
and, in the terminal part of its course, by the infra-trochlear nerve.
Branches. The brandies of the ophthalmic artery are numerous, (a) The posterior ciliary,
usually six to eight in number, run forwards at the sides of the optic nerve ; they soon divide
into numerous branches which pierce the posterior part of the sclera ; the, majority terminate
in the chorioid coat of the eye as the short posterior ciliary arteries, but two of larger size,
the long posterior ciliary arteries, run forwards, one on each side of the eyeball, almost in
the horizontal plane, between the sclera and the chorioid coat, to the periphery of the iris,
where they divide. The resulting branches anastomose together and form a circle at the periphery
if the iris, from which secondary branches run inwards and anastomose together in a second
circle near the papillary margin of the iris.
(6) The central artery of the retina arises near to, or in common with, the preceding vessels.
It pierces the infero-medial aspect of the optic nerve, about 12 mm. (half an inch) posterior
to the sclera, and runs in its centre to the retina, where it breaks up into terminal branches.
(c) Anterior meningeal. A small branch which passes backwards through the superior orbital
Ascending parietal artery Ascending frontal arteries
Inferior lateral
frontal artery
Lateral orbital artery
Parieto-temporal artery Temporal branches of middle cerebral
FIG. 763. DISTRIBUTION OF CEREBRAL ARTERIES ON THE CONVEX SURFACE OF THE CEREBRUM.
Anterior cerebral artery is coloured green, the middle cerebral red, and the posterior cerebral orange.
fissure into the middle fossa of the cranium, where it anastomoses with the middle and accessory
meningeal arteries, and with the meningeal branches of the internal carotid and lacrimal arteries.
(d) The lacrimal artery arises from the ophthalmic on the lateral side of the optic nerve.
It runs forwards, along the upper border of the lateral rectus, to the upper lateral angle of the
orbit, and in its course gives off glandular branches to the lacrimal gland, muscular branches to
the lateral and superior recti, palpebral branches to the upper eyelid and the upper and lateral
part of the forehead, temporal and zygomatic branches, which accompany the zygomatico-temporal
and zygomatico- facial branches of the zygomatic (temporo-malar) nerve, to the face and the
infra -temporal fossa respectively ; anterior ciliary branches, which perforate the sclera behind
the corneo-scleral junction and anastomose with the posterior ciliary arteries ; and a recurrent
meningeal branch, which passes backwards, through the lateral part of the superior orbital
fissure, to anastomose, in the middle fossa of the skull, with the middle meningeal artery.
() Muscular. These branches are usually arranged in two sets, lateral and medial. The
former supply the upper and lateral, and the latter the lower and medial orbital muscles. They
anastomose with muscular branches from the lacrimal and the supra-orbital vessels, and they
give off anterior ciliary branches.
(/) The supra-orbital branch is given off as the ophthalmic artery crosses above the optic
nerve. It passes round the medial borders of the superior rectus and levator palpebrse muscles,
and rims forwards, between the levator and the periosteum, to the supra-orbital notch, accompany-
ing the frontal nerve and its supra-orbital branch. Passing through the notch it reaches the scalp,
and, after it has perforated the frontalis muscle, it anastomoses with the frontal branches of the
superficial temporal and ophthalmic arteries.
(g) Anterior and posterior ethmoidal branches arise from the ophthalmic as it runs forwards
along the medial boundary of the orbit. They pass medially, between the superior oblique and
the medial rectus. The posterior, which is much the smaller of the two, traverses the posterior
ethmoidal canal, and supplies the posterior ethmoidal cells and the posterior and upper part of
904 THE VASCULAE SYSTEM.
the lateral wall of the nasal cavity. The anterior ethmoidal artery passes through the anterior
ethmoidal canal with the anterior ethmoidal nerve, enters the anterior fossa of the skull and
crosses the lamina cribrosa of the ethmoid to the nasal slit, through which it reaches the
nasal cavity where it descends, with the external branch of the nasal nerve, in a groove on the
posterior surface of the nasal bone, and, finally, passes between the lateral cartilage and the
lower border of the nasal bone to the tip of the nose. It supplies branches to the membranes
of the brain in the anterior cranial fossa as well as to the anterior ethmoidal cells, the frontal
sinus, the anterior and upper part of the nasal rnuco- periosteum, and the skin on the dorsum
of the nose.
(h) Palpebral branches, upper and lower, are given off near the termination of the
ophthalmic. They are distributed to the upper and lower eyelids, and they anastomose with the
lacrimal, supra-orbital, and infra-orbital arteries.
(i) The dorsal nasal terminal branch passes out of the orbit above the medial tarsal
ligament. It pierces the palpebral fascia, and terminates on the side of the nose by anastomosing
with the angular branch of the external maxillary artery.
(j) The frontal terminal branch pierces the palpebral fascia at the upper and medial
part of the orbit, and ascends, with the supra-trochlear nerve, in the superficial fascia of the
anterior and medial part of the scalp, anastomosing with its fellow of the opposite side and
with the supra-orbital artery.
(6) The posterior communicating artery arises from the internal carotid near its
termination. It runs backwards, below the optic tract and anterior to the pedunculus
cerebri, and, passing above the oculomotor nerve, joins the posterior cerebral artery forming
part of the circulus arteriosus (Willis). It gives branches to the optic chiasma, the optic
tract, the pedunculus cerebri, the interpeduncular region, the internal capsule, and the optic
thalamus. The posterior communicating artery varies much in size ; it may be small
on one or both sides, sometimes it is very large on one side ; occasionally it replaces
the posterior cerebral artery, and it sometimes arises from the middle cerebral artery.
(7) The chorioidal is a small branch, which also arises near the termination of the
internal carotid ; it passes backwards and laterally, between the pedunculus cerebri and
the uncus, to the lower and anterior part of the chorioidal fissure which it enters, and
it terminates in the chorioidal plexus in the inferior cornu of the lateral ventricle.
It supplies the optic tract, the pedunculus cerebri, the uncus, the posterior part of the
internal capsule, the tail of the caudate nucleus, part of the lentiform nucleus, and the
amygdaloid nucleus.
(8) Arteria Cerebri Anterior. The anterior cerebral artery is the smaller
of the two terminal branches of the internal carotid. It passes forwards and
medially, above the optic chiasma and in front of the lamina terminalis,. to the
commencement of the longitudinal fissure ; there it turns round the genu of the
corpus callosum, and runs backwards to the parietal lobe of the brain. At
the commencement of the longitudinal fissure it is closely connected with its
fellow of the opposite side by a wide but short anterior communicating artery,
and in the remainder of its course it is closely accompanied by its fellow artery
of the opposite side.
Branches. Branches of all the cerebral arteries are distributed both to the basal
ganglionic masses of the brain and to the cerebral cortex ; they therefore form two distinct
groups which do not communicate with one another (a) central or basal ; (b) cortical.
The branches of the anterior cerebral include :
(a) Central or basal branches. The antero-medial basal arteries, a small group of
vessels, constitute the basal branches of the anterior cerebral artery ; they pass upwards
into the base of the brain, in front of the optic chiasma, and supply the rostrum of
the corpus callosum, the lamina terminalis, the head of the caudate nucleus, the anterior
part of the lentiform nucleus and internal capsule, the columns of the fornix, the septum
pellucidium, and the anterior commissure.
(b) Cortical branches. (b l ) Medial orbital, one or more small branches which
supply the medial orbital convolution, the gyrus rectus, and the olfactory lobe.
(6 2 ) Anterior medial frontal, one or more branches which are distributed to the an-
terior and lower part of the medial surface of the superior frontal gyrus, and to the anterioi
portions of the superior and middle frontal gyri on the lateral surface of the hemisphere.
(6 8 ) An intermediate medial frontal is distributed to the posterior part of the media
lateral surfaces of the superior frontal gyrus and to the upper parts of the anterior anc
posterior central gyri.
(6 4 ) The posterior medial frontal runs backwards to the preecimeus. It supplie
the corpus callosum, the praecuneus, and the upper part of the superior parietal lobule.
VEKTEBEAL AETEEY. 905
(9) Arteria Cerebri Media. The middle cerebral artery is the larger of the
two terminal branches, and the more direct continuation of the internal carotid
artery. It passes laterally, in the stem of the lateral fissure (Sylvius), to the
surface of the insula, and it divides, in the posterior part of the circular sulcus
(Eeil), into parieto-temporal and temporal terminal branches.
Branches. (a) The central or basal, which constitute the antero- lateral basal
arteries, are numerous and very variable in size. They arise at the base of the brain,
in the region of the anterior perforated substance. Two sets, known as the medial and
the lateral striate arteries, are distinguishable.
(a 1 ) The medial striate arteries pass upwards through the two medial segments
of the lentiform nucleus (globus pallidus) and the internal capsule to terminate in the
caudate nucleus. They supply the anterior portions of the lentiform and caudate nuclei
and of the internal capsule.
(a 2 ) The lateral striate arteries pass upwards through the lateral segment (puta-
men) of the lentiform nucleus, or between it and the external capsule, and they form two
sets : an anterior, the lenticulo-striate, and a posterior, the lenticulo-optic ; both sets
traverse the lentiform nucleus and the internal capsule, but the lenticulo-striate arteries
terminate in the caudate nucleus, and the lenticulo-optic in the thalamus. One of the
lenticulo-striate arteries, which passes in the first instance round the lateral side of the
lentiform nucleus, and afterwards through its substance, is larger than its companions ; it
frequently ruptures, and is known as the " artery of cerebral haemorrhage."
(b) Cortical branches are given off as the middle cerebral artery passes over the surface
of the insula at the bottom of the lateral fissure, as follows :
(6 1 ) The lateral orbital runs forwards and laterally, and is distributed to the
lateral part of the orbital surface of the frontal lobe and to the inferior frontal gyrus.
(b 2 ) The inferior lateral frontal, which supplies the inferior and middle frontal
gJ ri -
(6 3 ) The ascending frontal, which turns round the upper margin of the lateral fissure,
and is distributed to the anterior central gyrus and to the posterior part of the middle
frontal gyrus.
(6 4 ) The ascending parietal branch emerges from the lateral fissure (Sylvius) and
passes upwards along the posterior border of the posterior central gyrus, supplying that
gyrus and the superior parietal lobule.
(6 5 ) The temporal branch passes out of the lateral fissure, and turns downwards to
supply the superior and middle temporal gyri.
(6 6 ) The parieto-temporal branch continues backwards, in the direction of the main
stem of the middle cerebral artery, and emerges from the posterior end of the lateral
fissure ; it supplies the inferior parietal lobule, part of the lateral surface of the occipital
lobe, and the posterior part of the temporal lobe.
ARTERIA VERTEBRALIS.
The vertebral artery (Figs. 757 and 761) is the first branch given off from
the subclavian trunk; it arises from the upper and posterior part of the parent
stem, opposite the interval between the anterior scalene and the longus colli
muscles, and terminates at the lower border of the pons (Varolii) by uniting with
its fellow of the opposite side to form the basilar artery.
Course and Relations. The vertebral artery is divisible into four parts.
The first part runs upwards and backwards, between the scalenus anterior and
the lateral border of the longus colli, to the foramen in the transverse process of the
sixth cervical vertebra. It is surrounded by a plexus of sympathetic nerve fibres,
is covered anteriorly by the vertebral and internal jugular veins, and it may be
crossed anteriorly by the inferior thyreoid artery. On the left side the terminal
; part of the thoracic duct also passes anterior to it. The second part runs upwards
through the foramina in the transverse processes of the upper six cervical vertebrae.
far as the second cervical vertebra its course is almost vertical ; as it passes
through the transverse process of the epistropheus, however, it is directed obliquely
upwards and laterally to the atlas. It is surrounded by a plexus of sympathetic
nerve fibres, and also by a plexus of veins. The artery lies anterior to the trunks
of the cervical nerves, and medial to the intertransverse muscles. The third part
906
THE VASCULAE SYSTEM.
emerges from the foramen in the transverse process of the atlas, between the anterior
division of the sub-occipital nerve medially and the rectus capitis lateralis laterally,
and runs almost horizontally backwards and medially, round the lateral and posterior
aspects of the corresponding superior articular process of the atlas. In this part of
its course it enters the sub-occipital triangle, where it lies in the groove on the
upper surface of the posterior arch of the atlas (sulcus arteriae vertebralis). It is
separated from the bone by the sub-occipital nerve, and is overlapped superficially
by the adjacent borders of the superior and inferior oblique muscles. Finally, this
Anterior communicating artery
Olfactory tract
Anterior cerebral artery
Optic chiasma
Infundibulum
Oculomotor nerv
Glossopharyn
geal nerve
Vagus nerve
Accessory ner
Basilar artery
Anterior
inferior cere-
bellar artery
Posterior inferior
cerebellar artery
Vertebral artery
Hypoglossal nerve Anterior spinal artery
FIG. 764. THE ARTERIES OF THE BASE OF THE BRAIN. THE CIRCULDS ARTERIOSUS (WILLIS).
part of the artery passes anterior to the oblique ligament of the atlas and enters
the vertebral canal.
The fourth part pierces the spinal dura mater and runs upwards into the cranial
cavity. It passes between the roots of the hypoglossal nerve, posteriorly, and the
first dentation of the ligamentum denticulatum, anteriorly, pierces the arachnoid, and,
gradually inclining to the front of the medulla oblongata, reaches the lower border
of the pons, where it unites with its fellow of the opposite side to form the basilar
artery.
Branches. From the first part. As a rule there are only a few small muscular
twigs from this portion of the artery.
From the second part. (1) Muscular branches which vary in number and size,
supply the deep muscles of the neck, and anastomose with the profunda cervicis, the
ascending cervical, and the occipital arteries.
VERTEBRAL ARTERY. 907
(2) Spinal branches pass from the medial side of the second part of the vertebral
artery, through the intervertebral foramina, into the vertebral canal, where they give off
twigs which pass along the roots of the spinal nerves to reinforce the anterior and posterior
spinal arteries; they supply the bodies of the vertebrae and the intervertebral fibro-
cartilages, and they anastomose with corresponding arteries above and below.
From the third part. (1) Muscular branches to the sub-occipital muscles.
(2) Anastomotic branches which unite with the descending branch (O.T. princeps
cervicis) of the occipital and with the prof unda cervicis artery.
From the fourth part. (1) Meningeal. One or two small branches given off before
the vertebral artery pierces the dura mater. They ascend into the posterior fossa of the
skull, where they anastomose with meningeal branches of the occipital and ascending
pharyngeal arteries, and occasionally with branches of the middle meningeal artery.
(2) Posterior Spinal. The posterior spinal branch springs most commonly from the
posterior inferior cerebellar branch of the vertebral (Stopford, 1916), but occasionally it
arises from the vertebral directly. It runs downwards upon the side of the medulla
oblongata and the spinal medulla, either in front of or behind the posterior nerve-roots. It is
a slender artery, which is continued to the lower part of the spinal medulla by means of
reinforcements from the spinal branches of the vertebral and intercostal arteries. It gives
off branches to the pia mater, which form more or less regular anastomoses on the medial and
lateral sides of the posterior nerve-roots, and it ends by joining the anterior spinal artery.
(3) The anterior spinal branch arises near the termination of the vertebral. It runs
obliquely downwards and medially, in front of the medulla oblongata, and unites with its
fellow of the opposite side to form a single anterior spinal artery, which descends along
the anterior median fissure -of the spinal medulla, and is continued as a fine vessel along
the filum terminale. The anterior spinal artery is reinforced as it descends by anasto-
mosing twigs from the spinal branches of the vertebral, intercostal, and lumbar arteries.
It gives off branches which pierce the pia mater and supply the spinal medulla, and it
unites below with the posterior spinal arteries.
(4) The posterior inferior cerebellar is the largest branch of the vertebral artery.
It arises a short distance below the pons and passes obliquely backwards round the
medulla oblongata, at first between the fila of the hypoglossal nerve, and then between the
fila of the accessory and vagus nerves, into the vallecula of the cerebellum, where it divides
into lateral and medial terminal branches.
The trunk of the artery gives branches to the medulla oblongata and to the chorioid
plexus of the fourth ventricle. Some of these branches supply the nuclei of the glosso-
pharyngeal, the vagus, and the accessory nerves, the spino-thalamic, spino-cerebellar, rubro-
spinal, olivo-cerebellar tracts, and possibly also the vestibular root of the acoustic and the
spinal root of the fifth nerve (Bury and Stopford). The medial terminal runs backwards
between the inferior vermis and the hemisphere of the cerebellum ; it supplies the former
structure, and anastomoses with its fellow of the opposite side. The lateral branch passes
to the lower surface of the hemisphere and anastomoses with the superior cerebellar artery.
Arteria Basilaris. The basilar artery is formed by the junction of the two
vertebral arteries; it commences at the lower border and terminates at the upper
border of the pons (Varolii), bifurcating at its termination into the two posterior
cerebral arteries.
Course and Relations. It runs upwards, in the median part of the cisterna
pontis, in a shallow groove on the front of the pons, behind the sphenoidal section
of the basi-cranial axis and between the two abducent nerves.
Branches. (1) Pontine, a series of small arteries which pass across the front and
round the sides of the pons, supplying the pons, the brachia pontis (O.T. middle peduncles
<>f the cerebellum), and the roots of the trigeminal nerve.
(2) The internal auditory, a pair of long slender branches. Each internal auditory
branch may spring either from the basilar or from the 'anterior inferior cerebellar artery
of the same side (Stopford, 1916). It enters the corresponding internal acoustic meatus
with the facial and acoustic nerves, and, after it has passed through the lamina cribrosa,
it is distributed to the internal ear.
(3) The anterior inferior cerebellar, two branches which arise, one on each side, from
the middle of the basilar artery. They pass backwards, on the anterior parts of the
lower surfaces of the lateral lobes of the cerebellum, and anastomose with the posterior
inferior cerebellar branches of the vertebral arteries.
(4) The superior cerebellar branches, two in number, arise near the termination of the
basilar. Each passes laterally, at the upper border of the pons, directly below the
908 THE VASCULAB SYSTEM.
oculo-motor nerve of the same side, and, after turning round the lateral side of the
pedunculus cerebri, below the trochlear nerve, it reaches the 'upper surface of the
cerebellum, where it divides into a medial and a lateral branch. The medial branch
supplies the upper part of the vermis, and the anterior medullary velum. The lateral
branch is distributed over the upper surface of the lateral lobe; it anastomoses with the
inferior cerebellar arteries.
(5) Arterise Cerebri Posteriores. The posterior cerebral arteries (Figs. 762 and
764) are the two terminal branches of the basilar. They run backwards and
upwards, between the peduncles of the cerebrum and the uncinate gyri and parallel
to the superior cerebellar arteries, from which they are separated by the oculo-
motor and trochlear nerves. Each posterior cerebral artery is connected with the
internal carotid by the posterior communicating artery; it gives branches to the
inferior surface of the cerebrum, and is continued backwards, beneath the splenium
of the corpus callosum, to the calcarine fissure, where it divides into calcarine and
parieto-occipital branches, which pass to the lateral surface of the occipital lobe.
It supplies the medial and tentorial surfaces of the occipital lobe and the posterior
part of its lateral surface.
Branches. (A) Central or basal. This group includes (a 1 ) A postero-medial Bet
of small vessels which pass, on the medial side of the corresponding cerebral peduncle,
to the posterior perforated substance. They supply the peduncle, the posterior part of
the thalamus, the corpora mamillaria, and the walls of the third ventricle.
(a 2 ) A postero-lateral set of small vessels, which pass round the lateral side of the
peduncle. They supply the corpora quadrigemina, the brachia, the pineal body, the
peduncle, the posterior part of the thalamus, and the corpora geniculata.
(a 3 ) A posterior chorioidal set of small branches which pass through the upper part of
the chorioidal fissure ; they enter the posterior part of the tela chorioidea of the third
ventricle, and end in the chorioid plexus, in the body of the lateral ventricle, and the
upper part of its inferior cornu. They also supply the adjacent parts of the fornix.
(B) Cortical. (6 1 ) The anterior temporal, frequently a single branch of variable size,
but not uncommonly replaced by several small branches. It supplies the anterior parts of
the uncus, the hippocampal gyrus, and the fusiform gyrus.
(6 2 ) The posterior temporal is a larger branch than the anterior. It supplies the
posterior part of the hippocampal gyrus, part of the fusiform gyrus, and the lingual gyrus.
(6 3 ) The calcarine branch is the continuation of the posterior cerebral artery along
the calcarine fissure, it is especially associated with the supply of the visual area of the
cortex of the brain. It supplies the cuneus, the lingual gyrus, and the posterior part of
the lateral surface of the occipital lobe.
(6 4 ) The parieto-occipital branch, smaller than the calcarine, passes along the
corresponding fissure to the cuneus and praecuneus.
Circulus Arteriosus (Willis) (Fig. 764). The cerebral arteries of opposite sides
are intimately connected together at the base of the brain by anastomosing channels.
Thus, the two anterior cerebral arteries are connected with one another by the
anterior communicating artery, whilst the two posterior cerebrals are in continuity
through the basilar artery from which they arise. There is also a free anastomosis
on each side between the carotid system of cerebral arteries and the vertebral
system by means of the posterior communicating arteries, which connect the
internal carotid trunks and posterior cerebral arteries.
The vessels referred to form the so-called circulus arteriosus (O.T. circle of
Willis) which is situated at the base of the brain, in the interpeduncular and
chiasmatic subarachnoid cisterns. It encloses the following structures : the
posterior perforated substance, the corpora mamillaria, the tuber cinereum, the
infundibulum, and the optic chiasma. The "circle" is irregularly polygonal in
outline, and is formed posteriorly by the termination of the basilar and by the
two posterior cerebral arteries, postero-laterally by the posterior communicating
arteries and the internal carotids, antero-laterally by the anterior cerebral arteries,
and in front by the anterior communicating artery.
It is stated that this free anastomosis equalises the flow of blood to the various
parts of the cerebrum, and provides for the continuation of a regular blood-supply
if one or more of the main trunks should be obstructed.
THE SUBCLAVIAJST ARTEKIES. 909
ARTERIES OF THE UPPER EXTREMITY.
The main arterial stem of each upper extremity passes through the root of the
ineck, traverses the axillary space, and is continued through the arm to the
forearm. In the forearm its extent is short, for it terminates, opposite the neck
)f the radius, by bifurcating into the radial and ulnar arteries, which run through
the forearm to the hand. That portion of the common trunk which lies in the
root of the neck is known as the subclavian artery, the part in the axillary space
is termed the axillary artery, whilst the remaining part is called the brachial artery.
ARTERIvE SUBCLAVI.E.
On the right side the subclavian artery (Figs. 757, 759, 761, and 766)
iommences at the termination of the innominate artery, posterior to the sterno-
3lavicular articulation, whilst that on the left side arises from the arch of the
lorta, behind the upper half of the manubrium sterni.
The right artery is about 75 mm. (3 inches) long ; it lies in the root of the
leek. The left artery is about 100 mm. (4 inches) long, and is situated not only
.n the root of the neck, but also in the superior mediastinal part of the thorax,
[n the root of the neck each artery arches laterally, across the apex of the lung and
Behind the anterior scalene muscle, and is divided into three parts, which lie
respectively to the medial side, behind, and to the lateral side of the muscle.
The extent to which the arch rises above the level of the clavicle varies ; not un-
commonly it reaches the level of the lower part of the thyreoid gland. The first parts
)f the subclavian arteries differ materially from each other both in extent and re-
ations. The relations of the second and third parts are similar on the two sides.
The first part of the left subclavian artery springs from the arch of the
iorta, posterior to the commencement of the left common carotid and on the left
tide of the trachea. It ascends almost vertically, in the superior mediastinum, to
;he root of the neck, where it arches upwards and laterally to the medial border
)f the scalenus anterior muscle.
Relations. Posterior. In the superior mediastinum it is in relation with the lung
ind pleura.
Anterior. In front are the left vagus, the left superior cardiac branch of the
sympathetic, the left inferior cardiac branch of the vagus, the left phrenic nerve, and the
eft common carotid artery. It is also crossed obliquely by the left vagus nerve, and it is
1 Dverlapped on the left side by the left lung and pleura.
Medial. Medially it is in relation, from below upwards, with the trachea, the left
-ecurrent nerve, the oesophagus, and the thoracic duct, the latter lying in a plane posterior
:o the oesophagus and the artery.
Laterally it is closely invested by the left pleura, and it ascends in a groove on the
nedial aspect of the left lung.
At the root of the neck, as it turns laterally, it lies behind the commencement of the
left innominate vein, and the termination of the left vertebral vein, the phrenic nerve, the
iterno-thyreoid and sterno-hyoid muscles, the anterior jugular vein, and, more superficially,
the sterno-mastoid muscle and the deep cervical fascia ; the thoracic duct arches obliquely
5ver it ; and it lies in front of the apex of the pleural sac and lung.
The first part of the right subclavian artery (Fig. 761) extends from the
' back of the right sterno-clavicular articulation to the medial border of the scalenus
interior. It is thus limited to the root of the neck.
Relations. Posterior. Behind this part of the artery, and intervening between it
and the upper two thoracic vertebrae, are the recurrent nerve, the posterior part of the
insa subclavia, and the apex of the right pleural sac. Anterior. In front it is in relation
ith the right vagus, the cardiac branches of the vagus and the sympathetic, the anterior
;ion of the ansa subclavia, the internal jugular and vertebral veins, and more super-
cially the sterno-hyoid and sterno-thyreoid muscles, the anterior jugular vein, the sternal
i of the clavicle, the sterno-clavicular ligaments, and the sterno-mastoid muscle. The
urrent nerve passes below it and intervenes between it and the apex of the pleural sac.
910 THE VASCULAR SYSTEM.
The second part of the subclavian artery, on each side, extends from the
medial to the lateral border of the scalenus anterior, behind which it lies.
Relations. Posteriorly and below it is in relation with the pleural sac. Anteriorly
it is covered by the anterior scalene and the sterno-mastoid muscles. The anterior scalene
separates it from the subclavian vein, which lies at a slightly lower level, from the trans-
verse cervical and transverse scapular arteries, from the anterior jugular vein, and, on
the right side, from the phrenic nerve.
The third part of the subclavian artery is the most superficial portion.
It extends from the lateral border of the anterior t scalene to the outer border of
the first rib, lying partly in the clavicular portion of the posterior triangle of the
neck and partly behind the clavicle and the subclavius muscle.
Relations. It rests upon the upper surface of the first rib. Immediately posterior
to it is the lowest trunk of the brachial plexus, which separates it from the middle
scalene muscle. Anterior to it, and at a slightly lower level, lies the subclavian vein. The
external jugular vein crosses the medial part of this portion of the artery, and just before
its termination it receives the transverse cervical and transverse scapular veins ; those
vessels also pass superficial to the artery, which is thus covered superficially by venous
trunks ; it is also crossed vertically, behind the veins, by the nerve to the subclavius
muscle. The lateral section of this part of the artery lies posterior to the clavicle and
the subclavius muscle. It is crossed anteriorly by the transverse scapular artery, but
the layer of deep cervical fascia which binds the posterior belly of the omo-hyoid to the
posterior border of the subclavian groove intervenes " between the two vessels. More
superficially the third part of the artery is covered by the superficial layer of the deep
fascia, the supra-clavicular branches of the cervical nerves, the platysma, and the skin.
BRANCHES OF THE SUBCLAVIAN ARTERY.
(1) The vertebral artery is distributed almost entirely to the head and neck
and its chief function is to supply the posterior part of the brain. Its description
has therefore been given with that of the other cerebral arteries (see p. 905).
(2) Truncus Thyreocervicalis. The thyreo-cervical trunk (Figs. 757 and 759)
arises close to the medial border of the scalenus anterior, from the upper and front
part of the subclavian artery, directly above the origin of the internal mammary
artery. After a short upward course of about 4 mm. (two lines), it ends, under
cover of the internal jugular vein, by dividing into three branches viz., the inferior
thyreoid, the transverse cervical, and the transverse scapular.
(A) Arteria Thyreoidea Inferior. The inferior thyreoid artery (Figs. 757, 759)
ascends along the anterior border of the scalenus anterior, and turns medially,
opposite the cricoid cartilage, to the middle of the posterior border of the corre-
sponding lobe of the thyreoid gland ; it then curves medially and downwards, and
descends to the lower end of the lobe of the thyreoid gland, where it divides into
ascending and inferior terminal branches.
Relations. Posterior are the vertebral artery, and the longus colli muscle;
the recurrent nerve passes either anterior or posterior to the vessel, opposite the lower
border of the thyreoid gland. It is covered anteriorly by the carotid sheath, which
contains the common carotid artery, the internal jugular vein, and the vagus nerve; the
middle cervical ganglion of the sympathetic lies in front of the artery as it bends medially :
and on the left side the thoracic duct also passes in front of it.
Branches. It gives off the following branches :
(a) Muscular. Numerous small branches pass to the scalenus anterior, the longus
colli, the infra-hyoid muscles, and the inferior constrictor of the pharynx.
(6) The ascending cervical usually springs from the inferior thyreoid near its origin
but it may arise separately from the thyreo-cervical trunk. It ascends, parallel with anc
medial to the phrenic nerve, in the angle between the longus capitis and the scalenue
anterior, to both of which it gives branches. It also gives off spinal branches whicl
pass through the intervertebral foramina to the vertebral canal. It anastomoses witl
branches of the vertebral, occipital, ascending pharyngeal, and deep cervical arteries.
(c) (Esophageal. Small branches given to the walls of the ossophagus, whicl
anastomose with the oesophageal branches of the thoracic aorta.
9
BEANCHES OF THE SUBCLAVIAN AETEEY. 911
(d) Tracheal branches are distributed to the trachea ; they anastomose with branches
rf the superior thyreoid and with' the bronchial arteries.
(e) An inferior laryngeal branch, accompanies the recurrent nerve to the lower part
)f the larynx. It enters the larynx, at the lower border of the inferior constrictor,
1 rives branches to its muscles and mucous membrane, and anastomoses with the laryngeal
aranch of the superior thyreoid artery.
(/) The ascending terminal branch supplies the posterior and lower part of the
:hyreoid gland, and anastomoses with branches of the superior thyreoid artery.
(g) The inferior terminal branch is distributed to the lower and medial part of the
3orresponding lobe of the thyreoid gland. It anastomoses with its fellow of the opposite
Me and with branches of the superior thyreoid artery.
(B) Arteria Transversa Colli. The transverse cervical artery (Figs. 759 and
761) arises from the thyreo-cervical trunk and runs upwards and posteriorly across
the posterior triangle of the neck to the anterior border of the trapezius ; there
it divides into a ramus ascendens (O.T. superficial cervical) and a ramus descendens
'O.T. posterior scapular). It is very variable in size, and not infrequently the
ramus descendens arises separately from the third part of the subclavian.
Immediately after its origin, under cover of the internal jugular vein, it crosses
, the scalenus anterior, lying superficial to the phrenic nerve and under cover of the
sterno-mastoid muscle; on the left side it is also crossed, superficially, by the terminal
part of the thoracic duct. Passing from beneath the sterno-mastoid, it enters the
! lower part of the posterior triangle of the neck, where it lies upon the trunks of
the brachial plexus, and, as it runs upwards and backwards to its termination, it
passes medial to the posterior belly of the omo-hyoid.
The ascending branch may be a separate vessel which springs from the thyreo-cervical trunk
and takes the course described, whilst the descending branch arises from the third part of the
subclavian artery and lies at a lower level. In such cases the upper of the two vessels is called
the superficial cervical artery and the lower the transverse cervical artery. If the superficial
cervical artery is absent it is replaced by the ascending branch of the transverse cervical.
Branches. (a) Small muscular branches to the surrounding muscles.
(6) The ascending branch, usually a slender branch, passes beneath the trapezius ; it
1 sends branches upwards and downwards, superficial to the levator scapulae and upon the
i splenius ; the ascending branches anastomose with the descending branch of the occipital
artery, and the descending branches accompany the accessory nerve and anastomose with
the descending branch and transverse scapular artery.
(c) The descending branch runs downwards, deep to the levator scapulae and the
rhomboid muscles, close to the vertebral border of the scapula. It runs parallel with,
and a short distance away from, the dorsal scapular nerve (O.T. nerve to the rhomboid
1 muscles), and it sends branches into the supraspinous, the infraspinous, and the subscapular
fossae, which anastomose with branches of the transverse scapular and subscapular arteries.
It also sends branches backwards, through and between the rhomboid muscles, which
anastomose with the branches of the ascending division of the transverse cervical and
1 with the posterior branches of the intercostal arteries.
(C) Arteria Transversa Scapulae. The transverse scapular artery (O.T. supra-
scapular) springs from the thyreo-cervical trunk and terminates in the infraspinous
fossa of the scapula. As a rule it is smaller than the transverse cervical artery.
Commencing behind the internal jugular vein, it crosses the scalenus anterior
'and phrenic nerve, and is covered superficially by the sterno-mastoid and the
anterior jugular vein ; on the left side it lies behind the termination of the thoracic
duct also. Continuing, laterally, behind the clavicle, and crossing superficial to the
third part of the subclavian artery and the cords of the brachial plexus, it reaches
the scapular notch and passes over the superior transverse ligament. Then it
, descends, with the suprascapular nerve, through the supraspinous fossa and deep to
the supraspinatus muscle, and after passing through the great scapular notch, deep
to the inferior transverse ligament, it enters the infraspinous fossa, where it anas-
tomoses with the circumflex scapular branch of the subscapular artery and with
twigs of the descending branch of the transverse cervical artery.
Branches. (a) Muscular, to the sterno-mastoid, the subclavius, and the muscles on
the dorsum of the scapula.
(b) The medullary, a small branch to the clavicle.
912
THE VASCULAR SYSTEM.
(c) The suprasternal, to the sternal end of the clavicle and the sterno-clavicular
joint.
(d) Acromial branches, which ramify over the acromion, anastomosing with the
acromial branches of the thoraco-acromial and the posterior circumflex arteries.
Levator scapulae
scending branch of transverse cervical artery
Trapezius ^Transverse scapular artery
Rhomboideus minor
Descending branch
of transverse
cervical artery
Rhomboideus major
Infraspinatus
Long head of triceps
Teres major
Latissimus dorsi
Infraspinatus
Deltoid
Teres minor
Axillary nerve
Posterior circumflex
artery
Circumflex scapular-
artery
Triceps (lat. head)
rofunda artery
Radial nerve
Triceps (lat. head)
Brachialis
FIG. 765. DISSECTION OF THE BACK OF THE SHOULDER AND ARM, showing the anastomosing vessels
on the dorsum of the scapula, and the posterior humeral circumflex and the profunda arteries.
(e) Articular, to the acromio-clavicular and shoulder-joints.
(/) The subscapular, which is given off as the artery passes over the superio:
transverse ligament. It passes down into the subscapular fossa, gives branches to the
subscapularis, and it anastomoses with the branches of the subscapular artery and the
descending branch of the transverse cervical artery.
(g) Supraspinous, which ramify in the supraspinous fossa, supplying the muscle, and
anastomosing with the descending branch of the transverse cervical.
(A) Terminal branches ramify in the infraspinous fossa, and anastomose with thi
BKANCHES OF THE SUBCLAVIAN ARTEEY. 913
ircumflex scapular and with branches of the descending branch of the transverse
srvical artery.
(3) Arteria Mammaria Interna. The internal mammary artery (Figs. 757, 761)
rises from the lower and anterior part of the subclavian, at the medial border
f the scalenus anterior and immediately below the origin of the thyreo-cervical
runk. It terminates, behind the medial extremity of the sixth intercostal space,
y dividing into the musculo-phrenic and the superior epigastric arteries.
The artery passes at first downwards, forwards, and medially, lying upon the
leura, and behind the innominate vein, the sternal extremity of the clavicle, and
he cartilage of the first rib ; it is crossed obliquely, from the lateral to the
ledial side, by the phrenic nerve, which usually passes anterior to it. From the
artilage of the first rib it descends vertically, about 12 mm. (half an inch) from the
order of the sternum, and lies, in the upper part of its course, in front of the pleura,
ud, in the lower part, in front of the transversus thoracis muscle. It is covered
nteriorly by the cartilages of the upper six ribs, the intervening intercostal muscles,
nd the terminal portions of the intercostal nerves; and it is accompanied by
wo venae cornites, which unite together above, and on its medial side, to form a
ingle trunk which terminates in the innominate vein.
Branches. (a) The pericardiaco-phrenic (O.T. comes nervi phrenic!) is a long slender
ranch which is given off from the upper part of the internal mammary. It accompanies
tie phrenic nerve, through the superior and middle mediastina, to the diaphragm, where
; anastomoses with the inferior phrenic and musculo-phrenic arteries. In its course
ownwards this branch gives off numerous small rami to the pleura and pericardium,
rhich anastomose with offsets of the mediastinal and pericardial branches of the aorta
nd internal mammary arteries, and also with the bronchial arteries, forming the wide-
leshed subpleural plexus of Turner.
(6) Anterior mediastinal branches, small and numerous, pass to the areolar tissue of
he anterior mediastinum and supply the areolar tissue and the sternum.
(c) Thymic. Small twigs which supply the thymus.
(d) Bronchial. One or several small branches which pass to the lower end of the
rachea and to the bronchi.
(e) The intercostal are two in number in each of the upper six intercostal spaces,
'hey pass laterally and, for a short distance, they lie either between the pleura and the
iternal intercostal muscles or between the transversus thoracis and the internal inter-
ostal muscles ; they then pierce the internal intercostal muscles, and ramify between them
nd the external intercostal muscles, anastomosing with the aortic and superior intercostal
rteries and their collateral branches.
(/) The perforating branches, one in each of the upper six intercostal spaces, are small
essels which pass forwards, with the anterior branches of the thoracic nerves, piercing
be internal intercostal muscle, the anterior intercostal membrane, and the pectoralis
lajor. They terminate in the skin and subcutaneous tissue. They supply twigs to the
ternum, and those in the third and fourth spaces, usually the largest of the series, give
ff branches to the mammary gland.
(g) The musculo-phrenic, or lateral terminal branch of the internal mammary
rtery, runs downwards and laterally, from the sixth intercostal space to the tenth costal
artilage. In the upper part of its course it lies upon the thoracic surface of the
iaphragm, but it pierces the diaphragm about the level of the eighth costal cartilage, and
srminates on its abdominal surface. Its branches are :
(i.) Muscular, which supply the diaphragm and anastomose with the superior and inferior
hrenic arteries.
(ii.) Intercostal branches, two in each of the seventh, eighth, and ninth intercostal spaces ;
bey are distributed in the same manner as the corresponding branches of the internal mammary
rtery, and terminate by anastomosing with the aortic intercostals and tlieir collateral branches.
(h) The superior epigastric, or medial terminal branch of the internal mammary artery,
1 escends into the anterior wall of the abdomen. It leaves the thorax, between the sternal
nd costal origins of the diaphragm, and enters the sheath of the rectus abdominis
luscle, lying first behind, and then in the substance of the muscle. It terminates by
nastomosing with branches of the inferior epigastric artery. Its branches are :
(i.) Muscular, to the rectus, to the flat muscles of the abdominal wall, and to the diaphragm.
(ii.) Anterior Cutaneous. Small branches which pierce the rectus abdominis muscle and
be anterior portion of its sheath. They accompany the anterior terminal branches of the lower
59
914 THE VASCULAE SYSTEM.
thoracic nerves, and terminate in the subcutaneous tissues and skin of the middle portion of the
anterior abdominal wall.
(iii.) Xiphoid, a small branch which crosses the front of the xiphoid process to anastomose
with its fellow of the opposite side. It supplies the adjacent muscles and skin.
(iv.) Hepatic branches of small size pass backwards in the falciform ligament to the liver,
where they anastomose with branches of the hepatic artery.
(4) Truncus Costocervicalis. The costo-cervical trunk (Fig. *761) springs
from the posterior aspect of the second part of the subclavian artery on the right
side and from the first part on the left side. It runs upwards and backwards,
over the apex of the pleural sac, to the neck of the first rib, where it divides
into superior intercostal and deep cervical branches.
Branches. (a) Arteria Cervicalis Profunda The deep cervical branch sometimes
arises from the subclavian artery directly ; but more commonly it springs from the costo-
cervical trunk at the upper border of the neck of the first rib. It runs backwards, to the
back of the neck, passing between the first thoracic and last cervical nerves, and between
the transverse process of the last cervical vertebra and the neck of the first rib. In the
back of the neck it ascends, between the semispinalis capitis (O.T. complexus) and the
sernispinalis cervicis muscles and it terminates by anastomosing with the descending branch
of the occipital artery. It anastomoses also with branches of the ascending cervical and
vertebral arteries, supplies the adjacent muscles, and sends a spinal branch, through the
intervertebral foramen between the last cervical and the first thoracic vertebra, into the
vertebral canal ; this branch anastomoses with the spinal branches of the vertebral and
intercostal arteries.
(6) Arteria Intercostalis Suprema. The superior intercostal branch descends, anterior
to the neck of the first rib, between the first thoracic nerve laterally and the first thoracic
ganglion of the sympathetic trunk medially and, at the lower border of the neck -of the rib,
it gives off the posterior intercostal artery of the first space ; then, after crossing anterior
to the neck of the second rib, it becomes the posterior intercostal artery of the second inter-
costal space. The first two posterior intercostal arteries, which are respectively a branch
and the continuation of the superior intercostal artery, run laterally, each in its own space,
lying first between the pleura and the posterior intercostal membrane, and then between
the internal and external intercostal muscles. Their branches terminate by anastomosing
with anterior intercostal branches of the internal mammary artery. Each gives off
muscular branches to the intercostal muscles, a nutrient branch to the rib below which
it lies, and a collateral branch which runs along the lower border of the corresponding space.
ARTERIA AXILLARIS.
The axillary artery, which lies in the axillary space, is the direct continuation
of the subclavian artery, and it becomes the brachial artery.
It commences at the external border of the first rib, at the apex of the axillary
space. It passes distally, with a lateral inclination, along the lateral wall of the
space, i.e. to the medial side of the shoulder-joint and the humerus, to the lowei
border of the teres major, where it becomes the brachial artery. A line drawi
from the middle of the clavicle to the medial border of the prominence of th<
coracobrachialis muscle, when the arm is abducted until it is at right angles witl
the side, indicates the position and direction of the artery.
The position and direction, however, and to a certain extent the relations o
the axillary artery, are modified by changes in the position of the uppe
extremity. With the arm hanging by the side the axillary artery describes ;
curve with the concavity directed downwards and medially, and the vein is to it
medial side. When the arm is at right angles with the side, the axillary arter
is almost straight; it lies closer to the lateral wall of the axilla, and the veil
overlaps it antero- medially. When the arm is raised above the level of th
shoulder the axillary artery is curved over the head of the humerus, with th
convexity of the curve below, and the vein lies still more in front of it.
For descriptive purposes the artery is divided into three parts : the first pai
lies above, the second behind, and the third part below the pectoralis minor.
Though it is the usual custom to describe three parts of the axillary arter
a division which is of practical interest in so far as it emphasises the fact thc r
the axillary artery is surgically accessible above the pectoralis minor, it is to I
THE AXILLAKY AETEEY.
915
ioted that the upper border of the pectoralis minor is frequently exactly opposite
he external border of the first rib, at the point where the axillary artery begins,
n the strict sense, therefore; no part of the artery is above the pectoralis minor.
Relations of the First Part Posterior. The first part of the artery is enclosed,
ogether with the vein and the cords of the brachial plexus, in a prolongation of the
ervical fascia known as the axillary sheath. Posterior to the sheath are the upper serra-
ion of the serratus anterior, the contents of the first intercostal space, and the long
horacic nerve, the latter descending vertically between the artery and the serratus
A. transversa colli, ramus descenden
V. jugularis externa
A. subclavia s %
A. transversa scapulae .
Xn. thoracales anteriores '
romialis et rami deltoideus et pectoralis ' X \
A. et V., axillaris { \ X .'
M. deltoideus x \ \
A. carotis communis
V. jugularis interna |
M. omohyoideus
| M. sternothyreoideus
M. pectoralis minor
M. pectoralis major /~~
M. latissimus dorsi
M. serratus anterior
M. obliquus externus abdomini
FIG. 766. THE AXILLARY ARTERY AND ITS BRANCHES.
,
IE. --The middle third of the clavicle has been removed ; and the arm has been slightly abducted and
rotated laterally. Parts of the pectoralis major and minor have been removed ; the positipns of the
lower border of the pectoralis major and the upper and lower borders of the pectoralis minor are indi-
cated by broken black lines. Compare with Fig. 759, which represents a dissection of the same body
from a diiferent point of view.
anterior ; whilst, within the sheath, the medial anterior thoracic nerve and the medial
cord of the brachial plexus lie behind the artery. Anterior. -It is covered in front by the
costo-coracoid membrane. The membrane intervenes between the artery and the cephalic
vein, the branches of the lateral anterior thoracic nerve, the branches of the thoraco-
acromial artery with their accompanying veins, and the clavicular part of the pectoralis
major muscle, superficial to which are the deep fascia, the platysma, the supra-clavicular
branches of the cervical plexus, and the superficial fascia and the skin. Posterior to the
costo-coracoid membrane the artery is crossed by a loop of communication between the
lateral and medial anterior thoracic nerves. Lateral. Above and to the lateral side are
59 a
916 THE VASCULAK SYSTEM.
the lateral and posterior cords of the brachial plexus and the lateral anterior thoracic
nerve. Below and to the medial side is the axillary vein, the medial anterior thoracic
nerve intervening.
Relations of the Second Part Posterior. Behind the second part of the artery are
the posterior cord of the brachial plexus and a layer of fascia which separates it from the
subscapularis muscle. Anterior. In front is the pectoralis minor, and, more superficially,
the pectoralis major, the fasciae and skin. Lateral. To the lateral side lies the lateral cord
of the brachial plexus. Medial. On the medial side the medial cord of the plexus lies in
close relation to the artery, and intervenes between it and the axillary vein.
Relations Of the Third Part Posterior. The third part of the artery rests
posteriorly upon the lower border of the subscapularis, the latissimus dorsi, and the
teres major. It is separated from the fibres of the subscapularis by the axillary (O.T.
circumflex) and radial (O.T. musculo-spiral) nerves, and from the latissimus dorsi and
teres major by the radial nerve alone. Anterior. It is crossed in front by the medial
head of the median nerve. In its upper half it lies under cover of the lower part of
the pectoralis major, the fasciae and skin, whilst its lower part, which is superficial, is
covered by skin and fasciae only. Lateral. To the lateral side lie the median and
musculo-cutaneous nerves and the coraco-brachialis muscle. Medial. To the medial side
is the axillary vein. The two vessels are, however, separated by two of the chief branches
of the medial cord of the brachial plexus, for in the angle between the vein and the artery,
and somewhat in front of the latter, lies the medial cutaneous nerve of the forearm
(O.T. internal cutaneous nerve) ; and, in the angle behind is the ulnar nerve. The medial
cutaneous nerve of the arm (O.T. lesser internal cutaneous) lies medial to the vein, and
the venae comites of the brachial artery ascend along the medial side, to terminate in
the axillary vein at the lower border of the subscapularis muscle.
BRANCHES OF THE AXILLARY ARTERY.
(1) Arteria Thoracalis Suprema. The highest thoracic artery is a small
branch which arises from the first part of the axillary at the lower border of
the subclavius. It runs downwards and medially, across the first intercostal
space, pierces the medial part of the costo-coracoid membrane, and supplies branches
to the subclavius, the pectoralis major and minor, and to the serratus anterior
(O.T. magnus) and the intercostal muscles; it anastomoses with branches of the
transverse scapular, the internal mammary, and the thoraco-acromial arteries.
(2) Arteria Thoracoacromialis. The thoraco-acromial artery (Fig. 766) arises
near the upper border of the pectoralis minor, from the second part of the axillary
artery. It is a very short trunk, of considerable size, which passes forwards,
pierces the costo-coracoid membrane, and terminates, deep to the clavicular portion
of the pectoralis major, by dividing into four terminal branches clavicular, pectoral,
deltoid, and acromial.
(a) The clavicular branch is a long slender artery which runs upwards and medially,
to the sterno-clavicular joint, anastomosing with the supreme thoracic, with branches of
the transverse scapular, and with the first perforating branch of the internal mammary
artery. It supplies the adjacent muscles and the sterno-clavicular articulation.
(b) The pectoral is a large branch which descends between the two pectoral muscles,
to both of which it gives branches, and it anastomoses with the intercostal and lateral
thoracic arteries.
(c) The deltoid branch runs distally, in the groove between the pectoralis major and
the deltoid, where it lies by the side of the cephalic vein, as far as the insertion of the
deltoid. It anastomoses with the acromial branch and with the anterior circumflex artery,
and it gives branches to the pectoralis major and deltoid muscles and to the skin.
(d) The acromial branch runs upwards and laterally, across the tip of the coracoid
process, to the acromion ; it anastomoses with the deltoid branch, with the acromial
branches of the transverse scapular, and with the posterior circumflex arteries. It gives
branches to the deltoid.
(3) Arteria Thoracalis Lateralis. The lateral thoracic artery arises from the
second part of the axillary, and descends, along the lower border of the pectoralii-
minor, to anastomose with the intercostal and subscapular arteries and with the
pectoral branch of the thoraco-acromial. It supplies the adjacent muscles, anc
sends mammary branches to the lateral part of the corresponding mammary gland
THE BEACHIAL AETEEY. 917
(4) Arteria Subscapularis. The subscapular artery is the largest branch
>f the axillary artery. It arises from the third part of the artery, opposite the
ower border of the subscapularis, along which it descends, giving branches to
',he muscle and to the medial wall of the axillary space. After a short course
t divides into two terminal branches, the circumflexa scapulae and the thoraco-
lorsalis.
(1) The circumflex scapulae is frequently the larger branch. It arises about 37 mm.
one and a half inches) from the commencement of the subscapular trunk, and passes
mck wards into the triangular space which lies between the subscapularis above, the teres
najor below, and the long head of the triceps laterally. Turning round, and usually groov-
ng the axillary border of the scapula, under cover of the teres minor, it enters the infra-
ipinous fossa, where it breaks up into branches which anastomose with branches of the
Descending branch of the transverse cervical artery and the transverse scapular arteries.
tVhilst it is in the triangular space the artery gives off an infrascapular branch which
jasses into the subscapular fossa and terminates by anastomosing with the branches of
1 he descending branch of the transverse cervical and the transverse scapular arteries.
t gives off, in the same situation, a descending branch also, which runs downwards, to
he lower angle of the scapula, between the teres major and minor muscles, and small
>ranches are given to the deltoid and long head of triceps.
(2) The thoraco-dorsal continuation of the subscapular trunk accompanies the thoraco-
lorsal nerve (O.T. long subscapular) along the axillary border of the scapula to the wall
>f the thorax, where it anastomoses with the lateral thoracic artery and with branches
/f the intercostal arteries.
(5) Arteria Circumflexa Humeri Posterior. The posterior circumflex artery
irises from the third part of the axillary artery and passes backwards, accompanied
)y the axillary nerve, through an intermuscular cleft, the so-called quadrilateral
jpace, which is bounded by the teres minor and snbscapularis above, the teres
najor below, the long head of the triceps medially, and the humerus laterally. It
i ;urns round the surgical neck of the humerus, under cover of the deltoid muscle,
ind terminates in numerous branches which supply the deltoid. As a rule it
i s an artery of large size, only slightly smaller than the subscapular.
Branches. (a) Muscular to the teres major and minor, the long and lateral heads
)f the triceps, and the deltoid; (6) An acromial branch, which ascends to the
juoomion, where it anastomoses with the acromial branches of the transverse scapular
.uid the thoraco-acromial arteries; (c) A descending branch, which runs distally, along
he lateral head of the triceps, to anastomose with the profunda artery ; (d) Articular
^o the shoulder-joint; (e) Nutrient to the head of the humerus; (/) Terminal, which
.upply a large portion of the deltoid, and anastomose with the anterior circumflex and
.horaco-acromial arteries.
(6) Arteria Circumflexa Humeri Anterior. The anterior circumflex artery is
i small branch ; it is given off from the third part of the axillary close, to, or
n common with, the posterior circumflex. It passes laterally, posterior to the
joraco-brachialis and the two heads of the biceps, round the front of the surgical
leek of the humerus, and it terminates by anastomosing with the posterior circum-
At the intertubercular groove it gives a well-marked branch which accom-
panies the tendon of the long head of the biceps, supplying the sheath of the
oendon, and giving branches to the shoulder-joint. It also gives muscular
3ranches to the adjacent muscles, one of which runs distally along the tendon
if insertion of the pectoralis major.
AETERIA BEACHIALIS.
The brachial artery is the direct continuation of the axillary. It com-
mences at the lower border of the teres major, and ends, in the cubital fossa, at
the level of the neck of the radius, by dividing into the radial and uluar arteries.
The general course of the brachial artery is distally and laterally, along the
dial side of the arm, at first on the medial side and then in front of the
umerus. Its position and that of the axillary artery may be indicated on the
595
918
THE VASCULAE SYSTEM.
surface, when the arm is abducted, by a line drawn from the middle of the clavicle
to the centre of the bend of the elbow.
Relations Posterior. It lies, successively, anterior to the long head of the triceps,
the radial (O.T. musculo-spiral) nerve and the profunda vessels intervening ; the medial
head of the triceps ; the insertion of the coraco-
brachialis ; and the brachialis. Anterior. It is
overlapped anteriorly by the medial border of
the biceps ; it is crossed, at the middle of the
arm, by the median nerve, and, in addition, it
is covered by deep and superficial fascia and
skin. In the cubital fossa a thickened portion
of the deep fascia, the-lacertus fibrosus (O.T.
semilimar or bicipital fascia), separates it from
the median basilic vein and the volar branch of
the medial cutaneous nerve of the forearm, both
of which lie in the superficial fascia. Lateral.
To the lateral side it is in relation, proximally,
with the median nerve, and, distally, with the
biceps. Medial. To the medial side it is in
relation, in the proximal part of its extent, with
the basilic vein, the medial cutaneous nerve of the
forearm, the medial cutaneous nerve of the arm,
and the ulnar nerve, and in the distal part with
the median nerve. Two vense comites, a medial
and a lateral, accompany the artery, and com-
munications between these pass across the vessel.
Triceps
ofunda
artery
Ulnar nerve
Superior
ulnar
collateral
artery
Median
nerve
BRANCHES OF THE BRACHIAL ARTERY.
(1) Arteria Profunda Brachii. The
profunda artery of the arm (O.T. superior
profunda) is a large branch which arises
from the postero- medial aspect of the
brachial, soon after its commencement. It
runs distally and laterally, with the radial
(O.T. musculo-spiral) nerve, in the radial
inferior ui Mr ul s (O.T musculo -spiral groove), and
divides, at the back of the humerus, into
two terminal branches, anterior and posterior.
Not infrequently the division takes place
at a higher level, and the artery appears
double. The anterior terminal branch ac-
companies the radial nerve through the
lateral intermuscular septum, and passes
distally, between the brachio-radialis and
the brachialis, to the front of the lateral
epicondyle, where it anastomoses with the
radial recurrent artery. The posterior
FIG. 767.-THE BRACHIAL ARTERY AND ITS terminal branch continues distally, behind
BRANCHES. the lateral intermuscular septum, and anas
'tomoses, posterior to the lateral epicondyle
with the interosseous recurrent artery and with the inferior ulnar collateral artery
Whilst they are posterior to the humerus one of the terminal branches give^
off (a) a slender medial collateral twig, which descends in the substance of the
medial head of the triceps to the back of the elbow, where it anastomoses with the
inferior ulnar collateral artery ; (&) a nutrient branch, which enters a foramen or
the posterior surface of the humerus ; and (c) an ascending branch, which anasto
moses with the descending branch of the posterior circumflex artery.
(2) Muscular branches are given to the biceps, coraco-brachialis, brachialis
triceps, and pronator teres.
Brachio-
radialis
THE EADIAL AETEEY. 919
(3) Nutrient. A small artery which arises from the middle of the brachial and
enters the nutrient foramen 011 the antero-medial surface of the body of the
humerus.
(4) Arteria Collaterals Ulnaris Superior. The superior ulnar collateral artery
(O.T. inferior profunda) is smaller than the profunda, with which it sometimes arises
by a common trunk ; usually, however, it springs from the postero-medial aspect of
the middle of the brachial artery. It runs distally and posteriorly, with the ulnar
nerve, through the medial intermuscular septum, and then, passing more vertically,
reaches the back of the medial epicondyle of the humerus, where it terminates by
anastomosing with the dorsal and volar ulnar recurrent and inferior ulnar
collateral arteries.
(5) Arteria Collateralis Ulnaris Inferior. The inferior ulnar collateral artery
(O.T. anastomotic) arises from the medial side of the brachial artery about 50 mm. (2
inches) above its termination. It runs medially, posterior to the median nerve and
anterior to the brachialis. Then it pierces the medial intermuscular septum, and
turns laterally, between the medial head of the triceps and the posterior surface of the
bone, to the lateral epicondyle. It supplies the adjacent muscles and anastomoses,
anterior to the medial epicondyle, with the volar ulnar recurrent, behind the medial
epicondyle with the dorsal ulnar recurrent and the superior ulnar collateral, at
the middle of the back of the humerus with the medial collateral branch of the
profunda, and posterior to the lateral epicondyle with the posterior terminal branch
of the profunda and with the interosseous recurrent artery.
ARTEEIA RADIALIS.
The radial artery (Figs. 768, 769, and 770) is the smaller of the two terminal
branches of the brachial artery, but it is the more direct continuation of the parent
trunk. It commences, in the cubital fossa, opposite the neck of the radius, and
terminates in the palm of the hand, by anastomosing with the deep branch of the
ulnar artery, and thus completing the deep volar arch (O.T. palmar).
The trunk is divisible into three parts.
The first part lies in the volar part of the forearm. It runs distally and some-
what laterally to the apex of the styloid process of the radius. The second part
curves round the lateral side of the wrist, and across the back of the os mult-
angulum majus, to reach the proximal end of the first interosseous space. The
third part passes volarwards, through the first interosseous space, to the palm of the
hand, where it joins the deep branch of the ulnar artery.
Relations of the First Part Dorsal. It passes successively across the volar
aspects of the following structures : the tendon of insertion of the biceps, the supinator,
the pronator teres, the radial portion of the flexor digitorum sublimis, the flexor pollicis
longus, the pronator quadratus, and the volar ligament of the wrist- joint.
Volar. The artery is covered superficially, in the proximal half, by the volar border of
the brachio-radialis ; in the remainder of its extent it is covered only by skin and fasciae.
To the radial side are the brachio-radialis, and the superficial branch of the radial
nerve (O.T. radial nerve). The nerve lies quite near to the middle third of the artery.
To the ulnar side are the pronator teres, proximally, and the flexor carpi radialis, distally.
Two venae comites, one on each side, accompany the artery.
Branches of the First Part. (1) The radial recurrent arises in 'the cubital fossa
where it springs from the lateral side of the radial, on the volar surface of the supinator. It
runs towards the radial border of the forearm, passes between the superficial and deep divi-
sions of the radial (musculo-spiral) nerve, and then runs proximally to the lateral epicondyle
>f the humerus, where it anastomoses with the anterior terminal branch of the profunda.
The radial recurrent supplies numerous muscular branches to the brachio-radialis, the
supinator, the extensor carpi radialis longus, and the extensor carpi radialis brevis.
(2) Muscular branches to the muscles on the radial side of the volar aspect of the
forearm.
(3) The superficial volar branch (Fig. 768) is a slender vessel which arises a short
distance proximal to the wrist and runs distally, across the ball of the thumb. It usually
pierces the superficial muscles of the thenar eminence, and terminates either in their
substance or by uniting with the ulnar artery and completing the superficial arch of
the palm of the hand.
920
THE VASCULAE SYSTEM.
(4) A volar carpal branch passes ulnarwards, between the flexor tendons and their
synovial sheaths, and the radial attachments of the volar carpal ligaments. It anasto-
moses with the volar carpal branch of the ulnar artery to form the volar carpal arch
and it receives communications from
the volar interosseous artery and
from the deep volar arch.
Relations of the Second
Part. As it curves round the radial
side and the dorsum of the wrist, the
radial artery lies upon the radial
collateral ligament of the intercarpal
joint and upon the back of the os
multangulum majus. It is crossed
by the abductor pollicis longus, the
extensor pollicis brevis, and the ex-
tensor pollicis longus; more super-
ficially it is covered by skin, and by
fascia, which contains the cephalic vein
and some filaments of the superficial
branch of the radial nerve.
Branches of the Second
Part (1) Dorsales Pollicis. Two
small arteries which run along the
borders of the dorsal aspect of the
thumb ; they supply the skin, ten-
dons, and joints, and anastomose
with the volar digital arteries.
(2) Dorsalis Indicis Radialis.
A slender artery which runs dis-
tally, on the ulnar head of the first
dorsal interosseous muscle and along
the dorsal aspect of the radial border
of the index-finger.
(3) and (4) The first dorsal
paimaris metacarpal and the dorsal radial
longus
Median artery
Biceps
Brachial artery
Median nerve
Radial nerve (O.T.
musculo-spiral
Radial recurrent
artery'
Brachialis
Brachio-
radialis
Supinator_
Radial recurrent
artery"
Supinator--
Flexor digitorum
sublimis"
Radial artery
Radialis indicis
artery
Ulnar
artery
Pronator
teres
Flexor pollicis Ion
Ulnar artery
Flexor carpi
radialis
Ulnar nerve
Superficial volaris
artery
carpal arise by a common trunk
which crosses deep to the extensor
pollicis longus.
Deep branch
of ulnar artery
Superficial
volar (palmar)
arch
Digital
arteries
(a) The metacarpal branch passes
distally, on the dorsal aspect of the
second dorsal interosseous muscle, and
divides, opposite the heads of the meta-
carpal bones, into two dorsal digital
branches which supply the adjacent
sides of the index and middle fingers.
(6) The dorsal carpal branch runs ulnar-
wards, on the dorsal carpal ligaments,
deep to the extensor tendons, to anas-
tomose with the dorsal carpal branch of
the ulnar artery, and to complete the
dorsal carpal arch which receives the
terminations of the volar and dorsal
interosseous arteries. The dorsal carpal
arch gives off the second and third
dorsal metacarpal arteries, which run
distally, on the dorsal aspects of the
third and fourth dorsal interosseous
muscles, as far as the heads of the meta-
carpal bones, where each divides into
two dorsal digital branches for the ad-
jacent sides of the third and fourth and
the fourth and fifth digits, respectively.
Each dorsal metacarpal artery is connected with the deep volar (palmar) arch by a proximal
perforating branch which passes through the proximal part of the corresponding interosse
space, and with a digital branch from the superficial volar (palmar) arch by a distal perforating
branch which passes through the distal part of the space.
FIG. 768. SUPERFICIAL DISSECTION OF THE VOLAR ASPECT
OF THE FOREARM AND HAND, showing" the radial and
ulnar arteries and the superficial volar arch with its
branches.
921
Biceps
RTHE ULNAE AETEEY.
elations Of the third part. The third part of the radial artery passes volarwards,
Between the two heads of the first dorsal interosseous muscle, to reach the palm, where it
;urns ulnarwards, deep to the proximal oblique part of the adductor muscle of the thumb,
ind, after passing through the proximal
ibres of the transverse part of the
idductor pollicis, or between the ad-
acent borders of the oblique and trans-
Verse parts of that muscle, it unites
vith the deep branch of the ulnar
irtery, completing the deep volar
palmar) arch.
Branches of the third part.
1) The princeps pollicis branch is
;iven off as soon as the radial artery.
inters the palm. It runs distally, on
he volar aspect of the first metacarpal
,x>ne, between the adductor and the
>pponens pollicis, and under cover of the
ong flexor tendon, and divides, near the
listal end of the bone, into collateral
tranches which run along the sides of
;he thumb and anastomose with the
, lorsales pollicis arteries.
(2) The arteria volaris indicis radi-
ilis is a branch which runs distally
)etween the ulnar head of the first dorsal
nterosseous muscle and the adductor of
;he thumb and along the radial side of
;he index-finger to its tip. It supplies
;he adjacent tissues, and not uncommonly
t anastomoses with the superficial volar
palmar) arch.
Radial
recurrent
artery
Lig. annu-
lare rad
Brachio-
radialis
Muscular
branch of
artery
Radial artery
Pronator teres
ARTERIA ULNARIS.
The ulnar artery (Figs. 768 and
T69) is the larger terminal branch,
3ut the less direct continuation of
:he brachial artery. It commences
n the cubital fossa, opposite the
! leek of the radius, and terminates
n the palm of the hand, where it
mastomoses with the superficial
folar artery to form the superficial
v r olar (palmar) arch.
From its origin it runs obliquely,
listally and ulnarwards, deep to the
, muscles arising from the medial
]3picondyle, to the junction of the
proximal and middle thirds of the
forearm, where it comes into relation
with the ulnar nerve ; it then passes
directly distally, on the radial side of
the ulnar nerve, to the wrist ; crosses
anterior to the main part of the
transverse carpal ligament, on the
radial side of the pisiform bone, and
: enters the palm of the hand to form
'palmar) arch.
Volar
communicating
artery
Deep branch
of ulnar artery
Deep volar
(palmar) arth
Palmar
metacarpal
arteries
Digital
artery .
FIG. 769. DEEP DISSECTION OF THE FRONT OF THE
FOREARM AND HAND, showing the radial and ulnar
arteries and their branches and the deep volar arch
and its branches.
the main part of the superficial volar
Relations Dorsal. Proximo-distally it lies volar to the distal part of the brachialis,
922 THE VASCULAE SYSTEM.
the flexor digitorum profundus, and the transverse carpal ligament (O.T. anterior
annular). Volar. On its volar aspect it is crossed, in the oblique part of its course,
by the pronator teres, the median nerve, which is separated from the artery by the deep
head of the pronator teres, the flexor digitorum sublimis, the flexor carpi radialis, and the
palmaris longus. In the middle third of the forearm it is overlapped by the volar border
of the flexor carpi ulnaris, and in the distal third it is covered by skin and fasciae only.
A short distance proximal to the wrist the palmar cutaneous branch of the ulnar nerve lies
volar to it, and as it crosses the transverse carpal ligament, it is bound down by a fascial
expansion from the tendon of the flexor carpi ulnaris. Two vense comites, which
frequently communicate with one another, lie one on each side of the artery. On the
radial side there is also, in its distal two-thirds, the flexor digitorum sublimis. On its
ulnar side are the flexor carpi ulnaris and the ulnar nerve.
Branches. (1) The volar ulnar recurrent is a small branch which arises in the
cubital fossa, frequently in common with the dorsal ulnar recurrent. It passes proximally,
to the anterior aspect of the medial epicondyle, under cover of the pronator teres, and
anastomoses with branches of the superior and inferior ulnar collateral arteries.
(2) The dorsal ulnar recurrent branch, larger than the volar, arises in the cubital
fossa, from the ulnar side of the ulnar artery, and ascends, on the brachialis and under
cover of the muscles which arise from the medial epicondyle, to the posterior aspect of
that prominence, where it passes between the humeral and olecranoid heads of the flexor
carpi ulnaris, and anastomoses with the superior and inferior ulnar collateral arteries. It
gives branches to the adjacent muscles and to the elbow-joint.
(3) The common interosseous artery, a short trunk which springs from the radial
and dorsal aspect of the ulnar artery, in the distal part of the cubital fossa. It passes
dorsally, towards the proximal border of the interosseous membrane, and divides into
volar and dorsal interosseous branches.
(3a) The volar interosseous artery runs distally, on the volar surface of the
interosseous membrane, between the adjacent borders of the flexor pollicis longus and the
flexor digitorum profundus, to the proximal border of the pronator quadratus; there it
pierces the interosseous membrane, and continues distally, first on the dorsal surface of the
membrane, deep to the extensor pollicis longus and extensor indicis proprius, and then
on the dorsal surface of the radius, in the groove for the extensor digitorum commimis :
and it terminates, on the dorsum of the carpus,' by joining the dorsal carpal arch. It is
accompanied on the volar aspect of the interosseous membrane by the volar interosseous
nerve, and, after it has pierced the membrane, by the dorsal interosseous nerve.
Branches. (a) Nutrient to the radius and ulna; (6) Muscular to the adjacent muscles;
(c) The volar communicating, a slender branch which passes distally, deep to the pronator
quadratus and on the volar surface of the interosseous membrane, to anastomose with the
volar carpal arch ; (
transverse mesocolon, with the middle colic artery. The latter descends to anastomose
with the upper branch of the ileo-colic, and from the loops thus .formed branches are dis
tributed to the walls of the ascending colon and the beginning of the transverse colon.
(e) The ileo-colic artery arises by a common trunk with the right colic, or separately
from the right side of the superior mesenteric, and passes downwards and to the right
behind the peritoneum, towards the lower part of the ascending colon, where it terminate:
by dividing into an ascending branch which anastomoses with the lower branch of th<
right colic, and a descending branch which communicates with the colic termiua
branches of the superior mesenteric trunk.
(/) Terminal. The lower end of the superior mesenteric artery divides into fiv
branches (i.) ileal, (ii.) appendicular, (iii.) anterior ileo-csecal, (iv.) posterior ileo-caecal
and (v.) colic.
The ileal branch, turns upwards and to the left in the lowest part of the mesentery, an*
anastomoses with the intestinal arteries. The appendicular branch passes behind the termina
portion of the ileum, and through the mesentery of the vermiform process to the vermiform process
upon which it ends. The anterior ileo-caecal crosses the front of the ileo-caecal junction in
fold of peritoneum ; the posterior ileo-caecal crosses the ileo-caecal junction posteriorly, and th
colic runs upwards to the ascending colon. The ileo-caecal branches supply the walls of th
caecum, and, like the colic branch, anastomose with branches of the ileo-colic artery. In som
cases the majority or all of the above terminal branches spring from the ileo-colic.
3. Arteria Mesenterica Inferior. The inferior mesenteric artery (Fig. 77
arises from the front of the aorta towards the left side, 37 mm. above the bifurca
tion ; it passes downwards and slightly to the left, lying posterior to the peritoneui
and anterior to the left psoas major muscle, to the upper and left border of th
left common iliac artery, where it becomes the superior hseniorrhoidal.
Branches. (a) The left colic artery arises from the left side of the inferic
mesenteric near its origin, and almost immediately divides into an upper and a low<
branch. The upper branch runs upwards and to the left towards the left colic flexure, and 1
the lower pole of the left kidney, where it divides into (i.)a branch which enters the transver
mesocolon, and, turning medially, terminates by joining the left branch of the middle col
PAKIETAL BKANCHES OF THE ABDOMINAL AOETA. 933
artery, and (ii.) a descending branch to the upper part of the descending colon. The lower
branch passes to the left, behind the peritoneum, and divides into upper and lower divisions ;
the upper anastomoses with the descending division of the upper branch and supplies
the lower part of the descending colon. The lower division supplies the iliac colon, and it
anastomoses with the branches of the upper division and with the branches of. the sigmoid
arteries. Both branches of the left colic artery lie immediately behind the peritoneum,
and each branch crosses anterior to the ureter and the internal spermatic vessels.
(6) The sigmoid branches, usually two in number, arise from the convexity of the
inferior mesenteric, and pass downwards and to the left to the lower part of the iliac
colon and to the pelvic colon. They lie posterior to the peritoneum, and anterior to the
psoas major, the ureter, and the upper part of the iliacus. They terminate by dividing into
branches which anastomose with the terminal twigs of the lower branch of left colic
above and with branches of the superior hsemorrhoidal below, forming a series of arches
from which branches are distributed to the lower part of the iliac colon and the pelvic colon.
(c) The superior haemorrhoidal artery is the direct continuation of the inferior
mesenteric. It enters the mesentery of the pelvic colon, crosses the front of the left
common iliac artery, descends into the pelvis minor as far as the third piece of the sacrum,
or, in other words, the junction between the pelvic colon and the rectum, and divides
into two branches which pass downwards on the sides of the rectum. Half-way down
the rectum each of the two terminal branches of the superior hsemorrhoidal artery
divides into two or more branches which pass through the muscular coats and terminate
in the submucous tissue, where they divide into numerous small branches which pass
vertically downwards, anastomosing with one another, with offsets from the middle
haemorrhoidal branches of the internal iliac arteries, the inferior hsemorrhoidal branches
of the internal pudic arteries, and with branches from the middle sacral artery.
The superior haemorrhoidal artery supplies the mucous membrane of the pelvic colon
and the rectum and the muscular coats of the pelvic colon.
PARIETAL BRANCHES OF THE ABDOMINAL AORTA.
1. Arterise Phrenicae Inferiores. The inferior phrenic arteries (Fig. 773),
right and left, are of . small size ; they arise, either separately or ' by a common
i trunk, from the aorta, immediately below the diaphragm, to which they are dis-
tributed. Diverging from its fellow, each artery runs upwards and laterally, on
the corresponding crus of the diaphragm that on the right side passing posterior
to the inferior vena cava, that on the left side posterior to the oesophagus and just
1 before reaching the central tendon of the diaphragm each divides into medial and
lateral terminal branches. The medial branch runs forwards and anastomoses
with its fellow of the opposite side, forming an arch, convex forwards, along the
anterior border of the central tendon of the diaphragm. Offsets from this arch
, anastomose with the pericardiaco-phrenic, musculo-phrenic, and internal mammary
arteries. The lateral branch passes laterally towards the lower ribs, and anastomoses
with the musculo-phrenic and lower intercostal arteries.
In addition to supplying the diaphragm each inferior phrenic artery gives a
superior suprarenal branch, to the suprarenal gland of its own side, and, occasionally,
small hepatic branches which pass through the coronary ligament to the liver.
Further, the left artery gives oesophageal branches which anastomose with
1 oesophageal branches of the aorta and of the left gastric artery, whilst from the
artery of the right side minute branches pass to the inferior vena cava.
!. Arteriae Lumbales. The lumbar arteries correspond to the intercostal
branches of the thoracic aorta. They are in series with the intercostal arteries ;
their distribution is very similar; and, like the intercostals, they arise, either
separately or by common trunks, from the posterior aspect of the aorta.
There are usually four pairs of lumbar arteries, but occasionally a fifth pair
1 arises from or in common with the middle sacral artery.
From their origins the lumbar arteries pass laterally and posteriorly, across the
ront and sides of the bodies of the upper four lumbar vertebrae, to the intervals
bween the adjacent transverse processes, beyond which they are continued into
the lateral part of the abdominal wall.
Each artery lies on the body of the corresponding lumbar vertebra. In its back-
r course, and while still in relation with the vertebral body, it is crossed
60 I
934
THE VASCULAE SYSTEM.
by the sympathetic trunk, and then, after passing medial to and being protected
by the 'fibrous arches from which the psoas major muscle arises, it runs behind tht
muscle and the lumbar plexus. The upper two arteries, on each side, also pass
posterior to the crura of the diaphragm. Beyond the interval between the trans-
verse processes of the vertebrae each artery turns laterally and crosses the
Hepatic veil
Inferior phrenic artery
Suprarenal gland
Inferior vena cava
Renal artery
vein
Right ovarian vein
Ovarian artery
Ureter
Psoas major muscle
Ascending colon
Common iliac vein
Common iliac artery
Middle sacral artery
Ileum
Caecum
External iliac
artery
External iliac
vein
Middle um-
bilical liga-
ment (O.T. "~
urachus)
(Esophagus
Crus of diaphra
Inferior phrenic
artery
Suprarenal glan
Coeliac artery
Suprarenal veil
uperior
lesenteric arte
,umbar arteries
Ureter
Left colic artery
Ovarian artery
Inferior mesenteric
artery
Descending colon
Psoas major muscl
Commpn iliac artei
Sigmoid artery
^ Common iliac
Superior haemc
rhoidal artery
Iliac colon
Pelvic colon j
External iliac
artery
External iliac
Uterine tube
Uterus
FIG. 773. THE ABDOMINAL AORTA AND ITS BRANCHES.
quadratus lumboruni the last usually passing anterior to, and the othe
posterior to the muscle ; it then pierces the aponeurosis of origin of the trar
versus, and proceeds forwards in the lateral abdominal wall, in the interv
between the transversus and internal oblique muscles. The lumbar arteri
anastomose with one another, with the lower intercostal and subcostal arteries, a:
with branches of the superior and inferior epigastric and of the deep circumfl
iliac and ilio-lurnbar arteries.
Fine twigs also pass from the lumbar arteries to the extra-peritoneal fat ; th( i
anastomose with corresponding branches from the inferior phrenic and ilio-luml "
arteries, and with small branches from the hepatic, renal, and colic arteries, to foi .
the subperitoneal plexus of Turner.
THE COMMON ILIAC AETEKIES. 935
The abdominal aorta is almost median in position, consequently the right
lumbar arteries are scarcely longer than the left. On the right side the arteries
pass behind the inferior vena cava, the upper two arteries being separated from
that vessel by the right crus of the diaphragm. The upper two right arteries also
pass posterior to the cisterna chyli and the lower end of the azygos vein.
Branches. Dorsal. Each lumbar artery gives off, opposite the interval between
the vertebral transverse processes, a dorsal branch of considerable size. It is analogous
with and is distributed like the posterior branch of an aortic intercostal artery (p. 925).
Muscular branches are given off, both from the main trunk and its dorsal branch, to
the adjacent muscles.
3. Arteria Sacralis Media. The middle sacral artery (Fig. 773) is a single
median vessel. It is commonly regarded as a caudal aorta and as the direct
continuation of the abdominal aorta. It is, however, of small size, and almost
invariably arises from the back of the aorta, about 12 mm. (half an inch) above
its bifurcation. It descends, anterior to the lower two lumbar vertebrse and
to the sacrum and coccyx, and ends, opposite the tip of the coccyx, by
anastomosing with the lateral sacral arteries to form a loop from which branches
pass to the coccygeal glomus. Opposite the fifth lumbar vertebra it is crossed,
anteriorly, by the left common iliac vein, below which it is covered by peritoneum
and coils of small intestine as far -as the third segment of the sacrum, and in the
rest of its extent it is posterior to the rectum. It is accompanied below by
venae comites, which, however, unite, above, to form a single middle sacral vein.
As it lies anterior to the last lumbar vertebra it gives off on each side a
lumbar branch, the arteria lumbalis ima, which is distributed like an ordinary
lumbar artery, and as it descends in front of the sacrum it distributes small
parietal branches laterally which anastomose with the lateral sacral arteries. The
parietal branches usually give off small spinal offsets which enter the anterior sacral
foramina. Small and irregular visceral branches pass to the rectum and anastomose
with the superior and middle hgemorrhoidal arteries.
ARTERIA ILIAC.E COMMUNES.
, The common iliac arteries (Figs. 773 and 774) are the terminal branches
of the abdominal aorta. They commence opposite the middle of the body of the
fourth lumbar vertebra a little to the left of the median plane. Each artery passes
downwards and laterally, across the bodies of the fourth and fifth lumbar vertebrae
and the intervening intervertebral fibro-cartilage, and it terminates, at the level
of the lumbo-sacral articulation and anterior to the corresponding sacro-iliac joint,
by dividing into external iliac and hypogastric (O.T. internal iliac) branches.
The direction of each common iliac is indicated by a line drawn from the
bifurcation of the aorta to a point midway between the symphysis pubis and the
anterior superior spine of the ilium.
The right artery is a little longer than the left ; the former being about 50 mm.
two inches) and the latter 43 mm. (one and three-quarter inches) in length.
Relations. Anterior. Both arteries are covered anteriorly by peritoneum, and are
separated by it from coils of the small intestine. Communicating branches between the
aortic and hypogastric plexuses of the sympathetic pass in front of the arteries, each of which
is often crossed, anteriorly, near its termination by the corresponding ureter.
The left artery is crossed, in addition, by the superior hsemorrhoidal vessels.
Posterior. Behind the artery, of each side, are the bodies of the fourth and fifth
lumbar vertebra, and the intervening intervertebral fibro-cartilage, the sympathetic trunk,
the psoas major muscle. These relationships, however, are much closer on the left side
lan on the right. The right common iliac, except at its lower end, where it is in contact
ith the psoas major, is separated from the structures named by the terminations of the
right and left common iliac veins and the commencement of the inferior vena cava. The
common iliac, which is not so separated, lies on the medial border of the psoas major.
x>mewhat deeply placed, in the areolar tissue between the psoas major and the lumbar
936 THE VASCULAR SYSTEM.
vertebrae, are the obturator nerve, the lumbo-sacral trunk, and the ilio-lumbar artery, which
form posterior relations to the common iliac artery of the corresponding side.
Lateral. The lateral relations of each artery are coils of small intestine, and the
commencement of the inferior vena cava lies to the lateral side of the upper part of the
right artery.
Medial. On the medial side of the right common iliac artery are the right common
iliac vein, below, and the left common iliac vein, above. The last-named vein lies on the
medial side of the left common iliac artery.
Branches. The external iliac and the hypogastric are the only branches.
ARTERIA HYPOGASTRICA.
The hypogastric artery (O.T. internal iliac) (Figs. 773, 774, and 777) in the
foetus is the direct continuation of the common iliac trunk. It supplies numerous
branches to the pelvis, runs upwards on the anterior abdominal wall to the
umbilicus as the umbilical artery, and is prolonged through the umbilical cord
to the placenta. One of its pelvic branches the inferior glutaeal (O.T. sciatic) is
at first the main artery of the inferior extremity, but subsequently another branch
is given off which becomes the chief arterial trunk of the lower limb. This branch
is the external iliac artery ; it soon equals and ultimately exceeds the hypogastric
in size, and it is into these two vessels that the common iliac appears to bifurcate.
When the placental circulation ceases and the umbilical cord is severed, the
umbilical part of the hypogastric trunk which extends from the pelvis minor to
the umbilicus atrophies, and is afterwards represented almost entirely by a fibrous
cord, known as the obliterated umbilical artery. It is only at its proximal end
that the atrophied part remains pervious, and there it forms the commencement
of the superior vesical artery. The permanent hypogastric is a comparatively
short vessel. Owing to the arrangement of some of its branches it appears to
end in an anterior and a posterior division, the former of which is to be regarded
as the continuation of the vessel, whilst the latter is simply a common stem oil
origin for some of the branches.
With this explanation the artery may be described in the usual manner.
It arises from the common iliac opposite the sacro-iliac articulation and at the
level of the lumbo-sacral articulation, and descends into the pelvis minor, tc|
terminate, as a rule, opposite the upper border of the greater sciatic notch, in fcwc
divisions anterior and posterior from each of which branches of distribution art
given off. The artery measures about 37 mm. (one and a half inches) in length.
Relations. Anterior. Each hypogastric artery is covered antero-medially b}
peritoneum, behind which the corresponding ureter descends along the anterior borde]
of the artery. The pelvic colon crosses from the front to the medial side of the lefi
artery, and the terminal part of the ileum bears the same relation to the right artery.
Posterior to it are the hypogastric vein and the commencement of the common iliai
vein ; still more posteriorly are the lumbo-sacral trunk and the sacro-iliac joint.
Lateral. On its lateral side the external iliac vein separates it from the psoas majo
muscle, above. At a lower level the obturator nerve, embedded in a mass of fat, intervene:
between the hypogastric artery and the lateral wall of the pelvis. On its medial sid<
it is crossed by some of the tributaries of the hypogastric vein, and it is covered b;
peritoneum.
Branches. The hypogastric artery supplies the greater part of the pelvi
wall and contents, and its branches are distributed also to the buttock and thig]
and to the external organs of generation.
All the branches may be given off separately from a single undivided pareD
trunk, but as a rule they arise in two groups corresponding to the two divisions i
which the artery, under these circumstances, appears to end.
fllio-lurnbar
Posterior division | parietal \ Lateral sacral
[Superior gluteal
THE HYPOGASTEIC AETEEY
937
Anterior division
f Obturator
parietal -j Inferior gluteal
[internal pudendal
( Umbilical
J (Superior vesical)
visceral I Interior vesical
[ Middle hsemorrhoidal.
[n the female two additional branches are present a uterine and a vaginal.
ernal iliac vein
as major muscle
mbilical artery
) i circumflex il
artery
* i'rior vesical artery.
Obturator vein
gastric artery
Round ligament
Obturator nerv
Obturator artery
n-y of clitoris
r 'rofunda artery of th
clitori's
Sympathetic trunk
teral sacral artery
Hypogastric vein
Superior gluteal artery
Inferior gluteal artery
Internal pudendal
artery
Sacral plexus
FIG. 774. HYPOGASTRIC ARTERY AND ITS BRANCHES IN THE FEMALE.
1. Sacro-spinous ligament. 6. Dorsal nerve of clitoris.
2. Uterine artery. 7. Internal pudendal artery.
3. Vaginal artery. 8. Perineal nerve.
4. Inferior haemorrhoidal iierve. 9. Superficial perineal artery.
5. Inferior haemorrhoidal artery. 10. Artery to the bulb of the vestibule.
BRANCHES OF THE POSTERIOR DIVISION.
The posterior terminal division gives off the ilio-lumbar and lateral sacral
iries, and is continued as the superior glutseal artery.
. Arteria Ilio-lumbalis. The ilio-lumbar artery runs upwards and later-
Y, across the upper margin of the pelvis minor, to the iliac fossa. It passes
irior to the sacro-iliac articulation, between the lumbo-sacral trunk and the
irator nerve, and posterior to either the lower part of the common or the
>r part of the external iliac vessels, and the psoas and iliacus muscles.
In the iliac fossa it divides into an iliac and a lumbar branch. The iliac branch
iomoses with branches of the deep circumflex iliac and obturator arteries,
s offsets to the iliacus, and supplies a large nutrient branch to the ilium.
bar branch ascends, behind the psoas major, to the crest of the ilium. It supplies
e ipsoas and quadratus lumber urn, and anastomoses with the lumbar and deep
938 THE VASCULAE SYSTEM.
circumflex iliac arteries ; it also gives off a spinal branch, which enters the inter-
vertebral foramen between the fifth lumbar vertebra and the sacrum, and is dis-
tributed like the spinal branches of the lumbar and the aortic intercostal arteries.
2. Arterise Sacrales Laterales. There is sometimes only a single lateral
sacral artery on each side ; more commonly there are two, superior and inferior.
Both run downwards and medially, on the front of the sacrum. The inferior
passes anterior to the piriformis and the sacral nerves, and descends, on the lateral
side of the sympathetic trunk, to the coccyx, where it terminates by anastomosing
with the middle sacral. The superior branch reaches only as far as the first or the
second anterior sacral foramen ; then it enters the sacral canal. It anastomoses
with the lower branch and with the middle sacral artery. Branches are given off by
the lateral sacral arteries to the piriformis, and to the sacral nerves. Spinal offsets
are also given off, which pass through the anterior sacral foramina to the sacral
canal ; they supply the membranes of the spinal medulla, the roots of the sacral
nerves, and the filum terminale, and anastomose with other spinal arteries. They
then pass through the posterior sacral foramina, and anastomose on the back of the
sacrum with branches of the superior and inferior glutseal arteries.
3. Arteria Glutsea Superior (Figs. 774 and 776). After giving off the ilio-
lumbar and lateral sacral branches, the posterior division of the hypogastric
artery is continued as the superior gluteal artery. This is a large vessel which
pierces the pelvic fascia, and passes backwards, between the lumbo-sacral trunk and
the first sacral nerve. It leaves the pelvis through the upper part of the greater
sciatic foramen, above the piriformis muscle, and enters the buttock, where it
divides, under cover of the glutseus maximus and between the adjacent borders of
the piriformis and glutseus medius muscles, into superficial and deep branches.
(a) The superficial branch divides at once into numerous rami, some of which supply
the gluteeus maximus, whilst others pass through it, near its origin, to the overlying skin.
The branches freely anastomose with branches of the inferior gluteal, internal pudendal,
medial circumflex, deep circumflex iliac, and lateral sacral arteries.
(b) The deep terminal branch, accompanied by the superior gluteal nerve, runs forwards
between the glutseus medius and minimus, and, after giving a nutrient branch to the ilium,
subdivides into upper and lower branches. The upper branch, runs forwards along
the origin of the glutseus minimus from the anterior curved line of the ilium, and
passes beyond the anterior margins of the gluteeus medius and minimus to anastomose.
under cover of the tensor fasciae latse, with the ascending branch of the lateral circumflex
artery. It anastomoses with the deep circumflex iliac artery also, and it supplies musculai
branches to the adjacent muscles. The lower branch passes more directly forwards
across the glutaeus minimus, towards the trochanter major, along with the branch of the
superior gluteal nerve which supplies the tensor fasciae latse. It supplies the glutea
muscles, and anastomoses with the ascending branch of the lateral circumflex artery.
Before leaving the pelvis the gluteal artery gives muscular branches to the pelvi<
diaphragm and the obturator internus, small neural branches to the roots of the sacra
plexus, and nutrient branches to the hip-bone.
BRANCHES OF THE ANTERIOR DIVISION.
The anterior division gives off both parietal and visceral branches, and i
continued as the umbilical artery. The parietal branches are the obturator, th<
internal pudendal, and the inferior gluteal. The visceral branches include th<
superior and inferior vesical, and the middle hsemorrhoidal arteries in the malt
In the female the anterior division of the hypogastric artery gives off simila
visceral branches, and, in addition, a uterine and a vaginal branch.
VISCERAL BRANCHES.
1. Arteria Vesicalis Superior. The superior vesical artery arises from t
incompletely obliterated posterior part of the umbilical artery, as it lies at the sid
of the bladder. It passes medially to the upper part of the urinary bladder an
divides into numerous branches which anastomose with the other vesical arterie
and it also gives small branches to the urachus, and often to the lower pai
of the ureter. It may in addition give off a middle vesical branch, and nc
infrequently the long slender artery to the ductus de/erens arises from it.
VISCEEAL BEANCHES OF THE HYPOGASTEIC AETEEY. 939
2. Arteria Umbilicalis. -Atrophy of that portion of the umbilical artery
which extends from the anterior division of the hypogastric to the umbilicus has
already been referred to. The atrophy is complete between the umbilicus and
. the origin of the superior vesical artery, but between that origin and the apparent
ending of the hypogastric in its two divisions it is incomplete, and the lumen
of the vessel, though greatly diminished in size, remains patent. It is from
the incompletely obliterated portion that the superior vesical artery arises. The
completely obliterated part of the umbilical artery is reduced to a fibrous cord
which runs along the side of the bladder to its apex, and then ascends, on the
posterior surface of the anterior abdominal wall, to the umbilicus. In the latter
part of its course it is known as the ligamentum umbilicale laterale. As it passes
along the wall of the pelvis it is external to the peritoneum, and it is crossed by
the ductus deferens in the male, and by the round ligament in the female.
3. Arteria Vesicalis Inferior. The inferior vesical artery runs medially, upon
the upper surface of the levator ani, to the base of the bladder. It also gives
branches to the seminal vesicles, the ductus deferens, the lower part of the ureter
and the prostate, and it anastomoses with its fellow of the opposite side, with the
other vesical arteries, and with the middle hsemorrhoidal artery.
4. Arteria Deferentialis. The artery to the ductus deferens may arise from
either the superior vesical or the inferior. It is a long slender vessel which
accompanies the ductus deferens to the testis, where it anastomoses with the
. testicular artery. It also anastomoses with the external spermatic branch of- the
inferior epigastric artery.
5. Arteria Hsemorrhoidalis Media. The middle hsemorrhoidal artery is an
irregular branch which arises either directly from the anterior division of the
internal iliac or from the inferior vesical branch ; more rarely it springs from the
internal pudendal artery. It runs medially, and is distributed to the muscular
coats of the rectum ; it also gives branches to the prostate, the seminal vesicle,
and the ductus deferens, and it anastomoses with its fellow of the opposite side,
with the inferior vesical, and with the superior and inferior hsemorrhoidal arteries.
6. Arteria Vaginalis. The vaginal artery may arise either directly from the
anterior division of the hypogastric or from a stem common to it and the uterine
artery, and it may be represented by several branches.
It runs downwards and medially, on the floor of the pelvis, to the side of
the vagina, and divides into numerous branches which ramify on the anterior
and posterior walls of the passage. The corresponding branches of opposite
( sides anastomose and form anterior and posterior longitudinal vessels, the so-called
azygos arteries. They also anastomose above with the cervical branches of the
uterine artery, and below with the perineal branches of the internal pudendal.
In addition to supplying the vagina, small branches are given to the bulb of
i the vestibule, to the base of the bladder, and to the rectum.
7. Arteria Uterina. The uterine artery arises from the anterior division
of the internal iliac, either separately or in common with the vaginal or middle
haemorrhoidal arteries. It runs medially and slightly forwards, upon the upper
surface of the levator ani, to the lower border of the broad ligament, between the
I two layers of which it passes medially, and arches above the ureter about three-
quarters of an inch from the uterus. It passes above the lateral fornix of the
.vagina to the side of the neck of the uterus, and then ascends towards the fundus,
but at the level of the uterine tube it turns laterally, below the tube and between
the layers of the broad ligament, and anastomoses with the ovarian artery. It
supplies the uterus, the upper part of the vagina, the medial part of the uterine
tube, and gives branches to the round ligament of the uterus. It anastomoses
with its fellow of the opposite side, and with the vaginal, the ovarian, and the
inferior epigastric arteries, along the round ligament of the uterus.
ani
PARIETAL BRANCHES OF THE ANTERIOR DIVISION.
. Arteria Obturatoria. The obturator artery (Figs. 774 and 777) runs
anteriorly and downwards along the lateral wall of the pelvis minor, just below
940 THE VASCULAK SYSTEM.
its upper margin, to the obturator foramen, through the upper part of which it
passes. It terminates, immediately on entering the thigh, by dividing into anterior
and posterior terminal branches, which skirt round the margin of the obturator
foramen deep to the obturator externus muscle. It is accompanied, in the whole
of its course, by the obturator nerve and vein, the nerve being above the artery
and the vein below it.
To its lateral side is the pelvic fascia, which intervenes between it and the upper
part of the obturator internus muscle, whilst on its medial side it is covered by
peritoneum. The ureter intervenes between the posterior part of the artery and
the peritoneum. When the bladder is distended it also comes into close relation
with the lower and anterior part of the artery. In the female the ovarian vessels
and the broad ligament form the medial relations of the obturator artery.
Branches. All the branches except the terminal are given off before the artery
leaves the pelvis. They include : (a) Muscular branches to the obturator internus,
levator aui and ilio-psoas muscles. (6) A nutrient branch to the ilium, which passes
deep to the ilio-psoas muscle, supplies the bone, and anastomoses with the ilio-lumbar
artery, (c) A vesical branch or branches pass medially to the bladder beneath the
lateral false ligament, (d) A pubic branch ascends on the posterior surface of the pubis,
and anastomoses with its fellow of the opposite side and with the pubic branch of the
inferior epigastric. It is given off just before the artery leaves the pelvis, and, in its
upward course, it may pass either on the lateral or medial side of the external iliac vein,
whilst not infrequently it runs on the medial side of the femoral ring. In the latter
case it is important in relation to femoral hernia ; this importance is emphasised when,
as sometimes happens, the obturator artery arises as an enlarged pubic branch of
the inferior epigastric artery instead of from the hypogastric. (e) Terminal. The
anterior terminal branch runs forwards, and the posterior backwards around the margin
of the obturator foramen. They lie on the obturator membrane, under cover of
the obturator externus, and they anastomose together at the lower margin of the
foramen. Both give off offsets which anastomose with the medial circumflex artery,
and twigs of supply to the adjacent muscles. The posterior branch also gives an
acetabular branch to the hip-joint, which passes upwards, through the acetabular notch
on the medial side of the transverse ligament, to supply the ligamentum teres and the
head of the femur.
2. Arteria Pudenda Interna. The internal pudendal artery (Figs. 774
and 775) arises from the anterior division of the hypogastric, close to the origin
of the. inferior glutaeal artery, which slightly exceeds it in size. It runs downwards
and backwards, to the lower part of the greater sciatic foramen, lying anterior to
the piriformis muscle and the sacral plexus, from both of which it is separated by
the pelvic fascia. At the lower border of the piriformis it pierces the pelvic
fascia, passes between the piriformis and coccygeus muscles, and leaves the pelvis
to enter the buttock. It is accompanied by venae comites, the inferior gluteal
vessels and nerves, the pudendal nerve, and the nerve to the obturator internus. ;
In the buttock it lies on the spine of the ischium, under cover of the glutseus;
maximus, and between the pudendal nerve and the nerve to the obturator in-
ternus, the former being' medial to it. It next passes through the lesser sciatic
foramen and enters the perineum, in the anterior part of which it terminates by
dividing into the profunda artery of the penis and the dorsal artery of the penis.
In the first part of its course in the perineum the artery lies in the lateral
fascial wall of the ischio-rectal fossa, where it is enclosed in a canal in the fascia
(Alcock's canal). This canal, which is situated about one and a half inches above th<
lower margin of the tuberosity of the ischium, contains also the pudendal veint
and the terminal parts of the pudendal nerve, viz., the dorsal nerve of the penis
which lies above the artery, and the perineal division, which lies below the vessel
From the ischio-rectal fossa the internal pudendal artery is continued forward;
between the two layers of the fascia of the urogenital diaphragm (O.T. triangula
ligament of the urethra), and close to the ramus of the pubis. About half-an
inch below the arcuate ligament it turns somewhat abruptly forwards, pierces th 1
inferior fascia of the urogenital diaphragm, and immediately divides into it
terminal branches, viz., the profunda artery and the dorsal artery of the
PAKIETAL BEANCHES OF THE HYPOGASTEIC AETEEY. 941
The division sometimes takes place whilst the artery is still between the layers
of the urogenital diaphragm.
Branches. In the pelvis it gives small branches to the neighbouring muscles and to
the roots of the sacral plexus.
In the buttock. (a) Muscular branches are distributed to the adjacent muscles. (6)
Anastomotic branches unite with branches of the superior and inferior glutaeal, and
. medial circumflex arteries.
In the ischio-rectal fossa. (c) The inferior hsemorrhoidal artery pierces the wall of
the fascial canal, and runs obliquely forwards and medially. It soon divides into two or
three main branches, which may arise separately from the pudendal ; they pass across
' the space to the anal passage. The artery anastomoses in the walls of the anal passage
Superficial trans-
erse perineal muscle
/ Crus penis
Dorsal artery of penis
and profunda artery
of penis
Bulb of penis
Sphincter of
membranous urethras
Artery to bulb
Perineal artery
Transverse branch of
perineal artery
Internal pudendal
artery
Inferior hsemor-
rhoidal artery
i. Glutseus maxim us
.THE PERINEAL DISTRIBUTION OF THE INTERNAL PUDENDAL ARTERY IN THE MALE.
with its fellow of the opposite side, and with the middle and superior haBmorrhoidal
arteries ; it anastomoses with the transverse perineal arteries also ; and it supplies
cutaneous twigs to the region of the anus, and others, which turn round the lower
border of the glutseus maximus, to supply the lower part of the buttock.
(d) The perineal artery arises in the anterior part of the ischio-rectal fossa, pierces
I the base of the fascia of the urogenital diaphragm, and divides into long slender posterior
scrotal branches in the male, and posterior labial branches in the female. Those branches are
continued forwards, in the urethral triangle, to the scrotum or labium, deep to the super-
ficial perineal fascia. They anastomose with their fellows of the opposite side, with the
transverse perineal and the external pudendal arteries, and supply the muscles and
subcutaneous structures of the urethral triangle.
(e) The transverse perineal artery is a small branch which arises either directly from the
internal pudendal or from its perineal branch. It runs medially along the base of
the fascia of the urogenital diaphragm (O.T. triangular lig.) to the central point of
the perineum, where it anastomoses with its fellow of the opposite side, with the perineal
artery, and with the inferior hsemorrhoidal arteries. It supplies the sphincter ani,
; the bulbo-cavernosus or sphincter vaginae, and the anterior fibres of the levator ani.
In the urethral triangle. (/) The artery to the bulb, a branch which is usually of
tively large size, is given off between the fascial layers of the urogenital diaphragm.
t runs transversely along the posterior border of the sphincter of the membranous
942 THE VASCULAR SYSTEM.
urethrse, and then, turning forwards a short distance from the side of the urethra, i1
pierces the inferior fascia of the urogenital diaphragm and enters the substance of the
bulb. It passes onwards in the corpus cavernosuin urethrse to the glans, where il
anastomoses with its fellow and with the dorsal arteries of the penis.
It supplies the sphincter of the membranous urethrse, bulbo-urethral gland (Cowper)
the corpus cavernosum urethrse, and the penile part of the urethra. In the female thi;
artery supplies the bulb of the vestibule.
(g) The profunda artery of the penis (O.T. artery of the corpus cavernosum) in thq
male, and of the clitoris in the female, is usually the larger of . the two termina
branches. Immediately after its origin it enters the crus penis, and runs forwards li-
the corpus cavernosum penis, which it supplies.
(h) The dorsal artery of the penis in the male, and of the clitoris in the female ;
passes forwards between the layers of the suspensory ligament, and runs along th<
dorsal surface of the penis, with the dorsal nerve immediately to its lateral side, whilst i ;
is separated from its fellow of the opposite side by the deep dorsal vein, which lie
in the median plane. It supplies the superficial tissues on the dorsal aspect of th
penis, sends branches into the corpus cavernosum penis to anastomose with the profund;
artery of the penis, and its terminal branches enter the glans penis, where they anastc
mose with the arteries to the bulb. It anastomoses also with the external pudenda,
branches of the femoral.
3. Arteria Glutaeal Inferior. The inferior gluteal artery (O.T. sciatic), (Figs. 77' i
and 776) arises from the hypogastric artery, either separately or by a commo]
trunk with the internal pudendal artery. It descends a little postero-latera
to the internal pudendal vessels, pierces the pelvic fascia, runs backwards betwee: '
the first and second, or second and third sacral nerves, and, passing between th ;
piriformis and coccygeus muscles, leaves the pelvis through the lower part of th
greater sciatic foramen, and enters the buttock just below the piriformis. In th
buttock it descends posterior and to the medial side of the sciatic nerve deep t|
the glutseus maximus, and posterior to the obturator internus, the two gemell
the quadratus femoris, and upper part of the adductor magnus muscles, to th.;
proximal part of the thigh.
Below the lower border of the glutseus maximus the artery is comparative!
superficial, and having given off its largest branches, it runs distally, as a lonj
slender vessel, with the posterior femoral cutaneous nerve.
Branches In the pelvis. Small and irregular branches supply the adjacent visce;
and muscles and the sacral nerves ; they anastomose with branches of the intern
pudendal and lateral sacral arteries.
In the buttock. (a) Muscular branches are given off to the muscles of the buttoc
and to the proximal parts of the hamstring muscles. They anastomose with the intern
pudendal, medial circumflex, and obturator arteries. (&) The coccygeal branch aris
immediately after the artery leaves the pelvis. It runs medially, pierces the sacro-tuberoi
ligament and the glutseus maximus, and ends in the soft tissues over the posterior aspe
of the lower part of the sacrum and of the coccyx. It gives several branches to tl ;
glutaeus maximus, and anastomoses with branches of the glutseal and lateral sacr;
arteries, (c) An anastomotic branch passes laterally, superficial or deep to the sciat
nerve, towards the greater trochanter of the femur. It anastomoses with branches
the gluteal, internal pudendal, medial and lateral circumflex, and the first perforatii
arteries, taking part in the formation of the so-called "crucial anastomosis." (d) Cutaneo
branches, accompanying twigs of the posterior cutaneous nerve of the thigh, pass roui
the lower border of the gluteeus maximus muscle to the integument, (e) The a. comita
n. ischiadici is a long slender branch which runs distally on the surface, or in the substan
of the sciatic nerve. It supplies the nerve, and anastomoses with the perforating arteri
and with the termination of the profunda femoris artery.
AETEEIES OF THE INFEEIOK EXTKEMITY.
The main artery of each lower limb is continued from the corresponding coi
mon iliac artery. It descends as a single trunk as far as the lower border of t
popliteus, and ends there by dividing into the anterior and posterior tibial arteri
Distinctive names are, however, applied to different parts of the artery, correspon
ing to the several regions through which it passes. Thus in the abdomen it
call<
EXTEENAL ILIAC AETEEY.
943
ed the external iliac artery, in the proximal two-thirds of the thigh it receives
the name of the femoral artery, whilst its distal part, which is situated on the
flexor aspect of the knee, is termed the popliteal artery.
A. glutfea superior
(ramus profundus)
A. glutsea superior
(ramus superficialis)'"--,^
A. glutsea inferior
A. glutsea inferior
(ramus coccygeus)
r. cutaneus femoris -
posterior
M. glutseus maximus
N. ischiadicus
[. biceps femoris (caput longum) ~^i.
M. adductor magnus j
M. semitendinosus -
M. gastrocnemius -~~
Ramus musculari.s
M. glutaeus medius
' A. glutaea superior
- M. glutaeus minimus
I N. gluteeus superior
I A. glutaea superior
_.. M. piriformis
M. obturator internus
A. circumflexa femoris
medialis (deep terminal
branch)
_ M. glutaeus medius
- M. quadratus femoris
M. gluteus maximus
A. circumflexa
femoris medialis
(transverse terminal
branch)
- A. perforans prima
- M. vastus lateralis
A. poplitea et V. poplitea -
&&SOG&=a
Ramimusculares _
limembranosus
A. genu superior medialis -r
A. genu inferior medialis
Nerve to popliteus
V. saphena parva
A. perforans secunda
M. biceps femoris
(caput breve)
A. perforans tertia
N. ischiadicus
N. peronseus communis
N. tibialis
A. genu suprema lateralis
M. plantaris
A. etV., poplitea
- A. genu inferior lateralis
Nerve to soleus
N. peronseus communis
M. gastrocnemius (caput laterale)
FIG. 776. THE ARTERIES OP THE BUTTOCK AND THE POSTERIOR ASPECT OF THE THIGH AND KNEE.
In the specimen there was no anastomotic branch of the inferior gluteal artery, and the transverse
.erminal branch of the medial femoral circumflex artery pierced the upper part of the adductor magnus.
AETERIA ILIACA EXTEENA.
The external iliac artery (Figs. 77*7, 778) extends from a point opposite the
sacro-iliac joint, at the level of the lumbo-sacral articulation, to a point below the
944 THE VASCULAR SYSTEM.
inguinal ligament (Poupart's), midway between the anterior superior spine of the
ilium and the symphysis pubis, where it becomes the femoral artery. Its length
is about 87 to 100 mm. (three and a half to four inches), and in the adult it is
usually somewhat larger than the hypogastric artery.
It runs downwards, forwards, and laterally, along the superior aperture ol
the pelvis minor, resting upon the fascia iliaca, which separates it, above, frona
the medial border, and, below, from the anterior surface of the psoas inajoi
muscle ; and it is enclosed, with its accompanying vein, in a thin fascial sheath.
Relations. Anterior. It is covered in front by peritoneum, which separates it 01
the left side from the iliac colon, and coils of small intestine, and on the right side fron
the terminal portion of the ileum, and sometimes from the vermiform process. Thi
ureter, descending behind the peritoneum, sometimes crosses the front of the arter
near its origin, and in the female the ovarian vessels cross the upper part of the artery
Near its lower end the artery is crossed anteriorly by the external spermatic branch o
the geni to-femoral nerve and by the deep circumflex iliac vein. In the male this part o
the artery is crossed also by the ductus deferens, and in the female by the round ligamen
of the uterus. Several iliac lymph glands lie in front and at the sides of the externs
iliac artery, and almost invariably one of these is directly anterior to its termination.
Posterior. The fascia iliaca and psoas major muscle lie behind the artery. Near it
upper end the obturator nerve and the external iliac vein are posterior to the vessel.
Lateral. On its lateral side is the genito-femoral nerve. Medial. To the medk
side of its lower part is the external iliac vein.
Branches. In addition to small branches to the psoas major muscle and t
the lymph glands, two named branches of considerable size spring from the extern?
iliac artery, viz., the inferior epigastric and the deep circumflex iliac.
(1) Arteria Epigastrica Inferior. The inferior epigastric artery (Figs. 7*74 an
777) arises, immediately above the inguinal ligament, from the front of the extern;
iliac. It lies in the extra-peritoneal fat, it curves forwards from its origin, tun^
round the lower border of the peritoneal sac, and runs upwards and medially, alon
the medial side of the abdominal inguinal ring and along the lateral border of tl;
medial inguinal fossa ; it then pierces the transversalis fascia, passes over the sem
circular fold (Douglas) and enters the sheath of the rectus abdominis muscle. For I
short distance it ascends posterior to the rectus, but it soon penetrates the substan*
of the muscle, and breaks up into branches which anastomose with terminal offse
of the superior epigastric branch of the internal mammary artery and with tl
lower intercostal arteries. At the abdominal inguinal ring, in the male, the ducti
deferens, the testicular vessels, and the external spermatic branch of the genit
femoral nerve hook round the front and lateral side of the artery, the duct
deferens turning medially behind it; whilst in the female the round ligame:
of the uterus and the external spermatic branch of the genito-femoral ner .
occupy the corresponding positions.
Branches. (a) Muscular branches supply the rectus, the pyramidalis, the trai
versus, and the oblique muscles of the abdominal wall, and anastomose with branches
the deep circumflex iliac, the lumbar, and the lower intercostal arteries, (b) Cutaneo
branches, which pass from the front of the inferior epigastric, pierce the rectus abdomii
and the anterior part of its sheath, and terminate in the subcutaneous tissues of t
anterior abdominal wall, where they anastomose with corresponding branches of t
opposite side and with branches of the superficial epigastric artery, (c) The exten
spermatic in the male (artery of the round ligament of the uterus in the female)
small. It descends through the inguinal canal and anastomoses with the exteri
pudendal and the scrotal branches of the perineal artery, and in the male with 1 '
internal spermatic artery also. In the male it accompanies the spermatic funicul ,
supplying its coverings, including the cremaster. In the female it runs with the rot I
ligament, (d) The pubic branch descends, either on the lateral or the medial side of 3
femoral ring, to anastomose with the pubic branch of the obturator artery ; it anastomc 3
also with its fellow of the opposite side. Sometimes, when the obturator branch of
hypogastric artery is absent, the pubic branch of the inferior epigastric artery enlar 3
and becomes the obturator artery, which descends to the obturator foramen either 1
THE FEMORAL AETEEY.
945
the lateral or the medial side of the femoral ring. In the latter case the artery may be
injured in the operation for the relief of a strangulated femoral hernia.
(2) Arteria Circumflexa Ilium Profunda. The deep circumflex iliac artery
(Figs. 774 and 777) springs from the lateral side of the external iliac artery, usually
a little below the inferior epigastric, and immediately above the inguinal ligament.
It runs laterally and upwards to the anterior superior spine of the ilium. In that
part of its course it lies just above the lower border of the inguinal ligament, and
is enclosed in a fibrous canal formed by the union of the transversalis and iliac
fasciae. A little beyond the anterior superior spine it pierces the transversus
nd ligament
of uterus
Psoas major muscle
Ureter_ < , ;
Genito-femoral nerve
Lateral cutaneous nerve
of the thigh
Ilio-inguinal nerve
Iliac branches
of ilio-lumba
artery
loral nerve
;us muscl
Psoas major
muscle
external iliac
artery
Deep circumflex
iliac artery
External iliac vein
|
Inferior epigastric
artery
Round lii
Inferior vena cava
Common iliac artery
Left common iliac vein
Right common
iliac vein
Hypogastric vein
iypogastrie
artery
Telvic colon
-Ureter
'Uterine artery
"Ovary
terus
terine tube
bturator artery
Superior vesical
'artery
Urinary bladder
Obliterated um- ,
bilical artery
~~~ Urethra
Symphysis
FIG. 777. THE ILIAC AND HYPOGASTRIC ARTERIES AND VEINS IN THE FEMALE.
iominis, and is continued between the transversus and the internal oblique, to
terminate by anastomosing with branches of the ilio-lumbar artery.
Branches. (a) Muscular to the upper parts of the sartorius and the tensor fasciae
e, and to the muscles of the abdominal wall. One of the latter branches is frequently
)f considerable size; it pierces the transversus muscle a short distance anterior to the
nterior superior spine of the ilium, and ascends vertically, between the transversus and
internal oblique, anastomosing with the lumbar and the epigastric arteries. (6)
taneous branches pierce the muscles. They terminate in the skin over the crest of the
ium, and they anastomose with the superior gluteeal, the superficial circumflex iliac, and
the ilio-lumbar arteries.
iliac
ARTERIA FEMORALIS.
The femoral artery (Figs. 778 and 779) is the continuation of the external
into the thigh. It commences at the lower border of the inguinal ligament
61
946
THE VASCULAE SYSTEM.
(O.T. Poupart's), passes
terminates at the opening
to speak of the first one
through the proximal two-thirds of the thigh, and
in the adductor magnus. At one time it was customary
and a half inches, as far as the origin of the profunda
A. et V., circumflexa
ilium profunda'
M. sartorius-
N. femoralis
M. rectus femoris
Nerve to pectineus
Nerve to rectus femoris
M. tensor fascife latee
A. circumflexa femoris
lateralis (ramus asceudens)
Nerve to vastus lateralis
A. circumflexa femoris lateralis
(ramus transversus)
Medial cutaneous nerve of thigh
N. saphenus
Nerve to vastus medialis
Nerve to vastus lateralis
Nerve to vastus medialis.
A. circumflexa femoris lateralis
(ramus descendens)
M. vastus lateralis
M. vastus medialis
Nerve to vastus medialis
Ligamentum inguinale
M. ilio-psoas
A. et V. iliaca externa
__,-_ External iliac lymph glands
. femoralis
Canalis femoralis
V. femoralis
M. rectus femoris
N. saphemif
M. vastus medialis
Kami superficiales (epigastrica, circum-
?r ttexa ilium, pudenda externa)
_ V. saphena magna
. pectineus
A. pudenda externa profunda
Nerve to adductor
longus
N. obturatorius
(ramus super-
ficialis)
.M. adductor brevis
A. profunda femoris
- (ramus muscularis)
-M. adductor lojigus
- M. gracilis
M. adductor magnus
Fascial roof of adductor canal
_ M. adductor magnus
A. genu suprema (ramus saphenus)
FIG. 778. THE FEMORAL ARTERY AND ITS BRANCHES.
NOTE. The outlines of the sartorius, the upper part of the rectus femoris, and the adductor longus
are indicated by broken black lines.
branch, as the common femoral, and to say that it divided into the superfici
and deep femoral branches, of which the former was the direct continuation
the common trunk. The morphology and development of the vessel gives i
support for such terminology.
,
THE FEMOEAL ARTEKY. 947
Course. Its general direction is indicated by a line drawn from the point of
origin, midway between the anterior superior spine of the ilium and the symphysis
pubis, to the adductor tubercle, the thigh being flexed, abducted, and rotated laterally.
In its proximal half the femoral artery lies in the femoral trigone (O.T. Scarpa's
triangle), and is comparatively superficial; at the apex of the trigone it passes
deep to the sartorius, enters the adductor canal (Hunter's), and is thus more
deeply placed.
At their entry into the femoral trigone both the artery and its vein are
enclosed, for a distance of 31 mm. (one and a quarter inches), in a funnel-shaped
fascial sheath formed of the fascia transversalis anteriorly and the fascia iliaca
posteriorly. This is called the femoral sheath ; it is- divided, by antero-posterior
septa, into three compartments, of which the lateral is occupied by the femoral
artery and lumbo-inguinal branch of the genito-femoral nerve; the intermediate
compartment contains the femoral vein ; and the medial compartment constitutes
the femoral canal.
Relations. Anterior. In the femoral trigone the femoral artery is covered super-
ficially by skin and fasciae, by superficial sub-inguinal lymph glands and small superficial
vessels. The anterior part of the femoral sheath and the fascia cribrosa are in front
of the proximal part of the artery, and the fascia lata is in front of the distal part. Near
the apex of the triangle the artery is crossed by the medial cutaneous nerve, and not
infrequently by a tributary of the great saphenous vein. Posterior. It is in relation,
posteriorly, proximo-distally, with the posterior part of the femoral sheath, the pubic or
pectineal portion of the fascia lata and the psoas major, the pectineus, and the proximal
part of the adductor longus muscles. The nerve to the pectineus passes between the
artery and the psoas major ; the femoral vein and the profunda artery and vein intervene
between it and the pectineus, and the femoral vein also separates it from the adductor
longus.
The femoral vein, which lies on a plane posterior to the artery in the lower part of
the femoral trigone, passes to its medial side above, where it is separated from the artery
by the lateral septum of the femoral sheath. On the lateral side of the artery is the
femoral nerve (O.T. anterior crural) proximally ; more distally the saphenous nerve and
the nerve to the vastus medialis are continued on the lateral side. The lumbo-inguinal
branch of the genito-femoral nerve is anterior and to the lateral side, proximally, as it
runs for a short distance in the femoral sheath.
In the adductor canal the artery has posterior to it the adductor longus and the
adductor magnus, whilst anterior and to the lateral side is the vastus medialis. The
femoral vein is also posterior to the artery, but lies to its lateral side distally and to
its medial side proximally. Anterior to the artery is the fascial roof of the canal, with
the obturator or sub-sartorial plexus of nerves and the sartorius muscle. The saphenous
nerve enters the adductor canal with the artery, and runs first on its lateral side, then
anterior, and lastly on its medial side.
Branches. The femoral artery gives off the following branches :
(1) Superficial branches.
(a) The superficial circumflex iliac. P fc/v^^ju,./ .'/x/,
(b) The superficial epigastric. AtcUt^x^
(c) The superficial external pudenda!.
(2) Muscular. ^^ ^
(3) The deep external pudendal^^A^wv^ avA/v^k^
(4) The profunda.
(5) The arteria genu suprema.
(a) Arteria Circumflexa Ilium Superficialis. The superficial circumflex iliac
springs from the front of the femoral artery, just below the inguinal ligament.
.t pierces the femoral sheath and the fascia lata, lateral to the fossa ovalis (O.T.
saphenous opening), and runs, in the superficial fascia, as far as the anterior
superior spine of the ilium. It supplies the lateral set of sub-inguinal glands and the
kin of the groin, and it sends branches, through the fascia lata, which anastomose
ith branches of the deep circumflex iliac artery, and supply the upper parts
of the sartorius and tensor fasciae latse muscles.
) Arteria Epigastrica Superficialis. The superficial epigastric artery arises
near the preceding. It pierces the femoral sheath and the fascia cribrosa,
948
THE VASCULAE SYSTEM
and passes upwards and medially, between the superficial and deep layers of the
superficial fascia of the abdominal wall, towards the umbilicus. It supplies the
sub-inguinal glands and the integument, and anastomoses with its fellow of the
opposite side, with the inferior epigastric, and with the superficial circumflex
iliac and superficial external pudendal arteries.
(c) Arteria Pudenda Bxterna Superficialis. The superficial external pudendal
artery also springs from the front of the femoral artery, and, after piercing the
femoral sheath and the fascia cribrosa, runs upwards and medially towards the
Sartorius
Tensor fasciae
la
Superficial cir-
cumflex ilia
artery
Rectus femoris
Psoas and iliacus
Profunda arter
Lateral cir-
cumflex artery
Vastus lateralis^
Vastus medialis __
Femoral artery
Femoral vein
Femoral canal
Superficial ex-
ternal pudendal
artery
beep external pudenda!
artery
Great saphenous vein
.dductor longus
racilis
FIG. 779. THE FEMOKAL VESSELS IN FEMORAL TRIGONE.
pubic tubercle, where it crosses superficial to the spermatic cord and divide
into terminal anterior scrotal or labial branches according to the sex. It supplie
the integument of the lower part of the abdominal wall, the root of the dorsum c
the penis in the male, and the region of the mons Veneris in the female, and
anastomoses with its fellow of the opposite side, with the deep external pudenda
with the dorsal artery of the penis, and with the superficial epigastric artery.
(2) Kami Musculares. The muscular branches are distributed to the pectinei
and the adductor muscles on the medial side, and to the sartorius and the vasti
medialis on the lateral side.
(3) Arteria Pudenda Bxterna Profunda. The deep external pudendal artei
arises from the medial side of the femoral. It runs medially, anterior to t
pectineus, and either anterior or posterior to the adductor longus, to the niedi
THE FEMOEAL AETEEY. 949
side of the thigh ; it then pierces the deep fascia, and terminates in the scrotum,
where it anastomoses with the posterior scrotal branches of the perineal and the
anterior scrotal branches of the superficial external pudendal arteries, and with
the external spermatic branch of the inferior epigastric artery. In the female it
terminates in the labium majus.
(4) Arteria Profunda Femoris. The profunda artery (Fig. 778) is the largest
branch of the femoral artery. It arises about 37 mm. (an inch, and a half) distal
to the inguinal ligament, from the lateral side of the femoral artery. It curves
backwards and medially, passes posterior to the femoral artery, and runs distally,
close to the medial aspect of the femur, to the distal third of the thigh, where
it perforates the adductor magnus and passes to the back of the thigh. Its
termination is known as the fourth perforating artery. As the profunda descends
it lies anterior to the iliacus, the pectineus, the adductor brevis, and the adductor
magnus. It is separated from the femoral artery by its own vein, by the femoral
vein, and by the adductor longus muscle.
Aw-
Branches. (a) Muscular branches are given off from the profunda, both in the
femoral trigone and whilst it lies between the adductor muscles ; many of them terminate
in the adductors, others pass through the adductor magnus, and terminate in the
hamstrings, where they anastomose with the transverse branch of the medial circumflex
and with the proximal muscular branches of the popliteal artery.
(6) The lateral circumflex artery (Figs. 778 and 779) springs from the lateral side of
the profunda, or occasionally from the femoral artery proximal to the origin of the profunda.
It runs laterally, anterior to the iliacus and between the superficial and deep branches of
the femoral nerve, to the lateral border of the femoral trigone ; then, passing posterior to
the sartorius and the rectus femoris, it terminates by dividing into three terminal branches
the ascending, the transverse, and the descending. Before its termination it supplies
branches to the muscles mentioned and to the proximal part of the vastus iritermedius.
(i.) The ascending terminal branch runs proximally and laterally, posterior to the rectus
femoris and the tensor fasciae latae, along the linea intertrochanterica, to the anterior borders
of the glutaei, medius and minimus, between which it passes to anastomose with the deep
branches of the superior glutaeal artery. It supplies twigs to the neighbouring muscles, anasto-
moses with the glutaeal, the deep circumflex iliac, and the transverse branch of the lateral
circumflex arteries, and, as it ascends along the linea intertrochanterica, it gives off a branch
which passes, between the two limbs of the ilio-femoral ligament, into the hip-joint, (ii.) The
transverse terminal branch is small ; it runs laterally, between the vastus intermedius and the
rectus femoris, passes into the substance of the vastus lateralis, winds round the femur, and
anastomoses with the ascending and descending branches, with the perforating branches of the
profunda, and with the inferior glutaeal and medial circumflex arteries, (iii.) The descending
terminal branch runs distally, posterior to the rectus and along the anterior border of the vastus
lateralis, accompanied by the nerve to the latter muscle. It anastomoses with the transverse
branch, with twigs of the inferior perforating arteries, with the arteria genu suprema of the
femoral, and with the superior lateral genicular branch of the popliteal artery.
(c) The medial circumflex artery springs from the medial and posterior part of
the profunda, at the same level as the lateral circumflex, and runs backwards, through
the floor of the femoral trigone, passing between the psoas major and the pectineus ;
then it crosses the upper border of the adductor brevis, and continuing backwards, below the
neck of the femur, it passes between the adjacent borders of the obturator externus and the
adductor brevis to the upper border of the adductor magnus, where it divides into two
terminal branches, a transverse and a profunda branch (O.T. ascending).
Branches. (i.) An acetabular branch is given off as the artery passes below the neck of
the femur. It ascends to the acetabular notch where it anastomoses with twigs from the
posterior branch of the obturator artery, and it sends branches into the acetabular fossa and
.ong the ligamentum teres to the head of the femur, (ii.) A superficial branch, which passes
medially, anterior to the pectineus and between the adductors brevis and longus. (iii) Muscular
branches are given off to the neighbouring muscles. The largest of these branches usually arises
nmediately before the termination of the artery ; it runs distally, on the anterior aspect of the
Iductor magnus, and anastomoses with the muscular branches of the profunda artery, (iv.) The
ofunda terminal branch (ascending) passes upwards and laterally, between the obturator
ternus and the quadratus femoris to the trochanteric fossa of the femur, where it anastomoses
ith branches of the superior and inferior glutaeal arteries, (v.) The transverse terminal branch
3 backwards to the hamstring muscles, usually between the lower border of the quadratus
lemons and the upper border of the adductor magnus, but it may pierce the upper part of the
950
THE VASCULAK SYSTEM.
adductor magnus. It anastomoses, in front of the distal part of the glutseus maximus, with
the inferior glutaeal and first perforating arteries and with the transverse branch of the lateral
circumflex, and, in the substance of the hamstrings, with the muscular branches of the profunda.
(d) The perforating arteries (Fig. 780), including the terminal branch of the profunda,
are four in number.
They curve postero-
laterally, round the
posterior aspect of
the femur, lying close
to the bone and an-
terior to the well-
marked tendinous
arches which inter-
rupt the continuity
of muscular attach-
ments ; their ter-
minal branches enter
the vastus lateralis
and anastomose, in
its substance, with
one another, with
the descending
branch of the lateral
circumflex, with the
arteria genu sup-
rema, and with the
superior lateral geni-
cular branch of the
popliteal.
The first perforat-
ing artery pierces the
insertions of the ad-
ductors brevis and
magnus, and some of
its branches anasto-
mose, anterior to the
gluteeus maximus,
with the inferior
glutseal, witE tne
transverse branch of
the medial circumflex,
and with the trans-
verse branch of the
lateral circumflex,
forming what is
known as the crucial
anastomosis.
The second perfor-
ating artery pierces
the adductors brevis
and magnus, and then
passes between the
glutseus maximus and
the short head of the
biceps femoris into the
vastus lateralis. It
anastomoses with its
proximal and distal
fellows, and with the
medial circumflex and
the proximal muscular
branches of the pop-
liteal artery.
The third and fourth perforating arteries pass through the adductor magnus and the short
head of the biceps femoris into the vastus lateralis. Their anastomoses are similar to those o
the second perforating.
A nutrient branch to the femur is given off either from the second or third perforating
Glutseus maximus
Sacro-tuberous
ligament (/) , (
Internal _ ._ .'
pudendal artery
Inferior
gluteal artery
Arteria comitans
nervi ischiadici
Biceps and
semitendinosus
Semimembranosus
Adductor magnus
Muscular branch
of profunda artery
Gracilis
Popliteal artery
Superior medial
genicular artery
Semitendinosus
Gastrocnemius
Muscular artery
Glutaeus medius
dutseus minimus
Deep branch of
gluteal artery
riformis
Obturator interims
and gemelli
Profunda branch
of medial
circumflex artery
Quadratus femoris
Transverse branch
-of medial
circumflex artery
1st perforating
^artery
2nd perforating
artery
3rd perforating
artery
Termination of
profunda artery
(4th perforating)
Short head of biceps
Jjong head of biceps
Popliteal vein
Superior lateral genicular
artery
. ^Gastrocnemius
FIG. 780. THE ARTERIES OF THE BUTTOCK AND THE POSTERIOR ASPECT
OF THE THIGH AND KNEE.
THE POPLITEAL AETEEY. 951
artery, usually the former ; an additional nutrient branch may also be supplied by the first or
fourth perforating arteries.
(5) The arteria genu suprema (O.T. anastomotic) arises near the termination
of the femoral artery, in the distal part of the adductor canal, and divides, almost
immediately, into a superficial, saphenous, and a deep (musculo- articular) branch ;
indeed, very frequently the two branches arise separately from the femoral trunk.
(a) The saphenous branch passes through the distal end of the adductor canal with
the saphenous nerve, and appears superficially, on the medial side of the knee, between
the gracilis and the sartorius. It gives twigs to the integument of the proximal and
medial part of the leg, and it anastomoses with the inferior medial genicular artery.
(6) The musculo-articular branch runs towards the knee,> in the substance of the vastus
medialis, along the anterior aspect of the tendon of the adductor magnus. It anastomoses
with the superior medial genicular artery, and it sends branches laterally, one on the
surface of the femur and another along the proximal border of the patella, to anastomose
with the descending branch of the lateral circumflex, the fourth perforating artery, the
superior lateral genicular, and the anterior tibial recurrent.
AETERIA POPLITEA.
The popliteal artery is the direct continuation of the femoral. It commences
at the medial and proximal side of the popliteal fossa, under cover of the semi-
membranosus, and terminates at the distal border of the popliteus muscle, and on
a level with the distal part of the tuberosity of the tibia, by dividing into the
anterior and the posterior tibial arteries.
From its origin the artery passes distally, with a lateral inclination, to the
interspace between the condyles of the femur, whence it is continued vertically to
its termination.
Relations. Anterior. It is in contact in front and proximo-distally with the
popliteal surface of the femur, the posterior part of the capsule of the knee-joint, and the
fascia covering the posterior surface of the popliteus.
Posterior. The artery is overlapped behind, in the proximal part of its extent, by the
lateral border of the semimembranosus ; it is crossed, about its middle, by the popliteal
vein and the tibial (O.T. internal popliteal) nerve, the vein intervening between the
artery and the nerve ; whilst, in the distal part of its extent, it is overlapped by the
adjacent borders of the two heads of the gastrocnemius, and is crossed by the nerves
to the soleus and popliteus and by the plantaris muscle.
Lateral. On its lateral side it is in relation, proximally, with the tibial nerve and the
popliteal vein, then with the lateral condyle of the femur, and, distally, with the lateral
head of the gastrocnemius and the plantaris.
Medial. On the medial side it is in relation, proximally, with the semimembranosus, in
the middle with the medial condyle of the femur, and, distally, with the tibial nerve, the
popliteal vein, and the medial head of the gastrocnemius. Popliteal lymph glands are
arranged irregularly around the artery.
Branches. (1) Muscular branches are given off in two sets, proximal and distal.
The proximal muscular branches are distributed to the distal parts of the hamstring
muscles, in which they anastomose with branches of the profunda artery.
The distal muscular, or sural, arteries enter the proximal parts of the gastrocnemius,
the plantaris, the soleus, and the popliteus muscles, and they anastomose with branches
of the posterior tibial artery and the lower genicular arteries.
(2) The genicular branches are five in number viz., superior and inferior lateral,
superior and inferior medial, and a median branch.
(a) The superior lateral genicular artery passes laterally, proximal to the lateral
iondyle, behind the femur and in front of the biceps tendon, into the vastus lateralis,
where it anastomoses with the arteria genu suprema, the descending branch of the lateral
circumflex, and the fourth perforating artery ; it also sends branches distally to anastomose
ith the inferior lateral genicular and with the anterior tibial recurrent.
(6) The superior medial genicular artery passes medially, proximal to the medial
condyle, behind the femur, and anterior to the tendon of the adductor magnus, into the
vastus medialis. It anastomoses with branches of the arteria genu suprema and of the
superior lateral genicular artery.
61 a
952
THE VASCULAE SYSTEM.
A. et V., poplitea -i
A. genu superior j
medialis ""
M. gastrocnemius
(capnt late rale) ""
M. semi- ..
membranosus
Lig. popliteum__
arcuatum
A. genu inferior
lateralis
M. popliteus-
(c) The inferior lateral genicular artery runs laterally, across the popliteus muscle
and anterior to the plantaris and the lateral head of the gastroenemius ; then, turning
forwards, it is joined by the inferior lateral genicular nerve, and passes to the medial side
of the fibular collateral ligament.
M. semitendinosus It terminates by anastomosing
N. tibialis with its fellow of the opposite
side and with the superior lateral
genicular and anterior tibial re-
current arteries.
(d) The inferior medial geni-
cular artery passes medially,
distal to the medial condyle
of the tibia, along the proximal
border of the popliteus and in
front of the medial head of the
gastroenemius, to the medial side
of the knee, where it turns
forwards, between the bone and
the tibial collateral ligament, and
terminates anteriorly by anasto-
mosing with its fellow of the
opposite side, with the recurrent
branch of the anterior tibial
artery, and with the superior
medial genicular artery.
(e) The arteria genu media
passes directly forwards from the
front of the popliteal artery,
pierces the central part of the
posterior surface of the capsule
of the knee-joint, and enters the
intercondylar fossa. It supplies
branches to the crucial ligaments
and to the synovial membrane,
and is accompanied by the medial
genicular branch of the tibial
nerve, and sometimes by the
genicular branch of the obturator
nerve.
(3) Cutaneous branches are
distributed to the skin over the
popliteal fossa. One of these,
the superficial sural artery, runs
along the middle of the back of
the calf with the vena saphena
parva.
A. tibialis posterior ---i,_
M. soleus !-
M. flexor digitorum
longus
A. tibialis posterior..
A. genu superior
lateralis
M. gastroenemius
M. plantaris
A. genu inferior
lateralis
N. peronseus
conimunis
_. M. soleus
.. M. soleus
i A. peronsea
M. peronseus
"^ longus -.
M. tibialis posterior __;
M. flexor hallucis
longus
M. flexor digitorum
longus"
Ramus com-
municans --
Tibia..
Tendon of M. tibialis
posterior^"
N. plantaris medialis,-
A. plantaris medialis
A. plantaris lateralis,-"
N. plantaris lateralis^''
Lig. laciniatum-^''
Calcaneus. -"
Tendon of M.
_,--"" peronseus longus
- M. peronseus brevis
A. peronsea
M. flexor hallucis
"~ longus
_ Lig. talotibulare
L, --""' posterius
__,.Retinaculum mm.
peronneorum
superior
. .___ Bursa tendinis
"~ calcanei
ARTERIA TIBIALIS POSTERIOR.
-..Tendo calcaneus
FIG. 781. THE POPLITEAL AND POSTERIOR' TIBIAL ARTERIES
AND THEIR BRANCHES.
The posterior tibial
artery, the larger of the two
terminal branches of the pop-
liteal, commences at the distal
border of the popliteus and
terminates midway between the tip of the medial malleolus and the most pro-
minent part of the heel, at the distal border of the laciniate ligament (O.T. internal
annular). It ends by dividing into the medial and the lateral plantar arteries,
which pass onwards to the sole of the foot.
The posterior tibial artery runs distally and medially, in the posterior part of
the leg, between the superficial and deep layers of muscles and covered, posteriorly,
by the deep intermuscular fascia which intervenes between them.
THE POSTEKIOB, TIBIAL AKTEEY. 953
Relations. Anterior. It is in contact anteriorly, and proximo-distally, with the
tibialis posterior, the flexor digitorum longus, the posterior surface of the tibia, and the
posterior ligament of the ankle-joint.
Posterior. The artery is crossed about 37 mm. (an inch and a half) distal to its origin
by the tibial nerve. Elsewhere it is in contact with the intermuscular fascia which
binds down the deep layer of muscles. More superficially the proximal half of the artery
is covered by the fleshy parts of the soleus and gastrocnemius muscles, between which is
the plantaris ; the distal half of the artery is much nearer the surface, and is covered
only by skin and fasciae, except at its termination, where it lies deep to the laciniate
ligament.
Lateral and Medial. The artery is accompanied by two vense comites, one on each side.
The tibial nerve lies at first on the medial side of the vessel, then crosses posterior to it,
and is continued distally on its lateral side. In the most distal part of its course the artery
is separated from the medial malleolus by the tendons of the tibialis posterior and the flexor
digitorum longus, whilst the tendon of the flexor hallucis longus lies postero- lateral to it.
Branches. The posterior tibial gives off numerous branches, the largest of which,
the peroneal, forms one of the chief arteries of the leg. The branches include
(1) Large muscular branches which are distributed to the soleus, the tibialis
posterior, the flexor digitorum longus, and the flexor hallucis longus. They anastomose
with the deep sural branches of the popliteal artery and the lower medial genicular artery.
(2) A fibular branch passes laterally, to the neck of the fibula, where it anastomoses
with the inferior lateral genicular and the deep sural arteries, and supplies the adjacent
muscles.
(3) The peroneal artery (Fig. 781) is the largest branch of the posterior tibial.- It
arises about 25 mm. (an inch) below the distal border of the popliteus, curves laterally
across the proximal part of the tibialis posterior to the medial crest of the fibula,
along which "it passes to the distal part of the interosseous space. About 25 mm. (an
inch) proximal to the ankle-joint it gives off a perforating branch and then passes,
posterior to the tibio-fibular syndesmosis and lateral malleolus, to the lateral side of
the heel and the foot. It supplies the ankle, the tibio-fibular syndesmosis, and the
talo-calcanean joint, and anastomoses with the medial calcanean branch of the lateral
plantar artery, and with the tarsal and arcuate branches of the dorsalis pedis.
As the peroneal artery passes laterally from its origin it lies posterior to the tibialis
posterior, and is covered posteriorly by the deep intermuscular fascia and by the soleus.
As it descends along the medial crest of the fibula it lies in a fibrous canal
between the tibialis posterior in front and the flexor hallucis longus behind. The
peroneal artery is accompanied by two vense comites, and is crossed anteriorly and
posteriorly by communicating branches between them.
Branches. (a) Muscular branches are distributed to the soleus, tibialis posterior, flexor
hallucis longus, and the peroneal muscles. Some pass through the interosseous membrane and
supply the anterior muscles of the leg.
(6) A nutrient branch enters the nutrient foramen of the fibula.
(c) A communicating branch, passes across the back of the distal end of the shaft of the tibia,
about 25 mm. (an inch) above the tibio-fibular syndesmosis, to anastomose with the posterior
tibial artery.
(d) The perforating branch passes forwards at the junction of the distal border of the inter-
osseous membrane and the interosseous tibio-fibular ligament, and runs, in front of the ankle,
to the dorsum of the foot, where it anastomoses with the lateral malleolar branch of the anterior
tibial artery and with the tarsal branch of the dorsalis pedis ; it also supplies branches to the
tibio-fibular syndesmosis, to the ankle-joint, and to the peronaeus tertius.
(4) The nutrient branch, the largest of the nutrient group of arteries to long
bones, springs from the proximal part of the posterior tibial, pierces the tibialis
posterior, and enters the nutrient foramen on the posterior surface of the tibia. In the
interior of the bone it divides into proximal and distal branches, the former passing
towards the proximal extremity of the bone, and the latter towards the distal extremity.
Before entering the tibia the nutrient artery gives small muscular branches.
(5) A communicating branch unites the posterior tibial to the peroneal artery
about 25 mm. (an inch) above the tibio-fibular syndesmosis. It passes posterior to the
shaft of the tibia and anterior to the flexor hallucis longus.
(6) Cutaneous branches are distributed to the skin of the medial and posterior part
of the leg.
(7) A posterior medial malleolar branch is distributed to the medial surface of the
medial malleolus, anastomosing with a corresponding branch of the anterior tibial artery.
954
THE VASCULAE SYSTEM.
PLANTAR ARTERIES.
(8) The medial and lateral plantar arteries are the terminal branches of the
posterior tibial artery. They arise, under cover of the origin of the ligamentum
laciniatum, midway between the tip of the medial malleolus and the most
prominent part of the medial side of the os calcis (Figs. 781, 782).
Arteria Plantaris Medialis. The medial plantar artery is the smaller of the
two terminal branches of the posterior tibial artery. It passes forwards, along the
medial side of the foot,
in the interval between
the abductor hallucis and
the flexor digitorum
brevis, to the head of the
first metatarsal bone,
where it terminates by
uniting with the plantar
digital branch of the
dorsalis pedis, -which is
distributed to the medial
side of the great toe. In
its course forwards it
gives off a superficial
branch, which ramifies
on the superficial sur-
face of the abductor hal-
lucis ; branches to the
adjacent muscles and
articulations, and to the
subjacent skin ; it also
gives three digital
branches which anasto-
m ose, ftt the rootg Q f tfie
three medial interdigital
clefts, with the medial
plantar metatarsal
arteries. Some of the
cutaneous branches of
the medial plantar artery
anastomose, round the
medial border of the foot,
with the medial cutane-
ous branches of the
dorsalis pedis artery.
Arteria Plantaris
Lateralis. The lateral
plantar artery is the
larger of the two terminal
branches of the posterior tibial artery. It runs forwards and laterally, first between
the flexor digitorum brevis superficially and the quadratus plan tee deeply, and
then, in the interval between the flexor digitorum brevis and the abductor digiti
quinti, to the medial side of the base of the fifth metatarsal bone, where it turns
abruptly medially and, gaining a deeper plane, passes across the bases of the
metatarsal bones and the origins of the interossei, and above the oblique head
of the adductor of the great toe, to the lateral side of the base of the first meta-
tarsal bone, where it terminates by anastomosing with the dorsalis pedis artery.
The last part of the artery is convex forwards and forms the plantar arch, which
is completed by the profunda branch of the dorsalis pedis.
Branches. Between its origin and the base of the fifth metatarsal the lateral
Occasional calcanean
branch of posterior
tibial artery
Posterior tibial artery
Medial plantar
artery
Lateral plantar
artery
Flexor digitorum
longus tendon
Flexor hallucis
longus tendon
Flexor hallucis
brevis muscle
Deep branch of
dorsalis pedis
Medial calcanean
anch of lateral
lantar artery
^g plantar
ligament
Quadratus plant*
muscle
Abductor digiti
quinti muscle
Oblique head of
'adductor hallucis
Plantar arch
Metatarsal arteries
Transverse 1
of adductor
hallucis
FIG. 782. THE PLANTAR ARTERIES AND THEIR BRANCHES.
THE ANTEKIOK TIBIAL AETEEY. 955
plantar artery gives off (a) the medial calcanean branch, which is distributed to the skin
and the subcutaneous tissue of the heel.
(6) Muscular branches to the abductor hallucis, flexor digitorum brevis, quadratus
plantse, and abductor digiti quinti.
(c) Cutaneous branches to the skin of the lateral side of the foot.
Between the base of the fifth metatarsal bone and the first interosseous space it forms
the plantar arch, and gives off (d) four plantar metatarsal branches ; (e) three
posterior perforating arteries to the dorsal metatarsal arteries ; and (/) articular branches
to the tarsal joints.
The fifth or most lateral metatarsal branch runs along the lateral side of the little
toe, supplying the skin, joints, and the flexor tendons with their synovial sheaths. The
three medial plantar metatarsal branches, second, third, and fourth, run forwards on the
plantar surfaces of the interossei, the medial two lying dorsal to the oblique head of
the adductor of the great toe, and all three passing dorsal to the transverse head of the
adductor. At the bases of the interdigital clefts the second, third, and fourth plantar
metatarsal arteries divide into plantar digital arteries which run along the plantar aspects
of adjacent toes, and supply skin, joints, and the flexor tendons and sheaths. Opposite
the last phalanx of each toe the digital arteries of opposite sides of the toe anastomose
together.
The posterior perforating arteries are three in number ; they pass dorsal wards through
the three lateral intermetatarsal spaces, between the heads of the dorsal interosseous
muscles, and terminate by uniting with the corresponding dorsal metatarsal arteries.
Anterior perforating branches which communicate with the dorsal metatarsal arteries are
given off from two or three of the plantar metatarsal arteries just before they divide.
The articular branches are numerous and irregular ; they supply the joints and
ligaments of the tarsus on its plantar aspect.
ARTERIA TIBIALIS ANTERIOR.
The anterior tibial artery, the smaller of the two terminal divisions of
the popliteal, commences opposite the distal border of the popliteus muscle, and
terminates in front of the ankle, where it is continued into the dorsal artery of
the foot.
Course and Relations. From its origin, at the back of the leg, the artery
passes anteriorly, between the two slips of the proximal part of the tibialis
posterior and above the proximal border of the interosseous membrane. It then
runs distally, resting, in the proximal two-thirds of its course, against the anterior
surface of the interosseous membrane and, subsequently, on the distal part of the
tibia and the anterior ligament of the ankle-joint. In the proximal third of the
anterior compartment of the leg it lies between the extensor digitorum longus
laterally and the tibialis anterior medially; in the middle third it is between
the extensor hallucis longus and the tibialis anterior; in the distal third the
extensor hallucis longus crosses in front of the artery and reaches its medial
side, and the most distal part of the vessel lies between the tendon of the extensor
hallucis longus on the medial side and the most medial tendon of the extensor
digitorum longus on the lateral side.
The deep peronaeal nerve (O.T. anterior tibial) is at first well to the lateral side
of the artery, but it soon passes in front of the vessel, and it lies in front of the
middle third of the artery ; more distally the nerve is usually found on the
lateral side again, and at the ankle it intervenes between the artery and the most
medial tendon of the extensor digitorum longus.
Two vense comites, with numerous intercommunications, accompany the artery.
Obviously the anterior tibial artery is, at least in its proximal part, deeply placed;
moreover, its lateral muscular boundaries overlap it. In the distal two-thirds of
its extent it is, however, easily accessible from the surface ; and beyond being
covered by the nerve and crossed by the tendon, as already described, is only
covered, in addition, by skin, fascia, and the transverse crural ligament.
Branches. Close to its origin the artery gives off fibular and posterior tibial
recurrent branches; after it reaches' the front of the leg it gives off anterior tibial
recurrent, muscular, cutaneous, medial malleolar, and lateral malleolar branches:
956
THE VASCULAK SYSTEM.
Superior lateral
genicular artery
Inferior lateral
genicular artery
Anterior tibial
recurrent artery
Anterior tibial
artery
Superior medial
genicular artery
Inferior medial
genicular artery
Tibialis anterior
astrocnemius
leus
(1) The fibular branch is a small vessel which may arise separately from the anterior
tibial artery, or by a common stem with the posterior tibial recurrent ; occasionally
it springs from the lower end of the popliteal artery, or from the posterior tibial.
It runs upwards and later-
ally, behind the neck of the
fibula and through the fibres
Art. genu suprema of the soleus, and it ter-
.(O.T. anastomotic) m i na tes in branches which
supply the soleus, the pero-
nseus longus, and the skin
of the proximal and lateral
part of the leg. It anasto-
moses with the inferior
lateral genicular artery.
(2) The posterior tibial
recurrent branch, also
small, and not always
present, runs upwards, an-
terior to the popliteus
muscle, to the back of the
knee-joint. It anastomoses
with the inferior genicular
branches of the popliteal,
and gives branches to the
popliteus muscle and the
proximal tibio-fibular
articulation.
(3) The anterior tibial
recurrent branch arises
from the anterior tibial
artery in front of the inter-
osseous membrane. It runs
proximally and medially, be-
tween the proximal part of
the tibialis anterior and the
lateral condyle of the tibia,
accompanied by the recur-
rent articular branch of the
common peronaeal nerve,
and, after supplying the
tibialis anterior and the
proximal tibio-fibular articu-
lation, it pierces the deep
fascia of the leg ; it is con-
nected with the anastomoses
round the knee-joint, formed
by the genicular branches of
the popliteal artery, the de-
scending branch of the lat-
eral circumflex artery, and
the arteria genu suprema.
(4) The muscular
branches are distributed
to the muscles of the front
of the leg, and a few small
branches also pass back-
wards to the deep surface of
the tibialis posterior muscle.
(5) The cutaneous branches supply the skin of the front of the leg.
(6) The medial anterior malleolar branch arises from the lower part of the anterior tibial
artery, and is smaller than its companion on the lateral side. It runs medially, posterior
to the tibialis anterior tendon, ramifies over the medial malleolus, anastomosing with
branches of the posterior tibial artery, and is distributed to the skin and to the ankle-joint.
Deep peroneal
nerve
Peronreus brevi
Extensor digi-
torum longus
Extensor liallucis
longus
Perforating branch
of peroneal
artery
Lateral
malleolar artery
Tarsal artery
Dorsal metatarsal
artery
Dorsal metatarsal
artery
FIG. 783. THE ANTERIOR TIBIAL ARTERY AND ITS BRANCHES.
Dorsalis pedis
rtery
Cutaneous branch
Extensor digitorum
brevis
THE ANTEKIOK TIBIAL AKTEEY.
957
Peronseus brevis
Extensor digitoruin
longus
Anterior peroneal
artery
Lateral nialleolar
artery
Anterior tibial
artery
Extensor
hallucis
longus
Tibialis anterior
Medial
malleolar artery
Extensor
digitorum-
brevis
Tarsal artery.
Dorsalis pedis
artery
(7) The lateral anterior malleolar branch, more constant and larger than the medial,
passes laterally, posterior to the extensor digitorum longus and peroneeus tertius, towards
the lateral malleolus. It anastomoses with the perforating branch of the peroneal artery
and with the tarsal artery, and supplies the ankle-joint and the adjacent articulations.
Dorsalis Pedis Artery. The dorsal artery of the foot is the direct continuation
of the anterior tibial ; it commences opposite the front of the ankle-joint, and
extends to the posterior
extremity of the first in-
terosseous space, where it
divides into the first dorsal
metatarsal and the pro-
funda branch.
It is covered super-
ficially by skin and fascia,
including the cruciate
ligament, and it is crossed,
just before it reaches the
first interosseous space,
by the tendon of the ex-
tensor hallucis brevis. It
rests upon the anterior
ligament of the ankle, the
head of the talus, the talo-
navicular ligament, the
dorsum of the navicular
bone, and the dorsal
naviculo- cuneiform and
the inter-cuneiform liga-
ments between the first
and second cuneiform
bones. On its lateral side
is the medial terminal
branch of the deep pero-
nseal nerve (O.T. anterior
tibial), which intervenes
between it and the ex-
tensor digitorum brevis
and most medial tendon
of the extensor digitorum
longus. On its medial
side it is in relation with
the tendon of the extensor
hallucis longus.' Two venae
comites, one on each side,
accompany the artery.
Branches On the FlG - ? 84 - THE DO R SALIS PEDIS ARTERY AND ITS BRANCHES.
dorsum of the foot the
dorsalis pedis artery gives off cutaneous branches, lateral and medial tarsal branches, the
arcuate branch, and the first dorsal metatarsal and the profunda branch.
(1) Cutaneous branches, two or three in number, are distributed to the skin on the
dorsum and medial side of the foot ; they anastomose with branches of the medial plantar
artery.
(2) The tarsal branches, medial and lateral. The medial tarsal branches are small
vessels given off from the medial side of the artery. They pass to the medial border of
the foot and anastomose with branches of the medial plantar artery. The lateral tarsal
branch is given off opposite the head of the talus ; it runs laterally, deep to the extensor
hallucis brevis and the extensor digitorum brevis, supplying those muscles and the tarsal
joints, and it anastomoses with the perforating branch of the peroneal, the arcuate, and
lateral plantar arteries, and with the lateral malleolar artery.
958 THE VASCULAR SYSTEM.
(3) The arcuate artery arises opposite the first cuneiform bone. It runs laterally,
on the bases of the metatarsal bones, deep to the long and short extensor tendons, supplies
the extensor hallucis brevis and the extensor digitorum brevis, and anastomoses with
branches of the lateral tarsal and lateral plantar arteries. It gives off three dorsal
metatarsal arteries, second, third, and fourth, which run forwards on the muscles which
occupy the three lateral interosseous spaces to the clefts of the toes, where each divides
into two dorsal digital branches for the adjacent sides of the toes bounding the cleft to
which it goes. The lateral side of the little toe receives a branch from the most lateral
dorsal metatarsal artery. Each dorsal metatarsal artery gives off a posterior perforating
branch, which passes through the posterior part of the intermetatarsal space, between
the heads of the dorsal interosseous muscle, to anastomose with the plantar arch, and
an anterior perforating branch, which passes through the anterior part of the space
to anastomose with the corresponding plantar metatarsal artery.
(4) The first dorsal metatarsal artery is continued forwards from the dorsal artery
of the foot, and runs on the dorsal surface of the first dorsal interosseous muscle. It
ends by dividing into dorsal digital branches for the adjacent sides of the first and second
toes. Before it divides it usually gives off a dorsal digital branch which passes, deep to
the tendon of the extensor hallucis, to the medial side of the great toe.
(5) The profunda branch passes through the posterior end of the first intermetatarsal
space, between the two heads of the first dorsal interosseous muscle, to the plantar aspect
of the foot, where it unites with the lateral plantar artery and completes tne plantar arch.
As it unites with the lateral plantar artery it gives off the first plantar metatarsal
artery (O.T. arteria magna hallucis), which passes forwards, along the first intermetatarsal
space, to the base of the first interdigital cleft, where it divides into plantar digital arterie
for the adjacent sides of the great and second toes ; before it divides it gives off a plantar
digital artery to the medial side of the great toe.
VEN^E.
. Veins commence at the terminations of the capillaries. They converge towards
the heart, and unite with one another to form larger and still larger vessels, until,
finally, seven large trunks are formed which open into the atria of the heart.
Three of the trunks, the superior vena cava, the inferior vena cava, and the coronary
sinus, belong to the systemic circulation ; they contain venous blood, and open into
the right atrium. The remaining four, the pulmonary veins, belong to the pulmonary
circulation ; they return oxygenated blood from the lungs, and' open into the left
atrium.
In addition to the systemic and pulmonary veins, there is also a third group of
veins, constituting the portal system, in which blood from the abdominal part of
the alimentary canal, and from the spleen and pancreas, is conveyed to the liver.
The portal system is further peculiar in that it both begins and ends in capillaries.
From its terminal capillaries in the liver the hepatic veins arise, and as these open
into the inferior vena cava the blood of the portal system is finally poured into the
general systemic circulation. The hepatic veins also receive blood 'supplied to the
liver by the hepatic arteries.
VEN.E PULMONALES.
The terminal pulmonary veins (Figs. 750 and 757), two on each side, open into
the left atrium of the heart. Their tributaries arise in capillary plexuses in the
walls of the pulmonary alveoli. By the union of the smaller veins larger vessels
are formed which run along the anterior aspects of the bronchial tubes, and, uniting
together, ultimately form a single efferent vessel in each lobe, which passes into the
root of the lung. Thus there are five main pulmonary veins, but, immediately
after entering the root of the lung, the vessels from the upper and middle lobes of
the right lung join together, and so only four terminal pulmonary veins open into
the left atrium of the heart. Neither the main stems nor their tributaries possess
valves.
Relations. In the root of the lung the upper pulmonary vein, on each side, lies
below and in front of the pulmonary artery. The lower pulmonary vein, on each
THE CORONARY SINUS AND THE VEINS OF THE HEAET. 959
side, is in the lowest part of the root, and it is in a plane posterior to that in which
the upper vein lies.
On the right side the upper pulmonary vein passes behind to the superior vena cava,
and the lower passes behind the right atrium. They both terminate in the upper and
posterior part of the left atrium close to the interatrial septum.
On the left side both upper and lower pulmonary veins cross anterior to the descend-
ing aorta, and they terminate in the upper and posterior part of the left atrium near its
left border.
All four pulmonary veins perforate the fibrous layer of the pericardium, and receive
partial coverings of the serous layer before they enter the atrium.
SYSTEMIC VEINS.
The systemic veins return blood to the right atrium of the heart through the
superior vena cava, the inferior vena cava, and the coronary sinus. The two first-
named receive blood from the veins of the body and limbs and from most of the
abdominal and pelvic viscera. The coronary sinus receives blood from the veins of
the walls of the heart alone.
General Arrangement. The veins of the body wall and limbs form two groups
(1) the superficial veins ; (2) the deep veins.
The superficial veins lie in the superficial fascia; they commence in the
capillaries of the skin and subcutaneous tissues, and are very numerous. They
frequently anastomose with one another, and they also communicate with the deep
veins, in which, after piercing the deep fascia, they terminate. They may or may
not accompany superficial arteries.
The deep veins accompany arteries, and are known as vence comites. The large
arteries have only one accompanying vein, but with the medium-sized and small
arteries there are usually two venae comites, which anastomose freely with each
other by short transverse branches of communication.
Visceral veins usually accompany the arteries which supply viscera in the
head, neck, thorax, and abdomen. As a rule there is only one vein with each
visceral artery, and, with the exception of those which enter into the formation of
the portal system, they terminate in the deep systemic veins.
SINUS CORONARIUS ET VEN^ CORDIS.
The coronary sinus (Fig. 750) is a short, but relatively wide, venous trunk
which receives the majority of the veins of the heart. It lies in the inferior
portion of the coronary sulcus, between the left atrium and the left ventricle, and
it is covered superficially by some of the muscular fibres of the atrium.
It terminates in the lower and posterior part of the right atrium, between the
orifice of the inferior vena cava on the right, and the right atrio- ventricular
orifice anteriorly ; an imperfect valve, consisting of one cusp, called the valve of the
coronary sinus (Thebesius), is situated at the right margin of the opening of the
sinus into the atrium.
The apertures of the tributaries of the coronary sinus, except those of the great
and small cardiac veins, are not provided with valves, and the valves of the two
veins mentioned are often incompetent.
Tributaries. (1) The great cardiac vein (Fig. 754) commences at the apex of the
heart. It ascends, in the anterior interventricular sulcus, to the coronary sulcus ; it then
turns to the left, and, passing round the left margin of the heart, into the inferior part of
the coronary sulcus, terminates in the left extremity of the coronary sinus. It receives
tributaries from the walls of both ventricles and from the wall of the left atrium. It
receives also the left marginal vein ; that vein commences at the lower extremity of the
left margin of the heart, along which it ascends to its termination.
(2) The small cardiac vein is very variable ; as a rule it commences at the inferior
margin of the heart and passes to the right to the coronary sulcus in which it turns to
the left, on the inferior surface of the heart, and terminates in the right extremity of
the coronary sinus. It receives tributaries from the walls of the right atrium and the
right ventricle.
960 THE VASCULAK SYSTEM.
(3) The oblique vein of the left atrium (Marshall) (Fig. 750) is a small venous
channel which descends obliquely, on the posterior wall of the left atrium, and terminates
in the coronary sinus. Its orifice is not provided with a valve. It is of special interest,
inasmuch as it represents the left superior vena cava of some other mammals, and is
developed from the left duct of Cuvier.
(4) The inferior cardiac vein of the left ventricle runs along the inferior surface of
the left ventricle and ends in the coronary sinus.
(5) The middle cardiac vein commences at the apex of the heart, and, passing
posteriorly, in the inferior interventricular sulcus, terminates in the coronary sinus near
its right extremity. It receives tributaries from the inferior parts of the walls of both
ventricles.
Veins of the Heart which do not end in the Coronary Sinus. (a) The
anterior cardiac veins are two or three small vessels which ascend on the anterior wall
of the right ventricle to the coronary sulcus, where they either end in the right
atrium or terminate in the small cardiac vein, (b) The venae minimae cordis. A number
of small veins, which commence in the substance of the walls of the heart and terminate
directly in its cavities, principally in the atria ; some few, however, open into the
ventricles.
VENA CAVA SUPERIOR AND ITS TRIBUTARIES.
The superior vena cava (Figs. 756 and 757) returns the blood from the head
and neck, the upper extremities, the thoracic wall, and a portion of the upper part
of the wall of the abdomen. It is formed, at the lower border of the first right
costal cartilage, by the union of the two innominate veins, and it descends, with
a slight convexity to the right, to the level of the third right costal cartilage,
where it opens into the upper and posterior part of the right atrium. It is about
75 mm. (three inches) long ; in the lower half of its extent it is enclosed within
the fibrous layer of the pericardium, and it is covered in front and on each side by
the serous layer.
Relations. It is overlapped anteriorly by the margins of the right lung and pleural
sac and by the ascending aorta. The lung and pleura intervene between it and the
second and third costal cartilages, the internal intercostal muscles in the first and second
intercostal spaces, and the internal mammary vessels. It is in relation posteriorly with
the right margin of the trachea, the right vagus nerve, the vena azygos, which opens into
it at right angles, the right bronchus, the right pulmonary artery, and the upper right
pulmonary vein. On its left side are the ascending portion of the aorta, and the commence-
ment of the innominate artery, whilst on the right side it is in close relation with the
right pleura, the phrenic nerve and the pericardiaco-phrenic (O.T. comes nervi phrenici)
vessels intervening.
Tributaries. In addition to the two innominate veins, by the union of which it is
formed, the superior vena cava receives only one large tributary, viz., the vena azygos ;
but several small pericardial and mediastinal veins open into it
VENA AZYGOS AND ITS TRIBUTARIES.
The vena azygos (O.T. vena azygos major) (Fig. 798) commences either from
the posterior aspect of the inferior vena cava, at the level of the right renal vein,
or as the direct upward continuation of an anastomosing channel which connects
together the lumbar veins of the right side, and which is known as the right
ascending lumbar vein. It ascends through the aortic orifice of the diaphragm,
and is continued upwards through the posterior mediastinum. In the upper part
of its course, it first passes posterior to the root of the right lung, and then arches
anteriorly, above the root, to its termination in the posterior part of the superior
vena cava, immediately before the latter vessel pierces the pericardium and at the
level of the second costal cartilage. It frequently possesses imperfect valves.
Relations. In the abdomen it lies on the anterior surfaces of the bodies of the
upper lumbar vertebrae, posterior to the right crus of the diaphragm and the inferior
vena cava, and to the right side of the cisterna chyli.
In the thorax it lies on the anterior surfaces of the bodies of the lower eight thoracic verte-
brae, the intervening fibro-cartilages, and the anterior longitudinal ligament; and anterior to
THE AZYGOS VEIN AND ITS TKIBUTAKIES. 961
the right aortic intercostal arteries. In the lower part of the posterior mediastinum the
right pleura and lung lie anterior to it ; at a higher level it is overlapped by the right
margin of the oesophagus, and immediately before its termination it is crossed by the root
of the right lung.
On its left side it is in relation, in the greater part of its extent, with the thoracic duct and,
as it arches anteriorly over the root of the lung, with the right vagus nerve and the trachea.
About the level of the eighth thoracic vertebra it receives the accessory hemiazygos vein,
whilst at the level of the ninth thoracic vertebra the hemiazygos vein opens into it.
In addition to the two veins last mentioned it receives the right posterior intercostal
veins, except that from the first space but including the right superior intercostal vein,
the right subcostal vein, and, through the ascending lumbar vein, the upper right lumbar
veins. It also receives the right bronchial veins and some small oesophageal, pericardial,
and mediastinal tributaries.
Tributaries. (1) The vena hemiazygos accessoria (O.T. vena azygos minor
superior) is formed by the union of the fourth, fifth, sixth, seventh and eighth left
posterior intercostal veins. It lies on the left sides of the bodies of the fifth, sixth, and
seventh thoracic vertebrae, and the corresponding intercostal arteries. It crosses the
vertebral column, from left to right, opposite the body of the eighth thoracic vertebra,
passing posterior to the aorta, oesophagus, and thoracic duct ; and it terminates either in
the vena azygos or in the vena hemiazygos. In addition to its intercostal tributaries
it receives the left bronchial veins, and some small posterior mediastinal veins, and it
communicates with the left superior intercostal vein.
(2) The vena hemiazygos commences in the epigastric region of the abdomen. At its
origin it is connected either with the left ascending lumbar vein or with the left renal vein.
After piercing the left crus of the diaphragm it ascends, on the left sides of the bodies of the
lower thoracic vertebrae, and, opposite the eighth or ninth thoracic vertebra, it turns to
the right, crosses the front of the vertebral column, posterior to the aorta, oesophagus, and
thoracic duct, and terminates in the vena azygos. As it ascends, on the bodies of the
vertebrae, it lies lateral to the aorta, and medial to the roots, of the splanchnic
nerves, and anterior to the lower left intercostal arteries. Through the left ascending
lumbar vein it receives blood from the upper lumbar veins of the left side ; the left
subcostal vein, the lower three posterior intercostal veins, and small mediastinal tributaries
also terminate in it.
(3) The bronchial veins do not quite correspond to the bronchial arteries, and they are
not found on the walls of the smallest bronchi. On each side the tributaries run, anterior
or posterior to the bronchial tubes to reach the root of the lung, where they unite, as a rule,
into two small trunks ; those of the right side open into the vena azygos, and those of the
left into the accessory hemiazygos vein, or into the left superior intercostal vein. On
both sides they are joined by tracheal and posterior mediastinal veins. Some few small
bronchial veins, including most of those from the smaller tubes, open into the pulmonary
veins.
(4) Venae Intercostales. There are two sets of intercostal veins, the anterior
and the posterior.
The anterior intercostal veins are tributaries of the internal mammary or of the
musculo-phrenic veins, and are described with those vessels (pp. 962, 963).
The posterior intercostal veins (Fig. 798) are eleven in number on each side. A
single vein runs in each intercostal space it is situated in the costal, groove, above the
corresponding artery.
On the right side the posterior intercostal vein of the first space accompanies the
superior intercostal artery across the front of the neck of the first rib, and terminates
in the vertebral or innominate vein. The second, third, and fourth posterior intercostal
veins of the right side unite together to form a common trunk, the right superior
intercostal vein, which terminates by joining the vena azygos. The fifth to the
eleventh posterior intercostal veins of the right side open separately into the vena azygos.
On the left side the first posterior intercostal vein follows a course similar to that
taken by the corresponding vein on the right side, and terminates in the left vertebral or
innominate vein. The second, third, and sometimes the fourth posterior intercostal veins
of the left side unite to form the left superior intercostal vein, which runs from behind
forwards along the left or anterior aspect of the aortic arch. It passes obliquely between
the left vagus and phrenic nerves, crosses the root of the left subclavian artery, and ends
in the lower border of the left innominate vein. The fifth, sixth, seventh, and eighth, and
sometimes the fourth posterior intercostal veins of the left side terminate in the accessory
hemiazygos vein, and the ninth, tenth, and eleventh end in the hemiazygos vein.
62
962 THE VASCULAE SYSTEM.
Each posterior intercostal vein is provided with valves, both at its termination and
along its course, which prevent the blood flowing towards the anterior aspect of the
thoracic wall. Its tributaries are derived from the adjacent muscles and bones, and a
short distance from its termination it receives a posterior tributary which passes to it
between the transverse processes of the vertebrae. This posterior vessel is formed by the
union of small veins which issue from the muscles of the back, from the anterior and
posterior spinal plexuses which lie respectively in front of the bodies and behind the
arches of the vertebrae, and by venous channels which issue through the intervertebral
foramina ; the latter vessels commence in the vertebral canal, where they are connected with
the anterior and posterior spinal veins.
VEN^E ANONYMS.
The innominate veins (Figs. 756 and 757) are two in number, right and left.
They return blood from the head and neck, the upper extremities, the upper part,
of the posterior wall of the thorax, the anterior wall of the thorax, and the upper
part of the anterior wall of the abdomen. Each innominate vein commences
behind the medial end of the clavicle of the corresponding side, and is formed by
the union of the internal jugular and subclavian veins ; the two innominate veins
terminate by uniting together, at the lower border of the first costal cartilage of
the right side, to form the superior vena cava. To reach that point the left vein
has to pass from left to right behind the manubrium sterni, and it is therefore about
three times as long as the right vein. The innominate veins do not possess valves.
The right innominate vein is a little more than 25 mm. (1 inch) in length.
It descends almost vertically to the lower border of the first costal cartilage, and
terminates in the superior vena cava.
Relations. It is in relation, anteriorly, with the medial end of the clavicle and the
sterno-hyoid and sterno-thyreoid muscles. It partly overlaps the innominate artery, which
lies to its left side, and it is in front of the internal mammary artery, the right vagus
nerve, and the upper end of the right pleural sac. The phrenic nerve and the accompany-
ing vessels run along its right side, and intervene between it and the right pleural sac.
Tributaries. In addition to the veins by the union of which it is formed, the right
innominate vein receives the right vertebral and internal mammary veins, the first right
posterior intercostal vein, and sometimes the right inferior thyreoid vein. The right
lymphatic duct also opens into it.
The left innominate vein passes from left to right, with a slight obliquity
downwards, behind the upper part of the manubrium sterni, to the lower border
of the first right costal cartilage, where it terminates in the superior vena cava.
It is about 60 to 75 mm. (3 inches) long.
Relations. It is covered anteriorly, in the greater part of its extent, by the sterno-
hyoid and sterno-thyreoid muscles, but at its right extremity it is slightly overlapped by
the right pleura, and in the median plane the remains of the thymus intervene between it
and the posterior surface of the sternum. It rests, posteriorly, upon the left pleura, the
left internal mammary artery, the left subclavian artery, the left phrenic, and the left vagus
nerves, the left superior cardiac branch of the sympathetic, the inferior cervical branch
of the left vagus, the left common carotid artery, the trachea, and the innominate artery.
Its lower border is in relation with the arch of the aorta, and on its upper border it
receives the inferior thyreoid vein of one or both sides.
Tributaries. It receives the vertebral, internal mammary, inferior thyreoid, superior
intercostal veins of its own side, the first left posterior intercostal vein, and some peri-
cardial, thymic, anterior bronchial, and anterior mediastinal veins. Sometimes the right
inferior thyreoid vein joins it, but not uncommonly that vessel terminates in the right
innominate vein or in the commencement of the superior vena cava.
The thoracic duct opens into it just at the angle of junction of the internal jugular
and subclavian veins.
Venae Mammariae Internae The Internal Mammary Veins. Each internal
mammary artery is accompanied by vense comites ; they commence by the union of
the vene comites of the superior epigastric and musculo-phrenic arteries, between the
sixth costal cartilage and the trans versus thoracis ; and at the upper part of the thorax
THE VEETEBEAL VEINS. 963
they fuse into a single vessel which enters the superior mediastinum and ends in the
innominate vein of the s,ame side.
The tributaries of the internal mammary veins are (a) The venae comites of the
superior epigastric and musculo-phrenic arteries, which in their turn receive tributaries
which correspond with the branches of the arteries they accompany, (b) Six anterior
perforating veins which accompany the corresponding arteries, one lying in each of the
upper six intercostal spaces, (c) Twelve anterior intercostal veins from the upper six
intercostal spaces, two veins lying in each space with the corresponding branches of the
internal mammary artery, (d) Small and irregular pleural, muscular, mediastinal, and
sternal veins.
The internal mammary veins are provided with numerous valves which prevent the
blood from flowing downwards.
Venae Epigastricae Superiores The Superior Epigastric Veins. The venae
comites of the superior epigastric artery receive tributaries from the substance of the
rectus abdominis, the sheath of the muscle, and the superjacent skin and fascia; they
pass, with the artery, between the sternal and costal origins of the diaphragm, and
terminate in the internal mammary veins.
Musculo-phrenic Veins. The venae comites of the musculo-phrenic artery com-
mence in the abdomen, pass through the diaphragm with the musculo-phrenic artery,
and terminate in the internal mammary veins. They receive as tributaries the anterior
intercostal veins of the seventh, eighth, and ninth intercostal spaces, and small venules
from the substance of the diaphragm and walls of the abdomen.
Venae Vertebrales The Vertebral Veins correspond only to the extra-cranial
parts of the vertebral arteries. Each commences by the union of offsets from
the intraspinal venous plexuses, and, issuing from the vertebral canal, passes
across the posterior arch of the atlas, with the vertebral artery, to the foramen in
the transverse process of the atlas. In the foramina in the cervical transverse
processes, a plexus of venous channels surrounds the artery. At the lower part
of the neck efferents from the plexus unite to form a single trunk which issues
from the foramen in the transverse process of the sixth cervical vertebra, and
descends, in the interval between the longus colli and scalenus anterior muscles,
to terminate in the upper and posterior part of the innominate vein; at its
termination there is a uni- or bi-cuspidate valve.
Relations. In the first part of its course the vein lies in the sub-occipital triangle.
The second, plexiform portion, is in the canal formed by the foramina in the transverse
processes of the cervical vertebrae, and, with the artery, which it surrounds, lies anterior
to the trunks of the cervical spinal nerves. The third part, in the root of the neck, is
between the longus colli and scalenus anterior muscles, in front of the first part of the
vertebral artery, and behind the internal jugular vein.
Tributaries. In addition to the offsets from the intraspinal venous plexuses by the
union of which it is formed, each vertebral vein receives the following tributaries : (a)
Small vessels which issue from the muscles, ligaments, and bones of the deeper parts of the
neck, and the lower and posterior part of the head, (b) Offsets from the intraspinal venous
plexuses which pass out of the vertebral canal by the intervertebral foramina. (c) The
ascending cervical vein, a vessel which is formed by the union of tributaries which issue
from a venous plexus on the anterior aspects of the bodies and roots of the transverse
processes of the cervical vertebrae. This vessel accompanies the ascending cervical artery,
and terminates in the lower part of the vertebral vein, immediately after the latter has
issued from the foramen in the sixth cervical transverse process, (d) The deep cervical
vein ; this commences in the sub-occipital triangle from a venous plexus with which
the vertebral and occipital veins communicate. It descends, posterior to the transverse
processes of the cervical vertebrae, in company with the profunda cervicis artery, turns
forwards at the root of the neck, between the transverse processes of the sixth and
seventh cervical vertebrae or between the latter and the neck of the first rib, and opens
into the vertebral vein. It receives blood from the muscles, ligaments, and bones of the
back of the neck, (e) The posterior intercostal vein from the first intercostal space some-
times opens into the vertebral vein.
Occasionally the venous plexus around the vertebral artery ends below in two terminal
trunks, anterior and posterior, instead of one. In those cases the second terminal vessel
lies behind the lower part of the vertebral artery, passes through the foramen in the
transverse process of the seventh cervical vertebra, and turns forwards on the lateral side
62 a
964 THE VASCULAE SYSTEM.
of the artery to join the anterior trunk, thus forming a common terminal vein which
ends in the usual manner.
Venae Thyreoideae Inferiores. Each inferior thyreoid vein commences by the
union of tributaries which issue from the isthmus and the corresponding lobe of
the thyreoid gland. The two veins descend, along the front of the trachea, into
the superior mediastinum, where the right inferior thyreoid vein terminates
either in the right innominate vein or in the junction of the two innominate
veins, and the left in the upper border of the left innominate vein ; or the two
veins unite to form a single trunk, which ends, usually, in the left innominate
vein, but, occasionally, in the right. As they descend in the neck the inferior
thyreoid veins anastomose together, and sometimes the anastomoses are so frequent
that a venous plexus is formed in front of the lower cervical portion of the trachea.
VEINS OF THE HEAD AND NECK.
Vena Jugularis Interna (Figs. 756, 759, 787, 800 and 801). Each internal
jugular vein commences, in the posterior compartment of the jugular foramen,
as the direct continuation of the transverse sinus, and terminates, behind the
medial part of the clavicle, by uniting witji the subclavian vein of the same
side to form the innominate vein.
Its commencement, which is dilated, forms the superior bulb of the jugular vein.
In the upper part of the neck it lies postero-lateral to the internal carotid artery
and the last four cerebral nerves. As it descends it accompanies first the internal
and then the common carotid artery. It inclines forwards as it descends, and
gradually passes from its original position, behind and to the lateral side of the
internal carotid artery, until it lies more completely to the lateral side of the internal
and common carotid arteries, and, indeed, somewhat overlaps the latter anteriorly.
This is more especially the case on the left side, for both internal jugular veins
trend slightly towards the right as they descend ; consequently, at the root of the
neck, the right vein is separated from the right common carotid artery by a small
interval filled with areolar tissue, whilst the left vein is more directly in front of
the corresponding common carotid artery.
A dilatation, the inferior bulb, is present at the inferior extremity of the vein ;
it is bounded, either above or below, by a valve of two or three semilunar
cusps. Sometimes both the superior and inferior ends of the bulb are bounded
by valves.
Relations. The vein lies anterior to the transverse processes of the cervical verte-
brae, the rectus capitis lateralis, longus capitis, and scalenus anterior muscles, the ascend-
ing cervical artery, which runs upwards in the interval between the attachments of the
two latter muscles, and the phrenic nerve ; the transverse scapular and the transverse
cervical arteries intervene between it and the scalenus anterior. At the root of the neck
the vein lies in front of the first part of the subclavian artery and the origins of the
vertebral artery and the thyreo-cervical trunk, and on the left side it is anterior to the
terminal part of the thoracic duct.
On the antero-medial side of the internal jugular vein, immediately below the skull,
are the internal carotid artery and the last four cerebral nerves ; in the rest of its extent
it is in relation, medially, first with the internal and then with the common carotid artery
whilst to its medial side and somewhat posteriorly, between it and the large arteries
lies the vagus nerve.
Each internal jugular vein is covered, superficially, in the whole of its length, by th(
. sterno-mastoid muscle; near its upper end it is crossed by the styloid process, the stylo
pharyngeus and stylo-hyoid muscles, and the posterior belly of the digastric, whilst in
its lower half, the omo-hyoid, the sterno-hyoid, and the sterno-thyreoid muscles are
superficial to it, under cover of the sterno-mastoid. Just below the transverse process of th(
atlas, and under cover of the sterno-mastoid, the vein is crossed, on its lateral side, by
the accessory nerve and by the occipital artery ; about the middle of its course it is
crossed by the communicans cervicis nerve, and near its lower end by the anterior jugular
vein ; the latter vessel, however, is separated from it by the sterno-hyoid and sterno
thyreoid muscles. Superficial to the vein are numerous deep cervical lymph glands.
SUBCLAVIAN VEINS. 965
Tributaries. (a) A vein from the cochlea and (6) the inferior petrosal sinus- join
it near its commencement, (c) Pharyngeal branches from the venous plexus on the wall
of the pharynx, (d) Emissary veins from the cavernous sinus, (e) The common facial
vein, which receives the anterior and posterior facial veins. (/) The lingual veins, which
return part of the blood from the tongue, (g) The vena comitans hypoglossi, which
accompanies the hypoglossal nerve, (h) The superior thyreoid vein, which accompanies
the corresponding artery, (i) The middle thyreoid vein, which passes backwards from
the corresponding lobe of the thyreoid gland and crosses the middle of the lateral aspect of
the common carotid artery. (J) The occipital vein occasionally terminates in the internal
jugular vein. In many cases, however, it ends in the sub-occipital plexus, which is
drained by the vertebral and deep cervical veins (see p. 963).
The common facial vein is formed by the union of the anterior and posterior facial
veins. It accompanies the first part of the external maxillary artery in the carotid
triangle, and terminates in the anterior border of the internal jugular vein. Just before
it disappears beneath the sterno-mastoid, the common facial vein frequently gives off a
large branch which descends along the anterior border of the sterno-mastoid to the
supra-sternal fossa, where it joins the anterior jugular vein.
The anterior facial vein (Fig. 785) commences at the medial commissure of the eye-
lids as the angular vein, which is formed by the union of the supra-orbital and frontal
veins. It passes downwards and backwards, in the face, to the lower and anterior part
of the masseter muscle, which it crosseSj lying in the same plane as the external maxillary
artery, but following a much straighter course. After crossing the lower border of the
mandible it passes across the submaxillary triangle, superficial to the submaxillary gland,
and separate from the external maxillary artery, which there lies in a deeper plane. It
terminates, a short distance below the angle of the mandible, by uniting with the posterior
facial vein to form the common facial vein.
The anterior facial vein receives tributaries corresponding with all the branches of
the external maxillary artery, ex,cept the ascending palatine and the tonsillar, which have
no accompanying veins, the blood from the region which they supply being returned for
the most part through the pharyngeal plexus. The anterior facial vein also communicates
with the pterygoid plexus around the external pterygoid muscle, by means of an
anastomosing channel, called the deep facial vein, which passes posteriorly, between
the masseter and buccinator muscles, into the infra-temporal fossa.
The posterior facial vein, see p. 968.
The inferior thyreoid veins have already been described (see p. 964).
Venae Subclaviae. The subclavian vein, of each side, is the direct continua-
tion of the main vein of the upper extremity, i.e. the axillary vein ;* but through
its tributary, the external jugular vein, it receives blood both from the head and
from the superficial parts of the neck.
From its commencement, at the external border of the first rib, it runs medially,
below and anterior to the corresponding artery from which it is separated by
the lower part of the scalenus anterior muscle, and it terminates, behind the
medial end of the clavicle, in the innominate vein of the corresponding side. As
it passes medially it forms a slight curve, the convexity of which is directed
upwards.
Each subclavian vein possesses a single bicuspid valve which is situated imme-
diately to the distal side of the opening of the external jugular vein.
Relations. The subclavian vein is in relation anteriorly with the posterior layer of
the costo-coracoid membrane, which separates it from the subclavius muscle, and the
nerve to the subclavius, and with the back of the medial end of the clavicle, from which
t is partly separated, however, by the fibres of the sterno-hyoid and sterno-thyreoid
muscles.
It is closely attached, anteriorly, to the posterior surface of the costo-coracoid
membrane ; consequently it is expanded when the clavicle is moved forwards, an arrange-
ment which constitutes a distinct danger when operations are being performed in the
neighbourhood of the vein ; for, in the event of the vessel being wounded, forward
movement of the clavicle may cause air to be sucked into the vein, with fatal results.
Posterior to the vein, and on a higher plane, is the first part of the subclavian artery,
but it is separated from the second part by the scalenus anterior. As soon as it reaches
the medial border of the anterior scalene the subclavian vein unites with the internal
jugular vein, immediately anterior to the internal mammary artery.
966
THE VASCULAE SYSTEM.
The upper surface of the first rib is below the vein.
Tributaries. Whilst the subclavian vein is the direct continuation of the axillary
vein, and receives, therefore, the blood from the upper extremity, it has, as a general
rule, only one named tributary, viz., the external jugular vein.
Vena Jugularis Externa. The external jugular vein (Fig. 785) is formed on
the superficial surface of the sterno-mastoid muscle, a little below and posterior to
the angle of the mandible, by the union of the posterior auricular vein with a branch
from the posterior facial vein (O.T. temporo-maxillary). In many cases the branch
Superficial temporal vein
Occipital vein
Internal maxillary veins
Posterior facial vein
Posterior auricular vein
Posterior facial vein
Posterior external
jugular vein
Transverse cervical vein
Supra-orbital vein
Angular vein
Lateral nasal vein
Superior labial vein
Inferior labial vein
Anterior facial vein
Secondary inferior
labial vein
Anastomosis between
common facial and
anterior jugular veins
Anterior jugular vein
External jugular vein
FIG. 785. SUPERFICIAL VEINS OF THE HEAD AND NECK.
from the posterior facial vein is so preponderantly large that it is more correct to
describe the external jugular vein as commencing as a branch of the posterior facial
vein. After its formation the external jugular vein descends, with a slight obli-
quity backwards, to the anterior part of the subclavian portion of the posterior
triangle of the neck, where it pierces the deep fascia, crosses in front of the third
part of the subclavian artery, and terminates in the subclavian vein.
Whilst on the surface of the sterno-mastoid muscle it is covered by the super-
ficial fascia, and platysma muscle, and it lies parallel with the great auricular
nerve ; after crossing the nervus cutaneus colli (O.T. trans, cervical) it reaches the
posterior border of the sterno-mastoid, where it receives a tributary called the
posterior external jugular vein, which commences in the superficial tissues of
the upper and back part of the neck, and runs downwards and forwards, across the
VEINS OF THE SCALP. 967
roof of the upper part of the posterior triangle, to its termination in the external
jugular vein.
As the external jugular vein pierces the deep cervical fascia in the subclavian
triangle, its wall is closely attached to the margin of the opening through which
it passes ; and as it is crossing in front of the third part of the subclavian artery it
is joined by the transverse scapular, transverse cervical, and anterior jugular veins.
There are usually two valves in the lower part of the vein one, at its termina-
tion, which is generally incompetent, and a second at a higher level.
Tributaries. In addition to the posterior auricular vein and the branch from
the posterior facial vein by which it is formed, the external jugular vein receives the
posterior external jugular vein, which has already been described, the transverse
cervical and transverse scapular veins from the region of the shoulder, and the
anterior jugular vein. Occasionally the cephalic vein also opens into it.
The posterior auricular vein (Fig. 785) receives tributaries from the posterior parts
of the parietal and temporal regions and from the medial surface of the auricle. It is
considerably larger than the posterior auricular artery, which it accompanies only in the
scalp. At the base of the scalp it leaves the artery and descends in the superficial fascia,
over the upper part of the sterno-mastoid, to join the external jugular vein.
The transverse cervical and transverse scapular veins accompany the corresponding
arteries ; not infrequently they open directly into the subclavian vein.
The anterior jugular vein commences in the submental region, and is formed by the
union of small veins from the lower lip and chin. It descends, in the superficial fascia, at
a variable distance from the median plane, perforates the superficial layer of the deep
fascia, a short distance above the sternum, and enters the suprasternal space (Burns)
between the first and second layers of the deep fascia. In the space it anastomoses with
its fellow of the opposite side and receives a communication from the common facial vein.
Then it turns laterally, between the sterno-mastoid superficially and the sterno-hyoid,
sterno-thyreoid, and scalenus anterior muscles deeply, and terminates in the external
jugular vein at the posterior border of the sterno-mastoid.
The external jugular vein sometimes receives the occipital vein or a communication
from it.
THE VEINS OF THE SCALP.
The veins which drain the blood from the superficial parts of the scalp are the
frontal, the supra- orbital, the superficial temporal, the posterior auricular, and the
occipital. The blood from the deeper part of the scalp, in the region of the
temporal fossa, on each side, passes into the deep temporal veins, which are
tributaries of the pterygoid plexus.
The frontal and supra-orbital veins receive blood from the medial and anterior
part of the scalp. They unite together, near the medial commissure of the eyelids,
to form the angular vein ; before the union is effected the supra-orbital vein sends a'
branch backwards, through the supra-orbital notch, into the orbital cavity, where
it terminates in the ophthalmic vein, and as this branch passes through the notch
it receives the frontal diploic vein (p. 969).
The superficial temporal vein (Figs. 759, 785) is formed by frontal and parietal
tributaries which accompany the corresponding branches of the superficial temporal
artery. They drain the lateral frontal, the superficial part of the temporal, and the
anterior part of the parietal region of the scalp, and unite to form a single trunk
which descends to the upper border of the zygoma, immediately anterior to the
auricle, where it terminates in the posterior facial vein (see p. 968).
The posterior auricular vein drains the posterior portions of the temporal and
parietal areas of the scalp (see above).
The occipital vein (Figs. 759, 785) receives tributaries from the parietal and
occipital regions. As a rule it pierces the occipital origin of the trapezius, and,
passing into the sub-occipital triangle, terminates in a plexus of veins which is
drained by the vertebral and deep cervical veins. It sometimes communicates with
the external jugular vein, and occasionally an offset from it accompanies the corre-
sponding artery and ends in the internal jugular vein.
62 &
968 THE VASCULAE SYSTEM.
It generally receives the mastoid emissary vein ; one of its tributaries receives
the parietal emissary vein, and occasionally an emissary vein from the confluens
sinuum (O.T. torcular Herophili) opens into it.
THE VEINS OF THE ORBIT, THE NOSE, AND THE INFRA-TEMPORAL EEGION.
The veins of these three regions are closely associated together ; for although
the orbital blood is returned, for the most part, to the cavernous sinus, by the
ophthalmic vein, the latter vein is closely connected with the pterygoid plexus,
which lies in the infra-temporal region.
Veins of the Orbit. The veins of the orbit correspond, with the exception of
the naso-frontal vein, with the branches of the ophthalmic artery, and they
gradually converge, as they pass backwards in the orbit, until they form two main
trunks, a superior ophthalmic vein and an inferior ophthalmic vein. The two trunks
terminate separately, or by a single stem, in the anterior end of the cavernous
sinus, to which they pass through the superior orbital fissure, and between the
two heads of the lateral rectus muscle.
The superior ophthalmic vein communicates, at the super o-medial angle of the
orbit, with the angular vein, and it receives the naso-frontal vein which accompanies
the frontal nerve. The inferior ophthalmic vein communicates, through the inferior
orbital fissure, with the pterygoid plexus.
Veins of the Nose. The veins of the walls of the nasal cavity end partly in
the ethmoidal tributaries of the superior ophthalmic vein, partly in the septal
affluent of the superior labial and in the lateral nasal veins, both of which are
tributaries of the anterior facial vein ; but the majority of the veins of the nose,
both from the septal and lateral walls, join together to form a spheno-palatine
vein which passes through the spheno-palatine foramen and the pterygo-palatine
fossa, and terminates in the pterygoid plexus.
Plexus Pterygoideus and the Vena Maxillaris Interna. The pterygoid plexus
of veins lies in the infra- temporal and pterygoid fossse. It covers the lateral
surface of the internal pterygoid muscle, and surrounds the external pterygoid.
It receives tributaries which correspond with and accompany the branches
of the internal maxillary artery viz., spheno-palatine, pharyngeal, vein of pterygoid
canal, infra-orbital, posterior superior alveolar, descending palatine, buccinator, two
or three deep temporal, pterygoid, masseteric, and inferior alveolar veins, and the
middle meningeal vein. It communicates, superiorly, with the cavernous sinus
through the foramen ovale ; anteriorly with the inferior ophthalmic vein through
the inferior orbital fissure ; and between the masseter and the buccinator with the
anterior facial vein by the deep facial anastomosing branch. It also communicates
posteriorly and medially, on the medial side of the internal pterygoid, with the
pharyngeal plexus, and it terminates posteriorly in the internal maxillary vein.
The internal maxillary vein is a short vessel which accompanies the first part
of the internal maxillary artery, between the spheno-mandibular ligament and the
neck of the mandible. Between the neck of the mandible and the antero-medial
surface of the parotid gland it joins the upper part of the posterior facial vein.
Occasionally the internal maxillary vein is double, and sometimes it is represented
by several channels.
The posterior facial vein is formed, immediately above the zygomatic arch, by
the union of the superficial and middle temporal veins. It crosses the zygomatic
arch, dips deep to the upper part of the parotid gland, and, whilst lying between the
antero-medial surface of the gland and the posterior border of the mandible, it
receives the internal maxillary vein or veins. Then it descends, through the
substance of the parotid, and, emerging from its lower end at the angle of the
mandible, it passes forwards and downwards to unite with the anterior facial vein
in the formation of the common facial vein.
Whilst it is in the substance of the parotid it gives off a comparatively large
branch, which emerges from the lower and posterior part of the gland and forms
one of the two commencing tributaries of the external jugular vein.
DIPLOIC AND MENINGEAL VEINS.
969
VENOUS SINUSES AND VEINS OF THE CRANIUM AND OF ITS
CONTENTS.
The venous channels met with in the cranial walls and cranial cavity are :
(1) The diploic veins, which lie in the spongy tissue between the outer and
inner tables of the cranial bones.
(2) The meningeal veins, which accompany the meningeal arteries in the outer
layer of the dura mater.
(3) The veins of the brain, which lie between the folds of pia mater and in the
subarachnoid space.
(4) The cranial venous sinuses, channels which are situated between the outer
and inner layers of the dura mater; they receive the blood from the terminal
cerebral veins.
DIPLOIC AND MENINGEAL VEINS.
Venae Diploicse. The diploic veins are anastomosing spaces in the spongy
tissue of the flat bones of the skull ; they are lined with endothelium. The number
of efferent vessels which emerge from the diploic spaces is not constant, but usually
there are at least four on each side viz., a frontal, two temporal, anterior and
posterior, and an occipital.
The frontal diploic vein is one of the most constant ; it drains the anterior part
Posterior temporal
diploic vein
Occipital diploic
vein
Anterior temporal diploic vein
Frontal diploic vein
FIG. 786. THE VEINS OF .THE DIPLOE.
of the frontal bone, passes through a small aperture in the upper margin of the
supra-orbital notch, and terminates in the supra-orbital vein.
The anterior temporal diploic vein drains the posterior part of the frontal bone
and the anterior part of the parietal bone; it pierces the great wing of the
.sphenoid, and terminates either in the spheno-parietal sinus or in the anterior
deep temporal vein.
The posterior temporal diploic vein drains the posterior part of the parietal
bone; it runs downwards to the posterior inferior angle of the parietal bone
and terminates in the transverse sinus, to which it passes either through a
foramen in the inner table of the parietal bone or through the mastoid foramen.
970 THE VASCULAK SYSTEM,
The occipital diploic vein is usually the largest of the series ; it drains the
occipital bone, and terminates either externally in the occipital vein or internally
in the lateral sinus.
Venae Meningeae. The meningeal veins commence in two capillary plexuses,
a deep and a superficial. The deep plexus is a wide-meshed network in the inner
layer of the dura mater. Its efferent vessels terminate in the superficial plexus.
The superficial plexus lies in the outer layer of the dura mater. It consists of
numerous vessels of uniform calibre which frequently anastomose together, and
terminate in two sets of efferents ; of these, one set ends in the cranial blood sinuses,
and the other accompanies the meningeal arteries. The efferent meningeal veins
are peculiar, inasmuch as they do not alter much in size as they approach their
terminations. They lie external to the arteries in the grooves in the inner wall
of the cranium, and are very liable to be torn when the bones are fractured
(Wood Jones).
VEINS OF THE BRAIN.
The veins of the brain include the veins of the cerebrum, of the mid-brain, of
the cerebellum, of the pons, and of the medulla oblongata. They do not possess
valves.
Venae Cerebri The Veins of the Cerebrum. The cerebral veins are arranged
in two groups, (a) the deep and (&) the superficial.
The deep veins issue from the substance of the brain. The superficial veins lie
upon its surface in the pia mater and the subarachnoid space. The terminal
trunks of both sets pierce the arachnoid membrane and the inner layer of the dura
mater, and open into the cranial venous sinuses.
(a) The deep cerebral veins are the chorioid veins, the venee terminales,
the internal cerebral veins, the great cerebral vein (Galen), the vein of the septum
pellucidum and the inferior striate veins.
Each chorioid vein is formed by the union of tributaries which issue from the
chorioid plexus in the body and inferior horn of a lateral ventricle. It ascends,
along the lateral border of the tela chorioidea of the third ventricle (O.T.
velum interpositum), and passes forwards, in the lateral border of that fold of pia
mater, to the interventricular foramen (Monro), where it receives efferents from
the chorioid plexus of the third ventricle, and unites with the vena terminalis to
form the internal cerebral vein (Galen).
The vena terminalis (O.T. vein of corpus striatum), on ieach side, is formed by
the union of tributaries which issue from the corpus striatum and from the
thalamus. It runs forwards between the thalamus and the caudate nucleus, in a
groove in the floor of the lateral ventricle, and, after receiving tributaries from the
walls of the anterior horn of the ventricle, and the vein of the septum pellucidum,
it terminates at .the apex of the tela chorioidea, where it joins the chorioid vein to
form the internal cerebral vein (Galen).
Each internal cerebral vein (Galen) commences at the apex of the tela
chorioidea, near the interventricular foramen (Monro), by the union of the
vena terminalis with the chorioid vein. The two veins run backwards between the
layers of the tela, receiving tributaries from the chorioid plexuses of the third
ventricle and from the fornix and corpus callosum, and they terminate, beneath
the splenium of the corpus callosum, by uniting to form the great cerebral vein
(Galen).
The great cerebral vein (Galen) passes backwards and slightly upwards from its
origin, and ends in the anterior extremity of the straight sinus. In addition to
the two internal cerebral veins, by the union of which it is formed, it receives
tributaries from the posterior parts of the gyrus cinguli of each side, from the pineal
and quadrigeminate bodies, from the medial and inferior surfaces of the occipital
lobes of the brain, and from the upper surface of the cerebellum. It also receives
the basal vein of each side (see p. 971).
An inferior striate vein descends, on each side, from the substance of the corpus
striatum, and, after passing through the anterior perforated substance, ends in the
VEINS OF THE BKAIK 971
basal vein (see below), which, as already stated, is a tributary of the great cerebral
vein.
(&) The superficial cerebral veins are more numerous and of larger calibre
than the cerebral arteries. They lie upon the surface of the cerebrum, drain
blood from the cerebral cortex, and they are divisible into two sets, the superior
and the inferior.
The superior cerebral veins, twelve or more in number, lie in the pia mater
and subarachnoid space on the upper and lateral aspect of the cerebral hemispheres.
They run upwards and medially, to the margin of the longitudinal fissure where
they receive tributaries from the medial surface of the hemisphere, and they
terminate in the superior sagittal sinus or in the lateral lacunar expansions of the
sinus. The anterior veins of this set are small and run transversely, but the
posterior are large and run obliquely forwards and medially ; they are embedded
for some distance in the wall of the sinus, and their orifices are directed forwards
against the blood stream.
The inferior cerebral veins lie on the lower and lateral aspects of the cerebral
hemispheres ; they run downwards and medially, and terminate in the sinuses
which lie at the base of the skull viz., the cavernous, the superior petrosal, and
the transverse sinuses. One of these veins, the superficial middle cerebral vein
(O.T. superficial Sylvian), runs along the posterior horizontal branch and the stem of
the lateral fissure (Sylvius) to the cavernous sinus ; occasionally it is united by an
anastomotic loop, known as the great anastomotic vein (Trolard), with the superior
sagittal sinus, and sometimes by the inferior anastomotic vein with the transverse
sinus.
The anterior cerebral vein of each side lies in the longitudinal fissure, and
accompanies the corresponding anterior cerebral artery ; it receives tributaries from
the corpus callosum and the gyrus cinguli. Turning downwards, round the
genu of the corpus callosum, it reaches the base of the brain, and terminates in the
basal vein.
The deep middle vein (O.T. deep Sylvian) lies deeply in the lateral fissure
(Sylvius) ; it anastomoses freely with the superficial middle vein, receives tributaries
from the insula and the adjacent opercula, and terminates in the basal vein.
The basal vein commences at the anterior perforated substance ; it is formed by
the union of the anterior cerebral vein with the deep middle vein and with the
inferior striate vein. Passing backwards round the pedunculus cerebri, it terminates
in the great cerebral vein (Galen). Its tributaries are derived from the tuber
cinereum, the corpus mamillare, the posterior perforated substance, the uncus, the
inferior cornu of the lateral ventricle, and the pedunculus cerebri.
Veins of the Mid-brain. The veins of the mid-brain terminate for the most
part either in the great .cerebral vein (Galen) or in the basal veins.
Cerebellar Veins. These veins also are divisible into two groups, the super-
ficial and the deep. The former are quite independent of and much more
numerous than the arteries. They form two sets, the superior and the inferior.
The superior superficial cerebellar veins terminate in a single median or vermian
efferent vessel which is sometimes double, and in several lateral efferents. The
superior vermian vein runs anteriorly and ends in the great cerebral vein (Galen).
The lateral superior cerebellar veins terminate in the transverse sinuses or in
the superior petrosal sinuses.
The inferior superficial cerebellar veins also form a small vermian and numerous
lateral efferents; the former runs backwards and joins either the straight sinus
or one of the transverse sinuses, and the latter end in the inferior petrosal and
occipital sinuses.
The deep cerebellar veins issue from the substance of the cerebellum and
terminate in the superficial veins.
Veins of the Pons. The deep veins from the substance of the pons pass
forwards to its anterior surface, where they become superficial, and, anastomosing
together, form a plexus which is drained by superior and inferior efferent veins.
The superior efferent veins join the basal vein ; the inferior efferent veins either
unite with the cerebellar veins, or they open into the superior petrosal sinus.
972
THE VASCULAE SYSTEM.
Veins of the Medulla Oblongata. Deep veins of the medulla oblongata issue
from its substance and end in a superficial plexus. This plexus is drained by an
anterior and a posterior median vein and by radicular veins.
The anterior median vein is continuous below with the corresponding vein of the
spinal medulla ; it communicates above with the plexus on the surface of the pons.
The posterior median vein is continuous below with the posterior median vein
of the spinal medulla, from which it ascends to the lower end of the fourth
ventricle, where it divides into two branches which join the inferior petrosal sinus
or basil ar plexus.
The radicular veins issue from the lateral parts of the plexus and run with the
roots of the last four cerebral nerves ; they end in the inferior petrosal and occipital
sinuses or in the upper part of the internal jugular vein.
SINUS DUR.E MATRIS.
The venous sinuses of the cranium are spaces between the layers of the dura mater ;
and they are lined with an endothelium which is continuous with the endothelium
of the veins. They receive the veins of the brain, communicate frequently with the
Inferior sagittal sinus Great cerebral vein (Galen)
Straight sinus
Superior petrosal sinus
avernous sinus
Facial nerve
Posterior auricular
artery
Transverse sinus
Occipital sinus
Sup. oblique muscle
Occipital artery
Descending branch
of occipital artery
Vertebral artery
Semispinalis capitis
muscle (O.T. corn-
plexus)
Suboccipital nerve
Sterno-mastoid
muscle
Splenius capitis
muscle
External carotid
artery
arotid gland
Stylo-hyoid muscle
Hypoglossal nerve
Internal carotid artery
Digastric muscle (posterior belly)
Longissimus capitis muscle Accessory nerve Internal Sterno-mastoid " Common carotid artery
(O.T. trachelo-mastoid) jugular vein. artery
FIG. 787. DISSECTION OF THE HEAD AND NECK, showing the cranial blood sinuses and the upper part of
the internal jugular vein.
meningeal veins and with veins external to the cranium, and terminate directly or
indirectly in the internal jugular vein. Some of the cranial blood sinuses are
unpaired, others are paired.
Unpaired Sinuses. These are the superior sagittal, the inferior sagittal, the
straight, the anterior and posterior intercavernous, and the basilar.
BLOOD SINUSES OF THE CEANIUM.
973
Sinus Sagittalis Superior. The superior sagittal sinus commences in the
anterior fOssa of the cranium, at the crista galli, where it communicates, through
the foramen csecum, with the veins of the nasal cavity or with the angular vein.
It passes backwards in the convex margin of the falx cerebri, grooving the
frontal, both the parietal bones, and upper part of the occipital. As it descends
along the occipital bone it usually passes slightly to the right side, and it ends.
Sinus frontalis
Cellula ethmoidale anterior
A. frontalis
A. supraorbitalis X N ^\
/^<
Scalp
Ossa frontale
V. ophthalmica superior t
Aa. ethmoidales
A. lacrimal
A. oplithalmica "
leningea anterior-
>s Ossa frontale (pars orbitalis)
Sinus sphenoparietalis
M. temporalis
N. frontalis-
X. trochlearis "
caroti.s uiterna
~ N. opticus
\ Sinus intercavernosi
"."anterior
JL-- Sinus cavernosus
, oculomotorius
Plexus basilari.s
facialis et ,
acusticus
petrosus
superior
NM. glossopharyngeus
vagus et accessorius
.Sinus occipitalis
/
Sinus transversus
Sinus rectus
A. vertebralis
FIG. 788. THE LOWER BLOOD SINUSES OF THE DURA MATER.
the specimen represented the superior sagittal sinus opened into both transverse sinuses and chietty into
the left. The straight sinus also opened into both transverse sinuses. The medial part of the ]
transverse sinus was divided by a horizontal septum into upper and lower parts,
figure passes below the septum.
at the level of the internal occipital protuberance, by becoming the right transverse
sinus. Instead of passing to the right, it occasionally turns to the left, and ends in
the left transverse sinus, and in some cases it bifurcates and ends in both .transverse
sinuses. When it ends wholly in the right or the left transverse sinus its termina-
tion is associated with a well-marked dilatation, the confluens sinuum, which is
lodged in a depression at one side of the internal occipital protuberance,
confluens sinuum is connected, across the protuberance, by an anastomosing channel,
with a similar dilatation which marks the junction of the straight sinus with the
974 THE VASCULAE SYSTEM.
lateral sinus of the opposite side. Opening into the superior sagittal sinus are the
superior cerebral veins, and it communicates on each side by small openings with
a series of spaces in the dura mater, the lacunae laterales, into which the arach-
noideal granulations project. It also communicates, by emissary veins, which pass
through the foramen caecum and through each parietal foramen, with the veins on
the exterior of the cranium. Its cavity, which is triangular in transverse section,
is crossed by several fibrous strands called the chordae Willisii.
Sinus Sagittalis Inferior. The inferior sagittal sinus lies, usually, in the posterior
two-thirds of the lower free margin of the falx cerebri. It terminates posteriorly
by joining with the great cerebral vein (Galen) to form the straight sinus. It
receives tributaries from the falx cerebri and from the medial surface of the
middle third of each cerebral hemisphere.
Sinus Intercavernosi. The anterior intercavernous sinus is a small transverse
channel which crosses from one cavernous sinus to the other in the anterior border
of the diaphragma sellse.
The posterior intercavernous sinus also connects the two cavernous sinuses
together. It lies in the posterior border of the diaphragma sellse.
The anterior and posterior intercavernous sinuses and the intervening parts of
the cavernous sinuses form collectively the circular sinus.
Plexus Basilaris. The basilar plexus (O.T. basilar sinus) is situated in the dura
mater on the basilar part of the occipital bones. It connects the posterior ends
of the cavernous or the anterior ends of the inferior petrosal sinuses together, and
communicates below with the anterior spinal veins.
Sinus Rectus. The straight sinus is formed by the union of the inferior
sagittal sinus with the great cerebral vein (Galen). It runs downwards and
backwards, along the line of union between the falx cerebri and the tentorium
cerebelli. As a general rule it turns to the left at the internal occipital protuber-
ance, dilates somewhat, and becomes continuous with the left transverse sinus,
its dilatation being united with the corresponding dilatation on the lower end of
the superior sagittal sinus, the " confluens sinuum," by a transverse anastomosing
channel. Occasionally the straight sinus terminates in the right lateral sinus;
in that case the superior sagittal sinus ends in the left transverse sinus ; and
sometimes it bifurcates to join both transverse sinuses. It receives some of the
superior cerebellar veins and a few tributaries from the falx cerebri.
Paired Sinuses. There are six pairs of sinuses, viz., the transverse, the occipital,
the cavernous, the superior petrosal, the inferior petrosal, and the spheno-parietal.
Sinus Transvessi (O.T. Lateral Sinuses). Each transverse sinus commences
at the internal occipital protuberance, the right usually as the continuation of the
superior sagittal, and the left as the continuation of the straight sinus. Each
passes laterally in the postero-lateral part of the attached border of the tentorium
cerebelli and in a groove in the occipital bone. From the lateral angle of the
occipital bone it passes to the posterior inferior angle of the parietal bone, which
it grooves ; then it leaves the tentorium and turns downwards on the inner surface
of the mastoid portion of the temporal bone ; from the latter it passes to the upper
surface of the jugular process of the occipital bone, and turns forwards and then
downwards into the jugular foramen, where it becomes continuous with the internal
jugular vein. The part which descends on the temporal bone and turns forwards
on the jugular process of the occipital is called the sigmoid sinus.
Its tributaries are some of the superior and inferior cerebellar veins, a posterior
diploic vein, and the superior petrosal sinus. It is connected with the veins out-
side the cranium by emissary veins wjiich pass through the mastoid foramen and
the condyloid canal.
Sinus Occipitales. The occipital sinuses lie in the attached border of the
falx cerebelli and in the dura mater along the postero-lateral boundaries of the
foramen magnum ; frequently they unite above and open by a single channel into
the commencement of either the right or the left transverse sinus, but their upper
extremities may remain separate, and then each communicates with the commence-
ment of the transverse sinus of its own side. On the other hand either the right or
the left sinus may be absent. Each opens below into the terminal part of the corre-
BLOOD SINUSES OF THE CRANIUM. 975
spending transverse sinus, and both communicate with the posterior spinal veins.
Each occipital sinus is an anastomosing channel between the upper and lower
extremities of the transverse sinus of the same side, and each receives a few inferior
cerebellar veins.
Sinus Cavernosi. The cavernous sinuses lie at the sides of the body of the
sphenoid bone. Each sinus commences, anteriorly, at the medial end of the superior
orbital fissure, where it receives the corresponding ophthalmic veins, and it
terminates, at the apex of the petrous portion of the temporal bone, by dividing
into the superior and the inferior petrosal sinuses. Its cavity, which is irregular
in size and shape, is so divided by numerous fibrous strands that it assumes the
appearance of cavernous tissue ; and in its lateral wall are embedded the internal
carotid artery with its sympathetic plexus, the oculomotor, the trochlear, the
ophthalmic and maxillary divisions of the trigeminal and the abducent nerves. Its
tributaries are the ophthalmic vein, the spheno-parietal sinus and the inferior
cerebral veins, including the middle cerebral vein (O.T. superficial Sylvian vein).
It communicates with the opposite cavernous sinus by means of. the anterior and
posterior intercavernous sinuses ; with the pterygoid plexus, in the infra-temporal
fossa, by an emissary vein which passes either through the foramen ovale or through
the foramen Vesalii; with the internal jugular vein by small venous channels
rhich accompany the internal carotid artery through the carotid canal, and by the
tferior petrosal sinus ; with the transverse sinus by the superior petrosal sinus ;
id through the superior ophthalmic vein with the angular vein.
The spheno-parietal sinuses are lodged in the dura mater on the under surfaces
the small wings of the sphenoid bone close to their posterior borders. Each sinus
communicates with the middle meningeal veins, receives veins from the dura mater,
and terminates in the anterior part of the corresponding cavernous sinus.
Sinus Petrosi Superiores. Each superior petrosal sinus commences at the
apex of the petrous portion of the temporal bone, in the posterior end of the
corresponding cavernous sinus, and it runs backwards and laterally, in the attached
margin of the tentorium cerebelli, above the trigeminal nerve. It grooves the
superior angle of the petrous portion of the temporal bone, at the lateral end of
which it terminates in the transverse sinus, at the point where the latter is turning
downwards on the medial surface of the mastoid portion of the temporal bone. It
receives inferior cerebral, superior cerebellar, tympanic, and diploic veins.
Sinuus Petrosi Inferiores. An inferior petrosal sinus commences at the
posterior end of each cavernous sinus ; it runs backwards, laterally, and downwards,
in the posterior fossa of the cranium, in a groove formed by the lower angle of
the petrous part of the temporal bone and the adjacent border of the basilar part
of the occipital bone, to the anterior compartment of the jugular foramen of the
same side, through which it passes. It crosses the last four cerebral nerves either
on their lateral or on their medial sides, and it terminates in the internal jugular
vein. Its tributaries include inferior cerebellar veins and veins from the internal
ear, which pass to it through the internal acoustic meatus, the aquaeductus cochleae,
and the aquseductus vestibuli.
Emissaria. The emissary veins are veins which convey blood from the blood sinuses in the
interior of the cranium to the veins which lie outside the walls of the cranium. They may be
single veins, or plexiform channels surrounding other structures which are passing through the
walls of the cranium.
(1) Frontal. In the child, and sometimes in the adult, an emissary vein passes from the
anterior end of the superior sagittal sinus through the foramen caecum. Its lower end divides
into two channels which either terminate in the veins of the roof of the nasal cavities or they
perforate the nasal bones and join the angular veins.
(2) Parietal. The parietal emissary veins, one on each side, pass through the parietal foramina,
from the superior sagittal sinus to the occipital veins.
(3) Occipital. An occipital emissary vein is only occasionally present. It passes from the
" connuens sinuum " through the occipital protuberance to one of the tributaries of an occipital
vein, and it receives the occipital diploic vein.
(4) Condyloid. When the condyloid canals are present in the occipital bone each is traversed
by a condyloid emissary vein, which connects the lower end of the corresponding transverse sinus
with the plexus of veins in the sub-occipital triangle.
(5) Emissary Plexus of the Foramen Ovale. This plexus surrounds the mandibular nerve, as
it passes through the foramen ovale, and connects the cavernous sinus with the corresponding
976 THE VASCULAK SYSTEM.
pterygoid plexus in the infratemporal fossa. If the foramen Vesalii is present, the plexus of the
foramen ovale is replaced or supplemented by an emissary vein which passes through that foramen.
(6) Internal Carotid Plexus. The internal carotid plexus accompanies the internal carotid
artery through the carotid canal of the temporal bone, and connects the cavernous sinus either
with the pharyngeal plexus or with the upper part of the internal jugular vein.
(7) Plexus of the Hypoglossal Canal. As the hypoglossal nerve passes through the hypo-
glossal canal (O.T. anterior condyloid foramen) it is accompanied either by a venous plexus or by
a large vein which connects the veins of the medulla oblongata and the lower part of the occipital
sinus with the upper end of the internal jugular vein, or with the extra-cranial part of the inferior
petrosal sinus.
VERTEBRAL VEINS.
The vertebral veins include
(1) The basi-vertebral veins.
(2) The external vertebral plexuses.
(a) anterior fi
(b) posterior
(3) The internal vertebral plexus.
(4) Vertebral longitudinal sinuses.
-(5) Intervertebral veins.
Vense Basivertebrales. The basi-vertebral veins are venous channels, enclosed
by endothelial walls, which lie in the interiors of the bodies of the vertebrae. They
communicate anteriorly with the plexuses of veins on the anterior surfaces of the
bodies of the vertebrae, and they converge, radially, towards the posterior surfaces
of the bodies of the vertebrae where they open into the transverse anastomoses
between the longitudinal vertebral sinuses.
Plexus Venosi Vertebralis Extern! The external vertebral plexuses, (a)
anterior and (6) posterior.
(a) The anterior external vertebral plexuses are formed by anastomosing venous
channels which lie on the anterior surfaces of the vertebrae. They communicate
with the basi-vertebral veins and with the intervertebral veins.
(6) The posterior external vertebral plexuses lie around the postero-lateral aspects
of the vertebras, in the vertebral grooves, around the spines, the articular and the
transverse processes of the vertebrae. They communicate with the internal plexuses
and with the intervertebral veins, and they open into the vertebral, intercostal, and
lumbar veins.
Sinus Vertebrales Longitudinales. The Longitudinal Vertebral Sinuses. The
veins in the interior of the vertebral canal form a network, the vertebral venous
network, which lies external to the dura mater and covers the internal surfaces
of the arches and the posterior surfaces of the bodies of the vertebrae. The network
communicates laterally with the intervertebral veins, posteriorly with the posterior
external venous plexuses, whilst anteriorly it receives the basi-vertebral veins. In
the anterior part of the network, on the posterior surfaces of the bodies of the
vertebrae, at the sides of the posterior longitudinal ligament, there are two large
longitudinal channels, the anterior longitudinal vertebral sinuses. Two less marked
longitudinal channels, the posterior longitudinal vertebral sinuses, can sometimes be
distinguished on the internal surfaces of the vertebral arches.
The anterior longitudinal vertebral sinuses communicate above with the basilar
plexus, the terminal parts of the transverse sinuses, and with the network of veins
which accompanies each hypoglossal nerve through the hypoglossal canal.
The posterior longitudinal vertebral sinuses, when they are well established,
communicate above with the occipital sinuses.
Vense Intervertebrales. The Intervertebral Veins. The internal vertebral
venous network is drained not only above into the cranial venous sinuses by the
longitudinal vertebral sinuses, but also by a series of intervertebral veins which pass
through the intervertebral foramina. In the cervical region the intervertebral veins
open externally into the vertebral veins, in the thoracic region into the intercostal
veins, in the lumbar region into the lumbar veins, and in the sacral region into the
lateral sacral veins. The intervertebral veins convey blood both from the internal
vertebral venous plexus and also from the anterior and the posterior external
vertebral r>lexuses.
THE AXILLAEY VEIN. 977
THE VEINS OF THE SPINAL MEDULLA.
The veins of the spinal medulla issue from the substance of the spinal medulla, and
terminate in a plexus in the pia mater. In that plexus there are six longitudinal
channels one antero- median, along the anterior fissure, two antero-lateral,
immediately behind the anterior nerve -roots, two poster o-lateral, immediately
posterior to the posterior nerve -roots, and one poster v- median, dorsal to the
posterior septum. Radicular efferent vessels issue from the plexus, and pass along
the nerve roots to communicate with the internal vertebral venous network.
The veins of the spinal medulla vary very much in size, but they are largest on the
lower and on the posterior portions.
The postero-median and antero-rnedian veins are continued above into the
corresponding veins of the medulla oblongata.
The antero-lateral and postero-lateral veins pour their blood partly into the
median veins and partly into the radicular veins ; indeed, the greater part of the
blood from the spinal medulla is returned by the radicular veins.
THE VEINS OF THE SUPERIOR EXTREMITY.
The veins of each upper limb are divisible into two sets viz., superficial
and deep. Both sets open eventually into a common terminal trunk which is
known as the axillary vein. That vein is, therefore, the chief efferent vein of the
upper extremity. It is continued as the subclavian vein to the innominate vein,
through which its blood, together with that from the corresponding side of the head
and neck, reaches the superior vena cava.
THE DEEP VEINS OF THE UPPER EXTREMITY.
The deep veins of the upper limb, with the exception of the axillary vein, are
arranged in pairs, venae comites, which accompany the different arteries and are
similarly named. So far as these veins are concerned it will be sufficient to state
that they are provided with valves, that they are situated one on each side of
the artery with which they are associated, and that they are usually united
together by numerous transverse anastomoses which cross the line of the artery.
The axillary vein, however, requires more detailed consideration.
VENA AXILLARIS.
The axillary vein (Eigs. 766 and 806) commences, as the direct continuation
of the basilic vein, opposite the lower border of the teres major muscle. It passes
upwards and medially, through the axilla, along the medial side of the axillary
artery, and terminates, at the external border of the first rib, by becoming the
subclavian vein. It possesses one or more bicuspid valves of which one is usually
situated opposite the lower border of the subscapularis muscle.
Relations. Its anterior relations are similar to those of the axillary artery, but, in
addition, the vein is crossed anteriorly, under cover of the clavicular part of the pectoralis
major, by the pectoral branches of the thoraco-acromial artery, and by branches of the
medial anterior thoracic nerve, and it receives anteriorly, just above the upper border
of the pectoralis minor, the termination of the cephalic vein.
Posterior to it are the muscles which form the posterior wall of the axilla, the axillary
fat, and the first serration of the serratus anterior. The long thoracic nerve intervenes
between it and the serratus anterior, and the subscapular and thoraco-dorsal nerves and
the subscapular artery pass between it and the subscapularis.
It is separated from the third part of the axillary artery by the ulnar nerve and
medial cutaneous nerves of the forearm ; from the second part of the axillary artery
1 by the medial cord of the brachial plexus ; and in the proximal part of the axilla, behind
the costo-coracoid membrane, it is separated from the first part of the artery by the medial
anterior thoracic nerve. To its medial side lie the lateral set of axillary glands, and,
m the distal part of the axilla, the medial cutaneous nerve of the arm.
63
978
THE VASCULAE SYSTEM.
Tributaries. In addition to tributaries corresponding with the branches of the
axillary artery, it receives the venae comites of the brachial artery, at the lower border
of the subscapularis ; and the cephalic vein, which joins it above the upper border of the
pectoralis minor muscle.
THE SUPERFICIAL VEINS OF THE SUPERIOR EXTREMITY.
The superficial veins of the upper limb commence in the superficial fascia of
the palm and dorsum of the hand and of the digits.
The Veins of the Digits and Hand. The special volar digital veins are two or
more fine longitudinal channels which lie in the superficial fascia of the volar
aspects of the
digits. They com-
municate, proxim-
ally, with a fine
venous network
which lies in the
superficial fascia of
^Tributaries of cephalic vein
Tributary of
cephalic vein
Commencement,
of basilic vein
Dorsal
digital
Dorsal venous
arch
the palm, and, at
the proximal ends
of the interdigital
clefts, by means
of intercapitular
veins, which pass
dorsally between
the heads of the
metacarpal bones,
they open into
the special dorsal
digital veins.
The special
dorsal digital veins,
two in each digit,
anastomose freely
together on the
dorsal aspects of
the digits. At the
proximal ends of
the interdigital
clefts they com-
municate, through
the intercapitular
veins, with the
special volar digi-
tal veins, and then
they unite to-
gether to form an
indefinite series of
dorsal metacarpal
veins which ter-
minate, a little
distal to the middle of the dorsurn of the hand, in a dorsal venous arch.
The Veins of the Forearm and Arm. The veins of the forearm emerge from the
dorsal venous arch and from the volar venous plexus, and they vary considerably
in number and in size. As a rule there are two main longitudinal channels, the
cephalic vein on the radial side and the basilic vein on the ulnar side. In some
cases there is an additional median vein on the volar aspect of the forearm.
The cephalic vein commences in the radial end of the dorsal venous arch,
receives the metacarpal veins of the thumb, turns round the radial margin of
FIG. 789. SUPERFICIAL VEINS ON THE DORSUM OF THE HAND AND DIGITS.
THE SUPEKFICIAL VEINS OF THE SUPEKIOK EXTEEMITY. 979
Subclavius
Cephalic v
Deltoid.
P.
the distal part of the forearm, and runs proxirnally, parallel with the volar border
of the brachioradialis muscle, to the cubital region. There, frequently much
reduced in size, it turns laterally and runs,
along the lateral border of the prominence
of the biceps, to the interval between the costo-coracoid membrane
deltoid and pectoralis major, along which
it ascends to the delto-pectoral triangle.
At the delto-pectoral triangle it turns
medially, between the pectoralis minor and
the pectoralis major, to the anterior aspect
of the costo-coracoid membrane, which
separates it from the front of the first part
of the axillary artery ; then, turning back-
wards, it pierces the costo-coracoid mem-
brane and ends in the axillary vein. In
a few cases instead of piercing the costo-
coracoid membrane it crosses the front of
the clavicle, deep to the platysma, pierces
the deep cervical fascia, and joins the lower
rt of the external jugular vein.
As it runs proxirnally, on the volar
aspect of the forearm, a number of tribut-
aries join its lateral border. Some of these
commence in the dorsal venous arch of the
hand and others in the superficial fascia of
the dorsal aspect of the forearm.
In the cubital region it is connected
ith the basilic vein by a large obliquely
ed anastomosing channel, the median
bital vein, which runs along the medial
rder of the distal part of the biceps pro-
inence, superficial to the lacertus fibrosus
hich separates it from the distal part of
.e brachial artery. In the delto-pectoral
ngle it is joined by tributaries which
rrespond with the acromial and pectoral
nches of the thoraco-acromial artery.
The median cubital vein not only con-
ts together the cephalic and basilic
ins but it receives also the profunda vein
which pierces the deep fascia and connects
it with the deep veins of the forearm, and
one or more superficial veins, of varying size
which pass, proxirnally, along the volar
aspect of the forearm.
In many cases the median cubital vein
is relatively very large, and in such cases
the more proximal part of the cephalic
vein, which lies in the arm, is a compara-
tively small vessel.
The basilic vein commences in the ulnar
end of the dorsal venous arch of the hand.
It runs along the dorsal aspect of the
forearm to the junction of the proximal
and middle thirds, where it turns round
the ulnar border of the forearm, and runs, anterior to the medial epicondyle of the
humerus, to the medial bicipital groove. At the middle of the arm, it pierces
the deep fascia. After piercing the fascia, it runs proxirnally, along the medial
border of the brachial artery, to the axilla, and there becomes the axillary vein.
790. SDPEKFICIAL VEINS ON THE FLEXOR
ASPECT OF THE UPPER EXTREMITY.
980
THE VASCULAR SYSTEM.
As it runs proximally, in the
the volar and dorsal aspects and,
Brachialis
muscle
Biceps muscle
Cephalic vein
Radial
recurrent artery
Lateral
cutaneous nerve
of forearm
Median cephalic
vein
Accessory
radial vein
Brachio-radialis
muscle
Radial arte
Median A r ei
of forearm
Cephalic vei
Fia. 791. SUPERFICIAL VEINS AT THE BEND OF THE ELBOW.
arm it is either the median cubital
which is opened.
forearm, it is joined by tributaries from both
in the cubital region, by the median cubital
vein which connects it
with the cephalic vein.
The Median Vein of
the Forearm. In a cer-
tain number of cases a
vein, which commences
in the palmar venous
plexus, runs along the
middle of the volar
aspect of the forearm to
the cubital region. It is
called the median vein
of the forearm. At the
bend of the elbow it
receives the profunda
vein and then divides
into two branches, the
median cephalic and the
median basilic veins
(Fig. 791). The median
* cephalic vein runs along
the lateral bicipital
sulcus and joins the
cephalic vein. The
median basilic passes
along the medial bi-
cipital sulcus and joins
the basilic vein. When
the median vein of the
forearm is present the
median cubital vein is
absent.
When venesection
is performed in the fore-
vein or, in its absence, the median basilic vein
silic vein
Medial
utaneous
nerve of forearm
-Basilic vein
Median nerve
Brachialis
muscle
Brachial
artery
edian basilic
vein
Lacertus
h'brosus
vein
Inar artery
Profunda
vein
Pronator teres
muscle
VENA CAVA INFERIOR AND ITS TRIBUTARIES.
The inferior vena cava (Fig. 792) is a large venous trunk which receives the
whole of the blood from the lower extremities, and the greater part of the blood
from the walls and contents of the abdomen and pelvis. It commences opposite
the right side of the body of the fifth lumbar vertebra, behind and to the right of
the right common iliac artery. It ascends through the abdomen, anterior and to the
right of the vertebral column and the right crus of the diaphragm, and it pierces
the cupola of the diaphragm, between the middle and right sections of the central
tendinous leaflet, at the level of the lower part of the eighth thoracic vertebra. It
then enters the middle mediastinum, pierces the fibrous pericardium, and terminates
in the lower and posterior part of the right atrium. Its intra-thoracic portion is
very short, and its intra-pericardial portion, which is still shorter, is covered
anteriorly and on its right and left sides by the parietal portion of the serous layer.
Attached to the inferior and anterior margin of its atrial orifice is the valve of
the inferior vena cava (Eustachian). This is a remnant of an important fold of
endocardium by which, in the foetus, the blood from the inferior vena cava is
directed, through the foramen ovale, into the left atrium.
Relations. The inferior vena cava is in relation, posteriorly, with the bodies of the
THE INFEKIOK VENA CAVA AND ITS TEIBUTAEIES.
981
lower lumbar vertebrae and the corresponding part of the anterior longitudinal ligament, the
anterior portion of the right -psoas major muscle, the right lumbar sympathetic trunk, the
roots of the right lumbar arteries, the right crus of the diaphragm, the right renal artery,
the right suprarenal artery, the right coeliac ganglion, the right inferior phrenic artery, and
the medial and upper portion of the right suprarenal gland.
Anterior to it, from below upwards, are the following structures the right common
iliac artery, the lower end of the mesentery and the superior mesenteric artery, the right
Hepatic veins
Inferior phrenic artery
Suprarenal gland
Inferior vena cava
Renal artery
Renal rein
Right ovarian vein
Ovarian artery
Ureter
Psoas major muscle
Ascending colon
Common iliac vein
Common iliac artery
Middle sacral artery
Ileum
Caecum
External iliac
artery
rnal iliac
vein
Middle um-
bilical liga-
ment (O.T.
urachus)
_(Esophagus
Crus of diaphragm
Inferior phrenic
artery
Suprarenal gland
Cceliac artery
Suprarenal vein
Superior
-mesenteric artery
nal artery
nal vein
Lumbar arteries
Left colic artery
Ovarian artery
Inferior mesenteric
ry
Descending colon
Psoas major muscle
Commou iliac artery
Sigmoid artery
Common iliac vein
Superior hsemor-
rhoidal artery
Iliac colon
Pelvic colon
External iliac
artery
External iliac vein
rterine tube
Uterus
FIG. 792. THE INFERIOR VENA CAVA AND ITS TRIBUTARIES.
internal spermatic artery and the third part of the duodenum, the head of the pancreas,
the portal vein and the first part of the duodenum, the foramen epiploicum, and the
posterior surface of the liver. More superficially are coils of small intestine, the great
omentum, and the transverse colon and mesocolon.
To its left side are the aorta and the right crus of the diaphragm.
On its right side, below, is the right ureter, whilst at a higher level the right kidney
is separated from the vein by a short interval only.
Tributaries. In addition to the two common iliac veins, by the union of which it is
formed, and through which it receives blood from the pelvis and from the lower extremi-
ties, the inferior vena cava receives the following tributaries : The hepatic veins, the
982 THE YASCULAE SYSTEM.
right inferior phrenic vein, the right suprarenal vein, the right and left renal veins, the
right internal spermatic vein, and the right and left lumbar veins.
Venae Hepaticae (Fig. 792). The hepatic veins convey blood which has
passed through the liver from the portal veins and from the hepatic artery, and
they open into that portion of the inferior vena cava which lies immediately below
the diaphragm, and behind the right lobe of the liver. They form two groups, an
upper group of two or three large trunks, and a lower group of smaller veins.
The upper group occasionally consists of only two veins, a right and a left ;
more frequently there are three vessels, a right, a left, and a middle vein, and in
the latter case the middle vein issues from the caudate lobe (Spigelian).
The veins of the lower group vary in number from six to twenty ; they return
blood from the right and caudate lobes.
The hepatic veins commence in the interiors of the lobules of the liver as
central veins ; the central veins issue from the upper and posterior aspects of the
lobules, and unite together to form interlobular veins ; and the interlobular veins
unite with one another, as they converge towards the posterior surface of the liver,
to form the larger hepatic veins.
Venae Phrenicae Inferiores. The inferior phrenic veins are formed by
tributaries which issue from the substance of the diaphragm. The right inferior
phrenic vein terminates in the upper part of the inferior vena cava. The left
vein passes posterior to the oesophagus, and usually terminates in the left supra-
renal vein.
Venae Suprarenales. A single suprarenal vein issues from the hilum on the
anterior surface of each suprarenal gland ; the right vein terminates in the inferior
vena cava ; the left usually ends in the left renal vein, but sometimes it opens
directly into the inferior vena cava.
Venae Renales. Each renal vein is formed by the union of five or six tribu-
taries which issue from the hiluin of the kidney, where they lie anterior to or are
intermingled with the corresponding arteries.
The right renal vein is about 25 mm. (one inch long) ; it passes posterior to
the descending part of the duodenum, and terminates in the right side of the
inferior vena cava.
The left renal vein is about 75 mm. long. It crosses anterior to the left psoas
major, the left crus of the diaphragm, and the aorta immediately below the superior
mesenteric artery. It lies behind the pancreas and the ascending part of the
duodenum, and, running above the transverse part of the duodenum, terminates in
the left side of the inferior vena cava. The left testicular or ovarian vein, accord-
ing to the sex, and almost invariably the left suprarenal vein, open into it.
Venae Lumbales. There are usually four lumbar veins on each side, one
with each lumbar artery; the vein with the subcostal artery is not included
in this number. By their anterior and posterior branches the lumbar veins
drain the lateral and posterior walls of the abdomen. The anterior branches
commence in the lateral walls of the abdomen, where they communicate with the
superior and inferior epigastric veins. The posterior divisions issue from the
muscles of the back, in the lumbar region, and receive tributaries from the spinal
plexuses. The main stems pass forwards on the bodies of the vertebrae ; on each
side they run postero-medial to the psoas major muscle, whilst those of the
left side also pass posterior to the aorta. They terminate in the posterior part of
the inferior vena cava. Not uncommonly the corresponding veins of opposite sides
unite together to form a single trunk which enters the back of the inferior vena
cava. All the lumbar veins, of each side, are united together by a longitudinal
anastomosing vessel, the ascending lumbar vein.
The Ascending Lumbar Vein. Each ascending lumbar vein passes upwards,
between the psoas major and the roots of the transverse processes of the lumbar
vertebrae. It commences in the lateral sacral vein of the same side, anastomoses
with the ilio-lumbar vein, connects the lumbar veins together, receives tributaries
from the anterior external vertebral plexus and anastomoses with the inferior vena
cava and the renal vein. The right ascending lumbar vein terminates in the
azygos and the left in the hemiazygos vein.
THE COMMON ILIAC VEINS. 983
Venae Testiculares. The testicular veins, on each side, issue from the testis
and epididymis and form a plexus, the pampiniform plexus. The plexus is one
of the constituents of the spermatic cord, and consists of from eight to ten veins,
most of which lie anterior to the ductus deferens ; it passes upwards through the
scrotum and inguinal canal, and, near the abdominal inguinal ring, terminates in
two main trunks which ascend, with the corresponding testicular artery, for some
distance, receiving tributaries from the ureter; ultimately the two veins unite
together and a single terminal vein is formed. The terminal testicular vein on
the right side opens into the inferior vena cava, that on the left side into the left
renal vein. The left testicular vein is longer than the right, the left testis being
lower than the right, and the termination in the left renal vein being at a higher
level than the termination of the right vein in the inferior vena cava. The
testicular veins, on each side, lie anterior to the psoas major muscle and the ureter.
They are covered by peritoneum, and they are crossed on the right side by the
termination of the ileum and the third part of the duodenum, and on the left side
by the iliac colon and the lower part of the pancreas. They are provided with
valves, one of which usually lies at the terminations of each vein, but, occasionally,
the valve at the orifice of the left testicular vein is absent.
Vense Ovaricae. The ovarian veins, on each side, issue from the hilum in the
anterior border of the ovary. They pass between the layers of the broad Ligament,
where they anastomose freely and form the pampiniform plexus, which extends,
laterally, towards the upper margin of the pelvis minor. From the plexus two
veins issue which accompany the corresponding ovarian artery ; they pass anterior
to the external iliac artery, and then upwards, behind the peritoneum and anterior
to the psoas major muscle and ureter. The veins of the right side, like the corre-
sponding testicular veins, also pass behind the termination of the ileum and the
third part of the duodenum ; whilst the left veins, near the margin of the pelvis
minor, pass behind the commencement of the pelvic colon.
The two veins on each side ultimately fuse together to form a single terminal
vein which ends, on the right side in the inferior vena cava, and on the left side in
the left renal vein.
VEN.E ILIAC^E COMMUNES.
The common iliac veins (Figs. 777 and 792), right and left, are formed by the
union of the corresponding external iliac and hypogastric veins. Each commences
at the superior aperture of the pelvis minor, immediately posterior to the upper
part of the hypogastric artery of its own side, and both vessels pass upwards to
the right side of the body of the fifth lumbar vertebra, at the upper part of
which, posterior and lateral to the right common iliac artery, they unite together
to form the inferior vena cava.
The right common iliac vein is much shorter than the left ; it passes anterior
to the obturator nerve and the ilio-lumbar artery, and at first posterior and then
somewhat to the lateral side of the corresponding common iliac artery.
The left common iliac vein is much longer than the right, and is also placed
more obliquely. It passes upwards and to the right, anterior to the body of the fifth
lumbar vertebra, and the middle sacral artery. For some distance it runs along
the medial side of the left common iliac artery, and then passes posterior to the
right common iliac artery. It also passes posterior to the mesentery of the pelvic
colon and the superior hsemorrhoidal vessels.
Tributaries. Each common iliac vein receives the corresponding external iliac,
hypogastric and ilio-lumbar veins. The left common iliac vein receives, in addition,
the middle sacral vein.
The ilio-lumbar veins receive tributaries from the iliac fossa, from the lower parts of
the vertebral muscles, and from the vertebral canal. There is a single vein on each side
which accompanies the corresponding artery. It passes posterior to the psoas major
muscle and terminates in the corresponding common iliac vein.
Vena Sacralis Media. The venae comites of the middle sacral artery commence by
the union of tributaries which issue from the venous plexus in front of the sacrum,
63 a
984 THE VASCULAR SYSTEM.
through which they communicate with the lateral sacral veins and receive blood from the
interior of the sacral canal. They unite, above, into a single middle sacral vein, which
terminates in the left common iliac vein.
Vena Hypogastrica. The hypogastric vein (Fig. 777) is a short trunk formed
by the union of tributaries which correspond to all the branches of the hypogastric
artery, with the exception of the umbilical and the ilio-lumbar branches.
It commences at the upper border of the greater sciatic notch, and ascends to the
aperture of the pelvis minor ; there it unites with the external iliac vein to form the
common iliac vein. It lies immediately postero-medial to the hypogastric artery,
is crossed laterally by the obturator nerve, and is in relation medially, on the left
side with the pelvic colon, and on the right side with the lower part of the ileum.
Tributaries. The tributaries, which are numerous, are conveniently divisible into
extra-pelvic and intra-pelvic groups.
The extra-pelvic tributaries are all parietal, and include the obturator, internal
pudendal, inferior, and superior glutseal veins.
Obturator Vein. This vein is formed by the union of tributaries which issue from
the hip-joint and from the muscles of the proximal and medial part of the thigh. It
enters the pelvis minor through the obturator canal, runs backwards, along the lateral
wall of the pelvis minor, lying medial to the pelvic fascia, immediately below the corre-
sponding artery, and, passing between the hypogastric artery on the lateral side and the
ureter on the medial side, it terminates in the hypogastric vein.
Inferior Gluteal Veins (O.T. Sciatic). The vense comites of the inferior gluteal
artery commence in the subcutaneous tissues on the back of the thigh ; they ascend with
the artery, and pass into the buttock on the deep aspect of the glutseus maximus, where
they receive numerous tributaries from the surrounding muscles. Entering the pelvis,
through the greater sciatic foramen, they unite into a single vessel, which terminates in
the lower and anterior part of the hypogastric vein below the termination of the obturator
vein.
Superior Gluteal Veins (O.T. Glutseal). The vense comites of the superior gluteal
artery are formed by tributaries which issue from the muscles of the buttock. They
accompany the artery through the greater sciatic foramen, and terminate in the hypogastric
vein ; they frequently unite together before reaching their termination.
Internal Pudendal Veins. The venae comites of the internal pudendal artery commence
by tributaries which emerge from the pudendal plexus, which lies below and posterior to
the arcuate ligament of the pubis and constitutes the anterior part of the prostatic plexus.
They receive blood from the corpus cavernosum penis, or the corpus cavernosum clitoridis,
by the deep vein of the penis or clitoris. They follow the course of the internal
pudendal artery, and usually join together into a single vessel (the internal pudendal
vein) which terminates in the hypogastric vein. They receive as tributaries the veins
from the bulb, the perineal and inferior hsemorrhoidal veins, and veins from the muscles
of the buttock.
The inferior hsemorrhoidal veins, which commence in the substance of the external
sphincter of the anus and in the walls of the anal canal, anastomose with the middle and
superior hsemorrhoidal veins, and consequently connect the lowest parts of the portal and
vena caval systems together.
The intra-pelvic tributaries of the internal iliac vein are either (a) parietal or
(b) visceral; the former comprises the lateral sacral veins, the latter includes the
efferent vessels from the plexuses around the several pelvic viscera.
(a) Parietal : Lateral sacral veins accompany the lateral sacral arteries, and
terminate on each side in the postero-medial wall of the corresponding hypogastric vein.
(b) Visceral tributaries are derived from the rectum and from the plexuses associated
with the uterus, vagina, bladder, and prostate. They include the middle hsemorrhoidal,
the uterine, the vaginal, and the vesical veins.
The middle hsemorrhoidal veins are very irregular; sometimes they cannot be
distinguished. When present they are formed by tributaries which commence in the
submucous tissue of the rectum, where they communicate with the 'superior and inferior
hsemorrhoidal veins in the hsemorrhoidal plexus ; they pass through the muscular coat,
and fuse together to form two middle hsemorrhoidal veins, right and left, each of which
runs laterally, beneath the peritoneum, on the upper surface of the levator ani, to
terminate in the corresponding hypogastric vein. In the male each middle hsemorrhoidal
vein receives tributaries from the seminal vesicle and ductus deferens of its own side.
THE VEINS OF THE LOWEK EXTEEMITY. 985
Uterine Plexuses and Veins. The uterine plexuses lie along the borders of the
uterus; they receive tributaries, which are entirely devoid of valves, from the uterus;
and they communicate above with the ovarian, and below with the vaginal plexuses.
The uterine veins, usually two on each side, issue from the lower parts of the uterine
plexuses, above their communications with the vaginal plexuses. At first the uterine
veins, on each side, lies in the medial part of the base of the broad ligament, above the
lateral fornix of the vagina and the ureter ; then they pass backwards, accompanying the
corresponding artery, in a fold of peritoneum which lies between the back of the broad
ligament and the recto-uterine fold ; finally they ascend in the floor of the ovarian fossa,
and terminate in the corresponding hypogastric vein.
Vaginal Plexuses and Vaginal Veins. The vaginal plexuses lie at the sides
of the vagina. They receive tributaries from the walls of the vagina, and communicate
with the uterine plexuses above, and with the veins of the bulb below ; anteriorly, with the
vesical plexus ; and posteriorly with the veins which issue -from the middle and lower parts
of the ha3morrhoidal plexus. A single vaginal vein issues from the upper part of the
vaginal plexus on each side ; it accompanies the corresponding artery, and terminates
in the hypogastric vein.
Superior Vesical Plexus. The superior vesical plexus of veins lies on the outer
surface of the muscular coat of the bladder, at the fundus and the sides. It receives
tributaries from the mucous and muscular walls, and its efferent vessels terminate in the
prostatico- vesical plexus in the male, and in the inferior vesical plexus in the female.
Prostatico-vesical Plexus. This plexus is distributed around the prostate and the
neck of the bladder, and is enclosed between the proper fibrous capsule of the prostate
and its sheath of recto-vesical fascia. Anteriorly it is continuous with the pudendal
plexus which receives the dorsal vein of the penis ; postero-superiorly it communicates
with the superior vesical plexus, and receives tributaries from the seminal vesicles and
deferent ducts. One or more efferent vessels pass from it on each side and open into
the corresponding hypogastric vein.
The inferior vesical plexus of the female, which represents the prostatico-vesical
plexus of the male, surrounds the upper part of the urethra and the neck of tlie bladder.
It is continuous with the pudendal plexus which receives the dorsal vein of the clitoris,
and its efferent vessels terminate in the hypogastric vein.
Dorsal Veins of the Penis. There are two dorsal veins of the penis the
superficial and the deep.
The superficial dorsal vein receives tributaries from the prepuce, and runs backwards,
immediately beneath the skin, to the symphysis, where it divides into two branches which
terminate in the superficial external pudendal veins.
The deep dorsal vein lies on the dorsum of the penis, deep to the deep fascia. It
commences in the sulcus behind the glans, by the union of numerous tributaries from
the glans and the anterior parts of the corpora cavernosa penis ; and it runs backwards in
the mid-dorsal line, in the sulcus between the corpora cavernosa penis from which it
receives many additional tributaries. At the root of the penis the vein passes between the
two layers of the suspensory ligament, and then between the arcuate ligament and the
deep transverse ligament of the perineum, where it lies above the membranous part of
the urethra. It terminates by dividing into two branches which join the pudendal plexus.
The dorsal vein of the clitoris in the female has a similar course to that of the deep
dorsal vein of the penis in the male. It terminates in the pudendal plexus.
The veins of the inferior extremity, like those of the superior extremity, are
arranged in two groups, the superficial and the deep ; and in the lower as in the
upper limb the deep veins are associated with the arteries as venae comites, whilst
the trunks of the superficial veins, which lie, at first, in the subcutaneous tissues
ultimately terminate in the deep veins. There is, therefore, a general similarity in
the arrangement of the veins of the upper and the lower limbs, but there are
differences in the details of the arrangement which are of some importance. Thus,
in the superior extremity, there are two deep veins with each artery from the
fingers to the root of the limb, where a single trunk, the axillary vein, is formed ;
but in the inferior extremity each main artery has two venae comites only as far as
the middle of the limb, where a single trunk is frequently formed. That vessel,
the popliteal vein, is the commencement of the main venous stem of the lower
THE VEINS OF THE INFERIOR EXTREMITY.
986 THE VASCULAK SYSTEM.
extremity ; it is continued proximally, through the thigh, as the femoral vein, and
along the upper margin of the pelvis minor as the external iliac vein, which
terminates by uniting with the hypogastric vein to form the common iliac vein.
Further, the superficial veins of the upper limb are more numerous than those
of the lower limb, for in the arm there are two main superficial veins, and in the
thigh only one.
In the upper limb the blood which passes through the superficial veins is poured
into the efferent trunk vein at the root of the limb that is, into the axillary vein ;
but in the lower limb the blood from the superficies of the lateral parts of the leg
and foot passes into the commencement of the main efferent vein, the popliteal
vein, at the middle of the limb that is, in the region of the knee, whilst the
blood from the superficial parts of the medial aspect of the lower limb is poured
into the femoral vein near the root of the limb in the upper part of the femoral
trigone.
In addition to the above-mentioned differences in the general arrangement of the
veins of the superior and the inferior extremities, it must be noted also that in the
superior extremity all the blood of the limb, both that from the shoulder-girdle region
as well as that from the free portion of the limb, is returned to the main efferent
venous trunk ; but in the inferior extremity the greater part of the blood from
the region of the pelvic girdle, and a considerable portion from that of the thigh, is
returned by the glutseal, obturator, and pudenda! veins to the hypogastric vein,
which is not the main efferent vein of the inferior extremity.
THE DEEP VEINS OF THE INFERIOR EXTREMITY.
All the arteries of the lower limb, except the popliteal and femoral trunks, are
accompanied by two vence comites. They usually lie one on each side of the
artery ; they are connected with one another by transverse channels which pass
across the line of the artery, and they are provided with numerous valves.
Vena Poplitea. The popliteal vein (Figs. 776, 780, 781) is formed, at the
distal border of the popliteus muscle, by the union of the venae comites of the
anterior and posterior tibial arteries. At its commencement it lies to the medial
side of and somewhat superficial to the popliteal artery, and to the lateral side
of the tibial (O.T. internal popliteal) nerve. As it runs through the popliteal
fossa it inclines towards the lateral side of the artery, and in the middle of the
space it is directly posterior to the artery, separating the artery from the tibial
nerve, which is still more posterior, whilst at the proximal end of the space it is to
the lateral side of the artery, and still between it and the tibial nerve. It then
passes through the adductor magnus muscle and becomes the femoral vein.
The popliteal vein, which is provided with two or three bicuspid valves, is closely
bound to the artery by a dense fascial sheath. Not uncommonly there are one or
more additional satellite veins which anastomose with the popliteal vein, and in
those cases the artery is more or less completely surrounded by venous trunks.
Tributaries. In addition to the vense comites of the anterior and posterior tibial
arteries, it receives tributaries which correspond with the branches of the popliteal artery,
and it also receives one of the superficial veins of the leg, viz., the small saphenous vein.
Vena Femoralis. The femoral vein is the direct continuation of the popliteal
vein. It commences at the junction of the middle and distal thirds of the thigh,
at the opening in the adductor magnus muscle. It then ascends, through adductor
canal (Hunter's), and through the femoral trigone, and terminates, a little to the
medial side of the middle of the inguinal ligament (Poupart's), by becoming the
external iliac vein.
In the adductor canal it lies at first postero-lateral to the femoral artery, and
anterior to the adductors .magnus and longus which separate it from the profunda
vessels. In the distal part of femoral trigone it is postero-medial to the artery,
and immediately anterior to the profunda vein which separates it from the
profunda artery, but in the proximal part of the femoral trigone it is directly on
the medial side of the femoral artery. About 37 mm. (one and a half inches) below
THE DEEP VEINS OF THE LOWEE EXTKEMITY.
987
the inguinal ligament it enters the middle compartment of the femoral sheath,
through which it ascends to its termination, lying between the compartment for
the femoral artery on the lateral side and the femoral canal on the medial side.
It usually contains two bicuspid valves one near its termination and the
other just proximal to the entrance of its profunda tributary.
Tributaries. It receives tributaries which correspond with the branches of the
femoral artery and the larger of the two superficial veins of the lower extremity, viz., the
great saphenous vein, which enters the femoral vein where that vessel lies in the middle
Femoral artery
Femoral vein
Femoral canal
Superficial ex-
ternal pudendal
artery
Deep external pudendal
artery
enons vein
Adductor longus
racilis
FIG. 793. THE FEMORAL VESSELS IN THE FEMORAL TRIGONE.
compartment of the femoral sheath, and, not uncommonly, it is joined by the medial and
lateral circumflex veins.
Vena Iliaca Externa. The external iliac vein (Figs. 773, 774, and 777) is the
upward continuation of the femoral vein. It commences, on the medial side of the
termination of the external iliac artery, immediately posterior to the inguinal
ligament, and ascends, along the aperture of the pelvis minor, to a point opposite the
sacro-iliac joint, and at the level of the lumbo-sacral articulation, where it ends,
immediately behind the hypogastric artery, by joining the hypogastric vein to
form the common iliac vein. It lies, at first, on the medial side of the external
liac artery, but on a somewhat posterior plane, and then directly posterior to the
artery, whilst just before its termination it crosses the lateral side of the hypo-
988
THE VASCULAR SYSTEM.
gastric artery, and separates that vessel from the medial border of the psoas
major muscle. In its whole course the vein lies anterior to the obturator nerve.
It is usually provided with one bicuspid valve; sometimes there are two, but both
are usually incompetent. Its tributaries
correspond to the branches of the ex-
ternal iliac artery; that is, the deep
circumflex iliac and inferior epigastric
veins open into it, close to its com-
mencement, whilst, in addition, it fre-
quently receives the pubic vein.
The pubic vein forms a communica-
tion between the obturator vein and the
external iliac vein. It varies in size,
and may form the main termination of
the obturator vein, from which it arises.
Commencing in the obturator canal,
it ascends, along the pubic branch of
the inferior epigastric artery, to reach
the external iliac vein.
Superficial epigastric i
Superficial circumflex
,T iliac vein
Superficial external
pudendal vein
Femoral vein
Great saphenous vein
Lateral superficial
femoral vein
Medial superficial
femoral vein
Great saphenous vein
THE SUPEKFICIAL VEINS OF THE
INFEKIOK EXTREMITY.
The superficial veins of the lower
limb terminate in two trunks, one of
which, the small saphenous vein, passes
from the foot to the popliteal space;
whilst the other, the great saphenous vein,
extends from the foot to the groin.
The superficial veins of the sole of
the foot form a fine plexus, immediately
under cover of the skin, from which
anterior, medial, and lateral efferents
pass. The anterior efferents terminate
in a transverse arch which lies in the
furrow at the roots of the toes, and the
medial and lateral efferents pass round
the sides of the foot to the great or small
saphenous veins. The transverse arch
receives also small plantar digital veins
from the toes, and it communicates by
intercapitular veins with the veins on the
dorsum of the foot.
The superficial veins on the dorsal
aspect of each toe unite to form two
dorsal special digital veins, which run
along the borders of the dorsal surface.
The special dorsal digital veins of the
adjacent borders of the interdigital clefts
unite, at the apices of the clefts, to form
four dorsal me ta tar sal veins which ter-
minate in the dorsal venous arch. The
dorsal digital vein from the medial side of
the great toe ends in the great, and that
from the lateral side of the little toe in the small saphenous vein.
Arcus Venosus Dorsalis Pedis. The dorsal venous arch lies in the subcutaneous
tissue, between the skin and the dorsal digital branches of the superficial peronseal
nerve, opposite the anterior parts of the bodies of the metatarsal bones. It ends,
medially, by uniting with the medial dorsal digital vein of the great toe to form
Great saphenous vein
Dorsal venous arch
FIG. 794. THE GREAT SAPHENOUS VEIN AND ITS
TRIBUTARIES.
THE SUPEEFICIAL VEINS OF THE INFEBIOK EXTKEMITY. 989
the great saphenous vein, and laterally by joining the lateral dorsal digital vein
of the little toe to form the small saphenous vein. The dorsal venous arch
receives the dorsal metatarsal veins ; interdigital efferents from the plantar trans-
verse arch ; and numerous tributaries from the dorsum of the foot, which anastomose
freely together forming a wide-meshed dorsal venous plexus, open into it posteriorly.
Vena Saphena Magna. The great saphenous vein is formed by the union of
the medial extremity of the dorsal venous
arch with the medial dorsal digital vein of
the great toe. It passes anterior to the
medial malleolus, crosses the medial surface
of the distal third of the body of the tibia,
and ascends, immediately posterior to the
medial margin of the tibia, to the knee,
where it lies just posterior to the medial
condyle of the femur; continuing proxirually,
with an inclination forwards and laterally, it
gains the proximal part of the femoral tri-
gone, where it perforates the fascia cribrosa
and the femoral sheath to reach its termina-
tion in the femoral vein. In the foot and
leg it is accompanied by the saphenous nerve,
and for a short distance distal to the knee
by the superficial or saphenous branch of the
arteria genu suprema. In the thigh, branches
of the medial cutaneous nerve (O.T. internal)
lie in close relation with it. It contains from
eight to twenty bicuspid valves.
Tributaries. It communicates freely,
through the deep fascia, with the deep inter-
muscular veins. In the foot, it receives tribu-
taries from the medial part of the sole and from
the dorsal venous plexus. In the leg it is joined
by tributaries from the dorsum of the foot, the
medial and posterior parts of the heel, the front
of the leg and the back of the calf, and it anasto-
moses freely with the small saphenous vein. In
the thigh it receives numerous tributaries, and
amongst them are two superficial femoral veins.
Of these, the lateral ascends from the lateral
side of the knee and terminates in the great
saphenous vein at the distal part of the femoral
trigone ; the other, the medial, ascends from the
posterior aspect of the thigh, along its medial
side, and terminates in the great saphenous vein
near the fossa ovalis. In many cases the medial
superficial femoral vein communicates distally
with the small saphenous vein, and when that
condition exists the medial superficial femoral vein is called the accessory saphenous
vein. The last tributaries to enter the great saphenous vein are the superficial circumflex
iliac, superficial epigastric, and superficial external pudendal veins. They accompany
the corresponding arteries, and terminate in the great saphenous vein immediately
before it perforates the fascia cribrosa.
The superficial circumflex iliac vein receives blood from the lower and lateral part
of the abdominal wall and the proximal and lateral parts of the thigh. The superficial
epigastric vein drains the lower and medial part of the abdominal wall, and the superficial
external pudendal vein receives blood from the dorsum of the penis and the scrotum in
the male, and from the labium majus in the female.
Vena Saphena Parva. The small saphenous vein is formed by the union of
the lateral extremity of the dorsal venous arch with the lateral dorsal digital vein
FIG. 795. THE SMALL SAPHENOUS VEIN
AND ITS TRIBUTARIES.
990 THE VASCULAE SYSTEM.
of the little toe. At first it passes posteriorly, along the lateral side of the foot
and distal to the lateral malleolus, lying on the peronseal retinacula (O.T. ext. ann.
lig.), in company with the nervus suralis ; then it passes posterior to the lateral
malleolus, and along the lateral border of the tendo calcaneus, still in company
with the nervus suralis, to the middle of the calf, proximal to which it is continued
in the superficial fascia, accompanied by the superficial sural artery, to the distal
part of the popliteal fossa, where it pierces the deep fascia, and terminates in the
popliteal vein. It communicates, round the medial side of the leg, with the great
saphenous vein, and through the deep fascia with the deep veins, and it contains
from six to twelve bicuspid valves.
Tributaries. It receives tributaries from the lateral side of the foot, the lateral
side and back of the heel, the back of the leg, and, occasionally, a descending tributary
from the back of the thigh. Just before it pierces the popliteal fascia it frequently gives
off a small branch which ascends round the medial side of the thigh and unites with the
medial superficial femoral vein to form the accessory saphenous vein. In that way a
communication is established between the great and small saphenous veins, which may
become enlarged, and constitute the main continuation of the small saphenous vein.
THE POKTAL SYSTEM.
The veins which form the portal system are the portal, the superior and
inferior mesenteric and the splenic veins and their tributaries. They convey blood
to the liver (1) from almost the whole of the abdominal and pelvic parts of the
alimentary canal, (2) from the pancreas, and (3) from the spleen. The tributaries
of origin correspond closely with the terminal branches of the splenic, and the
superior and inferior mesenteric arteries, after which they are named and which
they accompany for a considerable distance. The larger or terminal vein.s, how-
ever, leave their associated arteries ; the inferior mesenteric vein joins the splenic
vein, and the latter unites with the superior mesenteric vein to form the portal vein,
which passes to the liver. AD the larger vessels of this system are devoid of
valves, but valves are present in the tributaries.
Vena Portse. The portal vein is a wide venous channel, about 75 mm. (three
inches) long, which conveys blood from the stomach, from the whole of the intestine,
except the terminal portion of the rectum, and from the spleen and pancreas to
the liver. Unlike other veins, it ends, like an artery, by breaking up into branches
which ultimately terminate in capillaries in the substance of the liver ; from the
capillaries, which also receive the blood conveyed to the liver by the hepatic artery,
the hepatic veins arise ; and, as the hepatic veins open into the inferior vena
cava, the portal blood ultimately reaches the general systemic circulation.
The portal vein commences by the union of the superior mesenteric and the
splenic veins, posterior and to the left of the neck of the pancreas, and either
anterior to the left border of the inferior vena cava, at the level of the body of the
second lumbar vertebra, or in front of the upturned extremity of the processus
uncinatus of the head of the pancreas. It ascends, anterior to the inferior vena
cava and posterior to the neck of the pancreas and the first part of the duodenum,
to the lower border of the epiploic foramen (Winslow), where it passes forwards, in
the right gastro-pancreatic fold of peritoneum, and enters the lower border of
the gastro-hepatic ligament. Continuing its upward course, it lies posterior to
the bile-duct and hepatic artery, and anterior to the epiploic foramen (Winslow) ;
it ultimately reaches the right end of the porta hepatis, where it ends by dividing
into a short and wide right and a longer and narrower left branch. Just before
its termination it enlarges, forming the sinus of the portal vein.
The right branch generally receives the cystic vein and then enters the right lobe
of the liver, in which it breaks up into numerous branches which terminate in the
portal capillaries around the periphery and in the substance of the liver lobules.
The left branch runs from right to left, along the porta hepatis, giving off
branches to the caudate and quadrate lobes ; it crosses the umbilical fossa, and
ends in the same manner as the right branch, but in the substance of the left
lobe of the liver.
THE PORTAL SYSTEM OF VEINS.
991
As it crosses the umbilical fossa, the left branch of the portal vein is joined,
anteriorly, by the round ligament of the liver and some small veins, and, posteriorly,
by the ligamentum venosum. The round ligament is a fibrous cord which passes
from the umbilicus to the left branch of the portal vein. It represents the
remains of the left umbilical vein of the foetus. The small veins which accompany
it connect the left branch of the portal vein with the superficial veins round the
umbilicus. The ligament venosum connects the left branch of the portal vein
with the upper part of the inferior vena cava. It is the remains of a foetal blood-
Lig. venosum
Vena cava inferior -
V. hepatis dextra
(systemic and portal blood)
Liver capillaries -
V. porta (ramus dextra)
V. cystica
V porta
V. pancreatico duodenal
V. mesenterica _
superior
V. colica media
V. colica dextra
V. hepatis sinistra (systemic and portal blood)
V. porta (ramus sinister)
Liver capillaries
Vv. oesophageae
V.coronaria
- ~ ventriculi
gastricse breves
v. lienales
V. gastroepi-
1 ploica sinistra .
V. lienalis
V. gastroepiploica dextra
- -V. mesenteric inferior
V. colica sinistra
_Lig. teres hepatis cum
vv. umbilicales
V. liypogastrica dextra ~
V. iliaca externn
V. htemorrhoidalis media"
V. hffimorrhoidalis inferior dextra__
Umbilicus
-Vv. jejunales
V. sigmoidea
V, iliaca communis
- .V. hsemorrhoidalis superior
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C-i
"bi)
1
1
1
1
1
5
1
'S
is
\
a
9
3
( r
Thyreo-cervi
Common lym
trunk from h
upper limb
Descending thoracic
lymphatic trunk
Descending thoracic
lymphatic trunk
Inferior phrenic
artery
Suprarenal-gland
Cceliac artery
Superior mesenterk-
artery
Common intestinal
lymphatic trunk
Renal artery
Renal vein
Thoracic duct
Cisterna chyli
Suprarenal gland
Inferior vena cava
Right renal artery
Left renal vein
Lumbar veins
ife i; , r^iiirrtn
Common lumbar
ymphatic trunks
FIG. 798. THE THORACIC DUCT AND ITS TRIBUTARIES.
the abdomen, as an elongated ovoid dilation the cisterna chyli which measures
6, to 8 mm. (| to J in.) in its broadest diameter, and from 50 to 75 mm. (2 to 3 in.)
in length. The cisterna chyli lies between the aorta and the lower part of
vena azygos, posterior to the right crus of the diaphragm, and opposite the f
and second lumbar vertebrae. Passing upwards from the cisterna, the thoracic
duct traverses the aortic opening of the diaphragm and enters the posterio
THE TERMINAL LYMPH VESSELS. 997
mediastinum, through which it ascends, lying anterior to the vertebral column and
to the right of the median plane, to the level of the fifth thoracic vertebra ; it then
crosses somewhat abruptly from the right to the left of the median plane, and
ascends through the superior mediastinum to the root of the neck, where it turns
laterally, between the vertebral and common carotid arteries, and it terminates, at
the medial border of the left scalenus anterior, by joining the left innominate vein
at its commencement.
Length and Diameter. The total length of the duct averages about 45 cm. (18
inches). It is dilated at both its origin and termination. As a rule it is narrowest
opposite the fifth thoracic vertebra, but its calibre is very variable, and sometimes
the thoracic portion is broken up into a series of anastomosing channels. The
widest portion of the tube is usually the cisterna, but occasionally that dilatation
is entirely absent. The duct is provided with several valves, formed by semilunar
folds of the tunica intima, arranged in pairs, and the most perfect of them is
situated at or near the orifice of communication with the left innominate vein.
Relations. In the abdomen the cisterna chyli lies anterior to the upper two lumbar
vertebrae and the corresponding lumbar arteries, between the aorta on the left and the
vena azygos and the right crus of the diaphragm on the right. In ike posterior
mediastinum the thoracic duct is separated from the vertebral column and the anterior
longitudinal ligament by the right aortic intercostal arteries and the transverse parts of
the hemiazygos and accessory hemiazygos veins ; it is covered, in front, in the lower part
of its extent by the right pleural sac, and in the upper part by the oesophagus ; to its
right is the vena azygos, and to its left the descending aorta. In the superior mediasti-
num it passes forwards from the vertebral column, and it is separated from the left
longus colli muscle by a mass of fatty tissue ; the oesophagus lies in front of it in that
region, but the left margin of the duct projects beyond the oesophagus, and is in relation
anteriorly, and from below upwards, with the termination of the arch of the aorta, the
left subclavian artery and the pleura. As the duct enters the root of the neck it passes
behind the left common carotid artery, whilst to its right and somewhat anterior is the
oesophagus, and the left pleura is still in association with its left border.
At the root of the neck it arches laterally above the apex of the pleura sac and the
first part of the left subclavian artery. It passes anterior to the vertebral artery and
vein, the roots of the inferior thyreoid, transverse cervical, and transverse scapular
arteries, the medial border of the scalenus anterior and the left phrenic nerve, and
posterior to the left carotid sheath and its contents.
Tributaries. -- The cisterna chyli commonly receives five tributaries. (1)
Truncus Intestinalis. The intestinal trunk, which is formed by the efferents of
mesenteric and upper pre-aortic glands, and which conveys lymph from the lower
and anterior part of the liver, the stomach, the small intestine, the spleen, and the
pancreas. (2) Two trunci lumbales, one on each side ; they are formed by the
efferents of the lumbar glands. They carry lymph from the lower extremities,
from the deep portions of the abdominal and pelvic walls, the large intestine and
the pelvic viscera, and from the kidneys, suprarenal glands, and genital glands.
(3) Two descending lymphatic trunks, one on each side, each of which is formed by
the efferent vessels from the corresponding lower intercostal glands ; these descend
to the cisterna through the aortic opening of the diaphragm. Occasionally they
unite to form a single trunk, and in others they, or the tributaries from which
they are usually formed, open directly into the thoracic duct (Figs. 797, 798).
In its course through the posterior mediastinum the thoracic duct receives
efferents from the upper and posterior part of the liver, and from the posterior
mediastinal and cesophageal glands ; the latter carry lymph from the oesophagus,
the pericardium, and the left side of the thoracic wall.
In the superior mediastinum the vessels which open into it are derived from
the upper left intercostal glands ; it receives lymph also from the heart and left
lung by efferents from the left peritracheo-bronchial glands and the intertracheo-
bronchial glands, but the efferents of those glands may unite with the internal
mammary lymphatic to form a common trunk which may open either into the
thoracic duct or into the innominate vein. In the superior mediastinum, there-
fore, it may receive lymph from the upper and median part of the abdominal wall,
646
998 THE VASCULAE SYSTEM.
the liver, the diaphragm, the wall of the thorax, and the mammary gland of the
left side, the thynius, the pericardium, the left lung, and the left part of the heart.
At the root of the neck, just before its termination, it receives the efferents
from the glands of the left superior extremity, which frequently unite to form a
subclavian trunk, and the left jugular trunk, which conveys the lymph from the
left side of the head and neck ; but either of those vessels or both of them may
end separately in the innominate vein.
Ductus Lymphaticus Dexter. The right lymph duct (Fig. 798) is not always
present. It is a short trunk, from 12 to 1*7 mm. (half to three-quarters of an
inch) in length, which lies at the right side of the root of the neck along the
medial border of the right scalenus anterior, and it is formed by the confluence of
(1) the right jugular trunk, (2) the right subclavian trunk, and (3) the right broncho-
mediastinal trunk, which carries lymph from the bronchial, the posterior, and the
anterior mediastinal and .tjie sternal glands. It thus receives lymph from the
right side of the head and neck, the right upper limb and the right side of the
trunk, including the upper part of the thoracic wall, the right lung and pleura,
the right half of the heart and pericardium, the right side of the diaphragm, and
the upper surface of the liver. As a rule, the right lymph duct is not present
as a definite stem, and the right jugular trunk carrying the lymph, from the head
and neck, the right subclavian trunk bearing lymph from the right upper ex-
tremity, and the right broncho-mediastinal trunk, end separately in the upper
part of the right innominate vein, but any two of the three main trunks of the
right side may unite together. The right broncho-mediastinal trunk frequently
communicates, below, with the thoracic duct.
LYMPH GLANDS OF HEAD AND NECK.
THE LYMPH GLANDS OF THE HEAD.
} All the lymph glands of the head are extracranial.
Lymphoglandulae Occipitales. The occipital lymph glands, two or three in
number, lie, in or deep to the deep fascia, upon the upper part of the trapezius
muscle, or, if the trapezius is small, upon the upper part of the semispinalis capitis
or on the splenius muscle. They receive afferent vessels from the occipital region of
the scalp and from the superficial parts of the upper and back portion of the neck.
Their efferents terminate in the deep cervical glands. Some of the lymph vessels
of the occipital region pass directly to the deep cervical glands (Fig. 799).
Lymphoglandulae Auriculares Posteriores. The posterior auricular lymph
glands (O.T. mastoid) lie on the upper part of the sterno-mastoid muscle and on
the mastoid portion of the temporal bone, and they are bound down by a sheathing
of deep cervical fascia. They receive afferent vessels from the posterior part of
the parietal region of the scalp, and from the medial surface of the auricle.
Their efferents join the superficial and the deep cervical glands (Fig. 799).
Lymphoglandulae Auriculares Anteriores. The anterior auricular lymph
glands (O.T. parotid) lie both superficial and deep to the parotid fascia on the
lateral surface of the parotid gland. They receive afferents from the frontal and
the temporal regions of the scalp, from the eyebrow, the upper and lower eyelids,
the upper part of the cheek, the root of the nose, and the lateral surface of the
auricle. Their efferents pass to the superficial and the upper deep cervical glands,
and to the parotid lymph glands (Fig. 799).
Lymphoglandulae Parotideae. The parotid lymph glands (O.T. deep parotid
glands) lie embedded in the deeper parts of the parotid gland. They receive afferents
from the external acoustic meatus, the tympanum, the soft palate, the posterior
part of the nose, and the deeper portions of the cheek. Their efferents open into
the upper deep cervical glands.
The Superficial Facial Lymph Glands. Several lymph glands, or groups of
lymph glands, have been found in the region of the face but, apparently, they are
irregular, both in occurrence and in position. Those which appear to be most
THE LYMPH GLANDS OF THE HEAD.
999
frequently found are : Infra-orbital, which lie along the angle between the nose and
the cheek, and below the -margin of the orbit. Their afferents are derived from the
surrounding parts ; and their efferents pass to the anterior auricular and the
submaxillary lymph glands. Buccinator lymph glands have been found on the
superficial surface of the anterior part of the buccinator, both anterior and pos-
terior to the anterior facial vein. Those posterior to the vein usually lie close
to the point where the parotid duct turns, medially, round the anterior border of
the masseter. They receive lymph from the eyelids and cheeks, and transmit it
Anterior auricular glands
Posterior auricular
glands
Occipital gland
An upper deep cervical gland
Upper deep cervical glands
of posterior croup
Submental glands
1 Submaxillary glands
An upper deep cervical gland
Superficial cervical glands
_ Inferior deep cervical glands
(supra-clavicular)
FIG. 799. LYMPH GLANDS OF THE HEAD AND NECK AS SEEN WHEN THE STERNO-MASTOID is IN ITS
USUAL POSITION. The occipital and the posterior and anterior auricular glands are inserted in accord-
ance \vith descriptions. The other glands were present in one or other of the two bodies from which
the drawing was made. Compare Fig. 801.
to the anterior auricular glands. Supra-mandibular lymph glands lie superficial to
the mandible at the anterior border of the masseter, between the anterior facial vein
and the external maxillary artery. They receive lymph from the region of the
lower lip, and transmit it to the anterior auricular and superficial cervical glands.
Lymphoglandulae Paciales Profundse, The deep facial -lymph glands are
very variable both in number and size ; they lie in association with the internal
maxillary artery on the external pterygoid muscle, or on the adjacent part of
the wall of the pharynx. Their afferent vessels are derived from the orbit,
the temporal fossa, the infra-temporal fossa, the palate, the nose, and the cerebral
meninges. Their efferent vessels open into the upper deep cervical glands.
Lymphoglandulae Linguales. The lingual lymph glands lie between the genio-
; glossi muscles and, on the lateral surfaces of the hyo-glossi and genio-glossi muscles,
1000 THE VASCULAE SYSTEM.
deep to the mylo-hyoid muscles; they are simply small lymph nodules interposed
in the course of the lymphatics which are passing from the tongue and, the floor
of the mouth to the deep cervical glands.
THE LYMPH GLANDS OF THE NECK.
Lymphoglandulae Cervicales Superficiales. The superficial cervical lymph
glands lie on or are embedded in the deep fascia along the course of the external
jugular vein, superficial to the sterno-mastoid (Fig. 799). They receive afferent
vessels from the superficial tissues of the neck, the posterior and anterior auricular,
and the submaxillary lymphatic glands. Their efferent vessels terminate in
the upper deep cervical glands and the supra-clavicular glands. The uppermost
superficial cervical glands are sometimes described as infra-auricular glands.
Lymphoglandulae Submaxillares. The submaxillary lymph glands vary in
number from three to six. They lie under cover of the deep fascia of the neck, in the
angle between the lower border of the mandible and the submaxillary gland, and the
largest of the series is usually situated near the point where the external maxillary
artery turns round the lower border of the mandible (Fig. 800). Occasionally some
smaller gland nodules are found on the deep surface of the submaxillary gland, but
these are comparatively rare. The afferent vessels of the submaxillary lymph glands
carry lymph from the side of the nose, the upper lip, the lateral part of the lower
lip, the anterior third of the border of the tongue, the gums, the submaxillary and
sublingual glands, and the adjacent parts of the floor of the mouth. The efferents
descend, over the superficial surface of the submaxillary gland, and terminate in
the upper deep cervical glands, more particularly in those in the immediate
neighbourhood of the termination of the common carotid artery.
Paramandibular Lymph Gland. This term is applied to one or more lymph glands
which lie inside the capsule of the submaxillary gland, in close relation with
the gland or embedded in its substance. They receive lymph from the gland
and the adjacent parts of the mouth and transmit it to the submaxillary and deep
cervical glands.
The Submental Lymph Glands lie below the chin, superficial to the mylo-hyoid
muscles and between the anterior bellies of the two digastric muscles. There are
usually two on each side, a medial or superior close to the median plane, and a.
lateral or inferior on the anterior border of the anterior belly of the digastric.
They are apt to become enlarged in diseased conditions of the middle part of the
lower lip, the adjacent part of the gums, the anterior part of the floor of the
mouth, the tip of the tongue, and the skin beneath the chin, for their afferent vessels
drain those parts. The efferents from this group of glands pass partly to the sub-
maxillary lymph glands, and partly to a deep cervical gland situated on the
superficial surface of the internal jugular vein at the level of the cricoid cartilage
(Figs. 799, 800, 801).
Lymphoglandulse Retropharyngeae. The retro-pharyngeal lymph glands lie
posterior to the upper part of the pharynx, embedded in the fascia covering the
superior constrictor muscle. They are separable into two groups, lateral and median
The lateral retro-pharyngeal glands, 1-3, appear to be constant both in children
and adults. Each lateral gland, or group of glands, lies at the level of the atlas
anterior to the upper part of the longus capitis, and posterior to the interna
carotid artery.
The median retro-pharyngeal glands, commonly present in children anc
frequently absent in adults, lie at the same level as the lateral glands, but in the
median plane. They are irregular in number and size.
The retro-pharyngeal lymph glands receive lymph from the adjacent muscles
and bones, from the nasal part of the pharynx, from the auditory tube anc
tympanum, and from the posterior parts of the nasal cavities. Their efferents pass
to the medial and the lateral deep cervical glands.
Lymphoglandulae Cervicales Anteriores. The lymph glands of the anterior
part of the neck are separable into two groups, superficial and deep.
The superficial anterior cervical lymph glands are very irregular in number anc
THE LYMPH GLANDS OF THE NECK.
1001
size. When they are present they lie in association with the anterior jugular veins.
The exact origin of their afferents and the terminations of their efferents are
unknown, but it is probable that they receive lymph from the superficial tissues of
the anterior parts of the neck, and transmit it to the lower deep cervical glands.
The deep anterior cervical lymph glands are
(a) Infra-hyoid glands, which lie anterior to the hyo-thyreoid membrane.
They receive lymph from the region of the epiglottis and transmit it to the deep
cervical glands. They are not constantly present.
(&) The prelaryngeal gland, which lies either anterior to the cricoid cartilage
or to the crico-thyreoid ligament. Its occurrence is very constant. It receives
Submaxillary glands
Submental gland
Anterior facial vein
Medial superior deep
cervical glands *
Sterno-mastoid, cut -
Superior thyreoid artery . _
Medial superior deep .
cervical glands IV
Internal jugular vein -r
A lateral superior deep
cervical gland
External jugular vrii
Medial superior deep
cervical gland ~~W
Part of brachial plexus ,.*
Prelaryngeal glands .
Omo-hyoid
Common carotid
Supra-clavicular
or inferior deep
cervical glands
jrno-mastoid muscle
Paratracheal glands
FIG. 800. LYMPH GLANDS OF THE NECK SEEN FROM THE FRONT.
Infra-hyoid glands and pretracheal glands were not present.
iph from the anterior part of the larynx and from the isthmus and the adjacent
of the right and left lobes of the thyreoid gland. Its efferents terminate
in the deep cervical and the pretracheal glands.
(c) The pretracheal lymph glands are numerous small nodules which lie along
the inferior thyreoid veins. They receive lymph from the trachea, the lower part of
the larynx, and from the lobes and the isthmus of the thyreoid gland ; and they
transmit it to the lower deep cervical glands.
(d) The paratracheal lymph glands lie along the sulcus between the larynx and
the trachea, anteriorly, and the pharynx and oesophagus, posteriorly, in association
with the branches of the superior and inferior thyreoid arteries and the recurrent
nerves. They receive lymph from the adjacent parts and transmit it to the deep
cervical glands (Fig. 800).
1002
THE VASCULAE SYSTEM.
Lymphoglandulae Cervicales Profundse Superiores et Inferiores. The deep
cervical lymph glands lie in the anterior and posterior triangles of the' neck and
under cover of the sterno-mastoid muscle. They form a more or less continuous
sheet of gland nodules and inter-communicating lymph vessels ; but the glands are
divided into two main groupsj the (a) superior, and (&) inferior, and each group is
separable into (1) medial, and (2) lateral components.
(a) The Superior Deep Cervical Lymph Glands. (1) The medial group of upper
deep cervical lymph glands lies on the superficial surface of the internal jugular
vein and in the carotid triangle of the neck. One of the largest, which is closely
associated with the tongue, lips, gums, cheeks, and the outer part of the nose, is
Anterior auricular glands
Posterior auricular J
glands
Occipital glands"
A superficial cervical gland"
Superior deep cervical glands,
lateral and medial
Superior deep cervical glands
Lateral inferior deep
cervical glands
(supra-clavicular)
\ x Submental glands
v , \Submaxillary glands
\Cut end of external
jugular vein
Common facial vein
Medial superior deep
lan
-Medial inferior deep cervical gland
Sterno-mastoid
FIG. 801. LYMPH GLANDS OF THE HEAD AND NECK AS SEEN AFTER THE REMOVAL OF THE STERNO-
MASTOID MUSCLE. The anterior and posterior auricular and the occipital glands are inserted in
accordance with descriptions. The other glands were present in one or other or in both the bodies from
which the figure was made. Compare Fig. 799.
frequently situated in the region of the union of the common facial vein with the
internal jugular vein. The lowest gland of the group lies on the lateral surface of
the internal jugular vein immediately above the omo-hyoid muscle ; it receives a
communication from the submental glands. The highest members of the group
may be under cover of the postero-medial surface of the parotid gland, in associa-
tion with the posterior belly of the digastric muscle. (2) The members of the
lateral group of superior deep cervical lymph glands lie under cover of the posterior
part of the upper portion of the sterno-mastoid, and in the upper part of the
posterior triangle of the neck. They are embedded in the fat-laden fascia which
covers the roots of the cervical plexus and the upper part of the brachial plexus,
THE LYMPH VESSELS OF HEAD AND NECK. 1003
and the levator scapulae and the scalene muscles, and several of them are in close
relation with the accessory, nerve (Fig. 801).
The superior deep cervical glands are connected by afferent vessels with the
various groups of glands which lie in the regions of the pharynx, the face, and the
upper part of the neck. They receive lymph, therefore, from the nose, the mouth,
the tongue, the upper parts of the pharynx and .larynx, the tonsil, the upper part
of the thyreoid gland, the submaxillary, sublingual, and parotid salivary glands, and
from the .interior of the cranium. Their efferents pass either to the inferior deep
cervical glands or to the jugular lymph trunk. In some cases the medial and
lateral members of the superior group are connected with the corresponding
members of the lower group only, but in other cases the medial or lateral
members of the superior group may be connected with both the medial and the
lateral members of the inferior glands.
The inferior deep cervical lymph glands (Figs. 800, 801), which are also termed
the supra-clavicular glands, are situated below the level of the omo-hyoid muscle.
(1) The members of the medial group lie in relation with the lower part of the
internal jugular vein, opposite the interval between the sternal and the clavicular
heads of the sterno-mastoid. They receive afferents from the members of the
upper medial group and from the pretracheal and the paratraeheal glands and from
the upper part of the thorax. Their efferents unite with some of the efferents of the
upper medial group and pass with them to the jugular lymph trunk.
(2) The members of the lateral group of inferior deep cervical glands lie in
the subclavian triangle, in the fatty tissue superficial to the lower part of the
brachial plexus and the third part of the subclavian artery. They receive lymph
from the lower parts of the neck, from the upper part of the thorax, and from
the upper lateral glands. They receive lymph also from the deep parts of the
mammary gland, and they are in communication with the axillary glands. Their
efferents join the jugular lymphatic trunk.
THE LYMPH VESSELS OF THE HEAD AND NECK.
The lymph vessels of the head and neck may be separated into two groups, intracranial and
extracranial.
Intracranial Lymph Vessels and Lymph Spaces. The cerebro-spinal fluid which fills the
ventricles of the brain, the central canal of the spinal medulla, and the subarachnoid and
subdural spaces, differs in chemical constitution from true lymph; nevertheless it plays the
part of lymph, to some extent, and there can be little doubt that some of it eventually passes
into lymph vessels ; therefore it may be considered as a modified form of lymph. The fluid is
secreted by the chorioid plexuses of the cerebral ventricles, and it passes through the medial and
lateral foramina of the fourth ventricle into the cerebello - medullary subarachnoid cistern,
Part of the fluid transudes through the arachnoideal granulations into the superior sagittal and
other cerebral blood sinuses ; and part, probably, passes by osmosis into the subdural space
and thence into the meningeal lymphatics, by which it is conveyed to the exterior of the
cranium.
Cerebral Lymph Channels. It appears probable that the so-called peri-vascular and peri-
cellular lymph spaces which have so frequently been described in the central nervous system are
merely artifacts produced by unsatisfactory methods of preparation. Nevertheless, the fluid
which pervades the cerebral substance must have some exit, and it is not unlikely that it passes,
with the lymphocytes, through cleft-like intercommunicating spaces in the adventitial coats of
the blood vessels, similar to those demonstrated by Bruce in the case of the spinal medulla, and
so reaches the pia-mater and subarachnoid space ; that is, it runs along the walls of the arteries,
enters the meningeal lymphatics, and passes through them to the exterior of the cranium and
where it enters the extracranial lymph vessels. The above statements are based upon Bruce's
researches and the fact that the lymph vessels of the nose, the ear, and the deep lymph vessels
of the neck have been injected from the subdural space.
The Superficial Lymph Vessels of the Head. (1) The superficial lymphatics from the
frontal and anterior temporal regions of the head accompany the branches of the superficial
temporal artery and terminate in anterior auricular glands, from which efferents pass to the
parotid, the superficial cervical, and to the medial glands of the superior deep cervical group.
(2) The lymphatics of the posterior temporal and parietal region run to the posterior auricular
glands. It is stated that they sometimes communicate directly with the lateral glands of the
superior deep cervical group.
(3) The lymphatics from the occipital part of the scalp pass along the branches of the occipital
artery and terminate in the occipital glands, which transmit the lymph to the lateral superior
deep cervical glands.
1004
THE VASCULAR SYSTEM.
The Superficial Lymph Vessels of the Neck. The majority of the lymph vessels from the
skin and the subcutaneous tissues of the upper part of the neck pass to the" inferior deep cervical
glands, but some end in the occipital glands and others in the superior deep cervical glands.
The superficial lymph channels of the lower part of the neck terminate in the axillary glands.
The Lymph Vessels of the Eyelids and the Conjunctiva. The lymph vessels which
drain the region of the eyelids and the conjunctiva form two groups, a medial and a lateral,
(a) The medial vessels pass from the superficial and deeper parts of the medial portions of the
superior and inferior eyelids and, following the course of the angular and the external maxillary
arteries, they pass to the submaxillary lymph glands. The more superficial vessels lie anterior,
and the deeper vessels posterior to the orbicularis oculi. Both groups may be connected with
infra-orbital and the anterior buccinator glands. (6) The lymph vessels from the lateral parts
of the eyelids pass posteriorly, along the line of the transverse facial artery. They end in the
anterior auricular and the parotid lymph glands. In some cases they become connected also
with the buccinator and superficial cervical glands.
Lymph Vessels of the Eyeball. It is doubtful if any true lymph vessels exist in the eyeball.
Lymph spaces have been described in association with the coats of the eyeball, and lymph
vessels are stated to exist in the chorioid coat, but their existence is uncertain. The sinus venosus
sclerae (Schlemm), formerly looked upon as a lymph channel, is probably a venous canal. If
lymph vessels are absent then the fluids in the tissues and spaces of the eye must pass into
Vallate papillae
IStyloglossus
Stylo-hyoid
Superficial lymph ^to*. i^ IP II 111' " \ ^WE^HB^VqM4 > . Digastric
vessels of side and
dorsura of tongue
Lymph vessels
of apex of
tongue
Afferents to
mandibular
glands
Sublingual gland
Submental gland
Mylo-hyoid cut
Afferent to deep cervical glands
Anterior belly of digastric (cut)
Afferents to
deep cervical
glands from
posterior third
of tongue
" Common facial vein
Upper deep cervical
lymph glands
Omo-hyoid f~~
FIG. 802. LYMPH VESSELS OF THE TONGUE.
the capillaries of the veins, unless channels exist in the adventitia of the vessels similar to those'
described by Bruce in the spinal medulla.
The Lymph Vessels of the Ear. The lymph vessels from the upper and lateral parts of
the auricle end in the anterior auricular glands. Those from the lower part of the auricle go
to the upper superficial cervical glands. The lymph channels from the medial surface of the
auricle end in the posterior auricular glands, but in a few cases they establish direct communica-
tion with the superior deep cervical glands.
The lymph vessels of the external acoustic meatus end in the anterior and posterior auricular
glands.
The lymph vessels of the middle ear pass in two directions. Those from the more laterally
situated parts of the walls of the cavity join the vessels of the external acoustic meatus and
terminate in the posterior auricular glands. The lymph vessels which drain the more medial
parts of the middle ear and the auditory tube terminate in the lateral retro-pharyngeal glands.
It is doubtful if any lymph vessels exist in the internal ear. It is possible that the
perilymph drains into the subarachnoid space of the posterior fossa of the skull along the line
of the ductus endolymphaticus and that the endolymph reaches the subarachnoid space along
the fibres of the acoustic nerve.
The Lymph Vessels of the Nose. The lymph vessels from the external part of the nose
form two groups, superior and inferior. The superior group accompany the vessels from the
lateral parts of the eyelids and end in the anterior auricular glands. The inferior group
accompanies the angular and the external maxillary arteries, and the majority of the vessels end
THE LYMPH VESSELS OF HEAD AND NECK.
1005
in the submaxillary glands, but in some cases one or more vessels of this group pass to the upper
superficial cervical glands.
The Lymph Vessels of the Nasal Muco-periosteum. The vessels from the anterior part of the
nasal muco-periosteum accompany
the vessels of the lower portion of
the external part of the nose and styioglossus
Lymph vessels of
the pharyngeal part
of the tongue
Stylopharyngeus v
'stylo-hyoid x \
Lymph vessels of the side
and dorsum of the anterior
two-thirds of the tongue
. Lymph vessels
I --^ of the tip
of the tongue
Digastric
Hyoglossus
end in the submaxillary glands.
Those from the posterior part of
the muco-periosteum end partly
in the medial superior deep cer-
vical glands, and partly in the
lateral retro- pharyngeal glands.
There is little definite know-
ledge regarding the lymph vessels
of the accessory sinuses of the
nose, but it is probable that they
follow the lines of the blood-
vessels which supply the muco-
periosteum of the cavities.
The Lymph Vessels of the
Lips. The vessels from the skin
of the medial part of the lower lip
pass to the submental glands and,
occasionally, direct to the superior
deep cervical glands. The vessels
from the deeper parts of the lower
lip unite with those from the up-
per lip and end in the submaxil-
lary glands, but some of the super-
ficial vessels of the upper lip may
end in the superficial cervical
glands.
The Lymph Vessels of the
Cheeks. The majority of the
superficial and deep lymph vessels of the cheeks pass to the submaxillary glands, but in some
cases they communicate directly with the superficial or with the superior deep cervical glands.
They may communicate also with the buccinator glands.
The Lymph Vessels of the Gums. The vessels from the outer part of the anterior portion
of the mandibular gum pass to the sub-
mental glands. Those from the posterior
part, together with the vessels from the
outer part of the gum of the maxilla,
terminate in the submaxillary glands.
The vessels of the gum of the maxilla
may also communicate with the buccinator
glands.
The vessels from the inner part of the
gum of the mandible end in the sub-
maxillary glands ; those of the inner part
of the gum of the maxilla, together with
the vessels of the hard and the soft palate,
end in the medial superior deep cervical
glands.
The Lymph Vessels of the Teeth.
It is known that lymph vessels exist in
connexion with the teeth of the mandible
well as with the mandible itself, but
Genio-hyoid
Submental glands
v Mylo-hyoid
Deep lymph
of tongue
- Lowest medial deep cervical gland
Omo-hyoid
FIG. 803. DIAGRAM OF SIDE- VIEW ORIGINS AND TERMINATIONS OF
THE LYMPH VESSELS OF THE TONGUE. (After Poirier,
modified.)
Lymph vessels ol
dorsum and sides
of anterior two-
thirds of tongue
Styioglossus-
Hyoglossus
Deep lymph
vessels of right
side of tongue
FIG. 804. DIAGRAM OF LYMPH VESSELS OF ANTERIOR
TWO-THIRDS OF TONGUE, SEEN "FROM BELOW.
Poirier, modified.)
as
their terminations are not definitely estab-
lished. It is probable that they end in
the submaxillary or the superior deep
cervical glands.
The lymph vessels of the teeth of the
maxilla pass partly into the infra - orbital
canal and so to the face, where they join
the vessels from the lateral parts of the
eyelids, and terminate in the anterior
(After aur icular and submaxillary glands. The
remaining vessels of the maxillary teeth
end in the submaxillary glands.
The Lymph Vessels of the Tongue. The lymph vessels of the tongue form three groups
rior, (2) middle, (3) posterior. The anterior and middle groups communicate freely with
s another and with their fellows of the opposite side, but the posterior group have little or no
mmunication with the middle group. (1) The anterior lymph vessels drain the tip and the
1006
THE VASCULAR SYSTEM.
!$&' Infra-clavicular
3P^~" glands
' . . .Delto-pectoral
gland
.-=- Central axillary
lower surface of the anterior free portion of the tongue. The main trunks pierce the mylo-
hyoid muscle and end in the submental glands. (2) The middle group of lymph vessels of the
tongue drain the anterior two-thirds, exclusive of the tip, and they terminate partly in the
submaxillary glands and partly in the medial superior deep cervical glands. Small lingual
glands are intercalated in the course of some of these vessels. (3) The posterior lymph vessels drain
the portion of the tongue which lies in the anterior wall of the pharynx posterior to the papillae
vallatae ; they pass to the medial superior deep cervical glands. (4) The lymph vessels from
the deeper central portions of the tongue go, mainly, to the upper deep cervical glands.
The Lymph Vessels of the Salivary Glands. The lymph vessels of the parotid gland
terminate in the parotid and superior deep cervical lymph glands. The lymph vessels of the
submaxillary gland terminate, according to Most, not in the submaxillary lymph glands but
in the medial superior deep cervical glands. Practically nothing is known of the lymph vessels
of the sublingual gland.
The Lymph Vessels of the Pharynx. From the upper part of the pharynx, and from the
posterior wall and lateral borders of the middle and lower parts, the lymph stream flows to the
median line posteriorly. There the larger vessels pierce the walls of the pharynx, then they
turn laterally and end in the lateral retro-pharyngeal glands.
From the lower and anterior part of the pharynx, that is, from the region of the piriform
recesses and the adjacent part of the larynx, the lymph vessels pass along the course of the
laryngeal branch of the superior thyreoid' artery, pierce the hyo- thyreoid membrane and
terminate in the medial superior deep cervical
glands ; they may be connected also with the
infra-hyoid, and with the prelaryngeal glands.
The lymph vessels of the palatine tonsil and
the adjacent parts of the glosso - palatine and
pharyngo -palatine arches pierce the lateral wall
of the pharynx and end in a gland, or group
of glands, which lies on the lateral surface of
the internal jugular vein, immediately below
the posterior belly of the digastric at the level
of the angle of the mandible.
The Lymph Vessels of the Thyreoid
Gland. The lymph vessels of the thyreoid
gland form a plexus common to both lobes and
the isthmus, therefore the lymph can pass from
the lobe of one side to the terminal glands of
the opposite side. The terminal vessels end in
the prelaryngeal, the pretracheal, the para-
tracheal, the superior and inferior deep cervical,
and the upper mediastinal glands.
The Lymph Vessels of the Larynx. The
lymph plexus of the larynx is separable into
upper and lower portions ; they are connected
together on the posterior wall of the cavity,
but are separated, laterally and anteriorly,
by the plicae vocales which contain extremely
few lymph vessels. The efferent stems of the
upper part pass mainly along the laryngeal
branch of the superior thyreoid artery, and they
end in the superior deep cervical glands, but are
frequently connected also with the infra-hyoid
glands. The efferent vessels from the lower
part of the larynx form two subordinate groups.
Those from the anterior region pierce the median
crico- thyreoid ligament and end in the pre-
laryngeal, the pretracheal, and the deep cervical
glands. The efferents from the posterior region
pierce the crico-tracheal membrane and end in
the paratracheal glands (Fig. 800).
The Lymph Vessels of the Cervical Part
of the Trachea and (Esophagus. The ter-
minal vessels of the cervical part of the trachea
and the adjacent portion of the cesophagus and
the paratracheal and the inferior deep cervical glands. From the upper part of the trachea
some vessels pass to the prelaryngeal glands also.
-Lateral axillary glands
s -Brachial glands
-Superficial cubital glands
Deep cubital glands and a
"deep gland of forearm
FIG. 805. SCHEMA OF THE LYMPH VESSELS AND
GLANDS OF THE UPPER EXTREMITY.
LYMPH GLANDS OF THE SUPEBIOB EXTEEMITY.
The lymph glands of the superior extremity form two groups (1) superficial,
(2) deep.
(1) Lymphoglandulae Cubitales Superficiales. The superficial cubital lymph
LYMPH GLANDS OF THE SUPEEIOE EXl-xV^KEMITY. 1009
glands, one or two in number, lie on the medial side of the basilic i/- um
distance proximal to the medial epicondyle of the humerus. They receive lyii^ e
from both aspects and from the ulnar border of the forearm, and their efferents pass
to the deep glands of the arm.
(2) Lymphoglandulae Cubitales Profundae. Occasionally small glands are
found in association with the arteries of the forearm, but in most cases the lymph
from the deeper parts of the hand and forearm, below the region of the elbow,
passes to the deep cubital glands or to the brachial or axillary glands.
Cephalic vein
Central axillary glands
( Delto-pcctoral gland
J i Infra-clavicular glands
l Gland superficial to costo-coracoid membrane
Inter-pectoral glands
Lymph vessels passing
to sternal glands
Lymph v
from arm
Lateral axillary glands
Posterior or subscapular
axillary glands
Anterior or pectoral axillary glands'
Lymph vessels from deep part of mamma
passing to inter-pectoral, infra-clavicular,
and also to supra-clavicular glands
Lymph vessels passing to extra- f
peritoneal tissue '
DISSECTION OF AXILLA AND ANTEKIOR PART OF THORACIC WALL, SHOWING LYMPH' GLANDS
AND VESSELS. (Semi-diagrammatic.)
The deep cubital lymph glands lie anterior to the elbow in the neighbourhood of
the terminal part of the brachial artery. They receive many of the deep lymph
vessels of the forearm and their efferents pass to the brachial and axillary glands.
Brachial lymph glands, irregular in number and size, are found along the course
of the brachial artery. Their afferents are derived from the forearm, from the
deep cubital and superficial cubital glands, from adjacent parts, and from the elbow-
joint. Their efferents end in lateral group of axillary glands.
In addition to the glands which lie along the course of the brachial artery
other deep glands are occasionally met with in the arm. (1) One in the sulcus
1008
THE VASCULAE SYSTEM.
1C
between the brachioradialis and the
brachialis ; (2) another in the radial
sulcus. When they are present both
of these glands receive lymph from
the ligaments of the elbow-joint as
well as from other adjacent soft
parts.
Lymphoglandulae Axillares. 1
The axillary lymph glands lie in the
region of the axilla, where they form
several groups, some of which are
practically constant, whilst others are
very variable.
(a) The lateral or brachial group
of axillary lymph glands, 1-7, lies in
relation with the lateral boundary
of the axillary space along the line
of the great axillary vessels. The
glands receive the lymph from the
greater part of the upper extremity.
Their efferents anastomose with the
lymph vessels of the central glands ;
some terminate in the inferior deep
cervical glands and others pass to the
subclavian lymph trunk (Fig. 806).
(6) The posterior or subscapular
lymph glands lie in relation with the
posterior wall of the axilla, along the
line of the subscapular vessels. Their
afferent s are the vessels of the lateral
and posterior walls of the body, above
the level of the umbilicus, and lymph
vessels from the lower and posterior
part of the neck. Their efferents join
the lateral, the central, and the infra-
clavicular axillary glands (Fig. 806).
(c) The anterior or pectoral group
of axillary lymph glands, 2-4, lies along
the line of the lateral thoracic artery,
in the angle between the lower border
of the pectoralis major and theserratus
anterior. The glands extend from the
third to the sixth intercostal space,
sometimes in a single and sometimes
in a double row. Occasionally one or
two outlying members of this group,
called the paramammary glands, are
found on the superficial surface of the
pectoralis major. The afferents of the
1 The B.N.A. axillary lymph glands are the
lateral glands of the axilla, but, as the other
groups mentioned also lie in the axillary region,
FIG. 807. SUPERFICIAL LYMPH VESSELS OF THE TRUNK, the general term "axillary" is used here to in-
AND THE LYMPH GLANDS AND VESSELS SUPERFICIAL clude a11 tne groups.
AND DEEP OF THE LIMBS (diagrammatic). All super-
ficial lymph vessels are printed black ; the deep lymph vessels throughout are coloured red. Afferent
vessels are represented by continuous lines ; efferent and interglandular vessels by dotted lines.
A.A. Anterior axillary glands. E.A. Lateral axillary glands. P.A. Posterior axillary glands.
A.C. Superficial cubital glands. I. Superficial subinguinal glands. S.C. Superficial cubital glands.
A.I. Superficial tibial glands. I.C. Infra-clavicular or subclavian glands. S.F. Subinguinal glands.
D.F. Duseep binguinal glands. P. Pubic glands. U. Urethral lymphatics.
THE LYMPH VESSELS OF THE SUPEEIOE EXTEEMITY. 1009
anterior glands are derived from the anterior wall of the body above the um-
bilicus from the lateral two-thirds of the mamma. Their efferents pass to the
central, lateral, and infra-clavicular axillary glands (Fig. 806).
(d) The central axillary lymph glands, 2-6, lie in the central part of the axilla, and
frequently along the line of the intercosto-brachial nerve. They receive afferents
from the anterior, the subscapular, and the lateral glands. Their efferents pass
to the infra-clavicular glands (Fig. 806).
(e) The subpectoral group of axillary lymph glands, 3-14, is formed by several
small glands which lie posterior to the pectoralis minor and anterior or medial to the
axillary artery. They receive lymph from the glands situated at a lower level and
from the lateral wall of the thorax. Their efferents pass to the infra-clavicular
glands.
(/) The infra-clavicular group of axillary lymph glands, 1-11, lies in the region
between the upper border of the pectoralis minor and the clavicle, along the medial
side of the axillary artery. The glands receive efferents from the arm, from the other
groups of axillary glands, and directly from the mamma and the pectoral muscles,
along the line of the pectoral branches of the thoraco-acromial artery, and from
the inter-pectoral glands. Their efferents pass to the inferior deep cervical glands
and to the subclaviau lymph trunk (Fig. 806).
(#) A delto-pectoral lymph gland is occasionally found in the groove between the
deltoid and the pectoralis major muscles. It receives afferents from the superficial
parts of the arm and the shoulder, and gives efferents to the subclavian trunk and
to the infra-clavicular glands.
(h) Small inter-pectoral lymph glands are sometimes found between the great and
small pectoral muscles. They are connected with the lymph vessels which pass
from the posterior part of the mamma to the infra-clavicular glands (Fig. 806).
THE LYMPH VESSELS OF THE SUPEKIOR EXTEEMITY.
The lymph vessels of the superior extremity, like the glands, form two groups (1) superficial,
and (2) deep.
(1) The superficial lymph vessels lie in the skin and the subcutaneous tissues. They
commence in cutaneous plexuses, which are finest and most dense on the volar aspects of the
fingers and hand. The efferents from the volar digital plexus of each finger pass to the dorsum
of the digit. There they unite to form dorsal digital vessels, 2-4, which run to the dorsum
of the hand where they unite together to form new vessels.
FIG. 808. SUPERFICIAL LYMPHATICS OF THE DIGITS AND OF THE DORSAL ASPECT OF THE HAND.
The efferents from the volar plexus of the hand run proximally, distally, and to the lateral
and medial margins of the hand. The lateral efferents, as they turn round the lateral border
of the hand, join the efferents of the thumb. The medial efferents turn round the medial
border of the hand, and join the efferents of the little finger. The afferents which run
proximally are few and variable ; when they are prese.nt they lie along the line of the superficial
median vein of the forearm. The efferents which run distally pass to the interdigital clefts
where they turn dorsally and join the vessels on the dorsum of the hand (Figs. 807, 808).
As the superficial lymphatics pass towards the elbow they tend to form two main streams
(1) a lateral stream which accompanies the cephalic vein, and (2) a medial stream which
accompanies the basilic vein. The lymph vessels which commence on the dorsum of the hand
and forearm converge to one or other of the two main groups of vessels. In the region of
65
1010 THE VASCULAR SYSTEM.
the elbow the vessels of the two streams anastomose together and some pass through the fascia
and join the deep cubital glands.
As they pass from the forearm to the arm, the majority of the lymph vessels converge
towards the medial side. Some join the superficial cubital glands, but others pass those glands
and accompany their efferents, along the basilic vein, to the axilla where they join the lateral
group of axillary glands. There is, however, a varying number of lymph vessels, from the
lateral stream of the forearm, which accompany the cephalic vein in the arm. Some of these
terminate in the delto-pectoral gland, if it is present, but, whether it is present or not, some
pass directly to the infra-clavicular glands.
The superficial lymph vessels of the arm terminate, for the most part, in the lateral group
of axillary glands.
The deep lymph vessels of the upper extremity accompany the deeper blood-vessels. Some
of the lymph vessels of the hand and forearm end in the deep glands, which are occasionally
present in the forearm, but the majority either end in the deep cubital glands, or they pass
directly to the lateral group of axillary glands.
The Lymph Vessels of the Mamma. As the mamma is a modified skin gland,
and as it is embedded in the superficial fascia, the lymph vessels which issue from it
pass first into the superficial fascia and thence into the deep fascia. Having traversed
the deep fascia, more or less obliquely, they either end in lymph glands or enter and
traverse other layers of the body wall.
The main outflow of lymph from the substance of the mamma is towards the areola,
where a subcutaneous plexus of lymph vessels is formed. From that plexus two or more
main vessels of large size pass laterally (Fig. 806), pierce the deep fascia and join the anterior
group of axillary glands. There are, however, other groups of vessels by which lymph
may pass from the rnamma. Some vessels issue from the medial border of the gland and
run along the lines of the neighbouring anterior perforating branches of the internal
mammary artery to the anterior ends of the intercostal spaces ; there they pass
through the deeper parts of the thoracic wall and end in the sternal lymph glands.
Clinical evidence (Sampson Handley) has shown that some vessels, from the lower
and medial part of the gland, pass to the angle between the seventh rib and the
xiphoid process, where they pierce the fibrous layers of the abdominal wall and join
the lymph vessels in the extra-peritoneal fascia of the upper part of the abdomen. It is
through those vessels that cancer cells not uncommonly travel from the mamma to the
abdomen (Fig. 806).
Lymph vessels pass also from the deep part of the mammary gland, through
the deep fascia and the pectoralis major, and then ascend, along the line of the pectoral
branches of the thoraco-acromial artery, to the infra-clavicular region, where they
terminate either in the inter-pectoral or the infra-clavicular glands, or in both groups.
It is possible that some of those vessels, after piercing the costo-coracoid membrane,
may pass directly to the inferior deep cervical glands (Fig. 806).
It is stated, further, that some of the lymph vessels which issue from the mamma
pierce the whole thickness of the thoracic wall and join the lymph vessels which lie
in the endo-thoracic fascia, which intervenes between the ribs and the intercostal muscles
externally and the pleural membrane internally.
THE LYMPH GLANDS OF THE THOKAX.
The lymph glands of the thorax form 5 named groups, with subdivisions.
(1) Lymphoglandulse Sternales. The sternal lymph glands form two groups
each of which lies at the corresponding margin of the sternum along the line of the
internal mammary artery. The glands are variable in number (4-18) and in size.
They receive afferents from the upper part of the muscles of the abdominal wall,
from the diaphragm, from the anterior part of the wall of the thorax, and from the
medial portions of the mammae. Their efferents communicate with the upper
anterior mediastinal glands and with the inferior deep cervical glands, and they
terminate on the right side in the right lymphatic or the right broncho-mediastinal
duct and on the left in the thoracic duct. Occasionally, also, they end directly in
the internal jugular or the subclavian vein.
(2) Lymphoglandulse Intercostales. The intercostal lymph glands are lateral
and medial. The lateral glands lie in the posterior parts of the intercostal spaces,
the medial are placed in front of the heads of the ribs. Their afferents are derived
from the boundaries and contents of the spaces. The efferents of the glands of the
upper spaces pass either to the posterior mediastinal glarids or to the thoracic
THE LYMPH GLANDS OF THE THOKAX.
1011
duct. Those of the lower spaces, on each side, form a descending trunk which
passes through the aortic opening of the diaphragm and ends in the cisterna
chyli.
(3) Lympho-
glandulse Medi-
astinales An-
teriores. The
anterior medias-
tinal lymph glands
form two groups,
a lower and an
upper. The lower
group consists of
3 or 4 glands, and
is situated, pos-
terior to the ster-
num, in the lower
partoftheanterior ' ~^WM t^^Tfl
mediastinum. It Wlm f^ ^ ^4 ^Ji
receives afferents
from immediately
adjacent parts and
from the liver and
the diaphragm.
Its efferent s com-
municate with
the upper ante-
rior mediastinal
glands, and they
end, for the main
part, in the
broncho - medias-
tinal trunk.
The upper
group consists of
from 8 to 19
glands which lie
posterior to the
inanubrium sterni
and anterior to
the thymus and
the great vessels
of the superior
mediastinum.
Their afferents are
derived from the
lower group of
anterior medias-
tinal glands, from
the pericardium,
the heart, the
thymus, the thy-
reoid gland, and
from the sternal
glands. Their
efferents pass
mainly tp the
broncho-mediastinal trunk, but they communicate with the medial inferior deep
cervical glands and possibly also with the thoracic duct.
65 a
FIG. 809. DEEP LYMPHATIC GLANDS AND VESSELS OF THE THORAX AND
ABDOMEN (diagrammatic).
Afferent vessels are represented by continuous lines, and efferent and interglandular
vessels by dotted lines.
C.
C.I.
B.C.
E.I.
I.
I.I.
L.
Common iliac glands.
Common intestinal trunk.
Deep cervical glands.
External iliac glands.
Intercostal glands and vessels.
Hypogastric glands.
Lumbar glands.
M. Mediastinal glands and vessels.
P. A. Pre-aortic glands and vessels.
R.C. Cisterna chyli.
R.L.D. Right lymphatic duct.
S. Sacral glands.
S.A. Scalenus anterior muscle.
T.D. Thoracic duct.
1012
THE VASCULAK SYSTEM
----Thyreoid cartilage
Crico-thyreoid ligament
Inferior laryngeal lymph vessels
*r~-/--Thyreoid gland
Left common carotid artery
Pretracheal lymph gland
IT--- Paratracheal lymph glands
Left subclavian artery
Arch of aorta
Left tracheo-bronchial glands
Left pulmonary artery
(4) Lymphoglandulae Mediastinales Posteriores. The posterior mediastinal
lymph glands, 8-12, lie along the descending part of the thoracic aorta and the
thoracic part of the oesophagus. They receive afferents from the diaphragm, the
pericardium, the oesophagus,
and other immediately adjacent
tissues. Some of their eferents
join the thoracic duct, others
the broncho-mediastinal trunk,
and some pass to the bronchial
glands.
(5) Lymphoglandulae
Bronchiales. Under the term
bronchial lymph glands are in-
cluded all the lymph glands
which are closely associated
with the walls of the intra-
thoracic part of the trachea and
with the main bronchi and
their intra - pulmonary
branches. The glands are ex-
tremely numerous, and they
are conveniently classified, by
Bartels, into four groups (1)
tracheo- bronchial right and
left; (2) the glands of the
bifurcation, also called inter-
tracheo-bronchial; (3) broncho-
pulmonary ; (4) pulmonary.
At birth and for some years
afterwards they are pink in
colour, but later they become
blackened by the deposit of
carbonaceous particles derived
from the atmosphere.
(1) The Tracheo-Bronchial
Lymph Glands are those which
are situated in the lateral angle between the trachea and the bronchus, on each
side. On the right side they vary in number from 5 to 9, on the left from 3 to 6.
Those on the left are in close relation with the left recurrent nerve. Their
afferents are derived from the other groups of bronchial glands and from the
adjacent parts of the trachea and bronchi. They are connected with the anterior
and posterior mediastinal glands. Their efferents pass to the broncho-mediastinal
trunk and also to the inferior deep cervical glands. They are associated, also, by
interglandular vessels, with the paratracheal glands.
(2) The Lymph Glands of the Bifurcation (intertracheo-bronchial) lie below the
trachea, in the angle between the two main bronchi. They are situated between the
roots of the great vessels anteriorly and the oesophagus and the aorta posteriorly.
Their afferents are derived from the broncho-pulmonary glands and from adjacent
parts ; their efferents terminate in the tracheo-bronchial glands. They are
connected with the posterior mediastinal glands.
(3) The Broncho-Pulmonary Lymph Glands. Each group of broncho-pulmonary
glands, right and left, lies in the hilum of the corresponding lung, in the angles
between the branches of the bronchial tube. The glands vary considerably in number,
and they receive afferents, either directly or through the pulmonary glands, from
the lung substance. They also receive afferents from the pleura ; and their efferents
pass to the tracheo-bronchial glands and to the glands of the bifurcation.
(4) The Pulmonary Lymph Glands lie in the lung substance and usually in the
angles between two bronchial tubes. Their afferents are derived from the lung
substance, and their efferents pass to the broncho-pulmonary glands.
Right pulmonary
artery
Broncho-pulmonary
glands.
FIG. 810.-
Glands of the bifurcation
(intertracheo-bronchial)
THE GLANDS IN RELATION TO THE TRACHEA AND THE
MAIN BRONCHI.
THE LYMPH GLANDS OF THE INFEKIOK EXTEEMITY. 1013
THE LYMPH VESSELS OF THE THORAX.
The lymph vessels of the thorax form two main groups (a) the vessels of the thoracic wall,
and (6) the vessels of the contents of the thorax.
(a) The Lymph Vessels of the Thoracic Wall are the intercostal lymph vessels and the
lymph vessels of the diaphragm.
(1) The Intercostal Lymph Vessels receive lymph from the ribs and from the content of the
intercostal spaces, and they terminate in the intercostal and sternal glands. Communications
are said to exist between the intercostal vessels and the glands of the axilla.
(2) The Lymph Vessels of the Diaphragm. The lymph vessels from the anterior part of the
diaphragm pass to the lower sternal and anterior mediastinal glands, and those from the posterior
part to the posterior mediastinal glands.
(6) The Lymph Vessels of the Contents of the Thorax are :
(1) The Lymph Vessels of the Heart, which follow the courses of the coronary arteries, and
pass to the anterior mediastinal glands.
(2) The Lymph Vessels of the Pericardium, which terminate in adjacent glands.
(3) The Lymph Vessels of the Thymus, some of which pass to the anterior mediastinal glands,
some to the tracheo-bronchial glands, others to the medial inferior deep cervical glands.
(4) The Lymph Vessels of the Thoracic Part of the (Esophagus, which are separable into
upper and lower groups. The upper pass to the bronchial, the posterior mediastinal, and the
lower deep cervical glands. The lower group end in the glands situated at the cardiac end of
the stomach. The two groups anastomose together.
(5) The Lymph Vessels of the Pleura. The vessels from
the apical parts of the parietal portion of the pleura pass to the
adjacent lymph trunks or their tributaries. The vessels from
the posterior part of the parietal pleura join the intercostal yCJ^X^J^feo'^- -j Proximal
glands, and those from the anterior part end in the sternal jL-^-^jfe^l l'!l U nS l o C i ial in,V?"
glands.
The Lymph Vessels of the Lungs and the Visceral Pleura
pass to the broncho-pulmonary glands.
Distal superficial
"subinguinal glands
THE LYMPH GLANDS OF THE
INFERIOE EXTEEMITY.
The lymph glands of the inferior extremity, like
those of the superior, are separable into a superficial
and a deep group.
The Superficial Lymph Glands lie, almost
entirely, in the subinguinal region, though occasion-
ally one or more may be situated above the level of
the inguinal ligament, and therefore in the inguinal
region. On this account they are separated in the
>.N.A. into inguinal and subinguinal groups. Both
groups lie in the superficial fascia.
Lymphoglandulse Inguinales. The inguinal
lymph glands, when they exist, are merely scattered
members of the subinguinal group which lie above the
level of the inguinal ligament. They receive afferents
from the lower and anterior part of the abdominal
wall. Their efferents terminate either in the super-
ficial or the deep subinguinal glands.
Lymphoglandulae Subinguinales Superficiales.
-The superficial subinguinal glands (Figs. 811, 817)
form two groups, a proximal and a distal, each of
which is separable into medial and lateral parts ; but
the various members of the groups are intimately
connected together by communicating vessels.
The proximal group lies along the line of the
inguinal ligament. It may extend from the anterior FIG. 811. DIAGRAM OF THE LYMPH
superior spine of the ilium to the pubic tubercle. Its VESSELS AND LYMPH GLANDS OP
lateral members receive afferents from the lower and THE LowER ExTREMITY '
lateral part of the abdominal wall, from the buttock, and the proximal and lateral
part of the thigh.
65 &
1014
THE VASCULAR SYSTEM.
Lymph vessels which pass
to the proximal superficial
subinguinal glands
Lymph vessels which
pass to the medial
group of proximal
superficial sub-
inguinal glands
Lymph vess
which pass to distal
group of superficial
subinguinal glands
Popliteal glands ir~Hr
Lymph vessels which
accompany the small-
saphenous vein
The more medial members of the proximal group receive afferents from the
anal canal, the perineum, the scrotum, the penis, and the pubic region in the male,
and from the corresponding parts, including the
lower part of the vagina, in the female.
The distal group of superficial subinguinal
glands lies along the line of the proximal part
of the great saphenous vein some on its lateral
and some on its medial side. They receive
afferents bearing lymph from the superficies of
the greater part of the inferior extremity, with
the exception of the lateral part of the foot, the
heel, and a part of the posterior aspect of the leg.
The efferents of both proximal and distal groups
of subinguinal glands pass to the deep subinguinal
glands.
The Deep Lymph Glands of the inferior
extremity are the popliteal and the deep sub-
inguinal glands. Occasionally a deep gland is
met with in the leg in relation with the proximal
third of the anterior tibial artery.
Lymphoglandulae Poplitese. The popliteal
lymph glands (Fig. 812) lie in the popliteal fossa.
One is usually situated, comparatively super-
ficially, at the point where the small saphenous
vein pierces the deep fascia and enters the fossa.
It receives afferents, which .accompany the small
saphenous vein, from the lateral part of the foot,
the heel, and the posterior part of the calf. Its
efferents pass to the deeper glands.
The deeper glands lie in the fat around the
popliteal vessels and are sometimes separated into
inter-condylar and supra-condylar groups. Their
afferents are derived from the more superficial
gland and from the deeper tissues of the leg and
foot. Their efferents pass to the deep subinguinal
glands.
Lymphoglandulae Subinguinales Profundse.
The deep subinguinal glands (Figs. 807, 811, 817)
lie in the femoral trigone. They are small glands,
FIG. 812. DIAGRAM OF THE LYMPH three to seven in number, which are difficult to
VESSELS OF THE POSTERIOR PART OF demonstrate. Some of them lie in the femoral
THE LOWER EXTREMITY. -, ,, i i -j. *. j
canal, the most proximal being situated in or
close to the femoral ring. Their afferents are the efferents of the other glands
of the lower extremity, and, in addition, vessels from the deeper parts of the penis
or the clitoris. Their efferents pass to the external iliac glands.
THE LYMPH VESSELS OF THE INFERIOR EXTREMITY.
The arrangement of the superficial lymph vessels of the toes and the foot is very similar
to that met with in the fingers and the hand. From lymph plexuses on the plantar aspect
vessels pass to the dorsum of the foot and toes, where they unite into a number of vessels, the
majority of which accompany the great saphenous vein and terminate in the distal group of
superficial subinguinal glands. Some of the lymph from the lateral part of the plantar surface
and from the lateral border of the foot, and the lymph from the heel enters vessels which
accompany the small saphenous vein; they end either in the more superficial gland of the
popliteal fossa or in the deeper glands of that region (Fig. 812).
With the exception of the lymph vessels from the lateral and posterior part of the leg, which
accompany the small saphenous vein to the popliteal glands, all the superficial lymph vessels o:
the leg, thigh, and buttock pass to the superficial subinguinal glands ; those from the leg ai
thigh mainly to the glands of the distal group ; those of the buttock chiefly to the latera
glands of the proximal group.
THE VISCERAL GLANDS OF THE PELVIS. 1015
The deep lymph vessels of the inferior extremity accompany the deep blood-vessels.
Many of the vessel from the leg and foot end in the popliteal glands, but some pass directly to
the deep subinguinal glands. ' The deep vessels of the more proximal parts of the inferior
extremity end in the deep subinguinal glands and in the hypogastric glands.
THE LYMPH GLANDS OF THE ANTEKIOR ABDOMINAL WALL.
Some lymph glands are regularly, and others are occasionally present in the anterior wall
of the abdomen. Those fairly regularly present are :
The inferior epigastric lymph glands, 3-6, which lie along the course of the inferior epigastric
artery. Their afferents are from the deep part of the umbilicus and their efferents pass to the
inferior external iliac glands.
The Pubic Gland or Glands. One or more small glands which lie anterior to the suspensory
ligament of the penis or clitoris. Their afferents are vessels from the superficial parts of the
penis or clitoris, and their efferents end in the proximal superficial subinguinal glands.
The occasional glands are :
(1) A superior epigastric gland which sometimes lies in the superficial fascia of the median
part of the epigastric region. Its afferents are from the adjacent parts and its efferents pass
to the sternal glands. It is probably very rare.
(2) Circumflex iliac glands, 2-4, which lie along the course of the deep circumflex iliac artery.
(3) An umbilical gland which lies in the extra-peritoneal tissue below the umbilicus. When
it is present it receives vessels from the umbilicus and its efferents go to the external iliac glands.
(4) Supra-umbilical glands, 1-2, small glands which lie in the extra-peritoneal tissue above
the umbilicus. Its afferents are from the region of the umbilicus. The efferents probably pass to
the inferior anterior mediastinal glands.
THE LYMPH VESSELS OF THE ANTERIOR WALL OF THE ABDOMEN.
The superficial lymph vessels of the upper part of the anterior wall of the abdomen go, for
the most part, to the anterior or pectoral group of axillary glands ; but some pierce the wall of
the lower part of the thorax and end in the sternal glands.
The superficial lymph vessels of the lower part of the anterior wall of the abdomen terminate
either in the inguinal glands or in the proximal group of superficial subinguinal glands.
The deep lymph vessels of the upper part of the anterior abdominal wall accompany the
superior epigastric vessels and terminate in the sternal glands ; but some may be connected with
the supra-umbilical glands if they are present.
The deep lymph vessels of the lower part of the anterior wall of the abdomen accompany the
inferior epigastric vessels, and end in the inferior external iliac glands or the inferior epigastric
glands.
THE LYMPH VESSELS OF THE EXTERNAL GENITALS.
The lymph vessels of the scrotum in the male and of the labia majora in the female pass
to the proximal superficial subinguinal glands, and mostly to the medial group.
The superficial lymph vessels of the penis go to the medial glands of the proximal subinguinal
group.
The deep lymph vessels of the penis, including those of the penile portion of the urethra, end
either in 'the medial glands of the proximal subinguinal group or in the deep subinguinal
glands.
The termination of the lymph vessels of the clitoris is similar to that of the lymph vessels
of the penis.
LYMPH GLANDS OF THE PELVIS AND ABDOMEN.
The lymph glands of the pelvis are separable into visceral and parietal groups.
The Visceral Glands of the Pelvis.
Lymphoglandulae Vesicales. The lymph glands of the urinary bladder form an
anterior and two lateral groups.
(a) The anterior lymph glands of the bladder are variable in number. They
lie in the retro-pubic fat and receive afferents from the anterior and antero-lateral
parts of the bladder wall. Their efferents go to the external iliac glands.
(6) The lateral lymph glands of the bladder lie along the course of the umbilical
artery on each side. Their afferents are derived from the upper and lateral parts
of the bladder and their efferents end in the external iliac glands.
Lymphoglandulae Anorectales. The ano-rectal lymph glands (2-8) lie in the
lower part of the pelvis minor, in relation with the ampullary part of the rectum,
65 c
1016
THE VASCULAK SYSTEM.
between its muscular wall and its external fibrous coat. Their afferents are
derived from the muscular and mucous coats of the rectum and from the upper
part of the anal canal, and their efferents pass to the superior hsernorrhoidal glands.
Lymphoglandulse Parauterinae. The para-uterine lymph glands (1-6), lie at
the sides of the neck of the uterus in the bases of the broad ligaments. They
receive afferents from the neck of the uterus and the efferents pass to the hypo-
gastric glands.
Lymphoglandulse Haemorrhoidales Superiores. The superior haemorrhoidal
lymph glands lie along the course of the superior hsemorrhoidal artery in the
pelvic meso-colon. They receive afferents from the walls of the rectum, and from
the ano-rectal glands. Their efferents go to the inferior mesenteric glands.
The Parietal Lymph Glands of the Pelvis.
Lymphoglandulae Sacrales. The sacral lymph glands, variable in number,
lie along the anterior aspect of the sacrum, between the anterior sacral foramina.
Upper hypogastric lymph glands
^_JBB
WQ^^^^^^^K
Common iliac lymph glands ('.
External iliac lymph gland
Lymph vessels of
testes passing to
lumbar lymph glands
Lower external iliac
lymph gland
Lateral lymphll P
glands of"'
urinary bladder
Anterior lymph
glands of
urinary bladder
Urinary bladder -
Prostate - -
Gluteal lymph
glands
Pubo-gluteal
'lymph glands
-'-L-7 Sacral lymph gland
W-
I \ Middle
t haemorrhoidal
- 1 - lymph glands
~.~^7 Sacral lymph glai
? -Seminal vesicle
' Ductus deferens
Ano-rectal
lymph glands
FIG. 813. DIAGRAM OP THE LYMPH GLANDS OF THE PELVIS.
Their afferents are from the rectum, the prostate, and the adjacent parts of the
wall of the pelvis. Their efferents end in the sub-aortic, the aortic, and the hypo-
gastric glands.
THE LYMPH VESSELS OF THE PELVIC VISCEEA. 1017
Lymphoglandulae Subaorticae. The subaortic lymph glands (1-3) lie on the
anterior aspect of the fifth lumbar vertebra. Their afferents are from the sacral
glands, the hypogastric glands, and the external iliac glands. Their efferents go
to the aortic glands (Fig. 817).
Lymphoglandulae Hypogastricae. The hypogastric lymph glands form right
and left groups, which are associated with the corresponding hypogastric vessels.
As a rule they he near the origins of the main branches of the hypogastric artery,
or in the angles between the branches, and they, therefore, are separable into a
number of groups.
The Gluteal Lymph Glands lie in relation to the superior gluteal artery and receive
afferents from the gluteal region. Their efferents pass to the common iliac glands.
The Pubo-gluteal Lymph Glands (1-2) he in relation to the origins of the inferior
gluteal and internal pudendal arteries. They receive afferents from the thigh
and perineum and their efferents end in the common iliac glands.
The Middle Hsemorrhoidal Gland lies more medially than the other glands of
the group, close to the lateral wall of the rectum at the point where the middle
hsemorrhoidal artery breaks up into its terminal branches. It receives afferents
from the rectum and gives efferents to the other hypogastric and to the external
iliac glands.
The Inter-iliac Glands lie in the angle between the external iliac and the
hypogastric arteries, and cannot be clearly disassociated from the medial external
iliac glands. They receive afferents from the lower parts of the pelvic portions
of the genito-urinary organs. Their efferents pass to the common iliac glands.
The Obturator Gland lies at the inner end of the obturator canal, above the
obturator vessels. It receives afferents from the upper and medial parts of the
thigh and its efferents join the inter-iliac and common iliac glands.
Lymphoglandulae Iliacae. The iliac lymph glands are separable into a lower
group, associated with the external iliac artery, lymphoglandulse iliacae externae,
and an upper group, the lymphoglandulae iliacse communes.
The External Iliac Glands. According to Poirier and Cuneo, the external iliac
lymph glands form three chains, lateral, intermediate, and medial, which lie,
respectively, at the lateral side, anterior to, and at the medial side of the external
iliac vessels. The three lowest members of the group, that is the lowest member
of each chain, lie in close relation to the abdominal aperture of the femoral ring,
and are frequently spoken of as supra-femoral glands. They receive afferents
from the superficial subinguinal and the deep subinguinal glands, from the
urethra and the deeper parts of the penis, and from the portions of the abdominal
wall supplied by the deep circumflex iliac and inferior epigastric arteries. Their
efferents end in the upper glands of the external iliac group.
The higher members of the external iliac lymph glands receive afferents from
the membranous part of the urethra, the prostate, the bladder, the vagina, and
the neck of the uterus. They are connected by anastomoses with the hypo-
gastric glands, particularly the middle hsemorrhoidal gland, and their efferents pass
to the common iliac glands.
The Common Iliac Lymph Glands. The glands of the common iliac group are
sometimes separated into a lateral and intermediate and a medial series. The
lateral and intermediate groups are quite distinct, the former lying along the
lateral margin of the artery and the latter posterior to it, but the medial group
is not clearly defined from the sub-aortic group already mentioned. Indeed
the sub-aortic group may be looked upon as constituted by the medial common
iliac glands of opposite sides.
The common iliac glands receive afferents from the external iliac and the
hypogastric glands, and consequently from practically the whole of the pelvic
contents, except the ovaries of the female.
THE LYMPH VESSELS OF THE PELVIC VISCERA.
The Lymph Vessels of the Urethra of the Male. It has been pointed put that the
lymph vessels of the greater part of the penile portion of the urethra are said to pass to
the deep subinguinal glands. The lymph vessels of the bulbar and membranous parts of the
1018
THE VASCULAE SYSTEM.
Fundus of uterus
Uterine tube
of uterus
Ovary
..^External iliac and sub-
''aortic lymph gland
..Subinguinal lymph gland
Hypogastric lymph glands
External iliac lymph glands
[gland
Vessels to ano-rectal, sacral, and sub-aortic lymph
urethra have not yet been satisfactorily demonstrated, but it is stated that they pass to the
hypogastric glands, to the medial supra-femoral gland of the external iliac group, and to the
higher glands of the external iliac group. The lymph vessels of the prostatic part of the urethra
unite with the other lymph vessels of the prostate.
The Lymph Vessels of the Prostate pass to the anterior and lateral vesical glands, to the
external iliac glands, to the hypogastric glands, and to the sacral and haemorrhoidal glands.
They anastomose with the lymph vessels of the bladder and the deferent duct.
The Lymph Vessels of the Urethra of the Female have terminations corresponding with
those of the vessels of the membranous and prostatic portions of the urethra of the male.
The Lymph Vessels of the Seminal Vesicle, on each side, pass to the medial glands of the
external iliac group.
The Lymph Vessels of the Ductus Deferens, on each side, anastomose with those of the
seminal vesicle, and they pass to the hypogastric and external iliac glands.
The Lymph Vessels of the Urinary Bladder. Many of the lymph vessels from the antero-
lateral aspect of the urinary bladder pass to the corresponding anterior and lateral vesical lymph
glands and, through them, become connected with the external iliac and hypogastric glands, but
some apparently pass directly to the hypogastric lymph glands.
The lymph vessels from the superior, and many from the posterior part of the bladder, on
each side, end in the external
**-*Lumbar lymph glands iliac and hypogastric glands, but
some from the posterior part pass
upper part directly to the sub-aortic glands.
The Lymph Vessels of the
Ureter. Little is known of the
lymph vessels of the ureter ex-
cept that those of its lower
extremity anastomose with the
lymph vessels of the urinary
bladder. It is suggested that the
vessels pass to the nearest lymph
glands.
The Lymph Vessels of the
Vagina. The lymph vessels of
the lower part of the vagina
anastomose with the lymph vessels
of the labia minora and so trans-
mit lymph to the superficial
subinguinal glands. The lymph
vessels of the upper parts of the
vagina pass to the hypogastric
glands and also, with the lymph
vessels of the cervix uteri, to the
external iliac glands. Some of
the lymph vessels from the pos-
terior wall of the vagina terminate
in the ano-rectal glands.
The Lymph Vessels of the
Uterus. The Lymph Vessels of
the Lower Part of the Uterus.
The majority of the lymph vessels
from the lower part of the uterus, including the cervix, unite with the lymph vessels of the
upper part of the vagina and pass to the hypogastric glands including the inter-iliac group
(p. 1017). Some pass to the external iliac glands, and others from the lower and posterior part
become associated with the ano-rectal, the sacral, and the sub-aortic glands.
The Lymph Vessels of the Body of the Uterus run in several directions. The most im-
portant outflow is along the upper part - of the broad ligament, below the uterine tube, to the
region of the ovary where there is an anastomosis with the ovarian lymph vessels. Afterwards the
lymph vessels of this stream cross the brim of the pelvis minor and ascend to the lumbar lymph
glands. The accessory outflows are to the external iliac glands; to the sub-aortic glands:
and, along the round ligament, to the superior group of sub-inguinal glands.
The Lymph Vessels of the Uterine Tube accompany the vessels of the main outflow from
the body of the uterus, and those from the ovary, and pass to the lumbar lymph glands.
The Lymph Vessels of the Ovaries. The lymph vessels of each ovary accompany the
ovarian artery and some of the uterine lymph vessels, along the upper part of the broad ligament,
to the brim of the pelvis minor and then upwards to the lumbar lymph glands.
The Lymph Vessels of the Testis and Epididymis. The testis and the epididymis i
not normally pelvic organs in the adult, but their lymph vessels may be considered here, inas-
much as the testes correspond, morphologically, with the ovaries. The lymph vessels of
testis and its epididymis accompany the testicular arteries and ascend to the lumbar regie
where they terminate in the lumbar lymph glands.
The Lymph Vessels of the Rectum. The lymph vessels of the rectum and the upper par
of the anal canal pass for the most part along the middle and superior heemorrhoidal ves
Cervix uteri
Ano-rectal lymph glands
P. Superficial subinguinal lymph glands
^---.. Labium ina.jus
FIG. 814. DIAGRAM OF
LYMPH VESSELS OF FEMALE GENITAL
ORGANS.
VISCEEAL LYMPH GLANDS OF THE ABDOMEN.
1019
Those which accompany the branches of the middle haemorrhoidal artery, on each side, pass to
the corresponding middle hsemorrhoidal gland of the hypogastric group ; whilst the lymph
vessels of the rectum which accompany the branches of the superior haemorrhoidal artery become
associated with the ano-rectal, the sacral, and the inferior mesenteric lymph glands. The lymph
vessels of the lower part of the anal canal go to the medial proximal subinguinal glands.
THE LYMPH GLANDS OF THE ABDOMEN.
The lymph glands of the abdomen are separated into visceral and parietal
groups. The visceral groups are those more directly associated with the lymph
vessels which issue from the walls of the abdominal part of the alimentary canal,
although they may lie posterior to the peritoneum in relation to the posterior wall
of the abdomen. The parietal glands lie in relation with the abdominal part
of the aorta and the inferior vena cava and the adjacent parts of the posterior
abdominal wall.
Right paracardial gland
Posterior left gastric glands^
Anterior left gastric glands v
Left paracardial glands
s, Cut edge of greater
omentum
Visceral Lymph Glands of the Abdomen.
Lymphoglandulae Gastricae. The gastric lymph glands are arranged in two
main groups, the lympTioglandulce superior 'es which lie in association with the arteries
of the smaller curvature, and the lympTioglandulce inferiores associated with the
greater curvature. Jamieson and Dobson have separated the superior gastric
glands into several subdivisions.
Lymphoglandulse Gastricae Superiores. (a) The Anterior Left Gastric Glands (lower
coronary glands, J. and D.). The anterior left gastric glands lie between the layers
of the lesser omentum
along the course of the
left gastric artery. They
receive afferents from the
greater part of the lesser Right supra . pancreatic gland
curvature of the stomach Right gastric gland
and the adjacent parts
of its anterior and pos-
terior walls, and they
send efferents to the pos-
terior left gastric glands.
(6) The Right Para-
cardial Glands are essenti-
ally members of the
anterior left gastric
group which lie to the
right of the cardiac orifice
of the stomach. Their afferents are derived from the cardiac part of the stomach
and their efferents go to the posterior left gastric glands.
(c) The Left Paracardial Glands lie to the left of the oesophageal orifice. They
receive afferents from the adjacent parts of the cardiac portion of the stomach, and
their efferents end in the posterior left gastric glands.
(d) The Posterior Paracardial Glands lie on the posterior aspect of the stomach,
between the layers of the gastro-phrenic ligament. Their afferents are from the
neighbouring parts of the cardia and their efferents go to the posterior left gastric
glands.
(e) The Posterior Left Gastric Glands (upper coronary, J. and D.) lie around the
left gastric artery as it passes forwards through the left gastro-pancreatic fold of
peritoneum. They receive afferents from the previously mentioned groups of gastric
glands and direct afferents from the cardiac portion of the stomach. Their efferents
pass to the middle supra-pancreatic glands of Jamieson and Dobson (cceliac
glands, B.N.A.).
(/) The Right Gastric Gland (pyloric of J. and D.) is a small gland, occasionally
present, which lies immediately above the pylorus or the first part of the duodenum,
Sub-pyloric
glands
Right gastro-epiploic glands-
FIG. 815. LYMPH VESSELS AND GLANDS OP THE STOMACH.
(After Jamieson and Dobson, modified.)
1020 THE VASCULAE SYSTEM.
in association with the right gastric artery. It receives afferents from the pylorus,
and its efferents end in the sub-pyloric glands.
(#) The Eight Gastro-epiploic Glands lie along the lower part of the greater
curvature of the stomach, in association with the right gastro-epiploic artery.
Their afferents are from the adjacent parts of the anterior and posterior surfaces
of the stomach and their efferent* pass to the sub-pyloric glands.
(h) The Left Supra-pancreatic Glands of Jamieson and Dobson (lympho-
glandulse pancreaticolienales, B.N.A.) lie along the course of the splenic artery
and in the gastro-splenic ligament : they receive afferents from the left part of the
stomach and from the spleen. Their eff events pass to the middle supra-pancreatic
glands.
(*) The Right Supra -pancreatic Glands (J. and D.) lie in relation with the stem of
the hepatic artery as it passes through the right gastro-pancreatic fold. They
receive afferents directly from the pyloric part of the stomach and the liver, and
give off efferents to the middle supra-pancreatic glands.
(f) The Sub-pyloric Glands (J. and D.). The sub-pyloric lymph glands lie at
the right border of the omental bursa, in the angle between the superior and
descending parts of the duodenum, between the head of the pancreas posteriorly
and the peritoneum of the posterior wall of the great sac anteriorly. Their afferents
are from the right gastro-epiploic glands, the right gastric gland, and from the pyloric
portion of the stomach. The efferents pass to the middle supra-pancreatic glands.
(&) The Biliary Lymph Glands (J. and D.) lie along the line of the bile duct.
They receive afferents from the gall-bladder and liver. One of the lower glands
of the group, which lies posterior to the head of the pancreas, close to the lower
end of the bile-duct, is associated, by direct afferents, with the upper part of the
pylorus. Their efferents pass to the right and middle supra-pancreatic glands.
The highest member of the series is associated with the cystic artery and the
gall-bladder and is called the cystic gland.
Lymphoglandulae Hepaticse (B.N.A.) The Hepatic Lymph Glands of the Basle
nomenclature are a few small glands which lie in the region of the porta hepatis,
between the layers of the lesser omentum ; they receive afferents from the liver
and give efferents to the right supra-pancreatic glands (J. and D.).
Lymphoglandulae Mesentericse (B.N.A.) The Mesenteric Lymph Glands lie
between the layers of the mesentery, where they form three main groups : (a) a
series of juxta-intestinal glands which lie close to the walls of the small gut ; (&)
an intermediate series of larger glands which lie in relation with the trunks of the
rarai intestinales of the superior mesenteric artery; and (c) a terminal group of
large glands which lie round the upper part of the stem of the superior mesenteric
artery. They receive lymph from all parts of the small intestine, from the
caecum, the vermiform process, the ascending colon, the transverse colon, and the
part of the descending colon. Their efferents unite to form a common intestinal
trunk, which enters the cisterna chyli.
The Lymph Glands of the Caecum and the Vermiform Process and the Terminal
part of the Ileum. The lymph glands particularly associated with the terminal
part of the ileum, the csecum and its vermiform process, according to Jamieson and
Dobson, are (1) the ileal, (2) the anterior ileo-colic, (3) the posterior ileo-colic,
and (4) the appendicular. All these glands give off vessels which pass to the
larger ileo-colic glands which lie along the ileo-colic branch of the superior
mesenteric artery.
The Ileal Glands lie in the lower part of the mesentery. They receive afferents
from the lower part of the ileum and give efferents to the main ileo-colic glands.
An Appendicular Lymph Gland is sometimes met with in the mesentery of the
vermiform process. When it is present it may be associated with the vessels which
pass from any part of the vermiform process. Its efferents pass to the main ileo-
colic glands.
The Anterior Ileo-colic Glands, 1-4, lie in the anterior ileo-colic fold of peritoneum.
Their afferents are derived from the anterior part of the caecum and the root of the
vermiform process, and efferents pass to the main ileo-colic glands.
The Posterior Ileo-colic Glands, more numerous than the anterior, lie in the
VISCERAL LYMPH GLANDS OF THE ABDOMEN.
1021
angle between the ileum and the csecum, and in the angle between the ileum and
the ascending colon. Their afferents are from the posterior part of the caecum
and the root of the vermiform process. Their e/erents pass to the main ileo-colic
glands.
The Lymph Glands of the Colon, according to Jamieson and Dobson, may be
considered as forming Main mese nteric glands
Middle colic artery
Common stem of ileo-colic and
right colic arteries
Epicolic glands
Paracolic glands
Main glands -
Lumbar glands
nferior mesenteric
artery
Main inferior
mesenteric glands
Mesenteric glan
four groups, epicolic,
paracolic, intermediate,
and main.
The Epicolic Glands
are small nodules which
lie in the appendices
epiploicae and in relation
with the wall of the gut.
The paracolic glands lie
along the medial borders
of the ascending, de-
scending, and iliac parts Ile - colic art ry
of the colon ; along
the upper border of
the transverse colon,
and on the mesenteric
border of the pelvic
*colon. The intermedi-
ate glands lie along the
branches of the colic
-, ,, FIG. 816. DIAGRAM OP THE LYMPH GLANDS AND LYMPH VESSELS OF THE
LARGE INTESTINE. (After Jamieson and Dobson.)
groups are situated
around the stems from which the colic arteries arise. The lymph gathered by the
lymph plexuses in the walls of the gut passes through one or more of the groups
of glands, and that which issues from the main group, in association with the
ileo-colic and middle colic arteries, enters the main mesenteric glands which
surround the upper part of the superior mesenteric artery. It is then carried by
the efferent s of those glands to the common intestinal lymphatic trunk. The
lymph from the descending, the iliac, and the pelvic parts of the colon passes to
the intermediate groups of inferior mesenteric glands and thence, for the main
part, to the lumbar glands, but some of the efferents from the upper intermediate
inferior mesenteric glands pass to the main group of superior mesenteric glands.
The lymph glands associated with the middle colic artery and its branches
are the lymphoglandulae mesocolicse of the Basle. nomenclature.
The Main Glands of the Inferior Mesenteric Group receive lymph from the
intermediate left colic glands and transmit it to the lumbar glands through which
it passes, by the lumbar lymph trunks, to the cisterna chyli; but some of the
lymph from the upper intermediate left colic glands passes to the main mesenteric
glands, and so to the common intestinal lymph trunk.
The Middle Supra-pancreatic Lymph Glands of Jamieson and Dobson correspond
fairly closely with the lymphoglandulae cceliacae of the Basle terminology. They
lie at the upper border of the pancreas around the coeliac artery. Their afferents
are from the right and left supra-pancreatic glands, from the posterior left gastric
glands, and from the subpyloric glands. They are connected by intermediate
channels with the superior mesenteric glands, and they give efferents to the
common intestinal lymph trunk and also to the common lumbar trunks.
Lymphoglandulse Lumbales, B.N.A. The Lumbar Lymph Glands lie behind
the peritoneum of the posterior wall of the abdomen, in association with the aorta,
the inferior vena cava, the psoas and quadratus lumborum muscles, and the crura
of the diaphragm. Those which are situated on the anterior aspect of the aorta
are frequently spoken of as pre-aortic glands and those situated more laterally
is para-aortic glands.
The afferents of the lumbar lymph glands are (1) the efferents of the common
1022
THE VASCULAR, SYSTEM.
iliac glands, (2) efferent s from the sub-aortic glands, (3) efferents from the sacral
glands, (4) some efferents from the hypogastric glands, (5) efferents from the
main inferior mesenteric glands, (6) the lymph vessels from the testes and
epididymides and their coverings in the male, and from the ovaries, the uterine
tubes, and the upper part of the uterus in the female, (7) lymph vessels from the
(Esophagus
Posterior left gastric
gland
Right supra-pancreatic
glands'
Main mesenteric glands-
Lumbar glands
A common iliac
gland "
Lymph vessels from
testis and epi-
didymis
Superior hsemor-
rhoidal glands"
An external iliac ,
gland
Lymph vessels of
testis and epi-
didymis
Deep subinguinal -
glands
Cut ends of lymph
vessels of penis"
Lymph vessels of
testis and epi-
didymis
Posterior paracardial
glands
Middle supra-pancreatic
glands
Left supra-pancreatic
glands
Splenic glands
Sub-aortic and medial
common iliac glands
An external iliac
lymph gland
Lymph vessels of
testis and epididymis
Lateral group of
proximal super-
ficial subinguinal
glands
Medial group of
proximal subin-
guinal glands
Lateral group of
distal superficial
subinguinal glands
Medial
p of distal superficial subinguinal glands
FIG. 817. SEMI-DIAGRAMMATIC VIEW OF THE LYMPH GLANDS AND VESSELS OF THE PROXIMAL PARTS
OF THE LOWER EXTREMITIES, THE PELVIS MAJOR AND THE POSTERIOR PART OF THE ABDOMEN.
kidneys, (8) lymph vessels from the suprarenal glands, (9) lymph vessels from the
muscles of the back and of the posterior wall of the abdomen.
The efferents of the lumbar glands form two common lumbar lymph trunks,
which pass to the cisterna chyli.
THE LYMPH VESSELS OF THE ABDOMINAL VISCERA AND THE
SUPERIOR AND POSTERIOR WALLS OF THE ABDOMEN.
The Lymph Vessels of the Abdominal Part of the Alimentary Canal. The lymph
vessels in the walls of the alimentary canal form four plexuses : (1) a mucous plexus, in the
mucous membrane, (2) a submucous plexus, in the submucous tissue, (3) a muscular plexus,
between the two muscle coats, (4) a subserous plexus which lies in the areolar tissue between
the peritoneal covering and the outer muscular coat. The four plexuses communicate freely
with each other. The lymph is eventually collected from the subserous plexus and carried to
the various groups of lymph glands. The vessels which carry away the lymph from the sub-
THE LYMPH VESSELS OF THE ABDOMINAL VISCERA. 1023
serous plexuses of the various parts of the alimentary canal are spoken of in the following
account as the lymph vessels of those parts.
The Lymph Vessels of the Stomach. The lymph vessels of the stomach communicate
freely with the lymph vessels of the O3sophagus on the one hand and those of the duodenum
on the other.
From the point of view of lymph outflow the area of each surface of the stomach may be
divided into four parts. First a small right portion of the region of the pyloric canal, and, second,
the remaining larger portion which is subdivided into three parts by two lines : (1) A line
from the apex of the fundus to the pyloric canal along the junction of the upper and right two
thirds with the left and lower third, (2) a line, parallel with the oesophagus, dividing the left
and lower part into left and right portions (J. and D.). It must be understood, however, that the
lymph vessels of the various areas communicate freely with one another (Fig. 815).
The Lymph Vessels of the Kegion of the Pyloric Canal pass (a) partly to the anterior left
gastric glands, (b) partly to the right supra-pancreatic lymph glands, and (c) partly to the lower
biliary group of lymph glands. If the right gastric gland is present some of the vessels of the
upper pyloric region go to it, and in some cases vessels from the pyloric region pass directly to
the posterior left gastric lymph glands.
The Lymph Vessels from the Eight Upper Area of the larger portion of the stomach pass (a)
to the anterior left gastric lymph glands, (6) to the posterior left gastric lymph glands, (c) to the
paracardial lymph glands.
The Lymph Vessels from the Left Section of the Left and Lower Portion of the stomach pass
along the gastro-splenic ligament to the splenic glands, which are occasionally present near the
hilum of the spleen, and partly to the left supra-pancreatic lymph glands.
The Lymph Vessels from the Eight Part of the Lower and Left Area follow the course of the
right gastro-epiploic artery and terminate in the sub-pyloric glands.
The Lymph Vessels of the Duodenum are apparently few and difficult to inject ; they
communicate with those of the stomach above and the jejunum below, and the collecting
vessels which pass from the subserous plexus end in the biliary, the sub-pyloric, and the mesen-
teric lymph glands.
The Lymph Vessels of the Jejunum and Ileum, with the exception of those from the
terminal part of the ileum, pass to the mesenteric lymph glands. The lymph vessels from the
terminal part of the ileum go to the ileo-colic lymph glands.
The Lymph Vessels of the Caecum, the Vermiform Process, and the Ascending Colon
pass to the ileo-colic lymph glands, either directly or after having traversed glands which lie
nearer to the walls of the various parts of the gut.
The Lymph Vessels of the Right Colic Flexure and the Transverse Colon pass to the
meso-colic and the superior mesenteric lymph glands.
The Lymph Vessels of the Left Colic Flexure, the Descending Colon, the Iliac Colon,
and the Pelvic Colon pass to the inferior mesenteric lymph glands. From those glands the
greater part of the lymph is conveyed to the lumbar lymph glands, but part passes to the
mesenteric lymph glands and part to the common intestinal lymph trunk.
The Lymph Vessels of the Liver. The lymph vessels of the liver are described as forming
superficial and deep groups. The superficial vessels pass to subserous plexuses from which
collecting vessels arise.
The collecting vessels from the superior, anterior, and right lateral surfaces converge to a series
of posterior and anterior efferent trunks.
The posterior collecting trunks form three groups : (1) a right group, which runs
through the right triangular ligament of the liver and then downwards and medially on the
posterior wall of the abdomen, to the middle supra-pancreatic lymph glands ; (2) the middle
group runs towards the inferior vena cava, passes with it through the diaphragm, and ends in
the posterior mediastinal lymph glands ; (3) the left group passes through the left triangular
ligament to the posterior left gastric glands and the posterior paracardial glands.
The anterior collecting trunks are inferior and superior. The inferior pass from the
anterior part of the right lobe, turn round the lower border, and end in the hepatic lymph glands.
The superior group pass to the falciform ligament. Some turn posteriorly towards the inferior
vena cava, pass through the diaphragm with it and end in the posterior mediastinal lymph glands ;
others turn forwards and downwards to the round ligament, which they accompany to the porta
hepatis where they join the hepatic glands. The remaining vessels pass upwards to the anterior
part of the diaphragm which they perforate, and they end in the anterior mediastinal glands.
The superficial collecting vessels of the inferior surface of the right lobe pass (a) backwards
to the inferior vena cava and along that vessel to the posterior mediastinal glands, (6) to the
cystic gland of the biliary chain. The collecting vessels of the lower part of the left lobe end in
the hepatic glands. The collecting vessels of the caudate lobe pass partly to the posterior
mediastinal glands, along the inferior vena cava ; and partly to the hepatic lymph glands in the
porta hepatis.
The Deep Lymph Vessels of the Liver pass to ascending and descending collecting trunks.
The ascending trunks follow the hepatic veins and the inferior vena cava and end in the
C' irior mediastinal lymph glands. The descending collectors accompany the bile -ducts, the
ches of the portal vein, and the branches of the hepatic artery, and terminate in the hepatic
lymph glands.
The Lymph Vessels of the Gall Bladder. The lymph vessels from the gall bladder
terminate chiefly in the cystic gland but some pass to other members of the biliary chain.
1024 THE VASCULAK SYSTEM.
The Lymph Vessels of the Pancreas. The efferent vessels from the pancreas end in the
adjacent glands, that is, some pass to the sub-pylori c, some to the supra-pancreatic, some to the
mesenteric glands, and some to the posterior left gastric lymph glands.
The Lymph Vessels of the Spleen. The collecting vessels from the spleen pass to the
splenic lymph glands which occasionally lie near the hilum of the spleen and the left supra-
pancreatic lymph glands.
The Lymph Vessels of the Kidneys. The lymph vessels of each kidney run along the
renal blood-vessels and terminate in the lumbar glands, especially in the pre- and para-aortic
lymph glands.
The Lymph Vessels of the Ureters. The lymph vessels from the abdominal part of each
ureter pass to the lumbar and the common iliac and the sub-aortic lymph glands.
The Lymph Vessels of the Suprarenal Glands anastomose with the vessels of the kidneys
and pass to the lumbar and to the posterior mediastinal lymph glands.
The Lymph Vessels of the Diaphragm. The collecting lymph vessels from the diaphragm
pass to the thoracic lymph glands, that is, to the anterior and posterior mediastinal lymph glands,
and lower sternal glands.
The Lymph Vessels of the Posterior Wall of the Abdomen terminate in the lumbar
lymph glands.
DEVELOPMENT OF THE BLOOD-VASCULAR SYSTEM.
Dorsal aortse
1st aortic
arch
Common trunk formed
by umbilical and
yolk-sac veins
umbilicalis
impar
mbilical arteries
Vitelline arteries
FIG. 818. SCHEMA OF CIRCULATION OF AN EMBRYO, 1'35 MM. LONG, WITH
Six SOMITES. (After Felix, modified. )
THE ARTERIES AND THE HEART.
In the general account of the development of the primitive vascular system and the establish-
ment of the foetal circulation, given in a previous chapter, it was pointed out that the germ of
the whole blood -vascular system appears in the wall of the yolk-sac as a series of strands of cells
which constitute the
angioblast. Some of the Dorsal intersegmental branches
angioblast cells remain
in situ and form the
blood-vessels of the walls
of the yolk-sac and the
corpuscular contents of
the blood-vessels ; other
angioblastic cells wander
into the embryonic area
and form the blood-
vessels of the embryo ;
whilst still others be-
come located in the de-
veloping liver and other
organs, where they be-
come foci for the
formation of new blood
corpuscles. 1
The first blood-
vessels developed in the
embryonic area are the
primitive aortae. They
appear, either just before the embryonic area begins to be folded into the form of the embryo
or as the folding is commencing, in the pericardial or anterior region of the embryonic area,
where they are continuous with the earlier-formed vessels on the wall of the yolk-sac. From
the pericardial region they extend caudal wards, one on each side of the notochord, and as they
pass caudal wards they
give off a series of dorsal
and ventral branches.
The dorsal branches are
intersegmental in
arrangement, inasmuch
as they lie in the inter-
vals between the meso-
dermal somites. The
ventral branches are
more irregular, and are
neither strictly seg-
mental nor interseg-
mental in arrangement ;
moreover, they are not
only distributed to the
wall of the alimentary
canal, but they also pass
across it to the yolk-sac.
Further, those which are
situated nearest the tail
anastomose together, on
the side wall of the
hind-gut area, forming
_ lexus, and it is from that plexus, on each side, that the umbilical artery is prolonged along
the body-stalk to the chorion (Figs. 818, 819).
As the head fold forms, the cephalic part of each primitive aorta is bent into the form of a
loop, and the whole vessel assumes a hook-shaped form. The long or dorsal limb of the hook,
Dorsal intersegmental branches
,' Dorsal aortae
rtic arcl
Heart
Stem formed by union of'
lateral umbilical arid
vitelline veins
Vena umbilicalis
| impar
Umbilical arteries
Vitelline veins
819. SCHEMA OF VASCULAR SYSTEM OF AN EMBRYO, 2 '6 MM. LONG,
WITH FOURTEEN SOMITES. (Arteries after Felix, modified.)
1 See note, p. 1059.
1025
66
1026 THE VASCULAK SYSTEM.
which lies along the dorsal wall of the primitive alimentary canal, is the primitive dorsal aorta ;
the bend of the hook is the first aortic arch ; the short ventral limb of the hook, which lies
in the ventral wall of the fore-gut and the dorsal wall of the pericardium, is the primitive ventral
aorta; it is continuous, at the anterior margin of the umbilical orifice, that is at its own
caudal end, with the vitelline vein, which is carrying blood from the yolk-sac to the embryo.
The condition described is that found in embryos about 1'4 mm. long, possessing six meso-
dermal somites (Fig. 818).
In embryos in which the mesodermal somites have increased to fourteen pairs the posterior,
or caudal, portions of the primitive ventral aortae have fused together to form a single heart
(Fig. 819).
The Primitive Heart. The primitive heart lies in the dorsal wall of the pericardium and,
therefore, in the ventral wall of the fore -gut. As it grows more rapidly in length than the wall
to which it is attached, it bends upon its long axis and bulges ventrally into the interior of the
pericardium. As it projects into the pericardium it pushes before it the immediate bounding
wall of the pericardia! cavity, which thus becomes converted into the visceral pericardium. The
visceral pericardium surrounds the heart, and passes from its dorsal border to the ventral wall of
the fore-gut as a double layer which constitutes the dorsal mesocardium.
The portion of each primitive ventral aorta which lies cephalwards of the heart forms the
ventral root of the first aortic arch. At this stage the primitive dorsal aortae are still separate
from one another, and each gives off a series of dorsal intersegmental branches, and a series of
ventral branches which pass across the side walls of the primitive gut on their way to the wall
of the yolk-sac.
The caudally situated ventral vessels, as in the earlier stage, form a plexus on the side walls
of the primitive gut from
Posterior cardinal veins which the umbilical arteries
When
mesenteric) When the embryo has
2nd aortic arches | fcw and P ossesses about twenty-
ist aortic arches MT\^^^^ / l^^fc^. three mesodermal somites,
Anterior cardinal veins thT^e To^of ^fusion *a
Sinus venosus Umbilical , ft a slightly iater stage
arteries the fusion of the two primi-
Vena umbiiicalis impar tive dorsal aortae extends
PIG. 820.-SCHEMA OF VASCULAR SYSTEM OF AN EMBRYO WITH TWENTY-
THREE SOMITES. (Arteries after Felix, modified.) - .
where one of the ventral
branches of each primitive
vessel becomes enlarged and forms the origin of the stem of the primitive umbilical artery. Still
later the comparatively small continuations of the primitive dorsal aortae, which are continued
caudalwards from the twenty-third somite to the end of the caudal region, fuse together to form
the middle sacral artery the dorsal aorta, as such, terminating at the twenty-third body somite.
The Primitive Veins. In embryos 1*4 mm. long two primitive veins are present on each
side in the body of the embryo the lateral umbilical veins and the vitelline veins. The lateral
umbilical veins are the divisions of the vena umbiiicalis impar, which returns blood from the
placenta to the embryo ; and the vitelline veins return blood from the yolk-sac (Fig. 819). During
the time in which the embryo increases from 1-4 mm. to 2 '6 mm. additional veins appear. As
the body and head of the embryo become larger definite venous channels are formed to return
blood from them to the heart, and. in association with the more rapid development of the
cephalic portion of the embryo the first entirely intra-embryonic veins to appear are the anterior
cardinal veins, one on each side, which return blood from the head, and from the cephalic or
anterior portion of the body of the embryo. These veins are present in embryos possessing
fourteen mesodermal somites, and each terminates in the 'common trunks formed by the union
of the vitelline and umbilical veins of the same side (Fig. 819).
A little later the posterior cardinal veins, one on each side, develop in the caudal or posterior
part of the body. They join the anterior cardinal veins at the level of the caudal end of the
heart, and the common trunk formed by the union is the duct of Cuvier, which opens directly
into the caudal part of the heart. In the meantime the venous trunk, produced by the union of
the lateral umbilical with the vitelline vein, and into which the anterior cardinal vein opened,
is absorbed into the heart ; therefore, when the ducts of Cuvier are formed, six vessels, three on
each side, open into the caudal portion of the heart the vitelline veins, the lateral umbilical
veins, and the ducts of Cuvier. Whilst these changes in the veins are taking place, two additional
aortic arches are formed, one on each side. They spring from the cephalic extremity of the heart,
immediately caudal and somewhat dorsal to the ventral roots of the first arch ; and they terminate,
dorsally, in the dorsal aortae (Fig. 820).
DEVELOPMENT OF THE AKTEEIES.
1027
7th pair of inter-
segmental arteries
Vertebral
arteries
1st pair of inter-
segmental arteries
1st cephalic aortic arch
2nd cephalic aortic arch
3rd cephalic aortic arch
4th cephalic aortic arch
6th cephalic aortic arch
Bulbus cordis
Ventricle
The Aortic Arches and their Ventral and Dorsal Roots. The aortic arches are the vessels
which connect the ventral portions of the primitive ventral aortse with the primitive dorsal
aortas. Six such arches are formed on each side. They spring from the ventral aortse or from
the heart, they pass round the side walls of the fore-gut, in the branchial arches, and they
terminate, in relation with the dorsal wall
of the pharynx, in the primitive dorsal
aortae. All six arches are not present at
the same time, for as the more caudally
situated arches are formed those situated
more cranialwards disappear (Figs. 821, 822).
Five pairs of arches, the first four and the
sixth, are present in embryos 5 mm. long ;
but by the time the length of the embryo
has increased to 7 mm. the first two arches
on each side have begun to disappear, and the
very transitory fifth arch has been formed
(Fig. 822).
The first aortic arch, on each side, is part of
the primitive aorta, and is formed as the head
fold is developed and the fore-gut is enclosed.
It passes through the mandibular or first
branchial arch, and connects the cephalic parts
of the ventral and dorsal portions of the
primitive aortae together (Fig. 821). When
the number of mesodermal somites has in-
creased to twenty-three pairs and the embryo
is about 2-5 mm. long, a second pair of aortic
arches has appeared. They spring from the Atrium
cephalic end of the heart, dorsal to the ventral sinus venosus
roots of the first arches, and pass through the
hyoid or second pair of branchial arches to FIG. 821. SCHEMA OF THE STAGE OF FIVE AORTIC
the dorsal aortae ARCHES. The cardinal veins and ducts of Cuvier
In embryos 5 mm. long the number of are not shown -
aortic arches has increased to five on each
side the first four and the sixth, the fifth appearing later, between the fourth and the sixth. At
the period when five pairs of arches are present only four vessels spring from the cephalic end of
the heart, which is now called the bulbus cordis ; they are, on each side, an anterior stem which
forms the ventral roots of the first and second arches, and a posterior stem common to the third,
fourth, and sixth arches (Fig. 821). Up to this period the head lies quite close to the thorax,
and a distinct neck can scarcely be said to exist.
As the neck appears and the head is moved away from the thorax the third and fourth aortic
arches also move headwards
and are transposed from the
I 4th arches posterior to the anterior
[ ; 5th arches stem, which is simultane-
*^ ^^^^^^^^ j 6th arches ously elongated. When the
T^MHM|M^^^^ transposition is completed
^^^MW^^^MfMnBj ^Rll^B ^ 1C con dition depicted in
^^^^^^^^P! . Fig. 822 is attained ; the
J Vjf most cephalic, or anterior,
I/ ^~-^4 824 )'
Union of ductus arteriosus
f with aorta
Union of dorsal roots of
i 6th arches
Internal carotid
Internal carotid i
Internal carotid;
Arch of aorta
Right subclavian artery
I Left subclavian artery
Dorsal aorta
Jfc.
Left 6th arch
Right pul-
monary artery
Left pulmonary artery
External carotid/ / /^^/^l ' Innoniinate artery
External carotid / ' /^ m: R ^t 6th arch
Left common carotid
Right common carotid j /
Arch of aorta /
Left 6th arch /
Ascending aorta
FIG. 823. SCHEMA OF PART OF THE ARTERIAL SYSTEM OF A FCETUS SEEN FROM THE LEFT
SIDE. Parts of the first and second arches, the dorsal roots of the third arches, the
dorsal part of the right sixth arch, and the dorsal roots of the right fourth and fifth
arches have atrophied. The position of the fifth arch is not indicated ; see Fig. 822.
The ventral roots
of the first and
second arches form
the external caro-
tid. The third
arches themselves
and the -dorsal
roots of the second
and first arches
are converted into
the internal caro-
tids, which are
prolonged head-
wards into the
cerebral region, co-
incidently with
t;he growth of
the head.
The ventral
root of the third
arch on each side
becomes the common carotid. The ventral root of the fourth arch on the right side is converted
into the innominate artery, and the fourth arch of the right side forms part of the right
subclavian artery, i.e. a portion of that part of the right subclavian artery which lies medial to
the vertebral artery. On the left side the ventral root of the fourth arch, and the fourth arch
itself and its dorsal root, take part in the formation of the arch of the aorta, and the dorsal root
of the sixth arch is converted into the most cephalward or anterior portion of the thoracic part
of the descending aorta; the remainder of the descending aorta being formed by the earlier
fusion of the primitive dorsal aortae. Occasionally the dorsal roots of the fourth and sixth
arches on the right side persist (see p. 1051), and in such cases the right subclavian artery, of
which they form a part, springs from the descending aorta at the level of the fifth thoracic
vertebra. It is probable, therefore, that the portion of the descending aorta formed from the
dorsal roots of the left fourth and sixth arches is a comparatively small part. The left subclavian
artery, which springs from the aortic arch, in the adult, is an intersegmental artery which sprang
originally from the primitive dorsal aorta. It may be presumed, therefore, that that portion of
the aortic arch which lies dorsal to the origin of the left subclavian artery is formed from the
dorsal roots of the fourth and sixth arches of the left side a presumption which is strengthened
by the fact that the ligamentum arteriosum, which is a remnant of the left sixth arch, is attached
to the opposite border of the aortic arch immediately dorsal to the origin of the left subclavian
artery.
The sixth arch on the right side forms part of the extra-pulmonary portion of the right
pulmonary artery, the remainder of the extra-pulmonary part of the artery being derived from a
branch given off from the right sixth arch to the lung bud.
The ventral part of the left sixth arch becomes absorbed into the stem of the pulmonary artery ;
therefore the left pulmonary artery is merely the branch from the left sixth arch to the lung bud.
The dorsal part of the left sixth arch forms, during foetal life, the ductus arteriosus, which
carries the venous blood from the right ventricle of the heart to the aorta. After birth it is con-
verted into the ligamentum arteriosum.
The Branches of the External Carotid Artery. All the typical branches of the external carotid
artery are present in embryos 15-5 mm. long ; little is known, however, regarding the details
of their development. It is probable that the internal maxillary artery and its branches are
evolved partly from the ventral part of the first aortic arch and partly from an anastomosis with
the branches of a temporary stapedial artery, which develops from the dorsal end of the second
arch ; but it is not known whether the other branches of the external carotid spring as offsets
from the ventral roots of the first or second arches or from the ventral parts of the arches
themselves.
The Descending Aorta. The greater part of the descending aorta is formed by the fusion
of the primitive dorsal aortae. In embryos about 2-6 mm. long, possessing twenty-three mesoder-
mal somites, the primitive dorsal aortae are fused together ' from the tenth to the sixteenth
segment (Fig. 820). At a later period the fusion is continued caudalwards to the twenty-third
body segment the level of the fourth lumbar vertebra where the common iliac arteries arise.
Still later the small terminal portions of the primitive dorsal aortae fuse together to form the
unpaired middle sacral artery, which terminates at the extremity of the coccygeal region.
If the three somites which lie nearest the head end, in embryos possessing twenty-three somites,
DEVELOPMENT OF THE AETEEIES.
1029
External carotids
i
I
A
1st arch \
2nd arch\
Internal carotid
Internal carotid
Internal carotid
Right common carotid_"J^|
Right sub _
clavian artery ~ j_
Innominate artery
Right pulmonary"',
artery ^
Ascending aorta~
Pulmonary artery
Dorsal root of-
right 6th arch
Internal carotid
.External
carotid
External
carotid
s Dorsal root of
/' left 3rd arch
_. Left common
carotid
Arch of aorta
th arch)
Left subcla-
/vian artery
~" Arch of aorta
"" \ s Ductus
arteriosus
\ Arch of
s aorta
N Left pulmon-
ary artery
Dorsal aorta
are cephalic somites, then the point of commencement of the median aorta would be situated at
the level of the seventh body somite, that is, at the situation of the future seventh cervical
vertebra. The position of the anterior point of fusion of the primitive dorsal aortae is indicated
in the adult by the origin of the abnormal right subclavian artery, and is situated at the
level of the fifth thoracic vertebra ; therefore
the anterior end of that part of the descending
aorta which is formed by the process of the
primitive dorsal aortae must move caudalwards
during the developmental period.
The Branches of the Dorsal Aortae. Each
primitive dorsal aorta gives off a series of dorsal,
lateral, and ventral branches. The dorsal
branches are distributed to the neural tube and
body wall ; the lateral branches to the primi-
tive excretory organs the Wolffian bodies ;
and the ventral branches pass to the alimentary
canal, the yolk-sac, and to the placenta.
The dorsal branches are intersegmental in
arrangement, and when they first appear they
pass dorsally, in the intervals between the DorsafrootofSrdarci
mesodermal somites, supplying the walls of the
neural tube and the adjacent mesoderm and
nerve ganglia. After a time each primitive
dorsal intersegmental artery gives off a ventral
branch which passes first laterally and then
ventrally in the body wall, towards the ventral
median line. At this time each interseg-
mental artery consists of a stem and a dorsal
and a ventral branch. As the ventral part of
the body increases in size more rapidly than
the neural tube and the vertebral region, the
ventral branch of each primitive interseg-
mental artery soon exceeds in size the dorsal
continuation, and simultaneously the stem of
each primitive iiitersegmental vessel enlarges.
Thus it is that the stems of the intersegmental
arteries and their lateral branches become the
trunks of the intercostal and lumbar arteries,
whilst the dorsal continuation of each primi-
tive vessel is reduced to the position of" a
posterior ramus.
The dorsal branches of the intersegmental
arteries become connected together by longi-
tudinal anastomosing channels, some of which
lie ventral and others dorsal to the rudiments of
the transverse processes of the vertebras. Each
ventral branch of an intersegmental artery, as
it passes towards the mid-ventral line, gives off
a lateral branch to the tissues of the lateral part of the body wall, and at its termination it
becomes connected, by longitudinal anastomosing channels, with its more cranialward and caudal
neighbours. The lateral branches also become connected by longitudinal anastomoses.
The dorsal branch of each intersegmental artery gives off a neural ramus to the walls of the
neural tube, which divides into dorsal and ventral neural branches ; these accompany the posterior
and anterior roots of the spinal nerves. As the dorsal and ventral neural branches approach the
median plane, those of each side become connected together by a longitudinal plexus of fine
vessels, and on the ventral surface of the neural tube the longitudinal plexuses of opposite
i sides are connected together at or near the median plane.
The permanent arteries derived partially or wholly from the primitive dorsal intersegmental
arteries and their branches and anastomoses are : (1) The intercostal and lumbar arteries and
their posterior or dorsal rami ; (2) the subclavian and axillary arteries and their continuations
i in the upper extremities ; (3) the vertebral arteries ; (4) the spinal arteries ; (5) the basilar
artery ; (6) the superior intercostal arteries ; (7) the internal mammary and the superior and
inferior epigastric arteries.
In the cervical region the stems of the first six intersegmental arteries disappear, but the
seventh persists and forms, on each side, a portion of the stem of the corresponding subclavian
artery. The dorsal branch of the seventh segmental artery and the anastomoses, between it and
the first six dorsal branches, which pass ventral to the true transverse processes of the cervical
vertebrae, form the vertical part of the vertebral artery of the adult. The neural ramus of the
first cervical segmental artery and its preneural branch form the part of the vertebral artery
which lies on the atlas and passes to the ventral surface of the medulla oblongata. The cranial
or upward prolongation of the vertebral, to its union with the basilar, is developed from the
network of vessels which connects the medial ends of the preneural arteries.
66 &
Dorsal aorta
FIG. 824. SCHEMA OF PART OF THE VASCULAR SYSTEM
OF A F(ETUS SEEN FROM THE FRONT. The Origin
of the positions of the first and second arches,
the dorsal roots of the third arches on both sides,
and the dorsal roots of the fourth and fifth arches
on the right side are shown in dotted lines. The
positions of the fifth arches are not shown.
1030 THE VASCULAK SYSTEM.
The ventral branch of the seventh cervical segmental artery on each side forms the trunk of
the subclavian artery, from the origin of the vertebral to the origin of the internal mammary,
and that part of the internal mammary which extends from its origin to the upper margin of
the first costal cartilage. The remainder of the internal mammary artery, and the superior and
inferior epigastric arteries, are derived from a longitudinal anastomosis which forms between the
terminal extremities of the ventral branches of the intersegmental arteries.
The lateral ramus of the ventral branch of the seventh cervical intersegmental artery forms
the trunk of the subclavian artery beyond the origin of the internal mammary branch, and from
its prolongation into the upper extremity are formed the main arterial stems of the upper limb.
The superior intercostal arteries are derived from longitudinal anastomoses which connect
together the ventral branches of the intersegmental arteries, on the inner sides of the dorsal
parts of the ribs.
The anterior and posterior spinal arteries are derived from plexiform anastomoses which form
on the dorsal and ventral aspects of the neural tube between the terminal ends of the dorsal and
ventral neural branches of the neural rami of the posterior divisions of the intersegmental arteries.
The lateral branches of the primitive dorsal aortse supply structures derived from the inter-
mediate cell tract, and from them are formed the renal, the suprarenal, the inferior phrenic, and
the internal spermatic and ovarian arteries.
The ventral branches of the primitive dorsal aortse are not definitely segmental or inter-
segmental in arrangement. In the early stages they pass not only to the gut wall but also,
beyond it, to the wall of the yolk-sac. They are connected together by longitudinal anastomosing
channels which lie in the dorsal mesentery of the gut and also upon the wall of the gut itself.
As the yolk-sac atrophies the prolongations of the ventral branches which pass to its walls
disappear and, simultaneously, the portions of the corresponding vessels of opposite sides, which
lie in the mesentery, dorsal to the gut, and the longitudinal anastomoses which connect them,
fuse together to form unpaired stem-trunks from which the three great vessels of the abdominal
part of the alimentary canal are derived, namely, the cceliac, the superior mesenteric, and the
inferior mesenteric arteries ; but the original stem of each of these three important vessels is not
that which eventually forms its origin from the abdominal part of the aorta, for the coeliac
artery, which originally arose opposite the seventh cervical segment, wanders caudalwards to the
twelfth thoracic segment as the roots of origin of the ventral vessels which are situated nearer
the head disappear ; and in the same manner the superior mesenteric is transposed from the
level of the second thoracic to the level of the first lumbar segment, and the inferior mesenteric
wanders from the twelfth thoracic to the third lumbar segment.
The Umbilical and Iliac Arteries. It was pointed out, in the account of general features of
embryology, that the umbilical arteries which carry blood to the placental area of the chorion
arise, in a human embryo about 1*38 mm. long, about the level where the fourth cervical
mesodermal somite will be developed at a later stage. They spring from plexuses formed, on
the lateral walls of the caudal
Aorta Aorta part of the primitive gut, by
^^j|^^^^ the anastomosis of some of the
dfftj Hfei most caudally situated ventral
. External iliac artery,_^^T\ Jvb&L T vitelline branches of the
Pronephric duct - ^^^^^ ^f primitive dorsal aorta. The
Secondary part of-- --m- Jp origins of the arteries are
umbilical artery ^^ ^ gradually moved caudally as
' Primary part of -5k f the J^T , S rOWS > U ? M1 '
umbilical artery qj fj eventually, they spring trom
the primitive dorsal aorta,
FIG. 825. DIAGRAM SHOWING THE FORMATION OF THE SECONDARY
PART OF THE PRIMITIVE UMBILICAL ARTERY.
lumbar segment. As each
umbilical artery passes from
its origin on the ventral wall of the primitive dorsal aorta to the body-stalk it lies to the medial
side of the pronephric duct. The ventral origin is, however, but temporary ; for, by the time the
embryo has attained a length of 5 mm., and the primitive dorsal aortas have fused to form the
permanent descending aorta, a new vessel has arisen, on each side, from the lateral part of the
caudal end of the aorta. This new vessel passes ventrally, to the lateral side of the Wolffian duct,
and then unites, on a plane ventral to the aorta, with the primitive umbilical artery of the same
side. After the union has taken place the ventral origin of the umbilical artery disappears, and
the primitive umbilical artery then arises from the side of the caudal end of the aorta. From
the newly formed vessel, which now constitutes the only origin of the umbilical artery, the
inferior glutseal artery, which is the primitive main artery of the lower limb, arises. At a later
period, and at a more dorsal level, a second branch arises from the dorsal root of origin of the
umbilical artery ; this is the second main vessel of the lower extremity, which becomes the
external iliac and the femoral arteries of the adult. As soon as the external iliac artery is formed
that portion of the umbilical stem which lies dorsal to it becomes the common iliac artery, and
the more ventral part, which descends into the pelvis minor, becomes the hypogastric artery.
But that portion of the original umbilical artery which runs along the side of the pelvis minor to
the ventral wall of the abdomen, then cephalwards to the umbilicus and through the umbilicus
to the placenta, is still called the umbilical artery. After birth, when the placental circulation
ceases, the greater part of the intra-abdominal portion of the umbilical artery atrophies and
DEVELOPMENT OF THE AETEEIES AND THE HEAET. 1031
Primitive ventral aorta
becomes converted into the lateral umbilical ligament, but a portion of the part which lies in the
pelvis minor remains pervious and from it springs the superior vesical artery.
The Arteries of the Limbs. Our knowledge of the development of the arteries of the limbs
is still very deficient, but during the last few years some investigations have been made and
certain facts have been established. The veiy earliest stages of development have not yet been
seen in the human subject, but it is not probable that they differ, in any essential respects, from
those found in other mammals ; therefore it may be assumed that the upper limb is supplied,
at first, by a number of branches which spring from the sides of the primitive dorsal aortae. As
development proceeds the
number of the vessels is re-
duced until only one remains.
That loses its direct connexion
with the aorta and becomes
attached to the seventh seg-
mental artery forming the
ventral branch of that vessel,
and the lateral division of the
branch ; the ventral continua-
tion, past the lateral branch,
being, apparently, a later for-
mation. In the earlier stages
the portion of the artery which
lies in the free part of the limb
does not consist of a single stem
but of a plexiform series of
vessels which only gradually
become reduced to a stem.
When the stem is definitely
established it is divisible into
subclavian, axillary, brachial,
and volar interosseous portions.
The median, the radial, and
the ulnar arteries are of later
formation.
In the case of the lower
limb the earliest known artery
is the primitive inferior
gluteal, which springs from
the secondary root of origin of
the umbilical artery. It is con-
verted into the inferior gluteal
and popliteal arteries of the
adult. The external iliac and
femoral arteries are parts of a
later formation which arises
from the cephalic aspect of the
secondary root of the umbilical
artery dorsal to the origin of the
inferior gluteal. This second-
ary vessel anastomoses distally,
at the level of the proximal
part of the popliteal fossa, with
the primitive inferior gluteal,
and, afterwards, the proximal
part of the primitive inferior
gluteal undergoes a certain
amount of atrophy. The de-
velopmental history of the
arteries of the leg and foot is Diagram showing the changes of form and external appearances at different
stages. Modified from His's models.
views ;
Primitive ventral aorta
Truncus arteriosus
Bulbus cordis
Ventricle
Atrium
Sinus venosus
Vitelline vein
Truncus arteriosus
Bulbus cordis
Atrium
Atrio-ventricular
canal
Ventricle
Vitelline vein
Truncus arteriosus
Bulbus cordis
Atrium
Position of orifice
of atrio-
ventricular canal
Ventricle
Vitelline vein
Auricle of atrium
Position of orifice
of atrio
ventricular canal
Right ventricle
Bulbus cordis
Atrium
Atrio-ventricular
canal
Sinus venosus
Ventricle
Vitelline vein
Truncus arteriosus
Bulbus cordis
Atrium
Sinus venosus
Atrio-ventri-
cular canal
Ventricle
Vitelline vein
Auricle of atrium
Bulbus cordis
Left ventricle
FIG. 826. DEVELOPMENT OF THE HEART.
III.B and IV.B are side
the other figures represent the heart as seen from the front.
not definitely known.
The Heart. The rudi-
ments of the heart are the
caudal portions of the primitive ventral aortae, which lie in the ventral wall of the fore-gut and
the dorsal wall of the pericardium ; therefore the heart may be said to consist, at first, of two
tubes ; the two tubes fuse, and the heart is then a single median tube, separated by constrictions
into five compartments which, from the caudal to the cephalic end, are the sinus venosus, the
atrium, the ventricle, the bulbus cordis, and the truncus arteriosus. The constricted region between
the atrium and the ventricle is called the atrio-ventricular canal.
At a later stage the longitudinal tube becomes folded on its long axis and at the same time
twisted. The caudal limb of the loop thus produced is formed by the sinus venosus, the atrium,
and part of the ventricle ; and the cranial limb by the remainder of the ventricle, the bulbus
cordis, and the short truncus arteriosus. " Subsequently, for a time, the ventricular and bulbar
66 c
1032
THE VASCULAE SYSTEM.
part of the cephalic limb of the loop become placed transversely (Fig. 827), but after a short
period its ventricular extremity again passes caudally until the original cranial limb of the
loop lies to the right and somewhat ventral to the original dorsal limb. Still later, the bulbus
cordis is partly absorbed into the truncus arteriosus and partly into the ventricle ; the right
segment of the sinus venosus is absorbed into the atrium, and the left segment forms the
coronary sinus. At a still later period the atrium is divided, by intra-atrial septa, into right
and left atria. The atrio- ventricular canal becomes converted into the right and left a trio -
ventricular apertures. The ventricle, including the absorbed portion of the bulbus cordis, is
Ventricle
Truncus arteriosus
Truncus arteriosus
Ventricle
Atrium
Anterior
cardinal vein
Bulbus cordis
Atrio-ventrieular
canal
Sinus venosus
Ventricle
FIG. 827. VENTRAL VIEW OF A MODEL OF THE
HEART OF A HUMAN EMBRYO 2*5 MM. LONG.
(Meyer's collection. Modelled by Professor P.
Thompson.)
_ Anterior
cardinal vein
..Right horn of
sinus venosus
Left horn of
sinus venosus ! Intermediate part of sinus venosus
Ventricle
FIG. 828. DORSAL VIEW OF A MODEL OF THE
HEART OF A HUMAN EMBRYO 2 '5 MM. LONG.
(Meyer's collection. Modelled by Professor P.
Thompson.)
separated into the right and left ventricles of the adult heart ; and the truncus arteriosus, and
the part of the bulbus cordis which becomes incorporated with it, is separated into the ascending
aorta and the pulmonary artery. Thus, from the embryonic heart are eventually produced the
adult heart, the ascending aorta, the pulmonary artery, and the coronary sinus.
The main outlines of the transformation of the simple tubular heart of the young embryo
into the four-chambered heart of the adult are, therefore, comparatively simple, but the details
of the process are intricate and some of them are still imperfectly understood.
The Sinus Venosus. In embryos possessing fourteen mesodermal somites the primitive single
heart, formed by the fusion of the caudal portions of the primitive ventral aortae, receives at its
caudal end two venous stems, each of which is the common termination of the lateral umbilical
vein, the vitelline vein, and the anterior cardinal veins of the same side (Fig. 819). At a later
period, after the heart has begun to fold on its longitudinal axis, the two common venous stems
are absorbed into the heart and form its most caudal section, the sinus venosus, which consists
of a right and a left cornu, united by an intermediate segment. In the meantime, however, the
posterior cardinal veins have appeared and have united with the anterior cardinals. After this
union occurs the portion of the anterior cardinal vein ventral to the point of union becomes the
duct of Cuvier. At this period, therefore, each cornu of the sinus venosus receives three veins
the vitelline vein, the lateral umbilical vein, and the duct of Cuvier.
As development proceeds the left vitelline vein and the left lateral umbilical vein lose their
connexion with the left horn of the sinus venosus and pour their blood into the liver, through
which it reaches the cranial end of the right vitelline vein. The latter in the meantime has
become the only outflow from the liver to the heart, and it ultimately forms the terminal part
of the inferior vena cava. In association with these changes the right horn of the sinus venosus
becomes considerably larger than the left horn (Fig. 828), and the left horn and the intermediate
portion of the sinus become reduced to the form of a comparatively narrow channel which opens
into the right horn, whilst the latter opens into the dorsal part of the atrial chamber, by a cleft-
like aperture which is bounded by right and left lateral lips called the right and left venous
valves (Figs. 829, 830).
As the right horn of the sinus venosus is absorbed into the right part of the dorsal portion of
the atrium the caudal or lower portion of right venous valve becomes the valve of the inferior
vena cava and the valve of the coronary sinus. The cephalic or upper portion is united with
a septal projection into the cavity of the atrium called the septum spurium, and forms with it
the crista terminalis of the completed heart, which indicates, therefore, the line of union of the
right horn of the sinus with the atrium proper. The left venous valve becomes incorporated with
the interatrial septum, and the angle in the posterior wall of the sinus venosus which indicates
the line of union of the right cornua and the intermediate part of the sinus appears in the dorsal
wall of the right atrium, where it unites with the dorsal pa'rt of the caudal or inferior portion of
the septum secundum of the atrium, and takes part in the formation of the limbus ovalis.
Whilst these changes have been proceeding the right duct of Cuvier has become the lower
part of the superior vena cava, the intermediate part of the sinus venosus and the left cornu are
transformed into the coronary sinus, and the left duct of Cuvier has become the oblique vein of
the left atrium. Thus when the changes mentioned are completed the right part of the atrium
receives the superior and the inferior vena cava and the coronary sinus.
DEVELOPMENT OF THE HEAET.
1033
The Atrio-ventricular Canal. In the early stages the atrio-ventricular canal opens through
the dorsal wall of the ventricular .chamber towards the left side, but, as the ventricle increases in
size, the atrio-ventricular opening moves to the right till it occupies the middle part of the dorsal
wall of the ventricle. Whilst the
change in position is occurring (Esophagus
the atrio-ventricular canal becomes
compressed into a transverse cleft
which is bounded by a cranial
(upper in adult position) and a
caudal wall. On the middle part
of each of those walls an endocardial
thickening appears which is called Duct of Cuvier
an endocardial cushion. Each
cushion is a flattened eminence,
and when the two eminences meet
and fuse the atrio-ventricular canal
is divided into right and left
portions, of which the right por-
tion forms a passage from the
right part of the still incompletely
divided atrium into the right por-
tion of the incompletely divided
ventricle, and the left portion in
a similar manner forms a channel
of communication between the left
part of the atrial chamber and the
left part of the ventricle. The
two parts of the primitively single
atrio-ventricular canal become the
right and left atrio-ventricular
apertures of the adult heart, and the margins of the apertures take part in the formation of the
cusps of the atrio-ventricular valves.
The Division of the Atrium. It has already been pointed out that as the tubular heart
bends on its long axis the atrial chamber forms part of the dorsal limb of the loop. It lies,
therefore, dorsal to the truncus arteriosus and the bulbus cordis, and retains that position
throughout all the later stages of development ; consequently, it forms the dorsal part or base of
the fully developed heart. It has been stated also that, as development proceeds and the atrial
chamber expands, the right horn of the sinus venosus is absorbed into the right segment of the
dorsal portion of the expanding atrium. Whilst this process of absorption of the sinus venosus is
proceeding two other events are taking place : (1) The right and left margins of the atrium grow
ventrally round the sides
Truncus arteriosus
Right horn of sinus venosus
Secondary foramen ovale
Left venous valve
Right venous valve
Septum primum
Pericardial cavit;
Primary foramen ov
Cushion of atrio-
ventricular canal
Interventricular septum -
Interventricular sulcus
FIG. 829. SECTION OF THE HEART OF A HUMAN EMBRYO.
(Edinburgh. University collection.)
6th aortic archesx.'.
__ Septum primum
Atrio-ventricular
orifice
Bulbus cordis
of the truncus arteriosus
and the adjacent part of the
bulbus cordis ; and (2) the
primitive atrium is divided
into the right and left per-
manent atria by the forma-
tion of two interatrial septa.
By the ventral growth
of the right and left margins
of the atrium the auricles
of the right and left per-
manent atria are formed,
and by the formation and
fusion of the two interatrial
septa the permanent inter-
atrial septum of the fully de-
veloped heart is established.
The septa by which the
atrial chamber is divided
are the septum primum and
the septum secundum ; so
named because the first ap-
pears and partly disappears
before the: second is formed.
Both the septum primum and the septum secundum grow from the dorsal towards the
Central wall of the primitive atrium, the septum secundum to the right of the septum primum.
When the septum primum reaches the ventral wall of the atrium it fuses with the dorsal
mds of the endocardial cushions of the atrio-ventricular canal. Until this fusion occurs an
iperture, the primary foramen ovale, exists between the two atria and a number of perforations
formed in the more dorsal portion of the septum ; therefore the passage of blood from the
nlerior vena cava through the right part of the atrium into the left part is never prevented.
Right posterior , . __ ._ _- ^_-
cardinal vein ] / ^ ^fca^^B Ventricle
Right duct of Cuvier r'
Left venous valve j
Right venous valve
PIG. 830. MODEL SHOWING THE INTERIOR OF THE RIGHT ATRIUM OF A
HUMAN EMBRYO 5 '5 MM. LONG. (Edinburgh University collection.
Modelled by C. C. Wang.)
1034
THE VASCULAE SYSTEM.
The perforations eventually blend together to form the secondary foramen ovale of the inter-
atrial septum. As soon as the septum primum is completed the primitive atrium is divided into
the permanent right and left atria, each of which communicates through the secondary foramen
ovale, with the atrium of the
Left part of atrio-ventricular orifice Truncus arteriosus
Septum primum fusing with
superior atrio-ventricular cushion
Wall of left ' ' '
atrium
Left
posterior
cardinal
veins opened
opposite side, and with the
corresponding portion of the
ventricle through an atrio-
ventricular aperture which is
completely separate from its
fellow of the opposite side.
As the ventral border of
the septum primum fuses with
the endocardial cushions of the
atrio - ventricular canal, the
septum secundum appears, im-
mediately to the right of the
septum primum. It grows
from the dorsal and cranial
(superior in adult) walls of the
atrium. As the septum secun-
dum develops, the right cornu
of the sinus venosus is ab-
sorbed into the atrium, the
left venous valve fuses with
the septum primum or dis-
appears, and the angle between
the right horn and the inter-
FIG. 831. VIEW OF THE INTERIORS OF THE RIGHT AND LEFT ATRIA OF mediate part of the sinus ap-
A HUMA'N EMBRYO 5'5 MM. LONG. (Edinburgh University collection, pears in the caudal part of the
Modelled by C. C. Wang.) dorsal wall of the right atrium.
As the septum secundum in-
creases in size its cephalic part grows first ventrally and then caudally and lastly dorsally ; conse-
quently the free border soon becomes concave and the concavity of its margin is directed dorsally.
Both extremities of the free margin of the septum secundum fuse with the right lateral surface
of the septum primum, and the more ventrally situated part of the border, growing along the
Wall of right
atrium
Septum primui
fusing with
inferior atrio-
ventricular
cushion
Septum
" primum
Left venou
" valve
Right"
- venous
valve
Inferior atrio-
ventricular cushion
Right posterior cardinal veins opened
Right duct of Cuvier opening
into right horn of sinus venosus
7th intersegmental artery Dorsal aorta
Vertebral artery
Basilar artery
Posterior
/ cerebral artery
Aorta
1st cephalic
I aortic arch
2nd cephalic aortic arch
3rd cephalic aortic arch
4th cephalic aortic arch
Superior vena
caval blood-
stream
6th cephalic aortic arch
Septum dividing the bulbus cordis
Internal carotid artery
Interventricular septum
Foramen ovale
Inferior vena
caval blood- _
stream
Middle
'cerebral artei
Anterior cerebral
artery
Intera trial
septn m
FIG. 832. DEVELOPMENT OF THE HEART AND THE MAIN ARTERIES.
Diagram of the heart, showing the formation of its septa, and of the cephalic portion of the arterial system.
septum primum, fuses with the angle between the right horn and the intermediate part of the
sinus venosus forming with it the lower part of the limbus fossae oval is of the fully developed heart.
The remainder of the limbus is formed by the thickened free margin of the septum secundum.
As soon as the septum secundum passes beyond the level of the foramen ovale that portion
DEVELOPMENT OF THE VEINS. 1035
of the dorsal part of the septum primum which is not yet fused with the septum secundum
acts as a flap valve, permitting blood to pass from the right to the left atrium, but preventing
its return. This condition persists until birth, when the thickened free margin of the septum
secundum fuses with the right lateral face of the septum primum, and the foramen ovale of the
foetus becomes the fossa ovalis of the child. The fossa ovalis is bounded ventrally and caudally
(anteriorly and inferiorly) by the limbus fossae ovalis, which is formed mainly by the originally
free margin of the septum secundum, but to a small extent also by the angle between the right
cornu and the intermediate part of the sinus venosus.
The Division of the Primitive Ventricle, the Bulbus Cordis, and the Truncus
Arteriosus. Two facts have already been pointed out with regard to the bulbus cordis ; firstly,
that it forms part of the cranial or anterior limb of the early loop-shaped heart, and secondly,
that it disappears by being absorbed partly into the ventricle and partly into the truncus
arteriosus. The part absorbed into the ventricle enters into the formation of that part of the
ventricle which afterwards becomes the right ventricle of the completed heart, and the part
absorbed into the truncus arteriosus lengthens that trunk.
The division of the elongated truncus arteriosus into the pulmonary artery and the ascending
aorta is a complicated process in which three factors are associated : (1) a proximal and (2) a
distal set of eiidocardial swellings in the bulbar part of the truncus aorticus, which are known as
the proximal and distal bulbar swellings, and (3) a septum called the aorto-pulmonary septum,
which appears at the cephalic end of the truncus aorticus, growing from the angle between the
orifices of the more dorsally situated sixth aortic arches, and the orifices of the two stems which
form the ventral roots of the first four aortic arches. The three sets of elements are, at first,
entirely distinct from one another, but ultimately they blend together to form a spiral septum
by which the lumen of the truncus arteriosus is divided into two channels. One of the two
channels communicates with the right ventricle and the other with the left ventricle. After
the septum is completed it is cleft longitudinally into two parts, and so the truncus is divided
into two vessels, the pulmonary artery which communicates with the right ventricle, and the
aorta which is connected with the left ventricle.
The proximal bulbar swellings, which take part in the separation of the truncus into
pulmonary artery and aorta, are. prolonged into the ventricular region as the ventral part of the
bulbus cordis is absorbed into the ventricle, consequently the septum which they form by their
fusion is prolonged into the ventricular chamber, and helps to separate that cavity into two parts,
by fusing with the dorsal end of the cephalic or anterior portion of the interventricular septum.
The interventricular septum appears as a semilunar ridge on the inner surface of the ventral
part of the wall of the ventricle. At a later period its position is marked on the outer surface of
the ventricle by the interventricular sulcus (Fig. 829) which persists in the completed heart. As
the interventricular septum increases in height it fuses with the fused endocardial cushions which
divided the atrio-ventricular canal into right and left parts, and with the ventral border of the
bulbar septum which projects into the dorsal part of the ventricular chamber. The completed
interventricular septum consists, therefore, of two distinct parts : a ventral part formed by the
proper interventricular septum, and a dorsal part formed by the lower portion of the fused bulbar
endocardial cushions. The twojparts can be distinguished quite easily in the adult heart, for the
interventricular septum is muscular, and it forms by far the greater part of the permanent
septum, whilst the bulbar part of the septum, being developed from endocardial thickenings, is
membranous, and it forms the small pars membranacea of the permanent septum, which lies
between the aortic vestibule of the left ventricle and the dorsal part of the right ventricle and
the adjacent ventral part of the right atrium.
DEVELOPMENT OF THE VEINS.
Simultaneously with the formation of the arteries, by which blood is distributed to the
embryo and to all parts of the zygote, and in a similar manner, a series of vessels is developed
by means of which the blood is returned to the heart. These vessels are the primitive veins ;
they form two main groups which make their appearance at different periods.
The first group consists of (1) the vitelline veins which return blood from the yolk sac, and
(2) the umbilical veins which return the blood from the placenta.
The second group consists of (1) the anterior cardinal veins, (2) the posterior cardinal veins,
the (3) ducts of Cuvier, and (4) the subcardinal veins.
The ducts of Cuvier, one on each side, are the common stems by which the blood of the
anterior and posterior cardinal veins is conveyed to the primitive heart. The anterior cardinal
vein returns blood from the head and neck and fore limbs. The posterior cardinal veins carry
blood from the body walls, the Wolffian bodies, and the hind limbs. The subcardinal veins also
are closely associated with the return of blood from the Wolffian bodies.
The veins of the first group are largely transitory. The umbilical veins entirely disappear
as blood channels, but a part of the left lateral umbilical vein is recognisable in the adult as the
ligamentum teres of the liver. Portions of the intra-embryonic parts of the vitelline veins,
and anastomoses which form between them, remain as the portal vein, its right and left
branches, and the upper end of the inferior vena cava.
The anterior cardinal veins, their tributaries, and a transverse anastomosis which forms
between them in the more cranialward or upper portion of the thoracic region, are converted
into the (1) cavernous sinuses of the cranium, (2) the internal jugular veins, (3) the innominate
veins, (4) the upper part of the superior vena cava, and (5) the upper part of the left superior
1036
THE VASCULAE SYSTEM.
intercostal vein. The other venous channels of the cranium and the head and neck and the
upper extremities are later formations.
The right duct of Cuvier forms the inferior half of the superior vena cava, and the left duct
of Cuvier becomes the oblique vein of the left atrium.
The posterior cardinal veins take part in the formation of the inferior vena cava, the azygos
herniazygos, and accessory hemiazygos veins, and the hypogastric veins. The right subcardinal
takes part in the formation of the inferior vena cava, and an anastomosis between the right and
left subcardinal veins forms a large part of the left renal vein.
The Vitelline and Umbilical Veins and their Association with the Formation of the
Portal System and the Upper End of the Inferior Vena Cava. The vitelline veins, left and
Upper or cephalic part of inferior vena cava
Right vena revehen
Sinus venosus
Left lateral
mbilieal vein
Right branch oP
portal vein
Atrophied part of right- \
vitelline vein V
,, Left vena reveheus
jjPjr-- Ductus venosus
Left branch of portal vein
_ Atrophied part of left
vitelline vein
"" Left lateral umbilical vein
- - Superior uiesenteric vein
Right vitelline vein
3
Upper or cephalic part of inferior vena cava
j Left hepatic vein
Right hepatic vein JJ^J_ Ductus ven osus
Azygos vein
Sinus venosus
\
Left lateral
'" umbilical
vein
Left lateral
umbilical vein
" Left vitelline vein
N Right vitelline vein
2
Right renal vein
Part of inferior vena
cava derived from right
posterior cardinal vein
Left renal vein
Left spermatic vein
Left suprarenal vein
Liver
Inferior vena cava ;
down growth from
upper part
Left branch of
portal vein
Right branch of portal vein
_. Left branch of portal vein
Left lateral
umbilical vein
Part of inferior vena
cava formed from
right subcardinal vein
Splenic vein
Superior mesenteric
vein
\ Right vitelline vein
Left renal vein
PIG. 833. SCHEMATA, showing four stages of the development of the portal system and
part of the inferior vena cava.
right, pass over the wall of the yolk-sac, and, later, along the sides of the vitello-intestinal duct
and the duodenum, towards the caudal end of the heart. For a time each unites with the corre-
sponding lateral umbilical vein to form a common stem, but at a later period each vitelline vein
opens separately into the corresponding cornu of the sinus venosus of the heart.
The umbilical veins are three in number the vena umbilicalis impar, which passes first along
the body stalk, and later along the umbilical cord, and divides into the right and left lateral
umbilical veins, which run, in the edges of the body wall, along the margin of the umbilical orifice,
to their union, first, with the corresponding vitelline veins, and later with the corresponding
cornua of the sinus venosus of the heart.
On their way to the heart, both the vitelline and the lateral umbilical veins pass through
DEVELOPMENT OF THE VEINS. 1037
the mass of mesoderm, called the septum transversum, which lies in the cranial margin of the
umbilical orifice and at the caudal end of the pericardium. The septum transversum afterwards
takes part in the formation of the diaphragm, the liver, the falciform ligament of the liver and
the lesser omentum. As the liver is formed from it the cardiac ends of the vitelline and lateral
umbilical veins become enclosed in the liver substance, and pour their blood into a number of
freely communicating channels or sinusoidal spaces, which form by far the greater portion of the
liver in the early stages of its development.
Whilst the formation of the sinusoidal spaces is occurring in the liver, the parts of the fore-
gut have been denned, and the viteliine veins, as they approach the growing liver, pass along
the sides of the duodenum and become connected, around it, by three transverse anastomoses, two
of which lie ventral and one dorsal to the duodenum. Cranialwards of these anastomoses each
vitelline vein is broken up by the formation of the sinusoidal channels in the liver substance,
into a caudal part, the vena advehens, which enters the liver substance, and a cranial part, the
vena revehens, which passes from the liver to the heart. After a time the left vena revehens
loses its direct connexion with the heart, moves across towards the right, and opens into the
cranial end of the right vena revehens. When this change has occurred all the blood passing to
the liver by the vitelline veins reaches the heart by the cranial extremity of the right vena
revehens, which now becomes the upper end of the inferior vena cava. This also receives the
ductus venosus a new channel, which is evolved from the sinusoidal spaces, and carries the major
part of the blood from the left lateral umbilical vein to the upper end of the inferior vena cava.
In the meantime degeneration takes place in the ventral and caudal parts of the vitelline veins
and the loops formed by the three transverse anastomoses between them. The ventral parts of the
veins disappear with the degeneration of the yolk-sac, and the right half of the caudalward and
the left part of the more cranialward situated loops also disappear. Simultaneously the superior
mesenteric vein, which has been evolved in association with the formation of the intestine from
the mid-gut, opens into the left vitelline vein, caudal to the dorsal transverse anastomosis, and,
a little later, the splenic vein enters at the same point. The final result is the formation of the
permanent vena portse, which is formed from (1) the cephalic end of the left limb of the caudal
loop between the vitelline veins ; (2) the dorsal anastomosis between the vitelline veins ; (3)
the right limb of the cephalic loop formed by the vitelline veins. The right branch of the portal
vein is the right vena advehens. The left branch of the portal vein is formed from the left vena
advehens, and the most cranialward of the two ventral anastomoses between the vitelline veins. It
is connected with the ligamentum teres of the liver, because the left lateral umbilical vein, which
opened at one time into the left horn of the sinus venosus of the heart, and afterwards into the
sinusoids of the liver, finally becomes connected with the left vena advehens, at the level of the
cranialward ventral anastomosis between the two vitelline veins ; and it is connected with the
ductus venosus so that a channel may exist by which the blood from the placenta can pass to the
right vena revehens without much admixture with the venous blood passing to the liver through
the left branch of the portal vein and the left vena advehens. Therefore the ductus venosus
is developed from the sinusoidal spaces of the liver when the left lateral umbilical vein is trans-
ferred to the left vitelline vein.
The venae revehentes, which transfer the blood from the liver to the heart, are the cranial
ends of the primitive vitelline veins. The left vena revehens, as already stated, eventually loses
its connexion with the heart and ends in the right vena revehens, which receives the ductus venosus
also. The right vena revehens thus becomes the only channel by which blood is returned to the
heart from the alimentary canal and from the placenta : that is, it becomes the upper or cranial
end of the inferior vena cava. The stems of the right and left venae revehentes become the right
and left hepatic veins which convey to the inferior vena cava the blood which was carried from
the alimentary canal to the liver by the portal vein and its branches.
The sinusoidal spaces become reduced to the blood capillaries of the liver, and the ductus
venosus which, during foetal life, conveyed the greater part of the placental blood to the inferior
vena cava becomes reduced, after birth, to the ligamentum venosum, which connects the left
branch of the portal vein with the upper end of the inferior vena cava.
As the cranial part of the right vitelline vein is transformed from the right vena revehens
into the upper end of the inferior vena cava, an outgrowth passes caudally from it, along the
dorsal aspect of the liver ; this becomes connected, at its caudal end, with the right subcardinal
vein, and it forms that part of the inferior vena cava which lies in the groove on the dorsal aspect
of the right lobe of the liver.
The Umbilical Veins. In the earliest stages of development there are three umbilical veins,
the vena umbilicalis impar and the left and right lateral umbilical veins. The vena umbilicalis
impar and the left lateral vein persist until birth, and a remnant of the latter is found, in the
adult, as the ligamentum teres of the liver ; the right lateral vein disappears entirely at an
. early stage of development.
The vena umbilicalis impar passes from the placenta to the caudal boundary of the umbilical
i orifice, where it terminates in the left and right lateral umbilical veins. Each of the latter
unites, for a time, with the corresponding vitelline vein ; then it becomes directly connected with
the corresponding cornu of the sinus venosus of the heart, and still later with sinusoidal spaces
of the liver. The right lateral umbilical vein has also a temporary secondary connexion with
the right vitelline vein, but at an early period it undergoes atrophy and all parts of it completely
disappear.
The left lateral umbilical vein, which is connected first with the left vitelline vein, next with
; the heart, still later with the liver, and finally with the left vitelline again, at the point where
1038
THE VASCULAK SYSTEM.
the latter becomes the left vena advehens, persists until birth and, after the disappearance of the
right lateral umbilical vein, it conveys the blood from the placenta to the liver, where part of the
placental blood passes into the left vena advehens and so through the left vena revehens to the
inferior vena cava, and part passes into the ductus venosus, by which it reaches that portion of
the cranial part of the right vena revehens which becomes the cranial or upper end of the
permanent inferior vena cava.
After birth when the placental circulation ceases the left lateral umbilical vein becomes the
ligamentum teres of the liver.
Middle plexus
Posterior plexus
Anterior plexus
Posterior stem
Otic vesicle
'"^ Anterior stem
' x Ophthalmic vein
Anterior cardinal vein j Semilunar ganglion
Middle stem
Primary head vein
FIG. 834. DIAGRAM OP THE PRIMARY HEAD VEIN AND ITS TRIBUTARIES. (After Streeter.)
The Ductus Venosus. The ductus venosus is developed as the left lateral umbilical vein
loses its direct connexion with the liver and becomes united to the left vena advehens. It is
formed from the sinusoidal spaces of the rudimentary liver and connects the commencement of
the left vena advehens with the cranial part of the right vena revehens. It forms the more
direct channel by which blood from the placenta is passed to the heart through that part of the
right vena revehens which becomes the upper end of the inferior vena cava. After birth it
converted into the fibrous ligamentum venosum, which connects the left branch of the port
vein with the upper end of the inferior vena cava.
Middle and anterior plexuses
Posterior plexus
Upper part of anterior stem
Middle stem
_! Lower part of anterior stem
Ophthalmic vein
Internal jugular vein
V
Parts of primary head vein
FIG. 835. DIAGRAM or THK HEAD VEINS OF A 21 MM. EMBRYO. (After Streeter.)
The Anterior Cardinal Veins. The anterior cardinal veins are the veins by which t.
blood is returned to the heart from the head and neck and, ultimately, from the upper extn
ties also, although the primitive veins of the upper extremities are, in the first place, trib
of the posterior cardinal veins.
Each anterior cardinal vein may be separated into two parts the intra- cranial and
extra- cranial
In the majority of vertebrates the portion of each anterior cardinal vein which is
in the head region, and which afterwards becomes intra-cranial, lies to the medial side c
otic vesicle and the 5th, 7th, 8th, 9th, 10th, and llth cerebral nerves.
DEVELOPMENT OF THE VEINS.
1039
At a later period that portion of the vein which lay medial to the otic vesicle and the 7th,
8th, 9th, 10th, and llth cerebral -nerves has disappeared and has been replaced by a new channel,
which is placed lateral to the otic vesicle and the 7th, 8th, 9th, 10th, and llth cerebral nerves.
The new channel extends from the semilnnar ganglion of the trigeminal nerve to the upper end
of the extra-cranial part of the anterior cardinal vein, that is, to the upper end of the internal
jugular vein. This secondary vessel follows the course of the facial nerve and in part of its
extent it is extra-cranial.
In the human embryo the stage in which the primitive stem vein lies to the medial side of
the otic vesicle and the 7th, 8th, 9th, 10th, and llth nerves does not seem to occur. At all
events in a 3 mm. embryo in the Edinburgh University Collection, and in a 4 mm. embryo in
the Collection of the Carnegie Institution of Washington (Streeter), the second stage, in which
the posterior part of the cranial portion of the primitive vein lies lateral to the otic vesicle and
the 7th, 8th, 9th, 10th, and llth cerebral nerves, is already present and there is no indication
of a vein medial to the otic vesicle.
In the human embryo, therefore, the primitive venous stem in the head region, on each side,
consists of an anterior portion medial to the semilunar ganglion of the trigeminal nerve, and a
posterior portion lateral to the otic vesicle and the 7th, 8th, 9th, 10th, and llth cerebral nerves ;
for this stem Streeter has suggested the convenient term "primary head vein" (Fig. 834).
The most anterior tributaries of the primary head vein are derived from the region of the
otic vesicle and remnants of them become converted into the ophthalmic vein, but in addition to
the anterior tributaries there are numerous dorsal or upper tributaries which become arranged
in three main groups : an anterior plexus associated with the regions of the fore-brain and the
Longitudinal anastomoses of vessels
of anterior and middle plexuses
Veins of
anterior plexus
Veins of
anterior plexus
Primary head vein
FIG. 836 A. DIAGRAM OP A TRANSVERSE
SECTION OF THE SECONDARY FORE-
BRAIN AND THE VENOUS PLEXUSES.
Longitudinal
anastomosis
nterventricular
.men
Third ventricle
Inferior cerebral vein
FIG. 836 B. DIAGRAM OF A TRANSVERSE SECTION OF THE
BRAIN SHOWING THE FOLDING OF THE UPPER PARTS OF
THE PLEXUSES BETWEEN THK CEREBRAL HEMISPHERES.
mid-brain ; a middle plexus associated with the cerebellar region of the hind-brain ; and a
posterior plexus associated with the region of the medulla oblongata (Fig. 834).
The vessels of each plexus tend to run together as they approach the stem of the primary
head vein and so three stems are formed, the anterior, middle, ana posterior ; they were described
by Mall in 1904 (Fig. 834). This condition persists until the embryo attains a length of about
18 mm. when an anastomosis forms, above the otic vesicle, between the stems from the middle
and posterior plexuses (Fig. 835), and at the same time that part of the primary head vein which
lay lateral to the otic vesicle and the 7th, 8th, 9th, 10th, and llth cerebral nerves disappears.
By the time the embryo has become 21 mm. long the anastomosis mentioned has become
very important, and a separation has occurred between the lower and the upper portions of the
anterior stem tributary ; therefore, at that period, the blood from the eye region flows backwards
to the anterior end of the primary head vein, then upwards along what was the lower part of
the middle stem tributary, next backwards along the anastomosis above the otic region to the
posterior stem tributary, down which it passes to the upper part of the extra-cranial portion of
the anterior cardinal vein which has now become the internal jugular vein (Fig. 835). At this
, time the blood from the anterior and middle plexuses reaches the supra-otic anastomosis through
( the upper or dorsal part of the middle stem tributary (Fig. 835).
In the meantime the subdural and subarachnoid spaces have been forming, and with the
formation of those spaces the main parts of the venous plexuses are carried away from the brain,
ith the membrane which will be transformed into the dura mater, but in part the plexuses
still retain their connections with the piamater on the brain surface, and they afterwards
establish new connections with the veins which appear on the surfaces of the developing
cerebral hemispheres. In the meantime on each side the upper or dorsal tributaries of the
anterior and the middle plexus anastomose together (Fig. 835).
1040
THE VASCULAE SYSTEM.
^x Superior sagittal sinus
Cerebral hemisphere
Inferior sagittal sinus
Internal cerebral vein
7 Chorioid plexus of third ventricle
Tr^r=r^T.Vena basalis
Vena basalis
When the cerebral hemispheres increase in size the dura-matral tissue is compressed between
them, and between the cerebral hemispheres above and the mid- and hind -brain below, in the
form of folds (Figs. 836 A and B). As the folds are formed the conjoined anterior and middle
plexuses of one side are carried into relation with those of the opposite side in the median plane
of the head ; there the vessels of opposite sides unite together and are finally resolved into the
superior and inferior sagittal sinuses and the straight sinus (Figs. 837 A and B), and at the same
time some of the
smaller vessels of the
plexuses which re-
tain their connection
with the piamater
are transformed into
the internal cerebral
veins and the great
cerebral vein ; and
from some of the
lower or ventral
Lateral ventricle tributaries, on each
Chorioid plexus of lateral ventricle S } d *> } B . Produced
the inferior cerebral
vein of the embryo
which probably be-
comes the vena
basalis of the adult
(Figs. 837 B, 838).
Whilst the changes
last mentioned are
taking place the
growth of the hemi-
spheres forces the
upper part of the
middle stem tribu-
tary on each side
backwards and then
downwards until it
becomes the hori-
zontal part of the
transverse sinus (Fig.
838), whilst the an-
astomosis above the
otic region and the
posterior stem tribu-
tary are converted
into the sigmoid
portion of the trans-
verse sinus (Fig. 838).
By the time this
stage is attained the
anterior portion of
the primary head
vein which lies to
the medial side of
the semilunar gang-
lion has become the
cavernous sinus, and
the lower or ventral
part of the middle
stem tributary has been converted into the superior petrosal sinus (Fig. 838).
The inferior petrosal sinus appears to be an independently formed anastomosis which
connects the posterior end of the cavernous sinus with the upper end of the internal jugular
vein across the medial side of the otic region (Fig. 838).
The extra-cranial parts of the anterior cardinal veins become connected together, in the
upper or cephalic part of the thoracic region, by a transverse anastomosis which becomes the
greater part of the left innominate vein. A short distance cranialwards to this transverse
connexion, the primitive vein of the upper limb ultimately opens into the anterior cardinal
vein. The portion of the anterior cardinal vein of the right side, which lies between the
entrance of the limb vein and the transverse anastomosis, becomes the right innominate vein
(Fig. 839), and the corresponding part on the left side forms the commencement of the left
innominate vein.
The part of the extra-cranial portion of each anterior cardinal vein which lies cephalwards
of the entrance of the limb vein forms the internal jugular vein ; and the part of the right
anterior cardinal vein which lies caudalwards of the transverse anastomosis becomes the upper
FIG. 837 A. DIAGRAM OF A TRANSVERSE SECTION OF THE BRAIN SHOWING
SAGITTAL SINUSES STILL CONNECTED BY REMAINS OF THE PLEXUSES.
Superior sagittal sinus
- Cerebral
Lateral ventricle
Inferior sagittal
sinus
Great cerebral
vein
/ Vena basalis
Mid-brain
FIG. 837 B. DIAGRAM OF A TRANSVERSE SECTION OF THE BRAIN AFTER
COMPLETION OF THE SAGITTAL SINUSES.
DEVELOPMENT OF THE VEINS.
1041
or cephalic part of the superior vena cava, whilst the corresponding portion of the left vein is
converted into the upper part of the left superior intercostal vein (Fig. 839).
The external jugular vein is a new formation which receives for a time the cephalic vein of
the upper extremity ; but the cephalic vein, which is a secondary vessel, is eventually transposed
to the axillary vein, which is a part of the primitive upper limb vein.
The Posterior Cardinal Veins, the Subcardinal Veins, and the Inferior Vena Cava.
The posterior cardinal veins appear later than the anterior cardinal veins and they terminate
cranialwards in the ducts of Cuvier. They lie dorsal to the Wolman bodies and they
become connected with each other, dorsal to the descending aorta, by numerous transverse
anastomoses.
The subcardinal veins appear later than the posterior cardinals. They lie along the ventral
borders of the Wolman bodies and they are connected not only by dorso-ventral anastomoses with
the posterior cardinal veins, but also by transverse anastomoses with one another. The majority
of both sets of anastomosing vessels ultimately disappear, but two remain ; one which joins the
right subcardinal to the right posterior cardinal, at the level of the right renal vein ; and one
which connects the subcardinal veins together, across the ventral surface of the aorta, at the
same level.
After a time an anastomosis is formed between the right subcardinal vein and the cephalic
end of the right vena revehens, dorsal to the liver, by the caudal outgrowth of an anastomosing
Superior sagittal sinus
Inferior sagittal sinus
"* Internal cerebral veins
s verse sinus,
irizontal part
= upper part of |
middle stem
Sigmoid part of
transverse sinus
linal part of sigmoid portion"
of trans verse jsinus = posterior stem
FIG. 838. DIAGRAM OF
Straight sinus
'Great cerebral vein
~- Remnant of anterior stem
thalmic vein
Semilunar ganglion
Inferior petrosal sinus
N Superior petrosal sinus = lower part of middle stem
Internal jugular vein
VENOUS SINUSES. (Only one transverse sinus is shown).
i offset from the right vena revehens. As soon as the anastomosis is completed the blood from
the caudal portion of the body and from the lower limbs is short-circuited to the heart, and
extensive changes occur in the primitive posterior cardinal veins, into which in the meantime
. the veins from the lower extremities have opened.
The Posterior Cardinal Veins. The right posterior cardinal vein, cephalwards of the right
i renal vein, becomes the vena azygos. Betwe'en the right renal vein and the entrance of the
lower limb vein it forms the caudal or lower part of the inferior vena cava and the right common
iliac vein ; the remainder of the right posterior cardinal vein becomes the right hypogastric vein.
Two of the transverse anastomoses between the posterior cardinal veins form the transverse
parts of the hemiazygos and accessory hemiazygos veins ; others become converted into those parts
: of the left lumbar veins which lie dorsal to the aorta, and one, which lies opposite the fifth lumbar
somite, becomes the greater part of the left common iliac vein.
Portions of the left posterior cardinal vein remain as the left hypogastric vein, the
hemiazygos and the accessory hemiazygos veins and the lower part of the left superior intercostal
vein.
The tributaries of the right posterior cardinal vein become the right intercostal, subcostal,
md the right lumbar veins. The right renal vein is also one of its tributaries. The tributaries
3f the left posterior cardinal become the left intercostal and subcostal veins, and they form those
3arts of the left lumbar veins which lie to the left of the vertebral column, and the corresponding
aart of the left renal vein (Fig. 839).
The Subcardinal Veins. The only important parts of the subcardinal system which remain
n the adult are a portion of the right subcardinal vein, one of its anastomoses with the right
oosterior cardinal vein, and a transverse anastomosis between the subcardinal veins. The last
67
1042
THE VASCULAK SYSTEM.
forms the part of the left renal vein which crosses the front of the abdominal part of the aorta,
and the first two form that part of the inferior vena cava which extends from the liver to the
entrance of the renal veins.
The Inferior Vena Cava. It follows, from what has been said, that the inferior vena cava is
a composite vessel derived from five sources : (1) the cephalic end of the right vitelline vein ;
internal jugular vei
External jugular vein
Vertebral artery
Left innominate vein
Subclavian artery
Subclavian
Right pulmonary a
Superior vena cava
Right atrium
Vena azygos
Right ventricle
Inferior vena cava,
vitelline vein portion
Inferior vena cava, down-
growth from vitelline vein
Right and left branches
of portal vein
Portal vein
Remains of vitelline vei
Inferior vena cava
(subcardinal part)-
Right renal vein
Right lumbar vein
Inferior mesenteric artery
Common iliac artery
External iliac artery
1st aortic arch
"Internal carotid
-2nd aortic arch
External carotid
Internal carotid
-, - J Arch of aorta
Left subclavian artery
Left subclavian vein
_^, Ductus arteriosus
~ ~ ~ "Pulmonary artery
"""Left superior intercostal vein
"^--Left atrium
Left ventricle
Accessory hemiazygos vein
Hemiazygos vein
Aorta
Cceliac artery
Spleen
Splenic vein
.Superior mesenteric vein
^Superior mesenteric artery
-Kidney
""- --Left renal vein
Umbilical vein
^iLeft lumbar vein
Placenta
" Umbilical arteries
Umbilical artery -
FIG. 839. DIAGRAM OF THE COURSE OF THE FCETAL CIRCULATION.
(2) a caudal outgrowth from the cephalic part of the right vitelline vein; (3) a portion of the
right subcardinal vein ; (4) an anastomosis between the right subcardinal vein and the right
posterior cardinal vein ; and (5) a portion of the right posterior cardinal vein.
The Veins of the Extremities. The primitive veins of the extremities are superficial vein
which run along the corresponding borders of the two limbs, i.e. the ulnar border of the upper and
the fibular border of the lower limb.
The primitive vein of the upper extremity, which becomes the basilic vein, the axillary vein,
and the subclavian vein in different regions, opens at first into the posterior cardinal vein, after-
wards into the duct of Cuvier, and finally into the anterior cardinal vein.
DEVELOPMENT OF THE LYMPH VASCULAE SYSTEM. 1043
The cephalic vein of the upper extremity appears at a later period and, in the first instance,
joins the external jugular vein, the primitive termination being occasionally retained in adult
life. At a later period its terminal extremity is transferred to the axillary vein.
The deep veins which accompany the arteries are the latest venous formations of the
extremities.
The primitive vein in the lower extremity becomes the small saphenous vein, which is con-
tinued proximally, as the inferior glutseal vein, to that part of the posterior cardinal vein which
later becomes the hypogastric vein. The great saphenous vein and the femoral vein appear later
and are continued to the posterior cardinal vein as the external iliac vein. After the external
iliac vein joins the posterior cardinal vein the part of the latter vessel which lies caudal to the
i point of union is called the hypogastric vein.
THE DEVELOPMENT OF THE LYMPH VASCULAR SYSTEM.
Very little is known regarding the origin of the vessels of the lymph vascular system in man,
but during recent years numerous investigations have been made with the object of discovering
the various phases of the development of the lymph vascular system in other mammals ; some of
the main points are however still subjects of dispute.
It is generally admitted that the terminal parts of the great lymph vessels, that is, the
terminal part of the thoracic duct and the right lymphatic duct, are derived from venous channels,
which, for a time, lose their connexion with the larger veins and become modified into terminal
lymph sacs which obtained a secondary union with the great veins at the root of the neck j but
regarding the origin of the thoracic duct and the cisterna chyli and the peripheral lymph vessels
there is, as yet, no agreement. According to Florence Sabin, and those who agree with her, the
peripheral lymph vessels are outgrowths from a series of lymph sacs, themselves of venous origin,
and from veins. Of the lymph sacs the two cervical, a retro-peritoneal, a cisterna chyli, and two
posterior sacs, lying along the inferior glutaeal veins, are recognised in human embryos of about
24 mm. length. The origin of these sacs, in the human embryos, has not been proved, but it
appears probable that the cervical sacs are derived as in other mammals from venous capillary
vessels. There is no agreement, however, concerning the origin of the other sacs, for whilst, on
the one hand, Florence Sabin appears to believe that they have an origin like that of the
jugular lymph sacs and that the thoracic duct is developed in the same manner, Huntington, on
the other hand, believes that, with the exception of the jugular or cervical lymph sacs, all the
other lymph vessels, including the thoracic duct, are developed neither as outgrowths from
lymph sacs nor by the modification of venous capillaries, but by the formation of endothelial
lined spaces in the mesodermal tissues. The spaces are at first entirely closed but afterwards
attain union with one another and with the terminal lymph vessels.
According to the view upheld by Florence Sabin and her supporters, the lymph vessels are
outgrowths from the venous system, and are, therefore, lined with endothelium. which is
genetically the same as that in the veins. According to Huntington this is not the case ; for
his observations lead him to believe that the endothelium of the lymph vessels is formed, in
situ, from the mesodermal cells, and it has, therefore, no direct genetic connexion with the
endothelium of the veins, which is derived from the original angioblast. The evidence brought
forward by the supporters of the opposite views is interesting and instructive upon many
points, but the question must still be regarded as an open one.
The Development of Lymph Glands. Lymph glands are developed from plexuses of lymph
vessels. The transformation is brought about by the aggregation of numerous lymphocytes in
the connective tissue strands of the plexuses and the transformation of the lumina of the vessels
into .the peripheral and central portions of the lymph sinus. The stroma, the capsule, and the
proper substance of a lymph gland are therefore formed from the fibro-cellular reticulum of the
lymphatic plexus, and the cavity of the lymph sinus is formed from the lumina of lymph
capillaries. The rudimentary lymph glands possess blood vascular as well as lymphatic
capillary networks, and if the blood vascular network preponderates over the lymph vascular the
developing gland has a reddish appearance and is known as a haemal gland. Such glands are
found in man (Schafer) as well as in other mammals, and it would appear from the recent observa-
tions of S. v. Schumaker that haemal glands are merely rudimentary forms of true lymph glands
(Arch.f. mikr. Anat. H. 2., 1912).
MOEPHOLOGY OF THE VASCULAE SYSTEM.
In conformity with the general plan of the vertebrate body, the vascular system is essentially
segmeutal in character. This is obvious, even in the adult, in the intercostal and lumbar
vessels. It is distinguishable, though less obvious, in the vessels of the head and neck and of
! the pelvis.
The intersegmental arteries and veins form a series of bilaterally symmetrical vessels, each
which is united to the vessels of adjacent segments by segmental channels, which anastomose
,
1044
THE VASCULAK SYSTEM.
RD.A.
with one another, through the portions of the intersegmental vessels which they connect
together, and thus form longitudinal trunks. The longitudinal trunks are mainly, though
not exclusively, seg-
mental. From them
the main stem vessels
of the individual are
formed, and from or
to these latter the in-
tersegmental vessels
appear to proceed as*
branches or tribu-
taries.
In the course of
P' development the
longitudinal trunks
become the most im-
portant trunks in the
individual, and they
are formed before the
branches and tribu-
taries make their
appearance.
So.SA. 1.
CAA.I
V.So.
VV.
FIG. 840. DIAGRAM OP THE CEPHALIC AORTIC ARCHES, AND OF THE SEGMENTAL
AND INTERSEGMENTAL ARTERIES IN THE KEGION IN FRONT OF THE UMBILICUS.
C.A.A. I, II, III, IV, V. The cephalic
aortic arches.
Co. Anastomosing vessel between the
primitive ventral aorta and the
ventral somatic anastomosis.
D. D. Dorsal division of a somatic inter-
segmental artery.
D.Sp. Dorsal splanchnic anastomosis.
L.B. Lateral branch of ventral division
of somatic intersegmental
artery.
L.E.D. Branch to lateral enteric diver -
ticulum.
P.D.A. Primitive dorsal aorta.
Po.C. Post-costal anastomosis.
Po.T. Post-transverse anastomosis.
Pr.C. Pre-costal anastomosis.
P.V.A. Primitive ventral aorta.
So.S.A. 1, 2, 3, 4, 5, 6, 7, 8. Somatic
intersegmental arteries.
Sp.S.A. Splanchnic arteries.
V.D. Ventral division of a somatic
intersegmental artery.
V.E.D. Branch to ventral enteric diver-
ticulum.
V.V. Vitelline vessels.
V.So. Ventral somatic anastomosis.
V.Sp. Ventral splanchnic anastomosis.
THE SEGMENTAL
ARTERIES AND
THEIR ANAS-
TOMOSES.
The main longi-
tudinal trunks are
the primitive aortae.
The descending aorta
is formed, in the
greater part of its
extent, by the fusion
of the dorsal parts of
the primitive aortae,
and from it the inter-
seg mental, lateral,
and ventral arteries
In a typical portion of the body
from the dorsalsurface of the primi-
tive dorsal aorta, i.e. from the dorsal
longitudinal trunk, and runs later-
ally and ventrally in the tissues
developed from the somatic meso-
derm ; it is distributed to the body
wall, including the vertebral column
and its contents, and is termed
a somatic intersegmental artery.
A second vessel arises from the side
of the primitive dorsal aorta ; it is
distributed to the structures de-
veloped from the intermediate cell
mass, viz., the suprarenal gland, the
kidney, and the ovary or the testis,
and it is accordingly termed a
lateral or- an intermediate visceral
artery. The third artery, which
is known as the splanchnic artery,
springs from the ventral surface of
the aorta. It runs in the tissues
developed from the splanchnic
mesoderm, and supplies the wall
of the alimentary canal.
The somatic intersegmental
arteries form, in the early embryo,
a regular series of paired vessels
throughout the cervical, thoracic,
lumbar, and sacral regions. It is,
arise in pairs,
of the embryo there are three arteries on each side. One arises
MS
P.D.A
VED.(Hy)
VV.
FIG. 841. DIAGRAM OF THE ARTERIES IN THE KEGION CAUDAL
TO THE UMBILICUS.
Cd.A.A. Caudal aortic arch.
D.Sp. Dorsal splanchnic ana-
stomosis.
Middle sacral artery.
Parietal branch from
caudal arch.
Primitive dorsal aorta.
Primitive ventral aorta.
M.S.
Pa.C.
P.D.A.
P.V.A.
So.S.A. Somatic iutersegmeiital
arteries.
Sp.S.A. Splanchnic arteries.
V.E.D. (Hy). Branch to a ventral
enteric diverticulum.
Vi.C. Visceral branch from the
caudal arch.
V.V. Vitelline vessels.
however only in the thoracic and lumbar regions that their
INTEESEGMENTAL AKTEEIES AND THEIE ANASTOMOSES. 1045
original characters are retained. The paired vessels pass dorsally, by the sides of the vertebrae,
and divide into dorsal and ventral branches which accompany the corresponding anterior and
posterior divisions of the spinal nerves.
The ventral branches run ventro-laterally, between the ribs, in the thoracic region, and in
corresponding positions in the lumbar region, and together with the stems they form the main
parts or trunks of the vessels in the thoracic and lumbar regions. They are connected together,
near their commencements, by a series of pre-costal anastomoses which pass in front of the necks
of the ribs, and they are also connected together, near their terminations, by ventral anastomos-
ing channels which run, in the thoracic region, behind the costal cartilages, and in the lumbar
region behind or in the substance of the rectus abdominis muscle. Each ventral branch gives off
a lateral offset which is distributed like the lateral cutaneous branch of a spinal nerve, and
the ventral branch together with the stem of the intersegmental artery forms the trunk of
an intercostal or lumbar artery in the adult.
The dorsal branches, which are present before the ventral branches, run dorsally between the
transverse processes of the vertebrae, and form the posterior branches of the intercostal arteries and
the dorsal branches of the lumbar arteries of the adult ; they are connected, behind the necks of
the ribs, by post-costal anastomoses, and again, behind the transverse processes of the vertebrae, by
Pre-laminar anastomosis
Post-neural anastomosis \
Pre-neural anastomosis
Post-transverse anastomosis
Post-central anastomosi
Post-costal anastomosis
Pje-costal anastomosis
c intersegmental artery
rmediate visceral artery-
Primitive dorsal aorta
Splanchnic artery
Lateral branch of the ventral
division of a somatic
intersegmental artery
rsal splanchnic anastomosi
Ventral splanchnic anastomosis
Branch to a ventral enteric diverticulum
Ventral somatic anastomosis
842. DIAGRAM SHOWING THE ARRANGEMENT AND COMMUNICATIONS OF THE SEGMENTAL AND
INTERSEGMENTAL ARTERIES AT AN EARLY STAGE OF DEVELOPMENT.
C, Coelom ; IN, Intestine.
-transverse anastomosing channels. Moreover, each dorsal branch, as it passes by the cor-
esponding intervertebral foramen, gives off a spinal offset which enters the spinal canal, along
he corresponding nerve-root, and divides into a dorsal, a ventral, and a neural branch. The
lorsal branches of these spinal arteries are connected together along the ventral surfaces of the
aminae by pre-laminar anastomoses, and the ventral branches are united on the dorsal surfaces
f the vertebral bodies (or centra) with their fellows above and below by post-central anastomoses ;
hey are also united with their fellows of the opposite side by transverse communicating channels.
The neural branches of the spinal arteries divide similarly into dorsal and ventral branches ;
he dorsal branches of each side are connected together by post-neural anastomoses, which form
he posterior spinal arteries ; and the ventral branches unite, in the median line, both with their
ellows above and below and with those of the opposite side, forming a single longitudinal
>re-neural trunk, the anterior spinal artery.
In the thoracic and lumbar regions of the body the somatic intersegmental arteries persist, and
3rm the intercostal and lumbar arteries. These vessels spring from the dorsal aspect of the
ascending aorta, usually in pairs. The corresponding vessels of opposite sides, however, occasion -
lly fuse together at their origins, simultaneously with the fusion of the dorsal longitudinal
runks to form the descending aorta, and then the arteries of opposite sides arise by common
terns.
The pre-costal anastomoses between the ventral branches of the somatic intersegmental arteries
only represented in the thoracic region by the superior intercostal arteries ; in the lumbar
igion they disappear entirely. The anastomoses between the anterior ends of the ventral
1046
THE VASCULAR SYSTEM.
branches of the somatic intersegmental arteries persist as the internal mammary and superior
and inferior epigastric arteries.
The lateral offsets of the ventral branches are represented by the cutaneous arteries which
accompany the lateral cutaneous branches of the spinal nerves, and the lateral branch of the seventh
somatic intersegmental artery forms
the greater part of the arterial
stem of the upper limb.
The post-costal and post-trans-
verse anastomoses usually disappear
in the thoracic and lumbar regions,
but the post - costal anastomoses
occasionally persist in the upper
thoracic region, and take part in the
formation of the vertebral artery,
which in such cases arises from the
first or second intercostal artery.
In some carnivora the post-costal
longitudinal vessels persist in the
upper thoracic region, and form, on
each side, a trunk which is connected
with the first aortic intercostal, and
which supplies the first five inter-
costal spaces.
The pre -laminar, the post-
central, and the pre- and post-
neural anastomoses persist, the
latter two aiding in the formation
of the thoracic and lumbar portions
of the anterior and posterior spinal
arteries respectively.
It is in the cervical region,
however, that the most interesting
changes occur. The first six pairs
FIG. 843. DIAGRAM OF THE SEGMENTAL AND INTERSEGMENTAL of somatic intersegmental arteries
ARTERIES AT A LATER PERIOD OF DEVELOPMENT THAN IN lose their connexions with the
FIG. 842. dorsal roots of the aortic arches, i.e.,
C, Coelom ; D.A, Dorsal aorta ; D.Sp, Dorsal splanchnic anastomosis ; in other words, with the longi-
IN, Intestine ; V.E.D, Branch to ventral enteric diverticulum ; tudinal anastomosing channels in
. V.Sp, Ventral splanchnic anastomosis. that region. The seventh pair,
however, persist in their entirety ;
and from them are formed, on the right side, a portion of the subclavian trunk, and on the
left side the whole of the subclavian stem from its commencement up to the origin of the
vertebral artery. On each side the ventral branch of the seventh intersegmental artery forms
that portion of the
subclavian artery
which lies between
the origins of the
vertebral and internal
mammary arteries,
and also the trunk of
the internal
Somatic intersegmental
artery"
Post-neural anastomosis
Post-central anastomosis
Post-transverse anastomosis
Post-costal anastomosis
Pre-costal anastomosis
Pre-laminar anastomosis
| Prc-iieural anastomosis
mam-
mary artery as far as
the upper border of
the first costal cartil-
age. The remainder
of the internal mam-
mary artery repre-
sents the ventral
longitudinal anasto-
moses between the
ventral branches of
the seventh and the
following somatic in-
tersegmental arteries.
The continuation of
the subclavian artery,
beyond the inner
margin of the first
rib, is the persistent
Primitive dorsal aorta
Lateral branch of a somatic
intersegmental artery
Cephalic aortic arch
Branch to a lateral enteric
diverticulum
Primitive ventral aorta
Ventral somatic anastomosis
Branch to a ventral enteric diverticulun
FIG. 844. DIAGRAM SHOWING THE ARRANGEMENT AND COMMUNICATIONS OF THE
SEGMENTAL ARTERIES IN THE KEGION OF THE CEPHALIC AORTIC ARCHES.
IN, Intestine.
and enlarged lateral offset of the ventral branch of the seventh somatic intersegmental artery,
which is continued into the upper limb, caudal or postaxial to the shoulder girdle. The thyre
cervical trunk and the superior intercostal artery, both branches of the subclavian artery, ai
INTERSEGMENTAL ARTERIES AND THEIR ANASTOMOSES. 1047
persistent pre-costal anastomoses, and the ascending cervical artery belongs to the same series of
vessels. The vertebral artery, which appears as a branch of the subclavian in the adult, is,
morphologically, somewhat complex. The first part represents the dorsal branch of the seventh
somatic intersegmental artery ; the second part, that passing through the cervical transverse
processes, consists of the persistent post-costal anastomoses between the dorsal branches of the
first seven intersegmental arteries ; a third part, that lying on the arch of the atlas, is the spinal
branch of the first somatic intersegmental artery and its neural continuation ; whilst finally the
upper part of the vertebral artery, the part in the cranial cavity, appears to represent a pro-
longation of the pre-neural anastomoses, which still farther upwards are probably represented by
the basilar artery. As already stated, the post-costal anastomoses below the seventh intersegmental
artery occasionally persist, and in such cases the vertebral may lose its connexion with the sub-
clavian, and spring from one or other of the posterior branches of the upper intercostal arteries.
The profunda cervicis artery is to be regarded as a remnant of the post-transverse longi-
tudinal anastomoses.
The origin of the seventh somatic intersegmental artery from the dorsal longitudinal trunk
is, at first, some distance caudal to the sixth aortic arch, but, simultaneously with the elongation of
the neck and the retraction of the heart into the thoracic region, it is shifted cranialwards until
it is opposite the dorsal end of the fourth aortic arch.
The middle sacral artery is formed by the fusion of two vessels, each of which springs from the
dorsal surface of the aorta. It is regarded as the direct continuation of the descending aorta.
The lateral or intermediate visceral arteries supply the organs derived from the inter-
mediate cell mass. They form a somewhat irregular series of vessels in the adult, but pre-
sumably in the primitive condition there was a pair in each segment of the body ; many of
these disappear, however, and the series is only represented in the adult by the suprarenal,
the right renal, part of the left renal, and the testicular or ovarian arteries possibly, also, by
some of the branches of the hypogastric arteries.
The splanchnic arteries arise in the embryo from the ventral aspects of the primitive
dorsal aortse, and are not strictly either segmental or intersegmental in arrangement. They are
distributed to the walls of the alimentary canal. Each anastomoses with its immediate neigh-
bours on the dorsal wall and the ventral walls of the gut.
After the fusion of the dorsal longitudinal trunks to form the descending aorta, the roots of
each pair of the splanchnic arteries fuse into a common stem, or either the right or left artery
altogether disappears, whilst at a later period the majority of the splanchnic arteries lose their
, direct connexion with the descending aorta ; those which retain their connexion are the cceliac
: artery and the superior and inferior mesenteric arteries.
The bronchial and cesophageal arteries are later formations. They appear to correspond morpho-
. logically with the more primitive splanchnic arteries, but the developmental history is not known.
The left gastric branch of the coaliac artery, as it passes from its origin to the small
curvature of the stomach, represents a right splanchnic artery ; the remainder of the left gastric
artery and the right gastric branch of the hepatic are remnants of the ventral anastomoses between
r the splanchnic arteries cephalwards of the umbilicus.
The splenic artery is a branch given off from a splanchnic artery to an organ developed in the
mesogastrium, and the hepatic is a branch from the ventral splanchnic anastomoses to the
hepatic diverticulum from the wall of the duodenal portion of the fore-gut.
The superior and inferior mesenteric arteries represent at their origins splanchnic branches,
and in the remainder of their extent they represent the dorsal anastomoses on the gut wall.
THE A'ORTA, PULMONARY ARTERY, AND OTHER CHIEF STEM VESSELS.
The heart and the majority of the great arterial trunks of the body, including the aorta, the
innominate, part of the right subclavian, the common, external, and greater parts of the internal
carotids, and the pulmonary arteries, are all modified portions either of the primitive aortae or
of the aortic arches. The developmental changes, which result in the formation of the vessels
named, are described in the preceding chapter, and the morphology of these vessels is obviously
the same as that of the trunks from which they are derived.
It will be sufficient, therefore, to point out that the primitive aortas may be regarded
as the greatly enlarged pre-central or pre-vertebral longitudinal anastomoses between the
successive intersegmental arteries of each side ; obviously, therefore, each primitive aorta, like
the rest of the longitudinal anastomoses, consists chiefly of segmental elements. The origins of
the intersegmental vessels enter into its formation only in so far as they connect the segmental
vessels together, and so complete the longitudinal anastomoses.
The first cephalic aortic arches are simply portions of the primitive aortee. The other
aortic arches have possibly a different morphological significance, but their exact nature is not
definitely settled.
The second, third, fourth, fifth, and sixth cephalic aortic arches of each side are developed in
the undivided mesoderm of the head region, caudal to the first arch. They spring from the part
ol the primitive aorta which, after the head fold is formed, lies on the ventral aspect of the fore-
gut, and they extend, at the side of the pharyngeal part of the fore -gut, to the dorsal aorta. Thus,
in some respects they may be looked upon as segmental vessels. In addition to the vessels already
mentioned, there are given off from the ventral aortse and the aortic arches a series of branches
which supply ventral and lateral diverticula from the alimentary canal ; these are represented
! in the adult by the superior thyreoid, the thyreoidea ima.
1048 THE VASCULAK SYSTEM.
Iliac Arteries and their Branches. The common iliac arteries are formed from the
secondary roots of the umbilical arteries, and their exact morphological position is uncertain.
The true morphological position of the hypogastric arteries is not yet denned. They also are
parts of the secondary roots of the umbilical arteries, and they give off both somatic and
splanchnic branches ; therefore they do not correspond either with somatic intersegmental or
with splanchnic arteries. The branches of the hypogastric artery are arranged in two groups
(1) a visceral set which supplies the walls of the hind-gut and the genital organs, and (2) a
parietal set which is distributed to the body wall and to the hind-limbs. The branches dis-
tributed to the gut probably represent the splanchnic vessels, more or less homologous with
ordinary splanchnic branches of the primitive aortse, and the parietal branches are possibly
the homologues of intersegmental arteries.
THE LIMB ARTERIES.
In all probability the vessels of both the upper and the lower limbs are derived originally
from several somatic intersegmental arteries, the majority of which, however, have atrophied.
The upper limb is supplied in man by the lateral offset from the ventral branch of the seventh
somatic intersegmental artery. It passes into the extremity caudal to the shoulder girdle, courses
through the arm, enters the cubital fossa, and is continued through the forearm, in the early
stages, as the volar interosseous artery, which terminates in the deep part of the palm, in the
deep volar arch. At a later period, ontogenetically, a median artery appears as a branch of
the parent stem, and it terminates in a superficial volar arch ; still later the radial and ulnar
branches are formed. The latter grow rapidly, soon exceeding in size the parent stem, and they
terminate in the superficial and deep volar arches. The interosseous and median arteries decrease,
and generally lose their direct connexions with the volar arches. The dorsal interosseous artery
is also a secondary branch from the parent stem, and the digital arteries are offsets from the volar
arterial arches.
The chief arteries of the lower extremities spring directly from the secondary roots of the
umbilical arteries, and may be looked upon as being essentially intersegmental ; whether they
represent the whole or only parts of typical somatic intersegmental arteries, however, is not clear.
The arteries of the lower limbs certainly show no very obvious indications of division into
dorsal and ventral branches, though such indications are not entirely wanting. In their com-
parative absence it is supposed that the dorsal branches have been either suppressed or incor-
porated with the common stems ; that similarly the ventral branches and their lateral offsets
are indistinguishably fused, and that probably both are represented in a limb artery.
The original stem vessel of the lower limb is the inferior glutaeal artery, which is continued
distally, caudal to the pelvic girdle, into the popliteal and peroneal arteries, and so to the
plantar arch. Subsequently the external iliac artery is given off from the secondary root of the
umbilical artery, dorsal to the origin of the inferior glutseal, and, passing into the limb cranial-
ward of the pelvic girdle, it becomes the femoral artery. This vessel ultimately unites with
the proximal part of the popliteal artery, and after this communication is established the distal
part of the inferior glutaeal atrophies and loses its connexion with the popliteal, which hence-
forth appears to be the direct continuation of the femoral trunk ; therefore, whilst the main
artery of the upper limb is formed by the prolongation of the lateral branch of one segments,!
artery, the corresponding vessel of the lower extremity is developed from representatives of,
probably, two somatic segmental arteries, the external iliac and femoral trunks being the
representatives of one, whilst the popliteal and its continuation, the peroneal, are parts of
another.
The first main artery of the leg, ontogenetically, is the peroneal, which is continued into
the plantar arch ; after a time, however, the posterior and anterior tibial branches are given
off from the stem, over which, as a rule, they soon preponderate in size, and they terminate in the
plantar arch, whilst the parent trunk diminishes and loses its direct connexion with the arch.
The peroneal artery corresponds in position and development with the common interosseous
trunk and the volar interosseous artery in the forearm. The posterior tibial apparently corre-
sponds with the median artery; it develops in a similar way, and has similar relations to
homologous nerves, the tibial nerve representing the combined median and ulnar nerves
of the upper extremity.
The anterior tibial artery represents the dorsal interosseous, whilst the radial and ulnar
arteries of the upper extremity are not represented in the lower limb.
MORPHOLOGY OF THE VEINS.
Two dorsal longitudinal vessels, one on each side, connect the successive intersegmental
veins together. They do not, however, in any part of their course, fuse together to form a
single vessel comparable to the descending aorta.
Of these dorsal longitudinal vessels, that on the right side greatly enlarges, and from it t
main stem vessels which return blood from the body walls, the head and neck, and the limbs, are
almost entirely formed. The left dorsal longitudinal vessel remains relatively small in parts,
indeed, it altogether disappears and the blood conveyed to it by the corresponding intei
segmental veins is transmitted, across the median plane, to the chief functional stem by later
deve
DEVELOPMENT OF THE VEINS. 1049
eveloped and superadded transverse communicating channels, which are formed between the
more primitive longitudinal anastomoses.
The primitive dorsal longitudinal anastomosing channels include on each side (1) the anterior
cardinal vein, (2) the posterior cardinal vein, and (3) the duct of Cuvier ; the last-named vessel,
which opens into the sinus venosus of the primitive heart, is, originally, part of the anterior
cardinal vein ; it becomes enlarged and receives a special name after the union of the posterior
with the anterior cardinal vein.
The cardinal veins return blood not only from the limbs and body wall, but they are also, in
the early stages, the only vessels by which blood is returned from the derivatives of the inter-
mediate cell tract, i.e. the kidneys, the genital glands, and the suprarenal glands. At a later
period other longitudinal anastomoses, called the subcardinal veins, appear, and into these a large
part of the blood from the derivatives of the intermediate cell tract is poured. It is from these
vessels, and from the transverse communications which are established between the cardinal and
subcardinal veins of opposite sides, that the chief veins of the head and neck and the body are
formed ; there is in addition, however, a later-formed vessel, the upper part of the inferior vena
cava, which is developed independently of the veins previously mentioned. Moreover, it must not
be forgotten that the veins of the extremities are, like the extremities themselves, secondary
structures, and that they are developed at a later period than the veins of the trunk, with which,
however, they ultimately communicate.
In the light of these facts the morphology of the chief veins of the head and neck, the
trunk and limbs may now be considered.
The cavernous sinuses are remnants of the primary head vein. The other blood sinuses of
the cranium are either secondarily formed vessels, or anastomoses between the tributaries
of the anterior cardinal veins, or anastomoses between those tributaries and other newly
formed veins.
The internal jugular veins are also portions of the anterior cardinal veins.
The right innominate vein is a part of the right anterior cardinal vein. A small part
of the left innominate vein is formed from the left anterior cardinal vein, the greater part is
derived from a transverse anastomosis between the two anterior cardinal veins.
Other remnants of the anterior cardinal veins are the upper parts of the superior vena cava
and left superior intercostal vein.
The basilic vein and its prolongations, the axillary vein and the subclavian vein, are derived
from the ulnar or post-axial primitive veins of the superior extremities. The external jugular vein
; is a secondary formation, and the cephalic vein is the radial or pre-axial vein of the upper
extremity which opens first into the external jugular vein and at a later period into the
axillary vein.
The superior vena cava represents the lower part of the anterior cardinal vein and the right
duct of Cuvier, and the oblique vein of the left atrium represents the left duct of Cuvier.
The azygos vein is the upper or cephalic part of the right posterior cardinal vein, and the
vertical parts of the hemiazygos and accessory hemiazygos veins are remnants of the left
posterior cardinal vein, whilst the transverse portions of the hemiazygos and accessory hemi-
azygos veins represent transverse anastomoses between the posterior cardinal veins.
The inferior vena cava is a compound structure representing parts of five different structures.
Its upper end is the transformed cephalic end of the right vitelline vein. The portion posterior
to the liver is a secondary outgrowth from the right vitelline vein. The part between the
liver and the right renal vein represents a part of the right subcardinal vein and an anastomosis
between it and the posterior cardinal vein, and the remainder is a portion of the right posterior
cardinal vein.
The right common iliac vein is a part of the right posterior cardinal vein, but the left is
a compound structure. Its lower part probably represents a portion of the left posterior
sardinal vein, but the greater part is a persistent transverse anastomosis between the posterior
.irdinal veins.
The hypogastric veins are remnants of the posterior cardinal veins.
The popliteal and the inferior gluteal veins are remnants of the primitive fibular vein of the
lower limb, and the external iliac vein is the trunk formed by the union of the tibial and the
leep veins of the lower limb which are secondary formations.
Visceral Veins. The portal vein represents portions of both vitelline veins and of the middle
inastomosis between them.
The right gastric vein is a splanchnic ventral longitudinal anastomosing vein. The left
gastric vein is partly a ventral and partly a dorsal splanchnic longitudinal anastomosis, and
;he superior and inferior mesenteric veins are dorsal splanchnic longitudinal venous anastomoses,
ihe splenic vein being merely a tributary from a lymphoid organ developed in the dorsal
neso-gastrium.
The anterior facial vein is a combination of somatic and splanchnic veins of several segments,
md the internal maxillary vein is probably of similar nature. The thyreoid and bronchial veins
'eturn blood from organs developed from diverticula from the walls of the alimentary canal ; they
ire, therefore, more or less modified splanchnic veins ; so also apparently are the vesical and the
niddle and inferior hsemorrhoidal veins.
The cardiac veins are simply " vasa vasorum," and they belong therefore to the splanchnic
;roup of vessels, but it is impossible to say whether they are segmental or intersegmental. The
oronary sinus into which they open is a portion of the sinus venosus of the heart, and therefore
f an originally segmental vessel.
1050 THE VASCULAR SYSTEM.
The hepatic veins are parts of the primitive vitelline veins ; and the pulmonary veins are
splanchnic veins returning blood from a diverticula of the gut.
It is noteworthy that some parts of the splanchnic venous system, i.e. the portal vein and the
coronary sinus, are portions of the most primitive vascular system, and that others, the
thyreoid, bronchial, mesenteric, vesical, and haemorrhoidal veins appear to belong to a somewhat
secondary group of splanchnic veins of combined segmental and intersegmental character ; more-
over, some of the secondary group of veins open into the primary splanchnic veins, e.g. the
superior and inferior mesenteric into the portal vein ; some open into the dorsal longitudinal
anastomosing veins, e.g. the vesical and haemorrhoidal veins open into the cardinal veins, which
are intersegmental anastomoses ; others again open into the internal jugular, which is part of
the anterior cardinal vein.
Veins of the Limbs. The veins of the limbs, like the arteries, were probably at one time
intersegmental in character, but we have no indisputable proof that this was the case. Looked at
from an embryological standpoint, the most primitive limb veins are a superficial distal arch and
a post-axial trunk vein in each extremity ; at a later period digital veins are connected with the
distal arch, and a pre-axial trunk is formed. In the upper extremity the distal arch and its
tributaries remain as the dorsal venous arch and the digital veins, and the post-axial vein becomes
the basilic, axillary, and subclavian veins. The pre-axial vein of the upper extremity is
represented in the adult by the cephalic vein ; the latter vessel originally terminated in the
external jugular vein, above the clavicle, the union with the axillary portion of the post-axial
vessel being a secondary condition ; the primary condition is, however, frequently retained in
man, and is constant in many monkeys. The anastomosis between the pre-axial and post-axial
veins in the region of the elbow, and the connexion of the anastomosing channels, is brought'
about by newly -formed vessels of secondary character.
The distal arch in the lower extremity and the tributaries connected with it remain in the
adult as the dorsal venous arch of the foot and the digital veins. The post-axial vein becomes
the small saphenous vein, which was originally continued proximally as the popliteal and
inferior glutaeal veins to the hypogastric portion of the posterior cardinal vein.
The pre-axial vein of the lower limb becomes the great saphenous vein, which is continued
proximally to the cardinal portion of the left common iliac vein as the proximal part of the
femoral and the external iliac veins.
The venae comites of the arteries in both the upper and lower extremities are secondarily
developed vessels which become connected with the upper portions of the pre-axial venous
trunks.
ABNOKMALITIES AND VARIATIONS OF THE VASCULAR
SYSTEM.
Abnormalities are of special interest to the anatomist because of their morphological signifi-
cance, and the vascular system is, perhaps more than any other, rich in such abnormalities, many
of which are of great practical importance.
With the exception of those irregularities which are directly due to the effect of morbid
conditions and external influences, all abnormalities are the result of modifications of normal
developmental processes. The exceptions referred to are, however, very numerous ; thus disease
and external influences may lead to the obliteration of vessels, a condition which is invariably
associated with the enlargement of collateral vessels, and it will be obvious that abnormalities
so produced may occur in almost any situation.
Abnormalities which are determined by, or are dependent upon, modifications of the usual
developmental processes are of greater interest. In the human subject they are generally due
either to the retention of conditions which, normally, are only transitory in ontogenetic develop-
ment, or to the acquirement of conditions which, though not as a rule present at any time in
man, occur normally in some animals.
There are, in addition, other variations from the normal, such as the division of the axillary
artery into radial and ulnar branches ; the higher or lower division of the brachial artery ; the
formation of " vasa aberrantia," e.g. of long slender vessels connecting the axillary or brachial to
the radial, ulnar, or interosseous arteries ; the altered position of certain vessels, e.g. the trans-
ference of the subclavian artery to the front of the scalenus anterior, or of the ulnar artery to the
front of the superficial flexor muscles ; all of which, though undoubtedly due to alterations ot
ordinary developmental processes, still do not represent any known conditions met with, either
temporarily or permanently, in man or in other animals. Their occurrence cannot at present
be adequately explained, and their retention in the adult is entirely dependent upon their
utility.
To the first and the last of these different groups of abnormalities it is not necessary to refer
further, whilst with regard to the rest it will be sufficient to indicate those of greatest
importance. They can only, however, be fully understood and explained on the basis of *
comprehensive knowledge of the development and morphology of the vascular system, to tl
chapters on which the reader is referred.
ABNOEMALITIES OF AETEEIES. 1051
ABNOEMALITIES OF THE HEAET.
The heart may be transposed from the left to the right side of the body, a condition which
is usually associated with general transposition of the viscera, and with the presence of a right
instead of a left aortic arch.
The external form of the heart does not as a rule vary much, but occasionally the apex is
slightly bifid, a character it normally possesses at an early stage of its development, and which is
retained in the adult in many cetaceans and sirenians. The internal conformation of the heart
deviates from the normal much more frequently ; more particularly is this the case with regard
to the septa which separate the right from the left chambers. The interatrial septum may be
entirely absent, as in fishes ; it may be fenestrated and incomplete, as in some amphibians ; or
the foramen ovale may remain patent, as in amphibians and reptiles.
The interventricular septum may be absent, as in fishes and amphibians, or incomplete, as in
reptiles ; when incomplete, it is usually the " pars membranacea septi " which is deficient, but
perforations are occasionally found in the muscular portion.
The communication between the infundibular part of the right ventricle and the body of the
ventricle may be constricted or the infundibular part may be entirely cut off from the remainder
of the cavity.
ABNOEMALITIES OF AETEEIES.
The pulmonary artery and the aorta may arise by a common stem, as in fishes and some
amphibians, and the common stem may spring either from the right or the left ventricle, or from
both. In these cases the truncus arteriosus has remained undivided, and the normal position of
the interventricular septum in relation to the lower orifice of the aortic bulb has been altered.
Again, owing to malposition of the aortic septum, the pulmonary artery may spring from the
left ventricle and the aorta from the right ventricle. . In some cases the root of the pulmonary
artery is obliterated, and the blood passes to the lungs along the patent ductus arteriosus.
Occasionally the arch of the aorta is on the right side instead of the left, a condition which is
normal in birds. More rarely there are two permanent aortic arches, right and left, as in reptiles ;
the oesophagus and trachea in these cases are enclosed in a vascular collar, the two arches unite
dorsally, and the beginning of the descending aorta is double. Quite independent of this condi-
tion, however, the two primitive dorsal aortse sometimes fail, either altogether or partially, to
unite together, and the descending aorta is accordingly represented, to a corresponding extent, by
two tubes. A more common, though still rare, form of double aorta is that due to the persistence,
in whole or in part, of the septum formed by the fused walls of the primitive dorsal aortae
from which the descending aorta is developed.
The length of the descending aorta is determined largely by the extent to which fusion of the
two primitive aortse takes place. Accordingly, when this deviates from the normal, the termi-
nation of the descending aorta is at a correspondingly higher or lower level than usual, and
resulting from this the lengths of the common iliac arteries are almost invariably proportionately
modified. The bifurcation of the aorta may be as low as the fifth lumbar vertebra ; less
frequently it is higher than usual ; it is rare, however, to find it as high as the third, and still
more rare to find it at the level of the second, lumbar vertebra.
The aorta, instead of bifurcating into two common iliac arteries, may terminate in a common
iliac artery on one side and a hypogastric artery on the opposite side, the external iliac artery
on the irregular side arising, at a higher level, as a branch of the aortic stem. This arrangement
approaches the condition met with in carnivores and many other mammals, in which the aorta
bifurcates into two hypogastric arteries, the external iliacs arising from the aorta at a higher
level as lateral branches ; it is probably due either to a fusion of the secondary roots of the
umbilical arteries of opposite sides.
THE BRANCHES OF THE AORTA.
The coronary or cardiac arteries may arise by a single stem. When arising separately
both may spring from the same aortic sinus ; or again, their interventricular and circumflex
branches may arise as distinct vessels from a single aortic sinus. This variability is not
very remarkable, seeing that the arteries in question are merely enlarged " vasa vasorum "
raised to a position of special importance by the development of the heart.
The branches of the arch of the aorta are sometimes increased and sometimes decreased in
number.
The highest number recorded is six, viz., right subclavian, right vertebral, right common
( carotid, left common carotid, left vertebral, and left subclavian. Apparently this condition is the
result of the absorption into the arch of the innominate artery and of the roots of the sub-
clavian arteries, to points beyond the origins of the vertebrals. By variations of this process of
absorption other combinations may be produced ; thus, instead of the roots of the subclavian
i arteries being absorbed, the right common carotid and innominate arteries may alone be absorbed,
in which case the five following branches spring separately from the arch of the aorta : right
i subclavian, right external carotid, right internal carotid, left common carotid, and left
subclavian. The trunk most commonly absorbed is the initial part of the left subclavian ; the
1052 THE VASCULAR SYSTEM.
number of branches then, arising from the arch of the aorta is four, the additional vessel
being the left vertebral, which arises between the left common carotid and the left subclavian.
Occasionally the usual three branches from the arch are increased to four by the formation of a
new vessel, the " thyreoidea ima." This may be placed between the innominate and left carotid
trunks, in which case it represents a persistent ventral visceral branch from the ventral root of the
fourth left aortic arch ; in other cases the thyreoidea ima springs from the innominate artery and
represents a ventral visceral branch of the ventral root of the fourth right arch. Very rarely
the right vertebral artery arises separately, and forms a fourth branch of the arch of the aorta,
the rest of the branches being normal. This condition cannot be accounted for by any modifica-
tion of the ordinary developmental processes. It may possibly be due to the persistence of an
irregular or unimportant anastomosis between the ventral root of an aortic arch and the seventh
somatic segmental artery.
Decrease in the number of branches from the arch of the aorta is most frequently due to
fusion of the ventral roots of the fourth aortic arches, the result being that a stem is formed
common to the right subclavian and the right and left common carotid arteries ; whilst the left
subclavian, arising separately, is the only other branch which springs from the arch of the aorta.
If the fusion of the ventral roots proceeds further and includes those of the third arches, the
result, as regards the branches given off from the arch of the aorta, is the same, viz., there is a
common stem for the right subclavian and both carotids, and a separate left subclavian trunk ; but
the common stem now gives off the right subclavian artery, and then continues as a single vessel
for some distance before it divides into the two common carotids, of which the left crosses in
front of the trachea. This arrangement is common in many quadrumana and in some other
mammals.
It is only in rare cases when the number of branches from the arch of the aorta is
reduced to two, that these consist of a right subclavian artery and of a single stem common to
the two carotids and the left subclavian artery. In such cases, however, the right common
carotid crosses in front of the trachea, and the variation is one of practical importance, but it does
not appear to exist as a normal condition in any mammal. Probably it is due to fusion of the
ventral roots of the fourth aortic arches, with absorption of the left fourth arch and the left sub-'
clavian into the stem so formed, whilst the right subclavian is relatively displaced. The two
common carotids may arise by a common stem, and the left subclavian arise separately from
the arch of the aorta, whilst the right subclavian springs from the descending aorta. This
arrangement probably results from the disappearance of the fourth right arch, the fusion of the
ventral roots of the fourth arches of opposite sides and the persistence of the dorsal roots of the
right fourth and sixth arches.
Sometimes two innominate arteries, right and left, replace the usual three branches of the
arch of the aorta. This , is the normal arrangement in bats, moles and hedgehogs. It is
obviously the result of the disappearance of that portion of the arch which intervenes between
the left carotid and left subclavian arteries, and the consequent fusion of these two vessels.
In a similar way may be explained the rarer condition in which the three ordinary
branches of the arch arise by one single stem, which divides into right and left innominate
arteries. In most ruminants, in the horse and in the tapir, this arrangement is constant.
It will be evident that other combinations and modifications may be met with in the branches
of the arch of the aorta as the result of fusions and absorption.
The right subclavian or the right vertebral may spring from the commencement of the
descending aorta.
The bronchial arteries obviously correspond to splanchnic arteries and their continuations
to diverticula from the walls of the gut ; therefore the usual origin of the right bronchial artery
from the first right aortic intercostal artery must result from the persistence of an anastomosis
between a splanchnic artery and the first part of a somatic intersegmental artery ; the origin
of the right from the upper left bronchial artery, which sometimes occurs, is due to the fusion
of the roots of two splanchnic arteries. The occasional origin of a bronchial vessel from an
internal mammary artery can result only from the persistence and enlargement of an anastomosis
between a splanchnic artery and the ventral branch of a somatic segmental artery. The origin
of a bronchial branch from a subclavian artery may have the same or a different significance
on opposite sides of the body. A bronchial artery arising from the left subclavian artery
corresponds with the origin of the right bronchial artery from the first aortic intercostal artery ;
it is due to the persistence of an anastomosis between a splanchnic artery and the root of a
somatic intersegmental artery ; and the origin of a bronchial artery from a right subclavian artery
may be due to a similar cause. It may, on the other hand, be due to the enlargement of an
anastomosis between a splanchnic branch of the descending aorta and a splanchnic branch of the
fourth right aortic arch. When, as occasionally happens, the bronchial artery arises from the
inferior thyreoid, it is due to the persistence and enlargement of an anastomosis between splanchnic
arteries.
Intercostal Arteries. Variations of the intercostal arteries are not very common, but
they are significant and interesting. Corresponding vessels of opposite sides may arise from a
common stem which has been formed by the fusion of the roots of two somatic intersegmental
arteries after or simultaneously with the fusion of the primitive dorsal aortae. The number of
intercostal arteries may be reduced, one artery supplying two or more intercostal spaces ; in these
cases the roots of origin of some of the somatic intersegmental arteries in the thoracic region
have disappeared, and the precostal anastomoses between their ventral branches have persisted.
Occasionally the number of the aortic intercostal arteries is increased, an additional artery
ABNOKMALITIES OF AETEEIES. 1053
being given to the second intercostal space, which is usually supplied by the superior intercostal
artery ; this is brought about by. the persistence of the root of the tenth somatic intersegmental
artery and the disappearance' of the precostal anastomosis between the ventral branches of the
ninth and tenth somatic intersegmental arteries. Very rarely the first aortic intercostal artery
sends a branch upwards between the necks of the ribs and the transverse processes of the upper
thoracic region ; this branch supplies the upper intercostal spaces, the superior intercostal artery
being small or absent, and it terminates by becoming the profunda cervicis artery. It is due to
the persistence of the postcostal anastomoses in the upper thoracic region, and is a repetition of a
condition regularly present in some carnivores.
There are no very important variations of the cesophageal, pericardial, and mediastinal
arteries.
Lumbar Arteries. Variations of the lumbar arteries are very similar to those of the
intercostal arteries, and they are due to similar causes. The lumbar arteries of opposite sides
may arise by common stems from the back of the aorta ; and the last pair of lumbar arteries
may arise in common with the middle sacral artery. Further, a lumbar artery may have its
area of distribution extended into the adjacent segment.
The inferior phrenic arteries are very variable ; they may arise by a common trunk either
from the cceliac artery or from the aorta ; they may arise separately either from the aorta or
from the coeliac artery and more commonly from the latter vessel ; or again, one may spring
from the aorta or cceliac artery, and the other from the coronary, renal, or even from the
superior mesenteric artery.
The middle sacral artery usually springs from the back of the aorta above its bifurcation ;
it may be considerably above, or more rarely it may spring directly from the bifurcation. Not
infrequently it arises from the last lumbar artery or from a stem common to the two last
lumbar arteries, and occasionally it arises from a common or internal iliac artery. Some-
times it gives off the last pair of lumbar arteries, and, in a few cases, an accessory, renal, or a
haemorrhoidal branch arises from it. The vessel is not always present, it may be double,
entirely or in part, and it may bifurcate at its termination.
The renal arteries frequently deviate from the normal arrangement. The arteries of
opposite sides may spring from a common stem, or there may be two or more renal arteries on
one or both sides. The accessory arteries are more common on the left than on the right side,
and an accessory artery arising below the ordinary vessel is more common than one arising
above it.
Accessory renal arteries may be derived not only from the aorta, but also from the common
iliac or hypogastric arteries ; they have been described as arising also from the inferior phrenic,
spermatic, lumbar, or middle sacral arteries,, and even from the external iliac artery. As the
kidney is developed in the region of the first sacral vertebra, and afterwards ascends to its perma-
nent position, it is not surprising that it occasionally receives arteries from the main stem of
more than one of the segments of the body through which it has passed, and it is usually found
that the lower the position of the kidney in the abdomen the more likely it is to receive its
arteries from the lower part of the aorta or from the common iliac arteries. The accessory renal
arteries which spring from the inferior phrenic, the spermatic, and lumbar arteries can only be
the result of the persistence and enlargement of anastomosing channels between the renal and
either another intermediate visceral, or a somatic artery.
The testicular or ovarian arteries may be double on one or both sides ; the arteries of the
two sides may spring from a common trunk, or each may arise from the renal, accessory renal,
or suprarenal arteries. The right artery may pass behind instead of in front of the inferior
vena cava. The spermatic and ovarian arteries arise from the upper lumbar portion of the
aorta, because the testes and ovaries are developed in and obtain their arterial supply in that
region, and the vessels are elongated as the testes and ovaries descend to their permanent
positions. The occurrence of two spermatic arteries on one side is probably an indication that
the testis was developed in two segments of the body. The origin of a spermatic artery from a
renal or suprarenal artery is due to the obliteration of the root of the original vessel and the
enlargement of an anastomosis between the intermediate visceral arteries of adjacent segments.
The cOBliac artery may be absent, its branches arising separately from the aorta or from some
other source. Sometimes it gives off only two branches, usually the left gastric and splenic, and
occasionally it gives four branches, the additional branch being either a second left gastric artery
or a separate gastro-duodenal artery.
The hepatic artery may spring directly from the aorta or from the superior mesenteric
artery, and the left hepatic artery arises occasionally from the left gastric artery. Accessory hepatic
arteries are not uncommon, and they originate either from the left gastric, superior mesenteric,
renal, or inferior mesenteric artery.
The left gastric artery is occasionally double ; it may spring directly from the aorta, and it
may give off the left hepatic or an accessory hepatic artery.
The splenic artery may arise from the middle colic, from the left hepatic, or from the
superior or inferior mesenteric artery.
The superior mesenteric artery may be double, and it may supply the whole of the
alimentary canal from the second part of the duodenum to the end of the rectum, the inferior
mesenteric artery being absent. In addition to its ordinary branches it may give off a hepatic,
a splenic, a pancreatic, a gastric, a gastro-epiploic or a gastro-duodenal branch. Very rarely
"* gives off an omphalo -mesenteric branch, which passes to the region of the umbilicus and
es connected with capillary vessels in the falciform ligament of the liver.
1054 THE VASCULAK SYSTEM.
The inferior mesenteric artery may give hepatic, renal, or middle colic branches ; occasion-
ally it is absent, being replaced by branches of the superior mesenteric, and sometimes, as in
ruminants and some rodents, its left colic branch does not anastomose with the middle
colic artery.
All these variations of the unpaired visceral branches of the abdominal aorta are merely due
to modifications of the usual processes by which the vessels are developed.
The hepatic, splenic, and left gastric arteries may arise directly from the aorta, a condition
which is due to the retention of a greater number of the splanchnic arteries than usual. A
double superior mesenteric artery results from the persistence of both the right and left
splanchnic vessels from which the superior mesenteric artery is formed, these remaining separate
instead of fusing together. All the other variations are the results of the obliteration of the
usual channels, combined with the enlargement of anastomoses which exist both between the
splanchnic arteries of adjacent segments and between the splanchnic and intermediate visceral
arteries.
THE ARTERIES OF THE HEAD AND NECK.
Innominate Artery. From what has already been said, with reference to the branches
of the arch of the aorta, it will be noted that the innominate artery may be absent. On the other
hand there may be two innominate arteries, a right and a left, each ending in corresponding
common carotid and subclavian trunks, and the two vessels may themselves arise by a common
stem.
The branches given off by the innominate artery may be increased in number, or the innomi-
nate may vary from the normal only as regards length. As a consequence of such modifications
in length, the origins of the right common carotid and right subclavian arteries may be situated
at a higher or lower level than usual, whilst, in the absence of the innominate artery, both these
branches may arise directly from the aorta.
Common Carotid Arteries. When the right common carotid artery arises separately from
the arch of the aorta, it may be the first, or, much more rarely, the second branch. In the
former case the fourth right aortic arch has been obliterated, and the right subclavian artery
springs from the descending aorta; in the latter case either the innominate stem has been
absorbed into the arch of the aorta, or the ventral root of the fourth right aortic arch has fused
with part of an elongated fourth left arch.
Whether arising as the first or second branch, the origin may be to the left of the median plane,
and the trunk may pass in front of the trachea, or behind the oesophagus, before it ascends into
the neck.
The left common carotid artery varies, as regards its origin, much more frequently than the
right vessel ; not uncommonly, and apparently because of the fusion of the ventral roots of the
fourth aortic arches, it arises "from a stem common to it and to the right common carotid and
right subclavian arteries.
Both common carotids may vary a's regards their termination. They may divide at a higher
or lower level than usual, the former more commonly than the latter ; whilst in a few exceptional
cases the common carotid does not divide, but is continued directly into the internal carotid, and
from this the branches usually given off by the external carotid are derived.
This arrangement is probably due to obliteration of the ventral roots of the first and second
aortic arches, the arches persisting and being divided into the branches which generally arise
from their ventral extremities.
Usually the common carotids give off no branches, but not infrequently one or more of the
branches of the external carotids arise from them.
The external carotid artery may be absent, or it may, in rare cases, arise directly from the
arch of the aorta. The number of its branches may be diminished either by fusion of their roots
or by transference to the internal or common carotid arteries. On the other hand, the number of
its branches may be increased ; thus, the sterno-mastoid artery, the hyoid branch usually given off
by the superior thyreoid artery, or the ascending palatine branch of the external maxillary, may
arise from it. Sometimes the branches may arise in the usual way, but may deviate from the
course generally taken ; more particularly is this the case with the internal maxillary artery,
which may pass either between the heads, or entirely lateral or medial to both heads of the
external pterygoid muscle.
The internal carotid artery is rarely absent, but its absence has been noted upon one side,
more commonly the left ; and upon both sides. Occasionally it springs from the arch of the
aorta, and in its course through the neck it may vary somewhat in length and in tortuosity. One
or more of the branches usually derived from the external carotid artery may arise from it, and it
sometimes gives off a large meningeal branch to the posterior fossa of the skull. Its posterior
communicating branch may replace the posterior cerebral artery ; on the other hand, the upper
part of the internal carotid may be absent, and the posterior communicating artery may become
the middle cerebral artery. The anterior cerebral branch of the internal carotid may be absent,
or rather it may arise from the corresponding artery of the opposite side ; or there may be three
anterior cerebral arteries, the third arising from the anterior communicating artery which connects
the two anterior cerebrals together. The ophthalmic artery, as it traverses the orbit, may pas*
either above or below the optic nerve. It is occasionally replaced by a branch of the rniddl*
meningeal artery.
The vertebral artery may have a double origin one from the subclavian, and one from th<
inferior thyreoid artery or from the aorta.
ABNOKMALITIES OF AETEEIES. 1055
The right vertebral may arise from the common carotid or from the arch of the aorta.
Occasionally it springs from the descending aorta, an arrangement associated with the persistence
of the dorsal roots of the fourth and fifth right arches.
The left vertebral artery not infrequently springs from the arch of the aorta, arising between
the left common carotid and left subclavian arteries ; this is evidently due to the, absorption of
the stem of the seventh segmental artery into the aortic arch. Very exceptionally the left
vertebral is a branch of an intercostal artery.
In its course upwards either vertebral artery may enter the vertebrarterial foramen of any of
the lower six cervical vertebra.
The cases in which it does not enter one of the lowest of these are apparently associated with
its formation, in part, from the precostal instead of from the postcostal anastomosing channels.
The artery may enter the vertebral canal with the second instead of with the first cervical
nerve, or, after leaving the foramen in the transverse process of the third vertebra, it may divide
into two branches, one of which accompanies the second and the other the first cervical nerve ; the
two branches unite together again in the vertebral canal to form a single trunk.
Sometimes, though rarely, it gives off superior intercostal and inferior thyreoid branches. The
upper end of one of the vertebrals is sometimes very small, or it may be entirely wanting ; in
the latter case the basilar artery is formed by the direct continuation of the opposite vertebral.
The basilar artery may be double in part or the whole of its extent, or its cavity may be
divided by a more or less complete septum. It may terminate in one instead of two posterior
cerebral arteries, the missing vessel being supplied by the enlargement of the posterior com-
municating branch of the internal carotid.
THE ARTERIES OF THE UPPER LIMB.
Subclavian Arteries. The variations, so far as regards the origins of the subclavian
sries, have already been mentioned (p. 1051). Other interesting modifications are met with in
respect of its position and branches.
The subclavian artery may reach as high as 25 or 37 mm. (1-H in.) above the clavicle, though
as a rule it does not reach higher than 19 mm. above that bone. On the other hand, it may
not rise even to the level of the upper border of the clavicle. These differences appear to be
associated with the descent of the clavicle and sternum, which occurs as age increases.
The artery may pass in front of or through the scalenus anterior instead of behind it, or
the vein may accompany it behind the muscle.
The branches of the subclavian artery may be modified with reference to their points of origin ;
thus, those of the first part may be further medial or lateral than usual, the transverse scapular
or some other branch of the thyreo-cervical trunk may arise separately from the third part
of the subclavian, and not uncommonly the descending branch of the transverse cervical artery
is a branch of that part. The abnormalities of the vertebral branch have already been described ;
those of the thyreo-cervical trunk and its branches are numerous but not important.
The internal mammary artery, usually a branch of the first part of the subclavian, is very
variable as regards its origin. It may arise from the second or third parts, or from the thyreo-
cervical, or it may spring from the aorta, or from the innominate or axillary arteries. All these
variations are due to obliteration of the normal origin and the opening up of anastomoses.
The internal mammary artery sometimes descends in front of the cartilages of one or more of
the lower true ribs ; and occasionally it gives off a large lateral branch (a. mammaria lateralis)
which descends on the inner side of the chest wall, close to the mid -axillary line, a point of
importance in paracentesis.
A few cases have also been noticed in which a bronchial artery has arisen from the internal
mammary.
The superior intercostal branch of the costo-cervical trunk may be absent, and the pro-
funda cervicis branch may arise directly from the subclavian trunk. The superior intercostal is
sometimes formed from a postcostal instead of a precostal primitive channel. In such cases it
passes between the necks of the ribs and the transverse processes of the vertebrae instead of, as
usual, in front of the necks of the ribs.
The axillary artery does not vary much as regards its origin or course. Its relations may be
modified by the existence of a muscular or tendinous " axillary arch," which, passing from the
latissimus dorsi to the pectoralis major, crosses the distal part of the artery superficially ; and
a further interesting modification is associated with an anomalous arrangement of its branches.
Occasionally the sub-scapular, circumflex, and profunda and superior ulnar collateral arteries
arise from the axillary by a common stem. In those cases the chief branches of the brachial
plexus are grouped round the common stem instead of round the main trunk. The arrangement
is due to the persistence of a different part of the original vascular plexus.
Sometimes the axillary artery divides into the radial and ulnar arteries, and more rarely the
interosseous artery may spring from it.
Obviously there is no brachial artery when the radial and ulnar arteries are formed by the
vision of the axillary ; its place is taken by the two abnormal vessels which, as a rule, are
separated by the median nerve as they run through the arm ; the radial is usually more super-
ficial than the ulnar, and crosses laterally in front of it at the bend of the elbow.
The brachial artery is rarely prolonged beyond its usual point of bifurcation ; not uncommonly,
however, it bifurcates at a more proximal level. Of the two terminal branches of the brachial,
"~ may divide into radial and interosseous, the other forming the ulnar ; or one may divide into
one
1056 THE VASCULAR SYSTEM.
radial and ulnar, whilst the other is the interosseous artery. Occasionally the brachial artery
terminates by dividing into three branches viz., the radial, the ulnar, and the interosseous.
In any case, the branch which gives origin to or becomes the interosseous was, in all probability,
the original trunk.
Division of the brachial artery at a more proximal level than usual occurs most commonly in
the proximal third of the arm, and least commonly in the distal third ; the resulting trunks
are often united near the bend of the elbow by a more or less oblique anastomosis.
In cases of proximal division of the brachial artery the radial branch may pierce the deep
fascia of the arm near the bend of the elbow, and passes distally in the forearm immediately deep
to the skin ; in other cases the radial runs deeper, and passes behind the tendon of the biceps. The
ulnar branch sometimes runs, on the medial intermuscular septum, towards the medial epicondyle,
and then laterally towards the middle of the bend of the elbow, under a band of fascia from
which the proximal fibres of the pronator teres arise, or round the supracondylar process of the
humerus if it is present. More commonly the ulnar branch runs distally towards the medial
epicondyle, and crosses superficial to the flexor muscles or deep to the palmaris longus ; and in
a few cases it is subcutaneous. In rare cases the ulnar artery accompanies the ulnar nerve
behind the medial epicondyle ; in those cases it has obviously been formed by enlargement
of the ordinary superior ulnar collateral and dorsal ulnar recurrent arteries.
Instead of following its usual course along the brachialis muscle, the brachial artery may
accompany 'the median nerve behind a supracondylar or epicondylic process, or ligament, as in
many carnivora ; it may pass in front of the median nerve instead of behind it. It may give
off a " vas aberrans " or a median artery, and any of its ordinary branches may be absent.
The vas aberrans given off from the brachial artery usually ends in the radial artery, some-
times in the radial recurrent, and rarely in the ulnar artery.
The ulnar artery may be absent, being replaced by the median artery or the inter-
osseous artery, and it may terminate in the deep instead of in the superficial volar arch. It
rarely arises more distally than usual, and when it arises at a more proximal point it most
commonly passes superficial to the muscles which spring from the medial epicondyle. Moreover,
in those cases it frequently has no interosseous branch, the latter vessel springing from the radial
artery, and in all probability variations of this description are produced by the ulnar artery
taking origin from the main trunk, which is represented by the radio-interosseous vessel, at a
more proximal level than usual Even when it commences in the usual way the ulnar artery
may pass superficial to the muscles arising from the medial epicondyle, and in those cases its
interosseous and recurrent branches spring from the radial artery.
The volar and dorsal interosseous arteries may arise separately from the ulnar instead of;
by a common interosseous trunk. The recurrent branches of the ulnar may spring from the
interosseous, and the interosseous itself may be a branch of the radial.
The small median artery, the companion artery of the median nerve, usually a branch of the
volar interosseous, may spring from the axillary, brachial, or ulnar arteries ; it may be much
larger than usual, and it may terminate either by breaking up into digital branches, or by j
joining one or more digital branches of the superficial volar arch or the arch itself.
The radial artery may be absent, its place being taken by branches of the ulnar or inter-
osseous arteries ; it may arise, more proximal than usual, from the axillary, or from the bracliial.
It may terminate in muscular branches in the volar part of the forearm, or as the superficial
volar, or in carpal branches ; the distal portion of the artery, in those cases, is usually replaced
by branches of the ulnar or interosseous arteries. Occasionally the radial divides some distance
proximal to the wrist into two terminal branches, one of which gives off the carpal branches,
and becomes the superficial volar, whilst the other crosses superficial to the extensor tendons
and passes to the dorsum of the wrist.
The radial artery may run a superficial course, or, and especially when it commences at a
more distal level than usual, it may pass deep to the pronator teres and the radial origin of thej
flexor digitorum sublimis. In some cases it passes to the dorsum of the wrist across the brachio-a
radialis, and in others it lies superficial, instead of deep to, the extensor tendons of the thumb.
Its branches may be diminished or increased in number. The radial recurrent may spring
from the brachial or ulnar arteries, or may be represented by several branches from the proxima
part of the radial. The dorsal artery of the index digit may be large, and may replace th<|
princeps pollicis and the volaris indicis radialis. On the contrary, the dorsal carpal artery anc
dorsal digital branches of the radial may be small, or the former may be replaced by branches o j-i
the metacarpal arteries, and the latter by the proximal perforating branches of the deep volar arch j
The princeps pollicis and volaris indicis radialis arteries may be absent, their places bein^
taken either by branches of the superficial volar arch or by the dorsalis indicis radialis artery.
The superficial volar arch is sometimes absent ; its branches are then given off from the dee-
arch. On the other hand, it may be larger than normal, and it may be completed on the radia
side by the volaris indicis radialis, the princeps pollicis, or the comes nervi median! arteries.
The deep volar arch is much more rarely absent than the superficial arch. When absen
its branches are supplied by the superficial arch, the proximal perforating arteries, or the vola
carpal arch.
THE ILIAC ARTERIES AND THEIR BRANCHES.
The common iliac artery may be longer or shorter than usual, a modification which
determined largely, though not altogether, by the point at which the bifurcation of the aorl;
ABNOKMALITIES OF AETEEIES. . 1057
takes place. If exceptionally long, it is usually tortuous. In rare cases in man the artery is
absent. It occasionally gives off .the middle or a lateral sacral artery, and ilio-lumbar, spermatic,
or accessory renal branches may arise from it.
The hypogastric artery varies as regards length. It is usually longer, and arises at a
higher level when the common iliac is short. In rare cases it has been found to arise from the
aorta without the intervention of a common iliac. Frequently it does not, even in appearance,
end in anterior and posterior divisions, but obviously forms a single trunk, as in the foetus, from
which the several branches are given off.
The visceral branches vary much in number and size, and the middle haemorrhoidal may not
be present, its place being taken by branches from the vesical arteries. A renal branch some-
times arises from the hypogastric artery.
The ilio-lumbar branch may arise from the common iliac instead of from the hypogastric artery ;
the superior glutaeal and inferior glutseal arteries may arise by a common stem, or the superior
glutseal may be absent, and its place taken by a branch from the femoral artery ; the inferior
glutseal artery may, as in the fcetus, constitute the main artery of the lower limb, and run distally
to become continuous with the popliteal artery. Probably the arteria comitans nervi ischiadici
represents the original continuity of the two vessels. Occasionally the lateral sacral arteries do
not arise from the hypogastric trunks.
In some instances the obturator artery arises from the' inferior epigastric artery instead of
from the hypogastric. The condition is apparently due to obliteration of the usual origin of the
obturator artery and to the subsequent enlargement of the anastomosing pubic branches of the
obturator and inferior epigastric arteries. The course of the abnormal obturator artery is of
importance. From its origin it descends, into the pelvis minor, on the medial side of the external
iliac vein, and in the majority of cases on the lateral side of the crural ring, but in three-tenths
of the cases, and more frequently in males than in females, it descends on the medial side of the
The obturator artery sometimes gives off an accessory pudendal branch which passes along
the side of the prostate, pierces the urogenital diaphragm, and terminates by dividing into the
profunda artery of the penis and the dorsal artery of the penis. When this occurs the internal
pudendal artery is small, and it terminates in the artery to the bulb. Occasionally the accessory
pudendal arises from the internal pudendal artery in the pelvis, or from one of the vesical arteries.
The external iliac artery may be much smaller than usual, especially if the inferior glutseal
artery persists as the main vessel of the lower limb. It may give off two deep circumflex iliac
branches, a dorsal artery of the penis, a medial circumflex artery of the thigh, or a vas aberrans,
and its deep circumflex iliac and inferior epigastric branches may arise at higher or lower levels
, than usual.
THE ARTERIES OF THE LOWER LIMB.
The femoral artery is small, and ends in the profunda and circumflex branches, when the
inferior glutseal artery forms the principal vessel of the lower limb. The profunda branch, which
arises usually from the lateral side of the femoral trunk, about 37 mm. (1^ in.) distal to the
inguinal ligament, may commence at a more proximal or a more distal level, and from the back
or the medial side of the femoral trunk. In rare cases when the profunda arises at a more
proximal level than usual it may cross anterior to the femoral vein, above the entrance of the
. great saphenous vein, after which it passes distally and laterally posterior to the femoral vessels
(Johnston, Anat. Anz., Bd., 42, 1912). Absence of the profunda has been noted, and in those
cases the branches usually given off by it spring directly from the femoral artery.
The femoral artery may be double for a portion of its extent, or it may be joined by a vas
aberrans given off from the external iliac artery. In addition to its ordinary branches, it may
furnish one or both of the circumflex arteries of the thigh, and sometimes it gives off, near the
origin of the profunda, a great saphenous artery, such as exists normally in many mammals.
This vessel runs distally through femoral trigone and the adductor canal, and accompanies the
saphenous nerve to the medial side of the foot.
The deep circumflex iliac, the obturator, and the inferior epigastric arteries are occasionally
given off from the femoral.
The popliteal artery may exceptionally form the direct continuation of the inferior glutseal
artery. It sometimes divides at a more proximal or more distal level than usual, and the
i vision may be into either two or three branches ; if three terminal branches are present, they
are the anterior and posterior tibial and the peroneal arteries, and if only two, either the
anterior and posterior tibial, or the anterior tibial and the peroneal arteries.
Occasionally the artery is double for a short portion of its course, and it has been found to
cross first posterior to the medial head of the gastrocnemius to the medial side of the knee, and
then anterior to the medial head of the gastrocnemius to regain the popliteal fossa. The
number of its branches may be reduced, or they may be increased by the addition of a vas
aberrans which connects it with the posterior tibial artery. Its superficial sural branch may
enlarge to form a well-marked small saphenous artery.
The posterior tibial artery may be small or altogether absent, its place being taken by
tranches of the peroneal artery ; again, it may be longer or shorter than usual, in conformity with
te more proximal or more distal division of the popliteal trunk. The peroneal artery is large,
ither the anterior or the posterior tibial artery is small. The perforating branch of the
peroneal is almost invariably large when the anterior tibial artery is small; in some cases,
68
1058 . THE VASCULAR SYSTEM.
indeed, it replaces the whole of the dorsalis pedis continuation of the latter vessel ; in others,
however, only the lateral tarsal and arcuate branches are so replaced. The peroneal sometimes
arises from a stem common to it and the anterior tibial artery.
The anterior tibial artery may be absent, its place being taken by branches of the posterior
tibial and peroneal arteries. It is longer than normal when the popliteal artery divides at a
more proximal level than usual, and in those cases it may pass either posterior or anterior to
the popliteus muscle. Occasionally the anterior tibial artery and its dorsalis pedis continuation
are larger than normal, and the terminal part of the dorsalis pedis takes the place, more or less
completely, of the lateral plantar artery.
The medial plantar artery is sometimes very small, and it may be absent ; its place is
taken by branches of the dorsalis pedis or lateral plantar arteries. The lateral plantar
artery also may be small or absent, the plantar arch being formed entirely by the dorsalis pedis.
ABNORMALITIES OF VEINS.
Abnormalities or variations of veins are as frequently met with as those of arteries, and they
are due to similar causes.
THE SUPERIOR VENA CAVA.
The superior vena caya may develop on the left side instead of on the right. This peculiarity
is due to the persistence of the left duct of Cuvier instead of that on 'the right side, and it is
associated with absence of the coronary sinus, which is replaced by the lower part of the left
superior vena cava. An exceptional case is recorded in which the opening of the coronary sinus
into the heart was obliterated, and the cardiac veins terminated in a trunk which passed upwards
to the left innominate vein. This trunk was obviously formed by enlargement of the left duct of
Cuvier and the lower part of the left anterior cardinal vein. Not very uncommonly, as the
result of the persistence of both ducts of Cuvier, there are two superior venae cavse, the transverse
anastomosis which usually forms the left innominate vein being small or entirely absent. In
such cases the left innominate vein descends in the left part of the superior mediastinum, crosses
the aortic arch, is joined by the left superior intercostal vein, and becomes the left superior
vena cava ; which descends anterior to the root of the left lung, and terminates in the lower and
back part of the right atrium. It receives the great cardiac vein, and, turning to the back
of the heart, replaces the coronary sinus. This arrangement is normal in many mammals.
Occasionally^in man the left superior vena cava terminates in the left atrium, and the coronary
sinus, which represents a pa/rt of the sinus venosus, has been seen to have a similar ending ; both
these abnormal endings must be the result of malposition of the interatrial septum.
The vena azygos may be formed on the left side ; it then arches over the root of the left
lung, and terminates in the left end of the coronary sinus. This is the normal arrangement in
some mammals, and it is due to the persistence of the left posterior cardinal vein and the left
duct of Cuvier.
Occasionally the azygos vein is the only vessel by which blood is returned to the heart from
the lower limbs and the lower parts of the body walls. In such cases that portion of the inferior
vena cava which usually extends from the right renal vein to the heart is absent and the azygos
vein is the direct continuation of the inferior vena cava. This condition probably results from
the absence of those parts of the inferior vena cava which are usually formed from the right
vitelline and the right subcardinal veins, and to the enlargement of the whole of the supra-
pelvic portion of the right posterior cardinal vein.
The hemiazygos and the accessory hemiazygos veins may be absent. In such cases each
left intercostal vein opens separately into the vena azygos. On the other hand the hemiazygot-
and the accessory hemiazygos veins may form a continuous trunk which may open \>y a transverse
anastomosis into the azygos vein, or it may join the left innominate vein. When the hemiazygos
and the accessory hemiazygos veins form a single trunk, which receives the left intercostal vein:-
and opens into the left innominate vein, the condition is due to the persistence of the whole of
the thoracic part of the left posterior cardinal vein and of the lower part of the left anterior
cardinal vein.
Cases also occur in which the thoracic part of the posterior cardinal vein is represented
by three instead of two stems, either the hemiazygos or the accessory hemiazygos vein being
represented by two vessels.
The internal jugular vein may be either smaller or larger than normal. In. either case com-
pensatory changes in size occur in the transverse sinus and internal jugular vein of the opposite
side, or in the external and anterior jugular veins of the same side.
The external jugular vein is sometimes absent, or it may be smaller than usual ; in botli
cases either the anterior or the internal jugular vein is enlarged. In some of the cases in whicl
the external jugular vein is small it receives no communication from the posterior facial vein
but is merely the continuation of the posterior auricular vein. On the other hand, it may b(
enlarged, and receive the whole of the posterior facial vein.
The anterior jugular vein may be absent, or it may be unusually large, especially in tin
lower part of its extent, and after it has received an occasional tributary from the common facia ;
vein.
ABNOEMALITIES OF VEINS. 1059
The posterior facial vein may terminate entirely in the common facial vein, or in the
external or the internal jugular vein. It may be very small, and occasionally it is absent.
Variations of the cranial blood sinuses are not numerous. One transverse sinus may be
absent or very small, when, as a rule, that of the opposite side is enlarged. The inferior sagittal,
the occipital, or the spheno-parietal sinuses may be absent, and there may be an additional petro-
squamous tributary to the transverse sinus. The petro-squamous sinus, when present, is the
remains of a sinus which crossed the temporal bone, passed through the post-condyloid foramen
and terminated in the lateral cerebral vein. In the human adult, in rare cases, it pierces
the skull behind the condyle of the mandible, and terminates in the posterior facial vein. This
is the normal arrangement in some mammals.
THE VEINS OF THE SUPERIOR EXTREMITY.
The superficial veins of the forearm are extremely variable ; any of them may be absent,
but most commonly it is the median or the cephalic vein which is wanting. The median cephalic
and the cephalic veins may be small or absent, and, on the other hand, the cephalic vein may be
larger than usual. Moreover the cephalic vein may end in the external jugular vein, its original
termination ; or it may be connected with the external jugular vein by an anastomosing channel
which sometimes passes over the clavicle and sometimes through that bone.
The basilic vein is sometimes larger and sometimes smaller than usual, and it may pierce the
fascia of the arm at a more proximal or at a more distal level than usual.
The venae comites of the arteries of the upper extremity generally terminate at the lower
border of the subscapularis, where they join the axillary vein, but they may end above or below
the position of their usual termination.
The subclavian vein sometimes passes behind instead of in front of the scalenus anterior
.e, and it has been seen passing between the clavicle and the subclavius muscle.
nmscl
THE INFERIOR VENA CAVA.
The lower part of the inferior vena cava is sometimes absent, in which case the common iliac
veins ascend, one on the right and the other on the left of the aorta, to the level of the second
lumbar vertebra, where the left common iliac vein receives the -left renal vein, and then crosses in
front of or behind the aorta to fuse with the corresponding vein of the right side ; in such cases,
therefore, the inferior vena cava commences at the level of the second lumbar vertebra, and it
represents only the upper and last-formed part of the ordinary vessel ; the common iliac veins,
each of which receives the lumbar veins of its own side, are exceptionally long, and they may
or may not be united at the pelvic brim by a small transverse anastomosing channel. Cases of
this kind are sometimes described as partial doubling of the inferior vena cava.
Occasionally the inferior vena cava does not terminate in the right atrium, but is continuous
with the vena azygos, which is much enlarged, all the inferior caval blood being then carried
to the superior vena cava. In such cases the hepatic veins open directly into the right atrium
without communicating with the inferior vena cava.
The lower part of the inferior vena cava sometimes lies to the left instead of to the right of
the aorta ; this condition is associated with a long right common iliac vein, which crosses obliquely
from right to left to join the shorter left common iliac vein. After receiving the left renal vein
the misplaced inferior vena cava crosses in front of the aorta, reaching the right side at the level of
the second or first lumbar vertebra. In other cases, however, the left inferior vena cava continues
upwards through the left cms of the diaphragm, usurping the place of a greater or smaller part
of the hemiazygos vein ; having entered the thorax, it may cross to the opposite side and terminate
in the vena azygos, or it may continue upwards on the same side, and after arching over the
root of the left lung, descend behind the left atrium to terminate in the right atrium in the
situation of the coronary sinus. In this group of cases also the hepatic veins open separately into
the right atrium.
The inferior vena cava may lie ventral instead of dorsal to the right internal spermatic artery,
in which case the lower part of the vessel has been derived from the subcardinal vein instead of
from the posterior cardinal vein. (Johnston, Journ. of Anat. and Phys. xlvii. 1913.)
The tributaries of the inferior vena cava are also subject to variation. Additional renal,
spermatic, ovarian, or suprarenal veins may be present. Two or three lumbar veins of one or
oth sides may unite into a common trunk which terminates in the inferior vena cava, and the
hepatic veins may open separately, or after fusing into a common trunk, into the right atrium
near the opening of the inferior vena cava.
No explanation of the variations of the inferior vena cava and its tributaries is necessary,
beyond the statement that they are due to persistence of portions of the cardinal and subcardinal
ems which usually disappear, and to the persistence of transverse anastomoses and tributaries
which usually atrophy, or to modifications of those which ordinarily take part in the formation
the inferior vena caval system.
The left common iliac vein is short and the right long when the inferior vena cava lies on
e left side. The common iliac veins may be absent, the hypogastric veins uniting to form the
commencement of the inferior vena cava, into which the external iliac veins open as lateral
tributaries.
1060 THE VASCULAR SYSTEM.
THE VEINS OF THE INFERIOR EXTREMITY.
The great saphenous vein is not subject to much variation, but the small saphenpus vein
may terminate by joining the great saphenous, or, after piercing the deep fascia in the distal part
of the thigh, it may ascend and join the inferior glutseal vein or one of the tributaries of the
profunda vein.
The venas comites are generally described as terminating in the lower extremity, at the
distal part of the popliteal fossa, but they may ascend as far as the femoral trigone ; as a matter
of fact, one or more small additional veins usually accompany the popliteal and femoral arteries,
although as a rule there is only one large popliteal and one large femoral vein.
In a few cases the popliteal vein does not pierce the distal part of the adductor magnus, but
ascends behind that muscle and becomes continuous with the profunda vein, the femoral artery
being unaccompanied by any large vein during its passage through the adductor canal.
ABNORMALITIES OF THE LYMPH VESSELS.
Variations of the glands and smaller vessels of the lymphatic system are so common that
they can hardly be regarded as abnormalities ; variations of the larger vessels, however, are
comparatively rare. This is especially the case with respect to the two terminal trunks, the thoracic
duct and the right lymph duct, the abnormalities of which are interesting and important.
When the arch of the aorta is on the right side instead of on the left side, the thoracic duct
terminates usually in the right innominate vein, in which case it receives the tributaries which
usually open into the right lymph duct, whilst the corresponding area on the left side is drained
by lymph vessels terminating in a left lymph duct which opens into the commencement of
the left innominate vein. A similar arrangement of the terminal lymph trunks sometimes occurs
even when the arch of the aorta is in its normal position on the left side. In either case the
thoracic duct may commence in the usual way, and after reaching the level of the fifth thoracic
vertebra continue upwards on the right side, instead of crossing to the left side of the vertebral
column ; more rarely it commences on the left side and crosses over to the right at a higher level.
In one case in which the thoracic duct opened into the right innominate vein, instead of the
left, no trace of a lymph duct was discovered on the left side.
Occasionally the thoracic duct commences and terminates in the usual manner, but crosses the j
vertebral column immediately after its origin and ascends on the left side.
Not uncommonly there is no distinct cisterna chyli, in which case the terminal lymph
vessels of the abdomen merely unite to form a larger vessel which does not present any obvious
dilatation, and from which the thoracic duct is continued. The terminal lymph trunk may open
into the internal jugular vein, previous to its junction with the subclavian, instead of into the |
commencement of the innominate vein.
Occasionally the thoracic duct is double, either in the whole or in part of its extent, and
sometimes it breaks up into a plexus of vessels which may reunite into a single trunk in the
upper part of the thorax. Both the thoracic duct and the right lymph duct may, before
terminating, divide into branches which, though sometimes reuniting on each side into a single
trunk, not infrequently open separately into the great veins at the root of the neck.
As a rule the thoracic duct joins the commencement of the left innominate vein, but it maj ;
end in the internal jugular, vertebral, or subclavian veins of the left side ; whilst very rarely, i j
opens into the vena azygos.
NOTES.
1 (see p. 995). It is stated by H. Downey (Anat. Record, 1915)"~that there are no endotlielia
cells covering the trabeculae of lymph glands. He asserts that the cells described as enelothelu
are connected with the fibrils of the reticulum.
2 (see p. 1025). More recent evidence throws doubt on this statement ; it appears probabl
that blood and blood-vessels may be formed in situ in the embryonic region.
THE RESPIRATORY SYSTEM.
THE ORGANS OF RESPIRATION AND VOICE.
By the late D. J. CUNNINGHAM, F.R.S.,
Professor of Anatomy, University of Edinburgh.
Kevised by KICHARD J. A. BERRY, F.E.C.S.,
Professor of Anatomy, University of Melbourne.
THE organs of respiration are the larynx and trachea, which, together, constitute a
median air-passage ; the two bronchi or branches into which the inferior end of the
trachea divides; and the two lungs to which the bronchi conduct the air. In
connexion with the lungs there are also the pleural membranes two serous sacs
which line the portions of the thoracic cavity which contain the lungs, and at
the same time give a thin coating to those organs.
The larynx opens above into the inferior or caudal part of the pharynx, and
the air which passes in and out from the air -passages likewise traverses the
pharynx, the nasal cavity, and also the oral cavity if the mouth be open. This
connexion between the digestive and respiratory systems is explained by the
fact that the respiratory apparatus is secondarily developed, as an outgrowth,
from the ventral aspect of the primitive fore -gut of the embryo. In most
mammals the superior or cranial aperture of the larynx opens into the part of
the pharynx which lies immediately dorsal, or posterior, to the nasal cavities.
In man, however, the superior opening of the larynx is placed below, that is
inferior or caudal to, the communication between the mouth and pharynx, and
both nasal and oral breathing may be carried on with very nearly equal ease.
The
LARYNX.
ie larynx or organ of voice is the upper part of the air-passage, specially
modified for the production of voice. Above it opens into the pharynx, whilst
below its cavity becomes continuous with the lumen of the trachea or windpipe.
Position and Relations of the Larynx. In the natural position of the neck,
and whilst the organ is at rest, the larynx is placed on the ventral side of the
bodies of the fourth, fifth, and sixth cervical vertebrae. Its highest point,
represented by the tip of the epiglottis, extends to the inferior border of
the body of the third cervical vertebra, whilst its lowest limit (the inferior
border of the cricoid cartilage) usually corresponds to the inferior border of the
body of the sixth cervical vertebra. From the vertebral column the larynx is
separated, not only by the prevertebral muscles and the prevertebral fascia, but
also by the dorsal wall of the pharynx indeed the dorsal surface of the larynx
forms the inferior part of the ventral or anterior wall of the pharynx, and is
covered by the lining mucous membrane of that section of the alimentary canal.
The larynx lies below the hyoid bone' and the tongue, and in the interval
between the great vessels of the neck. It forms a more or less marked projection
on the ventral side of the neck, and, in the median plane, it approaches very closely
to the surface, being merely covered by skin and the two layers of fascia. Laterally
1061
1062 THE EESPIKATOEY SYSTEM.
it is more deeply placed. There, it is overlapped by the sterno-cleido-mastoid muscle,
and is covered by the two strata of thin ribbon-like muscles which are attached to
the thyreoid cartilage and the hyoid bone ; and it is hidden, to some extent, by the
upper prolongations of the lateral lobe.s of the thyreoid gland.
The position of the larnyx is influenced by movements of the head and neck. Thus
it is elevated or raised when the head moves dorsally, and depressed when the chin
is carried downwards towards the chest. Again, if the finger is placed upon it during
deglutition, it will be noted that the larynx moves to a very considerable extent. The
pharyngeal muscles attached to it, and more especially the stylo-pharyngeal muscles, are
chiefly responsible for bringing about these movements. During singing, changes in the
position of the larynx may also be noted, a high note being accompanied by a slight
upward movement, and a low note by a similarly slight downward movement of the
organ.
The position of the larynx is not the same at all periods of development and growth.
In the foetus, shortly before birth, it lies much nearer the head, and its inferior border
corresponds to the inferior border of the fourth cervical vertebra. Its permanent position
is not reached until the period of puberty is attained (Symington). This downward
movement of the larynx has been stated to be due to the rapid and striking growth of
the facial part of the skull (Symington). It is very doubtful, however, if the facial
growth has any influence in this direction. In the anthropoid ape, in which the face
forms a much greater part of the skull than in man, and in which, in the transition
from the infantile to the adult condition, the facial growth is even more striking than it
is in man, the larynx occupies a relatively higher position in the neck. In the early
stages of growth all the thoracic viscera undergo a gradual subsidence and the larynx
follows them. Indeed, it cannot do otherwise, seeing that the bifurcation of the
trachea between infancy and puberty moves downwards towards the caudal end of
the body more than the depth of one thoracic vertebra.
General Construction of the Larynx. The wall of the larynx is constructed
upon a somewhat complicated plan. There is a framework composed of several
cartilages. These are connected together, at certain points, by distinct joints and
also by elastic membranes. Two elastic cords, which stretch in a ventro-dorsal
direction from the ventral to the dorsal wall of the larynx, form the groundwork
of the vocal folds (O.T. true vocal cords). Numerous muscles also are present.
These operate upon the cartilages of the larynx, and thereby not only bring about!
changes in the relative position of the vocal folds, but also produce different
degrees of tension of these folds. The cavity of the larynx is lined with mucougj
membrane, under which, in certain localities, are collected masses of mucous glands.
CARTILAGINES LARYNGIS.
Three single cartilages and three pairs of cartilages enter into the constructor
of the laryngeal wall. They are named as follows :
/ mi -j ( Aryteenoids.
Single cartilages \ Cricokl! ' Paired cartilages \ ^""l^
( Epiglottis. ( cuneiform eartilagw.
Cartilago Thyreoidea. The thyreoid cartilage, the largest of the laryngea
cartilages, is formed of two quadrilateral plates termed the laminae, which mee
ventrally at an angle, and become fused along the median plane. Dorsally th
laminae diverge from each other, and enclose a wide angular space which is opei
dorsally. The ventral borders of the laminae are fused only in their inferior parts
Above they are separated by a deep, narrow V-shaped median notch, called th
incisura thyreoidea or thyreoid notch. In the adult male the angle formed by th
meeting of the ventral borders of the two laminae, especially in its upper part, i
very projecting, and with the margins of the thyreoid notch, which lies abov(
constitutes a marked subcutaneous prominence in the neck, which receives th'
name of the prominentia laryngea (O.T. Adam's Apple).
LAKYNGEAL CAETILAGES.
1063
The angle which is formed by the meeting of the two laminae of the thyreoid cartilage varies,
to some extent, in different individuals of the same sex, and shows marked differences in the two
sexes and at different periods of life. In the
adult male the average angle is said to be 90 ;
in the adult female it is 120 ; whilst in the
infant the laminae meet in the form of a
gentle curve, convex ventrally.
Cartilage triticea
Superior cornu of
thyreoid cartilage
Thyreoid notch
Pomum Adami
Conus elasticus
Inferior cornu of
thyreoid cartilage
Cricoid cartilage
FIG. 845. VENTRAL ASPECT OF THE CARTILAGES
AND LIGAMENTS OF THE LARYNX.
Epiglottis
The dorsal border of each lamina of
the thyreoid cartilage is thick and
rounded, and is prolonged beyond the
superior and inferior borders in the
form of two slender cylindrical pro-
cesses, termed cornua. The superior
cornu is longer than the inferior cornu.
It is directed upwards, towards the
head, with a slight dorso- medial in-
clination, and ends in a rounded ex-
tremity, which is joined to the tip of
the great cornu of the hyoid bone by
the lateral hyo - thyreoid ligament.
The inferior cornu is shorter and stouter
than the superior cornu. As it pro-
ceeds downwards it curves slightly
towards the median plane, and upon the
medial face of its extremity there is a
circular, flat facet, by means of which
it articulates with a similar facet on the
lateral aspect of the cricoid cartilage.
The superior border of each lamina is, for the most part, slightly convex, and,
ventrally, it dips suddenly to become continuous with the margin of the thyreoid
notch. Dorsally, where it joins the superior cornu, it exhibits a shallow notch
or concavity. The inferior border is almost straight, but it is marked off by a
projection, termed the inferior thyreoid tubercle,
into a short clorsal part, which shows a shallow
concavity close to the inferior cornu and a
longer part which lies ventral to the tubercle,
and is also concave, but to a less degree.
The lateral surface of each lamina is divided
into two unequal areas by the linea obliqua.
This line begins above at the superior thyreoid
tubercle, a prominence situated immediately
below the superior border, and a short distance
ventral to the root of the superior cornu. From
the tubercle the oblique line proceeds forwards
and downwards to end in the inferior tubercle
on the inferior border of the lamina. The area
which lies dorsal to the oblique line is much
smaller than that which lies on its ventral
side. It is covered by the inferior constrictor
muscle of the pharynx. The larger ventral
area is for the most part covered by the thyreo-
hyoid muscle. To the oblique line are
K attached the sterno-thyreoid, thyreo-hyoid, and
inferior constrictor muscles. The medial sur-
face of the lamina of the thyreoid cartilage is
smooth and slightly concave.
Cartilage Cricoidea. The cricoid cartilage
is shaped like a signet-ring. Dorsally there is a broad, thick plate, somewhat
luadrilateral in form, termed the lamina ; whilst ventrally and laterally the
3ircumference of the ring is completed by a curved band, called the arch. The
Hyoid bone
Cartilago
tritieea
Hyo-thyreoid
membrane
Superior
cornu of
hyoid bone
Superior
tubercle on
the ala of
thyreoid
cartilage
Oblique line
Inferior tubercle
Inferior cornu of
thyreoid cartilage
Conus elasticus
Cricoid cartilage
Fn;. 846. PROFILE VIEW OF THE CARTILAGES
AND LIGAMENTS OF THE LARYNX.
1064
THE EESPIEATOEY SYSTEM.
Hyoid bone
Cartilago triticea
Thyreo-epiglottic
ligament
Superior cornu o.
thyreoid cartilage
lumen of the ring enclosed by these parts is circular below, but the upper part
of the ring is compressed laterally, so that the lumen becomes elliptical. The
upper border of the lamina presents a faintly marked median notch. On either
side of this there is an oval facet which looks more laterally than upwards; it
articulates with the base of the arytaenoid cartilage. The dorsal surface of the
lamina is divided by an elevated median ridge into two depressed areas which
give attachment to the posterior crico-arytaenoid muscles. The ventral part of
the arch of the cricoid is in the form of a narrow band, but as it proceeds
dorsally towards the lamina its upper border rises rapidly, and in consequence
the arch becomes much broader. The inferior border of the cricoid is nearly
straight, although it frequently presents a median ventral projection and two
lateral projections. It is joined to the first ring of the trachea by an elastic
membrane the crico-tracheal ligament. On the lateral surface of the cricoid
cartilage, at the place where the arch joins the lamina, a vertical ridge runs
downwards from the arytaenoid
articular facet. On this, a short
distance from the inferior border
of the cartilage, a prominent cir-
cular articular facet is visible, for
articulation with the inferior cornu
of the thyreoid cartilage (Fig. 848,
p. 1067). The medial surface of the
cricoid cartilage is smooth, and is
covered with mucous membrane.
The narrow band - like part of
the arch of the cricoid cartilage lies
below the inferior border of the'
th y reoid cartilage, whilst the lamina i
is received into the interval between
the dorsal portions of the laminae^
of the thyreoid cartilage.
Cartilagines Arytaenoideae.
The arytsenoid cartilages are placed!
one on each side of the median ;
plane, and rest upon the upper
border of the lamina of the cricoid!
cartilage, in the interval betweecj
the dorsal portions of the lamina
of the thyreoid cartilage. Each
presents a somewhat pyramida
form, the pointed apex of which ii
directed upwards, and at the sann
time curves dorsally and medially
It supports the corniculate cartilage (Santorini). Of the three surfaces, the media
one faces the corresponding surface of the opposite cartilage, from which it is separate<
by a narrow interval ; another looks dorsally ; whilst the third is directed lateral!;
and ventrally. The medial surface, which is the smallest of the three, is triangula
in outline. It is narrow, vertical, and even, and is clothed with the lining mucou
membrane of the larynx. The dorsal surface is smooth and concave in the cranic
caudal direction ; it lodges and gives attachment to the arytaenoideus transverse
muscle. The ventro-lateral surface is the most extensive of the three (Fig. 84! ;
p. 1067). Its middle part is marked by a deep depression in which is lodged a mass <
mucous glands. Upon this surface of the arytaenoid cartilage the vocalis and thyre<
arytaenoid muscles are inserted, whilst a small tubercle a short distance above tl:
base gives attachment to the ventricular ligament the feeble supporting ligamei
of the ventricular fold (O.T. false vocal cord). The three surfaces of the arytaeno :
cartilages are separated from each other by a ventral, a dorsal, and a lateral borde
The lateral border is the longest, and it pursues, as it is traced from the apex to tl
base, a sinuous course. Eeaching the base of the cartilage, it is prolonged lateral
Muscular process of
arytsenoid cartilage
Inferior cornu of
thyreoid cartilage
FIG. 847. DORSAL ASPECT OF THE CARTILAGES
AND LIGAMENTS OF THE LARYNX.
CARTILAGES OF THE LARYNX. 1065
and dorsally in the form of a stout prominent angle or process, termed the processus
muscularis. Into the ventral side of this process is inserted the crico-arytaenoideus
lateralis muscle; whilst into its dorsal aspect the crico-arytsenoideus posterior
muscle is inserted. A small nodule of yellow elastic cartilage, called the
sesamoid cartilage, is frequently found on the lateral border of the arytsenoid
cartilage, where it is held in position by the investing perichondrium. The
ventral border of the arytaenoid is vertical, and at the base of the cartilage is
prolonged ventrally into a small sharp-pointed process called the processus
vocalis, which receives this name because it gives attachment to the vocal ligament
or supporting band of the vocal fold (O.T. true vocal cord). The base of the
arytrenoid cartilage presents on its inferior surface, particularly in the region
of the processus muscularis, an elongated concave facet for articulation with the
facet on the superior border of the lamina of the cricoid cartilage.
Cartilaglnes Corniculatse (Santorini). The corniculate cartilages are two
minute conical nodules of yellow elastic cartilage which surmount the apices of the
arytasnoids, and prolong the upper curved ends of these cartilages in a dorso-
rnedial direction. Each corniculate cartilage is enclosed within the dorsal part of
the corresponding ary-epiglottic fold of mucous membrane.
Cartilagines Cuneiformes ( Wrisbergi). The cuneiform cartilages are not always
present. They are two minute rod-shaped pieces of yellow elastic cartilage, each
of which occupies a place in the corresponding ary-epiglottic fold, immediately
ventral to the arytsenoid cartilage and the corniculate cartilage of Santorini.
On the superficial surface of each a collection of mucous glands is present, and
this tends to make the cartilage stand out in relief under the mucous membrane.
Cartilago Epiglottica. The epiglottis is supported by a thin, leaf-like lamina of
yellow fibro-cartilage, the epiglottic cartilage, which is placed dorsal to the root of the
tongue and the body of the hyoid bone, and ventral to the aperture of the larynx.
When divested of the mucous membrane, which covers it dorsally and also to some
extent ventrally, the epiglottic cartilage is seen to present the outline of a bicycle-
saddle, and to be indented by pits and pierced by numerous perforations. In the
pits, glands are lodged, whilst through the foramina, blood-vessels and, in some cases,
nerves pass. The broad end of the epiglottic cartilage is directed upwards, and is
free. Its margins are, to a large extent, enclosed within the ary-epiglottic fold. The
ventral ^surface is free only in its upper part. This part is covered with mucous
membrane, and looks towards the pharyngeal part of the tongue. The dorsal
surface is covered throughout its whole extent with the lining mucous membrane of
the laryngeal cavity. The inferior pointed extremity is prolonged downwards in the
form of a strong fibrous band, termed the thyreo-epiglottic ligament.
r Ossification of the Cartilages of the Larynx. The thyreoid and cricoid
cartilages and the greater part of the arytsenoid cartilages are composed of the hyaline
variety of cartilage. The apical parts, and also the vocal processes of the arytaenoid
cartilages, the corniculate cartilages of Santorini, the cuneiform cartilages, and the
epiglottis, are formed of yellow fibro-cartilage, and at no period of life do they exhibit
any tendency towards ossific change. The thyreoid, cricoid, and basal portions of the
arytaenoids, as life advances, become more or less completely transformed into bone.
In males over twenty years of age, and in females over twenty-two years of age, the
process will usually be found to have begun (Chievitz). It is impossible, however, by an
examination of the laryngeal cartilages, to form an estimate of the age of the individual,
although in old age it is usual to find the thyreoid, cricoid, and the hyaline parts of the
arytsenoids completely ossified. It would appear that the process is somewhat slower in
the female than in the male. The thyreoid is the first to show the change ; then, but
almost at the same time, the cricoid ; and lastly, a few years later, the arytsenoids.
ARTICULATIONS, LIGAMENTS, AND MEMBRANES OF THE LARYNX.
Crico-thyreoid Joints. These are diarthrodial joints, and are formed by
5 apposition of the circular facets on the tips of the inferior cornua of
the thyreoid cartilage with the elevated circular facets on the sides of the cricoid
cartilage. An articular capsule surrounds each articulation, and this is lined with a
1066 THE EESPIEATOEY SYSTEM.
synovial layer (stratum synoviale). On the dorsal aspect of the joint a strengthen-
ing band is present in the capsule. The movements which take place at the
crico-thyreoid joints are of a twofold character, viz., gliding and rotatory. In the
first case the thyreoid facets glide upon the cricoid surfaces in different directions.
The rotatory movement is one in which the thyreoid cartilage rotates to a slight
extent around a transverse axis which passes through the centres of the two joints.
Crico-arytaenoid Joints. These also are diarthrodial articulations. In each
case there is a joint cavity surrounded by an articular capsule, which is lined with
a synovial layer. The cricoid articular surface is convex, whilst that of the
arytsenoid is concave ; both are elongated or elliptical in form, and they are applied
to each other so that the long axis of the one intersects or crosses that of the other
at an acute angle. In no position of the joint do the two surfaces accurately
coincide a portion of the cricoid facet is always left uncovered. The capsule of
the joint is strengthened dorsally by a band which is inserted into the dorso-
inedial part of the base of the arytsenoid cartilage, and plays a somewhat important
part in the mechanism of the joint ; it effectually arrests excessive ventral
movement of the arytsenoid cartilage.
The movements which take place at the crico-arytsenoid joints are of a two-
fold kind, viz., gliding and rotatory. The ordinary position of the arytaenoid during
easy, quiet breathing is one in which it rests upon the lateral part of the cricoid
facet. By a gliding movement it can move upon the cricoid facet, and advance
towards the median plane and its fellow of the opposite side. The gliding
movements, therefore, are of such a character that the two arytsenoid cartilages
approach or retreat from each other and from the median plane. In the rotatory
movement the arytsenoid cartilage revolves around a vertical axis. By this
movement the vocal process is swung laterally or medially, so as to open or close
the rima glottidis.
The joint between the arytaenoid and the corniculate cartilage (Santorini)
may either partake of the nature of an amphiarthrosis or of a diarthrosis. The tips
of the two corniculate cartilages can generally be made out to be connected to the
upper border of the lamina of the cricoid cartilage by a delicate Y-shaped band of
connective tissue termed the ligamentum corniculopharyngeum.
Hyothyreoid Membrane. This is a broad, membranous, and somewhat elastic
sheet which occupies the interval between the hyoid bone and the thyreoid
cartilage. It is not equally strong throughout. It presents a central thick portion
and cord-like right and left dorsal margins, whilst in the intervals between these it
is thin and weak (Figs. 845 and 846, p. 1063). The central thickened part, or the
ligamentum hyothyreoideum medium, is largely composed of elastic fibres. Below
it is attached to the margins of the thyreoid notch, whilst above* it is fixed to
the dorsal part of the upper border of the body of the hyoid bone. The upper part
of its ventral surface, therefore, is placed dorsal to the dorsal hollowed-out surface
of the body of the hyoid bone ; a synovial bursa of variable extent is placed between
them, and in certain movements of the head and larynx the upper border of the
thyreoid cartilage moves towards the head on the dorsal side of the hyoid bone.
On each side of the strong central part the hyothyreoid membrane is thin and
loose, and is there attached, below, to the upper border of the thyreoid cartilage, and
above, to the medial aspect of the great corriu of the hyoid bone. It is pierced by
the internal ramus of the superior laryngeal nerve and by the superior laryngeal
vessels. The dorsal border of the hyothyreoid membrane on each side is thickened,
round, and cord-like, and is chiefly composed of elastic fibres ; it is termed the liga-
mentum hyothyreoideum laterale, and extends from the tip of the great cornu of the
hyoid bone to the extremity of the upper cornu of the thyreoid cartilage. In this
ligament there is usually developed a small oval cartilaginous or bony nodule,
which receives the name of the cartilage triticea. The deep surface of the lateral
part of the hyothyreoid membrane is covered with the pharyngeal mucous
membrane, and its central part lies ventral to the epiglottis, but separated from it
by a mass of adipose tissue (Fig. 851, p. 10*70).
Conus Elasticus. The conus elasticus, formerly known as the crico-thyreoid
membrane, is a very important structure, which it is convenient to consider in three
LIGAMENTS OF THE LAKYNX. 1067
parts, viz., one median and two lateral, all of which are directly continuous with
one another, and differ only. in the nature of their upper connexions. The median
part (crico-thyreoid ligament) of the conus elasticus is strong, tense, and elastic.
It is triangular in shape, and is attached by its broad base to the -upper border
of the arch of the cricoid cartilage, whilst its apex is fixed to the medial part of
the lower border of the thyreoid cartilage (Fig. 845, p. 1063). It is pierced by
minute apertures, and is crossed superficially by the crico-thyreoid branch of the
superior thyreoid artery. The median part of the conus elasticus, therefore, closes,
ventrally, the interval between the cricoid and thyreoid cartilages. The lateral
part, on each side, presents very different connexions. It is not attached to the
interior border of the thyreoid cartilage, but slopes upwards and medially on the
inner side of the thyreoid lamina, and thus diminishes materially the transverse
or frontal width of the cavity of the larynx. Its attachments are very definite.
Inferiorly it is fixed to the superior border of the cricoid cartilage immediately
subjacent to the lining mucous membrane of the larynx ; above it is directly
continuous with the vocal ligament or
supporting band of the vocal fold. That g|
ligament, indeed, may be looked upon as | Arytamoid cartilage
> i -i -i P / Muscular process
constituting the superior thickened free \\ / /
border of the lateral part of the conus O^-J. ^r^~~~^\
elasticus. Ventrally the lateral part of X^/ ! / \^ Vocal proce8fl
the conus elasticus is attached to the ]!?( / / ikl
inferior half of the medial surface of the JjjJ^v^ j J
lamina of the thyreoid cartilage, close to ^sr^m^^^i '^f~jT Rima glottidis
the angle, and, dor sally, to the inferior / Aa^tegjS llSr /
f .LI. T J.-L / \ 1 y%&Sr~f- Ligament of
border of the processus vocans of the / V JS ^jmj ^ ^ vocal fold
arytsenoid cartilage. In contact with the Wij& ~ !?"* f c nus
OUter Surface Of the lateral, part Of the \ /* _|^F Facet on cricoid for inferior
conus elasticus, and separating it from ^
the thyreoid lamina, are the lateral crico- [^JfjjSjjjj^m ~~ Cricoid car t ila se
arytsenoid muscles ; the inner surface is jj^
clothed with the lining mucous membrane \r |< ffW
of the larynx. ll, = n ,^fjj m
Ligamentum Vocale. The vocal liga-
ment (O.T. inferior thyreo -arytsenoid lig.) FIG 848. -DISSECTION TO SHOW THE CONUS
.,, ,-, ELASTICUS. The right lamina of the thyreoid
18 formed in Connexion With the Superior cartilage has been removed.
border of the conus elasticus, and con-
stitutes the supporting ligament of the vocal fold (O.T. true vocal cord). It is
attached ventrally, close to its fellow of the opposite side, to the middle of the
angular depression between the two laminae of the thyreoid cartilage. From
there it stretches dor sally, and becomes incorporated with the tip and superior border
of the processus vocalis, which projects ventrally from the base of the arytsenoid
cartilage. The vocal ligament is composed of yellow elastic fibres, and embedded
in its ventral extremity there is, frequently, a minute nodule of elastic cartilage.
Its medial border is sharp and free, and is clothed with mucous membrane, which
I in that position is very thin and tightly bound down to the ligament.
Ligamentum Ventricular e. The ventricular ligament supports the ventricular
fold (O.T. false vocal cord). It is weak and indefinite, but somewhat longer than
the vocal ligament. Ventrally it is attached to the angular depression between
the two laminae of the thyreoid cartilage, above the vocal ligament and close to
the attachment of the thyreo-epiglottic ligament; it extends, dor sally, to be fixed
to a tubercle on the ventro-lateral surface of the arytsenoid cartilage, a short dis-
tance above the processus vocalis. It is composed of connective tissue and elastic
fibres which are continuous with the fibrous tissue in the ary-epiglottic fold.
Epiglottic Ligaments. The epiglottis is bound by ligaments to the base of
the tongue, to the wall of the pharynx, to the hyoid bone, and to the thyreoid
cartilage. The glosso-epiglottic fold is a prominent median fold of mucous
membrane which proceeds from the middle of the ventral free surface of the
epiglottis to the root of the tongue. The pharyngo-epiglottic folds are similar
1068
THE KESPIKATOEY SYSTEM.
elevations of mucous membrane which proceed from the lateral margins of the
epiglottis to the lateral walls of the pharynx at the side of the tongue. Between
the two layers of mucous membrane which form each of these folds is a certain
amount of elastic tissue. By the three folds the depression between the root
of the tongue and the epiglottis is marked off into two fossae, termed the epiglottic
valleculae. From the lateral margins of the epiglottis there also pass off the
plicae aryepiglotticae to the arytaenoids.
The ligamentum hyoepiglotticum is a short, broad elastic band, somewhat
broken up by adipose tissue, which connects the ventral surface of the epiglottic
cartilage to the upper border of the hyoid bone (Fig. 853, p. 1073). The liga-
mentum thyreoepiglotticum is strong and thick (Fig. 855, p. 1075). Composed
mainly of elastic tissue, it proceeds downwards, from the inferior pointed extremity
of the epiglottic cartilage, and is attached to the angular depression between the
two laminae of the thyreoid cartilage, below the median notch.
A triangular interval is left between the ventral surface of the epiglottis and
the hyo-thyreoid membrane. This is imperfectly closed above by the hyo-
epiglottic ligament, and contains a pad of soft fat (Fig. 851, p. 1070).
CAVUM LARYNGIS.
The cavity of the larynx is smaller than might be expected from an inspection
of its exterior. On looking into its interior, through the laryngeal aperture, it is
seen to be subdivided into three portions by two pairs of elevated folds of mucous
membrane, which extend ventro-dorsally (antero-posteriorly), and project medially
from each lateral wall of the cavity. The upper pair of folds are the ventricular
folds (O.T. false vocal cords) ; the lower, more definite pair, are the vocal folds (O.T.
true vocal cords) (Fig. 849).
The latter are the chief
agents in the production
of the voice, and the
larynx is so constructed
that changes in their
Pharyngo-
epiglottic
ligament
-Epiglottis
Pharyngeal
surface of
tongue
Hyoid bone
Glosso-
epiglottic
ligament
Vocal fold
Epiglottic, yjillecula
relative position and in
their degree of tension
are brought about by the
-Tubercieofepigiottis action of the muscles and
the recoil of the elastic
ligaments.
Aditus Laryngis. -
The laryngeal aperture is
a large obliquely placed
opening, which slopes
rapidly in a dorsal and
downwards direction and
looks upwards and dorsally
into the laryngeal part of
the pharynx. Somewhat
triangular in outline, the
basal part of the aperture,
placed superiorly and
vent rally, is formed by the
free border of the epiglottis. The opening rapidly narrows as it runs downwards,
and it ends in the interval between the two arytsenoid cartilages. The sides oi
the aperture are formed by two sharp and prominent folds of mucous membrane
called the ary-epiglottic folds, which stretch between the lateral margins of the
epiglottis, ventrally, and the arytaenoid cartilages dorsally. The two layers o:
mucous membrane which compose the ary-epiglottic folds, enclose, between them
some connective tissue, muscular fibres belonging to the ary-epiglottic muscles, anc
in their dorsal parts the cuneiform and corniculate cartilages, which latter surmoun 1
Ary-epiglottic
fold
Laryngeal ventricle
.Ventricular fold
Cuneiform tubercle
Corniculate
tubercle
Posterior aspect of
cricoid cartilage
Pharyngeal
wall (cut)
FIG. 849. ADITDS LARYNGIS, EXPOSED BY THE REMOVAL OF THE
DORSAL WALL OF THE PHARYNX.
CAVITY OF THE LAKYNX.
1069
Epiglottis
Hyoid bone
the arytsenoid cartilages. These small nodules of cartilage raise the dorsal part of
the ary-epiglottic fold in ( the form of two rounded eminences, termed respectively
the tuberculum cuneiforme [Wrisbergi] and the tuberculum corniculatum [Santorini].
On each side of the laryngeal opening there is, in the pharynx, a small recess,
directed downwards, which presents a wide entrance, but rapidly narrows towards
the bottom. It is termed the recessus piriformis, and is of importance to the surgeon,
because foreign bodies introduced into the pharynx are liable to be caught in this
little pocket. On the medial side the recessus piriformis is bounded by the
arytsenoid cartilage and the ary-epiglottic fold, whilst on the lateral side it is
limited by the inner surface of the laminae of the thyreoid cartilage, clothed with
the pharyngeal mucous membrane.
Vestibulum Laryngis. The vestibule of the larynx is the uppermost compart-
ment of the cavity of the larynx. It extends from the laryngeal aperture to the
ventricular folds. In its inferior part it ex-
hibits a marked lateral compression. Its width,
therefore, diminishes in the vertical direction,
whilst, owing to the obliquity of the laryngeal
aperture, its depth rapidly diminishes ventro-
dorsally. Ventrally it is bounded by the dorsal
surface of the epiglottis, clothed with mucous Ary . epi(Tlottic
membrane. This wall passes obliquely from its
superior end in an inferior ventral direction,
and becomes narrower as it approaches the
ventral or anterior ends of the ventricular folds.
The superior part of the dorsal surface of the
epiglottis is convex, owing to the manner in
which the upper margin is curved ventrally
towards the tongue; below the convexity
there is a slight concavity, and still lower a
marked bulging or convexity, over the superior
part of the thyreo-epiglottic ligament. This
swelling is called the tuberculum epiglotticum,
and it forms a conspicuous object in laryngo-
scopic examination of the larynx. Each lateral
wall of the vestibule of the larynx is formed by
the medial surface of the corresponding ary-
epiglottic fold. For the most part it is smooth
and slightly concave, and it diminishes con-
siderably in vertical depth as it passes dorsally. Fm< 850 ._ FRONTAL SECTION THROUGH THE
In its dorsal part the mucous membrane stands LARYNX TO SHOW ITS COMPARTMENTS.
out in two elongated vertical elevations, placed
one dorsal to the other (Fig. 849, p. 1068). The more ventral elevation is
formed by the subjacent cuneiform cartilage with the mass of glands associated
with it ; the more dorsal elevation is produced by the upper part of the arytsenoid
cartilage and the corniculate cartilage (Santorini). A shallow groove (philtrum
ventriculi of Merkel) passes downwards between these rounded elevations, and
terminates below by running into the interval between the ventricular and
vocal folds. The ventral elevation ends below in the dorsal extremity of the
ventricular fold; the arytsenoid or dorsal elevation, in its inferior part, bends
round the dorsal end of the ventricle of the larynx and becomes lost in the vocal
fold. The dorsal wall of the laryngeal vestibule is narrow, and corresponds to the
interval between the upper parts of the two arytsenoid 1 cartilages. Its width, to a
large extent, depends on the position of those cartilages, and when they .are placed
near each other the mucous membrane which covers the dorsal wall is thrown
into longitudinal folds.
The middle compartment of the larynx is much the smallest of the three. It
is bounded above by the ventricular fold and below by the vocal folds, whilst it
communicates between those folds with the vestibule on the one hand and the
inferior compartment on the other.
1070
THE KESPIKATOEY SYSTEM.
Hyoid bone
Hyo-epiglottie ligament
Cartilage of epiglottis
Fatty pad
Hyo-thyreoid membrane
Thyreoid cartilage
f Elevation produced by
' cuneiform cartilage
Ventricular fold
Philtrum ventriculi
Laryngeal ventricle
Vocal fold
Arytsenoid muscle
Processus vocalis
Cricoid cartilage
Cricoid cartilage
The ventricular folds (O.T. false vocal cords) are two prominent folds of
mucous membrane which extend ventro-dorsally on the lateral walls of the
laryngeal cavity. Ventrally they reach the
angle between the two laminae of the
thyreoid cartilage, but dorsally they do not
extend so far as the dorsal wall of the
larynx. They come to an end at the in-
ferior extremity of the elongated swelling
produced by the cuneiform cartilage. The
ventricular fold is soft and somewhat flaccid,
and presents a free border which is slightly
arched the concavity looking downwards.
Within the fold of mucous membrane which
forms this fold are contained : (1) the feeble
ventricular ligament ; (2) numerous glands
which are chiefly aggregated in its middle
part ; and (3) a few muscle fibres.
The interval between the ventricular
folds is sometimes termed the rima vestibuli
(O.T. false glottis), and is considerably wider
than the interval between the two vocal
folds, which is called the rima glottidis. It
follows, from this, that when the cavity of
the larynx is examined from above the four
folds are distinctly visible, but when ex-
amined from below the vocal folds alone
can be seen.
The vocal folds (O.T. true vocal cords),
placed below the ventricular folds, extend
from the angle between the laminae of the
FIG. 851. SECTION THROUGH LARYNX IN THE thyreoid cartilage ventrally, to the vocal
MEDIAN PLANE TO SHOW THE SIDE WALL pr0 cesses of the arytsenoid cartilages dorsally.
OF THE RIGHT HALF. *L t J
I he vocal told is sharp and prominent, and
the mucous' membrane which is stretched over it is very thin and firmly bound
down to the subjacent ligament. In colour it is pale, almost pearly white, whilst,
dorsally, the point of the processus
vocalis of the arytsenoid, which stands
out clearly in relief, presents a yellowish
tinge. In cross-section the vocal fold is
prismatic in form, and its free border
looks upwards as well as medially.
The vocal folds are the agents by
means of which the voice is produced.
The ventricular folds are of little im-
portance in this respect ; indeed, they
can in great part be destroyed and no
appreciable difference in the voice result.
Rima Glottidis. This name is ap-
plied to the elongated fissure by means
of which the middle compartment of the
Thyreoid cartilage
Vocal ligament
Rima
Arytsenoid
cartilage
Vocal process
of arytsenoid
cartilage
larynx communicates with the lower com-
partment. It is placed somewhat below
the middle of the laryngeal cavity, of
which it constitutes the narrowest part.
Ventrally it corresponds to the interval FIG. 852. DIAGRAM OF RIMA GLOTTIDIS.
between the VOCal folds ; dorsally it COrre- A. During ordinary easy breathing. B. Widely opened.
spends to the interval between the bases
and vocal processes of the arytsenoid cartilages. It is composed, therefore, of two
distinct parts: (1) a narrow ventral portion, between the vocal folds, involving
CAVITY OF THE LAKYNX. 1071
more than half of its length, and called the pars intermembranacea of the rima
glottidis ; (2) a broader, , shorter portion, between the arytaenoid cartilages, and
termed the pars intercartilaginea. By changes in the position of the arytsenoid
cartilages the form of the rima glottidis undergoes constant alterations. In
ordinary easy breathing it is somewhat lanceolate in outline. The pars inter-
membranacea presents, under these conditions, the form of an elongated triangle
the base of which is directed dorsally and corresponds to an imaginary line drawn
between the points of the vocal processes of the arytaenoid cartilages, whilst the
pars intercartilaginea is somewhat quadrangular. When the glottis is opened
widely the broadest part of the fissure is at the extremities of the vocal processes
of the arytsenoids, and there each side of the rima glottidis presents a marked angle.
The two vocal folds, on the other hand, may be approximated to each other so
closely, as in singing a high note, that the pars intermembranacea is reduced to a
linear chink.
The length of the rima glottidis differs very considerably in the two sexes, and upon this
depends the different character of the voice in the male and female. According to Moura, the
following are the average measurements in the quiescent condition of the rima :
Male-Length of entire ri ,na glottidia, 23 nun.
Female Length of entire rima glottidis, 17mm. / P ars intermembranacea, 11-5 mm.
( pars intercartilaginea, 5*5 mm.
By stretching the vocal folds, however, the length of the rima glottidis in the male may
be increased to 27'5 mm., and in the female to 20 mm.
The position of the rima glottidis may be indicated on the surface by marking a point on the
middle line of the neck 8'5 mm. below the thyreoid notch in the male and 6*5 mm. in the
female. This is the average position (Taguchi).
Ventriculus Laryngis (Morgagnii). The lateral wall of the larynx, in the
interval between the ventricular and the vocal folds, exhibits a marked pocket-
like depression or recess called the ventricle of the larynx. The ventricle passes
upwards, so as to undermine somewhat the ventricular fold, and its mouth is
somewhat narrower than its cavity. Ventrally it reaches to the angle between
the laminse of the thyreoid cartilage, whilst dorsally it ends at the ventral border
of the arytajnoid cartilage.
Under cover of the ventral part of the ventricular fold a small slit-like
aperture may be detected ; this leads upwards from the laryngeal ventricle into a
small diverticulum of mucous membrane, termed the appendix ventriculi laryngis,
which passes upwards, between the ventricular fold and the lamina of the
thyreoid cartilage. The laryngeal appendix is of variable extent, but as a rule it
ends blindly at the level of the upper border of the thyreoid cartilage.
Sometimes the appendix ventriculi laryngis extends much higher up, and may even
reach the dorsal part of the great cornu of the hyoid bone. This is of interest when
considered in connexion with the extensive laryngeal pouches of the anthropoid apes.
The lowest compartment of the cavity of the larynx leads caudally into the
trachea. Above it is narrow and compressed laterally, but it gradually widens
out until it becomes circular, in correspondence with the trachea, with which
is continuous. It is bounded by the sloping medial surfaces of the conus
elasticus (O.T. crico - thyreoid membrane) and by the medial aspect of the
cricoid cartilage both covered with smooth mucous membrane. In the operation
of laryngotomy the opening is made through the crico-thyreoid ligament in the
ventral wall of this compartment.
Tunica Mucosa Laryngis. The mucous membrane which lines the larynx
continuous above with the lining of the pharynx, and below with the mucous
tembrane of the trachea. Over the dorsal surface of the epiglottis it is closely
Iherent, but elsewhere, above the level of the vocal folds, it is loosely attached
ubmucous tissue which extends into the ary-epiglottic folds. As it passes over
' vocal folds the mucous membrane is very thin, and is tightly bound down.
t is important to bear these facts in mind, because, in certain inflammatory conditions, the
iubmucous tissue in the upper part of the larynx is liable to become infiltrated with fluid,
1072 THE KESPIKATOEY SYSTEM.
producing what is known as oedema glottidis. This may proceed so far as to cause occlusion of
the upper part of the cavity. The close adhesion of the mucous membrane to the vocal folds,
however, prevents the oedema -extending beyond the level of the rima glottidis, and the surgeon
is thus able to relieve the patient by making an opening through the ventral part of the conns
elasticus into the cavity of the larynx.
Above the level of the rima glottidis the laryngeal mucous membrane is
extremely sensitive, and when touched by a foreign body there is an immediate
response in the shape of an explosive cough. In the lower compartment of the
larynx the mucous membrane is lined with columnar ciliated epithelium. Over
the vocal folds this is replaced by squamous epithelium. In the ventricle of the
larynx and in the inferior part of the vestibule of the larynx the columnar ciliated
epithelium again reappears. The upper part of the epiglottis and the upper parts
of the lateral walls of the vestibule are covered with squamous epithelium similar
to that present in the mouth and pharynx.
The mucous membrane of the larynx has a plentiful supply of acinous glands,
and in only one place, viz., over the surface of the vocal folds, are these com-
pletely absent. For the most part the glands are aggregated in groups. The
following are the localities in which these groups are especially noticeable : (1) On
the dorsal surface of the epiglottis, many of the glands piercing the cartilage ; (2)
around the cuneiform cartilage, where they are chiefly responsible for the elongated
elevation seen in this part of the wall of the vestibule ; (3) in the ventricular folds
and over the wall of the laryngeal vestibule and the appendix ventriculi laryngis.
MUSCULI LARYNGIS.
Of the several muscles attached to the cartilages of the larynx all do not
physiologically belong to the larynx, as, for example, the inferior constrictor
muscles of the pharynx, which, though attached to both cricoid and thyreoid
cartilages, belong to the muscles of the pharynx, as do also the stylo-pharyngeus
and palato-pharyngeus muscles inserted in part into the thyreoid cartilage.
The true physiological muscles of the larynx may be divided into two great
groups, extrinsic and intrinsic. The extrinsic laryngeal muscles comprise all!
muscles passing to the os hyoideum, which is physiologically a part of the
laryngeal apparatus, as well as the m. sterno-thyreoideus. They have already been
described in the section on muscles.
The intrinsic laryngeal muscles are nineteen in number, nine paired and one|
unpaired. They may be roughly classified physiologically as follows :
A. Constrictor muscles of the larynx, including the adductors of the vocal folds
Mm. cricoarytsenoidei laterales. Paired.
Mm. thyreoarytsenoidei. Paired.
M. arytaenoideus transversus. Unpaired.
Mm. arytsenoidei obliqui. Paired.
Mm. aryepiglottici. Paired.
B. Dilator muscles of the larynx, including the abductors of the vocal folds
Mm. cricoarytsenoidei posteriores. Paired.
Mm. thyreoepiglottici. Paired.
C. Muscles modifying the tension of the vocal cords
Mm. cricothyreoidei. Paired.
Mm. vocales. Paired.
Mm. ventriculares. Paired.
Mm. thyreoarytaenoidei (also constrictors). Paired.
The mm. cricoarytsenoidei laterales are a pair of triangular muscles,
of which lies in the lateral wall of the larynx upon the conus elasticus and coi
cealed by the lamina of the thyreoid cartilage, the thyreoid gland, and the inf
hyoid muscles.
Each muscle arises from the upper border and the lateral surface of the
of the cricoid cartilage as far dorsally as the facet which supports the base of tl
arytrenoid cartilage, and also from the lateral part of the conus elasticus.
LAKYNGEAL MUSCLES.
1073
Epiglotti
Lesser cornu of.
hyoid
Body of hyoid-
Hyo-epiglottic
ligament
Lamina of
thyreoid cartilage"
M. thy
arytsenoideus -
M. crico-ary-
tteuoideus lateralis"
M. crico-
ary titmoideus" ~ "
posterior
Con us elasticus:
--M. ary-epiglotticu
M. thyreo-
epiglotticus
Corniculate
cartilage
Muscular pro-
cess of aryta;-
noid cartilage
From this origin the nmscular fibres run dorsally and upwards, and converge to
be inserted into the ventral surface of the processus muscularis of the arytsenoid
cartilage. The muscle is not infre-
quently inseparable from the (external)
thyreo-arytaenoid muscle.
By its action the lateral crico-ary-
tsenoid muscle draws the processus
muscularis of the arytsenoid cartilage
ventrally and downwards, thus turning
the processus vocalis of the same car-
tilage medially, and tending thereby to
stretch the vocal fold and to approxi-
mate it to its fellow of the opposite side,
thus assisting in closure of the rima
glottidis. Its nerve supply is the
anterior ventral branch of the inferior
laryngeal nerve.
The Mm. Thyreoarytaenoidei (O.T.
Thyreoarytaenoideus Externus).
Each thyreo - arytsenoid muscle is a
thin, quadrangular muscle, which is only
separable from the corresponding in.
vocalis, with which it forms a common
mass, by artificial means.
It lies in the lateral wall of the
larynx, immediately to the medial side
of the lamina of the thyreoid cartilage,
and lateral to the appendix ventriculi
laryngis, the m. vocalis, and the conus Fm 853 ._. Dl88KCTION OF THE MUSCLES OP THE-
elasticus ; its inferior border is in con- SIDE WALL OF THE LARYNX.
tact with the lateral crico-arytaenoid
muscle, whilst its superior border ex-
tends farther upwards than the vocal
fold, and is in contact with the inferior
border of the thyreo-epiglotticus.
It arises from the inferior half of
the medial surface of the lamina of the
thyreoid cartilage, close to its ventral
angle, and also from the lateral part of
the conus elasticus. The muscular fibre's
pass dorsally and upwards to be inserted
into the lateral border and muscular
process of the ary taenoid cartilage ; some
of the fibres, however, turn round this
cartilage and become continuous with
thearytaenoideus transversus. The upper
fibres of the thyreo-arytsenoideus vary
very greatly in their development and
arrangement.
By its action the muscle rotates the
arytsenoid cartilage and draws it ven-
trally in such a way that its vocal pro-
cess is carried ventrally and medially and
the vocal fold is rendered somewhat
flaccid. The muscle thus antagonises
the crico-thyreoideus. The main action
of the muscle must, however, be that of
a constrictor of the supraglottic region
of the larynx.
69
. 854. DISSECTION OF THE MUSCLES ON THE
DORSAL ASPECT OF THE LARYNX.
1074 THE EESPIKATOKY SYSTEM.
The nerve supply is the anterior branch of the inferior laryngeal nerve.
The m. arytaenoideus transversus is a thick, oblong, unpaired muscle which lies
in the dorsal wall of the larynx and bridges across the interval between the two
arytaenoid cartilages. The ventral surface of the muscle is in contact with the
dorsal concave surfaces of the arytaenoid cartilages, and between them with the
mucous membrane of the larynx. Its dorsal surface is partly concealed by the
arytaenoidei obliqui and by the submucous tissue of the pharynx. The inferior
border extends to the lamina of the cricoid cartilage, and its upper border does not
quite reach the apices of the arytaenoid cartilages.
The attachments of the muscle are, on both sides, to the dorsal surface of the
processus muscularis and the lateral edge of the arytaenoid cartilages. All the fibres
run in a frontal (coronal) direction, and some turn round the arytaenoid cartilage
to become continuous with the thyreo-arytaenoideus. The arytaenoideus trans-
versus and the thyreo-arytaenoid muscles form, together, a sphincter of the glottis.
By its action the arytaenoideus transversus approximates the arytaenoid
cartilages, thereby tending to close the pars intercartilaginea of the rima glottidis.
Its assistance in the sphincter action of the thyreo-arytaenoideus has already
been pointed out.
The' muscle is innervated by the posterior or dorsal rami of the inferior
laryngeal nerve of both sides.
The mm. arytaenoidei obliqui are a pair of muscles which lie in the dorsal wall
of the larynx, immediately dorsal to the arytaenoideus transversus and ventral
to the submucous tissue of the pharynx.
Each muscle consists of a bundle of muscular fibres which arise from the
dorsal aspect of the processus muscularis of the corresponding arytaenoid cartilage.
From their origins the two fleshy slips proceed upwards and medially, and cross
each other in the median plane like the two limbs of the letter X. Beaching
the apex of the arytaenoid cartilage of the opposite side, many, but not all, of the
fibres are inserted there, but others receiving a fresh attachment arise from the
apex of the arytaenoid cartilage as the m. aryepiglotticus, and extend ventrally and
upwards in a series of arches within the aryepiglottic fold to terminate in the
thyreo-epiglottic ligament and the lateral margin of the epiglottic cartilage ; and as
the muscle approaches the latter structure its fibres are joined by the fibres of the
thyreo-epiglotticus. With its superior border are also commingled some fibres
from the m. stylo-pharyngeus.
Action. The arytaenoideus obliquus and aryepiglotticus combined, act as a
rudimentary sphincter muscle for the aditus and the vestibulum laryngis, that is
for the superior aperture of the larynx, inasmuch as they extend from the base of
one arytaenoid cartilage to the apex of the arytaenoid cartilage of the opposite side,
and then on to the epiglottis within the ary-epiglottic fold.
The two muscular slips are innervated by the corresponding anterior rami
of the inferior laryngeal nerves.
The mm. cricoarytsenoidei posteriores are a pair of triangular muscles, each of
which lies on the dorsal surface of the lamina of the cricoid cartilage, under cover
of the tela submucosa of the pharynx. Each arises, by a broad origin, from the
medial and inferior* part of the depression on the dorsal surface of the lamina of
the cricoid cartilage at the side of the median ridge ; from that origin its fibres
converge upwards and laterally to be inserted into the dorsal surface and apex
of the processus muscularis of the corresponding arytaenoid cartilage. In
their course from origin to insertion the muscular fibres display very different
degrees of obliquity. The most superior fibres are short and nearly horizontal ; the
intermediate fibres are the longest and are very oblique ; whilst the most inferior
fibres are almost vertical in their direction.
By its action the crico-arytaenoidei posteriores draw the muscular processes
of the arytaenoid cartilages medially and dorsally, swing the vocal processes and
the vocal folds laterally, and thereby open the rima glottidis.
The muscle is innervated by the posterior ramus of the inferior larynge*
nerve.
The mm. thyreoepiglottici are a pair of thin, oblong, very variable muscles ;
LAKYNGEAL MUSCLES.
1075
which lie in the side walls of the
thyreo - arytsenoideus, medially by
appendix ventriculi laryngis, and later-
ally by the lamina of the thyreoid car-
tilage. It constitutes what was formerly
described as the uppermost fibres of the
thyreo-arytsenoideus externus muscle.
Each thyreo -epiglotticus arises from
the medial surface of the lamina of the
thyreoid cartilage, immediately above
the origin of the thyreo - aryteenoideus.
From this origin the fibres run in arches,
upwards and dorsally, to be inserted
partly into the margin of the ary-
epiglottic fold, and partly into the lateral
margin of the epiglottis, being inter-
mingled with the fibres of the ary-
epiglotticus.
By its action the^thyreo-epiglotticus
widens the aditus and the vestibulum
laryngis. Its innervation is derived
from the ventral ramus of the inferior
laryngeal nerve.
The mm. cricothyreoidei are a pair
of quadrangular muscles, broader and
larynx. Each is bounded below by
the thyreo - epiglottic ligament and
the
the
Epiglottis
Cartilage
_________ -triticea
Lesser cornu
-of hyoid
-Greater cornu
of hyoid
Body of hyoid
Thyreo-
----. epiglottic
ligament
Bpiglott
t surface of
>11 of vestibule
of larynx"
Epiglottic
tubercle 'V
Ventricular fold--W~
Ventricle of \
larynx
Vocal fold -'
M. vocal
M. thyreo-..
arytsenoideus
id cartilage
"-----Ring of trachea
of trachea --
. 856. FRONTAL SECTION OF THE LARYNX
SHOWING MUSCLES.
tilage; and (2) a pars obliqua
the inferior cornu. The muscle
FIG. 855. THE CRICO-THYREOID MUSCLE OF THE
RIGHT SIDE.
thicker above than below. They lie
on the cricoid cartilage and bridge
over the crico-thyreoid interval, and
are, therefore, the only intrinsic
laryngeal muscles which are visible
in an ordinary dissection of the neck.
Each is covered laterally and in part
by the thyreoid gland and the sterno-
thyreoid and the sterno-hyoid mus-
cles. Between the two muscles of
opposite sides there is an inter^
mediate triangular area left in which
the crico-thyreoid ligament is visible.
Each crico - thyreoideus arises
from the lower border and lateral
surface of the arch of the cricoid
cartilage, and from this origin its
fibres radiate dorsally and upwards
to be inserted into the inferior border
and medial surface of the lamina of
the thyreoid cartilage, as far as its
inferior cornu, and also into the in-
ferior cornu itself. As a general
rule each muscle is divided into two
parts, viz., (1) a pars recta composed
of those fibres which are inserted
into the lamina of the thyreoid car-
formed of those fibres which are inserted into
is closely associated with the inferior constrictor
1076 THE EESPIEATOEY SYSTEM.
muscle of the pharynx, and sometimes shows a certain amount of continuity
with it.
The general action of the crico-thyreoideus is to render the vocal fold tense,
as is more fully set forth in the paragraph dealing with the actions of the intrinsic
laryngeal muscles as a whole.
The innervation is derived from the external ramus of the superior laryngeal
nerve.
The Mm. Vocales (O.T. Internal Thyreo-arytsenoid Muscles). The vocalis
muscle of each side is a triangular, somewhat prismatic muscle, which forms with
the thyreo-arytaenoideus a common muscular mass separable only with difficulty
into its two constituent portions. The m. vocalis lies within the vocal fold, closely
applied to the lateral aspect of the ligamentum vocale, and receives its prismatic
form from this adaptation. Of its three surfaces, the medial lies adjacent to the
ligamentum vocale and the conus elasticus ; the upper surface is -bounded by the
labium vocale and the entrance to the ventricle of the larynx ; whilst the lateral
surface is bounded by, and is in contact with, the thyreo-arytaenoideus.
The in. vocalis arises from the inferior part of the angular depression between
the two laminae of the thyreoid cartilage, and also from the corresponding vocal fold,
whence the fibres run dorsally to be inserted into the lateral aspect of the vocal
process and the depression on the ventro-lateral surface of the arytaenoid cartilage.
The greater thickness of the m. vocalis dorsally than ventrally is due to the fact
that whilst all its fibres are attached dorsally to the arytaenoid cartilage, only a
certain proportion obtain attachment ventrally to the thyreoid cartilage. The
remainder are attached at irregular intervals to the lateral margin of the vocal
fold itself.
It follows that the action of the muscle is to draw the vocal process of the
arytaenoid cartilage ventrally, thereby relaxing the vocal fold and ligament.
The innervation is derived from the anterior ramus of the inferior laryngeal
nerve.
The m. ventricularis is composed of several bundles of fibres, visible under
the microscope, which pass, in a vertical direction, from the lateral edge of the
arytaenoid cartilage to the lateral margin of the cartilage of the epiglottis.
There are also intermingled with it fibres from the thyreo-arytaenoideus and
aryepiglotticus.
Action of the Intrinsic Laryngeal Muscles. By the action of the intrinsic
laryngeal muscles the position and tension of the vocal folds are so influenced that,
during the passage of air through the larynx, the tone and the pitch of the voice is
determined. Tension of the vocal folds is produced by the contraction of the two
crico-thyreoid muscles. The straight portions of the muscles pull the inferior border of
the thyreoid cartilage downwards, whilst the oblique portions, through their insertion into
the inferior cornua, draw the thyreoid cartilage ventrally, thereby increasing the distance
between the angle of the thyreoid cartilage and the vocal processes of the arytsenoid
cartilages. When the crico-thyreoid muscles cease to contract, the relaxation of the cords
is brought about by the elasticity of the ligaments. The thyreo-arytaenoid muscles must
be regarded as antagonistic to the crico-thyreoid muscles. When they contract they
approximate the angle of the thyreoid cartilage to the arytsenoid cartilages, and still further
relax the vocal folds ; and when they cease to act the elasticity of the ligaments of
the larynx again restores the state of equilibrium. They also act as constrictors of the
supraglottic region of the larynx. The vocales muscles, by the attachments of their
fibres into the vocal folds, may tighten portions of these folds, but their main action is
relaxation of the vocal folds and ligaments.
The width of the rima glottidis is regulated by the arytaenoideus transversus,
which draws together the two arytsenoid cartilages, and this may be done so effectually
that the medial surfaces of these cartilages come into contact ; the pars intercartilaginea
of the rima glottidis is thus completely closed. The crico-aryteenoidei, laterales
and posteriores, also modify the width of the rima glottidis. When they act together
they assist the aryteenoideus transversus in closing the glottis, but when they act
independently they are antagonistic muscles. Thus the crico-arytsenoidei posteriores
draw the muscular processes of the arytsenoid cartilages dorsally and medially, and
swing the vocal processes and the vocal folds laterally, and thereby open the rima. The
LAKYNGEAL MUSCLES. 1077
lateral crico-arytaenoid muscles act in exactly the opposite manner. By drawing the
muscular processes of the arytsenoid cartilages ventrally and medially, they approximate
the vocal processes and close the rima glottidis. The actions of the other muscles
have been sufficiently described already.
Closure of the Larynx during Deglutition. The muscles of the larynx have,
however, another function to perform besides vocalisation and regulating the amount of
air passing to and fro through the glottis. During deglutition it is requisite that the
communication between the pharynx and larynx should be closed, to prevent the fluid
or solid parts of the food entering the respiratory passages. In the process of closing
the laryngeal entrance the epiglottis stands erect, whilst the dorsal wall formed by the
arytsenoids is carried ventrally, the arytsenoid cartilages are closely approximated, glide
ventrally, and are then inclined towards the epiglottis. The result of this is that the
laryngeal opening is converted into a T-shaped fissure. The median limb of the T is formed
by the interval between the closely applied arytsenoid cartilages, whilst the cross limb,
which lies ventrally, is bounded ventrally (anteriorly) by the epiglottis and dorsally by the
aryepiglottic folds. The apices of the arytsenoid cartilages, with the corniculate cartilages
(Santorini), are pressed against the tubercle of the epiglottis, whilst the lateral margins
of the epiglottis are pulled dorsally so as to make the transverse limb of the fissure
distinctly concave in a dorsal direction. The muscles chiefly concerned in producing
these movements are the thyreo-arytsenoid and the transverse arytsenoid muscles. These
form a true sphincter vestibuli. The thyreo-epiglottic and aryepiglottic muscles also
come into play. They pull upon the epiglottis so as to produce tight application of
its tubercle to the arytenoid cartilages and the corniculate cartilages (Santorini), and
they also curve its margins dorsally so as to increase its dorsal concavity.
Vessels and Nerves of the Larynx. Two branches of the vagus nerve, viz., the" superior
laryngeal and the recurrent (laryngeal) nerves, supply the larynx. The superior laryngeal
divides into the internal and external laryngeal branches. The external laryngeal nerve
supplies the crico-thyreoid muscle ; whilst the internal laryngeal nerve enters the larynx, by
piercing the lateral part of the hyothyreoid membrane, to supply the laryngeal mucous mem-
brane. The recurrent nerve reaches the larynx from the thoracic direction, and, by its terminal
inferior laryngeal branch, supplies all the intrinsic laryngeal muscles, with the exception of
the crico-thyreoid.
The superior laryngeal artery, a branch of the superior thyreoid, accompanies the internal
laryngeal nerve ; whilst the inferior laryngeal artery, which springs from the inferior thyreoid,
accompanies the inferior laryngeal nerve. These two vessels ramify in the laryngeal wall and
supply the mucous membrane, the glands, and muscles.
Growth-Alteration and Sexual Differences in the Larynx. A considerable
amount of variation may be noticed in the size of the larynx in different individuals.
This is quite independent of stature, and explains to a great extent the difference in the
pitch of the voice in different persons. But quite apart from these individual variations,
there is a marked sexual difference in the size of the larynx. The male larynx is not
only absolutely, but also relatively, larger than the female larynx in all its diameters, but
more particularly in the ventro-dorsal diameter ; and to a large extent the increase in that
direction is produced by the strong development of the prominentia laryngea in the male.
The greater ventro-dorsal diameter of the male larynx necessarily implies a greater length
of the vocal folds and a lower or deeper tone of the voice in the male than in the female.
In a newly born child the larynx, in comparison with the rest of the body, is
somewhat large (C. L. Merker), and it continues to grow slowly and uniformly up
to the sixth year of childhood. At that period there is a cessation of growth until
puberty is reached, and then a stage of active growth supervenes. Up to that time the
larynx in both sexes is similar in its dimensions, and although the growth which now
occurs affects both the male and the female larynx, it is much more rapid and much more
accentuated in the male than in the female. As a result the voice of the male " breaks "
and assumes its deep tone.
It is interesting to note that the growth activity of the larynx, at puberty, is intimately
connected with the development of the sexual organs. In a male subject who has been
castrated, when young, the larynx attains a size which exceeds that of the female only to
a small degree, and the high pitch of the voice is retained.
Appearance of the Interior of the Larynx when examined by the Laryngoscope.
When the cavity of the larynx is illuminated and examined by laryngoscopic mirrors, the
parts which surround the superior aperture of the larynx, as well as the interior of the organ,
come into view. Not only this, but when the vocal folds are widely separated it is possible
to inspect the interior of the trachea as far as its bifurcation.
69 a
1078
THE KESPIEATOEY SYSTEM.
In such an examination the arched upper border of the epiglottis is a conspicuous object,
whilst, dorsal to that, the bulging on the ventral wall of the vestibule, formed by the tubercle
of the epiglottis, may also be a feature of the picture. The median glosso-epiglottic fold
with the glosso-epiglottic vallecula on either side of it, can also be inspected in the interval
between the epiglottis and the base of the tongue. The sharp aryepiglottic folds are
clearly visible, and in the dorsal portion of each can be seen the two prominent tubercles
which are formed by the enclosed cuneiform and corniculate cartilages. Dorsal to those
tubercles is the dorsal wall of the pharynx, whilst to their lateral side the deep piriform
Median glosso-epiglottic fold
Tuberculum epiglotticum I Dorsum of tongue
Plica vocalis
Vallecula
Ventriculus laryngis
Recessus pirifonnis
Aryepiglottic fold
Processus vocalis of
arytsenoid cartilage
Epiglottis
Rings of trachea
B
Tuberculum
Cuneiforms
Tuberculum corniculatum
FIG. 857. CAVITY OF THE LARYNX, as seen by means of the laryngoscope.
A. Eirna glottidis closed. B. Rima glottidis widely opened.
recess may be seen. In the interior of the larynx the ventricular and the vocal folds are easily
recognised, and the interval between the two, or, in other words, the entrance into the laryngeal
ventricle, appears as a dark line on the lateral wall of the larynx. The ventricular folds are red
and fleshy-looking ; the vocal folds during phonation are tightly stretched and pearly white
the white colour being usually more apparent in the female than in the male. The outline
and yellowish tinge of the vocal process at its attachment to the vocal fold, and the outline of the
ventral part of the base of the arytaenoid cartilage to a slight extent as well, can be made out in a
successful laryngoscopic examination. The vocal folds during ordinary inspiration are seldom
at rest, and with the laryngoscope their movements may be studied. It should be borne in mind
that the picture afforded by the laryngoscope does not give a true idea of the level at which the
different parts lie. The cavity appears greatly shortened, and its depth diminished.
TKACHEA.
The trachea or windpipe is a wide tube which is kept permanently patent by
a series of bent cartilaginous bars embedded in its wall. These bars are deficient
dorsally, and consequently the tube is not completely cylindrical : its dorsal wall
is flattened. The trachea begins at the inferior border of the cricoid cartilage,
opposite the inferior margin of the sixth cervical vertebra. From that level it
extends, through the neck, into the superior mediastinum of the thorax, and it
ends, at the level of the superior border of the fifth thoracic vertebra, by dividing
into the right and left bronchi. The length of the trachea in the male is from
four to four and a half inches, and in the female from three and a half to four
inches, but even in the same individual it varies considerably in length with the
movements of the head and neck.
The inferior end of the trachea is fixed in position. This is a necessary provision to
prevent dragging on the roots of the lung during movements of the head and neck.
The remainder of the tube is surrounded by a quantity of loose areolar tissue, and
possesses a considerable amount of mobility. Further, its wall is highly elastic, and thus
when the head is thrown back the tube elongates through stretching, and when the chin
is depressed its length is diminished by the recoil of its wall.
The trachea does not present an absolutely uniform calibre throughout its
whole length. About its middle it exhibits a slight expansion or dilatation, and
from that the calibre diminishes towards both extremities. Close to the bifurca-
tion it is again slightly expanded (Braune and Stahel).
THE TEACHEA.
1079
These differences in the calibre of the tube are determined by the surroundings of
the trachea. The cervical part is narrowed owing to its being clasped by the thyreoid
gland. Further, a short' distance above its bifurcation, an impression, sometimes
strongly marked, is usually seen on the left side of the trachea. It is due to the
close contact of the aortic arch as it passes dorsally against that part of the tube.
It is evident therefore that the second slight diminution in calibre which is described
by Braune and Stahel is pro-
duced by the proximity of the
aorta. Lejars gives the average
ventro-dorsal diameter of the
trachea in the living person as & U'^mm^r Thyreoid cartilage
11 mm., and the transverse
diameter as 12'5 mm. In the
dead subject the lumen of the
tube is considerably greater.
viciue
right
ward
ico-thyreoid membrane
Cricoid cartilage
I Part of trachea covered by
isthmus of thyreoid gland
Common carotid artery
Eparterial bronchus
Hyparterial bronchus
The trachea adheres
rigorously to the median
plane except towards its
termination, where it de-
viates very slightly to the
ht. As it passes down-
.8 it recedes rapidly from
the surface. This is due to
its following the curvature
of the vertebral column, from
which it is separated by the
cesophagus alone.
Relations of the
Trachea. In the study of
the relations of the trachea
it is convenient to consider
it in the two stages of cer-
vical and thoracic.
When the chin is held
so that the face looks directly
forwards the cervical part of
the trachea measures from
2 to 2 1 inches in length ; but
when the head is thrown
dorsally or backwards the
length is considerably in-
creased. It is clasped by the
thyreoid gland, the isthmus
of which is applied to its
ventral surface, and covers
the second, third, and fourth
rings ; while on each side
the corresponding lobe of the
thyreoid gland is applied
to the side of the trachea
and extends downwards to
the fifth or sixth ring. On
either side of the cervical part of the trachea is the common carotid artery, whilst
the recurrent nerve passes upwards in the groove between the trachea and the
oesophagus. Dorsally the trachea is in relation to the oesophagus, which intervenes
between it and the bodies of the vertebrae and deviates somewhat to the left as it
passes downwards.
In addition to the isthmus of the thyreoid gland two thin muscular strata,
composed of the sterno-hyoid and the ster no- thyreoid muscles, as well as the deep
69 &
Pulmonary artery
FIG. 858. THE TRACHEA AND BRONCHI.
The thyreoid gland is indicated by a dotted line and a purple tint.
1080
THE EESPIKATOEY SYSTEM.
Left common
carotid artery
Vagus nerve
Left snbclavian artery
Thoracic duct
Left common
carotid artery
Pleura
Vagus nerve
L. subclavian artery
Left recurrent nerve
Thyreoid gland
Trachea
Common carotid artery
Inferior thyreoid artery
Recurrent nerve
Innominate artery
Vagus nerve
Pleura
Trachea
(Esophagus
Phrenic nerve
Thoracic duct
cervical fascia and integument, separate the cervical part of the trachea from the
surface. In the median plane of the neck there is a narrow diamond-shaped space
between the medial margins of these muscles, within which the trachea is covered
merely by the integuments and fasciae. It is important to note that in the inferior
part of the neck the cervical
fascia is in two layers viz.,
a strong stratum applied to
the ventral surface of the
sterno-hyoid and sterno-thy-
reoid muscles, and a weaker
superficial layer stretching
across between the two
sterno-cleido-mastoid mus-
cles. Dorsal to these muscular
and fascial layers the inferior
thyreoid veins pass down-
wards on the ventral surface
of the trachea, and sometimes
the occasional thyreoidea
ima artery passes upwards
on the ventral aspect of the
tube. At the superior border
of the manubrium sterni the
innominate artery may be
seen crossing the trachea
obliquely.
The thoracic part of the
trachea is situated in the
dorsal part of the superior
mediastinum, being separated
from the bodies of the ver-
tebrae by the oesophagus alone.
Immediately above its bi-
furcation the deep cardiac
plexus of nerves is placed
on the ventral and lateral
aspects of the trachea. At the
level of the fourth thoracic
vertebra the aortic arch is
very intimately related to it,
lying first on the ventral
side of the tube, and there-
after on its left side. The
three great vessels which
spring from the aortic arch
are also placed in close
proximity to the trachea.
The innominate and the left
common carotid arteries lie
at first ventral to the trachea,
and then gradually diverging
as they proceed upwards,
CQme to He Qn either gide O f
it the innominate to the
right, and the left common carotid to the left. Ventral to these vessels are the
left innominate vein and the remains of the thymus. On the right side the
thoracic part of the trachea is in relation to the right vagus nerve, and is clothed
by the right mediastinal pleura ; on the left side are the left subclavian artery and
the left recurrent nerve.
(Esophagus
Thoracic duct
Vagus
Aorta
Thoracic duct
Vagus nerve
Intercostal arteries
Vena azygos
Bifurcation
of trachea
' Eparterial bronchus
Vagus nerve
Bronchial artery
Vena azygos
CEsophagus
FIG. 859. TRANSVERSE SECTIONS through the trachea and its imme-
** ^ ^ f **** of ^e upper five thoracic
THE TEACHEA. 1081
Structure of the Wall Of the Trachea. The walls of the trachea and bronchi
are composed of (1) a fibro-elastic membrane in which the cartilaginous bars are
embedded ; (2) within this, and on the dorsal aspect of the tube, a layer of muscular
tissue, termed the musculus trachealis ; and (3) the lining mucous membrane.
The fibre-elastic membrane is strong and dense. It passes round the whole circum-
ference of the tube, and becomes continuous, above, with the perichondrium which invests
the cricoid cartilage. Embedded in its substance are the series of cartilaginous bars.
These vary in number from 15 to 20, and are composed of hyaline cartilage. They
are horseshoe -shaped, the dorsal fourth of the circumference being deficient, so that
dorsally each bar ends in two rounded extremities. The outer surface of each tracheal bar
is flat and even, and /Joes not project much beyond the level of the membrane in which
Spinal medulla
Trachea
^ - (Esophagus
_- 4th thoracic vertebra
^-Innominate artery
Left common carotid
innominate vein
Manubrium sterni
___Synchondrosis
sternalis
Right pulmonary
""" artery
Pericardial cavity
... Left atrium
- Aortic valve
- Body of sternum
Right atrio-
ventricular valve
| Wall of right
ventricle
(Esophagus
Diaphragm
! _J Descending aorta
I Ji
Xiphoid process
r io. 860. SAGITTAL SECTION THKOTJGH THE THORAX OF AN OLD MAN. The superior border of the
manubrium sterni and the bifurcation of the trachea are lower than in the average adult.
i is embedded ; the inner surface, however, is convex in the vertical direction, and
consequently it bulges slightly into the lumen of the tube. The intervals between the
bars are somewhat narrower than the bars themselves, and neighbouring bars frequently
show a more or less complete fusion, whilst others present other irregularities, such as a
tendency to bifurcate. The lowermost bar is specially adapted to the tracheal bifurca-
tion. In the median plane, ventrally, it inclines downwards, and from this median peak a
cartilaginous strip is carried backwards in the fork between the two bronchi.
The m. trachealis is a continuous layer of involuntary muscular tissue, placed in
the dorsal part of the wall of the trachea internal to the fibro-elastic membrane. The
muscular bundles are arranged transversely, and are attached to the extremities of the
bars, and also to the inner surfaces of the bars for a short distance beyond their
ixtremities. In the intervals between the bars the transverse muscular bundles are
attached to the fibro-elastic membrane. It is evident that, by its contraction, this
muscle will reduce, in a marked degree, the lumen of the tube.
1082 THE KESPIEATOKY SYSTEM.
The mucous membrane is laid smoothly over the interior of the tube upon a layer of
submucous areolar tissue. Lymph tissue enters largely into the composition of the
tracheal mucous membrane, and its inner surface is lined with columnar ciliated epithelial
'cells. The action of the cilia exercises an important influence in producing an upward
movement of the mucus which is present on the surface of the mucous membrane.
Numerous longitudinal bundles of elastic tissue are present in the dorsal wall of
the trachea, more particularly in its inferior part, between the mucous membrane and the
trachealis muscle.
In connexion with the mucous membrane there is a plentiful supply of acinous mucous
glands. These are placed in the submucous tissue, and also, on the dorsal aspect of the
tube, on the exterior of the trachealis as well as amidst its muscular bundles. They
send their ducts to the surface of the mucous membrane, where they open by trumpet-
shaped mouths.
BRONCHI.
The two chief bronchi proceed obliquely downwards and laterally from the ter-
mination of the trachea, each towards the hilum of the corresponding lung. Like the
rachea
FIG. 861. DRAWING OF A STEREOSCOPIC SKIAGRAPH OF THE TRACHEA AND BRONCHI INJECTED
WITH STARCH AND RED LEAD.
trachea, they are kept permanently patent by the presence of cartilaginous bars in
their walls. These bars are deficient dorsally, so that each bronchus exhibits
flattened dorsal surface, in every respect similar to the trachea. The two
bronchi differ from each other, not only in the relations which they present
surrounding structures, but also in length, in width, and in the direction which
they pursue (Fig. 858, p. 1079).
The first collateral branch of the right bronchus (ramus bronchialis eparterialis
arises much nearer the trachea than the first branch of the left bronchus,
difference determines the length of the primary divisions of the trachea, anc
although there is much variation in the matter, it may be said that, as a rule, tl
THE THOBACIC CAVITY. 1083
left bronchus is at least twice as long as the right bronchus. According to Henle
there are from six to eight bars in the right, and from nine to twelve bars in the
left, bronchus. A marked difference is also noticeable in the calibre of the two
tubes. The right bronchus is wider than the left in the proportion of 100 to 78'4
(Braune and Stahel), and this asymmetry is clearly due to the fact that the right
lung is more bulky than the left. The right bronchus, as it passes towards the
hilum of the right lung, takes a more vertical course than the left bronchus. It
therefore lies more in the line of the trachea, and to this, as well as to its greater
width, is due the greater tendency which foreign bodies exhibit, when introduced
into the trachea, to drop into the right bronchus, in preference to the left. The
average angle which the right bronchus forms with the median plane is 24*8,
whilst the angle formed by the left bronchus with the median plane is 45 -6.
The more horizontal course of the left bronchus is probably determined by the
marked projection of the heart to the left side of the median plane (Merkel).
Relations of the Bronchi. Arching above the right bronchus, from behind
forwards, is the vena azygos, whilst arching above the left bronchus, from before
backwards, there is the arch of the aorta. Occupying the interval between
the bronchi there is a cluster of bronchial lymph glands, and an irregular
chain of similar glands is carried along each tube towards the hilum of the lung.
On the dorsal aspect of each bronchus the vagus nerve breaks up into the plexus
pulmonalis posterior, whilst the left bronchus, as it proceeds downwards and
laterally, crosses the ventral surfaces of the oesophagus and descending thoracic
aorta. The most interesting relation is, however, that presented on each side by
the corresponding pulmonary artery. On the left side the pulmonary artery
crosses ventral or anterior to the left bronchus on the superior side of its first
collateral branch, and then turns round its lateral side to gain its dorsal
aspect. All the left bronchial branches, therefore, are placed inferior to the
left pulmonary artery, and are in consequence termed hyparterial. The right
pulmonary artery, on the other hand, crosses ventral to the continuation of the
right bronchus, inferior to its first collateral branch. This branch is therefore
termed the eparterial bronchus, whilst all the others are classified as hyparterial.
Structure of the Walls of the Bronchi. The walls of the bronchi present a
structure similar to that seen in the trachea.
CAVUM THOKACIS.
The cavity of the thorax is divided into two large lateral chambers, which
contain the lungs, by a median partition termed the mediastinal septum, which
extends from the vertebral column to the ventral thoracic wall. From the fact
that each of these chambers is lined by an extensive and separate serous membrane
called the pleura, they receive the name of the pleural cavities.
Septum Mediastinale. The mediastinal septum is built up of. several structures
which lie in, or in close proximity to, the median plane. The more important of
these are the heart, enveloped in its pericardium, the thoracic aorta, with the great
sssels which spring from its arch, the pulmonary artery, and the great veins in
the neighbourhood of the heart, the thyrnus or its remains, the trachea, oesophagus,
and thoracic duct, and the vagi and phrenic nerves.
Cavum Pleurae. The pleural cavities, in which the two lungs lie, comprise
much the larger part of the thoracic cavity. Each pleural cavity is bounded in-
-riorly by the corresponding cupola of the diaphragm ; and as the right cupola
rises to a higher level than the left, the right pleural cavity presents a smaller
rtical depth than the left. Ventrally, the wall of each pleural chamber is
formed by the costal cartilages and the sternum ; laterally, by the bodies of the
tibs and the intercostal muscles as far as the costal angles ; dor sally, by the
portions of the ribs, with the intervening intercostal muscles, which lie medial to
costal angles ; and medially, by the bodies of the vertebrae and the medias-
tinal septum, which completely shuts off the one chamber from the other.
The mediastinal septum is not uniformly median in position. Owing to the
1084
THE EESPIEATOEY SYSTEM.
marked projection of the heart to the left side, and to the position of the thoracic
aorta on the left side of the median plane, the left pleural chamber, although it
is deepei than the right, is greatly reduced in width. The two pleural cavities,
therefore, are very far from being symmetrical in form, and consequently the
mediastinal septum tends to extend ^o the left of the median plane of the body.
Each pleural cavity is completely lined by a separate serous membrane termed
the pleura. The portion of this membrane which clothes the mediastinum or
intervening partition forms the lateral boundary of an area termed the mediastinal
or interpleural space, within which the parts which build up the mediastinal
septum are placed.
PLEUK^.
The pleura of each side not only lines the corresponding pleural cavity, but at
the pulmonary root, it is prolonged on to the lung so as to give it a complete
investment. It is customary, therefore, to recognise a pulmonary or investing part
(pleura pulmonalis) and a parietal or lining part (pleura parietalis). The inner
surface of the pleura (i.e. that surface which is turned towards the interior of the
cavity) is coated with squamous endothelium, and presents a smooth, glistening, and
polished appearance ; further, it is moistened by a small amount of serous fluid.
In consequence of this the surface
of the lung covered by pulmonary
visceral pleura pleura can glide on the wall of the
cavity, lined as it is by parietal
pleura, with the least possible
degree of friction. In the patho-
logical condition known as pleurisy
the inner surface of the pleura
becomes roughened by inflam-
matory exudation, and the so-called
Costal part of parietal pleura
Pleural cavity v
Visceral pleura
Costal
friction sounds" are heard when
the ear is applied to the chest.
Pleura Pulmonalis. The pul-
monary pleura is very thin, and is
so firmly bound down to the surface
of the lung that it cannot be de-
tached without laceration of the
FIG. 862.-DIAGRAM SHOWING ARRANGEMENT OP PLEURAL Pulmonary substance, and then
SACS AS SEEN IN TRANSVERSE SECTION. only m small pieces. It dips into
the fissures of the lungs, lines them
down to the very bottom, and thus completely separates the different lobes of the
lungs from each other. The pulmonary pleura becomes continuous with the
mediastinal pleura at the root of the lung, and also through the ligamentum
pulmonale.
Pleura Parietalis. Different names are applied to the parietal pleura as it
lines the different parts" of the wall of the cavity in which the lung lies. Thus
there are the costal pleura, the diaphragmatic pleura, the mediastinal pleura,
and the cupula pleura? ; but it must be borne in mind that these terms are
merely used for convenience in description, and that the portions of the pleura so
designated are all directly continuous with one another.
The cupula pleurae or the cervical pleura rises into the root of the neck, through
the superior aperture of the thorax, and forms a dome-shaped roof for the pleura]
cavity. Its highest point or summit reaches the level of the inferior border of the
neck of the first rib ; but owing to the great obliquity of the first costal arch, thit
point is placed from one to two inches above to the ventral or anterior extremit)
of the first rib, and from a half to one and a half inches above the clavicle. Tht
cupula pleurae is supported on the lateral side by the scalenus anterior anc
scalenus medius muscles, whilst the subclavian artery, arching laterally, lie;
in a groove on its medial and ventral aspects a short distance below its summit
THE PLEUE^E.
1085
At a lower level the innominate and subclavian veins also lie upon its medial and
ventral aspects.
The cupula pleurae is strengthened and held in place by an aponeurotic expansion, first
described by Sibson, which is spread over it, and is attached to the internal concave margin
of the first rib. This fascia is derived from a small muscular slip which takes origin from
the transverse
process of the
seventh cervical
vertebra.
Right vagus nerve Trachea
Right subclavian
arter
(Esophagus Left subclavian artery
Icus subclavius
Right
COS- innominate vein
Innominate
artery
ft vagus nerve
ft common
carotid artery
Left inno-
minate vein
Pleura Cos-
talis. The
tal pleura is the
strongest and
, thickest part of
the parietal
pleura. It lines
the internal sur-
; faces of the cos-
tal arches and of
the intervening
intercostal mus-
cles. Ventrally
it reaches the
sternum, whilst
dorsally it passes
from the ribs
over the sides of
the bodies of the
vertebrae. It is
. easily detached
from the parts
; which it covers,
, except as it
passes from the
heads of the ribs
, on to the ver-
tebral column.
There it is some-
what tightly
, bound down.
Pleura Dia-
phragmatica.
The diaphragm-
atic pleura covers
i that portion of
the thoracic sur-
face of the dia- F IG . 863. DISSECTION OF A SUBJECT HARDENED BY FORMALIN INJECTION, to show the
phragm which relations of the two pleural sacs, as viewed from the front. The anterior and
o lafoT-ol diaphragmatic lines of pleural reflection are exhibited by black dotted lines, whilst
the outlines of the lungs and their fissures are indicated by the blue lines.
side of the base
of the pericardium, but it does not dip down to the bottom of the narrow interval
between the thoracic wall and the diaphragm. In other words, a strip of the
; thoracic surface of the diaphragm adjoining its costal attachment is left uncovered.
Pleura Mediastinalis. The mediastinal pleura extends from the dorsal surface
of the ventral thoracic wall to the vertebral column, and clothes the side of the
mediastinal septum, which intervenes between the two pleural cavities. It is con-
tinuous with the costal pleura of its own side, both ventrally and dorsally,
two lines which are respectively termed the sternal and vertebral lines of
1086
THE EESPIEATOEY SYSTEM.
pleural reflection; whilst inferiorly it becomes continuous with the diaphrag-
matic pleura, of its own side, at the base of the pericardium.
Above the root of the lung the mediastinal pleura passes directly from the
sternum to the vertebral column. In that region the left mediastinal pleura
is applied to the arch of the aorta and the phrenic and vagus nerves ; to the left
innominate vein, the left superior intercostal vein and the left common carotid and
left subclavian arteries ; to the
oesophagus and the thoracic duct.
The right mediastinal pleura, on
the other hand, is applied, above
the root of the lung, to the superior
part of the vena cava superior and
the right innominate vein ; to the
innominate artery; to the vena
azygos, as it hooks forwards above
the bronchus; to the vagus and
phrenic nerves ; and to the right
side of the trachea.
Opposite the root of the lung,
as well as in the region below
it, the mediastinal pleura clothes
the corresponding aspect of the
pericardium (pleura pericardiaca),
and is somewhat firmly attached
to it. As the phrenic nerve passes
downwards upon the pericardium
it likewise is covered over by the
pleura. In the region correspond-
ing to the superior part of the
lateral aspect of the pericardium
the mediastinal pleura is prolonged
laterally, so as to form an invest-
ment for the root of the lung, and
becomes continuous around the
hilum of the lung with the pul-
monary pleura. Below the root
of the lung the two layers of pleura
which invest it come into apposi-
tion with each other, and are pro-
longed downwards as a distinct
fold, termed the ligamentmn pul-
monale. This fold stretches be-
tween the pericardium and the
inferior part of the mediastim"
surface of the lung, and ends in-
feriorly in a free border.
Dorsal to the root of the lu]
FIG. 864. LATERAL VIEW OF THE EIGHT PLEURAL SAC IN an d the ligamentum pulmonJ
the mediastinal pleura on the
right side passes over the oesophagi
to the vertebral column, whilst 01
the left side it passes dorsally over the thoracic aorta, and to a small extent ove
the lower end of the oesophagus, in the region immediately adjoining the dij
phragm and ventral to the thoracic aorta.
Lines Of Pleural Reflection. These are three in number viz., the sternal,
vertebral, and the diaphragmatic. The pleural cavities are not symmetrical. The left
longer and narrower than the right, and it thus happens that the lines of pleural refit
tion do not accurately correspond on the two sides of the body. Further, although th
A SUBJECT HARDENED BY FORMALIN INJECTION. The
blue lines indicate the outline of the right lung, and also
the position of its fissures.
THE PLEUK^E.
1087
Left innominate vein
pleura
(cut edge)
vertebral line of reflection is fairly constant, the other two reflection-lines are subject to
marked variations in different subjects. Consequently the following description must be
regarded as merely giving the average condition.
The vertebral line of pleural reflection is that along which the costal pleura is
continued ventrally from the vertebral column to become the mediastinal pleura. On
the right side, above the root of the lung, the pleura passes from the bodies of the
vertebrae on to the right
side of the trachea ; whilst
lower down, and dorsal to
the pericardium, it passes (Esophagus
from the vertebral bodies Leftsubcia\
on to the oesophagus. On Left common carotid artery *y^Vr^^HBI^M Parietal
the left side, and above Left superior intercostal vein
the arch of the aorta, the
, pleura along this line of
reflection is carried from
j the vertebral column on
to the oesophagus and
thoracic duct ; below that
level it passes on to the
thoracic aorta. In the
superior part of the chest
the right and left lines
of reflection are placed
well apart from each other,
and about equidistant
from the median plane.
As they are traced down-
wards they approach more
closely to each other and
deviate to the left, so that
whilst the reflection on the
right side takes place from
the ventral aspect of the
vertebral bodies, on the
left side it takes place from
the left aspect of the ver-
tebral column. This is \\ ^SKi^ jf / S~~ -/ IBS- -Diaphragm
due to the position of the
' thoracic aorta.
The sternal line of
pleural reflection is that
along which the costal
i pleura leaves the ventral
, thoracic wall to become
the mediastinal pleura.
The lines differ somewhat
on the two sides, and in
both cases show a tend-
ency to deviate to the left
(Fig. 863, p. 1085). In the FlG - 865 - LEFT PLEURAL SAC IN A SUBJECT HARDENED BY FORMALIN
vicinity of the rr ihrinm INJECTION, opened into by the removal of the costal part of the parietal
pleura. The lung has also been removed so as to display the media-
iterni the two pleural sacs stinal pleura.
are separated from each
other by an angular interval. The lines of reflection at the superior thoracic aperture or
inlet correspond to the sterno-clavicular joints. From those points the lines, as they
: are traced downwards, converge behind the manubrium, until at last they meet at its
inferior border. There the two sacs come into contact with each other, and the lines of
eflection coincide. Thence they proceed downwards, on the back of the body of
the sternum, with a slight deviation to the left of the median plane, until a point
immediately above the level of the sternal attachments of the fourth costal cartilages
3 reached, and there the two sacs part company. The line of reflection of the right
pleura is continued downwards in a straight line to the xiphoid process, where the
1088
THE EESPIEATORY SYSTEM.
sternal reflection-line passes into the right diaphragmatic reflection -line. Opposite the
sternal attachment of the fourth costal cartilage the reflection-line of the left pleura
deviates laterally, and is continued downwards at a variable distance from the right
pleura. A small triangular area of pericardium is thus left uncovered by pleura, and
therefore in direct contact with the ventral chest-wall. Leaving the sternum, the re-
flection-line of the left pleura passes downwards, parallel and close to the left margin
of the sternum, dorsal to the fourth intercostal space, the fifth costal cartilage and the
fifth intercostal
space, to the sixth
costal cartilage.
There it turns later-
ally and downwards,
and passes into the
diaphragmatic re-
flection-line of the
left side.
From the back
of the sternum the
right pleura is re-
flected, in the supe-
rior part of the
chest, on to the re-
mains of the thymus,
the right innominate
vein and the vena
cava superior, and,
at a lower level
directly on to the
ventral aspect of the
pericardium. The
left pleurais reflectec
from the back of the
manubrium sterni on
to the left innomin-
ate vein and the
aortic arch, and, at a
lower level, directly
on to the ventral side
of the pericardium.
The diaphragm-
atic line of reflection
is that along which
the pleura leaves the
thoracic wall and is
reflected on to the
thoracic surface
the diaphragm. This
reflection takes place
along a curved line,
which, except as it
approaches the ver-
tebral column, is
placed a short dis-
tance above the in-
ferior border of the thoracic wall. It differs somewhat on the two sides of the body.
On the left side the diaphragmatic line of reflection proceeds downwards along the
ascending part of the sixth costal cartilage, crosses the ventral end of the sixth intercostal
space and the descending part of the cartilage of the seventh rib (Fig. 865). Still c
tinuing to pass downwards, it crosses the eighth costal arch at the junction between
cartilaginous and bony portions. This is a fairly constant relation on both sides of
the body, and it should be noted that a vertical line the mamillary line, drawn
downwards from the nipple of the breast, intersects the line of pleural reflection, close tc
the point where it presents this relation to the eighth costal arch. Beyond that point
FIG. 866. DISSECTION OF THE PLEUIIAL SACS FROM BEHIND.
The blue lines indicate the outlines and the fissures of the lungs.
MEDIASTINUM. 1089
line of diaphragmatic reflection is carried downwards and laterally across the
extremities of the bony pprtions of the ninth and tenth ribs. As it crosses the
tenth rib, or, it may be, as it proceeds across the tenth intercostal space, the line of
pleural reflection reaches its lowest point, and it is important to observe that this
point lies in the mid-lateral line (i.e. in a vertical line drawn on the side of the
chest, midway between vertebral column and sternum). Thence, as it curves dorsally
towards the vertebral column, it passes slightly upwards. Thus it cuts across the eleventh
rib and reaches the twelfth rib. The relation which it presents to the twelfth rib varies
in accordance with the length of that rib. When the last rib is not abnormally short the
pleura clothes its medial half, and the line of reflection falls below that portion of the rib,
so as to reach the vertebral column, midway between the capitulum of the last rib and the
transverse process of the first lumbar vertebra (Fig. 866). There, therefore, the line of
diaphragmatic reflection falls below the inferior border of the thoracic wall ; and this is
a point of practical importance, because in operations upon the kidney the incision cannot
be carried above the level of the transverse process of the first lumbar vertebra and the
lateral lumbo-costal arch without the risk of wounding the pleura. On the right side
the line of diaphragmatic pleural reflection differs from that on the left chiefly ventrally
(Fig. 864, p. 1086). There it passes at a lower level, and proceeds laterally and downwards
from the dorsum of the xiphoid process along the dorsal aspect of the seventh costal
cartilage, and then behind the eighth costal arch, as a rule at the same point as on the
left side, viz., the junction of its cartilaginous and bony parts. From that point to the
vertebral column the relations are so similar to those of the left side that a separate
description is unnecessary.
It is commonly stated that the left pleural sac reaches a lower level than the
right. In certain cases there is no doubt that it does, but this condition is by no means
the rule. In those cases where the two pleural sacs do not reach the same level at their
lowest points, it is sometimes the right and sometimes the left pleura which oversteps
the mark.
As already stated, the lowest point which the pleura attains is usually found, on
both sides, in the mid-lateral line where the diaphragmatic reflection-line crosses the tenth
rib or the tenth intercostal space. That point can be very readily ascertained on the
surface by drawing a horizontal line round the trunk at the level of the lowest part of the
extremity of the spinous process of the first lumbar vertebra, and noting where it is
intersected by the mid-lateral line. In the majority of cases the point of intersection will
correspond with the lowest part of the pleural sac. Another horizontal line opposite the
spine of the twelfth thoracic vertebra will give the level of the diaphragmatic pleural
reflection in the maniillary line. 1
Along the line of the diaphragmatic reflection a strong fascia passes from the
uncovered part of the diaphragm, and from the costal cartilages to the surface of the
costal pleura, so as to hold it firmly in its place. It may be termed the phrenico-
pleural fascia.
MEDIASTINUM.
The term mediastinum is applied to the interval between the mediastinal
portions of the two pleural sacs. Ventrally it is bounded by the sternum, and
dorsally by the vertebral column. It is customary to subdivide this space in a
purely arbitrary manner into four portions, termed respectively the superior or
cranial, the ventral or anterior, the middle, and the dorsal or posterior part,
according to the relations which they present to the pericardium.
The superior mediastinum is that part of the general area which lies above
the level of the pericardium. Its boundaries are as follows: Ventrally, the
manubrium sterni, with the attached sterno-hyoid and sterno-thyreoid muscles;
dorsally, the bodies of the first four thoracic vertebrae ; below, an imaginary and
oblique plane, which extends from the inferior border of the manubrium sterni to
the inferior border of the fourth thoracic vertebra ; laterally, the mediastinal pleura.
Within the superior mediastinum are placed (1) the aortic arch and the three
The above description represents the average results which have been obtained from the study of
: the pleura in a large number of subjects, eight of which were specially hardened by formalin or other
re-agents for the purpose. For many of the dissections I have to thank my former assistant, Dr. H.
it. J. Brooks, and for others I am indebted to Professor C. J. Patten of Sheffield. D. J. C.
70
1090
THE KESPIKATOEY SYSTEM.
great arteries which spring from it ; (2) the innominate veins and part of the ven
cava superior; (3) the trachea, oesophagus, and thoracic duct; (4) the phrenic
vagi, and cardiac nerves, and the left recurrent nerve ; (5) the thymus.
The middle mediastinum is the wide part of the area which contains th
pericardium, and lies below the superior mediastinum. In addition to th
pericardium and its contents the middle mediastinum contains the phrenic nerve
and their accompanying vessels.
The ventral mediastinum is that part of the interpleural region which lies betwee:
the pericardium dorsally and the body of the sternum ventrally. In its superio
--.-.Spinal medulla
7777"- "
Trachea
_ _ , - - (Esoph agus
_---4th thoracic vertebra
^,-' Innominate artery
.-Left common carotid
-Left innominate vein
Manubrium sterni
__Synchondrosis
"sternal is
Right pulmonary
artery
----- Pericardial cavity
Aortic valve
- Body of sternum
. Right atrio-
ventricular valve
| .Wall of right
,jl ventricle
T| (Esophagus
Diaphragm
Descending aorta
Xiphoid process
-Liver
FIG. 867. SAGITTAL SECTION THROUGH THE THORAX OF AN OLD MAN. The superior border of the
manubrium sterni and the bifurcation of the trachea are lower than in the average adult
part this region can hardly be said to exist, seeing that there the two pleura
sacs come into contact with each other on the ventral aspect of the pericardium
but below the level of the sternal ends of the fourth costal cartilages the lef
pleura falls short of the right pleura, and an interval is apparent. The only content
to be noticed in the ventral mediastinum are a few lymph glands and some areola
tissue, in which ramify some lymph vessels, and some minute twigs from th
internal mammary artery.
The dorsal mediastinum is that part of the interpleural region which
situated dorsal to the pericardium. It may be regarded as an inferior continua
tion of the more dorsal part of the superior mediastinum, and many of th
structures in the one are prolonged into the other. The arbitrary superior limi
of the dorsal mediastinum is the inferior border of the fourth thoracic vertebr;
Ventrally it is bounded by the pericardium and the vertical part of th
diaphragm. Dorsally it is limited by the bodies of the last eight thoracic vertebr.
and 07i each lateral side by the mediastinal pleura. It contains the descendin
THE LUNGS. 1091
xracic aorta, the aortic intercostal arteries, the azygos, hemiazygos and accessory
hemiazygos veins, the thoracic duct and the oesophagus, with the two vagi.
Structure of the Pleura. The pleura on each side is a closed sac, and, like other
serous membranes, is attached to the wall of the cavity which it lines and to the
surface of the viscus which it covers. It is composed of a thin connective- tissue stratum,
in which bundles of fibres cross each other in various directions, and intermixed with
which there is a considerable quantity of elastic tissue. On the internal surface of this
there is a continuous coating of thin endothelial cells placed edge to edge. The pleura
so formed is attached to the parts which it lines and invests by a small amount of areolar
tissue termed the subserous layer. In the case of the pulmonary pleura the subserous
tissue is continuous with the areolar tissue in the substance of the lung, and this
accounts for the tight manner in which the membrane is bound down.
The pleura is plentifully supplied with blood. This is conveyed to it by. minute twigs
from the intercostal arteries, the internal mammary artery, and the bronchial arteries.
Lymph vessels are also particularly abundant in the pleura and in the subserous
layer, and it is by these that excess of fluid is conveyed from its cavity. Many lymph
vessels communicate directly with the cavity by means of excessively minute orifices
termed stomata. Dybkowsky has shown that the lymph vessels and stomata of the
pleura are not equally distributed throughout the membrane. Over the ribs and on the
mediastinal pleura they are absent.
PULMONES.
The Lungs. When healthy and sound each lung lies free within the corre-
sponding pleural cavity, and is attached only by its root and the ligamentum
pulmonale. It is uncommon, however, in the dissecting room, to meet with a
perfectly healthy lung. Adhesions between the pulmonary and parietal layers
of pleura, due to pleurisy, are generally present.
Like the cavities in which they are placed, the two lungs are not precisely
alike. The right lung is slightly larger than the left, in the proportion of about
11 to 10. The right lung is also shorter and wider than the left lung. This
difference is due partly to the great bulk of the right lobe of the liver, which forces
the right cupola of the diaphragm to a higher level than the left cupola, and
partly to the heart and pericardium projecting more to the left than to the right,
thus diminishing the width of the left lung.
The lung is light, soft, and spongy in texture ; when pressed between the
finger and thumb it crepitates, and when placed in water it floats. The elasticity
of the pulmonary tissue is very remarkable. A striking demonstration of this is
afforded when the thoracic cavity is opened, and the atmospheric pressure acting
upon the interior and exterior of the lung is equalised. Under these* conditions
the organ immediately collapses to about one-third of its original bulk, and it
becomes impossible in such a specimen to study its proper form and dimensions.
The surface of the adult lung presents a mottled appearance. The ground
colour is a light slate -blue, but scattered over this there are numerous dark
patches of various sizes, and also fine dark intersecting lines. The coloration of
the lung differs considerably at different periods of life. In early childhood the
:luug is rosy-pink, and the darker colour and the mottling of the surface, which
i appear later, are due to the pulmonary substance, and particularly its interstitial
areolar tissue, becoming impregnated, more or less completely, with atmospheric
I iust and minute particles of soot.
At every breath foreign matter of this kind is inhaled, but only a small proportion of it
n eaches the lung tissue. The greater part of it becomes entangled in the mucus which
'ioate the mucous membrane of the larger air - passages, and is gradually got rid of along
ith the mucus through the activity of the cilia attached to the lining epithelium. By the
;onstant upward sweep of these a current towards the pharynx is established. The fine dust and
>oot particles which reach the finer recesses of the lungs, and ultimately the interstitial tissue, are
>artly conveyed away by the lymph vessels to the bronchial glands, which in consequence
oecome, in many cases, quite black. The colour of the lung, therefore, depends, to some
extent, upon the purity of the atmosphere which is inhaled, and it thus happens that in coal-
nmers the surface of the lung may be very nearly uniformly black.
70 a
1092
THE EESPIEATORY SYSTEM.
The foetal lung differs in a marked degree from the lung of an individual who
has breathed. After respiration is fully established, the lung soon comes to occupy
almost the whole space aUotted to it in the pleural cavity ; in the foetus, on the
other hand, the lung is packed away at the dorsal aspect, and occupies a relatively
much smaller amount of space in the thoracic cavity. Further, it is firm to the touch,
and sinks in water. It is only when air and an increased supply of blood are
Recurrent nerve
Inferior thyreoid vein
Right vagus nerve
Bifurcation of inno-
minate artery
Right subclavian
vessels
Internal mammary
artery
Right inno-
minate vein
RIGHT LOBE OF
THYMUS
Sterno-hyoid muscle
Sterno-thyreoid muscle
Sterno-mastoid muscle
Thyreoid gland
Internal jugular vein
Phrenic nerve
Scalenus anterior
- Subclavian artery (left)
Left vagus nerve
Superior lobe
of right lung
Middle lobe
of right lung ~~|
Basal lobe of
right lung
ubclavian vein (left)
Common carotid artery
Left innominate vein
First rib
Aortic arch
LEFT LOBE OF
THYMUS
Left lung
Heart
Pulmonary fissure
Pericardium
FIG. 868. DISSECTION OF THORAX AND ROOT OF THE NECK FROM THE FRONT TO SHOW THE RELATIONS
OF THE LUNGS, PERICARDIUM, AND THYMUS.
introduced into the lung that it assumes the soft spongy and buoyant qualities
which are characteristic of the adult lung.
Form of the Lungs. The lungs are accurately adapted to the walls of the
pleural chambers in which they are placed, and in the natural state they bear OE
the surface impressions and elevations which are an exact counterpart of thf
irregularities on the walls of the cavity in which they lie.
When care has been taken to harden it in situ, each lung presents foi
examination an apex, diaphragmatic, mediastinal, and costal surfaces, and ventra
(anterior) and inferior borders.
The apex pulmonis is blunt and rounded, and rises above the level of th<
oblique first costal arch to the full height of the cupula pleurae. It therefor*
protrudes, above, through the superior aperture of the thorax, into the root of th-
THE LUNGS.
1093
Groove caused
by the first rib
Subclavian sulcus
Groove caused
by the first rib
Lower lobe
Cardiac notch
Lower lobe
neck. The subclavian artery arches laterally on its medial and ventral aspects a
short distance below its sum- Trachea
mit, and a groove, the sulcus subclavian suicus
subclavius, corresponding to
the vessel, is apparent upon it.
At a lower level on the apex
pulmonis a shallower and wider
groove upon its medial and
ventral aspects marks the
position of the innominate
vein. Although these vessels
impress the lung they are
separated from it by the cupula
pleurse.
The diaphragmatic surface,
or base of the lung, presents a
semilunar outline,being curved
around the base of the peri-
cardium. It is adapted to the
thoracic surface of the dia-
phragm, and is consequently
deeply hollowed out. As the
right cupola of the diaphragm
passes further upwards than
the left, the basal concavity of the right lung is deeper than that of the left
lung. Laterally and
,-^^f ^^ Groove for left subclavian artery dorsally, the dia-
M %. Groove for ,ea phragmatic surface of
JH |m/ innominate vein each lung IS limited
K\ by a thin salient mar-
L ,. Groove for first rib gin, called the inferior
OLBBaiiEBJ border or margin, which
e oTaoS' Ik. Groove f 0r tissue extends downwards for
*&. in mediastinum, some distance in a
narrow pleural recess,
j^Jl^JdS the sinus phrenico-
Left pulmonary ,JH -4B COStalis, between the
diaphragm and the
chest -wall. This in-
ferior border of the
lung extends further
downwards on the
lateral side and dorsally
than it does ventrally,
but it falls consider-
Hgament mi, BH; ably short of the bot-
tom of the phrenico-
|H\, B^--notch ac costal sinus. Thus,
after expiration, it
reaches the inferior
mr border of the sixth rib
in the mamillary line ;
the eighth rib, in the
axillary or mid-lateral
Fir;. 870. MEDIAL SURFACE OF A LEFT LUNG HARDENED IN SITU. line; whilst dorsally
it proceeds medially
t along a straight horizontal line so as to reach the vertebral column at the level
of the extremity of the spine of the tenth thoracic vertebra. During respiration
the thin inferior border moves freely in a vertical direction within the phrenico-
pulmonary
artery
Upper left
pulmonary vein
Left bronchu
Lower left
pulmonary
vein
Pulmonary
ligament
FIG. 869. THE TRACHEA, BRONCHI, AND LUNGS OF A CHILD,
HARDENED BY FORMALIN INJECTION.
Groove for
.comas
arteriosus
1094
THE EESPIEATOEY SYSTEM.
costal sinus, but even after the deepest breath it never reaches the extreme lower
limit of this recess.
The diaphragmatic surfaces of the lungs establish important relations with certain of
the viscera which occupy the costal zone of the abdominal cavity, the diaphragm alone
intervening. Thus the diaphragmatic surface of the right lung rests upon the right
lobe of the liver ; whilst that of the left lung is in relation to the left lobe of the
liver, the fundus of the stomach, the spleen, and in some cases to the left colic flexure.
The costal surface is extensive and convex. It is accurately adapted to that
part of the wall of the pleural cavity which is formed by the costal arches and
the intervening intercostal muscles, and it presents markings corresponding to
these. Thus the imprint of the ribs appear as shallow oblique grooves, while the
intercostal spaces show
as elongated intervening
bulgings.
The mediastinal sur-
face presents a smaller
*ppB r rrar,np,ai area
Groove for first rib
Groove for right subclavian artery
Groove for inferior end of.
internal jugular vein J
O3sophageal area
Tracheal area
Groove for superior .
vena cava.*
Groove for
ascending aorta
Groove for
azygos vein
Depression
for right
atrium
area than the costal sur-.
face. It is applied to
the mediastinal septum,
and presents markings in
accordance with the in-
equalities upon this (Figs.
870 and 871). Thus it is
deeply hollowed out in
adaptation to the peri-
cardium upon which it
fits. This pericardial
concavity comprises the
greater part of the medi-
astinal surface, and owing
to the greater projection
of the heart to the left
side, it is much deeper
and more extensive in
the left lung than in
the right lung. Above
and dorsal to the peri-
cardial hollow is the hilum
of the lung. This is a
wedge - shaped depressed
FIG. 871. THE MEDIAL SURFACE OF A RIGHT LUNG HARDENED /,v SITU, area, within which the
blood-vessels, nerves, and
lymph vessels, together with the bronchus, enter and leave the organ. Amidst
these structures there are also some bronchial glands. The hilum is surrounded by
the reflection of the pleura from the surface of the lung on to the pulmonary
root. Dorsal to the hilum and pericardial area there is on each lung a narrow
strip of the mediastinal surface of the lung which is in relation to the lateral wall
of the dorsal mediastinum. On the right lung this part of the surface is depressed,
and corresponds to the oesophagus ; on the left lung it presents a broad longitudinal
groove, which is produced by the contact of the lung with the thoracic aorta, and
also, close to the base, a small flattened area ventral to this which is applied
the oBSophagus where it pierces the diaphragm.
The portion of the mediastinal surface of the lung which lies above the hili
and pericardial hollow is applied to the lateral aspect of the superior mediastinui
and the markings are accordingly somewhat different on the two sides. On the 1
lung a broad deep groove, produced by the aortic arch, curves dorsally above 1
hilum, ajid becomes continuous with the aortic groove on the dorsal part of
mediastinal surface. From the groove for the aortic arch a narrower, deeper, anc
THE LUNGS. 1095
much more sharply marked groove runs upwards, and laterally over the apex
pulmonis a short distance, from the summit. This is the sulcus subclavius, and it
contains the left subclavian artery when the lung is in place. Ventral to the
subclavian sulcus a shallow wide groove, also leading to the ventral aspect of the
apex, corresponds to the left innominate vein. In the right lung the hilum is also
circumscribed above by a curved groove, which is narrow and more distinctly
curved than the aortic groove on the left side. It lodges the vena azygos as it
turns ventrally to join the vena cava superior. From the ventral end of the
azygos sulcus a wide shallow groove extends upward to the inferior part of the
anterior aspect of the apex pulmonis. This is produced by the apposition of the
lung with the vena cava superior and the right innominate vein. Close to the
summit of the apex there is also, on its medial aspect, a sulcus for the superior
end of the innominate artery.
In addition to the hilum, it must now be evident that the mediastinal surface of
each lung presents three areas which correspond respectively with (1) the middle
mediastinum (i.e. the pericardial hollow), (2) the dorsal mediastinum, and (3) the
superior mediastinum ; and that in each of these districts impressions corresponding
to structures contained within these portions of the interpleural space may be
noticed.
The dorsal part of the lung at the junction of the costal and mediastinal
surfaces is thick, long, and rounded. It forms the most bulky part of the organ,
and occupies the deep hollow in the thoracic cavity which is placed at the side
of the vertebral column.
The ventral border or margo anterior of the lung is short, and exceedingly
thin and sharp. It begins abruptly immediately below the groove on the apex
for the innominate vein, and extends to the base, where it becomes continuous
i with the sharp inferior border. The thin ventral part of the lung is carried
ventrally and medially, ventral to the pericardium, into the narrow pleural costo-
1 mediastinal sinus, dorsal to the sternum and costal cartilages. The ventral border
of the right lung fills up this recess completely, and in the upper par't of the
i chest is separated from the corresponding border of the left lung only by the two
i layers of mediastinal pleura which are reflected from the sternum to the pericardium.
The ventral border of the left lung, in its lower part, shows a marked deficiency
or notch, the incisura cardiaca, corresponding to the apex of the heart, and where
this exists the lung margin leaves a considerable portion of the pericardium un-
covered, and fails to fill up completely the costo-mediastinal sinus of the pleural
cavity. During respiration the ventral margin of the left lung at the incisura
cardiaca advances and retreats to a small extent in this pleural sinus, ventral to
the pericardium.
Fissures and Lobes of the Lung. The left lung is divided into two lobes
by a long deep fissure, the incisura interlobaris, which penetrates its substance to
within a short distance of the hilum. On the upper and lower sides of the hilum
this fissure cuts right through the lung and appears on the mediastinal surface.
| Viewed from the costal surface, it begins dorsally about two and a half inches
below the apex, about the level of the vertebral end of the third rib, and is
continued downwards and ventrally in a somewhat spiral direction to the
diaphragmatic surface of the lung, which it reaches a short distance from its
ventral end. The lobus superior lies above and ventral to this cleft. It is
conical in form, with an oblique base, and the apex and the whole of the ventral
border of the lung belong to it. The lobus inferior lies below and dorsal to the
fissure. It is the more bulky of the two, and includes almost the entire dia-
phragmatic surface and the greater part of the thick dorsal part of the lung.
In the right lung there are two incisurse interlobares, which subdivide it into
three lobes. One of the incisurse interlobares is very similar in its position and
relations to the fissure in the left lung. It is directed, however, rather more
vertically, and ends somewhat farther from the median plane. It separates the
lobus inferior from the lobus medius and lobus superior. The second incisura
interlobaris begins in the main fissure at the dorsal part of the lung, and proceeds
Centrally, to end at the ventral border of the lung at the level of the fourth costal
70 I
1096 THE EESPIEATOEY SYSTEM.
cartilage. The middle lobe of the right lung is triangular or wedge-shaped in
outline.
Variations. Variations in the pulmonary fissures are fairly common. Thus, it sometimes
happens that the middle lobe of the right lung is imperfectly cut off from the lobus superior.
Supernumerary fissures also are not infrequent, and in this way the left lung may be cut into
three lobes, and the right lung into four or even more lobes. The occurrence of the lobus azygos
in the right lung is a variation of some interest, seeing that such a lobe is constant in certain
mammals. It is a small accessory lobe, pyramidal in form, which makes its appearance on the
lower part of the mediastinal surface of the right lung. In certain cases the vena azygos
is enclosed within a fold of pleura, and is sunk so deeply in the pulmonary substance of the right
lung that it marks off a small accessory lobe.
RADIX PULMONIS.
The term root of the lung is applied to a number of structures which enter
and leave the lung at the hilurn on its mediastinal surface. They are held
together by an investment of pleura, and constitute a pedicle which attaches
the lung to the mediastinal wall of the pleural cavity. The phrenic nerve passes
downwards a short distance ventral to the pulmonary root, whilst the vagus nerve
breaks up into the dorsal or posterior pulmonary plexus on its dorsal aspect under
cover of the investing pleura. The delicate ventral or anterior pulmonary plexus
is placed ventral to the root of the lung under cover of the pleura, whilst from the
inferior border of the root of the lung the ligamentum pulmonale extends towards
the diaphragm. These relations are common to the pulmonary root on both sides
of the body, but there are others which are peculiar to each side. On the right
side the vena cava superior lies ventral to the pulmonary root, whilst the vena
azygos arches over its upper border. On the left side the aorta arches above the
root of the lung, whilst the descending thoracic aorta passes dorsal to it.
Constituent Parts of the Pulmonary Root. The large structures which enter
into the -formation of the pulmonary root are (1) the two pulmonary veins, (2)
the pulmonary artery, (3) the bronchus. But in addition to these there are
one or more small bronchial arteries and veins, the pulmonary nerves and the
pulmonary lymph vessels, and some bronchial glands.
The pulmonary nerves come from the vagus nerve and also from the sympathetic system.
They enter the lung and follow the air-tubes through the organ. The bronchial arteries are
small vessels which carry blood for the supply of the lung-tissue.. They arise from the aorta or
from an intercostal artery, and vary in number from one to three for each lung. In the root of
the lung they lie on the dorsal aspect of the bronchus, and they follow the air-tubes through
the organ. Part of the blood conveyed to the lung by the bronchial arteries is returned by the
pulmonary veins ; the remainder is returned by special bronchial veins which open on the right
side into the vena azygos, and on the left side into the vena hemiazygos.
The lymph-vessels of the lungs are numerous and well developed, and are divided into two
groups, superficial and deep.
The superficial lymph-vessels form a network on the surface of the lung and eventually
terminate by four or five vessels in the broncho-pulmonary glands of the hilum. It is usually
stated that the superficial lymph vessels communicate freely with the deep. This, however, is
denied by Miller, who maintains that anastomoses between the two systems of vessels are very
rare. A specimen of secondary carcinoma of the lung in the Pathology Museum of the University
of Melbourne shows a direct continuation of the disease through the lung-substance from the
surface to the tubes by way of the lymph vessels, and would thus tend to disprove Miller's
assertion.
The deep lymph-vessels are subdivided into bronchial accompanying the bronchi and vascular
accompanying the blood-vessels. Both systems communicate freely together, and at the level of
the hilum terminate in the broncho-pulmonary glands.
The pulmonary or broncho-pulmonary lymph-glands, found at the hilum, are usually numen
and variable in size. They are situated either just outside the lung or within the lung-substance
itself.
From these broncho-pulmonary glands the lymph-flow is continued onward from the lung,
partly directly into the thoracic duct, and partly by a more circuitous route as follows :
From the broncho-pulmonary lymph-glands vessels pass on to the tracheo-bronchial glai
situated at the angles produced by the bifurcation of the trachea into the two bronchi. Of these
glands there are, therefore, three groups, an inferior and right and left superior. From thesf
glands the lymph- flow is continued upwards through the tracheal lymph -glands lying on eitl
.side of the trachea into the deep cervical lymph-glands, and thence into the thdracic duct.
The bronchus in the root of the lung lies dorsal to the great pulmonary vessels
Tl
ROOT OF THE LUNG,
1097
Trachea
Eparterial bronchus*
Dorsal branches
of bronchus j^^L.
e pulmonary artery occupies a different position on the two sides, in relation to the
main or undivided part of the bronchus. On the right side it is placed below
it, whilst on the left side it crosses the bronchus and occupies a higher level in
the pulmonary root. The two pulmonary veins, on both sides, lie at a lower level in
the root of the lung than the pulmonary artery and bronchus, whilst the superior of
the two veins occupies a plane ventral to the pulmonary artery (Figs. 870 and 871).
Distribution of the Bronchial Tubes within the Lungs. The two lungs are
not symmetrical ; the right lung is subdivided into three lobes, and the left lung is
cleft into two lobes. The bronchi exhibit a corresponding want of symmetry. The
right bronchus, as it approaches the pulmonary hilum, gives off two branches for
the superior and middle lobes of the right lung respectively, and then the main
stem of the tube enters the inferior lobe. The left bronchus sends off a large branch
to the superior lobe of the left lung, and then sinks into the inferior lobe. The
first branch of the right bronchus, for the superior lobe, leaves the main stem about
one inch from the trachea. The first branch of the left bronchus, on the other
hand, takes origin about twice that distance from the trachea.
The relation of the pulmonary artery to the bronchial subdivisions is different
on the two sides. On the right side it turns dorsally, to reach the dorsal aspect
of the bronchus, inferior to the first, and superior to the second, bronchial branch.
On the left side the pul-
monary artery turns dorsally
above the level of the first
bronchial branch. On the
right side, therefore, the
first bronchial branch is
placed above the pulmonary
artery, and in consequence
it is termed the eparterial
bronchial ramus ; all the
others lie below the artery,
and are termed hyparterial
bronchial rami. On the left
side there is no eparterial
branch ; they are all hyp-
arterial.
When the main stem of
the bronchus is followed
into the inferior lobe of each
lung, it is seen to travel
downwards and dorsally in
the pulmonary substance
until it reaches the thin
iprsal part of the diaphragmatic surface of the lung which lies between the
laphragm and the thoracic wall, and there it ends. As it proceeds through
5 inferior lobe it gives off a series of large ventral and a series of smaller dorsal
inches. As a rule these are three in number in each case, and the dorsal and
bral branches do not arise opposite to each other, but alternately, one from
dorsum, and then another, after a slight interval, from the ventral surface of
i tube. The first hyparterial division on each side (i.e. the branch to the middle
e of the right lung and the branch to the superior lobe of the left side) is
aerally regarded as the first member of the ventral group.
t was Aeby who first recognised the existence in each lung of a main or stem bronchus
a ventral and dorsal series of branches, and who drew the distinction between the
1 hyparterial bronchial rami. A consideration of these relations led this author to
the eparterial bronchus and the superior lobe of the right lung have no morpho-
eqiuvalents on the left side of the body. In other words, he was led to believe that the
the right lung is the homologue of the superior lobe of the left lung. Hasse, who
stigated the subject, endorsed this view, with certain modifications and additions
sis, either in its original state as presented by Aeby, or as subsequently modified
sse, has been, until lately, very generally accepted by anatomists. More recent research,
^ Left pulmonary artery
Hyparterial
bronchus
_ Dorsal branch
of bronchus
FIG. 872. DIAGRAM OF THE RELATIONS OP THE PULMONARY
ARTERY TO THE BRONCHI.
1098 THE KESPIEATOEY SYSTEM.
however, has seriously affected the stability of this conclusion. Narath contends that the distinc-
tion between the eparterial bronchus of the right side and the hyparterial bronchi of both sides
is not one of fundamental importance, and that a branch which arises from the first
hyparterial bronchus on the left side and turns upwards into the apex of the left lung is the direct
equivalent of the eparterial bronchus of the right side. This he terms the apical bronchus, and
he believes that it represents the first dorsal branch of the left stem-bronchus. Huntington, in a
very convincing paper, strongly supports the contention of Narath, and holds that, except " for
purposes of topography, we should abandon the distinction between eparterial and hyparterial
bronchi." With Narath he regards the eparterial bronchus as a secondary branch which has
migrated in an upward direction on the main stem. According to Huntington, therefore, Aeby's
proposition should be amended as follows :
Right side. Left side.
Superior and middle lobes Superior lobe.
Inferior and cardiac lobes Inferior lobe.
The cardiac lobe mentioned in this table is the occasional azygos lobe to which reference has
already been made, and it is interesting to note that, whilst the lobe in question as a separate
entity is rarely seen in the human lung, the bronchus which corresponds to it is always
present in the pulmonary substance as an accessory branch, which proceeds from the main stem
as it traverses the inferior lobe of the right side. It receives the name of the cardiac bronchus.
STRUCTURE OF THE LUNG.
The lung is constructed so that the blood which reaches it through the pulmonary
artery is brought into the most intimate relation with the air which enters it through the
trachea and bronchi. An interchange of materials between the blood and the air is thus
rendered possible, and the object of respiration is attained. As a result of this inter-
change the dark, impure blood, wliich flows into the lung through the pulmonary artery, is
rendered bright red and arterial.
Lobules of the Lung 1 . A thin layer of subpleural connective tissues lies subjacent
to the continuous coating which the lung receives from the pulmonary pleura. From the
deep surface of this subpleural layer fine septal processes penetrate into the substance of
the lung, and those, with the connective tissue which enters at the hilum upon the vessels
and bronchi, constitute a supporting framework for the organ. The lung is lobular, and
on the surface the small polygonal areas which represent the lobules are indicated by the
pigment present in the connective tissue septa which intervene between them. Although
no pigment is present, the lobular character of the lung is particularly well marked in the
foetus, and with a little care the surface lobules in the foetal lung can be separated from
each other by gently tearing through the intervening connective tissue. The lobules thus
isolated are piriform or pyramidal in form. The broad bases of these lobules abut against
the subpleural layer, whilst each of the deep narrow ends receives a minute division from
the bronchial system of tubes. The lobules which lie more deeply in the substance of
the organ are not so large, and are irregularly polygonal in form.
The Lung Unit. The unit of lung-structure is the lung-lobule. This comprises
a terminal bronchus with its air-spaces, blood-vessels, lymph vessels, and nerves.
The terminal bronchus of the lung-unit is attained as follows : The larger branches
of the bronchi, as they traverse the lung, give off numerous divisions, which, by repeated
branching, ultimately form a system of tubes which pervade the entire organ. At first
the bronchial divisions come off at very acute angles, but as the finer ramifications are
reached this character becomes much less apparent. The finer ramifications of the bronchi
are termed bronchioles, which by subdivision give rise to the respiratory bronchiole of the
lung-unit.
Within the lung unit the respiratory bronchiole gives off a series of terminal bronchi
or alveolar ducts, each of which leads to a group of air-spaces termed atria. Each one of
the atria communicates, in its turn, with a further and secondary series of air-spaces
termed air-sacs or alveolar saccules, the walls of which are pouched out to form the very
numerous alveoli or air-cells of the lung-unit.
Structure of the Bronchi. When the large bronchi enter the lung they become
cylindrical, and lose the flattening on the dorsal aspect which is characteristic of the
primary bronchi outside the lung. They possess the same coats as are present in the case
of the trachea and primary bronchi, but as the tubes become smaller by repeated divisions,
these coats become correspondingly thinner and finer. Certain marked differences also in
the manner in which the constituents of these coats are arranged become apparent.
In the external fibro-cartilaginous coat the cartilage is no longer present in the form
of incomplete rings, but in irregular plates or flakes deposited at various points around
DEVELOPMENT OF THE KESPIKATOKY APPARATUS. 1099
the wall. As the tubes diminish, the cartilaginous deposits show a corresponding reduc-
tion in size, until at last, in bronchi of 1 mm. diameter, they disappear altogether. The
glands in relation to the tubes for the most part cease to exist about the same point.
The muscular or middle coat, which in the trachea and primary bronchi is confined to
the dorsal wall of the tube, forms a continuous layer of circularly arranged bundles in the
bronchi as they ramify within the lung. Spasmodic contraction of the muscular coat gives
rise to the serious symptoms which accompany asthmatic affections. The muscular fibres
of the middle coat may be traced as far as the atria, on the walls of which they are
present in considerable numbers. The mucous lining of the tubes becomes greatly thinned
as it is followed into the smaller bronchioles. It contains a large number of longitudinally
arranged elastic fibres, and is disposed in longitudinal folds, so that when ^he tube is cut
across the lumen presents a stellate appearance. The mucous membrane is lined with
ciliated columnar epithelium.
Structure of the Atria and Alveoli. The walls of the atria and alveoli
are exceedingly fine and delicate, but, nevertheless, constituents continuous with those
observed in the three coats of a bronchus are found entering into their construction.
The epithelium is reduced to a single layer. Further, it is no longer columnar and
ciliated, but it has become flat and pavement-like. Two kinds of epithelial cells may be
recognised (1) a few small granular polygonal cells, arranged singly or in groups of two
or three, (2) more numerous thin cells of large size and somewhat irregular in outline.
Outside the epithelium is a delicate layer of faintly fibrillated connective tissue. This is
strengthened by a network of elastic fibres, which is specially well marked around the
mouths of the alveoli, and is also to some extent carried over the walls of the air-cells.
Muscular fibres also are present on the walls of the atria, but it is questionable if any
are prolonged over the air-cells.
Pulmonary Vessels. The pulmonary artery, as it traverses the lung, divides with
the bronchi, and closely accompanies these tubes. The resultant branches do not anasto-
mose, and for the most part they lie above and dorsal to the corresponding bronchi.
The fine terminal divisions of the artery join a dense capillary plexus which is spread over
the alveoli or air-cells. This vascular network is so close that the meshes are barely
wider than the capillaries which form them. In the partition between adjacent alveoli
there is only one layer of the capillary network, and thus the blood flowing through
these vessels is exposed on both aspects to the action of the air in the air-cells. The
radicles of the pulmonary vein arise in, and carry the blood from, the pulmonary capillary
plexus. Each afferent arteriole supplies the blood which flows -through the capillaries
spread over a number of neighbouring alveoli, and in like manner each afferent venous
radicle drains an area corresponding to several adjoining air-cells. At first the veins run
apart from the arteries, but after they have attained a certain size they join them and
the bronchi. As a rule the pulmonary veins are placed on the inferior and ventral aspects
of the corresponding bronchi.
DEVELOPMENT OF THE KESPIRATORY APPARATUS.
The larynx, trachea, bronchi, and lungs all arise as an outgrowth from the ventral
aspect of the foregut. The first indication of a respiratory tract occurs in the human
embryo early in the third week, on or about the fifteenth day of development, and when
the embryo is but little more than 3 mm. in length. At that period a median longitudinal
groove makes its appearance in the ventral wall of the foregut, extending from the
primitive pharynx well towards the primitive stomach, and deepening gradually as it
passes caudal wards.
The cranial end of the respiratory tube becomes enlarged and forms the larynx,
the intermediate portion forms the trachea, and the caudal end bifurcates in the
floor of the groove into two tubes the future bronchi are already indicated by slight
bulgings before the two tubes divide which grow caudalwards on either side of the heart,
into a mesodermic mass, from which the connective tissue of the future lungs is ultimately
developed. The respiratory tube is lined with entoderm continuous with the entodermal
lining of the foregut.
The groove becomes deeper and constricted, its lateral margins approximate, and finally
meet dorsally, and the groove separates off from the foregut as a distinct tube. This
differentiation necessarily results in the production of two tubes or canals, a ventral one
forming the respiratory tube, and a dorsal one the oesophagus. The separation of the two
ubes commences at the caudal end and proceeds cranialwards towards the pharynx, into
which both the oesophagus and the respiratory tube open.
1100 THE KESPIEATOEY SYSTEM.
The Larynx. The rudiment of the larynx appears, at the cranial or pharyngeal
end of the primitive respiratory tube, about the twenty-fifth day, and before the trachea
separates off from the O3sophagus in the form of two lateral swellings the aryteenoid
swellings, which lie caudal to the fourth visceral pouches, and possibly represent
rudimentary fifth branchial arches (Kallius). The arytsenoid swellings are connected
by a ventral median ridge which intervenes between the ventral ends of the third visceral
arches. At this period the site of the future larynx is represented at the pharyngeal
end of the respiratory tube by a U-shaped ridge which surrounds the tube cranially
and laterally, and is known as the furcula.
The cranial or anterior portion of the furcula forms a median elevation from which
the epiglottis is developed, whilst the lateral portions of the furcula the arytoenoid
swellings eventually form the ary-epiglottic folds. On the medial side of the latter,
about the fourth month, a furrow marks the future site of the ventriculus laryngis
[Morgagni], the margins of which later become the vocal folds.
About the eighth week the cartilaginous framework of the larynx is indicated by
mesoblastic condensations of the connective tissue around the now slit-like rima glottidis ;
and at the same period the rudimentary arytsenoids, the cricoid and the cartilages of
the trachea are all continuous laterally.
The epiglottic cartilage is developed, as stated, in the anterior portion of the furcula,
and chondrifies relatively late. It may possibly represent a rudiment of the cartilage of
the sixth branchial arch, and according to Goppert it is at first continuous dorsally with
the cuneiform cartilages, which, therefore, are derivatives of the epiglottic cartilage.
The thyreoid cartilage is laid down in the form of two separate lateral mesoblastic
plates, in each of which chondrification proceeds from two centres, ventral and dorsal,
which probably represent the cartilages of the fourth and fifth branchial arches. As
development proceeds the sheets of cartilage formed from these centres fuse, and eventually
extend ventrally to fuse with their fellows of the opposite side, in the median plane.
Chondrification is completed comparatively late, and when incomplete it results in the
formation of an abnormality the thyreoid foramen. The superior cornu of the thyreoid
cartilage is at first continuous with the greater cornu of the os hyoideum, and the remains
of this cartilaginous connexion is seen in the presence of the cartilage triticea in the
lateral hyothyreoid ligament of the adult.
The pro-cartilaginous rudiments of the cricoid and arytsenoid cartilages are at first
continuous with each other, but later become differentiated by the appearance of separate
cartilaginous centres for the arytsenoids, and an incomplete ring, for a time deficient
dorsally, for the cricoid. The cricoid thus resembles develop men tally a tracheal ring,
with which it probably corresponds morphologically. Chondrification proceeds in the
cricoid by two centres, one on each lateral side. These centres unite ventrally, but
dorsally fusion does not take place until much later, and is finally completed by an exten-
sion of chondrification from the lateral into the dorsal plate. The cricoid thus differs
from the tracheal ring, in having its chondrification completed dorsally, whereas this
never takes place in the tracheal ring.
The arytcenoid cartilages are, as stated, at first continuous with the cricoid cartilage
by fibrous tissue, but become eventually completely separated from it by the appear-
ance of one chondrification centre for each arytsenoid.
The corniculate cartilages (Santorini) are merely portions of the arytaenoid cartilages
separated off by segmentation ; whilst the cuneiform cartilages ( Wrisbergi) are, as previ-
ously stated, derivatives of the epiglottic cartilage.
The Trachea. The trachea is developed from the intermediate portion, of the
median longitudinal groove. Originally, both this portion of the primitive respiratory
tube and the oesophageal portion of the primitive alimentary canal were of equal length ;
but as development proceeds both tubes lengthen, the latter more rapidly than the
former, so that eventually the lung rudiments no longer lie on the ventral and lateral
sides of the primitive stomach, but come to lie on the cephalic side of that viscus,
and are separated from each other by the oesophagus dorsally and the heart and
pericardium ventrally. In this way, that is by unequal growth, it comes about that the
trachea in the adult is shorter than the oesophagus, though originally both were <
equal length.
The cartilaginous rings of the trachea are developed like the cricoid cartilage, with the
difference that in the trachea the process of chondrification does not extend into their dorsal
portions, and hence, in the adult, the C-shaped rings of the trachea are deficient dorsally
an arrangement which admirably adapts itself to the functional uses of both trachea and
oasophagus.
DEVELOPMENT OF THE KESPIKATOKY APPAEATUS. 1101
The Lung's. The lungs are developed from the two diverticula of the caudal end
of the median longitudinal groove and the mesodermal tissue into which these grow.
Originally single, this caudal end soon becomes bilobed and pouches out on each side into
two lateral diverticula, which represent the primitive bronchi and lungs. From the first
the right pulmonary diverticulum or vesicle is slightly the larger of the two. Both
diverticula elongate, and almost immediately undergo a subdivision the right into three
vesicles, and the left into two vesicles thus early indicating the three lobes of the right
lung and the two lobes of the left lung. As the primitive respiratory tube lies in the
median plane in the dorsal attachment of the septum transversum, the pulmonary diver-
ticula grow laterally and dorsally into the dorsal parietal recesses, that is into the future
pleural cavities, carrying before them a covering of mesoblast. From this rnesoblast are
derived the blood-vessels and other tissues which build up the lung, whilst the entodermal
cells which form the lining membrane of the primitive respiratory tube eventually
develop into the epithelial lining of the air-passages, and are embedded within the
surrounding mesoderm. The main entodermal subdivisions continue to branch and
re-branch, pushing their way into the pulmonary mesoblast, until the complete bronchial
tree is formed.
The primary pulmonary diverticula increase in size and complexity as additional out-
growths arise by the subdivision of the enlarged terminal part of each diverticulum.
Their mode of subdivision is very characteristic, and from the first the various branches
are bulbous or flask-shaped at their extremities. These bifurcate, and although at first
the two main subdivisions appear, in each case, of equal importance, one grows out as the
continuation of the main bronchial stem the future hyparterial bronchus whilst the
other remains as a branch. When the ramification of the entodermal tubes into the
hmg-mesoderm is complete, the small terminal flask-shaped extremities of the various
branches represent the atria of the lung.
This repeated bifurcation results, as just stated, in the formation of a main bronchus
which traverses the entire length of the lung, and into which numerous secondary
bronchi open. The latter, from the manner in which they arrange themselves around the
main stem of the pulmonary artery, are divided into dorsal and ventral. These alternate
with each other, and usually number four in each series ; not infrequently the third dorsal
bronchus fails to develop. In the left lung the first dorsal bronchus arises, not from the
; main tube as on the right side, but from the first ventral bronchus an arrangement
which probably results from the fusion on the left side of the superior and middle lobes of
the left lung into one, namely, the so-called lobus superior of the adult left lung.
The secondary bronchi elongate, and give rise to the tertiary bronchi, and these in
turn to lesser bronchi, and so on down to the terminal bronchi, with their atria, air-sacs,
i and air-cells of the lung-unit. At first the lung-unit is devoid of air-cells, but between
the sixth month and full term the alveolar saccules and air-cells make their appearance
on the alveolar ducts ; and it is thus clear that the epithelial lining of the entire system
of bronchial subdivisions and ramifications is derived originally from the entodermal
lining of the primitive foregut. By the close of the fourth month of foetal life the
. columnar cells lining the trachea and bronchi have become ciliated.
At first the diverticula of the respiratory tube are surrounded by thick masses of
mesoblastic tissue, but as development proceeds the latter fails to keep pace with the
former, and hence the mesoblastic tissue becomes greatly reduced in amount and in
i thickness. Coincidently, this mesoblast becomes vascularised, and thus rich plexuses of
blood-vessels come to surround the terminal divisions of the epithelial tubes an arrange-
| ment obviously adapted to the interchange of gases from air to blood and vice versa.
The rudiments of the developing lungs grow dorsally on each side of the oesophagus
into the fissure-like portion of the coelom which occupies the thoracic region. They
.push before them the endothelial lining of the coelom, and thus come to acquire their
i covering of pulmonary pleura. By the development of the diaphragm and the peri-
cardium the pleural portions of the coelom become cut off from the peritoneal cavity and
from each other.
THE DIGESTIVE SYSTEM.
REVISED AND LARGELY REWRITTEN
BY DAYID WATERSTON.
APPARATUS DIGESTORIUS.
The Digestive System. The physical characters and the chemical composition
of much of the food taken into the body are such that it cannot at once be utilised
by the organism. Before it can be absorbed and used in nutrition it requires to
be acted upon, both chemically and mechanically. The performance of these
mechanical and chemical changes is known as digestion.
The term apparatus digestorius (digestive system) is applied collectively to the
organs which are concerned in this process, in the reception of food into the body,
and in the excretion of the undigested or unabsorbed residue.
The simple form of digestive system which is found in many of the lower
animals consists of a simple tube, passing through the interior of the body,
from an anterior or mouth aperture, to a posterior or anal orifice. The wall
and lining membrane of the tube are so constructed as to act mechanically and
chemically upon the food in its interior.
In man, a tube of this kind forms the basis of the digestive system. It
extends from the mouth, through the neck, thorax, abdomen, and pelvis, to the anal
orifice. But the tube, originally simple, has become modified, in different directions
in different parts, for the performance of the various stages of the complex
processes of digestion, absorption, and excretion.
The principal modifications which it has come to present are the following :
(1) The tube is very greatly elongated, so that its total length measures from
seven to eight times the length of the trunk. This is effected by the tube being
thrown into folds or coils, especially in that part known as the small intestine.
(2) Certain portions of the wall of the tube have become modified in structure
for the performance of special digestive changes. Thus, in the mouth there are
found the teeth and tongue, for mastication or triturition of food and for degluti-
tion, or swallowing. Further on in the course of the tube there is a dilated
chamber, the stomach, in whose wall special glands, called gastric glands, are
present, which produce the gastric juices ; while in the succeeding portion, or small
intestine, are found the villi very numerous papillary projections of minute size,
whose function is largely that of absorption.
(3) Certain special accumulations or masses of glandular tissue, producing
secretions useful in digestion, are situated altogether outside of the wall of
the tube, but communicating with its interior by means of ducts, through which
these secretions are conveyed.
The chief of such masses of glandular tissue are the salivary glands, which are
placed in the head and neck, and communicate with the mouth ; and the liver and
pancreas, which lie in the abdomen, and are connected with the duodenum.
These glandular masses, though lying external to the wall of the tube, have been developed
is outgrowths from it, and the ducts represent the stalks of connexion.
1103
1104
THE DIGESTIVE SYSTEM
The digestive system, then, may be considered to present the following parts
I. The alimentary canal, or digestive tube.
II. Special organs, found in the wall of this canal.
III. Accessory glands, placed external to the wall of the tuba
Cavum nasi
Palatum durum 1
Pars nasalis pharyngis
Cavum oris proprium
Pars oralis pharyngis
~- (Esophagus
I
undus of
;omach
Flexura coli
sinistra
_ * Pancreas
Position of
- umbilicus
Colon
descendens
Rectum
FIG. 873. DIAGRAM OF THE GENERAL ARRANGEMENT OF THE DIGESTIVE SYSTEM.
The processus vermiformis is seen hanging down from the caecum. The transverse colon is not represented,
in order that the duodenum and pancreas, which lie behind it, may be seen.
The greater part of the digestive system is found in the abdomen, and hence, in
this section, the abdominal cavity, together with its lining membrane the peritoneum
falls to be described.
I. Alimentary Canal. The alimentary canal, taken as a whole, measures, wher
fully extended, about 30 feet (9 metres) in length, and consists (Fig. 873) of the
ALIMENTAEY CANAL. 1105
following parts in order : mouth, pharynx, oesophagus, stomach, small and large
intestines. The term tubus digestorius is applied to the whole of the canal below
the lower end of the pharynx. The mouth cavity is the first division of the tube.
It is separated from the nasal cavities above by the palate, and opens posteriorly
into the pharynx. This latter is an expanded portion of the canal lying posterior
to the mouth, nasal cavity and larynx, the mouth opening into it through the
isthmus of the fauces, the nasal cavity through the choanae (O.T. posterior nares) ;
whilst lower down, immediately below the base of the tongue, the aperture of the
larynx is found in its anterior wall. Opposite the lower border of the larynx,
the pharynx is continued into the oesophagus, a long and comparatively straight
portion of the digestive tube, passing through the neck and thorax to the abdomen,
which it reaches by piercing the diaphragm. Immediately after entering the
abdomen the tube expands into a pear-shaped dilated chamber, the stomach. This
is followed by over 20 feet of small intestine, the junction of the two being
marked by a constriction, the pylorus. The small intestine presents three more
or less arbitrary divisions namely, (a) the duodenum, a part about 10 inches in
length, curved somewhat like a horse-shoe, and closely united to the posterior
abdominal wall ; (6) the jejunum, which includes the upper two-fifths, and (c) the
ileum, the lower three-fifths of the small intestine beyond the duodenum. The
jejunum and ileum are connected to the posterior abdominal wall by the mesentery,
a fan- shaped fold of connective tissue covered by the peritoneum, or lining mem-
brane of the abdominal cavity.
The terminal part of the ileum opens into the side of the large intestine,
a few inches (2) from the blind commencement of the latter. There is thus
formed at the beginning of the great intestine a cul-de-sac, called the caecum, in
connexion with which there is a small worm-shaped diverticulum, the vermiform
process.
The orifice through which the ileum opens into the large intestine is guarded
by the valve of the colon (O.T. ileo-csecal valve), which prevents the return of its
contents from the large into the small bowel. After the caecum comes the
ascending colon, which runs up on the right side of the abdomen. This is succeeded,
in order, by the transverse colon, crossing from right to left, the descending colon,
running down on the left side of the abdomen, and the iliac colon, lying in the left
iliac fossa. Beyond this are the pelvic colon, which lies in part or entirely within
the pelvis minor (O.T. true pelvis), the rectum, and the anal canal.
The rectum lies within the pelvis minor, and the anal canal, the terminal part
of the intestine, is a short channel passing between the muscles which form the
pelvic floor, to open on the surface at the anal orifice.
The B.N.A. term colon sigmoideum includes the portion named above as pelvic colon, and
the term colon descendens includes the descending and iliac colon.
II. Special Organs found in the Wall of the Tube. In the mouth are
found the teeth, gums, tongue, and behind them, in the pharynx, are the
palatine tonsils. The teeth, 32 in number in the adult, are portions of .the
mucous membrane of the mouth and of the subjacent tissue, calcified on the
surface, and specially formed for mastication, that is, the division and triturition
of the food which take place in the mouth before the bolus, as the resulting mass
is termed, can be swallowed. They are rooted in the jaws and are partly surrounded
by the gums.
The tongue is a muscular organ, useful alike in mastication, deglutition, and
speech. It is covered with epithelium, which in places is modified so as to form
taste corpuscles, which are the end organs of the gustatory sense.
The roof of the mouth is formed by the palate, which separates the mouth
from the nose. It consists of a bony part in front called the hard palate, and
a movable sheet, called the soft palate, behind.
The palatine tonsils are two large masses of lymph tissue, found one on each
side of the wall of the pharynx, just posterior to the mouth. They form the
most prominent portions of an almost complete ring of lymph tissue placed
around the circumference of the tube at this level.
71
1106
THE DIGESTIVE SYSTEM.
III. Accessory Digestive Glands. The largest of these is the liver (hepar),
which occupies the upper and right portion of the abdominal cavity, immediately
below the diaphragm, and its secretion the bile is conveyed into the duodenum by
the bile duct (ductus choledochus). The pancreas, next in size, lies across the front of
the vertebral column, with its right end or head resting in the concavity of the
duodenum, into which its secretion flows through the pancreatic duct. The salivary
glands consist mainly of three large paired glands, parotid, submaxillary, and sub-
lingual (glandula parotis, submaxillaris, and sublingualis), and their ducts, which
convey the saliva, open into the mouth. The saliva is a mechanical lubricant,
which facilitates swallowing and the movements of the tongue in speaking and
masticating, and also plays an important part in the chemical processes of
digestion.
CAVUM OEIS.
The philtrnm
Raphe of palate
Uvula
palatine arch
1. Parts. Rima oris, vestibulum oris, cavum oris proprium.
2. Boundaries. 1. Labia oris their structure.
2. Buccae their structure.
3. Palatum (palatum durum, palatum molle) arrangement and structure.
4. Isthmus faucium.
3. Structures found in the Mouth. Gringivae, gums.
Dentes, teeth.
Lingua, tongue.
4. G-landulse oris. Buccal and salivary glands.
The mouth is the upper expanded portion which forms the first division
of the alimentary canal. It lies between the maxillae and mandible, bounded ex-
ternally by the lips and the cheeks, and roofed in by the palate. It contains the
teeth and greater part of the tongue ; and the ducts of the salivary glands open
into it. The cavity is divisible into
two portions, the vestibule and the
cavity proper of the mouth. These
are separated from one another by the
alveolar ridges, gums, and teeth of the
maxillae and mandible. The cavity of
the m0 uth narrows at the back to a
. TIT i
slight constriction, marked by a vertical
fold on each side, called the arcus
glosso-palatinus (O.T. anterior pillar
of the fauces), and between them the
cavity of the mouth is continuous with
^at of the pharynx.
Rima Oris. The aperture of the
mouth is bounded above and below by
the corresponding lips, which, by their
junction at the sides, form the labial
commissures. In a state of rest, with
the lips in apposition, the rima appears
as a slightly curved line, corresponding
in length to the interval between the
first premolar teeth, and in level to
a line drawn across just below the
It also shows the two palatine arches, and the pharyngo- middle of the upper inClSOr crOWDS.
nasal isthmus, through which the naso-pharynx, above, The shape of the rima varies with
communicates with the oral portion of the pharynx, eve ry movement of the lips, from the
resting linear form, curved like the
conventional bow, to a circular or oval shape when the mouth is widely open,
or the "pursed-up" condition produced by the contraction of the orbicularis oris
muscle.
Vestibulum Oris. The vestibule of the mouth lies immediately internal 1 to the
fonsii ine
Ton ue
FIG. 874. OPEN MOUTH SHOWING PALATE AND
PALATINE TONSILS.
THE MOUTH.
1107
aperture of the mouth. It is that portion of the cavity which occupies the interval
between the lips and cheeks externally, and the teeth and gums internally
In the normal resting condition, when the mouth is closed and the lips and the
teeth are in contact, its cavity is practically obliterated by the meeting of its
walls and it becomes merely a slit-like interval, with a narrow roof and floor
by the reflection of the mucous membrane from the deep surface of the
lips and cheeks to the corresponding gum. This reflection is interrupted in the
median plane by a small but prominent fold of the mucous membrane, the frenulum
which connects the back of each lip to the front of the gum. The upper frenulum
j the better developed, and is readily brought into view by everting the lip The
frenulum of the lower lip is not always present.
On the outer wall of the vestibule, opposite the crown of the second upper
molar, upon a variably developed eminence, is placed the small opening of the duct
of the parotid gland,
Stylo-glossus
Stylo-pharyngeus
' Glossopharyngeal
nerve
Deep part of submaxillary gland pulled back
/ Submaxillary ganglion
Submaxillary duct (Wharton's)
Cut edge of mucous membrane
>Sublingual gland
Sublingual artery
Genio-
/glossus
Genio-hyoid
Lingual artery x
Middle constrictor
*Hypoglossal nerve
1 Hyoid branch of lingual artery
Lingual artery
FIG. 875. DISSECTION OF SUBMAXILLARY REGION.
which conveys the
saliva from the paro-
tid gland to the
mouth.
When the teeth
are in contact the
vestibule communi-
cates with the cavity
of the mouth only
through the small
and irregular spaces
left between the op-
posing teeth, and
posteriorly, on either
side, by a wider but
variable aperture be-
tween the last molars
and the ramus of the
mandible.
Advantage is some-
times taken of the pres-
ence of this aperture for the introduction into the cavity of the mouth of liquid food in certain
cases trismus, anchylosis, etc. in which the jaws are rigidly closed.
On the outer wall of the vestibule, the anterior border of the masseter can be distinctly felt
with the finger, when the muscle is thrown into a state of contraction. Still further back, the
front of the coronoid process, bearing the lower part of the insertion of the temporal muscle, can
also be made out. The spheno-mandibular ligament, which corresponds to, and is felt along with,
the anterior border of the internal pterygoid muscle, is distinguishable as a pliant ridge when
the finger is carried from the front of the coronoid process behind the last molar tooth into the
cavity of the mouth.
In addition to the duct of the parotid, the ducts of numerous small glands which are embedded
in the lips and cheeks open into the vestibule.
Under normal conditions, as pointed out above, the lips and cheeks lie against 'the teeth and
gums, obliterating the cavity of the vestibule, and helping, with the aid of the tongue, to keep
the food between the grinding surfaces of the molar teeth during mastication. In facial palsy,
however, owing to the paralysis of their muscles, and particularly of the buccinator muscle, the
lips and cheeks fall away from the dental arches, and allow the food to pass out from between
the teeth and to accumulate in the vestibule.
Cavnm Oris Proprium. The cavity proper of the mouth is the space situated
within the dental arches, extending backwards to the glosso-palatine arches (O.T.
anterior pillars of the fauces). Its boundaries consist of a roof, a floor, and a margin,
formed by the teeth and gums. The roof is formed by the hard palate and the
anterior portion of the soft palate, while the floor is formed by the anterior part of
the tongue in the middle, and on each side by the reflection of the mucous membrane
from the side of the tongue to the mandible.
On each side of the tongue, and in front of it, when it is at rest, there is only
a slit or sulcus between the tongue and the gums, into which the ducts of the
submaxillary and sublingual glands open.
71 a
1108
THE DIGESTIVE SYSTEM.
If, however, the tongue is raised, there is exposed a limited space to which the
term sublingual space is more usually applied (Fig. 876).
The term " floor of the mouth," or sublingual region, is frequently applied to the muscular
and other structures, especially the mylo-hyoid muscles, which fill in the interval between the
two halves of the body of the mandible. These structures, with the hyoid bone, form the basis
upon which the tongue and the mucous membrane of the sublingual space are supported, and
they extend from the symphysis menti, in front, to the body of the hyoid bone, behind.
The sublingual region (Fig. 876) is covered by the mucous membrane between
the deep surface of the gum and the inferior aspect of the tongue. When the tip
of the tongue is raised the membrane forms in the median plane a prominent fold,
the frenulum linguae, stretching from
the floor of the mouth to the inferior
surface of the tongue. On each
side of the frenulum, near its
junction with the floor, there can
be readily made out a prominent
soft papilla, the caruncula sub-
lingualis, on which the opening of
the duct of the submaxillary gland
(O.T. Wharton's duct) may be seen
(Fig- 8l76 )- Kenning laterally and
posteriorly, on each side, from this,
- t L o a Ihowthe U gtnd Ut and occupying the greater part of
i. Plica nmbriata th6 n ^\ { *** m Uth > ther6 ls a
well-marked ridge, plica sublmguahs,
due to the projection of the under-
lying sublingual gland. Most of
the ducts of this gland open near
the crest of the ridge on each side.
ni u a c ryg f iand submax ' There is also another fold, called
openings of ducts of the plica fimbriata, medial to each of
the submaxillary , , . .
the others, on the inferior surface
The philtrum
fongue r gland f
Frenulum linguae
gland
Sublingual gland
of the tongue.
Plica sublingualis,
v with openings of
ducts of sublingual
gland
FIG.
876. OPEN MOUTH WITH TONGUE RAISED, AND THE
SUBLINGUAL AND ANTERIOR GLANDS EXPOSED.
When the mouth is closed, and re-
spiration is carried on through the nose,
the cavum oris is reduced to a slit-like
space, and practically obliterated by the
tongue coming in contact with the palate
above, and with the gums and teeth
laterally and in front. When the
The sublingual gland of the left side has been laid bare by the mou j ih . is sli g htlv P en and th . e teeth
removal of the mucous membrane ; to expose the anterior nearly in contact, the tongue becomes
lingual gland of the right side a thin layer of muscle, in somewhat concave or grooved along tJ
addition to the mucous membrane, has been removed. A median plane, and leaves a channel-like
branch of the lingual nerve is seen running on the medial space between it and the palate, while it
aspect of the gland. The profunda vein also is faintly remains in contact with the roof and
indicated on this side. gums laterally. By depressing the hyoid
bone together with the root of the tongue,
the cavum oris can be increased to a considerable size even when the teeth are in contact. Finally,
by the simultaneous descent of the mandible and hyoid bone with the tongue, and the ascent of
the soft palate, the cavity is increased to its greatest dimensions (Fig. 874).
Labia Oris. The lips are the two movable folds, covered superficially by skin,
and on their deep surface by mucous membrane, which surround the rima oris. The
meeting of the lips at each side constitutes the commissure, and bounds the
angle of the mouth (angulus oris). Laterally, they are prolonged into the cheeks,
with which they are continuous. The junction of the lips and cheek is marked
on the surface by the sulcus naso-labialis, which passes downwards and laterally
from the margin of the nose towards the angle of the mouth, while the sulcus
mento-labialis separates the lower lip from the chin. The upper lip presents on
its superficial surface a well-marked vertical groove, the philtrum, bounded by two
distinct ridges descending from the columella nasi (Fig. 876) ; inferiorly the groove
THE MOUTH. 1109
widens out, and terminates opposite a slight projection the labial tubercle on the
free edge of the upper lip. This tubercle is particularly well developed in children,
ind is chiefly responsible for the characteristic curve of the rima oris. The lower
iip is usually longer and more movable than the upper lip.
For the manner in which the various muscles enter into the formation of the
.ip, see section on the Muscles (pages 450 to 451).
The lips include within them the greater part of the orbicularis oris muscle,
which surrounds the aperture of the mouth, and in each lip the following series of
structures can be recognised from the external to the internal surface : (1) The
skin, which is closely beset with hairs, small and fine in the child and female, long
ind stout in the adult male. (2) A layer of fatty superficial fascia continuous with
the fascia of the face generally. (3) The orbicularis oris muscle, continuous at its
periphery with the various muscles converging towards the mouth. A number
3f its fibres, or those of the muscles joining it, pass through the superficial fascia
ind are attached to the skin, thus establishing a close connexion between the
skin and the muscle. (4) The submucous tissue, which is occupied by an almost
iontinuous layer of racemose glands the labial glands. These open into the vesti-
bule, and their secretion is said to be mucous. (5) The mucous membrane of the
mouth, covered by stratified squamous epithelium. . Between the orbicularis and
mucous membrane, but nearer to the former, that is, in the deeper part of the
submucosa, the labial artery is found, a short distance from the free margin of
the lip, running to meet its fellow of the opposite side.
The free ma.rgin of the lip is covered with a dry and otherwise modified mucous^, membrane.
It begins where the integument changes colour at the outer edge of the lip, and ends posteriorly
just behind the line along which the two lips meet when closed, where it passes into the ordinary
moist mucous membrane of the vestibule. It presents numerous simple vascular papillge, and
its nerves terminate in special end organs, hence the acute sensitiveness of this part. In the
' child, at birth, the margin of the lip is divided by a very pronounced groove or fissure into an
outer and an inner zone, differing considerably in their appearance.
When the tongue is pressed firmly against the back of the lips and moved about, the labial
glands can be distinctly felt through the mucous membrane, giving the impression of a knobby
or irregular surface. The glands, which are about the size of hemp-seeds and can be readily
displayed by removing the mucous membrane, are more numerous in the lower than in the
upper lip. Stoppage of their ducts, with the resulting distension of the glands, gives rise to
" mucous cysts," a well-known pathological condition.
Blood-vessels, Nerves, and Lymph-vessels. The lips receive a free blood supply, the
lower lip from the inferior labial, and the upper from the superior labial branches of the
external maxillary artery.
The sensory nerve supply of the lips is derived from the trigeminal nerve, that of the upper
' through the infra-orbital branch of the maxillary division, and that of the lower from the mental
' branch of the inferior alveolar branch of the mandibular division, while the buccinator branch
of the mandibular division supplies the region of the angle. The lymph- vessels of the upper
'lip pass with the external maxillary artery to the submaxillary lymph-glands lying in the sub-
maxillary triangle, while those from the lower lip pass in part to the same glands, and in part
to the submental glands lying on the mylo-hyoid muscles, above the hyoid bone.
Buccae. The cheeks resemble the lips in structure, being formed of corresponding
layers, but the place of the orbicularis oris muscle is taken by the buccinator
| muscle. They are covered externally by the skin and internally by the mucous
'membrane. Under the skin lies the fatty superficial fascia of the face,
through which the parotid duct (O.T. Stenson's duct) runs inwards to pierce the
buccinator. Here too are placed some of the muscles of facial expression. Near
the end of the duct are found four or five mucous glands, as large as hemp-seeds.
These are known as the molar glands; their ducts pierce the cheek and open
'into the vestibule. Beneath the superficial fascia lies the buccinator muscle,
overed by the thin bucco-pharyngeal fascia. Deeper still is the submucosa^
which, like that of the lips, contains numerous racemose buccal glands. And
finally the mucous membrane is reached (Fig. 876).
An important constituent of the cheek of the infant is the corpus adiposum buccae (O.T. suck-
l Pad), an encapsuled mass of fat, distinct from the surrounding superficial fascia, which lies on
>uter side of the buccinator, and passes backwards into the large recess between that muscle
the overlying anterior part of the masseter. This fatty mass, which is relatively more
716
1110
THE DIGESTIVE SYSTEM.
developed in the child than in the adult, strengthens the cheek, and helps it to resist the effects
of atmospheric pressure during the act of sucking. In the adult the remains of the pad can be
distinctly made out under the anterior border of the masseter.
Some small superficial lymph -glands lie on the superficial surface of the buccinator, com-
municating with the vessels of the lips, while their efferent vessels pass onwards towards the
parotid region.
Palatum. The palate forms the roof of the mouth, and separates the mouth
from the nasal cavities and nasal part of the pharynx.
It is not confined to the mouth, but extends backwards also into the cavity of
the pharynx, forming the division between the oral and the nasal parts of the
pharynx. It terminates behind in a free conical projection, the uvula. It consists
of two distinct portions, an anterior, forming the anterior two-thirds, which has a
bony foundation (palatine processes of the maxillse and the horizontal parts of the
palatine bones), and a posterior, forming the posterior third, with a fibrous basis ; and
they are termed the hard and the soft palate, respectively. The palate is arched
antero-posteriorly, and also transversely. The latter curvature is the more pro-
nounced in the hard palate, but the shape and curvature of this portion depend
upon the configuration of its bony foundation.
The hard palate is, on the whole, horizontal in direction, both transversely and antero-
posteriorly. The soft palate is, on the other hand, during rest, as, for instance, in quiet nasal
breathing, very oblique in direction, and it shuts off the mouth from the nasal and largely from
the oral parts of the pharynx. When, however, the soft palate is raised by the action of its
muscles, it more nearly continues backwards the plane of the hard palate, and it projects across
the cavity of the pharynx, forming a nearly complete partition between the oral and the nasal
parts of the pharynx. In this position it prevents food from passing upwards into the nasal
part of the pharynx and nose.
Traversing the middle of the palate is seen a faint median ridge or raphe (Fig. 877), indicating
its original development from two halves. This raphe is continued posteriorly along the soft
palate to the base of the uvula, and in front it ends in a slight elevation, the papilla palatina
(O.T. incisive pad). From the anterior end of the raphe a series of transverse ridges of mucous
membrane, about six in number, run laterally, just behind the incisor teeth ; they are known as
the plicae palatinae, and are composed of dense fibrous tissue. Sometimes a small pit, which will
admit the point of a pin, is seen, on each side, immediately posterior to the central incisor teeth,
and about 2 mm. from the median plane. These pits correspond to the inferior openings of
the incisive canals, with which they are occasionally continuous.
Palatum Durum. The hard palate consists of a horizontal plate formed by
the palatine processes of the maxillae and the horizontal parts of the palatine bones,
covered on each surf ace, super-
Foramen incisi vum / -4^. Dentes incisivi j or an( j inferior, by periosteum.
The periosteum of the inferior
surface is thick, and is in
turn covered by a quantity of
dense fibrous tissue firmly
united both to the periosteum
and to the mucous mem-
brane. This dense tissue
contains in its posterior half
a large number of racemose
palatine glands, and it also
contains the larger nerves
and blood-vessels of the
palate. The mucous mem-
brane covering the superior
surface is largely ciliated in
character, and forms the floor
of the nasal cavity, while that
on the inferior surface is e
stratified squamous epi-
thelium.
Palatum Molle. The soft palate is attached anteriorly to the posterior margii
of the hard palate. Its lower and posterior margin is free, and forms an arch, e
tending from one side of the pharynx to the other, but the arch is interruptec
)ens caniims
Denies prsemolares
w
Foramen
paiatinuin majus
Sutura palatina transversa
FIG. 877. THE HARD PALATE AND UPPER PERMANENT TEETH,
SEEN FROM BELOW.
THE MOUTH. . 1111
in the centre by the conical projection of varying size, called the uvula, which hangs
down from its inferior margin. Laterally the soft palate is intimately connected on
each side with two prominent folds, called the palatine arches. The exact relation-
ship of the soft palate to these is as follows. The free posterior margin of the soft
palate passes into the pharyngo-palatine arch (O.T. posterior pillar of the fauces),
which passes downwards for some distance on the side wall of the pharynx.
The glosso-palatine arch (O.T. anterior pillar of the fauces), on the other hand,
passes below into the side of the tongue. Traced upwards, it runs on to the
inferior surface of the soft palate, and is continuous with the margin of the uvula.
The two palatine arches on each side are 7-8 mm. apart, and on the side wall,
between each pair, there is a fossa or depression which is occupied in part by the
palatine tonsil. This region belongs properly to the pharynx, and will be described
in detail when that part is dealt with, but at the present stage the relation of this
fossa of the tonsil to the soft palate should be carefully noticed.
The superior surface of the soft palate forms a continuation backwards and
downwards of the floor of the nasal cavity, and constitutes the floor of the nasal
part of the pharynx. It is covered by a prolongation of the nasal mucous membrane,
partly ciliated in character. The inferior surface is arched, and forms the backward
prolongation of the roof of the mouth.
In the foetus the whole of the epithelial covering of the soft palate is ciliated, but after birth
the ciliated epithelium is largely replaced by stratified squamous epithelium, except at the
. margin of the palate.
Structure. The framework of the soft palate is formed of a strong fibrous sheet, called the
palatine aponeurosis. To it several muscles are attached. These structures, together with fibrous
tissue, gland- vessels, and nerves, are covered by mucous membrane on each surface.
The palatine aponeurosis, which is confined to the anterior part of the soft palate, is in the
form of a thin flat sheet, constituting a common tendon for the palatine muscles which are
attached to (or blended with) its posterior margin. Its anterior margin is united to the posterior
edge of the horizontal parts of the palatine bones. With the exception of the aponeurosis of the
tensor veli palatini which passes into its lateral part, the muscles do not, as a rule, reach
further forwards than to within 8 or 10 mm. of the posterior edge of the hard palate.
The muscles entering into the formation of the soft palate are the mm.
pharyngo-palatini, uvulae, levatores veli palatini, tensores veli palatini, and glosso-
palatini. For the details of the attachments and arrangement of these muscles,
see p. 466.
The anterior part of the soft palate for 8 or 10 mm. (J in.) contains practically no
, muscular fibres ; it is composed of the palatine aponeurosis, covered by an extremely
, thick layer of glands on the inferior surface and by mucous membrane on both surfaces.
This anterior portion is much less movable than the rest of the soft palate, and forms a
relatively horizontal continuation backwards of the hard palate, stretching across between
the two medial pterygoid laminae. It is upon this portion chiefly that the tensor veli
palatini muscles act. The posterior and larger part contains muscular fibres in abundance,
slopes strongly downwards, and is freely movable, being the portion upon which the
remaining palatine muscles act.
The mucous membrane of the inferior surface of the palate, which is covered by stratified
squamous epithelium, is firmer and more closely adherent in front, near the rugae, than behind,
. near the soft palate.
Mucous glands, the orifices of which can be seen as dots with the naked eye, are extremely
abundant in the soft palate, and in the posterior half of the hard palate, except near the raphe.
They are wanting in the anterior part of the palate, where the mucous membrane is particularly
dense.
The plicae palatinse (which correspond to more strongly developed ridges in carnivora, etc.) are
very well marked in the child at birth, although, perhaps, relatively less distinct in the foetus of
five or six months ; in old age they become more or less obliterated and irregular. At birth,
also, and in the foetus, the incisive pad at the anterior end of the raphe is continued over the
edge of the gum into the frenulum of the upper lip.
The uvula, already referred to, is a conical projection, very variable in length, which is con-
tinued downwards and backwards from the middle of the posterior border of the soft palate. It
is composed chiefly of a mass of racemose glands and connective tissue covered by mucous mem-
brane, and containing a slender prolongation of the uvular muscle in its upper part.
The vessels oi' the palate are :
(1) Branches from the descending palatine artery, a branch of the internal maxillary artery.
Of these, some small vessels, the lesser palatine arteries, emerge from the foramina palatina
71 c
1112
THE DIGESTIVE SYSTEM.
The philtrum
Raphe of palate
Pharyngo-
latine arch
niinora, and are distributed to the palatine tonsil and palate, and anastomose with branches of the
ascending pharyngeal artery.
The largest branch, greater palatine artery, emerges through the foramen palatinum majus,
and runs forwards over the lateral margin of the hard palate, about ^ in. from the alveolar margin,
as far as to the foramen incisivum, where it anastomoses with the naso-palatine artery.
(2) Posterior nasal septal artery, a small vessel which enters through the foramen
incisivum.
(3) Ascending palatine artery, from the external maxillary, which anastomoses by a ramus
tonsillaris with the descending palatine.
(4) Branches from the ascending pharyngeal artery, which enter the soft palate.
(5) Branches from the rami dorsales linguae of the lingual artery, which pass in the glosso-
palatine fold to the palatine tonsil and soft palate.
The nerves are all derived from branches from the spheno -palatine ganglion.
(1) Nervi palatini. The most important of these is the nervus palatinus anterior, which
passes through the foramen palatinum majus, and divides in the roof of the mouth into branches
which run in grooves on the hard palate, and extend forwards nearly to the incisor teeth.
The others are the nn. palatini medius and posterior, which emerge from the foramina palatina
minora, and are distributed to the hard and soft palate.
(2) N. nasopalatinus (Scarpae). This nerve sends branches to the palate through the foramen
incisivum, which join with branches from the anterior palatine nerves.
For the motor nerves to the muscles of the soft palate, see p. 467.
The lymph-vessels of the palate pass lateral to the tonsil and the isthmus of the fauces to the
upper deep cervical lymph-glands.
Isthmus Faucium. The isthmus of the fauces is the aperture through which
the mouth communicates with the oral part of the pharynx (Fig. 878). It is
bounded at the sides by the glosso-
palatine arches, above by the inferior
surface of the soft palate, and below
by the dorsum of the tongue ; in width
it corresponds pretty closely to the
cavity of the mouth.
The arcus glosso - palatini (O.T.
anterior pillars of the fauces) are two
prominent folds of mucous membrane
which bound the isthmus of the fauces
on each side (Fig. 878). Each contains
a glosso-palatine muscle in its interior.
They are continuous above with
the inferior surface of the soft palate,
a little way (about 8 mm.) anterior
to its free edge, and near the base of
the uvula, and they pass downwards
and slightly anteriorly to join the
side of the tongue a little behind its
middle.
The arcus pharyngo- palatini (O. r
posterior palatine arches) are two verti-
FIG. 878. OPEN MOUTH SHOWING PALATE AND F . , , *
PALATINE TONSILS. ca l folds of mucous membrane whi(
It also shows the two palatine arches, and the pharyngo- P aSS from the Soft P alate to the si
nasal isthmus, through which the nasal part of the Wall of the pharynx. Each COntai
pharynx, above, communicates with the oral portion a muscle, the pharvngO - palatin
of the pharynx, below. mi _ , i *. -u
I he pnaryngo-paiatme arches are
scribed in connexion with the palatine tonsil (p. 1145).
Gingivse. The gums are composed of the red firm tissue which covers t
alveolar borders of the maxillae and. mandible, and surrounds the necks
the teeth. In structure they consist of dense fibrous tissue, inseparably uni
to the periosteum, covered by mucous membrane. They are richly suppli
with blood-vessels, but sparsely with nerves, and are covered by stratifi
squamous epithelium. Around the neck or more correctly the base of the crown
of each tooth, the gum forms a free overlapping collar, and at this
particularly it is closely studded with small papillae, visible to the naked eye.
In thickness it usually measures from 1 to 2 mm.
ongue
THE TEETH.
DENTES.
1113
Permanent canine
1st permanent premolar
2nd permanent premolar
1st permanent molar
Each tooth is a calcified papilla of the mucous membrane of the mouth, and
consists, like that membrane, of two chief portions namely, the substantia eburnea
or ivory (O.T. dentine) derived from the connective tissue, and the substantia adaman-
tina or adamant (O.T. enamel) from the epithelial layer of the mucous membrane.
The substantia eburnea constitutes the chief mass of the tooth, whilst the sub-
stantia adamantina forms a cap for the portion which projects above the gum.
There is also found in the teeth another special tissue the substantia ossea (O.T.
cement), a form of modified bone encasing the roots, which are formed chiefly of
substantia eburnea.
Both ivory and
adamant, but parti-
cularly the latter,
are the hardest and
most resistant struc-
tures in the body,
and are thus specially
fitted for the func-
tions which they
have to perform.
Dentes Decidui
and Dentes Per-
manentes (Decidu-
ous and permanent
teeth). The mouth
of the infant at
birth contains no
teeth, although a
number, partly de-
veloped, lie em-
bedded in the jaWS 2nd decidupus molar
> 1st deciduous molar
beneath _ the gum. Mental forameil
months FlG 879. TEETH OF A CHILD OVER SEVEN YEARS OLD (modified from Testut).
Mandibular
canal
later, teeth begin to
appear, and by the
end of the second
year a set, known as
the deciduous teeth
(O.T. milk teeth),
twenty in number,
has been " c u t."
Then follows a pause
of about four years,
during
By the removal of the bony outer wall of the alveoli, the roots of the teeth which
have been erupted, and the permanent teeth which are still embedded in the
mandible and maxilla, have been exposed. The deciduous teeth are coloured
blue, the permanent teeth yellow. It will be seen that the first permanent
molars have appeared, the central and lateral deciduous incisors have been
replaced by the corresponding permanent teeth in the maxilla, but the
deciduous canine and molars have not yet been shed. In the mandible
the central deciduous incisor has been replaced by the permanent central ;
the lateral has not yet been shed, but its permanent successor is making its
way up to the surface on its lingual side. In addition, the canine and two
molars of the deciduous set persist. The position of the crowns of the
permanent teeth between the roots of the deciduous molars, and the deep
situation occupied by the permanent canines, should be noted. Observe also
the absorption of the root of the lower lateral incisor.
which no
visible change takes
place in the mouth, although in reality an active preparation for further develop-
ment is going on beneath the gum.
At the end of this period, namely, about the sixth year, the next stage in the
production of the adult condition begins. It consists in the eruption of four new
teeth the first permanent molars one on each side, above and below, behind those
of the deciduous set. This is followed by the gradual falling out of the twenty teeth
which have occupied the mouth since the second year (Fig. 879), and the sub-
stitution for them of twenty new teeth, which take up, one by one, the vacancies
created by the dropping out of each of the deciduous set.. Finally, the adult condition
is attained by the eruption of eight additional teeth the 2nd and 3rd molars
two on each side, above and below, behind those which have already appeared.
11 of these the permanent teeth have appeared by the end of the twelfth or
thirteenth year, except the four dentes serotini (O.T. wisdom teeth), which are usually
1114
THE DIGESTIVE SYSTEM.
cut between the seventeenth and twenty- fifth year, but are often delayed until a
very much later period, and occasionally never appear.
The set of teeth which, as indicated above, begin to appear in the infant about
the sixth month, are known as the deciduous teeth (O.T. temporary, or milk teeth) ;
whilst those which succeed them and form the adult equipment are the permanent
teeth.
The deciduous teeth are twenty in number, and are named as follows in each jaw,
beginning at the median plane : dentes incisivi, or incisor teeth, central and lateral ;
dens caninus, or canine tooth ; dentes molares, or molar teeth, first and second ; or
more briefly, two incisors, one canine, two molars. This is conveniently expressed
by the " dental formula " for the deciduous teeth in man, which shows the number
of each class of teeth above and below on
one side of the mouth, viz. :
i. f , c. ^, ra. f = 20.
The permanent teeth, thirty -two in
number, are named dentes incisivi, or in-
cisor teeth, central and lateral ; dentes
canini, or canine teeth ; dentes praemolares,
premolar (O.T. bicuspid) teeth; dentes
molares, molar teeth ; and are arranged
as follows in each jaw, beginning at the
median plane : central incisor, lateral in-
cisor, canine, 1st premolar, 2nd premolar,
1st molar, 2nd molar, and 3rd molar or
dens serotinus (O.T. wisdom tooth). The
dental formula for the permanent set in
man is thus :
Crown
Substantia
adamantina
Snbstantia
eburnea
Cavum
dentis
Neck
Root
c.
pm. I, ra. |-32.
Bone
Substantia ossea
Alveolar periosteum or root-membrane
FIG. 880. VERTICAL SECTION OF CANINE TOOTH,
to illustrate its various parts, and its structure.
General Form and Structure. A
tooth consists (Fig. 880) of (1) the corona
dentis or crown, the portion projecting
above the gum. It varies in shape in the
different teeth, and in all, except th<
incisors and canines, bears on its masticating
surface a number of tubercles, the tuberci
coronae (O.T. cusps), varying in number froi
two to five in the different teeth ; (2) th(
collum dentis or neck, the faintly constricte<
part which is surrounded collar- wise by the
gum, and connects the crown with (3)
the radix dentis or root, the portion of
the tooth embedded in the alveolus of the jaw. In the majority of teeth,
namely, in all except the molars, the root, as a rule, is single, or nearly so, and
consists of a long, tapering, conical, or flattened piece, perfectly adapted to the
alveolus in which it lies. In the molar teeth (and in some of the others occasionally)
the root is divided into two or three tapering or flattened roots or fangs. At the
apex of each root there can be made out, even with the naked eye, a minute
opening, the foramen apicis, through which the vessels and nerves enter the tooth.
When a section of a tooth is made (Fig. 880), it will be seen that the interior
of the body is occupied by a cavity of some size, called the cavum dentis or
tooth cavity, which is filled in the natural state by the soft and sensitive
tissue known as the pulpa dentis or tooth pulp. The tooth cavity gradually narrows,
and is prolonged into each root of the tooth as a slender tapering passage, the
canalis radicis (root-canal), which opens at the apical foramen already referred
to. Through these root -canals, which also contain some pulp, the vessels and
nerves, which enter at the apex, pass to the interior of the tooth.
Short diverticula of the pulp cavity are prolonged into the bases of the tuberch
PERMANENT TEETH. 1115
in the molar and premolar teeth, and in the incisors also there are similar slight
prolongations of the cavity towards the angles of the crown.
The roots of the teeth are embedded in the alveoli or sockets of the jaws, to
which they are accurately adapted, and firmly united (Fig. 880) by a highly
vascular layer of connective tissue the periosteum alveolare. This is attached
to the wall of the alveolus on the one hand and to the root of the tooth on the
other, whilst above it is continuous with the connective tissues of the gum.
So accurately are the root and the alveolus adapted to each other over their
whole extent, and so firmly does the periosteum bind them together, that, under
normal conditions, the tooth is quite firmly fixed in the bone, and no movement
of the root within the alveolus can take place ; the vessels and nerves entering at
the apex are thus secured against pressure or strain.
When, however, the alveolar periosteum is inflamed it becomes swollen and exquisitely sensi-
tive ; the tooth, as a result of the swelling, is pushed partly out of its socket, its crown projects
above those of its neighbours, and strikes against the opposing tooth when the mouth is closed,
giving rise to much pain and discomfort.
The neck, although the term is useful, can scarcely be recognised as a distinct constriction in the
permanent teeth ; it corresponds to the line along which the gum and alveolar periosteum meet,
or along which the gum is united to the tooth ; but, as already pointed out, the gum does not
stop at the neck, but forms a free fold which surrounds the base of the crown collar-wise for a
short distance. The outline of the margin of the gum opposite the labial and lingual surfaces of
the crown is usually concave, but opposite the contact surfaces of the tooth it is convex, and
reaches much nearer to the edge of the crown than on the other surfaces.
In the incisors and canines the tooth, cavity, which is about ^ to j the'diameter of the tooth,
passes very gradually into the root-canal (Fig. 880), so that it is difficult to say where one ends
and the other begins. The reverse is the case in the molars, whilst the premolars are somewhat
variable in this respect.
Tartar is a hard calcareous deposit from the saliva (salivary calculus), often found on the teeth
near their necks. It is composed of lime salts, and its deposit is largely determined by the
presence of organisms (leptothrix, etc.) in the mouth.
DENTES PERMANENTES.
The permanent teeth (Figs. 881 and 882) are thirty-two in number, sixteen
above and sixteen below, or eight in each half of both jaws ; and, although they
can be grouped under four heads incisors, canines, premolars, and molars the
individual teeth differ so much in their characters that each tooth requires a
1 separate description.
Descriptive Terms. Before describing the permanent teeth, it is requisite that
certain terms which are employed to denote the surfaces of the teeth should be defined.
This is a matter of some importance, seeing that the terms medial and lateral, anterior
and posterior, cannot, owing to the curvature of the dental arches, be properly applied
to all the teeth in the same sense. The terms given below have been adopted seeing that
they are free from the danger of misconception.
The part of a tooth which comes in contact with the teeth of the opposite jaw is known
as the facies masticatoria (grinding or masticating surface) (Fig. 883). The surface in
contact with or looking towards its predecessor in the row is known as the facies medialis
in incisors and canines, facies anterior in premolars and molars ; the opposite surface,
namely, that which looks towards its successor in the row, is known as the facies lateralis
in incisors and canines, facies posterior in molars and premolars. The surface which
looks towards the tongue is the facies lingualis (lingual surface), and that looking in
the opposite direction, i.e. towards the lips and cheek, the facies labialis (labial surface).
The portion of a tooth which touches its neighbour in the same row is known as the
facies contacta (contact surface).
Dentes Incisivi (Figs. 881 and 882). The incisor teeth, four in number in
each jaw, are used specially for cutting the food, hence their name. The crown
of each is chisel-shaped, and presents a labial surface which is convex in all
directions, a concave lingual surface, and a chisel-like edge, which, when first
cut, is surmounted by three small tubercles separated by two grooves. These
tubercles, however, are soon worn down, and the edge becomes straight or nearly
so. Owing to the fact that the upper incisors overlap those in the mandible, the
1116
THE DIGESTIVE SYSTEM.
cutting edge is worn away, or becomes bevelled, on the lingual aspect in the
former, but on the labial aspect or summit in the latter. The upper, and par-
ticularly the central upper incisors, are of large size, and slope somewhat forwards ;
whilst the lower incisors, all of nearly equal size, are much smaller being
2nd molar 2nd premolar Canine Central incisor
1st premolar ^ Lateral incisor |
3rd molar
1st molar
3rd molar
1st molar
1st premolar t^ Lateral incisor
2nd molar 2nd premolar Canine Central incisor
FIG. 881. THE PERMANENT TEETH OF THE RIGHT SIDE, LABIAL ASPECT.
The upper row shows the upper teeth, the lower row the lower teeth. The wide vertical " labial ridge " is
distinct on the upper canine and premolar teeth.
the smallest of all the teeth and are placed vertically. The roots of the incisors
are single, though a groove is occasionally seen on each side, suggesting a division.
The central upper incisors are very much larger than the lateral upper incisors (Fig. 881), but in
the mandible the opposite is the case, the lateral incisors being slightly the'larger. In all incisors
Central incisor Canine 2nd premolar
Lateral incisor /V 1st premolar | 1st molar
2nd molar
3rd molar
Lateral incisor J* 1st premolar J 1st molar 3rd molar
Central incisor Canine 2nd premolar 2nd molar
FIG. 882. THE PERMANENT TEETH OF THE RIGHT SIDE, LINGUAL ASPECT.
The upper row shows the upper teeth, the lower row the lower teeth. The cingulum is distinct on the upper
incisors and both canines, the lingual tubercle on the upper lateral incisor and the upper canine.
the lateral angle of the crown is more rounded than the medial. The concave lingual surface
of the crown in the upper incisors is usually limited towards the gum by a A -shaped ridge
(Fig. 882), known as the cingulum. The two limbs of the A are continued up along the sides
of the lingual surface, whilst the apex is turned towards the gum ; and here, particularly in
the lateral incisor, there is often developed a small lingual tubercle (Fig. 882). The cingulum is
rarely found on the lower incisors.
The roots of the upper incisors and canines are conical and rounded (the lateral incisors and
canines not so distinctly as the central incisors) (Fig. 881), whilst those of the mandible are
flattened from side to side (medio-laterally).
PEEMANENT TEETH.
Foramen incisivum
Dentes incisivi
Dentes Canini. In the four canine teeth, which succeed the incisors in each
row (Figs. 881 and 886), the crown is large and conical, corresponding closely in
general form to a very large central incisor with its angles cut away, so that
the crown assumes a pointed or conical shape. The labial surface is convex,
the lingual usually somewhat concave. The root is single and long, particularly
in the upper canine, the root of which is longer than that of any other tooth,
and produces the canine eminence on the anterior surface of the maxilla. The
; upper canines are larger than the corresponding lower teeth, behind which they
bite ; and they are sometimes known as the " eye teeth."
The upper canine presents on its lingual surface a well-marked cingulum, and often a distinct
lingual tubercle; in addition, there is usually a median ridge running from the point of the crown
to the apex of the cingulum, which is separated from the lateral part of the cingulum on each
jide by a slight depression. These points are neither so well marked, nor so constant, in the
lower as in the upper canine.
Of the two margins sloping away from the apex of the crown, the lateral is the longer in both
;eeth. After it has been a little worn the lower canine is less distinctly pointed than the upper ;
its root is also more flattened. On the labial surface of the crown, of both canines and premolars,
i wide low vertical ridge (labial
ridge) can generally be made out
Tig. 882) ; it is most distinct on
the canine and first upper pre- ^^^^KYyfSX .JT / .^te^ Dens caninus
molar.
Dentes Praemolares
Tigs. 881 and 882). The
premolar teeth, eight in
aumber, two in each jaw
above and below, are placed
posterior to the canines, and
interior to the molars, as the
name indicates. The crown,
which, unlike that of the
incisors and canines, is flat-
tened antero - posteriorly, is
characterised by the presence
of two tubercles (O.T. cusps)
Tig. 883). One of the
tubercles, the larger, is placed
Dn the labial, the other on
the lingual side. The labial and lingual surfaces are both convex. The root
is single, but it is, as a rule, flattened antero -posteriorly and grooved, showing
in this a tendency to division, which often actually takes place in the first
upper premolar. The upper premolars are easily distinguished by the fact that
their two tubercles are large and are separated from one another by a distinct
antero-posterior fissure (Fig. 883) ; whilst in the lower premolars, on the other
hand, the separation between the two tubercles is not effected by a continuous
fissure as in the upper teeth, but by two dimple-like depressions separated by
a ridge which joins the two tubercles (Fig. 884). In the upper premolars, there-
fore, the two tubercles are separated by a fissure, in the lower they are united by
a ridge.
The first upper premolar is often slightly larger than the second ; the reverse is the case in
the mandible. The labial surface of the crown is usually somewhat larger than the lingual
surface in all premolars. As a general rule in the lower premolars the labial surface of the
3wn is sloped medially near the masticating surface. The first can usually be distinguished
from the second by the fact that, while the lingual tubercle and surface are smaller than the
labial in the first premolar, they are nearly of the same size in the second. In addition, the
root of the first upper premolar is bifid or nearly so, and its labial ridge is fairly distinct, but
s indistinct in the second. In the first lower premolar the lingual tubercle and surface are very
small, in fact the tubercle is quite rudimentary. It should, however, be added that it is often
extremely difficult to identify the various premolars.
Dentes Molares. The molar teeth are twelve in number three on each side
Spina nasalis
posterior
Foramen
palatinum majus
Sutnra palatina transversa
FIG. 883. THE HARD PALATE AND UPPER PERMANENT TEETH,
VIEWED FROM BELOW.
1118 THE DIGESTIVE SYSTEM.
above and below and are distinguished as first, second, and third molars. The
last in each jaw is also known as the dens serotinus. All the molars are charac-
terised by the large size of the crown and the possession of three or more trihedral
tubercles on the masticating surface (Figs. 883 and 884). They are the largest
of all the teeth, but they diminish in size, as a rule, from the first to the third.
In shape the crown is more or less quadrangular, with convex labial and lingual
surfaces. The roots are either two or three in number, but frequently in the last
molars they are united to a varying degree.
The molars of the maxilla and mandible differ so considerably in their further
details that they must be considered separately. They may be most readily dis-
tinguished from one another by the fact that normally the upper molars possess
three roots (Figs. 881 and 882), whilst the lower molars have two at most. The
number -of tubercles, though not so reliable a guide as the form of the root, is also
generally sufficient to distinguish them. In the upper molars there are either
three or four tubercles, whilst in the lower the number is most commonly five
(see, however, below).
In the upper molars, the crown, viewed from the masticating surface (Fig. 883),
is rhomboidal in shape (i.e. quadrangular with the angles not right angles). The
labial and the lingual surfaces are convex. The number of tubercles is either four
or three. On the first there are invariably four two on the labial and two on
the lingual side the anterior lingual of these being connected with the posterior
labial by an oblique ridge (Fig. 883), which is also found on the second and third
molars when these bear four distinct cusps. The second upper molar has either
four or three tubercles in about an equal proportion of European skulls, whilst in
the third the number is much more frequently three than four. The roots in the
upper molars are three in number (except, occasionally, when the three roots of
the third are confluent), two being labial, and the third lingual (Figs. 881, 882,
and 885).
In the lower molars, the crown, viewed from above (Fig. 884), is somewhat
cubical. The labial and lingual surfaces are convex, as in the upper molars. The
first, as a rule, bears five tubercles, two being on the labial side, two on the lingual,
and the fifth behind and lateral, that is, between the two posterior tubercles and
somewhat to the labial side. The second has usually only four tubercles ; a fifth,
however, is sometimes present. The third has either four or five, the former
number more frequently than the latter.
The roots of the lower molars are two in number, each wide, grooved, and
flattened antero-posteriorly. One root is anterior, the other posterior, and both
are usually recurved in their lower portions (Fig. 885). As in the corresponding
teeth of the maxilla, the roots of the lower last molars are often more or lese
united into a single mass.
The chief characters of the upper and lower molars may be summarised thus :
The first molar is usually larger than the second, and the second than the third. Th(
upper molars are directed downwards and laterally ; whilst the lower molars, which the forme: ,
partly overlap, slope upwards and medially, with the result that the labial tubercles of the lowe
molars lie in the groove separating the lingual from the labial tubercles of the upper teetl
(Fig. 886, p. 1120). As a result of this overlapping, the labial edge of the crown is sharp am
the lingual edge rounded in the upper molars ; whilst the lingual edge is sharp and the labia
edge rounded in the lower set.
The fissures which separate the cusps on the grinding surfaces of the molar teeth are generall;
continued as faint grooves on the labial and lingual surfaces.
Upper Molars. The crowns, as already stated, are rhomboidal in shape, and when vie win,
their masticating surfaces, as in Fig. 883, if the planes of separation between them be prolongec
they would strike the median plane near the posterior part of the hard palate ; in other word;
their anterior and posterior surfaces are not in transverse but in oblique planes, slopin
strongly postero -medially, and converging in that direction. A knowledge of this is useful i
determining the side to which an upper molar belongs, as is the fact that the anterior labial ro(
is broader than the posterior (Fig. 882).
As regards the number of tubercles (Fig. 883) : The first upper molar has four tubercles i
practically all skulls (99 per cent) ; occasionally, indeed, another, but very rudimentary, tubercle
present on the lingual side of the antero-lingual tubercle. The second molar has either three
four in an almost equal proportion of Europeans, but more frequently four, taking the teeth
all nations together. (According to Topinard, four are present in 66 per cent, of all race
PEEMANENT TEETH.
1119
nd in 58 per cent, of European, Semitic, and Egyptian skulls ; according to Zuckerkandl, in
3'5 per cent, of the lower races and 45'6 per cent, of Europeans.) The third upper molar has three
ubercles much more frequently than four amongst Europeans (four only in 36 per cent., although
; t has four more frequently in certain lower races). It should be remarked that, while there
,re practically always four tubercles in the first molar, still there is a tendency to the disappear-
\nce of the postero -lingual one, which tendency grows more pronounced as we pass backwards
o the second and third molars. The other tubercles are practically constant.
The three roots of the upper molars (Figs. 881, 882, and 885) are, a large palatine,
ubcylindrical in shape, and two labial roots, smaller and flattened from before back-
yards. The palatine root, which is placed opposite the posterior labial root, is often united
,;o one of the others. The lower part of the maxillary sinus generally extends down
jetween the palatine and the two labial roots (Fig. 879, p. 1113), but the latter project on its
loor more frequently than the palatine root. In the last molars the three roots are frequently
nore or less united into a single conical process (Fig. 881).
Lower Molars. The crowns are more massive than those of the upper molars, and are
elongated antero-posteriorly (Fig. 884). A crucial groove separates the four chief tubercles from
Central incisor
/" /Lateral incisor
Canine
1st premolar
2nd premolar
1st molar
FIG. 884. THE LOWER PERMANENT TEETH, VIEWED FROM ABOVE.
one another ; this bifurcates behind to enclose the fifth, which lies slightly to the labial side
)f the middle of the tooth. The number of tubercles present in the lower molars is as follows:
The first has usually five (62 per cent, of all races, 61 per cent, of Europeans) ; the second has
four, as a rule (five in only 24 per cent, of all skulls) ; the lower dens serotinus has four a little
more frequently than five (five in 46 per cent, of all skulls), but like the upper last molar tooth
it is extremely variable.
The roots of the lower molars (Fig. 881), two in number, are flattened from before backwards,
very wide. The anterior of these has two root-canals ; the posterior but one (Fig. 885).
The dens serotinus has commonly two roots like its fellows ; occasionally the two are united. In
determining the side to which a lower molar belongs, it should be remembered that the deep
part of the root is generally curved backwards, and also that the blunter margin of the crown
ee above) and the fifth tubercle, if present, are on the labial side.
Arrangement of the Teeth in the Jaws. The teeth are arranged in each jaw
in a curved row the arcus dentalis of approximately a semi-oval form (Figs.
4 and 885). The curve formed by the upper teeth, arcus dentalis superior,
however, is wider than that formed by the lower set, arcus dentalis inferior, so that
when the two are brought in contact the upper incisors and canines overlap their
ellows in front, and the labial tubercles of the upper premolars and molars overlap
the corresponding ones of the lower teeth (Fig. 886, p. 1120). It will also be
ien that, as a rule, the teeth in one jaw are not placed exactly opposite their
fellows, but rather opposite the interval between two teeth, in the other jaw
1120
THE DIGESTIVE SYSTEM.
(Fig. 886). This arrangement is brought about largely by the great width ol
the upper central incisors as com-
pared with their fellows of the
mandible, which throws the uppei
canines and the succeeding teeth
into a position behind that of the
same -named teeth of the lowei
set. But as the lower molars art
larger in their antero-posterioi
diameter than those of the uppei
row and this remark applies
particularly to the third molars
the two dental arches terminate
behind at approximately the sam<
point.
The upper dental arch is said fej
form an elliptical, the lower a parabolii
curve (Figs. 884 and 885). The Un-
formed by the masticating surfaces o
the upper teeth, as seen on profile vie\
(Fig. 886), is usually somewhat convex
owing largely to the failure of th<
third molar to descend into line wit!
the others. Similarly the line of th
lower teeth is as a rule concave.
In both jaws the crowns of the fron
teeth are higher (longer) than those o
FIG. 885. HORIZONTAL SECTIONS THROUGH BOTH THE MAX- +u e >_
ILLA AND MANDIBLE to show the roots of the teeth. The
3rd molar
2nd molar
1st molar
2nd premolar
1st premolar
Canine
Lateral incisor
Central incisor
::: = : ^ 3rd molar
2nd mola
1st molar
2nd premolar
s 1st premolar -
,, Canine
Lateral incisor
Central incisor
Period of Eruption of the Per
sections were carried through the bones a short distance
from the edge of their alveolar borders. The upper figure
shows the upper teeth, the lower figure the lower teeth, manent Teeth. Although then
Note the flattened roots of the lower incisors, the two j s considerable Variety in th<
root-canals in the anterior root of each lower molar, and j , v T. jv
the confluence of the three roots of the upper last molars. " a ^ S at Which the Various pel
manent teeth appear above th
gums, the order of eruption is practically constant in different individuals, am
is as follows: Before any of the
deciduous teeth are lost the first
permanent molars appear behind
the 2nd deciduous molars. Next,
the central deciduous incisors fall
out, and their places are taken by
the permanent teeth of the same
name; then follow the remaining
teeth in the following order:
Lateral incisors, 1st prernolars, 2nd
premolars, canines, 2nd molars,
and 3rd molars. It will be ob-
served that the eruption of the
canine is delayed until the two
premolars, which succeed it in the
row, are cut, so that it breaks the
otherwise regular order of eruption.
The 1st molar is sometimes popu-
larly known, owing to the date of
its eruption as the "six-year-old PIG> 886 ._ To show the relation of the upper To the low.
tooth, and the 2nd molar as " the teeth when the mouth is closed. The manner in which
twelve-year-old tOOth " tooth of one row usually strikes against two teeth of 1
The dates at which the erup- ^tfbVnoI'ed'^ ^ ^^ interlocking
tion usually takes place may be
simply stated as follows for the lower teeth ; those of the upper jaw appear a littl
later :
DECIDUOUS TEETH.
1121
1st molars appear soon after the 6th year.
Central incisors appear soon after the 7th year.
Lateral
1st pre molar
2nd
Canine
2nd molar
3rd
from the
8th
9th
10th
llth
12th
17th
to 21st year, or even later.
Variations in the Number of the Teeth. The presence of an additional tooth is by no
means uncommon. It may appear in connexion with the incisor, premolar, or the molar groups.
A distinction is drawn between " supernumerary " or imperfect additions to the dentition and
"supplemental" teeth which correspond in size with those with which they are associated.
When a supplemental incisor appears it has an interesting bearing upon the solution of the
much -debated point as to which incisor has disappeared from the primate dentition. A
fourth molar is occasionally present.
DENTES DECIDUI.
temporary or milk) are twenty in number,
five in each half of each jaw namely, two
1st molar
Canine
Lateral incisor
Central incisor
The deciduous teeth (O.T.
ten above and ten below, or
incisors, one canine, and two
i molars. They may be dis-
tinguished from the permanent
teeth by their smaller size,
their well-marked and con-
stricted necks, and, in the case
of the molars, by the wide
divergence of their roots (Fig.
887). Otherwise they corre-
spond so closely to the same-
named teeth of the permanent
set, that they require no separ-
ate description, except in the
case of the molars. The first
upper molar has but three
tubercles on its crown two
labial and one palatal ; the
first lower molar has four
two labial and two lingual,
and the crowns of both are
flattened from side to side.
The second molars of the max-
illa have four, those of the
mandible five tubercles each.
In every case the second are
much larger than the first
molars. The tubercles are sharper and are separated by deeper fissures or fossae
than those of the permanent teeth, whilst the roots of the deciduous molars,
except for their greater divergence, agree with those of the permanent set.
The marked constriction at the neck of the deciduous teeth (Fig. 887) is due to a great thicken-
ing of the cap of adamant on the crown, and its abrupt termination as the neck is reached. The
adamant, too, is much whiter as a rule than in the permanent teeth. It should be added
that the labial surface of the canines and molars departs very markedly from the vertical ;
' slopes strongly inwards towards the mouth cavity as it approaches the masticatory surface of
the crown, which latter is, as a result, much reduced in width.
The divergence of the roots in the deciduous molars allows the crowns of the permanent pre-
molars to fit in between them before the former molars are shed.
2nd molar
2nd molar
crown
1st molar
FIG. 887. THE DECIDUOUS TEETH OF THE LEFT SIDE.
The masticating surfaces of the two upper molars are shown above.
In the second row the upper teeth are viewed from the outer
or labial side. In the third row the lower teeth are shown
in a similar manner ; and below are the masticating surfaces
of the two lower molars. In the specimen from which the
first upper molar was drawn the two labial tubercles were not
distinctly separated, as is often the case.
1122
THE DIGESTIVE SYSTEM.
STKUCTURE OF THE TEETH.
As mentioned above, the teeth are composed of three special tissues, substantia adaman-
tina or adamant (O.T. enamel), substantia eburnea or ivory (O.T. dentine), and sub-
stantia ossea (O.T. crusta petrosa or cement), in addition to the pulp which occupies
the tooth cavity. The chief mass of the tooth is formed of substantia eburnea, which
surrounds the tooth cavity and extends from crown to root ; outside this is a covering
of substantia adamantina on the crown, and a layer of substantia ossea on the root.
The substantia adamantina is the dense, white, glistening layer which forms a
cap, thickest over the tubercles, for the portion of each tooth projecting above the
gum (Fig. 888). At the neck it ceases gradu-
ally, being here slightly overlapped by the sub-
stantia ossea.
Crow
cavity
Gum
Neck
Root
Adamant
It is composed chiefly of phosphate and carbon-
ate of lime (phosphate of calcium, 89'82 per cent,
carbonate of calcium, 4-37 per cent, magnesium
phosphate, 1/34 per cent., a trace of calcium fluoride,
other salts, -88 per cent), and has generally been
Tooth considered to contain about 3 '6 per cent of organic
substance ; but Tomes has recently shown this to
be inaccurate : " That which has heretofore been
set down as organic matter is simply water
combined with the lime salts. The substantia
adamantina is to be regarded as an inorganic
substance composed of lime salts, which have
been deposited in particular patterns and formed
under the influence of organic tissues, which
have themselves disappeared during its forma- j
tion."
The adamantine substance consists of calci
fied microscopic prisms, prismata adamantina,
radiating from the surface of the ivory, on which
their inner ends lie, to the surface of the crown,
on which they terminate by free ends. These
prisms are hexagonal in shape, solid, and oij
considerable length, for most of them reach
from the ivory to the surface of the crowr
without interruption. The prisms, which ar<
calcined themselves, are held together by th<
smallest possible amount of calcined matrix
(Tomes). In old teeth the cap of adamantin<
substance is often worn away over the tubercles
the ivory is then exposed, and is easily recog
nised by its yellowish colour, which contrast
strongly with the whiteness of the adamant.
Whilst adjacent adamantine prisms are in general parallel to one another, they do no
usually take a straight, but rather a wavy course, and in alternate layers they are oftei
inclined in opposite directions, thus giving rise to certain radial striations seen b;
reflected light (Schreger's lines). Certain other pigmented lines, more or less parallel t
the surface, are also seen in the adamant (brown striae of Retzius). They are due to tru
pigmentation (Williams), and mark the lines of deposit of the adamant during its develop
ment. The adamantine prisms are more or less tubular in certain animals viz., in ai
marsupials except the wombat, in the hyrax, certain insectivora, and certain rodents.
Cuticula dentis (O.T. Nasmyth's membrane) is an extremely thin (SIFOTRT of an inch
cuticular layer which covers the adamant of recently-cut teeth, and is very indestructiblt
resisting almost all reagents. Two chief views are held as to its origin. One that it i
the last formed layer of adamant, which has not yet been calcined, and therefore the fim
product of the adamant cells. The other that it is produced by the outer layer of cells c
the adamant organ. This latter seems to be the more probable view.
Substantia eburnea or ivory (O.T. dentine) is the hard and highly elastic substanc<
yellowish white in colour, which forms the greater part of the mass of every toot
(Fig. 888). Like the adamant it is highly calcined, but it differs from it in containin
Bone
Substantia ossea \
Alveolar periosteum or root-membrane
FIG. 888. VERTICAL SECTION OF CANINE TOOTH
to illustrate its various parts, and its structure.
STKUCTUKE OF THE TEETH. 1123
very considerable amount of organic matter and water incorporated with its salts,
which are chiefly phosphate and carbonate of lime.
Fresh human ivory contains 10 per cent, of water, 28 per cent, of organic and 62 per cent,
of inorganic material. The organic matter is composed chiefly of collagen, and to a less extent
of elastin. The organic matter consists of (1) calcium phosphate (with a trace of fluoride),
(2) calcium carbonate, and (3) magnesium phosphate, the percentages present in dried dentine
being 6672, 3 '36, 1*08, respectively.
Ivory consists of a highly calcined organic matrix, which is itself practically
structureless, although everywhere traversed by tubes the canaliculi dentales, or
dentinal canaliculi which give to this tissue a finely striated appearance, the striae
usually running in wavy lines. The canaliculi begin by open mouths on the wall of
the pulp cavity, whence they run an undulating, and at the same time a somewhat
spiral course, towards the periphery of the ivory. They give off fine anastomosing
branches, and occasionally divide into two. Somewhat reduced in size, they usually
end in the outer part of the ivory.
The canaliculi dentales are generally described as being lined by special sheaths
(dentinal sheaths of Neumann) which are composed of a most resistant material, and
possibly are calcified. It should be mentioned that the presence of these sheaths as
, separate structures is doubted by some authorities, who hold that the part described
as the sheath is only a modified portion of the ivory which forms the tubules.
The canaliculi dentales are occupied by processes, prolonged from the outermost cells
of the pulp the odontoblasts. These processes are called after their discoverer, Tomes'
fibrils (dentinal fibrils), and they are probably sensory in function.
The concentric lines of Schreger, frequently seen in the ivory, are due to bends in successive
, canaliculi along regular lines running parallel to the periphery of the ivory. Other lines
(the incremental lines of Salter), due to imperfect calcification, are found arching across the
substance of the ivory, chiefly in the crown. There must also be mentioned the interglobular
spaces, intervals left in the ivory, as a result of imperfect calcification, bounded by the fully
calcified surrounding tissue, the contour of which is in the form of a number of small projecting
globules. These interglobular spaces are very numerous in the outer or " granular layer " of the
, ivory, particularly beneath the osseous substance.
The substantia OSSea (O.T. cement) is a layer of modified bone which encases the
whole of the tooth except its crown. It begins as a very thin stratum, slightly
, overlapping the adamant at the neck. From there it is continued, increasing in
. amount, towards the apex, which is formed entirely of this substance. It is relatively
less in amount in the child, and increases during life. In places the ivory seems to
pass imperceptibly into the substantia ossea, the "granular layer" marking the junction
of the two, and some of the canaliculi dentales are continuous with the lacunae of the
. substantia ossea. Like true bone, it is laminated, it possesses lacunae, canaliculi, and,
, when in large masses, it may even contain a few Haversian canals.
The pulpa dentis occupies the tooth cavity and the root-canals of the teeth. It
is composed of a number of branched connective tissue cells, the anastomosing processes
( of which form a fine network, containing in its meshes a jelly-like material, in addition
to numerous vessels and nerves, but no lymph-vessels. The most superficial of these
cells are arranged in the young tooth as a continuous layer of columnar, epithelium-
, like cells, lying on the surface of the tooth pulp against the ivory ; they are known
I as odontoblasts, for they are the active agents in the formation of the ivory. From the
outer ends of these odontoblasts processes are continued into the canaliculi dentales,
. where they have been already referred to as Tomes' fibrils. The vessels of the tooth
pulp are numerous, and form a capillary plexus immediately within the odontoblasts.
The nerves form rich plexuses throughout the pulp, but their exact mode of ending
is unknown.
The periosteum alveolare is a layer of connective tissue free from elastic fibres,
but well supplied both with blood-vessels and nerves, which fixes the root of the tooth in
the alveolus, being firmly united by perforating fibres of Sharpey, to the substantia
ossea on the one hand, and to the bone of the alveolus on the other. It estab-
lishes a communication between the bone of the jaw and the substantia ossea, and it
is continuous with the tissue of the gum. Its blood comes chiefly from the arteries,
which subsequently enter the apical foramina for the supply of the tooth pulp, but in
part also from the vessels of the surrounding bone and of the gum (hence the relief
: obtained in dental periostitis by lancing the gum).
72 a
1124
THE DIGESTIVE SYSTEM
LINGUA.
The tongue is a large mobile mass, which occupies the floor, of the mouth
and forms the anterior wall of the oral part of the pharynx (Fig. 889). It is
composed chiefly of muscular tissue, and is covered by mucous membrane.
Whilst the sense of taste resides chiefly in its modified epithelium, the tongue
is also an important organ of speech, and, in addition, it assists in the mastica-
Middle concha
Middle meatus of nose
Inferior meatus
of nose
Superior meatus of nose
Sphenoidal sinus
Inferior concha
Genioglossus
Genio-hyoid
Posterior edge of nasal septum
Orifice of auditory
tube
Bursa pharyngea
Part of the
pharyngeal tonsil
_,, Recess of pharynx
Torus levatorius
Salpingo-
pharyngeal fold
Glands in soft
palate
Giosso-
palatine arch
_ Supra-tonsillar
fossa
Plica triangularis
Palatine tonsil
Pharyngo-palatine
arch
Epiglottis
Aryteno-
epiglottic fold
Cricoid cartilage
Lymph follicle
Hyoid bone
PIG. 889. SAGITTAL SECTION THROUGH MOUTH, TONGUE, LARYNX, PHARYNX, AND NASAL CAVITY.
The section was slightly oblique, and the posterior edge of the nasal septum has been preserved.
The specimen is viewed slightly from below, hence the apparently low position of the inferior
concha.
tion and deglutition of the food functions which it is well fitted to perform
owing to its muscular structure and great mobility. In length it measures
about three and a half inches (9 cms.), when at rest, but both its length
and width are constantly varying with every change in the condition of the
organ, an increase in length being always accompanied by a diminution in width
and vice versa.
In describing the tongue we distinguish the following parts : the corpus lingua
(body), made up chiefly of striped muscle, and forming the mass of the organ ; thf
dorsum linguae (Fig. 890), which looks towards the palate and pharynx, and is free
THE TONGUE.
1125
in its whole extent ; the base, the posterior wide end which is attached to the hyoid
bone ; the apex linguae, the pointed and free anterior extremity ; the margo
lateralis, which is free in 'its anterior half or more, i.e. in front of the attach-
ment of the anterior palatine arch (Fig. 890). Finally, the unattached portion
on the inferior aspect, seen when the apex is turned strongly upwards (Fig. 892),
constitutes the facies inferior, or inferior surface ; whilst the thick posterior portion,
fixed by muscles and mucous membrane to the hyoid bone and mandible, is known
as the radix linguae or root.
The dorsum of the tongue, when the organ is at rest, is strongly arched
antero-posteriorly in its whole length (Fig. 889), the greatest convexity correspond-
ing to the attachment of the glosso-palatine arch. When removed from the body
Internal jugular vein
Accessory nervt
Digastric muscle
Hypoglossal nerve
Into
ternal carotid artery
Vagus nerve
Sympathetic trunk
Ascending pharyngeal artery
iraiutj
Posterii
External
Stylo-hyoid
Glosso-
pharyngeal nerve
Parotid gland
terior facial
vein
,1 carotid
artery
Styloglossus
Ascending
palatine artery
Internal pterygoid
Epiglottis
Olosso-epiglottic
fold
Masseter-
ryngeal portion
of tongue
Dens
m
Fungiform papilla
Buccinator
Retro-phary n geal
lymph gland
Superior
constrictor muscle
Pharyngo-palatine
arch
Palatine tonsil
Pharyngo-epiglottic
fold
Glosso-palatine
arch
Vallate papillae
Raphe of tongue
Conical papilla
Fungiform papilla
FIG. 890. HORIZONTAL SECTION THROUGH MOUTH AND PHARYNX AT THE LEVEL OF THE PALATINE TONSILS.
The stylopharyngeus muscle, which is shown immediately to the medial side of the external carotid artery, and
the prevertebral muscles, are not indicated by reference lines.
the tongue, unless previously hardened in situ, loses its natural shape, and
appears as a flat, elongated oval structure, which gives a very erroneous idea of its
true form and connexions.
Both in structure and in function, as well as in embryological history, the
dorsum linguae is divisible into two areas an anterior or oral part, which
lies nearly horizontally on the floor of the mouth, and constitutes about two-thirds
of the length of the whole tongue (Fig. 890) ; and a posterior or pliaryngeal part,
the remaining third of the organ, which is placed nearly vertically, and forms the
anterior wall of the oral pharynx (Fig. 889). The separation between these two
parts, which differ in appearance as well as in direction, is indicated by a distinct
V-shaped groove, called the sulcus terminalis (Fig. 890), the apex of which is
1126 THE DIGESTIVE SYSTEM.
directed backwards, and corresponds to a depression on the surface of the
tongue, the foramen caecum, whilst its diverging limbs pass laterally and forwards
towards the attachments of the glosso-palatine arch. The foramen caecum is
the remains of a tubular downgrowth formed early in embryonic life, in the
floor of the primitive pharynx, from which the isthmus of the thyreoid glaiid
is developed (see p. 44).
The anterior portion presents a velvety surface and is covered with innumerable
papillae; the taste-buds are situated in it, and it is horizontal in position. It
is developed from the tissues of the floor of the pharynx behind the first visceral
arch. The posterior portion, on the other hand, has a smooth glistening surface,
contains numerous serous glands and small lymph follicles, and is more vertical
in position. It is developed from the tissue covering the ventral ends of the
second and third visceral arches (see p. 45).
The anterior or oral portion of the dorsum linguae (Fig. 890) is convex,
both from before backwards and from side to side in the resting condition of
the organ (Fig. 893). It usually presents a slight median depression, sulcus
medianus, in the form of an irregular crease, which ends posteriorly near the
foramen caecum. The mucous membrane of this portion of the dorsum is thickly
covered with the prominent and numerous papillae linguales which give this portion
of the tongue its characteristic appearance.
On the pharyngeal part of the tongue there are also small papillary projections of the
corium, but the epithelium fills up all the intervals between the papillae, and, as it were, levels
off the surface, so that none are visible to the eye as projections above the general level. Over
the anterior part of the tongue, on the contrary, the projections of the corium are large and
prominent, and the intervals between them, while they are covered, yet are not filled up, by the
epithelium, so that the projections stand out distinctly and independently, and in places attain a
height of nearly 2 mm. above the general surface.
The posterior or pharyngeal portion of the dorsum linguae (Fig. 889), nearly
vertical in direction, forms the greater portion of the anterior wall of the oral
part of the pharynx (Fig. 890). Its surface is free from evident papillae, but is
thickly studded with rounded projections, 'each presenting, as a rule, a little
pit, visible to the naked eye, at its centre ; the great majority of these folliculi
linguales (lingual follicles, Fig. 889), are similar to the lymph follicles found in
the palatine tonsils ; some few are said to be mucous glands ; all are covered by a
smooth mucous membrane, and they combine to give to this region a characteristic
nodular appearance. To this collection of follicles the name tonsilla lingualis
is applied.
The mucous membrane of this portion of the tongue is separated from the
muscular substance by a submucous layer in which the lymph follicles and the
mucous glands lie embedded (Fig. 893). At the sides it is continuous with
the tunica mucosa covering the palatine tonsils and the side wall of the pharynx ;
whilst posteriorly it is reflected on to the front of the epiglottis, forming in the
middle line a prominent fold, the plica glosso-epiglottica (Fig. 889), at each side
of which is a wide depression, the vallecula.
On each side is a pharyngo-epiglottic fold, which passes from the side of the epiglottis,
upwards along the wall of the pharynx, upon which it is soon lost.
Papillae of the Tongue (Fig. 891). These are formed by variously shaped
projections of the corium of the mucous membrane, covered by thick caps of epi-
thelium. They are of three main varieties : 1, Conical and filiform (jpapillce conicce,
p. filiformes) ; 2, Fungiform and lenticular (papillce fungiformeset p. lenticulares}]
and 3, Vallate and foliate (papillce vallatce et p. foliatce).
The conical and filiform papillae (Fig. 891) are the smallest and most numerous,
forming as they do a dense crop of minute projections all over the anterior two-
thirds of the dorsum, and also upon the superior part of the margin and tip, of the
tongue. Posteriorly they are arranged in divergent rows running laterally and
forwards from the raphe, parallel to the limbs of the sulcus terminalis. More
anteriorly, the rows become nearly transverse, and near the tip irregular. Each
THE TONGUE.
1127
papilla is composed of a conical projection of the corium, covered with microscopic
papillae like those of the skin, and covered by a thick long cap of stratified squamous
epithelium.
In many of them the cap of epithelium is broken up into several long slender hair-like
processes, giving rise to the variety known as filiform papillae. The cap of epithelium is
being constantly shed and renewed, and an excessive or diminished rate of shedding or
renewal, coupled with the presence of various fungi, gives rise to the several varieties of
" tongue " found in different diseases.
The conical papilla are longer and larger than the filiform, and have a wider base.
They are situated on the dorsum among the filiform papilla?, and resemble them in their
structure.
The conical and filiform papillae are probably of a prehensible or tactile nature, and
are highly developed, and horny, in carnivora.
The fungiform and lenticular papillae (Fig. 890) are larger and redder, but less
numerous than the first variety, and they are found chiefly near the tip and
margins of the tongue, comparatively few being present over the dorsum generally.
Epith
Tast(
Serous gland
elium covering |
papilla of corium
Vallum around
papilla
Epithelium of
summit of ;
vallate papilla
Loose epithelium on
surface of papilla conica
Stratifli
thelial
Iepi-
p Connective tissue
corium <
,; -'.' *.
; - :*
' "ft^ ' !
m
(ilamlula lingualis
mm
Blood-vest
A FIG. 891.
A. Section of a papilla vallaf a of tongue. B. Section of papillse conicae of tongue.
Each is in shape like a " puff-ball " fungus, consisting of an enlarged rounded head,
attached by a somewhat narrower base. As in the case of the conical papillae, the
corium is studded over with microscopic papillae, which are buried in the covering
1 of squamous epithelium and do not appear on the surface. Most of the fungiform
papillae, if not all, appear to be furnished with taste-buds, and they are probably
, intimately connected with the sense of taste. The lenticular papillae are placed on
the margin of the tongue. They are flatter than the fungiform papillae, and do
not contain taste-buds.
The vallate papillae (O.T. circumvallate) (Fig. 891), much the largest of all the
papillae of the tongue, are confined to the region immediately in front of the sulcus
terminalis and foramen caecum. Usually about nine to fourteen in number, they
are arranged in the form of the letter V, with the apex posteriorly, just in front
of and parallel to the sulcus terminalis. One or two of the papillae are usually
placed at the apex of the V, immediately anterior to the foramen caecum. In appear-
ance a vallate papilla resembles very closely the impression left by the barrel
of a small pen pressed on soft wax (Fig. 891). Each is composed of a cylindrical
72 1
1128
THE DIGESTIVE SYSTEM.
The philtrura
Anterior gland of
** tongue
Layer of muscle cut
to show the gland
Plica fimbriata
central part (1 to 2-5 mm. wide), slightly tapering towards its base, and flattened
on its crown, which projects a little above the general surface of the tongue. This
is surrounded by a deep, narrow, circular trench or fossa, the outer wall of which
is known as the vallum. The vallum appears in the form of an encircling collar
very slightly raised above the adjacent surface (Fig. 891).
As in the case of the other forms, the vallate papillae are made up of a central
mass of corium, studded with numerous microscopic papillae on the crowns, but not
on the sides, and covered over, as are the surfaces of the fossa and vallum, by
stratified squamous epithelium. Into the fossae open the ducts of some small
serous glands (Fig. 891 A).
On the sides of the vallate papillae, as well as upon the opposed surface of
the vallum, are found, in consider-
able numbers, the structures known
as taste-buds, the special end-organs
of the nerves of taste.
Just anterior to the glosso-
palatine arch, on the margin, are \
usually seen about five or six dis- ;
tinct vertical folds, forming the
folia linguae, which are studded with
taste-buds. They correspond to
the papillae foliatae on the side of
the tongue in certain animals
(rabbit, hare, etc.), in which they
form an important part of the
organ of taste.
The apex and the margin of
the tongue in front of the attach-
Frenuiumiinguaj men t of the glosso-palatine arch
Duct of the submax-
illary gland
Openings of ducts of
the submaxillary
gland
Sublingual gland
Plica sublingualis,
with openings of
ducts of sublingual
gland
the teeth when the tongue is at
rest.
On the superior half or more of the
margin and apex, papillae are present as
on the dorsum ; but on the inferior part
they are absent, and the surface is covered
by smooth mucous membrane.
FIG. 892. OPEN MOUTH WITH TONGUE RAISED, AND THE
SUBLINGUAL AND ANTERIOR LINGUAL GLANDS EXPOSED.
The sublingual gland of the left side has been laid bare by the
removal of the mucous membrane ; to expose the anterior
gland of the right side a thin layer of muscle, in addition
to the mucous membrane, has been removed. A branch
of the lingual nerve is seen running on the medial aspect
of the gland. The vena profunda linguae is faintly in
dicated on this side also.
The inferior surface of the
tongue, which is exposed by turn-
ing the apex of the organ upwards
is limited in extent (Fig. 892)
and is free from visible papillae
the surface being covered by a
smooth mucous membrane. Kun
ning along its middle, except
near the tip, is a depression, iron
which a fold of mucous membrane, the frenulum linguae, passes down to the flooi
of the mouth, and on towards the posterior aspect of the mandible. At eacl
side of the frenulum, and a short distance from it, the large profunda lingua
vein is distinctly seen through the mucous membrane. Further out still ar<
situated two indistinct, fringed folds of mucous membrane, the plicae fimbriatse
which converge somewhat as they are followed forward towards the tip, near whicl
they are lost.
From the inferior surface of the tongue the mucous membrane passes acros
the floor of the mouth to the medial surface of the gum, with the mucous coverin;
of which it becomes continuous.
The plicae nmbriatffl correspond pretty closely to the course of the deep lingual arteries as the
THE TONGUE.
1129
run towards the tip ; the arteries, however, are deeply placed in the substance of the tongue,
at a distance of 3 to 6 mm. from the inferior surface. The plicae, which are more distinct at birth
and in the foetus, are said to correspond to the under tongue found in the lemurs.
The root of the tongue is the portion of the inferior aspect which is con-
nected by muscles and mucous membrane to the mandible and hyoid bone. It is
of very considerable extent, and is, with the base, the most fixed part of the
organ. It is also the situation at which the vessels, nerves, and the extrinsic
muscles enter.
Structure of the Tongue. The tongue is composed chiefly of striped muscular
tissue, with a considerable admixture of fine fat. A median septum of connective
tissue occupies the central part of the organ. In addition, there are vessels, nerves,
glands, and lymph tissue, the whole being covered over by mucous membrane, except at
the root (Fig. 893).
The muscular tissue is derived partly from the terminations of the extrinsic muscles
namely, the hyoglossus, styloglossus, genioglossus, glossopalatinus, and chondroglossus ;
and also largely from the intrinsic muscles namely, the longitudinalis superior,
the longitudinales inferiores, the transversus linguae, and the verticalis linguse. These are
so arranged that they form a cortical portion, made up chiefly of longitudinal fibres
derived, above, from the longitudinalis superior and the hyoglossus, at the sides, from
Transversus M. verticalis
linguae lingupe
M. longitudinalis
superior
Nodules of
lymph tissue
>funda artery
Mucous glands
Transversus linguae
liongitiidinalis inferior
5. A, TRANSVERSE, AND B, LONGITUDINAL VERTICAL SECTION THROUGH THE TONGUE (Krause) ;
C, A LYMPH FOLLICLE FROM POSTERIOR PART OF THE TONGUE. (Macalister, slightly modified.)
the styloglossus, and, below, from the longitudinales inferiores. This cortex surrounds a
central or medullary portion, divided into two halves by the median septum, and formed
in great part by the transverse and vertical fibres, and also by the fibres of the genio-
glossi ascending to the dorsum. The muscular fibres derived from these various sources
end by being inserted into the deep surface of the mucous membrane.
The detailed description of the extrinsic and intrinsic muscles will be found on
page 462.
The septum is a median fibrous partition found in the medullary portion only, and
easily exposed by separating the two genioglossi on the inferior surface of the tongue.
Anteriorly it usually extends to the apex ; whilst posteriorly it grows gradually narrower,
and expanding transversely at the same time, it passes into a broad sheet (the hyoglossal
membrane) which is united to the upper border of the hyoid bone, and gives attachment
to the posterior fibres of the genioglossus. From the sides of the septum the fibres of the
transverse muscle of the tongue arise.
The mucous membrane on the anterior two-thirds of the dorsum, and on the free
margins, is firm and closely adherent to the underlying muscular substance, the fibres
)f which are inserted into it. On the posterior third of the dorsum, and on the inferior
surface, it is neither so firm nor so closely united to the muscular substance, from which
t is separated in both of these situations by a layer of submucous tissue.
1130
THE DIGESTIVE SYSTEM.
The mucous membrane of the tongue, like that of the rest of the mouth, is covered
by stratified squamous epithelium.
Glandulse Linguales. Numerous small racemose glands are found scattered beneath the
mucous membrane of the posterior third of the tongue ; and a small collection of similar glands
is present at the margin, opposite the vallate papillae. Small serous glands are also found
embedded in the dorsum near the vallate papillae, into the fossae of which their ducts oren
(Fig. 891). _
The chief collections of glandular tissue in the tongue, however, are found embedded in the
muscle of the under surface, a little way posterior to the apex, on each side of the middle line
(Fig. 892). They are known as the glandulae linguales anteriores of Blandin or Nuhn.
These glands are displayed after the removal, from the under surface of the tongue, of the
mucous membrane and a layer of muscle fibres about 2 mm. thick which is composed of fibres of
the styloglossus and the longitudinalis inferior muscles a little distance behind the apex. The
anterior lingual glands are oval in shape, often partly broken up by muscular fibres, and they
measure from to f in. (12 to 19 mm.) in length. They are mixed serous and mucous glands,
and they open by three or four very small ducts on the inferior surface of the tongue.
Vallate papillae
Styloglossus
Stylo-hyoid
Superficial lymph
vessels of side and
dorsurn of tongue
Lymph vessels
of apex of
tongue
Afferents to
mandibu
glands
Sublingual gland
Submental gland
Mylo-hyoid cut'
Afferent to deep cervical glands '
Anterior belly of digastric (cut) '
Digastric
Afferents to
deep cervical
glands from
posterior third
of tongue
Common facial vein
Upper deep cervical
lymph glands
Omo-hyoid
FIG. 894. LYMPH VESSELS OF THE TONGUE (after Poirier and Cuneo, modified).
Vessels. The chief artery is the lingual. This vessel passes forwards, on each side, medial to
the hyoglossus muscle, and then is continued on to the apex between the genioglossus on the
medial side and the longitudinalis inferior laterally under the name of the a. profunda linguae.
Anteriorly it is covered by the fibres of the longitudinalis inferior, and lies to in. from
the surface. Near the apex the arteries of opposite sides are connected by a branch which
pierces the septum ; but otherwise, with the exception of capillary anastomosis, they do not com-
municate. The rami dorsales linguae of the lingual artery are distributed to the pharyngeal part
of the tongue, whilst some twigs of the ramus tonsillaris of the external maxillary artery are
also distributed in the same region.
The veins are : The v. profunda linguae, the chief vein, which lies beneath the mucous
membrane at the side of the frenulum, and runs backwards over the hyoglossus with the
hypoglossal nerve ; two venae comites, which accompany the lingual artery ; and two dorsalis
linguae veins from the back of the tongue. These either unite and form a common trunk,
or open separately into the internal jugular vein.
The lymph-vessels of the tongue take their origin in an extensive lymph network in the
submucous coat, and a smaller network connected with the first, in the muscular substance of
the tongue. The network at the apex, including the tip, margins, and front of the dorsum, is
drained by some two to four vessels on each side, which pass downwards by the margin of the
genioglossus muscle and pass laterally to the inferior deep cervical lymph glands. These vessels
may be connected with the submental lymph glands also.
From the margins and dorsnm of the tongue, behind the former area, and extending back to
the vallate papillae, lymph- vessels pass to the submaxillary lymph glands, and also, on the hyo-
GLANDS. 1131
glossus muscle, to the upper deep cervical lymph glands, especially to some glands near the
bifurcation of the common carotid artery. From the posterior part of the tongue the lymph-
vessels pass laterally on each side" below the palatine tonsil, and thence follow the course of the
tonsillar lymph -vessels to the upper deep cervical lymph glands. Some central vessels, from
the median portion^ of the tongue, pass downwards to the submaxillary glands, and also to the
upper deep cervical glands, on the lateral side of the internal jugular vein.
Nerves. The nerves which supply the tongue are : (1) The hypoglossal nerve, the motor
nerve of the tongue, which enters the genioglossus and passes up in its substance to the intrinsic
muscles, in which it ends. (2) The lingual nerve, a branch of the mandibular nerve, which is
accompanied by the chorda tympani branch of the facial nerve. The lingual, after crossing the
hyoglossus, breaks up and enters the longitudinalis inferior and genioglossus muscles, and thus
makes its way upwards to the mucous membrane of the anterior two-thirds of the tongue the
lingual itself conferring common sensation on this part, the chorda tympani probably carrying to
it taste fibres. (3) The glosso-pharyngeal nerve passes forwards beneath the upper part of the
hyoglossus muscle, and sends its terminal branches to the mucous membrane of the posterior third
of the tongue, supplying the papillae vallatae, and the part of the tongue behind these, with
both gustatory and common sensory fibres. (4) Th,e internal laryngeal nerve also distributes a
few fibres to the posterior part of the base of the tongue, near the epiglottis.
GLANDULE.
Numerous organs, differing widely in structure, function, and development, are
commonly included under the term glands. It may indicate any of the following
structures :
(1) Glands producing a visible fluid or semi-fluid secretion, which is dis-
charged from the cells of the gland, either directly or by a duct, on to a free
surface, where it is useful chemically or mechanically, or by which it is drained
away. Glands of this type connected with the alimentary canal are serous and
mucous glands, salivary glands, gastric and intestinal glands, and the liver and
pancreas.
(2) The so-called ductless glands, which possess no ducts, but secrete some
substances, which are directly and gradually transmitted from the cells of the
gland to the blood or lymph stream, and are of use in the general metabolism of the
body. Such structures are the thyreoid gland, the suprarenal glands, the para-
thyreoids, and the hypophysis cerebri.
(3) Cytogenic or cell -producing glands, not always epithelial, and usually
with no distinct duct, consist of aggregations of special cells, enclosed in a more
or less definite framework of connective tissue, freely supplied with blood- and
lymph- vessels. Glands of this type are concerned in the production, from the cells
in the glands, of special cells, which are liberated - from the gland tissue, and pass
away from it. Such glands are lymph glands, the bone marrow, and the repro-
ductive glands testes and ovaries.
In structure they present wide differences.
Glands may also be classified according to their development, and on this basis
the following groups are recognised :
(1) Glandulse epitheliales, developed from epithelial cells. These may (a) possess
a duct, in which case they are termed glandulse evehentes ; or (6) they may be
constituted as ductless glands, and they are then termed glandulse clausse. To
this last group belong the thyreoid gland, the hypophysis, and the suprarenal
glands.
(2) Glandulse vasculares, developed in connexion with vessels, and not containing
epithelial cells. This group includes all the lymph glands, the lymph nodules
found in the intestine, the tonsils, the thymus, and the spleen.
In the following paragraphs only the true glands of the alimentary system
namely, the glands of epithelial origin, characterised by the possession of ducts
are considered.
Such glands may be defined as epithelial organs used for the secretion
or excretion of some particular substance or substances from the body. They
usually consist of a number of cells, and there may be different kinds of cells in a
gland.
1132
THE DIGESTIVE SYSTEM.
The simplest form of this type of gland is a portion of an epithelial surface,
continuous with adjacent portions of the surface, but involuted from the surface
to which it originally belonged.
The simplest form in which this involution occurs is as a single pocket, of uniform size
throughout, forming a simple tubular gland. Of this kind are the intestinal glands in the wall
of the small intestine.
In other cases there may be a bag -like enlargement of the end of the gland, forming a sort of
pocket, called an alveolus (alveolus, small stomach or bag), and this type of gland is known as
the simple alveolar gland. It does not exist in the alimentary canal.
In some cases the lower part or fundus of the gland does all the secretion, and the upper
part forms a tube or duct that carries the secretion to the surface.
When the outgrowth forming the gland remains undivided, the gland is known
as a simple gland. It may, on the other hand, break up into two or more branches,
and it then is known as a compound gland, and this compound gland may be
tubular, alveolar, or of a mixed tubular and alveolar form.
When the fundus of the gland at the extremities of the ducts becomes a
highly differentiated saccular region, consisting of several enlargements (alveoli)
Small duct from an alveolus at tne end of a duct,
Large duct ^ i /^O^jt^^^^^ it is called an acinus
4 ** ^mm^ ( , Kl a or
N ' O JL *
grape-stone), from the
fancied resemblance it
presents to a cluster
of grapes at the end
'^\^\^=^-/-' :G Jr- ' - ^ ttiKfy*-.
SSffiZKV /&&>, I \ %5g&SSfo>
Retro-pharyngeal
lymph gland
Superior
constrictor muscle
Pharyngo-palatine
arch
Palatine tonsil
Pharyn go- epiglottic
fold
Glosso-palatine
arch
JS^Srv Vallate papillae
Raphe of tongue
Conical papillae
Fungiform papi
FIG. 905. HORIZONTAL SECTION THROUGH MOUTH AND PHARYNX AT THE LEVEL OF THE PALATINE TONSILS.
The stylopharyngeus, which is shown immediately to the medial side of the external carotid artery, and the
prevertebral muscles, are not indicated by reference lines.
The palatine tonsils are oval in shape, with the long axes directed vertically.
and each presents a medial and a lateral surface, and a superior and inferior pole,
and an anterior and posterior margin.
The medial surface is prominent and free, studded with small pit-like depressions
called the fossulse or crypts of the tonsil.
The lateral, or attached surface, is enclosed in a distinct fibrous capsule, connected
with the pharyngo-basilar fascia, and this capsule separates the tonsil from the
superior constrictor muscle of the pharynx.
The superior pole is rounded and blunt, and presents numerous fossulae.
inferior pole projects downwards towards the tongue. The 'anterior margin loofo
towards the glosso-palatine arch, and is often overlapped by the plica triangularis
the posterior margin is directed towards the pharyngo-palatine arch.
THE PHAKYNX. 1147
Relations of the Tonsil. The lateral relations of the tonsil consist of the fibrous capsule
and the superior constrictor muscle. Lateral to the pharyngeal wall lies the internal pterygoid
muscle, and behind it a region filled with connective tissue, containing blood-vessels and nerves.
The nearest and most important vessel is the external maxillary artery, which, especially
if tortuous, has a very close relation to the pharyngeal wall at this level.
The ascending palatine and tonsillar branches of the artery are also in close relation.
The internal carotid artery and internal jugular vein lie considerably further back (f to 1
inch) and to the lateral side, and the external carotid artery is still more lateral.
The ascending pharyngeal artery is well behind the tonsil.
The size of the palatine tonsils is extremely variable, but as a rule, in early
life, they measure something under 1 inch (20 to 22 mm.) from above downwards,
about f inch (18 to 20 mm.) antero-posteriorly, and J inch (12 to 15 mm.) medio-
laterally.
The arteries of the palatine tonsil are derived from the ascending palatine and tonsillar
branches of the external maxillary artery, the ascending pharyngeal branch of the external
carotid, and the dorsalis linguae of the lingual. The veins pass to the tonsillar plexus, on the
lateral side of the tonsil, which is an offshoot of the pharyngeal venous plexus.
Nerves. The palatine tonsil receives a special branch from the glosso-pharyngeal ; this unites
with branches from the pharyngeal plexus to form a small plexus tonsillaris which supplies the
organ.
The lymph vessels are extremely numerous. They begin in a plexus which surrounds each
follicle, whence vessels pass to the lateral surface of the tonsil. Thence they pass through the
wall of the pharynx, and pass to the deep cervical glands in the neighbourhood of the greater
cornu of the hyoid bone, behind and inferior to the angle of the mandible.
Structure of the Palatine Tonsils. Each palatine tonsil is composed of masses of small rounded
lymph cells with a delicate connective tissue reticulum. These resemble in structure the folli-
culi linguales, q.v. . .
Upon its medial surface it is covered with epithelium, continuous with the epithelium cover-
ing the adjacent parts of the wall of the pharynx. This surface is very irregular, and on section
crypts, termed fossulae tonsillares, are seen to be formed by deep infoldings of the epithelial
wall. On its lateral surface, the lymph tissue is invested by a connective tissue capsule.
Pars Laryngea. The laryngeal part of the pharyngeal cavity lies posterior to
the larynx (Fig. 903). It is wide above, where it is continuous with the oral portion,
and maintains a considerable width until within about an inch of its termination,
where, posterior to the cricoid cartilage it narrows rapidly and passes down to join
the oesophagus. Except during the passage of food, the anterior and posterior walls
of this latter part are in contact, and its cavity is reduced to a mere transverse slit
(Fig. 906).
The anterior wall of the laryngeal portion of the pharynx is formed in its whole
extent by the posterior surface of the larynx, of which the following parts are seen
from the pharyngeal cavity (Fig. 901): The epiglottis above; below this the
superior aperture of the larynx, bounded at the sides by the ary-epiglottic folds ;
lateral to these folds is seen, on each side, a deep recess, the recessus piriformis
(Fig. 905). Lower down still, the muscles and mucous membrane which cover the
posterior surfaces of the arytenoid and cricoid cartilages are distinguishable.
Its posterior wall and side walls are directly continuous with the corresponding
walls of the oral portion, and present no features which require special notice.
The recessus piriformis (O.T. sinus pyriformis) is a deep depression, seen on each
side between the ary-epiglottic fold and the lamina of the thyreoid cartilage. When
viewed from above, as in laryngoscopic examinations, it appears of a piriform
shape, the wider end being directed upwards and forwards. When viewed from
behind, the recess is boat-shaped and elongated in the vertical direction. Its side
, wall is formed by the thyreoid cartilage and thyreo-hyoid membrane, covered with
mucous membrane ; its medial wall is formed by the ary-epiglottic fold, and slightly,
below, by the superior part of the cricoid cartilage.
Relations of the Pharynx. In considering the relations of the pharynx, it is
afc once evident that these are very different in the superior and inferior portions.
1. Throughout its whole extent it lies anterior to the cervical region of the
vertebral column, and is separated from the bodies 'of the vertebrse and the inter-
, vertebral fibro-cartilages by the loose areolar tissue of the prevertebral or retro-
pharyngeal space, posterior to which lie the anterior longitudinal ligament of the
vertebral column, and the longus capitis and longus colli muscles.
1148
THE DIGESTIVE SYSTEM.
2. In the neck, on each side, it is in contact with the superior part of the thyreoid
gland, the carotid sheath, and especially the common and external carotid arteries,
and, more posteriorly, the internal carotids.
The branches arising from the inferior part of the external carotid are also in
close relation to the pharyngeal wall, viz., the superior thyreoid and lingual arteries
in the lower part, while the external maxillary artery, as it passes under the
digastric and stylo-hyoid muscles, comes into contact with the superior constrictor ;
and the ascending pharyngeal artery runs upwards by the side of the pharyngeal wall.
3. The relations of the cranial portion are more complex, but are of great
importance. Eeference to Fig. 906 will help to elucidate them. At the upper
Internal jugular vein
Accessory nerve
Digastric muscle
Stylo-hyoid
Glosso-
pharyngeal nerve
Parotid gland
Posterior facial
vein
External carotid
artery
Styloglossus
Ascending
palatine artery
Internal pterygoid
Epiglottis
Glosso-epiglottic
fold
Hypoglossal nerve
Internal carotid artery
Vagus nerve
Sympathetic trunk
Ascending pharyngeal artery
Dens
Pharyngeal portion
of tongue
Retro-pharyngeal
lymph gland
Superior
constrictor muscle
Pharyngo-palatine
arch
Palatine tonsil
Pharyngo-epiglottic
fold
Glosso-palatine
arch
Vallate papillae
Raphe of tongue
Conical papilla;
Fungiform papilla
Buccinator
Fungiform papilla
PIG. 906. HORIZONTAL SECTION THROUGH MOUTH AND PHARYNX AT THE LEVEL OF THE PALATINE TONSILS.
The stylopharyngeus, which is shown immediately to the medial side of the external carotid artery, and the
prevertebral muscles, are not indicated by reference lines.
part, the wall of the pharynx is related to the internal pterygoid muscles, separated
from, them by the levator and tensor veli palatini muscles. As each internal pterygoid
passes posteriorly and downwards to its insertion, it diverges away from the pharynx,
and a triangular space is left between its medial surface and the wall of the pharynx.
The styloid process, and the muscles which arise from it, project downwards into
this space, and lying beside them are numerous vessels and some nerves. Thus,
the styloglossus and stylopharyngeus come into contact with the side wall, and, with
the stylo-pharyngeus, the glosso- pharyngeal nerve. The ascending palatine and
tonsillar branches of the external maxillary artery ascend in close relation to
the pharyngeal wall.
The internal carotid artery lies rather further back, with the vagus, accessory
and hypoglossal nerves.
THE PHAKYNX. 1149
The external carotid lies more superficially, and is here separated by a con-
siderable interval from the, pharyngeal wall.
Lastly, a process of the parotid gland may insert itself on the medial aspect of
the internal pterygoid, and come into contact with the pharynx.
The pharyngeal plexus of nerves lies in contact with the side wall.
Structure of the Pharyngeal Wall. The wall of the pharynx is strong and
mobile ; it is firmly fixed above to the base of the skull, but below that level it is not
attached firmly to any surrounding structures, except to the hyoid bone and the skeleton
of the larynx, and hence the inferior end can easily be displaced from side to side in
the neck.
The wall is composed of a strong fibrous membrane, called the fascia pharyngo-
basilaris (O.T. pharyngeal aponeurosis), lined internally by mucous membrane, and covered
incompletely on its outer surface by a series of three overlapping muscles, the constrictor
muscles of the pharynx.
These muscles are themselves covered externally by a thin layer of fibrous tissue
or fascia, which passes forwards, at its superior part, on to the surface of the buccinator
muscle, and is called the fascia buccopharyngea.
External to this fascia the wall of the pharynx is in contact with loose cellular tissue
by which it is connected to and separated from adjacent structures.
With the wall of the pharynx are associated several accessory muscles, viz., the
muscles of the soft palate and the stylopharyngeus and pharyngo-palatine muscles, which
blend with the wall but are also attached to the larynx (see p. 466).
The fibrous aponeurosis which forms the principal constituent of the pharyngeal
wall is firmly attached (round the margins of the openings into the pharynx) to other
structures as follows :
Above, it blends with the periosteum covering the basilar portion of the occipital
bone in front of the pharyngeal tubercle, and body of the sphenoid bone, and on each
side it extends out to the angular spine of the sphenoid and the apex of the petrous part
of the temporal bone.
On each side, it is attached to the structures which lie on each side of the orifices of
the nose, mouth, and larynx. As it descends it gradually becomes thinner, and is
eventually lost.
The fascia pharyngo-basilaris is particularly strong in the superior part, where there is
an area on each side which is not covered by the superior constrictor muscle. This area
forms the sinus of Morgagni, and here the tuba auditiva and tensor and levator veli
palatini muscles pass through the wall.
Mucous Membrane of the Pharynx. The superficial layer of the mucous
membrane of the pharynx consists, in the lower part, of a stratified squamous epithelium,
while in the upper or nasal portion it is, in part, composed of ciliated epithelium. In the
superior part of the pharynx and in the side wall, there are found large masses of lymph
tissue, constituting the pharyngeal tonsil in the roof, and the palatine tonsil on each side.
The same tissue is found in considerable amount in the pharyugeal recess and on the
pharyngeal portion of the dorsum of the tongue.
There are also numerous racemose glands, of the mucous type, in the walls of the
pars nasalis, and in the soft palate, and in the ary-epiglottic folds.
Pharyngeal Muscles. For the details of the attachment and relations of these
muscles, see pp. 464-467.
External to the pharyngeal muscles lies the fascia buccopharyngea.
The fascia pharyngobasilaris, which is thick above and thin belpw, and the fascia
bucco-pharyngea, which is thin above and stouter below, are practically blended into one
layer above, near the base of the skull, where the muscular coat is absent. Lower
down they are separated by the constrictors, and become two distinct sheets. They
are strengthened in the median plane posteriorly by a fibrous band descending from the
pharyngeal tubercle.
Vessels and Nerves of the Pharynx. The arteries of the pharynx are derived from 1,
the ascending pharyngeal ; 2, the ascending palatine branch of the external maxillary ; 3, the de-
scending palatine from the internal maxillary, with a few twigs from the dorsalis linguae,
toasillar (of external maxillary), the artery of the pterygoid canal, and the pharyngeal branch
the internal maxillary. The veins go to the pharyngeal venous plexus, which is found
ween the constrictors and the bucco- pharyngeal fascia. The plexus communicates with the
pterygoid plexus above and with the internal jugular or common facial vein below.
The lymph vessels of the pharynx pass chiefly to the superior set of deep cervical glands.
1150
THE DIGESTIVE SYSTEM.
Those from the superior part of the posterior wall join a few retro-pharyngeal glands which are
found on each side between the pharynx and the rectus capitis anterior muscle. These latter
glands, which are large in the child, small in the adult, but apparently always present (Fig.
906), are of considerable clinical interest, as they often form the starting-point of post-pharyngeal
abscess. For fuller details see section on Lymph Glands.
The nerves of the pharynx, both motor and sensory, are derived chiefly from the pharyngeal
plexus, which is formed by branches of the vagus, glosso-pharyngeal, and sympathetic. The
soft palate and the neighbourhood of the palatine tonsil are supplied by the palatine branches
of the spheno -palatine ganglion. The tonsil receives a branch from the glosso-pharyngeal direct.
The vault of the pharynx, and the region around the orifice of the tuba auditiva, as well as the
orifice itself, are supplied by branches from the spheno-palatine ganglion. Finally, the
internal laryngeal nerve supplies the mucous membrane of the back of the larynx, where it forms
the anterior wall of the laryngeal portion of the pharynx.
Hyoid bone
Thyreoid cartilage
Cricoid cartilage
Trachea
(Esophagus
(ESOPHAGUS.
The oesophagus or gullet is the portion of the digestive canal which intervenes
between the pharynx above and the stomach below. With the exception of the
pylorus, it is the narrowest, and at the
same time one of the most muscular parts
of the whole alimentary tube.
It extends from the termination of the
pharynx, at the inferior border of the cricoid
cartilage and opposite the sixth cervical
vertebra, to the cardiac orifice of the stomach,
opposite the eleventh thoracic vertebra.
Between those two points it traverses the
inferior part of the neck, the whole length of
the thorax, and, having pierced .the dia-
phragm, it enters the abdomen, and im-
mediately afterwards joins the stomach. In
its course it does not adhere to the median
plane of the body, but twice leaves it, and
curves to the left. The first of the curva-
tures corresponds to the inferior part of the
neck and the superior part of the thorax,
* Aperture in diaphragm where the oesophagus projects beyond the
left margin of the trachea to the extent
of J or J inch (4 to 6 mm.). It returns
to the median plane at the level of the
fourth thoracic vertebra, posterior to the
aortic arch. Lower down, posterior to the
pericardium, it again passes to the left, and
at the same time forwards, in order to
reach the cesophageal opening in the dia-
phragm (which is placed anterior to and
to the left of the aortic opening), and it
maintains this direction until the stomach
is reached. It leaves the median plane at
the seventh thoracic vertebra, crosses an-
terior to the aorta at the level of the
eighth thoracic vertebra, and traverses the
diaphragm at the level of the tenth.
In addition to the curvatures just de-
THE COURSE OF gcribedj it is a i so curved ^ t he antero-
posterior direction, in correspondence with
the form of the vertebral column, upon which it, in great part, lies.
In length it usually measures about ten inches (25 cm.).
Its breadth, where the tube is widest, varies between half an inch (13 mm.)
in the empty contracted condition and an inch or more (25 to 30 mm.) in the
fully distended state.
Thoracic duct
12th thoracic
vertebra
Abdominal aorta
Fio. OOT.-
THE (ESOPHAGUS.
1151
When seen in sections of the frozen
body (Fig. 908), the oesophagus usually
appears either as a flattened tube with a
transverse slit-like cavity, or as an oval or
rounded canal with a more or less stellate
lumen. The former condition is more
common in the neck, owing to the pressure
of the trachea, and the latter in the thorax.
When exposed in the ordinary post-
mortem examination soon after death, it
has rather the appearance of a solid muscular
rod or band than of a hollow tube.
The oesophagus presents three distinct
constrictions, one situated at its beginning,
another at the point where it is crossed by
the left bronchus, and the third where it
passes through the diaphragm. The two
upper constrictions are of the same size,
and will admit without injury an instru-
ment with a maximum diameter of -f- inch
(20 mm.). At each of these points the
tube is flattened from before backwards.
The oesophagus varies in length in different
individuals, from 8 to 14 inches (20 to 35 cm.).
The distance from the upper incisors to the begin-
ning of the oesophagus averages about 6 inches
(15 cm.).
During life the cervical portion is said, under
' ordinary circumstances, to be closed and flattened
from before backwards by outside pressure, whilst
the thoracic portion may be open owing to the
i negative pressure in the thorax. The passage into
the stomach is also said to be open (Mickulicz), but
this is doubtful.
The size at the two constrictions, when the tube
is fully distended, is 23 mm. transversely, and
17 mm. antero-posteriorly. The other parts vary
in diameter between 26 and 30 mm. (Jonnesco).
In its first curvature to the left the divergence
is greatest opposite the third thoracic vertebra.
The second inclination to the left begins about
i the seventh thoracic vertebra, and continues to the
: end of the oesophagus, being considerably increased
as the diaphragm is approached.
Relations of the (Esophagus. The
relations (Fig. 908) differ so widely in the
neck and thorax that they must be described
' separately for each of those regions.
In the Neck. Anteriorly lies, the trachea
-to the posterior membranous wall of
which the oesophagus is loosely connected by
'areolar tissue and in the groove at each
side, between the trachea and oesophagus,
the recurrent nerve ascends to the
larynx (Fig. 908, A). Posteriorly lie the
vertebral column and the longus colli
'muscles, from which the oesophagus is
separated by the prevertebral layer of the
vical fascia. On each side are placed the
carotid sheath with its contained vessels, and
the corresponding lobe of the thyreoid gland
and the inferior thyreoid artery. Owing
Fig. A is at level
of the superior
part 1st thoracic
vertebra, and
shows the 'chief
relations of the
oesophagus in
the neck and
also its diver-
gence to the
left.
|SJ THORACIC V.
Fig. B, at the 3rd
thoracic verte-
bra, shows the
thoracic duct
lying on left
side of the oeso-
phagus.
3 r . d THORACIC V.
In Fig. C, at the
C level of the 5th
thoracic verte-
bra, the left
bronchus is seen
in relation to
the anterior sur-
face of the
oesophagus.
Fig. D is at the
level of the 8th
thoracic verte-
bra, and shows
the pericardium
lying on the
anterior surface
of the oeso-
phagus.
Fig. B, at the 9th
thoracic verte-
bra, shows the
oesophagus in-
clining to the
left just before
piercing the
diaphragm.
THORACIC V.
FIG. 908. TRACINGS FROM FROZEN SECTIONS TO
SHOW THE RELATIONS OF THE (ESOPHAGUS
at the levels of the 1st, 3rd, 5th, 8th, and
9th thoracic vertebrae, respectively.
A, Aorta ; C, Common carotid artery ; D, Diaphragm ;
L.B, Left bronchus ; L.C, Left subclavian artery ;
L.R, Left recurrent nerve; L.V, Left vagus; OE,
(Esophagus; P, Pleura; PC, Pericardium; R.B,
Right bronchus ; R.R, Right recurrent nerve ;
R.V, Right vagus; T, Trachea; T.D, Thoracic
duct ; V.A, Vena azygos.
1152 THE DIGESTIVE SYSTEM.
to the deviation of the tube to the left in the inferior part of the neck, its relation
to the carotid sheath and thyreoid gland is much more intimate on the left than
on the right side.
In the Thorax. The oesophagus passes successively through the superior and
posterior mediastina, in the former lying close to the vertebral column, but in
the latter advancing somewhat into the thoracic cavity and coming into contact
with the back of the pericardium. The trachea still lies anterior to it as far as the
fifth thoracic vertebra, where the trachea bifurcates. Immediately below that the
oesophagus is crossed by the left bronchus (Fig. 908, C), and in the rest of its
thoracic course it lies in the closest relation to the back of the pericardium.
Posteriorly, in the upper part of the thorax, it rests on the longus colli muscles and
the vertebral column ; but below the bifurcation of the trachea, as already explained,
it advances into the cavity of the posterior mediastinum, and is soon separated
from the vertebral column by the vena azygos, the thoracic duct, the upper five
aortic intercostal arteries of the right side, and in its lower part by the thoracic
aorta as well.
On its left side, in the upper part of the thorax, lie the left pleura and the left
subclavian artery, with the thoracic duct in a plane posterior to the artery ; in the
middle region, the aorta, and lower down the left pleura again, for a little way,
before the oesophagus pierces the diaphragm. On the right side the tube conies
into relation with the arch ^of the vena azygos, whilst the right pleura clothes it
both below and above that level.
The two vagus nerves, after forming the anterior and posterior pulmonary
plexuses descend to the oesophagus, where they form, by uniting with one another
and with the branches of the sympathetic, the anterior and posterior cesophageal
plexuses. Lower down the left nerve winds round to the anterior, whilst the right
turns to the posterior surface of the oesophagus, and in this relation they pass with
the tube through the diaphragm to reach the stomach.
The diaphragmatic portion, about half an inch in length (1 to 1'5 cm.), corresponds to the
portion of the tube which lies in the cesophageal orifice (or canal) of the diaphragm. Tht
plane of this orifice is very oblique or almost vertical, and its abdominal opening looks forwards
and to the left, and but little downwards. Above and in front, where it is bounded either by tht
posterior edge of the central tendon or by a few decussating fibres of the muscular portion GJ
the diaphragm, which meet behind the tendon, the cesophageal orifice has practically no length
and consequently the oesophagus here passes into the abdominal cavity immediately after leaving
the thorax. At the sides and behind, on the other hand, the decussating bands from the twc
crura, which embrace the orifice, are so arranged that they turn a flat surface (not an edge
towards the opening, and thus, behind and at the sides, the orifice or canal is of some length
and on these aspects there is a portion of the tube in contact with the diaphragm for a distanct
of 1 to 1^ cm. But this contact takes place not around a horizontal line, but in a very obliqu<
plane corresponding to that of the orifice.
The oesophagus, in passing through the orifice, is connected to its boundaries by a considerabl-
amount of strong connective tissue, but it is extremely difficult, or impossible, to demonstrate an?
direct naked-eye connexion between the cesophageal muscular fibres and those of the diaphragm
The anterior or right boundary of the cesophageal orifice, formed of fibres derived from botJ
crura of the diaphragm, is strongly developed and prominent, and usually lies in the cesophagea
groove, on the back of the left lobe of the liver, which groove is rarely due to the pressure of th
O3sophagus alone.
The pars abdominalis of the oesophagus is very short, for immediately after piercing th
diaphragm the tube expands into the stomach. However, when the empty stomach is draw;
forcibly downwards, a portion of the front and left side of the tube, about half an inch in length
(1 to 1'5 cm.), is seen, to which the above term is applied. This part is covered with peritoneun
derived from the great sac in front and on the left, whilst its right and posterior surfaces ar
uncovered. It is generally described as lying against the cesophageal groove and the left triangula
ligament of the liver in front, but it never actually comes in contact with the latter of thes
structures, which is attached to the upper surface of the left lobe of the liver by one edge, an
to the diaphragm, over an inch in front of the oesophagus, by the other. As regards the forme
the cesophageal groove of the liver is generally occupied by the prominent right margin of t
cesophageal orifice of the diaphragm and occasionally by the oesophagus as well. Possibly th
margin is so strongly developed and so prominent in order that it may bear the pressure of the li
off the gullet, which otherwise might be interfered with in its dilatation during the passage of fc
When the stomach is fully distended the abdominal part of the oesophagus almost disappear
being absorbed into the stomach in its distension.
The portion of the oesophagus which adjoins the stomach is sometimes described as consis
of two parts, namely, the ampulla phrenica and the antrum cardiacum. The former n
THE OESOPHAGUS. 1153
i fusiform expansion of the tube, of variable length and girth, which lies within the thorax
i immediately above the point where the gullet is grasped between the two muscular margins
of the cBsophageal opening and the diaphragm. It lies in the lowest part of the posterior
mediastinum where this is bounded anteriorly by the back of the diaphragm.
The antrum cardiacum is another name for the abdominal portion of the oesophagus. It is
funnel-shaped, and expands towards the stomach.
Relation of the Aorta to the (Esophagus. The arch of the aorta, passing back to reach
the vertebral column, crosses to the left side of the oesophagus ; consequently the descending
thoracic aorta lies at first to its left ; lower down, however, as the aorta passes on to the anterior
aspect of the vertebral column, and the gullet inclines forwards and to the left, the aorta comes
to lie posteriorly, and then, as the diaphragm is approached, it lies not only posteriorly, but also
somewhat to the right of the oesophagus (Figs. 907 and 908).
Relation of the Thoracic Duct to the (Esophagus. The thoracic duct, lying to the right
of the aorta below, is not directly related to the oesophagus (Fig. 908, E) ; but higher up
(Fig. 908, D and E) it lies posterior to it. About the level of the aortic arch the duct passes to
the left, and above this (Fig. 908, B and A) will be found on the left side of the oesophagus, and
on a plane .somewhat posterior to it.
Relation of the Pleural Sacs to the (Esophagus. Above the level of the arches of the
aorta and of the vena azygos, between which the oesophagus descends, the pleurae, though
not lying in immediate contact with the oesophagus, are separated from it only by a little connec-
tive tissue, and on the left side also, behind the subclavian artery, by the thoracic duct (Fig.
908, B). Here, in thin bodies, the left pleura is very close to the oesophagus, and the thoracic duct,
lying on its left side, may occasionally be seen through the pleural membrane. Below the arch
i of the azygos vein the right pleura clothes the right side of the oesophagus and very often even a
considerable portion of its posterior surface too, thus forming a deep recess behind it almost as
low down as the opening in the diaphragm. On the left side, below the level of the aortic arch,
the left pleura comes in contact with the gullet, only for a short distance, just above the diaphragm
i (Fig. 908, E).
Variations. The chief anomalies found in the oesophagus are : (1) Annular or tubular con-
, strictions ; (2) diverticula, of which the most interesting known as " pressure pouches " are
usually situated on the posterior wall close to its junction with the pharynx, and these some-
times require surgical interference ; (3) doubling in part of its course ; and (4) communications
between the trachea and oesophagus.
Structure of the (Esophagus (Fig. 911). The cesophageal wall is composed of
three proper coats (1) tunica muscularis, (2) tela submucosa, and (3) tunica mucosa. In
addition, it is surrounded by an outer covering of areolar tissue (4) tunica adventitia, by
i which it is loosely connected to the various structures related to it in its course.
This loose covering permits of its free movement and of its increase in size, or of its
diminution, during the act of swallowing.
The tunica muscularis is composed of two layers an outer of longitudinal,
'and an inner of circular fibres. The longitudinal layer is highly developed, and,
.unlike the condition usually found in the digestive tube, it is as stout as, or in
places stouter than, the circular layer. Its fibres form along the greater length of the
tube an even covering outside the circular layer, and below they are continued
into the longitudinal fibres of the stomach. Above, near the superior end of the
oesophagus, the longitudinal fibres of each side, separating at the back, pass round
towards the anterior aspect and form two longitudinal bands (Fig. 909), which run up
an the front of the tube, and are attached by a tendinous band to the superior part of
;the posterior surface of the cricoid cartilage (Fig. 909).
The circular muscular fibres, though not forming such a thick layer as the longitudinal
fibres, are nevertheless well developed. Below, they are continued into both the circular
and oblique fibres of the stomach. Above, they pass into the inferior fibres of the inferior
3onstrictor of the pharynx.
At the superior end of the oesophagus the muscular fibres are entirely of the striated
variety. Soon unstriped fibres begin to appear in increasing numbers, and in the inferior
half or two-thirds only unstriped muscle is found.
The longitudinal fibres for about the superior fifth of the tube are entirely striped ; in
i the second fifth striped and unstriped are mixed ; whilst in the inferior three-fifths unstriped
fibres alone are present. The circular fibres are entirely striated for the first inch ; after
this unstriped fibres appear; and in the inferior two- thirds, only unstriped muscle fibres
are found.
The longitudinal fibres are often joined by slips of unstriped muscle, or elastic fibres,
which spring from various sources, including the left pleura (m. pleuro-cesophageus, constant,
Cunningham), the bronchi (m. broncho-ossophageus), back of trachea, pericardium, aorta, etc.
These slips assist in fixing the oesophagus to the surrounding structures in its passage through
the thorax, and have been aptly compared to the tendrils of a climbing plant (Treitz).
The tela submucosa, composed of areolar tissue, is of very considerable thickness, in
74
1154 THE DIGESTIVE SYSTEM.
order to allow of the expansion of the tube during swallowing. It connects the mucous
Longitudinal
fibres diverging
Trachea
FIG. 909. DISSECTION to show the
arrangement of the muscular fibres on
the posterior aspect of the oesophagus
and pharynx. Traced upwards, the
longitudinal muscular fibres of the oeso-
phagus are seen to separate posteriorly ;
passing round to the sides, they form
two longitudinal bands which meet
anteriorly and are united to the cricoid
cartilage, as shown in the next figure.
Upper border of
cricoid cartilage
Tendinous band
Circular fibres
'of O3sophagus
Longitudinal bands
FIG. 910. THE INFERIOR PART OP THE PHARYNX
AND THE SUPERIOR PART OF THE (ESOPHAGUS have
been slit up from behind, and the mucous mem-
brane removed to show the muscular fibres. The
two longitudinal bands are seen passing round
to the front to be attached by a common tendon
to the superior border of the cricoid cartilage. See
explanation of last figure.
Epithelium | Tunica
Papilla jmucosa
Conn, tissue
Lamina
muscularis
mucosae
Loose conn.
tissue
Glandula
Tela
subinucosa
membrane loosely to the muscular coat, and admits of the former being thrown into folds
when empty. In thL<
coat are contained th(
numerous racemose
mucous glands (glandula
oesophagese) which opei
into the cavity of th<
oesophagus (Fig. 911).
The tunica mucos*
is of 'a grayish-pinl
colour, much paler thai
that of the pharynx
and of a firm and resis
tant texture. It i
covered with a thicl
stratified, squamous epi
thelium, on the surfac
of which the opening
of numerous glands ar
found. Inferiorly, it
junction with the gastri
mucous membrane i
indicated by a distinc
irregularly dentated c
crenated line, which rur
transversely round th
tube. In carefully pr
oesophagus above this In
Tunica
muscularis
FIG. 911. TRANSVERSE SECTION OF WALL OF HUMAN (ESOPHAGUS.
served specimens the smooth mucous membrane of the
contrasts strongly with the mamillated gastric mucous membrane below.
Owing to the inelasticity of this coat, and the fact that it is but loosely connected
the
THE ABDOMINAL CAVITY. 1155
muscular coat by the submucosa, it is thrown into a series of longitudinal folds when
the oesophagus is empty and contracted ; hence the stellate lumen often seen in sections
of the gullet.
Glands. Numerous racemose mucous glands, the glandulas cesophageae, large enough
to be seen distinctly with the naked eye, are found in the submucosa. They are pretty
evenly distributed over the whole tube, and do not appear to be more numerous towards
either end. In addition to these, other glands, resembling closely those of the cardiac end
of the stomach, are found in the mucous membrane of certain portions of the oesophagus.
They are entirely confined to the mucosa, and do not extend beyond the lamina muscularis
mucosee. These glands are specially numerous at both the upper and lower ends of
the tube.
Vessels and Nerves. Its arteries consist of numerous small branches derived, in the neck,
from the inferior thyreoid, in the thorax, from the bronchial arteries and thoracic aorta, and in
the abdomen, from the left gastric artery, and also from the left inferior phrenic.
The veins form a plexus on the exterior of the oesophagus, from which branches pass, in
the lower part of the tube, to the coronary vein of the stomach, and, higher up, to the azygos,
and thyreoid veins. There is thus established on the lower part of the oesophagus a free com-
munication between the portal and systemic veins.
The lymph vessels pass to the inferior set of deep cervical glands in the neck, and to the pos-
terior mediastinal glands, many of which, of large size, are seen around the tube, in the thorax.
The nerves are derived from the recurrent, and from the cervical sympathetic in the neck,
the vagus and sympathetic nerves in the thorax.
THE ABDOMINAL CAVITY.
As the remaining parts of the digestive system lie within the abdomen it will
be necessary to describe that cavity, and to refer briefly to its lining membrane
the peritoneum before passing on to the consideration of the viscera which are
contained within it.
The abdomen is that portion of the trunk which lies below the diaphragm. It
consists of a wall, composed in part of bones, muscles, tendons, fascia, etc., enclosing
a large cavity, in which lie the greater part of the digestive, urinary, and generative
systems of organs, as well as blood-vessels, nerves, and other structures. The greater
part of the wall of the cavity, and the surfaces of the viscera, are clothed by a
continuous smooth membrane, the peritoneum. The cavity is completely filled by the
'organs mentioned. They lie in contact with one another, and when they are in situ
' the so-called cavity is merely a potential space between the peritoneal surfaces of
adjacent viscera. When air is admitted, as, for instance, by opening the abdominal
( wall in any place, the viscera fall away from one another and a space is formed, in
, place of the capillary interval which exists under normal conditions between them.
In the following description, the term abdomen or abdominal cavity is used to
.indicate the region enclosed by the muscular and bony walls, and the term
peritoneal cavity the potential space inside the peritoneal membrane between the
viscera.
Shape. In general shape the cavity is of a somewhat oval form, with the
long axis directed vertically. The superior end is wider than the inferior. It is
strongly flattened from before backwards, and is encroached upon in the median
plane posteriorly by the projection forwards of the vertebral column.
On transverse section, it will be noticed that the front of the vertebral column
lies at no great distance from the back of the anterior abdominal wall (usually
2J- to 3 inches), while on each side of the vertebral column there is a deep recess,
3ccupied by the kidneys and portions of the intestine.
The abdominal cavity is divisible into the abdominal cavity proper and the
pelvis minor. Vertical section of the trunk shows that the pelvis minor (O.T. true
pelvis) lies below and behind the abdominal cavity, of which it forms a funnel-shaped
termination. The long axis of the funnel is directed downwards and backwards.
As the walls of these two regions are markedly different, the boundaries will be
Considered separately.
Boundaries of the Abdomen Proper. The cavity is limited above by the concave
vault of the diaphragm, which is dome-shaped and presents a right and a left cupola
1156
THE DIGESTIVE SYSTEM.
separated- by an intervening depression. Into the right cupola fits the greater pan
of the liver ; in the left lie a part of the stomach and spleen. On the superio]
surface of each cupola is placed the base of the corresponding lung, whilst betweei
them, on the depression, rests the inferior surface of the heart.
During expiration, the right cupola ascends almost to the level of the righ
nipple ; it is highest at a point about one inch medial to the nipple line, and hen
it reaches the superior border of the fifth rib, or even the middle of the fourth inter
costal space. On the left side it is one-half to one inch (12-25 mm.) lower, am
in the median plane it crosses the inferior extremity of the body of the sternun
about the level of the seventh rib cartilage (Fig. 912).
6th costal cartilage.
7th costal cartilage
Lig. teres
8th costal cartilage
Gall-bladder
9th costal cartilage
Liver
10th costal cartilage
Duodenum
Right flexure of colon
Kidney
Caecum - -
Ileum -
Vermiform process--
Xiphoid process
-6th costal cartilage
7th costal cartilage
Stomach
8th costal cartilage
Transverse colon
9th costal cartilage
10th costal cartilage
Duodeno-jerj unal
flexure
Kidney
Descending colon
Mesentery, cut
Bifurcation of abdomin;
aorta
Iliac colon
Pelvic colon
-Urinary bladder
FIG. 912. THE ABDOMEN AFTER REMOVAL OF JEJUNUM AND ILEUM.
Below, the cavity is continued into the cavity of the pelvis minor.
The anterior wall is formed by the aponeuroses of the three flat abdominal muscle
obliquus externus, obliquus interims, and transversus abdominis, together with thi
two recti, which latter constitute powerful braces for the wall, on each side of th
median plane.
Anteriorly, below the junction of abdomen and pelvis, lies the pubic symphysi
The body of the pubis looks upwards as well as posteriorly, and appears to form
support or floor for the viscera contained within the anterior part of the abdomim.
cavity.
The side walls are formed by the muscular portions of the obliqui and tram
versi muscles, and below by the iliac bones and the iliacus muscles.
Finally, the cavity is limited posteriorly by the lumbar portion of the vertebr.-
column, with the crus of the diaphragm and psoas major muscle on each side, and tl
quadratus lumborum still more laterally. The iliac bones also enter into the form?
tion of the inferior portion of the posterior wall.
The superior portion of the cavity lies under cover of the ribs, which affoi
considerable protection to that part of the abdomen, particularly at the sides ar
THE ABDOMINAL CAVITY. 1157
'posteriorly, in which latter position the cavity is further protected by the vertebral
solumn. Anteriorly, on the other hand, the ribs are wanting below the sternum,
and there the abdominal wall is formed only of aponeuroses and muscles. But even
at the sides and back there is a considerable zone, usually one to two inches wide,
between the lower ribs above and the crest of the ilium below, which has no
bony support except that afforded by the vertebral column.
Whilst the circumference of the diaphragm is attached to the inferior part of
the thoracic framework anteriorly and laterally, and to the lumbar vertebrae
; ; posteriorly, the central portion of the dome, on the other hand, namely, the central
tendon, is placed high up, under cover of the ribs, and in a more or less horizontal
plane. As a result, the peripheral muscular part slopes upwards and medially from the
3ircumference of the thoracic framework to the central tendon, and lies for a con-
siderable distance in contact with the deep surface of the ribs ; thus the diaphragm
somes to form, not only the roof of. the cavity, but it also enters into the formation
of the sides, the posterior wall, and, to a less extent, of the anterior wall ; and almost
%s much of the cavity of the abdomen as of the thorax lies under shelter of the ribs.
Owing to the fact that the boundaries of the abdomen are formed chiefly of
muscles, it follows that its walls are capable of contraction to a very considerable
3xtent, and the size of the cavity can consequently be altered in all directions. Its
3hief changes in form are due to the descent or elevation of the diaphragm, the
contraction or relaxation of the anterior wall and the side walls, and the raising
IT lowering of the pelvic floor.
The superior aperture of the pelvis minor (Figs. 234 and 235, p. 236), which
separates the two natural divisions of the cavity, is formed behind by the base of
the sacrum, at the sides by the linea terminalis of each hip bone, and in front
by the pubic crests and the symphysis pubis. In the erect position it usually
makes an angle of about 55 to 60 degrees with the horizontal. The two portions
}f the abdominal cavity which the superior aperture separates meet at an angle,
the abdomen proper extending almost vertically upwards from it, whilst the pelvic
cavity slopes backwards and slightly downwards.
The pelvic cavity is bounded in front and at the sides by the portions of the
lip bones below the level of the linea terminalis. Those portions of the bony wall are
oartly clothed by the obturator internus muscles, and, internal to those muscles, by the
>arietal portion of the pelvic fascia, as low down as the arcus tendineus. The posterior
\VB\\ is formed by the pelvic surface of the sacrum, covered on each side by the piriformis
muscle. That wall (as represented by the piriformes muscles) meets the side wall
it the anterior border of the greater sciatic foramen ; through that foramen the piriformis
passes out, thus closing up what would otherwise be a large aperture in the parietes of
:he cavity. The floor is composed of the two pairs of muscles which form the pelvic
iiaphragm, namely, the levatores ani and the coccygei covered by the visceral layer of the
3iidopelvic' fascia. Those muscles pass, on each side, from the side wall of the pelvis,
iownwards and medially towards the median plane, and present a concave superior surface
bowards the pelvic cavity.
Within the muscles forming its walls, the abdomen is lined by an envelope of
fascia, which separates the muscles from the extraperitoneal connective tissue and
peritoneum. That fascial layer is distinguished in different localities as: (1)
the fascia transversalis, on the anterior wall and the side walls, lining the deep
surface of the transversalis muscle and continuous above with the fascia clothing
the inferior surface of the diaphragm; (2) the fascia iliaca, on the posterior wall,
3overing the psoas and iliacus muscles ; (3) the fascia diaphragmatica, covering the
inferior surface of the diaphragm ; and (4) the fascia endopelvina, lining the pelvis.
Apertures. Certain apertures are found in the walls of the abdomen, some of
which lead to a weakening of the parietes. They are: the three openings in the
diaphragm for the passage of the inferior vena cava, the oesophagus, and the aorta,
respectively; the apertures in the pelvic floor, through which the rectum, the
urethra, and the vagina in the female, reach the surface ; the inguinal canal,
through which the spermatic funiculus (or the round ligament) passes, in leaving the
abdominal cavity ; and lastly, the femoral canal, a small passage which extends down-
wards from the abdomen along the medial side of the femoral vessels. The latter two,
1158 THE DIGESTIVE SYSTEM.
particularly, constitute on each side weak points in the abdominal wall, through which
a piece of intestine occasionally makes its way, giving rise to inguinal or femoral
hernia respectively. Similar protrusions may also occur at other points in the
abdominal wall, and also through apertures in the pelvic wall.
Tela Subserosa t (O.T. Extraperitoneal or Subperitoneal Connective Tissue).
Between the fascia which covers the deep surfaces of the abdominal muscles, and the
peritoneum which lines the cavity, there is found a considerable quantity of con-
nective tissue, generally more or less loaded with fat, which is known as the.
tela subserosa. It is part of an extensive fascial system which lines the whole
of the body cavity, outside the various serous sacs, and it is continued on the
several vessels, nerves, and other structures which pass from the trunk into the
limbs and neck.
In the abdomen it is divisible into a parietal and a visceral portion, both com-
posed of loose connective tissue. The former -lines the cavity, whilst the latter
passes forwards between the layers of the mesenteries and other peritoneal folds tc
the viscera. The two portions of the extraperitoneal tissue are perfectly continu-
ous with one another, and contain in their whole extent a vascular plexus, througl
which a communication is established between the vessels of the abdominal wall
on the one hand, and those of the contained viscera, on the other.
The parietal portion is thin and comparatively free from fat over the roof anc
anterior wall of the abdomen, and there the peritoneum is more firmly attachec
than where the tissue is fatty and large in amount. In the pelvis minor, on th(
other hand, the tissue is loose and fatty, and, as such, it is continued up for some
inches on' the anterior abdominal wall above the pubes, to permit of the ascent o
the bladder during its distension, in the interval between the peritoneum and th<
anterior abdominal wall. There also the urachus and the obliterated umbilica
arteries will be found passing up in its substance. On the posterior wall thi
tissue is large in amount and fatty, particularly where it surrounds the grea !
vessels and the kidneys.
From the parietal portion the visceral expansions are derived, in the form o
prolongations around the various branches of the aorta. Those expansions ar
connected with the areolar coats of the blood - vessels and are conducted b;
them into the mesenteries and other folds of the peritoneum, and thus reach th
viscera.
The chief uses of the tela subserosa are : (1) to unite the peritoneum to the fascia
and muscular layers of the abdominal wall ; (2) to connect the viscera to those wall;
and to one another in such a loose manner that their distension or relaxation ma;
not be interfered with. That would not be the case if the connecting medium wer j 1
firm or rigid ; (3) in addition, it is a storehouse of fat, forms sheaths for the vessel
and nerves, and establishes, through its vascular plexus, communication betwee:
the parietal vessels and those distributed to the abdominal viscera.
Subdivision of the Abdomen Proper. Owing to the large size of the cavity
and in order to localise more correctly the position of the various organs containe
within it, the abdomen proper is artificially subdivided by two horizontal and tw
sagittal planes (Fig. 913).
Of the two horizontal planes, one divides the trunk at the level of the lowe
border of the tenth costal cartilage ; this is known as the subcostal plane, an
the line where it intersects the abdominal wall is the subcostal line. The secon
horizontal plane is at the level of the highest point of each iliac crest which i
visible from the front ; this point corresponds to the tubercle seen on the extern*
lip of the crest, about t\vo inches posterior to the anterior superior spine, and ca
be easily located ; the line and plane are consequently known as the intertubercuk
line and plane, respectively.
The sagittal planes are drawn, one on each side, perpendicularly upwards froi
a point on the inguinal ligament midway between the anterior superior spine an
the symphysis pubis. The planes and the corresponding lines are known as tt
lateral planes and lines respectively.
By the two horizontal planes the abdomen is divided into three zones, a superi<
or costal, a middle or umbilical, and an inferior or hypogastric zone. By the tv
THE ABDOMINAL CAVITY.
1159
i perpendicular planes each zone is subdivided into three regions, a central and two
lateral. Thus, in the upper zone, we get a hypochondriac region or hypochondrium
on each side, and an epigastric region or epigastrium in the centre. Similarly, the
umbilical zone is divided into right and left lumbar regions, with an umbilical region
between. And the hypogastric zone has a hypogastric region or hypogastrium in the
sentre, with right and left iliac regions at the sides.
In addition, the portion of the abdominal wall above the body of the pubis is
known as the suprapubic region, and that immediately above the inguinal liga-
ments as the inguinal region.
The three central divisions, namely, the epigastric, umbilical, and hypogastric
Right hypochondriac region
Xiphoid process
Epigastric region
Left hypochondriac region
Transpyloric plane
- Subcostal plane
Umbilical region
Left lumbar region
Intertubercular plane
Left iliac region
Hypogastric region
913. PLANES OF SUBDIVISION OF THE ABDOMINAL CAVITY, AND OUTLINE TRACING OF THE LIVER,
STOMACH, AND INTESTINE IN RELATION TO THE ANTERIOR ABDOMINAL WALL.
lique position of the stomach and the high position of the transverse colon are largely due to the fact
that the subject was in the horizontal position.
egions, can conveniently be further subdivided by the median sagittal plane, passing
trough the middle of the body, into right and left halves.
The superior horizontal, or subcostal, plane passes posteriorly, through the superior part of
he third lumbar vertebra, or the nbro-cartilage between the second and third lumbar vertebrae,
"'he intertubercular plane cuts through the middle or superior part of the fifth lumbar vertebra.
The inferior margin of the tenth costal cartilage frequently corresponds to the most dependent
art of the thoracic framework. Often, however, the eleventh costal cartilage descends ^ to ^
ich lower. Nevertheless, the tenth cartilage is selected in drawing the subcostal plane, for two
f reasons, namely, it is visible from the front as a rule, and it is comparatively fixed, whilst
'he eleventh, being a floating rib, is much more movable, is variable in length, and more
ifficult to locate.
Another plane which is of some practical value is the transpyloric plane
Addison). This is a horizontal plane which is taken to intersect the trunk at the
svel of the first lumbar vertebra. That level is ascertained during life by taking
he mid-point of a line drawn, on the surface of the trunk, from the superior border
74 b
1160
THE DIGESTIVE SYSTEM.
of the sternum to the upper border of the symphysis pubis. The same level is
obtained usually, but not so accurately, by taking the mid-point of a line drawn
from the xiphi-sternal articulation to the umbilicus.
Contents of the Abdomen. The following structures are found within the
abdominal and pelvic cavity :
1. The greater part of the alimentary canal, viz., stomach, small intestine, and large intestine.
2. Digestive glands : the liver and pancreas.
3. Ductless glands : the spleen and the two supra-renal glands.
4. Urinary apparatus : the kidneys, ureters, bladder, and part of urethra.
5. The internal generative organs, according to the sex.
6. Blood vessels and lymph vessels, and lymph glands.
7. The abdominal portion of the cerebro-spinal and sympathetic nervous systems.
8. Certain festal remains.
9. The peritoneum the serous membrane which lines the cavity, and is reflected over most of
its contained viscera.
Hepato-
gastric-
ligament
Foramen epi-
Pancreas
Inferior part
"of duodenum
-Transverse
colon
PEKITON^EUM.
The arrangement of the peritoneum is so complicated, and its relations to the
abdominal contents so intricate and detailed, that it will be expedient to postpone
its complete description until
the various organs, with their
special peritoneal relations, have
Liver been separately considered.
Nevertheless, it will be necessary
to give here a general account
of the disposition of the mem-
Srmv passed* 1 brane > and to refer to S0me f
through it. the folds which it forms in pass-
ing from organ to organ, or
from these to the abdominal wall.
The peritoneum is the serous
membrane which lines the ab-
dominal cavity and invests most
of the abdominal viscera, to a
The mesentery g rea t e r or less degree. Like the
pleurae, pericardium, and other
serous sacs, its walls are com-
posed of a thin layer of fibrous
tissue, containing numerous
elastic fibres, covered over on the
side turned towards the cavity
of the sac by a layer of flattened
endothelial cells forming the
tunica serosa. Like them, too
the peritoneum in the male is
completely closed bag, but in tht
female this is not the case, foi
FIG. 914. DIAGRAMMATIC MEDIAN SECTION OF FEMALE BODY, the OStium abdominale of eacl
to show the peritoneum on vertical tracing. The great sac u t e rine tube Opens into the Sac
of the peritoneum is black and is represented as being , ., ,
much larger than in nature ; the bursa omentalis is very whilst the OStium uteriE
darkly shaded ; the peritoneum on section is shown as a that tube Communicates With th'
white line ; and a white arrow is passed through the interior of the uterus, and thUE
omer!taHs eplpl0 a indirectly, with the exterior o
the body. Normally the mem
brane secretes only sufficient moisture to lubricate its surface, otherwise the sa
is perfectly empty, and its opposing walls lie in contact, thus practically obliteratm;
its cavity.
The use of these lubricated and highly polished serous linings, found in th
Uterus-
Bladder
Rectum
.Recto-uterine
pouch
THE PEEITONEUM.
1161
Falciform ligament
Foramen epiploicum
Stomach
Round ligament of liver
f
Lesser omentum (cut)
Portal vein
Vena cava
Lieno-renal
ligament
Small intestine
Eight kidney
The mesentery
abdomen and certain other cavities, is to facilitate the movements of the contained
viscera during any changes in size or form which they or their containing cavity
may undergo. As a result of this arrangement, notwithstanding the tonic pressure
of the abdominal wall on its contents, the stomach and intestines are free to move
with the greatest ease and the least degree of friction, when any change takes place
either in the organs themselves or in their surroundings.
The peritoneum is a thin glistening membrane, which may aptly be compared
to a coat of varnish
applied to the inner
aspect of the ab-
dominal walls, and
to the surface of the
contained viscera,
except where these
are directly applied
to the walls or to
one another. It
forms throughout its
entire extent a con-
tinuous and distinct
sheet, but it is united
so intimately to the
viscera, and follows
the irregularities of
their walls so closely,
that it appears at
first sight to be a
superficial layer of
these walls, rather
than a separate
membrane. Outside
the peritoneum lies
the tela subserosa
already described
by which the peri-
toneum is connected
more or less inti-
mately to the fascial
lining of the abdo-
minal walls and
to the abdominal
viscera.
The portion of
peritoneum which
lines the walls of the
cavity is known as
the peritoneum pari-
etale and that which
clothes the viscera
as the peritoneum
viscerale.
If we trace the peritoneum, beginning in front, we find that it lines the deep
surface of the anterior abdominal wall, and is continued upwards to the inferior
surface of the diaphragm (Fig. 914), the greater portion of which it covers. From
the posterior part of the diaphragm it is reflected or carried forwards on to the
superior surface of the liver. From the liver it can be traced over the stomach,
intestines, and other abdominal viscera to the pelvis. In like manner, when traced
laterally from the anterior wall, the membrane will be found to line the sides of
the cavity,. and passing backwards to clothe the posterior abdominal wall, and the
Ascending colon
Descending colon
FIG. 915. DIAGRAMMATIC TEAKS VERSE SECTIONS OF ABDOMEN, to show the
peritoneum on transverse tracing. A, at level of foramen epiploicum ; B,
lower down. In A note, one of the short gastric arteries passing to the
stomach between the layers of the gastro - lienal ligament, and also the
foramen epiploicum leading into the bursa omentalis which lies behind the
stomach.
1162 THE DIGESTIVE SYSTEM.
viscera lying upon it (Fig. 914). It should be pointed out that all the abdominal
viscera are either directly fixed by connective tissue to the posterior abdominal
wall, or connected by blood-vessels with it. In the former case the peritoneum is
reflected directly from the wall on to the viscera ; in the latter it runs along the
blood-vessels to reach the viscera, which it clothes, and then returns to the wall
on the opposite sides of the vessels, which it thus encloses in a fold.
Whilst the greater part of the general peritoneal cavity lies anterior to the
various abdominal viscera, covering them over and dipping down between them, it
should be mentioned that there is a special diverticulum derived from it, situated
mainly behind the stomach, and covering its posterior surface ; this is known as
the bursa omentalis (O.T. small sac), and it will be described in detail later. The
aperture through which one sac communicates with the other is termed the
foramen epiploicum (Winslowi) (O.T. foramen of Window}.
In passing from organ to organ, or from these to the abdominal wall, the
peritoneum forms numerous folds, the principal ones being as follows :
(1) Omentum Majus. rThe greater amentum hangs down like an apron from
the transverse colon, in front of the coils of the jejunum and ileum. It consists
embryologically of four layers of peritoneum, two anterior and two posterior, which
are usually, in the adult, adherent to one another. The four layers form a thin,
translucent, and often perforated membrane. The anterior two layers were origin-
ally connected with the stomach above, and passed down in front of the transverse
colon, but as development proceeds they become adherent to the anterior surface
of the transverse colon. The fold which extends from the stomach to the colon is
termed the gastro-colic ligament. If the anterior two layers are separated from the
posterior two and from the front of the transverse colon, a cavity is formed, con-
tinuous with the bursa omentalis, and the anterior layers of the greater omentum
are directly continuous with the layers of the gastro-colic ligament. This condition
is that usually described in English text-books as the normal adult condition and
is represented in Fig. 914, where the gastro-colic ligament is separated from the
transverse colon, and passes in front of the transverse colon directly into the
anterior layers of the omentum majus, and the great omentum thus descends from
the stomach above.
(2) Omentum Minus. The lesser omentum is a fold passing from the inferior
surface of the liver to adjacent organs. It consists of two, or occasionally three,
portions :
(a) The ligamentum liepatogastricum, a wide peritoneal fold, extending from the
left end of the porta hepatis, the fossa of the ductus venosus, and partly also from
the concave surface of the left lobe of the liver and the caudate process, to the
lesser curvature of the stomach, where it is continued into the peritoneal coats of
the anterior and posterior surfaces of that organ.
(b) The ligamentum hepatoduodenale passes from the porta hepatis to the pars
superior of the duodenum. On the left this fold is continuous with the hepato-
gastric ligament, on the right it ends in a rounded margin. Traced downwards,
the layers of peritoneum which form it clothe the commencement of the
duodenum on two sides, and are continued into the transverse mesocolon, and into
the duodeno-renal ligament.
(c) The ligamentum hepatocolicum is an occasional fold passing from the region
of the gall-bladder to the transverse colon and right colic flexure.
(3) Ligamentum Gastrolienale. The gastro-splenic ligament (O.T. gastro-splenic
omentum)is a double layer of peritoneum extending between the fundus of the stomach
and the hilum of the spleen, and continuous below with the gastro-colic ligament.
(4) The ligamentum gastrocolicum extends from the greater curvature of the
stomach to the transverse colon. It consists of two layers of peritoneum, continuous
above with the layers on the anterior and posterior surfaces of the stomach, and
below with the anterior layers of the great omentum.
In English text-books this is not usually recognised as a separate ligament, but
is considered to be a portion of the greater omentum, and to pass downwards in front
of the transverse colon. It will be found, however, that the arrangement in the
adult is usually that described above.
1THE STOMACH. 1163
esenteries are folds of peritoneum which unite portions of the intestine
^o cue posterior abdominal wall, and convey to them their vessels and nerves.
[ There are several mesenteries, e.g. the mesenterium (mesentery proper), which
connects the jejunum and ileum to the posterior abdominal wall, the mesocolon
transversum (transverse mesocolon), the mesocolon pelvinum (pelvic mesocolon),
' and occasionally others.
Other folds, specially named, but described elsewhere, are the ligaments of the
liver, the so-called " false ligaments " of the bladder, the lieno-renal ligament, and
the broad ligaments of the uterus.
VENTEICULUS.
The stomach is the large dilatation found on the digestive tube immediately
after it enters the abdomen (Figs. 916 and 920). It constitutes a receptacle in which
the food accumulates after its passage through the oesophagus, and in it take
place some of the earlier processes of digestion, resulting in the conversion of the
food into a viscid soup-like mixture, known as chyme. The chyme as it is formed
is allowed to escape intermittently through the pylorus, in to the small intestine, where
the digestive processes are continued.
The form and the position of the stomach present great variations, not only
among different individuals, but also in the same individual at different times.
The degree to which it is filled, the size and position of adjacent organs, the con-
' dition of the abdominal walls, and even the assumption of the erect or the recumbent
attitude can influence its shape and relations.
Of recent years, examination of the stomach by X-rays has afforded information,
otherwise unattainable, of the shape and position of the stomach in life, and of the
( changes which it undergoes. The results obtained by this method have consider-
ably modified current conceptions regarding the stomach in the living. A necessary
preliminary to the proper comprehension of these appearances is a careful study
of the stomach as it presents itself to anatomical examination.
General Shape and Position. In shape, the stomach may be described as an
irregularly piriform or conical organ, with a wide end directed upwards and
backwards, lying deeply in the hollow of the diaphragm, mainly in the left hypo-
chondriac region, and a narrow tapering extremity which passes downwards and
forwards, and is bent over to the right side, in the epigastric region.
The long axis of the organ forms a spiral curve, directed downwards, anteriorly
and to the right, and finally backwards.
The superior end, or fundus, is almost always dome-shaped, and is distended with
gas, and its wall is thinner and more flaccid than that of the lower portion, which
. is thicker and somewhat cylindrical in shape.
The walls of the stomach are composed of an inner thick layer of mucous membrane (tunica
, mucosa), supported by submucous tissue (tela submucosa), a muscular coat, consisting of three
layers, more or less complete, of muscle fibres (tunica muscularis), running in different directions,
vered externally by a serous, peritoneal investment (tunica serosa). The special characters of
' each of these walls will be described later.
The stomach presents the following parts for examination :
Two surfaces, an anterior (paries anterior) directed at the same time forwards and
to the left, and a posterior (paries posterior) which looks posteriorly and also to the
right. These surfaces meet above and to the right at the lesser curvature, curvatura
ainor, and below at the greater curvature, curvatura major. At the superior end of
3 lesser curvature the oesophagus enters the stomach, at the oesophageal opening,
while at the inferior end the stomach passes into the duodenum at the pylorus.
3 dome-shaped portion to the left of the CBsophagus is the fundus, while the
Bmainder of the stomach is divisible into the body, corpus ventriculi, and the
pyloric portion, pars pylorica.
The cesophageal opening is termed the cardia, and the portion of the stomach
ijacent to it the pars cardiaca, while the inferior orifice is termed the pylorus, and
the portion of the stomach adjacent to it is the pars pylorica, a dilated portion of
1164
THE DIGESTIVE SYSTEM,
Fundus
Paries anterior
(Esophagus
Autrum pyloricum
Pylorus -ijfcM
Sulcua intermedius
Paries
posterior
Ligamentum
gastrocolicum
B
Ligamentum gastrolienale
Omentum minus
Pylorus
Antrum pyloricum
Pylorus
Fundus
Inclsura angularis
Paries anterior
FIG. 916. THREE VIEWS OF A STOMACH FIXED BY FORMALIN INJECTION IN SITU.
A. From the front. B. From the back. C. From above.
The orientation of the stomach was determined by the insertion of long pins into it in
the sagittal, frontal, and transverse planes. These views show the comparatively
horizontal position of the stomach associated with the horizontal posture of the
trunk. They also show the partial division into chambers produced by temporary
constrictions of the stomach wall fixed by the action of formalin.
which forms the
antrum pyloricum.
Cardia. The
opening is situ-
ated at the su-
perior end of the
lesser curvature,
on the right side
of the fundus,and
more on the an-
terior than the
posterior surface
of the stomach.
Around this
opening the mus-
cular walls of the
oesophagus and
the mucous
membrane be-
come continuoi
with correspond-
ing coats of the
stomach wall,
The longitudrm
muscular coal
passes onwarc
into a longi
tudinal set
fibres, and tl
circular ces<
phageal fibri
pass into tl
circular rnui
cular coat,
whitish- coloui
stratified squai
ous epithelium
the oesophagus
continuous wil
the pinkish-c
oured column*
epithelial
of the stomacl
and the juncti(
is marked by
sharp irregul
line running
round them?
of the opening
The orifi
itself is oval
angular rathi
than round, bei]
compressed fi
side to side.
To the ngl
of the orifice, tl
right margin
the oesophagi
THE STOMACH. 1165
merges with a slight curve into the lesser curvature of the stomach, while ou the
left side there is a deep notch, the incisura cardiaca, between the inferior end of
jhe oesophagus and the fundus, in which lies a strong projecting ridge of the
right crus of the diaphragm.
This notch on the outer surface produces a fold in the interior of the stomach,
vvhich may assist in closing the cesophageal opening, and this, with the decussating
fibres of the diaphragm, and the strengthened circular fibres of the inferior end of the
oesophagus, forms a kind of sphincter for this orifice which serves to prevent
regurgitation from the stomach under ordinary condition.
The cardia is very deeply placed, and lies about four inches behind the sternal
,3nd of the seventh left costal cartilage, at a point one inch from its junction
vvith the sternum. Posteriorly it corresponds to the level of the eleventh thoracic
vertebra.
Owing to the fixation of the oesophagus by its passage through the diaphragm, and the close
;onnexion between the stomach and the diaphragm, near the cardia where the peritoneum is
ibsent, this is the most fixed part of the whole organ. The object of this immobility is
evidently to maintain a clear passage for the food entering the stomach.
Pylorus. The pyloric orifice or pylorus is the aperture by which the stomach
jommunicates with the duodenum. It is placed at the extremity of the pyloric
ind of the stomach, and its position is indicated upon the surface of the stomach
jy a slight annular constriction which is most marked at the curvatures.
Its position is also indicated by an arrangement of blood-vessels at the pyloric ring, which is
learly constant. On the peritoneal surface a thick vein passes upwards from the lower side
somewhat more than half-way on the anterior surface, and from the upper border a second vein
'caches downwards in the same line, nearly, if not quite, meeting the first (W. J. Mayo).
.
The pyloric constriction marks the junction of stomach and duodenum, and
jhere the various coats of these portions meet with one another. The peritoneal
iovering of the stomach is continued onwards on to the first part of the duodenum.
At the pylorus the muscular fibres have a special arrangement, which is due
;0 the presence of a mechanism for arresting the escape of food from the stomach
oefore it has undergone digestion. The longitudinal fibres of the stomach (stratum
; .ongitudinale) are in part continued onwards into the longitudinal fibres of the
luodenal coat, but many of them bend inwards into the thickened ring around the
' )pening, where they spread out in diverging bundles, which interlace with the most
i superficial of the circular fibres, and some of them reach and terminate in the
subjacent submucosa.
The circular muscular fibres of the stomach (stratum circulare) are not
: continuous directly with those of the duodenum. On the contrary, at the orifice
-hey become very much increased in number, and they form a thick ring, or
sphincter, which is separated from the circular muscular coat of the duodenum
)y a fibrous septum.
The length of this sphincteric ring is not easily estimated, for while it is
sharply marked off from the duodenum there is no sharp line of demarcation on
she gastric side. There the ring gradually merges into the circular muscular coat
>)f the cylindrical pyloric canal.
When the pyloric canal is contracted, its wall is nearly as thick as the sphinc-
eric ring.
The gastric mucous membrane (tunica muscosa) is continued into the mucous
neinbra.ne of the duodenum at the distal margin of the sphincter. The junction
cannot be recognised by superficial inspection. The gastric mucosa is considerably
< -hickened where it covers the sphincter muscle. When examined post-mortem in
* ;he ordinary way, the aperture, viewed from the duodenal side, is somewhat oval in
brai. When seen from the opposite side, it presents an irregular or stellate
Appearance, owing to the fact that the rugse of the gastric mucous membrane are
Continued up to the orifice.
The orifice is directed horizontally backwards, and to the right. When the
stomach is full, however, it looks almost directly backwards, or even slightly to the
eft side.
1166
THE DIGESTIVE SYSTEM.
The pylorus rests on the neck of the pancreas below and posteriorly, and is over-
lapped by the liver above and anteriorly. When the stomach is empty the pylorus
is usually placed near (i.e. within 1 inch, 12 mm. of) the median plane, below the left
lobe or sometimes the quadrate lobe of the liver, and at the level of the first lumbar
vertebra, or the fibre-car tilage between this and the second lumbar. During disten-
tion it is pushed over beneath the quadrate lobe for a variable distance, but very
rarely more than 1J or 2 inches to the right of the median plane. Its average
position can be marked on the surface of the body by the intersection of two lines ;
one drawn horizontally half-way between the top of the sternum and the pubic crest
(Addison), the other drawn vertically a little way (J inch, 12 mm.) to the rio-ht of
the median plane.
During the earlier stages of gastric digestion the sphincter pylori is strongly contracted
and the aperture firmly closed, but it opens intermittently to allow of tlie passage of properly
digested portions of the food. As digestion advances the sphincter probably relaxes somewhat
but in hardened bodies a really patent pylorus is rarely or never found, which would seem to
Pyloric sphincter
Longitudinal muscular coat
Circular muscle
fibres of the duodenum
Duodenal glands
Longitudinal muscular coat
(duodenum)
Mucous meinbraiK
of the duodenum
Duodenum
Pyloric canal ]
Longitudinal muscular coat |
Mucous coat
Pyloric sphincter
Pyloric orifice
Duodenal glands
FIG. 917. LONGITUDINAL SECTION THROUGH THE PYLORIC CANAL AND COMMENCEMENT OF THE
DUODENUM IN A NEW-BORN CHILD. (From Stiles.)
indicate that the pylorus is normally closed, or nearly so, and that its opening is an active rathei
than a passive condition, as in the case of the anal canal.
As regards its size, the pylorus is stated to be about \ inch (12 - 5 mm.) in diameter, but then
is no doubt that this represents neither its full size nor its calibre when at rest. Foreigr
bodies with a diameter of f to 1 inch have been known to pass through the pylorus withou
giving rise to trouble, even in children. On the other hand, when at rest, with an empt?
stomach and duodenum, the aperture is practically closed.
Curvatura Ventriculi Minor. The lesser curvature is directed towards tht
liver, and corresponds to the line along which a fold of peritoneum calle(
the hepa to- gastric ligament is attached to the stomach, between the pyloric am
cesophageal orifices (Fig. 916). The fold connects the stomach and liver, am
between its two layers the gastric vessels run along the curvature of the stomach.
While the lesser curvature is, on the whole, concave, it consists of two portion
which meet and form a sharp angle, called the incisura angularis, situated neare
the pyloric than the cardiac end, though its position varies with the condition of tb
stomach. The superior or left portion is nearly vertical, and continues the directioi
of the right margin of the oesophagus, while the inferior or right portion is mor
nearly horizontal, when viewed from the front. The depth and acuteness of the angl
between these two segments varies with the degree of distension of the stomacl
When the pyloric portion of the stomach is full, the inferior portion of the lesse
THE STOMACH.
1167
Falciform
ligament (cut)
Pyloric end of
stomach
Subcostal line
,/urvature becomes distended, and that portion of the border becomes convex in
tutline.
The lesser curvature does not form a straight line along the surface of the
toinach, for at the left end it turns forwards somewhat on to the anterior surface
f the stomach, to the place where the cardiac orifice is situated. In length, the
esser curvature measures some 3 to 4 inches.
Curvatura Ventriculi Major. The greater curvature of the stomach is usually
ver three times as long as the lesser curvature, and corresponds to a line drawn from
; he cardia over the summit of the fundus (Fig. 916), and then along the most project-
ng portion of the stomach as far as the pylorus. In general, it is directed to the left
md forwards, but at its beginning, near the cardia, it of course looks in a different
lirection. The great curvature corresponds in the greater part of its length to the
ittachment of the gastro-splenic
md gastro-colic ligaments,folds of
)eritoneum passing to the spleen
md to the transverse colon respec-
ively ; and in close relation to it,
retween their layers, run the right
tnd left gastro-epiploic vessels.
This border of the stomach,
ike the lesser curvature, does
lot present a uniformly curved
*utline. Towards the pylorus
i notch is often found, called the
,ulcus intermedius. The portion
,o the right of this sulcus is
mown as the pyloric canal.
On the left side of this notch,
.he greater curvature bulges for-
. vards, forming a chamber called
f digestion, marked off from the
est of the body of the stomach
>y a temporary indentation.
Other indentations which are
ometimes found on the greater
:urvature, or the body of the
tomach, are probably due to
1 emporary peristaltic waves of
ontraction.
Paries Anterior. The an-
erior surface of the stomach is
Descending
colon
SCALE IN INCHES
SCALE IN CENTIMETRES
FIG. 918. ABDOMEN OF FEMALE, SHOWING DISPLACEMENTS
RESULTING FROM TlGHT LACING.
The liver is much enlarged, and extends on the left side to the
ribs, where it was folded back on itself for over an inch.
The pyloric end of the stomach and the beginning of the
duodenum are quite superficial below the liver, and all the
viscera are displaced downwards. (From a photograph of a
body hardened by injections of formalin.)
nore convex and more extensive than the posterior. It lies, when the organ is
listended, in contact with the inferior surface of the left lobe of the liver medially,
- he vault of the diaphragm laterally, and the anterior abdominal wall below (Fig.
l>16). When the stomach is empty, on the other hand, the transverse colon doubles
ip in front of it, and separates its anterior surface from the liver and diaphragm
-nd abdominal wall.
Paries Posterior. The posterior surface looks downwards and posteriorly. It
is more flattened than the anterior, and is moulded by the structures upon which
1 1 rests.
Thus, to the left is a flattened area, passing on to the fundus, which is in con-
tact with the diaphragm and the spleen. To the right of the fundus, the posterior
.surface is divisible into two areas, lying in different horizontal planes, a superior
and an inferior, separated by a slight ridge. The superior portion, nearly vertical,
ies in contact with the left kidney and supra-renal gland and the diaphragm ;
tnd the inferior portion, more horizontal, is in contact with the pancreas,
1168
THE DIGESTIVE SYSTEM.
transverse mesocolon, and transverse colon. These structures constitute the
posterior wall of the bursa omentalis of the peritoneal cavity.
Between the two areas, the wall comes into contact with the splenic artery
as it runs along the superior border of the pancreas.
The different portions into which the stomach may be divided are as follows :
Aorta
Fossa for caudate lobe
Right inferior phrenic vessels
Inferior vena cava
Hepatic vein
Hepatic artery
Portal vein.
Pylorus
Bile-duct
Right supra-renal glan
(Esophagus
Left gastric artery
Diaphragm
Left supra-renal gland
Splenic artery
Kidney
Anterior surface of pancreas
Gastric surface of spleen
Right common iliac
vein
Right common iliac
artery
Left common iliac-
vein
nferior surface
()f pancreas
ttachment of
transverse
mesocolon
Duodeno-
ejunal flexure
Gastro-duodenal
rtery and neck
of pancreas
Superior meseu-
teric artery
Duodenum
Ureter
Colon
FIG. 919. THE VISCERA AND VESSELS ON THE POSTERIOR ABDOMINAL WALL
The stomach, liver, and most of the intestines have been removed. The peritoneum has been preserved on th<
right kidney, and also the fossa for the caudate lobe. When the liver was taken out, the vena cava wa
left behind. The stomach bed is well shown. (From a body hardened by chromic acid injections.)
Fundus Ventriculi. The fundus is that portion of the stomach which lies abcw
a horizontal plane drawn through the cesophageal opening. It is rounded or dome
shaped. This shape seldom alters, whatever the condition of the stomach maj
be. It is usually filled with gas.
Corpus Ventriculi. The body of the stomach extends from the fundus t<
KELATIONS AND CONNEXIONS OF THE STOMACH.
1169
he incisura angularis on the lesser curvature, and to the notch on the greater
.urvature already described. It forms a rounded chamber, capable of great disten-
iion, but when the stomach is empty it contracts to a narrow tube-like structure.
Is the stomach is seldom completely empty, the body usually tapers from the
undus to the proximal end of the pyloric portion (Fig. 925).
Pars Pylorica. The pyloric portion of the stomach extends from the incisura
,ngularis in the lesser curvature, and a variable and inconstant notch on the
greater curvature, as far as to the pyloric orifice (Fig. 925).
It differs from the body of the stomach in being more tubular in shape, and
assessing thicker walls.
It has been divided anatomically into two portions, the pyloric canal and the
,ntrum pyloricum respectively.
The pyloric canal is a short more or less tubular portion rather more than
,n inch in length, extending from the sulcus intermedius on the greater curva-
ure to the pyloric constriction. The proximal portion, called the pyloric antrum,
Incisura angularis
Lig. teres
Corpus ventriculi
Pancreas
Fold of stomach wall
Pylorus
Vesica fellea
rnentum inaj
Ductus hepaticus
and arteria
cystica
. Vena portse
, Vena cava
inferior
Splenic artery
anterior to supra-
renal gland
Left kidnej
Diaphragm
Left cms of diaphragm
abdomiua
Ductus ,
thoracicus Cauda equiua 1st lumbar
vertebra
J. 920. TRANSVEKSE SECTION OF THE TKUNK AT THE LEVEL OF THE FIKST LUMBAR VERTEBRA.
Showing relations of stomach, pancreas, kidneys, etc. From a subject ten years old.
i more expanded. It is not clearly demarcated from the body of the stomach
y any constant line of division on the greater curvature. On the lesser curvature
xtends from the incisura angularis to the pyloric canal, and it is occasionally
ouched outwards on the side of the greater curvature so as to form a chamber or
ouch, the " camera princeps " of His.
KELATIONS AND CONNEXIONS OF THE STOMACH.
iVhen the stomach has been removed, after the body has been hardened, a chamber or recess
exposed, known as the stomach chamber. It is (Figs. 920 and 921) a space in the upper and
ft portion of the abdominal cavity which is completely occupied by the stomach when that
gan is distended, but into which the transverse colon also passes, doubling up in front of the
omach, when the latter is empty.
The chamber presents an arched roof, an irregularly sloping floor, and an anterior wall,
he roof is formed partly by the visceral surface of the left lobe of the liver, and in the rest of
75
1170
THE DIGESTIVE SYSTEM.
its extent by the left cupola of the diaphragm, which arches gradually downwards behind
and on the left to meet the floor.
The floor or "stomach bed" (Fig. 921) is a sloping shelf on which the posterior surface of the
stomach rests, and by which it is supported. The bed is formed posteriorly by the superior pole of
the left kidney (with the supra-renal gland) and the gastric surface of the spleen ; anterior to
this, by the wide anterior surface of the pancreas ; and more anteriorly still, by the transverse
mesocolon running forwards above the small intestine, from the anterior edge of the pancreas to
the transverse colon (Fig. 921), which completes the floor anteriorly.
Finally, the anterior wall of the stomach chamber is formed by the abdominal wall, between
the ribs on the left and the liver on the right side.
This chamber is completely filled by the stomach, when that organ is distended. When, on
the other hand, the stomach is empty and contracted, it still rests on the floor, or stomach bed,
but occupies only the inferior portion of the chamber, whilst the rest of the space is filled by the
transverse colon, which turns gradually upwards as the stomach retracts, and finally comes to
lie both above and in front of that organ and immediately beneath the diaphragm a fact to be
remembered in clinical examinations of this region.
Peritoneal Relations. The stomach is almost completely covered by
A. epigastrica superior Xiphoid process
7th costal cartilage
7th costal cartilage Diaphragm, cut edge
Lobus hepatis dexter
Cut surface of liver
Lobus caudatus
A. gastrica sinistra
A. cceliaca
Lig. hepato-duodenale
A. hepatica propria
Vena port*
Ductus choledochus
Fundus vesicae felleas
Lig. triansrulare
sinistrum
Diaphragm
(Esophagus
Spleen
O-landula suprarenalis
Left kidney
A. lienalis
Flexura coli sinistra
Cauda pancreatis
A. lienalis
Peritoneum divided
transversum
A. gastro-duodenalis
Pars desceudeus duodeni
A. gastrica dextra
Pars superior duodeni
A. hepatica
Colon transversum !
Pancreas
Facies anterior panureatis
FIG. 921. STOMACH CHAMBER VIEWED FROM THE FRONT AND FROM BELOW.
From the specimen figured in Fig. 912, after removal of the stomach.
peritoneum the anterior surface being clothed by that of the general peritom
sac, and the posterior surface by the anterior layer of the bursa omen tails (see p. 1161
From the lesser curvature the hepato-gastric ligament extends to the liver, whil
to the greater curvature the gastro-lienal and gastro-colic ligaments are attacl
Finally, a small peritoneal fold, known as the gastro-phrenic ligament, is foui
running from the stomach up to the diaphragm along the left side of tl
oesophagus.
A small irregularly triangular area (Fig. 919), about 2 inches wide and 1| inches from abov<
downwards, during moderate distension of the stomach, on the posterior surface below and to t)
left of the cardia, is not covered with peritoneum, and over it the organ is in direct contact wit
the diaphragm, occasionally also with the superior extremity of the left kidney and the supra
renal gland. From the left angle of this " uncovered area " the attachment of the gastro-liena
ligament starts ; and at the right angle is the commencement of a fold through which the I
gastric artery passes to the stomach. This fold is called the left gastro -pancreatic fold.
The right gastro -pancreatic fold is a fold of peritoneum passing from the right extremity o
RELATIONS AND CONNEXIONS OF THE STOMACH. 1171
kipex-ior part of the pancreas to the first part of the duodenum. It encloses the hepatic
ize and Capacity Of the Stomach. Probably no organ in the body varies more
} within the limits of health than the stomach. Moreover, as its tissues change so
apidly after death, measurements made on softened and relaxed organs are not only
vorthless but quite misleading. Consequently it is difficult, perhaps impossible, to arrive
it a correct estimate of its size and capacity.
The length of the stomach in the fully distended condition is about 10 to 11 inches
25 to 27'5 cm.), and its greatest diameter not more than 4 to 4J inches (10 to 11 -2 cm.) ;
" ilst its capacity in the average state rarely exceeds 40 ounces, or 1 quart.
6th costal cartilage -
rth costal cartilage-
Lig. teres'
8th costal cartilage'
Gall-bladder'
costal cartilage 1
Liver-
costal cartilage'
Duodenum'
it flexure of colon '
Kidney
Ileunu-
Vermiform process.-.
Xiphoid process
,.6th costal cartilage
'Ttli costal cartilage
i "-Stomach
8th costal cartilage
Transverse colon
9th costal cartilage
-10th costal cartilage
Duodeno-jejunal
flexure
"Kidney
Descending colon
Mesentery, (cut)
Bifurcation of abdominal
'aorta
Iliac colon
Pelvic colon
-Urinary bladder
FIG. 922. THE COURSE OF THE LARGE INTESTINE. The jejunum and ileum have been removed.
The length has been estimated by different authorities at from 10 to 13i inches (26 to 34
cm.) ; its diameter, from 3| to 6 inches (8 to 15 cm.) ; and its capacity from l| to 5 pints. The
measurements of the capacity given by Dr. Sidney Martin are probably the most accurate : he
states that the capacity varies between 9 and 59 oz., with an average of from 35 to 40, or a little
1 over a litre.
The distance in a direct line from the cardiac to the pyloric orifice varies from 3 to 5 inches
i (7 '5 to 12 '5 cm.), and that from the cardia to the summit of the fundus from 2^ to 4 inches
i (6-2 to 10-0 cm.).
As regards the weight, the average of twelve wet specimens freed from their omenta was
found to be 4| oz. (135 grms.), with a maximum of 7 oz. (198 '45 grms,) and a minimum of.
3 cz. (99-22 grms.). Glendinning gives the weight as 4^ oz.
In the child at birth the stomach is scarcely as large as a small hen's egg, and its
capacity is about 1 oz. (28-3 grms.). In shape it corresponds pretty closely to that of
the adult, and the fundus is well developed. It is vertical in position.
Displaced Stomach (Fig. 918). As a result of disease, or of constriction of the
superior part of the abdomen, the stomach is occasionally displaced in position and distorted
in shape, so that instead of running obliquely forwards, downwards, and to the right,
it is placed nearly vertically along the left side of the vertebral column, in which direction
t has a very considerable length. Its inferior part bends rather suddenly, and runs upwards
75 a
1172
THE DIGESTIVE SYSTEM.
and to the right to join the pylorus, which is often placed quite superficially below the
liver. As a result of the displacement, the left extremity of the pancreas is pushed
downwards from the horizontal until it almost assumes a vertical position. The narrowing
and inversion of the inferior margin of the thoracic framework at the same time constri
the stomach about its middle, and may lead to a bilocular condition.
'icts
Hour-glass or Bilocular Stomach. This is a condition of the organ, by no means rare,
in which the stomach is more or less completely separated into two divisions a cardiac and
a pyloric the normal arrangement in certain rodents and other animals. As a rule the former
division is the larger, but occasionally the two are nearly equal, or the pyloric portion may
exceed the cardiac in size. Sometimes the condition is temporary, and the result of a vigorous
contraction of the circular muscular fibres at the seat of constriction. In other cases it is
FIG. 923.
A. Empty stomach in vertical position as denned by the X-rays.
B. Filled stomach in vertical position as seen with the X-rays.
C. Half-filled stomach in vertical position as seen with the X-rays.
D. Half-filled stomach in horizontal position as seen with the X-rays.
permanent, and may be due to cicatricial contraction after gastric ulcer, or to some other patho-
logical condition. The condition is more frequent in the female than the male, and is rarely
found in the fo3tus or child.
Position of the Stomach. When empty, or nearly so, the stomach lies in the
left hypochondrium and left part of the epigastrium, with its fundus directed
posteriorly towards the diaphragm, its long axis lying almost in a horizontal
plane and its pyloric part running to the right to join the duodenum. In
this state the whole organ is narrow and attenuated, particularly the pyloric part,
which is contracted, and resembles a piece of thick-walled small intestine.
When distended, both the cardiac and pyloric parts become full and rounded
(Fig. 923). It still lies within the hypochondriac and epigastric regions ; but in
exceptional cases, or in extreme distension, it may pass down below the subcostal
plane and reach into the umbilical and left lumbar regions. As a result of the
TAN i
KELATIONS AND CONNEXIONS OF THE STOMACH. 1173
/eneral increase in length which takes place during distension, the pylorus is
r xtoved a variable distance to the right beneath the quadrate lobe of the liver,
ind at the same time the long axis of the whole organ becomes much more
)blique, running forwards, downwards, and to the right. Finally there is
leveloped a special dilatation of- the pyloric part, known as the antrum pyloricum,
,vhich in extreme distension is carried so far to the right that it may even reach
}0 the hypochondrium.
Shape and Position of the Stomach as seen by X-Ray Examination. Examination
of the stomach by means of X-rays after a " bismuth meal " has given important
.uformation about the shape and position of the stomach in the living, and about
ihe changes which occur as the stomach fills and empties.
These examinations corroborate, in great part, the conclusions which have been
irrived at by the study of formalin specimens so far as the shape of the stomach,
ind its division into parts, is concerned. In regard, however, to the position and
lirection of the stomach, X-rays show that the stomach in the living, and especially
.n the erect attitude, is more vertical than it is after death, and when the body
3 examined in the horizontal position. In the upright position, in fact, the long
ixis of the organ appears to be nearly vertical. The general shape and position
)f the stomach in the vertical position, moderately distended, is shown in Fig. 923.
From this it will be seen that not only is the body of the stomach nearly vertical,
Dut that the greater curvature reaches down to the umbilicus, and may descend
3ven beyond it. The pyloric part is directed upwards, as well as backwards, and
:he pylorus is not usually the lowest point of the stomach.
The other anatomical features of the stomach described above are well brought
)ut. Thus the fundus is a hemispherical dome, lying to the left of the terminal
portion of the oesophagus, and continuous in outline with the body of the stomach.
It usually contains gas, and appears translucent to X-rays. The body is of uniform
Dutline, and the pyloric part is marked off from it by the incisura angularis, on
ihe lesser curvature. Further, the pyloric part shows division into pyloric antrum
md pyloric canal. The incisura angularia and sulcus intermedius are distinct.
The position of the stomach is greatly influenced by attitude and by the con-
lition of the abdominal muscles. Contraction of the abdominal muscles can elevate
]he stomach from 5 to 13 cm., or 2 to 5 inches, and the change from the horizontal
]0 the erect attitude alters the height of the inferior border from 2 to 10 cm. This
sinking which occurs in the alteration from the horizontal to the erect attitude,
iccounts largely for the differences found between the stomach seen in the post-
mortem room or on the operating table and the stomach displayed by means of
X-rays. Thus, if the stomach figured on p. 1167 be considered fixed at the cardiac
3nd, and somewhat fixed at the pylorus, and the pyloric antrum and greater
iurvature should sink downwards, the shape, as seen from the front, would closely
resemble the X-ray appearances found often in the living.
The empty stomach is a contracted tubular organ, except at the fundus, where
it appears to be always dilated. When food is taken, when the individual is
standing or sitting, it runs down to the point where the gastric walls are in contact
with one another. The distal portion of the stomach dilates for some distance, or
it least as far as the pyloric canal.
As the stomach becomes filled the whole of the body of the organ becomes
lilated, but the fundus and cardiac portion more particularly so, and these two latter
regions act as a storehouse.
There is no definite division of this portion from the remainder of the stomach
by a permanent sphincter, but the peristaltic waves of contraction begin about the
middle of the organ, and form a fleeting constriction between the two parts.
As peristalsis goes on, the tubular pyloric part relaxes somewhat. The waves
3f peristalsis here become so deep as to divide this portion into chambers. The
food substances are forced through the pylorus by successive waves of peristalsis,
and in the form, usually, of jets which impinge against the posterior aspect of
the duodenal wall.
Should there be undigested masses, the pyloric valve relaxes to allow them also
to pass into the duodenum.
1174
THE DIGESTIVE SYSTEM.
STRUCTURE OF THE STOMACH.
The stomach wall is composed of four coats namely, from without inwards: (1)
Tunica serosa, (2) tunica muscularis, (3) tela submucosa, and (4) tunica mucosa (Fig. 924).
Tunica Serosa. The serous coat is formed of the peritoneum, the relations of which
to the stomach have already been described. It is
closely attached to the subjacent muscular coat,
except near the curvatures, where the connexion
is more lax; and it confers on the stomach its
smooth and glistening appearance.
Tunica Muscularis. The muscular coat, which
is composed of unstriped muscle, is thinnest in the
fundus and body, much thicker in the pyloric
portion, and very highly developed at the pylorus.
It is made up of three incomplete layers an
external, stratum longitudinale ; a middle, stratum
circulare ; and an internal of oblique muscular fibres,
fibrce obliquce.
The stratum longitudinale consists of longitu-
dinal fibres, continuous with those of the oesophagus
on the one hand, and those of the duodenum on
the other (Fig. 926, A). They are most easily
demonstrated on the lesser curvature, where they
can be traced down from the right side of the
oesophagus. Over the greater curvature and on the
two surfaces they are present as an extremely thin
and irregular sheet. Towards the pylorus the longi-
tudinal fibres grow much thicker, and, also much
tougher and more closely united, and they take part
in the formation of the pyloric valve.
A specially condensed band of these can be often
Stratum
longitudinale
Tunica serosa
FIG. 924. TRANSVERSE SECTION THROUGH
THE WALL OF A HUMAN STOMACH, x 250.
made out both on the front and back at the antrum pyloricum, the form of which is said to
due to their presence. These bands are known as the ligamenta pylori (pyloric ligaments).
Pyloric
N opening
Pyloric canal
Icus intermedius
--' Pyloric antrum
FIG. 925. MUSCULAR COAT OF THE STOMACH, seen from within after removal of the mucous and submucous
layers. The anterior half of the stomach is shown, viewed from behind (Cunningham).
The stratum circulare is composed mainly of circular fibres, continuous with the more
superficial of the circular fibres at the lower end of the oesophagus (Fig. 925). They
begin as a set of U-shaped bundles which loop over the lesser curvature at the right of
STKUCTUEE OF THE STOMACH.
1175
the cardia, and pass downwards and to the left on both surfaces. Further to the right
these looped fibres are succeeded by circles which surround the organ completely. Traced
towards the narrow end of the stomach, the circular bundles grow thicker, and at the
pylorus they undergo a further, in-
crease, giving rise to the pyloric
sphincter which surrounds the orifice
as a thick muscular ring.
The fibrce obliquce, forming the
inner layer, consist of fibres which
are arranged on the fundus and ad-
jacent parts of the stomach, in much
the same manner as those of the
middle layer are on the body and
pyloric part of the organ (Fig. 926,
C). They are continuous above with
the deeper circular fibres of the in-
ferior end of the oesophagus, and form
U-shaped bundles which loop over
the stomach immediately to the left
of the cardia, and run very obliquely
i downwards and to the right for a
considerable distance on both surfaces
of the organ. These looped fibres,
as they pass to the left, gradually
become less oblique, and finally form
circles which surround the wide end
of the stomach completely, even as
far as the summit of the fundus.
The oblique fibres can be most readily
shown by removing the circular fibres
on either surface below the cardia.
When traced towards the right, they
will be found to terminate by turning
down and joining the fibres of the
circular layer.
Tela Submucosa. The sub-
mucous coat is a layer of strong but
loose connective tissue, which lies
between and unites the muscular and
mucous coats (Fig. 924). It is more
loosely attached to the muscular and
more closely to the mucous coat, and
it forms a bed in which the vessels
and nerves break up before entering
the mucous membrane.
Tunica Mucosa. If examined in
the fresh state soon after death, the
mucous coat is of a reddish -gray
colour and of moderate consistence.
When examined some time after
death, the colour turns to a darker
gray, and the whole membrane be-
comes softer and more pulpy. It is
thicker (over 2 mm.) and firmer in
the pyloric than in the cardiac part,
and is thinnest at the fundus, where it often shows signs of post-mortem digestion.
When the stomach is empty all three outer coats, which are extensile, contract ; whilst
the inextensile mucous coat, as a result of its want of elasticity, is thrown into
numerous prominent folds or rugce, which project into the interior and, as it were, occupy
the cavity of the contracted organ. These are, in general, longitudinal in direction,
ith numerous cross branches, and they are largest and most numerous along the
greater curvature. They disappear when the stomach is distended.
When the surface of the mucous coat is examined in a fresh stomach, it_is seen to
FIG. 926. THE THREE LAYERS OP THE MUSCULAR COAT OP
THE STOMACH. A, External or longitudinal layer ; B,
Middle or circular layer ; C, Internal or oblique layer.
a, Longitudinal fibres of oesophagus ; b, Superficial circular
fibres of oesophagus passing into circular fibres of stomach
in B ; c, Deep circular fibres of oesophagus passing into
oblique fibres of stomach in C ; d, Oblique fibres forming
rings at the fundus ; e, Submucosa.
1176
THE DIGESTIVE SYSTEM.
be marked out into a number of small, slightly elevated, polygonal areas, arece gastricce,
by numerous linear depressions ; the mucous membrane is consequently said to be
mamillated (Fig. 927, A). These little areas, which measure from 1 to 6 mm. in
diameter, are beset with numerous small pits, foveolce gastricce, about '2 mm. wide,
which are the mouths of the gastric glands, and they are so closely placed that the
amount of surface separating them is reduced (particularly in the pyloric portion, where
the gland mouths are widest) to a series of elevated ridges, plicae villosce, resembling
villi on section. Although the gland mouths cannot be seen with the naked eye, a very
slight magnification is sufficient to show them clearly ; it is also possible to see the
gland tubes leading off from the bottom of each (Fig. 927, B).
Minute Structure of the Mucous Coat. In structure the mucous coat consists of an
epithelial covering composed of long columnar cells, and of numerous tubular glands, glandules
gastricw, which are prolonged out-
wards from this surface, and which
are enclosed in a delicate connective
tissue stroma, with some small lymph
nodules, noduli lymphatici gastrici.
The bases of the glands reach out-
wards to the lamina mnscularis
mucosae, a layer consisting of an ex-
ternal longitudinal and an internal
circular layer of plain muscle fibres.
Glandulse Gastricae. These con-
sist of a duct terminating in one or
more secreting tubules. The duct is
lined with columnar epithelial cells,
similar to those which cover the sur-
face of the mucous membrane. Three
varieties of glands are found in dif-
ferent regions of the stomach, and
are named from their position
(1) Cardiac Glands. These
glands are situated close to the ceso-
phageal opening. The duct ter-
minates in a single long tubule,
which is lined with short columnar
granular cells.
(2) Fundus Glands. In these
glands the duct terminates in one
or more tubules, lined with poly-
hedral cells, termed the chief or cen-
tral cells. At intervals, between this
layer of cells and the basement mem-
brane, are placed larger spheroidal
Rugae
Mamillae
Mouths of
gastric glands,
with gland
tubes at
bottom
Depression
between two
mamillae
Mouth of
gastric gland ^j
FIG. 927. Mucous MEMBRANE OF THE STOMACH. A, Natural
size ; B, Magnified 25 diameters. In A the rugae and the
mamillated surface are shown. In B the gland mouths -
(foveolse gastric*), with the gland tubes leading off from some cells, which stain more deeply as a
of them, and the ridges separating the mouths (plicae villosae) rule, termed the parietal or oxyntic
are seen. cells. These glands are found in the
fundus and body of the stomach.
(3) Pyloric glands are found in the pyloric portion of the stomach. These consist of a short
duct, terminated in a group of short but tortuous gland tubules. These tubules are lined with
short columnar or polyhedral cells, similar to the central cells of the fundus glands.
Blood-vessels. The arteries of the stomach are all derived ultimately from the cceliac artery.
The gastric artery arises from this trunk direct. Having reached the lesser curvature and given off
an cesophageal branch, it divides into two large branches, which run, one on each side of the organ,
along this curvature, and join below with two similarly -disposed arteries derived from the right
gastric branch of the hepatic. From the two arches thus formed, four or five large branches pass to
each surface of the stomach, and soon pierce the muscular coat. Along the greater curvature several
smaller branches reach the stomach from the right and left gastro-epiploic arteries, which are
branches respectively of the gastro- duodenal and the splenic, and run in the gastro-colic ligament
close to its attachment to the stomach. Finally, four or five short gastric arteries, branches of the
splenic, are distributed to the fundus of the stomach, which they reach by passing forwards between
the layers of the gastro-lienal ligament. At first the arteries lie beneath the peritoneum ; very
soon, however, they pierce the muscular coat, which they supply, and, reaching the submucosa,
break up to form a close network of vessels. From these arise numerous small branches, which
enter the mucous membrane and form capillary plexuses around the glands as far as the surface.
The veins begin in the capillary plexuses around the glands ; uniting, they form a network
in the submucosa, from which arise branches that pierce the muscular coat, and finally end in
the following veins : the right gastro-epiploic, which joins the superior mesenteric ; the left gastr
epiploic, and four or five veins corresponding to the short gastric arteries, which join the splenic
the coronary vein of the stomach, which runs along the lesser curvature from left to right, and joins
INTESTINUM TENUE. 1177
the portal vein. These veins contain numerous valves which, though competent to prevent the
return of blood in the child, are rarely so in the adult.
The lymph vessels of the .stomach arise in an extensive plexus in the mucous membrane
around the gastric glands. They then join a plexus of vessels in the tela submucosa, from which
some vessels pass at intervals to join another plexus of vessels, subserous in position ; piercing
the muscular coats obliquely in their course. The efferent vessels pass mainly from the subserous
plexus, and are arranged in three main groups, which pass in different directions, and drain
three different areas of the stomach wall
One set of vessels is connected mainly with the whole of the lesser curvature, from fundus
to pylorus, and the adjacent half or two-thirds of the anterior and posterior surfaces of the
stomach. These vessels pass to the superior gastric glands, along the lesser curvature, and, in
company with the left gastric artery, to the cceliac glands.
The second set of vessels drains an area which includes the greater curvature below the
fundus, and the adjacent portions of the anterior and posterior surfaces of the stomach. These
vessels pass with the right gastro-epiploic artery to some inferior gastric glands which lie below
and behind the pylorus, and thence they pass with the hepatic artery to the coeliac glands.
The third set of vessels drains the region of the fundus. The vessels from this area pass in
the gastro-lienal ligament to the spleen, where they are connected with some splenic glands,
and pass onwards, along the superior border of the pancreas, to the coeliac glands also.
The superior and inferior gastric glands and the splenic glands are the first glands interposed
in the course of the lymph vessels. The coeliac glands form the second set.
The nerves are derived from the two vagus nerves and from the cceliac ganglia of the
sympathetic. The vagi nerves pass through the diaphragm with the oesophagus, the left
lying on its anterior, the right on its posterior aspect ; in this way they reach the anterior and
posterior surfaces of the stomach respectively. Here they unite with the sympathetic fibres from
the coeliac plexus, which pass to the stomach with the branches of the coeliac artery. The nerve
fibres, which are chiefly non-medullated, form two gangliated plexuses, those of the myenteric
plexus and the submucous plexus, in the muscular and submucous coats respectively.
The development of the stomach is described with that of the intestines on pp. 47 and 1249.
INTESTINUM TENUE.
The small intestine is the portion of the digestive tube which is placed
between the stomach and the beginning of the large intestine. It commences at
the pylorus, where it is continuous with the stomach, and ends at the valvula
coli by joining the large intestine. It occupies the greater portion of the
abdominal cavity below the liver and stomach (Fig. 913), and is found in the
umbilical, hypogastric, and both lumbar regions ; also, but to a less extent, in the
other regions of the abdomen, and in the pelvic cavity.
In length, the small intestine usually measures over 20 feet. According to
Treves, it is 22 J ft. in the male, 23 in the female, whilst Jonnesco gives the average
length at 24 ft. 7 ins., or 7J metres. In form it is cylindrical, with a diameter
varying from nearly two inches (47 mm.) in the duodenum to a little over an inch
(27 mm.) at the end of the ileum ; there is thus a gradual diminution in its size
from the pylorus to the valvula coli.
The small intestine is relatively longer in the child than in the adult ; at birth it is to the total
height of the child as 7 to 1, whilst in the adult the proportion is as 4 to 1. Notwithstanding
Treves' results, it is generally held that the small gut is relatively longer in the male than the
female.
While the former figures, 20 to 22 feet, represent the entire length of the intestine in its most
extended form, after death, when muscular tonus has disappeared, it is probable that during life
the length is not so great. The muscular coats, both longitudinal and circular, are more or less
contracted, and probably the total length during life may be estimated as 15 to 17 feet.
In formalin-hardened bodies the small bowel rarely measures more than 12 or 13 feet in
length. Similarly its diameter is often reduced in places to or inch (12 '5 to 187 mm.),
although the greater part of the gut may retain its usual width : these narrow parts have
apparently been fixed in a state of contraction.
The small intestine is divided more or less arbitrarily into three parts (Fig. 873)
namely, the duodenum, constituting the first eleven inches, distinctly marked off
from the rest by its fixation and the absence of a mesentery ; the intestinum jejunum
("empty intestine") which comprises the upper two-fifths, and the intestinum
ileum (" twisted intestine ") the lower three-fifths of the remainder. The jejunum
and ileum pass imperceptibly into one another, and the line of division drawn between
them is entirely artificial; however, if typical parts of the two namely, the
beginning of the jejunum and the end of the ileum are selected, they differ so
1178
THE DIGESTIVE SYSTEM.
much in size and in the appearance presented by their lining -mucous membrane,
that they can be distinguished from one another without difficulty.
Both the jejunum and ileum are irregularly disposed in the form of crowded
loops or coils (Fig. 913) which are connected to the posterior abdominal wall by a
great fan -shaped fold of peritoneum, containing their vessels and nerves, and
known as the mesentery. Hence the name of intestinum tenue mesenteriale is
applied to them. The mesentery is of such a length that the coils are able to move
about freely in the abdominal cavity, and consequently the position occupied by
any portion of the tube, with the exception of the beginning of the jejunum and
the ending of the ileum, can never be stated with certainty. Nevertheless, it may
be said that, in general, the jejunum occupies the superior and left portions of the
cavity below the stomach, the ileum the inferior and right divisions, its terminal
part almost always lying in the pelvis, just before it joins the large gut.
According to Mall, the most usual arrangement is to find the proximal coils of the jejunum
on the left side, and high up. Then the tube crosses the vertebral column below the duodenum,
and a few coils are placed 011 the right side. It then crosses to the left side again, and several
coils are formed, some of which may descend into the pelvis. Thence it passes again to the
Two mesenteric lymph glands
Mesentery
*./ xm FJU s>.
Lymph vessel
Peritoneal coat^B
Circular
muscular fibres
Longitudinal muscular fibres
Fia. 928. A PORTION OF SMALL INTESTINE, WITH MESENTERY AND VESSELS.
The peritoneal coat has been removed from the right half, and the two layers of the muscular coat exposed.
right side, where it is coiled up, and then finally descends into the pelvis. The terminal
portion almost always lies in the pelvis, just before it ascends to join the large intestine.
As the coats of the large and small intestine agree in many particulars, it will
be convenient to describe the general structure of the intestines here. Subsequently,
any peculiarities of structure in particular regions will be described with the corre-
sponding division of the tube.
STRUCTURE OF THE INTESTINES.
The wall of the intestines, like that of the stomach, is made up of four coats, which
are named from without inwards tunica serosa, tunica muscularis, tela submucosa, and
tunica mucosa (Figs. 928 and 929).
1. Tunica Serosa. The serous coat is formed of peritoneum, and confers on the
intestines their smooth arid glossy appearance. It varies in the extent to which it clothes
the different divisions of the tube, giving the duodenum, the ascending, descending, and
iliac colons, and the rectum only a partial covering ; whilst it clothes the jejunum and
ileum, the caecum, the transverse and the pelvic colons completely. The detailed
arrangement of this coat will be given with the description of each division of the
intestinal tube.
2. Tunica Muscularis. This consists of unstriped muscle arranged in two layers
STKUCTUKE OF THE INTESTINES.
1179
an outer stratum longitudinale, in which the fibres run longitudinally, and an inner
stratum circular e, in which they are circularly disposed. The muscular coat is thicker in
the duodenum than in any other part of the small intestine, and it gradually diminishes
in thickness until the end of the ileuin is reached. On the other hand, in the large
intestine, it is thickest in the rectum and thinner towards the beginning of the colon.
The stratum longitudinale of the muscular coat is much thinner than the underlying
stratum circulare. In the small intestine it forms a complete sheet, continuous all round
the gut (Fig. 928), but thickest at its free margin ; whilst in the large intestine it is
divided up into three longitudinal bands known as the tcenice coli, which will be more
fully described in connexion with the colon.
The stratum circulare, much thicker than the longitudinal layer, is composed of
bundles of muscular fibres arranged circularly round the tube (Fig. 929), and forming in
all parts a continuous sheet. Unlike the longitudinal fibres, those of the circular layer
take part in the formation of the valves of the pylorus and colon.
3. Tela Submucosa. The submucous coat is a loose but strong layer of areolar
tissue connecting the muscular and mucous coats, on which chiefly depends the strength
of the intestinal wall. In addition to forming a bed in which the vessels break up before
entering the mucous coat, it contains the glandulce duodenales (Brunneri) (Fig. 929); and, in
both small and large intestines, the bases of the solitary lymph nodules lie in it (Fig. 929).
4. Tunica Mucosa. The mucous membrane constitutes the inner coat of the
intestine. It is everywhere composed (Fig. 929) of the following parts : (1) A layer of
striated, columnar, epithelial cells, resting on (2) a basement membrane. Outside this
lies (3) a layer of retiform tissue, containing a considerable number of scattered lymph
cells. This layer is limited towards the tela submucosa by (4) an extremely thin sheet
of unstriped muscle, the lamina muscularis mucosae, which is not visible to the naked eye.
The mucous membrane is very vascular, particularly in the small intestine. It is thicker
in the duodenum than in the jejunum, and thicker in the jejunum than in the ileum.
Throughout both the small and large intestines the substance of the mucous membrane
is closely set with innumerable (small microscopic) tubular glands, known as the gland-
ulse intestinales
[Lieberkiihni] (O.T.
glands or follicles).
In shape they are
minute straight tubes,
like diminutive test-
tubes. Their mouths
open on the free sur-
face of the mucous
membrane : their
closed ends lie in the
deeper part of the
mucous coat, and
their cavities are lined
with columnar epi-
thelium. They open
on the surface be-
tween the bases of
the villi of the small
intestine, and in the
large gut their orifices
are found all over the
surface of the non-
villous mucous mem-
brane.
Submucosa
Circular,
muscular fibres
Longitudinal, ;
muscular fibres
Peritoneum
Lieberkiihn's
gland
Submucosa -
Circular_
muscular fibres
Longitudinal
muscular fibres""
Peritoneum -
Villi
_ Lieberkiihn's
gland
Muscularis
mucosae
Brunner's
glands
Circular
muscular fibres
Longitudinal
muscular fibres
Peritoneum
Villi
Blood-vessels
forming net-
work in sub-
mucosa
. Blood-vessel
SMM.U INTESTI
. . FIG. 929. DIAGRAM to show the structure of the large intestiue, the duodenum,
Certain Special and the jejunum.
developments of the
mucous coat, found in particular regions of the intestinal tube, must next be con-
sidered : these are the (1) villi intestinales ; (2) plicae circulares [Kerkringi] (O.T.
valvulse conniventes) ; (3) noduli lymphatici solitarii (O.T. solitary glands) ; and (4)
noduli lymphatici aggregati [Peyeri] (O.T. Peyer's patches).
Villi Intestinales. If the mucous membrane of any part of the small .in-
1180
THE DIGESTIVE SYSTEM.
testine is examined, it is seen to present a soft, velvety, or fleecy appearance
(Fig. 930, B); this is due to the presence of an enormous number of minute
processes, known as villi, which cover its surface.
They are minute cylindrical or finger-like projections of the tunica mucosa
(Fig. 929) about
^th or ^th of
an inch (1/2 to
1'6 mm.) in height,
and barely visible
to the naked eye,
which are closely
set all over the
surface of the
lining membrane
of the small in-
testine. Begin-
ning at the edge
of the pyloric
valve, they are
broad but short
in the duodenum,
and grow nar-
rower as they are
followed down
through the in-
testine to the
valvula coli, at
the edge of which
FIG. 930. PLIC.E CIROULARES (natural size).
A, as seen in a portion of jejunum which has been filled with alcohol and hardened
B, a portion of fresh intestine spread out under water.
they cease. They are found, not only on the general surface of the mucous mem-
brane, but also upon the plicae circulares, and, while they are not present over
the solitary lymph nodules, they are found in the intervals between the individual
nodules of the aggregated nodules.
They play an important part in the absorption of the products of digestion
which takes place in the small intestine.
Plicae Circulares [Kerkringi]. When the intestine is empty and contracted,
its mucous membrane is thrown into effaceable folds or rugae, which disappear
on distension. But in addition to these, there are found in certain portions of
the small intestine a series of large, permanent transverse folds, which are not
effaceable ; these are known as plicae circulares (Fig. 930). These are usually more
or less crescentic in shape, and resemble a series of closely placed shelves running
transversely around the gut. They rarely form more than two-thirds of a circle ;
sometimes, however, they present a circular or even a spiral arrangement, the spiral
extending little more than once round the tube, as a rule. Occasionally they
bifurcate at one or both ends ; sometimes, too, short irregularly directed branches
pass off from them. They are usually about 2 to 3 inches (5 to 7*5 cm.) in length,
and their breadth, that is their projection into the cavity, may be as much as Jrd
of an inch (8 mm.), whilst in thickness, as seen when cut across, they measure about
|th inch (3 mm.).
They are composed of two layers of the tunica mucosa, with a prolongation
from the tela submucosa between, to bind the two together. They are covered with
villi, and are permeated by intestinal glands. Their use is to increase the amount
of surface available for secretion and absorption.
Plicae circulares are not found in the upper part of the duodenum. They begin
at a distance varying' from 1 to 2 inches (2*5 to 5 cm.) from the pylorus. At first
they are small, irregular, and scattered ; but they are larger lower down, and at the
opening of the bile duct (4 inches from the pylorus) they are distinct and prominent.
In the rest of the duodenum, and in the superior half of the jejunum, they are highly
developed, being large, broad, and closely set. In the inferior half of the jejunum
they become gradually smaller and fewer. Passing down into the ileum, they
STKUCTUKE OF THE INTESTINES.
1181
become still smaller and more irregular, and, as a rule, they practically cease a
little below the middle of the ileum.
Often patches of plicae circulares, much reduced in size, can be traced to within a short dis-
tance of the valvula coli. According to Sappey, Luschka, and others, they usually reach to
within two or three feet of the end of the ileum.
Aggregated lymph
nodule
Noduli Lymphatic! Solitarii. The solitary lymph nodules are minute masses of
lymph tissue, opaque and of a whitish colour, found
projecting on the surface of the mucous membrane TWO solitary glands
throughout the whole length of both the small and
large intestines.
Isolated lymph cells are found in abundance
scattered through the connective- tissue layer of the
intestinal mucous membrane generally; in places
these cells are gathered together to form little nodules,
supported by a framework of retiform tissue, and sur-
rounded by a lymph space which communicates below
with the lymph vessels of the tela submucosa. Such a
collection of lymph cells constitutes a solitary nodule.
They are usually of a rounded or oval shape (Fig. 931),
the wide end resting in the tela submucosa, the nodule
itself piercing the lamina muscularis mucosse, and the
narrow end projecting slightly above the general sur-
face of the mucous membrane. In size they vary from
T ^th to Jth of an inch (*6 to 3'0 mm.), but their
average bulk is about that of a small grain of sago, to
which they bear some resemblance.
As already mentioned, they are present throughout
the small and large intestines, being particularly
abundant in the vermiform process and the caecum. In
the small intestine they are found on the plicae cir-
culares, as well as upon the general surface of the solitary gland
mucous membrane between them.
Noduli Lymphatici Aggregati. These lymph nodules
(O.T. Peyer's patches) consist of a large number of
minute lymph nodules grouped closely together so as
to form a slightly elevated area, usually of an oblong
form, on the surface of the mucous membrane (Fig.
931). In length they vary from half an inch (12
mm.), or less, to three or four inches (100 mm.), and
in width they commonly measure from a third to half an inch (8 to 12 mm.).
Their number is variable, buti in the average condition about 30 or 40 are found.
They are best marked in young subjects, where they form considerable elevations
above the general surface, and may be as many as 45 in number. After middle
life they atrophy, and in old age, although usually present, they are indis-
tinct, occasionally being marked by little more than a dark discoloration of the
mucous membrane. They are invariably situated along the surface of the intestine
opposite the line of mesenteric attachment, with their long axis corresponding to
that of the bowel. Consequently, in order to display them, the tube must be slit
up along its attached or mesenteric border.
These aggregated nodules are entirely confined to the small intestine, being
largest and most numerous in the ileum, particularly in its inferior part, where
they usually assume an oblong shape; in the inferior half of the jejunum they
are small, circular, and few in number ; in its superior part they are rare ; and,
although their presence has been noted in the inferior portion of the duodenum,
they may be said to be absent, as a general rule, from this division of the intestine.
Intermediate form
FIG. 931. NODULI LTMPHATICI
AGGREGATI and SOLITAEII,
from intestine of child two years
old (natural size).
Near the lower border are seen a
few small patches made up of
two or three lymph nodules ;
they are marked " intermediate
form."
The plicae circulares stop at the margins of the
across them ; but villi are found on the surface of
the individual lymph nodules.
nodules, and are not continued
nodules, in the intervals between
1182 THE DIGESTIVE SYSTEM.
The chief bowel lesion in typhoid fever is found in these aggregated and in the solitary
nodules.
When the surface of one of these nodules from a child's intestine (in which these structures
are particularly well developed) is carefully examined, it is seen to be made up, not of a series
of separate, rounded nodules grouped together, but rather of a number of wavy, irregular, and
branching ridges connected with one another by cross branches (Fig. 981), the whole recalling
in miniature the appearance of a raised map of a very mountainous district in which the
chief chains run irregular courses, and are joined to one another by connecting ridges.
Small patches, intermediate in form between solitary and aggregated nodules, and consist-
ing of two or three lymph nodules, are also usually present.
DUODENUM.
The duodenum, the portion of the digestive tube which immediately succeeds
the stomach, is the first part of the small intestine, and differs from the rest of
that tube in having no mesentery, and hence it is closely fixed to the posterior
abdominal wall. The ducts of the liver and pancreas open into it, and
some special glands are found in its wall, known as the duodenal glands of
Brunner.
Shape and Divisions. The duodenum begins at the pylorus, about the level
of the first lumbar vertebra, and ends at the left side of the first or second lumbar
vertebra (Fig. 932). Between those two points it pursues an irregular course,
which has some resemblance to the outline of a horse-shoe. It is made up of
three main parts, namely : (1) The pars superior, which begins at the pylorus,
passes posteriorly and to the right beneath the liver, and ends at the neck of
the gall-bladder by turning down, forming the flexura superior, and joining
(2) the pars descendens. This begins at the neck of the gall-bladder, runs down
on the posterior abdominal wall, on the right of the vertebral column, behind the
transverse colon (Fig. 932), and ends opposite the third or fourth lumbar vertebra.
There it turns to the left, and passes into (3) the pars inferior. This portion at
first runs more or less transversely to the left, across the vena cava, aorta, and
vertebral column (pars horizontalis), and then ascends as far as the inferior surface
of the pancreas (pars ascendens). There, at the level of the first or second
lumbar vertebra, it bends abruptly forwards, forming the duodeno-jejunal flexure
(Fig. 932), and passes into the jejunum. The junction of the pars descendens and
pars inferior constitutes the flexura inferior.
Taking the whole of the duodenum together, it forms an irregular horseshoe-
shaped curve, with the opening directed upwards and to the left, and the ends
reaching to within about two inches of one another. Within the concavity of
the curve the head of the pancreas is placed.
The incomplete ring which the duodenum makes does not all lie in the same
plane ; for, whilst its greater part is placed in a frontal plane, the superior part,
and the commencement and termination of the inferior part, lie more in a sagittal
plane (Fig. 932).
Position and Size. As a rule, a little more than half of the duodenum lies
in the epigastrium ; the remainder namely, about the inferior third of the descend-
ing portion and the adjoining two-thirds of the inferior portion are placed in the
umbilical region. With the exception of the terminal ascending portion of the
third part, the whole of the duodenum lies to the right of the median plane.
Its length is usually about 11 inches (27*5 cm.), its first portion being the shortest
and its third portion the longest. Its diameter varies considerably, and may be
stated to average about 1 J inches when empty, but it may be as much as two
inches when distended.
Relations. Pars Superior. The superior part (O.T. first portion) begins at the
pylorus, opposite the first lumbar vertebra. From there it runs to the right, and
then posteriorly, beneath the liver, when the stomach is empty, but directly back-
wards when it is full; and ends at the neck of the gall-bladder by turning downwards
and passing into the descending part. Its length varies from about 1J to 2 inches
(3*7 to 5*0 cm.), and is said to be greater when the stomach is empty than when
distended.
THE DUODENUM.
1183
Its relations are as follows : It forms the inferior boundary of the foramen epiploicum, and,
above that foramen, it is in relation to the caudate process of the liver, while the quadrate lobe
of the liver hangs downwards over it and to the right. The hepatic artery is in contact for a
short distance with the superior border. Below, it rests on the head and neck of the pancreas.
The portal vein, gastro-duodenal artery, and the bile-duct lie in contact with it on the left
Aorta
Fossa for caudate lobe
Right Inferior phrenic vesse
Inferior Vena cava
Hepatic vein
Hepatic artery
Portal veii^
Pylorus
Bile-duct
Right supra-renal gland
phagus
ft gastric artery
iaphragra
Left supra-renal gland
Splenic artery
Kidney
Anterior surface of pancreas
Gastric surface of spleen
Head of
pancreas
Superior
mesenteric
vein
Ureter
Inferior mesen-
teric artery
Internal sper-
matic vein
Ureter
Right common iliac,-
vein
Right common iliac
artery
Left common iliac
vein
ferior surface
of pancreas
Attachment of
transverse
mesocolon
uodeno-
jejunal flexure
Gastro-duodenal
artery and neck
of pancreas
^Superior mesen-
teric artery
Duodeimii
Colon
FIG. 932. THE VISCERA AND VESSELS ON THE POSTERIOR ABDOMINAL WALL.
The stomach, liver, and most of the intestines have been removed. The peritoneum has been preserved on the
right kidney, and the fossa for the caudate lobe. When the liver was taken out, the vena cava was left
behind. The stomach bed is well shown. (From a body hardened by injection of chromic acid. )
side, and behind them the duodenum comes into contact with the right aspect of the inferior
vena cava. The superior pancreatico-duodenal and the right gastro-epiploic vessels pass forwards
below its inferior margin.
Its peritoneal relations are similar to those of the pyloric end of the stomach for about an
inch. It is therefore at first invested by peritoneum on the right and left aspects, and the
peritoneum passes upwards from its superior border as the right portion of the lesser omentum,
forming the hepato -duodenal ligament, while from its inferior border the descending folds of the
1184
THE DIGESTIVE SYSTEM.
peritoneum pass downwards. The peritoneum is reflected from off the left surface on to the
pancreas and abdominal wall, and forms a fold known as the right gastro-pancreatic fold, while
the peritoneal covering of the right side is continued onwards along the whole of this part
of the duodenum.
Pars Descendens. The descending part (O.T. second portion) begins at the neck
of the gall-bladder, passes down behind the transverse colon, and ends at the right
side of the third or fourth lumbar vertebra. In length it measures 3J or 4 inches
(8-7 to 10 cm.).
Its relations are as follows : It lies on the right of the vertebral column and the interior
vena cava, from the first to the third or fourth lumbar vertebra, and is anterior to the pelvis
Top of omental bursa
Inferior vena cava
Lesser omentum (cut)
Right triangular
ligament of liver
Left triangular ligament of liver
I CEsophageal opening in diaphragm
/ Gastro-phrenic ligament
/ / Corresponds to ' uncovered area of stomacV
Gastro-splenic ligament (cut)
Transverse colon crossing duodenum
Head of pancreas
Gastro-colic ligament (cut)
Part of omental bursa
Phrenico-colic ligament
Left end of transverse mesocolon
Left colic flexure
Transverse mesocolon (cut)
Root of mesentery (cut)
FIG. 933. THE PERITONEAL RELATIONS OF THE DUODENUM, PANCREAS, SPLEEN, KIDNEYS, ETC.
From a body hardened by injections of formalin. When the liver, stomach and intestines were removed the
lines of the peritoneal reflections were carefully preserved. The peritoneum is coloured blue.
of the right kidney, the right renal vessels, and ureter, and also, to a varying extent, the front of
the right kidney itself; while, below the level of those structures, it rests upon the psoas major
muscle.
The lateral aspect is in contact with the sloping inferior surfaces of the liver in its superior
part, and with the right flexure of the colon below.
Peritoneal Relations. The anterior aspect is covered by peritoneum, except about its middle,
where the root of the transverse mesocolon crosses the duodenum. Not infrequently, the
transverse colon has no mesentery, but is itself in direct contact with the wall of the duodenum.
In other cases, the colon is in contact with the peritoneal surface of the duodenum, below the
line of reflection of the transverse mesocolon.
The head of the pancreas is in contact with its concave left margin, and occasionally overlaps
it anteriorly and posteriorly ; and along the margin of the pancreas, both anteriorly and pos-
teriorly, are branches of the superior and inferior pancreatico-duodenal vessels, the veins often
forming a dense network on the posterior aspect.
THE DUODENUM.
1185
The bile-duct, after passing down behind the- superior part of the duodenum, descends between
the head of the pancreas and the descending part, nearly as far as its middle ; there it is joined
by the pancreatic duct, and the two, piercing the wall of the duodenum obliquely, open by a
common orifice on its inner aspect, about 3 to 4 inches (87 to 10 cm.) beyond the pylorus.
Pars Inferior. The inferior part (O.T. third portion) begins at the right side of
the third or fourth lumbar vertebra. It is described in two parts, fars horizontals,
transverse in direction, and pars ascendens', and it shows that arrangement in
Fig. 933.
The pars horizontalis runs more or less transversely to the left across the inferior vena cava
(Fig. 933) for one or two inches, and the pars ascendens passes very obliquely, or even vertically,
upwards in front of the aorta and left psoas major muscle. Finally, having reached the inferior
surface of the pancreas, it bends forwards, and passes into the jejunum.
Anteriorly, it is crossed (about the junction of its two divisions) by the superior mesenteric
vessels, and also by the root of the mesentery (Fig. 933). On each side of this it is covered by
coils of small intestine. Posteriorly, the pars horizontalis lies across the vena cava inferior ; the pars
ascendens lies on the aorta, the left renal vein and occasionally also the artery, and the left psoas
major muscle, all of which separate it from the vertebral column, Above, it is closely applied in
its whole extent to the head of the pancreas. The left side of the pars ascendens, which is free,
lies in contact with some coils of the small intestine.
Peritoneal Relations. The inferior part of the duodenum is covered by peritoneum on its
anterior surface throughout, except where it is crossed by the superior mesenteric vessels and the
root of the mesentery, which contains these vessels (Fig. 933). In addition, its ascending part
is also clothed by this membrane on its left side.
The attachment of the root of the mesentery begins, above, quite close to the duodeno-jejunal
flexure, on the front of the duodenum ; thence it runs down on the anterior aspect of the
ascending part, and finally leaves the duodenum about the union of the two divisions of its third
portion.
Duodenal Fossae. In the neighbourhood of the pars ascendens are found three
well-known fossse of the peritoneum which are of some surgical interest ; they are the
superior and inferior duodenal and the paraduodenal fossse (Fig. 934). Other rarer forms
are occasionally present.
When the ascending part of the duodenum is drawn over to the right, and the
angle between its left side and the posterior abdominal wall is examined, one or two
triangular folds of peritoneum
Transverse colon.
will generally be found cross-
ing over that angle from the
duodenum to the abdominal
wall. Each fold has one edge
attached to the duodenum,
another to the parietal peri-
toneum at the left of the
duodenum, whilst the third is
free, and bounds the opening
of a small pouch which lies
behind the fold, the recessus
duodeno -jejunalis. Of these
folds, the upper is termed the
plica duodeno-jejunalis, and it
is situated near the termina-
tion of the duodenum, with its
apex directed up and its free
margin down. It sometimes FIG. 934. THE DUODENAL Foss^ AND FOLDS.
contains between its two layers The transverse colon and mesocolon have been thrown up, and the
the termination of the inferior mesentery has been turned to the right and cut. The paraduodenal
mesenteric vein. Behind it fossa < of Landzert ) is situated to the medial side of the inferior
lies a prolongation from the
recessus duodeno-jejunalis
termed the superior duodenal fossa. Its opening looks downwards, and will usually
admit the tip of a finger (Fig. 934). The second, known as the plica duodeno-mesocolica,
is placed lower down, at the side of the same part of the duodenum. Its free border is
directed upwards, as is the mouth of the inferior duodenal fossa, which lies behind it.
This latter is larger and more constant than the superior duodenal fossa, and is present
in 75 per cent, of bodies, whilst the superior is present in 50 per cent. (Jonnesco).
Paraduodenal Fossa (fossa of Landzert). This fossa, which is seen best in the
76
Transverse meso-
colon
Duodenum
3rior
duodenal' fossa
Inferior
duodenal fossa
The mesentery (cut)
Inferior mesenteric vein
Left colic artery
mesenteric vein, between it and the terminal part of the duodenum.
It is not shown in the illustration.
1186 THE DIGESTIVE SYSTEM.
infant, is placed some distance to the left of the ascending part of the duodenum. It is
produced by the inferior mesenteric vein raising up a fold of peritoneum, as it runs
medially along the side of the fossa, and then above it (see Fig. 934, where the vein, but
not the fossa, is shown). It is limited below by a special fold (the mesenterico-meso-
colic fold). According to Moynihan, this is the
only fossa to the left of the duodenum capable
of developing into the sac of a hernia ; and
when this occurs, the inferior mesenteric vein
always lies in the anterior margin of the orifice
Duodenal of tlie sac (accompanied for some distance by
papilla the ascending branch of the left colic artery).
-Common open-
'ancreaticduct Peritoneal Relations of the Duodenum. Whilst
^puJaSnAtiidi- t ^ ie re l at> i ns of the peritoneum to the second and
nalis duodeni third portions of the duodenum are usually described
as in the foregoing account, it should perhaps be
pointed out, that it is not really the front, but the
right half of the circumference of the descending
portion which has a serous coat. Similarly, it is
the inferior and anterior half of the circumference
FIG. 935. THE PAPILLA DUODENI IN THE of the horizontal portion of the inferior part which
INTERIOR OP THE DUODENUM. is clothed by peritoneum, whilst considerably more
than half of the circumference of its ascending
portion is covered ; for the peritoneum forms a fold running in behind this portion, in addition
to covering its left side and half its anterior aspect.
Interior of Duodenum. No plicae circulares are found in the duodenum for
an inch or two beyond the pylorus. They then begin ; at first as low, scattered,
and irregular folds ; further down, they gradually become larger, more regular
and more numerous ; and by the time the middle of the descending part is
reached they have attained a considerable development. In the inferior part of the
duodenum the folds are large, prominent, and closely set.
On the inner aspect of the descending portion, about its middle namely, 3J
or 4 inches (8'7 to 10 cm.) beyond the pylorus is seen a prominent papilla, on
which the bile and pancreatic ducts open by a common orifice (Fig. 935). This is
known as the papilla duodeni (Santorini).
The papilla duodeni is placed beneath, and protected by, a prominent, hood-like plica circu-
laris, which is situated immediately above it. From its lower margin a firm ridge of the
mucous membrane, the plica longitudinalis duodeni^ descends for a considerable distance, and
acts as a frenum, which fixes the papilla and directs its apex somewhat downwards (Fig. 935).
The papilla is prominent, and nipple or dome-shaped, and at its summit is placed the small
orifice, which will usually admit the point of a pencil ; the whole bears a close resemblance to
the nozzle of a perfume-spray.
Nearly an inch higher up, and invariably on the ventral side of the papilla (sometimes as
much as a -^ to f inch distant), is seen a second and smaller papilla, the caruncula minor of
Santorini, at the point of which is placed the very small orifice of the accessory pancreatic
duct. This second papilla seems to be constantly present, although sometimes so small that it
may easily escape detection unless carefully sought for. When well developed, it may have a
hood -like plica circularis and a little frenulum, like those of the bile papilla.
Structure of the Duodenum. The tunica serosa, which is incomplete, has already
been described in detail, in connexion with each part of the duodenum.
The tunica muscularis is well developed, and is pierced by the bile and pancreatic
ducts, but otherwise calls for no special description.
The tela submucosa diners from that of the rest of the small intestine, in that it
contains, especially in the superior half of the duodenum, the glandulse duodenales
[Brunneri]. These are small acino-tubular glands, closely resembling the pyloric glands
of the stomach; they lie in the submucous coat, and send their ducts through the
muscularis mucosse to open on the surface between the glandulse intestinales, or sometimes
into these glands themselves (Fig. 929). They can be exposed by the removal of the peritoneal
and muscular coats, and also some of the submucosa, when they appear as little round
or flattened masses of a reddish-gray colour, varying in size from -g^th to -^-th of an inch
in diameter ( - 5 to 2'0 mm.). They form an almost continuous layer as far as the opening
of the bile duct ; beyond this they diminish progressively, and completely disappear near
the duodeno-jejunal flexure.
The tunica mucosa, which is thicker in the duodenum than in any other part of
the small intestine, is covered throughout with broad, short villi.
THE LIVER 1187
Various Forms of Duodenum. Three different types of duodenum have been described
(1) The annular, in which the curves separating the various parts are open, and the two
extremities come fairly close to one another. (2) The U-shaped, in which the horizontal part of
the inferior part is very long, and the ascending part is nearly vertical; and (3) the V-shaped
duodenum, in which the horizontal portion of the inferior part is very short or absent.
Vessels and Nerves. The duodenum receives its blood from the superior and inferior
pancreatico-duodenal arteries, branches of the gastro -duodenal and superior meseriteric arteries
respectively. The blood is returned by the corresponding veins, the superior of which opens into
the superior mesenteric, and the inferior into the beginning of the portal vein.
The lymph vessels of the duodenum follow for the most part the course of the blood-vessels.
From the anterior surface, lymph vessels pass along the course of the inferior pancreatico-
duodenal artery, and communicate with lymph glands found along the course of that vessel.
Thence they pass to the inferior cceliac glands, beside the origin of the superior mesenteric artery.
The vessels from the posterior aspect accompany the superior pancreatico-duodenal artery,
communicate with the inferior gastric glands, and terminate in the cceliac glands.
The nerves come from the cceliac plexus of the sympathetic.
Flexura Duodenojejunalis. When the ascending part of the duodenum
reaches the inferior surface of the pancreas, at a point opposite the left side of
the first or second lumbar vertebra, it turns abruptly forwards, downwards, and
to the left, and passes into the jejunum. This abrupt bend is known as the
duodeno-jejunal flexure. Unlike the rest of the duodenum, which is subject to
considerable variations in position in different individuals, the duodeno-jejunal
flexure is fixed by a thin band of unstriped muscle, which is attached above to the
strong connective tissue around the cceliac artery, as well as to the left crus of the
diaphragm. This band passes posterior to the pancreas, and inferiorly it joins the
muscular coat of the duodenum at the flexure. It is known as the m. suspensorius
duodeni (O.T. muscle of Treitz).
The duodeno-jejunal flexure is occasionally directed to the right, and it lies at
a variable distance from the root of the transverse mesocolon. When the attach-
ment of the transverse mesocolon is low, the duodeno-jejunal flexure is in contact
with it.
Duodenal Pouches or Diverticula. Occasional diverticula are found passing from the
duodenal wall in different directions. Such diverticula may be hernial protrusions of the
mucous and submucous coats through the muscular wall, termed false diverticula, or they may
be " true " diverticula, in which all the coats are represented.
They are usually situated on the aspect of the duodenum which is in contact with the pancreas,
and frequently in the neighbourhood of the orifice of the bile duct.
Some of these appear to be due to the pressure from the interior of the duodenum, while
others, and the majority of the true diverticula, are rather congenital in origin, and are
possibly associated with the diverticula which give rise to the liver and pancreas.
HEPAR
The liver is the large glandular organ which secretes the fluid called bile
(fel). It occupies the superior and mainly the right portion of the abdominal cavity,
and lies immediately below the diaphragm.
Its secretion is conveyed away from it by the hepatic ducts and the bile-duct to
the duodenum. With the bile duct there is connected a pear-shaped diverticulum,
the gall-bladder (vesica fellea), which lies -in contact with the liver, and which
serves apparently for the temporary storage of bile.
In addition to secreting bile, the liver plays an important part in the
metabolism of both the carbohydrate and nitrogenous materials absorbed from the
intestine which are conveyed to it by the portal vein, and it also has to do with
the production and the destruction of some of the blood-cells.
Physical Characters. The liver is a large irregularly shaped mass, of a
reddish-brown colour, soft and pliant to the touch, somewhat readily lacerated, and
highly vascular.
It is of uniform consistence throughout, and little of its internal structure can
be made out by naked-eye examination. If, however, a torn surface is examined,
the liver tissue is seen to be somewhat granular. Under the investing peritoneum
the surface is somewhat mottled.
This mottled or granular appearance is due to the lobules (lobuli hepatis) of
76 a
1188 THE DIGESTIVE SYSTEM.
which the liver is composed. Each lobule is a small irregular or polygonal
area, measuring from ^V^h to rV tn f an i ncn i n diameter, or 1 to 2 mm., with a
partial covering of line connective tissue, forming a delicate stroma.
In the adult, the liver weighs from 3 to 3J pounds, or about ^_th of the body
weight, and it is somewhat heavier in the male than in the female, its weight in
the former being from 50 to 55 ounces and in the latter 43 to 48 ounces. The
ratio to the body weight is the same in both sexes. In the foetus and child it
is relatively very large and heavy. At birth it occupies the greater part of the
abdominal cavity, and constitutes from -^th to T Vth of the body weight. In the
young foetus the ratio is even larger.
The average size of the liver may be briefly expressed as follows : It measures in the trans-
verse direction about seven inches (17*5 cm.) ; in the vertical, six to seven inches (15 to 17*5 cm.) ;
and in the antero-posterior, on the right side where greatest, about six inches (15 cm.). Its
Vena cava inferior
Lig. coronarium hepatis
Bare area
ulare sinistrum
Lig. falciforme hepatis
Lig. teres hepatis
~~ Fund us vesicse felleee
FIG. 936. LIVER VIEWED FROM THE FRONT.
greatest width, measured obliquely from side to side along the inferior or visceral surface, is ten
inches (25 cm.).
The liver is capable of being greatly distended by fluid forced into its blood-vessels. Its
surface then becomes tense, and the consistence of the whole organ becomes much firmer.
Shape. If the liver is hardened in situ and then removed from the body, it
will be found to present a form which is fairly constant, but which is modified
by the shape and size of the adjacent viscera, and hence shows minor variations
in different individuals.
If the liver has not been hardened, it does not retain, after removal, the shape
and form which it had when it lay in the abdomen, but tends to collapse into
a flattened cake-like mass.
The description of the shape, surfaces, and borders given below is drawn from
examination of specimens hardened in situ.
The liver possesses three principal surfaces, a superior, a posterior and an
inferior or visceral.
The fades superior is in contact chiefly with the rounded vault of the abdominal
cavity, and hence it is uniformly rounded and convex.
The fades posterior, directed backwards, is in contact with the structures
THE LIVER 1189
forming the superior portion of the posterior abdominal wall. It is deeply indented
by the projecting vertebral column, and it is nearly flat in the vertical axis.
The fades inferior is directed obliquely downwards and posteriorly, is in contact
with a number of the abdominal viscera, especially the right kidney, stomach,
duodenum, and colon, and its general configuration is influenced to a marked
degree by the shape and position of these organs.
This surface is sometimes termed the visceral, in contrast to the other sur-
faces, which constitute the parietal surface of the organ.
The parietal and visceral surfaces are marked off from one another by the
inferior margin of the liver. Posteriorly, this margin is indistinctly marked and
corresponds to the inferior edge of the posterior area, or back, of the parietal
surface : it is in contact with the right kidney, and lies along the course of the
eleventh rib. At the right side the margin is stout but distinct, and usually
corresponds to, or projects a little way below, the inferior border of the thoracic
Bare area
Lig. teres ""
A. hepatica propria
Vena portae
Ductus choledochu
Lobus quadratus
Vesica feilea
Fossa for gl. suprarenalis
Impressio reualis
Lig. triangulare dextrumX
FIG. 937. THE LIVER VIEWED FROM BEHIND.
framework. Anteriorly, the border is thin and sharp, and passes obliquely upwards
from the right to the left side behind the anterior abdominal wall. This portion
forms the margo anterior. Its direction corresponds to a line drawn from a point
half an inch (12 mm.) below the margin of the ribs (tip of tenth costal cartilage)
on the right side to a point an inch below the nipple on the left. It extends down
in the median plane to a point half-way between the body of the sternum and the
umbilicus. This portion of the lower border usually, but not invariably, presents
one or two notches. The incisura umbilicalis, the more constant of the two
(Fig. 936), is situated at the anterior end of a cleft on the inferior surface, known
as the fossa sagittalis sinistra (see p. 1191), and corresponds to the upper part of
the ligament um teres hepatis. It is usually placed from one to two inches (2*5
to 5'0 cm.) to the right of the median plane. The second notch, less frequently
mt, corresponds to the fundus of the gall-bladder, and is called the incisura
fellese.
At its left extremity the margo anterior turns posteriorly round the edge of
left lobe, and ends at a groove on the posterior surface, termed the impressio
>phagea, in which the oesophagus lies.
1190 THE DIGESTIVE SYSTEM.
The division between the superior surface and the posterior surface is not
marked by a border of any prominence, but by an indefinite margin which runs
transversely from side to side.
The superior surface may be further divided into three areas, a superior, an
anterior, and a right, following the general direction of these portions of the
surface, but they are not clearly marked off from one another by borders.
Their arrangement is as follows :
The superior area of the superior surface lies in contact with the roof of the abdomen ; it is
convex on each side, and depressed near the median plane. The two convexities, of which the
right is the more prominent, fit into the two cupolae of the diaphragm ; whilst the central
depression, depressio cardiaca; corresponds to the position of the heart. The superior area (with the
exception of a small triangle at its posterior part, between the separating layers of the ligamentum
falciform e) is completely covered by peritoneum, and on it the division of the liver into right
and left lobes is indicated by the attachment of the ligamentuni falciforme.
The anterior area of the superior surface is triangular in shape, and after death is usually
flattened, owing to the falling in of the anterior abdominal wall. In part it lies in contact with
the diaphragm, which separates it from the rib-cartilages on each side, but at the subcostal
triangle it comes into direct relation with the anterior wall of the abdomen, for a distance
usually of two or three inches below the xiphi-sternal articulation. It has a complete peritoneal
covering, and gives attachment, as far down as the umbilical notch at the inferior border, to the
ligamentuni falciforme, which connects it to the anterior abdominal wall.
The anterior passes gradually into the upper and right areas, but it is distinctly separated
from the visceral surface by the sharp margo anterior of the organ. The umbilical notch is
often continued upwards for some distance on the surface as a slit-like fissure.
The right area of the superior surface is convex and extensive, and lies in contact with the
diaphragm, which separates it from the inner surface of the lower ribs, and also, above, from the
inferior margin of the lung and pleura. Though sharply marked off by the inferior margin from
the visceral surface, it passes without distinct limits into the other areas of the parietal surface.
It is completely covered by peritoneum.
The superior surface is smooth and shows no fissures, but the line of attachment of the
ligamentum falciforme is taken as dividing the liver on this surface into a right and a left lobe.
Upon the posterior surface and inferior surface there are several clefts or depressions upon
the surface of the liver, termed fossae or fissures, which further subdivide the surfaces into lobes.
These fossae, it should be noted, do not indicate any deep division of the liver into separate
parts, but are only indentations upon the surface.
Porta Hepatis. (1) The gate of the liver (O.T. portal or transverse fissure) is the
equivalent in the liver of the hilum of other glands. It is a slit-like depression,
where the vessels enter the gland, and whence the ducts emerge.
It is placed on the inferior surface, runs transversely from right to left, and
measures about 2 to 2J inches in length. It is bounded anteriorly and posteriorly
by prominent margins, and through it the hepatic artery, vena portse, and hepatic
plexus of nerves enter the liver, and the hepatic ducts and many of the lymph
vessels leave. To the anterior and posterior margins of the fissure are attached
layers of peritoneum which constitute part of the lesser omentum.
The various structures found in the porta hepatis are arranged in the following
way. The vena portse lies posteriorly, and divides, in the fissure, into right and
left branches, which run to right and left. The neck of the gall-bladder, with the
cystic duct coming from it, lies at the right extremity of the fissure, and there the
cystic duct bends downwards between the layers of the hepato-duodenal ligament.
The right and left bile ducts lie at their respective ends of the porta hepatis,
and converge towards each other at the right extremity and lie anterior to the
corresponding branches of the hepatic artery, and to the right side of the main
vessel at their junction in the hepato-duodenal ligament. The nerves mainly
invest the arteries, and the lymph vessels lie in the connective tissue which invests
all these structures.
Two or three lymph glands are occasionally found in the porta hepatis, especially
at the right end, near the neck of the gall-bladder, and when enlarged, they may
press upon the ducts, and interfere with the passage of the bile.
The intervals between the vessels and other structures are filled in by loose
connective tissue, which is continued inwards with the vessels as the fibrous capsule
of Glisson.
When the porta hepatis is opened up, it is found to extend on the left as far as
to the fossa vense umbilicalis.
THE LIVEK. 1191
(2) Fossa Venae Umbilicalis (O.T. Umbilical Fissure). The fossa for the umbilical
vein is a deep crevice-like fissure, situated in the inferior surface, running from
before backwards, parallel to the gall-bladder, but about 1 to 1J inches to its left
side. It begins in front at the margo anterior, which it intersects, and runs
backwards to the left extremity of the porta hepatis. Within this fissure lies a
rounded cord-like structure, the ligamentum teres hepatis, the remains of the left
umbilical vein of the foetus. The fissure is often crossed by a bridge of liver tissue,
the pons hepatis, which may even extend for the whole length of the fissure, and
conceal the round ligament from view.
(3) Fossa Ductus Venosi. At the posterior termination of the fossa venae
umbilicalis the ligamentum teres is usually attached to the left branch of the portal
vein. Beyond that point it is continued backwards as a fine fibrous band, the
ligamentum venosum (Arantii), which runs onwards to join the vena cava inferior.
This fibrous cord is the remains of the ductus venosus, and it lies in a groove on
the posterior aspect of the liver, called the fossa for the ductus venosus.
The umbilical vein and the ductus venosus in the foetus serve to convey the
blood back from the placenta to the inferior vena cava.
The umbilical fossa and the fossa for the ductus venosus together form a
continuous fossa on the inferior and posterior surfaces which divides them into
a right and left lobe. This fossa is known as the fossa sagittalis sinistra, in
contrast to the porta hepatis, and to the fossa sagittalis dextra, lying to the right
of two fossae which is made up of the following two fossae :
(4) Fossa Vesicse Fellese. The fossa for the gall-bladder is a slight depression
which begins (often as a notch) at or near the margo anterior of the liver,
and runs backwards and to the left, as far as the porta hepatis (Fig. 938).
Its surface is, as a rule, not covered by peritoneum, and in it lies the gall-bladder,
which is united to it by areolar tissue.
(5) Fossa Venae Cavae. The fossa for the vena cava is a deep groove, on the
posterior surface, on the right side of the caudate lobe, in which the superior part
of the vena cava inferior is embedded, immediately before it pierces the diaphragm.
The depressions for the gall-bladder and the vena cava are rightly called fossae. In hardened
specimens it will be seen that the fossa for the umbilical vein, the porta hepatis, and the fossa for
the ductus venosus are really fissures.
Taken together, the five fossae are arranged somewhat in the form of the letter
A (Fig. 938) ; the two lower divisions of the diverging limbs being formed by the
fossa venae umbilicalis and the fossa vesicae fellese respectively, and the cross-piece
by the porta hepatis all of which are placed on the inferior surface. The two
upper divisions of the limbs are represented by the fossa ductus venosi and that of
the vena cava, which meet above and are both placed on the posterior surface. The
latter of these two namely, the fossa of the vena cava, represented by the right
upper division of the A does not join the cross-piece (the porta hepatis), but is
separated from it below by a narrow ridge of liver substance the processus caudatus
(Fig. 938).
To the right of the A is the lobus hepatis dexter, to its left the lobus hepatis sinister.
The interior of the A is filled by the lobus quadratus anteriorly and the lobus
caudatus [Spigeli] posteriorly, both of which are described as parts of the right lobe,
while the processus caudatus cuts across the stem of the A behind the cross-piece,
and connects the lobus caudatus (Spigeli) to the lobus hepatis dexter.
Lobi Hepatis (Lobes of the Liver). As has been pointed out, the attachment
of the ligamentum falciforme to the superior surface of the liver divides that
aspect of the organ into right and left lobes. Similarly, upon the inferior surface,
" e fossa sagittalis sinistra is taken as dividing this aspect into right and left lobes.
Lobus Hepatis Sinister. The left lobe is much smaller and flatter than the
.ght, and forms only about one-fifth of the whole mass.
Lobus Hepatis Dexter. Its inferior and posterior surfaces of the right lobe are
intersected by the three additional fossae described above, and by them it is
subdivided into other parts, which also are called lobes. These are the lobus
caudatus [Spigeli] with the processus caudatus, and the lobus quadratus.
76 &
1192 THE DIGESTIVE SYSTEM.
(1) The Lobus Quadratus. This is a quadrilateral area upon the inferior surface,
extending from the margo anterior in front to the porta hepatis behind. On the
right, it extends as far as the fossa for the gall-bladder, and on the left to the fossa
for the umbilical vein. The surface is flattened or concave, and is mainly in con-
tact with the pyloric part of the stomach and the duodenum.
(2) The Lobus Caudatus [Spigeli] (O.T. Spigelian Lobe). This is a prominent
rather quadrilateral area on the posterior surface of the liver, between the fossa for
the inferior vena cava on its right, and the fossa for the ductus venosus on its
left side.
Its superior limit is formed by the terminal part of the ductus venosus, as it
bends to the right to join the vena cava inferior, while, inferioiiy, it is free and forms
the posterior boundary of the porta hepatis.
This extremity is often cut into by a notch or fissure (in which the coeliac
artery lies, particularly in the foetus), which marks off a larger and more prominent
left part, the processus papillaris, projecting downwards behind the porta hepatis,
and a smaller right part, the processus caudatus, which connects it (Fig. 938) with
the inferior surface of the right lobe.
The posterior surface of the caudate lobe is free ; it is placed vertically, and
looks backwards and slightly to the left. The lobe has also another surface, which
is hidden when in the body and in the hardened liver by the folding of the left
lobe across it. By this folding there is formed a deep fossa (fossa for the ductus
venosus), at the bottom of which will be found the remains of the ductus venosus.
(3) The processus caudatus (O.T. caudate lobe) is merely a narrow bridge of
liver tissue which connects the caudate lobe with the right lobe proper. It is
limited anteriorly by the porta hepatis, arid posteriorly by the fossa for the inferior
vena cava. It forms the superior boundary for the epiploic foramen, and when the
finger is placed in the foramen it rests against the caudate process, and has a vein
on each side, i.e., in front and behind, separated by a layer of peritoneum.
Facies Posterior (Posterior Surface). This portion of the parietal surface is
directed backwards, and lies in contact with the diaphragm, as the latter passes
down on the posterior abdominal wall. It is very irregular in shape, and presents
the following parts : (1) The " uncovered area " of the right lobe ; (2) the supra-
renal impression ; (3) the fossa for the vena cava ; (4) the caudate lobe, separated
by the fossa for the ductus venosus from (5) the oesophageal groove, which belongs
to the left lobe.
(1) The " uncovered area " of the right lobe (Fig. 938) is a considerable portion
of the posterior surface of the right lobe varying from 1J to 3 inches (3'7 to
7'5 cm.) in width, and from 3 to 5 inches (7'5 to 12*5 cm.) in transverse measure-
ment which is devoid of peritoneum. Over this uncovered portion, which looks
more medially than backwards, the liver and diaphragm are in direct contact, and
are united by areolar tissue ; here too is established a communication by small
veins between the portal circulation of the liver and the systemic circulation of the
diaphragm.
(2) Impressio Suprarenalis. On the " uncovered area," immediately fco the right
of the vena cava, is a triangular impression (Fig. 938), produced by a portion of
the right suprarenal gland, which projects upwards from the superior extremity of
the right kidney, between the diaphragm and liver.
(3) Fossa Venae Cavse. At the left extremity of the " uncovered area " the
inferior vena cava lies vertically, embedded in a fossa of the liver substance,
between the caudate lobe on the left and the adjacent part of the uncovered
area on the right, both of which project over the sides of the vein, almost hiding
it from view (Fig. 938) ; sometimes they actually meet and form a pons hepatis
across the back of the vein.
(4) Lobus Caudatus [Spigeli]. This has already been described see above. The
superior recess of the omental bursa separates the posterior surface of the caudate
lobe from the diaphragm, which latter, in turn, separates it from the -thoracic
part of the descending aorta just before that vessel enters the abdomen.
(5) The Impressio CEsophagea, or oesophageal groove, is situated on the posterior
surface of the left lobe, to the left of the superior end of the caudate lobe, but
THE LIVER,
1193
is separated from it by the fossa for the ductus venosus. The groove leads down
into the gastric impression on the inferior surface of the left lobe (Fig. 938), and,
when in the body, lies in contact with the prominent right or anterior margin of
the oesophageal orifice of the diaphragm (see p. 1152 and Fig. 912), sometimes also
with the oesophagus itself.
Facies Inferior. The inferior or visceral is an irregular, obliquely sloping
surface (Fig. 938), which looks downwards, posteriorly, and to the left, and rests
upon the stomach, lesser omenturn, intestines, and right kidney. The division
into right and left lobes is indicated on this surface by the left sagittal fossa,
which passes from the umbilical notch at the anterior border back to the porta
hepatis, and thence backwards as the fossa for the ductus venosus.
The inferior surface of the left lobe is directed downwards and posteriorly, and
Inferior vena cava in its fossa
Caudate lobe
Fossa for ductus venosus
Tuber omentale
(Esophageal groove
End of right suprarenal vein
Suprarenal impression
Bight end of caudate process
Uncovered area of right lobe
Renal impression
Attachment of right
triangular ligament
Gastric impression
Porta hepati
Fossa for umbilical vein
Quadrate lobe
Portal vein
Gall-bladder
Duodenal impression
Colic impression
FIG. 938. INFERIOR OR VISCERAL SURFACE OF THE LIVER.
rests on the superior surface of the stomach, in front of the cardia ; also on the
lesser curvature with its attached lesser omentum. The part which rests upon
the anterior surface of the stomach is rendered concave by the pressure of that
organ (Fig. 938), and is known as the impressio gastrica ; whilst the portion to the
right of this, being free from the pressure of the stomach, projects backwards over
the lesser curvature against the lesser omentum in the form of a smooth rounded
minence, and is known as the tuber omentale.
The inferior surface of the right lobe may be divided into two portions by the
e of the gall-bladder, which extends forwards in its fossa to the anterior sharp
margin of the liver (Fig. 936).
(a) To the left of the line of the gall-lladder are found from before backwards :
e lobus quadratus, porta hepatis, and processus caudatus.
The quadrate lobe is of an oblong shape, the antero-posterior diameter being the greatest Its
" ce is generally concave, and is related to the pylorus and the adjacent parts of the stomach
duodenum, when the former is distended. When the stomach is empty, however, the
1194 THE DIGESTIVE SYSTEM.
pylorus usually lies beneath the right portion of the left lobe, and the superior part of the
duodenum lies beneath the quadrate lobe, the transverse colon also coming in contact with it
anteriorly (Fig. 938). ^
(b) The surface to the right of the gall-bladder, which is more extensive than
that on its left, is entirely occupied by three impressions, produced by the under-
lying viscera namely : (1) The impressio colica lies in front and to the right of
the gall-bladder. It is formed by the right flexure of the colon and the beginning
of the transverse colon. (2) Behind this is the impressio renalis, larger than the
preceding, which is produced by the superior half or two-thirds of the right kidney.
It is placed behind the colic impression just as the kidney itself is placed behind
the colon. The superior end of the renal impression is frequently devoid of
peritoneum (Fig. 938), that is to say, the "uncovered area" of the right lobe
extends down over the impression for a little way. This impression is very deep,
and accommodates nearly the whole thickness of the kidney. In many hardened
specimens it would appear to belong more to the posterior part of the parietal
surface than to the inferior or visceral surface. (3) To the medial side of the renal
impression, and near the neck of the gall-bladder, is placed the narrow impressio
duodenalis, which lies in contact with the descending part of the duodenum down
to the point at which it is crossed by the colon.
Surface Markings of the Liver. The limits even of the normal liver are very
variable, but, taking the average condition in the male, they may be marked out
on the anterior surface of the body by the following method : Three points are
determined (a) half an inch (12'5 mm.) below the right nipple ; (ft) half an inch
(12-5 mm.) below the right margin of the thorax (or below the tip of the tenth rib) ;
and (c) one inch (25 mm.) below the left nipple. If these points are joined by
three lines, slightly concave towards the liver, they will give the outline of the
organ with sufficient accuracy for all ordinary purposes. (For variations in position
see below.)
To state the matter somewhat more in detail : If the two " nipple points " (a) and (c) be
joined by a line, slightly convex upwards on each side, but a little depressed at the centre corre-
sponding to the position of the heart, and crossing the inferior end of the sternum about the level
of the seventh cartilage, it will mark the superior limit. A line, convex upwards, from the right
nipple point (a) to the subcostal point (6) will indicate the right limit, while the inferior limit is
marked by a line, convex downwards, drawn from the subcostal point (6) to the left nipple point
(c), and passing through a point half-way between the umbilicus and the inferior end of the
body of the sternum, in the median line.
The line indicating the superior limit of the liver is elevated on each side, corresponding to the
cupolae of the diaphragm, and depressed in the centre beneath the heart. On the right side
where highest, namely, about one inch (25 mm.), medial to the mammary line, it reaches during
expiration to the superior border of the fifth rib ; on the left side it is one-half to three-quarters of
an inch (12 to 18 mm.) lower ; and it crosses behind the sternum at the level of the sixth sterno-
costal junction or sometimes lower. It must be remembered, however, that, whilst the liver
reaches up to the levels just given, it does so only at the highest part of its convex parietal surface,
and is separated from the ribs all round by the thin lower margin of the lung (which extends
down between the chest wall and diaphragm to the sixth rib in front, to the eighth in the mid-
lateral line, and to the level of the tip of the spine of the tenth thoracic vertebra behind), so that,
in percussing over the liver, its dulness is obscured by the resonance of the lungs above these
points.
From the back, the superior margin of the liver rises as high as to the superior margin of the
eighth rib or to the inferior margin of the scapula on the right side. On the left, it rises to the
inferior margin of the eighth rib, and terminates about an inch medial to the inferior angle of
the scapula.
The inferior margin slopes upwards along the eleventh rib of the right side, along a line leading
to the superior part of the tenth thoracic vertebra. On the right side the liver extends vertically
in the mid-axillary line, from the sixth to the eleventh ribs.
Variations in Size, Form, and Position. Few organs will be found to vary more in size in
different bodies than the liver ; these variations, however, are very frequently to be looked upon
as pathological But even the normal, healthy liver may vary in weight from 48 to 58 ounces
in the adult male, and from 40 to 50 ounces in the female.
Variations in form and position doubtlessly take place physiologically, as a result of the condi-
tions of fulness or emptiness of the adjacent viscera ; for, though the liver, like the other solid
abdominal organs, has an intrinsic shape of its own, this is capable of modification within certain
limits by the varying pressure of the surrounding parts. Thus, distension of the stomach, or of
a portion of the transverse colon lying in the stomach chamber, may push the liver over to the
right, so that it may hardly reach the median plane, and at the same time it increases its vertical
THE LIVER 1195
depth. On the other hand, a distended state of the small intestines, with a contracted stomach
and colon, may have the opposite effect, flattening it from below upwards and enlarging it in
the transverse direction.
Variations in form and position due to malformations of the thoracic framework, either con-
genital or acquired, are very common, particularly in females as a result of tight-lacing, which
presses the lower ribs inwards. Sometimes in these cases the constriction of the waist lies
chiefly below the liver. The organ is then forced up against the diaphragm, filling its whole vault,
and extending across to the left abdominal wall, where its left margin may lie in the interval
between the diaphragm and the spleen. But more commonly it would seem that the liver is
caught by the constriction : its upper part is then closely pressed into the vault of the diaphragm,
which, owing to the narrowing of the thorax, is unable to accommodate the whole organ, so
that its inferior part is crushed down for a considerable distance into the umbilical zone of the
abdomen (Fig. 918, p. 1167), particularly on the right side. Often, too, a wide, tongue-like
process (the so-called "Reidel's lobe") descends from the inferior margin, lateral to the gall-
bladder. This process, which when very large may reach to the iliac crest, is sometimes found
in men, although more common in women, and is liable to be mistaken for a tumour. A some-
what similar process occasionally descends from the left lobe.
Again, in apparently healthy bodies the liver may extend up on the right side almost to the
fourth rib ; whilst in other cases it may be as low as the sixth rib, or even lower. Nor is it
rare particularly in females to find the anterior border projecting two or three inches (5'0 to 7 '5
cm.) below the margin of the thorax on the right side (Fig. 918, p. 1167).
Reference should be made here to certain grooves often seen on the liver. Some of these are
found running obliquely low down at the right side where the liver is in contact with the ribs ;
they are particularly common in females, and are due to the pressure of the ribs resulting from
tight-lacing. Grooves of a different kind are found at the superior part of the parietal surface ;
where the liver is in contact with the diaphragm ; these usually run radially, that is, in the
direction of the muscular fibres of the diaphragm, and are apparently produced by a wrinkling,
or irregular contraction, of the diaphragm. At least, ridges of the diaphragm are found lying in
the grooves, and these ridges or wrinkles would seem to be responsible for the production of the
grooves.
Finally, the liver may present certain congenital irregularities in the direction of additional
fossae and lobes, which reproduce the conditions found in the higher apes, and are very
commonly present in the foetus (Thomson). Or the liver may be divided up into a large number
of distinct lobes, as in most other animals.
Changes in position have been already referred to in connexion with variations in form ;
there need only be added here that the liver ascends and descends at every expiration and inspira-
tion respectively, and that it also descends, but very slightly, in changing from the reclining to
the erect posture. Occasionally, without any evident cause, the liver and diaphragm are found
to occupy a higher or lower position than usual.
Fixation of the Liver. At first sight it is not easy to understand the means by which
the liver maintains its position in the abdomen (and the same remark applies, perhaps, to other
solid abdominal organs). The falciform ligament gives it no support, as it is quite lax when
in the body. Nor can it be said that its vessels, except perhaps the hepatic veins, assist.
However, on considering the conditions under which the viscera are placed in the abdominal
cavity the problem becomes less difficult.
The abdomen is a closed cavity, with a firm framework to its superior part, a tightly stretched
diaphragm for its roof, and muscular walls all round. Into the concavity of this roof the parietal
surface of the liver is fitted with perfect accuracy, so that the two are in absolute contact, and
cannot be separated without producing a vacuum, unless some other structure is in a position to
fill the space. But there is hardly any other viscus movable enough to pass up over the front
of the liver into the vault of the diaphragm, so that atmospheric pressure alone is probably
sufficient to retain the organ in situ, as in the case of the shoulder joint. In addition, the abdominal
muscles are always in a condition of tonic contraction or " tone," which gives rise to an intra-
abdominal pressure. This is effective in all directions, and consequently there is a considerable
pressure on all the abdominal walls. The liver, being in absolute contact with the roof, may be
considered a part of this wall, and it is consequently affected by this pressure which helps to
sustain it. Add to this, the support which the organ receives from the intestines, the stomach,
and the pancreas ; from the coronary and triangular ligaments ; from the connexion of the back of
the right lobe by areolar tissue to the diaphragm ; and, finally, from the inferior vena cava
embedded in the liver and sending its hepatic veins forwards to all parts of the organ, just
before the vein itself is firmly attached to the margins of the caval orifice in the central tendon
of the diaphragm, and we will probably find sufficient cause for the maintenance of the organ
in its position in the abdominal cavity.
Relation to Peritoneum. The relation of the liver to the peritoneum is some-
what complex in its details. The greater part of the liver is covered with peri-
meum, forming the tunica serosa, but there is an area of some size upon its superior
id posterior aspects where it is directly in contact with the diaphragm, and round
margins of this area the peritoneum passes from liver to diaphragm. This is
lown as the bare area, and the peritoneum around this area is known as the
famentum coronarium (coronary ligament). Further, the liver is attached to the
1196 THE DIGESTIVE SYSTEM.
anterior portion of the diaphragm, and to the abdominal wall as low as to the
umbilicus by a fold of peritoneum which is known as the ligamentum falciforme.
This fold runs forwards from and is continuous with the folds of peritoneum which
limit the bare area, and the whole forms a sort of mesentery or meso-hepaticum.
The peritoneum is also reflected off from the margins of the porta hepatis and
from the fossa for the ductus venosus, and passes thence to the lesser curvature
of the stomach and the first part of the duodenum, forming the omentum minus,
The liver may, in fact, be regarded as lying inside a peritoneal fold which stretches
from the lesser curvature of the stomach below to the diaphragm and anterior
abdominal wall above. This fold is embryologically the ventral mesentery of
the stomach, or ventral meso-gastrium, and its original simple character has
become complicated by the growth of the liver within it and by the rotation
which the stomach undergoes to the right side at its inferior part.
The various ligaments of the liver are as follows :
(1) Ligamentum Falciforme Hepatis. The falciform ligament of the liver is a
crescentic fold of peritoneum, which is attached by its convex border to the inferior surface
of the diaphragm, arid to the anterior abdominal wall (an inch or more to the right of
the median plane) to within a short distance (1 to 2 inches, 2-5 to 5 cm.) of the umbilicus.
Its concave border is attached to the superior and anterior aspects of the liver ; below
this level it presents a free rounded edge, stretching from near the umbilicus to the
umbilical notch of the liver, and it contains within its layers a stout fibrous cord called the
round ligament.
Near the posterior part of the superior surface of the liver the two layers of which the falciform
ligament is composed separate, and enclose a triangular area on the posterior surface, in front of
the superior end of the vena cava, uncovered by peritoneum. Traced backwards, the right layer
passes into the superior layer of the coronary ligament, the left into that of the left triangular
ligament. It is the remains of a part of the ventral mesentery of the embryo, and has no
supporting or suspensory action on the liver of the adult.
(2) Ligamentum Coronarium Hepatis. The coronary ligament consists of the layers
of peritoneum which are reflected from the liver to the diaphragm at the margins of the
uncovered area of the right lobe. The name of right triangular ligament has been given
to its pointed right extremity (Fig. 938).
The coronary ligament consists of a superior and an inferior layer. The superior is
formed by the prolongation to the right of the right layer of the falciform ligament. The
inferior layer is formed by the continuation of the inferior layer of the right triangular
ligament to the left side, and by the reflection from the margin of the caudate lobe by
the side of the inferior vena cava (see Fig. 938).
(3) Ligamentum Triangulare Dextrum. The right triangular ligament (O.T. right
lateral ligament) is merely the pointed right extremity of the coronary ligament, where
the superior and inferior layers become continuous with one another.
(4) Ligamentum Triangulare Smistrum. The left triangular ligament (O.T. left
lateral ligament) is a considerable triangular fold, continuous with the left layer of the
falciform ligament, which is attached by one border to the superior surface of the left lobe
near its posterior border, and by the other to the diaphragm, for a distance of several
inches as a rule.
Its attachment to the diaphragm lies nearly altogether to the left of the cesophageal orifice,
and about f inch (18 mm.) anterior to the plane of this opening.
Two other structures, termed ligaments, are not peritoneal folds, but obliterated blood-
vessels, namely the ligamentum teres hepatis or round ligament and the ligamentum
venosum (Arantii).
(5) Ligamentum Teres Hepatis. The round ligament of the liver is a stout fibrous
band which passes from the umbilicus, backwards and upwards, within the free margin of
the falciform ligament, to the umbilical notch of the liver, and thence upwards and
backwards in the umbilical fossa, to join the left branch of the portal vein. It is the
remains of the left umbilical vein, which, before birth, carries the arterial blood from the
placenta to the body of the foetus (Fig. 88).
(6) Ligamentum Venosum Arantii. The venous ligament of Arantius (O.T. obliter-
ated ductus venosus) is a slender fibrous cord, which passes from the left branch of the
portal vein, nearly opposite the attachment of the round ligament, upwards in the fossa
THE LIVER
1197
bearing its name, to be connected with the inferior vena cava as it leaves the liver.
In the foetus this structure is a considerable vessel, which conveys some of the blood
brought to the porta hepatis by the left umbilical vein directly backwards to the vena
cava. At the time of birth the ductus venosus and umbilical vein cease to carry blood,
their cavities become obliterated, and they are converted into fibrous cords.
(7) Omentum Minus. The lesser omentum is a fold of peritoneum which extends
from the liver to the lesser curvature of the stomach and to the duodenum.
It is attached, above, to the margins of the porta hepatis, and also to the bottom of the
fossa for the ductus venosus. Below, it is connected to the lesser curvature of the
stomach, where its two layers separate to enclose that organ, and also to the upper border
of the duodenum for an inch or more beyond the pylorus. Between its layers, close to
its right or free border, are contained the bile duct, the hepatic artery, the portal vein, and
the nerves and lymph vessels passing to and from the porta hepatis (Fig. 939). Its
central part is wide, but it is narrow at each end. Of the two ends, the right is free, and
7th costal cartilage
Xiphoid process
7th costal cartilage
Lig. falciforme
hepatis
Lobus dexter,
hepatis
Vena portse
Fundus vesicse
fellese
Pars descendens duodeni
Ductus cysticus '
Peritoneum (cut edge) ',
Ductus choledochus
A. hepatica
Lig. triangulare
sinistrum
Diaphragm
Fundus
'Oesophagus
Lig. gastrolienale
Incisura angularis
Paries 'anterior
ventriculi
Lig. gastro-
eolicum
'i \ i Pars pylorica
Omentum minus
i Commencement of duodenum
Duodenum pars superior
Omentum minus (cut edge)
A. gastrica d extra
FIG. 939. THE LESSER OMENTUM.
The left lobe of the liver has been removed, and also the anterior layer of the hepato-duodenal ligament.
The view is taken looking upwards as well as backwards.
stretches from the liver to the duodenum, forming the anterior boundary of the foramen
epiploicum. The left end is very narrow, and is attached to the diaphragm between the
cesophageal and caval openings. The portion of the lesser omentum passing between the
liver and the stomach is known as the ligamentum hepatogastricum ; that between the liver
and the duodenum is called the ligamentum hepatoduodenale.
The reflection from the liver to the superior part of the right kidney (a portion of the
inferior layer of the coronary ligament) is termed the hepato-renal ligament.
The " bare area " of the liver is triangular in shape, and measures about 3 inches
its greatest vertical extent, and some 5 inches transversely. It is in contact
ith the diaphragm, a portion of the right suprarenal gland, and the inferior
ma cava. It is bounded above and below by the superior and inferior folds of
coronary ligament, and on the left by the attachment of peritoneum to the
'in of the caudate lobe. It is prolonged upwards for a short distance on the
iperior surface of . the liver, in front of the inferior vena cava, between the layers
the falciform ligament as they diverge from one another.
1198
THE DIGESTIVE SYSTEM.
STRUCTURE OF THE LIVER.
The liver is invested by an outer tunica serosa described in connexion with the
peritoneum. Within this is a thin capsula fibrosa [Glissonii] (O.T. Glisson's capsule)
Intralobular capillary plexus
Intralobular s
capillary plexus <>%
Central vein
Sublobular vein
FIG. 940. LIVER OF A PIG INJECTED FROM THE HEPATIC VEIN BY T. A. CARTER. (From a specimen
presented to the Anatomical Department of Edinburgh University by Sir William Turner.)
Liver lobules
of delicate fibrous tissue, which is most evident where the serous coat is absent. In
the neighbourhood of the porta hepatis it is particularly abundant, and here it surrounds
the vessels entering the porta, and
accompanies them through the portal
canals in the liver substance. This
coat is continuous with the fine areolar
tissue which pervades the liver, sur-
rounding its lobules and holding them
together.
The liver substance proper is made
up of an enormous number of small
lobules ^-th to T \th inch (1 to 2 mm.)
in diameter, closely packed, and held
together by a small amount of con-
nective tissue. In man the lobules are
not completely separated from one
another all round their circumference,
but coalesce in places ; the reverse is
the case in certain animals such as the
camel and the pig. The lobules are
arranged around the branches of the
hepatic veins, to form the compact mass
of the liver, in the following manner :
The hepatic veins radiate from the
inferior vena cava, at the posterior
surface of the liver, to all parts of the
organ, dividing and re-dividing until
A, Arrangement of liver lobules around the sublobular the vessels are reduced to branches of
branches of the hepatic vein ; B, Section of a portal a very small size, known as sublobular
canal, showing its contained branches of the portal vein, yging _ the whole arrangement may be
hepatic artery, and bile-duct, surrounded by a pro- , compared SO far to the branching
longation of Glisson s fibrous capsule. P * ^ ^ . ^ ^ ^ ^ ^
there open into these sublobular veins numerous closely crowded vessels the venae centrales
(O.T. intralobular veins) (which, following our simile, may be compared to an enormous
Vena cava
Hepatic
cells'
ibrous
capsule
Bile-duct
FIG. 941. DIAGRAMS ILLUSTRATING THE STRUCTURE
OF THE LIVER.
VESSELS OF THE LIVER
1199
number of thorns growing out on all sides from the sublobular twigs of the tree). On
each of these little central veins there is impaled, as it were, a lobule. These little
conical lobules, with their -central veins running through them, are so numerous and so
closely packed together, that they give rise to the practically solid liver tissue.
The lobules are surrounded by the venae interlobulares, branches of the portal vein,
from which numerous twigs enter the lobule on all sides, and converging, join the central
vein (Fig. 940). This runs through the centre of the lobule (Fig. 941, A), and opens
at its base into a sublobular vein. The sublobular veins, uniting and growing larger by
constant additions, finally form the hepatic veins, which open into the vena cava.
Hepatic Cells. In the intervals between the branches of the capillaries, running from
the interlobular to the central veins (Fig. 940), are placed the polygonal-shaped epithelial,
hepatic cells. Between the cells run the ductus biliferi (O.T. bile canaliculi) which,
passing out of the lobule (Fig. 941), join the ductus interlobulares, and these uniting,
finally end in the hepatic ducts.
The liver cells are very intimately connected both with the blood capillaries and the
radicles of the bile-ducts. From both sets of vessels minute channels pass into the interior
of the hepatic cells, forming intracellular canals. The blood plasma is thus brought into
very intimate relation with the plasma of the hepatic cells, and the small fine intracellular
biliary canaliculi facilitate the secretion of bile by the cells.
VESSELS OF THE LIVER.
Like many other glands, the liver presents, as has been seen, a hilum, or slit-like
fissure, upon its surface, where vessels are found, and where the ducts emerge. In the
liver, the hilum is placed upon the inferior aspect, and is represented by the porta hepatis.
6th costal cartilage
Diaphragm
7th costal cartilage
Falciform ligament
8th costal cartilage
Gall-bladder
9th costal cartilage
10th costal cartilage
Right flexure of colon
Csecum
Xiphoid process
Left flexure of colon
Transverse colon
Position of umbilicus
Small intestine
FIG. 942. THE ABDOMINAL VISCERA, AFTER REMOVAL OF THE OMENTOM MAJUS
AND THE LlG. GASTROCOLICUM.
The blood-vessels here are all afferent, conveying blood to the liver. The blood is
conveyed away from the liver by various channels which emerge from its posterior aspect
(venae hepaticae) and enter the vena cava inferior, which is partially embedded in the
substance of the liver in this region.
1200 THE DIGESTIVE SYSTEM.
The circulation within the liver is, therefore, arranged differently from that of other
glands, and in order to understand properly the structure of the liver, it is necessary to
give some account of the relations which it presents to the blood vessels which pass to and
from it.
The vena portae and the arteria hepatica propria pass up to the liver between the two
layers of the hepato-duodenal ligament, anterior to the foramen epiploicum. Here they
are accompanied by the bile-duct, which lies to the right, whilst the artery is placed to
the left, and the portal vein posterior to both. In this order they enter the porta
hepatis, and there become rearranged, so that the vein lies behind, the artery in the
middle, and the duct in front. Each breaks up into two chief branches a right and
a left and several smaller ones, which enter the liver substance, surrounded by a
prolongation of the connective tissue coat of the liver (O.T. Glisson's capsule). Within
the organ the three vessels run and divide together, so that every branch of the portal
vein is accompanied by a corresponding (but much smaller) branch of the hepatic artery
and of the hepatic duct : and the three, surrounded by a prolongation of the fibrpus capsule,
Hepatic
cells '
Veins Bile-ducts
FIG. 943. DIAGRAM illustrating the arrangement of the blood-vessels (on left) and of the hepatic cells and
bile-ducts (on right) within a lobule of the liver. The first diagram shows the interlobular veins
running around the outside of the lobule, and sending their capillaries into the lobule to join the central
vein. In the second diagram the bile capillaries are seen, with the hepatic cells between them,
radiating to the periphery of the lobule, where they join the interlobular bile-ducts.
and accompanied by branches of the hepatic nerves and lymph vessels, run in special
tunnels of the liver substance, which are known as portal canals (Fig. 941, B).
The hepatic artery has but a small part to play in the hepatic circulation within the
liver, and it is distributed in the following way. Reaching the porta hepatis of the liver
it breaks up into branches which accompany the branches of the bile-ducts and of the
portal vein into the interior, and it supplies minute branches, known as the vaginal and
capsular branches, to the fibrous tissue which accompanies these vessels, and which also
invests the surface of the liver. The terminal branches of the artery end in the branches
from the portal vein which go to the liver lobules.
The portal vein within the liver divides, like an artery, into numerous branches, which
pass in all directions in company with small branches of the bile-ducts.
Finally, the small terminal branches form an elaborate mesh work, whose vessels
anastomose freely with one another, around the periphery of the liver lobules, and are
known as interlobular vessels. From this meshwork small capillary-like channels pass
into the interior of each lobule between columns of liver cells, towards a channel placed in
the centre of the lobule, called the central vein. From the central veins the blood is
carried into larger channels or sublobular veins, which pass to the hepatic veins, and so
to the inferior vena cava.
The hepatic veins, formed by the union of the sublobular vessels, gradually unite with
one another, and run towards the inferior vena cava. Their mode of termination is
variable, but presents the following general arrangement : The left lobe is drained by a
vessel which joins the superior part of the inferior vena cava. The right lobe is drained by
one or two vessels which join the superior part of the inferior vena cava, and by a series of
small vessels, 4 to 12 in number, which pass from the inferior portion of the right lobe to
the inferior vena cava. The caudate lobe and central portion of the liver are drained by
THE GALL-BLADDEK AND BILE-PASSAGES. 1201
vessels which mostly pass to the inferior part of the inferior vena cava. The hepatic
veins and their branches are not accompanied by branches of the bile-ducts, and are
surrounded by a very small amount of connective tissue.
The lymph vessels of the liver are arranged in a superficial and a deep set : 1. The superficial
set lies beneath the peritoneum on both (a) the visceral and (&) the parietal surfaces of the organ.
(a) The vessels from the visceral surface pass chiefly to the hepatic glands, which lie between the
layers of the lesser omentum ; but some of them, from the posterior surface on the right lobe,
join the lumbar glands, and others, from the posterior surface on the left lobe, go to the cceliac glands.
(&) The vessels from the inferior surface pass in various directions. Those from the adjacent
parts of the right and left lobes pass up in the falciform ligament, and pierce the diaphragm to
reach the anterior mediastinal glands, and end finally in the right lymphatic duct. Those from
the anterior part of this surface pass down to the inferior aspect, and join the hepatic glands
in the lesser omentum. The lymph vessels from the back of the right lobe pierce the diaphragm
between the layers of the coronary ligament, and join some glands in the thorax around the upper
end of the inferior cava ; others run in the right triangular ligament, and either pierce the
diaphragm and end in the anterior mediastinal glands, or, turning down, join the coeliac group,
2. The deep lymph vessels accompany either (a) the portal or (6) the hepatic veins, (a) The
former set pass out through the porta hepatis and join the hepatic glands, the efferent vessels of
which join the cceliac glands. (6) Those which accompany the hepatic veins pierce the diaphragm
with the vena cava, and having formed connexions with the group of glands at its superior end,
within the thorax, turn down and join the beginning of the thoracic duct.
The nerves, which are chiefly of the non-medullated variety, are derived from the left
vagus and the cceliac plexus of the sympathetic. The branches of the former pass from
the front of the stomach up between the layers of the lesser omentum to the liver. Those of
the latter pass from the cceliac plexus along the hepatic artery forming the hepatic plexus to
the porta hepatis, where they enter the liver with the blood-vessels. They are distributed chiefly
to the walls of the vessels and of the bile -ducts.
THE GALL-BLADDER AND BILE-PASSAGES.
Under this heading we have to consider the hepatic ducts, the gall-bladder, the
cystic duct, and the bile-duct.
The excretory ducts of the liver (Fig. 943) begin within the hepatic cells as minute
channels. Thence they run between the hepatic cells (Fig. 943), and are known as the
ductus biliferi.
Outside the lobules these join (Fig. 943) the ductus interlobulares which, by
uniting, form larger and larger ducts, and finally end in two, or more, chief branches,
a larger from the right, and a smaller from the left lobe, which unite immediately
after leaving the liver to form the ductus hepaticus.
As a rule, five or six ducts leave the liver at the porta hepatis ; they generally unite into
right and left main ducts ; sometimes they all converge towards, and unite at the beginning
of the hepatic duct. It is interesting to note that the ducts from the caudate lobes and process,
join the left branch of the main duct.
Ductus Hepaticus. The hepatic duct is formed within the porta hepatis by
the union of right and left chief ducts (Fig. 944), and passes downwards, with an
irregular course, and, just beyond the porta hepatis, is joined by the cystic duct
(Fig. 944) to form the ductus choledochus or bile-duct (O.T. common bile-duct).
In length the hepatic duct usually measures about 1 to 1J inch (25 to 31 mm.),
and in breadth, when flattened out, nearly J inch (6 mm.), or about as much as a
goose quill. It lies, practically altogether, within the porta hepatis.
Vesica Fellea (Gall-bladder). The gall-bladder, with the cystic duct, may be
looked upon as a diverticulum of the bile-duct, enlarged at its extremity to form a
reservoir for the bile. It is pear-shaped, and lies obliquely on the inferior surface of
the liver (Fig. 944). The wide end, or fundus, usually reaches the anterior border of
the liver where there is sometimes a notch to receive it and comes in contact with
the anterior abdominal wall (Fig. 944). The corpus (body) runs backwards, upwards,
and to the left, lying in the fossa for the gall-bladder, and near the porta hepatis passes
rather abruptly into the narrow neck. The collum (neck) is curved medially towards
the porta hepatis, in the form of the italic letter s, and when distended it presents
on its surface a spiral constriction which is continued into the beginning of the
cystic duct, and is due to a series of crescentic folds placed somewhat spirally
round the interior of its cavity, forming the valvula spiralis (Heisteri). Having
arrived near the porta hepatis, much reduced in size, it passes into the cystic duct.
As a rule the gall-bladder is covered by the peritoneum of the inferior surface
77
1202
THE DIGESTIVE SYSTEM.
of the liver, except on its antero-superior aspect, which is united to the fossa for the
gall-bladder by areolar tissue. Sometimes, but rarely, this surface also is covered,
and the gall-
bladder is
suspended
Round ligament
Quadrate lobe
Hepatic duct
Gall-bladder
Cystic duct
Duodenal
impression
Omental tuberosity
Gastric impression
Posterior layer of
sser omentum
Esophagus
Free edge
of lesser
omentum
Bile-duct
Duodenui
tal vein
Hepatic artery
Pylorus
Right gastro-epiploic artery
s. Superior pancreatico-duodenal artery
Pancreatic duct
FIG. 944. STRUCTURES BETWEEN THE LAYERS OF THE LESSER OMENTUM.
the transverse colon in front, and behind, near
then
from
the liver by a
short peritoneal
ligament. The
fundus usually
lies in contact
with the anterior
abdominal wall, at
or immediately be-
neath the point
where the right
vertical lateral
plane meets the
lower margin of
the ribs (i.e. in
the angle between
the lateral border
of the right rectus
muscle and the
inferior margin of
the ribs). Above,
the gall - bladder
lies against the
liver ; and below,
its neck, on the
it rests on
duodenum.
In some cases the fundus of the gall-bladder does not reach the anterior border of the liver
or the abdominal wall. In others it may be moved considerably to the right of the vertical
lateral plane possibly as a result of distension of the stomach and colon or as a result of tight-
lacing, it may b6 moved to the left, and may then lie near the median plane and far below the
ribs (Fig. 918, p. 1167).
Its total absence, as well as the presence of two distinct gall-bladders, and several other
irregularities in form, have been recorded.
Its size is usually about 3 inches (75 mm.) in length, and 1 to 1^ inches (25 to 31 mm.) in
diameter. Its capacity varies between 1 and 1^ fluid ounces.
Structure of Gall-bladder. The wall of the gall-bladder is composed of an outer
coat of peritoneum, the tunica serosa, usually incomplete ; a middle coat of unstriped
muscle intermixed with fibrous tissue, the tunica muscularis ; and an inner coat of mucous
membrane, the tunica mucosa, which is covered with columnar epithelium, and is raised into
a number of small ridges, the plica tunicas, mucosce, which confer on it a reticulated
appearance. The mucous membrane is always deeply stained with bile when the gall-
bladder is opened after death.
The cystic artery which supplies it with blood arises from the hepatic artery itself, or its right
division, and divides into two branches, which run on the sides of the gall-bladder. The veins
join the vena portae, and the nerves come from the sympathetic plexus on the hepatic artery.
Ductus Cysticus. The cystic duct, about half the diameter of the hepatic duct
(3 mm.), but usually slightly longer (1J to 1 \ inches : 31 to 37 mm.), begins at the
neck of the gall-bladder, and running an irregular course backwards and medially
joins the hepatic duct at the mouth of the porta hepatis, to form the bile-duct.
The spiral constriction found in the neck of the gall-bladder is continued into
the beginning of this duct. Sometimes the cystic duct joins the right hepatic duct
instead of the hepatic duct proper.
Ductus Choledochus. The bile-duct (O.T. common bile-duct) begins at the
mouth of the porta hepatis, where it is formed by the union of the hepatic and cystic
ducts. From this it passes downwards, anterior to the foramen epiploicum, lying
between the two layers of the lig. hepato-duodenale, with the portal vein behind
PANCEEAS. 1203
and the hepatic artery to its left. It next descends behind and to the left of the
superior part of the duodenum (Fig. 944), and then M Q
between the pancreas -and descending part of the
duodenum. Finally, it meets the pancreatic duct, and
the two, running together, pierce the medial wall of the
descending part of the duodenum very obliquely, and
open by a common orifice on the papilla duodenalis
about 3J or 4 inches (8 '7 to 10 cm.) beyond the pylorus
(see p. 1185).
The length of the bile-duct is about 3 inches
(75 mm.), and its diameter, which is very variable, is
generally about J inch (6 to 7 mm.).
Structure of the Excretory Ducts. With the
exception of the peritoneal coat, which is absent, the r
n i jj FIG. 945. DIAGRAM SHOWING THE
hepatic, cystic, and bile-ducts agree with the gall-bladder BlLB AND PANCREATIC DuCT s
in general structure. The tunica mucosa contains a large PIERCING THE WALL OF THE
number of mucous-producing glands, the glandulse mucosse DUODENUM OBLIQUELY.
A.D.S., Accessory pancreatic duct
The bile and pancreatic ducte in piercing the wall of the
duodenum, run obliquely through its coats for about or f of muscu i ar fibr es ; M, Mucous
an inch (12 to 18 mm.), and, as a rule, do not unite until they coat>
have almost reached the opening on the duodenal papilla (Fig.
945). This orifice is very much smaller than either duct, and the short and relatively wide
common cavity which precedes it is sometimes known as the " ampulla of Vater." Occasionally
the cystic and hepatic ducts open into the duodenum separately.
PANCREAS.
The pancreas is an elongated glandular mass which lies transversely on the
posterior abdominal wall, with its right end resting in, the concavity of the
duodenum (Fig. 946), and its left end touching the spleen. It secretes a
digestive fluid the pancreatic juice which is conveyed to the duodenum by the
pancreatic duct, and which constitutes one of the chief agents in intestinal digestion.
The absence of a true capsule, and the distinct lobulation of the gland, give the
pancreas a very characteristic appearance (Fig. 948).
Position. The greater part of the gland lies in the epigastrium, but the tail
and adjacent part of the body extend into the left hypochondrium.
The head is placed opposite the second and upper part of the third lumbar vertebra, whilst
the body runs to the left, about the level of the first lumbar vertebra. It should be added, that
very often the inferior portion of the head projects some distance below the subcostal plane, and
thus lies in the umbilical region.
In shape the pancreas, when hardened in situ, is very irregular (Fig. 946),
its right end being flattened and hook-like, whilst the rest of the organ is pris-
matic and three-sided. It may, perhaps, in general form be best compared to
the letter J placed thus c~, particularly if the stem and hook of the letter are
thickened.
The gland is divisible into a head (caput) with a processus uncinatus, a body
(corpus), and a tail (cauda). The head corresponds to the hook of the c~, and
runs downwards and to the left along the descending and transverse portions of
the duodenum. The stem of the c~ represents the body of the gland, and the
thin left extremity of the body forms the tail. The narrow part connecting the
head and body is the neck (Symington).
When removed from the body without previous hardening, the pancreas loses
its true form, and becomes drawn out into a slender, elongated, tongue-shaped
mass, with a wider end turned towards the duodenum, and a narrow end corre-
Konding to the tail.
Its total length, when fixed in situ, is about 5 or 6 inches (12 '5 to 15 cm.) ; after removal, if
t previously hardened, it is easily extended to a length of 8 inches (20 cm.).
Its weight is usually about 3 ounces (87 grammes).
Relations. The general position and relations of the pancreas may be briefly
1204
THE DIGESTIVE SYSTEM.
expressed as follows : The head (Fig. 946) lies in the concavity of the duodenum,
with the vena cava inferior and abdominal aorta behind it ; the body crosses the
Aorta
Fossa for caudate lobe
Right phrenic vessels
Vena cava
Hepatic veil
Hepatic artery
Portal vein
Pylorus
Bile-duct
(Esophagus
Left gastric artery
Diaphragm
/ i Left supra-renal gland
Splenic artery
Kidney
Right supra-renal gland
Upper surface of pancreas
Gastric surface of spleen
Ureter
Inferior mesen-
teric artery
Internal sper-
matic vein
Ureter "
Right common iliac
vein
Right common iliac
artery
Left common iliac
vein
Under surface
N of pancreas
"Attachment of
transverse
mesocolon
S Duodeno-
jejunal flexure
Gastro- duodenal
artery and neck
of pancreas
xSuperior mesen-
teric artery
Duodenum
reter
Colon
FIG. 946. THE VISCERA AND VESSELS ON THE POSTERIOR ABDOMINAL WALL.
The stomach, liver, and most of the intestines have been removed. The peritoneum has been preserved on the
right kidney and the fossa for the caudate lobe. When the liver was taken out. the inferior vena cava
was left behind. The stomach bed is well shown. (From a body hardened by chromic acid injections.)
left kidney and supra-renal gland ; and the tail touches the inferior part of the
spleen. The greater part of the organ lies behind the stomach, which must be
detached from the gastro-colic ligament, and turned upwards, in order to expose it.
In describing the detailed relations, each part of the organ will require to
be considered separately.
Caput Pancreatis. The head of the pancreas is the large flattened and somewhat
disc-shaped portion of the gland which lies in the concavity of the duodenum, extending
along its second and third portions almost as far as the duodenal-jejunal flexure. Above,
PANCKEAS.
1205
in its right half, it is continuous with the neck ; whilst to the left of this it is separated
from the neck by a deep notch, incisura pancreatis, in which lie the superior mesenteric
vessels (Fig. 946). Its right and inferior borders are moulded on to the side of the
duodenum, which lies in a groove of the gland substance the bile-duct being interposed
as far down as the middle of the descending part of the duodenum. The posterior
surface of the head is applied to the front of the vena cava inferior ; it also lies on
the right renal vessels and the left renal vein, and, at its left end, on the aorta as well.
Its anterior surface is in contact above and on the right with the beginning of the
Top of omental bursa
Inferior vena cava
Lesser omentum (cut)
Right triangu
ligament of live
Left triangular ligament of liver
(Esophageal opening in diaphragm
' Gastro-phrenic ligament
/ Corresponds to ' uncovered area ' of stomach
Gastro-splenic ligament (cut)
Transverse colon crossing duodenum
Head of pancreas
Gastro-colic ligament (cut)
Part of omental bursa
Phrenico-colic ligament
Left end of transverse mesocolon
Left colic flexure
Transverse mesocolon (cut)
Root of mesentery (cut)
FIG. 947. THE PERITONEAL KELATIONS OF 'THE DUODENUM, PANCREAS, SPLEEN, KIDNEYS, ETC.
transverse colon (Fig. 947), without the interposition of the peritoneum as a rule. Below
this it is clothed by peritoneum, and is covered by the small intestine.
The superior mesenteric vessels, after passing forward through the pancreatic notch,
descend in front of that portion of the head (processus uncinatus) which runs to the left
along the third part of the duodenum. The superior pancreatico- duodenal vessels run
downwards, and break up on the front of the head (Fig. 946).
The neck (Fig. 946) is a comparatively attenuated portion of the gland which lies
in front of the portal vein, and connects the head to the body. Springing from the upper
portion of the head, it runs forwards, upwards, and to the left for about 1 inch (25 mm.),
and then passes into the body.
The neck is about f inch (18 mm.) in width, and less than | inch (12*5 mm.) in thickness. In
front and to its right lie the first part of the duodenum and the pylorus ; behind and to the left it
rests upon the beginning of the portal vein, which is formed under cover of its lower border by the
union of the splenic and superior mesenteric veins. It has a partial covering of peritoneum on its
anterior surface ; and its beginning is generally marked off from the head by the gastro-duodenal
artery, with its continuation the superior pancreatico-duodenal, which lies in a groove of the
gland substance between the head and neck.
77 a
1206 THE DIGESTIVE SYSTEM.
Corpus Pancreatis. The body is of a prismatic form, largest where it lies in
front of the left kidney, and usually somewhat tapering towards the tail (Fig. 948).
Beginning at the termination of the neck, it runs backwards and to the left across the
front of the left kidney, beyond which its extremity or tail comes in contact with the
spleen. When hardened in situ it presents three surfaces anterior, inferior, and
posterior all of which are of nearly equal width (namely, about 1 J inches : 31 mm.).
Facies Anterior. The anterior surface is widest towards the left end ; it looks
upwards and forwards (Fig. 947), and forms a considerable portion of the stomach-bed.
This surface is completely covered by peritoneum, derived from the posterior wall of the
bursa omentalis, which latter separates the pancreas from the posterior surface of the
stomach. Towards its right extremity it usually presents an elevation or prominence
where the body joins the neck. This projects against the back of the lesser omen turn
when the stomach is distended, and is consequently known as the tuber omentale.
Facies Inferior. The inferior surface, which, like the anterior, is, as a rule, widest
towards its left end, looks downwards and slightly forwards. It is completely covered
by peritoneum, continuous with that forming the posterior layer of the transverse meso-
colon (Fig. 947). It lies in contact with the duodeno-jejunal flexure towards its right
end, with the left flexure of the colon near its left end, and with a mass of small intestine
(jejunum, which is always found packed in beneath it) in the rest of its extent.
Facies Posterior. The posterior surface looks directly backwards, and is entirely
destitute of peritoneum. It is connected by areolar tissue to the posterior abdominal
wall with the organs lying upon it. From right to left these are : the aorta with the origin
of the superior mesenteric artery, the left renal vessels, the left supra-renal gland, and the
left kidney. In addition, the splenic artery runs its tortuous course to the left along
the superior border of the pancreas, whilst the splenic vein runs, behind the gland, at
a lower level than the artery.
The three surfaces of the body of the pancreas are separated by three borders. The
margo anterior is the most prominent, and gives attachment to the transverse mesocolon
(Fig. 947). It is, as it were, squeezed forward, by the pressure of the stomach above and
the small intestine below, into the interval between these two sets of viscera, thus follow-
ing the line of least resistance (Cunningham). Towards the neck this border is no
longer prominent, but becomes rounded off, so that here the superior and inferior surfaces
are confluent.
The coeliac artery projects over the margo superior, and sends its hepatic branch to the
right, resting upon it, whilst the splenic artery runs to the left along it (Fig. 947). The
margo inferior calls for no special description.
Cauda Pancreatis. The tail of the pancreas is the somewhat pointed left end of
the body, which is in contact with the inferior portion of the gastric surface of the spleen.
It usually presents an abrupt, blunt ending, in which case it is related to the spleen in the
manner just described; or it may be elongated .and narrow, when it bends backwards
around the lateral aspect of the kidney, and beneath the base of the spleen. In either
case it is in near relation below with the left flexure of the colon (Fig. 947).
Peritoneal Relations of the Pancreas. The posterior surface of the pancreas
is entirely free from peritoneum. The other surfaces derive their peritoneal covering
from the prolongation of the two layers of the transverse mesocolon, which is attached
to the anterior border of the gland, from the tail to the neck. At this border the two
layers separate (Fig. 914, p. 1160), the anterior derived from the bursa omentalis
passing backwards and upwards over the anterior surface ; the posterior derived
from the large sac turning downwards and backwards along the inferior surface.
As the transverse mesocolon is followed to the right it is, as a rule, found to terminate near
the neck of the pancreas (Fig. 947). Beyond this, the posterior surface of the colon is generally
free from peritoneum, and is connected by areolar tissue to the anterior aspect of the head of the
gland. Below the level of the colon the head is covered by the continuation downwards of the
peritoneum from the inferior surface of that gut. Often, however, the transverse mesocolon is
continued to the right as far as the right colic flexure, and the anterior surface of the head is
then completely covered by peritoneum.
Ducts of the Pancreas. Almost invariably two ducts are found in the interior
of the pancreas the ductus pancreaticus [Wirsungi] or pancreatic duct proper and
the ductus pancreaticus accessorius [Santorini], accessory pancreatic duct (O.T. duct
of Santorini).
The pancreatic duct [Wirsungi] begins near the tip of the tail by the union of
small ducts from the lobules forming that part of the organ. From there it pursues
PANCEEAS. 1207
a rather sinuous or zigzag course (Fig. 948) through the axis of the gland, at first
running transversely to the right, until the neck is reached, then it bends down-
wards into the head, approaches the descending part of the duodenum, and meets
the bile-duct. The two ducts pierce the medial wall of the gut obliquely (for
to j of an inch, 12 to 18 mm.), and open, by a common orifice on the duodenal
papilla, about 3J or 4 inches (8'7 to 10 cm.) beyond the pylorus (see p. 1203).
In its course through the gland the pancreatic duct receives numerous tributaries,
which join it, as a rule, nearly at a right angle. The tributaries, as well as the main
duct itself, are easily recognised by the whiteness of their walls, which contrasts
with the darker colour of the gland tissue. The main duct receives tributaries from
all portions of the pancreas, and towards its termination attains a considerable size
(namely, T Vth to ^th of an inch 2'5 to 4 mm. when flattened out, or somewhat
larger than a crow quill).
Superior part of duodenum
Accessory pancreatic
Xduct
Pancreatic duct ^ ^ES^fc V- Bile-duct
Superior mesenteric artery ^'
Superior mesenteric vein
Head of pancreas ^||fe^^^M Branch of accessory duct
FIG. 948. POSTERIOR ASPECT OF THE PANCREAS AND DUODENUM, with the pancreatic duct exposed.
The superior mesenteric vessels also are shown in section, passing forwards, surrounded by the
recurved portion of the head of the pancreas.
The pancreatic accessory duct (O.T. duct of Santorini) is a small and variably
developed duct (Fig. 948) which opens into the duodenum about J of an inch above
and somewhat anterior to the pancreatic duct. From the duodenum it runs to the left
and downwards, and soon divides into two or more branches, one of which joins the
pancreatic duct, the others pass down and receive tributaries from the lower part of
the head. It is generally supposed that the current flows from this into the main duct,
and not into the duodenum, as a rule, except in early life.
Physical Characters and Structure of the Pancreas. The pancreas is of a
reddish cream colour, soft to the touch, and distinctly lobulated. The lobules
are but loosely held together by their small ducts and by loose areolar tissue ;
for, as already pointed out, the pancreas is devoid of a regular capsule, and
possesses instead merely an adventitious coat of fine connective tissue.
The gland belongs to the class of acino-tubular glands, its alveoli or acini being
elongated like those of the duodenal glands ; otherwise it corresponds very closely
to a serous salivary gland, the general structure of which will be found on p. 1140.
The secretion is termed succus pancreaticus.
Variations. The chief variations found are : (1) A separation of the part of the head,
known as the uncinate process, which then forms a lesser pancreas. (2) A growth of the pancreas
around the duodenum, which it may practically encircle for a short part of its course. And (3)
an opening of its duct into the duodenum, independently of the bile-duct. An accessory pancreas
(pancreas accessorium) is also sometimes found in the wall of the stomach or of the jejunum.
Diverticula of the duodenum, already described (p. 1187), ought perhaps to be mentioned in
this connexion.
Vessels. The arteries of the pancreas are: (l)The superior pancreatico-duodenal, a branch
of the gastro -duodenal artery, which runs down on the front of the head (Fig. 946), sending branches
laterally to the duodenum, as well as numerous twigs into the substance of the pancreas.
(2) The inferior pancreatico-duodenal, a branch of the upper part of the superior mesenteric
artery ; or from the root of one of the rami jejunales ; it runs upwards and to the right across the
back of the head, and sends branches to it and to the duodenum, one of which runs between the
head and the duodenum. These two pancreatico-duodenal arteries anastomose around the inferior
border of the head. (3) Pancreatic rami from the splenic artery, are several (3 to 5) fair-sized branches
77 b
1208 THE DIGESTIVE SYSTEM.
which, come off from the splenic as it runs behind the superior border of the gland ; they enter
the pancreas immediately, and traverse its substance from above downwards, some sending
branches in both directions along the course of the pancreatic duct.
The veins are : (1) The joancreatico-duodenal veins (Fig. 947), of which some pass downwards
and to the left, on the front of the head, and join the superior mesenteric ; while others cross the
back of the head, and open into the superior mesenteric ; (2) several small pancreatic veins which
join the splenic.
The lymph vessels pass chiefly with the splenic lymph vessels to the cceliac glands ; some also
are connected with a few glands which lie near the upper end of the superior mesenteric vessels.
All the lymph of the organ passes ultimately to the cceliac glands.
The nerves, which are almost entirely non-medullated, come from the plexus cceliacus,
through the hepatic and splenic plexuses.
INTESTINUM TENUE MESENTERIALE.
INTESTINUM JEJUNUM AND INTESTINUM ILEUM.
The upper two-fifths, that is, about 8 feet, of the small intestine beyond the
duodenum, are known as the intestinum jejunum. The succeeding three-fifths,
which usually measure about 12 feet, constitute the intestinum ileum. The ileum
opens into the large intestine at the junction of the caecum and ascending colon,
where its orifice is guarded by the valvula coli.
Both the jejunum and ileum are connected to the parietes by a large fold of
peritoneum the mesentery which conveys vessels and nerves from the posterior
abdominal wall to these divisions of the intestine.
The part of the tube to which the mesentery is connected is known as the
mesenteric or attached border ; the opposite side is the free border.
Mesenterium. The mesentery is a broad fan-shaped fold, composed of two
layers of peritoneum, which connects the small intestine to the posterior wall of the
abdomen. The long free border of the fold contains the intestine within it (Fig. 949).
The other, or attached border, known as the radix mesenterii (root of the mesentery),
is comparatively short, being only 6 or 7 inches long ; but it is much thicker
than the part near the gut, for it contains between its layers a considerable
amount of fatty extra-peritoneal tissue, in addition to the large vascular trunks
passing to the intestine. The root is attached to the posterior abdominal
wall along an oblique line, extending approximately from the left side of the
second lumbar vertebra to the right iliac fossa (Fig. 949). In this course its
line of attachment passes from the duodeno-jejunal flexure down over the front
of the terminal part of the duodenum, then obliquely across the aorta, the inferior
vena cava, the right ureter, and psoas major muscle, to reach the right iliac region.
The unattached border of the mesentery is frilled out to an enormous degree, so
that, while the root measures but 6 or 7 inches, the free border is extended to
some 20 feet, thus resembling a fan, one border of which may be twenty or thirty
times as long as the other. The length of the mesentery, measured from its root
to the attached edge of the intestine directly opposite, usually measures at its
longest part about 6 inches (8 or 9 inches, Treves and Lockwood).
Between the two layers of the mesentery (Fig. 928) are contained (a) the
jejunal and ileal branches of the superior mesenteric vessels, accompanied by the
mesenteric nerve plexus and lymph vessels; (&) the mesenteric lymph glands,
which vary from 40 to 150 in number; (c) a considerable amount of fatty con-
nective tissue, continuous with the extra -peritoneal areolar tissue; and (d) the
intestine itself.
The peritoneum from the right side of the mesentery passes out on the posterior abdominal
wall to clothe the ascending colon, and, above, it is connected by a fold with the transverse meso-
colon. That of the left side, similarly, passes across the parietes to the descending and iliac
portions of the colon.
The mesentery begins above, immediately beyond the ending of the duodenum that is, in
the angle of the duodeno-jejunal flexure and it ends below in the angle between the ileum and
ascending colon. It is very short at each end, but soon attains the average length. Its longest
part goes to the portion of the small intestine situated between two points, one six feet, the other
eleven feet from the duodenum (Treves).
Whilst the root of the mesentery pursues at its attachment an almost straight line from one end
SMALL INTESTINE.
1209
to the other, if cut across a very short distance from the posterior abdominal wall, it will here be
found to form a wavy or undulating line. Further away still this condition becomes more and more
marked ; and finally, if the bowel is removed by cutting through the mesentery close to its attach-
ment to the intestinal wall, it will be seen that its free edge is not only undulating, but is frilled or
plaited to an extreme degree. When shown in this way, it is found that the plaiting or folding
is not quite indiscriminate, but that the main folds, of which there are usually six, run alter-
nately to the right and left. As a rule, the first fold runs to the left from the duodeno-jejunal
flexure, and goes to a coil of jejunum which lies under the transverse mesocolon, and helps to
support the stomach. The second fold passes to the right, the third to the left, and so on up to
the fifth and sixth, which are usually small. From the margins of these primary folds secondary
folds project in all directions, and from these again even a third series may be formed.
6th costal cartilage
Yth costal cartilage
Lig. teres
8th costal cartilage
Gall-bladder
9th costal cartilage
Liver
10th costal cartilage
Duodenum
Right flexure of colon
Kidney
Caecun
Ileun
Vermiform process ._
-Xiphoid process
-,6th costal cartilage
f-Ttli costal cartilage
i~ Stomach
-.8th costal cartilage
Transverse colon
-9th costal cartilage
-10th costal cartilage
-_ Duodeno-jejunal
flexure
-Kidney
-Descending colon
-Mesentery, (cut)
Bifurcation of abdominal
aorta
..Iliac colon
-Pelvic colon
-Urinary bladder
.FIG. 949. ABDOMEN, AFTER REMOVAL OF SMALL INTESTINE.
This order is of course by no means constant, but if the intestine is removed from a hardened
body in the way suggested, without disturbing the mesentery, it will be found to be arranged
with more or less regularity, on some such plan as that indicated.
Differences between Jejunum and Ileum. If the small intestine is followed
down from the duodenum to the caecum no noticeable change in appearance will
be found at any one part of its course, to indicate the transition from jejunum to
ileum ; for the one passes insensibly into the other. Nevertheless, a gradual change
takes place, and if typical parts of the two, namely, the upper portion of the
jejunum and the lower portion of the ileum, is examined, they will be found to
present characteristic differences, which are set forth in the following table :
Jejunum.
Wider, 1J- to 1^ inch in diameter.
Wall, thicker and heavier.
Redder and more vascular.
Plicae circulares, well developed.
Noduli lymphatici aggregati [Peyeri],
few and small.
Ileum.
Narrower, lj to 1 inch in diameter.
Wall, thinner and lighter.
Paler and less vascular.
Plicae circulares, absent or very small.
Noduli lymphatici aggregati [Peyeri], large
and numerous.
1210 THE DIGESTIVE SYSTEM.
The villi are also said to be shorter and broader in the jejunum, more slender
and filiform in the ileum (Kauber).
The terminal portion of the ileum, after crossing the margin of the superior
aperture of the pelvis minor, runs upwards, and also slightly backwards and to the
right, in close contact with the csecum, until the ileo-ccecal orifice is reached.
Diverticulum Ilei (O.T. Meckel's Diverticulum). This is a short finger-like protrusion
which is found springing from the lower part of the ileum in a little over 2 per cent, of the bodies
examined. It is usually about 2 inches long, and of the same width as the intestine from which
it comes off. Most commonly it is found about 2| feet from the valvula coli, and opposite
the original termination of the superior mesenteric artery. As a rule, its end is free ; but
occasionally it is adherent either to the abdominal wall, the adjacent viscera, or the mesentery,
and in such cases it may be the cause of strangulation of the intestine.
The diverticulum is due to the persistence of the proximal portion of the vitelline (or vitello-
intestinal) duct, which connects the primitive intestine of the embryo with the yolk sac. In
shape it may be cylindrical, conical, or cord-like, and it may present secondary diverticula near
its tip. It arises most frequently from the free border of the intestine, but it sometimes conies
off from the side. It runs at right angles to the gut most commonly, but it may assume any
direction, and it is often provided with a mesentery. In 3302 bodies specially examined with
reference to its existence, it was present in 73, or 2'2 per cent., and it appeared to be more common
in the male than in the female. In 59 out of the 73 cases its position with reference to the end
of the ileum was examined : its average distance from the ileo-csecal valve was 321 inches
measured along the gut, the greatest distance being 12 feet, and the smallest 6 inches. In
52 specimens the average length was 2'1 inches, the longest being 5j inches, the shortest ^ inch.
The diameter usually equals that of the intestine from which it springs ; but occasionally it
is cord -like, and pervious only for a short way ; on the other hand, it may attain a diameter of
3| inches.
Vessels and Nerves of the Jejunum and Ileum. The arteries for both the jejunum and
ileum the jejunal and ileal come from the superior mesenteric, and are contained between
the two layers of the mesentery. After breaking up and forming three tiers of arches, the terminal
branches (Fig. 772, p. 931) reach the intestine, where they bifurcate, giving a branch to each side
of the gut. These latter run transversely round the intestines, at first under the peritoneal coat ;
soon, however, they pierce the muscular coat and form a plexus in the submucosa, from which
numerous branches pass to the mucous membrane, where some form plexuses around the
intestinal glands whilst others pass to the villi. The veins are similarly disposed, and the
blood from the whole of the small intestine beyond the duodenum is returned by the superior
mesenteric vein, which joins with the splenic to form the portal vein.
The lymph vessels of the small intestine (known as lacteals) begin in the villi, and also
as lymph sinuses surrounding the bases of the solitary nodules ; a large plexus is formed in the
submucosa, a second between the two layers of the muscular coat, and a third beneath the
peritoneum. The vessels from all these pass up in the mesentery, being connected on the way
with the numerous (from 40 to 150) mesenteric glands, and finally unite to form the truncus
intestinalis, which opens into the cisterna chyli.
The nerves come from the coeliac plexus, through the superior mesenteric plexus, which
accompanies the superior mesenteric artery between the layers of the mesentery, and thus
reaches the intestine. Some of the fibres are derived ultimately from the right vagus. The
nerve-fibres are non-medullated, and form, as in other parts of the canal, two gangliated
plexuses the my enteric in the muscular coat, and the submucosal in the submucosa.
Structure. The tunica serosa is complete in all parts of the jejunum and ileum.
The tunica muscularis is thicker in the jejunum, and grows gradually thinner as it is
traced down along the ileum. The tela submucosa contains the bases of the solitary
nodules (Fig. 929), but otherwise calls for no special remark. The tunica mucosa is thicker
and redder above in the jejunum, thinner and paler in the ileum. It is covered through-
out by villi intestinal es, which are shorter and broader in the jejunum, longer and narrower
in the ileum. In its whole extent it is closely set with intestinal glands, and numerous
solitary nodules are seen projecting on its surface. Aggregated lymph nodules are
particularly large and numerous in the ileum ; they are fewer, smaller, and usually
circular in the jejunum. Finally, the mucous membrane forms plicae circulares, which
are much more prominent in the jejunum ; they are smaller and fewer in the superior
part of the ileum, and usually disappear a little below its middle.
INTESTINUM CEASSUM.
The ileum is succeeded by the intestinum crassum (large intestine), which
begins on the right side, some 2J inches below the ileo-csecal junction, and com-
prises the following parts :
LAKGE INTESTINE. 1211
1. Caecum. The caecum is a wide, short cul-de-sac, consisting of the portion of
the large bowel below the valvula coli. It. lies in the right iliac region, and from
its medial and posterior, part a worm-shaped outgrowth, the vermiform process, is
prolonged (Fig. 951).
2. Colon Ascendens. The ascending colon ascends vertically in the right
lumbar region as far as the inferior surface of the liver: here the gut bends to
the left, forming the flexura coli dextra (O.T. hepatic flexure), and then passes trans-
versely across the abdomen, towards the spleen, as the transverse colon.
3. Colon Transversum. The transverse colon, a loop of intestine which passes
across the abdominal cavity in an irregular looped manner. It ends at the
inferior extremity of the spleen. There it turns downward, forming the flexura
coli sinistra (O.T. splenic flexure), and passes into the descending colon.
Haustra (Sacculations)
Appendices epiploicae
FIG. 950. LARGE INTESTINE.
A piece of transverse colon from a child two years old. The three chief characteristics of the large intestine
sacculations, taenise, and appendices epiploicae are shown.
4. Colon Descendens. The descending colon runs down on the left side, from
the splenic flexure to the rectum.
It is usually divided into the following parts :
(a) Descending colon, which extends down to the crest of the ilium.
(&) The iliac colon extends from the crest of the ilium to the superior aperture
of the pelvis, where it is succeeded by the pelvic colon.
(c) The pelvic colon is a large loop of intestine which is usually found in the
pelvis. The iliac and pelvic portions of the colon taken together are
sometimes described as the colon sigmoideum.
5. Intestinum Rectum. The rectum, the terminal part of the large bowel,
succeeds the pelvic colon, and ends in the anal canal, which opens on the surface
at the anal orifice.
In its course the large bowel is arranged in an arched manner around the
small intestine, which lies within the concavity of the curve (Fig. 912).
In length, the great intestine is equal to about one-fifth of the whole intestinal
canal, and usually measures between 5 and 5| feet (180 to 195 cm.). Its breadth
is greatest at the caecum, and from this with the exception of a dilation at the
rectum it gradually decreases to the anus. At the csecum it measures, when
distended, about 3 inches (75 mm.) in diameter; beyond this it gradually
diminishes, and measures only 1 J inches (37 mm.) or less in the descending and
iliac divisions of the colon.
The large intestine, with the exception of the rectum and vermiform process,
may be easily distinguished from the regularly cylindrical small intestine by (a)
the presence of three longitudinal bands the tsenise coli running along its surface
(Fig. 950); (V) by the fact that its walls are sacculated; and (c) by the presence
of numerous little peritoneal processes, known as appendices epiploicse, projecting
from its serous coat. In addition, the larger intestine is usually wider than the
small, but reliance cannot be placed on this character, for the jejunum is often
indeed, generally wider than the empty and contracted descending colon.
Taenise Coli. In the large bowel, unlike the small, the longitudinal fibres of
the muscular coat do not form a complete layer, continuous all round the tube,
1212 THE DIGESTIVE SYSTEM.
but, on the contrary, are broken up (Fig. 950) into three bands, known as the
tseniae coli. These bands, which are about J inch (6 mm.) wide, begin at the base
of the vermiform process, and run along the surface of the gut at nearly equal
distances from one another until the rectum is reached. There they spread out
and form a layer of longitudinal muscular fibres, which is continuous all round the
tube (see p. 1229). The bands are about one-sixth shorter than the intestine to
which they belong ; consequently, in order to accommodate the bowel to the length
of the tsenise, the gut is tucked up, giving rise to a sacculated condition (Fig. 950).
Three -rows of pouches or saccules are thus produced, along the length of the tube,
between the tsenise. If the tseniae are dissected off, the sacculations largely disappear,
the intestine becomes cylindrical, and at the same time about one-sixth longer.
The appendices epiploicae (Fig. 950) are little processes or pouches of peritoneum,
generally more or less distended with fat, except in emaciated subjects, which
project from the serous coat along the whole length of the large intestine, with the
exception of the rectum proper.
When the interior of a piece of distended and dried large intestine is examined, its
saccules appear as rounded pouches, haustra, separated by crescentic folds, plicae
semilunares coli, corresponding to the creases on the exterior separating the saccules
from one another.
The position of the three teeniae on the intestines is as follows : On the ascending, descending,
and iliac colons one taenia lies, on the anterior aspect of the gut, and two on the posterior aspect,
namely, one to the lateral side (postero- lateral), the other to the medial side (postero-medial). It
is chiefly along the first of these (the anterior) that the appendices epiploicae are found. On the
transverse colon their arrangement is different, but is rendered exactly similar by turning the
great omentum, with the colon, up over the thorax. On the transverse colon in the natural
position, the anterior taenia of the ascending and descending colons becomes the posterior (or
postero-inferior) termed tcenia libera, the postero-lateral becomes anterior or tcenia omentalis,
and the postero-medial becomes superior in position and is termed tcenia mesocolica. The anterior
and postero-lateral tseniae of the iliac colon pass below on to the front of the pelvic colon and
rectum.
In formalin-hardened bodies portions of the large intestine, but particularly of the descending
and sigmoid colons, are often found fixed in what appears to be a state of contraction, when
they are reduced to a diameter of about or of an inch (16 to 19 mm.). Under similar con-
ditions parts of the small intestine are found correspondingly reduced.
The appendices epiploicae, although generally said to be absent in the foetus, can be distinctly
seen as early as the seventh month, but at this time they contain no fat
Structure of the Large Intestine. The tunica serosa is complete on the
vermiform process, caecum, transverse colon, and pelvic colon ; incomplete on the
ascending, descending, and iliac divisions of the colon and on the rectum. It will be
described in detail with each of these portions of the intestine.
The tunica nmcosa is of a pale, or yellowish, ash colour in the colon, but
becomes much redder in the rectum. Unlike that of the small intestine, its surface
is smooth, owing to the absence of villi, but it is closely studded with the orifices
of numerous large intestinal glands. Solitary lymph nodules are also numerous,
particularly in the vermiform process (Fig. 955).
Vessels and Nerves. The caecum and vermiform process receive their blood from the
ileo-colic artery ; the ascending colon from the right colic artery ; and the transverse colon from
the middle colic artery, which lies in the transverse mesocolon. These are all branches of the
superior mesenteric. The descending colon is supplied by the left colic, and the iliac and
pelvic colons by the sigmoid arteries, branches of the inferior mesenteric. The rectum derives
its blood from the three haemorrhoidal arteries, which will be described with that division of
the gut.
The veins correspond largely to the arteries, and join the inferior and superior mesenteric
vessels, which send their blood into the portal vein.
The lymph vessels of the large intestine arise from plexuses in the submucous and sub-
peritoneal coats, as in other parts of the alimentary canal.
The deeper vessels escape chiefly along the entering blood-vessels, those from the lateral
aspects passing behind the intestine.
The vessels pass medially to a series of glands lying along the medial border of the intestine
(" paracolic " glands (Jamieson)) ; thence they pass along the lines of the main arteries, passing
then to glands disposed at intervals about these vessels (intermediate and main glands). The
lymph vessels from the lower half of the descending colon, and from the iliac and pelvic colons,
join the left lymph trunk of the lumbar glands. Those of the rectum and caecum will be described
later.
CLECUM AND VERMIFORM PEOCESS.
1213
Nerves. The nerves come from the superior mesenteric plexus, an offshoot of the coeliac
plexus, and from the inferior mesenteric, a derivative of the aortic plexus. The arrangement is
similar to that of the nerves of the small intestine.
INTESTINUM (LECUM AND PROCESSUS VERMIFORMIS.
Intestinum Caecum. After leaving the pelvic cavity, as already described,
terminal portion of the small intestine passes upwards, backwards, and to
right, and opens, by the ileo-
csecal orifice, into the large in-
testine some 2J inches from its
lower end. The portion of the
large gut which lies below the
level of this orifice is known as
the intestinum caecum. In shape
(Fig. 951) it is a wide, asym-
metrical, or lop-sided cul-de-sac,
furnished with the tsenise and
sacculations usually found in the
large intestine. Its lower end
o? fundus is directed downwards
and medially, and usually rests
on the right psoas major muscle,
close to the brim of the pelvis ;
whilst the opposite end is
directed upwards and laterally,
and is continued into the ascend-
ing colon.
the
the
Colon ascendena
A. ileocolica
Plica ileocsecalis
Fossa ileo-
ctucalis
Pelvic colon
Mesenteriolum
proc. verm.
Processus
vermiformis
Vesica urinaria
Urachus
FIG. 951. THE C^CUM AND VERMIFORM PIIOCESS FROM THE FRONT.
Its asymmetrical form is due to the
fact that the lateral and medial por-
tions of the organ undergo an unequal
development in the child. The medial (or medial and posterior) section lags behind, whilst the
lateral (or lateral and anterior) division grows much more rapidly, and, projecting downwards,
soon comes to form the inferior end or fundus of the caecum. As a result the original extremity
of the giit, with the vermiform process springing from it, is hidden away behind and to the
medial side of the fundus.
In length the distended csecum usually measures about 2J inches (60 mm.) ;
whilst its breadth is usually more, and averages about 3 inches (75 mm.).
Position. It is usually situated almost entirely within the right iliac
region of the abdomen, immediately above the lateral half or third of the inguinal
ligament ; but its inferior end projects medially in front of the psoas major and
reaches the hypogastrium (Fig. 951). On the other hand, it is sometimes found
high up in the right lumbar region (owing to the persistence of the foetal position), or
hanging over the pelvic brim and dipping into the pelvic cavity to a varying extent.
In the great majority of cases the csecum is completely covered with peri-
toneum on all aspects, and lies quite free in the abdominal cavity. In a
small proportion, namely, about 6 or 7 per cent, of bodies, the posterior surface
(probably as a result of adhesions) is not completely covered, but over a
greater or less portion of its extent is bound down to the posterior abdominal
wall by connective tissue.
Relations. Posteriorly, the csecum rests on the ilio-psoas muscle ; generally, too,
on the vermiform process and the femoral nerve. Anteriorly, it usually lies in
contact with the omentum and anterior abdominal wall ; but when the csecum
is empty, the small intestine intervenes. Its lateral side is placed immediately
above the lateral half or third of the inguinal ligament (Fig. 951), whilst the medial
side has the termination of the ileum lying in contact with it. On the medial
and posterior aspect, but more on the former than the latter, the small intestine
joins the csecum. On the same aspect, and usually from 1 to 1J inches (25 to
37 mm.) lower down, the vermiform process comes off.
1214
THE DIGESTIVE SYSTEM.
The interior of the caecum corresponds in general appearance to that of
the large intestine ; but it presents two special features on the posterior part of
its medial wall, namely, the ileo-csecal orifice, guarded by the valvula coli (O.T. ileo-
csecal valve), and below that the small opening of the processus vermiformis, both
of which call for further notice.
Valvula Coli (O.T. Ileo-caecal
Valve). Where the ileum enters the
large intestine, the end of the small gut
is, as it were, thrust through the wall of
the large bowel, carrying with it certain
layers of that wall, which project into
the csecum in the form of two folds,
lying respectively above and below its
orifice, and constituting the two seg-
ments of the valve (Fig. 952). The
condition may be compared to a partial
inversion or telescoping of the small
into the large intestine : it must be
added that the peritoneum and longi-
tudinal muscular fibres of the bowel
take no part in this infolding ; on the
contrary, they are stretched tightly
across the crease produced on the ex-
terior by the inversion, and thus serve
to preserve the fold and the formation
of the valve.
As seen from the interior, in speci-
mens which have been distended and
dried (Fig. 953), the valve is made up
of two crescentic segments a superior,
labium superius, in a more or less
horizontal plane, forming the superior
margin of the aperture ; and an inferior,
labium inferius, which is larger, placed in
an oblique plane, and sloping upwards
and inwards (i.e., towards the cavity of
the csecum). Between the two seg-
ments is situated the slit-shaped open-
ing, which runs in an almost antero-
posterior direction, with a rounded an-
terior and a pointed posterior extremity
(Fig. 952). At each end of the orifice
the two segments of the valve meet,
^^-^^^^tgZLZZ unite, and are then prolonged around
formalin. the wall of the cavity as two prominent
The hardening was not so complete in the case of the folds the frenula Valvulse COli. It is
highest of the three valves represented. In each thought that when the C83CUni is dis-
tended, and its circumference thereby
increased, these frenula are put on the
stretch, and, pulling upon the two segments of the valve, they bring them into
apposition, and effect the closure of the orifice.
The position of the valvula coli, in the average condition, may be indicated
on the surface of the body by the point of intersection of the intertubercular and
vertical lateral lines. A point 1 to 1J inches (2*5 to 3'7 cm.) lower down would
correspond to the orifice of the vermiform process.
In bodies hardened in situ with formalin, the valve and orifice present an entirely different
appearance (see Fig. 952, in which three different forms of hardened valves are shown), suggesting,
much more closely than in the dried state, the appearance of telescoping or inversion mentioned
above. In them also the two segments of the valve are much thicker and shorter, but they can
Orifice
Lower
segment
Orifice of
vermiform
process
Orifice f
CAECUM AND VEKMIFOKM PKOCESS.
1215
always be distinguished, and are found to bear the same relation to one another as in the dried
condition, although this may be obscured by foldings or rugae. The aperture may be slit-like or
rounded, with sloping or funnel-shaped edges ; the frenula are not so prominent at times ; but
the whole valve projects mucn more abruptly into the cavity of the caecum than in the distended
and dried specimen.
Structure of the Valvula Coli. Each labium of the valve is formed of an
infolding of all the coats of the gut, except the peritoneum and the longitudinal muscular
fibres, and consequently consists of two layers of mucous membrane, with the sub-
mucosa and the circular muscular fibres between, all of
which are continuous with those of the ileum on the one
hand and of the large intestine on the other. The surface
of each labium turned towards the small intestine is
covered with villi, and conforms in the structure of its
mucous membrane to that of the ileum ; whilst the
mucous membrane of the opposite surface resembles the
mucous coat of the large bowel.
UCOUS MEMBRA
THROUGH THE JUNCTION OF THE
ILEUM WITH THE CAECUM, TO SHOW
THE FORMATION OP THE VAL-
VULA COLI.
In the dried specimen the superior labium usually projects
further into the cavity of the caecum than the inferior, so
that the aperture appears to be placed between the edge of
the inferior segment and the inferior surface of the superior.
There is little doubt that the efliciency of the valvula
coli is largely due to the oblique manner in which the ileum
enters or in vagina tes the large intestine ; this oblique passage
alone, as in the case of the ureter piercing the wall of the
bladder, would probably be sufficient to prevent a return of
the C33cal contents. In the great majority of cases, when in
position within the body, the ileum is perfectly protected from -----
such a return, although when the parts are removed, and then FlG> 953. DIAGRAMMATIC SECTION
distended with fluid, this fluid often passes through the valve,
and reaches the small intestine. Still, the efficiency of such a
test, applied when the parts are deprived of their natural
supports, cannot be relied upon.
The size of the segments of the valve, as seen in the dried
condition, varies considerably ; they are sometimes very imperfect ; and even the absence of
both has been recorded. But here again there is danger of falling into error, through examining
the parts under such artificial conditions.
Types of Csecum. Three chief types of caecum may be distinguished the fatal type, conical
in shape and nearly symmetrical, with the inferior end gradually passing into the vermiform
process ; the infantile, in which the passage from the caecum to the vermiform process becomes
more abrupt, the lateral wall more prominent, and the whole sac more asymmetrical ; and the lop-
sided adult form, as described above, which is the condition found in 93 or 94 per cent, of adults.
Structure. Nothing in the arrangement of the mucous and submucous coats calls
for special notice. The taenise or longitudinal bands of the muscular coat all spring
from the base of the vermiform process (Fig. 954) ; the anterior runs up on the front,
medial to the main prominence of the caecum ; the postero-lateral runs up behind this
prominence ; whilst the postero-medial passes directly upwards behind the ileum (Fig.
954). The longitudinal fibres on the superior aspect of the ileum partly join the postero-
medial tsenia ; those on the anterior and posterior aspects join the circular fibres of the
large gut.
The serous coat has, in connexion with it, certain folds and fossae which are described
1218.
Processus Vermiformis (Fig. 954). The vermiform process (O.T. appendix,
vermiform appendix) is a worm-like tubular segment which springs from the
medial and posterior part of. the caecum about 1 to 1 \ inches (2*5 to 3'75 cm.) below
the ileo-caecal orifice. From that point it generally runs in one of three chief direc-
tions, namely (1) over the brim, into the pelvis ; (2) upwards behind the caecum ;
or (3) upwards and medially, thus pointing towards the spleen ; each of which has
been considered to be the normal position by one or more observers. In the first
of these situations it is quite evident as it hangs over the pelvic brim ; in order
to expose it in the second, the caecum must be turned upwards ; whilst, in the third
position, it lies behind the end of the ileum and its mesentery, and these must
be raised up in order to display it. In addition to the positions just mentioned, it
1216 THE DIGESTIVE SYSTEM.
has been found in almost every possible situation in the abdomen which its length
and the extent of its mesentery would allow it to attain. In every case the
anterior taenia of the caecum, which is always distinct, offers the surest guide to
the vermiform process, and its base can be located with certainty by following
this taenia to the back of the caecum (Fig. 954).
Its size is almost as variable as its position. Taking the average of numerous
measurements, its length may be given as about 3J inches (92 mm., Berry), and
its breadth as J inch (6 mm., Berry). On the other hand, it has been found as
long as 9 inches (230 mm.), and as short as f inch (18 mm.). Even its absence
has been recorded (Fawcett), but this must be looked upon as an extremely rare
occurrence.
Its lumen or cavity is variable in its development, and is found to be totally
or partially occluded in at least one-fourth of all adult and old bodies examined.
This is looked upon as a sign of degeneracy in the process of gradual oblitera-
tion, which it is by many considered to be undergoing, in the human species. It
opens into the cavity of the caecum on its medial, or medial and posterior aspect
ANT
GAECAL
FIG. 954. THE BLOOD-SUPPLY OP THE C^CUM AND VERMIFORM PROCESS.
The illustration to the left gives a front view ; in that to the right the caecum is viewed from behind. In the
latter the artery of the process, and three taeniae coli springing from the base of the vermiform process
should be specially noted. (Modified from Jonnesco).
(Fig. 952), at a point 1 to 1 inches (2*5 to 3*8 cm.) below, and somewhat posterior to
the ileo-caecal orifice. These are the relative positions of the two orifices, as seen
from the interior of the caecum ; viewed from the exterior, the base of the vermiform
process is within f inch of the lower border of the ileum. This apparent difference
is due to the fact that the ileum adheres to the medial side of the caecum for a
distance of nearly 1 inch before it opens into it.
Sometimes the orifice of the vermiform process has a crescentic fold or valve,
the valvula processus vermiformis, placed at its superior border ; but it is probably of
very little functional importance, for the aperture of the process is usually so
small that its cavity is not likely to be invaded by the contents of the caecum.
The vermiform process is completely covered with peritoneum, and has a con-
siderable mesentery, the mesenteriolum processus vermiformis (O.T. meso-appendix),
which extends to its tip as a rule, and connects the process to the inferior surface of
that part of the mesentery proper which goes to the inferior extremity of the ileum.
The vermiform process is relatively, to the rest of the large intestine, longer in the child at
birth than in the adult, the proportion being about 1 to 16 or 17 at birth and 1 to 19 or 20 in
the adult. (The difference is certainly not as great as stated by Ribbert, who makes the
proportion 1 to 10 at birth and 1 to 20 in the adult.) The process attains its greatest length and
diameter during adult and middle age, and atrophies slowly after that time. It is said to be
slightly longer in the male than in the female.
Total occlusion of its cavity is found in 3 or 4 per cent, of bodies ; it is then converted into a
fibrous cord. Partial occlusion is present in 25 per cent, of all cases, and in more than 50 per cent.
(LECUM AND VEKMIFOKM PEOCESS.
1217
of those over 60 years old, whilst it is unknown in the child. This frequency of occlusion, the
physiological atrophy which takes place after middle life, the great variations in length, and other
signs of instability, have been considered to point to the retrogressive character of the vermiform
process.
A vermiform process is found only in man, the higher apes, and the wombat, although in
certain rodents a somewhat similar arrangement exists. In carnivorous animals the caecum is very
slightly developed ; in herbivorous animals (with a simple stomach) it is, as a rule, extremely large.
It has been suggested that the vermiform process in man is the degenerated remains of the
herbivorous caecum, which has been replaced by the carnivorous form. Another and perhaps
more probable view regards the process as a lymph organ, having the same functions as lymph
nodules, and, like these, undergoing degeneration after middle life (Berry).
In the foetus and child, as well as in the adult with the infantile type of caecum, the vermi-
form process springs from the true apex, not from the medial and posterior aspect.
FIG. 955. STRUCTURE OF THE VERMIFORM PROCESS.
A. From a child two years old. B. From a male, age 56.
It will be observed that the tela submucosa is almost entirely occupied by lymph nodules and patches. The
lamina muscularis mucosae is very faint, and lies quite close to the bases of the intestinal glands. The
longitudinal layer of muscular fibres forms a continuous sheet.
Foreign bodies, although reputed to find their way very easily into the vermiform process, are
rarely found there after death. On the other hand, concretions or calculi, formed of mucus,
faeces, and various salts, are often present (Berry).
Structure (Fig. 955). The tunica serosa is complete, and forms a perfect investment
for the process. The tunica muscularis, unlike that of the rest of the large intestine, has a
continuous and stout layer of longitudinal fibres, which passes at the root of the process
into the three tsenise coli (Fig. 954). The layer of circular fibres is well developed. The
tela submucosa is almost entirely occupied by large masses of lymph tissue surrounded
by sinus-like lymph spaces. Owing to the large size of these lymph nodules, the areolar
tissue of the submucosa is compressed against the inner surface of the muscular coat, and
forms a well-marked fibrous ring, which sends processes at intervals between the lymph
masses towards the mucous membrane. These lymph nodules, which correspond to
solitary lymphoid nodules, have, owing to their great number, been almost completely
crushed out of the mucosa (in which they chiefly lie in the intestine) into the submucosa.
The mucous coat corresponds to that of the large intestine in its general characters,
but the intestinal glands are fewer, and irregular in their direction ; the lamina muscularis
mucosse is thin and ill-defined ; it lies just internal to the lymphoid nodules of the sub-
mucosa, and immediately outside the base of the intestinal glands. Some few lymph
nodules lie in the mucous coat also.
Blood-vessels of the Csecum and Vermiform Process (Fig. 954). These parts are
supplied with blood by the ileo-colic artery. This gives off, near the upper angle formed by the
junction of the ileum with the small intestine (a) an anterior ileo-ccecal artery, which passes
down on the front of the ileo-caecal junction to the caecum, and breaks up into numerous branches
for the supply of that part ; (6) a posterior ileo-ccecal artery, similarly disposed on the back ; and
i the artery for the vermiform process. The last-named branch passes down behind the ileum (Fig.
954), then enters the mesentery of the process, and running along this near its free border, sends off
several branches across the little mesentery to the process, before finally ending in it. The course
of the artery behind the ileum is said to render it subject to pressure from faecal masses in that
gut, and thus to predispose to an interference with the blood supply of the vermiform process,
and to morbid changes in it.
78
1218
THE DIGESTIVE SYSTEM.
The lymph, vessels of the caecum and vermiform process arise mainly from networks in the
mucous and serous coats.
The first of these networks communicates with a lymph sinus which is found at the base of
the lymph nodules in the process, and the vessels from it pierce the muscular coats, and pass
in company with the blood-vessels. They are connected with mucous lymph glands found near
the ileo-caecal junction, especially on the posterior and medial aspect, in the angle between the
ileum and colon.
Small isolated glands may be found lying in close contact with the medial part of the caecum,
on its anterior and posterior aspects. From these glands, the lymph stream is directed upwards
and medially towards the cceliac and lumbar glands. The lymph vessels of the vermiform
process may also communicate with the lymph nodes in the iliac fossa, and also, it has been
stated, with the lymph vessels of the right ovary.
Caecal Folds and Fossae. The peritoneum in the neighbourhood of the caecum
forms certain fossae, of which the most interesting and important are (a) the fossa
caecalis ; (b) the recessus ileocaecalis inferior ; (c) the recessus ileocaecalis superior ; and
(d) the recessus retrocsecalis.
(a) The fossa caecalis (Fig. 956, B) is only occasionally present, and can be exposed by
turning the caecum and adjacent part of the ileum upwards. It is a fossa in the
VERMIEORM
PROCESS
ETRO-CAECAL FOSSA
B
FIG. 956. THE C^ECAL FOLDS AND FOSS.E.
In A, the caecum is viewed from the front ; the mesentery of the vermiform process is distinct, and is attached
above to the inferior surface of the portion of the mesentery going to the end of the ileum. In B, the
caecum is turned upwards to show a retro-caecal fossa, which lies behind it and behind the beginning
of the ascending colon.
parietal peritoneum on the posterior abdominal wall, open above, in which the lower end
of the ceecum occasionally lies. It is produced by the plica ccecalis, a peritoneal fold which
passes from the surface of the iliacus to the right lateral aspect of the caecum. Two forms,
lateral and medial, are described ; the first lies behind the lateral part of the ascending
colon, immediately above the caecum ; the second behind its medial part. These fossae
are specially interesting because, when present, they frequently lodge the vermiform pro-
cess (see Fig. 956, B), a condition which is said to favour the production of appendicitis.
(b and c) Recessus Ileocaecales and Plica Ileocsecalis. If the vermiform process is
drawn down, and the finger run towards the caecum, along the inferior border of the terminal
part of the ileum, its point will generally run into a fossa situated in the angle between
the ileum and caecum (Fig. 956, A), which is known as the recessus ileoccecalis inferior.
The fold which bounds the fossa in front is the plica ileoccecalis (O.T. the "bloodless
fold of Treves "). It passes from the ileum to the front of the mesentery of the
vermiform process, which forms the posterior wall of the fossa.
The plica ileocaecalis contains some unstriped muscle fibres continuous with the
longitudinal muscle coat of the caecum, and some fat especially at its free margin.
The recessus ileocaecalis inferior is bounded above by the lower end of the ileum, to
the right by the caecum, in front by the plica ileocaecalis, behind by the root of the
mesenteriolum of the processus vermiformis, while it is open to the left or medially.
Similarly, if the finger is run out along the superior border of the ileum towards the
caecum, it will usually lodge in a smaller fossa, the recessus ileoccecalis superior, which is
COLON. 1219
bounded in front by a small peritoneal process, the ileo-colic fold (Fig. 956, A), containing
the anterior csecal artery.
The recessus ileocsecalis superior lies at the upper margin of the opening of the
ileum into the colon, and is bounded behind by the ileum, to the right by the
Ccecum.
(d) Recessus Retrocaecalis. This is an occasional recess which passes upwards between
the ascending colon and the posterior abdominal wall. Its orifice looks downwards or to
the left, and lies in the fossa ctecalis behind the caecum.
COLON.
Colon Ascendens. The ascending colon begins about the level of the inter-
tubercular plane, opposite the ileo-caecal orifice, where it is continuous with the
caecum. From there it runs upwards and somewhat posteriorly, with a slight con-
cavity to the left, until it reaches the inferior surface of the liver, where it bends
forwards and to the left, and passes into the right flexure of the colon (Fig. 957).
In its course it lies in the angle between the quadratus lumborum, and the more
prominent psoas major medially (Fig. 957).
It is situated chiefly in the right lumbar region, but it extends slightly into
the hypochondrium above ; and, although ifr usually begins about the level of the
intertubercular plane, still with a low position of the caecum it will extend further
down, and may occupy a considerable part of the iliac region.
Its length is extremely variable, depending upon the extent to which the caecum
has descended from the position it occupied during development, viz., in contact
with the under surface of the liver.
It is from 5 to 8 inches long, and it is wider and more prominent than the
descending colon. It generally presents several minor curves or flexures, and
it often has the appearance of being pushed into a space which is too short to
accommodate it.
Relations. Anteriorly, it is usually in contact with the abdominal wall, but the
small intestine frequently intervenes, particularly above (Fig. 957). To its medial
side lie the coils of the small bowel and the psoas major ; to the lateral side is the
side wall of the abdomen. Its posterior surface, which is free from peritoneum
as a rule (Fig. 968), is connected by areolar tissue to the iliacus muscle as far up as
the crest of the ilium, to the quadratus lumborum above that, and finally to the
inferior part of the right kidney.
In the great majority of cases only the two sides and the anterior surface are
covered with peritoneum, the posterior surface being destitute of a serous coat (Fig.
968). In a small proportion of bodies, however, the ascending colon is provided
with a complete peritoneal coat and a mesentery, but this latter is so short that it
admits of but a slight amount of movement in the gut.
On the lateral aspect of the caecum and colon there are occasionally found
small peritoneal pockets termed recessus paracolici.
Like the csecum, the ascending colon is frequently found distended with gas or faeces after
death, hence in part its large size and prominence as compared with the descending colon, which
is generally empty.
Flexura Coli Dextra. The right (O.T. hepatic) flexure of the colon is the
bent piece of the large intestine between the end of the ascending colon and the
beginning of the transverse colon (Figs. 947 and 957).
When the ascending colon reaches the inferior surface of the liver, it bends
usually acutely, sometimes obtusely forwards and to the left on the anterior surface
of the right kidney, and on reaching the front of the descending portion of the
duodenum, passes into the transverse colon.
The flexure is placed between the descending duodenum medially and the
anterior thin margin of the liver, or the side wall of the abdomen, laterally ; above,
it corresponds to the colic impression on the liver, and posteriorly it rests on the
kidney. Its peritoneal relations are similar to those of the ascending colon.
Colon Transversum. This is the long and looped portion of the large intestine
78 a
1220 THE DIGESTIVE SYSTEM.
which lies between the right and left flexures. It begins at the end of the right
flexure, at the point where the colon passes forwards from the anterior surface
of the kidney, and, turning to the left, crosses the descending duodenum (Fig. 957).
It runs at first transversely to the left, and for the first few inches is compara-
tively fixed, being united to the front of the descending part of the duodenum 'and
the head of the pancreas either by a very short mesentery or by areolar tissue.
Immediately to the left of the head of the pancreas a long mesentery is developed,
which allows the colon to hang down in front of the small intestine, at a con-
siderable distance from the posterior abdominal wall. The portion of the colon
so suspended is therefore very movable, and consequently its position is very variable,
and is influenced by posture and by the condition of the other viscera. Towards
its left extremity the mesentery shortens again, thus bringing the gut towards the
tail of the pancreas (Fig. 957), along which it runs upwards into the left hypo-
chondrium, under cover of the stomach, as far as the inferior end of the spleen,
where it passes into the left (O.T. splenic) flexure (Fig. 942). Its two ends lie in
the right and left hypochondriac regions respectively, whilst its middle portion
hangs down into the umbilical, or even the hypogastric region.
Its average length is about 19 or 20 inches (47'5 to 50*0 cm.), that is, more
than twice the distance, in a direct line, between its two extremities. This great
length is accounted for by the curved and somewhat irregular course which the
bowel pursues.
Relations. The greater part 'of the transverse colon lies behind the greater
omentum, which must consequently be turned upwards in order to expose it.
Above, it is in contact, from right to left (Fig. 957), with the liver and gall-bladder
(which also descend in front of the colon), the stomach, and, near its left end, with
the tail of the pancreas and inferior end of the spleen (Fig. 947). Anteriorly are placed
the omentum and the anterior abdominal wall ; towards its termination the stomach
also is anterior. Posteriorly, it first lies in contact with the descending duodenum
and head of the pancreas; further to the left, where it hangs down, the small intestine
is placed below and posteriorly, and it is connected to the posterior abdominal wall
(more correctly, to the anterior border of the pancreas) by the transverse mesocolon.
It is also loosely connected to the stomach by the gastro-colic ligament which is
attached to its anterior surface. The transverse mesocolon and the gastro-colic
ligament are described with the peritoneum, p. 1242.
The transverse colon is completely covered with peritoneum, with the exception
of the first few inches of its posterior surface, which are often, if not usually,
uncovered.
The state of the peritoneal covering on the posterior surface of the first part of the transverse
colon would seem to depend, in some degree, on the extent to which the liver passes downwards
on the right side. With a small, high liver no mesentery is present, and the posterior surface ia
devoid of peritoneum ; on the other hand, when the liver is enlarged in the vertical direction,
it pushes the colon downwards before it, and brings the upper line of the peritoneal reflection
from its back, into contact with the lower, thus giving rise to the mesentery. In the foetus of
three or four months every part of the colon is supplied with a long mesentery ; subsequently
this, as a rule, disappears at the beginning of the transverse colon, but it may be reproduced in
the manner stated.
Flexura Coli Sinistra (Left Flexure of the Colon (O.T. Splenic Flexure)).
The terminal portion of the transverse colon runs upwards (also posteriorly and
to the left) until the inferior end or base of the spleen is reached ; here it bends
sharply, forming the left flexure, and runs down into the descending colon. The
flexure is placed deeply in the left hypochondrium, posterior to the stomach, and
in contact with the base of the spleen. It lies at a higher level than the right
colic flexure, and is' connected to the abdominal parietes by the phrenico-colic
ligament, which helps to maintain it in this position.
Ligamentum Phrenicocolicum (Fig. 947). This is a triangular fold of peritoneum,
with a free anterior border, which is attached medially to the left flexure and
laterally to the diaphragm opposite the ninth to the eleventh rib. (Owing to the
fact that the base of the spleen rests upon it, the ligament has also received the
older name of sustentaculum lienis.)
COLON.
1221
The phrenico-colic ligament is formed in the fcetus from the left margin of the greater
lentum (Jonnesco).
The peritoneal covering o.f the left colic flexure is similar to that of the descending colon.
Colon Descendens. The descending colon is much narrower and less obtrusive
than the ascending colon : indeed in a large number of cases it is found firmly
contracted. It begins in the left hypochondrium at the left flexure, passes down
on the left side of the abdomen, and ends in the lumbar region, opposite the crest
of the ilium, by passing into the iliac colon. Its course is not quite straight, for it
first curves downwards and medially along the lateral border of the left kidney,
and then descends almost vertically to the iliac crest (Fig. 957).
Its length is usually from 4 to 6 inches (10 to 15 cm.), and its width, which is
less than that of the ascending colon, about 1J inches (37 mm.).
6th costal cartilas
7th costal cartilage
Lig. teres
8th costal cartilage
Gall-bladder
9th costal cartilage
Liver
10th costal cartilage
Duodenum
light flexure of colon
Kidney
Caecum
Ileum*
Vermiform process
.
Xiphoid process
th costal cartilage
7th costal cartilage %
Stomach
8th costal cartilage
Transverse colon
9th costal cartilage
10th costal cartilage
Duodeno-jejunal
flexure
~ Kidney
Descending colon
Mesentery, cut
Bifurcation of abdominal
aorta
...- Iliac colon
.- Pelvic colon
- Urinary bladder
. 957. THE ABDOMINAL VISCERA AFTER THE REMOVAL OF THE JEJUNUM AND ILEUM (from a photograph
of the same body as depicted in Fig. 942). The transverse colon is much more regular than usual. -
Relations. The descending colon first lies in contact with the lateral border of
the left kidney; below that it is placed, like the colon of the opposite side, in the angle
between the psoas and quadratus lumborum muscles. Posteriorly, it rests upon the
lower part of the diaphragm above, and on the quadratus lumborum below.
Anteriorly (and somewhat laterally also, except when the bowel is distended)
are placed numerous coils of small intestine, which hide the colon completely from
view, and compress it against the posterior abdominal wall. To its medial side lies
the inferior part of the kidney above, the psoas major below.
In the great majority of bodies only the front and sides of the descending
colon are covered with peritoneum (Fig. 968) ; the posterior surface, being destitute
of a serous coat, is connected to the posterior wall of the abdomen by areolar
tissue. In a small proportion of cases, on the other hand, the serous coat is com-
plete, and the colon is furnished with a short mesentery.
Up to the fourth or fifth month of foetal life the descending colon has a complete investment
of peritoneum and a long mesentery. After the fifth month the mesentery adheres to, and soon
78 I
1222
THE DIGESTIVE SYSTEM.
blends with, the parietal peritoneum on the posterior abdominal wall, and is completely lost as
a rule. The persistence of this mesentery, in a greater or less degree, explains the occasional
presence of a descending mesocolon in the adult.
Iliac Colon. This corresponds to the portion of the "sigmoid flexure" which
lies in the iliac fossa, and it has no mesentery. It is the direct continuation of
the descending colon, with which it agrees in every detail, except as regards its
relations. Beginning at the crest of the ilium, it passes downwards and somewhat
medially, lying in front of the iliacus muscle. A little way above the inguinal
ligament it turns medially over the psoas major, and ends at the medial border of
this muscle by dipping into the pelvis and becoming the pelvic colon (Fig. 958). It
usually measures about 5 or 6 inches (12'5 to 15 cm.) in length, but it varies
considerably in this respect.
Fibro-cartilage between
4th and 5th lumbar vertebrae
V. iliaca communis
Pelvic mesocolon
A. iliaca communis
Commencement of iliac colon
Sacculation
V. hypo-
gastrica
A. hypo-
gastrica
Pararectal
Appendix
epiploica'
Tsenia anterior
V. iliaca externa
A. umbilicalis dextra ,
Median umbilical ligament artery (urachus)
A. umbilicalis sinistra
Urinary bladder, superior surface
A. umbilicalis sinistra
FIG. 958. THE ILIAC AND PELVIC COLON IN SITU.
Relations. Posteriorly, it lies upon, and, as a rule, is connected by areolar
tissue to, the front of the ilio-psoas muscle. It also crosses the left ureter, the
left internal spermatic vessels, and the femoral nerve. Anteriorly, it is usually
covered by coils of smaU intestine, which hide it from view ; but when distended,
or when it occupies a lower position than usual, it comes into direct contact, wit
the anterior abdominal waU. As a rule (90 per cent, of bodies Jonnesco), it
covered with peritoneum only on its sides and anterior surface. Occasionally
(10 per cent, of cases) it is completely covered, has a short mesentery (1 inch, 2
3 cm.), and is slightly movable.
In its course it passes. down over the iliac fossa near its middle, generally forming a curve
with its concavity directed medially and upwards, and having reached a point 1| or 2 inch <
to 5 cm.) above the inguinal ligament, it turns medially across the psoas major towards the pel
cavity. Occasionally the iliac colon occupies a lower position than this, and runs along tl
surface of the inguinal ligament, immediately behind the anterior abdominal wall.
Pelvic Colon. The pelvic colon is a large coil of intestine, which begins at the
medial border of the left psoas major muscle, where it is continuous with the il
.
COLON. 1223
Ion, and ends at the level of the third sacral vertebra by passing into the rectum.
Between those two points it has a well-developed mesentery, and forms a large and
iously shaped coil, which usually lies in the cavity of the pelvis (93 per cent.).
Whilst the loop of the pelvic colon is very irregular in form, the following may
given as perhaps its most common arrangement. Beginning at the medial margin
of the left psoas major, it first plunges over the brim into the pelvis minor, and
crosses that cavity from left to right ; it next bends backwards and then returns
along the posterior wall of the pelvis towards the median plane, where it turns
down and passes into the rectum (Figs. 957 and 958).
Relations. In its passage into the pelvis it crosses the external iliac vessels ;
running from left to right across the cavity, it rests on the bladder or uterus,
according to the sex ; whilst the coils of the small intestine lie above it.
It is completely covered by peritoneum, and is furnished with an extensive
mesentery the pelvic mesocolon which permits of considerable movement.
In cases where the pelvic colon is unusually long (Fig. 957), in returning from the right
side of the pelvis it crosses the median plane, going even as far as the left wall, and then turns
back a second time towards the middle of the sacrum, where it joins the rectum at the usual
level, thus making an S-shaped curve within the pelvis. On the other hand, when the
loop is short (a not infrequent occurrence), all its curves are abridged, and it fails to pass
over to the right side, but runs more or less directly backwards after entering the pelvis.
From what has been said it will be seen that the loop of the pelvic colon is subject to
numerous and considerable variations, which are dependent chiefly upon its length and that of
its mesentery, and also upon the state of emptiness or distension of itself and of the other pelvic
viscera. When the intestine is long the loop is more complex ; when short, more simple. When
the bladder and rectum are distended, or when the pelvic colon itself is much distended, it is
unable to find accommodation in the pelvis minor, and consequently it passes up into the
abdominal cavity, almost any part of the lower half of which it may occupy. But, as already
stated, in the great majority of cases (92 per cent., according to Jonnesco) it is found after
death lying entirely within the pelvic cavity.
In length, the pelvic colon generally measures about 16 or 17 inches (40 to
42*5 cm.), but it may be as short as 5 inches (12 cm.), or as long as 35 inches
(84 cm.).
The pelvic mesocolon, which corresponds to both the sigmoid mesocolon and the meso-
rectum, is a fan-shaped fold, short at each extremity, and long in its middle portion (Figs. 957
and 958). Its root is attached along an inverted V-shaped line, one limb of which runs up close
to the medial border of the left psoas major, as high as the bifurcation of the common iliac artery
(or often higher) ; here it bends at an acute angle, and the second limb descends over the sacral
promontory and along the front of the sacrum to the middle of its third piece, where the
mesentery ceases, and the pelvic colon passes into the rectum. When the pelvic colon ascends
into the abdominal cavity this mesentery is doubled up on itself, the side which was naturally
posterior becoming anterior.
Recessus Intersigmoideus. When the pelvic colon with its mesentery is raised upwards,
a small orifice will usually be found beneath the mesentery, corresponding to the apex of
the V - shaped attachment of its root to the posterior abdominal wall. This orifice leads
into a fossa which is directed upwards, and will often admit the last joint of the little
finger. It is known as the intersigmoid fossa, and is due to the imperfect blending of the
mesentery of the descending colon of the foetus with the parietal peritoneum. The ureter is
found lying behind the apex of this fossa. In the foetus this mesenterv is well developed, and
extends from the region of the vertebral column out towards the descending colon. After
a time it begins to unite with the underlying parietal peritoneum ; but in the region of
the intersigmoid fossa the union is rarely perfect, hence the presence of the fossa.
In the child at birth only the terminal part of the pelvic colon lies in the pelvis. This
is chiefly owing to the small size of the pelvic cavity in the infant. Beginning at the end
of the iliac colon, the pelvic colon generally arches upwards and to the right across the
abdomen towards the right iliac fossa, where it forms one or two coils, and then passes down
over the right side of the pelvic brim into the pelvic cavity. In cases of imperforate arius, it is
important to remember, in connexion with the operation for forming an artificial anus, that,
whilst the iliac colon is found in the left iliac region, the pelvic colon (" sigmoid flexure ") usually
lies on the right side, and passes over the right portion of the brim to enter the pelvis.
Structure of the Pelvic Colon. Only the arrangement of the muscular coat need be referred
to. As the tseniae of the descending colon are followed down, it will be found that the postero-
lateral band gradually passes on to the front, and unites with the anterior taenia to form a broad
band, which occupies nearly the whole width of this bowel in its lower portion. The postero-
medial tsenia spreads out in a similar manner on the back ; so that in the inferior half of the
pelvic colon the longitudinal layer of the muscular coat is complete, with the exception of a
narrow part on each side ; there the circular fibres come to the surface, and the intestine presents
1224
THE DIGESTIVE SYSTEM.
a series of small sacculations. The sacculations disappear, and the longitudinal fibres, although
thicker in front and behind, form a continuous layer all round, as the rectum proper is
approached.
INTESTINUM RECTUM.
Intestinum Rectum. The rectum is the portion of the large bowel which
intervenes between the pelvic colon above and the anal canal the slit-like
passage through which it communicates with the exterior (Fig. 961).
Unlike the portion of the bowel which immediately precedes it, the rectum has
but a partial covering of peritoneum, and is entirely destitute of a mesentery ;
sacculations, too, which are so characteristic of the large intestine, cannot properly
be said to be present.
The rectum begins at the termination of the pelvic mesocolon, namely, about the
Posterior superior spine
Upper lateral inflexion
Peritoneum (pararectal
Superior hsemorrhoidal
artery
Rectur
Sacro-tuberous ligament
Ischio-rectal fossa
Anal canal
Anus
Third sacral vertebra
Fourth sacral vertebra
(cut)
Lower border of
piriformis (cut)
Superior heemorrhoidal
artery
Middle lateral inflexion
occygeus
Levator ani
External sphincter
FIG. 959. THB RBCTUM FROM BEHIND.
The sacrum has been sawn across through the 4th sacral vertebra, and its inferior part removed with the coccyx.
The posterior portions of the coccygei, levatores ani, and of the external sphincter have been cut away.
The " pinching in " of the lower end of the rectum by the medial edges of the levatores ani, resulting in the
formation of the flattened anal canal, is suggested in the illustration, which has been made from a
formalin-hardened male body, aged 30. The lateral inflexions of the rectum, corresponding to the
plicae transversales recti, are also shown.
level of the third sacral vertebra, and ends, where the bowel pierces the pelvic floor,
opposite the inferior and posterior part of the prostate in the male, or at a point
1J inches (3*7 cm.) in front of, but at a more inferior level than, the tip of the
coccyx in both sexes. It first descends along the front of the sacrum and coccyx,
following the curve of these bones ; beyond the coccyx, it rests, for about 1 J inches
(3*7 cm.), on the posterior part of the pelvic floor, there formed by the union of the
two levatores ani ; and finally, having reached the inferior part of the prostate,
it bends rather abruptly backwards and downwards, pierces the pelvic floor,
and passes into the anal canal (Fig. 959).
EECTUM.
1225
Its general direction is downwards, but this varies at its two extremities, being
downwards and backwards above, downwards and strongly forwards below.
Curvatures. The rectum is far from straight, notwithstanding its name,
for it is curved in both the an tero- posterior and the transverse planes.
Viewed from the side, it forms a gentle curve, with the convexity posteriorly,
which extends from the beginning of the rectum to the back of the
prostate, and fits into the hollow of the sacrum and coccyx (flexura sacralis). At
the back of the prostate a second curve (flexura perinealis) is formed where the rectum
joins the anal canal. The convexity of the perineal flexure is directed forwards,
Lateral inflexions
TTuper rectal val
Ureter (cut)
Vesicula seminalis
Ductus deferens
,,. Pudendal venous
plexus
White line of pelvic fascia
* Levator ani
Outline of empty urinary bladder
Urethra
Base of prostate
FIG. 960. DISTENDED KECTUM IN SITU.
>m a formalin -hardened male body, age 56. The peritoneum and extra-peritoneal tissue were removed, after
the pelvis had been sawn along a plane passing through the superior part of the symphysis pubis in front
and the lower part of the second sacral vertebra behind. The bladder, which was empty and contracted,
has also been removed, but its form is shown by a dotted line. The rectum was very much distended,
and almost completely occupied the pararectal fossse.
whilst its concavity embraces the ano-coccygeal body the mass of muscular and
connective tissue which lies between the tip of the coccyx and the anal canal.
When vieived from the front the rectum is seen to be regularly folded from side
to side in a zigzag fashion, the folding being slightly marked when the rectum is
empty, but becoming much more distinct with distension (Figs. 960 and 961). In
other words, when viewed from this aspect it presents, in the majority of cases, three
more or less distinct lateral flexures or inflexions. Of these the upper and lower
have their concavities directed to the left as a rule; the third flexure, which is the
best marked, lies between the other two, but on the right side. Not infrequently,
however, two are found on the right and one on the left side. The flexures, which
1226 THE DIGESTIVE SYSTEM.
are marked on the exterior by a crease, appear in the interior as three
prominent crescentic shelves (Fig.. 9 60), known as the plicae transversales recti
(O.T. Houston's valves), which help to support the faecal contents when the rectum
is distended.
This folding is maintained by the arrangement of the longitudinal muscular fibres, the
majority of which are accumulated in the form of two wide bands, one on the front, the other on
the back of the bowel. These two bands, which are continuous with, and comparable in their
functions to, the taeniae of the colon, are shorter than the other coats of the rectum ; hence they
give rise, as in the case of the colon, to a folding or sacculation of the tube, which can be effective
only at the sides where the longitudinal fibres are fewest, for the front and back are occupied by
the thickened longitudinal bands (see p. 960).
In addition to supporting the faeces, these foldings greatly increase the capacity of the rectum
without unduly dilating the tube. When the rectum is empty (Fig. 961) its course is comparatively
straight, its lateral flexure being but slightly marked, and its whole calibre very much reduced.
In this condition it occupies only a small portion of the posterior division of the pelvic cavity
near the median plane, and at each side, between it and the side^wall of the pelvis, is a large
fossa of the peritoneum (the pararectal fossa, p. 959), which, when the bowel is empty, contains
a mass of small intestine or pelvic colon (Figs. 959 and 961). When the rectum is distended the
lateral flexures become much more marked, and the gut, projecting alternately to each side, passes
out beneath the peritoneum, obliterating the pararectal fossae (Fig. 960), and fills the greater part
of the posterior division of the pelvis a condition which could not be brought about with a
straight rectum without an enormous increase in all the diameters of the tube.
According to Jonnesco, the rectum begins that is, the pelvic mesocolon ceases most frequently
opposite the fibro-cartilage between the third and fourth sacral vertebrae. It is our experience
that the mesocolon ends more frequently above than below the third sacral vertebra often, indeed,
at the level of the second (Birmingham).
At its superior end the rectum, following the curve of the sacrum, slopes downwards and at the
same time slightly backwards ; its middle portion is practically vertical, but the terminal third
or more is directed downwards and forwards at an angle varying from 45 to 60 with the horizontal.
The pelvic floor, upon which this latter part rests, forms here a similar angle with the horizontal.
The bend which the bowel makes behind the inferior end of the prostate, where the rectum passes
into the anal canal, is, as pointed out above, abrupt, and usually approaches a right angle, so
that the anal canal itself slopes downwards and backwards at an angle of nearly 45 with the
horizontal.
Not uncommonly the abrupt curve, at the junction of the rectum with the anal canal, presents
in front a knuckle-like projection (well seen on median section), immediately above the canal. It
is most marked in females, and sometimes appears as if the bowel were doubled back upon itself
at this point. The floor of the pouch thus formed may dip down in front, even below the level
of the upper aperture of the anal canal. This condition is most common in multiparae, and is
evidently due to the relaxed condition of the pelvic structures, and the slight support afforded
by the perineal body to this part of the gut in these, and the great capacity and shallowness of
the pelvis in the female.
In length the rectum usually measures about 5 or 6 inches (12*5 to 15'0 cm.), but
it may be much longer.
Its diameter is smallest above, near the junction with the pelvic colon, and is
greatest below, near the anal canal, where there is a special enlargement known as
the ampulla recti (rectal ampulla). When empty the rectum measures little over
an inch (2*5 cm.) in diameter, but in a state of extreme distension it may be as
much as 3 inches (7*5 cm.) in width.
Peritoneal Relations of the Rectum (Figs. 959, 961). As a rule the superior
two-thirds of the rectum has a partial covering of peritoneum anteriorly and at the
sides at first, lower down anteriorly only whilst the lowest third has no peritoneal
investment whatsoever. When the mesocolon ceases at the end of the pelvic colon,
its two layers separate and leave the posterior aspect of the rectum destitute of
peritoneum. Very soon the membrane quits its sides also, and is then found on
the front only ; so that the greater part of the rectum lies behind or beneath the
pelvic peritoneum, as it were, and is capable of expanding and contracting without
being in any way hampered by its partial peritoneal coat.
From the front of the rectum the peritoneum is carried forwards to the base of
the bladder in the male, forming the floor of the excavatio recto-vesicalis (recto-
vesical or recto-genital pouch, Fig. 961). In the female it passes to the superior part
of the posterior wall of the vagina, forming the floor of the excavatio recto-uterina
[cavum Douglasi] (O.T. pouch of Douglas, Fig. 961). At each side, in both sexes,
it passes from the front of the rectum on to the posterior wall of the pelvis, forming
the bottom of a large fossa, seen at the sides of the rectum when that bowel
EECTUM.
1227
is empty, and known as the pararectal fossa. As the rectum becomes distended
this fossa is encroached upon by the enlarging bowel, and soon is obliterated.
The level at which the" reflection of the peritoneum takes place from the front of
the rectum is of considerable practical importance in connexion with operations in
this region. As a general rule that reflection, that is, the bottom of the recto- vesical
pouch, is placed at a distance of 1 inch (2 - 5 cm.) above the base of the prostate, or
about 3 inches above the anus, but the level is subject to considerable variation,
being as a rule relatively much higher in well-developed muscular or fatty subjects,
whilst in emaciated bodies, owing to the thinness of the structures forming the
pelvic floor, it is usually lowef.
The bottom of the recto-vesical pouch may reach down in an extreme case to within an inch
(2'5 cm.) of the anus, whilst it is not at all rare to find it within 2 inches (5'0 cm.) of that orifice ;
on the other hand, it may be considerably higher than normal, sometimes being placed at a dis-
Second sacral-vertebra
Sacro-iliac. joint
Ending of pelvic mesocolon
Sacral nerves
Rectum
Pararectal fo;
Ureter (cut)
Crescentic fold of
peritoneum (recto-
genital fold)
Seminal vesicle
beneath this
Pararectal fossa
Ureter (cut)
Hypogastric artery
Obturator nerve
Ureter
Fossa
obturatoria
(Waldeyer)
Inferior epigastric! artery
Ureter
Paravesical fossa
Plica vesicalis transversa
Rectus
Pyramidalis
Iliacus
External iliac artery
Ductus deferens
Obliterated umbilical artery
Urinary bladder
Median umbilical ligament (urachus)
FIG. 961. THE PERITONEUM OF THE PELVIC CAVITY.
The pelvis of a thin male subject, aged 60, was sawn across obliquely. Owing to the absence of fat the various
pelvic organs are visible through the peritoneum, though not quite so distinctly as presented here.
The urinary bladder and rectum are both empty and contracted ; the paravesical and pararectal fossae, as
a result, are very well marked.
tance of 4 or 4^ inches (lO'O to 11-2 cm.) from the anus. It should also be added that the level is
generally believed to be somewhat raised by distension of the rectum and bladder, and lowered
when they are empty.
In the child at birth, the peritoneum extends down to the base of the prostate (Symington),
and is thus lower in relation to the bladder ; but this may be partly accounted for by the high
position of this organ in the child.
As a rule it will be found that 2 inches (5'0 cm.) of the front of the rectum, exclusive of the anal
canal, are entirely free from peritoneum, and it is this and the adjacent portion of the bowel which,
being free from the restraining influence of the peritoneum, is most distensible, and forms
the rectal ampulla. Including the anal canal, 3^ inches (87 cm.) of the rectum, measured along
the front of the tube, have no serous covering. On the other hand, the back is free from peri-
toneum for 5 or 6 inches (12'5 to 15'0 cm.) or sometimes much more above the anus.
It is also of interest to notice th'at the connexion of the peritoneum to the rectum varies in
its character at different parts : Above and in front it is closely adherent, and can be removed
only with the greatest difficulty ; at the sides and inferiorly the connexion is much looser. As a
result, the peritoneum can be stripped off the rectum in its inferior third or half without much
.ifficulty, whilst in its superior portion this is not the case an arrangement which admits of the
free expansion of the rectal ampulla.
1228 THE DIGESTIVE SYSTEM.
General Relations of the Rectum (Figs. 959 and 960). Posteriorly, the rectum
rests on the front of the sacrum and coccyx, and below them upon the posterior part
of the pelvic floor formed by the meeting of the two levatores ani in the ano-
coccygeal raphe. When much distended it also comes into relation, on each side,
with the lower part of the piriformis and the sacral plexus, but is separated from
them by a very considerable amount of connective tissue, arranged (apparently in
several layers) around the tube. In this tissue the two chief branches of fhe
superior hsemorrhoidal vessels lie behind the superior part of the bowel, but lower
down they are placed in relation to its sides.
At its sides above are the pararectal fossae and their contents (pelvic colon, or
ileum) ; below the pararectal fossae the rectum is in contact with the coccygei and
levatores ani muscles, which run backwards to the coccyx on each side of the
bowel. The branches of the superior haemorrhoidal vessels are also found running
down on its muscular coat, as far as the middle of the rectum, where they pierce
the wall of the bowel.
Anteriorly, in the male the rectum is separated from the bladder, to within an
inch of the prostate, by the recto-vesical pouch of peritoneum, which usually
contains some coils of small intestine. Below the reflection of the peritoneum the
front of the bowel is in contact with the posterior aspect of the bladder, the deferent
ducts, vesiculae seminales, and the posterior aspect of the prostate gland (Fig.
960), from all of which it is separated by the recto-vesical layer of the pelvic fascia.
The lower portions of the rectum and bladder in the male are separated by the
recto-vesical fascia only, over a narrow triangular area which measures about an
inch (2'5 cm.) in vertical height. The base of the triangle corresponds to the
reflection of the peritoneum from one organ to the other, and the apex to the
union of the sides formed by the deferent ducts, which lie very close to one
another except above, near the base of the triangle, where they diverge rather
abruptly (Fig. 960). Through the triangle the operation
D, duodenum ; E, pancreas ; F, greater omentum ; G, placed in the beginning of the large
great sac ; H, in omental bursa. intestine, with its mesentery,
is carried to the right across
e duodenum, and a fan -shaped portion of the general mesentery, lying within the
ncavity of the loop, is partially cut off; this, later on, forms the mesentery proper
the adult. At first it is continuous by its right border with the mesentery of the
Fia. 975. DIAGRAMS TO ILLUSTRATE THE DEVELOPMENT OF THE
. GREATER OMENTUM (after Hertwig).
1254 THE DIGESTIVE SYSTEM.
ascending colon, a part of the primitive mesentery (which is similarly continued into
the mesentery of the transverse, descending, iliac, and pelvic colons). Subsequently, as
shown by the darkly shaded parts in Fig. 974, the back of the mesenteries of the ascend-
ing, descending, and iliac portions of the colon adheres to the posterior abdominal wall,
and these mesenteries become lost ; whilst the mesenteries of the transverse and pelvic
portions of the colon remain free, and persist in the adult.
At the same time, the mesentery proper (which was at first attached only at its
narrow neck, between the duodenum and transverse colon, and below this was continuous
on the right with the ascending mesocolon) now acquires a new attachment to the
posterior abdominal wall through the absorption of the ascending mesocolon (Fig. 974),
and the adult condition is attained.
DEVELOPMENT OF THE LIVER AND PANCREAS.
The glandular tissue of the liver and pancreas, and the epithelial linings of the ducts
of these organs, including the gall-bladder and cystic duct, are formed from protrusions of
Bile-ducts
Veins
Fia. 976. DIAGRAM illustrating the arrangement of the blood-vessels (on left) and of the hepatic cells and
bile-ducts (on right) within a lobule of the liver. The first diagram shows the interlobular veins
running around the outside of the lobule, and sending their capillaries into the lobule to join the central
vein. In the second diagram the bile capillaries are seen, with the hepatic cells between them,
radiating to the periphery of the lobule, where they join the interlobular bile-ducts.
the endothelial wall of the foregut, below the stomach. The connective tissue framework
of the glands is formed from the mesodermic tissue into which the protrusions grow.
The process of formation is as follows :
1. Liver. A longitudinal groove appears on the interior of the ventral wall of the fore-
gut, close to its union with the midgut, at about the third week. This groove appears on
the external surface of the gut as a projection, which rapidly increases in size and grows
forwards and upwards towards the lower part of the septum transversum. This septum
is a mass of mesodermic tissue which lies in front of the foregut, just below the heart,
and which is attached to the anterior and side walls of the trunk. It conveys the
umbilical and vitelline veins as they pass to the sinus venosus.
The liver bud grows into the lower (caudal) portion of the septum transversum, and
sends out strands of cells termed trabeculae, which come into contact with the vessels in
the septum, and enclose them.
By the growth of capillary vessels, from the vitelline and umbilical veins, and of the
trabeculse, a spongy network is produced, the framework of which is formed by branching
and anastomosing trabeculse, while the spaces of the network represent portions of the
lumen of the vessels, and are filled with blood. This form of vascular network is known
as a " sinusoidal circulation."
The trabeculse become hollowed out, and are reduced in size, so that eventually a
minute channel is formed in the centre of each of them, surrounded by a single layer of
cells. The lumen of the channel forms a bile capillary, and the cells surrounding it form
the secreting cells of the liver lobule.
The bile capillaries of adjacent trabeculse meet and unite, and converging together
DEVELOPMENT OF THE LIVEE AND PANCKEAS.
1255
hepatic vein, and the capillary network
constitute the bile-ducts within the liver. Adjacent trabeculse become arranged into the
form of a lobule, each with a vascular channel in its interior, which communicates with
the vascular network in the surface of the lobule by capillary intervals between adjacent
trabeculse.
The central vein becomes a tributary of
becomes the terminal
distribution of branches
of the portal vein.
The proximal portion gtomach
Spleer _ ^
/ iaphragm
--Spleen
Line crosses
mesogastrium
-Pancreas
Superior mesen-
Small intestine^ VWV (^^^^ teric artery
Superior mesen-
CEsophagus
Ventral mesentery
Liver
Ventral mesentery
Bile-duct
Stomach
Duodenum
teric artery
Small
intestine
Vitelline
duct
Caecum
Inferior mesenteric artery
Rectum
i -Colon
Inferior mesen-
teric artery
Rectum
The mesentery
Aorta
FIG. 977. Two DIAGRAMS TO ILLUSTRATE THE DEVELOPMENT OF THE
INTESTINAL CANAL.
The figure to the right shows the rotation of the intestinal loop around the
superior mesenteric artery. In both figures the parts are supposed to be
viewed from the left side.
of the original hollow
diverticulum becomes
the bile-duct, and the
gall-bladder and cystic
duct are formed by an
evagination from it.
As the liver increases
in size, it begins to pro-
ject down from the in-
ferior part of the septum
transversum into the
ventral mesentery, so
that now, instead of
being situated within the
septum, it looks like an
appendage of its inferior
surface. In other words,
the septum begins to
differentiate into two
parts an inferior, the
liver, and a superior,
which constitutes the
greater portion of the diaphragm, both of these having been at first one continuous mass.
In the course of development the separation of the two becomes more marked, and finally
is complete everywhere except at the coronary and lateral ligaments behind, and at the
falciform ligament in front, where they are still connected.
As the liver separates off from the future diaphragm, and descends into the abdomen,
I lies between the layers of the ventral mesentery a fold which connects the stomach
and duodenum with the anterior abdominal wall.
f\ This is divided by the liver into two parts a
\^%M\ lower, stretching from the front (lesser curvature)
\ ija of the stomach to the liver, which becomes the
\ *.-M-stomach lesser omentum ; and an upper, stretching from
the liver to the diaphragm and anterior wall of
/ jjj the abdomen, which forms the falciform ligament.
ft / ' *^r 2. Pancreas. The pancreas is developed at
Hepatic ducts ^^\ '(ji a veI 7 ear ly period in man (being present in
Gall-bladder < NJ\ \ k^^^^ embryos of 5 mm.) from two outgrowths from
"* *iu^sJ ^^h s rowth the alimentary canal, a dorsal and a ventral.
Pancreas ^^N ^ "^^ The dorsal rudiment is an outgrowth from
ventral growth '~^~'"&/ i "-Duodenum ^ e d orS al aspect of the intestine, anterior to the
origin of the hepatic outgrowth. The ventral
rudiment grows at a later stage from the root
^^"\ I of the hepatic bud in the form of two ventral
offshoots, one on either side. That on the left
FIG. 978,-DiAGRAM OP THE ORIGIN OF THE side however, soon disappears.
LIVER AND PANCREAS. Through the rotation of the duodenum around
its long axis, the dorsal and ventral rudiments
approach one another and become fused, and their ducts open on the left side of the
duodenum. The connecting stalk between the ventral rudiment and the hepatic bud
becomes the main duct of the pancreas, while the connexion of the dorsal outgrowth
with the duodenum remains as the accessory pancreatic duct. In embryos of the fifth
week, a large dorsal pancreatic rudiment is present, and also a smaller ventral rudiment,
ich opens into the duodenum in common with the bile-duct, and lies on the right of
1256 THE DIGESTIVE SYSTEM.
the vena portse. In the sixth week, these two rudiments meet and unite with one
another, forming a long slender glandular mass which passes backwards within the dorsal
mesogastrium (meso-duodenum), between the vertebral column and the greater curvature
of the stomach. The pancreas, so formed, follows the changes which occur in the position
of the stomach and of the dorsal mesogastrium. Consequently its free dorsal extremity
comes to be directed to the left, while the right extremity or head is included within
the hollow of the curve formed by the duodenum. At first, it possesses a dorsal mesen-
tery, a part of the dorsal mesogastrium, but from the fifth month this disappears,
coincidently with the rotation of the gland into the transverse axis of the body.
The lower part of the head, the body, and tail of the gland arise from the ventral
element, and the upper part of the head arises from the dorsal bud.
The primary diverticula give off buds, lined with cylindrical epithelium, and these in
turn give off other buds, and the process goes on until the mass of the gland is formed.
The islets of Langerhans are formed at a very early stage, from the entodermal lining
cells of the branching diverticula which form the gland acini.
THE URO-GENITAL SYSTEM.
BY A. FRANCIS DIXON.
THE URINARY ORGANS.
kidneys, or glands which secrete the urine, are a pair of almost symmetric-
ally placed organs, situated in the posterior part, of the abdominal cavity, one
on each side of the lower movable portion of the vertebral column. The fluid,
or urine, secreted by the kidneys is received into the upper expanded portions of
a pair of long tubes, the ureters, and by them it is conducted to the bladder,
which is placed within the pelvic cavity. From the bladder the urine is passed,
during micturition, along a passage called the urethra to the exterior. In the
male the urethra is a relatively long passage, and traverses the prostate gland and
the whole length of the penis ; in the female it is a short tube, and opens on the
surface just above the vaginal orifice.
THE KIDNEYS.
The kidney (ren), when removed from a fresh subject, presents a bean-shaped
contour. It is of a dark brown-red colour, and is surrounded by a thin glistening
capsule, the tunica fibrosa, which gives to the whole organ a uniformly smooth
surface. The kidney is not a solid body, but contains a cavity called the sinus
renalis, the opening into which, termed the hilum renale, is situated on the medial
and anterior part of the organ. Each kidney measures about 4J inches in length,
2 inches in width, and about 1 inches in thickness, and is placed so that its
long axis is nearly vertical. The weight of the adult kidney is about 4J
ounces. In the freshly removed kidney the superior and inferior ends are
\ smoothly rounded, and the extremitas superior or superior end is usually a little
more bulky than the extremitas inferior or inferior end. The margo lateralis or
lateral border, which is opposite the hilum, is rounded and convex, while the
margo medialis or medial border, on which the hilum is placed, is concave from above
downwards. These two borders separate the fades anterior or anterior surface
from the facies posterior or posterior surface of the kidney.
The capsule, which envelops the whole organ, divides in the region of the
hilum into two layers, one of which is continued over the lips of the hilum
into the interior of the kidney, and lines the walls of the renal sinus.
The other layer is prolonged to form a tubular sheath for the vessels and nerves
of the kidney before they pass through the hilum to enter the sinus, within
which they break up into branches. These branches, piercing the wall of the
sinus, enter the substance of the kidney. The upper expanded portion of the
ureter leaves the sinus, through the hilum, in company with the blood-vessels and
nerves.
Position of the Kidneys. The precise level of the kidney in the abdominal
cavity is subject to a considerable amount of variation, and, further, it is usual to
find a difference in the level of the right and left kidney in the same individual.
Most frequently the left kidney is on a somewhat higher level than the right,
but in many cases the kidneys are found to occupy the same level, or, the more
usual condition being reversed, the right kidney is a little higher than the left.
1257
1258
THE UKO-GENITAL SYSTEM.
If a line is drawn round the body at the level of the lowest part of the thoracic
wall, the whole, or almost the whole, of the left kidney will be found to lie above
the level of the subcostal plane so determined. It is, therefore, situated in the
subcostal zone of the abdominal cavity. The right kidney, however, although it
lies for the most part in the subcostal zone, usually projects at its inferior part
somewhat below the subcostal plane, and hence lies to some extent in the umbilical
zone. It is often stated that the kidneys are placed on a somewhat lower level
in the female than in the male subject.
By far the greater part, usually two-thirds or more, of the kidney lies to
the medial side of a line drawn vertically upwards through the middle point of
the inguinal ligament.
The posterior aspect of the kidney is closely applied against the muscles
attached to the bodies of the last thoracic and upper three lumbar vertebrae, and is
placed in front of the last rib and of the transverse processes of the upper three
Hepatic artery
Inferior vena cava
Pancreas
Left suprarenal gland
Splenic artery
Right suprarenal gland
Portal vein
Spleen
Bile-duct
Descending part
of duodenum
Right
kidney
Left flexure
of colon
Right flexure
of colon
Left kidney
Right ureter Spermatic vein
Inferior Left ureter
mesenteric vein
FIG. 979. DISSECTION TO SHOW THE RELATIONSHIPS OF THE KIDNEYS. The greater part of the stomach
has been removed by an incision made close to the pylorus. The transverse colon has been taken away
and the small intestine has been cut across close to the duodeno-jejunal flexure.
A model prepared by the late Professor Birmingham has been made use of in this drawing.
lumbar vertebras. In some cases, more frequently on the left side of the body,
the eleventh rib also lies behind the upper part of the kidney. The relationship
of the kidney to the lower two ribs is, however, very inconstant, owing partly to
the great variability in size and inclination of these bones.
The inferior end of the kidney is usually situated from 1 J to 2 inches above the
highest part of the crest of the ilium ; the interval between the kidney and the
ilium being usually greater on the left side of the body.
Sometimes the inferior end of the kidney lies on the same level as, or only a
short distance above, the iliac crest ; this condition is sometimes due to the crest
rising to a higher level than usual, the kidney occupying its normal position in
relation to the vertebral column. It is important to remember that during life
the kidney moves upwards and downwards, following the respiratory movements
of the part of the diaphragm against which it rests.
The long axis of each kidney is somewhat oblique, its superior end approaching
nearer to the median plane than the inferior. The surface of the kidney which
is applied against the muscles forming the posterior wall of the abdomen looks,
THE KIDNEYS.
1259
as a whole, backwards and medially, and that which projects into the abdominal
cavity looks forwards and laterally. Hence it happens that the lateral border lies
on a more posterior plane , than the medial border. The kidney is rotated in this
manner on its long axis to such a degree that the medial margin and hilum are
scarcely visible from behind, and only a limited view of the lateral border can be
obtained from the front (Figs. 979 and 980).
The kidneys are placed behind the peritoneum, and project into the posterior
part of the abdominal cavity. Each is surrounded by a considerable amount of loose
tissue, often loaded with fat ; the fatty tissue, or capsula adiposa, being present
in greater quantity round the margins of the kidney, and only to a less extent in
front of and behind the organ. The renal vessels and nerves lie in this fat before
they enter the kidney, and the adipose tissue is continued, along with the vessels,
through the hilum into the renal sinus, where it fills up all the space unoccupied
by the vessels and nerves.
Embedded in the soft fatty tissue surrounding the kidney is a layer of fibrous
Duoderio-jejunal flexure
Stomach
Head of Pancreas
Liver (left lobe) i. Transverse colon just below right flexure
Gall-bladder
Ascending
colon just
below right
flexure
Liver (right
- lobe)
Descending
part of
duodenum
llth
" Paranephric fat "
! : Intervertebral nbro-cartilage
" Perinephric fat " ' Crus of diaphragm
Quadratus lumborum
Cartilage of 12th rib Body of pancreas
}. 980. TRANSVERSE SECTION THROUGH THE BODY OF A CHILD. The position and relationships of the
kidneys are well seen, and the arrangement of the fascia renalis is indicated. The fascia is coloured green.
tissue to which the term fascia renalis is applied. This fascia surrounds the
kidney and a considerable amount of its fatty capsule in the form of a loose
sheath, in which may be distinguished anterior and posterior walls. The sheath
is open inferiorly and medially, but closed above and to the lateral side of the
kidney by the apposition of its walls. Laterally, the anterior and posterior
walls of the sheath come into contact and are connected with the retro-peritoneal
; tissue. Medially they remain distinct, and the anterior wall is continued across
, the median plane, in front of the renal vessels and the aorta, to join the correspond-
ing layer of the opposite side, while the posterior wall fuses with the fascia
i covering the psoas and quadratus lumborum muscles. Inferiorly, below the level
of the kidney, the anterior and posterior layers of the renal fascia remain
i separate, and can be traced downwards into the iliac fossa. Above the level of
i the kidney and the suprarenal gland the layers of the renal fascia unite and
join the fascia covering the diaphragm. It has been suggested that the terms
'' tunica adiposa" and "perinephric fat" should be restricted to the loose fatty
bissue enclosed along with the kidney within the sheath of renal fascia, and that
the term " paranephric body," or " fat," should be used to denote the tissue outside the
sheath. The fibrous capsule of the kidney is joined to the loose sheath formed by
1260
THE UEO-GENITAL SYSTEM.
the renal fascia by numerous connective tissue strands. These traverse the peri-
nephric fat and undoubtedly assist in fixing the kidney in its place. The paranephric
fat is present in greatest quantity behind the inferior part of the kidney, and in
this position the layer of fibrous tissue, separating the two masses of fat and
forming the posterior layer of the sheath of renal fascia, is usually well marked.
Fixation of the Kidney. The kidney is not held in its place by any distinct
ligaments, or special folds of peritoneum, but its fixation depends, to a large
extent, on the pressure and counter-pressure which is exerted upon it by neigh-
bouring structures, and on its connexions with the fascia renalis above described.
Posterior Relations and the Posterior Surface of the Kidney. The muscles
of the posterior abdominal wall on which the kidney rests are the psoas major, the
Pleura
Pleura
/Cms of
\ diaphragm
/ 1st lumbar
\ vertebra
12th rib
(Lateral
lumbo-
costal arch
Diaphragm
Kidney
Liver
Fat behind
colon
Quadratus
lumboruin
Iliac crest
[liac crest
FIG. 981. THE POSTERIOR RELATIONSHIPS OF THE KIDNEYS. The dotted lines indicate the contours of the
kidneys. The drawing is made from a model prepared by the late Professor Cunningham.
quadratus lumborum, the diaphragm and the tendon of the transversus abdominis.
The abdominal surfaces of these muscles do not lie on the same plane, but slope
towards one another, and thus the bed on which the kidney rests is not flat. When
but little fat is present, the posterior aspect of the kidney adapts itself to the
inequalities of the surface against which it is placed, and so we may find on a
kidney which has been carefully fixed and hardened before it has been disturbed,
areas marked off for the different planes of these muscles. When such a kidney is
in position, slight ridges or elevations separating these areas correspond to the
angles along which the different muscular planes meet. These ridges can be
observed in the hardened kidney, after its removal from the body, but usually
they are not sharply defined, the angles between the muscular planes being
very obtuse.
A kidney removed from the body after having been hardened in situ (Fig. 982
THE KIDNEYS.
1261
presents an area along the medial part of its posterior surface adapted to the
anterior aspect of the psoas major muscle. .This part of the posterior surface
looks medially and slightly posteriorly. More laterally there is a larger area
which rests against the quadratus lumborum and looks more directly backwards.
These two areas are separated by a rounded ridge which fits into the angle be-
tween the muscles mentioned. Beyond the area in contact with the quadratus
lumborum is the thick lateral border of the kidney, which rests for the most
part on the tendon of the transversus abdominis and on the diaphragm.
Towards the superior end of the kidney the posterior surface slopes somewhat
forwards and rests upon the diaphragm. Indeed the superior part of the kidney
is, as a whole, bent slightly forwards, following that part of the arch of the
diaphragm on which it rests, and thus a narrow interval is left, in which the pleural
cavity passes down behind the superior end of the kidney (Fig. 981). This relation-
Area for
diaphragm
Area for eras of
diaphragm
Area for
diaphragm
Area for
quadratus
lumborum
Area for psoas
majorf"
Area for psoas
major
982. THE POSTERIOR ASPECT OP THE KIDNEYS. Same specimen as Fig. 981. The dotted lines mark
out the areas in contact with the various muscles forming the posterior abdominal wall.
a. Depression corresponding to the transverse process of the first lumbar vertebra.
b. Depression corresponding to the transverse process of the second lumbar vertebra.
c. Depression corresponding to the twelfth rib.
ship of the pleural cavity to the kidney is of great importance in connexion with
surgical operations performed through a lumbar incision. The portions of the
diaphragm to which the kidney is applied are the crus and the parts arising from
the last rib and lumbo-costal arches.
The posterior relationships of the kidney are well seen in Fig. 981.
In addition to these surfaces, or "facets," for the muscles with which it is in contact, the
posterior aspect or lateral border of the kidney often shows a groove for the last rib, another for
the lateral lumbo-costal arch, and two or three depressions for the tips of the transverse processes
of the upper two or three lumbar vertebrae. In some cases also faint narrow grooves are to be
seen for the nerves which pass downwards and laterally between the kidney and quadratus
lumborum namely, the last thoracic nerve and the ilio-hypogastric and ilio-inguinal nerves.
It is probable that some at least of the depressions on the posterior aspect of the kidney are
produced after death, and are caused by the weight of the other abdominal organs pressing the
kidney backwards against the more resisting structures of the abdominal wall, at a time when
the muscles behind the kidney have become flaccid. When much fat is present the posterior
aspect of the kidney is more uniformly convex.
The lateral border in its middle and inferior part is rather a surface than a
border, and looks for the most part directly backwards. It rests on the diaphragm
and on the anterior surface of the tendon of the transversus abdominis, to the
1262
THE URO-GENITAL SYSTEM.
lateral side of the quadratus luinborum muscle. The lateral border is narrowest
above, and widest just below its. middle point, corresponding to the greater
thickness of the kidney at this level.
In many ways it would be more satisfactory to apply the term facies muscularis
or muscular surface collectively to the areas above described as " posterior surface "
and " lateral border " ; in like manner the term facies visceralis, or visceral surface
might be suitably applied to the so-called anterior surface of the organ. The ed^e
separating the visceral from the muscular surface is the actual lateral edge or
border of the kidney.
Anterior Relations and the Anterior Surface of the Kidney. The anterior
relations of the kidneys not only differ on the two sides of the body, but also many
Inferior vena cava
Right inferior phrenic artery | Coeliac arter.v
Right suprarenal gland
Right renal vein j
Genito-femoral nerve .
Right ureter , \
Internal spermatic vein
Ilio-hypogastric nerve
Ilio-inguinal nerve
Superior mesenteric artery
, Left crus of diaphragm
, Medial lumbo- costal arch
Diaphragm
Psoas major
Lateral lum bo-costal arch
uadratus lumborum
Transversus abdominis
Lateral cutaneous nerve of thigh Iliacus
External iliac artery j : External iliac artery
Hypogastric artery 1 Hypogastric artery
Common iliac artery 1
Internal spermatic artery Inferior mesenteric artery
FIG. 983. DISSECTION TO SHOW THE KELATIONSHIPS OF TEE KIDNETS AND OF THE URETERS
TO THE MUSCLES OF THE POSTERIOR ABDOMINAL WALL.
of the structures related to the anterior surface of each kidney undergo frequent
changes in position during life. Hence it is not possible to give more than a
general account of the anterior relationships of the kidneys.
Right Kidney. A small area on the superior part of the anterior surface of
the right kidney is in relation to the corresponding suprarenal gland (Fig. 983).
The rest of the superior part of the anterior surface is in contact with the visceral
surface of the liver, which is often hollowed out to form a fossa for the kidney.
The suprarenal gland is bound to the kidney by connective tissue, while the
part of the kidney in relation to the liver is, like the liver itself, covered by
peritoneum, and thus the two organs, although closely applied, are really separated
by a part of the general peritoneal cavity. Immediately anterior to the inferior end
of the right kidney are usually found two parts of the alimentary canal namely,
the descending part of the duodenum and the right flexure of the colon, or the
THE KIDNEYS.
1263
commencement of the transverse colon. The part of the kidney related to the
duodenum lies to the medial side of the area which touches the colon, but the exact
amount of the kidney in 'contact with each of these two parts of intestine varies
much in different subjects. Frequently the colon and the kidney are both covered
by peritoneum where they are in contact, but the duodenum is bound down to the
kidney by connective tissue. In addition to the structures mentioned, some portion
of the ileum, or of the jejunum, is often found in contact with a small part of the
right kidney near its inferior end.
In some cases the peritoneal membrane does not cover the whole of the surface
in contact with the liver, and then the superior part of the hepatic area of the
kidney is, like the anterior aspect of the suprarenal gland, bound by connective
tissue to the " uncovered " area on the posterior aspect of the liver.
Suprarenal area
Suprarenal area
Gastric area
plenic area
itic area
lodenal area
Colic area
sta iliaca
rista iliaca
FIG. 984. ANTERIOR ASPECT OF THE KIDNEYS AND GREAT VESSELS. The drawing' was made, before
removal of the organs, from a specimen in which the viscera had been hardened in situ. The dotted lines
mark out the areas which were in contact with the various other abdominal viscera.
Left Kidney. The extreme superior and medial part of the anterior aspect of
the left kidney is united by connective tissue to the lower part of the left supra-
renal gland, and the area immediately below this is in contact with the stomach
and the pancreas. The pancreas, like the suprarenal gland, is bound down to the
kidney by connective tissue, but the stomach is separated from the area with which
it is in apposition by a portion of the omental bursa. The area in actual contact
: with the stomach is a small somewhat triangular district situated above the level
at which the pancreas is related to the kidney. The superior and lateral part of the
. anterior aspect of the kidney is related to the spleen, the two organs being separated
by a portion of the general peritoneal cavity, except along the area where spleen
and kidney are connected by the lieno-renal ligament. The anterior surface of
i the inferior end of the left kidney is related, towards the medial side, to a part of
1 the jejunum, and, towards the lateral side, to the left flexure of the colon or to a
i part of the descending portion of the colon. In most cases, however, the colon
* lies against the posterior abdominal wall to the lateral side rather than on the
i anterior surface of the left kidney.
1264
THE URO-GENITAL SYSTEM.
/^--^ Cortical substance of kidney
L
Pyramid
Basal part
of pyramid
The right and left colic arteries, or their branches, as they pass laterally to reach the
colon, are often related to the anterior aspects of the corresponding kidneys. The splenic
vessels pass laterally in front of the left kidney (Fig. 979).
The anterior surface of a kidney which has been hardened in situ is, like the
posterior surface, not uniformly rounded, but marked by a series of impressions
corresponding to the different structures which lie in contact with it. In the case
of each kidney, the most prominent region on the anterior surface lies below the
level of the middle of the kidney, and corresponds to the thickest part of the organ.
From this promin-
ence on the anterior
surface a series of
more or less flattened
planes slope away to-
wards the borders of
the kidney. These
flattened areas are the
impressions formed
by the viscera which
lie on the anterior
surface of the
kidney.
In the case of the
right kidney, three
impressions can usu-
ally be distinguished
on the anterior sur-
face. One occupies
the whole of the
upper part of the
organ, and is known
as the impressio he-
patica ; another
stretches from the
most prominent point
to the inferior end of
the kidney, and is
related to the colon ;
while the third ex-
tends along the
medial margin, below
the hilum, and is in
contact with the
second part of the
Branch of renal __j
artery
-Pyramid
Radiate part ["medullary rays "] of cortex 7 "''
FIG. 985. LONGITUDINAL SECTION THROUGH THE KIDNEY.
The vessels and fat have been removed to give a view of the wall of the kidney
sinus. The points where the vessels enter the kidney substance are seen as
holes in the sinus wall.
duodenum (Fig. 9 79).
The relative sizes of these three areas or impressions vary much in different specimens.
On the left kidney, also, three more or less defined, flattened impressions slope
towards the borders of the organ from the most prominent part of the anterior
surface. One of these, on the superior and lateral part of the kidney, is the splenic
impression ; another, extending downwards to the lower end of the kidney, is for
the jejunum, or for the jejunum and colon ; the third, above and in the region of the
hilum, is called the impressio gastrica, and corresponds to the position of the over-
lying stomach. Only a small portion of this impression is in direct contact with
the stomach, since the pancreas and a part of the suprarenal gland intervene
between the stomach and the kidney (Fig. 979).
It is common to find the left kidney thicker and less flattened antero-posteriorly than
the right, the impressions, or "facets," upon its surface being at the same time bett(
marked. With this probably is to be associated the fact that floating kidney is mor
rarely met with on the left than on the right side of the body.
THE KIDNEYS. 1265
Extremities of the Kidney. The kidney, fixed and hardened in situ, is usually
more pointed at its inferior than at its superior end. The latter is wider from
side to side, and often somewhat flattened from before backwards. The superior
end of the kidney is bent somewhat forwards and rests upon the diaphragm, which
separates it from the inferior part of the pleural cavity.
Sinus Renalis. The sinus of the kidney (Fig. 985), into which the hilum opens,
is a narrow space, having its long axis corresponding to that of the kidney. The
thick walls of the sinus cavity are formed by the substance of the kidney, and are lined
by a part of the fibrous kidney capsule which enters the sinus over the lips of the
hilum. The floor of the sinus is not even, but presents a series of small projecting
conical elevations called papillae renales, which vary from six to fifteen in number.
Eadiating from each papilla are a number of somewhat raised bars, or ridges, of
kidney substance, separated by depressed areas. The blood-vessels and nerves enter
and leave the kidney by piercing the wall of the sinus where it is formed by these
little depressed areas (Fig. 985). The rounded summit of each renal papilla is
pierced by a number of minute openings called foramina papillaria, which are the
terminal apertures of the secreting tubules of which the kidney is mainly com-
posed. These openings all lie close together, and give rise to the so-called area
cribrosa upon the apex of the renal papilla. The urine secreted by the kidney
escapes through the foramina papillaria into the subdivisions (or calyces) of the
ureter or kidney duct.
Kidney in Section. Sections through the kidney (Fig. 985) show that it
is composed to a large extent of a number of conical masses, known as pyramides
renales or pyramids. These together constitute the substantia medullaris or medulla
of the kidney, and are arranged with their bases directed towards the surface, and
their apices projecting into the renal sinus, where they form the papillae renales
already mentioned. The pyramids are more numerous than the papillae, two or
three usually ending in each papilla in the middle part of the kidney, and some-
times as many as six or more in each papilla near the superior and inferior ends
of the organ. The bases of the pyramids do not reach the surface of the kidney,
but are separated from it by a thin layer of kidney substance called the cortex,
or substantia corticalis of the kidney. The cortical substance not only covers over
the bases of the pyramids, but also sends in prolongations, called columnae renales
or renal columns, between the pyramids, towards the sinus. The medullary part
of the kidney exhibits in section a striated appearance, while the cortical part is
more granular and usually different in colour. The outer part of each pyramid is
called the basis pyramidis, and appears in section to be composed of alternate
dark and light streaks, while the inner, or papillary part, is often of a lighter colour,
and more uniformly and faintly striated.
In sections of the kidney the larger blood-vessels are seen, after they have
entered the kidney substance, to lie between the pyramids ; and some of their
main branches are visible passing across the bases of the pyramids.
In the foetus and young child, and sometimes, though much less distinctly, in the adult,
the surface of the kidney is marked by a number of grooves dividing it into polygonal
areas. These represent the lobes, lobi renales or reniculi, of which the kidney is
originally composed, and each corresponds to one papilla with its pyramids and surrounding
cortical substance.
An examination, with an ordinary pocket lens, of a section through the kidney
shows that the lighter striae of the bases of the pyramids are continued into the
cortex. As they pass through the cortex towards the surface of the kidney the
striae become less distinct, and appear, when cut longitudinally, as separate ray-
like prolongations carried outward from the bases of the pyramids. These parts
' of the cortex, which seem, in this way, to be continuations of the medulla,
are called " medullary rays " and constitute the pars radiata ; the portions which
intervene between them form what is known as the pars convoluta or " labyrinth."
The appearance presented by the cortex of the kidney in section varies much
according to the plane in which the section has been taken. If the section
passes through and lies parallel to the axis of a pyramid, the radiate part met
81
1266
THE UKO-GENITAL SYSTEM.
Pars convoluta
Pars radiata
th e p kidne e y 0f
convolute
lum renis
(glomerulus)
Arciform
arteries
Arteriolse
rectse
Collecting
tube
Loop 01
Henle
Efferent
glomerular
vessel
Afferent
glomerular
vessel
Glomerulus
with will appear as isolated streaks directed from the base of the pyramid towards
the surface of the kidney, and separated from one another by narrow strips, or
intervals, of the convoluted part. On the other hand, in sections made at right
angles to the axis of a pyramid, or cutting this axis obliquely, the convoluted
portion of the cortex presents the
appearance of a continuous net,
the meshes of which are occupied
by the radiate parts, and these
latter now exhibit a circular or
oval outline. In a similar manner
interiobuiar sections through the bases of the
Corpuscu- pyramids differ much in the -appear-
ances they afford according to the
plane in which they are cut.
Kidney Tubules. The glandular
substance of the kidney is composed
of a vast number of minute tubules,
called tubuli renales or uriniferous
tubules, all of which have an exceed-
ingly complicated course. The wall
of each tubule consists throughout of
a basement membrane and of an
epithelial lining, but the lumen of
the tubule and the character of the
epithelium vary much in its different
parts. Every tubule begins in a thin-
walled spherical dilatation, known as
capsula glomeruli (O.T. Bowman's
capsule), in which a complicated loop
of capillary blood-vessels is contained.
The tuft of capillaries is covered by a
In the middle part ; of the figure the course of one .of the kidney reflection o f the delicate wall of the
tubules is indicated, and in the lateral parts the disposition , . .
of the larger arteries. A, Cortex; B, Basal portion; capsule, and IS, as it were, mvagmate.
and C, Papillary portion of pyramid. into the capsule (Fig. 986).
The diagram at the right-hand side of the lower part of the capsules with their enclosed capillaries
figure illustrates the connexions of the structures com- are called the corpuscu l a ren is or kid-
posing a renal corpuscle. ney corpusclegj and are all placed
in the convoluted portion of the kidney cortex, where they may be recognised as minute
red points just visible to the unaided eye and best marked when the renal vessels are con-
gested. The part of the tubule leading from the capsule first convoluted tubule is very
tortuous, and lies within the convoluted part of the cortex. Passing from the convoluted
part, the tubule enters a radiate part, in which its course becomes less complicated, and
here it receives the name of spiral tubule. From the radiate part the tubule enters the
basal portion of the pyramid, and, diminishing in diameter, it pursues a straight course
towards the apex of the pyramid, forming the so-called descending limb of Henle's loop.
Within the apical portion of the pyramid the tubule suddenly bends upon itself, forming
the loop of Henle, and reversing its direction, it passes back again through the base of the
pyramid into the radiate part of the cortex as the ascending limb of Henle's loop. This
ascending limb exhibits a slight spiral twisting. Leaving the radiate part, the tubule
once more enters the convoluted part of the cortex, where its outline becomes so uneven
that the name irregular tubule is applied to it. While still within the convoluted part,
its contour having acquired a more uniform appearance, the tubule receives the name of
second convoluted tubule ; this latter finally ends in a short junctional tubule, which passes
back into a radiate part of the cortex and joins a collecting tube. Each collecting tube
receives numerous kidney tubules, and pursues a straight course through the radiate part
of the cortex and the pyramid. Finally, several collecting tubes, uniting together, form
an excretory tube, which opens on the summit of a renal papilla into a calyx of the ureter
by one of the foramina papillaria already described. In microscopic sections the various
portions of the kidney tubule may be distinguished by the position which they occupy and
by the character of the lining epithelium.
Connective Tissue of the Kidney. The tubules and the blood-vessels forming tl
substance of the kidney are all united together by a very small amount of connective
Capsule
FIG. 986. DIAGRAMMATIC REPRESENTATION OF THE
STRUCTURES FORMING A KIDNEY LOBE.
THE KIDNEYS. 1267
tissue, which completely surrounds each tubule and blood-vessel, and binds it to its
neighbours. It has been found possible to obtain an accurate idea of the arrangement of
this connective tissue by submitting thin sections of the kidney to the action of certain
digestive fluids. When this is done the tubules and blood-vessels are removed, and the
connective tissue stroma is left behind. The connective tissue thus revealed is seen to
form a continuous network, the spaces in which faithfully reproduce the outlines and
the arrangement of the kidney tubules. The network of the stroma is continuous with
the capsule of the kidney.
Vessels of the Kidney. The renal artery comes directly from the aorta, and is
very large in proportion to the size of the organ to which it conveys blood. Its main
branches, as they approach the kidney to enter the hilum, lie between the tributaries of
the renal vein in front and the ureter behind. Within the sinus of the kidney the
branches of the renal artery become arranged in a dorsal and a ventral group, the dorsal
vessels lying behind, the ventral ones in front of the subdivisions of the ureter. The
ventral group of vessels supplies the part of the kidney which forms the anterior and
lateral walls of the sinus; the distribution of the dorsal group is for the most part
restricted to the portion of the kidney which lies behind, and to the medial side of
the sinus.
Entering the substance of the kidney in the manner described above (p. 1265), the larger
arteries lie in the intervals between the pyramids, and are called the arterise interlobares
renis or interlobar arteries. These vessels dividing, form a series of incomplete arterial
arches, the arteriae arciformes, which pass across the bases of the pyramids. Although
we speak of arterial arches, it must be understood that no anastomosis between the
branches of the interlobar arteries actually takes place, but that each artery which
enters the wall of the kidney sinus has an isolated distribution and possesses the
characters of an "end artery." Each arterial arch gives off a number of vessels which
pass through the convoluted part of the cortex towards the surface of the kidney. These
are known as the arteriae interlobulares, and lie at very regular intervals. From them a
number of short branches arise, termed vasa afferentia, each of which proceeds to the
dilated extremity, or capsule, of a uriniferous tubule. Here the vas afferens breaks up
into a much convoluted capillary mass, called a glomerulus, which is contained within the
invagination of the capsule. The little vein which issues from the glomerulus, or vas
efferens, instead of running directly into a larger vein, breaks up, after the manner of
an artery, into capillaries which supply the tubules of the convoluted and radiate parts
of the kidney cortex. Hence almost all the blood which supplies the tubules of 'the
cortical part of the kidney passes in the first instance through the glomeruli. The tubules
of the bases of the pyramids also receive their blood-supply through vasa efferentia derived
from the glomeruli which lie near. The little vessels passing from these glomeruli break
up into bundles of fine arteries, which give the bases of the pyramids their coarsely
striated appearance. They are known as arteriolae rectae, and, like the arterise inter-
lobulares, are very conspicuous in injected preparations of the kidney.
The fibrous capsule of the kidney receives minute branches from the interlobular
arteries, some of which, piercing the capsule, communicate by capillaries with the vessels of
the tunica adiposa.
Veins corresponding to the interlobular arteries and arteriolse rectse collect the blood
from the capillaries surrounding the tubules, and unite to form a series of complete arches
across the bases of the pyramids. From these venous arcades vessels arise, which traverse
the intervals between the pyramids and reach the sinus of the kidney, where they unite
to form the dorsal and ventral tributaries of the renal vein. Some small veins in the
superficial part of the cortex communicate through the fibrous capsule with minute veins
in the capsula adiposa. Issuing from the kidney sinus, the veins run a direct course to
end in the inferior vena cava.
Nerves of the Kidney. The nerves of the kidney accompany the branches of the
artery, and are derived from the renal plexus. Their minute branches form regular
net-like plexuses on the walls of the fine arteries and kidney tubules, and the presence of
nerve terminations occurring among the epithelial cells lining the tubules has within
recent years been demonstrated.
From clinical evidence it would appear that the nerve fibres which supply the kidney
are portions of the tenth, eleventh, and twelfth thoracic nerves.
Variations. A marked difference in the size of the two kidneys is sometimes observed,
a small kidney on one side of the body being usually compensated for by a large kidney on the
opposite side. Cases of complete absence of one or other kidney are recorded.
A few cases are on record in which an extra kidney was found on the right or left side.
81 a
1268 THE UKO-GENITAL SYSTEM.
Traces of the superficial lobulation of the kidney, present in the foetus and young child, are
often retained in the adult.
Horse-shoe kidney is not an infrequent abnormality. In these cases the two kidneys are
united at their inferior ends, across the median plane, by a connecting piece of kidney substance.
The amount of fusion between the two kidneys varies much ; it is sometimes very complete,
while in other cases it is but slight, the connexion being chiefly composed of fibrous tissue.
In very rare cases the kidney appears to be almost entirely surrounded by peritoneum and to
be attached to the abdominal wall by a kind of mesentery, enclosing the vessels and nerves passing
to the hilus. The condition is believed to be congenital.
Not very infrequently one or both kidneys are found at a much lower level than usual, and
occupying a position in the iliac fossa or the pelvic cavity. This condition, when congenital, is
associated with an arrest in the normal change in position, relative to surrounding structures,
which the kidney experiences during development. In such cases the kidney does not
receive its blood -supply from usually placed renal arteries, but from vessels which arise from
the lower end of the aorta, or from the iliac, or the middle sacral artery. These congenitally
abnormally situated kidneys do not usually possess the typical outline of the normal organ, but
vary much in shape, and the hilum is often directed downwards or backwards, and not medially.
In some mammalian animals, such as the bear, the ox, the porpoise, etc., the kidneys are
composed of a number of completely isolated lobes, each of which corresponds to one papilla, its
pyramids and surrounding cortex ; while in others, such as the horse, the fusion of the lobes is
more complete even than in the human kidney, and a single mass represents the united papillae.
THE DUCT OF THE KIDNEY.
The duct of the kidney is called the ureter, and begins above in a thin-walled
funnel-shaped expansion called the pelvis renalis, which is placed partly within
and partly outside the sinus of the kidney. Towards the level of the inferior
end of the kidney the part of the pelvis which lies outside the sinus diminishes
in calibre, and forms a tube-like duct, the ureter, which conveys the urine to the
bladder.
Pelvis of the Kidney. Within the sinus of the kidney the pelvis lies among
the larger renal vessels. It is formed by the junction of two, or more rarely three,
thin-walled tubes, the calyces maj ores, each of which has a number. of branches.
These latter, called calyces renales minores, are short, and increase in diameter as
they approach the sinus wall, to which they are attached. Their wide, somewhat
funnel-like ends enclose the renal papillae, and receive the urine, which enters them
through the foramina papillaria. The calyces are usually about eight in number,
one calyx sometimes surrounding two or even three papillae. The portion of the
pelvis that lies outside the kidney has in front of it, in addition to the renal
vessels, on the right side, the descending part of the duodenum, and on the left side,
a part of the pancreas and sometimes the duodeno-jejunal flexure (Fig. 979).
Ureter. The ureter is the vessel which carries the urine from the pelvis of the
kidney to the bladder. It is a pale-coloured thick-walled duct with a small lumen.
While in situ it has a total length of about ten inches, and lies throughout its
whole course in the subperitoneal tissue, behind the peritoneum, to which it is
closely connected. In its superior part the ureter lies in the abdominal cavity, and
in its inferior part in the pelvis minor (Figs. 983 and 988).
The normal ureter, in the flaccid condition, measures after its removal from the body eleven
to fourteen inches.
The pars abdominalis, or abdominal portion of the ureter, about five or five and
a half inches in length, is directed downwards and slightly medially, and lies upon
the psoas major muscle. Certain structures are related to the ureters in a similar
manner on each side of the body ; for instance, the abdominal portion of each ureter
is crossed very obliquely, on its anterior aspect, by the internal spermatic vessels,
and behind each ureter the genito-femoral nerve passes downwards and laterally
(Fig. 983). Other structures are related to the duct of the right or left side
alone ; on the right side, the descending part of the duodenum lies in front of the
upper part of the ureter, and the line of attachment of the mesentery crosses it lower
down, just before the ureter enters the cavity of the pelvis minor. On the left
side the line of attachment of the mesentery of the pelvic colon crosses the ureter.
Crossing the common iliac, or the external iliac artery, the ureter enters the
pelvis minor. The left ureter usually crosses the common iliac artery, and the right
THE DUCT OF THE KIDNEY.
1269
Cortical
Basal part of j,
pyramid'7^
Papilla
~ Pelvis
ureter, in most cases, lies across the external iliac ; but this arrangement is by no
means constant. The course and position occupied by the abdominal portion of
the ureter is well seen in Fig. 983.
In X-ray photographs, the shadow cast by the abdominal portion of the ureter when the
latter has been rendered opaque, is seen to fall immediately in front of the tips of the transverse
processes of the lower lumbar vertebrae.
The pars pelvina or pelvis minor portion of the ureter is about four and a half or
five inches in length ; it passes downwards on the side wall of the pelvis, immedi-
ately behind the peritoneum, describing a curve which is convex backwards and
laterally (Fig. 988). The most convex portion of this curve lies close to the deepest
part of the greater sciatic
notch (Fig. 988). As it
descends upon the side
wall of the pelvis the
ureter forms the pos-
terior boundary of the
triangular district known
as the obturator triangle.
The lower limit of this
triangle is formed by the
ductus deferens, and the
upper and anterior
boundary by the external
iliac vessels and the
pelvic brim (Fig. 988).
In its course within
the pelvis minor the
ureter lies in front of the
hypogastric artery, and
crosses the medial aspect
of the obturator nerve
and vessels and of the
obliterated umbilical
artery. About the level
of the ischial spine, the
Ureter is Crossed from Oolumna renalls of 'cortex
before backwards by the
ductus deferens, and
from this point onwards
it is not so intimately re-
lated to the peritoneum The P elvis of the kidne Y and some of its calyces have been laid open as they
It now bends some-
what medially and forwards, to reach the posterior angle of the bladder, and
comes into relationship with the upper end of the vesicula seminalis, in front
of which it lies. The ductus deferens having crossed the ureter also turns
medially, and as it does so it lies at a higher level and on a posterior plane to the
ureter. The inferior end of the ureter is surrounded by a dense plexus of veins which
brings the vesical plexus into communication with the hypogastric vein. The great
nerve cord which connects the hypogastric plexus with the pelvic plexus, also
comes into relationship with the lower part of the pelvic portion of the ureter,
in the region where the latter is crossed by the ductus deferens (Fig. 988).
When the right and left ureters reach the bladder they are a little more than
two inches apart. They pierce the bladder wall very obliquely, and are embedded
within its muscular tissue for nearly three-quarters of an inch of their length.
Finally, they open into the bladder by two small slit-like apertures which are
of a valvular nature, and prevent a backward passage of fluid from the bladder.
It is probable, however, that an exaggerated idea of the valvular nature of
the openings of the ureters into the bladder is obtained by an examination
of the parts in the dead subject. When the bladder is empty the openings of
81 &
--Renal arterj
- Ureter
Pars radiata of cortex
/
. LONGITUDINAL SECTION OF THE KIDNEY, OPENING UP THE KIDNEY
SINUS.
1270
THE URO-GENITAL SYSTEM.
the ureters are placed about one inch apart, but when that viscus is distended they
are often two inches, or more, distant from one another. As the ureter pierces
the bladder wall the muscular fibres of the bladder and ureter remain quite distinct,
and so the ureter, remaining a thick -walled tubular structure, appears to pass
through a gap in the muscular wall of the bladder. The mucous coat alone of
the ureter becomes continuous with that of the bladder.
The canal of the ureter is not uniform throughout, but is somewhat constricted
in certain places, corresponding to the regions where the ureter is most sharply
curved or changes its direction. These more constricted parts of the tube are
described as occurring one in the middle of the abdominal portion, one at the
Branches of hypogastric artery Right ureter
Obturator artery Nerve cord from hypogastric plexus
Exterrtal iliac vessel
Inferior
epigastric
artery
\
'f?
S aero-genital fold
Obliterated umbilical
artery (lig. umbilicale)
Plica vesicalis transversa
Vesical arteries
Ductus deferens Paravesical peritoneal fossa
FIG.
3. MEDIAN SECTION OF AN ADULT MALE PELVIS.
The coils of the small intestine and of the colon which lay within the pelvis have been lifted out in order to
give a view of the side wall of the pelvic cavity.
junction of the abdominal and pelvic portions, and one in the pelvic part of the
ureter. Also just before the ureter joins the pelvis of the kidney and just as it
reaches the bladder wall its lumen is usually somewhat constricted.
In the female, the ureter, near its termination, passes beneath the lower part of the
broad ligament of the uterus, and lies to the lateral side of the cervix uteri and the
upper part of the lateral wall of the vagina. It is accompanied in the inferior part of
its course by the uterine artery, which crosses it on its anterior aspect not far from
its termination (Fig. 1002). Higher up it lies in the peritoneal ridge which forms
the posterior boundary of the fossa ovarica, a posterior subdivision of the obturator
fossa (Fig. 1002).
STRUCTURE OF THE URETER.
The wall of the ureter, which is thick and of a whitish colour, is composed of
mucous, muscular, and fibrous coats. The tunica mucosa or mucous coat possesses an
epithelium composed of many layers of cells, those nearest the surface being of
THE UKINARY BLADDEK. 1271
large size. When the canal is empty the mucous coat is thrown into numerous
longitudinal folds, and so its lumen exhibits a stellate outline in transverse section.
The submucous tissue varies much in thickness in different parts of the ureter,
and contains some elastic fibres. The unstriated muscle fibres which compose the
tunica muscularis or muscular coat are collected into bundles which are separated by
a considerable amount of connective tissue, and are arranged, some longitudinally,
some circularly. In the upper part of the ureter a relatively large amount
of connective tissue is present deep to and among the bundles of muscle
fibres, which are arranged in three distinct strata an inner longitudinal, an
intermediate circular, and an outer longitudinal. In the middle part of the
vessel the same layers may be recognised, but the circularly disposed bundles of
fibres are more numerous than higher up. In the lower part of the ureter the
connective tissue is relatively scanty and the inner longitudinal fibres lie close to
the lining epithelium; in this region also the longitudinal folds of the mucous
coat become fewer and less marked. A short distance above the point where it
reaches the bladder, the wall of the ureter becomes much thickened by the
addition of a number of coarse bundles of longitudinally arranged muscle
fibres, which are applied to the outer surface of the muscular coat. These muscle
fibres form the so-called " sheath of the ureter," and are continued on the super-
ficial aspect of the vessel as it passes through the bladder wall. In the portion of
the ureter which traverses the wall of the bladder (pars intramuralis) nearly all
the fibres of the muscular coat are disposed longitudinally, i.e., in a direction
parallel to that of the vessel. The muscle fibres lie close beneath the epithelium,
and end just where the mucous coats of the bladder and ureter become continuous.
The tunica adventitia or outer fibrous coat of the ureter varies in thickness at
different levels, and in its lower part blends with the connective tissue which lies
among the muscle fibres forming the sheath of the ureter just mentioned.
The mucous membrane of the calyces and of the pelvis of the kidney possesses an
epithelium resembling that of the ureter. Where each renal papilla projects into
one of the calyces a deep circular recess, or fornix, is formed between the wall of
the calyx and the sloping side of the papilla ; at the bottom of this recess the
epithelium of the calyx becomes continuous with that covering the papilla. At
the foramina papillaria the epithelium joins that of the kidney tubules. The
muscular fibres in the wall of the calyces and of the pelvis are collected into loosely
arranged bundles separated by wide intervals occupied by fibrous connective tissue.
As in the ureter, the outermost and innermost fibres run in a longitudinal, the
intermediate ones in a circular direction. The circularly arranged fibres alone
form a distinct layer.
Vessels and Nerves of the Ureter. The abdominal part of the ureter receives
its blood-supply from the renal and internal spermatic arteries ; the pelvic portion
is supplied by the superior vesical and middle haemorrhoidal vessels.
The nerves of the ureter reach it through the renal, the spermatic, and the
hypogastric, plexuses.
Variations. The ureter is sometimes represented by two tubes in its upper portion. In rarer
cases it is double throughout the greater part of its extent, or even in its whole length from the
pelvis of the kidney to the bladder. In such cases there may be two openings into the bladder.
Asymmetry as regards such abnormalities is very common.
Variations in the form of the pelvis of the kidney are of frequent occurrence. Most usually
the pelvis divides into two large subdivisions, one of which passes in the direction of the tipper,
the other in that of the lower pole of the kidney. In some cases these branches come off directly
from the ureter without the intervention of a pelvis, or a marked subdivision may lead to the
formation of two pelves.
VESICA UEINAKIA.
The vesica urinaria or urinary bladder is a hollow muscular organ situated in
the anterior part of the pelvic cavity, above and behind the symphysis pubis. It lies
in front of the rectum, from which it is separated in the male by the seminal vesicles
and the terminal portions of the ductus deferentes, and in the female by the vagina
and uterus. The ureters, which convey the fluid secreted by the kidneys, open into
the base of the bladder about half an inch from the median plane.
81 G
1272
THE UKO-GENITAL SYSTEM.
The urethra, or canal by which the urine reaches the surface, leads from the
bladder, its aperture lying in the median plane, not far from the openings of the
ureters, but on a lower and anterior plane. The size and shape of the bladder,
the thickness of its wall, and also to a great extent its relations, vary with the
amount of distension, or contraction, of the organ. When the bladder is empty,
or only slightly distended, it lies within the pelvis minor; as it becomes filled
with urine it rises above the pubis, and crossing the pelvic brim, enters the
Inferior
epigastric artery
Superior peritoneal lig.
of bladder
Urinary bladder
Sacro-genital fold
Recto-vesical pouch
Ductus deferens
Retro-pubic pad of fat
Prostatic urethra
Dorsal vein of penis
Corpus cavernosum penis
Corpus cavernosum
urethrae
Anal canal
j Membranous urethra
Bulb of urethra
Cavernous portion of urethra
Fm. 989. MEDIAN SECTION THROUGH THE PELVIS OF AN ADULT MALE SUBJECT.
The urinary bladder is empty and firmly contracted. The coils of small intestine have been removed to afford
a view of the side wall of the pelvic cavity.
abdominal cavity. These changes affect chiefly the upper part of the bladder, which
becomes altered in shape and size, and acquires new connexions and relations ; the
lower portion varies but slightly with the amount of distension of the organ (see
Figs. 989 and 990). The upper part of the bladder is covered with peritoneum, which
is reflected on to it from the anterior abdominal wall in front, from the sides of the
pelvis laterally, and, in the male, across the seminal vesicles and terminal parts of
the ductus deferentes from the rectum behind. In the female the peritoneum passes
on to the bladder posteriorly from the anterior surface of the uterus. The
peritoneum dips down posteriorly for a certain distance between the bladder and
THE UEINAEY BLADDEE.
1273
rectum in the male, forming the recto-vesical or recto-genital pouch ; in the female
a slit-like peritoneal depression, called the utero-vesical pouch, intervenes between
the anterior surface of the' uterus and the bladder (Fig. 996). The inferior part of
the bladder lies below the peritoneum, and is for the most' part directed towards
the pelvic floor. In the median plane it is supported by the symphysis pubis and the
retro-pubic pad of fat ; farther back in the male it rests upon the prostate and on
the lower part of the rectum, from the latter of which it is separated by the vesiculse
seminales and the terminal parts of the ductus deferentes. In the female it rests
Intestine
icavernosum..
urethr
Drpus cavernosum-
penis
Urinary bladder
..eflection of peritoneum
anterior abdominal wall"
Rectum-
scto-vesical pouch -4 -
Terminal part of !_
ductus deferens |
'-'
Prostate-
Ejaculatory duct ""'
Sphincter urethrse membranacese
Anal canal
Sphincter urethrse membranaceae
Bulb of urethra Bulbo-cavernosus muscle
FIG. 990. MEDIAN SECTION OP THE PELVIS OF AN ADULT MALE SUBJECT.
The urinary bladder and rectum are both greatly distended.
upon the anterior wall of the vagina. Laterally the bladder is supported by the
levatores ani muscles, and farther from the median plane it rests on each side on
the obturator internus ; it is separated from the layer of the pelvic fascia covering
these muscles by loose areolar tissue.
The opening of the urethra, orificium urethrae internum or internal urethral
' orifice, is placed in, or near, the part of the bladder wall which lies lowest in
the pelvic cavity. The term neck, or cervix, is often applied to this region, the
1274
THE UEO-GENITAL SYSTEM.
Apex of bladder
Lateral border
Infero-lateral
with prostate
Fundus of
bladder
Ureter
bladder appearing as if it were suddenly constricted to form the urethra. The
portion of the bladder wall posterior to the urethral orifice, which is directed in the
male towards the anterior wall of the rectum and lies below and in front of the
recto-vesical pouch, is called the fundus vesicae or base of the bladder ; it is closely
related to the seminal vesicles and ampullae of the ductus deferentes. The corre-
sponding part of the bladder in the female rests against the anterior wall of the
vagina. The term vertex vesicse, or apex of the bladder, is applied to the portion
which lies nearest to the upper border of the symphysis when the organ is empty,
and rises high above the pubis into
the abdominal cavity when the bladder
is distended. Connected with the
vertex of the bladder is a fibrous cord,
the ligamentum umbilicale medium, or
urachus, which passes upwards, in the
Area continuous median plane, on the posterior aspect
of the anterior abdominal wall, and
reaches the umbilicus. It represents
the passage which in the embryo
connects the developing bladder with
the allantois. The part of the bladder
FIG. 991,-iNFERioR ASPECT OF THE EMPTY MALE connecting the apex with the base, and
URINARY BLADDER. From a subject in which the not Sharply marked Otl Irom either, IS
viscera had been hardened in situ. Called the Corpus VCSicas, Or body of
The prostate has been severed from the bladder, and the the bladder.
white area in the drawing indicates the position Position Of the Urethral Orifice.
where the two structures were continuous. TV_ i_
During the various changes in shape
and size which the bladder undergoes, the region of the internal urethral orifice
remains almost fixed in position. The urethral orifice lies immediately above the pros-
tate, and behind and slightly below the level of the upper margin of the symphysis
pubis, from which it is distant about two to two and a half inches. It can be
easily reached by a finger introduced into the bladder through the abdominal wall
above the symphysis pubis. It is usually placed half an inch to one inch above
the level of a plane passing through the lower margin of the symphysis and the
lower end of the sacrum, but in some
cases it is found to be somewhat lower.
In the female it normally occupies a
lower level than in the male. The
comparatively slight variations in the
level of the internal urethral orifice
which do occur, depend partly upon
the quantity of fluid contained in the
bladder, and partly upon the amount
of distension of the lower portion of
the rectum. When the bladder is
very much distended this region lies
at a slightly lower level in the pelvis
than it does when the organ is empty ;
on the other hand, distension of the
lower part of the rectum raises, to some
extent, the level of the urethral orifice.
Since the position of the internal
Bladder apex
Infero-lateral
area
Urethra
Jl
Ureter
__ Posterior surface of prostate
Seminal vesicle
FIG. 992. THE URINARY BLADDER, PROSTATE, AND
SEMINAL VESICLES, VIEWED FROM BELOW.
urethral orifice varies, in the manner Taken from a subject in which the viscera were hardened
., , .,, '-, -,.,. f in situ. Same specimen as Fig. 993, A. The bladder
JUSt described With the condition Of con tained but a small amount of fluid.'
the rectum and of the bladder it
follows that it lies at its lowest limit when the bladder is full and the rectum empty,
and at its highest level when the bladder is empty and the rectum distended.
Inferior Aspect of the Bladder. The lower part of the bladder, which is direct!
towards the pelvic floor, changes, as we have seen, but slightly with the varying
amount of distension of the viscus. When the organ has been carefully hardened
THE UKINAKY BLADDER
1275
before its removal from the body, it is possible to map out on its inferior aspect three
convex triangular areas, which may be distinguished from one another by the
directions in which they 'look. The three areas approach one another in the
region of the urethral orifice, where, in the male, a portion of the inferior aspect of
the bladder wall is structurally continuous with the upper part of the prostate.
Posterior to the urethral orifice is a triangular district, directed downwards and back-
wards, and related, in the male, to the seminal vesicles and the terminal portions
of the ductus deferentes, which, together with the recto- vesical layer of the pelvic
fascia, intervene in this position between the bladder and the rectum. This
triangular area is known as the fundus, base, or postero-inferior surface of the
bladder, and in the female it is directed against the anterior wall of the vagina.
The rest of the inferior aspect of the bladder is formed by two infero-lateral
areas, or surfaces, which meet in the median plane in front of the urethral orifice,
and are directed for the most part downwards and laterally (see Fig. 993). Each of
these areas extends backwards to join the fundus or postero-inferior surface, along
a rounded border which lies between the point where the ureter reaches the bladder
and the urethral orifice. The infero-lateral part of the bladder wall rests on the
areolar tissue covering the fascia of the leva tor ani and the obturator internus muscles,
and, nearer the median plane, upon the os pubis and the retro-pubic pad of fat.
Superior surface
of bladder
-Ureter
Seminal
vesicle
Lateral aspect
of prostate
Urethra
Lig. ura- Seminal
bilicale vesicle
medium
Infero-lateral
area of bladder
Lateral
aspect of
prostate
Infero-lateral
area of bladder
Urethra
FIG. 993. THE URINARY BLADDER, PROSTATE, AND VESICULA SEMINALIS, VIEWED FROM THE LATERAL ASPECT.
Drawn from specimens in which the viscera were hardened before removal from the body. In A the bladder
contained but a very small quantity of fluid ; in B the quantity was somewhat greater. In A the
peritoneum is shown covering the superior surface of the bladder, and its cut edge is seen where it is
reflected along the lateral border of the organ. In B the level of the peritoneal reflexion is indicated by
a dotted line.
The three rounded borders which mark off the three triangular areas on the
inferior aspect of the bladder, just described, extend from the region of the urethral
orifice to the bladder apex, and to the points where the ureters reach the bladder
wall (see Figs. 991, 992).
Shape and Relations, of the Empty Bladder. When the bladder is empty, or
nearly so, it has, roughly speaking, the shape of an inverted tetrahedron, whose
apex corresponds to the point where the urethra leaves the organ, while the base
of the tetrahedron is formed by the superior surface of the bladder. The three
basal angles of the tetrahedron correspond to the bladder apex and to the two
posterior angles of the bladder, or points where the ureters join the organ. The three
surfaces, which meet inferiorly at the urethral orifice, are only marked off from one
another by rounded borders, but as long as the organ is empty, or nearly so, they
are separated by distinct borders from the superior surface. These three areas
have been already described as the infero-lateral surfaces and the base of the
bladder (Figs. 991 and 992). Their relations have also been indicated. The
superior surface of the empty bladder looks upwards into the pelvic cavity ; it is
sonvex when the organ is contracted, concave when relaxed. This surface is covered
with peritoneum, and its outline, which is approximately triangular, is determined
by lateral and posterior borders (Fig. 993). The lateral borders of the empty
bladder are sharply marked, and extend from the bladder apex to the posterior angles
1276
THE UKO-GENITAL SYSTEM.
of the bladder, or points where the ureters join the organ. They separate the
superior surface from the infero-lateral portions of the inferior aspect of the bladder
wall (Fig. 993, A). The posterior border stretches across between the posterior angles
of the bladder, and separates the superior from the basal surface of the viscus. The
superior surface is related in the male to coils of intestine ; in the female it is
related also to the anterior surface of the uterus. The lateral border of the empty
bladder lies against the pelvic fascia just above, or at the level of, the arcus tendineus
of the levator ani muscle. The ductus deferens crosses the side wall of the pelvis
parallel to it, but at a considerably higher level. In median section the cavity of
the empty and relaxed bladder often presents the appearance of a Y-shaped chink,
the stem of the Y being represented by the urethra as it leaves the organ, and the two
limbs by the narrow intervals between the superior surface and the under parts of
the bladder wall which lie in front of and behind the urethral orifice. This relaxed
form is sometimes described as the diastolic condition of the empty bladder, and is
found associated with a bladder wall of but little thickness, and with a concave upper
surface. The condition is usually the result of an escape of fluid after death,
when the bladder wall has lost the power of contracting. It does not represent
Lig. umbilicale medium
[urachus]
Tuberculum pubicum
Obliterated part
of the umbilical artery
Inferior epigastric artery
Ductus deferens
Colon
Ureter
Ilio-pectineal eminence
Inferior epigastric
artery
Ductus deferens
__Urinary bladder
(highest point)
Sacral promontory
Ureter
Common iliac artery
FIG. 994. VIEW LOOKING INTO THE PELVIS FROM ABOVE AND SOMEWHAT BEHIND.
The bladder has been artificially distended.
a normal condition of the organ in the living. The normal empty bladder
is strongly contracted, and its wall is thick and firm. A distinctly Y-shaped
appearance is not presented by its cavity in median section, but the interior of the
organ is seen as a simple narrow interval continuous with the canal of the urethra.
Distended Bladder. As the bladder fills with fluid the superior wall i
raised upwards from the infero-lateral and basal walls, and, at the same time, the
borders separating the superior from the other surfaces of the bladder become at
first more rounded and then nearly obliterated. The lateral borders of the bladder
becoming in this manner opened out, give rise to so-called lateral surfaces i
the distended organ. These surfaces, however, are not sharply marked off,
and are directly continuous with the superior surface. During distension,
also, the angles present in the empty condition of the organ become rounde<
as the entire bladder wall becomes more uniformly convex. The general
shape of the bladder becomes altered during distension; the tetrahedral form
of the empty organ is lost, and the bladder as it becomes filled assumes first
somewhat spherical, then an oval contour. During distension the enlargii
bladder comes to occupy more and more of the pelvic cavity, displacing upwards
the portions of the colon and small intestine which may lie in the pelvis when tl
organ is empty. Until all the available pelvic space has been filled up, the form
THE UBINAKY BLADDER 1277
of the distended bladder is spherical, or oval, with the larger end directed down-
wards and backwards. When the pelvic wall prevents further expansion of this
portion, the outline of the' organ may become an oval with the larger end directed
upwards and forwards into the abdominal cavity. The highest part of the dis-
tended bladder lies at some distance above the pelvic brim, and does not correspond
to the attachment of the urachus at the apex, but to a point farther back (Fig. 994).
As the superior wall of the bladder is raised up during distension it carries with it
the peritoneum, and thus the reflexion of that membrane, from the anterior
abdominal wall on to the apex of the bladder, comes to lie one and a half inches, or
even higher, above the upper margin of the symphysis pubis (Fig. 990). It is,
therefore, possible to puncture, or open into the distended bladder, through the
anterior abdominal wall above the symphysis pubis, without at the same time
opening into the peritoneal cavity. In a similar manner the line of reflexion of
the peritoneum, from the side wall of the pelvis on to the lateral aspect of the
bladder, is raised higher during distension, and may come to correspond, in part, to
the level of the ductus deferens, or to that of the obliterated part of the umbilical
artery. On the other hand, the level of the reflexion of the peritoneum from the
rectum towards the basal aspect of the bladder does not appear to vary much with
the distension, or contraction, of the organ (compare Figs. 989 and 990), and thus the
fossa between the bladder and rectum becomes relatively very deep when the bladder is
full. The bladder in normal distension may contain nearly one pint, but in most cases
the organ is emptied when its contents reach from six to ten ounces. Under abnormal
or pathological conditions the bladder capacity may be very much increased.
Varying Relationships, according to the degree of Distension of the Bladder.
When the bladder is distended the obliterated part of the umbilical artery may
cross forwards against its side, but when it is empty the obliterated vessel at its
nearest point often lies as much as one and a quarter inches above the lateral
border of the organ. The ductus deferens, during a part of its course, is in contact
with the lateral wall of the distended bladder, but when the organ is empty it lies
above and parallel to the lateral border, only coming into relationship with the
basal surface of the bladder beyond the point where it crosses the ureter. The side
wall of the distended bladder is closely related to the obturator vessels and nerves.
Interior of the Bladder. The mucous membrane lining the bladder is
loosely connected to the muscular coat, and when the bladder is contracted the
mucous lining of the upper wall is thrown into a number of prominent wrinkles
or folds (Fig. 995). At one place only the mucous membrane is firmly connected
to the subjacent muscular coat, and the inner surface of this part of the bladder
wall is smooth and free from wrinkles. This smooth area corresponds to a tri-
angular surface behind the urethral orifice, called the trigonum vesicse, and to the
part of the bladder wall which immediately surrounds the opening. The apex
of the triangle lies at the beginning of the urethra, and the base is formed by a
line drawn between the openings of the ureters into the bladder. Just behind
'the urethral opening the bladder wall sometimes bulges slightly into the cavity,
owing to the presence of the middle lobe of the prostate, which lies beneath the
mucous coat in this position. When well marked, as it often is in old people,
this bulging is termed the uvula vesicse. Stretching across between the openings
}f the ureters there is usually to be seen a smooth ridge, due to the presence of a
bundle of transversely disposed muscle fibres, which lies within this part of the
bladder wall, beneath the mucous membrane. This ridge has been called the
' torus uretericus." It may be deficient near the median plane, and it is curved
.no as to be convex forwards. The lateral portions of the ridge which lie outside
jhe openings of the ureters are called the plicae uretericse, and are produced by the
terminal parts of the ureters as they traverse the bladder wall and lie beneath the
:nucous coat of the bladder (Fig. 995). In old people the region behind the
irigonum is usually distinctly depressed and forms a shallow fossa, sometimes
jailed the retro-ureteric fossa. A less distinct shallow depression may sometimes
3e observed on each side of the trigone. Eound the urethral orifice are a number
)f minute radially disposed folds which, disappearing into the urethra, become
i Continuous with the longitudinal folds of the mucous membrane of the first part
1278
THE UKO-GENITAL SYSTEM.
of that canal. The ureters pierce the bladder wall very obliquely, and so the
minute orificium ureteris, or opening, of each has an elliptical outline. The lateral
boundary of each opening is formed by a thin, cresceiitic fold, which, when the
bladder is artificially distended in the dead subject, acts as a valve in preventing
water or air from entering the ureter. Hence the term " valvula ureteris " is some-
times used to designate the fold. In the empty bladder the urethral orifice and
the openings of the two ureters lie at the angles of an approximately equilateral
triangle, whose sides are about one inch in length. When the bladder is distended the
distance between the openings may be increased to one and a half inches or more.
Bladder in the Female. In the female the bladder is related posteriorly to
Urethral orifice
Folds of mucous
membrane
Muscular coat
of bladder
Trigonum vesicse Retro-ureteric fossa
Torus uretericus
FIG. 995. EMPTY AND CONTRACTED URINARY BLADDER, OPENED UP BY THE REMOVAL OF ITS UPPER WALL.
The peritoneum is seen spreading out from the lateral and posterior borders of the organ. Compare with
Fig. 1000.
the uterus and upper part of the vagina. The anterior surface of the uterus in its
upper part is separated from the upper surface of the bladder by the shallow utero-
vesical pouch of peritoneum, but the two organs are nevertheless normally in
apposition. So close is this relationship that the upper surface of the bladder very
often shows a slight concavity, due to contact with the convex anterior wall of the
uterus. The lower part of the uterus and upper part of the vagina are not
separated by peritoneum from the basal surface of the bladder, but are in actual
apposition with it (Fig. 996). Thus, below the level of the utero-vesical pouch,
the female bladder is related in much the same manner to the uterus and anterior
wall of the vagina as the male bladder is related to the vesiculse seminales and
ductus deferentes. The apex of the bladder, where the urachus is attached, often lies
on a lower level than in the male, so that the organ, even when distended, rises
less freely into the abdomen. The bladder as a whole is placed deeper in the pelvis
than in the male, and the internal urethral orifice lies just above, or just below, a
line drawn from the lower margin of the symphysis to the lower end of the sacrum
(p. 1274). The lower level of the internal urethral orifice is probably correlated
with the absence of a distinct prostate in the female. It is probable that as
regards capacity no difference exists between the bladder in the male and in the
female ; the conflicting results arrived at by different observers are probably due to the
faulty methods which have been employed in estimating the capacity of the organ.
THE UKINAKY BLADDER 1279
Bladder in the Newly Born Infant and in the Child. At birth the empty
Cavity of uterus
Cavity of
urinary bladder
Labium anterius
(cervicig uteri)
Symphysis pubis
Urethra
Labium minus
pudendi
Labium posterius
(cervicis uteri)
Recto-vaginal
reflexion of
peritoneum
Vaginal canal
Anal canal
| Sphincter ani
Median
umbilical
ligament
(urachus)
Ureter
FIG. 996. MEDIAN SECTION OF THE PELVIS IN AN ADULT FEMALE.
The cavity of the uterus is indicated diagrammatically.
bladder is spindle- or torpedo-shaped, and its long axis, which extends from the
point of attachment of the urachus to
the internal urethral orifice, is directed
downwards and backwards (Fig. 997).
The lateral and posterior borders seen
in the adult organ cannot be recognised
at birth, nor is there any part of the
ibladder wall directed downwards and
: backwards, as is the basal surface of
the adult organ. In the foetus and
i young child the bladder occupies rela-
; tively a much higher level than it does
;in the adult, and, even when empty,
: it extends upwards "into the abdominal
cavity. Its anterior aspect is in con-
tact with the posterior surface of the
anterior abdominal wall. At birth the
peritoneum forming the recto -vesical
'pouch covers the whole of the posterior surface of the bladder, and reaches as low
i as the upper limit of the prostate. The internal urethral orifice is placed at a high
level, and sinks gradually after birth (Fig. 998, A). In the newly born child this
Prostate r
Musculus pubo-vesicalis
Urethra
FIG. 997. THE URINARY BLADDER OF A NEWLY
BORN MALE CHILD, viewed from the side.
The drawing is from a specimen which had been
hardened in situ.
1280
THE UEO-GENITAL SYSTEM.
Urinary bladder
Symphysis pubis
Corpus cavernosum_
penis'
Corpus cavernosuni
urethras'
Bulbo-cavernosus
muscle
Rectum
Internal sphincter ani
External sphincter ani
Anal canal
opening lies on a level with the upper margin of the symphysis pubis, and the
openings of the ureters lie almost on a level with the plane of the pelvic brim.
The obliterated portions of the umbilical arteries are more intimately related to
the bladder in the foetus and child than in the adult, and lie close against its
sides as they pass upwards towards the umbilicus (Fig. 999).
Peritoneal Relations and Connexions of the Bladder. We have already
seen that the
superior surface of
the empty bladder
is covered by peri-
toneum, which
leaves it along the
lateral border on
each side to reach
the pelvic wall at
about the level of
the arcus ten-
dineus or white line
of the pelvic fascia.
To this peritoneal
reflection the term
External sphincter ani lateral false (or peri-
toneal) ligament is
often applied. The
lateral ligaments of
opposite sides are
continuous in front,
at the bladder apex,
where the periton-
eum is conducted
over the fibrous
cord of the urachus
to reach the anterior
abdominal wall,
forming the so-
called superior false
(or peritoneal) liga-
ment. When the
bladder is empty
the level of this
anterior reflection
lies just behind, or
just below, the
upper margin of the
symphysis pubis.
FIG. 998. MEDIAN SECTION THROUGH THE PELVIS OF NEWLY BORN CHILD. When the bladder
A, Male, and B, Female. becomes filled the
level of the peri-
toneal reflection forming the superior false ligament is raised upwards, and may
reach a point two inches, or more, above the upper margin of the symphysis pubis.
Similarly, the line along which the lateral peritoneal ligament reaches the pelvic
wall is also carried upwards in distension of the bladder, and may reach the level
of the ductus deferens and of the obliterated umbilical artery.
When the bladder is empty the peritoneum is carried downwards upon the side
wall of the pelvis as low as the lateral border of the organ, and lines a shallow
depression which receives the name of paravesical fossa. This peritoneal fossa lies
below the level of the obturator peritoneal fossa (p. 1269), from which it is separated
by the ductus deferens. As the bladder fills, the peritoneum is raised off this part
of the pelvic wall, and certain structures, such as the obturator vessels and nerve
Urinary bladder
Symphysis pubis
Vagina
Urethra
Carina urethralis
Labium minus
pudendi
Uterus
Rectum
Internal sphincter ani
External sphincter ani
Anal canal
External sphincter ani
THE UKINAKY BLADDER.
Urinary bladder Umbilical artery
1281
Testis
Epididymis
Gubernaculum
and the ductus deferens,
which lie on the lateral
wall of the pelvis, come
into direct relationship
with the lateral aspect of
the distended bladder.
Posteriorly the peri-
toneum leaves the superior
surface of the empty
bladder at its posterior
border, and is carried back-
wards, forming a kind of
horizontal shelf, or fold,
for a distance of about
half an inch, giving at
the same time a partial
covering to the ductus de-
ferentes and superior ends
of the seminal vesicles.
The peritoneum then sud-
denly dips downwards to
reach the bottom of the recto-vesical, or recto-genital, pouch, where it is reflected
on to the anterior surface of the rectum (Fig. 1001). As a rule, no part of the
Psoas major
Rectum
FIG. 999. VIEW LOOKING FROM ABOVE INTO THE PELVIS AND LOWER
PART OF THE ABDOMINAL CAVITY IN A F(ETUS OF ABOUT THE
SEVENTH MONTH.
On the left side, which represents a slightly more advanced condition than
the right, the testis has entered the inguinal canal ; on the right side
the testis is still within the abdominal cavity.
Median umbilical ligament (urachus)
Plica vesicalis transversa
Trigonum femorale
External |
iliac vessels
Urinary bladder
, . Paravesical peritoneal fossa
BQl^^tah^ Obliterated umbilical artery
Inferior
>^ epigastric artery
Internal spermatic artery
Ductus deferens
Recto-vesical pouch
Intervertebral fibro-cartilage
Rectum
Ureter
External iliac artery
Hypogastric artery
Sacro-genital fold
FIG. 1000. VIEW LOOKING INTO THE MALE PELVIS FROM ABOVE AND SOMEWHAT BEHIND.
From a specimen in which the bladder was firmly contracted and contained but a small amount of fluid. The
paravesical fossa is seen on each side of the bladder. The deep peritoneal pouch in front of the rectum
is bounded on each side by crescentic sacro-genital folds or " posterior false ligaments of the bladder, "
which meet together in the median plane some distance behind the posterior border of the bladder.
82
1282
THE UKO-GENITAL SYSTEM.
basal surface of the contracted and empty bladder receives a covering from the
peritoneum, since the seminal vesicles and terminal portions of the ductus de-
ferentes intervene as they lie in the anterior wall of the recto-vesical or recto-
genital pouch. When the bladder is distended the posterior border, separating
the upper and basal surfaces, is rounded out, and the peritoneum forming the
horizontal shelf, just described, is taken up (compare Figs. 989 and 990). It is
Superior peritoneal lig.
of b ladder
Urinary bladder
Sacro-genital fold .
Recto-vesical pouch
Ductus deferens -
Retro-pubic pad of fat
Prostatic urethra--
Dorsal vein of penis
Corpus cavernosum penis
Corpus cavernosum
urethrse
Anal canal
Membranous urethra
Cavernous portion of urethra Bulb of urethra
FIG. 1001. MEDIAN SECTION OP THE PELVIS IN AN ADULT MALE.
The coils of small intestine which lay within the pelvis have been lifted out in order to give a view of the side
wall of the pelvic cavity.
to be specially noted that the level of the peritoneal reflection, forming the bottom
of the recto-vesical pouch, does not vary much, as regards its relationship to the
prostate, during distension and contraction of the bladder (Figs. 989 and 990).
ri'An examination of median sections of the pelvis shows the great danger run by the ampullae
of the ductus deferentes in any operation for reaching the bladder through the anterior wall of
the rectum, and the difficulty in avoiding injury to the peritoneum.
The term " posterior false (or peritoneal) ligament " is often applied to the some-
what variable crescentic fold of peritoneum which bounds, on each side, the
entrance to the recto-vesical or recto-genital pouch, and which often unites with
THE UKINAKY BLADDER 1283
the fold of the opposite side across the median plane, behind the posterior border of
the bladder and the ductus deferentes. These folds represent the plicae rectouterinse
or folds of Douglas in the female, and are to be regarded as connexions of the ductus
deferentes rather than of the bladder ; hence the term sacro-genital folds is applicable
to these structures in both sexes. The folds are seen in Figs. 990 and 995.
The peritoneum covering the upper surface of the empty or partly distended bladder
often exhibits a transversely disposed fold or wrinkle, to which the term plica vesicalis
transversa has been applied. This fold, when well developed, can be traced on to the
side wall of the pelvis, where it traverses the paravesical fossa, and in some cases it is
found to cross the pelvic brim and to be directed towards the abdominal inguinal ring
(Fig. 995).
In the female the peritoneum is reflected posteriorly from the upper surface of
the bladder on to the anterior aspect of the uterus.
Fixation of the Bladder. When the ligamentum umbilicale medium, or fibrous
cord of the urachus, which binds the bladder apex to the anterior abdominal wall,
and the peritoneal folds, already described as the false ligaments, are severed, the
bladder is easily moved about, except in its lower and basal parts. Anteriorly it
is connected to the pubis, and laterally to the fascial lining of the pelvis by loose
areolar tissue only, which permits free movement during expansion and contraction.
The lower fixed part of the bladder is held in place chiefly by processes of the
pelvic fascia, continuous with those forming the sheath of the prostate. The
fascial connexions constitute the true ligaments of the bladder, and are described
as pubo -pro static or anterior ligaments, reaching the bladder from the pubis in front,
and lateral ligaments, reaching the bladder from the fascial lining of the side wall
of the pelvis.
In addition to the urachus and the peritoneal and the true ligaments already
mentioned, the bladder is supported and fixed in position, in the region of its
basal surface, by the dense fibrous and unstriped muscular tissue which surrounds
the seminal vesicles, the terminal portions of the ductus deferentes and the ureters.
Laterally the strands of connective tissue and the bundles of muscle fibres forming this sup-
port pass backwards and are continued into the fascia which surrounds the branches of the
hypogastric artery. Muscle fibres connected with the bladder wall are also found within the
pubo-prostatic ligaments, through which they are attached to the pubis.
In the female the basal part of the bladder wall is supported and held in place
by its connexion with the anterior wall of the vagina. The region of the urethral
orifice is the most firmly fixed part of the bladder wall in both sexes.
Structure of the Bladder Wall. The wall of the bladder from without inwards
is composed of a serous, a muscular, a submucous, and a mucous coat. The tunica serosa
or serous coat, formed by peritoneum, is incomplete, and covers only the upper and
posterior parts of the distended bladder (Fig. 993).
A considerable amount of fibrous connective tissue surrounds the tunica muscularis
or muscular coat, and penetrating it, divides it into numerous coarse bundles of muscle
fibres. All the muscle fibres are of the unstriped variety, and the bundles which they
Form are arranged in three very imperfectly separated strata called external, middle,
'j-nd internal. The stratum externum is for the most part made up of fibres which are
iirected longitudinally, and it is best marked near the median plane on the upper and under
ispects of the bladder. Farther from the median plane, on the sides of the bladder, the
ibres composing the external stratum run more obliquely, and their directions frequently
iross one another. In the male, many of the fibres of the external stratum are attached
30th anteriorly and posteriorly to the prostate, and in the female the corresponding fibres
oin the dense tissue which in this sex forms the upper part of the wall of the urethra.
3ther fibres of this stratum on each side of the body join the lower part of the symphysis
mbis and constitute the musculus pubo vesicalis, which lies in the substance of pubo-
)rostatic ligament. Lastly some fibres of the external stratum blend posteriorly with the
''interior aspect of the rectum and receive the name of musculus rectovesicalis. The
itratum medium is composed of fibres which for the most part run circularly, and
orms the greater part of the thickness of the muscular coat. In the region of, and
82 a
1284 THE UKO-GENITAL SYSTEM.
behind, the urethral orifice the bundles of fibres are finer and more densely arranged, and
surround the opening in a plane which is directed obliquely downwards and forwards.
This part of the middle stratum is often spoken of as the " sphincter vesicse." Inferiorly
the fibres of the sphincter vesicse are continuous with the muscular tissue of the prostate
in the male, and with the muscular wall of the urethra in the female. In other parts of the
bladder the bundles of the middle stratum are coarser and separated by intervals filled with
connective tissue. The stratum internum is a thin layer of fibres directed for the most
part longitudinally.
The tela submucosa or submucous coat is composed of areolar tissue, but contains
numerous fine elastic fibres.
The tunica mucosa or mucous coat is loosely attached, by means of the submucous
layer, to the subjacent muscular coat, except in the region of the trigonum vesicae, where
the muscular fibres lie close beneath, and are firmly adherent to the mucous
membrane. Over the trigonum the mucous coat is always smooth and flat ; elsewhere it is
thrown into folds when the bladder is empty. The mucous membrane of the bladder is
continuous with that of the ureters and urethra. The epithelium, covering it, varies
much in appearance in different conditions of the organ, and is of the variety known as
transitional stratified epithelium. The appearance of the mucous coat is described
on p. 1277.
Vessels and Nerves of the Bladder. The bladder receives its blood supply on each side
from the superior and inferior vesical arteries. The inferior vesical artery arises from the
hypogastric artery, and the superior vesical arises from the umbilical artery just before it becomes
obliterated. The largest veins are found just above the prostate, and in the region where the
ureter reaches the bladder. They form a dense plexus which pours its blood into tributaries of
the hypogastric vein, and communicates below with the pudendal venous plexus.
The lymph-vessels from the bladder join the iliac group of lymph -glands.
The nerve supply of the bladder is derived on each side from the vesical plexus, the fibres of
which come from two sources, namely (1) from the upper lumbar nerves through the hypogastric
plexus, and (2) from the third and fourth sacral nerves. The fibres from the latter sources join
the vesical plexus directly.
THE URETHRA.
The urethra is the channel which serves to convey the urine from the bladder
to the exterior. In the male it consists of two portions, a proximal part, less than
one inch in length, extending from the bladder to the points where the ducts of
the reproductive glands join the canal, and a much longer distal portion which
serves as a common passage for the secretion of the kidneys and for the generative
products. An account of the male urethra follows the description of the male
reproductive glands and passages (see p. 1304). In the female the urethra is more
simple in its arrangement, and represents only the proximal part of the male
canal. It is a short passage leading from the bladder to the external urethral
orifice an aperture placed within the rima pudendi or urino-genital cleft, imme-
diately above and in front of the opening of the vagina.
Urethra Muliebris. The female urethra is a canal of about one to one and
a half inches in length which follows a slightly curved direction downwards and
forwards, below and behind the lower border of the symphysis pubis. As it
leaves the pelvis the urethra pierces the urogenital diaphragm and its fasciae,
and the part of the passage which lies between the superior and inferior layers
of fascia is surrounded by the fibres of the sphincter urethrse membranaceee
muscle. Except during the passage of fluid the canal is closed by the apposition
of its anterior and posterior walls. The orificium urethrae externum or external
orifice is placed between the labia minora, immediately in front of the opening
of the vagina, and lies about one inch below and behind the clitoris (Fig. 1002).
The opening is slit-like, and is bounded by slightly marked lateral lips. The
posterior wall of the urethra, except in its upper part, is very intimately connected
with the anterior wall of the vagina. The mucous lining of the canal is raised
into a number of slightly marked longitudinal folds, one of which, more distinct
than the others, and placed upon the posterior wall of the passage, receives the
name of crista urethralis.
THE FEMALE UKETHKA.
1285
,
Structure. The wall of the female urethra is thick and contains much fibrous
tissue, which passes without any sharp line of demarkation into the surrounding mass of
connective tissue. The tunica muscularis or muscular coat of the urethra is continuous
above with that of the bladder, and is composed of layers of circularly and longitudi-
nally disposed smooth muscle fibres arranged to form outer and inner strata. Within
the muscular coat the wall of the urethra is very vascular, and the canal itself is lined
by a pale mucous membrane which is thrown into longitudinally directed folds, one of
which is the crista urethralis mentioned above. The epithelium of the canal, in its upper
part, is of the transitional variety, like that of the bladder ; in its lower part it becomes
scaly. Numerous minute glands, the glandulse urethrales, and pit-like depressions
Ureter
Nerve cords
from hypo-
gastric plexus
Recto-uterine
fold
Utero-vesical
pouch
Recto-uterine
pouch
Orificium exter-
num uteri
Vagina
abium minus
abium majus
FIG. 1002.-
-MEDIAN SECTION THROUGH THE FEMALE PELVIS. Drawn for the most part from a model
of a dissection by Professor Edward H. Taylor.
[lacunae urethrales) open into the urethral canal. One group of these glands on each
dde possesses a minute common duct known as the ductus paraurethralis, which opens
; nto the rima pudendi or urino-genital cleft by the side of the urethral orifice. It is
aelieved that these latter glands represent the prostatic glands of the male subject.
The vascular layer which lies between the muscular coat and the mucous membrane
contains elastic fibres, and in appearance resembles erectile tissue. Striped muscle fibres
ire present on the outer aspect of the muscular coat of the urethra. In the upper part
')f the canal these fibres form a complete ring-like sphincter, but in the middle and lower
)arts the striped muscle fibres though present in front are absent on the posterior wall of
-he urethra, as at this level they pass backwards on the outer aspect of the vagina, and
'snclose this latter passage together with the urethra in a single loop of muscle tissue.
The lower fibres, therefore, form a urino-genital sphincter.
82
1286
THE UKO-GENITAL SYSTEM.
THE MALE KEPKODUCTIVE OKGANS.
We have here to describe (1) the testes or essential reproductive glands of the
male, together with their (2) coverings and (3) ducts, (4) the prostate, (5) the bulbo-
urethral glands, (6) the external genital organs, and (7) the male urethra.
The reproductive glands of the male, or testes, are a pair of nearly symmetrical
oval-shaped bodies situated in the scrotum. The duct of each gland, at first
much twisted and intertwined, forms a structure known as the epididymis, which
is applied against the posterior and lateral part of the testis. From the epi-
didymis the excretory duct, or ductus deferens, passes upwards towards the inferior
part of the anterior abdominal wall, which it pierces very obliquely, to enter the
abdominal cavity. Here each ductus deferens is covered by the peritoneum, and
almost at once crossing the pelvic brim, enters the pelvis. The duct now runs on
the side wall of the pelvis towards the base of the bladder, where it comes into
relation with a branched tubular structure termed the vesicula seminalis. Joined
by the duct of the vesicula seminalis, the ductus deferens forms a short canal
called the ejaculatory duct, which terminates by opening into the prostatic part
of the urethra. The prostate, a partly glandular, partly muscular structure,
surrounding the first part of the urethra, and also a pair of small glandular bodies
called the bulbo-urethral glands, are accessory organs connected with the male
reproductive system. The
ducts of the bulbo-urethral
glands and those of the pro-
state, like the ejaculatory ducts,
open into the urethra, which
thus serves not only as a pas-
sage for urine, but also for the
generative products. The ex-
ternal genitals are the penis and
scrotum.
THE TESTIS.
The male reproductive
glands, the testes, are a pair of
somewhat oval, slightly flat-
tened bodies of a whitish colour,
measuring about an inch and a
half in length, one inch from
before backwards, and rather
less in thickness. Each testis
is placed within the cavity of
the scrotum in such a manner
that its long axis is directed
upwards, slightly forwards, and
laterally, and usually the left
gland occupies a lower level
than the right. The testis
(Fig. 1003) has two somewhat
flattened surfaces, one of which,
called the facies lateralis, or
lateral surface, looks backwards as well as laterally ; the other, the facies medialis,.
or medial surface, looks forwards as well as medially, and is usually the more
flattened. The two surfaces are separated by two rounded borders, one of which
the margo anterior, is the more convex and free ; while the other, the margo posterior
is less rounded, and by it the organ is suspended within the scrotum. The
epididymis and the lowest portion of the funiculus spermaticus, or spermatic cord, art
FIG. 1003. RIGHT TESTIS AND EPIDIDYMIS, EXPOSED BY THE
REMOVAL OP THE ANTERIOR WALL OF THE SCROTUM.
THE TESTIS.
1287
attached to the posterior border of the testis. Each border ends above in the
superior extremity, and below in the inferior extremity of the testis. Owing to an
obliquity of the long axis of the gland, the superior extremity of the testis lies on
a more anterior and lateral plane than the inferior extremity.
Epididymis. The epididymis is a somewhat crescentic structure, which is curved
round the posterior border of the testis and overlaps to some extent the posterior
part of the lateral surface of that organ. The superior, somewhat swollen part of
the epididymis, is called the caput epididymidis or head, and overhangs the superior
end of the testis, to which it is directly connected by numerous emerging ducts, by
connective tissue, and by the serous covering of the organ. The inferior and smaller
end is termed the cauda epididymidis or tail, and is attached by loose areolar tissue
and by the serous covering to the inferior end of the testis. The intermediate part,
the body, or corpus epididymidis, is applied against, but is separated from, the
posterior part of the lateral surface of the testis by an involution of the serous
covering of the organ, which forms an intervening pocket termed the sinus epi-
didymidis (O.T. digital fossa).
The main mass of the epididymis is composed of an irregularly twisted canal,
the ductus epididymidis, which forms the first part of the duct of the testis.
Minute sessile, or pedunculated, bodies are often found attached to the head of the
epididymis or to the superior end of the testis. These are called appendices of the
epididymis and testis (O.T. hydatids of Morgagni), and have a developmental interest.
The minute body which lies on the superior end of the testis represents the free end of
Miiller's duct in the embryo and the fimbriated 'fend of the uterine tube of the female ; it
is usually sessile. Above the head of the epididymis, and in front of the lower part of
the spermatic cord, there may also be present a small rudimentary body called the
paradidymis. This is rarely seen in the adult, and is best marked in young children.
Tunica Vaginalis. The cavity within which the testis and epididymis are
placed is lined by a smooth serous membrane the tunica vaginalis which
resembles in appearance and structure
the peritoneum, from which it is origin-
ally derived. The cavity is considerably
larger than the contained structures,
and extends not only down to a lower
level than the testis, but also reaches
upwards to a higher level than the
gland. The sac, or cavity, tapers as
it is traced upwards, and above the
level of the testis the funiculus sper-
maticus or spermatic cord bulges
forwards into its posterior part. The
tunica vaginalis lines the cavity for
the testis, and is reflected from the
posterior wall of the scrotal chamber
over the testis and epididymis, giving
a covering to each. The part of the
membrane lining the cavity is called
the lamina parietalis or parietal portion
of the tunica vaginalis, while the part
clothing the testis and epididymis is
termed the lamina visceralis or visceral FlG ' 1004 -- LEFT TESTIS
DOrtion TWwppn rha latArol enrfpnp A part of the tunica vaginalis has been removed in order to
show the ductuli efferentes and lobuli epididymidis.
the testis and the body of the
epididymis, the visceral part of the tunica vaginalis dips in and lines a narrow
interval called the sinus epididymidis (O.T. digital fossa). The entrance to the sinus
is limited above and below by short crescentic folds of the tunica vaginalis, which
pass from the testis to the head and tail of the epididymis. These folds are spoken
of as the superior and inferior ligaments of the epididymis. In three positions the
surface of the testis receives no covering from the tunica vaginalis superiorly
Spermatic cord
Body of
epididymis
Sinus of
epididymis
1288 THE URO-GENITAL SYSTEM.
where the globus major is attached, inferiorly where the cauda epididymidis is in
contact, and posteriorly where the blood-vessels and nerves enter the organ from
the funiculus spermaticus or spermatic cord.
Structure of the Testis and Epididymis. Beneath the serous tunica vaginalis
the testis is invested by an external coat, composed of dense white inelastic fibrous
tissue called the tunica albuginea, from the deep surface of which a number of
slender fibrous bands or septa dip into the gland. These the septula testis im-
perfectly divide the organ into a number of wedge-shaped parts called lobuli testis
(Fig. 1005). All the septa end posteriorly in a mass of fibrous tissue which is
Tunica albuginea directly continuous with the tunica al-
septuia testis s" W-^ buginea, and which projects forwards into
Lobuli ^ e testis along its posterior border. This
structure receives the name of mediastinum
testis, or corpus Highmori, and is traversed
by an exceedingly complicated network of
fine canals, into which the minute tubules
which compose the substance proper of the
testis open. The mediastinum is also pierced
by the arteries, veins, and lymph vessels of
the testis. These vessels enter the posterior
border of the organ, and traversing the
mediastinum, spread out on the fibrous septa
which radiate towards all parts of the deep
surface of the tunica albuginea. In this way
Medium S ym ' s *&>*** network of vessels (tunica vasculosa)
is formed on the deep surface of the tunica
FIG. 1005. TRANSVERSE SECTION OF THE ,, , ,, r . -, ,,
TESTIS AND EPIDIDYMIS. albuginea and on the sides 01 the septa.
The mediastinum, the septa, and the
tunica albuginea form a framework enclosing a number of imperfectly isolated
spaces which are filled by a loosely packed substance of a light brown colour
called the parenchyma testis.
The parenchyma is composed of enormous numbers of much-convoluted semini-
ferous tubules, called tubuli seminiferi contort!, and completely fills up the intervals
between the septa. The minute tubules look like fine threads to the unaided eye,
and are but loosely held together by a small amount of connective tissue. Usually
three or four tubules are found in each lobule of the gland, and the total number
in the testis has been estimated at about 600. The seminiferous tubules, after a
course of about_two feet in length, pass towards the mediastinum testis and unite
at acute angles, to form a smaller number of slender tubes which run a straight
course. These latter are called tubuli seminiferi recti, and open into a complicated
network of fine canals situated in the substance of the mediastinum, called the rete
testis. The tubules are much more twisted and convoluted in the cortical part of]
the gland, near the tunica vaginalis, than in the region of the mediastinum, and '
often give off side branches which, according to some observers, may effect
anastomoses between, the tubules. It appears doubtful, however, if the semini-j
ferous tubules of the testis do really anastomose.
Microscopic sections show that the walls of the seminiferous tubules are composed oi|
a basement membrane and of an epithelial lining, formed of several layers of cells,.
Certain cells of this epithelium are, in the adult, constantly undergoing transformation j
into spermatozoa, and the appearance of the tubules in section varies much, according tc
age and to the greater or less activity of the epithelial cells.
The secretion of the seminiferous tubules is carried through the tubul:
seminiferi recti into the rete testis, and leaves the latter, to reach the canal o
the epididymis, through from fifteen to twenty minute tubules called ductul:
efferentes testis or efferent ductules. These latter pierce the tunica albuginea anc
enter the caput epididymidis where it is in direct contact with the superio:
extremity of the testis. Each efferent ductule is at first straight, but soor'
becomes much convoluted, and forms a little conical mass of twisted tubule, callec
THE DEFEEENT DUCT.
1289
a lobule of the epididymis (O.T. conus vasculosus). Within the head of the
epididymis the little canals finally open into the single much-convoluted tube
which constitutes the chief bulk of the epididymis, and is called the duct of the
epididymis. This canal, which is not less than 19 or 20 feet in length, may be
said to begin in the head of the epididymis, and to end, after an extraordinarily
tortuous course, at the tail by becoming the ductus deferens (Fig. 1006).
In most cases one or more slender convoluted diverticula from the duct of the epi-
didymis may be found near its lower end. These receive the name of ductuli aberrantes,
and one of them which is very constantly present often measures a foot or more in
length.
Minute Structure. The duct of the epididymis and the efferent ductules are
lined by a ciliated epithelium, the cilia of which maintain a constant current towards
the ductus deferens. The duct of the epididymis possesses a muscular coat composed of
an inner stratum of transversely and an
outer stratum of longitudinally directed
fibres. The wall, at first thin, becomes
much thicker as the ductus epididymidis
approaches the ductus de'ferens.
Vessels and Nerves of the Testis. The
testis is supplied by the internal spermatic artery,
a branch of the aorta. This slender vessel, after
Head of epididymis
Tail of
epididymis
FIG. 1006.
DIAGRAM to illustrate the structure of the testis
and epididymis.
c. Duct of epididymis. v.e. Ductuli efferentes testis.
c.v. Lobuli of epididymis.
r.v. Rete testis.
Head of epididymis
Appendix of testis
Testi
Cut edge c
tunica -^aa
vaginali
Pampiniform
plexus
Tubuli seminiferi recti.
Duct of epididymis
FIG. 1007. LEFT TESTIS AND EPIDIDTMIS VIEWED
FROM BEHIND, showing the ductus epididymidis
and the first part of the ductus deferens.
a long course, reaches the posterior border of the testis, where it breaks up into branches
which enter the mediastinum testis, and are distributed along the septa and on the deep surface
of the tunica albuginea.
The veins issuing from the posterior border of the testis form a dense plexus, called the plexus
pampiniformis, which finally pours its blood through the spermatic vein, on the right side, into the
inferior vena cava ; on the left side the spermatic vein joins the left renal vein.
The nerves for the testis accompany the internal spermatic artery, and are derived through
the .aortic and renal plexuses from the tenth thoracic segment of the spinal medulla. The
afferent fibres from the epididymis appear to reach the spinal medulla through the posterior
roots of the eleventh and twelfth thoracic and first lumbar nerves. The arteries and nerves of
the testis communicate with those on the lower part of the ductus deferens, namely, with the
artery of the ductus deferens and with twigs from the hypogastric plexus.
The lymph-vessels of the testis pass upwards in the spermatic funiculus, and end in the
lumbar lymph -glands.
DUCTUS DEFERENS.
The ductus deferens (O.T. vas deferens) is the direct continuation of the duct
of the epididymis. Beginning at the inferior extremity of the epididymis, it ends,
after a course of nearly 18 inches, by opening as the ejaculatory duct into the
prostatic or first part of the urethra. The duct in parts of its course is somewhat
convoluted, and the actual distance traversed by it is not more than 12 inches.
Placed in the first instance outside the abdominal cavity, the ductus deferens ascends
1290
THE UKO-GENITAL SYSTEM.
within the scrotum towards the lower part of the anterior abdominal wall, which it
reaches not far from the median plane. During this part of its course the duct,
together with the vessels and nerves of the testis, is surrounded by a number of
loose coverings derived from certain layers of the abdominal wall, and the cord-like
structure so formed is termed the funiculus spermaticus or spermatic cord. The
ductus deferens, together with the accompanying vessels and nerves, now passes
through the abdominal wall in an oblique passage, to which the name canalis
inguinalis is applied. Within the abdomen the duct lies immediately beneath the
peritoneum, and soon crossing over the pelvic brim, it enters the pelvis minor, on
the side wall of which it proceeds backwards towards the base of the bladder. Here,
near the median plane, the ductus deferens is joined by the duct of the correspond-
Median umbilical ligament (urachtis)
Plica vesicalis transversa
Urinary bladdei
Trigonum femorale
External
iliac vessels
'aravesical peritoneal fossa
rr--.L Obliterated umbilical artery
Inferior
**- epigastric artery
Internal spermatic artery
Ductus deferens
Recto-vesical pouch
Intervertebral fibro-cartilage
Ureter
i External iliac artery
Hypogastric artery
Rectum feacro-genital fold
FIG. 1008. VIEW OF THE MALE PELVIS SEEN FROM ABOVE AND BEHIND. The course
of the ductus deferens is well seen.
ing vesicula seminalis, and the ejaculatory duct, thus formed, having tra versed 'th
prostate, opens into the urethra.
At first the ductus deferens, like the canal from which it takes its origin, is verj
tortuous, but soon increasing in thickness, the duct becomes less twisted, and passe
upwards along the medial side of the epididymis, behind the testis, to enter the
spermatic funiculus (Fig. 1007). Its course is now almost vertically upward
towards the pubic tubercle, near which, crossing the medial part of the inguina
ligament [Pouparti], the duct enters the inguinal canal by the subcutaneous inguina
ring (Fig. 1017). Of the structures composing the funiculus spermaticus the due
is the most posterior, and it can be readily distinguished, even in the undissectec
subject, by its hard firm feel, when it is taken between the finger and thumb. Ir
the inguinal canal the ductus deferens is directed laterally, upwards, and a little
backwards to the abdominal inguinal ring, where, at a point half an inch abov<
the inguinal ligament, and midway between the symphysis pubis and the anterio:
THE DEFEKENT DUCT.
1291
jrior iliac spine, it enters the abdomen. The distance between the point where
the cord enters the inguinal canal to the point where it leaves it to enter the
abdomen is about one and a half inches. While passing from the subcutaneous
to the abdominal inguinal ring the ductus deferens, together with the other
structures of the funiculus spermaticus, rests upon the upper grooved surface
of the inguinal ligament, and is placed behind the aponeurosis of the external
oblique and some of the lower fibres of the internal oblique muscle. From before
backwards the duct rests, in the first instance, upon the falx aponeurotica or con-
joined tendon of the internal oblique and transversus abdominis muscles, and farther
laterally upon the fascia transversalis. Above the funiculus are some arching fibres
of the internal oblique muscle which enter the falx. As the ductus deferens leaves
the inguinal canal by the abdominal inguinal ring, it turns round the inferior
Branches of hypogastric artery
Obturator artery
Right ureter
Nerve cord from hypogastric plexus
Obliterated umbilical
artery (lig. nmbilicale)
Plica vesicalis transversa
Sacro-genital fold
Vesical arteries (
Ductus deferens
Paravesical peritoneal fossa
FIG. 1009. MEDIAN SECTION OF THE PELVIS IN AN ADULT MALE.
le coils of small intestine and colon which lay within the pelvis have been lifted out in order to give a view
of the side wall of the pelvic cavity.
epigastric artery on its lateral and posterior aspect. Completely changing the
direction of its course, the duct now runs for a short distance backwards, medially,
and upwards, beneath the peritoneum, to a point one and a half to two inches from
the pubic tubercle, where it crosses the ilio-pectineal line and enters the pelvis minor.
In this part of its course the duct usually lies at first in front of the external iliac
vessels, and then in the floor of a little triangular fossa, the trigonum femorale,
between these vessels and the pelvic brim (Fig. 1009). On the side wall of the
pelvis minor the ductus deferens is continued backwards, and a little downwards and
medially, in the direction of the ischial spine, and lies immediately external to the
peritoneum, through which it can usually be seen shining. In the pelvic part of
its course the ductus deferens crosses on the medial side of (1) the obliterated part
of the umbilical artery, (2) the obturator nerve and vessels, (3) the vesical vessels,
and (4) the ureter (Fig. 1009).
1292
THE UKO-GENITAL SYSTEM.
Beyond the ureter the duct takes a somewhat sudden bend, and passes down-
wards and medially towards the median plane, beneath the peritoneum of the pelvic
floor. Beaching the interval between the base of the bladder in front and the
rectum behind, the ducts of opposite sides occupy the angle formed between the
vesiculse seminales (Fig. 1012). As they approach one another each duct becomes
somewhat tortuous, sacculated, and dilated, and assumes a general resemblance in
structure to a portion of the seminal vesicle. This dilated part of the ductus
deferens is termed the ampulla ductus deferentis. As it turns medially the duct
lies a short distance behind the ureter, and immediately in front of the free edge of
the peritoneal fold (sacro-genital) which bounds the recto-vesical or recto-genital
pouch of the peritoneum. Just above the base of the prostate the ductus deferens
becomes once more a narrow canal, and in this position it is joined by the duct
of the corresponding seminal vesicle to form the ductus ejaculatorius, which, after
a short course downwards, forwards, and medially through the prostate, opens into
the urethra.
In some cases the ductus deferens crosses the obliterated umbilical artery before it enters the
cavity of the pelvis minor ; it normally does so in the fetus.
Ejaculatory
duct
Seminal vesicle
A and B. Drawings illustrating the seminal vesicle and the ampulla of the ductus deferens taken from two j
different subjects.
C. The seminal vesicle and ductus deferens have been cut into to show the pitted structure of their walls.
Ductus Ejaculatorius (O.T. common ejaculatory duct). The ejaculatory d\
is a very slender canal, formed by the union of the ductus deferens with th<
duct of the corresponding seminal vesicle. It is less than one inch in lengtl
and lies very close to its fellow of the opposite side as it passes through the prostat
behind its median lobe. The ducts open by slit-like apertures into the first part
the urethra, one on each side of the utriculus prostaticus. They are well seen ii
sections through the upper part of the prostate (Fig. 1011).
The mucous membrane of the duct is thrown into numerous complicated folds, and ii
connexion with it are a number of remarkable minute diverticula, which are enck
within the muscular coat of the duct.
Vesiculse Seminales. The seminal vesicles are a pair of hollow sacculat
structures placed in front of the rectum and behind the bladder (Fig. 1012). Eacl
vesicle is usually about two inches in length, and has its long axis direcl
downwards, medially, and somewhat forwards. The superior extremity of
vesicle, which is partly covered by peritoneum, is large and rounded, and lies at
considerable distance from the median plane, behind the inferior end of the ureter
The peritoneum of the recto-vesical or recto-genital pouch separates the upj
end of the seminal vesicle from the rectum ; below the peritoneal cavity the vesic
THE DEFEKENT DUCT
1293
and rectum are more intimately related. The vesicle tapers towards its inferior
end, which is placed close to the median plane and immediately above the prostate.
Inferiorly, the vesicle be-
comes constricted to form
a short duct, the ductus
excretorius, which joins the
lateral side of the corre-
sponding ductus deferens
at an acute angle to form
the ejaculatory duct. The
medial side of each vesicle
is related to the ductus
deferens, and the lateral
side, when the bladder is
empty, lies close to the 1J !MH ? ^
Pyv * -&E
Ureter
Internal urethral orifice
Trigonum
Ureter
T Ductus deferens
Rectum
-f-a
sloping pelvic floor. The
seminal vesicle often
assumes a more vertical
position when the bladder is FIG.
distended; a more horizontal
direction when the bladder
is empty. Its superior end
is sometimes found to be curved backwards against the side of the rectum.
KECTUM AND
THE URETERS
ion. HORIZONTAL SECTION THROUGH THE
URINARY BLADDER AT THE LEVEL AT WHICH
PIERCE THE BLADDER WALL.
From a specimen in the Surgical Museum, Trinity College, Dublin.
In
Sphincter
an
FIG. 1012. DISSECTION TO DISPLAY THE POSTERIOR ASPECT OF THE VESICUL.E SEMINALES, THE AMPULLA
OF THE DUCTUS DEFERENTES, AND THE PROSTATE. The coccyx and portions of the levatores ani
have been removed, also a considerable portion of the rectum.
some cases the seminal vesicles are much smaller than usual, and may be less
than one inch in length. Frequently they are asymmetrical as regards size and
1294
THE UKO-GENITAL SYSTEM
shape. The seminal vesicles are more intimately related to the wall of the bladder
than to that of the rectum. Their superior ends are, as we have seen, separated
from the rectum by a portion of the recto-vesical pouch of peritoneum, and
lower down the septum of fascia which intervenes between the vesiculse seminales
and the rectum is denser than that which separates them from the bladder.
Each vesicula seminalis is in reality a tube bent in a tortuous manner on itself,
and if the dense connective tissue which envelops it is taken away, the length of
the tube when untwisted may be found to be as much as five inches. The tube is
closed above, and a variable number of short tortuous branches come off it at
different levels. The blind end of the tube usually lies at the superior and lateral
extremity of the seminal vesicle, but in some cases the tubular vesicle is so bent
upon itself that the blind terminal part lies against the side of the issuing duct
The development of the vesiculse seminales shows that they are to be regardec
as diverticula of the ductus deferentes, from which they originally arise as smal
pouches.
The dense tissue in which the seminal vesicles are embedded contains much unstriped muscle
tissue, which sweeps round in the side wall of the recto-vesical pouch. Inferiorly this tissue
is attached to the capsule of the prostate. The large veins coming from the prostatic anc
vesical plexuses are closely related to the seminal vesicles.
Superior surface
of bladder
. um- Seminr
vesicl
Lateral aspect
of prostate
Urethra
Lateral
aspect of
prostate
Median
umbilict
ligamenl
(urachus
Infero-lateral
area of bladder
Urethra
FIG. 1013. THE URINARY BLADDER; PROSTATE, AND SEMINAL VESICLE VIEWED FROM THE SIDE.
Drawn from specimens hardened in situ.
In A the bladder contained but a small amount of fluid ; in B the quantity was somewhat greater.
Structure of the Ductus Deferens and of the Vesicula Seminalis.
Except near its termination, where it is dilated to form the ampulla, the ductus deferens
is a thick-walled tube with relatively a very small lumen. The hard cord-like sensation
which the ductus deferens conveys to the touch is due to the thickness and toughness oi
its wall, which is composed of three layers an outer fibrous tunica adventitia, an inter-
mediate tunica muscularis, and an inner tunica mucosa. The thickness of the wall is
due to the great development of the middle or muscular coat, which is composed of an
intermediate layer of circularly and an inner and outer layer of longitudinally directed
unstriped muscular fibres. Of these layers the middle one is by far the thickest, and
forms the chief part of the thickness of the wall of the ductus deferens. The mucous
membrane of the duct exhibits a number of slight longitudinal folds and possesses a ciliated
epithelium. The ampulla, or terminal part, possesses a much thinner wall, and, as the
surface of its mucous membrane has a number of ridges separating depressed areas, the
lining of this part of the tube presents a pitted or honeycombed appearance. The wall oi
the vesicula seminalis resembles that of the ampulla in being thin, and in having a mucous
lining with uneven honeycomb-like ridges and depressions. In it the same coats are tc
be recognised as in the ductus deferens, but the muscular layer is much thinner, and the
strata composing it less regularly arranged.
DESCENT OF THE TESTIS.
1295
Vessels and Nerves of the Ductus Deferens and of the Vesicula Seminalis. The
ductus deferens receives its arterial supply from the superior or inferior vesical artery. The
artery to the duct accompanies' that structure, supplying it as far as the testis, where it ends by
anastomosing with branches of the internal spermatic artery. The vesicula seminalis is supplied
by the inferior vesical artery. The nerves of the ductus deferens and vesicula seminalis are
derived from the hypogastric plexus. In lower animals the nerves for the seminal vesicles
are derived from the nerve roots of the second, third, and fourth lumbar nerves.
DESCENT OF THE TESTIS.
The peculiar course pursued by the ductus deferens in the adult, and the manner in
which it is related to the anterior abdominal wall, are rendered clear by a study of the
arrangement of the parts in the foetus. The testes until nearly the end of intra-uterine
life are placed in the abdominal cavity. Lying at first on the posterior wall of the abdomen
at the level of the upper two lumbar vertebrae, and just below the level assumed at
this time by the permanent kidney, the testis is held in place by a fold of peritoneum or
mesentery, called the mesorchium. As growth goes on the testis is found to occupy a
lower level in the abdominal cavity ; in the third month it lies in the iliac fossa, and in
the seventh it is situated
Urinary bladder Umbilical artery
Abdominal \~~52-^--^Jzr-/L
inguinal ring /^\ " -J^.'A^Sv Testis
Epididymis
Gubernaculum
Mesorchium
Ductus
deferens
Internal sper-
matic vessels
Psoas major
Rectum
PART OF THE ABDOMINAL CAVITY IN A FCETUS OF ABOUT THE
SEVENTH MoNTH '
( - )n
represents a slightly more advanced condition than
the right, the testis has entered the inguinal canal ; on the right side
the testis is still within the abdominal cavity.
near the abdominal inguinal
ring. Meanwhile a blind
pouch or diverticulum of
the peritoneal membrane,
termed the processus
vaginalis peritonsei, has
grown downwards and in-
wards through the anterior Ductug
abdominal wall towards the deferens
scrotum, deriving as it goes
a covering from each of the
layers of the abdominal
wall through which it
passes. The testis with its
mesorchium enters the
diverticulum of the ab-
dominal cavity, and de- FIG. 1014. VIEW LOOKING FROM ABOVE INTO THE PELVIS AND LOWER
scends within it until the
scrotum is reached. At a
later stage the connexion
between the part of the
processus vaginalis that lies
in the scrotum and the peritoneal lining of the abdomen becomes lost by the oblitera-
tion of the upper part of the pouch. Thus the part of the processus vaginalis that
persists in the scrotum becomes the parietal portion of the tunica vaginalis ; while the
visceral part of that membrane is the primitive peritoneal covering of the testis and
epididymis (Figs. 1014 and 1015).
Often a small fibrous band the " ligamentum vaginale " may be found in the adult
passing through the inguinal canal and joining the peritoneum superiorly in the region of
the abdominal inguinal ring. Sometimes this band is connected below with the tunica
vaginalis, but more often it does not reach so far downwards. When present it represents
the obliterated portion of the processus vaginalis, ' and is therefore known as the
rudimentum processus vaginalis.
In other rare cases the processus vaginalis may persist after birth as a channel freely
open to the abdominal cavity above, or the passage, becoming closed at intervals, may
give rise to one or more cysts within the coverings of the spermatic funiculus.
It sometimes happens that the descent of the testis is arrested, and then, either
failing to enter the processus vaginalis, the testis remains within the abdominal cavity ;
or entering the processus vaginalis, it fails to reach the scrotum, and lies in the inguinal
canal. The term " cryptorchism " is frequently applied to such cases.
In connexion with the descent of the testis a remarkable cord-like structure the
gubernaculum testis [Hunteri] must be mentioned. The gubernaculum arises for the
most part within a peritoneal fold which, at an early time in the development of the
foetus, may be seen stretching from the inguinal region to the Wolffian duct (future
duct of the testis) and inferior end of the mesonephros or primitive kidney. This peritoneal
1296
THE UBO-GENITAL SYSTEM.
fold, termed the plica inguinalis (or plica inguino-mesonephrica), is joined from above
by a less marked fold (the plica testis inferior) which extends downwards from the
inferior end of the testis, which, at this time, is situated in the abdomen close to the inner
aspect of the mesonephros. Within both these folds smooth muscular and fibrous tissue
arises and gives origin to a continuous band, or ligament the gubernaculum testis.
The gubernaculum is, therefore, to be regarded as originally composed of two portions
a part developed within the plica inguinalis, and a part formed within the plica testis
inferior. It is interesting to note that in the female the representatives of these two parts
of the gubernaculum remain separate i
throughout life, and constitute the round
ligament of the uterus and the ligament
of the ovary. The gubernaculum, when
it is at its greatest development (about
the sixth month), is rounded and cord-like,
and is attached above to the lower end of
the testis, while inferiorly it is fixed near
the inguinal region. In the lower part
of its course it is closely related to, and is
FIG. 1015. DIAGRAM to illustrate the descent of the part iy COV ered by, the peritoneum of the
processus vaginalis. Striped muscular
scrotum, fibres are present in the lower part of the
t.v. Tunica vaginalis. gubernaculum, and have their origin from
the muscles of the inguinal part of the
anterior abdominal wall. As the testis
enters the processus vaginalis the gubernaculum atrophies, but at birth a short part of j
the gubernaculum may still be found passing downwards towards the inferior part of the i
scrotum and lying below the level of the tunica vaginalis. It is considered by some]
anatomists that the movement downwards of the testis may be partly due to a pull caused]
by the shrinking of the gubernaculum as it atrophies.
In some mammals, such as the elephant, the testes remain permanently within thej
abdominal cavity ; while in others, such as the rabbit and the hedgehog, the peritoneal
pouches remain widely open throughout life, and the testes are periodically withdrawn^
into the abdomen.
testis and the manner in which the tunica vaginalis
is derived.
a.c. Abdominal cavity.
p.v. Processus vaginalis.
t. Testis.
External spermatic fascia
I Internal spermatic fascia
Testicular
artery p amp i n if O ri]
,, plexus
FUNICULUS SPERMATICUS (SPERMATIC CORD).
The testis in its course downwards through the abdominal wall into t
scrotum takes with it its duct the ductus deferens blood and lymph vessels, and
nerves of supply. All these lie together in the inguinal canal as they traverse the
abdominal wall, and when they leave the canal by the subcutaneous inguinal rin
they extend downwards to the posterior border of the testis. The ductus deferens
the spermatic "vessels, and the nerves and
lymph vessels of the testis, loosely con-
nected together, form the funiculus sper-
maticus, or spermatic cord. At the ab-
dominal inguinal ring its constituent parts
separate from one another, and the funi-
culus may therefore be considered to extend
from the abdominal inguinal ring to the
posterior border of the testis. The struc-
tures which form the spermatic cord are en-
closed within a number of coverings derived
from the layers of the anterior abdominal
wall, and these, when the constituents of Fia
the cord reach the posterior border of the
testis, surround the tunica vaginalis, and
so form a part of the wall of the scrotum.
The sheaths or coverings of the cord derived from the abdominal wall are three i
number, and are named external spermatic fascia, fascia cremasterica, and inte
spermatic fascia. The external spermatic fascia is the most superficial of
three sheaths, and is derived from the aponeurosis of the external oblique mu
Deep fascia
Ductus deferens ! ^^
Artery to ductus deferens
1016. TRANSVERSE SECTION OF THE
CULUS SPERMATICUS, OR SPERMATIC
JUST BELOW THE SUBCUTANEOUS
RING.
THE SCKOTUM.
1297
with which it is continuous round the margins of the subcutaneous inguinal ring.
The fascia cremasterica consists partly of muscular fibres derived from the lower
part of the internal oblique muscle, and partly of delicate connective tissue.
The muscular fibres constitute the cremaster muscle and, passing down over the
funiculus, form a series of loops round the testis and tunica vaginalis. The internal
spermatic fascia is derived from the fascia transversalis of the abdomen. It
passes downwards as a continuous sheath over the cord, and encloses its various
structures, together with a certain amount of areolar tissue derived from the
subperitoneal tissue of the abdominal wall and some smooth muscle fibres.
In addition to the structures enumerated above, the artery to the ductus deferens, the
external spermatic (O.T. cremasteric) artery, and the genital branch (n. spermaticus externus)
of the genito-femoral nerve, accompany the structures forming the funiculus spermaticus.
1
SCROTUM.
The scrotum, in which the testes are placed, varies much in appearance in
different subjects, and even in the same individual at different times. As the
Cut edge of aponeurosis of external oblique
Internal oblique
Burosis of external oblique
edge) _ J^
Subcutaneous inguinal ring
Aponeurosis of
external oblique
Ligamentum inguinale
Cremaster innscle
Funiculus spermaticus
Falx aponeurotica ("conjoined tendon ")
Suspensory ligament of penis
: ; '. Ductus deferens
| Pubic tubercle
| Ductus deferens
Inter columnar fascia
-DISSECTION TO SHOW THE FUNICULUS SPERMATICUS AS IT ISSUES FROM THE SUBCUTANEOUS
NGUINAL RING. On the right-hand side of the figure the funiculus has been cut across, and the
structures composing it are seen in section. On the left-hand side of the figure the external oblique
muscle has been removed.
result of cold or of exercise, the wall of the scrotum becomes contracted and firm,
the skin covering it wrinkled; at other times the wall may be relaxed
flaccid, the scrotum then assuming the appearance of a pendulous bag. .The
:t side of the scrotum reaches to a lower level than the right, in correspondence
ith the lower level of the testis on that side of the body. The skin covering
scrotum is of a darker colour than the general skin of the body, and is
red with hair. It is marked in the median plane by the raphe scroti, which is
Continued backwards towards the anus, and forwards on to the inferior, or
Jthral, surface of the penis. The difference in the appearance of the scrotum
t different times is due to the amount of contraction or relaxation of a layer of
83
1298 THE UKO-GENITAL SYSTEM.
muscular fibres, constituting the tunica dartos, situated in the superficial fascia.
When this muscular layer is contracted, the scrotum becomes smaller and some-
what globular, and the skin is thrown into folds or wrinkles called rugae; when
it is relaxed, the scrotum is flaccid and pendulous, and the skin becomes more
smooth and even. The layer of fascia which contains the smooth muscle fibres
can be shown to be continuous superiorly with the superficial fascia of the penis,
and with the deep layer of the superficial fascia of the abdomen, and to be attached
laterally to the bones forming the pubic arch. The muscle fibres are arranged
in a thick layer of interlacing bundles, and many of the deeper fibres are continued
info the septum scroti, which divides the scrotum into two cavities, one for each
testis. The wall of each of these cavities is formed by the corresponding tunica
vaginalis, infundibuliform fascia, fascia cremasterica, and intercolumnar fascia; while
the skin, the superficial fascia, and the superficial part of the dartos muscle form
coverings which are common to the whole scrotum, and enclose both cavities.
The layer of tissue immediately beneath the dartos tunic is made up of exceedingly
loose and easily stretched areolar connective tissue, and in it, as throughout
in the superficial fascia of the scrotum, there is an entire absence of fat.
The scrotum in the foetus contains no cavity, but, like the labia majora in the female, it is
composed entirely of vascular connective tissue.
Vessels and Nerves of the Scrotum. The scrotum receives its vascular supply from the
posterior scrotal branches of the perineal divisions of the internal pudendal arteries, which reach
it from behind, and from the external pudendal branches of the femoral artery, which reach its
upper and anterior part.
The nerves of the scrotum are derived on each side from the posterior scrotal branches of the
perineal division of the pudendal nerve, from the perineal branch of the posterior cutaneous
nerve of the thigh, and from the ilio-inguinal nerve. The branches from the pudendal and
posterior cutaneous nerves reach the scrotum from behind, while the ilio-inguinal supplies its
upper and anterior part. The nerve fibres for the dartos muscle fibres are believed to have their
origin from the hypogastric plexus.
PENIS.
The penis is composed chiefly of erectile tissue, and is traversed by the canal
of the urethra. The surface nearest to which the canal of the urethra lies is
called the facies urethralis, or urethral surface ; the opposite and more extensive
aspect is the dorsum penis. The erectile tissue is for the most part disposed
in three longitudinal columns, which in the body of the organ are placed side by
side, while at the root of the penis they separate from one another, and become
attached to the fascia inferior of the urogenital diaphragm and to the pubic arch.
Two of these masses of erectile tissue, placed one on each side of the median plane,
and forming the dorsum and sides of the penis, are called the corpora cavernosa
penis, while the third, which is called the corpus cavernosum urethrae (O.T. corpus
spongiosum), is situated in the median plane near the urethral surface. The corpus
cavernosum urethrse is the part of the penis which is traversed by the urethra.
and it is considerably smaller than the corpora cavernosa penis, which form the
chief bulk of the organ.
In the corpus penis, or body of the penis, each corpus cavernosum penis is placed
close to the median plane, and presents a rounded surface, except where it is
flattened by contact with its fellow of the opposite side. The corpora cavernosa
penis are separated on the anterior or dorsal surface by a shallow groove, and OD
the posterior or urethral aspect by a deeper and wider furrow, in which lies the corpus
cavernosum urethrse (Fig. 1018). Towards the distal end of the penis the corpus
cavernosum urethrae appears to expand, and, spreading towards the dorsal surface oi
the organ, it forms a kind of conical cap, the glans penis, which covers over the blunt
rounded termination of the corpora cavernosa penis. The prominent margin oi
the glans, called the corona glandis, projects dorsally and laterally beyond the
extremities of the corpora cavernosa penis. The glans is traversed by the termina
part of the urethra, which ends near the summit of the glans in a slit-like opening
called the orificium urethrse externum, or external urethral orifice. The unitec
corpora cavernosa penis end in a blunt conical extremity, the apex of which is
THE PENIS.
1299
jived into a hollow in the base of the glans. The skin covering the body of
the penis is thin, delicate, and freely movable, and, except near the root of the
organ, is free from hairs ; on the urethral aspect of the penis the skin is marked
by a median raphe, continuous with the raphe of the scrotum. Traced towards
the base of the glans, the skin forms a free fold called the prseputhim, or prepuce,
which overlaps the glans to a variable extent. From the deep surface of the
prepuce the skin is reflected on to the terminal' part of the penis, along a line just
proximal to the corona glandis, and is continued over the entire glans to the
external urethral orifice. A small median fold, the frenulum prseputii, passes to the
deep surface of the prepuce from a point immediately below the orificium urethrse
externurn. The skin covering the glans is firmly attached to the underlying
erectile tissue, and here, as well as on the deep surface of the prepuce, it presents
some resemblance to mucous membrane.
Sometimes minute sebaceous glands, glandulse praeputiales, are found in very variable
numbers on the glans and inner surface of the prepuce ; the secretion from these when
they are present may help to form the smegma prseputii, which tends to collect in the
groove between the glans and the prepuce. The main source of the smegma is to be
found in the desquamated and broken-down epithelial cells derived from the surface of
the glans and prepuce.
At the radix penis, or root, the three component parts of the organ separate
from one another (Fig. 1018).
The corpora cavernosa
penis, diverging from
each other laterally, at first
become somewhat swollen,
and then, gradually tapering,
gain a firm, fibrous attach-
ment to the periosteum on the
medial surface of the pubic
arch. These diverging parts
of the corpora cavernosa are
called the crura penis, and
each is covered by the cor-
responding ischio-cavernosus
muscle. The corpus caver-
nosum urethrse lying between
the crura becomes enlarged,
and forms a somewhat spheri-
cal mass which receives the
name bulbus urethrse. The
bulb varies much in size in
different individuals, and is
ittached to the under sur- p IG . 1018. STRUCTURES COMPOSING THE RADIX PENIS.
face of the fascia inferior of The corpus penis is seen in section.
the urogenital diaphragm,
against which it rests. , The posterior part and under surface of the bulb usually
show a median notch or groove an indication that the bulb is originally composed
of two symmetrical portions, which during development have become fused in the
median plane. These two portions are termed the hemispheria bulbi urethrse, and
are best seen in subjects whose tissues have been hardened by in tra vascular
injection. A slightly marked median septum, situated within the bulb tissue,
indicates on a deeper plane the line along which fusion has taken place. The
canal of the urethra, piercing the fascia inferior of the urogenital diaphragm, enters
the bulb obliquely a short distance in front of its posterior extremity (Fig. 1024).
Covering the superficial surface of the bulb is the bulbo-cavernosus muscle.
A somewhat triangular band of strong fibrous tissue, called the ligamentum
suspensorium penis, is attached to the front of the symphysis pubis, and extends
to the fibrous capsule of the penis, with which it becomes continuous (Fig. 1017).
83 a
Corpus caver-
-nosum penis
Urethra
Corpus i caver-
nosum urethrae
Bulb of urethra
[ Inferior fascia of
j urogenital diaphragm
Corpus cavernosum penis
1300
THE UKO-GENITAL SYSTEM.
Structure of the Penis. Each corpus cavernosum penis is enclosed by a dense
white fibrous coat tunica albuginea corporum cavernosorum, which, fusing with
the corresponding coat of the opposite side, forms a median septum penis. The septum
is very incomplete, especially near the terminal part of the penis, where it is interrupted
by a number of nearly parallel slit- like perforations; hence the term "septum
pectiniforme " is often applied to it (Figs. 1019 and 1020). Through these openings the
erectile tissue of the corpora cavernosa of opposite sides is continuous.
The fibrous coat contains some elastic fibres, and may be divided into an outer layer
of longitudinally directed fibres and an inner layer of circular fibres, some of which
latter are continued into the septum. Numerous fibrous strands, called trabecula
corporum cavernosorum, proceed from the deep surface of the tunica albuginea, and
stretching across the interior of the corpus cavernosum, form a fine sponge-like framework
whose interspaces communicate freely with one another, and are filled with blood.
These blood-containing spaces lead directly into the veins of the penis, and, like the veins,
have a lining of flat endothelial cells. The size of the penis varies with the amount ofj
blood in this cavernous tissue. The structure of the corpus cavernosum urethrse
resembles that of the corpora cavernosa penis, but the fibrous coat is much thinner and
more elastic, and the trabeculae are finer (Fig. 1019).
The glans penis is also composed of cavernous tissue which communicates by a rich
venous plexus, situated on the ventral aspect of the urethra, with the corpus spongiosum
urethrse. No strongly marked tunica albuginea is present, and the erectile tissue is
practically bounded by the firmly adherent skin. Surrounding the urethra, which in this
part of the penis is represented by a laterally compressed slit -like passage, is a mass of
fibre-elastic tissue which forms a kind of median septum within the glans. This septum
Dorsal vein
Dorsal artery | Dorsal nerve
Corpus cavernosum
penis
Corpus cavernosurn
urethrae
Glans peni
Corpu
penis
s cavernosum
Septum
pectiniforme
Urethra
FIG. 1019. TRANSVERSE SECTION THROUGH THE
BODY OP THE PENIS.
Urethra
FIG. 1020. A LONGITUDINAL SECTION OF THE
TERMINAL PORTION OF THE PENIS.
is continued backwards to join the sheath of the conical end of the corpora cavernosa, an
ventrally it gives attachment to the frenulum of the prepuce. It imperfectly divides the
erectile tissue of the glans into right and left portions, which, however, freely communicai
dorsally. From the septum, trabeculse pass out in all directions into the tissue of the glam
Loosely surrounding the corpora cavernosa penis and the corpus cavernosum urethi
is a fibrous sheath containing numerous elastic tissue fibres. This sheath is termed
fascia penis, and reaches as far as the base of the glans, where it becomes fixed to the
floor of the groove limited by the corona glandis. In its proximal part the sheath give
insertion to many of the fibres of the bulbo-cavernosus and ischio-cavernosus muscles.
Superficial to the fascia penis is a layer of extremely lax areolar tissue, and E
superficial still is a prolongation of the tunica dartos of the scrotum, covered by
delicate skin of the penis. Numerous sebaceous glands are present in the skin
especially on the urethral aspect of the penis.
In some mammals, such as the walrus, dog, bear, baboon, etc., a bone called the os penis it
developed in the septum which intervenes between the corpora cavernosa penis.
Vessels and Nerves of the Penis. The penis receives its arterial supply from branches
the internal pudendal artery. The erectile tissue of the corpora cavernosa penis is supplie
chiefly by the deep arteries of the penis, while that of the corpus cavernosum urethrae receives ife
arterial supply from the artery to the bulb. Branches of the dorsal artery of the penis piercir
the fibrous coat of the corpora cavernosa penis furnish additional twigs to the erectile tissue
these structures. The glans receives its chief blood-supply from branches of the dorsal art"
The small branches of these arteries run in the trabeculae of the erectile tissue, and
capillaries, into which they lead, open directly into the cavernous venous spaces. As the
lie in the finer trabeculae the smaller branches often present a peculiar twisted apj
and hence the name arterise helicinae is sometimes applied to them.
THE PKOSTATE.
1301
The veins with which the cavernous spaces communicate, carry the blood, for the most part,
either directly into the pudendal plexus, or into the dorsal vein and so to the pudendal plexus.
The dorsal vein of the penis begins in tributaries from the glans and prepuce, and lies in the
groove between the corpora cavernosa penis as it ascends to pass beneath the arcuate ligament
of the pubis to join the pudendal plexus. On each side of it lies the dorsal artery, and still
farther from the median plane lies the dorsal nerve (Fig. 1019).
The lymph.- vessels of the penis are arranged in a deep and superficial series, and end in the
medial glands of the inguinal group of lymph -glands.
The nerve-supply of the penis is derived from the pudendal nerve and from the hypo-
gastric and pelvic plexuses. The branches of the pudendal are the dorsal nerve of the penis,
and branches from the perineal nerves. These supply the cutaneous structures of the penis,
while the sympathetic filaments from the hypogastric and pelvic plexuses, which reach the
penis through the prostatic nerve plexus, end in the erectile tissue.
PROSTATA.
The prostata, or prostate, is a partly glandular, partly muscular organ of a dark
brown-red colour which surrounds the beginning of the urethra in the male. It
lies within the pelvis' behind the pubes, and is enclosed by a dense sheath derived
from the pelvic fascia. Through the various connexions of this sheath the
prostate is firmly fixed within the pelvic cavity. The ejaculatory ducts traverse
the prostate in their course downwards and forwards to join the urethra as it
Superior surface
of bladder
Lig. urn- Seiuma
bilieale vesicle
medium
Infero-lateral
area of bladder
Lateral
aspect of
prostate
ral aspect
of prostate
.Urethra
edian
umbilical
ligament
(urachus)
Infero-lateral
area of bladder
Urethra
FIG. 1021. URINARY BLADDER, PROSTATE, AND SEMINAL VESICLES VIEWED FROM THE SIDE.
Drawn from specimens hardened in situ.
nds through the gland (Fig. 1023). The size of the prostate varies con-
siderably in different individuals, but its transverse, or longest, diameter is usually
from one and a quarter to one and a half inches; its an tero- posterior diameter
: about three-quarters of an inch ; and its vertical diameter about one and a quarter
inches. Superficially the prostate is separated from the bladder by deep wide
; lateral grooves directed downwards and forwards, and by a narrow posterior groove
which is horizontal.
In connexion with the prostate we describe an apex which is directed down-
; wards, a base looking upwards, a posterior, and two lateral surfaces. The general
outline of the organ has been often compared with that of a Spanish chestnut.
The upper surface, or basis prostatse, is directed upwards against the inferior aspect
of the bladder, in the neighbourhood of its urethral opening. The greater part of
this surface is structurally continuous with the bladder wall, only a narrow portion
remains free on each side, and forms the lower limit of the deep groove which
marks the separation of the bladder and prostate (Fig. 1021). The lateral surfaces
of the prostate are convex and prominent, especially in their posterior and upper
portions, and rest against the fascia covering the levator ani muscle. They are
' directed for the most part laterally, downwards, and somewhat forwards, and meet
together in front in a rounded anterior border, sometimes called the "anterior
; surface," or " facies anterior," of the prostate. Posteriorly the prostate presents a
flattened somewhat triangular posterior surface, directed backwards and downwards
1302
THE UKO-GENITAL SYSTEM.
Bladder apex
against the anterior wall of the rectum, from which it is separated by a layer
of the pelvic fascia. This flattened facies posterior is separated on each side from
the lateral surfaces by a rounded border which, beginning above at the prominent
lateral part of the prostate, ends below at the apex of the organ. The apex
prostatae points downwards, and is in relation to the sphincter urethras membranacese
muscle, from which it is separated by the fascia superior of the urogenital
diaphragm. From the apex the rounded anterior border, which separates the lateral
surfaces, passes upwards in the median plane behind the symphysis pubis and retro-
pubic pad of fat. This border is interrupted in its lower part by the passage of the
urethra.
When the sheath formed by the pelvic fascia is stripped off the prostate the
organ has a more rounded outline, and the surfaces just described are not so
clearly defined. The anterior border may now appear to be rather a surface than a
border, and the antero-posterior diameter of the whole organ is considerably
reduced.
The urethra enters the prostate at a point near the middle of its upper surface,
and leaves it at a point situated on its anterior border, just above and in front of
the apex. As it descends, the urethra describes a curve which is concave forwards,
and in median section it is seen to lie, on the whole, nearer to the posterior surface
than to the anterior border of the gland.
The ejaculatory'ducts, entering a slit-like interval, or hilum, situated just in front
of the border which separates the base from the posterior surface of the prostate,
run downwards, medially, and forwards,
to open into the prostatic portion of
the urethra very close to one another.
The somewhat wedge-shaped portion
of the prostate, which lies between
these ducts and the posterior aspect
of the urethra, receives the name of
lobus medius (Fig. 1023). The base of
this middle lobe projects upwards
against the bladder, and is continuous
with the part of the bladder wall lying
immediately behind the urethral orifice.
When hypertrophied, as it often is in
lobe of the
considerable
elevation in the cavity of the bladder,
to which the term uvula vesicae is
applied. This elevation possesses con-
Drawn from a specimen hardened in situ. The lateral gamble Surgical interest (p. 1277).
surfaces of the prostate are seen one on each side of mi _ O r , ,
the urethra and in front of the posterior surface. ine rest ot tne prostate IS deSCrib
as being composed of two large lateral
lobes, which are, however, not marked off from one another superficially.
In front of the prostate, between it and the pubis, is a rich venous plexus plexus
pudendalis in which the dorsal vein of the penis terminates. This plexus :
continued backwards, on each side, round the lateral aspect of the prostate, ai
joins the large thin-walled veins which are collected for the most part in the de
sulcus between the bladder wall and the prostate, and form the prostatico-vesk
plexus. Most of the veins forming this plexus lie partly within and pai
outside the dense fibrous sheath of the prostate, which is derived from the viscei
pelvic fascia (Figs. 1023 and 1024).
Fibrous Sheath of the Prostate. The sheath of the prostate is formed bi
the visceral pelvic fascia, and closely invests the gland on its lateral and posteric
aspects. Inferiorly at the apex of the prostate the sheath becomes continuous wit
the fascia superior of the urogenital diaphragm, which lies above the sphinct
urethree membranacese muscle, and is attached to the pubic arch. In front
thickened bands pass forwards from the anterior aspect of the sheath, one on
side of the median plane, to reach the back of the lower part of the pubis, whei
Infero-lateral
area
Ureter
Ductus
Posterior surface of prostate
Seminal vesicle
FIG. 1022. PROSTATE, URINAIIY BLADDER, AND
SEMINAL VESICLES SEEN FROM BELOW.
s old people, the middle
prostate may cause a
tin
THE PKOSTATE.
1303
ey are attached to the periosteum. These constitute the pubo-prostatic liga-
ments, and contain smooth muscle fibres, as well as dense connective tissue,
me of the muscle fibres in connexion with the pubo-prostatic ligaments, passing
wards as well as backwards, gain the bladder wall, and are spoken of as the
bo-vesical muscles. Below the pubo-prostatic ligaments the medial edges of
e levatores ani muscles pass medially and almost meet together in front of the
apex of the prostate. When followed backwards, the medial edge's of these muscles
are seen to closely embrace the apex of the prostate. This layer forms a part of
the wall of the retro-pubic space which lies in front of the prostate and below the
bladder (Fig. 1024).
Between the pubo-prostatic ligaments there is a shallow fossa, or depression, the
floor of which is formed by a thin layer of fascia connecting the anterior aspect of
the sheath of the prostate with the back of the pubis. On each side of the body
the lateral aspect of the sheath of the prostate is continuous with the strong fascia
which covers the pelvic surface of the levator ani muscle. When the fibrous sheath
of the prostate is traced upwards beyond the level of the upper margin of the gland
it becomes thinned out and joins the fascial covering of the bladder. Posteriorly the
Pubo-prostatic ligaments
Crista urothralis
..JJtriculus
5\ prostaticus
Urethra
Capsule
Ejaculatory ducts Lobules of gland
A B
1023, A and B. HORIZONTAL SECTIONS THROUGH THE PROSTATE. Section A lies at a higher level than B.
upward prolongation of the sheath is continuous with the fascial layers which
enclose the ampullae of the ductus deferentes and the seminal vesicles, and it is
adherent to the peritoneum of the recto-vesical pouch. In this position it is often
ST ^ of as the recto-vesical fascia.
Wken
Str
Structure of the Prostate. Beneath the fibrous sheath of the gland the
superficial part of the prostate is seen to be largely composed of matted interlacing
ndles of smooth muscle and connective tissue fibres, which form a kind of capsule for
deeper parts of the organ. This layer, or capsule of the prostate, is not sharply
ned, but from its deep aspect fibrous and muscular strands pass inwards, converging
ards the posterior wall of the urethra, to become continuous with the mass of smooth*
uscular tissue which surrounds this canal as it traverses the prostate. These somewhat
radially arranged strands divide the prostate into a number of incompletely defined
lobules, of which there appear to be about fifty. The yellowish-coloured glandular tissue,
or corpus glandulare, which forms the lobules is composed of minute, slightly branched
tubules, the walls of which in certain places show numerous saccular dilatations. In the
upper portion of the gland the tubules are slightly dilated and shorter than in the lower
part, where they are longer and more convoluted. The glandular tubules lead into the
minute prostatic ducts, which open into the urethral canal as it traverses the prostate.
The ductus prostatici number about twenty or thirty, and open for the most part into
a groove on each side of the median elevation, or crista urethralis, in the posterior wall
of the urethra (Fig. 1023 A).
The bulk of the glandular tissue is situated at the sides of and behind the urethra.
In front of the upper part of the prostatic portion of the urethra there is a mass of
83 &
1304 THE URO-GENITAL SYSTEM.
smooth muscular fibres, which is continued upwards and backwards on the sides of the
urethra to form a part of the " sphincter vesicse." At a lower level striped muscular
tissue, which is continuous with the deep part of the sphincter urethras membranacese
muscle, occupies a position in front of the urethral canal.
The muscular tissue of the prostate is to be regarded as the thickened muscular
layer of the wall of the urethra, broken up and invaded by the prostatic glands
which arise and are developed from the lining layer of the canal during embryonic life.
In old age the prostate frequently undergoes a hypertrophy, which may affect chiefly
the glandular tissue, or the entire organ. Not infrequently calcareous concretions are
found embedded in the prostate.
Vessels and Nerves of the Prostate. The prostate receives its blood -supply from branches
of the haemorrhoidal and inferior vesical arteries, while the large plexus of veins plexus pudendalis
which surrounds it, and into which the veins of the penis open, communicates with the vesical
plexus, and drains into the hypogastric veins. In old people the veins of the prostate usually
become much enlarged.
The nerves of the prostate are derived from the hypogastric plexus.
GLANDULJE BULBO-URETHRALES.
The bulbo-urethral glands (O.T. glands of Cowper) are a pair of small bodies
placed in relation to the second, or membranous, part of the urethra. They are
each about the size of a pea, and are of a yellowish-brown colour. Situated
in the space between the two fasciae of the urogenital diaphragm, they lie
below the level of the apex of the prostate, and above that of the bulbus urethrae
(Figs. 1024 arid 1026). Each gland is made up of a number of closely applied
lobes or lobules, and is of the compound racemose type. The ductules -of the gland
unite to form a single ductus excretorius, which pierces the bulbus urethrse, and,
after a relatively long course, ends by opening into the cavernous portion of the
urethra by a minute aperture. The secreting acini are lined with columnar
epithelium.
The glands receive their arterial supply from the artery to the bulb.
In old age these glands are often difficult to find without a microscopic examination.
URETHRA VIRILIS.
The urethra in the male is a channel of about eight inches in length leading
from the bladder to the external urethral orifice at the extremity of the glans
penis. The canal serves not only for the passage of urine, but it also affords an
exit for the seminal products, which enter by the ejaculatory ducts, and for the
secretion of the prostatic and bulbo- urethral glands. In addition, numerous
minute glandulse urethrales pour their secretion into the urethra.
As it passes from the internal urethral orifice, to its external opening, the
urethra describes a somewhat LP shaped course, and it is customary to divide it into
certain sections, which have received distinctive names. The first part of the
urethra lies within the pelvic cavity, and has a somewhat vertical course as it
traverses the prostate. Turning more forwards, the urethra passes below the
pubic arch, and pierces the fibrous layers which form the pelvic wall in this
region. Leaving the pelvis minor, the canal enters the bulbus urethrse, where
the latter is attached to the fascia inferior of the urogenital diaphragm, and
throughout the rest of its course it lies in the erectile tissue of the corpus caver-
nosum urethras and of the glans penis. The part of the urethra which lies
embedded' in the prostate is called the pars prostatica, or prostatic portion ; the short
part which pierces the pelvic wall is called the pars membranacea, or membranous
portion, and the part surrounded by the corpus cavernosuin urethras receives the
name of pars cavernosa, or cavernous portion. Of these three sections of the urethra
the cavernous portion is much the longest, and the membranous is the shortest.
THE MALE UKETHEA.
1305
Pars Prostatica Urethrse Virilis. The prostatic part of the male urethra
descends through the prostate from the base towards the apex, describing
ight curve which is concave forwards. It is about one inch in length,
Seminal vesicle
Bladder
Prostate \ .
Retro-pubic pad of fat \
! Bulb of urethra
Membranous urethra
Corpus cavernosum penis
FIG. 1024. DISSECTION OF THE MALE PELVIC ORGANS AND OF THE PENIS,
FROM THE SIDE.
The dorsal vein of the penis and the pudendal venous plexus are coloured blue.
and is narrower above and below than in its middle portion, which is, indeed,
the widest part of the whole urethral canal. Except while fluid is passing,
the canal is collapsed, and the mucous membrane of the anterior and posterior
walls is in contact, and thrown into a series of longitudinal folds. ^ When
distended, the middle, or widest part of the canal, may normally have a diameter
1306
THE UEO-GENITAL SYSTEM.
of about one-third of an inch. The posterior wall, often termed the " floor " of
the prostatic urethra, presents a distinct median ridge or elevation called the
crista urethralis (Fig. 1026). This projects forwards into the urethra to such
an extent that the canal in transverse section presents a somewhat crescentic
outline. In the depressions, or grooves, on each side of the crista urethralis
Ductus deferens
Inferior
epigastric artery
Superior peritoneal lig.
of bladder .-.-
Urinary bladder E-
Sacro-genital fold
Recto-vesical pouch
Ductus deferens
Retro-pubic pad of fat
Prostatic urethra
Dorsal vein of penis
Corpus cavernosum penis
Corpus cavernosum
urethra
Anal canal
Membranous urethra
Cavernous portion of urethra Bulb of urethra
FIG. 1025. ADULT MALE PELVIS IN MEDIAN SECTION.
The urinary bladder is empty and firmly contracted. The urethra is opened up in its entire length.
the numerous ducts of the prostatic glands open by minute apertures. Some
few ducts from the middle part of the gland open nearer the median plane, on
the sides of the urethral crest. On the summit of the crista urethralis is
a slit -like opening which leads backwards and upwards for a distance of
about a quarter of an inch, as a blind pouch, in the substance of the prostate.
This little cavity is known as the utriculus prostaticus, and represents the
fused posterior ends of the Miillerian ducts, from which the uterus and vagina
of the female are developed. The term uterus masculinus is therefore some-
times applied to this little pouch. On each side of the mouth of the utricle
is the much more minute opening of the ejaculatory duct. When traced upwards
towards the bladder, the urethral crest, diminishing in height, becomes indistinct.
but
THE MALE UEETHKA.
1307
ut in it can often be traced as a slight median ridge as far as the uvula vesicse.
When followed in the opposite direction the ridge becomes less marked, and
can be followed on the urethral wall into the membranous portion of the canal,
where it divides into a pair of inconspicuous folds or elevations, which gradually
fade out into the urethral wall (Fig. 1026).
The curvature and, to a less degree, the length of the prostatic urethra depends
upon the amount of distension of the bladder and of the rectum (compare Figs. 989
990).
Pars Membranacea Urethrse. The second, or membranous portion, of the
Ureter
-Orifice of ureter
Trigonum vesicae
Uvula vesicse
- Crista urethralis
Opening of ejaculatory duct'
- Utriculus prostaticus
Bulbo-urethral gland
Membranous urethra
Opening of duct of bulbo-
urethral gland
-Crus penis
Corpus cavernosum penis (cut)
1026. DISSECTION SHOWING THE TRIGONUM VESIC.E AKD THE POSTERIOR WALL OB FLOOR OF THE
FRETHRA IN ITS PROSTATIC, MEMBRANOUS, AND THE PROXIMAL PART OF ITS CAVERNOUS SUBDIVISIONS.
The canal has been opened up by removing its anterior and upper wail.
urethra leads downwards and forwards from the apex of the prostate to the
bulbus urethrse, and is the shortest and narrowest of the three subdivisions of the
canal, its length being somewhat less than half an inch. It begins at the superior
fascia of the urogenital diaphragm, a layer of pelvic fascia which lies above the
sphincter urethras membranacese muscle. Here it is continuous with the prostatic
portion of the urethra. It ends, having pierced the inferior fascia of the uro-
genital diaphragm, by becoming continuous with the cavernous portion of the
urethra. Placed in front of the anal canal, it lies about one inch behind and below
the arcuate ligament of the pubis (O.T. sub-pubic ligament). It is surrounded by
fibres of the sphincter urethras membranacese muscle, and behind it, on each side of
the median plane, lies the bulbo-urethral gland. The posterior part of the bulbus
1308 THE UEO-GENITAL SYSTEM.
urethras projects backwards and overlaps the posterior wall of the membranous
part of the urethra to a considerable extent (Fig. 1024).
The membranous portion of the urethra is the most firmly fixed and least
dilatable part of the passage.
A slight medial elevation, which is continuous above with the crista urethras,
projects into the canal from its posterior wall, and, becoming less marked as it is
traced downwards, is often seen to divide into two faint ridges. When the canal
is empty other longitudinal folds or ridges are usually to be seen on the mucous
membrane, but these become obliterated when the passage is distended. The
lumen of the empty tube, in transverse section, presents a stellate outline.
It is important to note that the terminal portion of the pars membranacea urethrse,
where it is overlapped posteriorly by the urethral bulb, lies in front of the urogenital
diaphragm. It is considerably wider than the upper part of this subdivision of the canal,
and is very thin-walled. This is the part of the canal which is most liable to rupture
(Figs. 1024 and 1026).
Pars Cavernosa Urethrse. The third, or cavernous portion, of the urethra
is much the longest of the three subdivisions. It begins at a point about half
an inch in front of the posterior end of the bulbus urethras, and ends at the
external urethral orifice on the glans penis. Its proximal, or perineal, portion
has a fixed position and direction, while its distal part varies with the position
of the penis. The canal is about six inches in length, and is related throughout
its whole extent to the erectile tissue of the corpus cavernosum urethras and
of the glans penis. Directed at first forwards through the bulbus urethras, the
canal turns downwards and forwards at the point where it comes to lie in front
of the lower part of the symphysis pubis (Fig. 1025). This bend in the direction
of the canal, roughly speaking, corresponds to the place of attachment of the
suspensory ligament to the dorsum of the penis. When the penis is drawn
upwards towards the front of the abdomen, the direction of the terminal half of
the canal is, of course, changed, and at the same time the whole length of this
subdivision of the urethra becomes more uniformly curved.
The urethra passing obliquely downwards and forwards enters the bulb at a point
nearly half an inch from its posterior extremity. Immediately after the canal has
pierced the fascia inferior of the urogenital diaphragm its posterior aspect becomes
surrounded by the erectile tissue of the bulb, but the anterior wall remains un-
covered for a distance of about a quarter of an inch (Fig. 1025). The wall of the
urethra is here very thin, and the passage is more readily dilatable than in other
parts. In this region the urethral wall may readily be torn through, if undue
force is used, or if the handle is depressed too soon when attempting to pass an
instrument into the narrower more fixed part of the canal. The urethra lies at
first in the upper part of the erectile tissue, but as it passes forwards it sinks
deeper, and comes to occupy the middle part of the corpus cavernosum urethras
(Fig. 1025). In the glans, on the other hand, the erectile tissue lies on the dorsal
and lateral aspects of the urethra. Like the other parts of the urethral passage,
the pars cavernosa is closed except during the passage of fluid, the closure being
effected by the apposition of its dorsal and ventral walls except in the portion
of the canal which lies in the glans penis, where the side walls of the canal
come into contact. Thus the lumen of the first part of the canal, when empty,
is represented in cross section by a transverse slit, and that of the terminal part
by a vertical slit (Fig. 1027). The cavernous part of the urethra does not
present a uniform calibre throughout, but is narrower in its intermediate part,
where it traverses the corpus cavernosum urethras, than it is in those portions
of its course which are surrounded by the bulb and the glans. The terminal
dilated part of the passage is termed the fossa navicularis urethrae, and opens on
the surface by the vertically placed slit-like orificium urethrse externum, or external
urethral orifice, which is the narrowest and least dilatable part of the whole
urethral canal.
The ducts of the bulbo-urethral glands open by very minute apertures in the
inferior wall of the proximal part of the cavernous portion of the urethra. Before
THE MALE UEETHRA.
1309
ling into the canal, they lie for some distance immediately beneath its mucous
niembrane. A number of little pit-like recesses, called the lacunae urethrales, also
open into the cavernous part of the urethra, and are so disposed that their openings
lead for the most part obliquely into the canal in the direction of its external orifice.
In some cases a somewhat valve -like fold of the mucous membrane, the valvula fosses
navicularis, is found in the upper wall of the urethra in the region of the fossa navicularis.
The free edge of this fold is directed towards the external urethral orifice, and may engage
the point of a fine instrument introduced into the urethra.
Structure. The mucous membrane of the urethra contains numerous elastic fibres
and varies in thickness in different parts of the canal. In many positions it shows
distinct longitudinal folds and also minute depressions or pits the lacunse urethrales,
already mentioned. The lining epithelium is composed of many layers of cells, and is
continuous through the internal urethral orifice with the epithelium of the bladder,
which at first it closely resembles. In the region of the fossa navicularis the lining cells,
which throughout the cavernous portion of the canal are of a columnar type, become flat
and scaly.
Numerous minute glands glandulse urethrales open into the urethra. These are
most plentiful in the upper, or anterior, wall, but they also occur in smaller numbers in
the floor and side walls. They are most numerous in the anterior half of the cavernous
portion of the canal, and in the membranous subdivision of the urethra.
Dorsal vein
jrsal artery ! Dorsal nerve
Corpus cavernosum
penis
Corpus cavernosum
urethra;
Glaus penis
Corpus cavernosum
penis
Urethra
G. 1027. A, TRANSVERSE SECTION THROUGH THE BODY OF THE PENIS. B, LONGITUDINAL SECTION
OF THE TERMINAL PORTION OF THE PENIS.
The larger glands are deeply placed beneath the mucous coat, and communicate with
urethra by long slender obliquely placed branched ducts. The smaller glands lie in
the mucous coat and form flask-like depressions with very short ducts. The ducts of some
of the glands open into the lacunae, but many of the latter have no connexion with the
urethral glands.
Frequently two or more elongated ducts belonging to some of the larger glands open
into the urethra quite close to its termination. These are sometimes spoken of as para-
urethral ducts, and may be traced backwards for some distance beneath the mucous
membrane forming the roof of the urethra. Morphologically they do not correspond to
the ducts which in the female have received the same name.
The muscular wall in the upper part of the urethra consists of smooth muscle fibres
I directed for the most part longitudinally, but some circularly arranged fibres are also
present. It is probable that throughout the greater part of the cavernous urethra a
muscular coat is not represented.
Round the beginning of the urethra there is an obliquely placed band of circularly
arranged smooth muscle fibres, which is continued downwards and forwards from below
the anterior part of the trigone of the bladder. The lower and anterior fibres of this
band lie in the anterior wall of the upper part of the prostatic urethra. The band is
! sometimes spoken of as the sphincter vesicse internus. At a lower level, in front of the
' prostatic urethra, is a band of striped muscular fibres which is continuous inferiorly with
the inner circularly disposed part of the sphincter urethrse membranacese.
Like the latter it is probably to be regarded as a part of a primitive voluntary
urogenital sphincter muscle, such as is represented also in the female subject.
1310
THE URO-GENITAL SYSTEM.
THE FEMALE REPRODUCTIVE ORGANS.
The reproductive glands in the female are a pair of ovaries placed one on each
side of the cavity of the pelvis. In connexion with each ovary is an elongated
passage or tube the uterine (O.T. Fallopian) tube which leads to the uterus and
opens into its cavity. There is no direct continuity between the ovary and the
uterine tube, such as exists between the other glands of the body and their ducts,
but the ova, when shed from the ovary, pass into the open end of the tube, and are
thus conducted to the uterine cavity. The uterus is a hollow muscular organ which
Ileum
Suspensory
ligament
Caecum
Vermiform
process
Ovary
Tuba uterina
Inf. epigastric ~ ~
Round ligament --
Fundus uteri ""
Obliterated .
umbilical artery
Urinary bladder "
Urethra
Labi urn minus -
Labium majus
-Ureter
Nerve cords
from hypo-
gastric plext
FIG. 1028. MEDIAN SECTION THROUGH THE FEMALE PELVIS.
Drawn for the most part from a model made from a dissection by Professor Edward H. Taylor.
occupies a nearly median position in the pelvis ; it is joined by the uterine tubes
above, and it communicates with the upper part of the vagina below. The ovum,
having passed through the tube, reaches the cavity of the uterus, and in it, if
fertilisation has taken place, the ovum undergoes its development into the embryo
and foetus. The vagina is the passage which leads from the uterus to the exterior, and
has its external opening behind that of the urethra, within the rima pudendi or
uro-genital space. In connexion with the uro-genital space are a number ol
structures which are included under the term external genital organs, and which
represent in the female the various parts of the penis and scrotum in the male.
These are the labia majora and the mons Veneris, the labia minora, the clitoris,
and the bulbus vestibuli. The larger vestibular glands, placed one on each side oi
the lower part of the vagina, are accessory organs of the female reproductive
system, and are represented by the bulbo-urethral glands in the male.
THE OVAKY.
1311
OVAEIUM.
The ovary is a solid body, flattened from side to side, and about the size and
shape of a large almond. Its length is usually between one and one and a half
inches, and the thickness from side to side between a quarter and half an inch.
In the adult the ovary is placed against the side wall of the pelvic cavity, and is
connected by peritoneal folds with the broad ligament of the uterus and with the
side wall of the pelvis. The position occupied by the ovary within the pelvic
cavity is fairly constant, although these ligaments do not hold the organ firmly
fixed in any definite place.
In the ovary we recognise two extremities a superior extremity, larger and
more rounded, and an inferior extremity, somewhat pointed. The term extremitas
External iliac artery
External iliac vein
Hypogastric artery
/'Ureter
Ovary
Obliterated
umbilical artery
Round ligament
of uterus
Superior vesical
artery
Pubic ramus
Obturator externus
FIG. 1029. SIDE WALL OF THE FEMALE PELVIS, showing the position of the ovary and its relation to the
uterine tube. The pelvis has been cut in section parallel to, but at some distance from, the median
plane.
tubaria is applied to the superior end of the ovary, as it is most intimately
connected with the uterine tube ; the term extremitas uterina is used with reference
to the inferior extremity, since this part of the ovary is connected with the uterus
by a fibrous cord, termed the ligament of the ovary. The flattened surfaces of the
ovary are called facies medialis and facies lateralis, and the borders separating
them margo meso various or mesovarian border, and margo liber or free border. The
free border is convex ; while the mesovarian, which is straighter and narrower, is
connected by a very short peritoneal fold, the mesovarium, with the posterior layer
of the broad ligament of the uterus. The vessels and nerves enter the ovary at
this mesovarian border, which is therefore often termed the hilum of the ovary.
Position and Relations of the Ovary. When the ovary occupies its most
usual, or typical, position the long axis of the gland is vertical. Its lateral
surface lies against the wall of the pelvis, and its medial surface looks medially
towards the pelvic cavity. The peritoneum of the pelvic wall, where the ovary lies
1312
THE UKO-GENITAL SYSTEM.
against it, is depressed to form a little fossa termed the fossa ovarii, within which
the ovary is placed. In the floor of this fossa are the obturator nerve and vessels.
The tubal extremity of the ovary lies below the level of the external iliac vessels,
and its uterine extremity is placed just above the level of the peritoneum covering
the pelvic floor. The fossa ovarii, in which the ovary lies, extends as far forwards
as the obliterated umbilical artery, and backwards as far as the ureter and
uterine vessels. Thus the mesovarian border of the ovary lies just behind the line
of the obliterated umbilical artery, and the free border is on a plane anterior
to the ureter (Fig. 1029). The medial surface of the ovary is almost completely
covered by the uterine tube, which, passing upwards on it near its mesovarian
border, arches over the tubal extremity, and then turns downwards in relation to the
free border and posterior part of the medial surface (Fig. 1029).
In some cases the ovary is found to lie behind, or more rarely in front, of the fossa described
above, and its long axis may be oblique instead of vertical. The above description, however,
corresponds to the typical position of the organ in women who have not borne children. When
Ep-oophoron Ligament
Tuba uterina | Ovary of ovary Uterus a
Fundus uteri
Vesicular
append-
age of
Morgagni
Lateral angle
of uterus
Cavity
of body
Cavity
of cervix
Infundibulum of tube
Round ligament
of uterus
Broad
ligament
Cavity of vagina
A B
FIG. 1030. A, THE POSTERIOR ASPECT OF THE UTERUS AND BROAD LIGAMENT (the broad ligament has
been spread out).
a, b, and c, the isthmus tubse, the ligament of the ovary, and the round ligament of the right side cut short.
B, DIAGRAMMATIC EEPRESENTATION OF THE UTERINE CAVITY OPENED UP FROM ITS ANTERIOR ASPECT.
the uterus is much inclined towards the right side of the body the left ovary has its long axis
directed obliquely downwards and medially, the right gland remaining vertical
Connexions of the Ovary. When the ovary is in position a small somewhat
triangular peritoneal fold passes upwards from its tubal extremity, and becomes 1(
in the peritoneum covering the external iliac vessels and the psoas major musclt
(Fig. 1028). This fold has received the name of ligamentum suspensorium ovarii, and it
a portion of the superior and lateral part of the broad ligament of the uterus, whicl
here contains between its two layers the ovarian vessels and nerves as they _
down into the pelvis to reach the hilum of the ovary. The vessels and nerves enter-
ing the ovary along its mesovarian border are enclosed in a sheath of peritoneui
derived from the posterior layer of the broad ligament. In this way the ovary it
connected along the whole length of its anterior border by a very short mesentery,
or mesovarium, to the posterior aspect of the broad ligament (Fig. 1030).
uterine extremity of the ovary is connected with the lateral angle of the uterus by a<
ligament called the ligamentum ovarii proprium or ligament of the ovary. This hf"'
the form of a rounded cord enclosed between the peritoneal folds of the bi
ligament, and is attached to the uterus, behind and below the point of entran(
of the uterine tube. It is composed chiefly of smooth muscle fibres continue!
with those of the uterus. The tubal extremity of the ovary is directly connect
with one of the largest of the fimbrise surrounding the abdominal end of th<
uterine tube, which receives the name fimbria ovarica, or ovarian fimbria of J
tube (Fig. 1030).
THE OVAEY.
1313
Descent of the Ovary. Like the testes, the ovaries at first lie in the abdominal
cavity, and only later assume a lower position. At birth the ovary lies partly in the
abdominal, and partly in the pelvic cavity ; soon, however, it takes up a position entirely
within the pelvis minor. As in the male a gubernaculum is present in the early stages of
development. The ligament of the ovary represents the upper part of the gubernaculum
which is developed within the plica testis inferior in the male, and the round ligament of the
uterus represents the inferior part, which is formed within the plica inguinalis (see p. 1295).
It is a rare abnormality for the ovary, instead of entering the pelvis, to take a course similar
to that of the testis, and pass through the inguinal canal into the tissue of the labium majus.
Structure of the Ovary. The ovary is for the most part composed of a connective
tissue, called the stroma ovarii, richly supplied by blood-vessels and nerves. The stroma
contains very numerous spindle-shaped connective tissue fibres, and some elastic tissue.
The surface of the ovary is covered by a layer of epithelium, which is composed of
columnar cubical cells, and is continuous with the epithelium of the peritoneum
forming the mesovarium. The ovarian epithelium is a persistent portion of the
germinal epithelium of the embryo which covers the genital ridges, and from which the
ova and other cells of the Graafian follicles are derived. The position in which it be-
comes continuous with the peritoneum can usually be distinguished as a fine white line
near the hilum of the ovary. Shining through the epithelium of the fresh ovary (except
Down-growths of epithelium
Germinal epithelium
Ovum with its investing cells
Stratum granulosum
Nests of epithelial cells Ovarian stroma Vesicular ovarian follicle Ovum
Liquor folliculi
Cumulus oophorus
1031. A. DIAGRAMMATIC REPRESENTATION OF THE MANNER IN WHICH THE FOLLICULI VESICULOSI
ARISE DURING THE DEVELOPMENT OF THE OVARY. B. DIAGRAM ILLUSTRATING THE STRUCTURE
OF A RIPE OR VESICULAR OVARIAN (GRAAFIAN) FOLLICLE.
in old age) are usually to be seen a variable number of small vesicles the folliculi
oophori vesiculosi (O.T. Graafian follicles), in which the ovula, or ova, are contained. The
number of follicles visible, and also the size which each follicle reaches before it ruptures
and sheds its contents, is by no means constant. When a follicle ruptures and discharges
the ovum its walls at first collapse, but later the cavity becomes filled with extravasated
blood and cellular tissue of a yellowish colour. The resulting structure, called a corpus
luteum, slowly degenerates unless impregnation has taken place, in which case it develops
and becomes larger during pregnancy. As it atrophies the cells of the corpus luteum
disappear, and the structure, losing its yellow colour, receives the name of corpus albicans.
After a time the corpus albicans completely disappears. Owing to the periodic rupture
of the folliculi vesiculosi, the surface of the ovary, which is at first smooth and even,
becomes in old age dimpled and puckered.
A section through the ovary, especially in young children, presents in its superficial
part a somewhat granular appearance, which is due to the presence of enormous numbers
of small follicles, or collections of epithelial cells, embedded in the connective tissue
near the surface of the ovary. The larger follicles lie deeper in the stroma, but when
they become fully developed they pass towards the surface, where the ripe follicles are
often seen slightly projecting and ready to burst. In the deepest part of the ovary the
blood-vessels are most numerous, and here also some smooth muscle fibres are found.
The ova and the other cells that compose the folliculi vesiculosi are derived originally
from the germinal epithelium which covers the developing ovary in the embryo. The
epithelium, at first simple, grows down into the underlying tissue in the form of branching
84
1314 THE UEO-GENITAL SYSTEM.
tube-like processes, or " egg tubes." This takes place during foetal development, and the
branching cellular processes so formed become broken up, within the stroma, into little
nests or clumps of cells, each of which becomes a vesicular follicle. From the beginning
some cells of the egg tubes are larger than the others ; these become the future ova,
while the cells round them become the investing cells of the follicle. The investing cells,
at first flattened, form a single layer round each ovum. Later, becoming columnar, as the
follicle increases in size and sinks more deeply in the stroma, these cells divide in such a
manner that the ovum becomes surrounded by a double layer of cells. Fluid liquor
folliculi accumulates between the two cellular layers, except at one place where the
inner cells surrounding the ovum remain attached to the outer layer or stratum granu-
losum. To the inner cellular mass Enclosing the ovulum, or ovum, the term cumulus
oophorus (O.T. discus proligerus) is applied (Fig. 1031). The ripe follicle contains a rela-
tively large amount of fluid, and the surrounding stroma becomes differentiated to form
for it a theca folliculi, or capsule. This capsule is composed of an inner more vascular
layer, the tunica interna, and an outer more fibrous layer, the tunica externa. There is
reason to believe that in the human subject the formation of ova and follicles ceases
before birth, and that the appearances which have led to the belief that they may
originate during the first years of extra-uterine life have been due to pathological con-
ditions. In the young child there are enormous numbers of small follicles in the super-
ficial parts of the ovary, but in old age none are found in this situation.
The appearance and structure of the ripe ova are described on pp. 13-16.
Vessels and Nerves of the Ovary. The ovarian arteries, corresponding to the internal
spermatic arteries of the male, are a pair of long slender vessels which spring from the anterior
aspect of the aorta, below the level of origin of the renal vessels. Each gains the pelvis in the
fold of peritoneum forming the suspensory ligament of the ovary, and enters the ovary at its ;
mesovarian border, or hilum. The ovarian artery anastomoses freely, near the hilum, with
other vessels, derived from the uterine arteries. The blood is returned by a series of communicat- j
ing veins, similar to the plexus pampiniformis in the male.
The nerves of the ovary are derived chiefly from a plexus which accompanies the ovarian
artery, and which is continuous above with the renal plexus. Other fibres are derived from the
inferior part of the aortic plexus, and join the plexus on the ovarian artery (plexus arteriae
ovaricae). The afferent impulses from the ovary reach the central nervous system through the
posterior root fibres of the tenth thoracic nerve.
The lymph-vessels of the ovary join with those from the upper part of the uterus, and end
in the lumbar lymph-glands.
TUB.E UTERINE.
The uterine tubes (O.T. Fallopian tubes) are a pair of ducts or passages which
convey the ova, discharged from the vesicular follicles of the ovaries, to the cavity of
the uterus. Each tube is about four and a quarter inches in length, and opens at one
end into the pelvic cavity near the ovary, and at the other end by a smaller opening
into the lateral part of the uterine cavity. The tube is enclosed in a fold of peri-
toneum called the mesosalpinx, which is a portion of the broad ligament of the uterus.
The opening of the tube into the pelvic cavity or ostium abdominale is of j
small size, being only about 2 mm. in diameter when its walls are relaxed, and
much narrower when the muscular coat of the tube is contracted. This opening is
placed at the bottom of a funnel-like expansion of the tube called the infundibulum
tubae uterinas, the margins of which are produced into a number of irregular processes
or fimbriae tubas. The presence of these fimbrise, many of which are branched or :
fringed, has given the name fimbriated extremity to this end of the uterine tube.
The surface of the fimbrige which looks into the cavity of the infundibulum is
covered by a mucous membrane continuous with that lining the tube, while the
outer surface is clothed by peritoneum. The mucous surfaces of the larger fimbriae
present ridges and grooves which are continued into the folds and furrows of the
mucous coat of the tube. One of the fimbriae, usually much larger than the rest, is j
connected either directly or indirectly with the tubal extremity of the ovary, and
it the name fimbria ovarica, or ovarian fimbria, is applied. The part of the tube
continuous with the infundibulum, and into which the ostium abdominale leads, is
called the ampulla tubas uterinse. This, the widest and longest portion of th(
uterine tube, is usually tortuous and of varying diameter, being in some pi
slightly constricted, and in others distended. The wide, thin -walled arnpi
ends in the narrower, thicker -walled, and much shorter isthmus tubas utei
THE EP-OOPHORON AND PAR-OOPHOROK 1315
which joins the lateral angle of the uterus. The last portion of the canal, or pars
uterina, is embedded in the substance of the uterine wall, which it traverses to
reach the cavity of the titerus (Fig. 1032, B). The opening into the uterus, or
ostium uterinum tubse, is smaller than the ostium abdominale, being about 1 mm. in
diameter. The lumen of the canal gradually increases in width as it is traced out-
wards from the uterus towards the ovary.
Course of the Uterine Tube. Traced from the lateral angle of the uterus the
uterine tube is directed at first horizontally in a lateral direction towards the uterine
extremity of the ovary. It then passes upwards in relation to the medial side of
the mesovarian border of the ovary, until it reaches the tubal extremity, where,
arching backwards, it descends along the posterior or free border, resting against
the medial surface of the ovary (Fig. 1028). As the uterine tube describes this loop
it often covers almost the entire medial surface of the ovary. The fimbriated
end of the tube is applied against the free border and inferior part of the medial
surface of the ovary, and from it the ovarian fimbria pass upwards to gain attach-
ment to the tubal extremity of the gland.
The fimbriated end of the uterine tube lies in the abdominal cavity until the ovary in its
descent has entered the pelvis.
Structure of the Uterine Tubes. The wall of each tube, which is surrounded
by a covering of peritoneum or tunica serosa, is composed of a number of concentric layers
or coats. Immediately beneath the peritoneum is a layer of loose connective tissue,
the tunica adventitia, in which lie many vessels and nerves. Beneath this is the tunica
muscularis, composed of two strata of smooth muscle fibres a more superficial thin
stratum of longitudinally arranged fibres, the stratum longitudinale, and a deeper
thicker layer, the fibres of which are circularly disposed, the stratum circulare. Deeper
is a submucous layer or tela submucosa, and then the lining membrane or tunica mucosa.
In the part of the tube near the uterus the muscular layer is thicker than towards the
other end, and in the isthmus it forms the chief part of the wall. The mucous membrane,
on the contrary, is thickest towards the fimbriated end, and here it forms the chief part
of the tube wall. The stratum of circular muscle fibres is especially well developed near
the uterus. The mucous membrane is thrown into numerous longitudinal folds, the plicae
tubarise, which in the ampulla are exceedingly complex, the larger ones being beset on
the surface by smaller folds. In transverse sections of this part of the tube the folds of
the mucous membrane look like large branching processes projecting into, and almost
completely filling up, the lumen of the tube. The mucous membrane is covered by a
ciliated epithelium, the cilia of which tend to drive the contents of the tube towards the
uterus. The epithelium is continuous with that of the uterus, and at the fimbriated end
joins the peritoneum.
Vessels and Nerves of the Uterine Tube. The uterine tube receives its chief blood-supply
from a ramus tubarius of the uterine artery, but it also receives small branches derived from the
ovarian artery. The veins of the tube pour their blood partly into the uterine and partly into
the ovarian veins. The lymph-vessels join the lumbar group of lymph-glands. The nerves are
derived from the plexus that supplies the ovary, and also from the plexus in connexion with the
uterus. The afferent fibres appear to belong to the eleventh and twelfth thoracic and the first
lumbar nerves.
EP-OOPHORON AND PAR-OOPHORON.
These are two rudimentary structures found between the layers of the broad
ligament.
The ep-obphoron (O.T. parovarium ; often called the organ of Kosenmiiller) lies in
the mesosalpinx between the uterine tube and the ovary. In the adult it consists
of a number of small rudimentary blind tubules lined by an epithelium. One of
these tubules the ductus epoophori longitudinalis (O.T. duct of Gartner) lies
close to, and runs nearly parallel with, the uterine tube. It is joined by a number
of the other tubules, or ductuli transversi, which enter it at right angles, from the
neighbourhood of the ovary. The longitudinal duct is a persistent portion of the
Wolffian duct, and represents the canal of the epididymis in the male, while the
tubules which join it are derived from the mesonephros and represent the efferent
ductules of the testis (and probably also the ductuli aberrantes of the duct of the
epididymis). The ep-oophoron is best seen when the part of the broad ligament
in which it lies is held up to the light.
84 a
1316 THE UKO-GENITAL SYSTEM.
One or more small pedunculated cystic structures, called appendices vesiculosi
(O.T. hydatids of Morgagni), are often seen near the infundibulum of the uterine tube.
These are supposed to represent portions of the upper end of the Wolffian duct.
The par-odphoron is a collection of rudimentary tubules also enclosed by the
layers of the mesosalpinx, but lying nearer the uterus than the ep-oophoron.
These very rudimentary tubules represent the paradidymis in the male, and are
derived from the part of the mesonephros which lies nearer the caudal end of the
body of the embryo. Though sometimes visible in the child at birth, the par-
oophoron in the adult can only be made out with the aid of a lens.
UTERUS.
The uterus, or womb, is a hollow, thick-walled, muscular organ placed within the
pelvis between the bladder in front and the rectum behind. The ova discharged
from the ovary enter the uterus through the uterine tubes, and, if fertilisation has
taken place, undergo their development within it. In form the uterus is somewhat
pear-shaped, the wide upper end of the organ projecting freely upwards and for-
wards into the pelvic cavity, while the lower more constricted part is connected
with the vagina. The usual length of the adult uterus (when non-pregnant) is
three inches, its greatest breadth is nearly two inches, and its maximum thickness
is about one inch. In the description of the uterus we distinguish between an
upper larger portion, somewhat flattened from before backwards, composed of
fundus and body, and a lower more cylindrical part called the cervix (Fig. 1032).
The part of the uterus that lies above the level of a line joining the points of
entrance of the uterine tubes is called the fundus uteri. The fundus is convex
from before backwards and from side to side, its anterior and posterior aspects being
directly continuous with the anterior and posterior surfaces of the body of the organ.
The corpus uteri, when seen from in front or from behind, has a somewhat
triangular outline, and lies below the fundus, with which it is continuous. The
base of the triangle is directed upwards and is formed by a line joining the lateral
angles of the uterus, or points of entrance of the uterine tubes ; and the sides of
the triangle correspond to the lateral borders of the uterus, which extend on
each side from the lateral angle to the cervix. The margo lateralis or lateral
border separates, on each side, the facies vesicalis (or anterior surface) from the
facies intestinalis (or posterior surface) of the body. Both these surfaces are
rounded, but the intestinal is much the more convex. The vesical surface rests
against the upper aspect of the bladder, from which usually it is separated only
by the layers of peritoneum forming the utero- vesical pouch. The intestinal
surface forms the chief part of the anterior wall of the deep recess situated
between the uterus and rectum, and is usually in contact with some part of the
small intestine or the pelvic colon. The broad ligament passes laterally on each
side of the uterus from the lateral border of the organ.
The cervix uteri is cylindrical, and at its commencement it is sometimes
marked off from the body by a slight constriction. Its length is about one inch, and
its inferior end, tapering somewhat, enters the upper part of the vagina. The cervix is
attached to the margin of the opening in the vaginal wall, through which it passes,
and in thrs"way a portio supravaginalis is marked off from a portio vaginalis of the
cervix. In the vaginal portion of the cervix there is an opening the orificium
externum uteri (O.T. external os uteri) through which the cavity of the uterus com-
municates with that of the vagina. In a uterus which has not been pregnant
this opening is nearly circular, but in women who have borne children it is usually
a transverse slit with a somewhat irregular outline. In front of, and behind, this
opening the cervix forms two lips, an anterior and a posterior, the labium anterius
and the labium posterius. The anterior lip is thicker, and slightly more rounded ; it
is placed upon a lower level than the posterior lip, which is slightly longer and
thinner. The cervix enters the vagina through the upper part of its anterior wall
in such a manner that the external orifice of the uterus is directed backwards and
downwards against the upper part of the posterior vaginal wall (Fig. 1033).
THE UTERUS.
1317
Cavum Uteri. In comparison with the size of the organ, the cavity of the
uterus is of small size owing to the great thickness of the uterine wall. In the body,
the cavity is merely a narrow chink between the anterior and posterior walls,
which are almost in contact (Fig. 1033). When, however, the uterus is opened
from above downwards in frontal section of the organ, the cavity of the body
has a triangular outline (Fig. 1 032). The base of the triangle is directed upwards, and
corresponds to a line drawn between the openings of the uterine tubes, while the
apex is directed downwards towards the cervix. The sides of the triangle are
convex inwards towards the cavity. The cavity of the body becomes continuous
with that of the cervix by an opening called the orificium internum uteri (O.T.
internal os uteri), which is a little smaller and more circular than the external
orifice of the uterus. The cavity of the cervix, canalis cervicis uteri, or cervical
canal, extends from the internal orifice of the uterus, where it joins the cavity of
the body, to the external orifice, where it opens into the vagina. It is a somewhat
spindle-shaped passage, which is narrower above and below than in its middle part ;
sections show also that its antero-posterior diameter is shorter than its transverse
one, owing to an approximation of its anterior and posterior walls. In the body of
Ep-oophoron Ligament
Tuba uterina ] Ovary of ovary Uterus a
Fundus uteri
Vesicular
append
age of
Morgagni
Lateral angle
of uterus
Cavity
of body
Cavity
'of cervix
Infundibulum of tube
Round ligament Broad
of uterus ligament
Vaginal cavity
B
FIG. 1032. A. THE POSTERIOR ASPECT OF THE UTERUS AND BROAD LIGAMENT (the broad ligament has
been spread out).
a, b, and c, the isthmus tubae, the ligament of the ovary, and the round ligament of the right side cut short.
B. DIAGRAMMATIC REPRESENTATION OF THE UTERINE CAVITY OPENED UP FROM ITS ANTERIOR ASPECT.
the uterus the walls of the cavity are smooth and even, but in the cervical canal the
mucous membrane forms a remarkable series of folds, called the plicae palmatae (O.T.
arbor vitas uteri). These consist of an anterior and a posterior longitudinally
directed fold or ridge, from which a large number of secondary folds, or rugye,
branch off obliquely upwards and laterally (Fig. 1032, B).
Connexions of the Uterus and its Relations to the Peritoneum. In addition
to the uterine tubes at its upper lateral angles, and the vagina below, the uterus
possesses other important connexions. Some of these are simply peritoneal folds
passing from the uterus to neighbouring structures; others contain fibrous con-
nective tissue, or smooth muscle fibres.
The peritoneum covering the fundus of the uterus is continued down over the
vesical surface as far as the junction of the body and cervix, where it leaves the
uterus to be reflected on to the bladder, forming the utero-vesical fold, or "anterior
ligament of the uterus." The peritoneal recess between the bladder and the uterus
is called the excavatio vesicouterina, or utero-vesical pouch. Below the level of
this pouch the anterior aspect of the cervix is connected by loose tissue with
the posterior, or basal, part of the bladder. Posteriorly the peritoneum covers the
whole of the uterus, except the small portion of the cervix which projects into
the upper part of the vagina. The peritoneum covering the intestinal surface of
the uterus is continued to such a depth that it invests a small portion of the upper
part of the posterior wall of the vagina before it is reflected on to the rectum,
to form the recto-vaginal fold (Fig. 1033). The deep pouch between the uterus and
84 a
1318 THE UKO-GENITAL SYSTEM.
vagina in front and the rectum behind is called the excavatio rectouterina, or recto-
uterine pouch of Douglas, and its entrance is bounded on each side by a crescentic
peritoneal fold, which passes from the posterior surface of the cervix uteri to the
posterior wall of the pelvis, and ends near the side of the rectum. These crescentic
folds are called the plicae rectouterinae, or recto-uterine folds of Douglas, and each
contains between its layers a considerable amount of fibrous and smooth muscular
tissue. A few of these fibres, which are continuous with the uterine wall, pass
backwards to reach the rectum and constitute the musculus rectouterinus ; others
are said to gain an attachment to the front of the sacrum, and form a utero-sacral
ligament. In many cases the recto-uterine folds become continuous with one
another across the median plane behind the cervix uteri, and form, in this position,
a transverse ridge termed the torus uterinus. The recto-uterine pouch of the
female represents the recto- vesical pouch of the male, and the folds which bound
it on each side, namely, the recto-uterine folds, correspond to the sacro-genital
folds (sometimes called posterior false ligaments of the bladder) in the male sex.
The peritoneum of the vesical and intestinal surfaces, leaving the uterus along
each lateral border to reach the side wall of the pelvis, forms the broad ligament
of the uterus.
The ligamentum latum uteri, or broad ligament, is a wide peritoneal fold which
passes from the lateral border of the uterus to the pelvic wall, and contains between
its layers several important structures (Fig. 1032). The plane of the medial part of
the ligament is determined by the position of the uterus. When the uterus is
normally placed, the ligament has an anterior surface which looks downwards as
well as forwards, and a posterior one which looks upwards and backwards. Near
its attachment to the pelvis the ligament is placed more vertically. The free edge
of the ligament contains the uterine tube, and follows the course pursued by
that structure. Thus, in the undisturbed condition of parts, it at first passes
horizontally laterally towards the uterine extremity of the ovary, where it ascends
to arch over the tubal pole of the ovary on its medial side. Owing to the course
pursued by the uterine tube round the ovary, the broad ligament forms a kind
of curtain over the gland, and the ovary lies in a little pocket formed by the broad
ligament, to which the name of bursa ovarica is applied (Figs. 1028 and 1029). This
bursa ovarica is not to be confused with the fossa ovarii, or depression on the side
wall of the pelvis, against which the ovary is usually placed.
The various structures in connexion with the broad ligament are most easily
demonstrated when the ligament is spread out as flat as possible.
The ovary is connected with the posterior layer of the broad ligament by a
very short mesentery, called the mesovarium, which, passing to the hilum, encloses
the ovarian vessels and nerves as they reach the ovary. The part of the broad
ligament which slings the uterine tube is called the mesosalpinx. When the
ligament is spread out, the mesosalpinx has the form of a narrow triangle, the
apex of which is at the lateral angle of the uterus, while the upper side is formed
by the uterine tube, and the inferior one by the ligament of the ovary and the ovary
itself. The narrow base of the triangle is directed laterally. Between the layers
of this part of the broad ligament are situated the ep-oophoron (O.T. parovarium),
and the par-oophoron (Fig. 1032). The part of the broad ligament below the level of
the mesosalpinx is termed the mesometrium, and contains, especially in its lower part,
a considerable amount of fatty connective tissue, the parametrium, and unstriped
muscle fibres. The ureter and the uterine vessels lie in the lowest part of the
broad ligament where it joins the pelvic floor. The fibrous and smooth muscle
tissue which lies in the lower part of the broad ligament, immediately below
the uterine artery, forms what is known as the lateral cervical ligament of the
uterus. It is continuous with the dense tissue surrounding the branches of the
hypogastric artery, and in vertical antero-posterior section has a triangular outline
near its attachment to the cervix uteri.
The highest part of the attached lateral portion of the broad ligament forms the
ligamentum suspensorium ovarii or suspensory ligament of the ovary, and contains
between its layers the ovarian vessels and nerves as they enter or leave the pelvis.
The ligamentum ovarii proprium, or ligament of the ovary, is a rounded fibrous
THE UTEKUS. 1319
cord, of about one inch in length, which is attached by its lateral end to the
uterine pole of the ovary, and by its medial end to the lateral angle of the uterus
immediately below and behind the entrance of the uterine tube. This liga-
ment, which is largely composed of unstriped muscle fibres continuous with those
of the uterus, is enclosed in a slight fold derived from the posterior layer of the
broad ligament.
The ligament of the ovary represents the upper portion of the gubernaculum which appears
in the embryo.
The ligamentum teres uteri, or round ligament of the uterus, is a narrow flat
band attached to the uterus just in front of, and a little below, the opening of the
uterine tube. Near the uterus it contains numerous smooth muscle fibres, which
are continuous with those of the uterus ; more laterally it is composed chiefly of
fibrous connective tissue. Lying in the anterior part of the broad ligament, it
reaches the wall of the pelvis minor, and is then directed forwards and slightly
upwards to cross the obliterated umbilical artery and the pelvic brim. After it has
reached the pelvic wall its course is comparable to that of the ductus deferens in the
male, and, like the latter, it leaves the abdomen to traverse the inguinal canal (Figs.
1028 and 1029). It finally ends in the subcutaneous tissue and skin of the labium
majus. Its terminal part is composed of connective tissue only.
In some cases a small diverticulum of the peritoneal cavity can be traced accompanying the
round ligament through the abdominal wall. This is called the processus vaginalis peritonei
(O.T. canal of Nuck), and corresponds to the processus vaginalis of the male (p. 1294).
The round ligament of the uterus represents the lower portion of the gubernaculum testis
which appears in the male embryo (see pp. 1294 and 1313).
Position and Relations of the Uterus. The position occupied by the
uterus in the pelvis is not always the same, but varies with the conditions of the
neighbouring organs. The lower cervical part is, however, much more firmly fixed
in place than the body and fundus, which possess a considerable amount of mobility.
Usually the level of the external orifice of the uterus will be found to correspond
to that of a horizontal plane passing through the upper margin of the symphysis
pubis. The uterus rarely lies exactly in the median plane of the body, but usually
bends to one or other side, most frequently towards the right. The vesical surface
of the uterus rests against the bladder, and follows the rising or falling of its superior
wall as that organ becomes filled or emptied. When the bladder is ^mpty the long
axis of the uterus points forwards and upwards, and the organ is said to be in an
anteverted position. Also, the long axis of the uterus is bent on itself where the body
joins the cervix, and so the organ is said to be anteflexed. The anteflexion is due
to the fact that the more rigid cervix is fixed, while the movable upper part of the
uterus sinks forwards, following the bladder wall. With the empty condition of
the bladder the angle formed between the long axis of the uterus and that of the
vagina is about a right angle. When the bladder becomes filled, the anteversion
and anteflexion of the uterus become less marked, owing to the body and fundus
being pushed backwards. Finally, if the, rectum is empty and the bladder very
much distended, the uterus is pushed so much backwards that the long axis of the
organ may nearly correspond to that of the vagina. The uterus is then said to be
retroverted. Superiorly a part of the peritoneal cavity intervenes between the
vesical surface of the uterus and the bladder, but lower down the two organs are
separated merely by a small quantity of connective tissue. The intestinal surface
of the uterus looks into the pouch of Douglas, and is usually, like the fundus, in
relation to some loops of the small intestine or pelvic colon. Laterally the uterus
is related to the broad ligaments. The terminal parts of the ureters pass downwards,
medially, and a little forwards on the lateral aspects of the cervix, but are separated
from it by an interval of about three-quarters of an inch. The lowest part of the
cervix is, as we have seen, enclosed within the cavity of the vagina.
On each side of the cervix uteri and upper part of the vagina there is an
interval in which lie numerous large vessels. These are surrounded by loose fatty
tissue, which is continued upwards for a considerable distance between the layers
of the broad ligament. This loose tissue, which is of surgical importance, has
received the name parametrium.
84 c
1320 THE UKO-GENITAL SYSTEM.
Structure of the Uterus. The thick uterine wall is composed of three chief layers,
which are termed respectively the serous, the muscular, and the mucous coats.
Tunica Serosa. The serous coat, or perimetrium, is derived from the peritoneum, and
covers the whole organ except the part of the cervix which projects into the vagina
and the anterior surface of its supra-vaginal portion. At the borders it is continued
into the broad ligaments. Over the fundus and body of the uterus the serous coat
is very firmly adherent to the deeper layers, and cannot be easily peeled off without
tearing either it or the underlying muscular tissue. Near the borders the peritoneum
is less firmly attached, and over the posterior aspect of the cervix it may readily be
stripped off without injury to the underlying structures.
Tunica Muscularis. The muscular coat is composed of unstriped fibres, and forms the
chief part of the uterine wall. Inferiorly the muscular coat of the uterus becomes
continuous with that of the vagina. The more superficial layer of the muscular coat sends
prolongations into the recto-uterine folds, into the round and broad ligaments of the
uterus, and into the ovarian ligaments. Other fibres join the walls of the uterine tubes.
The main branches of the blood-vessels and nerves of the uterus lie among the muscle
fibres. In the deeper layers of the muscular coat a considerable amount of connective
tissue and some elastic fibres are to be found. The muscular coat of the cervix, or
tunica muscularis cervicis, contains more connective and elastic tissue than that of the
body, and hence the greater firmness and rigidity of the cervical part of the uterus.
The deeper and thicker part of the muscular tissue of the uterus is considered by some
anatomists to represent a muscularis mucosee, and is therefore described as part of the
mucous coat. The deep and superficial portions of the muscular coat are, however, quite
continuous, and there is no representative of a submucous vascular layer of tissue such
as in the alimentary canal separates the muscular coat from the muscularis mucosse. In
the uterus the blood-vessels lie in the muscular coat.
Tunica Mucosa. The mucous coat in the body of the uterus is smooth and soft, and
covered with columnar ciliated epithelium. Simple tubular glands, glandulse uterinse, also
lined with a ciliated epithelium, are present in the mucous membrane, and penetrate in their
deeper parts into the muscular coat. In the cervix of the uterus the mucous coat is
firmer and more fibrous than in the body, and its surface is not smooth, but presents
a number of peculiarly disposed ridges which have been already described. Like
the mucous membrane of the body of the uterus, that of the cervix is covered with a
ciliated epithelium which passes into squamous epithelium just inside the external orifice of
the uterus. The cervix uteri possesses, in addition to unbranched tubular glands, re-
sembling those present in the body, numerous somewhat branched glands, the glandulae
cervicales uteri. Both kinds of glands are lined by ciliated epithelium. In many
cases little clear retention cysts, "ovules of Naboth," are to be seen in the cervical
mucous membrane. These arise as a result of obstruction at the mouths of the glands.
Differences in the Uterus at Different Ages. At birth the cervix uteri is
relatively larger than in the adult organ, and its cavity is not distinctly marked
off from the interior of the body by an internal orifice. At this time also the
plicae palmatse extend throughout the whole length of the uterus. The organ grows
slowly until just before puberty, when its growth is rapid for a time. As the
body of the uterus increases in size the mucous membrane becomes smooth and the
plicae palmatae become restricted to the cervix. In women who have borne
children the cavity remains permanently somewhat wider and larger than in cases
where the uterus has never been pregnant.
In old age the uterine wall becomes harder and has a paler colour than it
possesses in the young subject.
Variations. In rare cases the uterus may be divided by a septum into two distinct cavities,
or its lateral angles may be produced into straight or curved processes, called " horns " or cornua.
The latter abnormality recalls the appearance of the bicornuate uteri of some animals. Both the
above conditions arise from an arrest in the fusion of the two separate tubes the Miillerian
ducts which normally unite in the embryo to form the uterus.
Periodic Changes in the Uterine Wall. At each menstrual period a remark-
able series of changes occurs which results in a periodic shedding of the super-
ficial parts of the uterine mucous membrane. For a few days before menstruation
begins, the mucous membrane gradually thickens and becomes more vascular, while
at the same time its surface becomes uneven. Soon the superficial parts of the
THE VAGINA. 1321
mucous membrane disintegrate and haemorrhage takes place from the small super-
ficial blood-vessels. In this way a hsemorrhagic discharge is caused, and the
superficial parts of the uterine mucous membrane are shed at each period. When
menstruation is over the mucous membrane is rapidly regenerated.
Pregnant Uterus. The pregnant uterus increases rapidly in size and weight,
so that from being three inches in length and one ounce in weight, it becomes by
the eighth month about seven or eight inches in length and sometimes as much
as two pounds in weight. In shape the uterus is now oval or rounded, with a thick
wall composed chiefly of muscle fibres arranged in distinct layers. The rounded
fundus is very prominent. The round ligaments are stronger and better marked,
and the layers of the broad ligament become separated in their medial parts by the
growth of the uterus between them. The blood-vessels, especially the arteries, are
very large and tortuous. The changes which occur in the mucous membrane of
the pregnant uterus are intimately connected with the manner in which the
developing foetus receives its nutrition, and have been noticed on pp. 56 et seq.
Vessels and Nerves of the Uterus. The uterus receives its arterial supply mainly from
the uterine arteries, which are branches of the hypogastric arteries, and also from the ovarian
arteries, branches of the aorta. The vessels derived from these two sources communicate freely
with one another. Each uterine artery, reaching the side of the lower part of the uterus, divides
into a large branch which passes upwards to supply the body and fundus, and a much smaller
branch which passes downwards to supply the cervix. The vessels distributed to the body and
fundus have an exceedingly tortuous course. The branches of the uterine artery, having entered
the muscular coat, break up within its deeper layers into smaller twigs which supply the muscular
tissue and the mucous coat. The small uterine branch from the ovarian artery reaches the
uterus in the region of the lateral angle. During pregnancy the arteries become enormously
enlarged.
The thin-walled veins form a plexus which pours its blood into the tributaries of the hypo-
gastric vein.
The nerves of the uterus are derived chiefly from a plexus placed in the neighbourhood of
the cervix uteri, to which the term plexus uterovaginalis or " cervical ganglion " is applied.
Superiorly this plexus is continuous with the hypogastric plexus, but it also receives fibres from
the third and fourth sacral nerves. In addition to fibres from the plexus uterovaginalis, the
uterus receives fibres directly from the hypogastric plexus, and also from the plexus vesicalis.
Clinical observations indicate that afferent impulses reach the central nervous system from the
uterus through the posterior roots of the tenth, eleventh, and twelfth thoracic nerves, the first
lumbar, and the second, third, and fourth sacral nerves.
The numerous lymph-vessels coming from the body of the uterus join those from the ovary,
and end for the most part in the lumbar lymph -glands. Along the course of the round
ligament of the uterus there are a few lymph-vessels which establish a connexion between
the lymph -network surrounding the uterus and the inguinal lymph - glands. The lymph -
vessels from the cervix uteri end in the gland placed near the bifurcation of the common
iliac artery.
VAGINA.
The vagina is a passage about three inches in length, open at its lower
end, and communicating above with the cavity of the uterus. The passage is
directed downwards and forwards, describing a slight curve which is convex back-
wards. The axis of the vagina forms with that of the uterus an angle which is open
forwards. This angle is usually somewhat greater than a right angle, but varies
with the condition of the neighbouring viscera (p. 1319). The vagina is widest at
its upper end (Fig. 1034), and normally its anterior wall and its posterior wall
are in contact. In transverse section the lower part is usually an H -shaped cleft,
the middle part a simple transverse slit, while the lumen of the upper portion, into
which the cervix uteri projects, is more open. The lower part of the cervix uteri has
the appearance of entering the vagina through the upper portion of its anterior
wall (Fig. 1033). As more of the posterior than of the anterior part of the cervix
projects into the vagina, a deeper recess is formed between the vaginal wall and
the cervix behind than in front or laterally. The term anterior fornix is often
applied to the angle, or recess, in front ; posterior fornix to the deeper angle behind,
and lateral fornix to the recess on each side of the cervix uteri, between it and the
wall of the vagina. The anterior wall of the vagina (paries anterior) is shorter
than the posterior (paries posterior), the former being about three inches in length,
1322
THE UKO-G-ENITAL SYSTEM.
the latter about three and a half inches. At its lower end the vagina opens into
the rima pudendi, the opening being situated behind the orifice of the urethra
and the clitoris, and between the labia niinora. The opening is partly closed in
the virgin by a thin crescentic or annular fold, called the hymen, torn fragments
of which persist round the opening, as the carunculse hymenales, after the fold
itself has been ruptured.
Relations of the Vagina. The anterior wall of the vagina in its upper part
lies against the base of the bladder, but is separated from it by loose connective
Cavity of uterus
Cavity of urinary
bladder
Labium anterius
(cervicis uteri)
Hymphysis pubis
Urethra
Labium minus,
(pudendi)'
Labium posterius
(cervicis uteri)
Rpcto-vaginal
reflexion of
peritoneum
Vaginal canal
Anal canal
j- Sphincter ani
FIG. 1033. MEDIAN SECTION OF THE PELVIS IN AN ADULT FEMALE.
The cavity of the uterus is indicated diagrammatically.
tissue. Lower down, the anterior wall in the median plane is intimately connected
with the urethra (Fig. 1033). Near the median plane, the posterior wall in its upper
portion is covered for a distance of about a quarter of an inch by the peritoneum,
which here forms the anterior boundary of the deepest part of the recto-uterine
pouch. The depth to which the peritoneum; of this pouch descends practically
corresponds to the level of the spina ischiadica. Lower down, the posterior
wall lies close against the rectum, from which it is separated by a layer of the
pelvic fascia. As, however, the orifice of the vagina is approached, the rectum and
vagina become separated by a considerable interval, which is occupied by a mass of
fibrous and fatty tissue, often called the " perineum " or " perineal body." At the
sides the vagina is supported by the levatores ani muscles. The terminal part of
the ureter lies not far from the side wall of the upper part of the vagina, as il
passes from above and behind downwards, medially and a little forwards to reach
THE VAGINA.
1323
the bladder. Near its termination the vagina pierces the fascia inferior of the uro-
genital diaphragm, and is related on each side to the bulbus vestibuli, the larger
vestibular glands, and the r/ulbo-cavernosus (sphincter vaginae) muscle.
Structure of the Vagina. The vaginal wall has a distinct tunica muscularis,
composed of unstriped muscle fibres, most of which are longitudinally disposed. Towards
Spina iliaea
superior posterior
Apex of os sacrum
Incisura ischiadica
major
Rectum
Peritoneum
Ureter
Spina ischiadica
Uterine artery
Bladder wall
Ureter
Levator ani
Ligamentum sacro-
tuberosum
Ischio-rectal fossa
Tuber ischiadicum
Glutseus maximus
/ External sphincter ani
Recto-vaginal pouch / Rectum
Vaginal wall
1034. POSTERIOK ASPECT OP THE VAGINA, THE BASE OF BLADDER, AND THE RECTO-VAGINAL POUCH
OP PERITONEUM.
coccyx and the ligamentum sacrotuberosum and ligamentum sacrospinosum, together with the muscles
attached to them, have been removed. The levatores ani have been separated along the median raphe,
and drawn laterally. A considerable portion of the rectum has been removed, but the position which it
occupied is indicated by the dotted lines. The peritoneum is indicated by a blue colour. The recto-
vaginal pouch is probably not quite so deep as usual. The triangular, interval between the ureter and
uterine artery was filled by a mass of fibre-muscular tissue, forming the lateral cervical ligament of
the uterus.
jthe lower end of the passage circularly disposed bundles of striped muscle fibres, some of
which are continuous with those forming a part of the urethral wall, are found in the
'muscular coat. The thick tunica mucosa, which has a stratified scaly epithelium, is
corrugated, and presents a number of transverse ridges or elevations called rugae vaginales.
In addition to these transverse rugse, a slightly marked longitudinal ridge, or column, is
to be seen on the anterior and on the posterior wall of the vagina. These receive the
name columnae rugarum, and, like the transverse rugse, are best seen in young subjects
and in the lower part of the vagina. The urethral canal lies in close relationship to the
anterior column of the vagina in its lower part, and hence this portion of the anterior
column is sometimes called the carina urethralis.
1324 THE URO-GENITAL SYSTEM.
Within the tunica mucosa are to be found small collections, or nodules, of lymph-
tissue.
The vaginal wall is surrounded by a layer of loose vascular connective tissue containing
numerous large communicating veins.
Vessels and Nerves of the Vagina. The blood -supply of the vagina is for the most part
derived from the vaginal artery, the vaginal branch of the uterine artery, the vaginal branches
of the middle haemorrhoidal artery, and from the branches of the internal pudendal. The veins
form a plexus surrounding the vaginal wall, and drain their blood into the tributaries of the
hypogastric.
The lymph- vessels from the upper part of the vagina join the hypogastric group of glands,
while those from the lower part end in the superficial inguinal glands.
The nerves of the vagina are derived from the plexus uterovaginalis and from the plexus
vesicalis. Other fibres are derived directly from the third and fourth sacral nerves.
THE FEMALE EXTERNAL GENITAL ORGANS.
(PUDENDUM MULIEBRE.)
The term pudendum muliebre, or vulva, is applied collectively to the female
external genital organs, i.e. to the labia majora and the structures which lie
between them.
Labia Majora. The labia majora represent the scrotum in the male, and form
the largest part of the female external genital organs. They form the boundaries,
on each side, of the rima pudendi or uro-genital cleft, into which the urethra and
vagina open. Each labium is a prominent rounded fold of skin, narrow behind
where it approaches the anus, but increasing in size as it passes forwards and
upwards to end in a median elevation, the commissura labiorum anterior, or the mons
pubis or Veneris. The mons Veneris lies over the symphysis pubis, and, like the
labia majora, it is composed chiefly of fatty and areolar tissue, and is covered with
hair. The lateral convex surface of each labium majus is covered by skin con-
taining numerous sebaceous glands and resembling that of the scrotum in the male,
but the medial, flatter surface is smooth, and presents a more delicate integumentary
covering. In some cases the posterior narrow ends of the labia majora are
connected across the middle line, in front of the anus, by a slight transverse fold
the commissura labiorum posterior or posterior commissure.
Usually, especially in young adult subjects, the labia majora are the only visible
parts of the external genital organs, since they are in contact with one another,
and completely enclose the structures within the rima -pudendi.
The round ligament of the uterus ends in the fatty tissue of the labium majus.
The superficial subcutaneous tissue resembles that of the scrotum, but contains no
muscular fibres.
The nerve-supply corresponds with that of the scrotum, the anterior part of each labium being
supplied by the branches of the ilio-inguinal nerve, and the posterior part by branches from the
internal pudendal and by the perineal branch from the posterior cutaneous nerve of the thigh.
The blood-vessels of the labia majora are derived from the external pudendal arteries and from
the perineal branches of the internal pudendal vessels.
Labia Minora. The labia minora pudendi (O.T. nymph) are a pair of much
smaller and narrower longitudinal folds, usually completely enclosed within the
cleft between the labia majora. Diminishing in size, and becoming less marked
in their posterior parts, the labia minora end by gradually joining the medial
surfaces of the labia majora. In the young subject, a slightly raised transverse
fold is usually seen connecting the posterior ends of the labia minora ; to this
fold the term frenulum labiorum pudendi (O.T. fourchette) is applied. Traced
forwards, each labium minus divides into two portions, a lateral and a medial.
The lateral portions of the two labia unite over the glans clitoridis, and
form for it a fold or covering called the praeputium clitoridis. The medial
portions, uniting at an acute angle, join the glans and form the frenulum clitoridis.
The skin of the labia minora resembles the integument on the medial or deep
surface of the labia majora, being smooth, moist, and pink in colour. The medial
surfaces of the labia minora are in contact with one another ; their lateral surfaces
are applied against the medial aspects of the labia majora.
THE FEMALE EXTEKNAL GENITAL OKGANS.
1325
Glaus clitoridis
Frenulum clitoridis
Labium majus
Labium minus
Orificium uretlirse
externum
Commissura
posterior
The openings of the urethra and vagina are placed in the median plane, in the
interval between the labia minora, which must be separated to bring them into
view.
Vestibulum vaginae. The vestibule is the name applied to the cleft that lies
between the labia minora and behind the glans clitoridis. In its floor are the
openings of the urethra, the vagina, and the minute ducts of the larger vestibular
glands.
The fossa navi-
cularis is the part
of the vestibule
placed behind the
vaginal opening
and in front of
the frenulum
labiorum pudendi.
The orificium
urethrse externum,
or external ure-
thral orifice, lies
immediately in
front of that of
the vagina, and
is about one inch
behind the glans
clitoridis. The
opening has the
appearance of a
vertical slit, or of
an inverted V-
shaped cleft, the
slightly promi-
nent margins of
which are in con-
tact. On each side
of the urethral
orifice there may
sometimes be seen
the minute open-
ing of the ductus
paraurethr a lis FIG. 1035. FEMALE EXTERNAL GENITAL ORGANS.
(see p. 1285). The frenulum labiorum is seen stretching across behind the fossa navicularis and in
The orificium front of the posterior commissure.
136, o. vaginal,
opening, lies be-
hind and below the orifice of the urethra. The appearance of the opening
varies with the condition of the hymen a membrane which in the young subject
partly closes the aperture. When the hymen is intact the opening is small, and
is seen only when the membrane is put on the stretch. When the hymen has
been ruptured the opening is much larger, and round its margins are often seen
small projections carunculse hymenales which are to be looked upon as persistent
fragments of the hymen.
The hymen is a thin membranous fold, partially closing the lower end of the
vagina, and usually perforated somewhat in front of its middle point. The posi-
tion of the opening gives the fold, when stretched, a crescentic appearance. The
opening in the hymen is sometimes cleanly cut, sometimes fringed. The membrane
is not stretched tightly across the lower end of the vagina, but is so ample
that it projects downwards into the rima pudendi, and the parts of its upper
surface are in contact with one another on each side of the opening. The
opening is thus a median slit whose margins are normally in contact. The upper
The ducts of the larger vestibular glands open
in the intervals between the vaginal orifice and the medial edges of the labia
minora.
1326 THE UKO-GENITAL SYSTEM.
surface of the hymen is directly continuous with the vaginal wall, and on it are
to be seen slight ridges continuous with the vaginal rugae.
Development ally the hymen appears to be a portion of the vagina.
On each side of the vaginal opening, and close against the medial side of the
attached margin of the labium minus, is the minute opening of the duct of
the glandula vestibularis major (O.T. Bartholin's gland). This is usually just large
enough to be visible to the unaided eye.
Numerous minute mucous glands, the glandulse vestibulares minores, open on the surface
of the mucous membrane of the vestibule, between the urethral and vaginal orifices. The
opening of the ductus para-urethralis at the side of the urethral orifice has been already noted,
p. 1285.
Clitoris. The clitoris is the morphological equivalent of the penis, and is
composed of a body and two crura. Upon the summit of the body is a minute
glans. Unlike the penis, the clitoris is not traversed by the urethra.
The corpus clitoridis is composed for the most part of erectile tissue resembling
that of the penis in the male. It is about an inch or an inch and a half in length,
and is bent upon itself, forming an angle open downwards. The body of the
clitoris tapers towards its distal end, which is covered by the glans clitoridis.
The organ is enclosed in a dense fibrous coat, and is divided by an incomplete
septum, the septum corporum cavernosomm, into two symmetrical and somewhat
cylindrical portions, the corpora cavernosa clitoridis. These represent the corpora
cavernosa penis of the male, and diverge from one another at the root of the
clitoris to form the crura clitoridis. A ligamentum suspensorium clitoridis passes
from the fibrous coat of the body of the clitoris to the symphysis pubis (Fig. 1036).
The glans clitoridis is a small mass of erectile tissue which is fitted over the
pointed end of the body. It possesses, like the glans penis, which it represents, a
very sensitive epithelium. The prseputium, or fold of skin which covers it, and the
frenulum clitoridis, which is attached to it inferiorly, are continuous with the labia
minora (Fig. 1036).
The crura clitoridis diverge from the body posteriorly, and are attached to the
sides of the pubic arch. Each is continuous with one of the corpora cavernosa, and
has a firm fibrous sheath, which is covered by the corresponding ischio-cavernosus
or erector clitoridis muscle. In structure the crura and body of the clitoris
resemble the corpora cavernosa penis, while the glans more closely resembles the
bulbus vestibuli, with which it is continuous through a structure known as the
pars intermedia.
In the seal and some other animals, a bone, which represents the os" penis of the male, is
developed in the septum of the clitoris. This bone receives the name os clitoridis.
Arteries and Nerves of the Clitoris. Each cms receives a branch, the arteria profunda
clitoridis, from the internal pudendal, while the glans is supplied by branches of the arteria
dorsalis clitoridis.
The nerve-supply of the clitoris is derived partly from the hypogastric sympathetic plexus
and partly from the dorsal nerves of the clitoris, which are branches of the pudendal nerves.
Bulbus Vestibuli. The bulbus vestibuli is a mass of erectile tissue, in the
female, which corresponds developmentally to the corpus cavernosum urethrse of
the male. In the female the fusion of the two halves of this structure is not
nearly so complete as in the male, for the vagina and urethra separate the bulbus
vestibuli into a right and a left portion which are only slightly connected in front
by a narrow median part called the pars intermedia. Each half of the bulb is
thick and massive posteriorly, and more pointed in front, where it joins the pars
intermedia. It rests against the lateral wall of the vagina, and upon the -superficial
aspect of the fascia inferior of the urogenital diaphragm. It represents one-
half of the corpus cavernosum urethrse of the male. Superficially it is covered by
the bulbo-cavernosus muscle. The pars intermedia lies above the opening of the
urethra, and becomes continuous with the tissue of the glans clitoridis.
The bulbus vestibuli is for the most part composed of minute convoluted blood-
vessels, held together by a very small amount of connective tissue. These vessels
frequently anastomose with one another, and those of each half communicate
with the vessels of the pars intermedia and the glans clitoridis.
DEVELOPMENT OF THE UKO-GENITAL OBGANS
1327
The blood-supply of the bulb is derived, on each side, from the arteria bulbi vestibuli,
a branch of the internal pudendal.
GLANDULE VESTIBULARES MAJORES.
The greater vestibular glands (O.T. glands of Bartholin) are placed one on
each side of the lower part of the vagina, and represent the bulbo-urethral glands in
US URINARIUS.
UB.
^-TR I ANGULAR [FASCIA INFERIOR OF
LIQT UROGENITAL DIAPHRAGM]
Larger vestibular glands V
, Vagina
Central point of perineum
FIG. 1036. DISSECTION OP FEMALE PERINEUM TO SHOW THE CLITORIS, THE BULB OF THE VESTIBULE,
AND THE LARGER VESTIBULAR GLANDS (D. J. Cunningham).
the male. They are often overlapped by the posterior ends of the bulbus vestibuli,
and are covered by the bulbo-cavernosus muscle. Each is about the size and
shape of a small bean, and possesses a long slender duct which opens into the
rima pudendi in the angle between the attached border of the labium minus and the
vaginal opening.
DEVELOPMENT OF THE URO-GENITAL ORGANS.
THE URO-GENITAL PASSAGES.
General Account. In tracing the developmental history of the uro -genital
passages we may for convenience begin with an embryo of fifteen days old. About this
1 time a duct, which runs in a longitudinal direction, and occupies a position on the lateral
side of the proto vertebral somites, begins to develop on each side of the body. With the
exception of the anterior portion of the cloaca and the proximal part of the allantois, this
duct, which has received the name of primary excretory or Wolffian duct, is the earliest
formed structure from which, or in connexion with which, the parts of the adult
urine-genital system arise.
The Wolffian duct serves as the canal, or duct, for the primitive secretory organs
the pronephros and the mesonephros of the embryo. With the atrophy of these the
! duct suffers modification, yet both sexes in the adult possess structures which have
their embryonic origin from the Wolffian duct. In the male the duct of the epididymis,
the ductus deferens, and the ejaculatory duct, are to be looked upon as directly developed
from the Wolffian duct of the embryo ; while in the female the longitudinal duct of
the ep-oophoron and the appendices vesiculosi are rudimentary structures having a like
origin. Further, the ureter and its pelvis arise in both sexes as an outgrowth from the
Wolffian duct (Fig. 1037). In the male the vesicula seminalis is developed as a diverti-
culum of the Wolffian duct.
The primitive secretory organs, the pronephros and the mesonephros, develop in
lexion with the anterior part of the Wolffian duct (p. 48), and, during the early life
the embryo, the latter of these is a most important structure. Even in the embryo
1328
THE UKO-GENITAL SYSTEM.
WD
the pronephros is a vestigial organ, and its development in all higher vertebrates is
very incomplete. It disappears almost as soon as it is formed, and it is replaced by the
far more important mesonephros. With the development of the permanent kidney the
mesonephros atrophies, yet some of its tubules persist in the adult. The ductuli
efferentes, the ductuli aberrantes, and the rudimentary
paradidymis (organ of Giraldes) in the male, and the
rudimentary tubules of the ep-oophoron and of the
par-ob'phoron in the female, are structures which owe
their origin to the tubules of the mesonephros.
Soon after the formation of the Wolffian ducts two
other longitudinally disposed canals, called the
Mullerian ducts, are developed. These open at their
cephalic ends into the body cavity, and at their caudal
ends, unlike the Wolffian ducts, they unite with one
another in the median plane. From them are formed,
in the female the uterine tubes, the uterus, and the
vagina ; and in the male the appendices of the testis
and the utriculus prostaticus.
The Wolffian and Mullerian ducts open at their
caudal ends into the ventral or urogenital part of
the cloaca, which in the course of development becomes
transformed into the bladder and the uro-genital
canal of the embryo. The developing ureter at first
arises as a diverticulum from the Wolffian duct, at a
short distance from the point where the latter joins
the cloaca. Soon, however, the ureters acquire inde-
pendent openings into the cloaca, which become gradu-
ally shifted further from one another and from those
of the Wolffian ducts. The ureters are now found to
open into the anterior portion of the cloaca which lies
nearer to the head of the embryo than the part with
which the Wolffian ducts are connected. This cephalic
portion of the anterior subdivision of the cloaca which
receives the ureters becomes the bladder and the
upper part of the urethra. The caudal part, lying
below the level of the entrance of the Wolffian ducts,
is called the uro-genital canal, and is represented in
the adult male by the lower part of the prostatic and
by the membranous portions of the urethra ; in the
female by the lower part of the urethra and the part of
FIG. 1037,-DiAGRAM TO ILLUSTRATE THE the uro-genital fissure which immediately surrounds
MANNER IN WHICH THE URETER, THE the openings of the urethra and vagina (Figs. 1
DUCTUS DEPERENS, AND THE URINARY 1045). The united Mullerian ducts open into the lower
BLADDER ARISE IN THE EMBRYO. part of the cloaca or ur0 -genital canal between the
The structures developed from the cloaca Wolffian ducts of opposite sides. In the male the
are indicated in blue, those from the position of this opening, which is represented in the
Wolffian duct in red, and the ectoderm ^^ , the Qrifice Qf the utriculug prostaticuS| rem ains
111 DlctCK. *' . i i i i J
, almost unchanged ; in the female, on the other hand,
^adTTecle^ird rlTcqute a downgrowthVm the fused Mullerian ducts giv-
openings into the ectodermal cloacal origin to a new passage, the vagina, which establis
fossa is shown in II. and III. (A. H. an opening behind that of the urethra in the uro-
genital fissure of the adult.
After the complete separation of the cloaca into
anterior or uro-genital and posterior or rectal sub-
divisions, the rectum establishes a communication with
the exterior in the floor of the shallow depression
known as the ectodermal cloacal fossa. At a little later
time the uro-genital canal also joins this fossa at a point in front of the opening of the
rectum. The ectodermal cloacal fossa lies in front of the vestigial tail, and extends
forwards as far as a tubercle known as the cloacal tubercle, which later gives rise to the
genital eminence and a pair of elevations called the labio-scrotal folds. The genital
eminence becomes converted into the clitoris or penis according to the sex. The labio-
scrotal folds extending backwards on each side form the labia majora of the female, and,
III
CM
Young and A. Kobinson).
A. Allantois. R. Rectum.
B. Bladder. Ur. Uro-genital canal.
C. Cloaca. U. Ureter.
CM. Ectoderm of VD. Ductus deferens.
cloacal fossa. VS. Seminal vesicle.
K. Pelvis of kidney. WD. Wolffian duct.
DEVELOPMENT OF THE UKO-GEN1TAL OEGANS.
1329
fusing posteriorly, give rise to the scrotum in the male. In the female the slit-like
opening of the uro-genital canal retains its position, and its margins becoming elongated,
form the labia minora. The vaginal opening arises, as we have seen, by a downgrowth
of the fused Miillerian ducts which lies in front of the rectum and behind the primitive
uro-genital canal. The latter becomes the urethra in the female. In the male the slit-
like opening of the uro-genital canal is prolonged anteriorly by an active growth at the
base of the genital eminence, and its margins uniting, give rise to the penile portion of
the urethra.
Notochord
^Muscle plate
Mesentery
Wolffian duct
Mesonephric
'tubule
Umbilical vein
Alimentary canal
Body cavity
THE WOLFFIAN DUCT AND EMBRYONIC SECRETORY ORGAN.
The Wblffian Duct. The Wolffian duct arises in the mesoderm, about the
fifteenth day, as a solid cord of cells occupying a position immediately to the lateral side
of the protovertebral somites and to the medial side of the body cavity (Fig. 1038). When
first recognised the duct lies immediately beneath the ectoderm, and as it grows backwards
to reach the cloaca it is often
; found to be intimately con- v^S^v Neural tube
nected with the ectoderm.
This close connexion of the
duct with the ectoderm, in
the early stages, is by some
authorities supposed to in-
dicate a primitive ectodermal
origin of the canal, but by
others, and apparently with
more reason, to be a trace
I of the opening of ducts on
the surface of the body, such
as exists in connexion with
the excretory organs of
lower animals. During
the third week the cellular
cord which represents the
Wolffian duct acquires a
lumen, and about the end
of the same week the duct FlG - 1038. TRANSVERSE SECTION THROUGH THE TRUNK OF A HUMAN
in its growth reaches the EMBRYO OF ABOUT 5 MM ' LENGTH '
cloaca. As soon as the
cloaca has become divided into dorsal and ventral subdivisions, the Wolffian duct is
seen to end in the caudal part of the ventral subdivision, which becomes the bladder
and uro-genital canal (Fig. 1040).
The mesonephros or Wolffian body is developed in the mesoderm of the " intermediate
cell mass," immediately adjoining the Wolffian duct, and consists of a number of trans-
versely arranged canals or tubules, each of which opens by one end into the Wolffian
duct, while its other extremity ends blindly. These transverse tubules, like the canal
into which they open, are at first solid cellular structures, and only later acquire a distinct
lumen. Increasing rapidly in size and number, the tubules become twisted and tortuous,
and the blind end of each dilates to form a capsule invaginated upon itself and containing
a bunch of capillary blood-vessels similar to the glomeruli of the adult kidney. It would
appear that primitively one tubule is developed in the portion of the intermediate cell
mass (nephrotome) corresponding to each mesodermic somite, but, in higher vertebrates
.at all events, such a correspondence between the number of somites and the number
<>f tubules cannot be demonstrated. In the posterior part of the mesonephros the
number of tubules is very numerous, and greater than the number of segments in
this region. The tubules of the mesonephros arise in all segments from the sixth cervical
to the third lumbar. The tubules in the anterior part atrophy and disappear at a very
early time, even while others are being formed towards the caudal end of the embryo.
When at its greatest development (fifth to eighth week) the mesonephros forms a
relatively large glandular mass, composed of tubules resembling in a general way
those of the adult kidney, which projects into the dorsal part of the body cavity, and
extends from the region of the liver to the caudal end of the body cavity. Along its
lateral aspect lies the Wolffian duct.
85
1330
THE UKO-GENITAL SYSTEM.
In anamniate vertebrates, fishes, and amphibia, the mesonephros persists as the
secretory organ of the adult.
Allantois
Uro-genital^
part of cloaca*""-..^
Rectum
Wolffian duct
Bladder
-Rectal part
of cloaca t.
Neural tube
Notochord
FIG. 1039. TAIL END OF HUMAN EMBRYO BEFOKE
THK TlMB AT WHICH THE WOLFFIAN DUCTS
REACH THE CLOACA. (Drawn from a model con-
structed by Prof. F. Keibel. )
Post anal gut
Notochord
FIG. 1040. TAIL END OF HUMAN EMBRYO. The
Wolffian ducts open into the anterior part
of the cloaca. (Drawn from a model con-
structed by Prof. F. Keibel. )
Pronephros. From what is known regarding the development of lower animals, it seems
certain that the Wolffian duct originally served as the duct of the still earlier secretory organ-
Body of vertebra
Spinal ganglion
Spinal medulla
wrw'. r <4
Arch of vertebra v ,,,
Ilium (cartilage)
V
Wolffian duct ^
Miillerian'duct
} Intestine
Genital gland
Mesonephros
FIG. 1041. TRANSVERSE SECTION THROUGH THE LOWER PART OF THE TRUNK OF A HUMAN EMBRYO OF
ABOUT 7 WEEKS. (Specimen in the possession of Prof. J. Symington. )
the Pronephros. In man the pronephros arises nearer to the head end of the embryo than
the later formed mesonephros, and its tubules can only with difficulty be distinguished
R DEVELOPMENT OF THE UBO-GENITAL OEGANS. 1331
i
segments from the
m those of the later appearing mesonephros. The tubules of the pronephros arise in all the
fifth cervical to the third lumbar.
As the permanent kidney, or metanephros, is developed the mesonephros atrophies ;
a portion of it, however, is retained in the male, and forms the excretory apparatus of
the testis. The Wolffian duct becomes the canal of the epididymis and the ductus
deferens of the adult (see p. 1334). In the female, when the permanent kidney is
formed, the mesonephros and its duct undergo atrophy to a greater extent than in the
male, and they are only represented in the adult by the vestigial structures present in
the broad ligament of the uterus (see pp. 1315 and 1316).
Wolffian duct
Kidney bud
Notochord
/ Neuial tube
THE URETER AND PERMANENT KIDNEY.
The ureter arises as a tubular diverticulum from the W T olffian duct close to the point
where the latter joins the cloaca (Figs. 1039 and 1042). This diverticulum is seen first
during the fourth week, and grows from behind forwards, dorsal to the body cavity. Even
in its very early condition the portion of Rectum
the outgrowth which lies nearest to the
Wolffian duct, and from which the adult
ureter is developed, is more slender than
the distal part, which becomes branched,
and grows out to form the pelvis and r
calyces of the ureter. From the calyces Bladder- "'^P^K
numerous collecting tubules grow out into
the developing kidney and acquire con-
nexions with the glandular or uriniferous
tubules of the kidney. The uriniferous
tubules of the kidney arise independently
of the ureter in a backward prolongation
of the tissue which, further forward, gives
origin to the tubules of the mesonephros.
The tissue in which the permanent kidney
tubules arise lies behind the third lumbar
segment. The blind distal end of each
tubule soon dilates to form a capsule
which, becoming invaginated on itself,
Post anal gut
the Wolffian duct. (Drawn from
stmcted by Prof. F. Keibel. )
model con -
FIG. 1042. TAIL END OF A HUMAN EMBRYO ABOUT
25 DAYS OLD.
encloses a tuft of capillary blood-vessels. The cloaca is dividing into rectal and urino- genital
The renal corpuscles arising in this manner subdivisions. The ureter is arising as a bud from
are found in the human kidney as
early as the eighth week.
As regards their origin in the embryo we distinguish between the collecting tubules
and their branches, and the uriniferous secretory tubules of the kidney. The former
arise from the calyces of the ureter, and hence are derived from the Wolffian duct ; the
latter are formed in mesoderm, known as the metanephric cellmass, which is continuous
at its anterior end with the tissue from which the mesonephros is derived. The short
ju notional tubules of the adult lie in the region where these developmen tally distinct
portions of the kidney unite.
As the ureter increases in length, it becomes separated from the Wolffian duct, and
acquires a distinct opening into the anterior part of the cloaca nearer the head of the
embryo than that of the Wolffian duct. This part of the cloaca receiving the ureters
becomes the bladder. The kidney is at first a distinctly lobulated body, and shows
at birth, and sometimes even in the adult, distinct traces of its original subdivision
into lobule.
The metanephric cell mass, in which the uriniferous tubules arise, lies at first on the medial
side of the bud-like outgrowth, which represents the ureter ; at a later time it comes to lie
dorsally. As the ureter grows towards the head end of the embryo the cell mass which gives
rise to the uriniferous tubules follows it ; hence the metanephric tissue ceases to lie to the caudal
end of the mesonephros. As the ureter divides to form the calyces, the metanephric cell mass
becomes broken up into cap-like portions, one for each branch of the ureter, and later one for
each of the collecting tubes which grow out from the calyces.
kThe formation of uriniferous tubules within the nephrogenic cell mass is continued until
w days after birth.
85 a
1332
THE UKO-GEOTTAL SYSTEM.
Bladder
/
Large intestine
I Wolfflan duct
Pelvis of kidney
THE BLADDER.
The main portion of the bladder is formed from the superior (cephalic) part of the
anterior subdivision of the cloaca. This at an early time becomes flattened dorso-ventrally,
and produced laterally into two horn-like projections in the region where the Wolffian
ducts open (Fig. 1043). Inferiorly
Aiiantois it becomes constricted to form the
uro-genital canal. Little by little
the lower ends of the Wolffian ducts
open out and are absorbed into the
wall of the developing bladder, and
soon it comes about that the ureters,
which originally were outgrowths
of the Wolffian ducts, open directly
into the bladder. The openings
of the ureters become shifted latter-
ally, but the final position of the
openings of the Wolffian ducts is
close to the median plane in the
upper prostatic part of the urethra.
The bladder has therefore a double
origin : its main portion is derived
from the entodermal cloaca ; its
smaller basal part arises from the
opened-out lower ends of the Wolffian
The cloaca is becoming separated into rectal and uro-genital ducts. The latter portion approxi-
portions by the formation of the septum recto- urethrale. rnatp i v oorrpsrirmr l, to thp triovm
The ureter has acquired a separate opening into the anterior matel 7 corresponds
division of the cloaca. (Drawn from a model constructed VCSlCSe of the adult, and must
by Prof. F. Keibel. ) be regarded as having its source
from the mesoderm. The extreme
cephalic end of the anterior part of the cloaca tapers gradually, and beyond the umbilicus
is continuous with the allantois. This part of the cloaca loses its lumen about the fifth
week, and from it is derived the fibrous cord of the urachus or median umbilical ligament,
which in the adult reaches from the bladder apex to the umbilicus.
The cavity of the urachus is sometimes not lost so early, and in rare cases it has been
found persisting in the child or adult as a pervious channel extending from the apex of
the bladder to the umbilicus. Here it may open on the surface of the body.
THE MALE URETHRA.
The first part of the male urethra has an origin similar to that of the basal part of
Cloacf
Ureter
Septum recto-urethra le
FIG. 1043. TAIL END OF HUMAN EMBRYO ABOUT 33 DAYS OLD.
Ureter
Wolfflan duct
Rectum j
Miillerian ducts \ ,
Bladder \
Symphysis pubi
[/ '
Vertebra (body)
i Neural tube
V 1 S
Urino-genital canal , \l
Clitoris *
Notochord
FIG. 1044. TAIL END OF FEMALE HUMAN EMBRYO ABOUT 9 WEEKS OLD.
The rectum has acquired an opening and the entoderm of the uro-genital canal is continued into the genital
eminence (clitoris). (Drawn from a model constructed by Prof. F. Keibel. )
DEVELOPMENT OF THE UBO-GENITAL OKGANS. 1333
the bladder, and is derived from the ends of the Wolffian ducts (see above, p. 1332).
The remaining portion, beyond . the openings of the ductus deferentes of the adult, is
derived from the uro-genital canal, or caudal subdivision of the anterior part of the
cloaca. The uro-genital canal is early subdivided into a pelvic part lying within the
future pelvis minor and a penile part which occupies the region in which the corpus
cavernosum urethne is developed. The latter part of the uro-genital canal becomes
filled with closely and irregularly packed cells, which later, breaking down, re-establish
the canal and give origin to a slit-like opening in the region in front of the anus. The
canal for some time opens at a rhomboidal fossa situated in the groove at the base of the
glans. In the glans penis a septum of densely packed cells passes forwards from this
fossa and is known as the urethral septum. At a later stage these cells also break
down and form a groove, the lips of which unite and enclose the terminal portion of the
urethra. It is doubtful if any of the male urethra owes its origin to the ectoderm, but
there is some evidence to show that the urethral septum is to be regarded as ectodermal,
in which case the part of the canal which traverses the glans must have a like origin.
THE FEMALE URETHRA.
In the female the part of the urethra near the internal urethral orifice is developed from
the inferior ends of the Wolffian ducts and has an origin similar to that of the basal portion
of the bladder. The inferior part of the passage is derived from the uro-genital canal. When
the uro-genital canal opens on the surface it is continued forwards as a sulcus on the
genital eminence, as in the male sex. The margins of the slit-like opening do not unite,
but form the labia minora of the adult, and the sulcus which appears on the glans
3litoridis is closed without forming a canal. At first the fused caudal ends of the Mlillerian
lucts open into the uro-genital canal, but later a downgrowth, which is at first solid,
3stablishes a connexion between these ducts and the surface immediately in front of the
:-ectum and behind the opening of the uro-genital canal. This new connexion becomes the
vagina, and the uro-genital canal the urethra. By some embryologists it is believed
:hat a shortening and spreading out of the inferior portion of the uro-genital canal, to form
i part of the uro-genital cleft of the adult, is responsible for bringing the opening of the
'used Mullerian ducts to the surface. If this latter view is accepted, the female urethra
corresponds to the part of the male passage which lies above the opening of the utriculus
Drostaticus.
THE SEXUAL GLANDS.
Sexual Glands. In the development of the sexual glands, male and female, a
lifferentiated thickened portion of the peritoneal epithelium is first recognised. This
specialised epithelium, which has received the name of germinal epithelium, is situated to
hhe medial side of the mesonephros and of the Wolffian and Mullerian ducts. Here it
covers a longitudinally disposed ridge or elevation called the genital ridge. The germinal
epithelium is not strictly limited to this ridge, but extends to some extent beyond its
imits. The genital ridge is soon found to have numerous epithelial cells embedded in its
connective-tissue stroma which appear to originate, in both sexes, by a proliferation from
:he deep surface of the germinal epithelium covering the ridge. From these epithelial
cells the seminiferous tubules of the male, and vesicular follicles with their contained ova
)f the female are developed. The tissue which gives rise to the genital ridge occurs in
ill the body segments from the sixth thoracic to the second sacral, but the cephalic end
)f the ridge atrophies before the germinal epithelium can be recognised in the more caudal
segments, and only about one-fourth of the ridge gives origin to the permanent sexual
*land. The part of the genital ridge which persists appears to correspond to three or
'our segments in the region of the 4th or 5th lumbar to the 1st or 2nd sacral segments.
In the male, as early as the thirty-third day, the epithelial cells embedded in the
itroma of the developing testis have become arranged into a network of anastomosing
cords within which certain larger cells are seen to be irregularly scattered. These larger
cells have received the name of primitive sperm cells, and are relatively few in number.
They undergo frequent division, and in the later stages are not to be distinguished
'rom the other cells of the cords. The cellular cords undergo direct transformation into
:he seminiferous tubules of the testis, the tubuli recti and the rete testis. At a very early
itage the superficial part of the stroma of the developing testis becomes denser, and gives
)rigin to the tunica albuginea. The tissue surrounding the cellular cords becomes
converted into the septula testis and the mediastinum. A lumen can first be recognised
n the seminiferous tubules in the seventh month. The rete testis becomes connected
85 &
1334
THE UEO-GENITAL SYSTEM.
secondarily with the ductuli efferentes which are derived from the tubules of the meso-
nephros, and thus the mesonephric or Wolffian duct becomes the passage for the secretion
of the testis.
In the female large epithelial cells are found in the stroma of the developing ovary,
beneath the germinal epithelium, as early as the thirty-third day. These primitive ova
are much more numerous than the primitive sperm cells of the male, and form a very
characteristic feature of the developing ovary. At first they lie isolated, but later about
the fifth week they become surrounded by other smaller cells having a like origin from
the germinal epithelium. Each primitive
ovum surrounded by its cells becomes a
primitive follicle, the further development
of which has already been described (p.
1318). During the later stages the epi-
thelium has the appearance of growing
down into the stroma in the form of long
branching cellular processes which break up
into little nests of cells to form the future
follicles (p. 1318). The proliferation of cells
from the surface epithelium goes on until
the seventh month, but it is extremely
doubtful if any new ova arise in the later
months of gestation or after birth.
THE
FIG. 1045. THE URINO-GENITAL PASSAGES AT
INDIFFERENT STAGE OF DEVELOPMENT.
Ureter, green solid outline. Wolffiau duct, green dotted
outline. The origin of the vesicula seminalis is
indicated. Miillerian ducts, orange. Rectum,
bladder, and urino-genital canal, red.
THE GENERATIVE DUCTS.
Generative Ducts. As has been
already stated, the male ducts arise from
the Wolffian, and the female from the Mullerian ducts of the embryo. Both sexes at
first possess well-developed Wolffian and Mullerian ducts, which are arranged in a very
definite manner. The Wolffian ducts, communicating directly with the tubules of the
mesonephros, lie at first parallel to, and at
a considerable distance from, one another.
As they pass towards the caudal end
of the embryo they approach one another,
and each becomes enclosed in a fold of
peritoneum called the plica urogenitalis.
More caudally the ducts become closely
approximated to each other, are embedded
in a cord-like mass of connective tissue,
to which the term genital cord is applied.
They finally open into the anterior sub-
division of the cloaca (Fig. 1042).
The Mullerian ducts, opening freely into
the body cavity at their cephalic ends, lie
to the lateral side of the Wolffian ducts. As
they are traced caudally they cross the
Wolffian ducts and enter the genital cord,
within which they unite and form a canal,
which occupies the median plane, and opens
into the anterior subdivision of the cloaca,
between the Wolffian ducts (Fig. 1042).
The manner in which the ureters become
separated from the Wolffian ducts has
already been described.
Ducts in the Male. The seminiferous
tubules of the testis become connected
with the Wolffian duct through a fusion of
certain tubules of the mesonephros with the
rete testis. The connexion is definitely established in the third month. The number o:
tubules taking part varies considerably, but corresponds to the number of ductul:
efferentes found in the adult. The connecting tubules becoming much convoluted, jusi
as they join the Wolffian duct, form the lobuli of the epididymis. The canal of th<
epididymis is directly formed from the cephalic part of the Wolffian duct, and the ductui
FIG. 1046. THE URINO-GENITAL PASSAGES IN
THE MALE.
Ductus deferens, dotted green outline. Ureter, solic
green outline. Utriculus prostaticus, orange.
Bladder and pelvic part of urethra, red.
portion of urethra, black.
Penilt
DEVELOPMENT OF THE UKO-GENITAL OKGANS.
1335
deferens from the more caudal portion. The ductuli aberrantes and the rudimentary
tubules of the paradidymis are to be looked upon as persistent tubules, of a more caudal
portion of the Wolffian body, which have failed to become connected with the tubules of
the testis.
The seminal vesicles are developed in the third month as evaginations which arise from
the Wolffian ducts, near their caudal extremities. Each at first has the appearance of a
longitudinal groove in the wall of the ductus deferens, which closes over and becomes cut off
from the main tube except at the point where, later, the duct of the seminal vesicle joins
the ductus deferens.
The Miillerian ducts atrophy in the male embryo, but the appendices of the testis are
vestigial remains of their cephalic portions, while the utriculus prostaticus represents the
caudal fused portions which, in the embryo, occupy the genital cord.
Ducts in the Female. The Mtillerian ducts in the female retain their openings into
the body cavity, and their cephalic portions become the uterine tubes. Their fused
caudal parts, which at first join the uro-genital canal, give rise to the uterus and
vagina. The manner in which the original position of the opening of the Miillerian ducts
becomes shifted, by the formation of a new passage or by the shortening of the uro-
genital canal, has already been mentioned
(p. 1333). The final position of the opening
is in the uro-genital cleft of the adult.
The vaginal portion of the fused
Miillerian ducts is at first relatively very
short, and at the point where it opens into
the uro-genital canal a slight fold appears,
which is the future hymen. The vagina
increases rapidly in length as its opening
moves downwards towards the uro-genital
cleft. In the human embryo during the
third month the closely applied Miillerian
ducts, which higher up have fused to form
the uterus, are represented at their inferior
ends by a pair of rapidly elongating solid
cellular cords, which at a later stage break
down to form the vagina.
The Wolffian ducts and the mesonephros
atrophy in the female, but traces of them are
to be found in the ep-oophoron and par-ooph-
oron of the adult. In the foetus the Wolffian
duct can be traced along the side of the
uterus as far as the upper end of the vagina.
Prostate. The glandular portion of
the prostate arises as a series of solid out- FIG. 1047. THE URO-GENITAL PASSAGES m THE
FEMALE.
Derivations of the Miillerian duct, orange. Ureter,
green solid outline. The ep-oophoron is indicated
in green near the opening of Miillerian duct and
near the ovary.
growths from the epithelium of the uro-
genital canal during the third month. The
outgrowths, which are at first simple, be-
come branched and finally acquire a lumen.
They are arranged in three groups an
upper and a lower dorsal, and a ventral group. The glands of the ventral group soon
became reduced in number and often completely disappear ; those of the upper dorsal
group form the chief part of the gland.
The prostatic glands arise in both sexes, but in the female, where they are known as
para-urethral glands, they are few in number and not densely packed as in the male. The
muscular tissue of the prostate is derived from the muscular wall of the urethra.
The bulbo-urethral glands arise in the third month, and appear to be developed
from the epithelium of the uro-genital canal.
The larger vestibular glands in the female arise as epithelial outgrowths in the
same manner as the bulbo-urethral glands.
EXTERNAL GENITAL ORGANS.
The external genital organs are developed in the region of the ectodermal cloacal
fossa, and those of . the male and female cannot be distinguished from one another in
the earlier stages. The fossa at first extends on the ventral aspect of the body almost
1336
THE UKO-GENITAL SYSTEM.
from the tail to the umbilical cord. At its cephalic end is a tubercle known as the
cloacal tubercle, and behind lies the coccygeal tubercle. Immediately in front of the latter
the anus is formed, and between this opening and the cloacal tubercle the uro-genital canal
opens on the surface by a median slit-like aperture, the primitive uro-genital opening.
The cloacal tubercle early becomes subdivided into an apical genital eminence which
occupies the middle line and lies at the cephalic end of the slit-like uro-genital opening,
and a basal portion which lies nearer to the umbilicus and also curves round the sides of
the genital eminence. At a later time the basal part is continued to form a prominent
fold on each side of the ectodermal cloacal fossa. These folds are called the labio-scrotal
folds and, in' the female, give rise to the labia majora. The lateral margins of the primitive
uro-genital opening give origin to the labia minora, and the genital eminence becomes
the clitoris. On the clitoris at a very early date a relatively large glans is marked off by
a surrounding sulcus. In the male the scrotal folds grow backwards, and meeting behind
the primitive uro-genital opening, fuse together. In this way the opening is pushed
forwards. The genital eminence elongates rapidly owing to a growth at its basal part, and
FIG. 1048. EXTERNAL GENITAL
ORGANS, HUMAN EMBRYOS.
Indifferent stage. A. Embryo
of 20 mm. B. Slightly larger.
The genital eminence and the
labio-scrotal folds are well
FIG. 1049. EXTERNAL GENITAL
ORGANS, MALE EMBRYO.
Formation of scrotum. The labio-
scrotal folds, formerly best
marked at the sides of the genital
eminence, have grown backwards
and united behind the primitive
uro-genital opening, to form the
raphe scroti. The genital folds
embrace the base of the genital
eminence or penis. The glans is
very prominent.
FIG. 1050. EXTERNAL GENITAL
ORGANS, MALE EMBRYO.
Behind the glans penis the urethra
opens in a diamond-shaped fossa
in the posterior wall of which
the median raphe ends. The pre-
puce is formed behind the con-
striction which marks off the
glans, and as it grows forwards
the constriction disappears.
A little horn-like process of epi-
thelium is present on the summit
of the genital eminence.
a sulcus which is formed on its cloacal aspect gradually becomes converted into a canal
by the closure of the lateral lips of the primitive uro-genital opening. Soon the uro-
genital opening is found to lie nearer the apex than the base of the eminence, which has
now given rise to the penis. For some time the opening in the male lies at the base of
the glans penis and is somewhat rhomboidal in outline. At a later time, owing to the
breaking down of a dense septum of epithelial cells which appears within the glans, a sulcus
and finally a canal arises within this part of the penis and thus the terminal part of the
urethra is formed. When the opening at the base of the glans is closed the continuous
urethral passage is established. The main portion of the urethra is entodermal in origin,
but there is some evidence to indicate that the part which traverses the glans has its origin
from the ectoderm.
THE MAMMAEY GLANDS.
The mammae or breasts are accessory organs connected with the female repro-
ductive system. Each gland is situated in the superficial fascia covering the
anterior aspect of the thorax, and usually extends from the level of the second or
third to that of the sixth rib. The hemispherical projection formed by the gland
THE MAMMAEY GLANDS. 1337
lies upon the superficial aspect of the pectoralis major and to a less extent upon the
serratus anterior muscle. Near the summit of each mammary elevation, and usually
at the level of the fourth or fifth rib, is placed the wart-like nipple .or papilla
mammae, which is pierced by the minute openings of the lactiferous ducts and is
surrounded by a coloured circular area of skin called the areola. The skin
covering the nipple is thrown into numerous wrinkles, and on the areola exhibits
many minute rounded projections due to the presence of underlying cutaneous
glands. These have received the name of glandulas areolares, and are considered to
represent rudimentary portions of the mamma. The colour of the nipple and
areola varies with the complexion of the individual, but in young subjects they
are usually of a somewhat rosy-pink colour, which changes to a deep brown during
the second and third months of first pregnancy. Also, during pregnancy, the
areola increases in size and its glands become more marked. The nipple contains
a considerable number of unstriped muscle fibres, and becomes firmer and more
prominent as a result of mechanical stimulation.
The size and appearance of the mammae vary much, not only in the different
races of mankind, but also in >the same individual under different conditions. In
the young child the mammae are small, and there is little difference between those
of the male and female. Their growth is slow until the approach of puberty,
and then the female mammas increase rapidly in size. At each pregnancy
the mammae become large, and they attain their greatest development during
lactation. The size of the
mamma depends partly on the
amount of superficial fat and
partly on the amount of gland-
ular tissue present. 4
Structure of the Mamma. \
The mamma is composed of
a mass of glandular tissue
traversed and supported by
strands of fibrous connective
tissue, and covered by a thick
layer of fat. The glandular
tissue, to which the term corpus
mammae is applied, forms a
somewhat conical mass whose
apex corresponds to the posi-
tion of the nipple while its
base is loosely connected to the
fascia covering the pectoralis FIG 105L _ DlsSECTION OF THE MAMMA .
major and serratus anterior
muscles. In section the corpus mammae is readily distinguished from the sur-
rounding fat by its firmer consistency and by its pinkish- white colour. The corpus
mammae is composed of lobes and lobules, and its superficial aspect- and edges are
very uneven, the inequalities of its surface being filled up by processes of the fatty
tissue which forms a covering for the gland. This fatty covering is incomplete
beneath the areola, and here the lactiferous ducts pass into the nipple. The
gland is composed of fifteen to twenty lobes, or lobi mammas, which radiate
from the nipple, each lobe being quite distinct from the others and possessing
its own duct. The lobes are subdivided into secondary lobes and lobules, bound
together and supported by a considerable amount of connective tissue which forms
the stroma of the gland.
The alveoli of the gland and the secretory epithelium lining them vary
much under different conditions. At puberty the corpus mammae is composed
chiefly of connective tissue stroma and the ducts of the gland. At this time
the alveoli are small and few in number. During lactation, when the gland is
fully functional, the alveoli are enlarged, distended with fluid, and much more
numerous. The epithelial cells are cubical and filled with fat globules. When
the gland is not secreting, the alveoli become small and reduced in number
1338
THE URO-GENITAL SYSTEM.
while the cells of the lining epithelium, which are now small and glandular, do
not contain fat globules.
The ducts, or ductus lactiferi, passing towards the nipple, become enlarged
to form small spindle-shaped dilatations, called ampullae, or sinus lactiferi; then
becoming once more constricted, each duct passes, without communicating with its
neighbours, to the summit of the nipple, where it opens.
In the male subject the various parts of the mamma are represented in a
vestigial condition.
The presence of milk-glands is characteristic of the class mammalia, and the
number of pairs of glands in each group
of animals bears some relation to the
number of young usually produced at each
birth.
Processes radiating out
from the corpus mammae
Ampulla
Ductus lactiferi
Fat lobule
Variations. Asymmetry in the development
of the mammae is very common the left mamma
being very often larger than the right. Absence
of one or both mammae is a very rare abnorm-
ality, which may or may not be associated with
absence of the nipples. When one nipple only
is present it is usually the left. The presence of
supernumerary glands or nipples is not very un-
common, and a large number of examples are
recorded. The term polymasty has been applied
to cases in which more than the normal number
of mammae are present, and polythely to those
in which additional glands, in a vestigial
condition, are represented by accessory nipples.
Usually the accessory glands, or nipples, are pre-
sent on the anterior aspect of the thorax, and in
most instances they occur below and a little to
the medial side of the normal site. When the
abnormal glands are found above the normal site
they generally lie further from the median plane.
Much more rarely accessory glands have been
found on the abdomen, in the axilla, or in some
other situation, including even the dorsal aspect
of the trunk. As many as three extra pairs of
mammae have been found in the same individual,
and cases in which the probable representatives
FIG. 1052. SECTION THROUGH A MAMMARY GLAND, of mammary glands were even more numerous
Prepared after immersion in nitric acid as recom- have been recorded. Asymmetry is very common
mended by Mr. Harold Stiles. (D.J. Cunningham.) in these abnormal structures. It is interesting
to note that examples of polymasty and polythely
occur in the male rather more frequently than in the female. In some women the accessory
breasts have yielded milk during lactation ; in most cases the abnormal organs are very
rudimentary, and represented only by a minute nipple or pigmented areola. These cases of poly-
masty and polythely are supposed to represent a reversion to an ancestral condition, in which
more than two mammary glands were normally present, and in which probably many young were
produced at each birth. In this connexion it is interesting to observe that usually the accessory
glands occur in positions normally occupied by mammae in lower animals. In the course of the
development of the mammae in man, specialised areas of the epidermis, similar to those
which give origin to the mammae, have been observed both superior and inferior to the region
in which the adult mammae are developed. These areas appear to be present normally,
but in most cases they disappear at an early stage in the history of the embryo. In some other
mammals rudimentary mammae may occur, as, for instance, in lemurs and in some cows.
A slight functional activity of the mammary glands of the male at birth and about the time
of puberty is stated to be. not a very uncommon occurrence.
Vessels and Nerves of the Mamma. The breast receives its arterial supply from the per-
forating branches of the internal mammary artery and from the external mammary branches of the
lateral thoracic. Additional supply is sometimes derived from some of the intercostal vessels.
The veins coming from the gland pour their blood into the axillary and internal mammary
veins. Some small superficial veins from the breast join tributaries of the external jugular.
The lymph vessels of the breast are very numerous, and form extensive lymph spaces round
the alveoli of the gland. These freely anastomose with the lymph vessels of the skin and more
especially with the vessels of a very large anastomotic circle deep to the skin of the nipple. The
lymph vessels coming from the deep parts of the mamma for the most part join the lymph
glands of the axilla. They first run directly towards the deep surface of the breast, where they
enter the fascial lymph vessels contained in,* or lying deep to, the fascia of the pectoralis major.
These fascial vessels end for the most part in the axillary glands. It is important to remember
DEVELOPMENT OF THE MAMJVLE. 1339
that while the majority of the lymph vessels first reach the lymph glands lying on the lateral
border of the pectoralis major, some free vessels may "short circuit" to glands (1) in the floor of
the axilla, (2) along the circumflex vessels, (3) even to glands along the axillary vein. Yet other
lymph vessels of the breast may reach first the glands in the costo-coracoid space. Some vessels
from the medial part of the breast, following the course pursued by the perforating arteries, may
join the lymph glands situated along the course of the internal mammary artery, but these
vessels are fortunately often absent. It is also to be remembered that a few, probably irregular, com-
munications exist across the middle line with the lymph vessels of the opposite breast ; and
further that lymph vessels from the infero-medial area of the breast regularly join the fascial
lymph vessels of the upper part of the sheath of the rectus abdominis, and through these make
communication with the lymph vessels of (1) the round ligament of the liver, (2) the peritoneum
generally, and ultimately with the abdominal lymph glands. The surgical importance of the
facts regarding the lymphatic drainage of the breast cannot be exaggerated.
The nerve-supply of the gland is derived from the intercostal nerves of the fourth, fifth, and
sixth intercostal spaces. Along the course of these nerves sympathetic filaments reach the breast
from the thoracic part of the sympathetic trunk.
DEVELOPMENT OF THE MAMMAE.
The mammae are developed as downgrowths of the ectoderm into the underlying
mesodermic tissue. In the human embryo a thickened raised area of the ectoderm
can be recognised in the region of the future mamma at the end of the fourth
week. This thickened ectoderm becomes depressed in the underlying mesoderm, and thus
the mammary area soon becomes flat, and finally sunk below the level of the surrounding
epidermis. The mesoderm, where it is in contact with this downgrowth of the ectoderm,
is compressed, and its elements become arranged in concentric layers, which, at a later
stage, give rise to the connective-tissue stroma of the gland. The depressed mass of ecto-
derm cells soon becomes somewhat flask-shaped, and grows out into the surrounding
mesoderm as a number of solid processes, which represent the future ducts of the gland.
These processes, by dividing and branching, give rise to the future lobes and lobules, and
much later to the alveoli. The mammary area becomes gradually raised again in its
central part to form the nipple. A lumen is formed in the different parts of this branch-
ing system of cellular processes only at birth, and with its establishment is associated
the secretion of a fluid resembling milk, which often takes place at this time. The
ampullae appear as thickenings on the developing ducts before birth.
In those animals which possess a number of mammary glands such as the cat, pig,
etc. the thickening of the ectoderm, which is the first indication of the development of
these structures, takes the form of a pair of ridges extending from the level of the fore-
limb towards the inguinal region. These converge posteriorly, and at their terminations
lie not far from the middle line. By the absorption of the intermediate portions the
ridges become divided up into a number of isolated areas, in connexion with which the
future glands arise. Somewhat similar linear thickenings of the ectoderm have also been
recognised in the human embryo, and the usual positions assumed by the accessory glands
when present, leads us to suspect that in all probability the ancestors of man possessed
numerous mammae arranged, as in lower animals, in lines converging towards the
inguinal region.
THE DUCTLESS GLANDS.
OKIGINALLY BY THE LATE D. J. CUNNINGHAM, F.E.S.,
Late Professor of Anatomy, University of Edinburgh ;
EEVISED AND EEWRITTEN BY A. C. GEDDES, M.D., F.E.S.E.,
Professor of Anatomy, M^Gill University, Montreal.
THE title, the ductless glands, denotes a group of organs whose function is to
elaborate a special product and to discharge it into the blood or lymph. These
activities constitute the act of internal secretion.
The group includes the hypophysis and the pineal body, which are described with
the brain ; the suprarenal glands, which are compound organs and are the principal
representatives of two important systems of glandular tissue called respectively the
chromaphil and cortical systems ; the glandule caroticse, which are outlying parts
of the chromaphil system ; the thyreoid and parathyreoid glands, and the thymus,
which are developed from the entodermal lining of the embryonic pharynx ; the
spleen and the glomus coccygeum, which are associated with the circulatory system.
Physiologically, the liver, pancreas, gastric and intestinal mucous membranes ; the kidneys,
prostate, and testes ; the uterus, ovaries, corpus luteum, and possibly some other organs form
internal secretions, and act therefore as "ductless glands" in addition to fulfilling their more
obvious functions. Anatomically, the lymph and haemo-lymph glands are "ductless glands,"
but it is not customary to speak of them as such.
1. THE CHEOMAPHIL AND COETICAL SYSTEMS AND THE
SUPEAEENAL GLANDS.
A. THE CHROMAPHIL SYSTEM.
(SYNONYMS : Chromophil, Chromaffin, Phceochrome, Phaochrome System.)
The chromaphil system is composed of a number of discrete masses of tissue
which produce and discharge adrenin (Isevo-adrenalin, C 9 H 13 N0 3 (Aldrich)). The
name chromaphil is given to the tissue because the cells forming it contain
granules which, in the presence of chromium salts, stain to any tint between
bright yellow and dark brown. The distribution of the masses of tissue forming
the system is shown in Fig. 1053. There are (i.) a series of isolated masses, the
paraganglia, associated singly or in groups with the ganglia of the sympathetic
nervous system, (ii.) a number of masses, chromaphil bodies of the sympathetic
plexuses (aortic bodies) in close relation to the abdominal sympathetic plexuses,
(iii.) the glandulse caroticse, and (iv.) the medullary portions of the suprarenal
glands.
(i.) The paraganglia are rounded masses of chromaphil tissue, 1-3 mm. in diameter,
placed inside, half inside, or immediately outside the capsules of the ganglia of the
sympathetic system. Typically one paraganglion, exceptionally a pair of paraganglia, is
associated with each ganglion of the gangliated trunks and with each ganglion of the
cceliac, renal, suprarenal, aortic, and hypogastric plexuses. Inconstantly, paraganglia
1341
1342
THE DUCTLESS GLANDS.
are associated with the ganglia of the cardiac and inferior mesenteric plexuses. They
have been reported in association with ganglia situated upon the surface of the suprarenal
glands, upon the surface and in the sinus of the kidney, in relation to the ureter, the
prostate, the epididymis, the ovary, the paroophoron, and the retro-peritoneal Pacinian
corpuscles, but have not been discovered in association with the ganglia of the branches
of the nervus trigeminus.
Superior Cervical Ganglion
___-_- = .^. Glandulae Caroticae
of GangTiated
_ Accessory Cortical Body
_- Medulla of Suprarenal Gland
Cortex of Suprarenal Gland
-Chromaphil Bodies of the
Abdominal Sympathetic Plexuses
Aortic Bodies
Accessory Cortical Body
(in neighbourhood of
Accessory Cortical Body
(in neighbourhood of Testis)
Accessory Suprarenal Gland
consisting of cortex & medulla)
FIG. 1053. DIAGRAM OF THE CHROMAPHIL AND CORTICAL SYSTEMS. Modified from Swale Vincent.
Chromaphil tissues = yellow ; cortical tissue = blue.
(ii.) The Chromaphil Bodies of the Sympathetic Plexuses. From seven tc
seventy masses of chromaphil tissue are developed in relation to the abdominal
sympathetic plexuses, independently of the ganglia and in addition to the paraganglia,
Of these, the most important are the two aortic bodies, which lie one on either side of the
aorta in the region of the origin of the inferior mesenteric artery. In the new-bon
child they are smooth brownish structures, 8-11 mm. in length, not infrequently united
by an isthmus superiorly (Zuckerkandl). They degenerate as life advances, ceasing tc ;
be visible soon after puberty, but remaining discoverable, microscopically, until about th<
age of forty.
THE SUPEAKENAL GLANDS. 1343
(iii.) The glandula carotica (B.N.A. glomus caroticum; O.T. intercarotid body)
, is a bilateral paired organ situated in close but slightly variable relation to the bifurcation
of the common carotid artery. Frequently it lies deep to the bifurcation ; sometimes it
is wedged in between the internal and external carotids at their commencement ; some-
times it is placed between them at a slightly higher level. Its shape varies with its
position. When free from pressure it is oval ; when compressed by the internal and
external carotids it is wedge-shaped. On the average, its height is 7 mm., its breadth
1-5-5 mm. Not infrequently it is split into two or more nodules. Its colour is grayish,
yellowish, or brownish red.
Structure. The glandula carotica is built up of nodules of chromaphil tissue surrounded
and supported by fibrous tissue. The nodules are penetrated by a mass of sinus-like blood
capillaries and surrounded by large lymph vessels. Scattered nerve-cells are present, and the
whole organ is permeated by non-medullated nerve-fibres, which establish intimate connexion
with the chromaphil cells.
(iv.) The meduMary portions of the suprarenal glands, although belonging to
the chromaphil system, are described below (p. 1346).
Development of the Chromaphil System. All chromaphil tissue develops in intimate
relation with the sympathetic nervous system. It is not derived from the sympathetic tissue
nor is the sympathetic tissue derived from it. Both are the descendants of a primitive,
indifferent, sympatho- chromaphil blastema, which in a 16-mm. embryo occupies the regions
corresponding to those occupied by the sympathetic system of the adult. It is composed of
tightly packed deeply staining cells about 5 ^ in diameter. The ancestry of these cells can be
traced back with strong probability to the cells of the neural crest (see Development of the
Sympathetic Nervous System).
The differentiation of chromaphiloblasts from sympathoblasts begins when the embryo is
about 18 mm. in length, but is not completed until late in gestation, if then. The process is
marked by an increase in size of the chromaphil formative cells and by a diminution in the
intensity of their reaction to ordinary stains. Later, the specific chrome reaction develops, but
the exact stage at which this occurs is unknown. It is important to note that if any cells in an
area differentiate, all do. The result is that, in spite of their intimate relations and common
origin, an intermixture of chromaphil and sympathetic cells is extremely rare.
The first of the chromaphil masses to differentiate are the aortic bodies. They are prominent
structures in a 20-mm. embryo. Later, the paraganglia of the sympathetic plexuses develop,
and last the paraganglia of the gangliated trunk.
The development of the glandula carotica requires special description. It takes origin from
a strand of sympatho -chromaphil blastema, which extends ventrally from the region of the
superior cervical sympathetic ganglion, deep to the internal carotid artery or between the
internal and external carotids. Differentiation begins when the embryo is about 20 mm. in
length, and is completed by the time it is 30 mm. long. In connexion with the development
of the glandula, there is a peculiar thickening of the wall of the internal carotid artery near the
developing gland. In the dog a similar thickening of the wall of the internal carotid artery
takes place, although in that animal the glandula lies beside the external carotid. Further, in
a 45-mm. foetus in which the glandula is fully differentiated the thickening is still present.
These facts show that in the higher animals the thickening has no connexion with the develop-
ment of the glandula, though the association of chromaphil bodies with blood-vessels in
cyclostomata and elasmobranchs (see Comparative Anatomy of the Chromaphil and Cortical
Systems) compels caution in excluding the possibility of there being at least some phylogenetic
relation between the two. It has frequently been stated, and is widely held, that the glandula
carotica is developed from or receives some contribution from the entoderm of the third
pliaryngeal pouch. This is not the case (see Parathyreoid Glands, Development).
B. THE CORTICAL SYSTEM.
The cortical system is composed of several masses of glandular tissue peculiarly
rich in lipoids. Its function is undetermined. The distribution of the masses is
shown in Fig. 1053. There are (i.) the cortical portions of the suprarenal glands,
(ii.) accessory cortical bodies. These are described below (see Accessory Suprarenal
G-lands and Cortical System, Development).
C. GLANDULE SUPRARENALES.
The suprarenal glands (O.T. suprarenal bodies or capsules, adrenal glands)
are compound organs consisting of a capsule of cortical substance enclosing a
medulla of chromaphil tissue. Typically, there are two suprarenal glands, a
right and left, placed in the epigastric region, one on each side of the vertebral
1344
THE DUCTLESS GLANDS.
column. They lie in the same plane as, and in intimate relation to, the supero-
medial aspects of the kidneys. Their colour is yellowish brown ; their size varies
within wide limits. To some extent it depends upon the cause of death being
large in subjects dead of acute septic intoxication, small after sudden death from
violence. Average dimensions are : height, 5 cm. ; breadth, 3 cm. ; thickness,
slightly under 1 cm. ; weight about 7 gm.
Surface in contact
with liver
Suprarenal vein
Surface covered
by inferior cava
Surface covered by
peritoneum
B
FIG. 1054.
A. Anterior surface of right suprarenal gland, B. Anterior surface of left suprarenal gland.
The superior and medial parts of each kidney are indicated in outline. On the right gland the dotted line
indicates the superior limit of the peritoneal covering.
Rarely only one gland is present ; occasionally one is quite small, the other unusually
large ; as a rule they are unequal in size, the left being more frequently the larger.
Sometimes the two glands are fused (cf . horse-shoe kidney). Frequently there are accessory
glands. These develop in the neighbourhood of the main gland, and usually remain there,
but may become attached, early in embryonic life, to organs which subsequently change
their position. As a result, they may be found not only beside the main gland but also in
Surface in relation
to diaphragm
Surface in relation to
left crus of diaphragm
Surface in relation
to kidney
Surface in relation
A -to kidney
FIG. 1055.
A. Posterior surface of right suprarenal gland. B. Posterior surface of left suprarenal gland.
the ligamentum latum, on the spermatic funiculus, or even attached to the epididymis.
Like the main glands, accessory suprarenals are compounded of cortex and medulla, and
require to be distinguished from chromaphil bodies and accessory cortical bodies, which
may be found in any of the positions in which accessory suprarenal glands occur.
Forms and Relations. The suprarenal glands possess fairly constant forms and
relations. The right gland is flat and triangular in outline. It is moulded, antero- laterally
THE SUPKAKENAL GLANDS.
1345
by the liver ; antero-medially by the vena cava inferior ; postero-medially by the diaphragm
i above, and by the kidney below. In a formalin-hardened specimen these areas are
i separated by prominent ridges. Near the apex of the gland, within the area of contact
: with the vena cava inferior, there is a short fissure, the hilum. From this emerges a vein
j which immediately joins the vena cava. The left gland is also flat, but is semilunar in
outline. It is moulded antero-laterally, by the stomach above, and by the pancreas
Medulla of suprarenal gland
Cortex of suprarenal gland
Aorta
Left crus of diaphragm
Intervertebral fibre-cartilage
Spinal medulla
FIG. 1056.-
-TRANSVBRSE SECTION THROUGH THE SUPRARENAL GLAND OF A NEW-BORN CHILD
IN SITU.
below ; postero-medially by the: diaphragm above, and by the kidney below. Upon the
anterior surface, near its loj^er end, is a well-marked fissure, the hilum. From this emerges
a, vein which almost immediately joins the left'renal vein.
The relations of the right and left glands to the kidneys are different. The right lies
like a cap upon the superior pole of the right kidney; the left is in contact with the
antero-medial border of the left kidney from the hilus to the superior pole. The relation
FIG. 1057. RECONSTRUCTION OP SUPRARENAL GLAND OF A DOG. (From Marshall Flint.)
le upper part shows the arrangement of blood-vessels upon the surface of the gland, the lower part
their arrangement within its substance.
'}f the glands to the peritoneum is not only different but variable. On the right side the
peritoneum may cover the lower part of the antero-lateral surface of the gland ; or this
part may be in contact with the duodenum, in which case a small area about the middle
of the surface may be covered by peritoneum ; or the peritoneum may not come into
'relation with the gland at all. On the left side the upper part of the anterior surface
'is commonly covered by the peritoneum of the omental bursa, the lower part being
86
1346 THE DUCTLESS GLANDS.
crossed by the pancreas and splenic vessels. Sometimes these structures lie at a
lower level, when the whole antero-lateral surface is covered by peritoneum of the
omental bursa.
Blood and Lymph Vessels. Typically, each gland receives three arteries : one direct from
the aorta, one from the inferior phrenic, and one from the renal artery ; and is drained by one
vein, which emerges at the hilum, the right to join the vena cava inferior, the left to join the
left renal vein. Numerous lymph vessels pass from the suprarenal glands to the lateral aortic
lymph glands.
Nerves. The nerves passing to and from the glands constitute the suprarenal plexuses.
They connect with the. renal and cceliac plexuses and with the cceliac ganglia, and include
numerous fibresTrom the greater splanchnic nerves, with a smaller number from the vagus and
phrenic nerves. Most of them are medullated, but lose their sheaths on passing into small
ganglia in, or just within, the fibrous capsule of the gland. Thereafter they pass to the
chromaphil tissue of the medulla, either directly, or after first supplying the cortex.
Structure. A suprarenal gland consists of a highly vascular central mass of chromaphil
tissue, the medulla, enclosed within a thick capsule of cortical substance, the cortex, which in
turn is enclosed within a capsule of fibrous tissue, tunica fibrosa. From the deep aspect of the
fibrous tunic trabeculaa pass inwards to support the glandular tissue. In the superficial part of
.the cortex the trabeculae interlace freely to enclose rounded loculi, zona glomerulosa ; in the
intermediate part they run vertically to the surface to enclose columnar spaces, zona fasciculata ;
in the deepest part of the cortex they become broken up and form a reticulum, zona reticulata.
The cortex consists of polyhedral cells arranged in the interstices of the fibrous trabeculae. ;
These cells contain a lipoid substance, which is present in sufficient quantity to give the cortex a
yellow colour.
The medulla is formed of a spongework of cell columns bounding anastomosing venous j
sinuses. The cells are large, contain numerous granules, and possess the specific chromaphil \
reaction. In a fresh gland the medulla is of a dark red colour owing to the presence of blood in ;
its sinuses.
- The blood-vessels enter at numerous points in the fibrous capsule and run in the trabeculae, |
forming a network around the cell masses and columns of the zona glomerulosa and zona ,j
fasciculata. ^n the zona reticulata the blood-vessels open up to form a venous plexus, which is
continued through large sinuses in the medulla to reach a central vein. This is the vein
which emerges at the hilus.
Development of the Cortical System and of the Suprarenal Glands. The cortical system
is a Derivative of the ccelomic epithelium (mesoderm). The first indication of its development
is given, when the embryo is about 6 mm. in length, by the rapid proliferation of the epithelial
cells placed between the mesonephros and the root of the mesentery. Numerous buds form and
-penetrate the mesenchyme at the sides of and ventral to the aorta. In an 8-rnm. embryo these
buds have already lost their connexion with the coelomic epithelium. By the time the embryo
is 9 mm. long the developing cortical masses are vascularised. In man the greater part of the
tissue thus formed is ultimately included in the cortex of the suprarenal glands, but small
_ may escape, either at this stage or subsequently, to form independent cortical bodies.
In 12 -mm. embryos the developing suprarenal glands lie in a caudal ward continuation of the
dorsal portion of the pleuro-peritoneal membrane called the suprarenal ridge, and are composed of
cortical tissue only. When the embryo is about 20 mm. in length sympatho-chromaphil cells,
destined to form the medulla of the gland, begin to migrate into the developing cortex. The
two kinds of tissue are in contact in 10-12 mm. embryos, but penetration of cortical masses by
- sympatho-chromaphil cells has not been observed earlier than the stage mentioned.
At first the immigrating cells are scattered in numerous columns and strands, and it is not
until the embryo is about 10 cm. in length that they begin to reach the central vein and to form a
true medulla. When the process of immigration ceases is unknown, probably not until after birth.
The final specialisation of the cortex is a late phenomenon, and does not take place until long
after birth. The zona reticularis develops early and is recognisable in a 15-mm. embryo ; the
- zona glomerulosa is not formed until the second or third year, but is represented until then by a
layer of small incompletely specialised cells immediately under the fibrous capsule.
During foetal life the cortex is relatively enormous. This is due to a great proliferation
the cells of the fcetal zona reticularis, which differ from the adult cells of the same zone in
containing lipoids. This foetal cortex begins to undergo a fatty degeneration soon after bii
. and by the end of the first year has disappeared. The new cortex which replaces it develc
from the small, superficially placed, incompletely specialised cells already referred to.
Comparative Anatomy of the Chromaphil and Cortical Systems. A knowledge of the
main facts of the comparative anatomy of the chromaphil system is a help to understanding its
distribution in man. Chromaphil tissue is first recognised with certainty in the cyclostomata, in
which it is arranged in thin strips on the walls of the larger .arteries and their branches. In
elasmobranchs chromaphil bodies are present and are arranged segmentally on branches of
'the aorta in close relation to the ganglia of the sympathetic chain. Cortical tissue is also re-
cognisable in the cyclostomata, in which it is arranged in small lobulated masses in the walls o ;
the posterior cardinal veins and renal arteries. Even in this rudimentary form it is rich ii
lipoids. In the rays (elasmobranchs) the cortical system is represented by a pair of yellow-
coloured, rod-shaped structures in the region of the kidney. In batrachians the chromaphil am'
cortical representatives first begin to come together. In the frog the adrenals are golden yellow
THE THYKEOID GLAND.
1347
streaks on the ventral surface of the kidney. The greater part of these are made up of columns
of cortical cells, but at the borders or ends of the cell columns masses of chromaphil cells occur.
This arrangement is transitional between the complete independence of the chromaphil and cortical
systems in elasmobranchs and the partial inclusion of chromaphil tissue within cortical char-
acteristic of the higher mammals (Swale Vincent). But even in man the union of the systems is
far from complete. All the chromaphil tissue except the medulla of the suprarenal gland lies
out of touch with cortical substance. It appears therefore (i.) that the paraganglia of the
sympathetic trunk are homologous with the segmental chromaphil bodies of elasmobranchs ; (ii.)
that the chromaphil bodies of the abdominal plexuses are a new formation confined to the higher
vertebrates ; (iii.) that the inclusion of chromaphil tissue within a capsule of cortical tissue, as
in the suprarenal glands, is a still later development confined to the highest classes of animals.
2. THE DUCTLESS GLANDS OF ENTODEEMAL OEIGIN.
A group of ductless glands, (i.) the thyreoid gland, (ii.) the para thy reoid
glands, (iii.) the thymus, and two pairs of inconstant, apparently functionless
structures, (iv.) the cervical thymus glands, and (v.) the ultimo-branchial bodies,
are developed from the entoderrrial lining of the embryonic pharynx.
the neck, firmly bound
the upper part of the
Thyreoid cartilage
Crico-thyreoid
ligament
Superior thyreoid
vein
Cricoid cartilage
Internal j ugular vein
Isthmus of thyreoid
gland
Left lobe of
thyreoid gland
(i.) GLANDULA THYREOIDEA.
The thyreoid gland (O.T. thyroid body) is placed in
by fibrous tissue to the anterior and lateral aspects of
trachea and to the sides of
the larynx. It is yellowish
red, soft, and vascular. It
varies in size with age, sex,
and general nutrition, being
relatively large in youth, in
females, and in the well nour-
ished. In women it increases
1 temporarily with menstrua-
, tion and pregnancy. Its
average dimensions are, height
5 cm., breadth 6 cm., weight
25 gm. ; but these measure-
ments are of little value be-
caus,e of the range of varia-
tion.
Conventionally, the thyreoid
gland is said to consist of two
conical lobes united across
the middle line by a narrow
strand of gland tissue, the
i isthmus. To many thyreoids
this description is inapplicable.
1 In men and thin elderly spinsters
the gland is not uncommonly
horse -shoe 'Shaped; in young Innominate artery
well-nourished women and in FIG. 1058. DISSECTION OF THE THYREOID GLAND AND OF THE PARTS
pregnancy its general contour IN IMMEDIATE RELATION TO IT.
\ suggests a sphere, deeply notched
superiorly to accommodate the larynx and deeply grooved posteriorly for the trachea and
IJesophagus. Rarely, the gland is in two parts. Not infrequently, it is asymmetrical.
Ln about 40 per cent of specimens a process of gland tissue, the pyramidal lobe, extends
:rom the upper border of the isthmus, upwards, in front of the cricoid and thyreoid
Cartilages, towards the hyoid bone. This process is seldom median, lying more often on
Dhe left than on the right. In rare cases, it is double. Less rarely, it is double below
md single above. Sometimes it is represented by a strip of fibrous tissue or a narrow
nuscle (lig. suspensorium, or m. levator, glandulse thyreoideae).
Small oval accessory thyreoid glands are common in the region of the hyoid bone,
: tnd are occasionally met with in relation to the right and left lobes.
The relations of the gland are variable, depending upon its size and its relative level.
Common
carotid artery
Inferior
thyreoid vein
1348 THE DUCTLESS GLANDS.
In a majority of cases the isthmus covers the second, third, and fourth rings of the
trachea, but it may cover the cricoid cartilage, or the fourth, fifth, and sixth tracheal
rings. Anteriorly, the gland is clothed by the pretracheal fascia, which separates it from
the sterno-thyreoid, sterno-hyoid, and omo-hyoid muscles. Extensions of this fascial layer
form an indefinite capsule for the gland. Postero-medially, the thyreoid gland is moulded
by the sides of the trachea and lower part of the larynx, and, when large, comes into
contact, behind them, with the pharynx and oesophagus. Postero-laterally, it is in
relation to the common carotid arteries, and when large is in intimate relation to the
recurrent nerves. Further, it has important relations to the parathyreoid glands (see
Parathyreoid Glands, Relations).
Blood and Lymph Vessels. The blood supply is effected through the superior thyreoid
arteries, branches of the external carotids, and Jhrough the inferior thyreoid arteries, branches
of the thyreo-cervical trunks. Occasionally a fifth artery is present, the thyreoidea ima, a
branch of the innominate. The pyramidal lobe, if well developed, receives a special branch
from one of the superior thyreoids, usually the left. These arteries are remarkable for their
large size and for the frequence and freedom of their anastomoses. An anastomosing trunk
courses up the posterior aspect of each lateral lobe, uniting the inferior and superior thyreoid
arteries. It is of interest in connexion with the recognition of the parathyreoid glands.
Typically, three pairs of veins drain the gland. The upper two pairs, the superior and middle
thyreoid veins, join the internal jugulars ; the lower pair, the inferior thyreoid veins, join the
left innominate. These vessels take origin from a venous plexus on the surface of the gland or,
in the case of the inferior, from a downward extension of the plexus in front of the trachea.
When the gland is very large, accessory veins are present, sometimes in considerable numbers.
Most of these pass to the internal jugulars. A free, transverse, venous anastomosis is effected
along the borders of the isthmus through the superior and inferior communicating veins.
The lymph vessels anastomose freely in the substance and on the surface of the gland. Most
pass direct to the deep cervical lymph glands, a few descend in front of the trachea to the
pretracheal lymph glands.
Nerves. The nerves are derived from the middle and inferior cervical ganglia of the
sympathetic. They accompany the blood-vessels.
Structure. The gland is enclosed in a fibrous capsule (tunica propria) which sends
prolongations inward to form a framework for the gland tissue proper. This consists of
spheroidal vesicles, -04 mm. to 1 mm. in diameter, lined with cubical epithelium, and filled with
" colloid." The size, shape, and cellular characters of the vesicles vary with diet and environ-
ment. The vesicles are surrounded by networks of blood capillaries and of lymph vessels.
Development. The thyreoid gland takes origin from a single median outgrowth from
the pharyngeal floor (entoderm). It is recognisable as a shallow bay in a 1'8-mm. embryo,
practically simultaneously with the demarkation of the foregut. As the bud grows its end
expands whilst its stalk narrows to form the thyreo-glossal duct.
In a 4-mm. embryo an elevation is present round the pharyngeal opening of the duct. This
is the tuberculum impar. It migrates forwards, the duct backwards, so that in a 5-mm. embryo
the duct opens into the furrow immediately caudal to the tuberculum (see Tongue, Development).
At about this stage the duct begins to obliterate. This process proceeds slowly and is seldom
quite complete, a vestige of the duct, the foramen ccecum of the tongue, remaining in the adult,
While these processes are proceeding growth and lateral expansion of the bud continue. It
becomes bilobed and has a divided lumen, and all the while it undergoes a continuous relative
displacement caudalwards. Soon its lumen disappears. In a 9-mm. embryo the developing
thyreoid gland is a transverse bar composed of transversely disposed cell columns. At about the
tenth week of development, 55-mm. embryo, the formation of vesicles commences but is not com-
pleted until after birth. The remaining changes are due to simple growth and the moulding
effects of the pressure of surrounding structures.
The thyreoid gland does not arise in any of its parts from any of the pharyngeal pouches
(see Ultimo-branchial Bodies).
The developmental history of the gland affords a ready explanation of its variations in the
adult. Thus the development of a pyramidal lobe and its variations, partial and complete
duplication, are due to the development of gland tissue from that part of the thyreo-glossal duct
which has a double lumen and the more or less complete fusion or separation of the masses thus
formed. Accessory thyreoid glands near the hyoid bone are the result of a similar process in
connexion with isolated remnants of the duct.
The occurrence in the adult of a duct leading from the foramen caecum to, or towards, the
hyoid bone (lingual . duct) is due to a persistence of the upper part of the thyreo-glossal duct.
Similarly, thyreo-glossal cysts are due to the persistence of short intermediate lengths of the duct.
' (ii.) GLANDULE PARATHYREOIDE^E.
The parathyreoid glands (O.T. parathyroid bodies ; Synonyms : epithelial
bodies, parathymic glands, branchiogenie glands) are finely granular,' yellowish
brown, lenticular or spheroidal structures, from 2 to 20 rnm. in diameter and from
THE PARATHYEEOID GLANDS.
1349
Internal jugular vein
Vagus nerve
01 to 3 gm. in weight. Most commonly they are lenticular, 5-7 mm. in length,
1-2 mm. in thickness, and from -01 to -1 gm. in weight. Normally there are two pairs
of parathyreoids, distinguished by the Roman numerals IV. and III. to signify that
they develop from the fourth and third pharyngeal pouches. Sometimes, in course
of development, the parathyreoid buds divide so that more than four, five to twelve,
glands may be present: the numerals are then applied to the groups of glands
formed from the pouches.
Parathyreoid IV. is commonly embedded in the tunica propria of the thyreoid gland
'and lies posterior to the corresponding lateral lobe of that organ, about its middle. Para-
thyreoid III., similarly embedded, usually lies on the posterioi aspect of the inferior ex-
tremity of the lateral lobe of the thyreoid gland. As a rule the anastomosing channel,
which connects the inferior and superior thyreoid arteries (see Thyreoid Gland, Blood
'Supply), passes near both parathyreoids and furnishes the best guide to their discovery, but
the range of the exceptional positions which the glands may occupy is wide. Thus, para-
thyreoid IV. may be found (1) behind the pharynx or oesophagus, (2) in the fibrous tissue
at the side of the larynx, above the level of the thyreoid gland, (3) behind any part of the
corresponding lobe of the thyreoid gland or even embedded in the thyreoid substance
'(internal parathyreoid) ; whereas parathyreoid III. may be found (1) near the bifurcation
iof the common carotid artery, (2) behind any part of the corresponding lobe of the
thyreoid gland, (3) on the
sides of the trachea, or (4)
in the thorax.
Blood-vessels. The
blood supply of each para-
thyreoid is effected by a
single artery which enters
the gland at its hilum. It
' may spring from any branch
of the inferior or superior
thyreoid arteries, but most
commonly is a branch of the Common carotid artery
large anastomosing channel innominate artery
already referred to.
Structure. The para- Subclavian artery
thyreoids are built up of in-
tercommunicating trabecilla? Subclavian vein
af epithelial cells with
.strands of vascular connec-
tive tissue between them.
L?The cells are of two kinds,
Dne clear, the other, the min-
ority, containing oxyphyl
granules. Sometimes they
|r surround spaces recalling
fchyreoid vesicles ,but there
is no formation of " colloid,"
except possibly after thy-
"eoidectomy.
Development. The
parathyreoid bodies develop
from the dorsal diverticula
Jpf the third and fourth
! i pharyngeal pouches. The
p first indication of their de-
velopment is a proliferation
| md thickening of the epi-
:helium on the cranial and
ateral aspects of the diver-
i icula. This is present in
)oth the third and fourth
xraches in 9-10 mm. embryos
)ut appears to be rather
rregular in the time of its
ippearance. The cells forming it are vacuolated, difficult to stain, and indistinct in outline.
; 3ords of cells grow out from the thickening and fibrous tissue penetrates between the out-
growing cords, which, soon lose their connexion with the pharynx. The differentiation of the
1 ;wo kinds of cells takes place after birth.
Left lobe of thyreoid
gland
Isthmus of thyreoid
gland
Common carotid artery
^ Internal jugular vein
Band connecting
-" thymus with thyreoid
^ Vagus nerve
Subclavian artery
Subclavian vein
Innominate vein
Innominate
vein
FIG 1059. THYMUS IN A FULL-TIME FCETUS^ HARDENED BY
FORMALIN-INJECTION.
1350
THE DUCTLESS GLANDS.
Parathyreoid III. is normally drawn by the thymus, as it migrates, caudal to parathyreoid IV.
As a rule it halts at the level of the inferior extremijty of the lateral lobe of the thyreoid gland,
but may continue its descent into the thorax or may not descend at all. In the latter case it
remains near the bifurcation of the common carotid artery, where it is apt to be confused with
the glandula carotica. It is from this confusion th'at the idea, that the chromaphil glandula
carotica arises from the third pharyngeal pouch, has obtained a foothold in anatomical teaching.
(iii.) THYMUS.
Strictly, there are two thymus glands, a right and a left, but they are so
closely bound to one another that it is customary to speak of them as a unit,
Sterno-hyoid muscle
- Sterno-thyreoid muscle
Sterno-mastoid muscle
Thyreoid gland
Internal jugular vein
Phrenic nerve
Scalenus anterior
-Subclavian artery (left)
Left vagus nerve
Subclavian vein (left)
Recurrent ner
Inferior thyreoid vein
Right vagus nerve
Bifurcation of inno-
minate artery
Right subclavian
Internal mammary
artery
Right inno-
minate vein
RIGHT LOBE OK
THYMUS
Superior lob<
of right lun
Common carotid artery
Left innominate vein
First rib
Aortic arch
LEFT LOBE OF
THYMUS
Left lung
Heart
Pulmonary fisaur
PTTL- Pericardium
FIG. 1060. DISSECTION TO SHOW THE THYMDS GLAND IN AN ADULT FEMALE.
the thymus. This is an irregular pinkish mass of glandular tissue placed in tl
lower part of the neck and in the superior and anterior mediastina. Its si:
varies, relatively and absolutely, with age, sex, and nutrition, being relatively
largest in infancy, absolutely largest at puberty; larger in females and the \\el
nourished than in males and the emaciated ; large in healthy adults accidentally
killed ; small in persons, even children, who have died of a slow wasting disease,
It is supposed that it undergoes a premature permanent involution as the resr u
of severe illness even though, to all appearance, the individual completely recove
THE CEEVICAL THYMUS VESTIGES. 1351
1 It is impossible to say what should be the normal dimensions of the gland at the
various ages. In some new-born babes it weighs as little as 2 or 3 gm., in others
( as much as 15-17 gm. At puberty it may be difficult to find, or may weigh as
much as 40 gm. After the age of fifty it may require careful dissection to dis-
cover, or may be quite large. When large it fills all the space available between
the pleural sacs laterally, the back of the sternum in front, and the pericardium
and great vessels behind; when small it is embedded in fat and fibrous tissue.
The shape of the gland varies with its size and the age of the individual. In
infants with short thoraces it is broad and squat; in adults with long thoraces
it is drawn out into two finger-like strands. The details of its shape are deter-
mined by its size and by the structures upon which it is moulded, viz., the peri-
cardium and the great vessels of the superior mediastinum and the root of the
neck. One or both of its lobes may be connected by a strand of fibrous tissue
to the tunica propria of the thyreoid gland.
Blood and Lymph Vessels. The blood supply of the thymus is effected through inconstant
branches of the inferior thyreoid and internal mammary arteries. Its veins are irregular and
join the inferior thyreoid, internal mammary, and innominate veins. Its lymph vessels are
large and pass to glands close to the organ.
Its nerves are minute and are derived from the vagus and sympathetic. The branches of
' the vagus descend directly to the thymus from about the level of the thyreoid cartilage ; the
sympathetic fibres run with the blood-vessels. The fibrous capsule of the thymus receives small
irregular branches from the phrenic nerves, but these do not supply the gland tissue in any way.
Structure. The thymus is invested by a
a , , 1--IJ A. i Groove tor ^t*^^j^^ Groovft for Ipff-
fibrous Capsule which sends septa into Its sub- pulmonary artery JM Rpifc" innominate vein
5 tance to divide it into lobules The lobules are Mediastinal $M jf^kg* Groove for .
i similarly divided into follicles (secondary lobules) surfaceX J^^H |Q-- fl^il^ vena ? ava
ibout 1'5 mm. in diameter. Each follicle consists superior
of a medulla not quite completely surrounded by
i cortex. In a general way, the structure of the
iortex resembles a lymph gland, but the reticulum,
instead of being fibrous, is syncytiaL The spaces
)f the reticulum are crowded with lymphocytes,
out there are no germinal centres. The medulla
resembles the cortex, but the reticulum is coarser
md contains cell nests, the concentric corpuscles
)f Hassall. As age advances the thymus under- Pericardial surface
*oes involution. This process is marked by an FIG. 1061. DEEP SURFACE OF THYMUS, TAKEN
.ncrease of fibrous tissue and a reduced cellularity. FROM A FCETUS HARDENED BY FORMALIN -
Tlie number of lymphocytes and of concentric INJECTION.
corpuscles varies with nutrition.
Development. As has been stated, there are in reality two thymus glands, a right and a
eft ; they arise from the ventral diverticula of the third pharyngeal pouches. The first
ndications of the developing glands, cylindrical elongations of the diverticula, are present in
j 3-mm. embryos ; the walls of the cylinders, more particularly their dorsal parts, soon thicken.
Uoincidently the necks of the pharyngeal pouches become constricted to form the pharyngo-
jranchial ducts III. These soon disappear when the thymus rudiments lose all connexion
vith the pharynx. At this time the upper parts of the rudiments still have a lumen ; the
ower parts are solid. Soon the lumen vanishes ; the solid parts thicken and the developing
ihymus migrates caudaiwards to reach the pericardium at the 15-rnni. stage. As a result of the
uigration the upper part gets drawn out and finally disappears. It is in this process that
)ara thyreoid III. is involved. It is attached to the upper part of the migrating thymus, the part
vhich disappears. The relative time of this disappearance determines the permanent level of
)arathyreoid III., for until it happens that gland is dragged in the wake of the thymus (see
Parathyreoids, Development of). Sometimes a small detached mass of thymus formative tissue
nay persist beside parathyreoid III., and may differentiate to form an Accessory Cervical
Miymus III.
During migration and after, the cells continue to proliferate and the thymus rudiment
ncreases in mass. At the 40-mm. stage lymphocytes begin to appear in it. Differentiation
>f cortex and medulla is visible at the 45 mm. stage. The details of the process of thymic
listogenesis are undetermined. It is believed that the syncytial reticulum and concentric
orpuscles are of entodermal origin, but whether the lymphocytes arise in situ or are immigrants
: s unknown.
(iv.) THE CERVICAL THYMUS VESTIGES.
Small masses of thymus tissue are frequently found in close relation to parathyreoid s
-V. They are developed from the ventral diverticula of the fourth pharyngeal pouches
11 a manner generally similar to that in which the main thymus gland develops. Not
86 a
1352 THE DUCTLESS GLANDS.
infrequently they are embedded in the thyreoid gland, internal thymus. Less frequently
they are sausage-shaped bodies, 5 '25 mm. in length, lying at the sides of the trachea.
Sometimes they are long enough to extend into the thorax, where they come into relation
with the main thymus gland. Rarely they migrate into the thorax and develop to form
considerable portions of the main thymus gland, which then consists of four development-
ally distinct parts. Cervical Thymus Vestiges IV. require to be distinguished from the
Accessory Cervical Thymus Glands III., which are sometimes found in close relation to
parathyreoids III. (see Thymus Gland, Development).
(v.) THE ULTIMO-BRANCHIAL BODIES.
The fifth pharyngeal pouches give rise to a pair of gland rudiments called ultimo-
branchial bodies. Their fate is not known it is possible that they may become the
strands of parathyreoid-like tissue occasionally present in the lateral lobes of the thyreoid ;
more frequently, apparently, they degenerate and leave no vestiges.
Their chief interest is that, for long, they were erroneously regarded as the rudiments
of the lateral lobes of the thyreoid gland.
3. THE DUCTLESS GLANDS ASSOCIATED WITH THE
VASCULAR SYSTEM.
Two ductless glands of mesodermal origin are associated with the vascular
system. They are (i.) the spleen, (ii.) the glomus coccygeum.
i
(i.) LIEN.
The spleen is a soft, highly-elastic, contractile organ of purplish colour, placed
in the upper left posterior part of the abdominal cavity, partly in the epigastrium,
miinly in the left hypochondrium. It is moulded by the diaphragm, kidney,
stomach, and, sometimes, colon. Its dimensions vary widely, but on the average
are : length, 12 cm. ; breadth, 7 cm. ; thickness, 4 cm. ; weight, 160 gm. Its shape
is modified by the relaxation, distension, and contraction of the neighbouring hollow
viscera; its position and the details of its moulding, by the attitude of the
individual.
When the stomach is contracted and the colon distended, the spleen has the
form of an irregular tetrahedron ; when the conditions of the hollow viscera are
reversed, the form of a segment of an orange. These are the extremes of a series
of forms which the spleen presents when hardened in situ. In the recumbent
posture the long axis of the spleen corresponds in direction with the posterior part
of the tenth rib ; in the erect attitude the long axis is frequently vertical, more
especially in adult females.
Surfaces, Borders, and Angles of the Spleen. The surfaces of the spleen are
the facies diaphragmatica, facies renalis, facies gastrica, and, in the tetrahedral form only,
facies basalis (colica). Their contour is fairly constant. The diaphragmatic surface is
convex, moulded to the curve of the diaphragm ; the renal is slightly concave, moulded
to the kidney ; the basal is flat or slightly concave, moulded by the colon ; the gastric,
deeply concave, moulded by the stomach. The gastric surface is interrupted by an
irregular, not infrequently divided, slit, the hilum, through which the branches of the
splenic artery enter and the tributaries of the splenic vein leave the gland. On the same
surface, behind the hilum, there is a depression for the tail of the pancreas.
The borders of the spleen are margo anterior, between the gastric and diaphragmatic
surfaces ; margo posterior, between the diaphragmatic and renal surfaces ; margo inter-
medius, between the renal and gastric surfaces. When present the basal surface is
separated from the diaphragmatic by the margo inferior, from the gastric and renal by
the margines intermedii, anterior and posterior.
The anterior border of the spleen is almost invariably notched ; most frequently there
are two notches, but there may be six or seven. Sometimes the posterior border also is
notched. Rarely, the notches on the borders are joined by fissures extending across the
diaphragmatic surface.
The angles of a tetrahedral spleen are : superior, at the junction of the diaphragmatic,
THE SPLEEN.
1353
o-astric, and renal surfaces ; anterior, at the junction of the diaphragmatic, gastric, and
basal surfaces ; posterior, at ,the junction of the diaphragmatic, renal, and basal surfaces ;
intermediate, at the junction of the renal, gastric, and basal surfaces. In a spleen of
orange-segment form there are but two angles, a superior and an anterior. The superior
is bounded in the same way as in the tetrahedral form ; the anterior, by the dia-
phragmatic, gastric, and renal surfaces. In all spleens, but most commonly in those of
oblique, irregularly tetrahedral form, the superior angle may curve forward as a blunt
hook.
The spleen is entirely covered with peritoneum and is moored by two peritoneal folds,
the lieno-renal and gastro-splenic ligaments (pp. 1162 and 1236). Inferiorly it is supported
by the peritoneal phrenico-colic ligament (p. 1242).
Rib IX
RibX
Rib XI
Descending colon
Rib IX
RibX
Rib XI
Ascending colon
FIG. 1062. DISSECTION OF THE SPLEEN, LIVER, AND KIDNEYS FROM BEHIND, IN A SUBJECT HARDENED BY
FORMALIN-INJECTION.
Small globular accessory spleens are often present. As a rule they are attached to
the gastro-splenic ligament near the splenic hilum.
Blood and Lymph Vessels. The spleen receives its- blood from the splenic artery, which
passes through the lieno-renal ligament. Before reaching the gland it breaks up into six or
more branches which enter the hilum independently. The vein of the spleen, the splenic vein,
is formed in the lieno-renal ligament by the union of several unnamed tributaries which emerge
from the hilum. The lymph vessels also leave the spleen at the hilum. They are small and come
from the capsule and trabeculse only, not from the glandular part of the organ.
Nerves. The nerves are almost entirely non-medullated and come from the cceliac plexus.
They accompany the splenic artery and its branches.
Structure. The spleen is composed of a soft substance called pulp, supported by fibrous
trabeculee and enclosed within a fibrous capsule, tunica propria, which, in turn, is enclosed within
a peritoneal capsule, tunica serosa. Embedded in the pulp are nodules of lymph tissue, noduli
lymphatici lienales (O.T. Malpighian corpuscles).
The tunica serosa closely invests the organ, except where it is reflected on to the lieno-renal
and gastro-splenic ligaments and at the hilum. It is very firmly bound to the tunica propria.
The tunica propria is stout and strong but highly elastic. It is composed mainly of fibrous
1354
THE DUCTLESS GLANDS.
tissue but includes many elastic and muscle fibres. From its deep surface, more especially at the
hilum, strong trabeculae pass into the organ to support the blood-vessels and nerves.
Hilum
Pancreatic impression
Intermediate angle Posterior angle
FIG. 1063. THE SPLEEN VISCERAL ASPECT.
The pulp is a spongework of fine fibres covered, at places entirely concealed, by branched
connective-tissue corpuscles, reticulum cells. Associated with these, occupying some of the
Central blood-space
Capillaries- -
*% Capillaries
"Capillari
Central blood-space
FIG. 1064. SECTION THROUGH GLOMUS COCCYGEUM (highly magnified). From J. W. Thomson Walker.
smaller spaces of the spongework, are cells like very large leucocytes, spleen phagocytes. These
are amoeboid and often contain the debris of red blood corpuscles.
GLOMUS COCCYGEUM.
1355
The arteries enter at the hilum, run in the trabeculoe, and branch freely. The smaller
arteries have a lymphoid sheath developed in their walls. This replaces the fibrous sheath which
the larger arteries receive from the trabeculae. Every here and there the lymphoid sheath
expands symmetrically or asymmetrically to form a lymphatic nodule (nodulus lymphaticus
lienalis). Many of the nodules thus formed are quite small ; others are visible to the naked eye
as white specks, but, however large or small they may be, each contains a network of capillaries.
Towards their termination the arteries lose their sheaths and become reduced to simple tubes of
endothelial cells ; gaps appear in their walls and finally the cells forming them become con-
tinuous with the reticulum cells of the pulp. The veins begin in the same way as the arteries
end. The pulp is, therefore, the modified capillary system of the spleen.
Development. The spleen is mesodermal in origin. The first indication of its develop-
ment, in a 9-mm. embryo, is a thickening of the dorsal mesogastrium. In 10-12 mm. embryos
the ccelomic epithelium over the splenic rudiment is several layers thick. Soon the deeper
layers of the thickening are transformed into mesenchyme and the epithelium is reduced again
to a single layer. The first vascularisation of the spleen is effected by a capillary network. Out
of this the intra -splenic arteries and veins
differentiate. The undift'erentiated capil-
laries between them form capillary tufts
or spherules. These become transformed
into the pulp. The exact method of this
transformation is undetermined, but during
its progress great numbers of red blood
cells are produced. The lymphatic nodules
are developed in the later part of foetal
life, and with their contained lymphocytes
differentiate from the tunica adventitia of
the arteries.
Arterial branches
Accessory glomus -
(ii.) GLOMUS COCCYGEUM.
Accessory glomus -O
The glomus coccygeum is a
small body, 2-2-5 mm. in diameter,
placed immediately anterior to the tip
of the coccyx, upon a branch of the
middle sacral artery. Usually it is Entrance of artery
. n .. m ti into mam glomus
accompanied by a group of smaller Accessory Q
bodies of similar structure and arterial glomus
relation.
Accessory
glomus""
_ Arterial branches
Accessory
""glomus
Structure. The glomus is enclosed
in a fibrous capsule and consists of round
or polyhedral cells with large nuclei lining
a considerable blood space, which is an
anastomosing channel between an artery
and a vein.
Development. The glomus develops
from the capillary network of the region
of the tip of the embryonic taiL At first
the capillary walls differentiate as if to form an artery, then the cells of the middle coat,
instead of forming muscle, assume an epithelioid character.
The position of the glomus coccygeum at the posterior end of the axis of the body, and the
fact that its blood-spaces form a wide arterio-venous anastomosis, suggest that it is a sort of
safety-valve on the peripheral circulation. No evidence that it produces an internal secretion
has, as yet, been obtained, and in spite of frequent statements' to the contrary it contains no
chromaphil cells (Stoerk).
FIG. 1065. -SCHEMA OF THE RELATION PRESENTED BY THE
GLOMUS COCCYGEUM AND ITS ACCESSORY OUTLYING
PARTS TO THE BRANCHES OF THE MIDDLE SACRAL
ARTERY. (Reconstructed from serial sections through
the region.) From J. W. Thomson Walker.
SURFACE AND SURGICAL ANATOMY.
BY HAROLD J. STILES, F.B.C.S.
THE HEAD AND NECK.
THE CRANIUM.
Scalp. The first and third layers of the scalp, "namely, the skin and the epi-
cranius muscle, are firmly united by fibrous processes which pass from the one to
the other through the second or subcutaneous fatty layer. Intervening between
these three layers and the pericranium is a loose cellular layer which supports the
small vessels passing between the scalp proper and pericranium. The thin peri-
cranium, although regarded anatomically as periosteum, possesses very limited
bone-forming properties ; over the vertex it is readily separated from the skull-cap,
except along the lines of the sutures, where it gives off intersutural processes to
join the endosteal layer of the dura.
The free blood-supply of the scalp is for the purpose of nourishing its abundant
hair follicles and glands. The main vessels lie in the dense subcutaneous tissue,
and are superficial, therefore, to the epicranius (Fig. 1066). The arteries supplying
the frontal region are derived from the internal carotid, while those for the remainder
of the scalp spring from the external carotid. These two sets of vessels anastomose
freely with one another, and freely also across the median plane ; hence the failure
of ligature of the external carotid to cure cirsoid aneurysm of the temporal artery.
"Wounds of the scalp bleed freely, and the vessels are difficult to ligature on account of the
adhesion of their walls to the dense subcutaneous tissue. In extensive flap wounds and in
diffuse suppuration beneath the epicranius there is little danger of sloughing of the scalp.
Abscesses and haemorrhages superficial to the epicranius are usually limited on account of
the density of the subcutaneous tissue. Haemorrhage beneath the epicranius is seldom
extensive on account of the small size of the vessels, but suppuration in this situation may
rapidly undermine the whole muscle and its aponeurosis the galea aponeurotica ; incisions to
evacuate the pus should be made early, and parallel to the main vessels of the scalp. Extravasa-
tion of blood beneath the pericranium leads to a haematoma which is limited by the sutures.
The veins of the scalp communicate with the intra-cranial venous sinuses
(1) directly through their anastomoses with the large emissary veins, namely, the
parietal, which opens into the superior sagittal sinus, and the mastoid and condyloid,
which open into the transverse sinus ; (2) through the anastomoses of the frontal
and supra-orbital veins with the ophthalmic vein, which opens into the cavernous
sinus ; (3) through the veins of the diploe, which connect the veins of the scalp
and the pericranium on the one hand with those of the dura mater and the venous
sinuses on the other; (4) through small veins which pass from the pericranium
through the bones and the intersutural membranes to the dura. It is along these
various channels that pyogenic infection may extend, from the scalp and pericranium,
through the bone to the dura mater and venous sinuses, and from the latter to the
cerebral veins, the pia-arachnoid, and the substance of the brain. More rarely the
infection spreads from the cranial cavity along the emissary veins to the scalp.
The lymph vessels of the anterior part of the scalp join the external maxillary
lymph vessels ; those of the temporal and parietal regions open into the pre-auricular
and parotid lymph glands, situated in front of and below the ear, and into the
post-auricular or mastoid glands, situated upon the insertion of the sterno-mastoid
muscle. The lymph vessels of the occipital region open into the occipital glands,
which lie. close to the occipital artery where it becomes superficial in the scalp.
1357
1358
SUEFACE AND SUEGICAL ANATOMY.
Bony Landmarks of the Cranium. At the root of the nose is the fron to-
nasal suture (nasion) ; a little above it is the glabella, a slight prominence which
connects the superciliary arches. About 1 in. below the posterior pole of the
Epicranial aponeurosis
Lax connective tissue
Pericranium
Outer table of cranial wall
Diploe
Anastomosis between arteries of
scalp and those of the dura mater
Inner table of cranial wall
Dura ma
Parasinoidal sinus 1
Cerebral vein opening into.
superior sagittal sinus
Integument
Artery in superficial fascia
Vein in superficial fascia
Vein of the diploe connecting
the veins of the scalp with those
of the dura mater
Vein in dura mater
Arachnoid mater
Pia mater
| Arachnoideal granulation
[Cortex cerebri
Superior sagittal sinus
Vein in pia-arachnoid
ub-arachnoid space
FIG. 1066. DIAGRAMMATIC REPRESENTATION OF A FRONTAL SECTION THROUGH THE SCALP, CRANIUM,
MENINGES, AND tlORTEX^ CEREBRI (modified from Cunningham).
cranium, and 2 in. above the spine of the epistropheus, is the external occipital
protuberance (inion). In the child the protuberance is not developed ; its position
may be denned by taking a point at the junction of the upper and middle thirds
of a line extending from the posterior pole of the skull to the spine of the epi-
stropheus. About a third of the distance from the nasion to the inion is the
bregma or junction of the coronal and sagittal sutures ; with the head in the
natural erect posture the bregma corresponds to the middle of a line carried across
the vertex between the pre-auricular points of the zygomatic arches.
At birth the position of the bregma is occupied by the fonticulus frontalis, a rhom-
boidal membranous area which generally becomes ossified at about the eighteenth
month. The size and date of closure of the fontanelle, as well as its tension and pulsa-
tion, are all points to be carefully noted in the clinical examination of children.
The lambda, or junction of the sagittal and lambdoidal sutures, situated 2 J in.
above the inion, can generally be felt through the scalp ; a line drawn from it to
the posterior border of the root of the mastoid process corresponds to the lambdoidal
suture. In the adult the parieto-occipital fissure of the brain lies opposite, or a few
millimetres in front of, the lambda ; in the child, however, the fissure may be as
much as 1 in. in front of it.
Crossing the supra-orbital margin close to its medial angle, a finger's-breadth
from the medial line, are the supra-trochlear nerve and the frontal branch of the
ophthalmic artery; the latter nourishes the flap in the operation of rhiuoplasty.
At the junction of the medial and intermediate thirds of the supra-orbital margin,
1 in. from the medial line, is the supra-orbital notch or foramen, the guide to the
supra-orbital vessels and nerves. A little above the level of the lateral can thus
of the eyelid is the fronto - zygomatic suture, immediately above which is the
zygomatic process of the frontal bone. At the posterior end of the suture the
zygomatico-temporal branch of the orbital nerve pierces the temporal fascia to reach
the scalp. Half an inch above the suture is the lower margin of the cerebral hemi-
sphere ; while half an inch below the suture is a small tubercle on the posterior border
THE CKANIUM. 1359
of the zygomatic bone ; a line drawn from this tubercle to the lambda gives the line
of the superior temporal sulcus and of the inferior cornu of the lateral ventricle.
The zygomatic arch, an important landmark, is horizontal when the head is in
the natural position, and is on the same level as the inferior margin of the orbit and
the inion ; its superior border is at, or not infrequently a little above, the level of
the lower lateral margin of the hemisphere. The superior border of the zygoma may
be traced backwards immediately above the tragus and the external acoustic meatus
to become continuous with the ridge formed by the supra-mastoid portion of the
temporal crest. The part of the posterior root of the zygoma which lies imme-
diately in front of the superior end of the tragus constitutes a valuable landmark
which may with advantage be termed the pre-auricular point of the zygoma, while by
the term post-auricular point is understood that point upon the supra-mastoid crest
which lies immediately behind, and a finger's-breadth below, the upper attachment
of the auricle. The temporal vessels and the auriculo-temporal nerve cross the
zygoma at the pre-auricular point, and it is there that the pulsations of the temporal
artery may be felt during the administration of an anaesthetic, or the vessel
compressed for the purpose of checking bleeding from the temporal region of the
scalp. The termination of the auriculo-temporal nerve in the neighbourhood
of the parietal tuber is often the seat of a .neuralgic pain in irritative conditions
about the external acoustic meatus, the latter being supplied by this nerve.
Two inches vertically above the pre-auricular point is the inferior end of the
central sulcus of Rolando. Two inches vertically above the middle of the zygomatic
arch is the pterion (spheno-parietal suture), a point which cannot be felt, but which
is nevertheless of topographical importance, as it overlies the lateral point (the point
where the lateral fissure of the brain breaks up into its three branches) and the
anterior branch of the middle meningeal artery.
The frontal tuber (better marked in the child) overlies the middle frontal con-
volution. The parietal tuber, which varies considerably in the definiteness with
which it can be recognised, overlies the termination of the posterior horizontal
limb of the lateral fissure of the brain, and therefore also the supra-marginal convolu-
tion, which is named by Turner the convolution of the parietal tuler. The part of
the temporal crest which intervenes between the zygomatic process of the frontal
bone and the coronal suture lies a little above the level of the inferior frontal sulcus.
The highest part of the temporal crest crosses the anterior central gyrus at the
junction of its middle and lower thirds, that is to say, at the junction of the motor
areas for the arm and face. In the child the temporal muscle, which is relatively
much smaller than in the adult, reaches only a short distance above the squamous
suture, and, therefore, only as far as the level of the inferior end of the central
sulcus of Eolando.
The thickness of the skull-cap varies at different parts and in different individuals. The
inner table is only half the thickness of the outer table, but both possess the same degree of elas-
ticity. When the vault is fractured from direct violence, the inner table is more extensively
fissured than the outer table, because the elements of the latter are compressed, while those of the
former are stretched apart. The weak areas at the base of the skull through which fractures are
liable to extend are : in the anterior cranial fossa, the orbital parts of the frontal bone, and the
cribriform plate of the ethmoid ; in the middle cranial fossa, the region of the glenoid cavity
of the temporal bone, and of the foramen ovale of the sphenoid ; in the posterior fossa, the fossae
of the occipital bone. The strong petrous part of the temporal is weakened by the tympanic
cavity and by the deep jugular fossa.
Cranio-Cerebral Topography. Of the many methods which have been
devised for mapping out the relations of the cranial contents to the scalp, that
introduced by Professor Chiene is, probably, the most useful from a clinical
point of view; no figures or angles have to be remembered, and the primary
surface lines are drawn from bony points which are not variable, whilst the
secondary lines are drawn, for the most part, between mid-points of the primary
lines. The method is as follows (Figs. 1067 and 1068) :
" The head being shaved, find in the median line of the skull between the .
glabella (G-) and the external occipital protuberance (O) the following points :
" First, the mid-point (M) ; second, the three-quarter point (T); third, the seven-
eighth point (S).
1360 SUKFACE AND SUKGICAL ANATOMY.
" Find also the zygomatic process (E), and the root of the zygoma (preauricular
point) (P), immediately above and in front of the external acoustic meatus.
Having found these five points, join EP, PS, and ET. Bisect EP and PS at N and
E. Join MN and ME. Bisect also AB at C, and draw CD parallel to AM."
The line MA corresponds to the superior and inferior precentral sulci, and may
therefore be termed the pre-central line. The origins of the superior and inferior
frontal sulci may be indicated by the points of union of the upper and middle and
the middle and lower thirds of the line MA, the lower point being at the level
of the temporal crest.
The line ET, termed the oblique or lateral line, intersects the pre-central line
at the point A, which overlies the pterion, and corresponds therefore to the lateral
point of the lateral cerebral fissure and to the anterior division of the middle meningeal
artery. AC overlies the posterior horizontal limb of the lateral fissure of the brain,
which terminates at the level of the temporal crest, in the inferior part of the
triangle HCB. This triangle contains the parietal tuber, and may, therefore, be
termed the supra-marginal triangle. The termination of the lateral line, at the
three-quarter sagittal point T, overlies the parieto-occipital fissure.
By joining TE, EO, a triangle is mapped out which delimits the surface of the
occipital lobe ; the line TE corresponds to the lambdoidal suture, while EO corresponds
to, or lies a little above, the tentorium and the upper border of the transverse sinus.
CD, the post-central line, corresponds to the superior post-central sulcus, and lies
a little behind the inferior post-central sulcus.
The parallelogram AMDC overlies the Rolandic area, i.e. the anterior central
gyrus and the posterior central gyrus, separated by the central sulcus.
The pentagon ABEPN maps out the temporal lobe, with the exception of its
apex, which is directed downwards, forwards, and inwards, a finger's-breadth in
front of the point N.
A finger's-breadth below AB is the superior temporal sulcus, the posterior
extremity of which turns upwards to terminate at B, the point which indicates,
therefore, the position of the angular gyrus.
The central sulcus of Rolando may be mapped out upon the scalp by drawing a
line downwards and forwards for a distance of 3| in. from a point half an inch behind
the mid-sagittal point M at an angle of 67 to the sagittal line (Hare). This angle
may readily be found by Chiene's plan of folding a sheet of paper first to half a right
angle and again to a quarter of a right angle (45 + 22-5 = 6 t 7'5). According to
Cunningham, the average angle which the fissure makes with the sagittal line is 70.
Kronlein's scheme for projecting the more important cerebral areas on the
surface of the cranium is as follows: A base line, the same as that advocated % by
Eeid, is drawn from the infra-orbital margin backwards through the upper border of
the external acoustic meatus to the occipital region, which it strikes a little below
the inion, Fig. 1068. A second line is drawn backwards parallel to it from the supra-
orbital margin. Three vertical lines are now projected between these two parallels:
the anterior from the centre of the zygomatic arch (C), the middle from the pre-
auricular point (D), the posterior from the posterior border of the base of the
mastoid process (E). The latter is prolonged upwards to the sagittal line on the
cranial vault, and the direction of the central sulcus of Eolando is obtained by
drawing a line from this point obliquely downwards and forwards to the point
where the anterior vertical meets the superior horizontal line (Sylvian point). The
inferior extremity of the sulcus corresponds to the point where the middle vertical
line, prolonged upwards, meets the Eolandic line. The lateral fissure line is obtained
by bisecting the angle formed by the Eolandic line and the superior horizontal line.
The topographical distribution of function in the cerebral cortex is shown in
Fig. 1068, in which the areas worked out by Grtinbaum and Sherrington in the
anthropoid apes have been transferred to the human brain. The above observers
have shown that, while the motor area occupies the whole length of the anterior
central convolution and of the central sulcus of Eolando (with the exception of its
very extremities), it nowhere extends on to the exposed surface of the posterior
central convolution ; nor does it extend as far down on the medial surface of the
hemisphere as the sulcus cinguli. Extirpation of the hand area, for example, is
THE CEANIUM.
1361
followed by severe paralysis of the hand, but the use and power of the hand is
; regained in a few weeks ; ablations, on the other hand, of even large portions of
she posterior central gyrus do not give rise even to transient paralysis.
In some of the animals experimented on, the motor area was found to extend
I to the deeper part of the posterior wall of the central sulcus of Eolando. Anteriorly
i it extended into the pre-central sulci as well as into the occasional sulci which cross
i the anterior central gyrus ; indeed the hidden part of the motor area fully equals in
FIG. 1067. CRANIO-CEREBRAL TOPOGRAPHY.
Shows relations of the motor and sensory areas to the gyri, and to Chiene's lines.
Glabella. C. Mid-point of AB.
External occipital protuberance (inion). CD is drawn parallel to AM.
Mid-point between G and 0. Z. Post-auricular point.
Mid-point between M and 0. VW. Guide to anterior limit of transverse sinus.
Mid-point between T and 0. Y. Tympanic antrum.
X 1 .
Zygomatic process of frontal.
Root of zygoma (pre-auricular point).
Mid-point of EP
Mid-point of PS r
Site at which subarachnoid space may be opened.
X 2 . Site for draining lateral ventricle (Kocher).
X 3 . Site for draining lateral ventricle (Keen).
extent that contributing to the free surface of the hemisphere. The motor areas
^xtend a little in front of the superior and inferior pre-central sulci, which cannot
therefore be regarded as physiological boundaries.
Reference to Fig. 1068 shows that, of the main areas, that for the lower extremity
occupies the upper third of the motor region, that for the upper extremity the
i middle third, while the face occupies the inferior third. The relative topography
of the chief subdivisions of these main areas is shown in Fig. 1069. It must be
remembered, however, that there exists much overlapping of the adjacent areas.
The body of the lateral ventricle, which is equal in length to the posterior
87
1362
SUEFACE AND SUEGICAL ANATOMY.
horizontal ramus of the lateral cerebral fissure, occupies a level midway
between it and the temporal line. The anterior horn of the ventricle is
opposite the lower part of the coronal suture while the posterior horn is opposite
the posterior part of the temporal line. The inferior horn corresponds to the
second temporal gyrus.
The lateral ventricle may be tapped or drained from above, by traversing brain
tissue for a depth of 4 to 5 cm. through the superior frontal sulcus, 1J in. (two
fingers'-breadth) in front of the point X 2 , Fig. 1067, the instrument being directed
downwards and backwards (Kocher).i
FIG. 1068. SCHEME SHOWING RELATIVE TOPOGRAPHY OP THE CHIEF SUBDIVISIONS OF THE MOTOR AREA
(adapted from Griinbaum and Sherrington). Guiding lines, red ; sulci, blue.
Keen drains the ventricles through an opening 1J in. behind the external
acoustic meatus and the same distance above Eeid's base-line (a line drawn back-
wards from the inferior margin of the orbit through the centre of the external
acoustic meatus, X 3 , Fig. 106*7), the instrument being passed into the brain towards
the summit of the opposite auricle. If the ventricle is not distended it will be
reached at a depth of two inches from the surface.
To open the subarachnoid space, the pin of a small trephine is placed over the
mid-point of the line EA, Fig. 1067 ; the dura is incised as it crosses the stem of the
lateral fissure of the brain from the frontal lobe to the anterior extremity of the
temporal lobe. Care must be taken to keep in front of the middle meningeal artery.
The cisterna cerebello-medullaris, situated between the under surface of the
cerebellum and the medulla obloiigata, may be reached by turning down a flap of soft
parts, and removing a circle of bone immediately above the foramen magnum. The
THE CKANIUM.
1363
fourth ventricle may be opened up by making a somewhat larger trephine opening
and separating the posterior extremities of the ton sillar lobes of the cerebellum.
To expose a hemisphere of the cerebellum, trephine over the centre of a line drawn
from the tip of the mastoid process to the external occipital protuberance.
To expose both hemispheres of the cerebellum a flap is turned downwards by
carrying a curved incision between the bases of the mastoid processes, the centre of
the incilion reaching upwards to a little above the inion. The occipital arteries are
FIG. 1069. CRANIO-CEREBRAL TOPOGRAPHY.
Guiding lines (Chiene's), deep black ; sutures, fine black ; meningeal arteries, red ; sulci, blue.
G. Glabella. C. Mid-point of AB.
0. Extemal occipital protuberance (inion). CD is drawn parallel to AM.
Mid-point between G and 0. Z. Post-auricular point.
Mid-point between M and 0. VW. Guide to anterior limit of transverse sinus.
Mid-point between T and 0.
Zygoraatic process of frontal.
Root of zygoma (pre- auricular point).
Mid- point of EP.
Mid-point of PS.
Y. Tympanic antrum.
X 1 . Site at which subarachnoid space may be opened.
X 2 . Site for draining lateral ventricle (Kocher).
X 3 . Site for draining lateral ventricle (Keen).
divided, but the anterior extremities of the incision should, if possible, be kept
behind the mastoid emissary veins. As the flap contains the suboccipital muscles
the bone itself may be removed. If more room is required, the opening in the
bone may reach above the level of the transverse sinuses without wounding them
as they can be displaced along with the dura. The occipital sinus is divided
between two ligatures. After dividing the dura a hemisphere of the cerebellum
may be displaced towards the median plane to enable the finger to be passed
1364 SUEFACE AND SUKGICAL ANATOMY.
between it and the posterior surface of the petrous portion of the temporal bone as far
as the acoustic nerve, which occupies the angle between the cerebellum and the pons.
Meningeal Arteries. When the calvaria is removed the meningeal arteries
are found to adhere firmly to the dura. Of these vessels the middle meningeal
artery is the only one of surgical importance. It is frequently lacerated in
fractures of the skull ; the blood is generally extra vasated between the dura and
the bone, and the bleeding point lies beneath the clot. After entering the cranial
cavity through the foramen spinosum, the main trunk, which is usually about
1 \ in. in length, runs laterally and slightly forwards to bifurcate into anterior and
posterior divisions at a point a finger's-breadth above the middle of the zygomatic
arch, viz., at or close behind the point N, Fig. 1069. When the main -trunk is
short the bifurcation takes place opposite the middle of the zygomatic arch.
The anterior and larger division passes upwards, with a slight forward con-
vexity, a little behind the spheno-squamosal suture and across the pterion to
the sphenoid angle of the parietal bone. From that point the vessel is continued
upwards and slightly backwards, behind the coronal suture ; it gives off branches
which ascend over the motor area. The. position and general direction of the
anterior branch may be said to correspond to the line MN ; it follows, therefore,
that the artery will be encountered in trephining over the lower and anterior part
of the Kolandic area, especially over the motor centres for the tongue and face.
The posterior division passes almost horizontally backwards, towards the
mastoid angle of the parietal bone.
To expose the trunk of the vessel and its bifurcation, the trephine is applied
immediately above the middle of the zygomatic arch. To expose the anterior
division the pin of the trephine may be applied at the point A, which strikes the
artery as it crosses the pterion and grooves the sphenoidal angle of the parietal
bone. The inferior segment of the disc of bone removed is much thicker than the
superior, as it involves the prominent ridge which passes from the tip of the great
wing of the sphenoid on to the sphenoidal angle of the parietal bone. At the
sphenoidal angle of the parietal bone, the artery frequently runs in a canal for a
distance of half an inch. It follows, therefore, that a considerable thickness of
bone has to be sawn through at the inferior segment of the circle before the disc
can be removed, and during the removal bleeding may occur from the artery as
it lies in the canal.
Vogt localises the anterior division at a point a thumb's-breadth behind the
tubercle on the posterior border of the zygomatic bone and two fingers'-breadth above
the zygoma. Kronlein trephines at a point 1J in. behind the zygomatic process of
the frontal, on a line drawn from the supra-orbital margin backwards parallel to
Keid's base-line. If the centre of the trephine be placed at the mid-point of the
lower third of the line MA. the anterior division will be reached above the canal and
the ridge at the sphenoidal angle of the parietal ; if the bleeding-point is lower
down, the trephine opening may be enlarged downwards along the line AN.
The course of the posterior division may be indicated upon the surface by draw-
ing a line backwards from the point N parallel to PK, that is to say, a finger's-
breadth above the zygoma and the supra-mastoid crest.
When the frontal branch of the anterior division is injured, the clot is in the fronto-temporal
region, and involves more especially the motor area for the face, and, on the left side, Broca's con-
volution ; when the anterior division is wounded, the clot, which is larger, involves the parieto-
temporal region, and the motor symptoms are due to pressure upon the centres for the arm and
face ; in injuries to the posterior division the clot overlies the parieto-occipital region, and the
localising symptoms are sensory (Kronlein). In more extensive meningeal haemorrhage the clot
may cover the" greater part of the hemisphere.
The superior sagittal sinus, which enlarges as it extends backwards, occupies the
median plane of the vertex from the glabella to the internal occipital protuberance,
where it opens into the confluens sinuum, and becomes continuous usually with the
right transverse sinus. Opening into the sinus, especially in the posterior part of
the parietal region, are the para-sinoidal sinuses, into which arachnoideal granulations
project. In opening the skull over the posterior part of the vertex, the edge of the
trephine should be kept at least three-quarters of an inch from the median plane.
THE CKANIUM. 1365
The transverse sinus may be mapped out on the surface by drawing a line,
slightly convex upwards, through a point a little above the inion to the asterion
(1-J in. behind and 1 in. above the centre of the external acoustic meatus) at, or
a little in front of, the point E, Fig. 1069, and thence in a downward and forward
direction to a point f in. inferior and posterior to the centre of the external acoustic
meatus, where it finally curves medially and forwards to open into the jugular
bulb, which occupies the jugular foramen. According to Moorhead the highest
part of the sinus lies a finger's-breadth above the middle of a line extending from
the inion to the middle of the external acoustic meatus. The anterior border of
the descending or mastoid portion of the sinus may be mapped out by drawing a
line VW from a point a finger's-breadth behind the post-auricular point of the
temporal crest to the anterior border of the tip of the mastoid process. In
wounds of the sinus the haemorrhage is very free, owing to the inability of its
walls to collapse, but the bleeding is easily controlled by plugging.
Of the cerebral arteries, the middle supplies almost the whole of the motor area,
and one of its lenticulo-striate branches, which enters the brain at the anterior per-
forated substance, is called " the artery of cerebral haemorrhage " from the frequency
of its rupture in apoplexy. The extravasated blood involves the motor part of the
internal capsule. The postero-medial central branches of the posterior cerebral
artery, which enter the brain at the posterior perforated substance, supply the
thalamus and walls of the third ventricle ; haemorrhage from one of these branches is
apt to rupture into the ventricle. The postero-lateral central branches of the pos-
terior cerebral artery supply the thalamus, and when one of these vessels ruptures
the haemorrhage is apt to invade the posterior or sensory part of the internal capsule.
Semilunar Ganglion. The topography of the semilunar ganglion is of im-
portance in relation to its surgical extirpation for trigeminal neuralgia.
The ganglion is situated in the dura at the apex of the petrous portion of the
temporal bone, at the medial part of the middle fossa of the base of the skull.
The surgeon reaches it by an extra-dural route through an opening in the anterior
and lower part of the temporal fossa immediately above the zygomatic arch. The
bone is removed down to or, even better, beyond the level of the infra- temporal
crest, which forms the boundary line between the lateral and basal portions of the
cranium. By temporarily resecting and depressing the zygomatic arch a portion
of the floor of the middle fossa, medial to the infra -temporal crest, can be
removed. The dura is separated from the fossa so as to admit of the ligature of
the middle meningeal artery immediately after its entrance into the cranium
through the foramen spinosum. By separating the dura still further in a medial
and forward direction, the mandibular division of the trigeminal nerve is exposed
as it enters the foramen ovale, and, after it, the smaller maxillary division, as it
passes in a forward and slightly downward direction to enter the foramen rotundum.
To expose the ganglion itself and the trunk of the nerve the dura is then carefully
separated in a backward and medial direction ; in doing this care must be taken
not to wound the cavernous sinus and the trochlear and abducent nerves which
lie in its lateral wall. The oculo-niotor nerve and the carotid artery are less
likely to be injured. The ganglion has a grayish-red colour and a felted surface,
while the portio major or trunk of the trigeminal nerve is almost white, and striated
longitudinally. After dividing the mandibular and maxillary divisions of the nerve
close to their foramina of exit, the ganglion is seized with forceps and removed by
twisting it away from its trunk and the first division.
Ear. The skin covering the lateral surface of the auricle is tightly bound
down to the perichondrium, hence inflammations of it are attended with little
swelling but much pain. The posterior auricular artery, which ascends along the
groove at the posterior attachment of the auricle, is immediately anterior to the
incision for opening the tympanic antrum.
The external acoustic canal, the general direction of which is medially, for-
wards, and downwards, possesses various curves of practical importance. The
highest part of the upward convexity, which is also the narrowest part of the canal,
'. is situated at the centre of its osseous portion ; beyond this the floor sinks to form
a recess in which foreign bodies are liable to be imprisoned. Of the two horizontal
87 a
1366
SUEFACE AND SUEGICAL ANATOMY.
curves the lateral is convex forwards, the medial concave forwards. The skin of
the osseous portion of the canal is thin and fused with the periosteum, hence
when chronically inflamed it is liable to give rise to secondary periostitis and
osseous narrowing of the canal.
The relations of the osseous walls of the canal are of importance to the surgeon.
The whole of the upper wall and the upper half of the posterior wall, developed
from the squamous portion of the temporal bone, consist of two layers of
Roof of tympanic antrura
Posterior part of middle fossa of skull
Posterior branch of middle meningeal artery
Anterior branch of middle meningeal artery
Portion of cerebellar fossa
forming posterior wall of
tympanic antrum
Interior of transverse sinus
Anterior limit of transverse sinus
Tympanic antrum
Incus
Membrana tympani
Spheno-temporal sinus
Trunk of middle meningeal artery
Tegmen tympani
Chorda tympani nerve
FIG.
Head of malleus
1070. VIEW OF THE LATERAL WALL OP THE MIDDLE EAR.
Section through the left temporal bone of a child, to show the relations of the tympanum and tympanic antrum
to the middle and posterior fossae of the skull.
compact bone, a superior and an inferior, which are continuous, the former with the
inner table, the latter with the outer table of the skull. The superior plate passes
medially to the petro-squamosal suture, where it becomes continuous with the lateral
edge of the tegmen tympani, which roofs over the epitympanic recess and the
tympanic antrum ; the lower plate bends downwards and medially at its deepest part
to form the lower and lateral wall of the recess and the anterior part of the lateral
wall of the antrum (Trautmann). It follows, therefore, that when the tympanic
antrum is abnormally small, due to sclerosis of the bone, or when it is encroached
upon by a far-forward transverse sinus, it, along with the epitympanic recess, can
be opened by perforating the junction of the upper and posterior walls of the osseous
canal, the instrument being directed medially and slightly upwards. Upon
the upper and posterior segment of the external acoustic margin is the supra-
meatal spine ; this small but important process, developed from the squamous portion,
can usually be distinctly
made out in the living sub-
ject by pressing upwards
and backwards with the
forefinger placed in the
external acoustic meatus.
The lower half of the
posterior wall of the osseous
canal (posterior part of the
tympanic plate) is fused
quadrant i SBE^li with the anterior part ol
the mastoid process, and
closes the lower and anterior
set of mastoid cells (border
cells).
Anteriorly and inferiorly the osseous canal is related respectively to the
mandibular articulation and the parotid gland ; hence it follows that blows upon the
Membrana flaccida
Anterior tympano-
malleolar fold
Handle of malleus
Antero-superior
quadrant
Posterior tympano-
malleolar fold
Lateral process of
malleus
Long crus of
incus
Postero-superior
quadrant
Postero-inferior
quadrant
Cone of light
FIG. 1071. LEFT TYMPANIC MEMBRANE (as viewed from the external
acoustic meatus). x 3. (From Howden.)
THE CKANIUM.
1367
chin may fracture the tympanic plate as well as the base of the skull, that pain on
mastication is usually complained of in acute inflammatory affections of the meatus
and middle ear, and that in young children, in whom the tympanic plate is incom-
pletely ossified, suppurative inflammation is liable to extend from the ear to the
parotid region.
Clinically, to obtain a view of the membrana tympani a speculum and a reflecting
)r are employed ; the auricle is pulled upwards, backwards, and laterally in order to
Middle fossa of skull
Tensor tympani muscle
Processus cochleariformis
Eminence of lateral
semicircular canal
/ Tympanic antrum
Auditory tube
Retro-pharyngeal lymph gland
Internal carotid artery
Internal jugular vein
-Tranverse sinus
Posterior fossa of skull
\Rudimentary mastoid process
Facial nerve
Pyramid
Section of jugular fossa
Stapes
Promontory
FIG. 1072. VIEW OF THE LABYRINTHINE WALL OF THE MIDDLE EAR.
tion through the left temporal bone of a child, to show the relations of the tympanum and tympanic antrum
to the middle and posterior fossae of the skull.
straighten the cartilaginous part of the canal. The healthy membrane is pearly gray, semi-
opaque, slightly concave, and obliquely placed, being inclined laterally, especially above
and behind.
The handle and lateral process of the malleus, both embedded in the membrana tympani,
: are the only objects distinctly seen when the healthy ear is examined with the speculum.
Groove for posterior branch of middle meningeal artery
Aditus ad antrum
\
Tympanic antrum
Transverse sinus-
Incus
Middle cranial fossa
/ Tegmen tympani
^ Epitym panic recess
^-Chorda tympani nerve
I ^.Tensor tympani muscle
- Handle of malleus
-Carotid canal
.Tympanic membrane
_ Jugular fossa
i__Styloid process
Mastoid process
Stylo-mastoid foramen
i. 1073. SECTION THROUGH LEFT TEMPORAL BONE, SHOWING TYMPANIC WALL OF TYMPANIC CAVITY, ETC.
The lateral process of the malleus projects laterally, and presents itself, therefore, as a
distinct knob-like projection at the superior part of the membrane ; passing forwards and
1 backwards from this process are the anterior and posterior malleolar folds of the membrana;
they form the lower limit of the pars flaccida of the membrane, and correspond to the line
of the chorda tympani nerve. The handle of the malleus, situated at the junction of the
two upper quadrants, is seen passing downwards and backwards to the point of maximum
1368
SUKFACE AND SURGICAL ANATOMY.
concavity of the membrane (umbo), situated a little below its centre (Fig. 1071); passing
downwards and forwards from the umbo is the triangular cone of reflected light, to which
too much importance must not be attached, since its appearances vary considerably in
healthy ears. Normally, the long crus of the incus is but faintly visible, and still less
so are the promontory and fenestra cochleae; in the condition of obstruction of the
auditory tube (Eustachian), however, in which the membrane is indrawn, these structures,
along with the folds of the drum-head, become more distinct.
In performing the operation of paracentesis of the tympanic membrane the postero-
inferior quadrant is the site chosen for making the puncture, as, in addition to providing
good drainage, it is farthest removed from important structures, especially the chorda
tympani nerve.
In order to understand the clinical importance of the parts seen through the trans-
lucent membrane, it is necessary to study the relative position of the structure of the
" mesotympanum" that is to say, that part of the tympanum which lies opposite the
tympanic membrane. If the tympanic plate and the tympanic membrane be carefully
removed so as to leave the ossicles and chorda tympani nerve in position, it will be seen
Roof of tympanic antrum
Middle cranial fossa
Tympanic antrum
Groove for transverse sinus
Portion of lateral semi-
circular canal
Elevation caused by
canalis facialis
Groove for
middle menin-^
geal artery
Head of
malleus
Body of incus
Canal for tensor tympani muscle
Carotid canal
Membrana tympani
Styloid process
Facial nerve
Posterior margin of jugular foramen
FIG. 1074. SECTION THROUGH PETROUS PORTION OF TEMPORAL BONE OF ADULT.
Showing the relation of the tympanum to the middle and posterior fossae of the skull.
that the head of the malleus and the body and short crus of the incus are altogether
above the tympanic membrane, and that they occupy the tympanic attic or epitympanic
recess (Fig. 1074). At the junction of the two upper quadrants of the membrane is the handle
of the malleus, which is directed downwards, backwards, and medially. The lateral process
of the malleus is directed laterally a little below the deepest part of the roof of the
osseous external acoustic canal. Opposite the postero-superior quadrant are the long
crus of the incus, which descends behind and almost parallel to the handle of the
malleus, and the stapes, which is directed medially and slightly backwards to the fenestra
vestibuli. The chorda tympani nerve runs from behind forwards between the lateral surface
of the superior part of the long crus of the incus and the medial surface of the neck of
the malleus. At the deepest part of the roof of the osseous canal, above the chorda
tympani nerve and the lateral process of the malleus, is a notch (notch of Rivinus}, which
is occupied by the flaccid and highest portion of the membrana tympani (ShrapnelVs
membrane}. Opposite the postero-inferior quadrant of the drum-head is the promontory
caused by the first part of the cochlea, below and behind which is the fenestra cochleae.
Opposite the antero-superior quadrant are the processus cochleariformis, the tendon of the
tensor tympani, and the passage leading towards the auditory tube.
The labyrinthine wall of the tympanic cavity is related to the internal ear. The
tegmental wall is separated from the middle fossa of the skull and the under surface of the
temporal lobe of the brain by the tegmen tympani a thin plate of bone, which is continued
THE CKANIUM. 1369
[ anteriorly to form the roof of the osseous portion of the auditory tube, while posteriorly
|j it roofs over the tympanic antrum. Laterally the tegmen is limited by the petro-
squamous suture, which may remain unossified for some years after birth, thus
affording a channel along which pyogenic infection may spread from the middle ear to the
meninges and brain. Infection may also spread along the small veins which convey blood
from the tympanum to the superior petrosal and transverse sinuses.
The jugular wall of the tympanum is formed mainly by the bone forming the jugular
fossa, which is occupied by the bulb of the internal jugular vein. When the transverse sinus
is large and unusually far forward the bulb is likewise large, and the fossa, which is con-
sequently deeper, may arch up into the jugular wall of the tympanic cavity, from which it
may be separated merely by a thin and translucent plate of bone which occasionally shows
an osseous deficienc} 1 -. In cases where this condition existed the jugular bulb has been
wounded in the operation of paracentesis of the tympanic membrane.
Anteriorly the tympanic cavity leads into the auditory tube, which brings it into
communication with the nasal part of the pharynx. In the child the auditory tube is
shorter, wider, and more horizontal than in the adult, hence inflammations are more
liable to spread along it to the tympanum.
Above the level of the membrana tympani is the epitympanic recess, which communi-
cates posteriorly by means of a triangular opening (aditus ad antrum) with the tympanic
antrum ; the base of the triangle, directed upwards, is formed by the tegmen tympani ;
its apex, directed downwards, is formed by the meeting of the medial and lateral walls.
The opening will admit an instrument half a cm. in diameter. The epitympanic recess
contains from before backwards the head of the malleus, the body and short crus of
the incus, the latter projecting backwards into the aditus. When these structures
are covered with inflamed mucous membrane or granulations, drainage from the
tympanic antrum into the tympanum proper is interfered with. The boundaries of the
aditus, important surgically, are as follows : superiorly, the tegmen tympani ; medially, an
eminence of compact bone, containing the lateral semicircular canal, inferior and anterior to
which is a second smaller prominence, corresponding to that portion of the facial canal
which curves immediately above and behind the fenestra vestibuli. The wall of the facial
canal is here thin and not infrequently deficient, in which case inflammation may readily
spread from the tympanum to the facial nerve. The lateral wall of the aditus is formed by
the deepest part of the upper and lateral wall of the osseous external -acoustic meatus.
The posterior wall of the tympanum, below the aditus ad antrum, is formed by diploic
bone which contains the descending portion of the facial canal.
The tympanic antrum is to be considered, developmentally as well as anatomically,
as an extension upwards and posteriorly of the tympanum (Fig. 1073). Its ana-
tomy and relations will be best understood by studying it in the child, in whom it
is relatively larger than in the adult. Situated above and posterior to the tympanic
cavity proper, its lateral wall is formed by a triangular plate of bone which descends,
behind the external acoustic process, from the squamous portion. Posteriorly,
this triangular plate is separated from the petro-mastoid element by the squamo-
mastoid suture, which overlies the posterior part of the antrum and transmits
small veins to the surface. The suture does not become completely ossified until
a year or two after birth, and remains of it may frequently be detected in the
adult bone. The anterior and superior portion of the triangular plate turns medially
at an angle to form the upper and posterior wall of the rudimentary osseous canal,
as well as the floor of the epitympanic recess.
In the adult the lateral wall of the tympanic antrum is formed by a plate of bone,
from \ to | in. in thickness, which occupies the triangular and somewhat depressed
area between the ridge extending, posteriorly and slightly upwards, from the
posterior root of the zygoma (supra -mastoid portion of temporal crest), and
the superior and posterior quadrant of the osseous external acoustic meatus; upon
the latter is the supra-meatal spine, immediately posterior to which, upon the floor
of the above triangle, is a crescentic depression, the fossa mastoidea. The lateral
wall of the antrum is felt through the skin as a slight depression immediately
behind the auricle, and immediately inferior to the ridge formed by the supra-mastoid
crest ; below the depression is the prominence corresponding to the insertion of
the sterno-mastoid muscle. Trautmann has pointed out, however, that the supra-
mastoid crest, which varies considerably in its obliquity, is sometimes situated a
little above the level of the roof of the antrum, and that it is safer, therefore, to
1370
SUKFACE AND SUKGICAL ANATOMY.
take the level of the superior border of the osseous meatus as the guide in order to
avoid opening the middle fossa of the skull. In children the supra-mastoid crest
is not developed, so that if the operator mistake the posterior root of the zygoma
for the crest, he will open into the middle fossa of the skull immediately in front
of the epitympanic recess. The upper and posterior quadrant of the osseous meatus
is therefore the only reliable guide to the antrum in the child.
The medial wall is formed by a thick plate of spongy bone which separates the
antrum from that portion of the posterior fossa lying between the aqueduct of
the vestibule and the groove for the sigmoid portion of the transverse sinus, and
which contains the posterior semicircular canal.
The roof, which slopes downwards and forwards, is formed by the posterior and
thinnest part of the tegmen tympani.
The floor is on a lower level than the aditus, and is therefore unfavourably
placed for natural drainage.
The mastoid process begins to develop in the second year. As development
advances the diploe surrounding the antrum in the child becomes excavated to
FIG. 1075. FRONTAL SINUSES OF AVERAGE
DIMENSIONS, WITH A MEDIAN SEPTUM (Logan
Turner).
FIG. 1076. A LARGE RIGHT FRONTAL
SINUS WITH SEPTUM OBLIQUE TO THE
LEFT (Logan Turner).
form the mastoid cells, which radiate from the antrum, and either directly or
indirectly communicate with it by small openings. In the pneumatic type of
mastoid the whole of the process is excavated by these cells, which extend
upwards into the squamous portion, forwards to the posterior wall of the osseous
meatus (border-cells), and backwards into the occipital bone. Pus retained within
the " border-cells " may bulge into, and rupture through, the posterior wall of the
osseous meatus. Less frequently the mastoid cells are absent, the bone consisting
either of osseous tissue similar to that of the diploe, or of dense bone (sclerosed type).
The mastoid portion of the temporal bone is grooved, upon its medial surface,
by the sigmoid portion of the transverse sinus. The average distance of the fore-
most part of the sinus from the supra-meatal spine is 1 cm. The right sinus
usually receives the superior sagittal sinus, and when this is the case it is larger
and farther forward than the left ; in extreme cases it may reach to within 2 or
3 mm. of the meatus. The average minimum distance of the transverse sinus
from the outer surface of the mastoid is about 1 cm., but when the sinus is large
and far forward the thickness may be reduced to 1 or 2 mm.
The facial nerve, after entering the facial canal at the bottom of the internal
acoustic meatus, lies immediately above and behind the fenestra vestibuli, between
it and the prominence of the lateral semicircular canal ; thence it descends almost
vertically in the mastoid wall of the tympanum in. posterior and medial to the
THE CKANIUM.
1371
i nferior half of the deepest part of the posterior wall of the external osseous canal
und emerges through the stylo-mastoid foramen (Fig. 10*73).
In the infant, in consequence of the absence of the mastoid process, the exit of
,he facial nerve from the stylo-mastoid foramen is unprotected and exposed upon
*}he lateral rather than upon the basal surface of
j ;he skull, at a point immediately behind the
posterior segment of the tympanic horse-shoe.
tt follows, therefore, that, in infancy, the incision
;o expose the antrum should not be curved too
:ar downwards and forwards, otherwise the facial
; lerve may be divided. In the infant the position
)f the tympanic antrum is relatively higher than
J.n the adult, because in the former the upper
{.vail of the osseous canal inclines towards the
vertical plane instead of being horizontal.
The lymph vessels from the auricle and ex-
ternal meatus open into the posterior and anterior
luricular lymph glands, the latter receiving also
:he lymph from the middle ear. The efferent
vessels from those glands open into the superior
mb-sternomastoid glands ; hence it is that those
groups of glands are so frequently found to be
liseased secondary to tuberculosis of the middle
jar ; and care must be taken not to mistake an
ibscess in one of the mastoid glands for sub- FIG. 1077. RIGHT FRONTAL SINUS OF
)eriosteal mastoid suppuration associated with VEBY LARGE DIMENSIONS ; LEFT SINUS
niddle-ear disease.
UNOPENED (Logan Turner).
To open the tympanic antrum the surgeon makes a curved incision a little behind the
Attachment of the auricle, and chisels or drills away the bone immediately above and
>ehind the postero-superior quadrant of the external osseous meatus. In this operation
he middle fossa of the skull is avoided by keeping below the supra-mastoid crest ; the
ransverse sinus, by keeping close to the external acoustic canal and by chiselling obliquely
o the surface in opening the mastoid cells ; the descending portion of the facial nerve is
ivoided by not encroaching upon the inferior half of the deepest part of the posterior wall
>f the osseous canal. In extending the operation from the tympanic antrum through the
xlitus into the epitympanic recess, the lateral semicircular canal and the curve of the
'acial nerve, which lie in relation to the medial wall of the aditus, are liable to injury,
aid must be protected either by a curved probe, or, better, by a Stacke's protector, passed
rom the antrum through the aditus into the tympanic cavity.
The frontal air sinuses are two cavities situated immediately above the root of
be directed medially with a slight inclination upwards and backwards. After
i perforating the masseter and temporal muscles, the instrument enters the fatty
J tissue of the infra-temporal fossa, embedded in which is the internal maxillary
I artery and some veins. By passing the needle still more deeply, it is made to
[penetrate between the two heads of the external pterygoid muscle through the
I pterygo-maxillary fissure into the pterygo-palatine fossa. If the instrument be
i passed too far forwards it will strike the maxillary tuberosity ; if too far back-
i\ wards, the lateral pterygoid lamina. The oedema of the eyelids which not in-
frequently follows the operation is due to some of the fluid passing upwards into
I the orbit through the inferior orbital fissure. The distance from the skin to the
'i nerve, as it lies in the pterygo-palatine fossa, is practically 2 in. Should the
needle, after perforating the masseter, strike the coronoid process of the mandible,
[the latter may be depressed by opening the mouth.
The mandibular nerve is injected immediately beyond its exit from the
foramen ovale, which lies 4 cm. from the skin in the same vertical frontal plane
1376 SUKFACE AND SUKGICAL ANATOMY.
as the tuberculum articulare. When the mouth is opened widely the condyle of
the mandible travels forwards and can be distinctly felt immediately below
the tubercle. To avoid entering the mandibular joint the needle is intro-
duced through the skin immediately below the zygoma, a little in front of the
eminence. It is pushed medially and slightly backwards through the sigmoid
notch of the mandible, and thence through, or immediately above, the external
pterygoid muscle, into the nerve. Symington points out that "the chief dangers
connected with this operation are dependent upon the needle being passed in too
far. Thus, if it be directed straight inwards beyond the depth of the nerve (4 cm.)
it would penetrate the tensor veli palatini and the auditory tube and open on the
lateral wall of the naso-pharynx ; or, if directed somewhat upwards, it might pass
through the foramen ovale, and even reach the cavernous sinus and the internal
carotid artery, as the medial boundary of the foramen slopes upwards and inwards."
The facial nerve, after emerging -from the stylo-mastoid foramen, is embedded
in the parotid gland, where it is superficial to the external carotid artery; the
nerve can be rolled under the finger as it crosses the posterior border of the
ramus of the jaw^at the level of the lower margin of the tragus; incisions con-
tinued along the ramus above this point should be only skin deep if the nerve is
to be avoided. To expose the trunk of the nerve an incision is made from the
anterior border of the mastoid process to the angle of the mandible. Incisions
upon the cheek should, whenever possible, be planned so as to run parallel with the
branches of the nerve ; these radiate from the inferior end of the tragus. The
nerve may be paralysed by wounds of the cheek and by malignant tumours of the
parotid, as also by intra-cranial and middle-ear lesions.
The parotid gland is surrounded by a fascial envelope, the strongest portion of
which is continued from the deep cervical fascia over its superficial aspect to
become attached to the zygoma (Fig. 1085) ; hence abscesses in the parotid tend
to burrow deeply towards the pterygo-palatine fossa and the superior part of the
pharynx (Fig. 1085) ; the pus should therefore be evacuated by Hilton's method,
through an early incision over the angle of the mandible. A study of the relations
of the gland explains the surgical difficulties which attend its complete removal.
The parotid duct can be rolled beneath the finger as it crosses the masseter,
rather less than a finger's breadth below the zygoma. After winding round the
anterior border of the muscle it soon pierces the buccinator, and opens into the
mouth opposite to the second molar tooth of the maxilla. The duct corresponds
to the intermediate third of a line drawn from the inferior margin of the concha
to a point midway between the ala nasi and the margin of the upper lip.
Superficial to the parotid and a little in front of the tragus is the pre-auricular
lymph gland, which is frequently found to be inflamed in children suffering from
eczematous conditions of the eyelids, face, scalp, and external ear. In opening
an abscess connected with this gland care must be taken to make the incision as
low down as possible, so as to avoid the parotid duct.
The deep parotid lymph glands which lie partly in the substance of, and partly
deep to, the inferior part of the parotid, form the highest group of the medial superior
deep cervical lymph glands. They are especially liable to become infected secondary
to tuberculous disease of the middle ear and to malignant affections about the root
of the tongue, the fauces, and the naso-pharynx. In removing them it is generally
impossible to avoid dividing the cervical branch of the facial nerve, which pierces
the cervical fascia immediately below and behind the angle of the mandible.
This nerve supplies the platysma and the depressor labii inferioris muscles, so
that its division gives rise to inability to depress the lower lip on the affected side.
At the same operation some trouble may be caused by bleeding from the posterior
facial vein and its divisions, which traverse the substance of the gland.
Eyelids. The skin of the eyelids, more especially of the upper, is very thin and
connected with the orbicularis oculi muscle by delicate and lax subcutaneous tissue
destitute of fat ; hence the marked swelling which occurs in a " black eye " and in
oedema of the lids. Along the anterior edge of the free margins of the lids are the
eyelashes and the orifices of the sebaceous glands, suppurative inflammation of
which gives rise to a " stye " ; along the sharp posterior edge of the free margins
THE FACE. 1377
ire the minute orifices of the tarsal glands. These glands, embedded in the deep
surface of the tarsi, are seen through the palpebral conjunctiva as a row of parallel,
yellowish, granular-looking streaks. From the deep position of the glands it follows
bhat the skin over a Meibomian cyst is freely movable, and that to reach the cyst
in incision should be made through the coujunctival surface of the lid.
The palpebral conjunctiva is closely adherent to the ocular surface of the tarsi ;
it the fornix it is loose and contains small lymph follicles, which become hyper-
t brophied in the condition known as granular conjunctivitis. The ocular conjunctiva
is thin, transparent, and loosely attached to the sclera, so that in operating upon
*bhe eye a fold of the membrane can be picked up with forceps to steady the
3yeball.
In inflammatory affections of the eye the state of those vessels which are visible gives
\ mportant information as to the seat of the mischief. For example, in inflammation of
phe conjunctiva the posterior conjunctival vessels (derived from the palpebral arteries),
: scarcely visible normally, appear as a close network which fades away towards the corneal
inargin ; these vessels move freely with the conjunctiva, and do not disappear under pres-
sure. In superficial inflammations of the cornea the anterior conjunctival vessels (the
jnost superficial of the terminal branches of the anterior ciliary arteries) are seen to
j spread in a freely branching manner into its superficial layers. In iritis and deep inflam-
mations of the cornea there is a pink circumcorneal zone of vascular dilatation consisting
i )f delicate straight vessels which disappear under pressure and do not move with the con-
[ unctiva; they are the subconjunctival (episcleral) terminations of the anterior ciliary
irteries ; in health they are invisible.
Lacrimal Apparatus. The lacrimal gland, situated behind the lateral part
)f the supra-orbital margin, cannot be felt unless enlarged. By everting and
raising the upper eyelid, the accessory (palpebral) portion of the gland is seen to
; project beneath the lateral third of the fornix, in which situation also the minute
;:>rinces of the lacrimal ducts may be detected. By gently drawing downwards
ihe lower lid, the small punctum lacrimale is seen situated upon a slight papillary
Blevation of its margin about 4 mm. from the medial palpebral commissure , the
3orresponding orifice of the upper lid is placed a little nearer the commissure.
Normally the puncta are directed towards, and accurately applied to, the ocular
3onjunctiva immediately lateral to the lacrimal caruncle. By drawing the lids
laterally the medial palpebral ligament is put upon the stretch, and can be felt as
i a, narrow tense band passing transversely medially to be attached to the frontal
: process of the maxilla. The ligament is a guide to the position of the lacrimal
sac, which it crosses a little above its centre. Continuous with the inferior end
of the lacrimal sac is the naso-lacrimal duct, which passes downwards and slightly
backwards and laterally, to open into the inferior meatus of the nose, under cover
of the anterior end of the inferior concha. The lacrimal sac and naso-lacrimal
duct each measure about \ in. in length ; the latter is slightly contracted at its
commencement and termination, and it is in these situations that pathological
strictures of the duct are commonest. Spontaneous rupture of an abscess of the
lacrimal sac almost invariably occurs just below the medial palpebral ligament ;
it is in this situation that the abscess should be opened, the incision being made
: a little lateral to the angular termination of the external maxillary artery.
The canaliculi lacrimales, which convey the tears from the puncta to the lac-
rimal sac, run for the first 1-2 mm. almost vertically to the free margins of the
, lids, and thence parallel to them. Between the canaliculi is the lacrimal caruncle.
In the various morbid conditions which give rise either to misdirection of the
puncta or to stricture at any part of the lacrimal drainage apparatus, overflow
of the tears (epiphora) is the chief symptom. In passing a probe along a
icanaliculus the instrument, in consequence of the bend upon the duct, is
passed at first vertically to the margin of the lid, and afterwards parallel to it,
i until the point is felt to strike against the medial wall of the lacrimal sac; to
.pass the instrument onwards along the naso-lacrimal duct the handle is rotated
i forwards and upwards through a quarter of a circle, and then pushed gently down-
wards and slightly backwards and laterally into the inferior meatus of the nose.
88
1378 SUKFACE AND SUKGICAL ANATOMY.
The tarsi are attached to the periosteum of the orbital margins by the superior
and inferior palpebral ligaments which shut off the communication between the sub-
cutaneous tissue of the eyelids and the fatty tissue of the orbital cavity. In fracture
of the anterior fossa of the base of the skull involving the orbital part, the blood
extends forwards between the periosteum and the musculo-fascial envelope of the
orbit and appears under the conjunctiva.
To obtain free access to the cavity of the orbit, the surgeon first enlarges the
palpebral fissure by making a horizontal incision from the lateral palpebral com-
missure to the lateral margin of the orbit, and then, after everting the eyelid,
divides the conjunctiva along the fornix of the upper or lower lid, or of both, as
may be desired.
Nose. To examine the anterior nares (anterior rhinoscopy} a strong light is
reflected into the nostril, which is dilated by means of a nasal speculum. The
anterior extremity of the inferior concha appears as a rounded body projecting
from the lateral wall of the nose ; in turgescence of its erectile tissue it is liable
to come in contact with the nasal septum and so occlude the nostril. The inferior
meatus, situated between the inferior concha and the floor of the nasal cavity, is
brought into view by tilting forwards the head. The inferior aperture of the naso-
lacrimal duct is concealed from view by the anterior part of the inferior concha.
The floor of the nose is horizontal and placed on a slightly lower level than the
anterior nares. The septum, generally more or less deviated to one or other side,
is seen when the head is slightly rotated away from the side to be examined. The
anterior extremity of the middle concha, which lies a little behind and medial to
the lower-medial angle of the orbital margin, is seen when the patient's head is
thrown well back ; between it and the septum is a slit-like interval (olfactory cleft}.
By rotating the patient's head towards the corresponding shoulder the anterior part
of the middle meatus is brought into view ; pus in that situation may originate from
the frontal, the anterior ethmoidal, or the maxillary sinuses, all of which open into
the hiatus semilunaris of the middle meatus.
To make a satisfactory digital exploration of the anterior part of the nasal
cavities, it is necessary to divide the columella and the cartilaginous septum with
a strong pair of scissors, one blade being introduced into each nostril (Kocher) ;
blood spurts from the small arteries of the septum, but the bleeding soon ceases.
When these vessels, which are derived from the superior labial arteries, are the
source of the haemorrhage in epistaxis, the bleeding can be arrested either by com-
pressing the superior labial arteries, by plugging the anterior nares, or by grasp-
ing the cartilaginous part of the nose firmly between the finger and thumb.
The maxillary sinus (O.T. antrum of Highmore), situated in the maxilla, is a
pyramidal cavity with its base formed by the lateral wall of the nose and its
apex directed towards the zygomatic bone. The cavity is lined by a thin rnuco-
periosteal membrane, easily separable from the bone ; in the mucous layer are
numerous mucous glands from which cysts may develop. The floor of the sinus,
which is at or a little below the level of the floor of the nose, is separated from
the roots of the premolar and molar teeth by a plate of bone of varying thickness.
When this plate is thin and devoid of spongy bone, the floor of the sinus sinks below
the level of the floor of the nose, and suppuration at the roots of one of the teeth
above mentioned is, in these circumstances, very liable to extend to the sinus. In
a sinus of average dimensions the line of union of the nasal and facial walls of
the cavity corresponds externally to the lateral edge of the canine ridge (Logan
Turner). The nasal orifice is situated at the highest part of the sinus, and
is therefore unfavourably placed for natural drainage ; it opens into the posterior
and lower part of the infundibulum, which in its turn communicates with the
middle meatus of the nose through the hiatus semilunaris. In old age there is
frequently a second communication between the sinus and middle meatus, the
opening being situated posterior to and below the normal orifice ; when this accessory
aperture exists, pus from the sinus may drain backwards into the nasal part of
the pharynx (Logan Turner). In empyema of the sinus the opening to evacuate
and drain the cavity may be made (1) through the alveolus of the second premolar
or of the first or second molar tooth, the first molar being the site of election;
THE FACE.
1379
} (2) through the canine fossa, lateral to the prominence caused by the root of the
canine tooth ; or (3) through the lateral wall of the inferior meatus of the nose.
In an antero-posterior skiagram of the skull, the shadow of the maxillary sinus
r presents a pyramidal outline, the base corresponding to the floor of the orbit and
j pulmonary, aortic, mitral, and tricuspid. When delineated on the
surface they will be seen to lie within an ellipse whose long axis extends from the
superior border of the third left to the sixth right chondro-sternal junction.
The pulmonary orifice, directed upwards and slightly backwards and to the left,
lies opposite the superior border of the third left chondro-sternal junction ; the aortic
orifice, directed upwards, backwards, and to the right, lies further from the surface,
behind the left half of the sternum, opposite the inferior border of the third costal
cartilage ; the mitral orifice lies at an inferior level, behind the left half of the sternum,
opposite the fourth rib ; the orifice of the opening is directed downwards, forwards,
and to the left. The tricuspid orifice, situated nearer the anterior wall of the chest
than the mitral, lies very obliquely behind the right half of the sternum at the
level of the fourth and fifth cartilages and intervening space.
Although the first and second sounds of the heart are heard all over the cardiac area, the
sounds produced by the individual valves are heard most distinctly, not directly over their ana-
tomical situation, but over the area where the cavity in which the valve lies approaches nearest
to the surface. Hence the mitral sound is best heard over the apex (mitral area), the tricuspid
over the inferior part of the body of the sternum (tricuspid area), the aortic over the second right
costal cartilage (aortic area), and the pulmonary over the second left intercostal space (pulmonary
area).
In tapping the pericardium (paracentesis pericardii) the pleura will be avoided by making
the puncture through the fifth or sixth left intercostal space as close as possible to the edge of the
sternum. When, however, the pericardial sac is distended with fluid, the pleura is pushed
laterally, and will therefore escape injury if the puncture is made at a safe distance lateral to
the internal mammary vessels, viz. , one inch lateral to the left border of the sternum.
To establish free drainage in suppurative pericarditis, the sixth left costal cartilage must be
resected and the internal mammary vessels ligatured ; the transversus thoracis and the pleural
reflection are then pushed aside and the pericardium exposed and incised.
The ascending aorta lies behind the sternum, opposite the second and third ribs,
and, unless dilated, does not project beyond its right border. The superior border
of the aortic arch lies at or a little above the centre of the manubrium sterni ; in
the child the vessel may reach as high as the superior border of the manubrium.
The innominate and left common carotid arteries diverge from either side of the
median plane between the upper part of the manubrium sterni and the front of
the trachea. A pin pushed directly backwards immediately above the middle of
the supra-sternal notch will strike the medial border of the innominate artery a
little below its bifurcation.
The pulmonary artery lies behind the left border of the sternum opposite the
second interspace and the second costal cartilage.
The left innominate vein lies behind the superior part of the manubrium sterni,
the right behind the medial end of the right clavicle. The superior vena cava lies
immediately to the right of the margin of the sternum, opposite the first
and second interspaces and the intervening second rib ; its opening into the right
atrium, behind the third chondro-sternal articulation, corresponds to the centre of
the root of the right lung.
1406
SUKFACE AND SUKGICAL ANATOMY.
FIG. 1097.
FIG. 1098.
r
FIG. 1099.
FIG. 1100.
From photographs of a formalin-hardened subject, with the heart dissected in situ, to show the relations of :
cavities and valves to the anterior wall of the thorax.
In Fig. 1097 the anterior wall of the right ventricle has been removed and the pulmonary artery opened.
In Fig. 1098 the anterior walls of the ascending aorta and of the right atrium have been removed ; also t
anterior cusp of the tricuspid valve.
In Fig. 1099 the greater part of the interventricular septum has been removed, exposing the anterior cusp
mitral valve.
In Fig. 1100 the ascending aorta, anterior cusp of mitral valve, trunk of pulmonary artery, and interauricu!
septum have been removed ; the cavities of the left atrium and left ventricle are exposed, also the I
auricle and posterior cusp of mitral valve.
R.A. Right atrium. P. A. Pulmonary artery. M.V. Mitral valve.
R.V. Right ventricle. P.V. Pulmonary valve. S.V.C. Superior vena cava.
L.A. Left atrium. A. Aortic arch. P.V. Pulmonary vein.
L.A.A. Left auricle. A.V. Aortic valve. M. Moderator band.
S.V. Interventricular septum. T.V. Tricuspid valve.
THE ANTERIOE ABDOMINAL WALL. 1407
(ESOPHAGUS.
The average length of the oesophagus in the adult is 10 in. (25 cm.); the
distance from the incisor teeth to its commencement is 6 in. ; to the point or
level where it is crossed by the left bronchus, 9 in. ; to the oesophageal opening
of the diaphragm, 14 to 15 in. ; to the cardiac orifice of the stomach, 16 in. These
measurements, which are of great importance in diagnosing the seat of oesophageal
obstructions, should be marked off from below upwards upon all oesophageal
bougies and probangs. Posteriorly, the oesophagus extends from the level of the
sixth cervical spine to that of the tenth thoracic, a little to the left of which
is the. situation at which the stethoscope is placed in order to hear the sound pro-
duced by the passage of fluid into the stomach.
Clinically it is important to bear in mind the relation of the oesophagus to the trachea and
left bronchus, to the left recurrent nerve, to the bronchial and posterior mediastinal glands,
to the descending thoracic aorta, and to the right posterior mediastinal pleura. Ulcers of
the oesophagus are liable to open into either the trachea, the left bronchus, or the right pleura.
The veins of the inferior end of the oesophagus open partly into the systemic veins and partly
into the portal system ; like those at the inferior end of the rectum they are liable to become
varicose in conditions which give rise to chronic interference with the portal circulation.
The lymph vessels of the upper part of the oesophagus 'open into the inferior deep cervical
glands, the remainder into the posterior mediastinal glands.
The oesophagus is very distensible in the transverse but not in the antero -posterior direction,
hence the most useful forceps for removing foreign bodies from the oesophagus are those which open
laterally.
THE ABDOMEN.
THE ANTERIOR ABDOMINAL WALL.
The configuration of the abdomen varies with the age, sex, obesity, and muscular
development of the individual. In the child it is wider above than below, while
the reverse is the case in the adult female. It is most prominent in the region of
the umbilicus, which is situated, normally, below the mid-point between the infra-
sternal notch and the symphysis pubis, usually a little below the level of the highest
part of the iliac crest, and opposite the middle of the body of the fourth lumbar
vertebra. In the obese, and especially when the abdominal muscles have lost their
tone, the umbilical region becomes prominent and more or less pendulous, so that
the umbilicus may come to lie considerably below the normal level. In the child
it is relatively lower than in the adult, in consequence of the undeveloped state of
the pelvis.
In spare subjects the inferior end of the body of the sternum, the xiphoid
process, and the costal margin, can readily be traced. The slight depression or
notch formed by the seventh costal cartilages and the inferior border of the body
of the. sternum is termed the infrasternal notch. Below the notch, and bounded
on each side by the seventh, eighth, and ninth costal cartilages, is the infracostal
angle, which varies considerably according to the shape of the chest ; it is relatively
wider in the child than in the adult. The inferior border of the curve of the
tenth costal cartilage is easily recognisable, and was selected by Cunningham as
the level of the plane of separation (infracostal plane) between the upper and
middle abdominal zones.
The anterior abdominal wall is limited below by the fold of the groin and the
crest of the pubes. In a spare muscular subject the recti, the furrows correspond-
ing to the inscriptiones tendineae (O.T. linese transversse) and the supra-umbilical
portion of the linea alba, can be readily made out. When the outline of the
rectus is not visible the lateral border may be indicated by a line drawn from the
tip of the ninth costal cartilage to the mid-point of a line joining the umbilicus
and the anterior superior iliac spine, and from thence to the pubic tubercle. In
the angle between the lateral border of the rectus and the ninth costal cartilage,
on the right side, is a slight triangular depression which overlies the fundus of
the gall-bladder. Between the inferior part of the lateral border of the rectus and
the prominence above the anterior part of the iliac crest, caused by the lower
1408
SUKFACE AND SUKGICAL ANATOMY.
muscular fibres of the external oblique, is another slight triangular depression,
which corresponds to the inferior and narrow part of the aponeurosis of the external
oblique muscle.
Close above, and almost parallel to, the medial half of the inguinal ligament
is the inguinal canal, traversed by the spermatic funiculus (Fig. 1101); the latter
can be felt to emerge at the subcutaneous inguinal ring immediately above the
pubic tubercle. The abdominal and subcutaneous inguinal rings have been fully
described elsewhere; the former is triangular in shape, with its apex directed
superiorly and laterally, and its base immediately above the pubic crest. By
invaginating the skin of the scrotum the little finger may be passed through the
ring into the canal. It is to be noted that the neck of an inguinal hernia lies
above the pubic tubercle, whereas the neck of a femoral hernia emerges below the
medial end of the inguinal ligament, lateral to the pubic tubercle. The abdominal
inguinal ring, an opening in the fascia transversalis, lies half an inch above a
Obliquus externus abdominis
Obliquus interims abdominis
Obliquus interims
abdominis (cut)
Deep circumflex iliac artery
Abdominal inguinal ring and
internal spermatic fascia
Cremaster muscle
Obliquus externus abdominis
Spermatic funiculus passing
through cremaster muscle
)bliquus externus abdominis
bliquus internus abdominis (cut)
Transversus abdominis
Over inferior epigastric artery
Fascia transversalis
Inferior epigastric artery
Falx aponeurotica inguinal is
Over lateral border of rectus abdominis
Spermatic funiculus
Lig. retiexum inguinale
FIG. 1101. THE GROIN. The structures seen on reflection of part of the obliquus internus abdominis
(A. M. Paterson).
point a little medial to the middle of the inguinal ligament. The inferior epi-
gastric artery may be mapped out by drawing a line from a point midway between
the superior anterior iliac spine and the symphysis pubis towards the umbilicus.
The vessel, together with the medial third of the inguinal ligament and the
inferior part . of the lateral border of the rectus, bounds a triangle known as
Hesselbach's triangle. As the inferior epigastric artery passes superiorly and
medially to disappear behind the falx aponeurotica inguinalis and the lateral
border of the rectus, it lies behind the spermatic funiculus immediately medial
to, and below, the abdominal inguinal ring. The floor of Hesselbach's triangle
is formed throughout by the fascia transversalis, superficial to which, over the
medial half or so of the triangle, is the falx aponeurotica inguinalis. An oblique
inguinal hernia leaves the abdomen at the abdominal inguinal ring and traverses
the whole length of the inguinal canal ; its coverings are therefore the same as
those of the spermatic funiculus, and the neck of the sac lies lateral to the
inferior epigastric artery, hence this variety of hernia is also termed lateral inguinal
hernia. A direct inguinal hernia, on the other hand, instead of traversing the
whole length of the inguinal canal, pushes before it that part of its posterior
wall which is formed by the floor of Hesselbach's triangle. The neck of the sac,
therefore, lies medial to the inferior epigastric artery, and this variety of hernia
may be termed a medial inguinal hernia. If a direct hernia makes its way
through the medial part of Hesselbach's triangle, it derives a covering from the
ABDOMINAL INCISIONS. 1409
falx inguinalis, as well as from the fascia transversalis ; if through the lateral part
of the triangle, the lateral- edge of the falx inguinalis curves round the medial
side of the neck of the sac. To relieve the constriction at the neck of the sac,
in the case of an oblique inguinal hernia, the edge of the knife is directed
superiorly and laterally to avoid the inferior epigastric artery, while in a direct
hernia the artery is avoided by dividing the constriction in a superior and medial
direction. In an oblique inguinal hernia the sac lies within the internal spermatic
fascia (fascia propria of the hernia), whereas in a direct hernia the fascia propria
is derived froml the fascia transversalis of Hesselbach's triangle. The extra-
peritoneal fat which covers the outer surface of the hernial sac is sometimes
hypertrophied to such an extent as to amount to a fatty tumour.
In a large proportion of children, at birth, the vaginal process of peritoneum,
which connects the tunica vaginalis testis with the abdominal peritoneum, is still
patent, especially on the right side. Should the bowel force its way along the
patent process a congenital inguinal hernia arises. In the majority of the cases
of congenital inguinal hernia it will be found that the tunica vaginalis testis has
been shut off by closure of the lower part of the vaginal process, only the superior
part remaining patent and forming the sac of the hernia.
In the child the persistence of a patent vaginal process can almost invariably
be detected by rolling the cord between the finger and thumb ; after the ductus
deferens and spermatic vessels have slipped away from one's grasp the edge of the
sac can be felt to follow them. In regard to the operation for the cure of inguinal
hernia, it should be borne in mind that in the acquired form the hernia produces
the sac, whereas in the congenital variety the sac is the cause of the hernia ; it
follows, therefore, that in the operation for acquired hernia the closure of the canal
is as important as the removal or obliteration of the sac, while in a congenital
hernia the most essentia*! part of the operation is the closure of the neck of the
sac, and as the muscular and fascial apparatus forming the walls of the canal are
often well developed (especially in children), they should be interfered with as
little as possible. A patent vaginal process may persist during adult life
without any bowel descending into it ; on the other hand, years after birth, bowel
may suddenly enter it. In practically all oblique inguinal hernise, which develop
suddenly in children as well as in adolescents and young adults, the sac is of
congenital origin.
In the ordinary form of hydrocele the fluid is confined to the tunica vaginalis testis,
but when the vaginal portion of the processus vaginalis remains patent, the hydrocele
may extend upwards into the inguinal canal, and may or may not communicate with the
general peritoneal cavity. In the condition known as encysted hydrocele of the cord the
patent funicular process is shut off both from the tunica vaginalis testis and from the
peritoneal cavity.
ABDOMINAL INCISIONS.
Before proceeding to deal with the abdominal cavity reference must be made
to some anatomical points connected with the more typical incisions made by
surgeons in opening the abdomen.
Incisions in the Median Plane. Median line incisions through the linea alba
have the advantage of being comparatively bloodless and rapid of execution, of
dividing no motor nerves, and of enabling the surgeon to expose a wide area of
the abdomen. Unless special precautions are taken, however, they are more liable
to be followed by a ventral hernia.
Above the umbilicus the linea alba is comparatively broad, so that the edges of
the recti are separated by a distinct interval, which may be of considerable width
1 in obese subjects and multiparous women. Deep to the linea alba is the trans-
versalis fascia, which is so thin and adherent that the two structures form
practically a single layer. The extraperitoneal fat, which forms a comparatively
thick stratum, must not be mistaken for omentum. The peritoneum presents itself
as a thin, bluish, semi- transparent membrane. If it is necessary to prolong the incision
downwards below the level of the umbilicus, it should skirt its left margin so as to
90
1410 SUKFACE AND SUKGICAL ANATOMY.
avoid the round ligament of the liver. If, in closing a median supra-umbilica
laparotomy wound, the surgeon merely sutures the edges of the stretched line*
alba without opening into the rectal sheaths, a hernia may result. To ensur<
against it the medial borders of the recti are exposed by opening into thei:
sheaths along each edge of the wound. In closing the wound, the deepes
suture (continuous) includes on each side the posterior layer of the rectal sheatl
along with the split linea alba, the transversalis fascia and the peritoneum. Thi:
gives a substantial " first line of defence." The next suture takes up some of th<
fibres of the medial edges of the recti, along with the anterior layer of their sheaths
The skin is sutured separately. By the above procedure the edges of the recti an
brought into actual contact and a double-layered linea alba is fashioned, one laye:
behind the margins of the recti and the other in front of them.
Below the umbilicus the medial edges of the recti are practically in contact, s<
that an incision between them opens into the rectal sheath on both sides.
The nearer the opening into the abdomen approaches the symphysis pubig
the more likely is the bladder to be encountered ; this applies more especially ii
children in whom the bladder extends higher up out of the pelvis. Before opening
the abdomen, therefore, by a low median incision, the bladder should be emptied
in supra-pubic cystotomy, on the other hand, it is intentionally filled so as t<
elevate the peritoneum (superior false ligament of the bladder) well above thi
symphysis. Below this peritoneal layer is the space of Eetzius, occupied by a pat
of extra-peritoneal fat which must be separated by blunt dissection before th<
bladder wall is actually exposed. In opening the bladder the pre-vesical veins
which ramify on its surface, are avoided as far as possible. Above the pubes th<
fascia transversalis recedes somewhat from the posterior surface of the recti, leaving
behind it a cellular interval which must not be mistaken for the space of Eetzius.
If a transverse incision is added to the inferior end of a supra-umbilical mediai
incision, free access may be obtained to the hypochondriac as well as to the epi
gastric region. Before dividing the fibres of the rectus, however, the anterio
layer of the sheath is stitched to them to prevent their retraction. In dividing thi
posterior layer of its sheath the terminal portions of the ninth and tenth inter
costal nerves need not be injured as they run in a transverse direction.
Incisions through the Recti. In opening the abdomen by longitudina
incisions through the recti, the superior epigastric artery will be encountered abov<
the umbilicus, and the inferior epigastric below it. The nearer the opening
approaches the lateral border of the rectus, the more will its nerve-supply b<
injured. Above the level of the umbilicus, the posterior layer of the rectal sheath i
well developed ; and in closing the wound it is included in the same suture as th<
transversalis fascia and the peritoneum, the three together forming a most efficien
"first line of defence." The higher up and further lateral the incision is mad'
through the rectus, the more will the posterior layer of the sheath be found to b
made up of transverse muscular fibres prolonged inwards from the transversu
abdominis muscle. Below the level of the umbilicus, the posterior layer of th<
rectal sheath is much thinner, and where it ceases, namely, about midway betweei
the umbilicus and the pubes, it constitutes what is known as the linea semicirculari
(semilunar fold of Douglas). Below this level, therefore, the " deep closure " of ;
laparotomy wound through the rectus is less secure than is the case at a highe
level. It is all the more important, therefore, to see that the edges of the anterio
layer of the sheath are accurately sutured.
Incisions Lateral to the Rectus. Longitudinal incisions lateral and paralle
to the lateral border of the rectus are as far as possible to be avoided, firstly
because they divide the motor nerves, and, secondly, because the abdominal wall i
almost entirely aponeurotic, and, therefore, a hernia is liable to result.
Incisions lateral to the rectus, above the level of the umbilicus, are general!;
made more or less parallel to the costal margin. Such incisions give excellen
access to the gall-bladder and bile-ducts. The fibres of the external obliqu*
muscles are divided transversely; but, fortunately, those of the internal obliqui
and transversus muscles may be divided more or less parallel to the fibres. Th
abdominal portions of the eighth, ninth, and tenth thoracic nerves which course
(THE ABDOMINAL CAVITY. 1411
tween the two deep muscles, run in a medial and slightly downward direction,
so that it is practically impossible to avoid dividing one or other of them.
In the iliac regions, to reach the csecurn and vermiform process on the right side,
and the pelvic colon on the left side (colostomy), it is customary, by using what
is known as the " gridiron incision," to split the three abdominal muscles in the
direction of their fibres. The external oblique is split in the direction of the skin
incision, which is made obliquely from above downwards and medially. After
retracting the edges of this muscle the fibres of the internal oblique and trans-
versalis muscles are split horizontally. The abdomen is then opened by dividing
the transversalis fascia and peritoneum. If a comparatively large opening is
required the branch of the deep circumflex iliac artery, which ascends between the
internal oblique and trans versus muscles, a little medial to the anterior superior
iliac spine, is divided and ligatured, while the ilio-hypogastric and ilio-inguinal
nerves are to be avoided. If it is necessary to extend the incision in a medial
direction, the lateral part of the anterior layer of the sheath of the rectus is opened
and the rectus muscle retracted medially; while the inferior epigastric artery,
now exposed, is pushed aside or ligatured before the opening in the fascia trans-
versalis and peritoneum is enlarged.
DISTRIBUTION OF SENSORY NERVES IN ANTERIOR ABDOMINAL WALL.
A knowledge of the segmental distribution of the sensory fibres of the anterior
rami of the lower intercostal nerves enables us to appreciate the significance of the
so-called girdle pain often associated with lesions of the spinal medulla and its
nerve-roots. In tuberculous disease of the vertebral column, for example, the
girdle pain may be an early symptom of the disease, and when present it affords
a valuable guide to the situation of the disease in the vertebral column. The
seventh thoracic nerve supplies the skin at the level of the epigastric triangle, the
eighth and ninth, that between it and the umbilicus, the tenth that at the level of
the umbilicus, the eleventh and twelfth that between the umbilicus and groin.
I Subdivisions of the Abdominal Cavity. To simplify the topography of the
ominal viscera the abdomen is arbitrarily divided into nine regions by two
horizontal and two vertical planes. Of the two horizontal planes, the superior or
infracostal plane is at the level of the lowest part of the tenth costal cartilages ;
the inferior or intertubercular plane is at the level of the tubercles of the iliac crests.
The two vertical planes correspond upon the surface to a line drawn vertically
upwards on each side from a point midway between the anterior superior iliac
spine and the pubic symphysis. Superiorly, these vertical planes generally strike
the tip of the ninth costal cartilages. The subdivisions of the superior zone are
termed the epigastric and right and left hypochondriac regions, of the middle zone
the umbilical and right and left lumbar regions, of the inferior zone the hypogastric
and right and left iliac regions. The epigastric, umbilical, and hypogastric regions
may be further divided into right and left halves by the median plane. The
xiphisternal junction is on a level with the fibro-cartilage between the ninth and
tenth thoracic vertebrae. The infracostal plane passes through the superior part of
the third lumbar vertebra; the intertubercular plane through the fifth lumbar
vertebra, about one inch above the sacral promontory. The umbilicus is situated
usually from one to two inches above the intertubercular line.
In the method of surface topography employed by Addison the plane of separa-
tion between the superior and middle abdominal zones is placed midway between
the superior border of the manubrium sterni and the superior border of the pubic
symphysis. It will be found to lie at or near the mid-point between the xiphisternal
junction and the umbilicus. Posteriorly, this plane strikes the inferior border
of the first lumbar vertebra, and it passes so constantly through the pylorus that it
r with advantage be termed the transpyloric plane.
The peritoneal cavity may be regarded as a large and complicated lymph sac
ch is intimately related to the abdominal viscera, and more especially to the
THE ABDOMINAL CAVITY.
1412
SUKFACE AND SUEGICAL ANATOMY.
gastrointestinal canal. Inflammatory infections of the peritoneum are therefore
almost always secondary to lesions of the viscera. The peritoneal lymph sac is
brought into direct communication with the subperitoneal lymph vessels of the
diaphragm through stomata which open upon the peritoneum covering the abdominal
surface of that muscle. With the object, therefore, of diminishing septic absorption
after operations for peritonitis, the patient is kept in the half-sitting posture, and
pelvic drainage is established. The healthy peritoneum, in virtue of the vital action
of its endothelial cells, is endowed with great absorptive properties, and, when irritated,
has the power of throwing out an
abundant exudation, the cell-
elements of which are actively
phagocytic.
The reflection of the peritoneum
and its relations to the various
organs have been fully described in
the section on the Digestive System.
The attachment of the transverse
mesocolon to the posterior abdominal
wall is at the level of the first
lumbar vertebra, and lies, therefore,
a little above the infracostal plane.
The attachment, which ascends
slightly as it passes from right to
left, crosses the right kidney, the
descending part of the duodenum,
and the head of the pancreas, after
which its attachment follows the
anterior border of the pancreas. The
peritoneal subdivision above this
attachment is roofed in by the dia-
phragm, and includes the superior
part of the great sac, and, behind
it, the larger portion of the omental
bursa. The organs related to this
area of the peritoneum are the liver,
along with the bile-ducts and gall-
bladder, the stomach and part of
the duodenum, the spleen, the
pancreas, the upper parts of the
kidneys, and the suprarenal glands.
Suppuration connected with any of
these organs is liable to spread up-
wards under the cupola of the dia-
phragm,, producing what is known
as subphrenic abscess.
The attachment of the mesentery
of. the small intestine extends from
the left side of the second lumbar
Fro. 1102. LATERAL ASPECT OP TRUNK, SHOWING SURFACE
TOPOGRAPHY OF VISCERA.
R.L. Right lung.
L. Liver.
R.K. Right kidney.
P.L. Pleura.
vertebra downwards to the right
iliac fossa. The attachment may be
mapped out on the surface by drawing a line from a point on the transpyloric line,
one inch to the left of the median plane, to the mid -point of a line drawn
horizontally between the right anterior superior iliac spine and the median plane.
Subdivisions of the Peritoneal Cavity. From the surgical point of view the
peritoneal cavity may be arbitrarily divided into four great subdivisions : namely,
a supracolic, a right infracolic, a left infracolic, and a pelvic. All these sub-
divisions communicate freely with one another behind the anterior abdominal
wall, as well as on each side, along the gutter -like channels in the loins. It
is along these gutters that pus readily makes its way from the upper part of
THE ABDOMINAL CAVITY.
1413
FIG. 1103. ANTERIOR ASPECT OF TRUNK, SHOWING SURFACE TOPOGRAPHY OF VISCERA.
M.C. Mid-clavicular line.
P.S. Para-sternal line.
Inguinal vertical line.
I.C. Infra-costal line.
T. Intertubercular line.
Transpyloric line of Addison.
Aorta.
Heart.
P. Pulmonary orifice.
A. Aortic orifice.
M. Mitral orifice.
T. Tricuspid orifice.
R.L. Right lung.
L.L. Left Lung.
PL Pleura.
L. Liver.
0. (Esophagus.
St. Stomach.
Py. Pylorus.
D. Duodenum.
1. Ileum.
V. Valve of the colon.
A.C.
T.C.
B.C.
II. C.
P.O.
R.
C.I.
E.I.
Ascending colon.
Transverse colon.
Descending colon.
Iliac colon.
Pelvic colon.
Rectum.
Common iliac artery.
External iliac artery,
I.V.C. Inferior vena cava.
U. Umbilicus.
1414 SUKFACE AND SUKGICAL ANATOMY.
the abdomen along the lumbar regions into the iliac regions, and thence into the
pelvis ; and, on the other hand, the pus may ascend from the pelvis along the same
channels, especially when the patient is in the recumbent posture.
The highest (subphrenic) region of the supracolic compartment is further sub-
divided into a right and left portion by the falciform ligament.
The omental bursa may be looked upon as a diverticulum of the first-mentioned
subdivision.
The subphrenic lymph plexus communicates, by means of lymph vessels
which pierce the diaphragm, with the subpleural plexus on its superior surface;
hence pus confined under tension in either of these spaces is liable to give rise
to secondary infection of the corresponding pleural cavity. By adhesions of the
transverse colon and greater omentum to the anterior abdominal wall, the supra-
colic subdivision of the peritoneal cavity may become more or less completely shut
off from the rest of the abdomen. Suppuration in the right half of the phrenico-
colic subdivision is generally secondary to leakage from an ulcer of the first part
of the duodenum or to disease of the gall-bladder and bile-ducts ; while the left
half of the space is more usually infected from the stomach. The best method of
draining the supracolic subdivision of the peritoneal cavity is to pass a tube through
the hepato-renal pouch of Morrison. The entrance to this pouch lies lateral to the
gall-bladder between the inferior margin of the liver above and the right flexure of
the colon below. The bottom of the pouch is formed by the reflection of the
peritoneum from the superior part of the kidney on to the fascia transversalis cover-
ing the aponeurosis of origin of the transversus abdominis muscle below the tip of
the twelfth rib. To drain it, a tube is introduced into it either from the wound
in the anterior abdominal wall, or, still better, through a puncture opening made
through the loin lateral to the kidney, in the angle between the twelfth rib and
the lateral border of the sacro-spinalis muscle. Another drainage route is by a
tube passed from the wound in the anterior abdominal wall into the omental bursa,
through either the gastro-hepatic ligament or the great omentum.
The right infra-colic subdivision lies above and to the right of the mesentery of
the small intestine. It is bounded, above, by the right and middle two-thirds of
the transverse colon and the corresponding part of its mesentery, while laterally it
is limited by the caecum and ascending colon. At its right inferior angle are the
ileo-csecal junction and the vermiform process ; at its right upper angle is the
right flexure of the colon, while at its left upper angle is the inferior part of the
duodenum, crossed by the superior mesenteric vessels.
The organs related to this subdivision are, in addition to the parts of the large
intestine already mentioned, coils of small intestine, the inferior third of the right
kidney, the right ureter, the inferior half of the descending and the horizontal part
of the inferior portions of the duodenum.
Suppuration in connexion with the organs in this area involves more especially
the right lumbar region, and may extend upwards along the colon into the sub-
diaphragmatic region, or downwards into the pelvis minor. To drain this region
a tube is introduced into the right lumbar region either through the anterior
abdominal wall or through a stab-wound in the loin lateral to the ascending colon.
The left infra-colic subdivision, which lies below and to the left of the mesentery,
narrows as it passes upwards and reaches to a higher level than the right infra-colic
subdivision. Inferiorly, it is directly continuous at the superior aperture of the
pelvis with the peritoneal cavity of the pelvis minor. Above, it is bounded by the
left third of the transverse colon and its mesentery, and, still more posteriorly, by
the inferior surface of the body of the pancreas ; laterally it is bounded by the
descending and iliac portions of the colon. At its right upper angle is the duodeno-
jejunal flexure, lying immediately to the left of the vertebral column, in the angle
between it and the inferior surface of the pancreas. At its left superior angle is
the left flexure of the colon, while at its left inferior angle is the junction of
iliac with pelvic colon. This subdivision of the peritoneal cavity, in addition to
containing the majority of the coils of the small intestine, is related to the inferior
third of the left kidney, the left ureter, the lower part of the abdominal aorta and
vena cava, and the inferior mesenteric and common iliac vessels. Drainage of this i
THE ABDOMINAL V1SCEKA. 1415
subdivision may be established through the left loin, or by a tube introduced down
to the bottom of the pelvis, namely, into the recto-vesical pouch in the male, and
into or through the recto-vaginal pouch (pouch of Douglas) in the female.
On account of the oblique manner in which the mesentery proper is attached
to the posterior abdominal wall, it follows that in order to examine the organs
related to the right infra-colic subdivision of the abdomen, the coils of small
intestine should be displaced downwards and to the left, while to investigate the
left infra-colic subdivision they should be carried upwards and to the right.
ABDOMINAL VISCERA.
Liver. The anterior margin of the liver, as it crosses the costal angle, can readily
be determined by palpation and light percussion ; it passes from the eighth left to
the tip of the tenth right costal cartilage, and crosses the median plane at the level
of the transpyloric line. In the mid-clavicular line it reaches down to a point a
little below the most inferior part of the tenth right costal cartilage. Above the
left costal margin the anterior margin passes upwards and to the left to join the
left border of the liver at the fifth interspace in the mammary line. The highest
part of the liver, which corresponds also to the highest part of the right arch of the
diaphragm, reaches, during expiration, to the level of the fourth intercostal space in
the mammary line. To the right of the median plane the superior surface of the
liver is too far removed from the anterior wall of the chest, and overlapped by too
thick a layer of lung substance, to be accurately determined by percussion.
Behind the sternum the superior surface reaches to the level of the sixth chondro-
sternal junctions. To the left of the median plane the superior limit of the liver
cannot be determined by percussion since it merges into the cardiac dulness. The
base or right lateral surface extends from the level of the seventh to the level
of the eleventh rib in the mid-axillary line and is separated by the diaphragm
from the lower part of the right lung and pleura.
The falciform ligament of the liver lies, as a rule, a little to the right of the
median plane.
The anterior surface of the liver may be reached through a median incision,
extending downwards from the xiphoid process, or by an oblique incision, a finger's
breadth below and parallel to the right costal margin. To obtain free access to the
superior surface the eighth and ninth costal cartilages must be resected ; the seventh
cartilage should, if possible, be avoided ; otherwise the pleural cavity may be opened
into. Division of the round and falciform ligaments allows of greater downward
displacement of the liver. To reach the upper part of the lateral surface of the
right lobe, portions of the seventh and eighth ribs should be resected in the mid-
axillary line, and both the pleural and peritoneal cavities must be traversed.
Gail-Bladder. The relation of the fundus of the gall-bladder to the surface of
the body is subject to considerable variation. Normally it is situated behind the
angle between the ninth costal cartilage and the lateral border of the right rectus ;
exceptionally, it is pendulous and suspended from the liver by a more or less
distinct mesentery; or it may be elongated and drawn downwards by adhesion
to the duodenum or colon. When displaced downwards it is liable to be mistaken
for a movable kidney, but may be distinguished from that by the fact that although
it may be pushed backwards into the lumbar region it returns at once to its
habitual position, immediately behind the anterior abdominal wall, as soon as it
ceases to be manipulated.
The cystic duct is enclosed in the right extremity of the superior border of the
gastro-hepatic ligament. It is about an inch and a half in length, is sharply bent
upon itself close to its origin at the neck of the gall-bladder. It joins the hepatic
duct at a very acute angle. The passage of a probe along the normal duct is
rendered difficult by the marked flexure at its commencement, as well as by the folded
condition of its mucous membrane ; hence also the frequency with which calculi
become impacted at the neck of the gall-bladder. In excising the gall-bladder,
it is an advantage to ligature and divide the cystic artery and duct before pro-
ceeding to detach the organ from the inferior surface of the liver.
90 a
1416 SURFACE AND SURGICAL ANATOMY.
The bile-duct, about three and a half inches in length, lies, in its superior
third, close to the right free border of the gastro-hepatic ligament. When cutting
into this, the most accessible part of the duct, it should be drawn forwards by the
finger introduced behind it, through the epiploic foramen ; the portal vein, which
must be avoided, lies posterior and a little to the left of the duct. The middle
third of the duct lies a little to the right of the commencement of the gastro-
duodenal artery behind the superior part of the duodenum about a finger's breadth
from the pyloro-duodenal junction. The inferior third of the duct, which passes
downwards and to the right, is intimately related to the pancreas ; in about two out
of three instances it is so embedded in the posterior aspect of its head that it cannot
be freed by blunt dissection. Close to its termination the duct is joined by the
main pancreatic duct of Wirsung, the two opening separately, but close together, at
the bottom of a diverticulum, which pierces the wall of the duodenum obliquely,
and opens at the summit of a small papilla situated at the inferior part of the medial
wall of the descending part of the duodenum, about four inches from the pylorus.
When a calculus becomes impacted in the ampulla there is retention of the
pancreatic as well as of the biliary secretion. Frequently, however, the gland
possesses an accessory pancreatic duct (duct of Santorini) which opens into the
duodenum at a higher level than the main duct, with which it also communicates.
A calculus in the ampulla may be reached either by opening the duodenum from
the front (trans-duodenal route), or by freeing the duodenum and gaining access
to the duodenum from behind (retro-duodenal route). In the latter instance an
incision is made, lateral to the right border of the descending part of the duodenum,
through that portion of the peritoneum which passes upwards and to the right
from the superior layer of the transverse mesocolon, over the superior part of the pars
descendens of the duodenum on to the anterior surface of the right kidney. By
blunt dissection, directed medially, behind the duodenum, that organ, along with the
adjacent part of the head of the pancreas, can be separated from the kidney and
vena cava, and folded over towards the left like a door on its hinges. In
freeing the bile-duct from the posterior aspect of the head of the pancreas a
vein of considerable size will be encountered ; this vein, which returns the
blood from the pancreatic-duodenal system of arteries, lies close to the bile-duct
as it ascends behind the head of the pancreas to open into the commencement of
the vena portse. Of the lymph glands related to the bile passages it is to be
remembered that one lies at the neck of the gall-bladder, another at the junction
of the cystic and hepatic ducts, while a third lies close to the termination of
the bile-duct. When these glands are enlarged and indurated, care must be
taken not to mistake them for impacted gall-stones.
Stomach. The stomach lies almost entirely within the left half of the epi-
gastric region and in the left hypochondriac region. The cardiac orifice, which
lies 1 in. below and to the left of the oesophageal opening in the diaphragm, is
about 4 in. from the surface, and corresponds, on the anterior surface of the
body, to a point over the seventh left costal cartilage 1 in. from the median
plane. The pylorus, which is generally partly overlapped by the anterior margin of
the liver, lies in, or a little to the right of the median plane ; when the stomach
is empty it generally lies in the median plane, when distended it may reach two,
or even three inches to the right of the median plane. Passing from the superior to
the inferior border of the pylorus opposite its junction with the duodenum is the
anterior pyloric vein of Mayo. This vein affords a useful visible guide to the position
of the pylorus. Another guide is furnished by the ring -like thickening of the
pyloric sphincter which projects into the commencement of the duodenum (like
the cervix uteri into the vagina), and can be readily palpated through its thin
wall. The pyloric portion of the stomach is practically bisected by a horizontal
plane which passes through the abdomen at the level of a point midway between
the jugular notch of the sternum and pubic symphysis (Addison) ; it lies, there-
fore, three to four inches below the infra-sternal notch, midway between it and
the umbilicus, opposite the first lumbar vertebra. The highest part of the
fundus of the stomach corresponds to the left vault of the diaphragm, and lies
at the level of the fifth rib in the mammary line, a little above and behind the
THE ABDOMINAL VISCERA. 1417
apex of the heart. The greater curvature crosses behind the left costal margin
opposite the tip of the ninth costal cartilage, that is to say, where the transpyloric
line intersects the left lateral line. The lowest part of the great curvature,
situated generally in the median plane, extends down to, or a little above, the infra-
costal plane, about two inches above the umbilicus. The lesser curvature and the
adjacent part of the anterior wall of the stomach are overlapped by the anterior
margin of the liver.
Radiography of Stomach. Radiograms of the stomach, taken after a "bismuth
meal," show that the form and position of the stomach in the living subject differ
considerably from that which it presents in the cadaver.
In the cadaver, owing to loss of muscular tone, it presents itself as a more
or less empty pear-shaped bag with collapsed and flaccid walls. The same applies
to a large extent to the stomach as seen in the operating room, its normal tonicity
being almost entirely held in abeyance by the anaesthetic.
In the living subject, the form and position of the stomach are found to vary
not only according to the amount of food it contains, but also according to
whether the patient occupies the erect or the recumbent posture. The most reliable
as well as the most useful, information regarding the form, the position, and the
motor activity of the stomach is obtained by " screen " examinations and radiograms
taken with the patient in the erect posture. When examined in this way, after
partly filling the stomach with a " bismuth meal," the organ is seen to possess a
distinctly J -shaped form. The stem of the J, which is represented by the body of
the stomach, lies immediately and entirely to the left of the vertebral column. The
fundus, which is slightly more expanded than the body, reaches up to the left cupola
of the diaphragm ; it is represented in the skiagram as a light semilunar shadow,
the horizontal inferior margin of which corresponds to the superior limit of the
bismuth. This clear semilunar area is due to the rising up of the gaseous contents
of the stomach to the highest part of the cavity. The cardiac orifice is seen to lie
opposite the left side of the fibre-cartilage between the tenth and eleventh thoracic
vertebrae. The shadow of the curved pyloric portion of the stomach, after crossing
the left side of the vertebral column opposite the third and fourth lumbar vertebrae,
ascends as the pyloric canal to join the duodenum at or a little to the right of the
median plane, opposite the second (not infrequently the third) lumbar vertebra.
The pylorus itself is represented by a light disc due to a break in the continuity
of the bismuth, caused by contraction of the pyloric sphincter. The lowest portion
of the greater curvature, which generally lies at or a little to the left of the median
plane, reaches, in the erect posture, down to the level of the middle or inferior border
of the fourth lumbar vertebra, or, in other words, to the umbilicus and the highest
part of the iliac crest.
As more food enters the stomach its capacity is increased by lateral expansion
rather than by any elevation of its fundus or downward expansion of its greater
curvature. The normal tonic action of the gastric muscle is able to hold up the
meal against the action of gravity to the level of the cardiac orifice.
When, as not infrequently happens, the normal muscular tonicity of the
stomach is lost, the bismuth meal is no longer held up against the action of gravity,
but at once sinks to the most dependent part of the stomach where it lies as in a
flaccid sac, and gives rise to a crescentic shadow which may reach down almost, or
even quite, to the level of the pubes.
In gastroptosis, and in general visceroptosis, the whole stomach may be displaced
downwards without any great loss of its tonicity.
During a " screen " examination after a bismuth meal, the peristaltic movements
of the stomach can be seen to pass in distinct wave-like indentations from left to
right along the greater curvature, and to increase in force as they approach the
pylorus.
When the stomach is hypertrophied and dilated, as a result of pyloric obstruc-
tion, the peristaltic waves are more pronounced, and the bismuth shadow extends
well over to the right of the median plane, owing to the dilated pyloric antruin
and pyloric canal being carried over to the right, in front of the superior part of
the duodenum. The stomach tends, therefore, to lose its somewhat J -shaped
1418 SUKFACE AND SUKGICAL ANATOMY.
tubular form, and the axis of its body becomes more oblique. In the infant and
young child the stomach is flask-shaped rather than J -shaped, and its axis is less
vertical than in the adult. The elongated form of the adult stomach is acquired
as a result of the erect posture.
It must be remembered that the only really fixed part of the stomach is the
region of the cardia, so that the form and position of the organ may be considerably
influenced by the condition of the neighbouring organs. For example, it may be
displaced downwards and to the left by enlargement of the liver, upwards by
distension of the intestines, and to the right by distension of the left colic flexure.
Overlying the stomach is an important surface area known to clinicians as the
semilunar space of Traube. This space, which yields a deeply tympanitic note on
percussion, is bounded, above, by the inferior margin of the left lung ; below, by the
left costal margin ; t to the right, by the anterior margin of the left lobe of the liver ;
behind and to the left, by the anterior border and anterior basal angle of the spleen.
The line of the costo-diaphragmatic pleural reflection crosses the space about mid-
way between its superior and inferior limits. The tympanitic area of the space is
diminished superiorly by pleuritic effusion, towards the right by enlargement of
the liver, and towards the left by enlargement of the spleen.
Perforation of an ulcer on the anterior wall of the stomach leads to extravasa-
tion into the greater sac of the peritoneum, while if the perforated ulcer is on the
posterior wall, extravasation takes place into the omental bursa. The close relation
of the splenic artery and its branches to the posterior wall of the stomach explains
the severe haemorrhage which is sometimes caused by a posterior gastric ulcer.
The surgeon may reach the posterior wall of the stomach through the gastro-colic
ligament, or, after throwing upwards the greater omentum and transverse colon, by
traversing the transverse mesocolon ; by the former route the posterior wall of the
stomach is reached through the anterior wall of the omental bursa, in the latter
through its posterior wall.
When a partial resection of the stomach, for malignant disease, is performed, the
bleeding is controlled by ligaturing the main vessels at an early stage of the opera-
tion. These are the right and left gastrics at the lesser curvature, the gastro-
duodenal behind the first part of the duodenum, and the right and left gastro-
epiploics at the greater curvature. The left gastric should be ligatured as near
the cardia as possible, so that the whole chain of lymph glands along the lesser
curvature may be removed. Care is taken to remove also all the glands which lie
behind the first part of the duodenum in relation to the gastro-duodenal artery and
head of the pancreas, as well as those along the right half of the greater curvature
in relation to the right gastro-epiploic artery. If the disease has spread to the
retro-peritoneal lymph glands, surrounding the cceliac artery, above the pancreas,
the chances of a permanent recovery are very remote.
In the classical " no-loop " gastro-enterostomy operation a longitudinal opening
in the commencement of the jejunum is anastomosed by suturing it to an opening
in the posterior wall of the stomach, near the 'greater curvature. The jejunum is
applied to the stomach in such a way that it maintains its normal direction, namely,
obliquely upwards and to the left. To bring the surfaces of the two organs in
contact, surgeons are in the habit of protruding the posterior wall of the stomach
through an opening made in the transverse mesocolon, on the proximal side of the
arch formed by the middle and left colic arteries. A better plan, however, is to
make an opening also into the omental bursa through the gastro-colic ligament a
little below the gastro-epiploic vessels, and then to bring the jejunum into contact
with the posterior wall of the stomach by pushing it (the jejunum) upwards
through the opening in the transverse mesocolon. By this plan the posterior wall
of the stomach along with the jejunum can be protruded through an opening in
the gastro-colic ligament, and can be more easily delivered out of the abdominal
cavity.
When the posterior wall of the stomach and transverse colon are held down by
adhesions, a long loop of jejunum is brought up in front of the greater omentum
and transverse colon and anastomosed to the anterior wall of the stomach.
The Duodenum. The duodenum is the widest, thickest, and most fixed part
THE ABDOMINAL VISCEEA. 1419
of the small intestine. For descriptive purposes it is divided by anatomists into
three parts. From the surgical standpoint it may with advantage be subdivided
into a supra-colic and an infra-colic portion, the former, comprising the superior and
the upper half of the descending part, being situated above the attachment of the
transverse mesocolon ; while the latter, comprising the lower half of the descending
part along with both subdivisions of the third part, being situated below this
attachment. To expose the supra-colic portion the greater omentum and the
transverse colon must be pulled downwards, while to expose the infra-colic portion
they are thrown upwards along with the transverse mesocolon.
The first portion proper (pars superior) lies in the right part of the epigastric
region, medial to the gall-bladder, where it is overlapped by the quadrate lobe of
the liver. As regards its blood-supply, it occupies the frontier zone between the
coeliac and superior mesenteric vascular areas, and the vessels which supply it
vary considerably in their size and mode of origin.
This peculiarity of its blood- supply may partly account for the relative
frequency with which this portion of the intestine is found to be the seat of
ulceration. The first inch or so the duodenum possesses some degree of mobility,
being surrounded by the same two layers of peritoneum which invest the stomach.
Beyond this it is in direct contact posteriorly and inferiorly with the pancreas,
while descending behind it are the common bile-duct and the gastro-duodenal
artery. The relations must be borne in inind in performing the operation of
pylorectomy. When an ulcer of the superior part perforates, extravasation takes
place, in the first instance, into the supra-colic compartment of the peritoneum,
thence into its hepato-renal pouch, and subsequently down along the ascending
colon into the right iliac fossa, hence the possibility of mistaking the condition
for an acute appendicitis. Perforation of the ulcer, however, is often prevented
by the duodenum becoming adherent especially to the gall-bladder, to the omentum,
or to the transverse colon.
If the finger is passed upwards, backwards, and to the left, immediately above
the first part of the duodenum and behind the right free border of the lesser
omentum, it will pass through the foramen epiploicuin into the omental bursa of
the peritoneum.
The second portion of the duodenum (pars descendens) descends in the epigastric
and umbilical regions a little medial to the right lateral plane. The attachment
of the transverse mesocolon crosses it about its middle, while posteriorly it lies in
front of the hilum and medial border of the right kidney, from which it is separated
by loose areolar tissue. The procedure necessary to mobilise this portion of the
duodenum has been referred to already.
The horizontal portion of the inferior part of the duodenum occupies the
superior part of the umbilical region, and crosses the median plane about one inch
above a line joining the highest part of the iliac crests ; behind its commencement
is the superior part of the right ureter.
The ascending portion of the inferior part of the duodenum crosses the infra-
costal plane, and ascends upon the left side of the vertebral column opposite the
second and third lumbar vertebra.
The duodeno-jejunal flexure, which lies in the transpyloric plane one inch to the
left of the median plane, is the landmark which the surgeon makes for when he
wishes to identify the commencement of the jejunum (Fig. 946, p. 1204). To find
the flexure the greater omentum and transverse colon should be thrown upwards
and the finger passed along the inferior layer of the transverse mesocolon to the
left side of the vertebral column. The flexure lies in the angle or recess formed by
the left side of the second lumbar vertebra and the inferior surface of the body of
the pancreas. With the finger in this recess the commencement of the jejunum
may be hooked forward a little to the left of the superior mesenteric vessels at
the root of the mesentery. In connexion with the duodeno-jejunal junction is the
inferior duodenal fossa of Jonnesco, formed by a fold of peritoneum which stretches
from the left side of the fourth or ascending part of the duodenum upwards
to become attached to the peritoneum of the posterior abdominal wall close to the
medial border of the left kidney. The free edge of the fold and the mouth of the
1420
SUKFACE AND SUEGICAL ANATOMY.
fossa look upwards. This is one of the situations at which an internal hernia
sometimes develops, the sac, as it enlarges, extending further and further into the
extra-peritoneal tissue on the posterior abdominal wall. Should strangulation
occur, the inferior edge of the orifice must be divided in a downward direction, in
order to avoid the inferior mesenteric vein which curves round the anterior and
superior aspects of the orifice (Treves).
Jejunum and Ileum. To expose the coils of the jejunum and ileum completely,
the greater omentum, along with the transverse colon and the greater curvature
of the stomach, must be turned upwards. On account of the oblique attachment
of the mesentery, the greater number of the coils lie in the left infra-colic peritoneal
compartment, where they extend upwards to the left of the vertebral column as
far as the attachment of the transverse mesocolon and the inferior surface of the
pancreas ; here they lie in front of the inferior pole of the left kidney, in the angle
of the left colic flexure.
The only certain means which the surgeon has of distinguishing the superior
from the inferior coils of small intestine is by their relation to the duodeno-
jejunal flexure and the ileo-caecal junction. Occasionally the plicae circulares
VERMIEORM
PROCESS
FIG. 1104. THE C^CAL FOLDS AND FOSS.E,
In A, the caecum is viewed from the front ; the mesentery of the vermiform process is distinct, and is attached
above to the inferior surface of the portion of the mesentery going to the end of the ileum. In B, the
caecum is turned upwards to show a retro-caecal fossa, which lies behind it, and the beginning of the
ascending colon (from Birmingham).
and the aggregated lymph nodules can be seen from the peritoneal aspect and
the jejunum and ileum thereby respectively identified. The terminal portion
of the ileum, which is attached by the inferior end of the mesentery to the
superior part of the right wall of the pelvis major, crosses the superior
aperture of the pelvis minor, and ascends along the medial edge of the caecum
before opening into it. The terminal loop of the ileum may be hooked up by passing
the finger along the medial side of the caecum downwards over the medial border
of the psoas major and the external iliac vessels into the pelvis minor.
Meckel's diverticulum, which is due to persistent patency of the proximal portion of
the vitelline duct, is situated usually from two to three feet above the valve of the colon ;
its average length is two inches. Springing from the anti-mesenteric border of the ileum,
its termination is usually free, but it may be adherent either to the anterior abdominal
wall, to the mesentery, or, more rarely, to one of the adjacent viscera. When its termina-
tion is fixed it may give rise to strangulation of the intestine.
Caecum. The caecum occupies the right iliac region and extends from the
anterior superior spine of the ilium to the superior aperture of the pelvis minor.
When empty, it is generally more or less completely overlapped by small intestine, and
frequently also by the greater omentum. When partly distended, the caecum comes
THE ABDOMINAL VISCEEA. 1421
in contact with the anterior abdominal wall immediately above the lateral half of
the inguinal ligament. In "the normal condition it is completely surrounded by
peritoneum, and can, therefore, along with the vermiform process, be readily
delivered out of the abdomen. In chronic constipation, associated with intestinal
atony, the caecum is thin- walled, dilated, abnormally movable, and often prolapses
into the pelvis.
The position of the ileo-caecal valve corresponds, on the surface of the body, to
the medial angle between the intertubercular and right lateral lines, while the
orifice of the vermiform process is one inch lower. It is to be noted that the lower
end of the ileum protrudes somewhat into the caecum, and that its circular muscular
fibres are prolonged into the flaps of the colic valve. Both of these anatomical
arrangements favour the occurrence of intussusception. In infants, other
predisposing causes are : (1) the relatively rapid enlargement of the lumen of the
large intestine as compared with the small ; (2) the greater mobility of the caecum ;
and (3) the frequent presence of a mesentery to the ascending colon.
Vermiform Process. The vermiform process (O.T. vermiform appendix),
which springs from the postero-medial aspect of the caecum, one inch below the
ileo-caecal junction, is provided with a well-developed " meso-enteriole " derived from
the posterior aspect of the lowest part of the ileac mesentery. It is this portion of
the posterior layer of the mesentery which sometimes develops a band -like
thickening, which, by dragging upon the inferior end of the ileum, produces the kink
to which attention has been directed by Arbuthnot Lane. The artery of the
vermiform process is the only vessel which supplies the process ; it occupies the
free border of the meso-enteriole and gives off several branches which pass between
its two layers to reach the organ. In amputating the vermiform process the artery
is ligatured on the proximal side of its first branch in order to control the blood-
supply to the stump of the process. The fact that the vermiform process is supplied
by a single artery predisposes it to
gangrene should the vessel become
thrombosed, or should the circulation
in it be interfered with by kinking i LEO-COLIC ARTERY-
as a result of adhesions.
,, . p .,, ILIAC BRANCH-
Ihe vermnorm process will gener-
ally be found to pass either upwards
and medially, behind the lower end of
the ileum, or downwards and medially,
so as to overhang the external iliac
vessels at the superior aperture of
the pelvis minor ; less frequently it
ascends in the pouch behind the com-
mencement Of the ascending COlon. ARTERY OF THE
A . p ,11 VERMIFORM
When, as not infrequently happens, PROCESS
i the retro-caecal fossa is prolonged up-
wards to form a pouch behind the
colon, the vermiform process almost 1105 ._ THE BLOOD . SDPPLY OF IHE C * CCM AND Vra .
invariably ascends into it, and should MIFORM PROCESS.
1 it be diseased, it may give rise to a The miration gives a view of the c^cum from behind.
I retro-caecal abscess. The abscess may The artery of the vermiform process, and the three
: perforate the posterior wall Of the taenia coli springing from the .base of the process, should
T ,, i be specially noted. (Modified by Birmingham from
caecum, or it may ulcerate through jonnesco.)
the posterior peritoneum ; in the
latter case the suppuration may spread upwards, in the loose fatty sub-peritoneal
< tissue behind the colon, into the lumbar and perinephric regions; and it may
i reach even the under surface of the diaphragm and form a subphrenic abscess.
i When, in the course of its development, the caecum has failed to complete its
! descent, the vermiform process may lie in the lumbar region in relation to the
^ inferior pole of the kidney. When it dips downwards into the pelvis minor it may
: become adherent to the pelvic colon, the rectum, or the bladder, and in the female
I, to the uterine tube or the ovary. To find the vermiform process, the best plan
1422 SUEFACE AND SUKGICAL ANATOMY.
is simply to pull the caecum out of the wound, and if the parts are normal the
process will be delivered along with it ; if, on the other hand, the csecum and
vermiform process are tacked down by adhesions, the vermiform process is best
discovered by following the anterior tsenia coli to the root of the process.
Ascending Colon. The ascending colon, after crossing the iliac crest, lies deeply
in the right lumbar region upon the fascia covering the quadratus lumborum and
the adjacent aponeurotic origin of the transversus abdominis. Between the bowel
and the fascia is a quantity of loose cellular- tissue and fat, which may be< the seat
of a large abscess, secondary, (1) more especially, to disease of the colon itself, (2)
to disease of a retro-colic vermiform process, or (3) to disease of the right kidney.
This cellular tissue is directly continuous above with a thin layer lining the inferior
surface of the diaphragm; hence the suppurative process may extend upwards,
giving rise to one form of subphrenic abscess. In some cases the ascending colon is
completely surrounded by peritoneum, and it may even be provided with a distinct
mesentery. The latter condition is almost invariably present in infants sufferiug
from extensive ileo-csecal intussusception. After the invagination has been
reduced the mesentery proper is seen to be continuous, through the ascending
mesocolon, with the mesentery of the transverse colon.
In order to resect the ascending colon the surgeon mobilises it by dividing the
peritoneum along its line of reflection from the lateral aspect of the colon on to
the abdominal wall. The colon, along with the posterior peritoneum medial to it,
is then stripped, from the lateral side towards the median plane, off the quadratus
lumborum, the psoas, and the inferior pole of the right kidney. While this is being
done, the branches of the ileo-colic and right colic vessels which pass laterally to
supply the gut are secured, and the lymph vessels and associated lymph glands are
removed along with the bowel. As the peritoneum is stripped off, care must be taken
not to injure the important structures which lie behind it, namely, the duodenum,
the ureter, and the spermatic vessels.
The right colic flexure reaches upwards beneath the tenth costal cartilage
into the most inferior part of the right hypochondrium, where it lies immediately
to the right of the gall-bladder, between the liver and the inferior half of the
anterior surface of the kidney. Posteriorly, it is separated from the anterior surface
of the right kidney by a quantity of loose cellular tissue ; hence by dividing the
peritoneum to the right side of the flexure it can readily be mobilised and separated
from the kidney.
Transverse Colon. The transverse colon crosses the lower part of the umbilical
region immediately below the greater curvature of the stomach. In cases of chronic
constipation it may form a U-shaped or V-shaped loop, extending down to the level]
of the pubes. When this is the case the natural kinking at the right and left colic |
flexures becomes more acute, and tends, therefore, to aggravate the constipation. Ii
such cases the right and left portions of the transverse colon often lie parallel an<
close to the ascending and descending colon, respectively, like the barrels of a gun.
The transverse colon receives its blood-supply from the arch formed by the
middle and left colic arteries. The arch lies in the posterior wall of the bursa
ornentalis between the two layers of the transverse mesocolon. In resecting portiom
of the stomach for malignant disease, the surgeon removes also the glands whict
lie between the two layers of the gastro-colic ligament in relation to the right
gastro-epiploic vessels. At this step of the operation care must be taken not to en-
danger the blood-supply of the transverse colon by injuring the middle colic artery
The left colic flexure is more acute and more fixed than the right flexure ; anc
it is situated at a higher level as well as more deeply. A tumour originating ii
this portion of intestine lies generally under cover of the left costal margin, and i
therefore difficult to palpate. To expose the left colic flexure, the omentum alond
with the transverse colon and the body of the stomach is turned upwards. T
mobilise it for the purpose of resection the surgeon must divide : (1) the phrenicoj
colic ligament, which attaches it to the diaphragm opposite the eleventh rib; (2J
the left border of the greater omentum, which attaches it to the stomach ; an
(3) the left portion of the transverse mesocolon, which attaches it to the
extremity of the pancreas.
THE ABDOMINAL VISCEEA. 1423
Descending Colon. The descending colon, like the ascending, is deeply placed
in the lumbar region and is related to the inferior half of the lateral border of the
left kidney. It is less frequently provided with a mesentery than is the ascending
colon.
Iliac Colon. The iliac colon commences at the junction of the posterior and
middle thirds of the iliac crest, and ends at the superior aperture of the pelvis
minor by joining the pelvic colon. It possesses no mesentery 'and is connected to
the fascia covering the iliacus and psoas major muscles by loose areolar tissue.
Towards its termination it turns medially immediately above and parallel to the
inguinal ligament, and at its junction with the pelvic colon it lies in front of the
external iliac artery. Although, as a rule, it is entirely overlapped by coils of
small intestine, it can frequently be felt by firm palpation at the lateral part of the
left iliac fossa, because its muscular wall is comparatively thick and generally
contracted.
Pelvic Colon. The pelvic colon, in consequence of possessing a well-developed
mesentery, forms a freely movable loop which, though usually confined to the
pelvis minor, may, when distended, rise well up into the abdomen. It is this
section of the large intestine which is opened for the purpose of making an
artificial anus in malignant disease of the rectum.
The pelvic colon varies considerably in length, the average being sixteen or
seventeen inches. It is relatively longer and of greater calibre in the child than
in the adult. It is the part of the large intestine especially involved in the
condition known as megalocolon or Hirschsprung's disease a congenital abnormality
in which the large intestine is greatly dilated and hypertrophied.
When the pelvic colon is thrown upwards and to the right so as to spread out
its mesentery, the latter is seen to be attached in an inverted V-shaped manner to
the posterior wall of the pelvis. At the apex of the V is a small peritoneal pouch
the inter-sigmoid fossa, situated just in front of the ureter as it crosses the
termination of the common iliac artery to enter the pelvis minor. This fossa is
one of the situations at which an internal retro-peritoneal hernia may originate.
The mouth of the fossa looks downwards and to the left, while above and to its
right is the sigrnoid artery. The fossa affords a guide to the commencement of the
pelvic portion of the left ureter. On account of the V-shaped attachment of this
mesentery it is convenient to speak of the pelvic colon as possessing an ascending
or proximal and a descending or distal limb. At the junction of the proximal
limb with the termination of the iliac colon is a more or less well-marked flexure
(the "last kink" of Arbuthnot Lane). It is to the proximal limb of the pelvic
colon that the divided inferior end of the ileum is anastomosed in the short-circuiting
operation of ileo-sigmoidostomy.
In the author's operation of transplanting the ureters into the large intestine
for incontinence of urine, the result of epispadias in the female, and of ectopia
vesicse in either fcex, the left ureter is implanted into the ascending limb of the
pelvic colon and the right ureter into its descending limb.
By dividing the attachment of the mesentery of the pelvic colon in the
operation of excision of the rectum, the pelvic colon may be mobilised sufficiently
to allow of its being brought down and sutured to the skin in the sacral region or
even to the anal region. Further, the mobility of the pelvic colon is such that
after resection of the descending and iliac colon and mobilisation of the left colic
flexure, the divided ends of the bowel can be sutured together without undue
traction.
After operations on the female genital organs by the abdominal route for
example, after abdominal hysterectomy the surgeon makes use of the pelvic
colon and its mesentery by spreading them out over the pelvis so as to roof it in,
and so prevent any of the coils of small intestine from becoming adherent in the
pelvis.
Kidneys. The kidneys lie behind the peritoneum, and extend higher up than
is often supposed, and laterally they do not extend so far away from the vertebral
column as is almost invariably depicted ; hence it is that, unless enlarged, the kidneys
can seldom be felt through the abdominal wall. The right kidney as a rule lies a
1424
SUEFACE AND SUEGICAL ANATOMY.
FIG. 1106. ANTERIOR ASPECT OP TRUNK, SHOWING SURFACE TOPOGRAPHY OF VISCERA.
M.C. Mid-clavicular line.
P.S. Para-sternal line.
P. Inguinal vertical line.
I.C. Infra-costal line.
T. Inter-tubercular line.
Py. Transpyloric line.
T. Trachea.
A. Aorta.
R.L. Right lung.
L.L. Left lung.
PL Pleura.
0. (Esophagus.
R.K. Right kidney.
L.K. Lett kidney.
Sp. Spleen.
S.R. Suprarenal gland.
Pa. Pancreas.
D. Duodenum.
Q.L. Quadratus lumborum.
Ps. Psoas major.
R.U. Right ureter. .
L.U. Left ureter.
C.I. Common iliac artery.
E.I. External iliac artery.
I.V.C. Inferior vena cava.
U. Umbilicus.
littL
THE ABDOMINAL VISCEEA. 1425
le lower than the left, as well as a little further away from the median plane.
The hilum of the right kidney lies 2 in. from the median plane ; that of the left
1| in. from the median plane. For practical purposes the hilum of the kidney may
be regarded as opposite a point on the anterior abdominal wall a finger's breadth
medial to the tip of the ninth costal cartilage ; and a line joining the two hila
crosses the vertebral column opposite the fibro-cartilage between the first and second
lumbar vertebrae, that is to say, a little below the transpyloric line. The highest
point of the kidney is situated two inches from the median plane, on a level with a
line crossing the abdomen midway between the xiphisternal and transpyloric
planes. The lowest point of the kidney reaches down to, or a little below, the
infra-costal plane.
The student should make himself familiar with the feel of the parts in relation
to the kidneys, as far as they can be made out by introducing the hand through a
median abdominal incision.
The superior half of the anterior surface of the right kidney is felt, at the bottom
of the hepato-renal peritoneal pouch, by passing the hand deeply into the right
hypochondrium, between the anterior margin of the liver and the right flexure of the
colon. The inferior half is palpated by passing the hand deeply into the highest
part of the right infra-colic peritoneal compartment ; its free peritoneal suri'ace lies
in the angle of the right flexure of the colon. The second portion of the duodenum
overlaps both the supra- and infra-colic portions of the medial border of the right
kidney. When the right kidney is excised by the abdominal route, the peritoneum
is divided lateral to the ascending colon and right colic flexure, and these structures,
along with the descending part of the duodenum, are stripped off the organ in a
medial direction, until the hilum and the renal vessels are reached.
The left kidney is crossed transversely, about its middle, by the body of the
pancreas and the splenic vessels. To palpate the supra-pancreatic portion, the
hand is passed through the left portion of the gastro-colic ligament, upwards
behind the stomach, into the superior part of the omental bursa. The spleen will
be felt to overlap the lateral border of the kidney. To palpate the infra-pancreatic
portion of the organ, which is covered by the peritoneum continued downwards
from the attachment of the inferior layer of the transverse mesocolon, the hand is
passed deeply into the upper part of the left infra-colic peritoneal compartment as
far as the angle of the left flexure of the colon. This area of the kidney is over-
lapped by coils of small intestine, while passing transversely laterally in front of
it are the left colic artery and its branches. When the left kidney is excised by
the transperitoneal route, the left colic flexure and the descending colon are
mobilised by dividing the peritoneum lateral to them so as not to injure the left
colic artery.
In addition to their true fibrous capsules, the kidneys are surrounded by and
enveloped in a well-marked fatty capsule. Outside this perinephric fat is a more or
less well-defined fibrous envelope, known as the renal fascia or fascia of Gerota,
which forms, as it were, a sheath to the organ. Hence, just as in the case of the
prostate and thyreoid glands, the kidney possesses, in addition to its true capsule,
a sheath derived from the neighbouring fasciae. The anterior and posterior layers
of the sheath remain distinct at the medial border of the kidney and are prolonged,
the one in front of, and the other behind the renal vessels. The two layers
remain separate also for some distance below the inferior pole of the kidney, and it
is into this downward extension of the fascial compartment that the kidney descends
in the condition known as movable kidney. Above and laterally the sheath joins
the fascial lining of the diaphragm and transversus muscles respectively. Outside
the perinephric fascia is a second layer of fat sometimes spoken of as the
paranephric fat.
When the inferior pole of the kidney receives a special blood supply, either
directly from the aorta, or from the renal artery, the abnormal vessel may, by
passing either in front or behind the superior part of the ureter, cause the latter to
be so kinked over the vessel as to cause a secondary hydronephrosis.
Brodel has shown that the branches of the renal artery are distributed to the
cortex of the kidney in an anterior and a posterior group ; hence, in splitting the
91
1426 SUKFACE AND SUKGICAL ANATOMY.
kidney substance to reach the renal pelvis, the incision should be made along the
frontier line between the two vascular areas, viz., about half an inch behind and
parallel to the lateral border of the kidney.
The ureters lie behind the peritoneum covering the psoas major muscles ; they
descend almost vertically in the umbilical region 1J in. from the median plane.
At the level of the intertubercular plane they lie in front of the termination of the
common iliac arteries, and then pass down into the pelvis minor, in front of the
hypogastric arteries.
The ureter possesses a well-developed muscular wall so that it is well adapted for
suturing, while its rich blood supply favours rapid healing. Its abdominal portion
is supplied by the renal and internal spermatic arteries ; its pelvic portion by the
superior vesical, the inferior vesical, and the middle hsemorrhoidal arteries. By
their anastomosis they form a continuous and somewhat tortuous chain which is
generally visible beneath the peritoneum along the whole course of the tube.
In reading skiagrams with a view of ascertaining the presence or absence of
calculi in the abdominal portion, of the urinary tract, Hurry Fen wick makes use
of a line projected vertically upwards from the highest part, i.e. the centre, of the
iliac crest to the twelfth rib. As this line corresponds to the lateral limit of the
kidney, it follows that a " calculus shadow " close to the medial side of this line
will generally occupy one of the calyces and be situated, therefore, towards the
cortex, while if the shadow be situated close to the tips of the transverse processes
of the vertebrae, the calculus will usually be found either in the pelvis of the kidney
or in the abdominal portion of the ureter. The other points to be kept in mind
in reading the radiogram are that the pelvis of the kidney lies opposite the interval
between the transverse process of the first and second lumbar vertebrae, and,
secondly, that the abdominal portion of the ureter descends in the line of the tips
of the transverse processes of the second, third, fourth, and fifth lumbar vertebrae.
Pancreas. The head of the pancreas occupies the curve of the duodenum,
and lies in the lowest part of the right half of the epigastric region, on a level with
the second lumbar vertebra. The neck, which crosses the median plane opposite
the fibre-cartilage between the first and second lumbar vertebrae, lies in the trans-
pyloric plane, while the body lies immediately above that plane. The tail lies in
the left hypochondriac region. The relations of the pancreas to the transverse rneso-
colon and to the neighbouring viscera have already been sufficiently referred to.
After opening the abdomen in the median line, the pancreas is best exposed by
passing through the gastro-colic ligament ; access to the organ through either the
hepato-gastric ligament or the transverse mesocolon is more limited and therefore
less satisfactory.
A pancreatic cyst gives rise to a tumefaction of the abdomen either in the
epigastric or in the umbilical region, depending on whether it pushes the hepato-
gastric ligament before it and develops between the liver and stomach, or whether
it extends forwards below the stomach. In severe contusions of the abdomen the
pancreas may be ruptured against the vertebral column.
Vessels of the Abdomen. The commencement of the abdominal aorta and the
coeliac artery are situated two fingers' breadth above the transpyloric plane. The
superior mesenteric artery arises a finger's breadth above the transpyloric plane, the
renal arteries a finger's breadth below it. The inferior mesenteric artery arises mid-
way between the transpyloric and the intertubercular plane that is to say, about
1 in. above the level of the umbilicus. The abdominal aorta bifurcates in, or a little
to the left of, the median plane, on a level with the highest part of the iliac crest,
and about f in. below the level of the umbilicus.
The inferior vena cava lies immediately to the right of the aorta; its most
important surgical relation is the right ureter, which lies close to its right side.
The common and external iliac arteries may be mapped out by drawing a line,
curved slightly laterally, from a point opposite the bifurcation of the aorta to a
point midway between the superior anterior iliac spine and the pubic symphysis :
the superior third of this line corresponds to the common iliac, the inferior two-
thirds to the external iliac.
In ligaturing the common iliac artery, or the superior part of the external iliac,
THE MALE PERINEUM. 1427
the close relation of the ureter and the ovarian vessels must be borne in mind, while
in ligaturing the inferior part of the external iliac it is the internal spermatic
vessels and the ductus de'ferens which have to be avoided.
The common iliac veins lie mainly to the right of the corresponding arteries, the
left vein, however, crossing behind the right artery to join its fellow to form the
inferior vena cava.
The fact that the left common iliac vein passes behind the right common iliac
artery to reach the vena cava would seem to afford a sufficient explanation for the
much greater frequency with which thrombosis of the femoral vein is met with on
the left side as compared with the right side.
The great vessels upon the posterior abdominal wall, along with the adjacent
lymph vessels and glands, lie in the tela subserosa, and therefore within the
general fascial envelope of the abdomen. Abscesses originating from the retro-
peritoneal lymph glands are, therefore, like perinephric abscesses, extra-peritoneal
but intra-fascial ; abscesses of vertebral origin, whether lumbar, iliac, or psoas,
are, on the other hand, extra-fascial. Abscesses connected with the vermiform
process are primarily intra-peritoneal ; occasionally they ulcerate through the
parietal peritoneum and burrow in the extra-peritoneal fat.
THE MALE PERINEUM.
RThe male perineum is a heart-shaped space, the osseous boundaries of which are
5 same as those which form the inferior aperture of the pelvis. A line drawn
transversely across the perineum between the anterior part of the tuberosities of
the ischium crosses the median plane, immediately in front of the anus, and divides
the space into an anterior or urogenital triangle and a posterior or rectal triangle.
The urogenital triangle is subdivided into a superficial and a deep compartment
by the inferior fascia of the urogenital diaphragm ; in the superficial compartment
is the root of the penis, which gives rise to a longitudinal fulness upon the surface.
Anteriorly, the surface of the urogenital triangle is continued on to the scrotum,
whilst laterally a distinct groove separates it from the medial surface of the thighs.
The central point of the perineum (common tendon of the perineal muscles) is con-
tinuous with the centre of the base of the fasciae of the urogenital diaphragm, and
lies a finger's breadth in front of the anus. Immediately in front of it, and about
1 in. from the centre of the anus, is the posterior edge of the bulb of the corpus
cavernosum urethrse. The superficial compartment of the urogenital triangle is
bounded below by the perineal fascia of Colles, which is attached posteriorly
to the base of the fa-scia of the urogenital diaphragm, and laterally, on each side,
to the margins of the pubic arch. Anteriorly, the fascia of Colles passes on to the
scrotum, the penis, and spermatic funiculi, to become continuous with the fascia
of Scarpa upon the anterior surface of the abdomen.
When the urethra is ruptured below the inferior fascia of the urogenital
diaphragm, the course of infiltration of the extravasated urine is determined by
these attachments ; at first, therefore, the urine is confined within the superficial
compartment, but gradually travels forwards, under the fascia of Colles, on to the
inferior part of the anterior abdominal wall ; it is prevented from passing into the
front of the thigh by the attachment of Scarpa's fascia to the fascia lata, a little
distal to the inguinal ligament.
The deep compartment of the urogenital division of the perineum corresponds
to the interval between the inferior and superior fascise of the urogenital diaphragm.
The most important structures which this compartment contains are the membranous
part of the urethra, the bulbo-urethral glands, the internal pudendal vessels, and
the artery to the bulb.
The membranous part of the urethra lies one inch behind the inferior border of the
pubic symphysis. When this division of the urethra is ruptured, the extravasated
urine, after filling the deep compartment, may reach the superficial compartment
by bursting through the inferior fascia of the urogenital diaphragm where the
vessels pierce it ; or it may penetrate the superior fascia, infiltrate the perivesical
91 a
1428 SUKFACE AND SUEGICAL ANATOMY.
connective tissue and the space of Betzius, and ultimately ascend on the anterior
abdominal wall between the fascia transversalis and the parietal peritoneum.
The bulbo-urethral glands, which lie immediately behind the membranous part of
the urethra, are overlapped by the bulb of the urethra, from which they are separated
by the inferior fascia of the urogenital diaphragm. The internal pudendal
artery lies just within the margin of the pubic arch. The artery to the bulb
runs transversely medially ^ in. above the base of the urogenital diaphragm, i.e.
above the level of a line drawn from the front of the tuberosities to the central
point of the perineum.
The male urethra measures about eight inches from the external to the internal
orifice; the narrowest portion is at the external orifice; a second narrowing
occurs at the urogenital diaphragm. It is behind these constrictions that a
calculus is liable to become impacted. The most dependent part of the urethra
is the bulbous portion, and it is in this situation that an organic stricture is
most frequently met with. The membranous part of the urethra, situated between
the two fascise of the urogenital diaphragm, is surrounded by the sphincter urethrae
membranacese muscle, which, when thrown into spasm, may firmly grip an instru-
ment as it is passed into the bladder. Rupture of the urethra from a fall on
the perineum generally involves the bulbous portion. A. false passage made during
the passage of an instrument generally traverses the floor of the urethra at the uro-
genital diaphragm ; to prevent this the point of the instrument should always be
directed upwards, and the handle at the same time depressed as soon as the instru-
ment is felt to encounter the resistance of the inferior fascia of the urogenital
diaphragm. When the prostate is hypertrophied the prostatic part of the urethra
is elongated, and the internal orifice may look directly forwards, while if the lateral
lobes are unequally enlarged it may deviate laterally. Patients with prostatic
hypertrophy are seldom able to empty the bladder completely, on account of the
dependent well which exists behind the prostate.
Cystoscopic Examination of the Bladder. On making a cystoscopic examina-
tion of the bladder special attention is paid to the trigone, as most of the patho-
logical lesions are associated with this region. At its anterior angle is the internal
urethral orifice, while at its postero- lateral angles are the small oblique slit-like
orifices of the ureters, surrounded by a very slight lip-like elevation of the mucous
membrane. At the base of the trigone the mucous membrane is raised into a
smooth transverse ridge which stretches between the ureteric openings, with a
slight forward convexity. The elevation is caused by a bundle of transverse
muscular fibres, continuous with the longitudinal fibres of the ureters. The
distance of the ureteric orifices from one another is rather more than an inch,
while their distance from the internal urethral orifice is slightly less than an inch.
The urine is ejected into the bladder intermittently at intervals of a minute or
so. During each ejection the ureteric orifice is seen to pucker up, and as it relaxes
the gush of urine takes place in the form of a characteristic whirl "resembling an
injection of glycerine into water." The mucous membrane of the trigone is closely
connected with the subjacent muscular wall, so that it presents a smooth appear-
ance ; whereas over the rest of the- bladder it is thrown into folds owing to the
looseness of the submucous tissue. Further, the mucous membrane of the trigone
presents a pink injection, while over the rest of the bladder it is of a pale straw
colour. This contrast is due to the difference in the arrangement of the, blood-
vessels ; over the trigone they are larger, more numerous, and form a close network ;
hence, when this surface is inflamed, the congested vessels form a continuous vascular
layer. Over the rest of the bladder one sees, here and there in the mucous mem-
brane, small segments of fine vessels giving off a cluster of short branches, the finer
anastomoses of which are not visible when the mucous membrane is healthy.
The form and shape of the trigone in women may be distorted by prolapse of
the bladder, by alterations in the size and position of the cervix, and by the
presence of fibroids. In the male, distortion is usually due either to the enlarge-
ment of the prostate or to disease of the vesiculse seminales.
When the normal bladder is comfortably filled, the bladder walls appear
almost smooth, but when the bladder contracts the delicate muscular trabeculae
THE PKOSTATE. 1429
become visible through the mucous membrane. When the bladder is hyper-
trophied as the result of, urinary obstruction the muscular trabeculse become
greatly hypertrophied, and stand out prominently, even when the bladder is full.
The spaces between the trabeculse may become so deeply pitted as to lead to the
formation of little pockets, known as false diverticula.
THE PROSTATE.
The operation of prostatectomy has proved so successful in removing
urinary complications associated with enlargement of the prostate that a fresh
impetus has been given to the study of the anatomy of the gland from the surgical
point of view. With the body erect the base of the prostate lies in a horizontal plane
at the level of the middle of the symphysis pubis, while its apex lies \ in. behind
and below the sub-pubic angle. It follows, therefore, that the vesical orifice and
the base of the prostate are within easy reach of the finger introduced through a
supra-pubic cystotomy incision. The anterior surface of the prostate lies about
| in. behind the pubes, to which it is connected by the pubo-prostatic ligaments.
Above those ligaments is the space of JRetzius, occupied by fatty tissue which
passes upwards in front of the anterior wall of the bladder, between the umbilical
arteries, as far as the umbilicus, while laterally it extends on each side, between the
peritoneum and pelvic fascia, as far back as the hypogastric arteries. The
posterior surface of the prostate is related to that part of the rectal ampulla
immediately above the anal canal, and is therefore accessible to palpation per
rectum. Between the rectum and the posterior part of the sheath of the prostate
(formed by the recto-vesical layer of pelvic fascia) is a loose cellular interval, which
is taken advantage of in the operation of excision of the rectum, and in exposing
the posterior surface of the prostate in the operation of perineal prostatectomy.
The lateral surfaces of the prostate cannot be felt through the rectum ; they are
related to the anterior or pubo-rectal fibres of the levatores ani, from which they
are separated by the lateral portion of the fascial envelope of the gland.
The prostate substance is made up of branching tubular glands supported
by a fibro-muscular stroma. The gland tissue is most abundant in the posterior
and lateral aspects of the organ ; anteriorly the stroma is more abundant and
extends backwards from the capsule to the urethra to form a sort of anterior
commissure. By the term " capsule " of the prostate is understood the immediate
or proper envelope of the gland ; this envelope consists of parallel layers of fibro-
muscular tissue, continuous with, and forming part of, the stroma of the organ. In
some instances it is so thin that the gland tissue reaches almost to its surface,
while in other instances it is so thick as to deserve to be regarded as forming the
cortical portion of the gland. By the term " sheath " of the prostate is meant the
fibrous envelope derived from the pelvic fascia ; the veins of the pudendal plexus
lie between its lamellae.
In what is known as " senile " hypertrophy of the prostate the organ may be uniformly
enlarged, or the enlargement may affect chiefly one or other of the lateral lobes, one
or both of which may enlarge more particularly in an upward direction so as to project
into the bladder. This intra-vesical overgrowth may take the form either of a more or
less pedunculated projection, situated immediately behind the internal urethral orifice, or it
may surround the orifice to form a prominent ring-like elevation. As the intra-vesical
growth enlarges, it makes its way towards the bladder within the ring of the sphincter
vesicae, and, having pushed before, or separated, the internal longitudinal fibres of the
bladder, it comes ultimately to be separated from the cavity of the bladder by mucous
membrane only. In the operation of supra-pubic prostatectomy the true capsule of the
prostate is at once reached by simply tearing through the mucous membrane immediately
behind the vesical orifice. By keeping close to the capsule, the entire organ, including the
capsule, may be enucleated from its sheath. As the latter is markedly thicker and denser
in the liypertrophied than in the normal prostate, this enucleation can be accomplished
without injuring the veins of the pudendal plexus. As a rule, the only part where any
difficulty in the enucleation is encountered is anteriorly, where the capsule is more
intimately connected with the sheath by the interposition of a layer of striated longi-
tudinal muscular fibres which pass from the urethra to be continuous with the outer
91 &
1430 SUKFACE AND SUKGICAL ANATOMY.
longitudinal fibres of the bladder. In " total " prostatectomy, practically the whole of
the prostatic urethra is removed along with the gland. In some instances, instead of
removing the entire prostate and its capsule along with the prostatic urethra, the surgeon,
by working within the capsule, is able to enucleate each lateral glandular mass either
separately or united to its fellow in the form of a horse-shoe shaped mass, the urethra
and the anterior commissure being left more or less intact. The cavity, which is left
behind after the removal of the prostate, at once contracts owing to the approximation of
the bladder and rectum antero-posteriorly, and of the levatores ani at the sides.
In perineal prostatectomy the posterior surface of the prostate is exposed by making a
horse-shoe shaped incision with the convexity reaching forwards to a point immediately
behind the bulb ; at the sides, the incision sinks into the ischio-rectal fossae, its extremities
ending at the anterior part of the ischial tuberosities (Fig. 1108). After reflecting the skin
and subcutaneous tissue, the incision is carried through the central point of the perineum.
The bulb, the superficial transverse perineal muscles, and the inferior fascia of the
urogenital diaphragm are now drawn forwards, and the fibres of the recto-urethral
muscle (which connect the anterior wall of the rectal ampulla with the sphincter
urethrse) are divided ; this allows the anal canal and the inferior end of the rectum to be
retracted backwards. The dissection is now carried in a forward direction, between
the anterior borders of the levatores ani, towards the prostate, so as to strike the loose
non-vascular space which intervenes between the posterior part of the prostatic sheath and
the thin fascia outside the muscular wall of the rectum. The posterior surface of the
prostate, covered by its true capsule, is reached by incising the fascial sheath. The
prostate, along with its true capsule and the urethra, may either be enucleated entire
from the sheath, or the true capsule may be incised as well as the sheath, and the
adenomatous masses removed separately. The operation is greatly facilitated by pulling
the prostate down into the wound by a special retractor (Young) inserted into the bladder
through a median incision into the floor of the membranous part of the urethra.
The epididymis, which can be felt, as an elongated curved body applied
vertically to the posterior margin of the testis, is especially involved in gonorrhoaal
and tubercular infections of the testis. Occupying the posterior part of the
spermatic funiculus is the ductus deferens, which, when grasped between the
finger and thumb, feels like a piece of whip-cord. The spermatic veins form a
plexus in the substance of the funiculus, known as the pampiniform plexus ; a varicose
condition of these veins gives rise to the condition known as varicocele. In operating
for varicocele the veins are reached by dividing, in succession, all the coverings of
the funiculus ; the deepest covering, viz., the internal spermatic fascia, derived from
the fascia ( transversalis, forms a well-marked fibrous envelope which immediately
surrounds the veins and other constituents of the funiculus. Besides the internal
spermatic artery, the testis receives its blood supply from the artery accompanying the
ductus deferens and from the external spermatic branch of the inferior epigastric.
The marked swelling which attends cedema and hcematoma of the scrotum is due
to the loose and delicate character of the cellular tissue which occupies the space
between the dartos muscle and the subjacent membrane derived from the inter-
columnar fascia.
The anus is situated in the rectal division of the perineum about 1 J in. in front
of and below the tip of the coccyx. The skin around the orifice is pigmented and
thrown into radiating folds. The painful linear crack or ulcer, known as fissure of
the anus, generally occupies one of the furrows at the posterior margin of the
anus. The skin of the anus is provided with large sebaceous and sweat glands,
which are occasionally the site of small and very painful anal abscesses.
On making a rectal examination it will be observed that the finger, before it
reaches the cavity of the rectum, traverses the narrow or sphincteric portion of the
rectum, appropriately named by Symington the anal canal. This canal, which is
directed from below upwards and forwards, extends from the anal orifice to the I
ampulla of the rectum ; it is from one to one and a half inches in length ; its
upper end is on a level with the medial borders of the pubo-rectal portions of the -
levatores ani.
External haemorrhoids are developed from the anal folds situated outside the
white line corresponding to the muco-cutaneous junction; internal piles are
developed from the veins of the mucosa at the upper part of the anal canal.
THE PEOSTATE.
1431
Anal canal
FIG. 1107. THE INTERIOR OF THE ANAL CANAL AND INFERIOR PART
OF THE EECTUM.
In the superior half of the anal canal are the rectal columns of Morgagni. Accord-
ing to Ball, fissure of the, anus is generally caused by the tearing downwards of one
of the posterior rectal sinuses (Fig. 1107) during the passage of a scybalous mass.
According to Birmingham, the pubo-coccygeal fibres of the levator ani close the
superior parf of the anal canal, whilst the external sphincter closes the remaining
part. The internal
sphincter, according to
the same author, acts
probably as a detrusor,
its use being to empty
the anal canal completely
after the passage of the
faecal mass.
Ischio-rectal Fossa.
The apex of the ischio-
rectal fossa (Fig. 1108),
formed by the attach-
ment of the inferior fascia
of the pelvic diaphragm
(anal fascia) to the ob-
turator portion of the
parietal pelvic fascia, is
directed up wards towards
the pelvis, and lies 2J in.
from the Surface. The Showing the rectal columns of Morgagni and the rectal sinuses between their
medial Wall Of the fossa inferior ends. The columns were more numerous in this specimen
,-, -i than usual. (From Birmingham.)
is bounded by the levator
ani and coccygeal muscles covered by the inferior fascia of the pelvic diaphragm
(Fig. 1108); the lateral wall by the obturator internus muscle covered by the
obturator fascia. An abscess in the ischio-rectal fossa should be opened early, other-
wise it is liable to burst through the medial wall into the rectum ; should it open
also upon the skin surface a complete "fistula in ano " is formed. When a " fistula
in ano " results from the bursting of a submucous abscess of the anal canal the
track of the fistula runs either medial to or through the fibres of the internal
and external sphincter muscles, and the external or skin opening is, as a rule, close
to the anus, while the internal opening is generally within the upper end of the
anal canal. Occasionally the ischio-rectal abscess perforates the levator ani towards
the apex of the fossa ; it then burrows into the peri-rectal cellular tissue of the
pelvis, and opens into the ampulla of the rectum. In other cases, again, the
abscess starts in the peri-rectal tissue internal to the levator ani, and either
bursts into the rectal ampulla or through the levator ani into the ischio-rectal
fossa, and so reaches the surface. Or the pus may burrow between the rectum and
coccyx, whence it may pass outwards through the greater sciatic foramen, behind
the parietal pelvic fascia, into the buttock ; or, by piercing the visceral layer of
the pelvic fascia, may reach the tela subserosa of fatty tissue of the pelvis and
ascend in it to form an iliac abscess.
The lymph vessels from the skin of the anus pass along the perineo-femoral
folds to the most medial glands of the groin, both superficial and deep subinguinal.
According to Poirier and Cune*o, those from the region of the white line end in
the hypogastric glands which lie in front of the hypogastric artery, while those
which issue from the mucous membrane of the upper part of the anal canal
and the rectum proper traverse a few minute glands (ano-rectal glands of Gerota)
placed between the muscular and fibrous coats of the rectum, along the superior
hsemorrhoidal vein and its two branches, and pass thence to the sacral glands
which lie internal to the anterior sacral foramina.
Digital Examination of Rectum. In making a rectal examination the finger
uld be carried forwards from the tip of the coccyx so as to enter the anus from behind,
finger is then gently pressed upwards and slightly forwards through the sphincteric
91 c
1432
SUEFACE AND SUKGICAL ANATOMY.
region, in the axis of the anal canal, until it reaches the cavity of the rectum, the inferior
part of which is dilated to form the ampulla. The transverse folds of the rectum or
valves of Houston, three in number, project into the cavity of the bowel in the form of
prominent crescentic shelves, which are produced by the three permanent or true flexures
into which the rectum ' is thrown (Birmingham) ; the inferior valve, which may be
sufficiently prominent to impede the passage of the finger, must not be mistaken for a
pathological condition. Through the anterior wall the finger can palpate from below up-
wards the bulb of the urethra, the membranous part of the urethra, the bulbo-urethral
glands (when inflamed and enlarged), the apex and lateral lobes of the prostate, the
vesiculas seminales, and the external trigone of the bladder. With the left forefinger in the
rectum, an instrument passed into the bladder can be distinctly felt as it traverses the mem-
Posterior superior spine
Upper lateral inflexio;
Peritoneum (pararectal
fossa)
Superior hsemorrhoidal
artery
Rectum
Sacro-tuberous ligament
Ischio-rectal fossa
Anal canal
Anus
Third sacral vertebra
Fourth sacral vertebra
(cut)
Inferior border of
piriformis (cut)
Superior hsemorrhoidal
artery
Lateral inflexion
Coccygeus
Levator ani
External sphincter
FIG. 1108. THE RECTUM FROM BEHIND.
The sacrum has been sawn across through the 4th sacral vertebra, and its inferior part removed with the coccyx.
The posterior portions of the coccygei, levatores ani, and of the external sphincter have been cut away.
The "pinching in " of the inferior end of the rectum by the medial edges of the levatores ani, resulting
in the formation of the flattened anal canal, is suggested in the illustration, which has been made from a
formalin-hardened male body, aged thirty. The lateral inflections of the rectum, corresponding to
Houston's rectal valves, are also shown. (From Birmingham.)
branous urethra ; as it lies in the prostatic urethra it is separated from the finger by the
prostate. Hence, when a false passage is made through the bulbous or membranous portion of
the urethra, the instrument, if pushed onwards towards the bladder, will be felt immediately
outside the rectum between it and the prostate. In the child, owing to the rudimentary
condition of the prostate, the instrument is distinctly felt close to the rectum, as it lies in
the prostatic as well as in the membranous portion of the urethra. When the prostate is
not enlarged the tip of the finger can just reach the external trigone, which is most
distinctly felt when the bladder is full. The vesiculse seminales, indistinctly felt when
healthy, may be readily palpated when enlarged and indurated from disease. Through
the side wall of the rectum may be palpated the ischio-rectal fossa, the bony wall of the
pelvis minor, and, when enlarged, the hypogastric lymph glands ; through the posterior
wall the hollow "of the sacrum and coccyx, and the lymph glands lying in the retro-
rectal cellular tissue.
THE PEOSTATE. 1433
In the child rectal examination enables one to palpate, in addition to the structures in the
cavity of the pelvis minor, those which occupy the lower segment of the abdomen. When
the bladder is empty even a small calculus can be readily felt by recto-abdominal palpation.
The distance of the apex of the recto-vesical pouch of peritoneum from the anus
varies considerably, according to the degree of distension of the bladder and rectum ;
when both are empty it reaches to about 2 in. from the anus ; when both are dis-
tended it is at least one inch higher (Fig. 1108).
Examination by Sigmoidoscope. In introducing the sigmoidoscope into
the pelvic colon the direction of the anal canal and the curve of the rectum must
be borne in mind ; as the instrument traverses the anal canal it must be directed
forwards as well as upwards, after which it is pushed onwards, in a backward and
upward direction, towards the hollow of the sacrum ; while, finally, in order to
reach the pelvic colon, it is again directed forwards and a little to the left so as to
clear the promontory of the sacrum. The instrument is more difficult to pass in
women, on account of the greater abruptness of the curvature of the sacrum in the
female as compared with the male.
When examined with the sigmoidoscope the mucous membrane of the rectum
is seen to possess a deep red colour, and an excellent view is obtained of the rectal
valves of Houston. The most conspicuous fold, known as the plica transversalis,
projects from the right wall about the level of the recta-vesical peritoneal
reflection, i.e. about three inches from the anus. The highest valve, situated at
the colo-rectal junction, gives rise to a distinct narrowing which must not be
mistaken for a stricture. The pulsations of the left common iliac artery can
generally be seen to be communicated to the postero-lateral wall of the pelvic colon
about four inches from the anus.
Removal of the Rectum. In removing the rectum and anal canal for
malignant disease, an incision is carried round the anus and then upwards and
backwards over the coccyx and inferior half of the sacrum. The ano-coccygeal
raphe is divided longitudinally and the coccyx (either alone or along with more or
less of the lower part of the sacrum) is excised by dividing the structures
attached to its margins, viz., the inferior fibres of the glutseus maximus, the
coccygeus, and the sacro-tuberous and sacro-spinous ligaments (O.T. greater and
lesser sacro-sciatic). The parietal pelvic fascia, here very thin and adherent, is
removed along with the bone. The middle sacral artery is ligatured. This is now
seen, stretching across the floor of the wound, a well-defined sheet of fascia, viz.,
the rectal layer of the visceral pelvic fascia, which is divided longitudinally and
stripped to either side off the posterior surface of the rectum ; in doing this the
branches of the middle hsemorrhoidal arteries, and, higher up, the two divisions of
the superior haemorrhoidal are encountered and ligatured. Anteriorly, the anal
canal is detached from the central point of the perineum, after which the anterior
surface of the rectum is freed from below upwards from the urogenital
diaphragm containing the membranous urethra, the posterior surface of the
prostate, the trigone of the bladder and the vesiculae seminales and the ductus
deferentes. This procedure is facilitated by the existence of a cellular interval
between the anterior wall of the rectum and the strong recto-vesical layer of
visceral pelvic fascia, which forms the posterior part of the sheath of the prostate,
and, higher up, encloses the vesiculse seminales and ductus deferentes. In order
to strike this cellular interspace, the surgeon, after dividing the central point of
the perineum transversely, deepens the incision down to the apex of the prostate.
In doing this he divides a band of muscular fibres (recto-urethral muscle) which
passes from the anterior wall of the lowest part of the rectal ampulla to blend
with the sphincter ure three muscle surrounding the urethra at the apex of the
prostate. It is these recto-urethral fibres, which, by pulling forwards the ampulla,
bring it into close relation with the urethra ; hence it is especially at this stage of
the operation that great care must be taken not to open into the rectum or to
wound the urethra. After exposing the apex of the prostate the next step is to
retract the anal canal well backwards and to define the anterior of pubo-prostatic
borders of the levator ani muscle. These muscles are then divided, on each side,
1434 SUKFACE AND SURGICAL ANATOMY.
a little above their insertion into the rectum. The posterior surface of the prostate,
covered with recto-vesical fascia, is now exposed.
By continuing the separation of the rectum upwards in the cellular plane above
mentioned, the bottom of the recto-vesical pouch of peritoneum is reached ; it can
usually be stripped for some distance off the rectum, without opening into the peri-
toneal cavity. In freeing the rectum laterally, bands of connective tissue containing
branches of the middle and superior haemorrhoidal vessels are divided. If the
tumour is situated at the superior part of the rectum, the recto-vesical pouch of
peritoneum is freely opened in a transverse direction. The colo-rectal junction is
then mobilised by dividing the sacral attachment of the pelvic mesocolon and secur-
ing the superior haemorrhoidal artery. After dividing the rectum well above the
tumour, the opening into the peritoneal cavity is closed by suturing together the
anterior and posterior walls of the recto-vesical pouch. If a permanent colostomy
has been established, the divided bowel is closed ; if not, a sacral anus is made.
FEMALE PELVIS.
On opening the abdomen by a median incision extending from the umbilicus to
the pubes, and looking into the pelvis minor from above, after displacing some coils
of the small intestine upwards, the fundus of the uterus, directed forwards and
a little upwards, is seen resting upon the superior surface of the bladder. Behind
the uterus is the rectum, and between the two the recto-uterine pouch of Douglas,
containing the pelvic colon and the inferior part of the ileum. The ovary lies__
little below the level of the superior aperture of the pelvis minor upon a triangular
shelf, bounded in front by the broad ligament, behind and medially by the uterp-
^ sacral ligament, and behind and laterally by the pelvic wall. When the vermi-
7V- form process overhangs the superior aperture of the pelvis minor its tip may come
ff into close relation with the right ovary, a condition which often leads to a difficulty
in distinguishing an inflammation of that ovary from appendicitis. The round
ligaments are seen passing forwards and laterally from the upper parts of the right and
left borders of the uterus to the abdominal inguinal rings, which lie immediately in
front and to the medial side of the terminations of the external iliac arteries.
Inferiorly and at the medial side of the round ligament, as it leaves the pelvis, is
the inferior epigastric artery. By pulling the uterus upwards the attachments of
the broad ligament to the floor and side walls of the pelvis are brought into
evidence, as also are the utero-vesical and recto-vaginal peritoneal pouches ; the
former is shallow, while the deepest part of the latter covers the upper fourth of
the posterior wall of the vagina, and comes into relation, therefore, with the
posterior fornix.
The utero-vesical peritoneal reflection takes place at the level of the junction
of the body of the uterus with the cervix. The anterior wall of the cervix comes
into relation, therefore, with the superior part of the base of the bladder, from which,
owever, it is separated by a layer of loose connective tissue. It is the existence
this cellular plane which enables the surgeon to separate the bladder readily
from the uterus in the operation of hysterectomy.
While the anterior wall of the vagina is firmly united to the urethra, its
posterior wall, on the other hand, can be readily separated from the rectum, in
consequence of the interposition between the two organs of the recto-vaginal fascia.
The ureter crosses the brim of the pelvis in front of the bifurcation of the
common iliac artery 1J in. lateral to and a little below the centre of the sacral
promontory. The corresponding point on the anterior abdominal wall is at the
junction of the lateral and middle thirds of a line joining the anterior superior
spines of the ilium.
After crossing the termination of the common iliac artery from lateral to
medial side, the ureter dips vertically into the pelvis minor behind the peri-
toneum covering the hypogastric artery. It then courses medially in the para-
metric cellular tissue below the base of the broad ligamenta. In this position
it lies a little above the lateral fornix of the vagina, about three-quarters of an
inch lateral to the superior part of the cervix uteri ; finally, just before it pierces
THE FEMALE PELVIS. 1435
the lateral angle of the bladder, it lies in front of the antero-lateral aspect of the
upper part of the vaginal- wall.
The relation of the pelvic portions of the ureters are of special importance in
the female as their close relation to the cervix uteri and upper part of the vagina
renders them liable to injury, more especially in the -operation of hysterectomy
performed for malignant disease of the uterus.
The uterine artery, in the first part of its course, passes downwards and forwards
a little anterior and lateral to the ureter. At the level of the orificium internum
uteri it takes a medial direction and passes along the inferior border of the broad
ligament, and crosses, above and in front of the inferior part of the ureter, from
lateral to medial side ; it then passes above the lateral fornix of the vagina and
finally ascends close to the side of the body of the uterus, and ends by anasto-
mosing with the ovarian artery below the isthmus of the uterine tube.
The ovarian artery enters the pelvis minor between the layers of that portion of
the broad ligament known as the ligamentum suspensorium ovarii ; it is here that the
vessel may be most readily ligatured in abdominal hysterectomy, and in ovariotomy.
The lymph vessels from the inferior part of the vagina pass to the superficial
vaginal and sacral glands, while those from the rest of the vagina, from the cervix
uteri and from the body of the uterus, pass to the hypogastric, the external iliac,
and the sacral glands. The hypogastric glands are situated on the side wall of
the pelvis in close relation to the origins of the branches of the hypogastric artery.
The sacral glands form a chain along the medial side of the anterior sacral foramina.
The lymph vessels from the fundus of the uterus, and from the ovary, terminate in
the glands around the aorta.
The external genitals are fully described elsewhere (p. 1324). The external
orifice of the urethra, surrounded by a slight annular prominence of the mucous
membrane, is situated about 1 in. behind the clitoris, immediately above the centre
of the base of the vestibule a smooth triangular area at the anterior part of the
vulva, with its sides formed by the labia minora and its base by the anterior margin
of the ostium vaginse. In passing a catheter the instrument is directed along
the forefinger (introduced just within the ostium vaginae with the palmar surface
towards the symphysis pubis) to the base of the smooth vestibule, where it is
tilted slightly upwards so as to bring its point opposite the urethral orifice.
The larger vestibular glands, about the size of a bean, are placed on each side
of the posterior third of the orifice of the vagina, below the urogenital diaphragm.
Their ducts, nearly one inch in length, open posteriorly between the hymen and
the posterior commissure (fossa navicularis). Abscesses and cysts not infrequently
develop in connexion with these glands. The bulbs of the vestibule are two piri-
form collections of erectile tissue situated on each side of the vestibule, between
the bulbo-cavernosus muscle and the inferior fascia of the urogenital diaphragm.
Kupture of these bodies gives rise to the condition known as pudendal hcematocele.
The cervix uteri projects downwards and backwards into the roof of the vagina
so as to leave a distinct fornix between the two. The relations of the fornix are of
so much practical importance that for descriptive purposes it is customary to sub-
divide it into an anterior, a posterior, and two lateral portions. The anterior fornix,
which is shallow, is related to the base of the bladder and to the utero-vesical pouch
of peritoneum. The posterior fornix, which is deeper, extends upwards for some
little distance in front of the anterior wall of the lowest part of the pouch of
Douglas. The septum between the two is formed merely by the wall of the vagina ;
hence the readiness with which the pelvis may be drained by puncturing it and
pulling a tube through the opening from the pelvis into the vagina.
The lateral fornix lies below the medial part of the base of the broad ligament.
An incision carried through it would therefore open into 'the parametric cellular
tissue and would expose the uterine artery as it passes transversely to the uterus,
after crossing above and in front of the lower part of the ureters.
Vaginal Examination. In making a vaginal examination the patient should be
placed in the dorsal position, with the thighs well flexed ; the index-finger of the right
hand is now carried along the fold of the buttock towards the median plane, where it
will impinge against the posterior aspect of the introitus vaginae, whence it is inserted
1436 SURFACE AND SUEGICAL ANATOMY.
upwards and backwards into the canal ; to render the examination more thorough the
middle finger also may be introduced. When the uterus is in its normal position the
vaginal part of the cervix uteri is felt as a knob-like body projecting downwards and back-
wards into the upper part of the canal. In nulliparse the orificium uteri externum is a small
transverse slit, whereas in women who have borne children it is larger and more or less
fissured. Above and behind the cervix is the posterior fornix, which is in close proximity to
the recto-uterine pouch of Douglas ; this pouch, though normally empty, is the frequent
site of displaced abdominal and pelvic organs, and collections of intra-peritoneal effusions
and exudations. A loaded rectum can be detected through the vagina by the characteristic
way in which the contents can be pitted by the finger. In front of the cervix is the shallow
anterior fornix, through which may be felt the body of the uterus and the base of the
bladder, while through the inferior half of the anterior vaginal wall the urethra may
be detected as a cylindrical, cord-like thickening which may be rolled against the inferior
border of the symphysis. The ureter, especially if enlarged, can be recognised through
the antero-lateral fornix, by compressing it against the pubic bone.
By the bimanual examination the pelvic organs are steadied and pushed downwards
towards the inferior aperture of the pelvic by the pressure of the left hand applied in the
hypogastric region, so that they can be more readily reached and palpated by the finger
placed in the vagina with its palmar aspect directed upwards. The ovary may be felt as
a firm body about the size of the end of the thumb by pushing the fingers well up into
the lateral fornix towards the side wall of the pelvis. In health the ovaries are freely
movable. The healthy uterine tubes cannot, as a rule, be felt per vaginam.
Examination of Interior of Bladder. The whole of the interior of the bladder
in the female can be readily seen by reflecting light into it through a speculum introduced
into the empty bladder after dilating the urethra. The patient is placed in the genu-
pectoral position, so that the bladder may become inflated with air, the coils of intestine
being displaced upwards. In the distended condition of the bladder the mucosa has a dull
white or straw-coloured appearance, except in the region of the trigone, which shows a pale
pink injection. The ureteral orifices placed a little more than one inch apart and con-
nected by a slight transverse ridge (inter-ureteric fold), present the appearance of fine
oblique slits situated upon small and somewhat injected elevations of the mucosa.
Rectal Examination. By rectal examination the finger can palpate, from below
upwards, the recto-vaginal septum, the cervix uteri, the posterior fornix of the vagina,
the apex of the recto-uterine pouch of Douglas, and the body of the uterus. By washing
out the rectum and introducing a speculum into the bowel, with the patient in the genu-
pectoral position, the rectum becomes inflated with air ; the finger can now feel very
distinctly the posterior surface of the uterus and the uterine tubes, and by running the
finger laterally, along the prominent fold formed by the utero-ovarian ligament, the ovary
is also very distinctly felt.
THE BACK.
Median Line of the Back. In the median line of the back is the vertebral
furrow, which is deepest in the inferior thoracic and superior lumbar regions, where
the sacro-spinales muscles are most prominent. Over the superior sacral region,
where the sacro-spinales muscles are tendinous, is a flattened area forming an equi-
lateral triangle, the angles of which correspond respectively to the posterior superior
spines of the two iliac bones and the third sacral spine. The vertebral spines can be
palpated at the bottom of the vertebral furrow ; they become more distinct when the
vertebral column is flexed, and, as pointed out by Holden, they become mapped out by
reddened areas when friction is applied along the furrow. The identification and
counting of the spines will be facilitated if it is remembered that the first thoracic
is more prominent than the vertebra prominens (seventh cervical), that the third
thoracic is on a level with the root of the spine of the scapula, the seventh thoracic
its inferior angle, the fourth lumbar with the highest part of the iliac crest, and
the second sacral with the posterior superior iliac spine.
Lateral Region of the Back. Above the spine of the scapula is the supra-
scapular region, which is padded by a thick mass of muscle consisting of the supra-
spinatus and levator scapulae, covered by the superior part of the trapezius ; the
two latter muscles may be thrown into relief by shrugging the shoulders.
In the interscapular region are the rhomboid muscles which are thrown into
prominence by bracing back the shoulders.
THE BACK. 1437
Below the inferior angle of the scapula the last five ribs can readily be felt
lateral to the sacro-spinales muscle ; when the twelfth rib does not reach beyond
this muscle, the eleventh' rib will be mistaken for it, unless the ribs are counted
from above downwards.
The inferior border of the trapezius is indicated by a line extending upwards and
laterally from the twelfth thoracic spine to the root of the spine of the scapula ; the
superior border of the latissimus dorsi by a line extending from the sixth thoracic spine
transversely laterally across the angle of the scapula. Between these two muscles and
the inferior part of the vertebral margin of the scapula is a triangular area, the floor
of which is formed by the rhomboideus major muscle and the sixth costal interspace.
The lateral border of the sacrospinalis is indicated on the surface by drawing a
line from a point on the iliac crest 3| in. (four fingers' breadth) from the median line,
upwards and slightly laterally to the angles of the ribs. The lateral border of the
quadratus lumborum, which passes upwards and slightly medially, lies a little lateral to
that of the sacrospinalis at the crest, and a little medial to it at the twelfth rib.
The anatomy of the muscles and fasciae which complete the abdominal wall
between the last rib and the iliac crest is of great importance in connexion with
operations in the region of the loin. The space between the last rib and the iliac
crest varies greatly according to the length of the rib, and according to the general
shape of the chest and slope of the ribs as a whole. As a rule, the tip of the
twelfth rib lies about two inches vertically above the centre of the iliac crest.
From a surgical point of view the costo-iliac space may be said to be limited medially
by the lateral edge of the sacrospinalis, and, more deeply, by the tips of the trans-
verse processes of the lumbar vertebrae, while laterally it is bounded by the posterior
free border of the external oblique, and, more deeply, by the line of reflection of the
peritoneum from the colon on to the side wall of the abdomen. The space is
roofed over by the latissimus dorsi, except below, where a narrow triangular interval
is left between its lateral border and the posterior border of the external oblique,
the base of the triangle being formed by the crest of the ilium, a little behind
its centre. This triangle, known as the lumbar triangle of Petit, represents a weak
area through which a lumbar abscess may come to the surface, and through which a
lumbar hernia occasionally develops. On removing the latissimus dorsi and the lower
part of the thin serratus posterior inferior, another triangle will be exposed, which
constitutes a second weak area in the loin ; it is bounded above by the last rib, medially
by the lateral border of the sacrospinalis, and laterally by the posterior muscular fibres
of the internal oblique ; the floor of the triangle is formed by the aponeurosis of
origin of the transversus abdominis muscle. At the lateral border of the quadratus
lumborum this aponeurosis splits into three layers to form two compartments, the
anterior enclosing the quadratus lumborum and the posterior the sacrospinalis.
Kidneys. The superior limit of the kidney is indicated by a line drawn trans-
versely across the loin opposite the eleventh thoracic spine, the inferior limit by a
line on a level with the third lumbar spine. The superior extremity reaches to the
eleventh rib ; the lower, which lies immediately lateral to the tip of the transverse
process of the third lumbar vertebra, reaches to within 1 J to 2 in. of the crest of the
ilium. About a third of the kidney lies above the inferior margin of the twelfth
rib. The left kidney usually lies about J in. higher than the right. The most
lateral point of the lateral border lies 4 in. from the median plane, while the hilum
lies 1 \ in. lateral to the median plane in front of the interval between the tips of
the transverse processes of the first and second lumbar vertebrae.
The psoas major muscle intervenes between the postero-medial surface of the
kidney and the transverse processes, and protects the organ from injury by a blow
directed from the front. Between the superior end of the kidney and the eleventh
and twelfth ribs is the diaphragm and the posterior costo-diaphragmatic reflection
of the pleura (Fig. 1110). The relations of the pleura to the last rib have already
been considered (p. 1401).
Posteriorly the course of the superior part of the ureter may be indicated by a
line drawn vertically upwards from the superior posterior iliac spine to the level of
the second lumbar spine ; the deep guides are the tips of the transverse processes
of the second, third, and fourth lumbar vertebrae, covered by the psoas major muscle.
1438
SUKFACE AND SUKGICAL ANATOMY.
Exposure of Kidney from behind. In exposing the kidney from the loin,
by a vertical incision between the lateral border of the sacrospinalis and the free
posterior border of the external oblique muscle, the following structures are
divided from without inwards: (1) the integuments; (2) the lower fibres of the
latissimus dorsi and serratus posterior inferior muscles ; (3) the middle layer of the
lumbar aponeurosis, just lateral to the sacrospinalis compartment, and parallel to the
lateral fibres of the quadratus lumborum muscles ; (4) the anterior layer of the lumbar
aponeurosis (which forms the aponeurotic origin of the transversus muscles), and the
transversalis fascia ; (5) the paranephric fat ; (6) the perinephric fascia ; (7) the
perinephric fat surrounding the true capsule of the kidney. The kidney may be
readily mobilised and brought to the surface by shelling it out of its fatty capsule
Rib IX
RibX
Rib XI
Descending colon
Rib IX
RibX
Rib XI
Ascending colon
FIG. 1109. DISSECTION OF THE SPLEEN, LIVER, AND KIDNEYS FROM BEHIND, IN A SUBJECT HARDENED BY
FORMALIN INJECTION. (From Cunningham.)
with the finger. Better access to the renal vessels can be obtained if the incision is
made a little nearer the median plane, so as to open into the sacrospinalis compart-
ment. This allows of the muscle itself being retracted medially more efficiently.
In exposing the kidney by an oblique incision in the loin, the latissimus dorsi
and serratus posterior inferior muscles are divided at the medial part of the
wound, while at its lateral part the posterior fibres of the external and internal
oblique muscles are divided; next, the aponeurotic origin of the transversus
muscle and the transversalis fascia are split so as to expose the extra-peritoneal
fat and the peritoneum, as it is reflected from the ascending colon on to the*
lateral aspect of the abdominal wall. The latter structures are then stripped
forwards and medially off the anterior surface of the kidney, until the hilum and
renal vessels are reached. The sacrospinalis and quadratus lumborum muscles
are retracted well medially, and it is often necessary to divide the lateral fibres
of the quadratus muscle.
THE BACK. 1439
The upper part of the ureter is exposed by extending the division of the
abdominal muscles still further downwards and forwards into the iliac region.
After stripping the peritoneum off the quadratus and psoas muscles, the ureter
will be found to cling to the deep surface of the membrane. Care is taken not
to injure the internal spermatic or ovarian vessels, which cross the ureter super-
ficially, and from the medial to the lateral side. The ureter is surrounded by a
quantity of loose cellular tissue, and, owing to an abundance of elastic fibres in its
adventitious coat, is very elastic, so that it can be readily pulled up to the surface.
To deliver an enlarged kidney out of the loin, it is generally necessary to
prolong the incision upwards so as to divide the lateral lumbo-costal arch ; and
it may be necessary to divide, fracture, or resect the twelfth rib also. In doing
this it is not always possible to avoid opening into the lowest part of the pleural
sinus, which descends in front of the medial half of the rib.
In operating on the kidney, the last thoracic, and the ilio-hypogastric and
ilio-inguinal nerves, which lie between it and the quadratus lumborum, must not
be injured ; the last thoracic nerve should be retracted upwards and laterally,
the other two downwards and medially.
A needle passed through the medial extremity of the eleventh intercostal
space will transfix the suprarenal gland.
The pus of a perinephric abscess occupies the fatty layer of the tela subserosa
(perinephric fat), and lies, therefore, within the fascial envelope of the abdomen ;
the pus in a psoas abscess, on the other hand, lies external to the fascia. In
opening a psoas abscess from behind, a vertical incision is made in the angle
formed by the lateral border of the sacrospinalis and the crest of the ilium ; in
the deeper part of the dissection the surgeon should keep close to the front of
the transverse process of the fourth lumbar vertebra.
Diaphragm, Liver, Stomach, and Large Intestine. Posteriorly the right
arch of the diaphragm and the right lobe of the liver extend upwards to the level
of the angle of the scapula (eighth rib), while the left arch and the fundus of the
stomach lie one inch lower (eighth interspace) ; the central tendon reaches up to
the eighth thoracic spine. The right lobe of the liver is covered posteriorly by
the eighth to the twelfth ribs, and is overlapped by the base of the right lung as
far as a line drawn horizontally laterally from the tenth thoracic spine; hence,
posteriorly, the superior limit of the liver cannot be defined by percussion, and its
inferior limit merges into the dulness of the loin muscles and kidney.
The cardiac orifice of the stomach lies one inch to the left of the ninth thoracic
spine. The cardiac portion, overlapped by the ninth to the twelfth ribs, extends
upwards to the level of the eighth thoracic spine, one inch below the inferior
angle of the scapula. The pyloric portion crosses the median plane opposite the
first and second lumbar spines, the pylorus itself being situated one inch to the
right of the first lumbar spine. The lesser curvature lies to the left of and below
the tenth, eleventh, and twelfth thoracic spines.
Viewed from behind, the large intestine, on both sides, overlaps the lateral
border of the kidneys and lies parallel to the lateral border of the sacrospinalis
muscles. The peritoneum is reflected from the colon on to the posterior abdominal
wall along a line drawn vertically upwards from the centre of the iliac crest. The
left flexure of the colon, which reaches up to the level of the twelfth thoracic spine
i and the tenth rib, lies about five inches above the iliac crest. The right flexure
. lies on a level with the first lumbar spine.
Spleen. The spleen, situated in the left hypochondrium, behind the cardiac end
of the stomach, is overlapped by the ninth, tenth, and eleventh ribs, the long axis
of the organ corresponding approximately to that of the tenth rib. Between the
:: superior third of the spleen and the chest wall (pleura and diaphragm intervening)
i is the base of the left lung, the inferior margin of which crosses the organ horizont-
ally at the level of the tenth thoracic spine. The costo-diaphragmatic reflection of
: the pleura reaches down as far as the inferior angle of the spleen. The superior
limit of the organ cannot therefore be defined by percussion ; and unless enlarged,
or displaced downwards, the spleen cannot be punctured from behind without travers-
ing the pleural as well as the peritoneal cavity.
1440
SUKFACE AND SUEGICAL ANATOMY.
Of the three angles of the spleen, the posterior or vertebral lies at the same level
as the inferior margin of the lung, H in. lateral to the tenth thoracic spine. The
FIG. 1110. POSTERIOR ASPECT OF TRUNK, SHOWING SURFACE TOPOGRAPHY OF VISCERA.
T. Trachea. Sp. Spleen. P. Pancreas.
A. Aorta. L. Liver. PI. Pleura.
L.L. Left lung S.R. Suprarenal gland. B.C. Descending colon.
R.L. Right lung. L.K. Left kidney. A.C. Ascending colon.
St. Stomach. R.K. Right kidney. R. Rectum.
inferior angle lies opposite the eleventh intercostal space on a level with the first
lumbar spine, in a line drawn vertically upwards from a point one inch behind the
THE BACK.
1441
centre of the iliac crest. This angle is situated behind the superior part of the
descending colon, immediately lateral to the middle of the lateral border of the
kidney. The anterior angle is at the level of the ninth interspace in the mid-
axillary line. Having placed a mark on the skin opposite these three angles the
organ is mapped out on the surface as follows : The posterior margin is obtained
by joining the posterior and inferior angles ; this margin, which gives the key to
the position of the spleen, will be found to follow the tenth intercostal space.
The short inferior margin corresponds to a line joining the anterior and the
Oblique fissure of lung
Superior lobe of lung -.__
Diaphragm --
Liver ...
Diaphragm
Stomach
Cut surface of base of lung
Spleen
Greater omen turn
Section of tenth rib opposite costo-
diaphragmatic reflection of the pleu
(indicated by dotted line)
11. DISSECTION OF THE LEFT HYPOCHONDRIUM TO SHOW THE EELATIONS OF THE SPLEEN TO THE
SIDE WALL OF THE CHEST, THE DIAPHRAGM, AND THE ADJACENT VISCERA. In addition to the
portions of ribs, there has been removed a part of the base of the left lung, and a window has been made
in the diaphragm almost down to the level of the costo-diaphragmatic reflection of the pleura.
inferior angles; it is related to the left flexure of the colon. Commencing at
the vertebral angle, the anterior margin is at first arched, the summit of the arch
reaching to the level of the upper border of the ninth rib in the scapular line ;
thence it is continued downwards and 'forwards across the posterior axillary line
as the " anterior crenated border " to the anterior angle. The upper arched portion
s parallel to and about one inch below the highest part of the fundus of the
/omach. The only parts of the splenic outline which can be defined by percus-
i are the lower crenated part of the anterior margin, the anterior angle, and the
iort postero-inferior or colic border ; and it is these parts which may be felt below
the costal margin when the organ is considerably enlarged.
Q9
1442
SUEFACE AND SUKGICAL ANATOMY.
In excising the spleen it is important to remember that the splenic vessels lie
between the two layers of the lieno-renal ligament, and not in the gastro-lienal
ligament, which contains the short gastric vessels. In a floating spleen these two
peritoneal ligaments are elongated to form a distinct pedicle.
Pancreas. The head of the pancreas lies opposite the last thoracic and first
lumbar spines ; the tail lies at the same level as the left flexure of the colon, a
little above the inferior basal angle of the spleen.
TABLE INDICATING THE LEVEL OF THE MORE IMPORTANT STRUCTURES IN
RELATION TO THE SPINES OF THE VERTEBRAE.
Spines of Vertebrae.
Origins of Spinal Nerves.
Level of other Structures.
1 Cervical .
2 Cervical
Soft palate.
2
3 and 4
Isthmus of fauces.
3
5
Upper part of epiglottis.
4
6
Vocal folds (O.T. cords).
5 .
7 "
Conns elasticus.
/Arch of thoracic duct.
6
55
I Commencement of trachea and oesophagus.
f Inferior end of cervical enlargement of
1 and 2 Thoracic
I spinal medulla.
I Inferior cervical ganglion of sympathetic.
l.Apices of lung.
1 Thoracic .
3
Summit of arch of subclavian artery.
( Medial angle of scapula.
2 .
4
I Just above level of highest part of arch of
1 aorta.
I Jugular notch.
Root of spine of scapula.
Arch of vena azygos.
3 . .
5 and 6
Highest part of inferior lobes of lungs.
- Termination of arch of aorta.
Bifurcation of trachea.
Lower limit of superior mediastinum.
^Angulus sterni.
f Commencement of descending thoracic
4
I aorta.
55
55
1 Bronchi.
I Superior limit of heart.
/Centre of root of lung.
55
55
1 Mitral orifice.
6
9
Tricuspid orifice.
( Inferior angle of scapula.
7 .
10
\ Orifice of inferior vena cava.
( Right arch of diaphragm.
f Lowest limit of heart.
8
1 Left arch of diaphragm.
55
55
1 Fund us of stomach.
9 5, -
12 Thoracic and 1 Lumbar
I Xiphi -sternal articulation.
Superior limit of spleen.
{Cardiac orifice of stomach.
Upper end of lumbar enlargement.
10 . .
2 Lumbar
Lower border of lung, posteriorly.
Vertebral angle of spleen (apex of spleen).-
Superior end of left kidney.
Lesser curvature of stomach.
/'Lower limit of pleura at vertebral column.
Superior end of right kidney.
11
3 and 4
J Suprarenal gland.
I Body of pancreas.
V. Lesser curvature of stomach.
1 Level at which pleura crosses twelfth rib.
Inferior end of spleen.
12 . .
1, 2, 3 Sacral
Left flexure of colon.
Superior part of head of pancreas.
Pylorus and pyloric portion of stomach.
THE BACK. 1443
TABLE INDICATING THE LEVEL OF THE MORE IMPORTANT STRUCTURES IN
RELATION TO THE SPINES OF THE VERTEBRAE Continued.
Spines of Vertebrae. Origins of Spinal Nerves.
Level of other Structures.
1 Lumbar . 4 and 5 Sacral
-Conus medullaris.
Lower limit of pleura (mid-axillary line).
Hila of kidneys.
Head of pancreas.
Right flexure of colon.
Portal vein.
Descending part of duodenum.
Greater curvature of stomach.
^Bile-duct.
f Commencement of ureters.
\ Lowest part of head of pancreas.
? Inferior limit of spinal medulla in child.
-! Inferior ends of kidneys.
(Horizontal part of duodenum.
l Highest part of crest of ilium.
4 . A Bifurcation of aorta.
( Umbilicus.
( Common iliac arteries.
' \Valveofthecolon.
1 Sacral Sacral promontory.
2 . ... . . . . Lower end of sub-dural space.
f Superior end of gluteal cleft.
3 . j-j Inferior limit of sub-arachnoid and sub-
j I dural spaces.
Spinal Medulla. The spinal medulla ends opposite the inferior border of the
first lumbar spine ; in the infant it reaches to the interval between the second and
third lumbar spines. The cervical enlargement, which corresponds to the lower four
cervical and the first two thoracic segments, ends opposite the seventh cervical
spine. The lumbar enlargement lies opposite the last three thoracic spines. The
five lumbar segments are opposite the ninth, tenth, and eleventh thoracic spines,
while the five sacral segments extend from the lower border of the eleventh
thoracic to the lower border of the first lumbar spine.
The sub-dural space extends down to the level of the second sacral spine. In
performing the operation of lumbar puncture (Quincke) a fine trochar and cannula
are introduced into the sub-arachnoid space below the level of the spinal medulla,
the puncture being made \ to J in. to one side of the interspinous ligament in the
interval between the third and fourth or fourth and fifth lumbar spines. The
instrument should be directed medially towards the median plane and very slightly
upwards. In the adult the distance of the dura mater from the surface is about
2 in., in the infant f in.
Fracture-dislocations of the vertebral column are commonest in the lower cervical
and thoracico-lumbar regions ; that is to say, where the movable cervical and lumbar
regions join the more fixed thoracic region. The vertebral column above the
injury is generally displaced forwards, so that the spinal medulla is often severely
lacerated or completely torn across by the superior end of the portion of the column
below the fracture. It is important to remember that in consequence of the short-
ness of the spinal medulla as compared with the vertebral column, the origins of
the spinal nerves are at a higher level than their exits from the vertebral canal.
The distance between origins from the spinal medulla and exits through the
intervertebral foramina becomes greater the further down the nerves are, the
lowest nerve trunks running almost vertically downwards. The cervical nerves
leave the vertebral canal above the vertebrae after which they are named (except
the eighth, which is above the first thoracic vertebra) ; the thoracic, lumbar, and
sacral nerves, on the other hand, leave the canal below the correspondingly named
vertebrae.
92 a
1444 SUEFACE AND SUEGICAL ANATOMY.
To understand the effect of lesions of the spinal medulla, it is necessary to be familiar
with the sensory and motor distributions of the various spinal segments (see Figs. 609,
p. 693, and 607, p. 688). Transverse lesions of the spinal medulla above the fifth cervical
spine (that is, above the nbro-cartilage between the fourth and fifth cervical vertebrae)
are quickly fatal, owing to paralysis of respiration, as the phrenic nerve arises mainly
from the fourth segment. In transverse lesions of the cervical enlargement the cutaneous
insensibility does not extend higher than a transverse line at the level of the second
intercostal space. The diagnosis of the particular segment involved is arrived at by
testing the motor and sensory functions of each segment. The sensory areas cor-
responding to the lower four cervical and the first two thoracic segments occupy the
upper extremities, and are placed in numerical order from the lateral to the medial side
of the limb. The sensory area corresponding to the second, third, and fourth cervical
segments occupy the occipital region of the scalp, the back of the auricle, and the
masseteric region, the whole of the neck, and the shoulders and upper part of the
chest down to a horizontal line at the level of the anterior end of the third intercostal
space. In a total transverse lesion of the spinal medulla in the thoracic region, the
superior limit of the anaesthesia is horizontal, and reaches to the level of the termina-
tions of the anterior rami of the spinal nerves which arise from the spinal segment
opposite the vertebral injury. Hence the superior limit of the anaesthesia is at a much
inferior level than that of the injured vertebra. For example, a fracture-dislocation at the
level of the eighth thoracic vertebra involves the origin of the tenth thoracic nerve which
ends at the level of the umbilicus. The sensory zone corresponding to the fifth thoracic
segment is at the level of the nipples, that of the seventh thoracic segment is at the level
of the xiphoid process, that of the tenth at the level of the umbilicus, while that of the
twelfth reaches down, anteriorly, to the superior border of the symphysis. The sensory
areas corresponding to the lumbar and sacral segments are seen in Figs. 627, p. 725, and
629, p. 733.
THE UPPEE EXTEEMITY.
THE SHOULDER.
The bony landmarks of the shoulder must be systematically examined in all
injuries about that region. The medial extremity of the clavicle is prominent ; its
articulation with the sternum forms essentially a weak joint, which is liable to be
dislocated, especially from blows upon the lateral part of the shoulder which drive
the medial end of the clavicle forwards against the weak anterior sterno-clavicular
ligament. The body of the clavicle, subcutaneous throughout, is weakest at the
junction of its two curves ; it is in that region that the bone is so frequently
fractured as the result of force transmitted through it to the trunk. The dis-
placement of the lateral fragment varies according to whether the break takes
place medial or lateral to the coraco-clavicular ligament ; in the former case the
weight of the upper extremity, acting through the coraco-clavicular ligament,
pulls the lateral fragment downwards ; when the fracture is lateral to the ligament,
the lateral end of the clavicle rotates forwards, but there is no downward displace-
ment. The lateral end of the clavicle is on a plane posterior to its medial end, so
that the shoulder is braced backwards away from the thorax ; hence in fractures
of the clavicle, both medial and lateral to the coraco-clavicular ligament, the point
of the shoulder rotates forwards and medially. The acromio- clavicular articulation
is somewhat difficult to feel ; the groove which corresponds to it runs in the sagittal
direction, and lies 1J in. medial to the lateral border of the acromion, and im-
mediately lateral to a slight prominence upon the lateral extremity of the clavicle.
"When the acromio-clavicular joint is dislocated the clavicle almost invariably over-
rides the acromion, and the summit of the shoulder presents a somewhat conical
or " sugar-loaf " appearance.
The tip of the acromion looks directly forwards, and lies a finger's breadth
lateral to and a little in front of the lateral extremity of the clavicle. The lateral
border of the acromion can readily be followed to its junction with the spine of the
scapula, and the latter to its root, which is situated on a level with the third
thoracic spine. The medial border of the acromion and the posterior border of the
lateral end of the clavicle meet at an angle into which the point of the finger can
THE UPPEE EXTREMITY. 1445
be pressed. The medial angle of the scapula, covered by the trapezius and the
supraspinatus muscles, is, too deeply placed to be palpated distinctly. The inferior
angle, and the vertebral border, from the root of the spine downwards, form visible
prominences which are readily felt ; the inferior angle overlies the seventh inter-
costal space on a level with the seventh thoracic spine, while the vertebral border
lies a little medial to the angles of the ribs.
To elicit crepitus in a transverse fracture of the scapula below the spine, ..the surgeon
stands behind the patient and grasps the upper fragment by placing the forefinger upon
the coracoid and the thumb upon the spine, while, with the other hand, he grasps the
inferior angle ; the two fragments are then moved the one upon the other.
The tip of the coracoid process may be felt by pressing the finger firmly upon the
anterior border of the deltoid at a point one inch below the junction of the middle
and lateral thirds of the clavicle. Medial to the coracoid is a triangular depres-
sion which corresponds to the superior end of the interval between the clavicular
fibres of the pectoralis major and deltoid muscles. Behind this triangular depres-
sion are the termination of the cephalic vein, a lymph gland, the first part of
the axillary vessels, and the cords of the brachial plexus. By firm pressure in this
situation the pulsation of the axillary artery can be felt, and by further pressure
the circulation in the vessel can be arrested by compressing the artery against the
second rib. The first part of the axillary artery may be cut down upon either by
a transverse incision through the clavicular origin of the pectoralis major, or by a
longitudinal incision in the interval between that muscular slip and the deltoid.
The companion vein lies in front of, as well as to the thoracic side of, the artery,
thus adding to the difficulty of exposing the vessel. In fractures of the middle
third of the clavicle the subclavian vessels are protected by the soft pad formed by
the subclavius muscle.
The proximal extremity of the humerus, covered by the deltoid, gives rotundity
to the shoulder. The greater tubercle projects beyond the acromion, and constitutes
the most lateral bony landmark of the shoulder. When the head of the bone is
dislocated, the lateral border of the acromion then becomes the most lateral bony
landmark, and the shoulder presents a square contour. The lesser tubercle, small
but conical, can be felt through the deltoid. Pointing directly forwards, it lies one
inch lateral to and a little below the level of the tip of the coracoid process. In
examining the proximal extremity of the humerus for fracture, the tubercles
should be grasped between the finger and thumb of one hand, while the flexed
elbow is rotated with the other hand. The head of the humerus has the same
direction as the medial epicondyle ; its distal part can be palpated through the
axilla, the arm being meanwhile abducted, to bring the head in contact with the
inferior surface of the capsule. It is through this, the weakest part of the capsule,
that the head is driven in the common varieties of dislocation of the shoulder,
viz., those due to forcible abduction. The proximal epiphysis of the humerus in-
cludes the head and the greater part of the tubercles. The capsule is attached
mainly to the epiphysis ; hence, in children, we find that separation of the
proximal epiphysis takes the place of dislocation. Disease in the proximal end
of the diaphysis does not necessarily involve the cavity of the joint. The inter-
tubercular sulcus of the humerus, which lies immediately lateral to the lesser
tubercle, may be mapped out upon the surface by drawing a line, two inches in
length, distally along the axis of the humerus from the tip of the acromion.
When there is effusion into the joint, the arm becomes slightly abducted, and
there is fulness in front, along the line of the long tendon of the biceps. With
the elbow at the side the lower part of the capsule of the shoulder-joint is loose
and folded upon itself to form a dependent pocket ; if, after an injury, the arm
is retained too long in this position, the patient may be unable to abduct the arm,
in consequence of the formation of adhesions in and around the pouch. To
evacuate pus from the shoulder - joint, the integuments, deltoid, and capsule
should be cut into by an incision passing vertically and distally from the tip of the
acromion.
92 b
1446 SUKFACE AND SUKGICAL ANATOMY.
THE AXILLA.
The anterior fold of the axilla, formed by the inferior border of the pectoralis
major, extends from the fifth rib to the middle of the anterior border of the deltoid.
With the arm abducted, the interval between the sternal and clavicular fibres of
the pectoralis major is indicated by a slight groove extending distally and
laterally from the medial end of the clavicle. The sternal fibres, along with the
pectoralis minor, are removed in a complete operation for malignant disease of the
breast, the pectoral branches of the thoraco-acromial artery being secured as they
cross the interval between the sternal and clavicular portions of the greater pectoral.
The posterior fold of the axilla, formed by the latissimus dorsi and the teres major
muscles, is on a lower level than the anterior fold, and leaves the chest a little in
front of the inferior angle of the scapula. Between the two folds, and running in
the long axis of the limb, from the axilla to the middle of the arm, is the prominence
of the coraco-brachialis muscle. The pulsations of the third part of the axillary
artery may be felt in the furrow, immediately behind this prominence, at the
junction of the anterior and middle thirds of the lateral wall of the axilla.
Female Mamma. The breast tissue proper is arranged to form a central
portion, the corpus mammae, and a peripheral portion, made up of branching
processes which radiate into the paramammary fat and become continuous
ultimately with the connective tissue septa of the subcutaneous fatty tissue. The
mamma, therefore, has no distinct capsule. In the young adult nullipara, the
corpus mammae is compact and well defined, and contains but little intramammary
fat, while the peripheral processes are relatively small. In multipara, the corpus
mammas contains more fat, and the peripheral processes extend more widely into
the paramammary fat.
The arrangement and extent of the parenchyma can be well seen by treating the breast with
a 5 per cent, solution of nitric acid. If slices of the fresh organ are placed in this solution for a
few minutes and then washed under running water, the albumen of the epithelial cells of the
parenchyma is coagulated, while the connective tissue is rendered translucent and somewhat
gelatinous. The ultimate lobules of the parenchyma now appear as little (1 to 2 mm.), dull, opaque,
white, sago-like bodies, arranged in grape-like clusters around the finer branches of the ducts.
The parenchyma is prolonged into the peripheral processes, into the suspensory
ligaments of Cooper, and into the loose retromammary cellular tissue and pectoral
fascia. The breast tissue, therefore, has a much wider distribution than was
formerly supposed. Vertically, it extends from the second rib to the sixth costal
cartilage at the angle where it begins to ascend towards the sternum ; horizontally,
from a little medial to the lateral border of the sternum, opposite the fourth rib, to
the fifth rib in the mid-axillary line. The medial hemisphere of the mamma rests
almost entirely on the pectoralis major ; at its lowest part it slightly overlies the
upper part of the aponeurosis covering the rectus abdominis muscle. The superior
quadrant of the lateral hemisphere rests upon the greater pectoral, on the edge of
the lesser pectoral, and to a slight extent on the serratus anterior, upon which
it extends upwards into the axilla as high as the third rib, where it comes into
relation with the thoracic group of axillary lymph glands. The remainder of the
lateral hemisphere rests almost entirely upon the serratus anterior, except the
lowest part, which overlaps the digitations of the external oblique arising from
the fifth and sixth ribs. It follows, therefore, that fully one-third of the whole
mamma lies inferior and lateral to the axillary border of the pectoralis major
muscle. The surgeon must cut beyond the above limits if he wishes to remove the
whole of the mammary tissue.
The axillary fascia resists the spontaneous rupture of an axillary abscess, which,
therefore, tends to spread upwards beneath the pectorals, and towards the root of the
neck. To open the abscess the incision should be made upon the medial wall, behind,
and parallel to, the lateral thoracic artery, which runs under cover of the anterior fold.
The axillary lymph glands vary greatly in size and number ; many are no larger than
a pin's head. In the female some of them undergo an adipose functional involution,
whereby they come to resemble fat lobules. In health, one or two glands can usually be
felt by thrusting the fingers upwards and medially beneath the anterior fold, the arm
THE AEM. 1447
being only slightly abducted, so as not to stretch the axillary fascia. The central group
(Leaf), imbedded in the fat immediately beneath the axillary fascia, become inflamed in
poisoned wounds of the upper extremity. The same group, along with the pectoral group
(related to the medial wall of the axilla, at the inferior border of the pectoralis minor), are
usually the first to become diseased in malignant affections of the breast. When the
disease is more advanced the posterior (subscapular) and the apical (subclavicular) groups
are generally affected as well ; and Rotter has shown that in a considerable porportion of
cases diseased glands are to be found in the retro-pectoral fascia, i.e. between the pectoralis
major and minor and, above the latter muscle, on the first intercostal space in relation to
the supreme thoracic artery. In operating for malignant disease of the breast, the
surgeon removes, in addition to the whole breast and the greater part of the skin over it,
both pectoral muscles (with the exception of the clavicular fibres of the pectoralis major),
Brachial artery Clavicle
Biceps tendon Anterior axillary fold
Brachio-radial
Coraco-brachialis Deltoid
Biceps
Flexor muscles
Lacertus fibrosus
Medial epicondyle
Brachialis
Ulnar nerve
Medial iritermuscular septum
Median nerve
Medial head of triceps
Long head of trice
Lower border of teres majo
Posterior axillary fold
FIG. 1112. AXILLA, MEDIAL ASPECT OF ARM AND ELBOW.
all the axillary lymph glands, and, as far as possible, all the fat and fascia, including the
sheath of the axillary vein. It must be remembered that the distal part of the axillary
vein lies immediately underneath the deep fascia of the lateral wall of the axilla ; in clean-
ing the medial wall the long thoracic nerve must not be injured; and in removing the
posterior group of lymph glands the thoraco - dorsal nerve, which accompanies the
subscapular vessels, must be avoided, as it is doubly important to retain the action of the
latissimus dorsi after removing the pectorals. The writer has so frequently met with
disease in these retro-pectoral glands, that he is convinced of the necessity of removing
the pectoral muscles.
THE ARM.
The anterior and posterior borders of the deltoid may be traced from the
shoulder girdle to the insertion of that muscle. The surface relations of the anterior
border have already been referred to ; the posterior border forms a well-marked
and important landmark as it crosses the angle between the axillary margin of the
scapula and the proximal part of the body of the humerus. By making an incision
along this part of the posterior border of the deltoid, and retracting the edge of the
muscle^ .upwards and laterally, we expose the surgical neck of the humerus, and the
Quadrilateral opening in the posterior wall of the axilla, transmitting the posterior
circumflex artery of the humerus and the axillary nerve ; a little more distally is the
radial nerve. The coraco-brachialis, the guide to the proximal half of the brachial
artery, forms a prominence occupying the proximal half of the medial licipilal
furrow. Traced distally the medial bicipital furrow widens out into an elongated
triangle. This triangle, which may be termed the medial supracondylar triangle,
becomes continuous, distally, with the medial part of the triangle in front of the bend
of the elbow, and is limited posteriorly by the medial intermuscular septum, which
may be felt as a cord-like band extending proximally from the medial epicondyle ;
the floor of the space is formed by the medial part of the brachialis. Within the
triangle are the following important structures, enumerated from the lateral to the
medial side, viz. : the brachial artery, the median nerve, the distal part of the basilic
1448
SUKFACE AND SUKGICAL ANATOMY.
vein, the medial cutaneous nerve of the forearm, and the superficial cubital lymph glands,
two or three in number. Extending proximally from the lateral epicondyle to the
insertion of the deltoid is the lateral intermuscular septum, which is pierced at the
junction of its proximal and middle thirds by the radial nerve. Between the
lateral intermuscular septum and the lateral edge of the biceps is the ill-defined
lateral bicipital furrow, the floor of which is formed by a strip of the brachialis,
and, nearer the elbow, by the brachio-radialis and extensor carpi radialis longus.
The posterior compartment of the arm is occupied by the triceps, the long head
of which can be traced proximally to the axillary margin of the scapula, in front
of the posterior border of the deltoid and behind the posterior fold of the axilla.
The lateral head of the triceps, after emerging from under cover of the distal part
of the posterior border of the deltoid, is continued obliquely along the lateral aspect
of the arm as a well-marked muscular elevation. Proximal to the olecranon is
the strap-like tendon of insertion of the triceps, which, when the elbow is fully
flexed, forms an admirable posterior splint in supracondylar fractures of the
humerus.
The brachial artery, slightly overlapped in the proximal half of the arm by the
coraco-brachialis and in the distal half by the biceps, can be felt pulsating through-
out the whole length of the anterior part of the medial bicipital furrow. The
Head of radius
Lateral epicondyle
Extensor carpi radialis longus
Radial nerve
Lateral intermuscular septum. Biceps
Axillary nerve
xtensor carpi radialis brevis
Deep branch of radial nerve
Abductor pollicis longus
Middle thecal tubercle
Styloid process of
third metacarpal
Head of ulna
Infraspinatus
Triceps tendon
Lateral head of triceps
Posterior border of deltoid
Long head of triceps
Teres major
Latissimus dorsi
. Dorsal border of ulna
II Flexor carpi ulnaris
I Extensor carpi ulnaris
Extensor digitorum communis
Anconaeus
Tip of olecranon
FIG. 1113. DORSAL ASPECT OF ARM.
course of the vessel may be mapped out upon the surface by drawing a line from
the medial border of the coraco-brachialis, at the level of the posterior fold of the
axilla, distally to a point (opposite the neck of the radius) J in. distal to the
middle of the bend of the elbow. In ligaturing the vessel, the edges of the
coraco-brachialis and biceps muscles, together with the median nerve, furnish valu-
able guides to the artery, the mobility of which is often a source of trouble in
performing the operation.
The basilic vein, which is superficial to the deep fascia in the distal third of the
arm, is visible in the medial supracondylar triangle and the distal part of the
medial bicipital groove. The cephalic vein ascends a little anterior and^edial to
the lateral edge of the triceps to reach the interval between the deltoid i^and
pectoralis major.
The surface guide for the median nerve is the same as that for the brachial
artery. The ulnar nerve is indicated superficially by a line extending from the
lateral wall of the axilla, immediately posterior to the prominence of the coraco-
brachialis, to the back of the medial epicondyle ; in the proximal half of the arm
the nerve lies close behind the brachial artery under cover of the basilic vein, while
in the distal half 'it lies a little posterior to the medial intermuscular septum,
partially imbedded in the fibres of the medial head of the triceps. To map out the
course of the radial nerve, first mark the point where it pierces the lateral inter-
muscular septum, viz., the junction of the proximal and middle thirds of a line
extending from the insertion of the deltoid to the lateral epicondyle ; from that
THE ELBOW. 1449
point draw a line obliquely distally and forwards to the front of the lateral epi-
condyle, where the nerve, divides into its superficial and deep branches. To map
out the nerve as it lies in the radial groove, draw a line from the same point
obliquely proximally across the prominence formed by the lateral head of the triceps
to the junction of the posterior fold of the axilla with the arm. In fractures of
the humerus in the neighbourhood of the insertion of the deltoid, the nerve is not
infrequently lacerated, or so involved in the callus as to produce the condition
known as " drop-wrist'' the result of paralysis of the extensor muscles of the
forearm. To cut down upon the nerve, commence the incision a little distal to the
point where it pierces the lateral intermuscular septum, and carry it obliquely
proximally and slightly backwards through the lateral head of the triceps.
The shaft of the humerus, nowhere subcutaneous, is most readily manipulated in
the region of the insertion of the deltoid, proximally along the lateral head of the
triceps, and distally behind the lateral supracondylar ridge. The surgical neck,
situated between the tubercles and the attachments of the muscles inserted into
the region of the intertubercular sulcus, is related to the lateral wall of the axilla, and
is on a level with the junction of the proximal and middle thirds of the deltoid ; at
the same level are the circumflex vessels and the axillary nerve.
The shaft may be cut down upon with least injury to soft parts : (1) in its proximal
third, anteriorly, by an incision extending distally through the anterior fibres of the
deltoid, parallel, and a little lateral, to the intertubercular sulcus ; the sheath of the biceps
will thus be avoided, and the small, anterior circumflex artery will be the only vessel
divided. (2) In the proximal third, posteriorly, by an incision through the posterior fibres
of the deltoid, the bone being reached just lateral to the origin of the lateral head of the
triceps, thus avoiding the radial nerve ; the circumflex vessels and the axillary nerve will be
exposed at the proximal part of the wound. (3) In the distal third, by an incision extending
upwards from the back of the lateral epicondyle a little to the medial side of the lateral
intermuscular septum.
THE ELBOW.
In injuries about the elbow the diagnosis rests mainly upon the relative
positions of the bony points, which are, therefore, of great importance. The
epicondyles of the humerus are both subcutaneous and upon the same level, the
medial being the more prominent. In the extended position of the elbow the
tip of the olecranon is on a level with a line joining the epicondyles ; when the
forearm is flexed the olecranon descends, and when full flexion is reached it
lies 1 in. distal to the epicondyles, and in a plane anterior to the posterior
surface of the distal end of the humerus. The head of the radius, which lies nearly
1 in. below the lateral epicondyle, is best manipulated from behind by placing
the thumb upon it, while the semi-flexed forearm is being alternately pronated
and supinated. Upon the lateral part of the posterior aspect of the extended
elbow is a distinct dimple, which overlies the radio-humeral articulation; this
dimple, along with the hollows on each side of the olecranon, becomes effaced in
synovial thickenings and effusions into the joint. The coronoid process is situated
too deeply to be distinctly felt. The distal epiphysis of the humerus includes the
articular portion of the distal extremity and the lateral epicondyle ; it is, therefore,
small and almost entirely intra-articular, so that foci of disease in its neighbour-
hood soon invade the cavity of the joint. The medial epicondyle ossifies as a
separate epiphysis which unites with the distal end of the diaphysis. In inter-
preting skiagrams of the elbow of children about six years of age and upwards, care
must be taken not to mistake the centre of ossification in the lateral portion of the
distal epiphysis of the humerus for a fracture. In the commonest dislocation of
the elbow, viz., with backward displacement of both bones of the forearm, the
normal relative position of the bony points is lost, whereas in a transverse supra-
condylar fracture the normal relations are maintained. In the child the head
of the radius is relatively smaller, and less firmly kept in position by the
annular ligament than in the adult, so that it is liable to be "partially dis-
located, giving rise to the condition known as "pulled elbow."
1450 SURFACE AND SUEGICAL ANATOMY.
To evacuate pus from the elbow-joint a vertical incision should be made over
the dorsal aspect of the joint, immediately lateral to the olecranon.
The median vein is seen to bifurcate into the median basilic and median cephalic
veins i in distal to the middle of the bend of the elbow; opposite the same point,
but beneath the deep fascia, is the bifurcation of the brachial artery The median
basilic and median cephalic veins diverge as they ascend one on each side of the
biceps tendon; the larger of the two veins, viz., the median basilic is usually
selected for the operations of venesection and transfusion. When the elbow i
flexed the biceps tendon can be traced vertically through the centre of the bend of
the elbow almost to its insertion. Passing distally and medially from the medial
Vena comes of brachial artery
Lateral cutaneous nerve of forearm
Tendon of biceps
Median cephalic vein
Braehio-radialis
Radial nerve
Radial extensors
Articular surface of hurnerus
Lateral epicondyle
Brachial artery
Median basilic vein
Vena comes of brachial artery
Tronator teres
Ulnar vein
Median nerve
Brachialis muscle
Common origin of
flexor muscles
Medial epicondyle
Uluar nerve
uperior ulnar
collateral artery
Olecranon
Anconseus Olecranon fossa of humerus
FIG. 1114. TRANSVERSE SECTION THROUGH THE BEND OF THE ELBOW.
edge of the tendon is the lacertus fibrosus, which separates the median basilic vein
from the brachial artery. If the finger nail is insinuated beneath the medial edge
of the lacertus fibrosus the point of the finger will rest upon, and feel the pulsations
of, the brachial artery. The median nerve descends through the space a little medial
to' the brachial artery. The bifurcation of the radial nerve takes place in front of
the lateral epicondyle under cover of the brachio-radialis. The ulnar nerve can
be rolled beneath the finger upon the back of the medial epicondyle ; its position
renders it liable to injury in severe fractures about the elbow ; and in excising
the joint care must be taken not to injure the nerve.
THE FOREARM AND HAND.
The proximal half of the radius is deeply placed ; the distal half, however, is
easily palpated. The anterior border of its distal extremity is felt as a prominent
transverse ridge, situated 1 in. proximal to the thenar eminence ; immediately distal
to the ridge is the radio-carpal articulation. The tip of the styloid process, situated
nearly J in. more distal than that of the ulna, is deeply placed at the lateral
side of the wrist, in the hollow between the extensor tendons of the first and-
second phalanges of the thumb. Upon the middle of the posterior surface of
the distal end of the radius is the dorsal radial tubercle, which intervenes
between the extensor pollicis longus and the short radial extensor of the wrist;
the tubercle can be distinctly felt, and may be taken as a guide to the proximal end
THE FOKEABM AND HAND.
1451
Brachialis
Cephalic vein
Biceps
Median cephalic vein ;
Tendon of biceps
Radial nerve
Deep ramus of
radial nerve
Brachio-radial
Radial nerve
(superficial ramus)
Radial artery
rachial artery
Median basilic
vein
ertus fibrosus
Ulnar artery
of Lister's dorso-radial incision for excision of the wrist. The dorsal border of
the ulna is subcutaneous throughout, and may be felt along the interval between
the flexor and extensor carpi ulnaris muscles. Upon the ulnar side of the
dorsal aspect of the wrist, when the forearm is in the prone position, there is a
well-marked rounded prominence formed by the distal extremity of the ulna, anterior
to which is the styloid process,
the deep groove between the
two being occupied by the
tendon of the extensor carpi
ulnaris.
The carpal bones are built
up so as to form an arch, con-
verted by the transverse carpal
ligament into a tunnel for the
transmission of the flexor ten-
dons. At each extremity of
the arch the two bony points
to which the ligament is at-
tached furnish important land-
marks. These bony points are :
laterally, the tuberosity of the
navicular and the ridge of the
greater multangular bone ;
medially, the pisiform and the
hamulus of the os hamatum.
The tuberosity of the navicular
is felt immediately proximal to
the root of the thenar eminence,
midway between the tendons
of the abductor pollicis longus
and the flexor carpi radialis ;
J in. distal to the tuberosity
of the navicular is the ridge
of the greater multangular bone,
felt deeply beneath the medial
part of the thenar eminence.
At the root of the hypothenar
eminence, and crossed by the
crease which separates the fore-
arm from the hand, is the pisi-
form bone, proximal to which is
the tendon of the flexor carpi
ulnaris, passing to be inserted
into it. The hamulus of the
os hamatum is felt deeply be-
neath the radial side of the
hypothenar eminence, and a
full finger's breadth distal and
lateral to the pisiform.
The bases of the first, third,
and fifth metacarpals, all of which
can be readily identified on the dorsal aspect, furnish a sufficient guide to the
line of the carpo-metacarpal articulations. At the base of the third metacarpal is
' a tubercle, which can be felt projecting from its dorsal aspect at a point If in.
; vertically distal to the tubercle upon the back of the distal end of the radius.
This metacarpal tubercle marks the insertion of the extensor carpi radialis brevis,
the favourite site for the development of a "ganglion" which may frequently
be ruptured by pressing it firmly against the tubercle. Anteriorly, the carpo-meta-
carpal articulations correspond to the distal border of the transverse carpal ligament.
Tendon of flexor carpi
radialis
Base of styldid process
Radial artery
Median nerve
Flexor carpi
ulnaris
Flexor digitorum
sublimis
Pisiform bone
Transverse carpal
ligament
Superficial
volar arch
Deep volar arch
FlG 1115> _ BEND OF ELBOW, VOLAR SURFACE OF FOREARM,
AND HAND.
1452
SUEFACE AND SUKGICAL ANATOMY.
The prominences of the knuckles are formed entirely by the heads of the
metacarpal bones. Anteriorly, the metacarpo-phalangeal articulations are situated
| in. proximal to the level of the web of the fingers ; posteriorly, the joints may be
felt as a groove immediately proximal to the projecting ridge at the base of the first
phalanges. A well-marked crease crosses obliquely over the anterior aspect of the
metacarpo-phalangeal joint of the thumb. To cut into the first interphalangeal joints
from the front, incise along the most proximal of the creases in front of the joints ;
whereas to cut into the terminal joints, incise along the most distal of the creases in
Superficial volar arch
Deep branch of ulnar
artery
Hamulus of os hamatum
Deep branch of ulnar nerve-
Ulnar. nerve
Pisiform bone
Palmaris longus
Styloid process of ulna
Ulnar artery
Deep volar arch
Transverse carpal ligament
Ridge of greater multangular bone
Radial artery
Median nerve
Styloid process of radius
Radial artery
Flexor carpi radialis
FIG. 1116. PALM OF HAND.
front of the joints. Dorsally, the first and the terminal interphalangeal articu-
lations are opposite the most distal of the various creases overlying the joints.
The most important muscular landmarks upon the front of the forearm are the
brachio-radialis, the flexor carpi radialis, and the pronator teres. The brachio-
radialis is thrown into prominence by flexing the semi-prone forearm against
resistance. At the junction of the proximal and middle thirds of the forearm the
pronator teres passes under cover of the brachio -radian's ; between the two is the radial
artery. The tendon of the flexor carpi radialis forms a prominent landmark
descending along the middle of the volar aspect of the forearm towards the
ridge of the multangulum majus ; the tendon of the palmaris longus, when
present, is seen to its medial side.
THE FOKEAKM AND HAND.
1453
At the dorsum of the forearm the intermuscular septum between the radial and
common extensors corresponds to the proximal part of a line extending from the
lateral epicondyle of the humerus to the tubercle on the dorsum of the distal end
of the radius. The dorsal interosseous nerve, at the point at which it emerges from
the substance of the supinator muscle, will be found at the bottom of this
septum, 2 in. distal to the head of the radius ; below that point the septum is the
best line along which to cut down upon the posterior surface of the radius.
Winding across the distal third of the dorsal surface is an oblique prominence,
caused by the abductor pollicis longus and extensor pollicis brevis muscles.
Styloid process of third metacarpal
Radial artery.
Extensor pollicis longus
Extensor carpi radialis longu
Extensor carpi radialis brevis
Extensor pollicis brevis.
Base of fifth metacarpal
Styloid process of ulna
Extensor digitorum communis
Extensor digiti quinti communis
Extensor carpi ulnaris
FIG. 1117. DORSAL ASPECT OF HAND.
The flexor sheaths of the palm and of the digits are of surgical importance in
'.onsequence of their liability to suppurative inflammation. The common flexor sheath
)egins 1J in. proximal to the transverse carpal ligament, under which it extends to a
ittle beyond the middle of the palm. The digital flexor sheaths extend from the bases
>f the terminal phalanges to the level of the distal transverse crease of the palm,
>pposite the necks of the metacarpal bones, with the exception of the sheath of the
ittle finger, which is continuous with the common flexor sheath of the palm. The
heath of the flexor pollicis longus extends from the base of the terminal phalanx
>roximally to a point about 1 in. proximal to the transverse carpal ligament; it
requently communicates with the common flexor sheath. From this anatomical
rrangement it follows that suppuration in the sheaths of the little finger and
1454 SUKFACE AND SUEGICAL ANATOMY.
thumb is specially liable to spread upwards into the palm, and thence underneath
the transverse carpal ligament into the forearm.
The pulsations of the radial artery can readily be felt in the distal third of the
forearm, midway between the lateral border of the radius and the tendon of the
flexor carpi radialis. The course of the vessel is indicated upon the surface by
a line extending from the bifurcation of the brachial (J in. distal to the middle of
the bend of the elbow) to the tubercle of the navicular, around which, and distal
to the tip of the styloid process, the artery winds to the dorsum of the radial side
of the wrist ; in the latter situation the vessel, after passing deep to the extensor
tendons of the thumb, dips into the palm through the proximal extremity of the
first interosseous space. Incisions for opening or resecting the wrist are planned
so as to avoid the vessel.
The proximal third of the ulnar artery is deeply placed, and takes a curved
course from the bifurcation of the brachial towards the medial part of the volar
surface of the forearm ; the distal two- thirds of the vessel correspond to the distal
two- thirds of a line drawn from the front of the medial epicondyle to the radial border
of the pisiform bone. The course of the ulnar nerve corresponds to the whole of the
above line.
The median nerve in the forearm may be mapped out by a line extending from
a point midway between the centre of the bend of the elbow and the medial epi-
condyle, to a point midway between the styloid processes ; in the distal third of
the forearm the line follows the medial border of the tendon of the flexor carpi
radialis. To evacuate pus spreading deeply up the front of the forearm, the
incisions should be made on either side of the line corresponding to the median
nerve. The superficial branch of the radial nerve winds to the dorsum of the
forearm round the lateral border of the radius deep to the tendon of the brachio-
radialis, at the junction of the middle and distal thirds of the forearm.
The summit, or most distal part of the superficial palmar arch, corresponds to
the mid-point of a line extending from the middle of the most distal transverse
crease of the wrist to the root of the middle finger ; a line drawn from the radial
border of the pisiform bone across the hamulus of the os hamatum, and thence
in a curved direction distally and laterally to this point, corresponds to the main
or proximal part of the arch; the first and fourth digital branches overlie the
fifth and third rnetacarpal bones respectively, while the second and third overlie
the fourth and third interspaces respectively. The deep arch lies almost trans-
versely, midway between the distal border of the transverse carpal ligament and
the superficial arch. The radialis indicis corresponds to the radial border of the
index -finger.
The ulnar nerve and the commencement of its two divisions lie immediately to
the medial side of the superficial palmar arch, so that the pisiform and the hamulus
of the os hamatum are the guides to the nerve. The median nerve emerges from
under the transverse carpal ligament opposite the medial edge of the thenar
eminence, while the digital branches to the thumb follow its distal margin.
Incisions for the removal of foreign bodies may therefore be made into the
thenar with greater freedom than into the hypo-thenar eminence.
. Incisions to evacuate deep-seated pus in the palm may be made in one or more of
the following situations : (1) over the distal two-thirds of the second metacarpal bone ; (2)
over the distal half of the fourth metacarpal bone ; (3) from the proximal part of the first
incision an opening may be made through the first interosseous space on to the dorsum,
care being taken to keep distal to the radial artery ; (4) a longitudinal incision between
the median and ulnar nerves, on the proximal side of the superficial palmar arch. At the
wrist a longitudinal incision may be made immediately to the ulnar side of the palmaris
longus tendon, thus falling between the lines of the median nerve and the ulnar artery.
To open the digital flexor sheaths, incisions are made along the middle of the palmar
surface of the fingers, opposite the first and second phalanges. The proper digital vessels
and nerves pass distally along the sides of the fingers, nearer the flexor than the
extensor surfaces. In cutting down upon the dorsal aspects of the phalanges, the incisions
should be made to one or other side of the extensor tendon, preferably upon the ulnar side,
to avoid division of the insertions of lumbrical muscles. The subcutaneous tissue of the
THE LOWEE EXTREMITY. 1455
palmar aspect of the terminal phalanges is connected by fibrous processes with the
periosteum ; hence the frequency of necrosis of the terminal phalanx in suppurative
inflammations in this region.
THE LOWEE EXTEEMITY.
THE BUTTOCK.
The region of the hip or buttock extends from the crest of the ilium above to
the gluteal fold below. The highest point of the iliac crest, situated a little
i posterior to its middle, is on a level with the fourth lumbar spine ; the anterior
superior spine of the ilium is directed forwards, and belongs to the groin, which
it limits laterally; the posterior superior spine, situated at the bottom of a
dimple or small depression, is on a level with the second sacral spine, and corre-
sponds, therefore, to the middle of the sacro-iliac joint. Two and a half inches
behind the anterior superior spine is a prominence upon the outer lip of the
iliac crest ; this prominence, which is termed the tubercular point, is the most lateral
part of the crest, and has been referred to in dealing with the surface anatomy
of the abdomen. A hand's breadth below the tubercle of the crest is the greater
trochanter of the femur, the most lateral bony landmark of the hip ; its anterior
and posterior borders are best felt between the fingers and thumb, while the
limb is slightly abducted to relax the ilio-tibial tract, and if the thigh is now
rotated, it will be noted that the trochanter rotates round the segment of a
circle, the radius of which is formed by the head and neck of 'the femur; in non-
impacted fractures of the neck of the femur the trochanter rotates round the
segment of a much smaller circle. Nelatoris line, drawn from the anterior superior
spine to the most prominent part of the ischial tuberosity, crosses the hip at the
level of the proximal border of the greater trochanter ; this line is employed to
ascertain the presence or absence of upward displacement of the trochanter.
: Chiene demonstrates the relative height of the trochanters by stretching two
tapes across the front of the pelvis, one between the anterior superior spines,
and the other between the proximal borders of the trochanters; the lower tape
will converge towards the upper on the side of the upward displacement. A line
' prolonging the anterior border of the greater trochanter vertically upwards touches
, the iliac crest at the tubercular point. The sciatic tuberosity, in the erect posture,
is overlapped by the distal border of the glutseus maximus ; its most prominent
part is felt a little proximal to the medial part of the gluteal fold. If the hip is
. rotated medially, the lesser trochanter of the femur may be felt by deep palpa-
tion proximal to the lateral end of the gluteal fold ; it corresponds to the interval
between the distal border of the quadratus femoris and the proximal border of the
adductor magnus, and therefore, also, to the level of the medial circumflex artery
of the thigh.
The lower border of the glutseus maximus lies a little above the gluteal fold
medially, crosses it about its middle, and is continued distally and laterally to
meet the proximal end of the furrow of the lateral intermuscular septum, at
: the junction of the proximal and middle thirds of the femur. The medial borders
jjof the two great gluteal muscles are separated by the deep gluteal cleft, which
'\ extends upwards and backwards from the perineum to the level of the fourth
sacral spine, where it opens out into the triangle upon the back of the sacrum.
| Anteriorly the buttock is limited by the prominence of the tensor fasciae latae
muscle, which extends distally and somewhat backwards from the anterior end of
the crest, to join the ilio-tibial tract distal to the root of the greater trochanter.
The superior gluteal artery reaches the buttock immediately below the upper
II border of the greater sciatic foramen, opposite a point corresponding to the junction
[ of the upper and middle thirds of a line drawn from the posterior superior iliac
\{ spine to the upper border of the greater trochanter. To expose the vessel the
1 3 incision should be made along this line, which has the advantage of running parallel
\l to the fibres of the glutseus maximus, as well as parallel to the interval between
the glutseus medius and piriformis muscles.
1456
SUKFACE AND SUKGICAL ANATOMY.
The sciatic nerve enters the buttock at a point corresponding to the junction of
the upper and -middle thirds of a line drawn from the superior posterior iliac
spine to the sciatic tuberosity; from this point the nerve passes downwards and
slightly laterally upon the ischium to a point midway between its sciatic tuber-
osity and the greater trochanter. The spine of the ischium and the pudendal
vessels are situated opposite the junction of the lower and middle thirds of the
above line. The vessels and nerves which enter the buttock through the greater
sciatic foramen below the piriformis, may be exposed through an incision below
and parallel to that above described for exposing the superior gluteal artery, viz.,
an incision corresponding to the middle two-fourths of a line extending from the
upper end of the gluteal cleft to the root of the greater trochanter ; the deep land-
marks are the lower border of the piriformis and the root of the sciatic spine.
THE BACK OF THE THIGH.
The hamstring muscles, and especially the tendon of the biceps and semi-
tendinosus, are thrown into prominence either by standing on tiptoes with the
knees slightly flexed, or by flexing the leg against resistance. By throwing the
Femur
Vastus intermedius
Rectus femoris
Vastus medialis
Nerve to vastus medialis
Saplienous nerve
Sartorius
Femoral vein
Femoral artery
Adductor longus
Great saphenous vein
Gracilis
Vastus lateralis
Lateral intermuscular septum
Sciatic nerve
Adductor magnus
Profunda femoris artery
Semitendinosus
Biceps | Semimembranosus
Adductor brevis
FIG. 1118. SECTION THROUGH THIGH AT THE LEVEL OF THE PROXIMAL PART OF THE ADDUCTOR CANAL. J
hamstrings into action, the line of the lateral intermuscular septum of the thigh is
indicated by a well-marked furrow, extending from the lower edge of the insertion
of the glutseus maximus to the lateral aspect of the knee; behind this furrow is the
biceps femoris, and in front of it is the large vastus lateralis, covered by the"
strong ilio-tibial tract of the fascia lata. The shaft of the femur may be cut
down upon along the whole length of this furrow with least injury to the soft parts ;
the popliteal surface of the femur and deep-seated popliteal abscesses are most
conveniently reached through the lower part of the same incision.
The course of the sciatic nerve corresponds to the proximal half of a line
THE POPLITEAL FOSSA.
1457
extending from a point midway between the sciatic tuberosity and the greater
trochanter to the centre of the popliteal fossa. The nerve enters the thigh under
cover of the lateral border of the biceps, whereas the posterior cutaneous nerve of
the thigh which takes the same line, descends superficial to the biceps, between
it and the fascia lata. In the operation of stretching the sciatic nerve it is cut
down upon immediately distal to the lower border of the glutseus maximus.
The surgeon, standing on the side of the patient opposite to the leg to be operated
upon (Chiene), makes an incision in the line of the nerve through the integuments
and fascia lata, and, sweeping the index-finger round the lateral border of the
Quadriceps extensor tendon
Extra-synovial fat
Vastus raedialis
Adductor tubercle
Musculo-articular
branch of arteria
genu suprema
Tendon of adductor
magnus
Sartorius
Stratum synoviale of knee
Vastus lateralis
Ilio-tibial tract
Proximal lateral
genicular artery
Fat
Popliteal artery
Biceps
Popliteal vein
Common peroneal nerve
Tibial nerve
Lymph gland
Gracilis
Semimembranosus Semitendinosus
FIG. 1119. SECTION THROUGH THE THIGH IMMEDIATELY PROXIMAL TO THE PATELLA.
biceps, hooks up the nerve as it lies between that muscle and the adductor
magnus.
The common peroneal nerve may be rolled under the finger as it passes distally
immediately behind the tendon of the biceps and the head of the fibula ; so close is
the nerve to the tendon that the tendon should be divided, in cases where this is
necessary, by the open method rather than subcutaneously.
Abscesses may reach the flexor compartment of the thigh from various sources, viz. : (1) from
the posterior aspect of the hip-joint; (2) from the pelvis, through the greater sciatic foramen;
(3) from one or other of the bursse under the glutseus maximus ; (4) from the front of the hip-
joint, by passing backwards under the tensor fasciae latae ; or by winding backwards beneath the
neck of the femur, and through the interval between the quadratus femoris and the adductor
magnus ; (5) from the iliac fossa under the inguinal ligament into the fascial trigone, and thence
to the back of the thigh by one or other of the routes already mentioned ; (6) the pus may spread
proximally from the popliteal surface of the femur, the knee, a popliteal gland, or from a bursa.
THE POPLITEAL FOSSA.
When the knee is extended the popliteal fascia is put upon the stretch, and
obliterates the hollow of the popliteal fossa ; by flexing the knee the fascia is
relaxed, and the fingers may be pressed deeply into the proximal or femoral
93
1458
SUEFACE AND SURGICAL ANATOMY.
division of the fossa ; as a rule, the pulsations of the popliteal artery can be felt.
Deep to the semitendinosus is the fleshy semimembranosus, which bulges into the
space and overlaps the proximal part of the popliteal artery. Between the semi-
membranosus and the medial head of the gastrocnemius is the most important
bursa in the popliteal region ; it not infrequently becomes distended with fluid,
and then presents usually a more or less sausage-shaped outline ; according to
Holden, the bursa communicates with the cavity of the knee-joint in one subject
out of five.
To map out the line of the popliteal vessels and the tibial nerve, draw a line
Glutseus medius
Tubercle of iliac crest i
Anterior superior iliac spine
Linea semilunaris
Sartorius
Rectus femoris
Tensor fasciae latae
Femoral artery at apex of the femoral trigone
Rectus femori
Distal end of femoral artery
Vastus mediali
Pubic tubercle
Pubic tubercle
Adductor magnus
Spermatic funiculus
Medial epicondyle
Sartorius
Lig. patellae
Medial condyle of tibia
Tuberosity of tibia
Subcutaneous inguinal ring
Medial
meniscus
Patella
L Tensor fasciae
Iat83
Vastus lateralis
rius
Abdominal inguinal ring
Gastrocnemius
Medial margin of tibia
FIG. 1120. THE THIGH AND GROIN.
from a point a little medial to the proximal angle of the space to a point midway
between the condyles of the femur, and thence dis tally along the middle of the
space to the level of the distal part of the tuberosity of the tibia. The tibial nerve
lies immediately under cover of the deep fascia ; the artery is separated from the
popliteal surface of the femur by a quantity of fat. The popliteal lymph glands
lie deep to the popliteal fascia, one upon the tibial nerve, the others deeply in the
space (Leaf).
THE FRONT OF THE THIGH.
Between the front of the thigh and the abdomen is the fold of the groin, at the
bottom of which the inguinal ligament can be felt as a tense band, stretching from
the anterior superior spine of the ilium to the pubic tubercle. The anterior
superior spine looks directly forwards; comparative measurements of the inferior
extremities are made by stretching a tape from it to the tip of one or other of the
malleoli, care being taken that the pelvis is horizontal, and the limbs in corre-
sponding positions. The pubic tubercle is felt under the proximal and lateral part
of the mons Veneris and at a corresponding point in the male; between the
tubercle and the symphysis is the crest of the pubis, the two crests together
THE FKONT OF THE THIGH. 1459
forming a rounded subcutaneous bony ridge. A line extending from the pubic
tubercle horizontally laterally across the front of the thigh crosses the front of the
hip-joint at the level of the inferior part of the head of the femur. The cord-like
tendon of the adductor longus is readily felt, and a point about 1 in. below the
pubic tubercle is selected for performing the operation of subcutaneous tenotomy
of the tendon.
The centre of the fossa ovalis is situated 1J in. distal and lateral to the pubic
tubercle ; it overlies the medial (hernial) and intermediate (venous) compartments
of the femoral sheath ; behind the lateral border of the opening is the arterial
compartment of the sheath ; crossing over the distal border is the termination of
the great saphenous vein. A femoral hernia makes its way into the thigh below
the proximal edge of the opening. The course of the great saphenous vein in the
thigh is indicated by a line extending from the adductor tubercle of the medial
epicondyle of the femur to the distal part of the fossa ovalis.
The horizontal or subinguinal chain of lymph glands can usually be felt along, and
a little distal to, the line of the inguinal ligament ; when the glands are inflamed
the surgeon should not neglect to examine the buttocks and anus as well as the
external genitals. The vertical or femoral chain lies in close relation to the upper
end of the great saphenous vein. Deeper glands also are met with deep to the
fascia cribrosa, close to the medial side of the femoral vein, and there is generally
one in the femoral canal. To clear out the glands in the groin an incision should
be made parallel to, and a finger's breadth distal to the whole length of the
inguinal ligament.
To map out the course of the femoral artery, the thigh being slightly flexed and
rotated laterally, draw a line from the mid-point between the anterior superior
iliac spine and the symphysis pubis to the adductor tubercle at the proximal and
posterior part of the medial epicondyle ; rather less than the proximal third of this
line corresponds to the femoral artery in the femoral trigone, while rather more
than its middle third corresponds to the artery as it lies in the adductor canal.
The seat of election for ligature of the vessel is at the apex of the femoral trigone.
To compress the femoral, pressure should be made directly backwards against
the ilio-pectineal eminence, and not against the head of the femur ; to compress
the femoral in the adductor canal, pressure should be made laterally against the
medial surface of the shaft of the femur.
On the lateral aspect of the thigh the fascia lata is thick, aponeurotic, and
loosely attached to the vastus lateralis ; hence the tendency of abscesses to travel
distally under cover of it towards the knee. The sartorius, which forms the most
important muscular landmark of the thigh, may be thrown into prominence by
maintaining the thigh unsupported, flexed, and slightly rotated laterally. Observe
that in the proximal third of the thigh it forms the lateral boundary of the femoral
trigone ; in the middle third it is placed superficial to the adductor canal ; while in
the distal third it lies in front of the medial hamstrings. Lateral and adjacent to
the proximal part of the sartorius is the prominence -of the tensor fasciae latae,
which, as it passes to its insertion, diverges from the sartorius; in the angle
between the two the tendon of the rectus femoris may be felt as it overlies the
distal part of the anterior aspect of the articular capsule of the hip.
The medial aspect of the distal half of the shaft of the femur may be conveniently cut down
upon through the vastus medialis, where it comes to the surface between the sartorius and rectus
muscles ; the incision should be made in the direction of a line extending from a point midway
between the medial border of the patella and the adductor tubercle, to the anterior superior
iliac spine.
The front of the hip-joint may be reached through an incision from the anterior superior
iliac spine distally, along either the medial or the lateral border of the sartorius ; in the former
case the deeper part of the dissection passes between the iliacus and the medial border of the
rectus femoris, while in the latter case the joint is reached lateral to the rectus tendon, between
it and the anterior borders of the glutseus medius and minimus muscles. The ascending branch of
the lateral circumflex artery of the thigh crosses the capsule parallel to, and immediately
above, the intertrochanteric line. The ilio-psoas crosses the anterior and the medial part
of the capsule ; between the two is a bursa, which frequently communicates with the joint
through the thin part of the capsule medial to the ilio-femoral ligament ; it is by way of this
communication that a psoas abscess occasionally gives rise to secondary tubercular disease of the
1460
SURFACE AND SURGICAL ANATOMY.
hip-joint. One of the commonest situations to meet with an abscess in' hip-joint disease is in
the cellular tissue and fat under the tensor fasciae latae ; or the pus may pass below and to the
medial side of the neck of the femur, and thence along the course of the medial circumflex artery
of the thigh to the back of the thigh. To tap or explore the hip-joint, the puncture should be
made in the interval between the sartorius and the tensor fasciae latae, 2 to 3 in. distal to the
anterior superior iliac spine ; if the instrument is then pushed upwards, medially and posteriorly
beneath the tendon of the rectus femoris, it will pass through the capsule a little above the inter-
trochanteric line. Regarded from the point of view of dislocation, the regions of the acetabular
notch and of the inferior part of the capsule are the weak points in the joint ; it follows,
therefore, that abduction favours dislocation by bringing the head of the femur into relation
with these two weak areas.
THE KNEE.
With the knee extended and the quadriceps -relaxed, the patella can be readily
outlined and moved from side to side upon the femoral condyles. When the
quadriceps is contracted its tendon
springs forwards and is felt as a
tense band above the patella ; while
the lig. patellae, which has become
tense and prominent, may be traced
to the distal part of the tuberosity
of the tibia. In front of the distal
part of the patella and of the proxi-
mal part of the lig. patellae is the
pre-patellar bursa, into which effusion
takes place in the condition known
as housemaid's knee. Deep to and
on each side of the ligamentum
patellae is a well-circumscribed pad
of fat, palpation of which gives rise
to a feeling closely resembling true
fluctuation. In extension, only the
distal pair of articular facets of
the patella are in contact with the
trochlear surface of the femur. In
semiflexion the middle pair of facets
tibia rests upon the trochlea ; in this posi-
tion the medial margin of the medial
condyle, the proximal border of the
medial condyle of the tibia, and the
distal part of the patella are all
distinctly visible, and together bound
a triangular depression, which over-
lies the line of the joint and con-
tains the anterior part of the medial
meniscus ; it is in -this triangle that
the surgeon searches for a displaced
or thickened medial meniscus, for a
loose body, and for " lipping " of the
edge of the articular cartilage in
chronic osteo- arthritis. A similar,
but less well-defined, triangle may
be felt immediately lateral to the
distal edge of the patella. When
the quadriceps is thrown into sud-
den or violent contraction, as in
preventing oneself from falling backwards, the patella may be transversely fractured
at the moment of partial flexion. In full flexion almost the whole of the trochlear
surface of the condyles is exposed to palpation, covered, however, by the stretched
quadriceps tendon.
racilis
Rectus femoris
rtorius
Vastus lateralis
Vastus medialis
Quadriceps extensor
tendon
Proximal border of
patella
Patella
Ilio-tibial tract
Medial epicondyle
Medial meniscus
Ligamentum patellae
Pad of fat
Medial condyle of
Head of fibula
Tuberosity of tibia
Medial margin of
tibia
Anterior crest of
tibia
astrocnemius
~-Soleus
FIG. 1121. ANTERIOR ASPECT OF KNEE.
THE LEG. 1461
The proximal part of the medial surface of the medial condyle is overlapped by
the muscular prominency of the distal fibres of the vastus medialis. Leading
proximally from the medial condyle is a slight furrow, corresponding to the
interval between the distal part of the vastus medialis and the sartorius ; at the
bottom of the furrow the cord-like tendon of the adductor magnus may readily be
felt, and followed to its insertion into the adductor tubercle ; the latter, situated at
the junction of the medial supra-condylar ridge with the proximal and posterior
part of the medial condyle, marks the level of the epiphyseal cartilage. Anteriorly
and posteriorly the epiphyseal cartilage lies just proximal to the highest part of
the articular cartilage.
Disease of the distal end of the body of the femur generally invades the popliteal surface
of the femur and the popliteal fossa rather than the cavity of the knee-joint. In Macewen's
operation for knock-knee, the incision (through which the osteotome is introduced to divide the
femur) is carried down to the bone through the vastus medialis a little proximal to the medial
condyle, a finger's breadth proximal to the summit of the trochlea, to avoid injury to the epi-
physeal cartilage, and the same distance in front of the adductor tendon, to avoid injury to the
musculo-articular branch of the arteria genu suprema.
Distal to the medial condyle is the subcutaneous medial condyle of the tibia,
across which the tendons of the sartorius, gracilis, and semitendinosus pass to their
insertions. Between those tendons and the medial head of the gastrocnemius is
a groove which winds distally and forwards from the popliteal space ; an incision
along this groove will expose the great saphenous vein and saphenous nerve and the
superficial or saphenous branch of the arteria genu suprema.
On the lateral side of the knee is the ilio-tibial tract, which, after crossing and
obscuring the line of the joint, is attached to the lateral condyle of the tibia. By
semiflexion of the knee the posterior border of the tract is thrown into relief, and a
well-marked furrow intervenes between it and the prominent tendon of the biceps ;
the distal part of the shaft of the femur and the popliteal surface may be reached
through an incision along this furrow. Under cover of the ilio-tibial tract, as it
crosses the line of the joint, are the lateral meniscus, the distal lateral genicular
artery, and the fibular collateral ligament. The head of the fibula, and the tendon
of the biceps passing to be inserted into it, are rendered distinctly visible by
semiflexing the knee ; the former lies on a level with the tuberosity of the tibia,
1J in. posterior and a little distal to the most prominent part of the lateral
condyle of the tibia. Immediately distal to the head of the fibula is the termina-
tion of the common peroneal nerve, which is liable to be contused from blows, and in
fractures of the neck of the fibula.
The synovial layer of the knee-joint extends distally, anteriorly, as far as the level
of the proximal border of the tibia ; posteriorly, it dips distally for a short distance be-
hind the popliteal notch of the tibia, to form a small cul-de-sac, the close relation of
which to the popliteal artery must be borne in mind in performing the operation of
excision of the knee. Anteriorly, the synovial layer extends proximally beneath the
quadriceps in the form of a pouch, which reaches nearly two inches proximal to the
articular surface of the femur ; posteriorly, there is no extension of the synovial cavity
proximal to the condyles ; at the sides of the knee the synovial layer covers the anterior
third of the superficial surface of each condyle.
In effusion into the knee-joint the hollows become obliterated, the patella is floated up, and
fluctuation may be obtained proximal, distal, and to either side of the patella.
To pass a tube through the knee-joint for drainage, two short vertical incisions should
be made one on each side of the joint at the level of the proximal part of the patella, and
a finger's breadth behind its lateral edges. In arthrectomy of the knee for tubercular disease, the
subsynovial fat facilitates the separation of the supra-patellar pouch from the distal and anterior
part of the shaft of the femur ; to expose the pouches posterior to the condyles, the cruciate liga-
ments must be divided.
THE LEG.
The medial surface of the tibia is subcutaneous throughout ; hence the seat of a
fracture of the shaft is, as a rule, easily felt, and the distal extremity of the proximal
fragment is liable to perforate the skin. The skin over the distal half of this
1462
SURFACE AND SUEGICAL ANATOMY.
Vastus lateralis
tendon
Patella
Lateral condyle
"of tibia
of tibia
Tibialis anterior
surface is the commonest seat of varicose and callous ulcers, which are frequently
prevented from healing by adhesion of the floor of the ulcer to the periosteum.
The shaft of the fibula, situated on a plane posterior to that of the tibia, is, with
the exception of the triangular subcutaneous surface proximal to the lateral malle-
olus, deeply placed amongst
the muscles. To examine the
fibula, the surgeon should
stand on the opposite side
of the patient and manipu-
late the bone along the line
Quadriceps extensor of the intermusculajseptum
between the peronaei and the
muscles of the calf.
The greater fulness of
the antero - lateral surface
of the leg, as compared with
Ligamentum paten* its medial surface, is due to
the presence of the extensor
and peroneal groups of
muscles. When those
groups are thrown into
action, the individual
muscles are mapped out
upon the surface by the
grooves corresponding to
their intermuscular septa.
The posterior peroneal sep-
tum is seen as a well-marked
furrow, extending from the
posterior aspect of the head
Peronaeus tertius of the fibllla to the hollow
behind the lateral mal-
leolus; in front of it are
the peronsei muscles, the
longus giving rise to a pro-
minence on the proximal
half of the leg, while the
brews is prominent on the
distal half; behind the
septum is a prominence
formed by the lateral border
of the soleus, which projects
beyond the border of the
gastro-cnemius.
It is along the line of
the posterior peroneal inter-
muscular septum that in-
cisions should be made to
expose the fibula ; to avoid the superficial peroneal nerve, however, the incision
must not extend to a more proximal level than 1 in. distal to the head of the
fibula.
The furrow between the extensors and the two peronaei, the anterior peroneal
septum, is much less distinct, and runs in a line from the anterior border of the
head of the fibula to the anterior border of the lateral malleolus ; the cutaneous
portion of the superficial peroneal nerve corresponds to the distal half of this line.
At the junction of the middle and distal thirds of the leg the extensor muscles
incline medially over the anterior aspect of the tibia.
The anterior tibial artery reaches the front of the interosseous membrane 2 in.
distal to the tuberosity of the tibia ; in the proximal two-thirds of its course it lies
Lateral
malleolus
Tip of
lateral
malleolus
FIG. 1122. LATERAL ASPECT OF KNEE AND LEG.
THE FOOT AND ANKLE. 1463
upon the interosseous membrane, while in its distal third it winds on to the front
of the tibia, to terminate at a point opposite the ankle-joint, midway between the
two malleoli. Incisions to expose the vessel should strike the lateral border of the
tibialis anterior, which corresponds to a line drawn from a point midway between
the lateral condyle of the tibia and the head of the fibula, to the termination of
the vessel.
When the muscles of the calf are thrown into action, a groove is seen between
the two heads of the gastrocnemius, the fleshy fibres of which extend a little distal
to the middle of the leg. The fleshy fibres of the soleus extend to the junction
of the middle and distal thirds of the leg, and project beyond the margins of the
gastrocnemius. The narrowest part of the tendo calcaneus is situated opposite the
bases of the malleoli, and it is there that the tendon is divided in the operation
of tenotomy. The small saphenous vein, which lies a little to the lateral side of
the tendon, gradually reaches the middle of the calf, along which it runs proximally
to the middle of the popliteal fossa. The great saphenous vein and the saphenous
nerve lie along the medial margin of the tibia.
The course of the posterior tibial artery is mapped out by drawing a line from
the distal angle of the popliteal fossa, at the level of the distal border of the
tuberosity of the tibia, to a point midway between the medial malleolus and the
tendo calcaneus. To expose the vessel in the proximal half of the leg, an incision
is made parallel to and \ in. posterior to the medial margin of the tibia ; after
retracting the medial border of the gastrocnemius and dividing the tibial origin
of the soleus, the artery is found lying on the tibialis posterior. In exposing the
artery below the soleus, divide two layers of deep fascia and keep the knife
directed towards the tibia.
The peroneal artery is given off 3 in. distal to the head of the fibula ; incisions
to expose the vessel are made in the direction of a line extending from the
posterior border of the head of the fibula to a point midway between the lateral
malleolus and the tendo calcaneus.
THE FOOT AND ANKLE.
The tip of the lateral malleolus is situated \ in. distal and f in. more
posterior than that of the medial malleolus. Proximal to the lateral malleolus is
Fibula
Line of ankle-joint
Extensor digitorum brevis
Tendon of flexor digitorum
longus to tifth toe
Second metatarso-
phalangeal joint
Fifth metatarso-phalangeal joint' Base of fifth metatarsal \ \ Lateral malleolus
Peronseus brevis . Trochlear process
Greater tubercle of calcaneus Peronseus longns
FIG. 1123. LATERAL ASPECT OF FOOT AND ANKLE.
the triangular subcutaneous surface of the fibula, the apex of which corresponds
to the distal end of the extensor-peroneal intermuscular septum.
The line of the ankle-joint can be felt on either side of the extensor tendons,
and when the foot is extended the anterior part of the proximal articular surface
of the talus forms a visible prominence distal to the anterior crest of the distal end
1464
SUKFACE AND SUKGICAL ANATOMY.
of the tibia. The small posterior surface of the talus is felt distal and posterior to
the medial malleolus, at the anterior part of the hollow between it and the heel.
In effusions into the ankle-joint the hollows in front and behind the malleoli are
obliterated, and the extensor tendons are raised from the front of the joint.
A finger's breadth distal to the tip of the medial malleolus is the sustentaculum
tali ; 1^ in. in front of the sustentaculum, and midway between the dorsal and
plantar margins of the medial aspect of the foot, is the tuberosity of the navicular
(the medial landmark in Chopart's amputation), which is generally visible, and
always distinctly palpable. The calcaneo-taloid joint lies immediately above the
sustentaculum, while close above it the tendon of the tibialis posterior may
be rendered visible, as it extends from behind the tip of the medial malleolus to
the tuberosity of the navicular. An inch and a half in front of the tuberosity
of the navicular is the joint between the first cuneiform and the first metatarsal ;
the ridge at the base of the first metatarsal furnishes a good guide to the articula-
tion. The first metatarso-phalangeal joint lies a little in front of the middle of the
ball of the great toe.
A finger's breadth vertically below the tip of the lateral malleolus is the
trochlear process of the calcaneus, and midway between the two is the calcaneo-
taloid joint ; the trochlear process is, when present, a trustworthy guide to the level
at which the two peronsei tendons cross the lateral surface of the calcaneus. The
Tibialis posterior
Anterior border of distal end of tibia
Line of ankle-joint
Tibialis anterior
Head of talus
Tuberosity of navicular
Tarso-metatarsal articulation.
First metatarso-
phalangeal articulation
Posterior tibial
artery
_Flexor hallucis
longus
-Medial malleolus
"Temlo calcaneus
lexor digitorum
longus'
Sustentaculum
tali
FIG. 1124. MEDIAL ASPECT OF FOOT AND ANKLE.
greater process of the calcaneus is felt in the triangular interval between the
tendons of the peronseus brevis and tertius ; the calcaneo-cuboid joint the lateral
landmark in Chopart's amputation is placed a little in front of the mid-point
between the tip of the lateral malleolus and the base of the fifth metatarsal bone.
To open the lateral tarso-metatarsal articulations, the knife, entered behind the
projecting base of the fifth metatarsal bone, should be directed forwards as well as
medially. On the dorsum of the foot the tarsal joints are obscured by the extensor
tendons. The synovial layer of the ankle-joint is prolonged on to the neck of the
talus, and care must be taken to avoid opening the ankle-joint in performing
Chopart's amputation.
The line of the tarso-metatarsal joints extends nearly 1 in. further forwards on
the medial than on the lateral border of the foot ; between these points the joint-
line takes a zigzag course on account of the second metatarsal bone extending
backwards between the first and third cuneiform bones. The joint between the
second metatarsal and second cuneiform is nearly J in. behind that between
the first metatarsal and first cuneiform, and nearly J in. behind that between
the third metatarsal and the third cuneiform. The strong transverse inter-
osseous ligament (Lisfrancs ligament), which connects the lateral surface of
the first cuneiform with the base of the second metatarsal, must be divided in
the tarso-metatarsal amputation of Lisfranc. In order to preserve the insertions
of the two tibial and the three peroneal muscles, it is advisable, when possible,
THE FOOT AND ANKLE. 1465
instead of disarticulating at " Lisfranc's joint," to saw through the metatarsal bones
just in front of their bases.
The metatarso-phalangeal articulations are situated 1 in. behind the web of the
toes. In disarticulating a toe, the transverse metatarsal ligament, which unites
the heads of the metatarsal bones, should not be injured.
The tendon of the tibialis posterior may be felt, and, by inverting the foot, seen,
as it extends from behind the tip of the medial malleolus to the tuberosity of the
navicular ; it crosses the talus immediately above the sustentaculum tali.
In the commonest form of club-foot, viz., talipes equino-varus, the tuberosity of the
navicular is approximated to the medial malleolus, so that tenotomy of the tendon
should be performed through a puncture a little distal to the tip of the medial malleolus ;
if the knife, after dividing the tendon, is carried down to the bone, the plantar calcaneo-
navicular ligament will be divided and the talo-navicular joint opened, a procedure
which is called for before the foot can be brought into good position.
Crossing the front of the ankle-joint, from medial to lateral side, are the
following tendons, viz. : the tibialis anterior, the largest and most prominent ; the
extensor hallucis longus, the extensor digitorum longus, and the peronaeus tertius. The
extensor digitorum brevis gives rise to a fleshy pad which overlies the dorsal aspect
of the calcaneo-cuboid joint. When the foot is everted, the tendon of the peronaeus
brevis may be seen extending from the tip of the lateral malleolus to the base of
the fifth metatarsal bone ; immediately below it is the tendon of the peronaeus longus,
which, as it winds round the cuboid, is obscured by the fleshy fibres of the abductor
digiti quinti muscle. The abductor hallucis muscle, although described along with
the sole, forms a fleshy pad along the medial border of the foot below the susten-
taculum tali.
An incision, extending from the tuberosity of the navicular to the middle of
the medial border of the heel, will expose the various tendons, vessels, and nerves,
as they pass from the medial malleolus into the sole, beneath the abductor hallucis.
The dorsalis pedis artery may be mapped out on the surface by drawing a line from
a point opposite the ankle-joint, midway between the tips of the two malleoli, to the
posterior end of the first interosseous space ; the vessel may be compressed against
the medial column of the tarsal bones. The great saphenous vein and the saphenous
nerve lie between the anterior border of the medial malleolus and the tendon of
the tibialis anterior; the small saphenous vein and the nervus suralis take the
same course as the tendon of the peronaeus brevis.
The medial plantar vessels and nerves lie along the medial intermuscular septum,
which corresponds to a line drawn from the inferior surface of the medial
tubercle of the calcaneus to the interval between the first and second toes. The
lateral plantar vessels and nerves may be exposed by an incision along the
lateral intermuscular septum, which runs in a line extending from the middle of
the inferior surface of the heel to the fourth toe (Kocher) ; to map out the course
of the plantar arch, draw a line across the sole from the medial side of the base of
the fifth metatarsal bone to the proximal end of the first interosseous space.
94
1 l
o
2 c
I :
a
PLATE II.
SKIAGRAM OF SKULL FROM THE FRONT, SHOWING THE FRONTAL SINUSES, THE ETHMOIDAL
AIR-CELLS, AND THE MAXILLARY SINUSES.
INDEX.
INDEX.
NOTE. The B.N.A. nomenclature, alone, is included in the index, as references to the English
terms will be found in the text. Figures in heavy type refer to the pages on which
structures are most exhaustively described.
Abdomen, 1155
apertures of, 1157
boundaries of, 1155
cavity of, 1155, 1411
contents of, 1160
fascise of, 474, 485, 489
intertubercular lines of, 1158
lymph vessels of, 1015
muscles of, 475
planes, intertubercular, 1158
planes, subcostal, 1158
regions of, 1159, 1411
shape of, 1155
subcostal line of, 1158
subdivision of abdomen proper, 1158
surface and surgical anatomy of, 1415
tela subserosa of, 1158
zones of, 1159, 1411
Abdominal aorta, 885
surface and surgical anatomy of, 1426
Abdominal cavity, 1155, 1411
apertures of, 1157
boundaries of, 1155
fasciae of, 474, 485, 489
pelvic portion of, 485
subdivisions of, 1159, 1411
vessels of, position of, 1426
Abdominal incisions, above umbilicus, 1409
below umbilicus, 1410
in iliac regions, 1411
lateral to recti, 1410
median, 1409
through the recti, 1410
Abdominal inguinal ring, 1408
surgical anatomy of, 1408
Abdominal part of sympathetic, 761
Abdominal wall, fasciae of, 474, 485, 489
muscles of, 475
surgical anatomy of, 1407
' Ibducens nerve, 781
development of, 683
morphology of, 795
nucleus of, 568, 600
origin of, deep, 600
superficial, 600, 781
Uxluction, 401
'Abductor hallucis muscle, 432, 434
action of, 434
nerve-supply of, 434
Abductor hallucis muscle (contd.), surgical
anatomy of, 1465
Abductor pollicis brevis muscle, 392
action of, 392
nerve-supply of, 392
pollicis longus muscle, 399
quinti digiti muscle of hand, 393
action of, 393
nerve-supply of, 393
quinti digiti muscle of foot, 433
action of, 433
nerve-supply of, 433
Aberrant arteries, 1054
Abnormalities of arteries, 1051
anterior tibial, 1057
aorta, 1051
branches of aortic arch, 1051
axillary, 1055
basilar, 1055
brachial, 1055
bronchial, 1052
cceliac, 1053
common carotid, 1054
coronary, 1051
external carotid, 1054
external iliac, 1057
femoral, 1057
gastric, 1053
hepatic, 1053
hypogastric, 1057
iliac, common, 1056
inferior mesenteric, 1054
innominate, 1054
intercostal, 1052
internal carotid, 1054
internal mammary, 1055
lumbar, 1053
obturator, 1057
phrenic, inferior, 1053
popliteal, 1057
posterior tibial, 1057
pulmonary, 1051
radial, 1056
renal, 1053
sacral, middle, 1053
splenic, 1053
subclavian, 1055
superior intercostal, 1055
mesenteric, 1053
1469
1470
INDEX.
Abnormalities of arteries (contd.)
testicular, 1053
ulnar, 1056
vertebral, 1055
Abnormalities of the heart, 1051
Abnormalities of the lymph vessels, 1060
Abnormalities of the vascular system, 1050
Abnormalities of veins, 1058
facial, posterior, 1059
hemiazygos veins, 1058
jugular, anterior, 1058
external, 1058
internal, 1058
of lower extremity, 1060
of upper extremity, 1059
vena azygos, 1058
vena cava inferior, 1059
superior, 1058
Abscesses of the scalp, 1357
abdominal, 1427
in back of thigh, 1457
Accessory nerve, 726
cerebral part of, 595
nucleus ambiguus, 595, 596
nucleus of origin of, 595
spinal part of, 595
surgical anatomy of, 1333
Accessory processes of vertebrae, 96
Acetabular artery, of obturator, 940 ; of medial
circumflex of thigh, 949
Acetabular fossa, 234
Acetabulum, 234
Achromatic spindle, 10, 13
substance, 8, 10
Acini, 1132
Acino-tubular glands, 1132
Acinous glands, 1132
Acoustic area and fibre tracts, 656
development of, 622
meatus of ear, external, lymph vessels of, 1004
radiation, 643, 656
Acoustic nerve, 784
area acustica, 604
cochlear nerve, 604
central connexions of, 606
development of, 683
Deiters' nucleus, 605
divisions of, 604
dorsal cochlear nucleus of, 604
lateral nucleus, 605
origin of, 604
roots of, 784
spiral ganglion of, 604
superior nucleus, 605
ventral cochlear nucleus, 604
vestibular ganglion, 604
vestibular nerve, 604
Bechterew's nucleus, 605
dorsal vestibular nucleus, 604
nucleus of descending tract, 605
principal nucleus, 604
Acromial angle, 203
artery, 916
morphology of, 297
Acromio-clavicular joint, 318
ligaments of, 319
movements at, 319, 373
surgical anatomy of, 1444
topography of, 1444
Acromion, 200
surgical anatomy of, 1444
Actions of muscles of forearm, 401
Actions of muscles (contd.), of leg and foot, 435
of thigh, 421
Adamant, 1113, 1122
cells, 1245, 1247
cuticle, 1122
development of, 1247
formation of, 1247
germs, 1245
organs, 1245
prisms, 1122
Addison's transpyloric plane, 1411
Adduction, 401
Adductor brevis muscle, 412
actions of, 412
nerve-supply of, 412
hallucis muscle, 434
action of, 434
nerve-supply of, 434
longus muscle, 411
actions of, 412
nerve -supply of, 412
surgical anatomy of, 1459
tenotomy of, 1459
magnus muscle, 412
actions of, 413
nerve-supply of, 413
relations, 413
surgical anatomy of, 1461
minimus muscle, 413
pollicis muscle, oblique part, 393
action of, 393
nerve-supply of, 393
transverse part, 393
action of, 393
nerve-supply of, 393
Adductor canal, 414
Adductor tubercle of femur, 242, 412
surgical anatomy of, 1459, 1461
Adenoids, 1385
Aditus ad antrum, Appendix A, 271
surgical anatomy of, 1365
laryngis, 1068
Adrenin, 1341
Adventitious ligaments, 305
Equator bulbi oculi, 807
lentis, 820
A/enspalte, 660
Agger nasi, 803
Aggregated lymph glands, 1181
Agitator caudse muscle, 415
Air-cells, ethmoidal, 140, 804, 1373
surgical anatomy of, 1372
of lung, 1099, 1101
mastoid, 133, 836, 1370
surgical anatomy of, 1370
Air-sinuses, 84, 183
frontal, 270, 1371
maxillary, 148, 188, 1378
nasal, 185
sphenoidal, 135, 183, 1373
Akanthion, 285
Akrocephalic skulls, 286
Ala cinerea, 551
lobuli centralis cerebelli, 575
magna ossis sphenoidalis, 134
nasi, 799
parva ossis sphenoidalis, 135
sacralis, 98
vomeris, 144
Alar folds of knee, 348
lamina of neural tube, 682
ligaments of epistropheus, 92, 311
INDEX.
1471-
Alar process of ethmoid, 140
sulcus of nose, 799
Albumen of ovum, 14
Alecithal ovum, 14
Alimentary canal, 1104
accessory digestive glands, 1106
anal canal, 1105, 1228, 1422
aperture of larynx, 1105
ascending colon, 1105, 1211, 1219
ca3cum, 1105, 1211, 1213
descending colon, 1105, 1211, 1221, 1423
development of, 41, 1249
duodenum, 1105, 1177, 1182
ileum, 1105, 1208
iliac colon, 1105, 1222, 1423
isthmus of the fauces, 1105, 1112, 1383,
1442
jejunum, 1105, 1210, 1420
mouth cavity, 1105, 1106, 1242
oesophagus, 45, 1105, 1150, 1249, 1393,
1407
palate, 49, 174, 1105, 1110, 1379, 1384
pancreas, 47, 1106, 1203, 1426, 1439
parts of, 1105
pelvic colon, 1105, 1222, 1423
pharynx, 1105, 1140, 1242, 1383, 1396
primitive entodermal development of, 38
rectum, 1105, 1224, 1252, 1430
salivary glands, 1106, 1133, 1140, 1249
special organs found in walls of, 1105
stomach, 47, 1105, 1163, 1416
transverse colon, 1105, 1219, 1422
valve of colon, 1105, 1214, 1421
vermiform process, 1105, 1215, 1421
Alisphenoids, 136
development of, 138
Allantoic arteries, 65
body-stalk, 54
diverticulum, 38
stalk, 54
veins, 68
Allantois, 38
Allelomorphs, 19
Alveolar arch, 148, 1119
artery, anterior superior, 899
inferior, 899
posterior superior, 899
canal, inferior, 156, 157
posterior, 147
ducts of lungs, 1101
glands, 1133
index, 287
nerve, anterior superior, 777
inferior, 780
middle superior, 777
posterior superior, 775
point, 285
process, 148
veins, 968
Alveoli of glands, 1133
of jaws, 156
development of, 149, 157
pulmonum, 1101
of the teeth, 1119
Alveolo-dental periosteum, 1115, 1123
Alveolo-glossal sulcus, 1383
Alveus, 627
Ameloblasts, 1245
Amitosis, 9
Amnion, 54, 55
cavity of, 54, 60
distention of, 55
Amnion (contd.), false, 22
fluid, 63
fold, 22
formation of, 54, 60
true, 22
Amphiarthroses, 300
development of, 304
Ampulla ductus deferentis, 1292
duodeni, 1186
lacrimalis, 825
of lactiferous ducts, 1338
membranacea, 848
ossea, lateralis, posterior, superior, 844
of rectum, 1226, 1227
of semicircular canals, membranous, 848 ;
osseous, 844
of uterine tube, 1314
Amygdala (tonsil), 1145
of cerebellum, 575
Amygdaloid nucleus, 641
tubercle, 636
Anal canal, 1228
columns of, 1230, 1231
course of, 1229
development of, 48
hsemorrhoidal ring of, 1233
orifice of, 1232
relations of, 1229
sinuses of, 1231
structure of, 1229
transverse folds of, 1230
surgical anatomy of, 1430
tunica mucosa of, 1230
vessels of, 1233
white line of, 1430
veins, 1233
Anal part of rectum, 1228
Anal valves, 1231
Analogy, 2
Anaphase, 10, 14
Anapophysis, 284
Anastomoses, arterial segmeiital, 1042
Anastomosis, 943, 951
Anastomotic arterial branches of brachial, 919
of femoral, 951
of inferior gluteal, 943
of vertebral, 971
vein of Trolard, 907
Anatomical neck of humerus, 205
Anatomy, 1
surgical, 1357
systematic, 4
topographical, 4
Ancona3us muscle, 398
action of, 398
nerve-supply of, 398
Angeiology, 3
Angle or Angulus
acromial, 203
cephalo-auricular, 828
facial, 286
frontalis of parietal bone, 119
inferior lateral, of sacrum, 99
inferior scapula, 201
infracostal, 1407
infrasternal, 114
lateralis scapulas, 201
of mandible, 155
differences in, due to age, 158
surgical anatomy of, 1392
mastoideus of parietal bone, 119
medialis scapulae, 201
1472
INDEX.
Angle or Aiigulus (contd.), occipi tails of parietal,
119
pubis, 217
of rib, 97, 98, 99, 100
sacro-vertebral, 109
sexual differences in, 238
sphenoidalis of parietal bone, 119
of the sternum, 107
Angular artery, 894
gyrus, 665
surface anatomy of, 1360
process of frontal bone, 115, 160, 166
surface and surgical anatomy f, 1364
spine of sphenoid, 136
vein, 967, 969
Animal cell, structure of, 7
Animal cells, division of, 9
amitotic, 9
mitotic, 9
reproduction of, 8
Ankle, surface and surgical anatomy of, 1464
Ankle-joint, 351
effusions into, 1464
line of, 1463
movements of, 353, 436
muscles producing, 436
nerves of, 731, 733
synovial layer of, 1464
surgical anatomy of, 1464
tendons around the, 1465
Annectant gyri of calcarine fissure, 660, 661
of interparietal sulcus, 664
of parieto -occipital fissure, 662
gyrus, deep, of central sulcus, 663
Annular ligament of base of stapes, 841
of the radius, 326
plexus of cornea, 810
Annuli fibrosi cordis, 879
Annulus femoralis, 405
fibro-cartilagineus of membrana tympani,
834
fibrosus, 307
inguinalis abdominalis, 481, 483, 1408
inguinalis subcutaneus, 477, 1408
tympanicus, 142
Aiio-coccygeal body, 1224
plexus, 738
Ano-cutaneous line, 491
Ansa hypoglossi, 698, 699, 794
lenticularis, 641
peduncularis, 545
subclavia, 759
Ante -cubital lymph glands, 759
Anterior ethmoidal artery, 903
cells, 1373
skiagraphs of, 1373
surgical anatomy of, 1372
Anterior rami of spinal nerves, 692
Antibrachium, 382, 1450
Anticlinal vertebra, 101
Antihelix, 828
development of, 52
fossa o, 828
Antithesis in muscular action, 452
Antitragicus muscle, 829
Antitragus, 828
development of, 52
Antrum, maxillary, 149, 804, 1378
relation of molar teeth to, 1113, 1119
surgical anatomy of, 1378
pyloricum, 1169, 1173
changes in, during digestion, 1173
Antrum (contd.), tympanic, 191, 834, 836
development of, 44, 842
in frontal section of skull, 191
formation of, 842
openings into, 834, 836, 1369, 1371
relation of, to tympanum, 836
surface and surgical anatomy of, 1369,
1371
Anus, 1232
development of, 48
imperforate, 1223
sphincter ani externus, 1232
surgical anatomy of, 1430
Aorta, 884
abdominal, 885 ; surface and surgical ana-
tomy of, 1426
branches of, 886, 927
paired visceral, 927
ovarian, 928
branches of, 928
renal, 927
spermatic, internal, 928
suprarenal, 927
branches of, 927
testicular, 928
branches of, 928
relations of, 928
parietal, 933
unpaired visceral, 928
relations of, 886
abnormalities of, 1051
arch of, 884
abnormalities of, 1050
branches of, 885
abnormalities of, 1050
development of, 968, 1027, 1028
relations of, 885
surface anatomy of, 1405
ascending, 884
branches of, 884
development of, 68
relations, 884
surface anatomy of, 1405
bifurcation of, 1050
variations in, 1050
descendens, 885
branches of, 924
parietal, intercostal, 926
subcostal, 926
visceral, bronchial, 925
mediastinal, 925
oesophageal, 925
pericardial, 925
formation of, 67, 1027
morphology of, 1045, 1047
relations, 885
development of, 67, 1027
great sinus of, 884
primitive, branches of, 1027
development of, 67, 1027
dorsal, 65
formation of, 1027
morphology of, 1045, 1047
subdivision of, 884
ventral, 65
relations of, 884
sinuses of, 884
thoracic, 885
descending, 885
branches of, 924
vas aberrans of, 927
ventral, 1026, 1027
INDEX.
1473
Aortic arches, 67, 1405
abnormalities of, 1050
branches of, 67
development of, 67, 1027, 1028
dorsal roots of, 67
first aortic arch, 65, 1027
morphology of, 67, 1046
segmental branches of, 1043
ventral roots of, 67
area, 1405
bulb, 1035
abnormalities of, 1051
division of, 1035
septum of, 1035
cusp of mitral valve, 878
opening of diaphragm, 473
opening of heart, 878, 884
surface anatomy of, 1405
plexus, 762, 765
valve, 878
vestibule, 843
Aortico-renal ganglion, 764
Apertura externa aquaeductus cochleae,
845
externa aquaeductus vestibuli, 843
lateralis ventriculi quarti, 553
medialis ventriculi quarti, 553
pelvis (minoris) inferior, 237
superior, 236
piriformis, 163
measurement of, 287
superior canaliculi tympani, 129
thoracis inferior, 114
superior, 114
tympanica canaliculi chordae, 834
Aperture, laryngeal, 1068
Apertures of abdominal cavity, 1 157
Apex auriculae (Darwini), 828
capituli fibulae, 250
columnae posterioris, 523
of heart, 872
of lung, 1092, 1398
ossis sacri, 99
patellae, 245
prostatae, 1302
Apical bronchus, 1098
Aponeurosis, 364
epicranial, 447, 449
intercostal, 470
of palate, 1111
palmar, 384
pharyngeal, 1149
plantar, 423
vertebral, 437
Apophysis, submalleolar, 282
Apparatus digestorius, 1103
lacrimalis, 824, 1377
respiratoriiis, 1061
urogenitalis, 1257
Appendages of skin, 858
Appendices of auricles, see Auricles
epiploicae, 1211, 1212
testis, 1287
vesiculosi (Morgagni), 1287
Appendicular artery, 932, 1421
lymph gland, 1020, 1023
muscles, 365
skeleton, 82
morphology of, 294
vein, 1421
Appendix epididymidis, 1287
ventriculi laryngis, 1071
129,
Aquaeductus cerebri, 542, 545, 581, 584,
618
cochleae, 129, 845
development of, 37, 592
Aquaeductus vestibuli, 843
external aperture of, 131
Aqueous humour, 821
Arachnoidea encephali, 670, 671
granulationes araclmoideales, 672
functions of, 673
spinalis, 670
Arachnoideal villi, 672
Arbor vitae cerebelli, 577
uteri, 1317
Arch, alveolar, superior, 148
anterior, of atlas, 91
aortic, 884
abnormalities of, 1050
branches of, 67
development of, 67, 1027, 1028
surface anatomy of, 1405
caudal, 68
cephalic, 67, 1405
arterial, of wrist and hand, 923
branches of, 923
carpal, anterior (volar), 923, 924
dorsal, 920
dental, 146, 1119
femoral, deep, 405
superficial, 405
glosso-palatine, 1111, 1112, 1145
hyoid, 43
muscles produced from, 496
nerve of, 796
mandibular, 43
branchial muscles produced from, 496
nerve of, 796
palmar, deep, 923, 924
abnormalities of, 1055
morphology of, 1055
surgical anatomy of, 1454
superficial, 923, 924
abnormalities of, 1055
morphology of, 1055
surgical anatomy of, 1454
pharyngo-palatine, 1111, 1112, 1145
plantar, 954
abnormality of, 1057
morphology of, 1057
surgical anatomy of, 1465
posterior, of atlas, 91
superciliary, 116, 1374
thyreo-hyoid, 42, 43
muscles produced from, 496
nerve of, 796
transverse (osseous), of foot, 361
transverse, venous, of foot, 988
venous, dorsal, of foot, 988
morphology of, 1050
of hand, 978
morphology of, 1050
vertebral, 88
of fifth lumbar, variation in, 275
ossification of, 104, 105
serial homology of, 283
volar, deep, 924
branches of, 924
superficial, 924
branches of, 924
zygomatic, 167, 169
surgical anatomy of, 1364, 1365, 1375
Arches, alveolar, 148, 1119
1474
INDEX.
Arches, aortic, 67, 1405
dorsal roots of, 1027
segmental branches of, 1042
ventral roots of, 1027
arterial, of wrist and hand, 924
axillary, 371
nerve-supply of, 371
of fauces, 1111, 1145
of foot, 361
superciliary, 116, 1374
tarsal, of eyelids, 823
visceral, 42, 43
muscles produced from, 496
relation of, to cerebral nerves, 796, 798
Architecture of bones
bones of foot, 274
carpus, 272
clavicle, 271
femur, 273
fibula, 274
frontal bone, 270
hip-bone, 273
humerus, 272
lacrimal, 271
mandible, 271
maxilla, 271
metacarpus, 272
occipital bone, 270
parietal bone, 270
patella, 274
phalanges, 272
radius, 272
ribs, 270
scapula, 271
sphenoid, 271
sternum, 270
temporal, 271
tibia, 274
ulna, 272
vertebrae, 270
vomer, 271
zygomatic, 271
Arcuate eminence, 130, 133
fibres, external, 548, 563, 566
development of, 566
internal, 556, 560, 561
development of, 566
posterior external, 563
ligament of pubis, 338
nucleus of medulla, 551, 554
development of, 566
Arcus lumbo-costalis lateralis (Halleri), 472
medialis (Halleri), 472
senilis, 810
superciliaris, 116
tarseus inferior et superior, 823
tendineus m. levatoris ani, 491
Area of absolute cardiac dulness, 1398
acustica, 656, 657
amniotic, 54
aortic, 1405
bucco-pharyngeal, 27, 42
chorionic, 21
cochleae, 844
embryonic, 22
facial, 846
mitral, 1405
motor, of the brain, 663
nervi facialis fundi meatus, 846
olfactory, 622
parasplenalis, 665
parastriata, 660
Area (contd.), parieto-occipital, 665
pericardial, 27, 65
peristriata, 660
piriformis, 624
of Eablet, 624
placental, 56
postrema, 551
praecentralis anterior, 666
intermedius, 666
posterior, 666
precentral, 666
pulmonary, 1405
sensory, 662
striata, 659
temporalis polaris, 657
tricuspid, 1405
vascular, 64
vestibularis inferior et superior, 846
visual, 658
Areas of Flechsig, 564
Areola mammae, 1337
Areolar coat of liver, 1198
Areolar glands, 1337
Arlt, sinus of, 825
Arm, development of, 39
fasciae of, 378
intermuscular septa of, 378
lateral bicipital furrow of, 1448
lymph vessels of, 1006
medial bicipital furrow of, 1447
medial supracondylar triangle of, 1447
muscles of, 378
surface and surgical anatomy of, 1447
Arrectores pilorum, 861
Arteria hyaloidea, 819
Arterial arches of wrist and hand, 923
Arteriola macularis inferior et superior,
818
nasalis retinae inferior et superior,
818
temporalis retinae inferior et superior,
818 -
Arteriolae rectae, 1269
Arterioles, capillary, 868
Artery or Arteries ; Arteria or Arteriae, 868,
882
aberrant, 1054
abnormalities of, 1050
acetabular, of medial circumflex of thigh,
949
acetabuli (of obturator), 940
acromial, 916
allantoic, 65
alveolar, anterior superior, 899
inferior, 899
posterior superior, 899
anastomotic, of arteria suprema genu, 951
of inferior ulnar collateral of brachial,
919
of inferior gluteal, 942
of vertebral, 910
angular, 894
anonyma, 888
appendicular, 1421
arciform, 1269
articular, art. genu media,' of popliteal, 952
of deep volar arch, 924
of dorsal carpal arch, 923
of lateral plantar arch, 357
lateral, of popliteal, 951
surgical anatomy of, 1461
of medial circumflex, 949
INDEX.
1475
Artery or Arteries (contd.)
articular (contd.), medial, of popliteal,
951
auditiva interna, 852
auditory, internal, 853
auricular, deep, 898
of occipital, 895
posterior, 895
branches, 895
auricular, 896
occipital, 896
stylo-mastoid branch of, 895
course and relations, 895
surgical anatomy of, 1365
axial skeleton, 82
axillary, 914
abnormalities of, 1055
branches of, 916
course of, 914
formation of, 1047
relations of first part, 915
of second part, 916
of third part, 916
surgical anatomy of, 1445
basilar, 907
abnormalities of, 1055
branches, 907
auditory, internal, 907
cerebellar, anterior inferior, 907
superior, 907
pontine, 907
course and relations, 907
formation of, 1046
morphology of, 1047
bicipital, 917
blood-vessels of, 870
brachial, 917
abnormalities of, 1055
bifurcation of, 1450
branches of, 918
inferior ulnar collateral, 919
muscular, 918
nutrient, 919
profunda artery of the arm, 918
superior ulnar collateral, 919
course of, 917
formation of, 1047
relations of, 918
surgical anatomy of, 1448
bronchial, 1096
abnormalities of, 1051
morphology of, 1046
buccal, of external maxillary, 894
of internal maxillary, 899
buccinator^ 899
bulbi urethra, 942
surgical anatomy of, 1427
vestibuli (vaginae), 942
caecal, 932
calcaneal, medial, 955
calcarine, 908
canalis pterygoidei (Vidii), 900
capsular, of liver, 933
carotico-tympanic, 902
carotid, common, 889
abnormalities of, 1054
formation of, 67
morphology of, 1047
surgical anatomy of, 1386, 1389,
1391
left, 889
abnormalities of, 1053
Artery or Arteries (contd.)
carotid, common, left (contd.), cervical portion
of, 889
relations of, 889
thoracic portion of, 889
right common, 890
abnormalities of, 1054
relations of, 890
external, 891
abnormalities of, 1054
branches, 891
course, 891
development of, 67
morphology of, 1047
relations, 891
surgical anatomy of, 1391
internal, 900
abnormalities of, 1054
branches of, 902
anterior cerebral, 904
branches of, 904
anterior medial frontal, 904
antero-medial basal, 904
medial orbital, 904
carotico-tympanic, 902
cavernous, 902
chorioidal, 904
hypophyseal, 902
meningeal, 902
posterior communicating, 904
course, 900
development of, 67
morphology of, 1047
relations, 900, 901
carpal, radial, dorsal, 920
volar, 920
ulnar, dorsal, 923
volar, 922
cavernous, 902
central, of middle cerebral, 905
of posterior cerebral, 908
centralis retinae, 903
cerebelli inferior anterior, 907
posterior, 907
superior, 907
cerebral, anterior, 904
abnormalities of, 1054
branches of, 904
anterior medial frontal, 904
antero-medial basal, 904
intermediate medial frontal, 904
medial orbital, 904
posterior medial frontal, 904
cerebral, middle, 905
branches of, 905
ascending frontal, 905
parietal, 905
inferior lateral frontal, 905
lateral striate, 905
orbital, 905
medial striate, 905
parieto-temporal, 905
temporal, 905
cerebral, posterior, 908
branches of, 908
calcarine, 908
chorioidal, posterior, 908
parieto-occipital, 908
postero-lateral, 908
temporal, anterior, 908
posterior, 908
cervical, ascending, 910
1476
INDEX.
Artery or Arteries (contd.)
cervical, ascending (contd.), morphology of,
1047
deep, 914
morpliology of, 1047
transverse, 911
branches, ascending, 911, 1320
descending, 911
chorioidal, anterior, 904
posterior, 908
ciliary, 903
anterior, 813, 903
long, 813
posterior, 903
short, 903
circumflex, anterior, of humerus, 917
surgical anatomy of, 1447
iliac, deep, 945
branches of, 946
course of, 946
superficial, 947
lateral, of thigh, 949
medial, of the thigh, 949
posterior, of humerus, 917
surgical anatomy of, 1447
of the scapula, 917
clavicular, 916
coccygeal, 935
ccBliac, 928
abnormalities of, 1053
branches of, 929
gastric left, 929
branches of, 929
hepatic, 930
splenic, 929
branches of, 929
left gastro-epiploic, 930
pancreatic, 930
short gastric, 930
morphology of, 1047
relations of, 929
surgical anatomy of, 1418
colic, 932
colica dextra, 932
media, 932
sinistra, 932
collaterals ulnaris inferior, 919
superior, 919
comitans nervi mediani, 922
nervi phrenici, 913
common digital, of foot, 955
of hand, 924
communicating, anterior, 904
of volar interosseous, 922
of deep volar arch, 924
peroneal, 953
posterior, 904
abnormality of, 1056
tibial, 953
coronary, of external maxillary, 894
surgical anatomy of, 1379
left, of heart, 887 ; right, 887
abnormalities of, 1051
of stomach, 929
abnormalities of, 1053
morphology of, 1047
of corpus cavernosum penis, 942
costo-cervical trunk, 914
branches of, 914
deep cervical artery, 914
superior intercostal artery, 914
crico-thyreoid, 892
Artery or Arteries (contd.)
cystic, 930
deferential, 939
diaphragmatic, of aorta, 933
of inferior phrenic, 933
of pericardiaco-phrenic, 913
of superior phrenic, 914, 926
digital, of foot, 955, 958
of hand, 920, 924
morphology of, 147
surgical anatomy of, 1454
digital plantar, 954
volar, 924
special digital arteries, 924
dorsal metatarsal arteries, 958
abnormalities of, 1055
dorsalis clitoridis, 942, 1428
linguae, 892
pedis, 957
branches of, 957
course of, 957
surgical anatomy of, 1465
penis, 942
pollicis, 920
radialis, 920
of ductus deferens, 939, 945
elastic lamina of, 868
endothelium of, 868
epigastric, inferior, 944
branches of, 944
pubic, 945
spermatic, external, 945
formation of, 1030
morphology of, 1045
surgical anatomy of, 1408
superficial, 947
superior, 913
ethmoidal, anterior, 903
posterior, 903
external iliac, 945
branches of, 944
external maxillary, 893
branches, 893
angular, 894
ascending palatine, 893
buccal, 894
inferior labial, 894
lateral nasal, 894
masseteric, 894
submaxillary, 893
submental, 894
superior labial, 894
tonsillar, 893
course, 893
formation of, 1028
relations, 893
surgical anatomy of, 1375, 1379, 1391
external spermatic of inferior epigastric,
945
facial, transverse, 897
femoral, 945
abnormalities of, 1057
branches, 947
course, 947
formation of, 1031
morphology of, 1048
relations, 947
sheath, 947
surgical anatomy of, 1459
fibular, 953
frontal, of ophthalmic, 904
surgical anatomy of, 1358
INDEX.
1477
Artery or Arteries (contd.)
frontal, of superficial temporal, 897
ganglionic, of middle meningeal, 898
of internal carotid, 902
gastric, 929
morphology of, 1046
short, 930
gastro-duodenal, 930
gastro-epiploic left, 930
right, 930
genu suprema, 951
branches of, 951
gluteal, inferior, 942
abnormalities..of, 1057
branches of, 943
anastomotic, 943
coccygeal, 943
comitans nervi ischiadici, 934
cutaneous, 943
muscular, 943
formation of, 1031
morphology of, 1048
superficial incisions to expose, 1455
superior, 938
branches of, 938
surgical anatomy of, 1455
hsemorrhoidal, inferior, 1232
middle, 939, 1232
superior, 1232
of head and neck, 888
helicine, of the corpus cavernosum penis,
1300
hepatic, 930
abnormalities of, 1053
branches of, 930
gastric, right, 930
gastro-duodenal, 930
gastro-epiploic, right, 930
pancreatico-duodenal, superior, 930
terminal, 930
of inferior phrenic, 933
morphology of, 1047
hyaloid, 826
hyoid, of lingual, 892
hypogastric, 936
abnormalities of, 1057
branches of, 937
of anterior division, 938
of posterior division, 937
course of, 936
morphology of, 1048
relations of, 936
hypophyseal, 902
ileo-caecal, 932
ileo-colic, 932
iliac, common, 935
abnormalities of, 1056
course of, 935
morphology of, 1048
relations of, 935
surgical anatomy of, 1426
external, 943
abnormalities of, 1057
formation of, 1031
morphology of, 1048
surgical anatomy of, 1426
ilio -lumbar, 938
abnormality of, 1057
of inferior extremity, 944
infra -hyoid, 892
infra-orbital, 899
infra -scapular, of circumflexa scapulae, 917
Artery or Arteries (contd.)
innominate, 888
abnormalities of, 1051, 1052
branches, 888
course, 888
development of, 1028
morphology of, 1047
relations, 888
surgical anatomy of, 1405
intercostal, 925
abnormalities of, 1051
formation of, 1045
morphology of, 1045
anterior, 913
superior, 914
abnormalities of, 1052
morphology of, 1045, 1046
interlobar, of the kidney, 1267
interlobulares, of the kidney, 1267
intermediate visceral, 1043, 1046
interosseous, common, 922
. dorsal, 922
abnormality of, 1056
formation of, 1031, 1047
of dorsal carpal arch, morphology of,
1048
volar, 922, 1048, 1057
interosseous recurrent, 922
intersegmental, 1043
intestinal, 932
jejunal, 932
labial, inferior, 894
posterior (vulvae), 942
superior, 894
lacrimal, 903
laryngeal, inferior, 911
superior, 892
lateral sacral, 938
lienal, 929
ligamenti teretis uteri, 945
lingual, 892
branches, 892
dorsalis linguae, 892
sublingual, 893
course, 892
development of, 1028
relations, 892
surgical anatomy of, 1382, 1383., 1391
of lower limb, 944
abnormalities of, 1057
formation of, 1031
morphology of, 1048
lumbar, 933
abnormalities of, 1053
formation of, 1029
morphology of, 1045
of ilio-lumbar, 938
lumbar, lowest, 935
lymph vessels of, 870
macular, 818
malleolar, lateral anterior, 957
medial anterior, of anterior tibial, 956
of posterior tibial, 953
mammary, external (of lateral thoracic), 916
internal, 913
abnormalities of, 1055
branches, 913
intercostal, 913
musculo-phrenic, 913
pericardiaco-phrenic, 913
smaller, 913
superior epigastric, 913
1478
INDEX.
Artery or Arteries (contd.)
mammary, internal (contd.) t course, 913
formation of, 1030
morphology of, 1045, 1046
surgical anatomy of, 1398
masseteric, 899
mastoid, of occipital, 895
of posterior auricular, 895
maxillary, external, 893
internal, 898
abnormalities of, 1054
branches, 898
alveolar, posterior superior, 899
anterior tympanic, 898
auricular, deep, 898
descending palatine, 899
infra -orbital, 899
middle meningeal, 898
pharyngeal, 900
pterygoid canal, artery of, 900
spheno-palatine, 900
course and relations, 898
development of, 1028
surgical anatomy of, 1398
median, 834
abnormality of, 1056
morphology of, 1031
mediastinal, anterior, 913
of aorta, 925
meningeal, accessory, 899
anterior, of ophthalmic, 903
of internal carotid, 902
middle, 898
surgical anatomy of, 1359, 1360, 1364
of occipital, 895
posterior (asc. phar.), 896
of vertebral, 907
mesenteric, inferior, 932
abnormalities of, 1054
branches, 932
colic, left, 932
hsemorrhoidal, superior, 933
. sigmoid, 933
morphology of, 1047
surgical anatomy of, 1426
superior, 931, 1205
abnormalities of, 1053
branches of, 931
appendicular, 932
colic, middle, 932
right, 932
ileae, 932
ileo-csecal, 932
ileo-colic, 932
intestinal, 932
pancreatico-duodenal, inferior, 932
terminal, 932
morphology of, 1047
surgical anatomy of, 1426
metacarpal, 920, 923
metatarsal, 958
dorsal, 920, 923
musculo-phrenic, 913
mylo-hyoid, 899
nasal, lateral, 894
of relina, 818
naso-palatine, 900
nerves of, 870
of nose, 899, 900
nutritiae ossium (nutrient, of bones), 87
clavicle, 912
femur 950
Artery or Arteries (contd.)
nutritise ossium (nutrient, of bones) (contd.),
fibula, 953
hip-bone, 940
humerus, 919
radius, 922
ulna, 922
obturator, 940
abnormalities of, 1057
branches of, 940
occipital, 895, 896
branches, 895
auricular, 895
descending, 895
mastoid, 895
meningeal, 895
sternomastoid, 895
terminal, 895
course, 894
relations, 894
of posterior auricular, 896
oesophageal, of aorta, 926
morphology of, 1047
of inferior thyreoid, 911
of left gastric, 929
ophthalmic, 902
abnormalities of, 1054
branches of, 903
anterior meningeal of, 903
central artery of retina, 903
ethmoidal, 903
lacrimal, 903
palpebral, 904
posterior ciliary, 903
supra -orbital, 903
terminal, 904
course of, 902
orbital, of middle meningeal, 898
of superficial temporal, 897
ovarian, 928
abnormalities of, 1053
morphology of, 1047
surgical anatomy of, 1427, 1438
palatine, ascending, 893
of ascending pharyngeal, 896
descending, 899
surgical anatomy of, 1384
palpebral, 904
pancreatic, 930, 1207
of hepatic, 930, 1207
of splenic, 930, 1207
of superior mesenteric, 932, 1207
pancreatica magna, 930, 1207
pancreatico-duodenal, inferior, 932, 1207
superior, 930, 1205, 1207
parietal, of superficial temporal, 897
parieto-occipital, 821
parotid, of posterior auricular, 895
of superficial temporal, 896
pectoral, of thoraco-acromial, 916
penis, 1300
perforating, anterior, of foot, 955, 958
posterior, 955, 958
distal, of hand, 920
of internal mammary, 913
of peroneal, 953
of profunda femoris, 950
proximal, of hand, 920, 924
pericardiaco-phrenic, 913
pericardial, of internal mammary, 913
of aorta, 925
perineal, 942
INDEX.
1479
Artery or Arteries (contd.)
perineal, transverse, 942
perirenal, 935
peroneal, 953
abnormalities of, 1057
formation of, 1031
morphology of, 1048
surgical anatomy of, 1463
pharyngeal, ascending, 896
branches, 896
inferior tympanic, 806
palatine, 896
pharyngeal, 896
posterior meningeal, 896
prevertebral, 896
course, 896
development of, 1028
relations, 896
phrenic, inferior, 933
abnormality of, 1052
plantar, lateral, 954
branches of, 955
medial, 954
abnormalities of, 1058
course of, 954
surgical anatomy of, 1465
popliteal, 951
abnormalities of, 1057
branches of, 951
art. genii media, 952
inferior genicular arteries, 952
superior genicular arteries, 951
formation of, 1048
morphology of, 1048
relations of, 951
surgical anatomy of, 1458
presegmental, 66
prevertebral, of ascending pharyngeal, 896
primitive vitelline, 56
princeps cervicis, 895
pollicis, 921
abnormality of, 1056
profunda brachii, 918
clitoridis, 942
femoris, 949
linguae, 892
penis, 942
of ulnar, 923
pterygoid, 899
pterygo-palatine, 899
pubic, of inferior epigastric, 945
of obturator, 852
pudendal, internal, 940
branches of, 940
bulb, artery of, 942
hsemorrhoidal inferior, 942
penis, dorsal artery of, 942
penis, profunda artery of, 942
perineal, 942
perineal, transverse, 942
course of, 940
pudendal, deep external, 948
surgical anatomy of, 1428
superficial external, 948
pulmonary, 882
abnormalities of, 1051
development of, 68
left branch of, 883
relations, 884
morphology of, 1047
relations of, 882
right branch of, 882
Artery or Arteries (contd.)
pulmonary, right branch of (contd.}, branches
of, 882
relations, 882
surface anatomy of, 1408
pyloric, 930
morphology of, 1047
radial, 919
abnormalities of, 1056
branches of first part, 919
radial recurrent, 919
superficial volar, 919
volar carpal, 920
branches of second part, 920
dorsal metacarpal, 920
dorsal of the thumb, 920
dorsalis indicis radialis, 920
formation of, 1047
morphology of, 1047
relations of first part, 919
of second part, 920
surgical anatomy of, 1454
radialis indicis, 921
abnormalities of, 1055
surgical anatomy of, 1454
recurrent, of deep palmar arch, 924
interosseous, 922
radial, 919
abnormalities of, 1055
tibial, anterior, 956
posterior, 956
ulnar, 922
renal, 927
abnormalities of, 1425
morphology of, 1046
surgical anatomy of, 1425
of retina, 814
of round ligament, 945
sacral, lateral, 938
morphology of, 943
middle, 935
abnormalities of, 1052
morphology of, 68
of scalp, 1357
scapular, circumflex, 917
branches of, 912
course of, 911
scrotal, posterior, 942
segmental, 66, 1044
anastomoses of, 1044
dorsal branches of, 1045
terminal, 913
somatic, 1044
splanchnic, 1044
septal, of nose, 900
sheath of, 870
sigmoid, 933
somatic intersegmental, 1044
spermatic, internal, 928
abnormalities of, 1052
morphology of, 1046
spheno-palatine, 900
spinal, formation of, 1029
of ilio-lumbar, 938
of intercostals, 926
of lateral sacral, 938
of vertebral, 907, 908
splanchnic, 1044, 1047
splenic, 929
abnormalities of, 1052
morphology of, 1047
stapedial, 1028
1480
INDEX.
Artery or Arteries (contd.)
sternomastoid, of occipital, 895
of superior thyreoid 892
of stomach, 928
striate, lateral, 905
medial, 905
structure of, 868
stylo-mastoid, 895
subclavian, left, first part of, 909
relations, 909
right, first part of, 909
relations, 909
second part of, 910
relations of, 910
third part of, 910
relations of, 910
abnormalities of, 1055
branches of, 910
thyreo- cervical trunk, 910
vertebral artery, 910
development of, 67, 1028
morphology of, 1046
surgical anatomy of, 1394
subcostal, 926
sublingual, 893
submaxillary, 893
submental, 894
subscapular, 912, 917
branches of, 917
circumflexa scapulae, 917
thoraco-dorsal, 917
of transverse scapular, 912
superficial petrosal, 898
volar, 924
supraorbital, 903
surgical anatomy of, 1358
suprarenal, inferior, 927
middle, 92
superior, 933
supraspinous, 912, 913
suprasternal, 912
sural, 952
systemic, 884
tarsal, lateral, 957
temporal, deep, anterior, 899
posterior, 899
middle, 897
of posterior cerebral, 908
of retina, 818
superficial, 896
branches, 896
frontal, 897
middle temporal, 897
parietal, 897
transverse facial, 897
zygomatico-orbital, 897
course, 896
development of, 1030
surgical anatomy of, 1359
testicular, 928
thoracic, lateral, 916
supreme, 828
thoraco-acromial, 916
branches of, 916
thoraco-dorsal, 917
thyreoid, inferior, 910
branches of, 910, 911
ascending cervical, 910
inferior laryngeal, 911
oesophageal, 911
terminal, 911
tracheal, 911
Artery or Arteries (contd.}
thyreoid, inferior, (contd.), relations of,
910
surgical anatomy of, 1389
superior, 891
branches, 892
crico-thyreoid, 892
sterno-mastoid, 892
superior laryngeal, 892
terminal, 892
course, 891
morphology of, 1047
relations, 891
surgical anatomy of, 1389
thyreoidea ima, 888
morphology of, 1047
tibial, anterior, 955
abnormalities of, 1058
branches of, 955
anterior tibial recurrent, 956
fibular, 956
lateral anterior malleolar, 957
medial anterior malleolar, 956
posterior tibial recurrent, 956
course and relations of, 955
formation of, 1031
morphology of, 1048
surgical anatomy of, 1462
posterior, 952
abnormalities of, 1057
branches of, 953
fibular, 953
peronaeal, 953
branches of, 953
communicating, 953
nutrient, 953
posterior malleolar (medial), 953
formation of, 1031
morphology of, 1048
relations of, 953
surgical anatomy of, 1463
incisions to expose, 1463
recurrent, 956
of tongue, 1130
of tonsil, 1147
tonsillar, of external maxillary, 893, 1147
tracheal, 911
transversa colli, 911
scapulae, 911
transverse, of basilar, 907
transverse cervical artery, 911
ascending branch, 911
descending branch, 911
tunica externa of, 868
intima of, 868
media of, 868
tympanic, of internal carotid, 902
tympanica anterior (of int. maxillary),
898
inferior (of asc. phar.), 896
posterior (of stylomastoid), 895
superior (of middle meningeal), 898
ulnar, 921
abnormalities of, 1056
branches, 922
common interosseous, 922
dorsal interosseous, 922
branches of, 922
ulnar recurrent, 922
volar interosseous, 922
branches of, 922.
formation of, 1031
INDEX.
1481
Artery or Arteries (contd.)
ulnar (contd.), morphology of, 1048
surgical anatomy of, 1454
umbilical, 939
of foetus, 65, 939
obliterated, 939
primitive, 65
of upper limb, 909
abnormalities of, 1055
formation of, 1048
morphology of, 1048
ureteral, of internal spermatic and ovarian,
928
of renal, 927
uterine, 940
surgical anatomy of, 1435
of ovarian, 928
of uterine tube, 928
vagina vasis of, 869
vaginal, 939
of vermiform process, 1217, 1421
vertebral, 905
abnormalities of, 1054
anastomosis of, 905
branches of, 906
anastomotic, 907
anterior spinal, 907
cerebellar, posterior inferior, 907
meningeal, 907
muscular, 906, 907
posterior spinal, 907
spinal, 907
course and relations, 905
development of, 1029
morphology of, 1047
surgical anatomy of, 1395
vesical, inferior, 939
middle, 940
of obturator, 940
superior, 939
vesico- vaginal, 939
visceral, intermediate, 1044, 1047
vitelline, primitive, 66
zygomatico-orbital, 897
Arthrectomy of the knee joint, 1461
Arthrodia, 301
Arthrology, 3, 299
Articular disc, 302
processes of atlas, 91
of cervical vertebrae, 90
of coccyx, 99
of epistropheus, 92
of lumbar vertebrae, 95
of sacrum, 97, 98
serial homology of, 283
of thoracic vertebrae, 94
of twelfth thoracic vertebras, 95
tubercle of temporal bone, 125, 167
Articulatio or Articulationes
acromio-clavicular, 318
surgical anatomy of, 1444
topography of, 1444
atlanto-epistropheal, 309
atlanto-occipital, 310
of auditory ossicles, 840
between bodies of vertebrae, 306
calcaneo-cuboid, 357
ligaments of, 357
surgical anatomy of, 1464
carpal, 329
distal row of, 330
proximal row of, 330
Articulatio or Articulationes (contd.)
carpal (contd.), synovial strata of, 331
transverse carpal, 330
carpo-metacarpal, of fingers, 332
ligaments of, 332
synovial stratum of, 332
of thumb, 332
costo-chondral, 315
costo-transverse, 314
costo-vertebral, 313
coxae, 339
articular surfaces of, 339
capsule of, 340
ligaments of, 340
movements of, 342
synovial stratum of, 341
crico-arytaenoid, 1066
crico-thyreoid, 1065
cubiti, 323
fibrous stratum of articular capsule of, 324
ligaments of, 324
movements at, 325
synovial pads of fat of, 325
layer of, 325
cuneo-cuboid, 358
cuneo-navicular, 357
of fingers, 334
of the foot, 351
genu, 342
articular surfaces of, 342
different parts of, 343
ligaments of, 344
menisci of, 347
movements of, 348
patellar surfaces in, 343
synovial stratum of, 348
of hand, 329
of heads of ribs, 313
humero-radial, 323
humero-ulnar, 323
of humerus, 320, 326
incudo-malleolar, 840
incudo-stapedial, 840
intercarpal, 329
interchondral, 315
intercoccygeal, 309
intercuneiform, 358
intermetacarpal, 332
movements at, 334
intermetatarsal, 360
interphalangeal, of hand, 334
articular capsule of, 334
ligaments of, 334
movements of, 334
synovial stratum of, 334
of foot, 361
intertarsal, 354
ligaments of, 354
movements at, 361
mandibular, 312
articular disc of, 312
movements of, 313
synovial stratum of, 312
metacarpo-phalangeal, 333
ligaments of, 333
movements at, 334
surgical anatomy of, 1454
metatarso-phalangeal, 360
movements at, 361
surgical anatomy of, 1464, 1465
of pelvis, 335
sacro-lumbar, 335
95
1482
INDEX.
Articulatio or Articulationes (contd.)
of pelvis (contd.), sacro-iliac, 335
articular capsule of, 336
articular cavity of, 336
ligaments of, 336
of pisiform bone, 331
radiocarpal, 328
articular capsule of, 328
movements at, 329
surgical anatomy of, 1450
synovial stratum of, 329
radio-ulnar, .distal, 327
synovial stratum of, 327
triangular disc of, 327
proximal, 326
sacro-coccygeal, 308
sacro-iliac, 335
topography of, 1455
of shoulder, bursae of, 322
fibrous stratum of capsule, 321
intra-capsular structures, 322
ligaments of, 321, 322
synovial stratum of, 322
sterno-clavicular, 317
articular disc of, 318
movements at, 319, 373
surgical anatomy of, 1444
sterno-costal, 315
of oternum, 317
talo-calcaneal, 354
talo-calcaneo-navicular, 355
ligaments of, 355
talo-crural, 351
ligaments of, 352
movements of, 353
synovial stratum of, 353
talo-navicular, 355
tarsal, transverse, 357
tarso-metatarsal, 359
. intermediate, 359
lateral, 359
medial, 359
surgical anatomy of, 1464
of the thumb, 332
articular capsule of, 332
movements of, 332
synovial stratum of, 332
tibio-fibular, 349
articular capsule of, 349
ligaments of, 350
of toes, 361
transverse tarsal, 357
cuneo-navicular, 357
articular capsule of, 358
synovial stratum of, 358
Articulations between vertebral arches, 307
Ary-epiglottic folds, 1068
development of, 45
muscle, 1074
Arytsenoid cartilage, 1064
development of, 44
ossification of, 1065
processus muscularis of, 1065
vocalis of, 1065
sesamoid cartilages of, 1065
muscle, 1074
action of, 1076
Ary -vocalis muscle, 1076
action of, 1076
Ascending aorta, surface markings of, 1405
Ascending branch of transverse cervical artery,
1320
Ascending colon, surgical anatomy of, 1422
Ascending degeneration of nerves, 532
palatine artery, 893
Association areas, 645
Association fibres, 648
of cerebral hemispheres, 648
intersegmental, 538
long, 648
of medulla oblongata, 556, 560
short, 648
of spinal medulla, 534, 538
Asterion, 165, 171, 285
Asymmetry, 4
Atlanto-epistropheal joint, 309
movements at, 311
Atlanto-occipital joint, 310
Atlas, 91
anterior arch of, 91
arches of, 91
articular facets of, 91
fovea dentis of, 91
lateral masses of, 91
ossification of, 104
posterior arch of, 91
tubercle of, 91
serial homology of, 283
transverse ligament of, 310
process of, 91
surgical anatomy of, 1393
tubercle of, 91
Atresia ani, 48
Atria of heart, 873
Atrio-ventricular apertures, 877
mitral, 876, 877
tricuspid, 877
sulcus, 871
surface anatomy of, 1403
Atrium dextrum, 873
left, 875
mitral orifice, 876
meatus nasi, 830
of primitive heart, 1033
right, 873
crista terminalis, 874
foramen ovale, 875
fossa ovalis, 874
interior of, 874
musculi pectinati, 874
tricuspid orifice of, 874
tuberculum intervenosum, 875
valve of the coronary sinus, 875
valve of the inferior vena cava, 874,
875
yense cordis minimse, 874
sinistrum, 875
Attic, tympanic, 1368, 1369
Auditory area of cerebral cortex, 656
artery, internal, 853
epithelium, development of, 50
labyrinth, 843
meatus, external, 830
blood-vessels of, 832
ceruminous glands of, 832
development of, 52
foramen of Huschke of, 832
isthmus of, 830
lymph vessels of, 832
nerves of, 832
structure of, 831
surgical anatomy of, 1365
variation in, 278
internal, 845
INDEX.
1483
Auditory, meatus, internal (contd.), absence of,
278
nerve, 852
organ, 827
ossicles, 838
articulations of, 840
development of, 841
incus, 840
ligaments of, 841
malleus, 839
stapes, 840
pit, 853
radiation, 643, 656
teeth of Huschke, 850
tube, 837, 838
blood-vessels of, 838
bony part of, 837
canal of, 128, 837, 838
cartilaginous part of, 837
catheter, passage of, 1385
in child, 838
cushion of, 1143
development of, 44, 52
dilator muscle of, 838
dilator tubae muscle, 838
fascia salpingo-pharyngea, 838
groove for, 138
isthmus of, 837
lamina, membranous, of, 838
nerves of, 838
ostium pharyngeum of, 838, 1143
tympanicum of, 834
pars cartilaginea of, 837
ossea of, 128, 837
pharyngeal orifice of, 837, 838
processus tubarius of, 838
sulcus of, 838
surgical anatomy of, 1368, 1369, 1385
tonsil of, 838
torus tubarius of, 838, 1143
tympanic orifice of, 837
vesicle, 506
Auricle of ear, 827
antihelix of, 828
antitragus, 828
apex of, 828
cartilage of, 829
cauda helicis, 829
concha of, 827
crura of, 828
crus helicis of, 827
cymba conchae of, 827
development of, 44, 52, 76, 78
fissure, antitrago-helicine, 829
fossa triangularis of, 828
helix of, 827
incisura intertragica, 828
terminalis, 829
isthmus of, 829
ligaments of, 829
lobule of, 828
muscles of, 829
antitragicus, 829
helicis major, 829
minor, 829
obliquus auriculas, 830
tragicus, 829
transversus auriculae, 830
nerves of, 830
ponticulus, 829
scapha of, 828
skin of, 830
Auricle (contd.), spina helicis, 829
structure of, 829
sulcus antihelicis transversus, 829
cruris helicis, 829
tragus, 828
tubercle of, 828
tuberculum supratragicum, 828
vessels of, 830
Auricles of heart, 874, 875, 1032
Auricula, 827
(cordis) dextra, 874
sinistra, 875
Auricular artery, deep, 830, 898
of occipital, 895
posterior, 895
surgical anatomy of, 1365
cartilage, 829
index, 828
muscle, anterior, 449
posterior, 449
superior, 449
nerve-supply of, 449
nerves, 830
of auriculo-temporal, 779
great, 695, 696
morphology of, 700
posterior, 783
of vagus, 788
septum, 1033
surface of ilium, 230
of sacrum, 99
vein, posterior, 967
Auriculo-temporal nerve, 779
Auriculo-ventricular groove, position of, 1403
Auscultation, triangle of, 366
Axial line, dorsal, of limbs, 741, 1397
ventral, of limbs, 741, 1397
muscles, 365, 437
skeleton, 82
Axilla, 1446
folds of, 1446
lymph glands of, 1008
surgical anatomy of, 1446
Axillary arches, 371
nerve-supply of, 371
artery, 914
abnormalities of, 1055
formation of, 1047
surgical anatomy of, 1445
fascia, 369
folds, 1446
lines, 1397
lymph glands, 1447
margin of scapula, 201
region, 1446
sheath, 1447
vein, 977
development of, 1042
morphology of, 1050
surgical anatomy of, 1447
Axis, basi-cranial, 183
cylinder, 509
lentis, 820
optic, 807
pelvis, 237
Axis-ligament of malleus, 841
Axon, 508, 680
Azygos lobe of lung, 1096
veins, 960
Bacillary layer of retina, 817
Back, fasciae of, 365, 437
1484
INDEX.
Back (contd.), muscles of, 365, 437
actions of, 366, 445
nerve-supply of, 365
regions of, 1437
surgical anatomy of, 1436
vertebral furrow of, 1436
Back of thigh, surgical anatomy of, 1456
Baillarger, bands of, 644
Ball-and-socket joint, 301, 303
Banderella of Giaconimi, 629
Bands of Baillarger, 644
Bands of Meckel, 841
Bar, branchial, 42
hyoid, 43, 159
pharyngeal, 42
thyreo-hyoid, 44, 159
Barbula hirci, 830
Bartholin, duct of, 1140
Basal cells of olfactory mucous membrane,
804
ganglia of cerebral hemispheres, 637
lamina, 682, 684
layer of placenta, 57, 58
plate, 31
vein, 97
Base of cranium, 179
of heart, 871
of mandible, 155
Base-line of Keid, 1360
Basement membrane, 1133
Basi-cranial axis, 183
Basihyal, 159
Basilar artery, 907
abnormalities of, 1055
morphology of, 1047
groove, 128
membrane of cochlea, 849, 850
part of occipital bone, 120, 123
development of, 124
sinus, 974
sulcus of pons, 548
venous plexus, 975
Basilic vein, 979
Basion, 178, 183, 285
Basiotic bone, 278
Basi-pharyngeal canal, 175
Basis cerebri, 540
cochleae, 844
cordis, 871
cranii, 179
mandibulae, 155
modioli cochleae, 844
ossis hyoidei, 158
pedunculi, 591
stapedis, 840
Basi-sphenoid, 139
Basket-cells, 580
Bechterew, nucleus of, 605
Beraud, valve of, 825
Bertin, bones of, 139
Bi-asterionic width of skull, 286
Bi-axial joints, 303
Biceps brachii muscle, 380
femoris muscle, 418
Bicipital furrow, 1447, 1448
groove, 206
topography of, 1445
sulci, surgical anatomy of, 1448
Bifurcation of aorta, 1050
of trachea, 1078
Bigelow, Y-shaped ligament of, 340
Bile canaliculi, 1199
Bile duct, 1202
development of, 1254
level of, 1443
relation of, to duodenum, 1185
retro -duodenal exposure of, 1416
surgical relations of, 1416
termination of, 1186, 1203
papilla, 1186, 1203
limanual
Bimanual examination, 1436
Bismuth meal, 1417
Bi-stephanic diameter of skull, 286
Bi venter cervicis muscle, 442
Biventral lobule of cerebellum, 575
Bladder, gall, 1201
urinary, 1271, 1278
capacity of, 1277
cystoscopic examination of, 1428
trigone of, 1428
development of, 1328, 1332
distended, 1276
diverticula of, 1429
empty, 1275
in female, 1278
fixation of, 1283
in infant, 1279
inferior aspect of, 1274
iiifero-lateral areas of, 1275
interior of, 1277
examination of, 1428
lateral false ligaments of, 1280
ligaments of, false, 1282
anterior, 1283
lateral, 1283
structure of, 1283
lymph vessels of, 1284
nerves of, 1284
in newly born infant and child, 1279
peritoneal relations and connexions of,
1280
plicae uretericae of, 1277
shape and relations when empty, 1275
distended, 1276
sphincter of, 1284
structure of, 1283, 1284
superior false ligaments of, 1280
torus uretericus, 1277
trigonum vesicae of, 1277
urachus of, 1280, 1283
development of, 1332
ureteral orifices of, 1278
examination of, 1428
urethral orifice of, 1273, 1274
uvula vesicae of, 1277
varying relationships, 1277
vessels and nerves of, 1284
Blastula, 21
Blind spot, 815
Blood capillaries, 867
development of, 64
islands, 64
Blood corpuscles, mesamoeboids, 64
blood plastids, 64
erythrocytes, 64
ichthyoid cells, 64
nucleated colourless corpuscles, 64, 79
sauroid blood cells, 64
Blood-vascular system, primitive formation
of, 64
abnormalities of, 1049
development of, 64, 1025
morphology of, 1043
Blood-vessels of rectum and anus, 1232
INDEX.
1485
Blood-vessels (contd.), anastomoses of, 1233
Body, para-thyreoid, development of, 44
ultimo-brachial, 44
cavity, 22, 27
polar, 15, 19
stalk, 38, 54
viteUine, 18
Wolffian, 1329
Bone or Bones, 81
air-spaces of, 82
articular surface of, 83
of Bertin, 139
blood-supply of, 87
bregmatic, 277
canaliculi of, 84
cancellar tissue of, 83
carpal, 217
cartilage, 83
of skull, 290
compact tissue of, 83
composition of, 82
descriptive terms, 82
diaphysis of, 85
diploe, 84
epiphyses of, 85
pressure and traction, 85
epiphyseal line of, 85
epipteric, 132, 145
of face, 146
flat, 82
of foot, 254
frontal, 115
fundamental lamellae of, 84
growth of, 86, 87
of hand, 217
Haversian systems of, 84
of head, 115
hip, 228
irregular, 82
lamellae of, 84
interstitial, 84
long, 82
of lower limb, 228
lymph vessels of, 87
marrow of, 83
medullary cavity of, 83
membrane, 83,
of skull, 292
metacarpal, 223
metatarsal, 265
of middle ear, 838
nerves of, 87
number of, 82
ossification of, 84, 85
in cartilage, 86
in membrane, 85
osteoblasts of, 85
periosteal membrane of, 84
periosteum of, 83
primary centre of, 84
primordial, 292
secondary, 292
sesamoid, of metacarpo - phalangeal joints,
228
of metatarso-phalangeal joint, 269
of peronaeus longus, 269, 427
short, 82
of skull, 115
strength of, 83
structure of, 83
microscopic, 84
sutural, 145, 146
Bone or Bones (contd.), tarsal, 254
thigh, 239
of thorax, 113
of upper limb, 197
vascular supply of, 87
of vertebral column, 87
Boundaries of abdominal cavity, 1155
Bowman, elastic lamina of, 810
Brachia conjunctiva, 33, 512, 542, 569, 578,
587
quadrigemina, 582
Brachial artery, 917
ligature of, 1448
surgical anatomy of, 1448
plexus, 700
branches of, 702
muscular of, 702
communications with sympathetic, 700
composition of, 700
pars infraclavicularis of, 703
pars supraclavicularis of, 702
branches of, 701
position of, 700
primary cords of, 700
secondary cords of, 701
Brachialis muscle, 381
action of, 381
nerve-supply of, 381
Brachio-radialis muscle, 396
action of, 396
nerve -supply of, 396
Brachium conjunctivum, 33, 512, 542, 569,
578, 587
quadrigeminum inferius, 582
superius, 582
Brachycephaly, 284
Brachyfacial skulls, 286
Brachy-kerkic limbs, 289
Brachy-knemic limbs, 289
Brachy-uranic skulls, 287
Brain, 512, 589
aqueduct of, 584
development, 37, 592
arteries of, 904, 905
development of, 33, 514
flexures of, 514
lymph vessels of, 1003
meninges of, 667
mesencephalon, 33, 514, 516, 581
nature of the, 512
nerve-cells of, 584
nerve-fibres of, 588
neuroglia of, 511
prosencephalon, 514, 607
development of, 33, 514
rhombencephalon, 514, 515
development of, 33, 515
isthmus of, 515
veins of, 970
vesicles, primitive, 33
weight of, 667
Branchial arches, 43
relation of, to cerebral nerves, 796-798
muscles derived from, 496
nerves of, 795-797
bars, 42
ducts, 43
pouches, 42
Breast, 1336
bone, 106
Bregma, 172, 285
topography of, 1223
1486
INDEX.
Bregmatic bone, 277
fontanelle, 194
Broad ligament of uterus, 1318
bursa ovarica of, 1318
surgical anatomy of, 1434
Bronchi (dexter et sinister), 1082
apical, 1098
cardiac, 1098
cartilaginous rings of, 1082
development of, 1099
differences in calibre and direction in,
1083
distribution of, within the lung, 1097
dorsal branches in lung, 1097
eparterial, 1097
external branch of right, 1082
fibro-cartilaginous coat of, 1083
hyparterial, 1083, 1097
mucous membrane of, 1083
muscular coat of, 1081
relations of, 1083
in root of lung, 1097
structure of, 1098
topography of, 1402
Bronchial arteries, 1096
abnormalities of, 1052
morphology of, 1047
lymph glands, 1012, 1096
veins, 961
morphology of, 1049
Bronchioli, 1097
Brimner, glands of, 1179
Buccae, 1109
corpus adiposum, 1109
lymph vessels, 1005
lymph glands of, 1005, 1109
Buccal branch of external maxillary artery,
894
glands, 1109
Buccinator artery of internal maxillary, 899
muscle, 451
action of, 452
nerve-supply of, 452
nerve of facial, 784
nerve of trigeminal, 779
Bucco-pharyngeal area, 27, 42
fascia, 1149
membrane, 25, 27
Buds, taste, 854, 1128
limb, 39
Bulb, aortic, 884
abnormality of, 1051
division of, 1035
septum of, 1035
of corpus cavernosum urethrae, 1308, 1427
of eye, 807, see also Bulbus
equator of, 807
fascia of, 807
optic axis of, 807
poles of, 807
sulcus sclerae of, 807
tunics of, 807
of hair root, 860
of jugular vein, 964
olfactory, 622, 623
of posterior cornu of lateral ventricle, 635
of urethra, 1308
artery of, 942
surgical anatomy of, 1427
of vagina, 1326
of vestibule, 1326
artery, 942
Bulb of vestibule (contd.\ surgical anatomy
of, 1427
Bulbo-cavernosus muscle, 487
Bulbo-urethral glands, 1286, 1304
Bulbus aortas, 884
cornu posterioris, 635
oculi, 806
anterior chamber of, 813
bursa of 452, 807
coats of, 807
dimensions of, 807
equator of, 807
fascia of, 807
lymph vessels of, 1004
muscles of, 453
nerves of, 773
nervous tunic of, 808, 814
optic axis of, 807
poles of, 807
posterior chamber of, 813
refracting media of, 819
sclero-corneal junction of, 806
shape of, 807
sulcus sclerae of, 809
tunica vasculosa of, 810
olfactorius, 622, 623
pili, 860
urethrae, 1308, 1427
vestibuli, 1326
Bulla ethmoidalis, 185, 803
Bundle, see Fasciculus or Tract
Burdach, see Fasciculus cuneatus
Burns, space of, 967
Bursa or Bursae, 364
of coraco-clavicular ligament, 319
of eyeball, 452, 807
of flexor carpi radialis, 386
under hyoid bone, 1066
of ilio-psoas, 410, 341
surgical anatomy of, 1459
at knee-joint, 348
surgical anatomy of, 1460
of muscles of arm, 378-382
of back, superficial, 365-369
of back of forearm, 396-400
of back of leg, 428-431
of back of thigh, 419-421
of buttock, 415-418
of front of leg, 424-426
of front of thigh, 406-414
of shoulder, 323, 324
omental, 1162, 1238
anterior wall of, 1240
gastro-pancreatic folds of, 1240
lienal folds of, 1240
posterior wall of, 1240
recessus inferior of, 1240
superior of, 1240
vestibulum of, 1238
of peroneal muscles, 427
pharyngea, 1143
praepatellaris subcutanea, 1460
at shoulder-joint, 323
subacromial, 323
subcutaneous, 364
subtendinous, 364
subscapular, 323
thecal, varieties of, 303
Buttock, fasciae of, 402
bony points of, 1455
muscles of, 414
actions of, 415-418
INDEX.
1487
Buttock, muscles of (contd.), nerve-supply of,
415-418
surgical anatomy of, 1455
Caecal artery, 932
folds, 1218
fossae, 1218
Caecum, 1213
development of, 48
dimensions of, 1213
foetal, 48, 1217
infantile, 1217
position of, 1213
relations of, 1213
structure of, 1215
surgical anatomy of, 1421
types of, 1215, 1217
vessels of, 1217
Caecum cupulare cochleae, 849
vestibulare, 849
Calamus scriptorius, 550
Calcaneal medial artery, 955
Calcanean facets, 259
nerve, medial, 734
Calcaneo-cuboid joint, 357
ligaments of, 357
functions of, 361
position of, 1464
surgical anatomy of, 1464
Calcaneo-fibular ligament, 352
Calcaneo-metatarsal ligament, 423
Calcaneo-navicular ligaments, 355
function of, 355
surgical anatomy of, 1464
Calcaneo-taloid joint, 354
position of, 1464
surgical anatomy of, 1464
Calcaneus, 259
facets of, 259
plantar surface of, 209
processes of, 259
sustentaculum of, 260
trochlear process of, 260
tuber of, 260
Calcar avis, 635, 659
femorale, 274
Calcarine artery, 908
fissure, 660
Calyces renales, 1268
development of, 1331
Camera oculi, 820
anterior, 821
posterior, 821
princeps of His, 1169
Canal or Canalis
adductor (Hunteri), 405, 414
alimentary, 1104
primitive, 41
alveolar, 147
anal, 1228
development of, 48
orifice of, 1232
relations of, 1229
surgical anatomy of, 1430
vessels of, 1233
for Arnold's nerve, 129
atrio-ventricular, 1033
auditory, 128, 176, 837
basi-pharyngeal, 175
carotid, 129, 176, 177
relation of, to tympanum, 271
variation in, 278
Canal or Canalis (contd.), central, of cochlea,
846
of medulla oblongata, 564
of spinal medulla, 564
development of, 35
of cervix uteri, 1317
condyloid, 177
cranio-pharyngeal, 135
closure of, 290
. of epididymis, see Ductus
ethmoidal, see Foramen
facialis, 129, 130, 833
hiatus of, 130
condition of, at birth, 133
femoral, 405
Haversian, 84
of Huguier, 125
relation of, to tympanum, 834
hyaloid, 826
development of, 826
hypoglossal, 177
infraorbital, 147, 162
inguinal, 483
surgical anatomy of, 1408
innominate, 137
lacrimal, membranous, 825
development of, 827
osseous, see C. of naso-lacrimal duct
mandibular, 156
musculo-tubarius, 128, 176, 837
of naso-lacrimal duct, 143, 147, 187
neural, 88
neurenteric, 23, 26
of Nuck, 1319
obturator, 338
palatine, anterior, 149
greater, 151
lesser, 152
superior openings of, 152
of Petit, 819
pharyngeal, 138, 152, 175
pleuro-pericardial, 72
portal, 1200
ptery go- palatine, 147, 151
pterygoid, 138, 180, 192
pyloric, 1169, 1173
radicis dentis, 1114, 1115
reuniens, 51, 854, see also Ductus
sacral, 99
semicircular, 847
spheno-vomerine, 279
spiralis cochleae, 845
of Stenson, 1109
for tensor tympani muscle, 128
tympanic, 129
urogenital, 1328
vertebral, 88
zygomatico-orbital, 154
zygpmatico-temporal, 154
Canaliculus or Canaliculi, bile, 1199
of bone, 84
carotico-tympanic, 129
innominate, 137
mastoid, 129
tympanic, 129
Canine fossa, 146
teeth, 1115
eruption of, 1120
Caninus muscle, 451
action of, 454
Capillaries, 867
blood, structure of, 868
1488
INDEX.
Capillary arterioles, 868
lymph vessels, 1042
veins, 867
Capitular process, 284
Capitulum of humerus, 208
of mandible, 156
of radius, 214
of ulna, 214
Capsula adiposa of kidney, 1259
articularis of joints, 302
externa, 644
fibrosa (Glissoni), 1198
interna, 642
pars frontalis, 642
occipitalis, 642
Capsular arteries of liver, 933
Capsule, external, 644
of Glisson, 1198
glomerular, 1266
internal, 642
acoustic radiation fibres of, 643, 656
anterior limb of, 642
cerebro-spinal tract of, 462
fasciculus cerebro-rubricus of, 643
fronto-pontine fibres of, 642
genu of, 642
lenticulo-caudate part of, 642
lenticulo-thalamic part of, 642
optic radiation fibres of, 643, 658
posterior limb of, 642
retro-lenticular part of, 643
sublenticular part of, 642
temporo-pontine fibres of, 643
of joints, 302
of lens, 819
Caput angulare m. quadrati labii superioris, 451
epididymidis, 1287
infraorbitale m. quadrati labii superioris, 451
of posterior column of spinal medulla, 523
zygomaticum m. quadrati labii superioris,
451
Cardia, 1164
topography of, 1416, 1417, 1439
Cardiac bronchus, 1098
dulness, 1398
ganglion of Wrisberg, 790
lobe of lung, 1098
nerves of sympathetic, inferior, 759
middle, 759
superior, 757
of vagus, 789
notch of lung, 1095
plexus, 790
portion of stomach, 1163, 1172, 1173
Cardiac veins, 959
Cardinal veins, anterior, 1038
morphology of, 1048
posterior, 1040
Carina vaginalis, 1323
Carotid artery, common, 889
abnormalities of, 1054
development of, 67
morphology of, 1047
surgical anatomy of, 1386, 1389,
1391
left, 889
abnormalities of, 1054
right, 890
abnormalities of, 1054
external, 891
abnormalities of, 1054
development of, 67
Carotid artery, external (contd.\ morphology
of, 1047
surgical anatomy of, 1391
internal, 900
abnormalities of, 1054
development of, 67
morphology of, 1047
canal, 129
relation of, to tympanum, 271
variation in, 278
glomus, 1343
groove, 135
lymph glands, 1009
plexus, 757, 758
sheath, 447
triangle, 1390, 1391
tubercle, 1393
Carpal arch, dorsal, 923
volar, 920, 922
artery, anterior radial, 919
ulnar, 921
posterior radial, 920
ulnar, 921
bones, 217
architecture of, 272
ossification of, 223
variations in, 280
joints, 329
movements at, 334
nerves to, 705, 713
synovial stratum of, 331
transverse, 380
Carpale, os, 280
Carpo-metacarpal joints of finger, 332
Carpus, as a whole, 222
bones of, 217
bony parts about the, 1451
ossification of, 223
Cartilage Cartilage Cartilagines
alares minores, 800
alarls major, 800
lateral crus of, 800
medial crus of, 800
articular, 83
arytaenoid, 1064
auricular, 829
bones, 86
of skull, 290
corniculate, 1065
costal, 113
joints of, 315
topography of, 1407
cricoid, 1063
development of, 1100
ossification of, 1065
surgical anatomy of, 1388
cuneiform, 961, 1068
epiglottic, 1065
of larynx, 1064
development of, 1100
meatus acustici, 829
of Meckel, 157, 841
nasal, 800
greater alar, 800
lateral, 800
lesser alar, 800
of septum, 800
processus sphenoidalis of, 801
vomerine, 801
parachordal, 290
of pinna, 829
prechordal, 290
INDEX.
1489
Cartilage Cartilage Cartilagines (contd.)
of Keichert, 159
of Santorini, 1065
semilunar, 347
surgical anatomy of, 1460, 1461
of septum of the nose, 800
sesamoid, of arytaenoid, 1065
sesamoid, of the nose, 800
tarsal, 1378
thyreoid, 1062
development of, 1100
ossification of, 1065
surgical anatomy of, 1388
tracheal, 1081
triticea, 1066
vomero-nasalis (Jacobsoni), 801
xiphoid, 108, 109
Cartilaginous cranium, 290
vertebral column, 103
Caruncula lacrimalis, 821
Carunculse hymenales, 1322
myrtiformes, 1322
Catheter, passage of female, 1435
Cauda epididymidis, 1287
equina, 519
fasciae dentatae, 629
helicis, 829
Caudal arches, 68
fold, 38, 48
nerves, 678
Caudate lobe of liver, 1192
nucleus, 635, 637
Cavernous arteries, 902
plexus, 759, 766
sinus, 975
Ca vitas glenoidalis, 201
Cavity, amniotic, 54, 55
mandibular, of temporal bone, 125, 167
condition of, at birth, 133
nasal, development of, 50
of scapula, 201
segmentation, 21
sigmoid, of ulna, 211
Cavum abdominis, 1155
articulare, 300
conchas, 827
dentis, 1114
epidurale, 669
Meckelii, 771
medullare, 83
nasi, 183, 801
oris, 1106
proprium, 1107
pelvis, 237, 1157
peritonaei, 1412
pharyngis, 1141
pleurae, 1083
Eetzii, 493
septi pellucidi, 628, 632
subarachnoideale, 671
subdurale, 670
thoracis, 1083
mediastinum, dorsal, 1090
ventral, 1090
tympani, 832
uteri, 1317
Cell, period of life, 10
period of resting stage, 10
Cell-body, 8
Cell-mass, inner, 21
intermediate, 21
history of, 21
Cells, basal, of olfactory mucous membrane, 804
basket, 580
body of, 8
ethmoidal, 140, 804
relation of, to orbit, 1373
to nasal fossae, 1373
surgical anatomy of, 1372
germinal, 502
of neural tube, 36
life, period of, 10
lymph, 906
of marrow, 83
mastoid, 133, 836, 1370
surgical anatomy of, 1370
nerve, 16, 497, 506 ,
nucleus of, 8
olfactory, 804, 805
reproduction of, 8
reproductive, 11
spermatocytes, 16
supporting, 16
Cellulae ethmoidales, 140, 804
mastoideae, 133, 836, 1370
Cement (substantia ossea), 1123
development of, 1245
Central arteries of middle cerebral, 905
of posterior cerebral, 908
of retina, 903
canal of medulla oblongata, 564
gray matter of medulla oblongata, 564
gyri,-654
lobule of cerebellum, 575
lymph vessels of hand, 1009
point of perineum, 1427
sulcus of insula, 654
Centrale, os, of wrist, 290
Centres, medullary, of cerebral hemispheres,
644, 647
of ossification, 85, 86
Centrioles, 8
Centrosome, 7, 8, 10, 11, 14
Centrum tendineum, 472
of vertebra, 88
Cephalic aortic arches, 65, 68, 1027, 1028, 1029,
1030, 1034
morphology of, 1047
flexure of brain, 514
fold, 37
index, 284
myotomes, 30
part of sympathetic, 756
somites, 28
vein, 978
Cephalo-auricular angle, 828
variations in, 830
Cerato-hyal, 159
Cerebellar artery, anterior inferior, 907
anterior superior, 907
posterior inferior, 907
tracts, 534, 536, 578
spino-cerebellar, anterior, 536, 537
posterior, 537
Cerebellar veins, 971
Cerebello-olivary tract, 556, 563
Cerebellum, 570
alae lobuli centralis, 575
amygdala of, 575
arbor vitae of, 577
arrangement of gray and white matter of,
576
association fibres of, 578
bi ventral lobule, 575
1490
INDEX.
Cerebellum (contd.\ brachium conjunct! vum
of, 569
commissural fibres of, 578
connections of peduncular fibres, 578
corpus dentatum of, 576
culmen monticuli, 575
declive monticuli of, 575
development of, 33
fissure, postnodular, of, 571
horizontal, of, 573
post-tonsillar, 573
pyramidal of, 573
supra-pyramidal, 573
fissures of, 571, 572, 573
prima, 572
secunda, 572, 573
development of, 571
flocculus, 571, 575
folium vermis of, 572
furrowed band of, 576
gray matter of, 576
hemispheres of, 571, 574
surgical anatomy of, 1363
incisura anterior, 574
posterior, 574
inferior vermis of, 574
lingula cerebelli, 575
lobes of, 575
lobes on inferior surface of, 575
lobes on superior surface of, 575
lobules of, 575
lobulus centralis, 575
gracilis, 576
medullary velum of, anterior, 549
posterior, 576
minute structure of, 579
monticulus, 574
nodulus, 571
notches of, 514
origin of, 515
nucleus emboliformis of, 577
dentatus, 576
fastigii, 577
globosus, 577
paraflocculus, 571
peduncles of, 577
brachium conjunctivum, 577, 578
pontis, 577, 578
restiform body, 577, 578
origin of fibres of, 578
in sections of pons, 576
posterior inferior lobule, 575
postlunar sulcus of, 573
pyramid of, 576
roof nucleus of, 577
structure and connexions 0f, 576
sulcus valleculae, 575
development of, 571
superior vermis of, 574
tonsil of, 573, 575
tuber vermis of, 575
uvula of, 507, 576
vallecula of, 574
vermis of, 572, 574
white matter of, 576
Cerebral artery, anterior, 904
abnormalities of, 1053
middle, 905
posterior, 908
surgical anatomy of, 1365
cortex, 644, 646
association, centres of, 645
Cerebral cortex (contd.}, association fibres of
648
auditory area of, 656
band of Baillarger of, 644, 645
of Bechterew of, 645
of Martinotti of, 645
commissural fibres of, 647
connexion of, with thalamus, 612
gray layers of, 645
layer of polymorphic cells of, 645
of pyramidal cells of, 645
lymph vessels, 1003
nerve-fibres of, 645
olfactory area of, 625
projection fibres of, 651
stratum zonale of, 645
stria of Gennari of, 644
structure of, 644
thickness of, 644
topography of, 1359
visual area of, 658
white layers of, 644
hemispheres, 620
association fibres of, 648
basal ganglia of, 637
borders of, 647
claustrum of, 641
commissural fibres of, 647
corpus callosum of, 629
cortex of, 644
development of, 34, 621, 623
external configuration of, 646
fimbria of, 627
fissures of, 653
form of, 646
frontal pole of, 647
general structure of, 644
gray matter of, 644
groove for transverse sinus on, 647
gyri of, 654
impressio petrosa of, 647
incisura longitudinalis, 540
internal capsule of, 642
intimate structure of, 644
island of Eeil of, 654
sulcus circularis of, 654
lateral fossa of, 655
level of lower margin of, 1359
limen insulae of, 654
lobes of, 665
nerves, list of, 678, 767
development of, 682
nuclei of, 637, 638
occipital pole of, 647
opercula of, 685
poles of, 647
primary olfactory function of, 517
projection fibres of, 651
Rolandic angle of, 662
septum pellucidum of, 628
development of, 628
structure of, 644
sulci of, 653
surfaces of, 646
surgical anatomy of, 1360
temporal pole of, 647
veins, 970
ventricles of, 549, 616, 632
white matter of, 647
Cerebral nerves, 767
1st nerve, olfactory, 767
2nd nerve, optic, 768
INDEX.
1491
Cerebral nerves (contd.\ 3rd nerve, oculo-
motor, 769
4th nerve, trochlear, 770
5th nerve, trigeminal, 771
6th nerve, abducens, 781
7th nerve, facial, 781
8th nerve, acoustic, 784
9th nerve, glossopharyngeal, 785
10th nerve, vagus, 786
llth nerve, accessory, 791
12th nerve, hypoglossal, 793
abducens nerve, nucleus of, 600
accessory nerve, nucleus of, 595
acoustic nerve, 604
deep connexions of, 592
dorsal, nuclei of, 597
facial nerve, intrapontine course of, 599
nuclei of, 598
glossopharyngeal, nuclei of, 596
gustatory nuclei of, 597
hypoglossal nerve, nucleus of 594
nervus intermedius, nuclei of, 598
nuclei of, lateral somatic, 593
medial somatic, 592
of origin, or motor nuclei of,
592
splanchnic, 593
terminal, 593
oculomotor nerve, 603
trigeminal nerve, nuclei of, 600
trochlear nerve, 602
vagus, nuclei of, 596
splanchnic nuclei of, 598
tractus solitarius, 597
vesicles, 514
Cerebro-spinal fluid, 1003
nervous system, 497
ganglionic part of, 511
gray matter of, 512
medullary part of, 507
nerve -cells of, 506
nerve -fibres of, 508
nerves of, 505
neuroglia of, 511
neurons of, 503
white matter of, 512
Cerebrum, 620
frontal region of the, 665
parietal region of the, 662
Cerumen, 832
Ceruminous glands, 832
Cervical artery, ascending, 910
morphology of, 1047
deep, 914
morphology of, 1047
transverse, 911
canal of uterus, 1317
fascia, 447
surgical anatomy of, 1385
flexure of neural tube, 514, 515
of brain, 514
ganglion, inferior, 759
surgical anatomy of, 1393, 1398
middle, 759
superior, 756
glands of uterus, 1320
lymph glands, 1000
surgical anatomy of, 1392
nerves, 688, 692
posterior rami of, 688
first, 688
second, 689
Cervical nerves, posterior rami of (contd.),
third, 690
fourth to sixth, 690
seventh and eighth, 690
pleura, 1398
plexus, 694
communicating branches of, 697
deep branches of, 696
morphology of, 700
muscular branches of, 696
ribs, 93, 275, 1375
serial homology of, 283
sympathetic, 756
development of, 681
surgical anatomy of, 1393
veins, 964
vertebrae, 90, 93
Cervix columnse posterioris, 523
uteri, 1316
arbor vitae of, 1317
glands of, 1320
mucous membrane of, 1320
muscular coat of, 1320
supra-vaginal portion of, 1316
vaginal portion of, 1316
surgical anatomy of, 1434
Chamaecephalic skulls, 286
Chamaeprosope, 286
Chamber, anterior, of eye, 813
development of, 825
endothelium of, 810
posterior, of eye, 813
recesses of, 818
Cheek bone, 153
Cheeks, 1109
buccal fatty body, 1109
glands of, 1109
lymph vessels of, 1005
Chest, 1395
Chiasma opticum, 619
Chiene's lines, 1359
Choanse, 175, 185, 190
surgical anatomy of, 1246
Chondro-cranium, 290
Chondro-epitrochlearis muscle, 371
Chondro-glossus muscle, 462
action of, 463
Chopart's amputation, 1464
Chorda obliqua (of forearm), 328
tympani nerve, 782
origin of, 598
Chordae tendineae, 877
Willisii, 974
Chordal portion of skull, 290
Chorioid plexuses of fourth ventricle, 553, 636
development of, 552
of lateral ventricle, 635
development of, 635
of inferior horn of, 636
of third ventricle, 617
Chorioidal artery, anterior, 904
posterior, 908
fissure of brain, 621, 636, 637, 675
of eye, 826
development, 826
veins, 970
Chorioidea, 810
development of, 825
lamina basalis of, 811, 812
chorio-capillaris of, 811
supra -chorioidea of, 811
vasculosa of, 811
1492
INDEX.
Chorioidea (contd.), nerves of, 814
pigment of, 814
proper tissue of, 811
spatium perichorioidale of, 808
stratum intermedium of, 811
tapetum of, 812
Chorion, 21, 53, 57
frondosum, 60
Iseve, 54, 60
Chorionic area, 21
plate, 58
vesicle, 55
villi, 58
absorbing, 59
anchoring, 59
Chromaflin cells, 32
Chromatin, 8
organs, 32
skein, 10
Chromogenic cells, 1331-32
Chromophil bodies, 1342
system, 1341
development of, 1343
Chromosomes, 8, 10, 11, 79 .
object of the reduction of, 18
Chyme, 1163
Cilia, 823
Ciliary arteries, 903
anterior, 813, 903
long, 813
posterior, 903
short, 903
body, 812
orbiculus of, 812
border of iris, 814
bundle of orbicularis palpebrarum, 450
ganglion, 773
development of, 699
morphology of, 701
motor root, 773
sensory root, 773
splanchnic efferent fibres of, 604
sympathetic root of, 773
glands, 861
muscle, 813
nerves, distribution of, on cornea, 808
in chorioid and iris, 814
innervation of, 604
entrance of, into eyeball, 814
long, 814
short, 814
processes, 812
veins, 814
Cingulum of brain, 649
extremitatis inferioris, 228
superioris, 197
of teeth, 1116
Circular sinus, 974
sulcus, 654
Circulation, foetal, development of, 63, 71
Circulus arteriosus, 908
major of iris, 813
minor of iris, 813
tonsillaris, 1147
Circum-anal glands, 1280
Circumduction, movement of, 303, 323, 436
Circumflex artery, anterior, of the humerus,
917
lateral, of the thigh, 949
surgical anatomy of, 1447
medial, of the thigh, 949
posterior, of the humerus, 903
Circumflex artery, posterior (contd.), surgical
anatomy of, 1447
iliac artery, deep, 945
surgical anatomy of, 1445
superficial, 947
vein, deep, 988
superficial, 989
nerve, 710
surgical anatomy of, 1447
Cisterna basalis, 672
cerebello-medullaris, 671
chiasmatis, 672
chyli, 996, 997
interpeduncularis, 672
magna, 671
surgical anatomy of, 1362
pontis, 672
Cisternae subarachnoideales, 671
Classification of joints, 299
Claudius, cells of, 850
Claustrum, 641
Clava, 547
Clavicle, 197
acromial end of, 199
architecture of, 271
articulations of, 317
coracoid tubercle of, 198
costal tuberosity of, 199
deltoid tubercle, 198
morphology of, 199
ossification of, 199
shaft, 198
surgical anatomy of, 1444
variations in, 279
Clavicular artery, 916
facet of sternum, 107
nerves, 695
morphology of, 700
Cleft, branchial, 42
gluteal, 1455
olfactory, 1378
palate, 1379
pharyngeal, 42
urogenital, 1324
visceral, 42
nerves of, 796, 798
stages of, at different ages, 42, 44, 52
Cleido-mastoid muscle, 458
Cleido-occipital muscle, 458
Clinoid process, anterior, 135
middle, 135
posterior, 135
Clitoris, 1326
arteries of, 1326
body of, 1326
bone of, 1326
corpora cavern osa of, 1326
crura of, 1326
development of, 1336
dorsal vein of, 942
frenulum of, 1326
glans of, 1326
prepuce of, 1326
septum corporum cavern osorum of, 1326
suspensory ligament of, 1326
vessels and nerves of, 1326
Clivus monticuli cerebelli, 575
Cloaca, 48
entodermal, 39
Cloacal fossa, 48
membrane, 39
Closing mouth, muscles of, 458
INDEX.
1493
Club-foot, 1465
Co-aptation in joints, 303
Coccygeal artery, 935
ganglion, 753, 763
glomus, 1355
nerves, 691
plexus, 738
vertebrae, 99
Coccyx, 99
cornua of, 99
ossification of, 106
Cochlea, 844
aquaeductus cochleae, 845
area, 844
auditory teeth of Huschke of, 830
base of, 844
basilar membrane of, 849, 850
canales spirales cochleae, 845
crista basilaris of, 849
crista semilunaris, 845
cupula of, 844
development of, 51
duct, 848, 849
foramen centrale, 844
foramina nervosa of, 849
ganglion spirale cochleae, 845
hair cells of, 851
hamulus laminae spiralis, 845
helicotrema of, 845
lagena of, 849
lamina spiralis ossea, 845
lamina spiralis secundaria, 845
ligament, spiral, of, 849
limbus laminae spiralis of, 849
membrana basilaris of, 845
membrana vestibularis of, 849
membranous, 848
modiolus of, 844
prominentia spiralis of, 849
scala tympani, 845
scala vestibuli, 845
spiral canal of, 845
spiral organ of, 849, 850
stria vascularis of, 849
sulcus spiralis externus, 849
sulcus spiralis internus of, 849
tractus spiralis foraminosus, 844
tunnel of Corti, 850
vas prominens of, 849
Cochlear nerve, 785
nucleus, 604
development of, 684
Cochleariform process, 128
Co3liac artery, 928
abnormalities of, 1053
morphology of, 1047
surgical anatomy of, 1426
ganglia, 763
lymph glands, 1021
plexus, 763, 765
Ccelom, 22, 71
embryonic, 27, 71, 72, 73
extra-embryonic, 22, 53, 57, 71
Colic artery, left, 932
middle, 932
right, 932
impression of liver, 1189, 1192
lymph glands, 1021
valve, 1214
vein, left, 993
middle, 992
right, 992
Collar bone, 197
Collateral digital artery of foot, 955
of hand, 924
Collateral eminence, 637
fissure, 662
nerve-fibres, 534
Collecting tubules, renal, 1266
Colles, perineal fascia of, 1427
Colliculi, origin of, 516
inferiores, 585
functions of, 586
nervi optici, 814
superiores, 620
functions of, 586
stratum griseum of, 586
lemnisci of, 586
opticum of, 586
zonale of, 586
Colon, 1211
appendices epiploicae of, 1211, 1212
ascending, 1211, 1219
length, 1219
position, 1219
relations, 1219
topography of, 1422
caecum of, 1211
descending, 1211, 1221
length of, 1221
relations of, 1221
topography of, 1423
dimensions of, 1211
haustra of, 1212
iliac, 1222
course of, 1222
relations of, 1222
topography of, 1423
left flexure of, 1211
level of, 1439
topography of, 1422
mesentery of, 1219
nerves of, 1213
pelvic, 1222
length of, 1223
mesentery of, 1219
in new-born child, 1223
position of, at birth, 1223
relations of, 1223
structure of, 1223
surgical anatomy of, 1423
variations in course of, 1223
plicae semilunares of, 1212
right flexure of, 1211
level of, 1439
topography of, 1422
sacculi of, 1212
sigmoid flexure of, 1211
sigmoideum (pelvic), 1222
structure of, 1212
taeniae of, 1179
transverse, 1219
position of, 1220
relations of, 1220
topography of, 1422
valve of, 1214
vessels of, 1212
Column, anterior, of spinal medulla, 528
of Burdach, 522, 533
of fornix, 616
of Goll, 522, 533
lateral, of spinal medulla, 529
membranous vertebral, 102
posterior, of spinal medulla, 537
1494
INDEX.
Column, posterior, of spinal medulla (contcL),
neck of, 523
vertebral, 87
Columnae carneae, 877
griseae, 523
rectales, 1230
renales (Bertini), 1265
rugarum vaginae, 1323
Columns of Bertin, 1265
of fornix, 34, 615
of the rectum, 1230
of spinal medulla, 523
" Comma tract," 533
Commissural fibres, cerebellar, 578
cerebral, 616, 631
Commissure, anterior, of brain, 616, 628,
647
olfactory portion of, 647
temporal portion of, 647
anterior gray, of spinal medulla, 539
dorsal, of brain, 34
gray, of spinal medulla, 539
of Gudden, 619, 769
habenularum, 615
of the hippocampus, 627, 648
labiorum pudendi anterior, 1324
posterior, 1324
of lips, 1108
medial and lateral, of eye, 821
of optic tract, 619
development of, 609
palpebrarum, 821
lateralis, 821
medialis, 821
posterior, of brain, 614, 615, 631
development of, 609
of spinal medulla, 539
of vulva, 1324
of spinal medulla, 539
white, anterior, of spinal medulla, 539
Common iliac artery, ligature of, 1426
peroneal nerve, surgical anatomy of,
1461
Communicating artery, anterior, of brain,
904
of deep palmar arch, 924
peroneal, 953
posterior, of brain, 904
abnormalities of, 1056
tibial, 953
of volar interosseous, 922
Compact tissue of bone, 83
Compound glands, 1132
Compressor bulbi muscle, 487
hemispheriorum bulbi, 487
naris muscle, 450
urethras membranaceae muscle, 488
Concentric corpuscles of Hassall, 1351
Concha auriculae, 827
nasalis inferior, 142
media, 141
superior, 141
Conchae, ethmoidal, 141
inferior, 142
ossification of, 143
sphenoidales, 139
Condyle of femur, lateral, 243
medial, 243
of humerus, 207
of jaw, 156
occipital, 122
third, 278
Condylic foramina, 122, 123, 124
fossa, 122
surface of tibia, 247
Condyloid joints, 301
Cone of attraction, 20
bipolars of retina, 817 ,
granules of retina, 817
retinal, 817
development of, 827
Confluens sinuum, 968, 973
Congenital diaphragmatic hernia, 473
Coni vasculosi, 1289
development of, 1204
Conical papillae, 1126
Conjugal ligament of ribs, 314
Conjunctiva, 823
fornices of, 823
nerves of, 823, 824
ocular, 821
palpebral and bulbar, 823
plica semilunaris of, 821
surgical anatomy of, 1377
, vessels of, 823, 824
Connexions, central, of olfactory nerves,
623
of the corpus striatum,"639
of thalamus, 612
Conoid ligament, 319
functions of, 319
tubercle, 198
Constrictor muscles of pharynx, 464
actions of, 467
development of, 496
nerve -supply of, 465
inferior, 465
middle, 464
superior, 464
of urethra, 488
Conus arteriosus, 876
elasticus, 1066
level of, 1442
surgical anatomy of, 1388
medullaris, 518
level of, 519
structure of, 526
vasculosus, 1289
Convoluted tubules of kidney, 1266
Convolutions of cerebrum, 653
Cor, 870
Coraco-acromial ligament, 320
Coraco-brachialis muscle, 378
action of, 380
nerve -supply of, 380
surgical anatomy of, 1446, 1447
superior or brevis, 379
Coraco-clavicular ligament, 319
Coraco-glenoid ligament, 322
Coraco-humeral ligament, 322
Coracoid process, 201
morphology of, 295
topography of, 1445
variations of, 280
Cord, gangliated, of sympathetic, 753
umbilical, 55
Cords of brachial plexus, 700
branches of, 702
formation of, 700
morphology of, 741
Corium, 857
papillae of, 857
stratum papillare of, 857
reticulare of, 857
INDEX.
1495
Cornea, 808
annular plexuses of, 810
anterior elastic lamina of, 810
arcus senilis of, 810
blood-vessels of, 810
cell spaces, 810
endothelium of anterior chamber, 810
nitration angle of, 809
lacunae, 810
ligamentum pectinatum of iris, 810
nerves of, 810
posterior elastic lamina of, 810
scleral spur, 810
spatia anguli iridis of, 810
structure of, 809
substantia propria, 810
sulcus circularis, 809
vascular and nervous supply, 810
Cornicula laryngis, 1065
Cornu ammonis, 625, 626, 636
anterius ventriculi lateralis, 633
inferius ventriculi lateralis, 633
inferius fossae ovalis, 403
majus oss. hyoidei, 159
minus oss. hyoidei, 159
posterius ventriculi lateralis, 635
bulb of, 635
superius fossse ovalis, 403
Cornua coccygea, 99
sacralia, 97
of fossa ovalis, 403
of thyreoid cartilage, 1062
of uterus, 1320
Corona dentis, 1114
glandis-, 1298
radiata, 631, 644
Coronal suture, 164
synostosis of, 197
Coronary arteries of face, 894
surgical anatomy of, 1379
of heart, 887
abnormalities of, 1051
of stomach, 929
abnormalities of, 1053
morphology of, 1047
Coronary ligament of liver, 1195, 1196
plexus, 765
sinus, 959
abnormalities of, 1057
development of, 1032
morphology of, 1050
opening of, 875
veins of heart, 959
of stomach, 991, 1176
Coronoid fossa of humerus, 208
process of mandible, 156
surface anatomy of, 1375
of ulna, 210
Corpora mamillaria, 541, 615
connexions of, 615
development of, 34, 608
peduncles of, 615
relation of, to third ventricle, 616
quadrigemina, 542, 582
brachia of, 582
connexion of, with cochlear nerve, 586
with thalamus, 586
development of, 34
lemniscus-fibres of, 586, 590
origin of, 516
structure of, 586
inferior, 585
Corpora mamillaria, quadrigemina, inferior
(contd.\ connexion of, with lateral
lemniscus, 590
superior, 586
connexion of, with optic tract, 620
with optic radiation, 586, 620
Corpus adiposum buccae, 446
albicans of ovary, 1313
callosum, 628, 629, 647
absence of, 588, 590
development of, 628
forceps major of, 631
genu of, 630
occipital part of, 631
radiation of, 631
rostrum of, 630
splenium of, 628, 630
striae longitudinales mediales of, 630
laterales of, 630
morphology of, 630
superior surface of, 629
tapetum of, 631
trunk of, 630
cavernosum clitoridis, 1326
penis, 1298
urethrae, 1298, 1300, 1427
ciliare, 812
dentatum cerebelli, 576
epididymidis, 1287
fornicis, 629
geniculatum laterale, 620
connexion of, with optic radiation, 620
with optic tract, 620
development of, 608
structure of, 613
mediale, 619
connexion of, with acoustic radiation, 656
with lateral lemniscus, 607
with medial root of optic tract, 619
development of, 608
glandulare prostatae, 1303
Highmori, 1288
hypothalamicum, 613
linguae, 1124
luteum, 1313
mandibulse, 155
maxillae, 146
ossis ischii, 232
pubis, 233
sphenoidalis, 133
paraterminale, 626, 628
pineale, 614
restiforme, 547
spongiosum penis, 1298, 1300
surface anatomy of, 1427
sterni, 106
striatum, 638
connexions of, 639
development of, 622
functions of, 639
morphology of, 638
vein of, 635
trapezoideum, 606
of cerebellum, 576
of pons, 606
vertebras, 88
vitreum, 819
Wolffi, 1329
Corpuscles, blood, origin of, 64
concentric, of Hassall, 1351
of Golgi and Mazzoni, 865
of Grandry, 864
1496
INDEX.
Corpuscles (contd.), of Krause, 863
lymph, 993
Malpighian, of spleen, 1353
of kidney, 1266
of Meissner, 865
of Pacini, 864
of Ruffini, 865
tactile, 863
of Wagner, 865
Corrugator cutis ani muscle, 486, 1229
supercilii muscle, 450
action of, 452
Oortex, cerebral, 644
renal, 1265
Corti, spiral ganglion of, 845, 852
organ of, 849, 850
ceUs of Claudius of, 850, 851
of Hensen of, 850, 851
development of, 853
hair-cells of, 850, 851
lamina reticularis of, 850, 851
membrana tectoria of, 850, 851
pillars of, 850
rods of, 850
space of Nuel of, 852
supporting cells of, 850, 851
fibres of, 851
phalangeal processes of, 851
tunnel of, 850
Cortical system, 1343
Corticifugal projection strands of brain, 652
Cortico-pontine tract, 653
in internal capsule, 642
in mid-brain, 591
in pons, 555
Costse, 109
floating, 109
spurise, 109
verae, 109
Costal cartilages, 113
joints of, 315
topography of, 1407
demi-facets of thoracic vertebrae, 93
pleura, 1084, 1085
transverse epiphyses, 106
zone of abdomen, 1158
Costo-central joints, 313
Costo-chondral joints, 315
topography of, 1398
Costo-clavicular ligament, 318, 319
Costo-colic ligament, 1220
Costo-coracoid ligament, 369
membrane, 369
Costo-iliac space, 1437
Costo-sternal joints, 315
Costo-transverse joints, 314 -
ligaments, 314
Costo-vertebral joints, 313
Costo-xiphoid ligaments, 316
Cotyloid ligament, 340
notch, 232
absence of, 281
Coxa, 339
Cranial fossa, anterior, 179, 183, 188, 189
middle, 180, 183, 190, 191
posterior, 182, 183
Cranio-cerebral topography, 1359
central sulcus of Eolando, 1360
lateral cerebral fissure, 1360
parieto-occipital fissure, 1360
Rolandic area, 1360
transverse sinus, 1360
Craiiiology, 284
Craniometry, 284
Cranio-pharyngeal canal, 135
closure of, 290
Cranium, 115
articulations of, with vertebral column, 310
base of, 179
bony landmarks of, 1358
capacity of, 284
cartilaginous, 290
cerebrale, 115
circumference of, 286
height of, 286
membranous, 290
sinuses of, 972
surgical anatomy of, 1357, 1359
thickness of, 1359
trabecular portion of, 290
veins of, 969, 972
vertebral portion of, 290
viscerale, 115
Cremaster muscle, 480
nerve-supply of, 484
Creinasteric artery of inferior epigastric, 944
of internal spermatic, 928
fascia, 480, 483, 1297
Crescents of Gianuzzi, 1132
Crest, anterior, of fibula, 252
of tibia, 248
conchal, of maxilla, 148
of nasal bones, 145
of palate, 151
ethmoidal, 151
falciform, 131
frontal, 117, 179
iliac, 228, 238
topography of, 1442, 1455
incisor, 149
infra-temporal, 137, 167, 168
interosseous, of fibula, 252
of radius, 215
of tibia, 248
of ulna, 212
lacrimal, posterior, 143
lateral, of fibula, 252
neural, 32, 500, 679
obturator, 233
occipital, external, 121
internal, 121
pubic, 233
sexual difference of, 238
topography of, 1408
sacral, articular, 97
lateral, 98
median, 97
sphenoidal, 135
supra -mastoid, 125
of tibia, anterior, 248
urethral, 1306
zygomatic, 154
Cribrous fascia, 403
lamina, 139
relation of, to cranial fossa, 179
to nasal cavity, 184, 187
Crico-arytsenoid joint, 1066
muscles, 1072, 1074
actions of, 1072, 1074
Cricoid cartilage, 1063
arch of, 1063
development of, 1100
lamina of, 1063
ossification of, 1065
INDEX.
1497
Cricoid cartilage (contd.}, surface anatomy of,
1388
Crico-thyreoid artery, 892
joint, 1065
muscle, 1075
action of, 1076
nerve of, 1076
Crista or Cristae
arnpullaris, 848
anterior, of the tibia, 248
basilaris cochleae, 849
conchalis, 148
cutis, 856
ethmoidalis, 151
of female urethra, 1284
galli, 140
of heads of ribs, 109
iliaca, 228, 238
infra-temporalis, 137, 167, 168
intertrochanterica, 240
lacrimalis anterior, 148
posterior, 143
of male urethra, 1306
mallei, 840
nasal, 802
of the necks of the ribs, 109
neural, formation of, 500
obturatoria, 233
sacral, articular, 97
lateral, 98
media, 97
sphenoidal, 135
spinarum, 831
terminalis, 874, 1032
development of, 1032
transversa, 846
tuberculi majoris et minoris, 206
vestibuli, 843
Crucial anastomosis, 943, 950
Cruciate ligament of atlas, 311
of knee, 346
in movements of knee, 348
Crura antihelicis, 828
cerebri, 383
basis of, 583
cerebro-poiitine fibres of, 591
development of, 592
position and connexions of, 583
pyramidal fibres of, 591
red nucleus of, 588, 613
tegmentum of, 583, 586
relation of, to thalamus, 610, 612, 613
to third ventricle, 610, 612, 614
temporo-pontine fibres of, 591
clitoridis, 1326
of diaphragm, 471
fornicis, 628
of penis, 1298
of subcutaneous inguinal ring, 477
Cms anterius stapedis, 840
breve incudis, 840
common, of semicircular canals, 844
helicis, 827
inferior, of subcutaneous inguinal ring, 477
intermedium of diaphragm, 471
lateral, of diaphragm, 471
longum incudis, 840
medial, of diaphragm, 472
posterius stapedis, 840
superior, of subcutaneous inguinal ring, 477
Cryptorchism, 1295
Cryptozygous skulls, 171, 286
Crystalline lens, 819
Cubitus, 323
Cuboid bone, 763
morphology of, 295
peroneal groove of, 263
tubercle of, 263
Culmen of cerebellum, 575
Cumulus oophorus, 1314
Cuneate funiculus, 533
gyrus, 661, 662
nucleus, 533
Cuneiform bones of foot, 261
first, 261
second, 262
third, 263
morphology of, 295
ossification of, 265
Cuneiform cartilages, 1068
tubercle, 1069
Cuneo-cuboid articulation, 358
Cuneo-lingual gyri, 660
Cuneo-metatarsal ligaments, 359
Cuneus, 660, 661
Cup, optic, of optic vesicle, 33, 825, 826
of retina, 815
Cupola of cochlea, 844
Cupula terminalis, 848
Curved lines of occipital bone, 121
Cushion, endocardial, 1033
of epiglottis, 1068, 1069
Eustachian, 1143
levator, 1143
Cusps of cardiac valves, 877, 878
of teeth, 1114
Cutaneous lamella, 30
Cuticula dentis, 1122
Cutis, 857
Cut-throat, 1388
Cuvier, duct of, 1026
abnormalities of, 1057
morphology of, 1048
Cylinder, axis, 507
Cymba conchas, 827
Cystic artery, 930
duct of liver, 1202
surgical relations of, 1415
vein, 992
Cytolymph, 8
Cytoplasm, 8
Cyto-reticulum, 8
Dacryon, 285
Dartos muscle, 485
Darwin, tubercle of, 828
Decidua, 56, 57
basalis, 57, 58, 62
capsularis, 57
layers of, 57
marginalis, 57
relation of ovum to, 57
vera, 57
Deciduous teeth, 1113, 1114, 1121
development of, 1244
Declive cerebelli, 575
Decussatio brachii conjunctivi, 548
of the pyramids, 545, 557
fountain, 589, 591
of the lemnisci, 560
of lemniscus medialis, 560
motor, 545, 557
in optic chiasma, 619
sensory, 562, 566
96
1498
INDEX.
Decussatio (contd.), transverse, of pons, 578
Defsecation centre, 1233
Deferent duct, 1289, 1290
ampulla of, 1292
Degeneration, ascending, 532
descending, 532
Wallerian, 532
Deglutition, movements in, 467
Deiters, nucleus of, 605
supporting cells of, 857
Deltoid ligament, 352
muscle, 337
action and nerve-supply of, 374
topography of, 1447
tubercle, 207
Demilunes of Gianuzzi, 1132
Dendrites, 507, 509
of cells of cerebellum, 580, 581
of cerebral cortex, 645
of spinal medulla, 528
of sympathetic ganglia, 704
development of, 36, 504, 512
function of, 498
Dens serotintis, 146
Dental arches, 1119
formula, 1114
index, 287
lamina, 1244, 1245
Dentate nucleus, 576, 577
Dentes or Teeth, 1113
canine, 1117
corona of, 1114
deciduous, 1121
incisive, 1115
molar, 1117
permanent, 1115
praemolar, 1117
Dentition, diphyodont, 1248
heterodont, 1248
homodont, 1248
of lower races, 1248
polyphyodont, 1248
typical mammalian, 1248
Depression in presternum, 108
Depressor alee nasi muscle, 450
septi muscle, 450
Dermal teeth, 1244
Dermic skull, 292
Dermis, 856
Descendens hypoglossi nerve, 698, 794
Descending degeneration, 532
palatine artery, 899
Descent of the testis, 1295
gubernaculum testis, 1295
processus vaginalis peritonei, 1295
rudimentum processus vaginalis, 1295
Descriptive terms, 4
Deutoplasm of ovum, 14, 79
Development, 7
of adamant and ivory, 1247
of adamant organs, 1245
of alimentary canal, 41, 1249
of alveolar canal, 149, 157
of anal canal, 48
of anterior cardinal veins, 1038
of anterior commissure of spinal medulla, 34
of aortic arches, 67, 1027, 1028
of appendicular skeleton, 294
of arcuate fibres, 566
of arteries of the limbs, 1031
of atrio-ventricular canal, 1033
of auditory ossicles, 841
Development (contd.), of auditory tube, 52
of the bladder (urinary) 1328, 1332
of blood-vascular system, 1025
of brain, 33, 34, 512, 514
of branches of dorsal aorta, 1029
of bulbo-urethral glands, 1335
of caecum and vermiform process, 1251
of cerebellum, 33, 571
of cerebral hemispheres, 34, 512, 621
of cerebral nerves, 593, 682, 796
of chondro-cranium, 290
of chromaphil system, 1343
of cortical system of glands, 1341
of dermal teeth, 1244
of descending aorta, 67, 1028
of digestive system, 1242
of division of the atrium, 1033
of division of primitive ventricle, 1035
of dorsal maxillary process, 1252
of ducts of Cuvier, 1035
of ductus venosus, 1038
of ep-oophoron, 1328
of external ear, 52, 53
of external genital organs, 1328, 1335
of eye, 825
of female urethra, 1333
of first blood-vessels, 1025
of foramen epiploicum, 1253
of gastro-intestinal glands, 1250
of generative ducts, 1334
in the female, 1335
in the male, 1334
of genital eminence, 1335
of glomus caroticum, 1343
of glomus coccygeum, 1355
of great anastomotic vein (of Trolard), 1040
of greater omentum, 1253
of greater vestibular glands, 1335
of hairs, 862
of head, 495
of heart, 65, 70, 1025, 1031
of hypophysis cerebri, 49
of interventricular septum, 1035
sulcus, 1035
of intestine, 1250
of .joints, 304
of labyrinth, 853
of larynx, 1100
of left superior intercostal vein, 1040
of limbs, 39
of liver, 1254
of lower lip, 1244
of lumbar veins, 1041
of lungs, 1101
of male urethra, 1332
of mamma, 1339
of medulla, 536
of mesencephalon, 33, 34, 592
of mesogastrium, 1252
of metencephalon of head, 495
of mouth, 1242
of muscles of limbs, 495
of nails, 862
of neck, 42
of nerve-cells, 35, 498
of nose, 49
of oesophagus, 1249
of palate, 49
of pancreas, 1255
of parathyreoid glands, 1349
of par-oophoron, 1328
of parotid glands, 1244
INDEX.
1499
Development (contd.\ of pericardium, 72, 74
of peripheral nerves, 679
of peritoneum, 1252
of pharynx, 1242
of philtrum, 1244
of pinna, 52
of placenta, 56
of pons (Varolii), 33, 514, 592
of portal system, 1036, 1037
of posterior cardinal veins, 1040
of primary foramen ovale, 1033
of primitive aorta, 67, 1027
of primitive cerebral veins, 1039
of primitive dorsal aorta, 1025
of primitive pharynx, 1248
of primitive veins, 1026
of prostate, 1335
of quadrigeminal bodies, 34, 592
of rectum, 1252
of renal veins, 1041
of respiratory apparatus, 1099
of salivary glands, 1249
of sebaceous glands, 862
of secondary foramen ovale, 1034
of sensory cells, 500
of septum primum, 1033
of septum secundum, 1033
of sexual glands, 1333
female, 1334
male, 1333
of sinus venosus, 1032
of skeletal muscles, 495
of skin, 861
of spinal medulla, 31, 33
of spinal nerves, 679
of spleen, 1253, 1355
of stomach, 1249
of submaxillary and sublingual glands, 1249
of sudiferous glands, 862
of superior vena cava, 1040
of suprarenal glands, 32, 1343
of sympathetic system, 681
of teeth, 1244
of thymus, 1351
of thyreoid gland, 134.8
of tongue, 1249
of tonsil, 1249
of trachea, 1100
of transverse sinus, 1040
of tympanic cavity, 52
of umbilical and iliac arteries, 1030
of umbilical veins, 1036, 1037
of upper lip, 1242
of ureter and permanent kidney, 1331
of uro-genital organs, 1327
of veins, 1035
of venous valves, 1032
of ventral mesentery, 1252
of vitelline veins, 1036
Diagonal sulcus, 666
Diameter obliqua pelvis, 238
transversa pelvis, 238
Diaphragm, 471
actions of, 474
anomalies of, 473
arch of, 1439
central tendon of, 472
crura of, 471
development of, 74
foramen venae cavse of, 472
foramina in, 472
formation of, 74
Diaphragm (contd.), hernia of, 473
hiatus aorticus of, 472
hiatus oesophageus, 473
lumbo-costal arches of, 472
middle arcuate ligament of, 472
nerve-supply of, 474
openings in, 473
pars costal is of, 471
parts of, 471
relation of, to abdominal cavity, 1439
surgical anatomy from the back, 1439
pelvic, 493
Diaphragma sellae, 669
urogenitale, 489, 491
Diaphragmatic arteries of aorta, 933
of inferior phrenic, 933
of musculo-phrenic, 913
of pericardiaco-phrenic, 913
ganglion, 765
line of pleura, 1088, 1399, 1401
lymph glands, 1011, 1013, 1024
pleura, 1085
plexus, 765
Diaphysis of bone, 85
Diapophysis, 284
Diarthroses, 301
development of, 304
Diencephalon, 541, 608
development of, 34
parts derived from, 609
Differences between jejunum and ileum, 1209
Digastric fossa, 155
muscle, 461
action of, 463
development of, 496
nerve -supply of, 461
triangle, 1391
Digestive system, 1103
development of, 1242
modifications of, 1103
parts of, 1104
Digital arteries of foot, 955, 958
of hand, 920, 924
morphology of, 1048
surgical anatomy of, 1454
depressions, 105, 108
flexor sheaths, 1453
sheaths of fingers, 388, 389
of toes, 430
veins of foot, 988
of hand, 978
morphology of, 1049
Digits, rudiments of the, 40
Digitus post minimus, 295
Dilatator pupillse, 815
Dilator naris muscle, 450
tubse muscle, 838
Diphyodont dentition, 1248
Diploe of bone, 84
Diploic veins, 969
Disc, interpubic, 337
intervertebral, 307
optic, 815
tactile, 863
Discus articularis acromio-clavicularis, 319
mandibularis, 312
radio-ulnaris distalis, 327
triangular, of distal radio-ulnar joint, 327
sterno-clavicularis, 318
proligerus, 1314
Dislocation of the shoulder, 1445
Displaced medial meniscus, 1460
1500
INDEX.
Diverticulum, allaiitoic, 38, 39, 54
ilei, 1210
Dolichocephalic skulls, 171, 285
Dolicho-facial skulls, 286
Dolicho-liieric sacrum, 289
Dolicho-kerkic limbs, 289
Dolicho-knemic limbs, 289
Dolicho-pellic pelves, 288
Dolicho-uranic skulls, 287
Dorsal arch, 924
axial line of limbs, 691
Dorsalis clitoridis artery, 942, 1428
nerve, 740
hallucis artery, 958
indicis artery, 920
abnormalities of, 1055
linguae artery, 892
pedis artery, 957
position of, 1465
surgical anatomy of, 1465
penis artery, 941, 942
nerve, 740
pollicis artery, 920
Dorsiflexion, 303
Dorso-epitrochlearis muscle, 370
Dorsum sellae, 134
development of, 139
Douglas, folds of, peritoneal, 1238, 1318
of sheath of rectus, 483
topography of, 1410
pouch of, 1237, 1318
surgical anatomy of, 1435, 1436
Drainage of left infra-colic compartment of
peritoneum, 1414
of right infra-colic compartment of peri-
toneum, 1414
of supra-colic compartment of peritoneum,
1414
of ventricle of brain, 1362
Drop- wrist, 1449
Ductuli aberrantes, 1289
efferentes testis, 1288
trans versi (of ep-oophoron), 1315
Duct or Ducts Ductus
alveolar, of lung, 1098
arteriosus, 68, 70, 71
abnormalities of, 1050
of Bartholin, 1140
bile, 1202
development of, 1255
level of, 1443
relation of, to duodenum, 1183
surgical anatomy of, 1416
termination of, 1186, 1203
biliferi, 1201
choledochus, 1201, 1202
cochlear, 848, 849, 1201
development of, 854
of Cuvier, 69, 1026
abnormalities of, 1057
morphology of, 1048
cystic, of liver, 1202
surgical anatomy of, 1415
deferent, 1289, 1290
ampulla of, 1292
arteries of, 939, 945
development of, 1335
structure of, 1294
surgical anatomy of, 1433
ejaculatory, 1292
opening of, 1292
endolyinphaticus, 51, 79
Duct or Ducts Ductus, endolymphaticus
(contd.), development of, 854
epididymidis, 1287
epoophori longitudinalis (Gartneri), 1315
excretorius glandular bulbo - urethralis.
1304
fronto-nasal, 804
hepatic, 1201
development of, 1255
interlobulares hepatis, 1199
development of, 1254
lactiferi mammae, 1338
lymph, right, 993
abnormality of, 1059
naso-lacrimal, 825, 1377, 1378
development of, 49
surgical anatomy of, 1377
pancreatic, 1186, 1203
para-urethral, of urethra (female), 1285
parotid, 1109, 1136
opening of, 1107
surgical anatomy of, 1376
pharyngo-branchial, 44
precervical, 43
prostatici, 1303
reunions (Henseni), 847
development of, 51
of Rivinus, 1139
of Santorini, larger, 1207
of Santorini, smaller, 1207
semicircular, 847
lateral, posterior, superior, : 844, 847
sublingual, 1108, 1138
sublingual larger, 1140
sublingual smaller, 1139
submaxillary, 1138
opening of, 1108
surgical anatomy of, 1383
sudoriferus, 861
thoracic, 993
abnormalities of, 1059
surgical anatomy of, 1394
thyreo-glossal, 1348
utriculo-saccular, 847
venosus, 71
fissure of, 1191, 1196
ligament of, 1196
vitelline, 38, 48, 55
vitello-intestinal, 48, 55
remnant of, in adult, 1196
of Wirsung, 1206
Wolffian, 1329
Ductless glands, 1341
associated with the vascular system, 1352
Duodenal folds, 1185
diverticula, 1187
fossae, 1185
impression, 1194
pouch, 1187
ulcer, 1419
Duodeno-jejuiial flexure, 1187
surgical anatomy, 1419
fossa, 1185, 1419
Duodenum, 1177. 1182
ampulla of, 1186
ascending part of, 1182
caruncula of, 1186
descending part, 1182
development, 47
diverticulum of, 1187
duodeno-jejunal flexure, 1182
first part of, 1082
INDEX.
1501
Duodenum (contd.), glands of, 1186
horizontal part of, 1182
inferior part of, 1182
interior of, 1186
nerves of, 1187
orifice of bile -duct in, 1186
papilla of, 1186
pars inferior, 1185
level of, 1185
peritoneal relations of, 1186
plicae longitudinales of, 1186
position and size, 1182
relations of, 1182
relations of descending part, 1184
relations of inferior part, 1185
second part of, 1184
shape and divisions of, 1182
structure of, 1186
superior part, 1182
surgical anatomy of, 1419
suspensory muscle of, 1187
various forms of, 1187
vessels and nerves of, 1187
Dura mater encephali, 667
diaphragma sellae of, 668
falx eerebelli of, 669
cerebri of, 668
lacunae laterales of, 974
layers of, 668
prolongations of, on nerves, 668
venous blood-sinuses of, 668, 972
spinalis, 669
Ear, 827
capsule, 131, 291
development of, 841
external, 827
auricle of, 827
development of, 52, 53
meatus of, 845
incus, 840
internal, 843
development of, 50
internal vessels of, 853
ligament of, 841
lymph vessels of the, 1004
malleus, 839
middle, 832
muscles of, extrinsic, 449
intrinsic, 841
ossicles, auditory, 838
semicircular canals, bony, 844
stapes, 840
surgical anatomy of, 1365
Ebner, glands of, 855
Ectochondral ossification, 86
Ectoderm, 21, 23
neural, 22, 30
structures formed from, 33
surface, 39
Effusion into the shoulder-joint, 1445
knee-joint, 1461
Egg-tubes, 1314
Ejaculatory duct, 1292, 1302, 1306
development of, 1304
opening of, 1306
Elastic lamina of arteries, 868
of Bowman, 810
of cornea, 810
Elbow, bony points about the, 1449
surgical anatomy of, 1449
Elbow-joint, 323
Elbow-joint (contd.), fat-pads of, 325
incisions into, 1449
movements at, 325
muscles acting on, 382, 401
nerves of, 705, 709, 711
surgical anatomy of, 1449
synovial stratum of, 325
Ellipsoid joints, 301
Embolus of cerebellum, 577
Embryo, ectoderm of, 39
entoderm of, 39, 40
external features of, at different periods, 74
fold, head, 37
tail, 38
folding off of, from blastodermic vesicle, 37
folds, lateral, of, 38
formation of the, 37
intermediate cell-tracta of, 30
lateral mesodermic plates of, 30
membranes of, 53-63
mesodermic somites of, 28, 29
nutrition of, 53
period of the, 7
protection of, 53
summary of, 39
Embryology, 1, 7
Embryonic area, 22
at different periods, 74, 79
Eminence, arcuate, 130, 182
genital, 48
ilio-pectineal, 231, 233
Eminentia arcuata, 130, 133
collateralis, 637
conch se, 828
fossae triangularis, 828
intercondyloidea, 247
medialis of fourth ventricle, 551
scaphie, 828
Emissary veins, 975
Empyema of maxillary sinus, 1378
Enarthrodial joints, 301
Encephalon, 539
general appearance of, 539
connexions of parts of, 541
End -bulbs of Krause, 864
End organs, special, 863
articular bulbs, 864
corpuscles of Pacini, 864
genital corpuscles, 864
of Grandry, 864
of Golgi and Mazzoni, 865
of Krause, 863
neuro-muscular spindles, 866
neuro-tendinous spindles, 865
of Rufiini, 865
tactile corpuscles of Wagner and Meissner,
865
Endocardial cushions, 1033
Endocardium, 879
structure of, 879
Endochondral ossification, 86
Endolymph, 846
Endoskeleton, 81
Entoderm, 21, 22, 42
Eparterial bronchus, 1083, 1097
Ependyma, 632, 636, 637
Ependymal cells, 632
layer, 632
Epibranchial organs, 796, 797
Epicardium, 879
Epicondyles of humerus, 207
ossification of, 210
1502
INDEX.
Epicondyles of humerus (contd.),
anatomy of, 1449
of femur, 243
Epicondylic lines, 207
process of humerus, 210, 280
ossification of, 210
ridges, 207
Epicranius muscle, 448
action of, 449
nerve -supply of, 449
Epidermis, 857
appendages of, 858
development of, 861
Malpighian layer of, 857
stratum corium of, 857, 859
filamentosum of, 859
germinativum of, 857
granulosum of, 858
mucosum of, 857
vessels and nerves of the, 859
Epididymal artery, 1289
Epididymis, 1286, 1287
aberrant ductules of, 1289
development of, 1327, 1334
appendix of, 1287
canal of, 1289
development of, 1327, 1334
caput of, 1287
cauda of, 1287
corpus of, 1287
sinus of, 1287
structure of, 1288
surgical anatomy of, 1430
Epidural space, 667, 669
Epigastric artery, inferior, 944
formation of, 1030
surgical anatomy of, 1408
superficial, 947
superior, 913
fossa, 1397
region, 1159, 1411
vein, inferior, 988
superficial, 986
superior, 963
Epigastrium, 1159
Epiglottic cartilage, 1065
Epiglottis, 1065
cartilage of, 1065
in deglutition, 1077
development of, 45, 1100
frenulum of, 1067
glands of, 1065
level of, 1442
ligaments, 1067
taste buds of, 1067
tubercle of, 1068, 1069
Epihyal, 159
Epiotic, 132
Epiphora, 1377
Epiphyses, 85
of bone, 85
development of, 34
distal of humerus, 1449
pressure and traction, 85
Epiphyseal line, 85
Epiploic foramen, 1163, 1238
surgical anatomy of, 1419
Epipteric bones, 132, 145
Epispinous process, 92
Episternal bones, 276
notch, level of, 1442
Epistropheus, 92
surgical
Epistropheus (contd.}, articular surface of, 92
body of, 92
dens of, 92
ossification of, 105
Epithalamus, 609, 614
development of, 35, 608
Epitrichium, 862
Epitrochleo-anconeus muscle, 398
Epitym panic recess, 1369
Eponychium, 859, 862
Ep-oophoron, 1315, 1316
appendices vesiculosi of, 1315
development of, 1335
longitudinal duct of, 1315
transverse ductules of, 1315
Erect position, 4
Erector clitoridis muscle, 488
penis muscle, 488
Eruption of teeth, 1120
deciduous, 1246
permanent, 1120, 1121
Erythroblasts, 83
Ethmoid bone, 139
alar processes of, 140
ossification of, 142
relation of, to cranial fossa, 179
to nasal cavity, 184
to orbit, 163
variations in, 278
Ethmoidal air-cells, 140, 804
surgical anatomy of, 1372, 1373
arteries, 903
canals, 116, 140
in anterior cranial fossa, 179
crest, 151
foramen, anterior, 140, 163
posterior, 140, 163
notch of frontal, 116
plate, 292
process, of inferior concha, 143
Ethmo-turbinals, 141, 292
Ethmo-vomerine region, 292
Eutelolecithal ovum, 14
Eversion of foot, 436
Examination of interior of female bladder, 1436
Excavatio of papilla of optic nerve, 815
recto-uterine, 1318
recto-vesical, 1226, 1237
vesico-uterine, 1226, 1237, 1238, 1317
Excision of the knee-joint, 1461
Exoskeleton, 81
Expiration, 474
Exposure of hemisphere of cerebellum, 1363
of meningeal arteries, 1364
of semilunar ganglion, 1365
Expression, facial, 452
Extension, movement of, 436
Extensor carpi radialis brevis muscle, 396
action of, 396
nerve-supply of, 396
longus muscle, 396
action of, 396
nerve -supply of, 396
ulnaris muscle, 398
action of, 398
nerve-supply of, 398
digiti quinti proprius muscle, 398
action of, 398
nerve-supply of, 398
digitorum brevis muscle, 426
action of, 426
nerve -supply of, 426
INDEX.
1503
Extensor digitorum brevis muscle (contd.\
topography of, 1465
communis muscle, 397
action of, 397
nerve-supply of, 397
longus muscle, 425
action of, 425
nerve-supply of, 425
topography of, 1465
is lon
hallacis longus muscle, 426
action of, 426
nerve -supply of, 426
indicis proprius muscle, 400
action of, 400
nerve-supply of, 400
ossis metatarsi hallucis muscle, 426
pollicis brevis muscle, 400, 426
action of, 400
nerve-supply of, 400
longus muscle, 400
action of, 400
nerve -supply of, 400
External acoustic meatus, surgical anatomy of,
1366
capsule, 644
urethral orifice of female, 1326
Extraperitoneal tissue, 475
of pelvis, 489
Extravasation of urine, 485
Eye, 806
anterior chamber of, 813
arteries of, 823
cameras of, 813, 821
commissures, medial and lateral, 821
development of, 825
glands of, 823
layers of optic vesicle, 820
movements of, 454
pineal, 547
Eyelashes, 822, 823
Eyelids, 821
blood-vessels of, 823
caruncula lacrimalis, 821
commissures, medial and lateral, 821
development of, 827
in foetus, 76, 78, 79
glands of Moll of, 823, 827
lacus lacrimalis of, 821
lymph vessels of, 824, 1004
mucous membrane of, 823
muscles of, 450
actions of, 454
nerves of, 824
palpebral ligament of, inferior, 822
medial, 822
superior, 822
fissure, 821
raphe, lateral, 822
papilla lacrimalis of, 821
plica semilimaris conjunctivae, 821
septum orbitale of, 822
skin of, 823
surgical anatomy of, 1376
tarsal arches of, 823
glands of, 823
tarsi of, 821
third, 821
Eye-teeth, 1117
Face, bones of, 146
bony landmarks of, 1374
measurements of, 286
Face (contd.\ muscles of, 450
actions and nerve supply of, 451
development of, 496
skeleton of, at birth, 196
surgical anatomy of, 1375
Facial bones, 146
canal, 129, 130
index, 286
nerve, 598, 781
ascending part of, 599
buccal branches of, 784
cervical branch, 784
cervico-facial division of, 784
colliculus facialis of, 599
development of, 683
emergent part of, 599
exposure of trunk of, 1375
intrapontine course of, 599
marginal branch of mandible, 784
migration of nucleus of, 600
nervus intermedius, nuclei of, 598
nucleus of, 567, 598
radicular part of, 599
relations of, to tympanic antrum, 1371
somatic fibres of, 599
splanchnic-efferent fibres of, 598
temporo-facial division of, 784
zygomatic branches of, 784
veins, 965
common, 965
surface anatomy of, 1375, 1391
deep, 965
Falciform crest, 131
ligament of fossa ovalis, 403
of liver, 1196
development of, 1196, 1252
topography of," 1415
margin, 404
process of sacro-tuberous ligament, 337
False passages in urethra, 1428
Falx cerebeUi, 669
cerebri, 668
inguinalis aponeurotica, 479, 481
surgical anatomy of, 1408
Fangs of teeth, 1114
Fascia or Fasciae, 364
of abdominal cavity, 474, 485, 489
of abdominal wall, 474
anal, 490
antibrachii, 382
of arm, 378
axiUary, 369
of back, 365, 437
brachii, 378
bucco-pharyngea, 1149
bulbi, 452, 807
check ligaments of, 807
suspensory ligament of, 807
of buttock, superficial, 402
cervical, deep, 447, 1385
muscular compartments of, 1386
suprasternal compartment of, 1386
surgical anatomy of, 1385
vascular compartment of, 1386
visceral compartment of, 1385
cremasterica, 480
cribrosa, 403, 405
cruris, 422
deep, 364
of arm, 378
of chest, 369
of shoulder, 373
1504
INDEX.
Fascia or Fasciae (contd.), dentata, 625, 626
diaphragmatis pelvis superior, 491
urogenitalis inferior, 338, 489
superior, 491
of foot, 423
of forearm, 382
deep, 382
superficial, 382
of groin, 402
deep, 403
superficial, 402
of hand, 384
of head, 446
deep, 447
superficial, 446
iliaca, 1157
infundibuliform, 475
intercolumnar, 477
lata, 403, 405
fossa ovalis of, 403
surgical anatomy of, 1459
of leg and foot, deep, 422
superficial, 422
lumbar, 437
lumbo-dorsal, 437
masseteric, 447, 454
of neck, 1386, 1389
obturator, 489
of orbit, 452
palmar, 384
parotid, 447, 1133
pectinea, 403
pectoralis, 369
pelvis, 485, 489
tendinous arch of, 491
penis, 1300
of perineum, 485
surgical anatomy of, 1427
pharyngo-basilar, 1149
phrenico-pleural, 1089
piriform, 489
plantar, 423
popliteal, 405
surgical anatomy of, 1457
of popliteus, 425
praevertebral, 448, 467, 1386
prostatse, 493, 1429
rectal, 1228
recto-vaginal, 493
recto-vesical, 493
renal, 1259
salpingo-pharyngea, 838
of shoulder, 373
spermatic external, 477
internal, 475
superficial, 364
of arm, 378
of chest, 369
temporal, 447
of thigh and buttock, 402
thyreoid, 1389
transversalis, 475
triangular, 478
of upper limb, 378
urethro- vaginal, 493
of urogenital diaphragm, inferior, 489
superior, 491
Fasciculus or Fasciculi
anterior propriua, 538
antero-lateral superficial, 536
bulbo-spinal, 538
bulbo-thalamic, 591, 651
Fasciculus or Fasciculi (contd.)
cerebello-spinal, 536
cerebro-pontine, 591
cerebro-spinal anterior, 536, 539
lateral, 536, 538, 545
circumolivary, 557
cuneatus, 526, 533, 559
gracilis, 522, 526
intra-fascicularis, 533, 559
lateralis (plexus brachialis), 701
lateralis proprius, 538
longitudinalis inferior, 650
medialis, 586-588
superior, 650
mamillo-thalamic, 612, 615
medialis (plexus brachialis), 701
occipito-frontal, superior, 651
olivo-spinal, 538
posterior (plexus brachialis), 701
postero -lateral, 534
proprius anterior, 535
lateralis, 535
posterior, 535
pyramidal, 591
retroflexus, 591, 614
rubro-spinal, 538, 588
origin of, 516
septo-marginal, 535
eolitarius, 564, 596, 597, 598
spino-cerebellar, 531, 563
anterior, 537, 578
posterior, 537
spino-tectal, 537
spino-thalamic, 535, 537, 545, 562, 591, 651
anterior, 537, 538
posterior, 537
spiralis of cochlear nerve, 852
strio-nigricus, 641
strio-rubricus, 641
strio-thalamicus, 641
tecto-bulbaris et spinalis, 591
tecto-spinal, 538, 562
origin of, 516
temporo-thalamic, 643
thalamo-mamillary, 612, 615
thalamo-olivary, 556, 568
uncinate, 649
vestibulo-spinal, 538, 605
of Vicq d'Azyr, 612, 615
Fasciola cinerea, 629, 946
Fat-pads, synovial of joints, 302
of elbow-joint, 325
of hip-joint, 341
of knee-joint, 348
Fauces, 1112
arches of, glosso-palatine, 1112
pharyngo-palatine, 1112
isthmus of, 1112
level of, 1442
surgical anatomy of, 1383
Female pronucleus, 16, 20
Female reproductive organs, 1310
bulbus vestibuli, 1310
clitoris, 1310
external genital organs, 1310
greater vestibular glands, 1310
labia majora, 1310
minora, 1310
mons Veneris, 1310
ovary, 1310, 1311
rima pudendi, 1310
uterine tube, 1310
INDEX.
1505
Female reproductive organs (con tcL), uterus, 1310
vagina, 1310
Femoral arch, deep, 405
superficial, 405
artery, 946
ligature of, 1459
surgical anatomy of, 1459
canal, 405
fossa, 1235
hernia, 405
lymph glands, 1013
ring, 405
septum, 405
sheath, 947
triangle, 414
vein, 985
Femur, 239
adductor tubercle of, 242, 412
architecture of, 273
condylar surface of, 244
condyles of, 243
connexions of, 244
distal epiphyseal line of, 1462
distal parts of shaft, 1459
epicondyles of, 243
fovea capitis of, 240
greater trochanter of, 241
head of, 239
homology of, 294
iiitertrocHanteric crest of, 240
line of, 240
lesser trochanter of, 242
linea aspera of, 242
neck of, 240
nutrient foramina of, 244
ossification of, 244
patellar surface of, 244
pectineal line of, 242
pilastered femur, 281
platymerie, 281
popliteal surface of, 242
sexual differences of, 244
shaft of, 242
spiral line of, 242
third trochanter of, 242, 281
trochanteric fossa of, 241
variations in, 281
Fenestra ovalis s. vestibuli, 832
rotunda s. cochleae, 833
Fenestrated membrane, 868
Fertilisation of ovum, 20
Fibrae arcuatae externae, 566
internae, 560
development of, 566
circulares Miilleri, 813
lentis, 820
meridionales (Brueckei), 813
obliquse ventriculi, 1174
Fibres, association, of spinal medulla, 534
commissural, of cerebellar, 578
cortico-striate, 653
cortico-thalamic, 612
intercolumnar, 477
internal arcuate, 560, 561
of medulla oblongata, 556, 560
of Purkinje", 879
thalamo-cortical, 612
Fibrils of ivory, 1123
Fibrocartilages, intervertebral, 306
Fibrous plate of fingers, 333
of toes, 361
tympanic, 831
Fibula, 250
anterior crest of, 252
apex of head, 250
architecture of shaft of, 250
connexions of, 253
incisions to expose the shaft of, 1462
interosseous crest of, 252
lateral crest of, 252
lateral malleolus of, 253
medial crest of, 253
morphology of head of, 250
ossification of, 253
shaft, examination of, 1462
surface of, 252
variations in, 282
Fibular artery, 953
Fibulare, os, 295
Field, polar, 13
Filament, axial, 18
Filiform papillae, 1126
Filtration angle of cornea, 809
Filum terminale, 518
Fimbria cerebri, 627
ovarica, 1312
tubae uterinae, 1314
Finger-cells, 857
Fingers, bones of, 226
movements of, 401
Fissure or Fissures Fissura
angular, 665
anterior median, of spinal medulla, 521
antitrago-helicine, 829
of anus, 1430
auricular, 127
calcarine, 660
central, of brain, 663
development of, 662, 663
topography of, 1360, 1361
transitional gyri of, 663
of cerebellum, 571
of cerebrum, 571, 572, 573
chorioidal, of brain, 621, 637, 675
development of, 621
chorioidal, of eye, 826
collateral, 661, 662
" complete," 646
of ductus venosus, 1191, 1197
floccular, of cerebellum, 572
development of, 573
frontal, inferior, 665
middle, 665
superior, 665
fronto-marginal, 665
hippocampi, 626
horizontal, of cerebellum, 573
development of, 572
inferior orbital, 137, 147
interparietal proprius, 664
lateral, of the brain, 653
anterior ascending ramus of, 653, 654
horizontal ramus, 654
ascending ramus, 654
development of, 655, 656
posterior ramus, 653
stem of, 653
terminal piece of, 665
topography of, 1359, 1360
longitudinal, of cerebrum, 540, 646
development of, 608
lunatus, 660
of lung, 1095
of medulla oblongata, 543
1506
INDEX.
Fissure or Fissures Fissura (contd.), occipital,
anterior, 665
lateral, 661
paramedial, 661
transverse, 664
olfactory, 666
orbital (of brain), 666
inferior, of skull, 137, 147, 162, 163, 189
ossa suturarum in connexion with, 146
superior, variations in, 136, 162, 180
palpebral, 821
paracentral, 664
paramedial, 661
parapyramidal, 573
development of, 573
parietal, superior, 665
parieto-occipital, 661
topography of, 1360
paroccipital, 661
petro-basilar, 130
petro-occipital, 176
petro-squamous, 131
petro- tympanic, 127, 834
portal, 1190
post-central, inferior, 664
superior, 664
post-lunar, 573
development of, 572
post-nodular, 571
development of, 571
post-tonsillar, of cerebellum, 573
prae-cuneal, 665
pre-central, inferior, 665
superior, 665
prim a of cerebellum, 572
pterygoid, 138
pterygo-maxillary, 168, 192
pterygo-palatine, 192
rhinal, 624
sagittal, of the lingual gyrus, 662
secundaria of cerebellum, 572
simial, 660
spheno-petrous, 175, 176
of spinal medulla, 521, 522
development of, 521
subparietal, 665
superior orbital, 160, 180
suprapyramidal, 573
development of, 572
temporal, inferior, 658
middle, 658
superior, 658
topography of, 1360
transverse, of the brain, 674
of liver, 1180
tympano-mastoid, 127
umbilical, 1191
urogenital, 1329
vestibuli, 844
Fistula in ano, 1431
Flat bones, 82, 85
Flechsig, areas of, 564
Flexion, 377
Flexor carpi radialis muscle, 385
action of, 386
bursa, 386
nerve-supply of, 386
surface anatomy of, 1452
ulnaris muscle, 386
action of, 387
nerve-supply of, 387
caudse muscle, 494
Flexor digiti quinti brevis of foot, 435
action of, 435
nerve-supply of, 435
of hand, 394
action of, 394
nerve -supply of, 394
digitorum brevis, 433
action of, 433
nerve-supply of, 433
longus muscle, 430
action of, 430
nerve-supply of, 430
profundus, 388
action of, 389
nerve-supply of, 389
sublimis muscle, 388
action of, 388
nerve-supply of, 388
hallucis brevis muscle, 434
action of, 434
nerve-supply of, 434
longus muscle, 431
action of, 431
nerve -supply of, 431
pollicis brevis muscle, 393
action of, 393
nerve-supply of, 393
longus muscle, 390
action of, 390
nerve -supply of, 390
surgical anatomy of, 1453
sheath, common, of hand, 1453
Flexura coli dextra, 1211
sinistra, 1211
Flexures of brain, 514
cephalic, of brain, 514
cervical, of brain, 514
duodeno-jejunal, 1182, 1187
topographical anatomy of, 1419
left, of colon, 1211, 1220
level of, 1442
topography of, 1422
perineal, of rectum, 1224
pontine, of brain, 514
right, of colon, 1211, 1220, 1422
level of, 1423
topography of, 1422
sacral, of rectum, 1224
sigmoid, 1211
Floating ribs, 1 12
Floccular fissure of cerebellum, 572
development of, 573
fossa, 131, 133
Flocculus cerebelli, 571
development of, 571
Floor, pelvic, 490
plate, 500, 502
FcEtus, circulation of, 71
estimate of age of, 78, 79
external characters of, at different periods, 74
membranes of, 53, 62
period of the, 7
Fold or folds, ary-epiglottic, 1068
development of, 1100
axillary, 1446
caudal, 38, 74
cephalic, 38, 74
of Douglas, of sheath of rectus, 483
topography of, 1410
genital, 1333
glosso-epiglottic, 1067
gluteal, 1455
INDEX.
1507
Fold or folds (contd.), ilio-caecal, 1218
labio-scrotal, 1328
of larynx, 1068
ary-epiglottic, 1068
ventricular, 1068
vocal, 1068
medullary, 23, 74
pharyngo-epiglottic, 1067
recto-genital, 1317
recto-uterine, 1317
of pelvic peritoneum, 1238, 1318
recto-vaginal, 1317
sacro-genital, 1283, 1318
salpingo -palatine, 838, 1143
salpingo-pliaryngeal, 838, 1143
semilunar, of Douglas, 483
transverse vesical, 1283
utero-vesical, 1317
ventricular, 1068
vestigial, of Marshall, 872, 882
vocal, 1068
Folds and fossae about the caecum, 1218
Folia of cerebellum, 571, 580
Folium vermis of cerebellum, 572
Follicles, of hair, 860
of Lieberkiihn, 1181
lymph, 995
primitive, of ovary, 1334
of teeth, 1245, 1246
Folliculi oophori primarii, 1331
vesiculosi, 1313
development of, 1334
Folliculus pili, 860
Fontana, spaces of, 810
Fontanelle, anterior, 194
antero-lateral, 194
posterior, 194
postero-lateral, 194
sagittal, 194
Fonticulus frontalis, 194
mastoideus, 194
occipitalis, 194
sphenoidalis, 194
Foot, articulations of, 351
bones of, 254
architecture of, 274
morphology of, 295
ossification of, 265, 267, 268
variations in, 282
fasciae of, 423
lymph vessels of, 1014, 1015
mechanism of, 361
muscles of, 424, 430, 432-435
actions and nerve-supplies of, 435, 436
surgical anatomy of, 1463, 1467
transverse arch of, 361
Foot-plate of stapes, 840
Foramen apicis aentis, 1114
caecum linguae, 1126, 1348
development of, 44, 1249, 1348
of medulla oblongata, 544
of skull, 140
centrale cochleae, 844
diaphragmatis (sellae), 699
epiploicum, 1162, 1183, 1238
development of, 1253
surgical anatomy of, 1272
ethmoidal, 142, 179
posterius, 140, 163
of Huschke, 832
incisivum, 149, 174
incisor, 149, 174
Foramen (contd.), infraorbital, 146, 162
surface anatomy of, 1375
interventricular, 543, 608, 618, 621, 832
development of, 608, 621
intervertebral, 89, 95
ischiadicum majus, 229, 337
minus, 232, 337
jugular, 176, 177, 182
lacerum, 176, 180
of Magendie, 553
magnum, 123, 178, 182
plane of, 124
mandibular, 156
mastoid, 128
mental, 155
surface anatomy of, 1375
obturator, 228, 234
occipital, 172, 178
optic, 180
abnormalities of, 278
ovale, of heart, 875
development of, 1033, 1034
persistence of, 1050
of sphenoid, 136, 169, 176, 180
abnormality of, 278
palatine, greater, 151, 174
surgical anatomy of, 1384
lesser, 152, 174
parietal, 171
origin of, 277
quadratum, 473
rotundum, 136, 180
abnormality of, 278
of Scarpa, 149, 174
sciatic, greater, 229, 337
lesser, 232, 337
singulare cochleae, 846
spheno-palatine, 185, 192
spinosum, 136, 169, 176, 180
abnormality of, 278
of Stenson, 149, 174
development of, 149
. stylomastoid, 129, 177
absence of, 278
supraorbital, 116, 160
surface anatomy of, 1358
supratrochlear, of humerus, 280
transversarium, 90, 92, 93
serial homology of, 284
venae cavae, 472
vertebral, 90, 93, .95, 96
of Vesalius, 136, 168, 180
zygomatico-facial, 153
zygomatico-orbital, 154
zygomatico-temporal, 154
Foramina alveolaria, 147
anterior, of sacrum, 96
ethmoidal, 162
interventricular, 618
intervertebral, 89
nervosa, 849
palatina minora, 152
papillaria of kidney, 1265
sacralia anteriora, 96
posteriora, 97
venarum minimarum cordis (Thebesii), 874,
960
Forearm, fasciae of, 382
lymph vessels of, 1006
muscles of, 382
superficial veins of, 978
surgical anatomy of, 1450
1508
INDEX.
Forearm and hand, 382
surgical anatomy of, 1450
Fore -brain, 514
development of the primitive, 33
second dilatation, 33
Fore-gut, 38
differentiation of the, 42
dorsal wall, developments of, 47
lateral wall of the, 42
branchial bars of, 42
pouches, 42
pharyngeal bars of, 42
pouches, 42
ventral wall, developments of, 44
Formatio hippocampalis, 625
reticularis of medulla oblongata, 564
alba, 564
grisea, 564
of pons, 564
of spinal medulla, 524
Formation of alveoli of teeth, 1246
Fornix cerebri, 625
body of, 629
columns of, 615, 627
connexion of, with hippocampus, 625
crura of, 628
crus of, 628
development of, 34, 628
fimbria of, 628
pharyngis, 1145
vaginae, 1321
Fossa or Fossae, acetabuli, 284
anterior cranial, 179
of antihelix, 828
caecalis, 1218
canina, 146, 179, 183, 188, 189
condylic, 122
coronoid, of humerus, 208
cranial, 179
anterior, 179, 188, 189
middle, 180, 190, 191
posterior, 182, 191
digastric, 155
ductus venosi, 1191, 1192
duodenal, inferior, 1185
superior, 1185
duodeno-jejunal, 1185, 1419
surgical anatomy of, 1419
epigastric, 1397
femoral, of peritoneum, 1235
floccular, 130, 133
for gall-bladder, 1191
glandulae lacrimalis, 143, 162
glenoid, of scapula, 201, 202
of temporal bone, 125
condition of, at birth, 133
surgical anatomy of, 1445
of helix, 828
hypophyseos, 134
development of, 291
hypotrochanterica, 281
ileo-caecal, 1218
ileo-colic, 1218
iliaca, 231
incisor, of mandible, 155, 156
incudis, 840
inferior duodenal, of Jonnesco, 1419
infraspinous, 202
infratemporal, 168
boundaries, 168
floor of, 169
inguinal, intermediate, 1235
Fossa or Fossae (contd.), inguinal, lateral, 1235
medial, 1235
intercondyloid, of femur, 243
anterior, of tibia, 247
posterior, of tibia, 247
interpeduncular, 180, 541
intersigmoid, 1223
surgical anatomy of, 1423
ischio-rectal, 1238
jugular, 177
condition of, at birth, 133
relation of, to jugular foramen, 177
to tympanum, 1369
lacrimal, 148, 163
of Landzert, 1185
lateral, of brain, 655
for ligamentum teres of hip, 284
variation in, 281
mandibular, 167
mastoid, 1369
middle cranial, 180
myrtiform, 146
nasal, 801
navicularis urethras (Morgagni), 1308
surgical anatomy of, 1428
vestibuli vaginae, 1325
olecrani, 208
orbital, 160
ovalis of heart, 874
development of, 1033
of thigh, 403
ovarian, 1312
paraduodenal, 1185
pararectal, 1227, 1238
paravesical, 1238, 1280
patellar, 819
post-condylic, 177
posterior cranial, 182
pterygoid, 174
pterygo-palatine, 170
radial, 208
retro-caecal, 1218
retro-colic, 1219
retro-mandibular, 1113
retro-ureteric, of bladder, 1277
rhomboid, 550
of Kosenmuller, 1144
development of, 1144
surgical anatomy of, 1385
sacci lacrimalis, 825
scaphoid, of auricle, 828
scaphoid, of sphenoid, 138, 175, 176
subarcuate, 130, 131
submaxillary, 155
supraspinous, 202
supratonsillar, 1145
development of, 1249
temporal, 166
lower part, 167
triangular, of auricle, 828
trochanteric, of femur, 241
venae cavse (inferioris), 1191, 1192
umbilical, 1191
vermiform, 278
vesicae felleae, 1191
zygomatic, 168, 175
Fossula fenestrse cochleae, 129, 833
vestibuli, 832
inferior, of internal acoustic meatus, 846
superior, of internal acoustic meatus, 846
Fossulae tonsillares, 1146
Fountain decussation, 589, 591
INDEX.
1509
Fountain decussation (contd.), functions of, 589
Fourchette, 1324
Fourth ventricle, 549
clava of, 579
obex of, 579
roof of, 578
Fovea capitis femoris, 240
capituli radii, 214
centralis retinae, 815
costalis inferior, 93
superior, 93
dentis, 91
femoralis, 1235
inferior of fourth ventricle, 550
inguinalis, 1235
lateral, 1235
medial, 1235
pterygoidea, 157
submaxillaris, 155
superior, of fourth ventricle, 551
supra vesical, 1235
trochlearis, 117, 162
Foveae articulares superiores atlantis, 91
Foveolae gastricae, 1176
Fracture of the clavicle, 1445
dislocations of the vertebral column, 1443
of sternum, 1397
Frenula valvulae coli, 1214
Frenulum clitoridis, 1324, 1326
epiglottidis, 1126
of Giacomini, 629
labii inferioris, 1106
superioris, 1106
labiorum pudendi, 1324
linguae, 1108, 1128
surgical anatomy of, 1383
praeputii, 1299
veli, 582
development of, 542
Front of thigh, surgical anatomy of, 1458
Frontal artery of ophthalmic, 904
surgical anatomy of, 1358
of superficial temporal, 897
bone, 115
angular process of, 115, 160, 166
architecture of, 270
cerebral surface of, 117
crest of, 117, 179
ethmoidal notch of, 116
ossification of, 118
sexual differences in, 115
superciliary arches of, 116
surgical anatomy of, 1364
tuberosities of, 115
variations in, 277
eminence, 115
difference in, due to sex, 193
relation of, to brain, 1360
gyrus, inferior, 665
middle, 665
precentral, 665
superior, 665
nerve, 772
plane, 5
process of maxilla, 148, 163
of zygomatic bone, 153
region of the brain, 665
sinus, 270
in coronal sections, 186
exploration of, 1372
growth of, 118
at puberty, 197
Frontal sinus, (contd.\ relation of, to infundi-
bulum, 141
to nose, 186
to orbit, 162
size of, 1371
skiagraphs of, 1372
surgical anatomy of, 1371
trans-illumination of, 1372
suture, 160
vein, 967, 969
Fronto-marginal sulcus, 665
Fron to -nasal process, 49
Fronto-pontine strand, 653
in crus cerebri, 591
in internal capsule, 642
Froriep's ganglion, 684, 796
Fundus of caecum, 1213
meatus acustici interni, 845
of stomach, 1163, 1168
level of, 1442
surgical anatomy of, 1417
tympani, 832
uteri, 1316, 1434
ventriculi, 1163
vesicae, 1274
Fungiform papillae, 1127
Funicular cells, 504
process, 1409
Funiculus anterior of spinal medulla, 538
cuneatus, 526, 533, 547
constitution of, 538
in section of medulla oblongata, 555
gracilis, 526, 547
constitution of, 532
in section of medulla oblongata, 555
lateralis of spinal medulla, 535
posterior of spinal medulla, 533
separans, 551
spermaticus, 1296
coverings of, 1297
umbilicalis, 56
Furcula, 45
Furrow, bicipital, 1445
nuchal, 1395
sternal, 1397
ulnar, 213
vertebral, 1436
Furrowed band of cerebellum, 576
Galea aponeurotica, 447, 449
Galen, great veins of, 674
Gall-bladder, 1201
body of, 1201
development of, 1250
duct of, 1201
fundus of, 1201
neck of, 1201
spiral valve of, 1201
structure of, 1202
surgical relations of, 1415
variations in, 1202
Gallstones, impacted, 1415, 1416
Gametes, 11
female, 11
male, 11
Ganglia, essentials of, 498
primitive, 32
spinal, 685
of sympathetic plexuses, 753
of trunk, sympathetic, 753
Gangliated cord of sympathetic, 753
Ganglion or Ganglia, aberrantia, 685
1510
INDEX.
Ganglion or Ganglia (contd.), aortico-renal,
764
basal, of central hemispheres, 637
of cardiac plexuses, 789, 880
cardiac (Wrisbergi), 790
of cerebral nerves, 678, 767
cervical, inferior, of sympathetic, 759
branches of, 759
surgical anatomy of, 1398, 1442
middle, of sympathetic, 759
branches of, 759
superior, 759
of uterus, 1321
ciliary, 773
development of, 683, 796
long root of, 773
morphology of, 796
roots of, 773
short root of, 770
sympathetic root of, 773
coccygeal, 753
cochlear, 554, 664, 785
cceliac, 763
of Corti, 845, 852
diaphragmatic, 765
of Froriep, 796
geniculi of facial nerve, 598, 782
development of, 683, 796
morphology of, 796
habenulse, 614
impar, 753, 763
inferior cervical, of sympathetic, 759
interpedunculare, 591, 614
relation of, to fasciculus retroflexus, 614
jugular of vagus, 786, 788
development of, 796
morphology of, 796
lumbar, 761, 762
mesenteric, superior, 765
middle cervical, of sympathetic, 759
nodosum of vagus, 786, 788
development of, 684, 796
morphology of, 796
olfactory, 622
morphology of, 622
otic, 781
development of, 684, 796
petrous, 785
branches of, 786
development of, 684, 796
morphology of, 796
phrenic, 765
sacral, 763
semilunar, 600, 772
development of, 683, 796
morphology of, 796
of sensory nerves, 510
spheno-palatine, 775, 777
development of, 683, 795, 796
spinal, 685
aberrant, 685
cells of, 685
development of, 679
spiral, of cochlear, 785, 845, 852
splanchnic, 761
submaxillary, 780
branches from, 780
roots of, 780
superior cervical, of sympathetic, 756
superius, of glossopharyngeal nerve, 785
development of, 684, 796
morphology, 796
Ganglion or Ganglia (contd.\ sympathetic, 504
cells of, 753
cervical superior, 756
branches of, 756
collateral, 754
development of, 681
gray rami of, 754
terminal, 754, 767
of the tendon sheath, 1451
thoracic, 759
central branches of, 761
first, 759
peripheral branches of, 761
plexuses of, 761
trunci sympathici, 753
of vagus, 786, 788
vestibular, 853
development of, 683, 796
Ganglionic crest, 679
layer of retina, 816
Gastric artery, 929
impression of liver, 1193
of kidney, 1264
lymph glands, 1019
ulcer, perforation of, 1418
veins, 992, 1019
Gastrocnemius muscle, 428
action of, 429
nerve-supply of, 429
surface anatomy of, 1463
Gastro-colic ligament, 1241
Gastro-duodenal artery, 930
Gastro-enterostomy, 1418
Gastro-epiploic artery right, 930
veins, 992
Gastro-lienal ligament, 1162, 1170, 1236, 1240,
1242
development of, 1256
Gastro-phrenic ligament, 1170, 1236
Gelatinous marrow, 83
Gemellus inferior muscle, 418
superior muscle, 418
actions of, 418
nerve -sup plies of, 418
General lumbar index, 288
Geniculate bodies, lateral, 620
development of, 35, 608
internal structure of, 613
medial, 582
ganglion, 598, 782
Genio-glossus muscle, 462
action of, 463
nerve -supply of, 463
surgical anatomy of, 1383
Genio-hyoid muscle, 461
action of, 462
nerve-supply of, 462
Genital cord, 1334
eminence, 78, 1328, 1336
fold, 1333
organs, development of, 1328
female, 1334, 1335, 1336
male, 1333, 1335, 1336
ridge, 1333
Genito-femoral nerve, 722
Gennari, stria of, 644, 659
Genu capsulae internee, 642
of central fissure of the brain, 663
of corpus callosum, 630
of facial nerve, 782
Germ cells, multiplication of, 12
primitive, 11
INDEX.
1511
Germs cells (could.), progenitors of, 21
enamel, 1245
nerve, 679
of tooth, 1245
Germinal cells, 502
of ovary and testis, 15, 17, 21
of spinal medulla, 30
epithelium, 21, 1333, 1334
layers, 7, 21
vesicle, 14, 22
Giacomini, banderella of, 629
Gianuzzi, crescents of, 1132
Gingivse, 1112
Ginglymus, 301
Girdle, pectoral, 203, 270
pelvic, 228, 273
Glabella, 160, 183, 285
surgical anatomy of, 1358, 1374
Glands or Glandulse, 1131
acini of, 1133
acino-tubular, 1132
acinous, 1132
alveolar, 1133
alveoli of, 1133
anterior, of tongue, 1130
areolar, 1837
basement membrane of, 1132
buccal, 1109
bulbo-urethral, 1304
development of, 1335
ducts of, 1304
surgical anatomy of, 1248
carotid, 1343
ceruminous, 832, 861
cervical, of the uterus, 1315
ciliary, 861
circum-anal, 1230
coccygeal, 1355
compound, 1132
cytogenic, 1131, 1132
digestive, 1106
ductless, 1341
duodenal, 1179, 1186
of Ebner, 855
epithelial, 1131
general structure of, 1133
Haversian, 341
of intestine, 1179
of colon, 1212
of rectum, 1230
of small intestine, 1210
labial, 1109
lacrimal, inferior, 824
superior, 824
surgical anatomy of, 1377
laryngeal, 1072
lingual, 1130
anterior, 1130
lymph, 993
mammary, 1336
molar, 1109
of Moll, 823, 827
mucous, 1131
nodules, lymph aggregate, 1179
olfactory, 804
palatine, 1110
parathyreoid, 1345
parotid, 1133
accessory parotid gland, 1136
deep part of the gland, 1135
duct of, 1136
facial process of, 1133, 1136
Glands or Glandulae, parotid (contd.), imme-
diate relations of, 1137
retro -mandibular process of, 1133
shape and relations of, 1134
superficial surface, 1134
vessels and nerves of, 1137
prseputial, 1299
prostatic, 1301, 1302, 1307
racemose, 1132
salivary, 1133
structure of, 1140
sebaceous, 861
serous, 1132
sexual, development of, 1333
shape and relations of, 1139
simple, 1132
solid, 1131
solitary, of large intestine, 1181
of small intestine, 1179
structure of, 1132
sublingual, 1138
development of, 1243
surgical anatomy of, 1383
vessels and nerves of, 1140
submaxillary, 1137
development of, 1243
position and relation of, 1137
surgical anatomy of, 1391
vessels and nerves of, 1 138
sudoriferous, 861
sudoriparous, 861
suprarenal, development of, 32, 1343
surgical anatomy of, 1437, 1442
sweat, 861
tarsal, 823
of Moll, 823
surgical anatomy of, 1377
thymus, 1350
thyreoid, 1347
accessory, 1349
of tongue, 1130
tubular, 1132
urethral, 1309
uterine, 1320
vascular, 1131
vestibular, greater (Bartholini), 1326
surface anatomy of, 1435
lesser, 1326
Glans clitoridis, 1326
penis, 1298, 1336
Gleno-humeral ligament, 322
Glenoid fossa of scapula, 201, 202
fossa of temporal bone, 125, 154
condition of, at birth, 133
surgical anatomy of, 1375
labrum, 320
Glisson (capsula fibrosa), 1198
Globular process, 49
Globus pallidus of lentiform nucleus, 639
Glomerular capsule, 1266
Glomerulus, olfactory, 623
renal, 1269
of sweat glands, 861
Wolffian, 1329
Glomus caroticum, 1343
development of, 1355
structure of, 1343, 1355
coccygeum, 1355
Glossp-epiglottic folds, 1067
Glosso-palatine arch, 1111, 1112
muscle, 467
action of, 467
1512
INDEX.
Glosso-palatine muscle (contd,\ nerve-supply
of, 467
Glossopharyngeal nerve, 785
nuclei of, 596
Glossopharyngeus muscle, 464
Glottis respiratoria, 1071
development of, 684
spuria, 1070
vera, 1070
pars intermembrana.cea, 1071
Glutaeus maximus muscle, 415
actions of, 415, 421
nerve-supply of, 415
surface anatomy of, 1455
medius muscle, 416
minimus muscle, 416
actions of, 417, 421
nerve -supply of, 417
Gluteal artery, 942
surgical anatomy of, 1455
cleft, 1455
fold, 1455
lines of ilium, 230
surface of ilium, 230
veins, 984
Gnathic index, 287
Goll, column of, 522, 533
Gonion, 286
Gowers ? tract, 535, 536, 546
Gracile funiculus, 547
lobule, 576
nucleus, 547, 559
Gracilis muscle, 411
action of, 411
nerve-supply of, 411
Granulationes arachnoideales, 672
Granule cells, 579
layers of retina, 817, 818
Gratiolet's optic radiation, 658
Gray matter, central, of mid-brain, 584
of cerebellum, 576
of cerebral cortex, 644, 645
cerebro-spinal, 36, 512
of spinal medulla, 527-531
development of, 33, 35
of medulla oblongata, 33, 515
of thalamus, 36
Gridiron incision, 1411
Groin, 1405
fasciae of, 402
Groove, of alveolar process, 148
anterior medial, of spinal medulla, 522
antero-lateral, of medulla oblongata, 544
for auditory tube, 136
carotid, of sphenoid, 135
for cerebral sinuses, 182
coronary, of heart, 871
topography of, 1403
costal, 110, 112
for greater superficial petrosal nerve, 130
for inferior petrosal sinus, 128
interosseous, of calcaneus, 259
of talus, 256
intertubercular, 206
interventricular, 872, 873, 1035
intervertebral, 89
lacrimal, 147
of lacrimal bone, 143, 163
of maxilla, 148, 163
longitudinal, of heart, 871
for meningeal arteries, 117, 119, 126
on frontal bone, 117
Groove for meningeal arteries (conttl), or
parietal, 119
on temporal, 126
mylo-hyoid, 156
development of, 158
naso-pharyngeal, 1143
neural, 23, 24, 31
obturator, 234
abnormality of, 281
for occipital sinus, 183
oesophageal, of liver, 1192
of lung, 1094
olfactory, 140, 141, 179
optic, 135
popliteal, 243
postero-lateral, of medulla oblongata, 544
primitive, 23
pterygo-palatine, of palate, 151
of sphenoid, 138
for radial nerve of humerus, 207
sacral, 97
subclavian, 111
for subclavius, 199
for superior petrosal sinus, 128, 182
for superior sagittal sinus, on cranial vault
117
on frontal, 117
on occipital, 121
on parietal, 119
for transverse sinus, 121
on cerebral hemisphere, 647
on occipital bone, 121-122
on parietal, 119 ,
on temporal, 128
partial absence of, 278
vertebral, of vertebral column, 100
of thorax, 114
Growth of bones, 86, 87
Gubernaculum dentis, 1247
testis, 1295
Gudden's commissure, 769
Gullet, 1150
Gums, 1112
lymph vessels of, 1005
Gustatory cells, 855
hair, 855
pore, 854
Gyrus or Gyri, 653
angular, 665
topography of, 1360
breves, 654
central, anterior, 665
posterior, 662
of cerebral hemispheres, 653
cinguli, 666
cunei, 662
cuneo-lingualis, anterior, 660
posterior, 660
frontal, inferior, 665
middle, 665
superior, 665
topography of, 1360
of Heschl, 656
lingualis, 660
longi, 654
orbitalis anterior, 666
paracentral (lobule), 665
pararhinal, 658
parasplenialis (area), 665
parietal, inferior (lobule), 664-665
superior (lobule), 664
parieto-occipital (area), 665
INDEX.
1513
Gyrus or Gyri (contd.), praecuneus, 662
precentral, 665
rectus, 666
supramarginal, 665
topography of, 1360
temporal, inferior, 658
medins, 658
parasplenal, 658
superior, 657
surface anatomy of, 1360
transverse, 656
transitional, deep, of calcarine and parieto-
occipital fissure, 660
of central fissure, 663
of intraparietal, 664
transitivi cerebri, 663
Habenula, commissure of, 615
ganglion of, 614
Haemal lymph glands, 995
Haematocele, pudendal, 1435
Hsematoma of the scrotum, 1430
Haemorrhages of the scalp, 1357
Hsemorrhoidal arteries, inferior, 1232
middle, 939
superior, 1232
nerve, inferior, 738
plexus, 766
venous, 985
veins, 984
Haemorrhoids, 1430
Hair, 859
development of, 862
erector muscles of, 861
of foetus, 79
follicle of, 860
bulb of, 860
root sheaths of, 860
papilla of, 860
root of, 859
scapus of, 859
shaft, 859
Hair-cells, auditory, 847, 848, 851
of cochlea, 851
Hair-follicles, 860
Hairs, gustatory, 855
olfactory, 805
Hamstring muscles, 418
surgical anatomy of, 1456
Hamulus cochleae, 845
lacrimalis, 143
laminae spiralis, 845
of medial pterygoid lamina, 138, 175
surgical anatomy of, 1385
of os hamatum, 221
pterygoideus, 138, 175
Hand, arterial arches of, 923
articulations of, 329
bones of, 217
architecture of, 272
morphology of, 295
ossification of, 223, 226, 227
variations in, 280
fasciae of, 384
movements of, 401
muscles of, 382, 391
surgical anatomy of, 1450
Hard palate, 174
in frontal section of skull, 189
relation of, to surface, 164
Hare-lip, 1379
Hasner, valve of, 825
Hassall, concentric corpuscles of, 1351
Haustra coli, 1212
Haversian canals, 84
gland of hip-joint, 341
systems, 84
Head, arteries of, 888
bones of, 115
development of, 495
fasciae of, 446
lymph vessels of, 1003
superficial, 1003
mesodermal somites of, 28, 29, 30, 496
movements of, 446
muscles of, 448
development of, 495
nerves of, 767
process, 24
segmental characters of, 293, 496
surgical anatomy of, 1357
veins of, 964
Head-cap, of spermatozoon, 17
Heart, 870
abnormalities of, 1050
aortic cusp of, 1050
orifice of, 878, 884
topography of, 1403
valve of, 878
vestibule of, 878
apex of, 872
abnormalities of, 1050
arteries of, 887
atria of, 874, 875
development of, 70
left, 875
right, 873
structure of, 879
topography of, 1403
atrio-ventricular apertures of, 877
auricles of, 874, 875
development of, 1032
left, 875
right, 874
surface anatomy of, 1404, 1405
base of, 871
bulbus cordis of, 70
capacity of, 880
central fibro-cartilage of, 876, 879
chambers of, 873
chordae tendineae of, 877
conus arteriosus of, 876
coronary groove of, 871
topography of, 1403
sinus of, 875, 959
abnormalities of, 1057
development of, 1032
morphology of, 1049
opening of, 875
sulcus of, 871
crista terminalis of, 874
development of, 70, 75, 1025, 1031
diaphragmatic surface of, 872
endocardium of, 875, 876, 877, 878
structure of, 879
epicardium of, 879
fibrous rings of, 877, 878, 879
foramen ovale of, 875
persistence of, 1050
foramina venarum minimarum, 874
fossa ovalis of, 874
development of, 1033, 1034
infundibulum of, 876
interauricular septum of, 873
97
1514
INDEX.
Heart, interauricular septum of (contd.), ab-
normalities of, 1051
development of, 1032
interventricular septum of, 878
abnormalities of, 1050
development of, 1032
sulcus of, 873
limbus fossa ovalis, 874
lunulse of valves of, 877
lymph vessels of, 880
margins of, 873
topography of, 1403
mitral orifice of, 878
level of, 1442
topography of, 1405
valve of, 878
moderator band of, 877
musculi papillares of, 877
structure of, 879
pectinati of, 874
myocardium of, 878
nerves of, 880
nodulus valvulse semilunaris, 877
orifices of pulmonary veins in, 875
of venae cavse in, 874, 875
outline of physiology of, 870
pars membranacea septi of, 878
abnormalities of, 1050
primitive, 70
atrium of, 1033
development of, 1026
rudiments of, 65
venous valves of, 1032
pulmonary orifice of, 877
topography of, 1045
valve of, 877
development of, 1032
Purkinje"'s fibres of, 879
relation of, to wall of thorax, 870, 871, 873
semilunar valves of, 877
development of, 1032
septum primum of atrium, 1033
secundum of atrium, 1033
shape of, 870
sinus venosus of, 1032
development of, 70
size of, 880
sterno-costal surface of, 872
structure of, 878
atrio-ventricular bundle, 879
endocardium, 879
epicardium, 879
fibres of, 879
sulcus, coronary, 871
sulcus terminalis of, 873, 874
developmental significance of, 1032
surface and surgical anatomy of, 1403
Thebesian valve of, 874
development of, 1032
trabeculae carneae of, 877
transposition of, 1050
tricuspid orifice of, 874, 877
level of, 1442
topography of, 1405
valve of, 877
trigona fibrosa of, 876
truncus aorticus of, 70
tuberculum intervenosum, 875
valvula venae cavae inferioris, 875
development of, 1032
vascular supply of, 880
veins of, 959
Heart, veins of (contd.}, morphology of, 1048
ventricles of, 876
development of, 70
structure of, 879
ventricular septum, 876
weight of, 880
Helicine arteries, 1300
Helicotrema, 845
Helix, 827
development of, 53
fossa of, 828
muscles of, 829
spine of, 828
tail of, 829
Helmholtz, ligaments, 841
Hemisphaeria bulbi urethras, 1308
Hemispheres, cerebellar, 570
cerebral, 620
Henle, layer of, 860
loop of, 1266
Hensen, cells of, 850, 851
ductus reunions of, 846
development of, 854
stripe of, 851
Hepatic artery, 930
cells, 1199 '
duct, 1201
development of, 1254
lobules, 1198
lymph glands, 1020
plexus, 765
veins, 982
Hepato - duodenal ligament, 1162, 1183,
1197
Hepato-gastric ligament, 1162, 1170, 1197
development of, 1255
Hepato-renal ligament, 1197
Heredity, theory of, 19
Hernia, congenital inguinal, 1409
diaphragmatic, 473
direct inguinal, 1408, 1409
femoral, 405
medial, 1409
oblique inguinal, 1408, 1409
surgical anatomy of, 1408, 1459
Heschl's convolution, 656
Hesselbach's triangle, 1235, 1408
Heterodont dentition, 1248
Hiatus aorticus, 472
canalis facialis, 130
condition of, at birth, 133
interosseus, 327
maxillaris, 804
cesophageus, 472
sacralis, 97
semilunaris, 186, 803
surgical anatomy of, 1378
Highmori, corpus, 1288
Hilum of kidney, 1251, 1258, 1437
topography of, 1425, 1437
of lung, 1094
topography of, 1399
of lymph glands, 995
of nucleus dentatus, 510
of olivary nucleus, 556
of ovary, 1311
of spleen, 1352
of suprarenal gland, 1345
Hind-brain, 33, 514
parts derived from, 514
Hind-gut, 38, 48
derivatives of the, 48
INDEX.
1515
Hinge -joints, 301
Hip-bone, 228
acetabnlum of, 228
architecture, 273
connexions of, 234
ilium, 228
morphology of, 294
nutrient foramina of, 234
obturator foramen of, 228
ossification of, 235
variations in, 281
Hip-joint, 339
disease, abscesses in, 1460
dislocation of, 1460
exposure of front of, 1459
movements at, 342
nerves to, 723, 724, 728, 729
surgical anatomy of, 1455, 1459
synovial stratum of, 341
Hippocampal commissure, 627
fissure, 626
Hippocampus, 625, 626, 627, 636
connexion of, with fornix, 625
with thalamus, 625
fimbria of, 627
inversus, 629
Hirschsprung's disease, 1423
Histology, 4
Homodont dentition, 1248
Homology, 2
of limb-bones, 294
of limb-girdles, 296
of scapula and ilium, 297
serial, 3
of vertebrae, 283
Homoplasy, 3
Horizontal fissure of cerebellum, 573
development of, 573
Horse-shoe kidney, 1268
Hour-glass stomach, 1172
Housemaid's knee, 1460
Huguier, canal of, 125
relation of, to tympanum, 834
Humero -femoral index, 289
Humero-ulnar joint, 323
Humerus, 204
anatomical neck of, 205
architecture of, 272
capitulum of, 208
connexions of, 209
coronoid fossa of, 208
deltoid tuberosity of, 207
distal extremity of, 208
epicondyles of, 207
epiphyses of, 209
groove for radial nerve, 207
head of, 205
intertubercular groove of, 206
morphology of, 294
nutrient foramina of, 209
olecranon of, 208
ossification of, 209
sexual differences of, 209
shaft of, 206
surgical anatomy of, 1449
trochlea of, 208
tubercles of, 205
variations in, 280
Humour, aqueous, 821
vitreous, 819
Huschke, foramen of, 832
Huxley, layer of, 860
Hyaloid artery, 826
history of, 819
canal, 826
development of, 819
fossa, 819
membrane, 819
Hyaloplasm, 8
Hydra, nervous system in, 497
Hydrocele, 1409
Hydronephrosis, caused by abnormal vessels,
1425
Hymen of vagina, 1322, 1325
carunculse hymenales of, 1325
development of, 1335
Hyo-epiglottic ligament, 1068
Hyo-glossal membrane, 1129
Hyo-glossus muscle, 462
action of, 463
nerve-supply of, 463
Hyoid arch, 43
muscles derived from, 496
produced from, 496
nerve of, 796
artery, of lingual, 892
of superior thyreoid, 892
bar, 43, 159
bone, 158
body of, 158
connexions of, 159
development of, 43, 159
greater cornua of, 159
lesser cornua of, 159
movements^ of, 463
ossification of, 159
surgical anatomy of, 1387
Hyparterial bronchus, 1083, 1097
Hypocartilaginous ring of membrana tym-
pani, 834
Hypochondriuni, 1159
Hypochordal bow, 103
spange, 936
Hypogastric artery, 936
abnormalities of, 1057
umbilical artery of, 939
relation of, to urachus, 939
nerves, 765, 766
plexus, 766
region, 1159
vein, 984
zone, 1158
Hypogastrium, 1158
surgical anatomy of, 1392
Hypoglossal nerve, 793
development of, 34
nucleus of origin of, 594
Hypophyseal artery, 902
fossa, 134, 183, 291
Hypophysis cerebri, 615, 616
arteries of, 902
development of, 34, 49, 616, 684
fossa of, 134, 183, 291
skiagrams of the sella turcica, 1374
infundibulum of, 616
method of exposure, 1374
surgical anatomy of, 1373
Hypothalamic tegmental region, 613
Hypothalamus, development of, 35
origin of, 517
pars mamillaris, 608, 609
optica, 608, 609
Hypotrochanteric fossa, 281
Hypsicephalic skulls, 286
1516
Heal artery, 932
Ileo-caecal artery, 932
fold, 1218
fossa, 1218
glands, 1217
orifice, 1214
valve, 1215
frenula of, 1214
structure of, 1215
topography of, 1421, 1443
vein, 990
Ileo-colic artery, 932
fossa, 1218
veins, 990
Ileo-sigmoidostomy, 1423
Ileum, 1208
diverticulum of, 1210
structure of, 1210
vessels and nerves of, 1210
Iliac arteries, 935
morphology of, 1048
colon, 1222
topography of, 1423
crest, 228, 238
topography of, 1423, 1443
fascia, 1157
fossa, 231
lymph glands, 1017
portion of fascia lata, 403
region, 1159
spine, anterior inferior, 229
anterior superior, 228
surface anatomy of, 1455, 1458
posterior inferior, 229
superior, 229
surface anatomy of, 1455
tuberosity, 230
veins, 983
Iliacus muscle, 410
action of, 411
nerve-supply of, 411
minor, 410
Ilio-capsularis muscle, 410
Ilio-coccygeus muscle, 494
Ilio-costalis cervicis muscle, 440
dorsi, 439
lumborum, 439
Ilio-femoral ligament, 340
Ilio-hypogastric nerve, 720
Ilio-inguinal nerve, 720
Ilio-lumbar artery, 938
abnormalities of, 1057
ligament, 337
inferior, 337
vein, 982
Ilio-pectineal eminence, 233
line, 231
Ilio-psoas muscle, 410
action of, 411
bursa of, 341, 410, 1459
nerve-supply of, 411
surgical anatomy of, 1459
Ilio-sacralis muscle, 494
Ilio-tibial tract, 404
relation of, to muscles, 416
surgical anatomy of, 1459, 1461
Ilio-trochanteric ligament, 340
Ilium, 228
anterior inferior spine of, 229
superior spine of, 228
arcuate line of, 231
auricular surface of, 230
INDEX.
Ilium (contd.), crest of, 228
fossa of, 231
gluteal lines of, 230
surface of, 230
greater sciatic notch of, 229
morphology of, 297
posterior inferior spine of, 229
superior spine of, 229
tuberosity of, 230
Immovable joints, 299, 300
Imperforate anus, 1233
Impressio trigemini, 130
Impression, gastric, of kidney, 1264
hepatic, of kidney, 1264
splenic, of kidney, 1264
Impressiones digitatse, 107
Incisions to evacuate pus in the palm, 1454
Incisive artery, 899
bundle, 451
centre, 150
fossa, 146
pad of palate, 1110
condition of, at birth, 1111
papilla palatina, 1110
suture, 149
Incisor crest, 149
foramen, 149, 174
fossa, 155
nerve, 780
teeth, 1115, 1116
eruption of, 1121
Incisura acetabuli, 234
cardiaca, 1095
cerebelli anterior, 574
posterior, 574
clavicularis, 107
ethmoidalis, 116
fibularis, 249
intertragica, 828
ischiadica major, 232
minor, 232
jugularis ossis occipitalis, 122
sterni, 107
mandibulae, 156
mastoidea, 128
nasalis, 115
pancreatis, 1205
parieto-occipitalis, 662
radialis, 211
scapulae, 201
semilunaris, 211
spheno-palatina, 152
supraorbitalis, 116
tentorii, 669
terminalis auris, 829
thyreoidea inferior, 1062
superior, 1062
ulnaris, 216
umbilicalis, 1189
vertebralis, inferior and superior, 89
of cervical vertebrae, 90
of lumbar vertebrae, 95
of thoracic vertebrae, 93
Inclinatio pelvis, 237
Incremental lines in ivory, 1114
Incudo-malleolar joint, 840
Incudo-stapedial joint, 840
Incus, 840
articulations of, 840
development of, 841
ligaments of, 840
movements of, 840
INDEX.
1517
Incus (contd.), processna lenticularis of, 840
Index, alveolar, 287
auricular, 828
cephalic, 286
dental, 287
facial, superior, 286
total, 287
gnathic, 287
humero-femoral, 289
innominate, 288
intermembral, 289
lumbar, 288
nasal, 287
orbital, 287
palato-maxillary, 287
pelvic, 288
platyknemic, 289
platymeric, 289
radio-humeral, 289
of sacrum, 99, 289
scapula, 288
superior facial, 286
thoracic, 114
tibio-fenioral, 289
vertical, of skull, 287
Indices of skulls, 284
Indifferent cells, 36, 503
Indusium griseum, 629
Inferior alveolar canal, 147
gluteal artery, 942
veins, 984
Infra -axillary region, 1397
Infraclavicular lymph glands, 1009
nerves, 703
region, 1397
Infracostal angle, 1397, 1407
plane, 1407, 1411
Infraglenoid tuberosity, 201
Infrahyoid artery, 892
muscles, 459
action of, 460
nerve -supply of, 460
Inframammary region, 1397
Infraorbital artery, 899
canal, 147, 162
relation of, to orbit, 162
variations in, 279
foramen, 146, 162
topography of, 1375
margin, 146
nerve, 777
plexus, 777
suture, 279
vein, 968
Infrapatellar bursa, 345
fat-pad, 348
Infrascapular artery, 917
Infraspinatus muscle, 375
action of, 375
nerve-supply of, 375
Infraspinous fossa, 202
Infrasternal depression, 108
notch, 1397, 1407
region, 1397
Infra temporal crest, 137, 167, 168
fossa, 168
Infratrochlear nerve, 773
Infundibuliform fascia, 475, 483, 1297
Infundibulo-pelvic ligament, 1435
Infundibulum of ethmoid, 141, 186, 803
relation of, to nasal fossae, 185
to orbit, 163
Infundibulum (contd.), of heart, 876
hypothalami, 541, 615
development of, 616
relation of, to third ventricle, 617
of pulmonary lobules, 1098
development of, 1099
of uterine tube, 1314
Inguinal canal, 1290, 1291
abdominal inguinal ring of, 483
fascia of, 483
subcutaneous inguinal ring of, 483
surgical anatomy of, 1408
walls of, 483
fossa, intermediate, 1235
lateral, 1235
medial, 1235
glands, 1013
hernia, surgical anatomy of, 1408, 1409
ligament, 477
region, 1458
rings, abdominal, 481, 483, 1408
position of, 1408
subcutaneous, 477, 1408
Inion, 166, 171, 285
topography of, 1358
Inner cell-mass, 21, 22
Innervation of muscles of limbs, laws of, 749
of skin of the limbs, 750
lower limb, 752
upper limb, 752
Innominate artery, 888
abnormalities of, 1051, 1052
development of, 1028
morphology of, 1047
topography of, 1405
veins, 1405
Inscriptions tendineae, 482
surface anatomy of, 1407
Insertion of muscles, 364
Inspiration, 474
muscles of, 373
Insula, 654
development of, 655
limen of, 654
opercula of, 655
sulcus centralis of, 654
Integument, 856
corium of, 857
papillae of, 857
structure of, 857
Interarticular ligaments, 302
of costo-trans verse joints, 314
of hip-joint, 339
of sterno-costal joints, 31 6
development of, 304
menisci, 302
of acromio-clavicular joint, 319
function of, 319
of distal radio-ulnar joint, 327
' of knee, 347
of mandibular joint, 312
of proximal radio-ulnar joint, 326
development of, 304
Interatrial septum of heart, 874, 875
abnormalities of, 1051
development of, 1033
sulcus of heart, 871
Intercavernous sinuses, 974
Intercentral articulations, 306
Interchondral joints, 315
Interclavicular ligament, 318
function of, 319
1518
INDEX.
Intercoccygeal joints, 309
Intel-columnar fascia, 477, 483
Intercondylic fossa of femur, 243
of tibia, 247
notch, 243
Intercostal aponeuroses, 470
arteries, 925
lymph glands, 1013
muscles, 470
action of, 474
nerve-supply of, 474
nerves, 713
spaces, 114
veins, 961
Intercosto-brachial nerves, 714
variations in, 716
Intercrural fibres, 477
Intercuneiform joints, 358
Interdigital veins of foot, 954
of hand, 924
Interglobular spaces of ivory, 1123
Interlobar fissures of lung, 1095
Intermaxillary suture, 148, 174
Intermediate visceral arteries, 1043, 1047
cutaneous nerve of thigh, 724
Intermedium, os, 295
Intermetacarpal articulations, 332
movements of, 334
Intermetatarsal articulations, 360
Intermuscular septa of arm, 378
of foot, 423
topography of, 1465
of leg, 422
of thigh, 403
topography of, 1459
Internal capsule, 610, 642
anterior limb of, 642
cerebro-spinal tract in, 642
genu of, 642
lenticulo-caudate fibres of, 642
lenticulo-thalamic fibres of, 642
motor tract of, 642
parts of, 642
posterior limb of, 642
retrolenticular fibres of, 642, 643
sublenticular fibres of, 642
ear, 843
mammary artery, 913
ligature of, 1398
structure of pons, 565
laternasal suture, 145
Interolivary stratum, 556
Interosseous arteries, 922
of dorsal carpal arch of foot, 923
groove of calcaneus, 259
of talus, 256
ligaments, calcaneo-cuboid, 357
carpal, 329
carpo-metacarpal, 332
cuboideo-navicular, 357
cuneo-cuboid, 358
cuneo-metatarsal, 359
intercuneiform, 358
intermetatarsal, 360
talo-calcaneal, 355
tibio-fibular, 350
membrane of forearm, 327
chorda obliqua of, 328
hiatus interosseus of, 327
of the leg, 350
muscles of foot, 432
action of, 435
Interosseous muscles of foot (contd.\ nerve-
supply of, 433-435
of hand, 391
action of, 395
nerve-supply of, 392-395
ridge of fibula, 252
of tibia, 248
veins of hand, 978
Interparietal bone, 124
sulcus, 664
Interpeduncular fossa, 54 1
ganglion, 614
relation of, to fasciculus retroflexus, 614
Interphalangeal joints of foot, 361
movements at, 361
of hand, 334
movements at, 334
position of, 1452
surgical anatomy of, 1452
Interpleural space, 1089
Interpubic fibro-cartilaginous lamina, 337
Interscapular region, 1436
Intersegmental association fibres of spinal
medulla, 535
vessels, 1043
Intersigmoid fossa, 1223
surgical anatomy of, 1423
Interspinales muscles, 445
Interspinous ligaments, 308
Intertarsal joints, 358
movements at, 361
synovial strata of, 334
Intertransversales muscles, 445
Intertransverse ligaments, 308
Intertrochanteric crest, 243
Intertubercular line, 1411
plane, 1411
Interventricular foramen, 618
sulcus of, 618
foramina, 543, 618, 621
grooves, 872, 873, 1035
septum, 876, 878
abnormalities of, 1050
development of, 1035
sulcus, 872
Intervertebral fibro-cartilages, 306
foramen, 89, 95
groove, 89
Intestinal arteries, 932
lymph trunks, 997
veins, 992, 1210
Intestine, 1178
aggregated lymph nodules of, 1181
agminated glands of, 1181
basement membrane of, 1179
caecum, 1211
circular folds of, 1180, 1209
colon, ascending, 1121
descending, 1211
transverse, 1211
development of, 1250
duodenal glands of, 1179, 1186
epithelium of, 1179
intestinal glands of, 1179, 1212
lamina muscularis mucosa, 1179
large intestine, 1121
appendices epiploicse of, 1211-1212
divisions of, 1211
haustra of, 1212
length of, 1211
nerves of, 1211
plicae semilunares, 1212
INDEX.
1519
Intestine, large (contd.), structure of, 1212
tajnise of, 1211, 1212
topography of, 1419, 1421
vessels of, 1212
left flexure of colon, 1211
length of, 1177
lymph vessels of, 1212
mucous membrane of, 1179
of anal canal, 1229
of large intestine, 1212
of small intestine, 1210
structure of, 1210
muscular coat of, 1178
of anal canal, 1229
of large intestine, 1212, 1223
of rectum, 1226
of small intestine, 1210
structure of, 1210
plicae circulares of, 1180
position of coils of, 1178, 1181, 1210, 1212
rectum, 1211
retiform tissue of, 1179
right flexure of colon, 1211
rotation of loop, 48 -
serous coat of, 1178
of large, 1212
of small, 1210
small intestine, 1177
coils of, 1208
divisions of, 1177
duodeno-jejunal flexure of, 1182
topography of, 1419
lacteals of, 1210
Meckel's diverticulum of, 1210
mesentery of, 1208
nerves of, 1210
topography of, 1419
vessels of, 1210
solitary lymph nodules of, 1181, 1210, 1212
structure of, 1178
submucous coat of, 1179, 1212, 1213
surgical anatomy of, 1419
tela submucosa of, 1179
tunica mucosa of, 1179
villi of, 1179
Intestinum caecum, 1213
crassum, 1210
ileum, 1208
jejunum, 1208
rectum, 1224
tenue, 1208
mesenteriale, 1178
Intracranial lymph vessels, 1003
Intrajugular process, 122
Intumescentia cervicalis, 519 '
lumbalis, 519
Inversion of foot, 361
muscles producing, 436
Iris, 813
blood-vessels of, 813
ciliary margin of, 813
circulus arteriosus major, 813
minor, 813
dilator pupillae of, 814
ligamentum pectinatum of, 810
muscular fibres of, 814
nerves of, 814
pupil of, 814
pupillary border of, 814
membrane of, 813
sphincter pupillae of, 814
stroma of, 813
Irregular tubules of kidney, 1267
Ischial spine, 232
sexual differences of, 237
topography of, 1455
tuberosity, 232
sexual differences of, 238
topography of, 1455
Ischio-bulbosus muscle, 487
Ischio-capsular ligament, 341
Ischio-cavernosus muscle, 488
Ischio-coccygeus muscle, 495
Ischio-pubicus muscle, 488
Ischio-rectal fossa, 1238, 1431
Ischium, 232
acetabulum, notch of, 232
body of, 232
morphology of, 295
rami of, 232
spine of, 232
tuberosity of, 232
Island of Reil, 654, 655
limiting sulcus of, 654
opercula of, 655
Isthmus of acoustic meatus, 830
of auditory tube, 827
of brain, 515
of cartilage of ear, 829
of fauces, 1112
level of, 1442
pharyngo-nasal, 1141, 1145
of pharynx, 1112
rhombencephali, 34
of thyreoid gland, 1347
topography of, 1388
of uterine tube, 1314
Iter chordae anterius, 834
posterius, 834
Ivory, 1113, 1123
development of, 1247
formation of, 1247
structure of, 1123
fibrils, 1123
development of, 1245
papilla, 1244, 1245
sheaths, 1123
development of, 1245
tubes, 1123
development of, 1245
Jacobson, nerve of, 786
vomero -nasal organ of, 802
Jaw, alveoli of, 148, 155
formation of, 1123
Jejunum and ileum, lymph vessels
1210
structure of, 1210
surgical anatomy of, 1420
vessels and nerves of, 1210
Joints, 299
development of, 304
abduction, 303
acromio-clavicular, 373
movements at, 319, 373
topography of, 1444
adduction, 303
adipose tissue of, 302
amphiarthrodial, 300, 301
development of, 304
ankle, 351
surgical anatomy of, 1463
arthrodial, 301
articular capsules, 302
of,
1520
INDEX.
Joints, articular capsules (contd.), topography
of, 1464
discs, 302
atlanto-epistroplieal, 309
movements at, 311
of auditory ossicles, 840
ball and socket, 301, 303
biaxial, 301
calcaneo-cuboid, 357
ligaments of, 357
surgical anatomy of, 1464
topography of, 1464
calcaneo-taloid, 354
surgical anatomy of, 1464
capsule of, 302
carpal, 329
movements at, 334
carpo-metacarpal, 332
cavity of, 301
circumduction, 303
classification of, 299
of clavicle, 317
co-aptation in, 303
condyloid, 301
costo-central, 313
costo-chondral, 315
topography of, 1398
cos to -sternal, 315
costo-transverse, 314
costo-vertebral, 313
crico-arytaenoid, 1066
crico-thyreoid, 1065
cubo-cuneiform, 357
cuneo-navicular, 357
development of, 304
diarthrodial, 301
development of, 304
elbow, 323
enarthrodial, 301
extension, 303
of finger, 334
flexion, 303
of foot, 351
nerves of, 731, 734
gliding, 303
hinge, 304
hip, 339
humero-radial, 323
humero-ulnar, 323
immovable, 299, 300
development of, 304
incudo-malleolar, 840
incudo-stapedial, 840
of inferior extremity, 339
interarticular ligaments, 302
intercarpal, 329
intercentral, 307
interchondral, 315
intercoccygeal, 309
intercuneiform, 358
intermetacarpal, 332
movements at, 334
intermetatarsal, 360
interneural, 307
interphalangeal, of foot, 334, 361
movements at, 334, 361
of hand, 334
movements at, 334
topography of, 1452, 1465
interpubic, 337, 338
intertarsal, 354, 358
synovial strata of, 334
Joints (contd.), knee, 342
of larynx, 1065
lumbo-sacral, 335
mandibular, 312
menisci, 302
metacarpo-phalangeal, 333
movements at, 334
surgical anatomy of, 1454
topography of, 1452
metatarso-phalangeal, 360
movements at, 361
surgical anatomy of, 1464, 1465
topography of, 1464, 1465
movable, 300
development of, 304
movements at, 303
multiaxial, 301, 303
occipito-atloid, 309
movements at, 311
of pelvis, 335
pisi -cuneiform, 330
of pisiform bone, 331
radio-carpal, 328
surgical anatomy of, 1450
topography of, 1456
radio-humeral, 323
topography of, 1449
radio-ulnar, distal, 327
proximal, 326
rotation, 303
sacro-coccygeal, 308
sacro-iliac, 335
topography of, 1455
scapulo-clavicular, 318
shoulder, 320
sternal, 315
sterno-clavicular, 317
action of muscles on, 373
movements at, 319, 373
surgical anatomy of, 1444
sterno- costal, 315
structures of, 302
synarthrodial, 301, 303
synovial stratum, 302
talo-calcaneal, 354
topography of, 1464
talo-calcaneo-navicular, 355
movements at, 361
tarsal, transverse, 357
movements at, 361
tarso-metatarsal, 359
movements at, 361
surgical anatomy of, 1464
temporo-mandibular, see Joint, mandibular
of thorax, 313
tibio-fibular, 349
movements at, 350
toe, 361
transverse carpal, 330
tarsal, 357
uniaxial, 301
of upper extremity, 317
varieties of movements in, 303
of vertebral column, 305
with cranium, 310
wrist, movements at, 334
xiphisternal, 316
level of, 1397, 1407, 1442
Juga alveolaria, 155
Jugal point, 286
Jugular foramen, 176, 177, 182
fossa, 177
INDEX.
1521
Jugular fossa (contd.}, development of, 133
relation of, to jugular foramen, 177
to tympanum, 1369
ganglion, superior, 785
lymph trunk, 998
notch, 122
Jugular process, 122, 172, 177
tubercle, 122
veins, 966
primitive, 1038, 1039
remains of, in adult, 1038, 1039
Junctional tubules of kidney, 1266
Junctura ossium, 299
Karyokiiiesis (mitosis), 9
Karyolymph, 8
Karyoplasm, 8
Karyo-reticulum, 8
Keratin, 858
Kerkring, ossicle of, 124
Kidneys, 1257
abnormal vessels, 1425
adipose capsule of, 1259 ,
anterior surface of, 1262
relations, 1262
arciform arteries of, 1267
area cribrosa of, 1265
arteries of, 1267
ascending limb of Henle's loop, 1266
irregular tubule, 1266
base of the pyramids, 1265
calyces, 1268
development of, 1331
capsula adiposa of, 1259
capsule of, 1259
collecting tube, 1266
columns of Bertin of, 1265
connective tissue of, 1266
convoluted part of, 1265
corpuscles of, 1266
cortex of, 1265
descending limb of Henle's loop, 1266
loop of Henle, 1266
development of, 1331
dimensions of, 1257
duct of, 1268
excretory tube, 1266
exposure of, from behind, 1438
extremities of, 1265
fascia renalis of, 1259
first convoluted tubule, 1266
fixation of, 1260
foramina papillaria of, 1265
gastric impression of, 1264
glomeruli of, 1266
hepatic impression of, 1264
hilum of, 1257, 1258, 1425, 1437
topography of, 1437
horse-shoe, 1268
interlobular arteries, 1267
Junctional tubule, 1266
lateral border of, 1261
left, 1263
lobes of, 1265
medullary substance of, 1265
nerves of, 1267
oblique incision for exposure of, 1438
papillae of, 1265
papillary part, 1265
paranephric fat of, 1209
pars radiata, 1265
convoluta, 1265
Kidneys (contd.), pelvis of, 1268
perinephric fat of, 1259
surgical anatomy of, 1425
position of, 1257, 1423
from behind, 1437
posterior relations of, 1260
surface of, 1260
primitive, 1331
pyramids of, 1265
on section, 1265
relations of, 1262
anterior, 1262
left, 1425
posterior, 1260
right, 1262, 1425
renal columns, 1265
corpuscles of, 1266
development of, 1333
reniculi, 1265
second convoluted tubule, 1266
sinus renalis, 1257, 1265
skiagraphs of pelvis of, 1426
splenic impression of, 1264
surface impressions of, 1264
surgical anatomy of, 1264
tubules of, 1266
development of, 1333
tunica fibrosa of, 1257
ureter of, 1268
development of, 1331
variations in, 1267
vasa afferentia of, 1267
efferentia of, 1267
development of, 1331
veins of, 1267
vessels of, 1267
arteriolae rectae, 1267
interlobular arteries, 1267
vasa afferentia, 1267
visceral surface of, 1262
Kink, intestinal, of Arbuthnot Lane, 1423
Knee-joint, 342
alar folds of, 348
articular surfaces of, 342
bursae connected with, 348
surgical anatomy of bursae, 1460
ligaments of, 344
menisci of, 347
surgical anatomy of, 1460
movements at, 348
muscles producing, 421
nerves of, from common peroneal nerve, 730
from femoral nerve, 724
from obturator nerve, 724
from sciatic nerve, 728, 729
from tibial nerve, 732
surgical anatomy of, 1460
synovial stratum of, 348
surgical anatomy of, 1461
Knuckles, prominences of, 1452
Krause, corpuscles of, 863
end-bulbs of, 864
Kronlein's method for cranio - cerebral topo-
graphy, 1360
Labia majora, 1324
commissures of, 1324
development of, 1336
minora, 1324
oris, 1108
Labial artery, branch of external maxillary
artery, 806
1522
INDEX.
Labial artery (contd.}, branch of superficial
perineal artery, 1324
glands, 1109
nerves, 1324
veins, 1324
Labio-scrotal folds, 1328
Labium anterius orificii externi uteri, 1316
externum cristae iliacae, 228
internum cristae iliacae, 228
oris inferius, 1108
superius, 1108
posterius orificii extend uteri, 1316
Labrum glenoidale of hip joint, 340
Labyrinth of ethmoid, 140
membranous of ear, 846
acoustic nerve in, 852
blood-vessels of, 853
cochlea of, 846
development of, 853
ductus endolymphaticus of, 847
reuniens of, 847
utriculosaccular, 847
endolymph of, 762, 846
hair-cells of crista acustica of, 848
of maculae of, 847
of spiral organ of Corti of, 847
mascula acustica utriculi, 846
otoconia of, 847
perilymph of, 846
recessus utriculi, 846
saccule of, 846
saccus endolymphaticus of, 847
semicircular ducts of, 847
sinuses superior and inferior of, 846
spiral organ of Corti of, 850
utricle of, 846
utricular sinus of, 847
Labyrinth, osseous, of ear, 843
cochlea of, 843
development of, 853
perilymph of, 846
vestibule of, 843
Lacertus fibrosus, 380
Lacrimal apparatus, 824, 1377
ampulla of, 825
surgical anatomy of, 1377
artery, 816
bone, 143, 163
ossification of, 144
relation of, to nasal fossae, 187
to orbit, 163
membranous, 825
development of, 827
caruncle, 821
crest, anterior (maxillae), 148
posterior (of lacrimal), 143
ducts, 825
fossa, 148, 163
gland, 824
inferior, 824
superior, 824
surgical anatomy of, 1377
groove, 143, 163
relation of, to orbit, 163
of maxilla, 187
nerve, 772
papillae, 821
plica, of Horsner, 825
process, 143
puncta lacrimalia, 825
sac, 825
development of, 49
Lacrimal sac (contd.\ surgical anatomy of, 13 1 /
sinus of Arlt, 825
sinus of Maier, 825
valve of Beraud, 825
inferior part, 824
superior part, 824
Lacteals, 1210
Lactiferous ducts, 1338
Lacunae of bone, 84
lateral sagittal, 974
urethral, 1309
Lacus lacrimalis, 821
Lagena cochleae, 849
Lambda, 171, 285
topography of^ 1358
Lambdoid suture, 171
topography of, 1360
Lamellae, fundamental, 84
interstitial, 84
osseous, 84
Lamina or Laminae
alar, 36, 505
basal, 36, 505
basal, of chorioid, 812
basilar, of chorioid, 811, 812
chorio-capillaris, 811
development of, 608
cribrosa of ethmoid, 139
sclerae, 808
of temporal bone, 131
dental, 1245
elastic, anterior, 810
posterior, 810
fibro-cartilaginous, interpubic, 337
fibrosa, 139
fusca, 808
lateralis process us pterygoidei, 137
medialis processus pterygoidei, 137
tubae auditivae, 838
medullary, lateral and medial, of thalanms
610, 611
of lentiform nucleus, 639
membranacea tubae auditivae, 838
papyracea of ethmoid, 140
perpendicular of ethmoid, 139, 140
quadrigemina, 584
reticularis, 851
septi pellucidi, 632
spiralis ossea, 845
secundaria, 845
suprachorioidea, 811
terminalis, 33, 616
of thyreoid cartilage, 1062
vasculosa of chorioid, 811
vertebral, 88, 90, 91, 93, 95
Landzert, fossa of, 1185
Lunghan's layer, 59
Lanugo, 862
Large intestine, 1210
Laryngotomy, 1388
Larynx, 1061
action of intrinsic muscles of, 1076
aperture of, 1068
appendix of ventricle of, 1071
articulations of, 1065
ary-epiglottic folds of, 1068
arytaenoid cartilages, 1064, 1074
apex of, 1064
base of, 1065
oblique muscles of, 1074
processus muscularis of, 1065
vocalis of, 1065
INDEX.
1523
Larynx, arytaenoid cartilages (contd.), surfaces
of, 1064
blood-vessels of, 911
cartilages of, 1062
development of, 1100
ossification of, 1065
cavity of, 1068
construction of, 1062
conns elasticus of, 1066
corniculate cartilages, 1065
crico -arytaenoid joints, 1066
crico-tliyreoid joints, 1065
cuneiform cartilages, 1065
in deglutition, 1077
development of, 1100
epiglottic cartilage, 1065
epithelium of, 1072
folds of, 1068
glands of, 1072
glottis, intercartilaginous part of, 1070
intermembranous part of, 1070
rima vestibuli of, 1070
growth -alterations of, 1077 *
hyo-thyreoid membrane of, 1066
interior of, 1068
intrinsic muscles of, 1072
joints of, 1065
laryngoscopical appearance of, 1077
ligaments of, 1066
lowest compartment of, 1071
middle compartment of, 1069
mucous glands of, 1072
membrane of, 1071
muscles of, 1072
nerves of, 788, 789
pars intercartilaginea of rima glottidis, 1071
intermembranacea, 1071
philtrum ventriculi of, 1069
piriform recess of, 1069
position and relations of, 1061
sesamoid cartilage of, 1065
sexual differences in, 1077
tubercle of Santorini of, 1065, 1069
tuberculum epiglotticum of, 1069, 1073
ventricle of, 1071
ventricular folds of, 1070
vessels and nerves of, 1077
vestibule of, 1069
vocal folds of, 1070
mucous membrane of, 1071
relation of, to thyreo - arytaenoideus
muscle, 1073
topography of, 1387
vocalis muscles of, 1076
Lateral angle, inferior, of sacrum, 99
fissure of the brain, 653
development of, 655
line, sense organs of, 501, 796
mass of atlas, 91
of sacrum, 99
ossification of, 106
part of occipital, 113
development of, 293
plantar vessels, position of, 1465
plates, mesodermic, 27
recess of fourth ventricle, 549
ventricles, 632
Latissimus dorsi muscle, 366
action of, 368
nerve-supply of, 368
topography of, 1437
Layers of blastoderm, 21
Layers of blastoderm (contd.\ germinal, 21
Left colic flexure, 1220
surgical anatomy of, 1422
Leg, development of, 39
fasciae of, 422
intermuscular septa of, 422
lymph vessels of, 1013
muscles of, 424
surgical anatomy of, 1461
Lemniscus, 560
connexion of, with cochlear nuclei, 586
with geniculate body, 591
with quadrigeminal body, 590
with superior olive, 556
with thalamus, 562, 591
decussation of, 560
interolivary stratum of, 568
lateral, 570, 584, 585, 586, 590, 606
nucleus of, 606
medial, 560, 561, 568, 570, 586, 590, 613
in mid-brain, 568, 570, 585, 590
in pons, 590
Lens, crystalline, 819
axis of, 820
capsule of, 819
cortical substance of, 820
curvatures of, 820
development of, 826
at different ages, 820
epithelium of, 820
history of, 826
equator of, 820
fibres of, 820
history of, 826
laminae of, 820
nucleus of, 820
poles of, 820
radii of, 820
refractive index of, 820
substance of, 820
suspensory ligament of, 819
vascular tunic of, 826
vesicle, 825
Lenticular process of incus, 840
Lenticulo-optic artery, 905
Lenticulo-striate artery, 905
Lentiform nucleus, globus pallidus of, 638,
639
medullary laminae of, 639
putamen of, 639
surfaces of, 638
Leptoprosope skulls, 286
Leptorhine skulls, 287
Lesions of the spinal medulla, 1444
Lesser multangular bone, 220, 295
Levator ani muscle, 493
action of, 495
cushion, 1143
glandulae thyreoideae, 1347
palpebrae superioris muscle, 452
action of, 454
nerve -supply of, 454
prostatae muscle, 494
scapulae muscle, 368
action of, 368
nerve -supply of, 368
veil palatini muscle, 466
action of, 467
nerve-supply of, 467
Levatores costarum muscles, 470
action of, 474
nerve-supply of, 474
1524
INDEX.
Level of structures in relation to spines of
vertebrae, 1442
Lien, 1352
accessor! us, 1353
artery of, 929
Lieno-renal ligament, 1236
development of, 1252
Ligament or Ligaments, 302
acetabular, transverse, 339
of acromio-clavicular joint, 319
adventitious, 305
alar, 311
of ankle-joint, anterior, 352
lateral, 352
posterior, 352
annular, of ankle (O.T.), 352
of radius, 326
of wrist (O.T.), 1451
surgical anatomy of, 1451
of stapes, 841
anterior costo-transverse, 314
covering atlanto-epistropheal, 309
of elbow-joint, 324
radio-ulnar, 327
sterno-clavicular, 318
of apex of dens, 311
arcuate, middle, of diaphragm, 472
arcuate of pubis, 338
arteriosum, 68
atlanto-epistropheal, 309, 310
of atlanto-occipital joint, 310
atlanto-occipital, 310
of atlas, transverse, 310
of auditory ossicles, 841
auriculare anterius, 829
posterius, 829
superius, 829
basium ossium metacarpalium, 360
metatarsalium, 360
bifurcate, 356, see Ligaments calcaneo-
navicular, calcaneo-cuboid
of Bigelow, 340
of bladder, 1280, 1283, 1303
broad, of uterus, 1238
surgical anatomy of, 1434
calcaneo-cuboid, 357
calcaneo-fibular, 352
calcaneo-metatarsal, 423
calcaneo-navicular, plantar, 355
part of bifurcate, 356
function of, 355
surgical anatomy of, 1464
capituli costse interarticulare, 1242
radiatum, 314
fibulae, 350
capitulorum ossium metacarpalium trans-
versa, 333
metatarsalium transversa, 360
carpal, 329
carpo-metacarpal, 332
dorsal, 332
interosseous, 332
volar, 332
collateral, of metacarpo-phalangeal joints, 333
of patella, 404
colli costae, 315
columnae vertebralis et cranii, 305
conjugal, of ribs, 314
conoid, 319
function of, 319
tubercle, 198
coraco-acromial, 320
Ligament or Ligaments (contd.)
coraco-clavicular, 319
coraco-glenoid, 322
coraco-humeral, 322
relation of, to pectoralis minor muscle, 322
corniculo-pharyngeal, 1066
coronary, 1195, 1196
of knee, 348
costo-clavicular, 318, 319
relations of, to movements of clavicle, 319
costo-colic, 1220
costo-coracoid, 369
of costo-sternal joints, 316
of costo-transverse joints, 314
costo-vertebral, 313
costo-xiphoid, 316
cotyloid, 340
of cranium, 313
crico-arytaenoid, posterior, 1066
crico-thyreoid, 1067
cruciate of atlas, 311
genu, 346
relation of, to movements at knee, 348
cruciatum anterius (of knee), 346
posterius, 347
cruris, 423
cruciform, of atlas, 311
cuboideo-navicular, 357
cuneo-cuboid, 358
cuneo-metatarsal, 359
cuneo-navicular, 357, 358
of apex of, 311
of dens, 92, 311
deltoid, 352
denticulate, 518
of elbow-joint, 323
epiglottic, 1067
falciform, 1196, 1235
development of, 1252
topography of, 1415
fibular collateral, 345
flava, 308
gastro-colic, 1162, 1170, 1242
gastro-lienal, 1162, 1170, 1236, 1240
gastro-phrenic, 1170, 1236
gleno -humeral, 322
glenoid, 322
glosso-epiglottic, 1067
of head of fibula, anterior, 350
posterior, 350
of heads of ribs, 313
hepato-duodenal, 1162, 1183, 1197
hepato-gastric, 1162, 1170, 1197
hepato-renal, 1197
of hip-joint, 339
hyo-epiglottic, 1068
hyo-thyreoid, lateral, 1066
middle, 1066
ilio-femoral, 340
ilio-lumbar, 337
ilio-trochanteric, 340
of incus, 840
inferior transverse scapular, 320
infundibulo-pelvic, 1435
inguinal, 477
reflex (Collesi), 478
interarticular, 302
development of, 304
of costo-transverse joints, 314
of head of rib, 314
of hip-joint, 339
of sacro-coccygeal joint, 308
INDEX.
1525
Ligament or Ligaments (contd.) -
interarticular (contd.), of sternal-costal joints,
316
intercarpal dorsal, 330
interosseous, 330
volar, 320
interchondral, 317
interclavicular, 318
intercuneiform, interosseous, 358
intermetatarsal, 360
interosseous, of carpal joints, 329
of carpo-metacarpal joints, 332
cuneo-cuboid, 358
of intertarsal joints, 357
of tarso-metatarsal joints, 359
of tibio-fibular joint, inferior, 350
interspinous, 308
intertransverse, 308
ischio-capsular, 341
relation of, to movements at hip-joint,
342
jugal, 314
of knee-joint, 344, 346
posterior, 345
topography of, 1458
laciniatum, 422
lacunar (Qimbernati), 405, 477
of larynx, 1066
of lateral malleolus, anterior, 351
distal, 351
interosseous, 351
posterior, 351
lateral radio-carpal, 328
latum uteri, 1318
lieno-renal, 1252
development of, 1253
of liver, 1196
longitudinal anterior, of vertebral column,
307
posterior, of vertebral column, 307
long plantar, 357
lumbo-costal, 315
lumbo- sacral, 335
malleolar, 351
of malleus, 841
of mandibular joint, 312
medial ulno-carpal, 328
metacarpo-phalangeal, 333
metatarsal transverse, 360
metatarso-phalangeal, 360
morphology of, 305
of neck of rib, 315
nuchae, 308
obliquum genu, 345
occipito-epistropheal, 310
orbito-tarsal, 1378
of ossicles of ear, 841
of ovary, 1311
palmar, 328-332
palpebral, topography of, 1377
of eyelids, 822
patellar, 345
collateral, 344, 409
relation of, to fascia lata, 344
topography of, 1460
pectinatum of iris, 810
of pelvis, 336
of peritoneum, 1162, 1196
phrenico-colic, 1220, 1242
of pinna, 829
pisi-metacarpal, 328, 331
pisi-unciform, 331
Ligament or Ligaments (contd.)
plantar, 355, 357
long, 357
popliteal, 342
posterior costo- transverse, 315
costo-sternal, 316
covering atlanto-epistropheal, 310
of elbow -joint, 324
radio-ulnar, 327
sterno-clavicular, 318
pterygo-spinous, 313
pubic, anterior, 337
arcuate, 338
posterior, 337
superior, 337
pubo-capsular, 340
pubo-vesical, lateral, 493
middle, 493
pulmonale, 1086
of pylorus, 1174
radial collateral carpal, 331
radiate carpal, 330
of head of rib, 314
sterno-costal, 316
radio-carpal, 328
radio-ulnar, 326
round, of liver, 1197
development of, 1255
of uterus, 1319
surgical anatomy of, 1434
sacro-coccygeal, 308
sacro-iliac, anterior, 336
interosseous, 336
long posterior, 336
posterior, 336
short posterior, 336
sacro-spinous, 337
sacro-tuberous, 337
processus falciformis of, 337
of scapula, 320
of shoulder-joint, 321
spheno -mandibular, 312
development of, 158
spirale cochleae, 849
of stapes, 841
of sterno-clavicular joint, 318
relation of, to movements of clavicle, 319
sterno-costal, 315
sterno-pericardial, 881
stylo-hyoid, 313
development of, 159
stylo-mandibular, 313, 1134
relation of, to parotid fascia, 1134
superficial transverse metacarpal, 384
metatarsal, 423
superior transverse scapular, 320
supraspinous, 308
suspensory, of clitoris, 1326
of fascia bulbi, 807
of lens, 819
of ovary, 1311
of penis, 1299
talo-calcaneal, 354-5
anterior, 354
interosseous, 355
lateral, 354
medial, 355
posterior, 355
talo-fibular, anterior, 352
posterior, 352
talo-navicular, 356
dorsal, 356
1526
INDEX.
Ligament or Ligaments (contd.}
talo-tibial, 353
tarsal, of eyelids, 822
tarso-metatarsal, dorsal, 359
interosseous, 359
plantar, 359
temporo-mandibular, 312
teres femoris, 341
relation of, to movements at hip-joint, 342
of liver, 1196
of uterus, 1319
thyreo-arytaenoid, 1067
thyreo-epiglottic, 1068
tibio-fibular, 349
tibio-navicular, 353
transverse, of acetabulum, 339
of atlas, 310
cruris, 423
genu, 348
of the heads of the metacarpal bones,
333
humeral, 321
metacarpal, 332
superficial, 384
metatarsal, 390
superficial, 423
pelvis, 493
perineal, 338
scapulae inferius, 320
superius, 320
trapezoid, 319
relation of, to movements of clavicle,
319
triangular, 1196
left, 1196
of tubercle of rib, 315
of tympanic membrane, 834
ulnar collateral carpal, 331
utero-sacral, 1318
of uterus, 1318
bursa ovarica of, 1318
vaginal, 384
venae cavae sinistrae, 882
venous, of Arantius, 1196
ventricular, of larynx, 1067
of vertebral column, 305
vocal, 1067
volar accessory, 333
Ligamentum carpi dorsale, 383
transversum, 382
denticulatum, 675
gastro-colicum, 1162
gastro-lienale, 1162
hepato-colicum, 1162
hepato-duodenale, 1162
hepato-gastricum, 1162
ovarii proprium, 1312
patellae, 408
pectinatum iridis, 810
suspensorium ovarii, 1312
teres hepatis, 1191
umbilicale medium, 1235, 1274
Limb-girdles, 295
Limb-plexuses, significance of, 753
Limbs, arteries of, morphology of, 1047
development of, 39, 1031
dorsal axial line of, 751
morphology of, 297
of muscles of, 495
of nerve-plexuses of, 741
nature of, 741
lower borders of primitive, 742
Limbs (contd.\ upper borders of primitive,
741
plexuses, composition of, 742
formation of, 680
morphology of, 741
variations in position, 752
post-axial border of, 741, 742
pre -axial border of, 741, 742
segmental relations of, 741
surfaces of, 742
ventral axial line of, 751
Limbus alveolaris mandibulaa, 155
maxillae, 148
fossae ovalis, 874
laminae spiralis, 849
Limen insulae, 654
nasi, 802
Limiting sulcus of Reil, 654
Line or Linea, alba, 476
surgical anatomy of, 1409, 1410
ano -cutaneous, 1232
aspera of femur, 242
axillary, 741, 1397
base, of Reid, 1360
of chest, 1397
dorsal axial, of limbs, 751
epicondylic, 207
epiphyseal, 85
gltiteal, anterior, 230
inferior, 230
posterior, 230
incremental, 1114
intercondyloid, 243
intermedia cristae iliacae, 228
intertrochanteric, 240
intertubercular, 1411
lateral cerebral, 1360
lateral sense-organs of, 796
mammary, 1397
mid-lateral, of thorax, 1089
mylo-hyoid, 156
of Nelaton, 1455
nuchal, 171
of occipital bone, 121
superior, 121
suprema, 121
obliqua mandibulae, 155
oblique, of tibia, 249
parasternal, 1397
pectinea, 231
pectineal, of femur, 242
of pleural reflection, 1399
popliteal, of tibia, 249
post-central, 1360
of Poupart, 1411
pre -central, 1360
scapular, 1397
of Schreger, 1128
semicircularis, 483
semilunaris, 482
spiral, of femur, 242
splendens, 675
sternal, 1397
subcostal, 1407
temporalis inferior, 118
ossis frontalis, 116
superior, 118
terminalis, of pelvis, 231, 232
relation of, to small pelvis, 232
ventral axial, of limbs, 751
white, of anus, 1232
Lingual artery, 892, 1130
INDEX.
1527
jingual artery (contd.}, development of, 1028
surgical anatomy of, 1382, 1383, 1391,
1393
; glands, 1130
gyms, 660
lymph glands, 1130
nerve, 1131
septum, 1129
tonsil, 1126
surgical anatomy of, 1383
tubercles of teeth, 1117
veins, 965, 1130
surgical anatomy of, 1382
Lingualis muscle, inferior, 463
superior, 463
, Lingula cerebelli, 575
mandibulae, 156
sphenoidalis, 134
Linin, 8
Lip, rhombic, 554
^Lips, 1108
commissures of, 1108
development of, 1244
frenulum of, 1108
glands of, 1109
surgical anatomy of, 1379
lymph vessels of, 1005
mucous membrane of, 1109
nerves of, 1109
philtrum of, 1108
structure of, 1109
sulcus mento-labialis of, 1108
naso-labial of, 1108
surgical anatomy of, 1379
tubercle of, 1109, 1379
vessels of the, 1109
Liquor folliculi, 1313
Lisfranc, ligament of, 1464
Lisfranc's amputation, 1464
joint, 1465
Lister's incision for excision of wrist, 1451
Liver, 1187
areolar coat of, 1198
arteries of, 1120
bile-ducts of, 1201
interlobular, 1201
capsule of Glisson of, 1190
cardiac depression of, 1190
caudate lobe of, 1192
cells of, 1199
in child, 1195
colic impression of, 1194
congenital irregularities in, 1195
coronary ligament of, 1195, 1196
development of, 47, 1254
duodenal impression of, 1194
excretory ducts of, 1201
development of, 1255
falciform ligament of, 1196
development of, 1252, 1255
topography of, 1415
fibrous coat of, 1198
fissures of, 1191
fixation of, 1195
form of, 1187
variations in, 1194
fossa ductus venosi, 1191
of gall-bladder, 1191, 1192
for ligamentum teres hepatis, 1191
sagittalis sinistra of, 1189
of umbilical vein, 1191
of venae cavae, 1191, 1192.
Liver (contd.), fossa vesicae felleae, 1191
gall-bladder, 1201
gastric, impression of, 1193
hepatic duct of, 1201
impressio colica, 1194
duodenalis, 1194
gastrica, 1193
oesophagea, 1189, 1192
renalis, 1194
suprarenalis, 1192
incisura umbilicalis, 1189
vesicse felleae, 1189
inferior margin of, 1189
surface of, 1193
interlobular ducts of, 1200
left sagittal fissure of, 1191
ligaments of, 1196
lobes of, 1191
left, 1191
right, 1191
topography of, 1415
lobules of, 1198
lobus caudatus, 1191, 1192
quadratus, 1191, 1192, 1193
lymph vessels of, 1201
margin, inferior, 1189
posterior, 1189
nerves of, 1201
notch of gall-bladder of, 1191, 1192
oesophageal groove of, 1192
omental tuberositv of, 1193
parietal surface of, 1188
peritoneal relations of, 1195
physical characters of, 1187
pons hepatis of, 1191
porta hepatis, 1190, 1196
portal canals of, 1200
position of, 1194
variations in, 1194
posterior surface of, 1192
processus caudatus, 1191, 1192
quadrate lobe of, 1193, 1194
relation to peritoneum, 1195
renal impression of, 1194
Riedel's lobe of, 1195
round ligament of, 1196
development of, 1191
serous coat of, 1196
shape of, 1188
size of, 1188
variations in, 1194
and weight of, 1188
structure of, 1198
suprarenal impression of, 1192
surface markings, 1194, 1415
surgical anatomy from the back, 1439
tuberculum papillare of, 1192
tuber omentale of, 1193
umbilical fissure of, 1191
notch of, 1191
uncovered area of, 1192, 1196
variations in form and position, 1194
veins of, 980, 990
central, 1198, 1200
interlobular, 1199, 1200
sublobular, 1198, 1200
vessels of, 1199
visceral surface of, 1193
weight of, 1188
Lobe or Lobus, anterior of hypophysis, 616
azygos of lung, 1096
caudate, of liver, 1192
1528
INDEX.
Lobe or Lobus (contd.), cen trails cerebelli, 575
cerebellar, 575
cerebral, 654
culminis cerebelli, 575
declivis of cerebellum, 575
frontal, of brain, 665
hepatis, 1191
insulae, 654
of lung, 1095
development of, 1101
mammae, 1337
noduli of cerebellum, 572, 576
occipital, of brain, 660
topography of, 1360
olfactory, of brain, 624
development of, 624
relation of, to anterior commissure, 626
parietal, of brain, 662
piriform, 624
posterior, of hypophysis, 616
of prostate gland, 1306
pyramidal, of thyreoid gland, 1347
development of, 1348
pyramidis of cerebellum, 576
quadrate, of liver, 1193
of Kiedel, 1195
temporal, of brain, 656
topography of, 1360
of testis, 1288
of thyreoid gland, 1347
tuberis vermis of cerebellum, 575
uvulae of cerebellum, 576
Lobule of auricle, 828
biventral, of cerebellum, 575
central, of cerebellum, 575
epididymidis, 1289
inferior parietal, 665
of lung, 1095
mammae, 1337
paracentral, 664, 666
parietal, inferior, 664
superior, 664
posterior superior, of cerebellum, 575
postero-inferior, of cerebellum, 575
quadrate, of liver, 1193, 1194
Locomotion, 436
Locus coeruleus, 551
Long bones, 82, 83, 84
Longissimus capitis muscle, 440
cervicis muscle, 440
dorsi muscle, 440
Longitudinal bundle, medial, 562, 570, 586, 588
connexions of, with lower visual centres,
589
in medulla oblongata, 562
in mesencephalon, 562, 570, 588
in pons, 570
relation of, to abducens nerve, 588, 589
to oculo-motor and trochlear nuclei, 588
Longitudinal fissure of brain, 621
development of, 621
Longus capitis muscle, 468
colli muscle, 468
Loop of Henle, 1266
subclavian, 759
Lower extremity, surgical anatomy of, 1455
Lumbar aponeurosis, 437
arteries, 933
abnormalities of, 1053
development of, 1029
morphology of, 1045
of aorta, 933
Lumbar arteries (contd.), of ilio-lumbar, 938
ganglia, 761, 762
lymph glands, 102
trunk, 997
nerves, 719
posterior rami of first three, 690
of fourth and fifth, 691
plexus, 719
branches of, 720
muscular branches of, 720
position and constitution, 719
puncture, 1443
region, 1411, 1425, 1437
rib, 104, 277, 284
sympathetic, 761
veins, 982
vertebrae, 95
Lumbo-costal ligament, 315
Lumbo-dorsal fascia, 437
Lumbo-sacral joint, 335
ligament, 335
plexus, 718
communications with sympathetic, 719
lumbar part of, 719
pudendal part of, 719
sacral part of, 719
trunk, 727
Lumbricales muscles of foot, 430
action of, 430
nerve -supply of, 430
of hand, 389
action of, 389
nerve -supply of, 389
Lung, 1091
air-cells of, 1101, 1099
development of, 1101
alveolar ducts of, 1101
anterior border, surface markings of, 1398
margin of, 1095
apex of, 1092, 1398
level of, 1398
topography of, 1398
atria, 1099
development of, 1101
azygos lobe of, 1096
sulcus of, 1095
blood-vessels of, 1099
bronchial tubes of, 1097
bronchioles of, 1099
cardiac lobe of, 1098
notch of, 1095
costal surface of, 1094
development of, 1101
diaphragmatic surface of, 1093
fissures of, 1095
topography of, 1398
foetal, 1092
form of, 1092
hilum of, 1064
relations of, 1094
incisura cardiaca of, 1095
interlobaris of, 1095
variations of, 1096
inferior border, surface markings of, 1398
lobe of, 1095
ligamentum pulmonale of, 1086, 1087
lobes of, 1095
lobules of, 1098
lymph vessels of, 1096
mediastinal surface of, 1094
middle lobe of, 1096
nerves of, 791
INDEX.
1529
Lung (contd.\ oblique fissure, surface markings
of, 1398
phrenico-costal sinus of, 1093
root of, 1096
constituent parts of, 1096
level of, 1403
relations of, 1096
topography of, 1403
structure of, 1098
sulcus subclavius of, 1093
superior lobe of, 1095
surgical anatomy of, 1398
units, 1098
variations in, 1096
Lungs and pleurae, surgical anatomy of, 1398
Lunula unguis, 859
Lunulse valvularum semilunarium, 877
Lymph, 993
capillaries, 994
channels, perivascular, 994
cords, 995
corpuscles, 993
development of lymph vascular system, 1043
duct, right, 993, 998
abnormalities of, 1059
follicles, 906
glands, 993
of abdomen, 1015, 1019
abdominal wall, 1015
aggregated, 1181
ano-rectal, 1015
anterior auricular, 998
surgical anatomy of, 1376
appendicular, 1020
auricular, 1020
posterior, 998
axillary, 1008
anterior, 1008
posterior, 1008
surgical anatomy of, 1446
biliary, 1020
blood-vessels of, 995
brachial, 1007
bronchial, 1012
broncho-pulmonary, 1012
buccinator, 999
of caecum, 1020
cervical, anterior, 1000
deep, inferior, 1001, 1003
superior, 1002
inferior lateral, 1392
medial, 1392
superficial, 1000
superior anterior, 1392
lateral, 1392
surgical anatomy of, 1392
circumflex iliac, 1015
coeliac, 1019
colic, 1021
of colon, 1021
epicolic, 1021
paracolic, 1021
suprapancreatic, middle, 1021
common iliac, 1017
cubital, 1006
deep, 1006
superficial, 1006
delto-pectoral, 1009
diaphragmatic, 1011, 1013, 1014
of digastric triangle, 1000
epigastric, inferior, 1015
superior, 1015
Lymph glands (contd.), external iliac, 1017
facial, deep, 998
superficial, 999
femoral, 1013
surgical anatomy of, 1459
follicles of, 995
gastric, 1019
left, 1019
right, 1019
anterior, left, 1019
biliary glands, 1020
inferiores, 1020
left para-cardial, 1019
supra -pancreatic, 1020
posterior para-cardial, 1019
gastro-epiloic, 1020
para-cardial, 1019
supra -pancreatic, 1020
sub-pyloric glands, 1020
superiores, 1019
gastro-epiploic, left, 1020
right, 1020
gluteal, 1017
haemal, 995
of head, 998
hepatic, 1020 r
hypogastric, 1017
ileo-caecal, 1020
ileo-colic, anterior, 1028
posterior, 1020
iliac, -common, 1017
external, 1017
of the inferior extremity, 1013
infra -clavicular, 1009
infra-orbital, 998
infra-umbilical, 1015
inguinal, 1013
surgical anatomy of, 1459
intercostal, 1010, 1013
inter-iliac, 1017
interpectoral, 1009
intertracheo -bronchial, 1012
lateral aortic, 1012
axillary, 1008
lingual, 999, 1130
of lower limb, 1013
lumbar, 1021
of the mamma, 1008, 1009
mediastinal, anterior, 1011
posterior, 1012
mesenteric, 1020
mesocolic, 1021
of the neck, 1000
nodules of spleen, 1353
obturator, 1017
occipital, 998 ;
para-aortic, 1021
para-cardial, 1019
left, 1019
posterior, 1019
right, 1019
para-mandibular, 1000
para-tracheal, 1001
para -uterine, 1016
parotid, 998
pectoral axillary, 1008
surgical anatomy of, 1446
of pelvis, 1015
pharyngeal, 1000
lateral, 1000
median, 1000
surgical anatomy of, 1385
98
1530
INDEX.
Lymph glands (contd.), popliteal, 1014
surgical anatomy of, 1458
posterior auricular, 998
mediastinal, 1012
of posterior triangle, 1394
pre -aortic, 1021
pre-laryngeal, 1001
pre-tracheal, 1001
pubic, 1015
pubo-gluteal, 1017
pulmonary, 1012
rectal, 1016, 1017
retro-peritoneal, 1427
sacral, 1016
sinuses of, 995
sternal, 1010
structure of, 994, 995
sub-aortic, 1017
sub -clavicular, 1009
sub-inguinal deep, 1014
distal group, 1014
proximal group, 1012
superficial, 1013
sub-maxillary, 1000
surgical anatomy of, 1391
sub-mental, 1000
surgical anatomy of, 1391
sub-pectoral group of axillary, 1009
sub-pyloric, 1020
sub-scapular, 1008
surgical anatomy of, 1447
sub-sternomastoid, 1002
of the superior extremity, 1006, 1009
superior haemorrhoidal, 1016
supra-clavicular, 1003
supra-hyoid, 1002
surgical anatomy of, 1392
supra-mandibular, 999
supra -pancreatic, 1020
left, 1020
right, 1020
supra-umbilical, 1015
of thorax, 1013
trabeculse of, 995
tracheo-bronchial, 1012
umbilical, 1015
of upper limb, 1006
visceral, of abdomen and pelvis, 1015
of thorax, 1010
nodules, aggregated, 1181
solitary, 1181
spaces, 994
perivascular, 995
trunk, of brain, 1003
broncho -mediastinal, 998
common lumbar, 998
descending, 997
intestinal, 997
jugular, 998
lumbar, 997
retro-aortic, 998
right jugular, 998
subclavian, 998
vessels, 993
of abdomen, 1017, 1022
of abdominal viscera, 1822
wall, 1015
abnormalities of, 1059
of anterior wall of abdomen, 1015
of anus, 1019
of arm, 1006
of blood-vessels, 870
Lymph vessels (contd.), of bones, 87
of breast, 1010
of buttock, 1014
capillary, 1042
central, of hand, 1009
cerebral, 1003
of cheeks, 1005
deep, 1015
of ductus deferens, 1018
of ear, 1004
endothelium of, 994
of external acoustic meatus, 1004
genitals, 1015
extra-cranial, 1003
of eyeball, 1004
of eyelids and conjunctiva, 1004
follicles, 995
of foot, 1014, 1015
of forearm, 1009
of gums, 1005
of hand, 1009
of head and neck, 1003, 1004,
of heart, 880
of inferior extremity, 1014
intra -cranial, 1003
of larynx, 1006
lateral aortic, 1024
of leg, 1014
of lips, 1005
of lower limb, 1014
of lung, 1013
meningeal, 1003
of middle ear, 1004
of nasal muco-periosteum, 1005
of the nose, 1004
of ovaries, 1018
of pelvic viscera, 1017
of pharynx, 1006
of pleura, 1013
pre -aortic, 1024
of prostate, 1018
of rectum, 1018
of rectum and anus, 1233
of salivary glands, 1006
of scalp, 1003
superficial, 1014
of head, 1003
of teeth, 1005
of testis, 1018
of thigh, 1014
of thorax, 1010
of the thyreoid gland, 1006
of tongue, 1005
surgical anatomy of, 1382
of trachea. and oesophagus, 1006
tunica externa of, 994
interna of, 994
media of, 994
of upper limb, 1009
of ureter, 1018
of urethra, female, 1018
male, 1017
of urinary bladder, 1018
of uterine tube, 1018
of uterus, 1018
lower part, 1018
of vagina, 1018
valves of, 994
vasa afferentia, 993
efferentia, 993
of vesicles, seminal, 1018
visceral, of abdomen and pelvis, 1017, 1021
INDEX.
1531
Lymph vessels (contd.), walls of, 994
Lymph-vascular system, 993
development of, 1042
Macewen's operations for knock -knee, 1461
Macrodont skulls, 288
Macula acustica sacculi, 847
utriculi, 846
cribrosa inferior, 844
media, 843
superior, 843
flava of vocal fold, 1070
lutea, 815
structure of, 817
Maculae, structure of, 847
Macular artery, 818
Maier, sinus of, 825
Male pronucleus, 20
Malleolar arteries, 957
of anterior tibial, 956
of posterior tibial, 953
Malleolus, lateral, 253
topography of, 1463
medial, 249
topography of, 1463
Malleus, 839
articulations of, 840
development of, 841
ligaments of, 841
movements of, 842
surgical anatomy of, 1368
Mamillary bodies, 541, 615
development of, 608
line, 1397
process of vertebrae, 96
ossification of, 104
Mamma, 1336
development of, 1339
lymph vessels of, 1010
Mammae accessories, 1338
r Mammary gland, 1336
alveoli of, 1337
ampullae of lactiferous ducts, 1338
areola of, 1337
areolar glands of, 1337
development of, 1339
lactiferous ducts of, 1338
lobes of, 1337
lymph vessels of, 1338
nerves of, 1339
papilla or nipple of, 1337
sinus of lactiferous ducts, 1338
stroma of, 1337
structure of, 1337
supernumerary, 1338
surgical anatomy of, 1446
variations in, 1338
vessels of, 1338
line, 1397
lymph glands, 1008
region, 1397
veins, 977
Mandible, 154
alveoli of, 156
angle of, 155
architecture of, 271
base of, 155
body of, 155
capitulum of, 156
condition at birth, 158
coronoid process of, 1 56
differences in, due to age, 158
Mandible (contd.}, movements of, 313
neck of, 156
ossification of, 157
ramus of, 156
surgical anatomy of, 1392
variations in, 279
Mandibular arch, 43
muscles derived from, 496
canal, 156
foramen, 156
nerve, 778
course and branches, 778
notch, 156
veins, 993
Mantle -layer of neural tube, 502
Manubrium mallei, 841
sterni, 107
Margin, falciform of fossa ovalis, 404
infraoAital, 146
liber of ovary, 1311
pupillary, 813
supraorbital, 115
Marginal artery of heart, 887
layer of neural tube, 502
veins of heart, 959
Marrow, 83
gelatinous, 83
red, 83
yellow, 83
Marrow-cells, 83
Marshall, oblique vein of, 872, 960
vestigial fold of, 872, 882
Massa lateralis of atlas, 91
development of, 608
intermedia of brain, 617
Masseter muscle, 454
action of, 458
nerve-supply of, 457
Masseteric artery, 899
border of zygomatic bone, 153
fascia, 447, 454
nerve, 779
vein, 965
Mastication, muscles of, 457
actions of, 457
nerve-supply of, 457
Mastoid cells, 836
surgical anatomy of, 1370
angle of parietal bone, 120
artery, 895
border-cells, 1370
canal, 129
foramen, 128
fossa, 1369
process, 128
development of, 1370
growth of, 1370
ossification of, 133
relation of, to transverse process, of atlas,
178
sexual differences in, 193
surgical anatomy of, 1370
Matrix unguis, 859
Maturation of ovum, 15
Maxillae, 146
anterior surfaces of, 146
antrum of, 149, 186, 804, 1378
architecture of, 271
body of, 146
conchal crests of, 148
connexions ot, 149
infra -temporal surfaces of, 147
1532
INDEX.
Maxillse (contd.\ nasal surfaces of, 147
orbital surfaces of, 147
ossification of, 149
processes of, 148
relation of, to nasal fossae, 183
to infra -temporal fossa, 168
to orbit, 162
tuberosity of, 148
variations in, 279
Maxillary antrum, see Maxillary Sinus
arteries, 898
lymph glands, internal, 998
nerve, 775
process, 49, 50, 76, 149
of inferior concha, 143
of palate bone, 151
sinus, 149
development of, 150
ossification of, 149
relation of, to nasal fossae, 148, 149, 162,
185, 186, 188
to orbit, 162
skiagraphs of, 1379
surgical anatomy of, 1379
vein, internal, 968
morphology of, 1048
Maximum occipital point, 285
Measurements and indices in anthropology,
284
humero-femoral index, 289
intermembral index, 289
of limb bones, 289
platyknemic index, 289
platymeric index, 289
radio-humeral index, 289
of skulls, 285
tibio-femoral index, 289
Meatus, acoustic external, 830
bony part, 830
cartilaginous part, 830
ceruminous glands of, 832
condition in infancy of, 831
development of, 52, 831
diameters of, 830
foramen of Huschke of, 832
isthmus of, 830
lymph vessels of, 832
nerves of, 832
structure of, 831
surgical anatomy of, 1365
variations in and absence of, 278
vascular and nervous supply of, 832
acoustic internal, 135, 845
absence of, 278
area of facial nerve, 846
vestibularis inferior, 846
crista transversa, 846
foramen singulare, 846
fossula inferior, 846
superior, 846
fundus of, 845
superior vestibular area, 846
tractus spinalis foraminosus, 846
of nose, atrium of, 803
inferior, 804
bony, 185, 188
surgical anatomy of, 1378
middle, 803
bony, 185, 188
surgical anatomy of, 1378
superior, 803
bony, 185, 188
Meatus (contd.), urinarius, 1284, 1308
Mechanism of foot, 361
of pelvis, 338
Meckel, band of, 841
cartilage of, 157, 841
diverticulum of, 1420
ganglion of, 777, 778
development of, 796
Medial longitudinal bundle of brain, 558, 562,
568, 570, 588
plantar artery, position of, 1465
Median artery, 834
abnormalities of, 1056
morphology of, 1048
nerve, 705
surgical anatomy of, at elbow, 1450
in forearm, 1454
in upper arm, 1447, 1448
plane, 4
veins, 980
position of, in forearm, 1454
surgical anatomy of, 1450
Median basilic vein, 980
surgical anatomy of, 1450
Median cephalic vein, 980
abnormalities of, 1058
surgical anatomy of, 1450
Mediastinal arteries, of aorta, 925
of internal mammary, 913
lymph glands, 1011, 1012
pleura, 1085, 1086, 1401, 1402
space, 1089
veins, 961, 963
Mediastinum, 1089
thoracis, 1089
dorsal, 1090
boundaries of, 1090
centres of, 1090
middle, 1090
superior, 1089
ventral, 1090
boundaries of, 1090
Medulla, of bone, 83
of kidney, 1265
Medulla oblongata, 543
ala cinerea of, 551
anterior area of, 545
fasciculus proprius of, 545, 558
relation of, to medial longitudinal
bundle, 558
antero-lateral furrow of, 544
antero-median groove of, 543
areas of, 545, 547
arcuate fibres of, 556
anterior external, 563, 548
external, 548
internal, 560
posterior external, 563
area acustica, 551
development of, 554
anterior, 545
lateral, 545
posterior, 547
postrema, 551
vestibularis, 551
association fibres of, 564
calamus scriptorius of, 550
central canal of, 564
chorioidal plexuses of fourth ventricle, 552
clava of, 547
closed part of, 544
corpus ponto-bulbare of, 548
INDEX.
1533
Medulla oblongata (contd.\ cuneate tubercle of,
547
decussation of the pyramids, 545
development of, 33, 515, 536
eminentia rnedialis, 551
external arcuate fibres, 548
fasciculus olivaris pyramidis, 548
fissures of, 543
foramen caecum of, 544
fossa rhomboidea of, 544
fovea inferior of, 550
development of, 554
funiculus cuneatus of, 559, 547
gracilis of, 559, 547
separans, 551
gray matter of, 33, 515
internal structure of, 551
lateral area of, 545
funiculus of, 564
recess of, 552
somatic column of, 551
lemniscus fibres of, 561
locus coeruleus, 551
medial longitudinal bundle in, 558, 562
somatic column of, 551
nuclei of, 551, 555, 559
oliva of, 546
olivary eminence of, 546
olivo-cerebellar fibres of, 556
open part of, 544
origin of nerves from, 481
position and connexions of, 564
posterior area of, 547
postero -lateral furrow of, 544
postero-median fissure of, 544
pyramidal (cerebrospinal) tract in, 545
decussation of, 545
development of, 533
pyramids of, 545
raphe of, 554, 561
development of, 554
restiform body of, 547, 562
sections of, 555, 563
spino-cerebellar tract of, 564
relation of, to restiform body, 563
striae medullares of, 550
substantia reticularis of, 564
development of, 551
sulcus lateralis anterior of, 544
posterior of, 544
tractus solitarius of, 597
development of, 593
trigonum, hypoglossi of, 551
development of, 554
vagi, 551
development of, 554
tuberculum cinereum of, 547
veins of, 972
white matter of, 557, 560, 562
Medulla ossium, 83
flava, 83
rubra, 83
Medullary arteries, 87
cavity, 83
centre of cerebral hemisphere, 644
corona radiata of, 644
folds, 23, 74
groove, 23
lamina, lateral, of lentiform nucleus, 639
of thalamus, 611
medial, of lentiform nucleus, 639
of thalamus, 611
Medullary rays, 1265
sheath, 508, 532
velum, 549
Megacephalic skulls, 284
Megadont skulls, 288
Megalocolon, 1423
Megaseme skulls, 287
Meissner, corpuscles of, 865
Melanin, 858
Membrana atlanto-occipitalis anterior, 310
posterior, 310
basilaris cochleae, 845, 849, 850
substantia propria of, 850
vas spirale of, 850
zona arcuata of, 850
pectinata of, 850
hyaloidea, 819
hyothyreoidea, 1066
interossea antibrachii, 327
cruris, 350
limitans retinae externa, 818
interna, 817
obturatoria, 338
pupillaris, 813
development of, 826
sterni, 316, 317
tectoria, 311
of organ of Corti, 851
tympani, 834
annulus fibro-cartilagineus of, 834
appearance of, on examination,
1367
blood-vessels of, 835
dendritic fibres of, 835
development of, 52
examination of, 1367
folds of, 835
lymph vessels of, 836
malleolar folds of, 835
membrana propria of, 835
nerves of, 836
otoscopic appearances of, 835
paracentesis of, 1368
pars flaccida of, 835
tensa of, 835
stratum circulare of, 835
cutaneum of, 835
mucosum of, 835
radiatum of, 835
surgical anatomy of, 1367
triangular cone of, 835
umbo of, 835
secundaria, 833
vestibularis, 833
Membranae deciduae, 57
Membrane, anal, 42
anterior occipito-atloid, 310
bones, 85, 292
of brain, development of, 37
bucco-pharyngeal, 39, 41, 42
chorionic, 53
cloacal, 39, 42, 48
costo-coracoid, 369
relation of, to axillary artery, 915
fenestrated, 868
foetal, 53, 62
hyoglossal, 1129
hyothyreoid, 1066
surgical anatomy of, 1387
interosseous, of forearm, 327
of leg, 350
of Nasmyth, 1122
1534
INDEX.
Membrane (contd.), nictitating, 821
nuclear, 8, 9
obturator, 338
periosteal, 83
posterior occipito-atloid, 310
of Keissner, 849
of Shrapnell, 835
surgical anatomy of, 1367
Membranes, foetal, 53
of spinal medulla, 669, 675
Membranous cranium, 292
labyrinth, 846
urethra, 1304, 1307
surgical anatomy of, 1427
vertebral column, 29, 102
Meningeal arteries, 902
lymph vessels, 1003
veins, 970
Meninges of brain, 667
Meniscus, 302, see also Articular Disc
development of, 304
interarticular, 302
of knee-joint, 347
surgical anatomy of, 1460, 1461
Mental artery, 899
foramen, 155
topography of, 1375
nerve, 780
protuberance, 155
spines, 156
tubercles, 155
Mentalis muscle, 451
action of, 454
Merkel, philtrum ventriculi of, 1069
Mesaticephalic skulls, 285
Mesencephalic root of trigeminal nerve, 601
Mesencephalon, 33, 514, 516, 542, 581
development of, 33, 34, 592
internal structure of, 584
lamina quadrigemina of, 584
nerve cells of, 584
fibres of, 588
stratum griseum centrale of, 584
Mesenteric arteries, inferior, 932
superior, 931, 1205
ganglion, superior, 765
lymph glands, 1020
plexus, inferior, 932
superior, 766
veins, 992
Mesenterico-mesocolic fold, 1185
Mesenteriolum processus vermiform is, 1216
Mesentery, 1163
development of, 1252
dorsal, 1252
folds of, 1163
of intestine, 1208
contents of, 1208
folds of, 1208
root of, 1208
structure of, 1252
surgical anatomy of, 1426
primitive, 1254
of testis, 1295
ventral, 1255
of vermiform process, 1216
Mesocephalic skulls, 284
Mesocolic glands, 1021
Mesocolon ascendens, 1219
descendens, 1220
development of, 1253, 1254
iliac, 1222
Mesocolon (contd.\ pelvic, 1223
sigmoid, 1223
transverse, 1206, 1220, 1242
attachment of, 1206
topography of, 1422
Mesoderm, 23, 24, 25, 28, 30
cephalic, 30
ecto-mesoderm, 21, 25
lateral plates of, 30
paraxial, 27, 28
primary, 21
secondary, 23
differentiation of, 25
somatic, 27
somites of, 27
splanchnic, 27
structures formed from, 30
Mesodoiit skulls, 288
Mesoduodeiium, 1185
Mesogastrium, 1252
Mesognathous skulls, 287
Mesometrium, 1318
Mesonephros, 1327
Mesorchium, 1295
Mesorectum, 1223
Mesorhine skulls, 287
Mesosalpinx of uterine tubes, 1314, 1318
Mesoseme skulls, 287
Mesotympanum, 1368
Mesovarium, 1312, 1318
Mesuranic skulls, 287
Metacarpal arteries, 920, 923
bones, 223
architecture of, 272
fifth, 226
first, 224
fourth, 226
ossification of, 226
second, 225
shafts of, 223
surgical anatomy of, 1454
third, 225
variations in, 280
ligament, superficial transverse, 333
tubercle, 1451
Metacarpo-phalangeal joints, 333
topography of, 1454
Metacarpus, 223
Metaphase, 10
Metatarsal artery, 955, 958
bones, 265
architecture, 275
fifth, 267
first, 266
fourth, 267
ossification of, 267
second, 266
third, 267
variations in, 282
ligaments, transverse, 360
superficial, 423
Metatarso-phalangeal joints, 360
movements at, 361
position of, 1465
surgical anatomy of, 1464, 1465
Metatarsus, 265
Metathalamus, development of, 35, 608
Metencephalon, 33, 515
early changes in, 515
Metopic skulls, 172
suture, 118
Metrio-cephalic skulls, 286
INDEX
1535
Meyiiert, decussatioii of, 591
Microcephalic skulls, 284
Microdont skulls, 288
Microseme skulls, 287
Mid-brain, 33, 581
aquaeductus cerebri of, 581, 584
development of, 592
brachiuni conjunctivum in, 587
central gray matter of, 584
cerebro-pontine fibres of, 591
corpora quadrigemina of, 582, 586
deep origin of nerves from, 591
development of, 592
fasciculus retroflexus of, 591
fountain decussation of, 589, 591
frenulum veli of, 582
development of, 592
ganglion interpedunculare of, 591
lamina quadrigemina of, 584
lateral sulcus of, 584
lemniscus fibres of, 590
medial longitudinal bundle of, 568, 570,
588
nuclei of, 582, 584, 588
oculo-motor sulcus of, 584
pedunculi cerebri, 583
pyramidal fibres of, 591
situation and connexions of, 581
stratum griseum centrale of, 584
intermedium of, 584
substantia nigra of, 584
in hypothalamic region, 584, 614
tegmentum of, 586
veins of, 971
Mid-clavicular line, 1357
Mid-gut, 48
derivatives of the, 47
relation of, to Meckel's diverticulum, 1210,
1250
structures derived from, 47
Mid-sternal line, 1357
Middle -ear, 832
Migrations of nerve-cells, 554
Milk-teeth, 1121
eruption of, 1113
surgical anatomy of, 1381
Mitochondria, 8
Mitochondria! sheath, 18
Mitosis, 9
heterotype, 11
homotype, 9
Mitral area, 1405
cells, 623
orifice, 876, 878
valve, 878
cusps of, 878
level of, 1442
topography of, 1405
Moderator band, 877
Modiolus, 844
Molar artery, 899
glands, li09
teeth, 1117
development and eruption of, 1244, 1246
deciduous dentition of, 1121
Molecular layers of retina, 816, 817
Moll, glands of, 823, 827
Mons Veneris, 1324
Montgomery, glands of, 1337
Monticulus, 574
Morgagni, appendices vesiculosi of, 1316
columns of, 1230
Morgagni, columns of (contd.\ surgical anatomy
of, 1431
Morphology, 2
of aorta, 1047
of aortic arches, 1047
of appendicular skeleton, 294
of arteries, 1042
of cerebral nerves, 795
of cervical plexus, 700
of descending aorta, 1047
of head -muscles, 496
of ligaments, 305
of limb-girdles, 295
of limb-muscles, 495
of limb-plexuses, 741
of limbs, 294
of posterior rami of spinal nerves, 691
of primitive streak, 26
of pudendal plexus, 748
of scapula, 203
of se^mental arteries, 1044
of skeletal muscles, 495
of skull, 293
of 'sympathetic system, 795
of tarsus, 295
of teeth, 1248
of vascular system, 1043
of veins, 1048
Morula, 21
Moss-fibres, 581
Motor area of the brain, 663
topography of, 1360
for face, 1361
for lower extremity, 1361
for upper extremity, 1361
Mouth, 1106
angle of the, 1108
aperture of, 1106
buccal glands of, 1109
cavity of, 1106
proper, 1107
corpus adiposum of, 1109
development of, 1242
floor of, 1107
labial glands of, 1109
molar glands of, 1109
mucous membrane of, 1111
muscles of, 450
plica sublingualis of, 1108
primitive, 41
roof of, 1107, 1110
sublingual caruncle of, 1108
region of, 1108
vestibule of, 1106
Movable joints, 300
kidney, 1425
Movements at ankle-joint, 353, 436
at atlanto-occipital joints, 311
of auditory ossicles, 842
at carpo-metacarpal joint of thumb, 332
at clavicular joints, 319
at elbow -joint, 325
of fingers, 401
of head, 446, 464
of the hip-joint, 342, 421
of hyoid bone, 464
at the joints of the foot, 361
of the joints of the hand, 334
in leaping, 437
in locomotion, 436
of lower limb, 436
of pelvis, 446
1536
INDEX.
Movements (contd.), of radio-carpal joint, 329
of radius on ulna, 328
in respiration, 474
in running, 437
of shoulder girdle, 464
at shoulder-joint, 323, 377
in swallowing, 467
of thumb, 401
of thyreoid cartilage, 464
of the toes, 436
of tongue, 464
of vertebral column, 309
in walking, 436
Mucous glands, 1131
Mullerian duct, 1328
development of, 1330
Multifidus spinae muscle, 442
action of, 444
nerve -supply of, 444
Multitubercular teeth, 1248
Muscle or Muscles ; Musculus or Musculi,
363
of abdominal wall, 474
actions of, 484
nerve-supply of, 484
abductor digiti quinti (of hand), 393, 433
action of, 393
nerve-supply of, 393, 433
(of foot), 433
action of, 433
nerve-supply "of, 433
hallucis, 432, 434
action of, 434
nerve-supply of, 434
oblique head of, 434
surgical anatomy of, 1465
transverse head, 434
pollicis brevis, 392
action of, 392
nerve-supply of, 392
pollicis longus, 399
actions of, 400
nerve-supply of, 400
adductor brevis, 412
action of, 412
nerve-supply of, 412
hallucis, caput obliquum, 434
action of, 434
nerve-supply of, 434
caput transversum, 434
action of, 434
nerve-supply of, 434
longus, 411
action of, 412
nerve-supply of, 412
surgical anatomy of, 1459
magnus, 412
action of, 413
nerve-supply of, 413
relations, 413
surgical anatomy of, 1461
minimus, 413
pollicis, caput obliquum, 393
action of, 393
nerve-supply of, 393
caput transversum, 393
action of, 393
nerve-supply of, 393
agitator caudae, 415
anconaeus, 398
action of, 398
nerve-supply of, 398
Muscle or Muscles (contd.)
of ankle-joint, 353, 436
antitragicus, 829
appendicular, 365
of arm, 378
arrectores pilorum, 861
articularis genu, 408
aryepiglotticus, 1074
action of, 1076
nerve-supply of, 1077
arytaenoideus obliquus, 1074
transversus, 1074
auricularis anterior, 449
posterior, 449
superior, 449
nerve-supply of, 449
axial, 365, 437
axillary arches, 371
of back, 438
superficial, 365
biceps brachii, 380
action of, 381
nerve -supply of, 381
surgical anatomy of, 1450
femoris, 418
action of, 420
nerve-supply of, 420
surgical anatomy of, 1460
biventer cervicis, 442
brachialis, 381
action of, 381
nerve -supply of, 381
brachio-radialis, 396
action of, 396
nerve-supply of, 396
topography of, 1454
buccinator, 451
action of, 452
nerve-supply of, 452
bucco-pharyngeus, 464
actions of, in female, 488
in male, 488
nerve-supply of, 488
bulbo-cavernosus (female), 487
(male), 487
of buttock, 414
actions of, 415
nerve-supplies of, 415
caninus, 451
action of, 452
nerve-supply of, 452
cerato-pharyngeus, 464
cervicalis ascendens, 440
action of, 442
nerve -supply of, 442
chondro-epitrochlearis, 371
chondro-glossus, 462
chondro-pharyngeus, 464
ciliaris, 813
cleido-mastoid, 458
cleido-occipitalis, 458
coccygeus, 495
actions, 495
nerve -supply, 495
compressor bulbi, 487
hemispheriorum bulbi, 487
naris, 450
urethras membranaceae, 488
constrictor pharyngis inferior, 465
development of, 496
nerve-supply of, 465
medius, 464
INDEX.
1537
Muscle or Muscles (contd.)
constrictor, medius (contd.\ action of, 467
development of, 496 '
nerve -supply of, 465
superior, 464
action of, 464
development of, 496
nerve -supply of, 465
coraco-brachialis, 378
action of, 380
morphology, 379
nerve-supply of, 380
surgical anatomy of, 1446, 1447
topography of, 1293, 1295
coraco-brachialis superior, 332
corrugator cutis ani, 486, 1229
supercilii, 450
action of, 487
nerve-supply of, 487
costo-coracoideus, 371
cremaster, 480
crico-arytaenoidei, 1072, 1074
action of, 1072, 1074
crico-pharyngeus, 465
crico-thyreoideus, 1075
action of, 1076
nerve-supply of, 1077
dartos, 485
deltoideus, 373
action of, 374
nerve -sup ply of, 374
relations of, 374
topography of, 374
depressor alse nasi, 450
development of, 495
diaphragm, 471
digastric, 461
action of, 458
development of, 496
nerve-supply of, 461
dilatator pupillae, 814
dilator naris, 450
tubse, 838
dorso-epitrochlearis, 370
with double nerve-supply, 750
of ear, extrinsic, 449
intrinsic, 829
epicranius, 448
action of, 449
nerve -supply of, 449
epitrochleo-anconeus, 398
erector clitoridis, 488
penis, 488
extensor carpi radialis brevis, 396
action of, 396
nerve-supply of, 396
longus, 396
action of, 396
nerve-supply of, 396
ulnaris, 398
action of, 398
nerve -supply of, 398
digiti quinti proprius, 398
action of, 398
nerve-supply, 398
digitorum brevis, 426
action of, 426
nerve-supply of, 426
topography of, 1465
digitorum communis, 397
action of, 397
nerve -supply of, 397
Muscle or Muscles (contd.)
extensor digitorum longus, 425
action of, 425
nerve -supply of, 425
topography of, 1465
hallucis longus, 426
action of, 426
additional slips of, 426
nerve-supply of, 426
topography of, 1465
indicis proprius, 400
action of, 400
nerve-supply of, 400
action, 375
nerve-supply, 400
pollicis brevis, 400, 426
action of, 400
nerve-supply of, 400
pollicis longus, 400
action of, 400
nerve-supply of, 400
quinti digiti proprius, 398
extrinsic, 462
of eye, action of, 454
nerve-supply of, 454
of eyeball, morphology of, 452
of eyelids, 450
action of, 452
nerve-supply of, 452
of face, 450
development of, 496
facial, actions of, 451
nerve-supply of, 457
fasciculi of muscles, 363
flexor carpi radialis, 385
action of, 386
bursa of, 386
nerve-supply of, 386
topography of, 1452
ulnaris, 386
action of, 387
nerve -supply of, 387
caudae, 494
digiti quinti brevis of hand, 394, 435
of foot, action of, 394, 435
nerve-supply of, 394, 435
digitorum brevis/ 433
action of, 433
nerve -supply of, 433
communis, 397
action of, 397
nerve-supply, 397
longus, 430
action of, 430
nerve-supply of, 430
profundus, 388
action of, 389
nerve-supply of, 389
sublimis, 388
action of, 388
nerve -supply of, 388
hallucis brevis, 434
action of, 434
nerve -supply of, 434
longus, 431
action of, 431
nerve-supply of, 431
pollicis brevis, 393
action of, 393
nerve-supply of, 393
longus, 390
action of, 390
1538
INDEX.
Muscle or Muscles (contd.)
flexor pollicis longus (contd.), nerve -supply
of, 390
of foot, 424, 430, 432, 435
actions of, 435, 436
nerve -supply of, 435, 436
surgical anatomy of, 1463, 1464
of forearm, 382
deep, 388, 398
dorsal, 395
superficial, 385, 395
on front of leg and dorsum of foot, 424
frontalis, 448
actions, 449
nerve-supply, 449
gastrocnemius, 428
action of, 429
nerve-supply of, 429
topography of, 1462, 1463
gemellus inferior, 418
action of, 418
nerve-supply of, 418
superior, 418
action of, 418
nerve-supply of, 418
genio-glossus, 462
action of, 463
nerve -supply of, 463
surgical anatomy of, 1383
genio-hyoid, 461
action of, 462
nerve-supply of, 462
glqsso-palatinus, 463, 467
action of, 467
nerve-supply of, 467
glosso-pharyngeus, 464
glutaeus maxirnus, 415
action of, 415
nerve -supply of, 415
topography of, 1455
medius, 416
action of, 416
nerve -supply of, 416
minimus, 416
action of, 417
nerve-supply of, 417
gracilis, 411
action of, 411
nerve -supply of, 411
hamstring, 418
topography of, 1456
of hand, 391
short, 382
of head, 448
of heart, 878
helicis major, 829
minor, 829
hyo-glossus, 462
action of, 463
nerve-supply of, 463
of hyoid bone, 459
iliacus, 410
action of, 411
nerve-supply of, 411
minor, 410
ilio-capsularis, 410
ilio-coccygeus, 494
ilio-costalis, 439
cervicis, 440
dorsi, 439
lumborum, 439
ilio-psoas, 409
Muscle or Muscles (contd.)
ilio-psoas (contd.), action of, 411
bursa of, 1459
nerve-supply of, 411
surgical anatomy of, 1459
ilio-sacralis, 494
infracostal, 470
infrahyoid, 459
action of, 460
nerve-supply of, 460
infraspinatus, 375
action of, 375
nerve-supply of, 375
insertion of, 364
intercostal, external, 470
action of, 474
nerve-supply of, 474
internal, 470
action of, 474
nerve-supply of, 474
interosseous, of foot, 435
action of, 435
nerve -supply of, 435
dorsal, of hand, 395
volar, 394
action of, 395
nerve -supply of, 395
interspinal, 445
intertransverse, 445
intrinsic, of tongue, 463
ischio-bulbosus, 487
ischio-cavernosus, 488
female, 488
male, 488
actions of, 488
nerve-supply of, 488
ischio-coccygeus, 494
ischio-pubicus, 488
laryiigeal, 1072
on lateral side of leg, 426
latissimus dorsi, 366
action of, 368
nerve -supply of, 368
Surgical anatomy of, 1437
levator ani, 490, 493, 1229, 1232
actions, 495
nerve -supply, 494
glandulae thyreoideae, 460
palpebrae superioris, 452
action of, 453
nerve-supply of, 453
scapulae, 368
action of, 368
nerve-supply of, 368
veli palatini, 466
action of, 467
nerve-supply of, 467
levatores costarum, 470
action of, 474
nerve -supply of, 474
of limbs, development of, 41
lingualis inferior, 462, 463
superior, 463
of little finger, 393
longissimus capitis, 440
action of, 442
nerve-supply of, 442
cervicis, 440
dorsi, 440
longus capitis, 468
colli, 468
action of, 468
INDEX.
1539
Muscle or Muscles (contd.)
longus colli (contd.\ nerve-supply, 468
lumbricales, 389, 430
of foot, 430
action of, 430
nerve-supply of, 430
of hand, 389
action of, 389
nerve -supply of, 389
masseter, 454
action of, 458
nerve -supply of, 457
of mastication, 454, 457
action of, 457
nerve-supply of, 457
mentalis, 451
action of, 452
nerve-supply of, 452
morphology of, 495
of mouth, 450
of Midler, 454
multifidus (spinee), 442
action of, 444
nerve-supply of, 444
mylo-hyoid, 461
action of, 463
nerve -supply of, 461
mylo-pharyngeus, 464
of neck, 458
of nose, 450
actions of, 452
nerve -supply of, 452
obliquus abdominis externus, 476
action of, 484
nerve -supply of, 484
iiiternus, 487
action of, 484
nerve-supply of, 484
auriculae, 830
capitis inferior, 444
action of, 444
nerve-supply of, 444
superior, 444
action of, 444
nerve-supply of, 444
inferior (of eye), 453
superior (of eye), 453
obturator externus, 413
action of, 414
nerve-supply of, 414
iiiternus, 418
action of, 418
nerve -supply of, 418
occipitalis, 448
omohyoid, 459
' action of, 460
nerve-supply of, 460
surgical anatomy of, 1391, 1394
opponens digiti quinti, 393
action of, 394
nerve -supply of, 394
opponens pollicis, 392
action of, 393
nerve-supply of, 393
orbicularis oculi, 450
action of, 452
ciliary bundle of, 450
lacrimal part of, 450
nerve -supply of, 452
orbital part of, 450
palpebral part of, 450
orbicularis oris, 450, 1100
Muscle or Muscles (contd.)
orbicularis oris (contd.\ action of, 452
inferior incisive bundle of, 451
naso-labial band of, 450
nerve -supply of, 452
superior incisive bundle of, 451
of orbit, 452
action of, 454
development of, 496
nerve -supply of, 454
orbitalis, 454
origin of, 364
palmaris brevis, 382
longus, 386
action of, 386
nerve -supply of, 386
papillares (of heart), 877, 878
structure of, 879
pectinati, 874
pectineus, 411
action of, 411
nerve-supply of, 411
of pectoral region, 369
pectoralis major, 369
action of, 370
nerve -supply of, 370
topography of, 1446
minimus, 371
minor, 371
action of, 371
nerve-supply of, 371
of pelvis, 493
of perineum, 486
peronaeo-calcaneus, 431
externus, 427
peronaeo-cuboideus, 427
peronaeus accessorius, 427
brevis, 427
action of, 427
additional slips of, 427
nerve-supply of, 427
topography of, 1462
of tendon of, 1464, 1465
digiti quinti, 427
longus, 426
action of, 427
nerve-supply, 427
topography of, 1462
of tendon of, 1464, 1465
tertius, 425
action of, 426
nerve -supply of, 426
topography of, 1465
peroneal, 427
pharyngo-palatinus, 465
action of, 467
nerve-supply of, 467
of pharynx, 464
action of, 467
development of, 496
nerve-supply of, 467
of pinna, 449, 829
piriformis, 417
action of, 418
nerve -supply of, 417
plantaris, 429
action of, 429
nerve-supply of, 429
platysma, 448
action of, 448
development of, 496
nerve-supply of, 448
1540
INDEX.
Muscle or Muscles (contd.)
popliteus, 429
action of, 429
nerve -supply of, 429
minor, 429
on posterior aspect of leg, 428
procerus, 450
action of, 452
pronator quadratus, 390
action of, 391
nerve-supply of, 391
pronator teres, 385
action of, 385
nerve -supply of, 385
psoas major, 410
action of, 411
nerve-supply of, 410
surgical anatomy of, 1459
psoas minor, 410
action of, 411
nerve -supply of, 410
pterygoideus externus, 455
action of, 457
nerve-supply of, 457
internus, 457
action of, 457
nerve-supply of, 457
pterygo-pharyngeus, 464
pubo-cavernosus, 488
pubo-coccygeus, 494
pubo-rectalis, 494
pubo-vesicalis, 1283
pyramidalis abdominis, 481
quadratus femoris, 418
action of, 418
nerve-supply of, 418
quadratus labii inferioris, 451
action of, 452
nerve-supply of, 452
quadratus labii superioris, 451
caput angulare, 451
infra-orbitale, 451
zygomaticum, 451
quadratus lumborum, 485
actions of, 485
nerve -supply, 485
surgical anatomy of, 1437
quadratus plantae, 431
action of, 431
nerve-supply of, 431
quadriceps femoris, 406
action of, 409
nerve-supply of, 409
recti (of eye), 453
recto-coccygeus, 1229
recto-urethralis, 1229
recto-uterinus, 1238, 1318
recto-vesicalis, 1283
rectus abdominis, 481
capitis anterior, 468
action, 468
nerve-supply, 468
lateralis, 445, 470
action of, 445, 470
nerve-supply of, 445, 470
posterior major, 444
actions, 444
nerve-supply, 444
posterior minor, 444
actions, 445
nerve-supply, 445
rectus femoris, 407
Muscle or Muscles (contd.)
rectus femoris (conld.), action of, 409
nerve-supply of, 409
rectus inferior of eyeball, 453
action of, 454
nerve -supply of, 454
rectus lateralis of eyeball, 453
action of, 454
nerve-supply of, 454
rectus medialis of eyeball, 453
action of, 454
nerve-supply of, 454
rectus superior of eyeball, 453
action of, 454
nerve-supply of, 454
of respiration, 470, 474
action of, 474
nerve -supply of, 474
rhomboid, action, 369
nerve-supply, 369
rliomboideus major, 368
action of, 369
nerve-supply of, 369
rliomboideus minor, 368
action of, 369
nerve -supply of, 369
of Kiolan, 823
risorius, 451
action of, 452
nerve -supply of, 452
rotatores (dorsi), 445
action of, 445
nerve-supply of, 445
sacro-spinalis, 439
salpingo-pharyngeus, 465
nerve-supply of, 465
relation of, to salpingo-pharyngeal fold, 838
sartorius, 406
action of, 406
nerve-supply of, 406
topography of, 1459
scalenus anterior, 467
action of, 468
nerve -supply of, 468
medius, 467
action of, 468
nerve-supply of, 468
posterior, 467
action of, 468
nerve -supply of, 468
of scalp, 448
action of, 449
nerve -supply of, 449
semimembranosus, 420
action of, 421
nerve -supply of, 421
topography of, 1458 +
semispinalis capitis, 442
actions of, 442
nerve -supply of, 442
cervicis, 442
action of, 444
nerve-supply of, 444
dorsi, 442
semitendinosus, 419
action of, 420
nerve-supply of, 420
topography of, 1450
septi, 450
serratus anterior, 372
action of, 372
insertion, 372
INDEX.
1541
Muscle or Muscles (contd.)
serratus anterior (contd.), nerve -supply of,
372
topography of, 1446
serratus posterior inferior, 439
action of, 439
nerve-supply of, 439
serratus posterior superior, 438
action of, 439
nerve -supply of, 439
of shoulder, 373
skeletal, 363
perimysium externum of, 363
internum of, 363
of soft palate, 466
actions, 467
development of, 496
nerve-supply of, 467
of sole of foot, 432, 434
soleus, 429
action of, 429
nerve-supply of, 429
topography of, 1461, 1462
sphincter ani externus, 486, 1232
action of, 1232
nerve-supply of, 1233
internus, 1229, 1232
pupillse, 814
pylori, 1166, 1174
recti, 1229
urethrae, in female, 489
actions, 489
nerve-supply, 489
sphincter urethrse membranacese, 488
sphincter vaginae, 487
sphincter vesicae, 1284
spinalis dorsi, 442
splenius capitis, 439
action of, 439
nerve -supply, 430
splenius cervicis, 439
action of, 439
nerve-supply of, 439
stapedius, 841
sternalis, 370
nerve -supply, 370
sterno-clavicularis, 372
sterno-cleido-mastoideus, 372, 458
action of, 458
nerve -supply of, 458
sterno-hyoideus, 459
action of, 460
nerve-supply of, 460
sterno-mastoid, action of, 458
nerve-supply of, 458
surgical anatomy of, 1390
sterno-thyreoideus, 459
action of, 460
nerve-supply of, 460
stylo-auricularis, 830
stylo-glossus, 463
action of, 463
nerve-supply of, 463
stylo-hyoicfeus, 461
action of, 462
development of, 496
nerve-supply of, 461
stylo-pharyngeus, 465
action of, 467
development of, 496
nerve-supply of, 465
subanconseus, 382
Muscle or Muscles (contd.)
subclavius, 371
action of, 371
insertion, 371
nerve-supply of, 371
subcostal, 470
action of, 474
nerve-supply of, 474
subscapularis, 377
actions, 377
nerve-supply of, 377
minor, 377
supinator, 398
action of, 399
nerve -supply of, 399
supra-hyoid, 460
action of, 462
nerve-supply of, 457, 461
supraspinatus, 375
action of, 375
nerve-supply of, 375
suspensory, of the duodenum, 1187
temporalis, 455
action of, 458
nerve-supply of, 457
tensor fasciae latae, 415
action of, 416
nerve-supply of, 416
topography, of, 1459
suralis, 419
tarsi, 450
action of, 452
nerve-supply of, 452
tympani, 841
surgical anatomy of, 1368
veli palatini, 466
relation of, to auditory tube, 838
surgical anatomy of, 1385
teres major, 376
action of, 377
nerve-supply of, 377
relations of, 377
minor, 375
action of, 376
nerve-supply of, 376
thigh, on anterior aspect of, 405
ot medial side of, 411
actions of, 411, 414
nerve-supplies of, 411, 414
on posterior aspect of, 418
thoracis, 470
actions of, 474
nerve-supplies of, 474
of thumb, 392, 393
actions of, 392, 393
nerve -supplies of, 392, 393
thyreo-arytaenoideus, 1073
action of, 1076
nerve-supply of, 1077
thyreo-epiglotticus, 1075
thyreo-hyoideus, 460
action of, 460
nerve -supply of, 460
thyreo-pharyngeus, 465
tibialis anterior, 424
action of, 424
nerve -supply of, 424
topography of tendon, 1465
tibialis posterior, 431
action of, 431
nerve-supply of, 431
topography, 1465
1542
INDEX.
Muscle or Muscles (contd.)
tibio-fascialis anterior, 424
of tongue, 462
action of, 463
arrangement of, 462
development of, 496
morphology of, 496
nerve-supply of, 463
surgical anatomy of, 1382
trachealis, 1081
tragicus, 829
transverse, of tongue, 463
transversus abdominis, 480
auriculae, 830
perinei profundus, 488
superficialis, 487
actions of, 487
nerve -supply, 487
thoracis, 470
action of, 474
nerve-supply of, 474
vaginae, 489 .
trapezius, 365
action of, 366
nerve -supply of, 366
topography of, 1437
triangularis oris, 451
triceps brachii, 381
actions of, 382
insertion, 381
nerve-supply of, 382
origin, 381
topography of, 1437
surae, 428
of tympanic cavity, 841
of upper limb, 365
uvulae, 466
nerve-supply of, 467
vastus intermedius, 408
action of, 409
nerve-supply of, 409
vastus lateralis, 407
action of, 409
nerve-supply of, 409
topography of, 1459
vastus medialis, 408
action of, 409
nerve -supply of, 409
topography of, 1459
verticalis linguae, 463
vocalis, 1076
zygomaticus, 451
action of, 452
nerve-supply of, 452
Muscle-cells, 363
Muscle-plate, 30
Muscular process of arytaenoid cartilage, 1065,
1074
of vertebrae, 95, 96
system, 363
triangle of neck, 1387
Musculo-cutaneous nerve, of arm, 704
Musculo-phrenic artery, 913
vein, 963
Myelencephalon, 575
development of, 33
Myelin, 508
Myelinisatioii of nerves, 533
Myelospongium, 503
Mylohyoid artery, 899
groove, 156
muscle, 461
Mylohyoid muscle (contd.), action of, 463
nerve-supply of, 461
nerve, 780
ridge, 156
Myocardium, 878
Myoccele, 29
Myology, 363
Myotomes, 495
cephalic, 496
cervical, 796
number of, 496
Myrtiform fossa, 146
Naboth, ovules of, 1320
Nail, 858
bed of, 859
development of, 41, 862
eponychium, 859
in foatus, 78
lunula of, 859
matrix of, 859
papillae of, 859
vallum of, 859
wall, 859
Nasal aperture, anterior, 163
arteries, 899, 900
bone, 145
ossification of, 145
relation of, to nasal aperture, 164
to nasal fossae, 184
cartilages, 800
greater alar, 800
lateral, 800
lesser alar, 800
of septum, 800
processus sphenoidalis of, 801
vomero-nasal, 801
cavity, 801
agger nasi of, 803
atrium of, 803
basal cells of, 805
blood-vessels of, 805, 806
Bowman's glands of, 804
bulla ethmoidalis of, 803
cavernous tissue of, 806
development of, 50
epithelium of, 804, 805
fron to -nasal duct of, 804
hiatus semilunaris of, 803
inferior meatus of, 804
surgical anatomy of, 1378
infundibulum of, 803
lateral wall of, 802
limen of, 802
lymph vessels of, 806, 1004
middle meatus of, 803
surgical anatomy of, 1378
nerve -supply ofj 805
olfactory cells of, 804
cleft of, 803
part of, 802, 803
mucous membrane of, 805
organ of Jacobson of, 802
orifices in, 801, 802, 803
ostium maxillare, 804
recessus naso-palatinus of, 802
spheno-ethmoidalis of, 802
respiratory part of, 802, 803
mucous membrane of, 804
sensory nerves of, 805
superior meatus of, 803
supporting cells of, 804
INDEX.
1543
Nasal cavity (contd.), vestibule of, 802
crest, 802
relation of, to nasal septum," 186
index, 287, 799
laminae, 50
muco-periosteum, 1005
notch, of frontal bone, 115
of maxilla, 146, 147
part of frontal bone, 117
of the pharnyx, 1141, 1142
development of, 1248
fossa of Rosenmiiller of, 1144
orifice of auditory tube, 1143
surgical anatomy of, 1383
tonsil of, 1145
pit, 798
septum, 802
bony, 175, 185
development of, 40
spine, anterior, 146, 149, 164
topography of, 1374
of frontal bone, 116
posterior, 151, 174
veins, 968
Nasion, 285
Nasmyth, membrane of, 1122
Naso -facial angle, 799
Naso-frontal suture, 160
Naso-labial band, 450
Naso-lacrimal duct, 825
bony canal of, 143, 148, 186, 188
development of, 49
surgical anatomy of, 1377
Naso-palatine artery, 900
nerve, 778
recess, 802
Naso-pharyngeal groove, 1143
Navicular bone, of foot, 261
morphology of, 1464
position of tuberosity of, 1464
of hand, 218
surface anatomy of, 1451
variations in, 286
Naviculo- cuboid joints, 357
Naviculo-cuneiform joints, 357
Neck, abscesses of, 1385
anterior triangle of, 1390
arteries of, 888
carotid triangle of, 1391
deep cervical glands, 1392
lateral muscles of, 467
development of, 42, 47
digastric triangle of, 1391
surgical anatomy of, 1391
fascise of, 1386, 1389
fascial compartments of, 1385
infrahyoid region of, 1387, 1388
lymph vessels of, 1003
median line of, 1387
muscles of, 458
muscular triangle of, 1383
nuchal furrow of, 1395
posterior triangle of, 1390
sub-occipital triangle of, 1395
suprahyoid region of, 1387
surgical anatomy of, 1385
triangles of, 1390
Nelaton, line of, 1455
Neopallium, 624, 628, 645
Nerve or Nerves ; Nervus or Nervi
abducens, 781
course and communications, 781
Nerve or Nerves (contd.)
abducens, (contd.) deep connexions of, 600
development of, 798
morphology of, 798
nucleus of, 600
relation of, to medial longitudinal
bundle, 600
origin of, deep, 600
superficial, 781
accessory (eleventh cerebral), 791
deep origin of, 595
development of, 592, 684
external ramus (spinal part) of, 791, 793
development of, 592, 684
morphology of, 797
internal ramus (accessory part) of, 791, 793
development of, 592, 684
morphology of, 797
medullary part of, 595
nucleus of, 595
superficial origin of, 596, 793
surgical anatomy of, 1393
accessory obturator, 726
acusticus, 852
ampullary branches of superior and
lateral, 785, 853
central connexions of, 606
cochlear division of, 604
termination of, 852
development of, 552-554, 796, 798
in labyrinth, 852
morphology of, 796
nuclei of, 604
origin of, deep, 604
superficial, 784
utricular branch of, 785, 853
nuclei of, 604
vestibular division of, 604
ganglion of, 853
termination of, 853
to adductor magnus muscle, from obturator,
723
from sciatic, 729
alveolar, anterior superior, 777
inferior, 780
branches of, 780
mental nerve, 780
mylohyoid nerve, 780
middle superior, 777
posterior superior, 775
to ankle-joint, from deep peroneal, 731, 733
from tibial, 732
ano-coccygeal, 738
anterior supra- clavicular, 696
morphology of, 700
to arteries, 870
to articulations of foot, from deep peroneal,
731
from lateral plantar, 735
from medial plantar, 734
from tibial, 733
of auditory tube, 838
auricular, anterior, of auriculo- temporal, 780
great, 695, 696
morphology of, 700
posterior, 783
auricular branch of vagus, 788
auriculo-temporal, 779
meatal branches of, 780
morphology of, 700
parotid branches of, 780
axillary, 710
1544
INDEX.
Nerve or Nerves (contd.)
axillary (contd.), surgical anatomy of, 1447
topography of, 1447
bigeminal, 727
of blood-vessels, 870
of bones, 87
to brachial artery, 765
buccal branch of facial, 784
buccinator branch of trigeminal, 779
to bulb of urethra, 740
calcanean, medial, 734
canalis pterygoidei (Vidii), 777
cardiac, of vagus, 789
of recurrent left, 789
right, 789
inferior, of sympathetic, 759
of vagus, 789
middle, 759
of sympathetic, 757, 759
of vagus, 789
carotici externi, 757
carotico-tympanic, 759, 786
caroticus internus, 757
to carpal joints, 329
caudal, 691, 738
cells, 497, 506, 507
cerebral, 767, 798
afferent roots of, development of, 796
morphology of, 796
connexion of, with superior cervical gang-
lion, 756
deep connexions of, in cerebrum, 619
in medulla oblongata and pons, 592
in mesencephalon, 600
development of, 795
efferent roots of, development of, 796
morphology of, 796
general distribution of, 767
list of, 678, 767
morphology of, 795, 796
motor nuclei of, 592
nuclei of origin of, 592
of termination of, 593
roots of, 767
segmental characters of, 795, 796
1st, olfactory, 767
2nd, optic, 768
3rd, oculomotor, 603, 769
4th, trochlear, 770
5th, trigeminal, 567, 569, 600, 771
6th, abducens, 568, 600, 781
7th, facial, 567, 598, 781
8th, acustic, 604, 784
9th, glossopharyngeal, 596, 785
10th, vagus, 596, 786
llth, accessory, 595, 791
12th, hypoglossal, 594, 793
cervical, 692
anterior rami, 692, 700
descending, 696
first, 688, 695
gray rami of, 692
chorda tympani, 782
branches of, to sublingual gland, 782, 1 140
to submaxillary gland, 782, 1138
development of, 796
morphology of, 796
relation of, to lingual nerve, 780
to taste, 855
tympanic aperture of, 834
in tympanum, 782, 1368
ciliary, long, 773
Nerve or Nerves (contd.}
ciliary (contd.), short, 773
circumflex, see Nerve, Axillary
clunium inferiores, 737
coccygeal, 691
to coccygeus muscle, 738
cochlear, 785
deep origin of, 604
common peroneal, 728, 729, 730
branches of, 730
surgical anatomy, 1457
tibial, 732
surgical anatomy of, 1458
to constrictors of pharynx, from glosso
pharyngeal, 786
from vagus, 788
to corpus cavernosum penis, 740
to cremaster muscle, 722
cutaneous, of abdomen, 716, 717
from ilio-inguinal nerve, 720
of lower limb, tables of, 747, 748
of upper limb, tables of, 744, 745
cutaneus antibrachii dorsalis, 711
lateralis, 705
medialis, 709
brachii lateralis, 710
medialis, 710
posterior, 711
colli, 696
dorsalis intermedius, 731
lateralis, 730
medialis, 731
femoris lateralis, 722
posterior, 737
surae lateralis, 730
deep peroneal, 730
descendens hypoglossi, 698, 794
co diaphragm, 699, 717
to digastric muscle, 780
digital, of foot, from deep peroneal, 731
from plantar, 734, 735
from superficial peroneal, 731
from sural nerve, 730
of hand, from median, 706
from superficial ramus of radial, 7 12
from ulnar, 709
to dilatator pupillae muscle, 773
dorsal cutaneous nerves of the foot, 731
lateral, 731
medial, 731
dorsalis clitoridis, 740
penis, 740
scapulse, 702
efferent, 504
of elbow-joint, 705, 709, 711
to epicranius muscle, 783
ethmoidal, anterior, 773
posterior, 773
of external acoustic meatus, 832
of eyelid, 824
facial, 781
in acoustic meatus, 782
afferent root of, 796
ascending part of, 599
auricular (posterior), branches of, 783
branches of, 782
central connexions of, 600
cervico-facial division of, 784
communications of, 781
course of, 781
deep origin of, 599
development of, 796
INDEX.
1545
Nerve or Nerves (contd.)
facial (contd.), efferent root of, 598
emergent part of, 598
facial branches of, 783
in facial canal, 782
geniculate ganglion of, 782
in infant, 600
intrapontine course of, 599
morphology of, 796
in neck, 783
n. intermedius of, 781
development of, 598
origin of, 598
relation of, to chorda tympani, 782,
796
to geniculate ganglion, 782, 796
to vestibular nerve, 781
nucleus of, 599
in parotid gland, 783
plexus parotideus, 783
roots of, 598, 781
surgical anatomy of, 1376
temporal, 783
temporo-facial, 783
terminal rami of, 783
femoral, 724
articular branches of, 724
cutaneous branches of, 724
intermediate cutaneous nerve of thigh,
724
medial cutaneous nerve of thigh, 725
saphenous nerve, 726
branches of, 726
muscular branches of, 724
to femoral artery, 723
to femur, 724
to fibula, 734
frontal, 772
furcalis, 727, 753
variations of, 753
to gemelli muscles, 728
genital, of genito-t'emoral, 722
genito -femoral, 722
external spermatic branch of, 722
lumbo-inguinal branch of, 722
glossopharyngeal, 785
afferent fibres of, 785
root of, 597, 598
branches of, 785, 786
communications of, 786
course of, 785
deep origin of, 596, 598
development of, 796
efferent fibres of, 517
root of, 596, 598
in jugular foramen, 786
morphology of, 796
in neck, 786
nucleus of, 596, 598
relation of, to fourth ventricle, 596
petrous ganglion of, 786
roots of, 785
superficial origin of, 596
superior ganglion of, 785
tympanic nerve of, 786
gluteal, inferior, 729
of posterior cutaneous of thigh, 737
superior, 729
hsemorrhoidal, inferior, 738
to hamstring muscles, 728
of heart, 880
of hip-joint, 723, 724, 728, 729
Nerve or Nerves (contd.)
of hip-joint (contd.), from femoral, 724
from nerves of sacral plexus, 729
from obturator, 723
to humerus, 705
hypogastric, 766
of aortic plexus, 765, 766
hypoglossal, 793
ansa hypoglossi of, 794
branches of, 794
communications of, 793
. course of, 793
deep origin of, 594
descending branch of, 794
development of, 798
nucleus of, 594
recurrent branch of, 794
relation of, to fourth ventricle, 594
superficial origin of, 594
surgical anatomy of, 1392
ilio-hypogastric, 720
ilio-inguinal, 720
incisor, 780
infra-clavicular, 703
to infra -hyoid muscles, 794
infra-orbital, of facial, 777
of trigeminal, 776
infra-trochlear, 773
intercostal, 713
intercosto-brachial, 716
intermedius, 781, 782
development of, 683
origin of, 598
relation of, to chorda tympani, 782
to geniculate ganglion, 782
to vestibule, 1326
to interossei muscles of foot, 734, 735
of hand, 709
interosseous, of common peroneal, 731
interosseous, dorsal, 713
surgical anatomy of, 1453
interosseous, volar, 705
ischiadicus, 728
of knee-joint, from common peroneal, 729
from femoral, 724
from obturator, 724
from sciatic, 729
from tibial, 732
labial, 1324
anterior, 721
posterior, 739
lacrimal, 772
canals, 825
of large intestine, 1213, 1233
laryngeal, external, 788, 789
inferior, 789
morphology of, 797
internal, 788
in tongue, 1131
recurrent, 789
surgical anatomy of, 1389
superior, 788
morphology of, 797
surgical anatomy of, 1388
lateral cutaneous, of thigh, 722
of thorax, 716
to latissimus dorsi muscle, 713
to levator ani muscle, from perineal nerve,
739
from pudendal plexus, 738
to levator scapulae muscle, 702
to levator veli palatini muscle, 467
99
1546
INDEX.
Nerve or Nerves (contd.)
lingual, 1131
surgical anatomy of, 1375
in tongue, 1131
of glossopharyngeal, 780
communications of, 780
morphology of, 796
of hypoglossal, 795
of vagus, 788
long scrotal, 739
thoracic, 702
to longus colli muscle, 468
lumbar, 719
anterior rami, 719
posterior rami, 690
lumbo-inguinal branch of genito-femoral,
722
to lumbrical muscles, of foot, 734, 735
of hand, 706, 709
of lung, 791
mandibular, 778
marginal, of mandible, 784
masseteric, 779
mastoid, 695
maxillary, 775
meatus acoustici externi, 780
medial cutaneous, of the arm, 710
of the calf, 732
of forearm, 709
of thigh, 724, 725
median, 705
branches in the forearm, 705
in hand, 706
communications, 705, 707
course of, 705
cutaneous branches, 706
muscular branches, 705
palmar ramus, 705
surgical anatomy of, at elbow, 1451
in arm, 1448
volar interosseons nerve of forearm, 705
of membrana tympani, 836
meningeal, of vagus, 788
(middle), 775
mental, 780
to muscles of abdominal wall, 485
of arm, 381
of back, 439
of buttock, 418
of face, 452
of foot, 425
of forearm, 400
of hand, 400
of hyoid bone, 460
of iris, 814
of leg, 435
of lower limb, 718
of mastication, 457
of orbit, 454
of pectoral region, 369
of pelvis, 494
of perineum, 489
of pinna, 830
prevertebral muscles, 470
of shoulder, 375, 376, 377
of soft palate, 786, 788
of thigh, 418
of thorax, 474
of tongue, 463
between trunk and upper limb,
372
of upper limb, 700
Nerve or Nerves (contd.)
musculo-cutaiieous, 704
variations of, 752
to mylo-hyoid, 780
nasal of infra -orbital, 777
lateral, 773
medial, 773
posterior inferior lateral, 778
superior lateral, 778
naso-ciliary, 773
naso-palatine, 778
to obliqui abdominis muscles, 716
obturator, 722
accessory, 726
to obturator externus muscle, 723
internus muscle, 728
occipital, greater, 689
branch of posterior auricular, 783
occipital, small, 695
morphology of, 700
occipital third, 690
oculo-motor, 769
branches of, 770
communications of, 770
course of, 770
deep origin of, 603
development of, 796
morphology of, 796
superficial origin of, 769
ossophageal, from sympathetic, 760
from vagus, 789
olfactory, 767, 768, 805
development of, 622
morphology of, 797
origin of, 624, 628
termination of, 768
ophthalmic, 772
branches of, 772
frontal, 772
lacrimal, 772
supra -orbital, 772
supra- trochlear, 773
course of, 772
development of, 796
optic, 768
development of, 825
morphology of, 797
origin of, 658
retinal portion of, 815
orbital, of spheno-palatine ganglion, 778
palatine, 778
anterior, 778
middle, 778
posterior, 778
palpebral, 824
to parotid gland, 1137
patellar, 726
perforans coccygeus major, 738
perforating cutaneous, 737
pericardiac, 791
perineal, 737
of fourth sacral, 738
of posterior cutaneous nerve of thigh, 737
superficial, 739
to perineal muscles, 739
peripheral, development of, 679
peroneal anastomotic ramus, 730
peroneal, deep, 730
superficial, 731
to peroneus brevis, 731
longus, 731
petrosal, deep, 758, 777
INDEX.
1547
Nerve or Nerves (contd.)
petrosal (contd.), superficial, external, 782
greater, 782
lesser, 759, 782, 786
pliaryngeal, 778, 1150
of glossopharyngeal nerve, 786
of spheno-palatine ganglion, 778
of sympathetic, 756
of vagus, 788
phrenic, 699
branches of, 699
communications of, 699, 702
surgical anatomy of, 1393
of pinna, 830
to piriformis muscle, 729
plantar, lateral, 734
surgical anatomy of, 1465
medial, 734
surgical anatomy of, 1465
posterior descending supra-clavicular, 696
morphology of, 700
to prevertebral muscles, 695
to psoas major muscle, 720
of pterygoid canal, 777
pterygoid, external, 779
internus, 778
pudendal, 738
pulmonary, 1096
from sympathetic, 761
from vagus, 789
to pyramidalis abdominis muscle, 717
to quadratus femoris muscle, 728
lumborum muscle, 720
radial, 710
collateral branches of, 711
cutaneus brachii posterior, 711
dorsal cutaneous nerve of forearm, 711
ulnar collateral nerve, 711
course of, 711
deep ramus of, 712
dorsal interosseous, 713
superficial rami of, 712
surgical anatomy of, 1454
topography of, at elbow, 1450
in arm, 710, 711
variations of, 752
to radio-carpal joint, 705
to radius, 705
ramus anastomoticus perona?.us, 730
of rectum, 1233
recurrens (vagi), 788
recurrent tibial, 730
to rhomboids, 702
sacral, 691, 727, 735
anterior rami of, 727, 735
visceral branches of, 736
posterior rami of, 691
sacro-coccygeal, anterior, 738
posterior, 691
saphenous, 726
surgical anatomy of, in foot, 1465
in leg, 1463
in thigh, 1461
to scaleni muscles, 695, 697
to scalp muscles, 783
scapular, dorsal, 702
sciatic, 728
course of, 728
division of nerve to hamstrings, 728
nerve to short head of biceps, 728
surgical anatomy of, 1456
scrotal anterior, 721
Nerve or Nerves (contd.)
scrotal (contd.) posterior, 739
segmental, of head, 796
to semicircular ducts, 785
sensory ganglion of, 510
to short head of biceps, 729
muscles of little finger, 709
of thumb, 706
to shoulder-joint, from axillary, 710
from supra-scapular, 703
of skin, 858
of small intestine, 1187
spermatic, external, 722
spheno-palatine, 775
to sphincter ani muscle, 738, 739
pupillse muscle, 814
spinal, 685
anterior rami of, 685
classification of, 678
development of, 679
distribution of, general, 680, 687
to limb -muscles, 687
to skin of limbs, 687
formation of, 680
ganglia of, 685
gray rami of, 680, 681
of brachial plexus, 700
of cervical plexus, 694
of lumbo-sacral plexus, 719
of pudendal plexus, 719
of sacral plexus, 719
of thoracic nerves, 714, 716, 717
morphology of rami, 681, 691, 741
number of, 678
origin of, 522, 528
posterior rami, 687, 691
recurrent branches of, 686
relation of, to meninges, 686
to vertebrse, 1442, 1443
roots of, 519
anterior, 519
development of, 679
posterior, 519
development of, 679
segmental disposition of, 687
size of, 678
somatic portion of, 680
splanchnic portion of, 680
visceral branches of, 680
white rami of, 687
development of, 681
of lumbar and sacral nerves, 719
of pudendal plexus, 719
of sacral plexus, 719
of thoracic, 714, 716, 717
spinosus, 778
splanchnic, 761
greater, 761, 764
lesser, 761
lowest, 76], 764
stapedius, 782
to sterno-mastoid muscle, 696, 793
from accessory, 793
of stomach, 1177
to stylo-pharyngeus muscle, 786
to subclavius, 702
of sublingual gland, 1140
of submaxillary gland, 1138
suboccipital, 688
morphology of, 691
subscapular, 713
lower, 713
1548
INDEX.
Nerve or Nerves (contd.)
subscapular (contd.), short, 713
supra--clavicular (descending cervical), 696
anterior, 696
middle, 696
posterior, 696
morphology of, 700
supra-orbital, 772
surgical anatomy of, 1358
supra-scapular, 703
variations of, 700, 752
supra-trochlear, 773
surgical anatomy of, 1358
sural, of common peroneal, 730
lateral, of posterior cutaneous nerve of
thigh, 737
medial, of tibial, 732
sympathetic, 753
of taste, 598
temporal, of auriculo-temporal, 780
deep, 779
of facial, 783
topography of, 1359
to tensor fasciae latae muscle, 729
tympani muscle, 835
veli palatini muscle, 786, 788
tentorii, 772
to teres minor muscle, 710
terminalis, 608
thoracic, 713
anterior rami of, 713
cutaneous branches of, 714
of first, 714
of second, 714
of twelfth, 717
communications of, 714, 716, 717, 719
muscular branches of, 703
of first, 714
of second, 714
of twelfth, 717
posterior rami of, 690
cutaneous branches of, 690
first, 713
lateral anterior, 703
long, 702
medi
ial anterior, 703
second, 690
twelfth, 690
thoraco-dorsal, 713
to tibia, 732
tibial, 729, 732
surgical anatomy of, 1458
communicating, 732
recurrent, 730
to tibio-fibular joint, from common peroneal,
730
from tibial, 732
of tongue, 1 136
of tonsil, 1149
to transversus abdominis, 484
thoracis muscle, 470
to trapezius muscle, 366
from accessory, 793
trigeminal, 771
ascending root of, 601
deep origin of, 600
development of, 683
divisions of, 772
mandibular, 778
maxillary, 775
ophthalmic, 772
mesencephalic root of, 601
Nerve or Nerves (contd.)
trigeminal, mesenceplialic root of (confd.),
in pons, 602
morphology of, 796
motor root of, 601
development of, 683
morphology of, 796
nuclei of, 600
development of, 683
of mesencephalic root of, 602
in pons, 602
semilunar ganglion of, 771
sensory root of, 600
development of, 683
morphology of, 796
spinal tract of, 601
development of, 602
superficial origin of, 600, 771
trochlear, 770
communications of, 771
course of, 770
deep origin of, 602
development of, 683
morphology of, 798
nucleus of, 602
superficial origin of, 602, 770
tympanic, 786, 836
morphology of, 796
to ulna, 705
ulnar, 708
course of, 708
surgical anatomy of, in arm, 1448
at elbow, 1451
collateral, 711
to utricle, 785
to uvular muscle, 786
vagus, 786
abdominal branches of, 789
afferent fibres of, 596
root of, 795
branches of, 789
cardio-inhibitory fibres of, 793
communications of, 788, 789
deep origin of, 596
development of, 795
efferent fibres of, 596
root of, 795
ganglion nodosum of, 788
in jugular foramen, 786
jugular ganglion of, 788
left, in thorax, 786
morphology of, 797
in neck, 788
nucleus of, 597
relation of, to fourth ventricle, 551
right, in thorax, 786
roots of, 596
development of, 795
morphology of, 796
superficial origin of, 786
surgical anatomy of, 1393
termination of, in coats of stomach, 1177
in thorax, 786
viscero-motor fibres of, 793
vesical, 766
vestibular, 853
connexion of, with cerebellum, 604
deep origin of, 604
descending root of, 605
nucleus of, 604, 605
relation of, to fourth ventricle, 551
zygomatic, of facial, 773, 775
INDEX.
1549
Nerve or Nerves (contd.)
zygomatic (contd.\ of maxillary, 776
zygomatico-facial, 776
zygomatico-temporal, 776
Nerve-cells, 506
axons of, 507
bipolar, 510
cellulipetal processes of, 511
of cerebellum, 579
of cerebral cortex, 645
dendrites of, 509
development of, 35, 498
ganglionic, 510
of Golgi, in cerebral cortex, 645
processes of, 528, 529, 530, 531
of Purkinje in cerebellum, 580, 581
radicular, 528
of spinal ganglia, 685
medulla, 529
of sympathetic ganglia, 753
unipolar, 510
Nerve-components, 505
Nerve-endings, 863
free, 863
special end organs, 863
Nerve-fibres, 508
afferent, 509
collateral, 512, 534, 535
efferent, 504, 509
medullated, 508
myelinisation of, 509
of lateral cerebro-spinal tract, 533
of medial longitudinal fasciculus, 589
order of occurrence of, in spinal medulla,
533
of sensory, 532
neurolemma of, 508
non-medullated, 508, 754
primitive sheath of, 508
somatic efferent, 505
splanchnic, afferent, 754, 760
in thoracic region, 759
efferent, 505, 754, 760
in thoracic region, 761
peripheral, 755
sympathetic, 754
cervical, 756
destinations of, 754
medullated, 754
non-medullated, 754
splanchnic, 754, 756
terminations of, 504, 509
Wallerian degeneration of, 532
Nerve-roots, 519
anterior, origin of fibres of, 528
cerebral, 592
spinal, 519
development of, 519
anterior, 519, 529
development of, 520
origin of, 529
relation of, to sympathetic, 754
posterior, 519, 533, 534, 536
development of, 520, 536
in posterior funiculus of spinal medulla,
533
relation of, to sympathetic, 754
fervous system, 497
cerebro-spinal, 497
early stages of development, 30
elements of the, 497
of hydra, 497
Nervous system (contd.) t scheme of the, 498
sympathetic, 753
Nervus, see Nerve
Neural arteries, of gluteal, 938
of intercostals, 926
canal, 31
crest, 32, 500, 679
ectoderm, 499, 501
fold, 31
groove, 23
plate, 30
syncytium, 504
tube, 31, 33
alar lamina of, 36, 505, 682
in fore-brain, 608
in hind-brain, 552, 553, 554
in mid -brain, 592
relation of. to origin of nerves, 553,
554, 682
basal lamina- of, 36, 505, 682
in fore-brain, 608
in hind-brain, 553
in mid -brain, 592
relation of, to origin of nerves, 553,
554, 682
central canal of, 564, 565
development of cerebral nerves from, 682
of spinal nerves from, 679
differentiation of, 33
ependymal layer of, 502
fate of spinal portion, 35
flexures of, 5.14
floor-plate of, 402, 520
germinal cells of, 35
istological differentiation of walls, 35
limiting membrane of, external, 35, 502
internal, 35, 502
mantle -layer of, 502
marginal layer of, 502
myelospongium of, 503
neuroblasts of, 503
perforations in wall of, 37
roof-plate of, 402, 520
sulcus limitans of, 36
Neurenteric canal, 23, 26
Neurobiotaxis, 554
Neuroblasts, 36, 503
N euro-central synchondrosis, 104
Neuroglia of brain, 511
of spinal medulla, 527
Neurolemma, 508
Neurology, 3
Neuro-muscular spindles, 866
Neuron, 503
Neurone theory, 503
objections to, 504
Neuropore, 31
anterior, 31, 500
posterior, 31, 500
Neuro-tendinous spindles, 865
Nictitating membrane, 821
Nipple, 1337
Nodule of cerebellum, 571
development of, 571
Noduli aggregati of vermiform process, 1217
lymphatici aggregati, 1181
intestini recti, 1230
lienales, 1355
solitarii, 1181
valvularum semilunarium, 877
Nose, 799
ala of, 799
1550
INDEX.
Nose (contd.}, alar sulcus of, 799
arteries of, 805
bridge of, 799
cartilages of, 800
cavity of, 801
choanae of, 175, 185, 196
surgical anatomy of, 1246
development of, 49
digital exploration of, 1378
external, 799
floor of, 804
hiatus semilunaris of, 803
infundibulum of, 803
lateral wall of, 802
limen of, 802
lymph vessels of, 1004
meatuses of, 803
mucous membrane of, 804
muscles of, 450
action of, 452
nerve -supply of, 452
nasal index of, 799
nerves of, 805
olfactory part of, 804
outer parts of, 799
piriform openings of, 163
recessus spheno-ethmoidalis of, 802
respiratory part of, 804
septum of, 802
surgical anatomy of, 1378
veins of, 806
vessels of, 805
vestibule of, 802
Nostril, 799
Notch, acetabular, of ischium, 232
variations in, 281
cardiac, of lung, 1095
of cerebellum, 574
ethmoidal, 116
greater sciatic, of ilium, 229
infra-sternal, 1397, 1407
intercondylic, of femur, 243
jugular, 107
mandibular, 156
nasal, 115
pterygoid, 137
pterygo-palatine, 151
radial, 211
of Rivinus, 834
of sacrum, 96
scapular, 201, 203
great, 202
sciatic, 229, 232
semilunar, 211
of spleen, 1352
supraorbital, 116
suprasternal, 107
ulnar of radius, 215
umbilical, 1191
Notochord, 23, 24, 290
formation of, 24
remnants of, 25
Nuchal furrow, 1395
lines, 166, 171
of occipital bone, 121
plane of occipital bone, 121
Nuck, canal of, 1319
Nuclear juice, 8
layer of retina, 816, 817
membrane, 8, 9
Nucleolus, 8, 9, 10
false, 8
Nucleus, 8
Nucleus or Nuclei, of abducens nerve, 600
relation of, to medial longitudinal
bundle, 588, 600
accessory, 560, 595
of acoustic nerve, 604-606
ambiguus, 595, 596
amygdalae, 641
anterior, of thalamus, 612
arcuate, 552, 563
development of, 552
of thalamus, 612
of Bechterew, 605
caudate, 635, 637
of cells, 8
during mitosis, 9, 13
segmentation, 10
central, of Luys, 612
cochlear, 554, 604
development of, 684
colliculi inferioris, 585
corporis geniculati lateralis, 613
medialis, 607
mamillaris, 615
of corpus trapezoideum, 606
cuneate, 533, 547, 560
development of, 552
relation of, to arcuate fibres, 560
of Deiters, 605
function of, 605
dentate, 576
dorsalis, 531
emboliformis, of cerebellum, 577
of facial, 599
fastigii, 577
fertilisation of, 20
first segmentation, 21
of funiculus solitarius, 598
globosus, 577
glossopharyngeal, 596-598
relation of, to fourth ventricle, 596
gracilis, 547
relation of, to arcuate fibres, 560
to lemniscus, 559
hypoglossal, 594
relation of, to fourth ventricle, 594
. hypothalamicus, 614
intercalatus, 551
laryngeal, 598
of lateral lemniscus, 606
lentiform, 638
lentis, 520
of Luys, 614
medial, of thalamus, 611
of medulla oblongata, 551
development of, 551, 592
of mesencephalon, 584, 585, 586, 588
motor, 592
motorius nervi trigemini, 601
oculo-motor, 603
olivary, accessory, 556
inferior, 556
relation of, to cerebello-olivary fibres, 556
surface elevation of, 547
superior, 567, 606
pedicle of, 606
relation of, to corpus trapezoideum, 606
to lateral lemniscus, 606
to nucleus of lateral lemniscus, 606
of optic nerve, 620
of origin, 592
of origin of cerebral nerves, 592
INDEX.
1551
Nucleus or Nuclei, of origin (contd.), develop-
ment of, 592
poiitis, 566
development of, 566
relation of, to transverse fibres of pons, 566
pulposus, 307
radicis descendentis nervi trigemini, 559
red, 613
roof, 577
relation of, to spino-cerebellar tract, 578
ruber, 586-588
origin of, 516
segmentation, 21
somatic afferent terminal, 506
efferent, 506
splanchnic afferent terminal, 506
efferent, 506
of tegmentum, 586
terminal, 505
of termination of nerves, 593
of thalamus, 611
tractus solitarii, 598
spinalis nervi trigemini, 559
trigeminal, 600
development of, 683
trochlear, 602
relation of, to medial longitudinal bundle,
602
vagus, 596
relation of, to fourth ventricle, 596
vestibular, 554, 604
early importance of, 575
relation of, to fourth ventricle, 604
Nuel, space of, 852
Number of bones, 265
Nutrient arteries, 87
Nymphae, see Labia pudendi minora
Obelion, 171, 285
Obex, 579
Oblique chord, 328
line, anterior, of radius, 215
external, of mandible, 155
Oblique line of tibia, 249
vein of Marshall, 960
Obliquus externus abdominis muscle, 476
inferior, of neck, 444
of orbit, 453
interims abdominis muscle, 478
superior muscle of neck, 444
of orbit, 453
action of, 454
nerve-supply of, 454
Obliterated umbilical artery, 936
Obstetrical paralysis of Duchenne, 1395
Obturator artery, 940
abnormalities of, 1057
canal, 338
crest, 233
externus muscle, 413
action of, 414
nerve-supply of, 414
fascia, 489
foramen, 234
gland, 1017
groove, 234
abnormalities of, 281
internus muscle, 418
action of, 418
nerve-supply of, 418
membrane, 338
nerve, 722
Obturator nerve (contd.), accessory, 726
plexus, 723
tubercle, anterior, 234
posterior, 234
vein, 984
Occipital angle of parietal bone, 119
arteries, 895
bone, 120
architecture of, 270
basilar part of, 123
ossification of, 124
cerebral surface of, 121
condyles of, 122
ossification of, 124
connexions of, 124
foramen magnum of, 123, 172, 178
lateral parts of, 121
morphology of, 290
nuchal lines of, 121
plane of, 121
ossification of, 124
relation of, to sutures, 165, 171
squamous part of, 121
ossification of, 124
variations in, 277
condyles, 122, 182
third, 278
crest, external, 121
internal, 121, 182
fontanelle, 293
lobe, 660
topography of, 1360
lymph glands, 998
nerves, 688-690
plane, 118
point, 183, 285
protuberance, external, 121, 178
internal, 121, 182
sinus, 183, 974
abnormalities of, 1058
sulcus, 661
triangle, 1395
vein, 965, 967
Occipito-atloid joint, 309
movements at, 311
ligaments, 310
Occipito-epistropheal ligaments, 311
Occipito-frontal fasciculus, 650
Occipito-mastoid suture, 165, 171
Oculo-motor nerve, 683
connexions of, 604
development of, 683
morphology of, 798
nucleus of, 603
splanchnic efferent nucleus of, 604
sulcus, 603
Oculo-nasal sulci, 49
Odontoblasts, 1245
processes of, 1247
(Esophageal arteries of aorta, 925
of coronary, 929
of inferior thyreoid, 611
morphology of, 1046
groove of liver, 1189
of lung, 1094
opening of diaphragm, 473
orifice of stomach, 1163
plexus, 791
veins, 961
(Esophagus, 1150
abdominal part of, 1152
cervical portion of, 1151
1552
INDEX.
(Esophagus, cervical (contd.), surgical anatomy
of, 1393
constrictions of, 1151
development of, 45, 1249
diaphragmatic part of, 1152
distensibility of, 1407
glands of, 1155
relations of, 1151, 1152, 1153
structure of, 1153
surgical anatomy of, 1407
thoracic part of, 1152
variations in, 1153
vessels and nerves of, 1155
Olecranon, 210
fossa, 208
topography of, 1449
Olfactory area, 500, 622
bulb, 622, 623
development of, 622
morphology of, 622
structure of, 623
bundle, 627
cells, 805
cleft, 1378
ganglion, 622
morphology of, 622
glands, 804
glomeruli, 623
groove, 140, 141, 179
hairs, 805
lobe, 624
development of, 624
relation of, to anterior cerebral commissure,
626
nerve, 767, 768, 805
central connexions of, 623
development of, 682
neurones, 625
organ, 799
for receptive impressions, 625
pits, 49, 682
sulcus, 666
tract, 622, 623
development of, 622
structure of, 623
triangle, 623
tubercle, 623
Oligolecithal ovum, 14
Olivary nucleus, 555
Olive of medulla oblongata, 547
Omental bursa, 1162, 1238
tuberosity of liver, 1193
of pancreas, 1206
Omentum, 1162
gastro-colic, 1162
gastro-hepatic, 1162
gastro-splenic, 1162
development of, 1253
relation of, to omental bursa, 1239
greater, 1162, 1241
development of, 1253
functions of, 1242
relation of, to duodenum, 1186
to omental bursa, 1239
to transverse colon, 1239
lesser, 1162, 1197, 1241
development of, 1253
relation of, to omental bursa, 1239
Omo-hyoid muscle, 459
action of, 394
nerve-supply of, 394
Ontogeny, 1
Oocyte, 12
of first order, 12
of second order, 15
Oogonia, 12, 15
Oolemma, 13
Opening of subaraclmoid part of brain,
1362
Opercula insulae, 655
orbital, 655
superior, 655
temporal, 655
Ophryon, 285
Ophthalmic artery, 902
abnormalities of, 1054
nerve, 772
morphology of, 797
veins, 968
Opisthion, 178, 183
Opponens digiti quinti muscle, 393
action of, 394
nerve -supply of, 394
Opponens pollicis muscle, 392
action of, 393
nerve-supply of, 393
Optic axis, 807
chiasma, 541, 619
decussation in, 769
development of, 609, 682, 826
morphology of, 798
commissure, 619
cup, 682, 826
of optic disc, 815
disc, 815
foramen, 180
abnormalities of, 278
groove, 135
nerve, 541, 768
deep connexions of, 620
development of, 33, 609, 682
morphology of, 798
papilla, 815
in retina, 816
radiation, 620, 643, 658
recess, 618
stalk, 682, 825, 826
morphology of, 798
tract, 541, 619
central connexions of, 619
cortical connexions of, 620
vesicle, 825
pigmentary layer of, 825
Ora serrata, 815
structure of, 815
Oral'part of the pharynx, 1144, 1145
Orbicularis oculi muscle, 450
Orbicularis oris muscle, 450
action of, 452
nerve -supply of, 452
Orbiculus ciliaris, 812
Orbit, 160, 162
fascia of, 452
floor of, 162
lateral wall of, 162
medial wall of, 163
muscles of, 452
action of, 454
morphology of, 496
nerve-supply of, 454
roof of, 160
veins of, 968
Orbital artery of middle meningeal, 898
of superficial temporal, 897
INDEX.
1553
Orbital (contd.), fossa, 160
gyri, 666
index, 287
margin, 115
sexual differences in, 193
part of frontal bone, 117, 162
plate of ethmoid bone, 140, 163
process of palate bone, 152, 162, 170
of zygomatic bone, 154
septum, 822
sulcus, 666
wings of sphenoid, 135
Orbito-maxillary -frontal suture, 279
Orbito-nasal centre, 150
Orbito-sphenoids, 135, 138
Orbito-tarsal ligaments, 1378
Organ of Corti, 849, 856
epibranchial, 796, 797
of lateral line, 796
of Ruffini, 865
of senses, 799
of taste, 854
vomero-nasal, of Jacobson, 802
Orifice, aortic, 878
topography of, 1405
external, of uterus, 1316
internal, of uterus, 1317
mitral, 876, 878
level of, 1442
topography of, 1405
pulmonary, 878
topography of, 1405
tricuspid, 877
level of, 1442
topography of, 1405
Origin of muscles, 364
Orthocephalic skulls, 286
Orthognathous skulls, 287
Os or Ossa, breve, 82
calcaneus, 259
capitate, 221
morphology of, 295
ossification of, 223
carpal, 280
carpi, 217
centrale, 280
morphology of, 295
clitoridis, 1326
coccygis, 99
cordis, 876
coxae, 228
cranii, 115
cuboideum, 263
cuneiforme, first, 261
second, 262
third, 263
ethmoidale, 139
extremitatis inferioris, 228
superior-is, 197
faciei, 146
fibulare, 295
frontale, 115
hamatum, 221
surface anatomy, 1451
variation in, 280
hyoideum, 158
ilium, 228
Incae, 278
intercuneiforme, 282
interfrontale, 277
intermetatarsale, 282
interparietale, 277
Os or Ossa (contd.\ ischii, 232
Japonicum, 279
lacrimale, 143
longum, 82
lunatum, 218
metacarpalia, 223
metatarsalia, 265
multangulum majus, 220
minus, 220
nasale, 145
naviculare, of the hand, 218
of the foot, 261
occipitale, 120
odontoideum, 275
orbiculare, 840
palatinum, 150
parietale, 118
penis, 1300
pisiforme, 219
pubis, 233
radiale, 295
sacrum, 96
sesamoidea, 269
sphenoidale, 133
subcapitulare, 280
sustentaculi, 282
suturarum, 145
tarsi, 254
temporal e, 125
tibiale, 295
trigonum, 282
triquetrum, 219
ulnare, 295
Vesaleanum, 282
zygomaticum, 153
Osseous labyrinth, 843
Ossicles, auditory, 838
articulations of, 840
development of, 841
joints of, 840
ligaments of, 841
movements of, 842
epipteric, 146
of Kerkring, 124
Ossification of bones, 84
of laryngeal cartilages, 1065
Osteoblasts of bone, 85
Osteology, 3, 81
descriptive terms of, 82
Ostium abdominale tubae uterinse, 1314
maxillare, 804
pharyngeum tubae auditivae, 837, 838
tympanicum tubae auditivee, 837
uterinum tubae, 1315
Otic ganglion, 781
branches of, 781
development of, 684, 796
roots of, 781
vesicle, 51, 853
Otoconia, 847
Ovarian artery, 928
fimbfia, 1312, 1314
fossa, 1312
ligament, 1312
plexus, 765
vein, 1048
abnormalities of, 1058
morphology of; 1048
Ovary, 1311
bursa of, 1318
connexions of, 1312
corpora albicantia of, 1313
1554
INDEX.
Ovary (contd.\ corpora lutea of, 1313
descent of, 1313
development of, 1334
egg-tubes of, 1314
extremities of, 1311
tubal extremity, 1311
uterine extremity, 1311
free border, 1311
hilum of, 1311
ligament of, 1311, 1312
lymph vessels of, 1314
mesovarial border, 1311
nerves of, 765, 1314
ova of, 1313
position and relations of, 1311, 1312
primitive follicles of, 1313
stroma of, 1313
structure of, 1313
surgical anatomy of, 1435, 1436
suspensory ligament of, 1312
vesicular follicles of, 1313
vessels of, 1314
Ovules of Naboth, 1320
Ovum, 13
alecithal, 14
centrosome of, 14
cone of attraction, 20
deutoplasm of, 14
eutelolecithal, 14
fertilisation of, 20
maturation of, 15
nucleus of, 14
oligolecithal, 14
in ovary, 1313, 1314
primitive, 1313, 1314
relation of, to decidua, 57
segmentation of, 15, 21
special characters of, 13
telolecithal, 14
Pacinian corpuscles, 864
Pad, 1110, 1111
infra-patellar, of knee-joint, 348
suctorial, 1109
Palate, 1110
aponeurosis, 466, 1111
arches of, 1111, 1112
arteries of, 1111
bone, 150
horizontal part of, 151
orbital process of, 152
perpendicular part of, 151
pyramidal process of, 152
relation of, to nasal fossae, 183
to orbit, 162
to zygomatic fossa, 168
sphenoidal process of, 152
ossification of, 153
development of, 49, 1379
foramen, greater, 151, 174
surgical anatomy of, 1384
lesser, 152, 174
glands, 1110
hard, 174, 1107, 1110
surgical anatomy of, 1384
incisive pad of, 1110, 1111
lymph vessels of, 1112
mucous membrane of, 1111
muscles of, 466
development of, 496
nerves of, 778, 1112
papilla palatina of, 1110
Palate (contd.}, plicse palatinae of, 1110
raphe of, 1110
rugae of, 1110, 1111
soft, 1107, 1110
folds of, 1111
level of, 1442
mucous membrane of, 1111
muscles of, 1111
structure of, 1111
uvula of, 1111
veins of, 965
Palatine canal, anterior, 149
greater, 152
lesser, 152
superior openings of, 152
cleft, 1379
surgical anatomy of, 1379
process, 148, 149
suture, median, 174
transverse, 174
taste-buds, 854
tonsils, 1106, 1145
primary haemorrhage after removal of, 1384
surgical anatomy of, 1584
Palato-ethmoidal suture, 162
Pallium, 621
Palm, surgical anatomy of, 1454
Palmar arch, deep, 923, 924
abnormalities of, 1055
morphology of, 1055
surface anatomy of, 1454
superficial, 923, 924
morphology of, 1047
surface anatomy of, 1454
fascia, 384
ligaments of carpal joints, 328
of carpo-metacarpal joints, 330
of metacarpo-phalangeal joints, 332
Palmaris brevis muscle, 382
longus muscle, 386
action of, 386
nerve-supply of, 386
Palpebrse, 821
Palpebral arteries, 823
fissure, 821
ligaments, medial, 822
surgical anatomy of, 1376
nerves, 824 '
raphe, lateral, 822
veins, 824
Pampiniform plexus, 983
Pancreas, 1203
accessory, 1207
body of, 1203, 1206
characters of, 1207
development of, 47
ducts of, 1206, 1207, 1255
termination of, 1186, 1203, 1207
accessory, 1207
head of, 1203, 1204
lesser, 1207
lymph vessels of, 1207
margin, anterior, 1206
inferior, 1206
superior, 1206
neck of, 1203, 1205
nerves of, 1208
omental tuberosity of, 1206
parts, 1203
peritoneal relations of, 1206
position, 1203
processus uncinatus of, 1203
INDEX.
1555
Pancreas (contd.), relations, 1203
shape, 1203
structure of, 1207
surface of, anterior, 1206
inferior, 1206
posterior, 1206
surgical anatomy of, 1426
from behind, 1439, 1442
tail of, 1203, 1206
variations in, 1207
vessels of, 1207
Pancreatic artery, 930, 1207
cysts, 1426
veins, 1208
Pancreatico-duodenal arteries, 930, 932, 1205,
1207
vein, 1208
Panniculus adiposus, 364
carnosus, 364
Papilla or Papillae, bile, 1186, 1203, 1207
conical and filiform, 1127
corii, 857
dentis, 1244
duodeni, 1186, 1203, 1207
fungiform and lenticular, 1127
of integument, 857
of kidney, 1265
lacrimal, 821
lenticular, 1127
lingual, 1126
mammae, 1337
of nail, 859
of optic nerve, 815
pili, 860
renal, 1265
of skin, 857
vallate, 1127
Paracentesis of the pericardium, 1405
of pleura, site for, 1402
of tympanic membrane, 1368
Paracentral lobule, 664, 666
Parachordal cartilages, 290
Paradidymis, 1287
origin of, 1335
Paraduodenal fossa, 1185
Paraflocculus, 571
Paramastoid process, 278
Parametrium, 1318, 1319
Paranephric fat, 1425
Parapophysis, 284
Parapyramidal fissure, 573
Pararectal fossa, 1227, 1238
Parasinoidal sinuses, 974
Parasternal line, 1397
Parathyreoid bodies, 44
glands, 1348
blood-vessels of, 1349
development of, 1349
number of, 1349
position of, 1349
structure of, 1349
surgical anatomy of, 1388
Para-urethral duct, 1285, 1309
Paravesical fossa, 1238, 1280
Paraxial mesoderm, 27
Parenchyma testis, 1288
Paries carotica of tympanic cavity, 834
jugularis, 832
labyrinthica, 832
mastoidea, 834
membranacea, 834
tegmentalis, 832
Parietal artery, 897
bones, 118
angles of, 119
cerebral surface of, 119
ossification of, 120
relation of, to sutures, 171
surface of, 118
topography of, 1359
tuberosities of, 118
variations in, 277
foramen, 171
abnormality of, 277
gyri, 662
lobe, 662
region of the brain, 662
Parieto-mastoid suture, 164
Parieto -occipital artery, 908
fissure or fossa, 661, 662
topography of, 1360
Parieto-temporal artery, 905
Paroccipital process, 278
Par-oophoron, 1316, 1335
Parotid artery, of posterior auricular, 895
of superficial temporal, 896
duct, 1109, 1376
surgical anatomy of, 1376
fascia, 447, 1133
gland, 1133
accessory, 1136
development of, 1244
duct of, 1136
surgical anatomy of, 1376
nerves of, 1137
relation of, to external acoustic meatus,
1135, 1366
surgical anatomy of, 1376
vessels of, 1137
lymph glands, 998
Pars or part abdominalis of oesophagus, 1152
et pelvina s. sympathici, 761
analis recti, 1228
basilaris ossis occipitalis, 123
pontis, 565
cavernosa ure three, 1308
centralis of lateral ventricle, 634
cephalica et cervicalis s. sympathici, 750
cervical of the oesophagus, 1151
ciliaris retinae, 815
development of, 826
convoluta of kidney, 1265
dorsalis pontis, 567
flaccida membranae tympani, 835
frontalis capsulae intern 33, 642
operculi, 655
iridica retinas, 813, 815
development of, 826
lacrimalis of orbicularis oculi, 450
laryngeal part of pharynx, 1147
majnillaris hypothalami, 609
membranacea of the urethra, 1307
nasal of the pharynx, 1142
occipitalis capsulae internae, 643
optica hypothalami, 609
retinae, 815
oral of pharynx, 1144
orbitalis operculi, 655
parietalis operculi, 655
prostatica of the urethra, 1305
radiata of kidney, 1265
squamous of occipital bone, 121
temporalis operculi, 655
tensa membranae tympani, 835
1556
INDEX.
Pars or part (contd.), thoracalis of the oesophagus,
1152
s. sympathici, 759
triangularis operculi, 655
Patella, 245
apex of, 245
articular surface of, 245
base of, 245
fracture of the, 1460
ligaments of, 344
relation of, to fascia lata, 404, 409, 422
to quadriceps (extensor) femoris, 409
ossification of, 245
topography of, 1460
Patellar plexus, 726
Pecten ossis pubis, 233
Pectinea fascia, 403
Pectineal line, 231
Pectineus muscle, 411
action of, 411
nerve -supply of, 411
Pectiniform septum of penis, 1300
Pectoral fascia, 369
girdle, 203, 270
lymph glands, 1008
muscles, nerve -supply of, 704
region, fascia, 369
muscles of, 369
ridge, 206
Pectoralis major muscle, 369
action of, 370
nerve-supply of, 370
minimus, 371
minor muscle, 371
action of, 371
nerve -supply of, 371
Pedicles (O.T.) of vertebrae, 89, 90, 93, 95
Peduncles of cerebellum, 577
of cerebrum, 34
of corpora mamillaria, 615
olivary, 556
of pineal body, 614
development of, 614
Pedunculi cerebri, 541, 542, 583
basis pedunculi of, 583
origin of, 517
sulcus lateralis of, 584
n. oculomotorii of, 584
tegmentum of, 583
Pelvic colon, 1222
topography of, 1423
diaphragm, 493
fasciae, 489
floor, 490
girdle, 228, 273
morphology of, 295
mesocolon, 1223
part of sympathetic, 762
plexus, 766
Pelvis, 235
articulations of, 335
axis of, 237
cavity of, 489
conjugate diameter, 237, 238
diameters of, 237, 238
dolichopellic, 288
fasciae of, 489
female, surgical anatomy of, 1434
growth of, 238
inferior aperture of, 237
sexual differences in, 237
ligaments of, 336
Pelvis (contd.), lymph vessels of, 1015
major, 235
measurements of, 238
mechanism and movements of, 338
mesatipellic, 288
minor, 236
muscles of, 493
oblique diameter of, 237
peritoneum of, 1237
planes of, 238
platypellic, 288
position of, 237
renal, 1268
calyces majores of, 1268
minores of, 1268
development of, 1331
sexual differences in, 237
superior aperture, 236
sexual differences in, 237
transverse diameter, 237
white line of, 491
Penis, 1298
artery of, 1300
bone of, 1300
bulbus urethrae of, 1299
corona glandis of, 1298
corpora cavernosa of, 1299
structure of, 1300
corpus cavernosum urethrae of, 1298
structure of, 1300
crura of, 1299
development of, 1336
dorsal vein of, 897
dorsum of, 1298
fascia of, 1300
fraenulum praeputii, 1299
glandulae pra&putiales, 1299
glans of, 1298
development of, 1336
hemispheria bulbi urethras of, 1299
ligamentum suspensorium of, 1299
nerves of, 740
praeputium, 1299
root of, 1299
bulbus urethrae of, 1299
crura of, 1299
septum of, 1300
structure of, 1300
suspensory -ligament of, 1299
tunica albuginea of, 1300
vessels and nerves of, 1300
Perforated substance, 624
Perforating arteries, 950
cutaneous nerve, 737
Pericardiac nerve, 791
Pericardiaco-phrenic artery, 913
Pericardial area, 27, 65
arteries, of aorta, 925
of internal mammary, 913
Pericardium, 880
development of, 72, 74
fibrous part of, 880
great oblique sinus of, 882
paracentesis of, 1405
serous, 881
sinuses of, 882
structure of, 882
transverse sinus of, 882
vestigial fold of, 882
Perichondrium, 85
Pericranium, 1357
Perilymph, 846
INDEX.
1557
Perimysium externum, 363
internum, 363
Perineal arteries, 942
body (female), 1322
fascia of Colles, 338, 1427
fold, 48
ligament, transverse, 338
nerves, 737
Perinephric arteries, 927, 928
Perineum, 1427
central point of, 1427
fascia) of, 485
male, surgical anatomy of, 1427
muscles of, 486
rectal triangle of, 1431
surgical anatomy of, 1427
urogenital diaphragm of, 338, 489, 491
triangle of, 1427
Period, pre -embryonic, 7
of embryo, 7
of fcetus, 7
Periosteum, 83
relation of, to ossification, 85
alveolar, 1115, 1123
development of, 1245
Peripheral nerves, development of, 679
Peritoneal cavity, 1412
hepato-renal pouch of Morrison, 1414
left infra-colic compartment of, 1414
right infra-colic compartment of, 1414
subdivisions of, 1412
supra-colic compartment of, 1414
surgical anatomy of, 1412
Perinephric abscess, 1439
Peritoneum, 1160, 1234
anterior layer of, 1234
bursa omentalis, 1234
development of, 1252
duodenal fossae of, 1185, 1186
duodeno-jejunal fossa of, 1185, 1186
femoral fossa of, 1235
folds of, 1162-1163, 1235-1242
foramen epiploicum, 1162, 1239
great sac of, 1234
inguinal fossae of, 1235
intersigmoid fossa of, 1223
surgical anatomy of, 1423
ligaments of, 1162, 1235-1242
surgical anatomy of, 1412
mesenterico-mesocolic fold of, 1186
mesenteries of, 1163, 1208, 1242
omenta of, 1162, 1241
functions of, 1242
omental bursa of, 1102, 1195, 1234, 1239
paraduodenal fossa of, 1186
pararectal fossa of, 1238
paravesical fossa of, 1238, 1280
parietal and visceral, 1161
pelvic, 1237
posterior wall of, 1236
pouch of Douglas of, 1237, 1238, 1318
surgical anatomy of, 1434, 1436
processus vaginalis of, 1295, 1319
recto-vesical pouch of, 1282, 1283
surgical anatomy of, 1434
relation of, to bladder, 1280
to caecum, 1218
to colon, 1219, 1220, 1221
to duodenum, 1186, 1239, 1240
to kidney, 1262
to liver, 1195
to pancreas, 1206
Peritoneum (contd.\ relation of, to rectum, 1226
to spleen, 1353
to stomach, 1170
to uterus, 1317
surgical anatomy of, 1412
transverse tracing of, 1238
utero-vesical pouch of, 1317
visceral, 1161
Peri vascular lymph -spaces, 994
Permanent teeth, 1115-1119
Peronseo-calcaiieus muscle, 431
lateralis muscle, 427
Peronaeo-cuboideus muscle, 427
Peronasus accessorius muscle, 427
brevis muscle, 427
action of, 427
digiti quinti muscle, 427
longus muscle, 426
action of, 427
tertius muscle, 425
action of, 426, 953
Peroneal artery, 953
muscles, surgical anatomy of, 1462
nerve, 731
retinaculum, superior, 422
Perpendicular plate of ethmoid, 139, 185
Petit, canal of, 839
Petro-basilar fissure, 130
Petro-mastoid suture, 1369
Petro-occipital fissure, 176
Petrosal artery, 898
ganglion, 785
nerve, deep, 758, 777
superficial, external, 782, 898
greater, 777
origin of, 598
smaller, 759, 786
process, 135
sinus, inferior, 975
superior, 975
Petro-squamous fissure, 131
suture, 125, 126
surgical anatomy of, 1369
Petro-tympanic fissure, 125, 133
Petrous ganglion, 785, 786
part of temporal bone, 131
Phaenozygous crania, 286
Phalangeal process of lamina reticularis, 851
Phalanges of foot, 267
of hand, 226
of rods of Corti, 851
ossification of, 227, 268
Pharyngeal artery, ascending, 896
bar, 42
development of, 1028
nerves, 1150
of glosso-pharyngeal nerve, 786
of spheno-palatine ganglion, 778
of sympathetic, 756
of vagus, 788
orifice of auditory tube, 1143
plexus, 756, 786, 788
tubercle, 123
veins, 965
Pharyngo-branchial duct, 44
Pharyngo-epiglottic fold, 1067
Pharyngo-glossus, 464
Pharyngo-palatine arch, 1111, 1112
muscle, 465
action of, 467
nerve-supply of, 467
Pharyngotomy, sub-hyoid, 1387
1558
INDEX.
Pharynx, 1140
aponeurosis of, 1149
auditory tubes of, 1142
boundaries of, 1143
bursa pharyngea, 1143, 1396
cavity of, 1141
choanse, 1142
development of, 1242
dimensions of, 1140
fascia pharyngo-basilaris, 1149
bucco-pharyngea, 1149
glands of, 1149
isthmus pharyngo-nasalis, 1141, 1145, 1383
laryngeal part of the, 1141, 1147
lateral recesses of, 1144
development of, 1144
levator cushion of, 1143
lymph vessels of, 1006, 1149
surgical anatomy of, 1386
mucous membrane of, 1149
muscles of, 464-467
action of, 467
development of, 496
nerve -supply of, 467
nasal part of the, 1141, 1142
surgical anatomy of, 1385
naso-pharyngeal groove of, 1143
nerves of, 1150
openings of, 1142
oral part of the, 1141, 1144, 1145
orifice of auditory tube, 1143
pharyngo-palatine arch of, 1145
plica triangularis of, 1146
recessus piriformis of, 1069
tonsillaris of, 1145
development of, 46
relations of, 1149
salpingo-palatine fold of, 1143
salpingo-pharyngeal fold of, 1143
structure of wall, 1149
supra -tonsillar fossa of, 1145
development of, 1144
tonsil of, palatine, 1145, 1146
pharyngeal, 1143
torus tubarius of, 1143
vault of, 1143
vessels and nerves of, 1149
Philtrum, 1108
ventriculi of Merkel, 1069
Phrenic artery, inferior, 933
ganglion, 765
nerve, 699
surgical anatomy of, 1393
vein, 982
Phrenico-colic ligament, 1242
Phrenico-pleural fascia, 1089
Phylogeny, 1
Pia mater, 518
of the brain, 673
chorioid plexuses of, 553, 611, 617, 635
ligamentum denticulatum of, 675
linea splendens of, 675
of the spinal medulla, 675
tela chorioidea of, 673
of third ventricle, 674
Pigmentary layer of optic vesicle, 825
Pillars of Corti, 850
Pineal body, 582, 614
development of, 608
morphology of, 619
teenia thalami of, 614
eye, 608
Pinna, 449
development of, 52
Piriform aperture, 163
measurement of, 287
surgical anatomy of, 1239
Piriformis fascia, 489
muscle, 417
action of, 418
nerve-supply of, 417, 729
Pisi-cuneiform joints, 330
Pisiform bone, 219
morphology of, 295
ossification of, 223
surgical anatomy of, 1451
Pisi-metacarpal ligament, 331
Pisi-unciform ligament, 331
Pit, auditory, 50, 853
nasal, 798
olfactory, 49
rectal, 1230
Placenta, 54, 56
basal layer of, 57, 58
completion of the, 61
detachment of, 63
development of, 56
foetal, 60
maternal, 57, 60, 62
Placental area, 61, 63
Placode, dorso-lateral, 501
epibranchial, 501
Plane, frontal, 5
of greatest pelvic extension, 238
infra-costal, 1407, 1411
of least pelvic extension, 238
median, 4
transpyloric, 1159
Plantar aponeurosis, 423
arch, 954
abnormalities, 1058
morphology of, 1048
position of, 1465
surgical anatomy of, 1465
artery, lateral, 954
medial, 954
fascia, 423
ligaments, 355
nerves, 734
lateral, 734
branches of, 735
deep branch of, 735
medial, 734
branches of, 734
Plantaris muscle, 429
action of, 429
Planum nuchale, 166
occipitale, 166
popliteum, 242
sternale, 107
temporale, 118
Plate, basal, 31
floor, 31
medullary, 513
neural, 31
roof, 31
Platyhieric sacrum, 289
Platyknemia, 281, 289
Platyknemic index, 289
Platymeria, 289
Platymeric index, 289
Platypellic pelvis, 288
Platyrhine skulls, 287
Platysma muscle, 448
INDEX.
1559
Platysma muscle (contd.), action of, 448
Pleura, pulmonary, 1084
Pleurae, 1084
blood-vessels of, 913, 926
cervical, 1398
costal, 1085
cupula of, 1084
diaphragmatic, 1085, 1088
left costo-diaphragmatic reflection of, 1401
ligamentum pulmonale of, 1086
lines of reflection of, 1086, 1399
lowest limit of, 1401
lymph vessels of, 1013
mediastinal, 1085, 1086, 1401, 1402
paracentesis of, 1403
parietal, 1084
pericardiac, 1086
phrenico-pleural fascia of, 1089
posterior mediastinal, 1402
pulmonary, 1084
relation of, to kidney, 1401
to oesophagus, 1152
to twelfth rib, 1401
right costo-diaphragmatic reflection of,
1399
sinus costo-mediastinalis of, 1094
phrenico-costalis of, 1093
stomata of, 1091
structure of, 1091
surgical anatomy of, 1399
vertebral line of, 1087
Pleural cavity, 1083
veins, 963
Pleuro-pericardial canal, 72
Plexus or Plexuses, annular, of cornea, 810
ano-coccygeal, 738
aortic, 762, 765
basilar venous, 974
brachial, 700
communications of, 700
composition of, 700
infra-clavicular branches of, 703
lateral cord of, 703
medial cord of, 703
morphology of, 742, 743
position of, 700
posterior cord of, 701
primary cord of, 700
secondary fasciculi of, 701
supra -clavicular branches of, 702
surgical anatomy of, 1395
variations in, 752
cardiac, deep, 759, 789, 790, 791, 880
superficial, 757, 789, 880
carotid, 757
external, 757
cavernosus, clitoridis, 766
penis, 766
cavernous, 759, 766
cervical, 694
ascending branches of, 695
branches of, 695
communications of, 697, 698
cutaneous branches of, 695
descending branches of, 696
lateral branches of, 695, 696
medial branches of, 695, 697
morphology of, 700
muscular branches of, 696, 697
superficial cutaneous of, 695
posterior, 688, 690
morphology of, 691
Plexus or Plexuses (contd.), chorioid, of fourth
ventricle, 553, 636
development of, 552
of lateral ventricle, 635
of inferior horn of, 636
development of, 635
of third ventricle, 617
coccygeal, 738
co3liac, of sympathetic, 761, 763, 765
coronary, 765
anterior, 791
posterior, 791
deferential, 765
dental, superior, 775
diaphragmatic, 765
fundamental, of cornea, 810
haemorrhoidal, 766
external venous, 984
internal venous, 984
hepatic, 765
hypogastric, 763, 1321
of sympathetic, 766
inferior mesenteric, 765
infra -orbital, 777
of limbs, 680
composition of, 742
development of, 743
distribution of nerves of, 750
formation of, 680
morphology of, 741
significance of, 753
trunks of, 742
variations in, 752
lumbar, 719
connexions of, with sympathetic, 719
constitution of, 719
subdivisions of, 720
variations in, 752
mesenteric, inferior, 732
superior, 766
myenteric, of intestines, 1185, 1210
of stomach, 1177
obturator, 723
cesophageal, 787, 788
anterior, 791
posterior, 791
ovarian, 765
pampiniform, 983
patellar, 726
pelvic, of sympathetic, 766
pharyngeal, 788
ascending, of sympathetic, 756
venous, 965
posterior cervical, 689
morphology of, 692
sacral, 691
morphology of, 692
post-vertebral venous, 976
prostatic, 766
(sympathetic), 766
prostatico-vesical (venous), 985
pterygoid (venous), 968
pudendal, 735
branches of, 736
morphology of, 740
position and constitution of, 735
pulmonary, 781
anterior, 791
posterior, 787, 791
renal, 765
sacral, 727
anterior branches of, 727
1560
INDEX.
Plexus or Plexuses, sacral (contd,}, articular
branches of, 729
communications of, with sympathetic,
727
muscular branches of, 728, 729
position and constitution of, 727
terminal branches of, 729
spermatic, 765
splenic, 765
subclavian, of sympathetic, 759
subepithelial, of cornea, 810
submucous, of intestine, 1177
subperitoneal (Turner), 935
subpleural (arterial), 913
superior mesenteric, 765
suprarenal, 765
thyreoid, 759
tonsillar, 1147
tympanic, 759
uterine, 765, 766
venous, 985
utero-vaginal, 985, 1321
vaginal, venous, 766, 985
vertebral, venous, 976
external (venous), 976
of sympathetic, 759
vesical, 766, 1321
venous inferior, 985
superior, 985
Plica or Plicae, alares of knee-joint, 348
aryepiglottic, 1068
circular, of intestine, 1180
duodeno-jejunal, 1185
duodeno-mesocolic, 1185
fimbriata, 1108, 1128
glosso-epiglottic median, 1067, 1126
ileo-csecal, 1218
inguinal, 1296
lacrimal, of Hasner, 825
longitudinal, of duodenum, 1186
palmatae of uterus, 1317
pharyngo-epiglottic, 1126
pubo-vesical, 1237
recto- uterine, 1226, 1238
salpingo-palatine, 1143
salpingo-pharyngeal, 1143
semilunar, of the colon, 1212
of the conjunctiva, 821
sublingual, 1108
synovial, of the patella, 348
transversales of rectum, 1226, 1230
triangular, of the tonsil, 1146
tubari, 1315 .
umbilical, lateral, 1235
medial, 1235
ureteric, 1277
urogenital, 1334
ventricular, 1070
vesical, transverse, 1238
vocal, 1070
Plugging the posterior nares, 1385
Pogonion, 286
Point, alveolar, 285
jugal, 286
occipital, 285
subnasal, 285
supra-auricular, 286
Polar bodies, 15, 19
projection, 15, 20
first, 15, 20
second, 15, 20
Poles of lens, 820
Polymasty, 1338
Polymorphic cells, 645
Polyphyodont dentition, 1248
Polythely, 1338
Pons hepatis, 1192
(Varolii), 540, 548, 567
acoustic area of, 551, 604
anterior medullary velum, 549
brachium of, 566
conj unctivum, 549, 569
pontis, 548
central tegmental tract of, 564
cerebro-pontine fibres of, 566
connexions of longitudinal and transverse
fibres of, 566
corpus ponto-bulbare of, 555
trapezoideum of, 567
development of, 33, 514, 592
dorsal or tegmental part of, 567
eminentia medialis of, 551
external arcuate fibres of, 555
fasciculi longitudinalis of, 565
fasciculus obliquus of, 549, 555
circumolivaris pyramidis, 555
fovea superior of, 551
gray matter of, 564
internal arcuate fibres of, 556
internal structure of, 565 et seq.
lemniscus fibres of, 566, 570
locus coeruleus of, 551
medial longitudinal bundle in, 558, 568
mesencephalic root of trigeminal nerve in,
569
nuclei of, 565, 566, 567
arcuate of, 555
olivary nuclei of, 567
origin of, 516, 567, 569
pars basilaris of, 565
position and connexions of, 540, 541
pyramidal tract in, 565
raphe of, 558, 567
restiform body in, 567
reticular formation of, 567
spinal root of trigeminal nerve in, 567
substantia ferruginea of, 370, 551
sulcus basilaris of, 548
tegmental part of, 567
. transverse fibres of, 566, 567
veins of, 971
ventral portion of, 565
Ponticulus, 829
Pontine flexure of brain, 514
Popliteal artery, 951
fascia, 405
fossa, surgical anatomy of, 1437, 1457
groove, 243
line of tibia, 249
lymph glands, 1014
surface of femur, 242
vein, 986
abnormality of, 1060
Popliteus fascia, 420
muscle, 429
action of, 429
minor, 429
Pore, gustatory, 854
Porta hepatis, 1190
Portal canals, 1200
system, development of, 1036, 1037
vein, 990
Portio supra vaginalis cervicis uteri, 1316
vaginalis cervicis uteri, 1316
INDEX.
1561
Poms sudoriferus, 861
Position of kidneys, 1257, 1258
of urethral orifice in bladder, 1274
Post-anal gut, 48
Post-auditory process, 132, 133
Post-auricular point, 1359
Post-branchial bodies, 43
Post-central anastomosis, 1044
arteries, 1044
gyri, 662, 663
line, 1360
Post-coronal depression, 166
Post-costal anastomoses, 1045
Posterior commissure of brain, 821
cutaneous nerve of thigh, surgical anatomy
of, 1457
rand of lumbar nerves, 691
morphology of, 691
of sacral and coccygeal nerves, 691
of spinal nerves, 687
of thoracic nerves, 690
Postero-lateral tract of spinal medulla, 534
Post-glenoid tubercle, 126
Post-neural anastomoses, 1044
Post-pharyngeal lymph glands, 1000
Post-sphenoid bone, 138
Post-transverse anastomoses, 1045
Post-vertebral venous plexus, 976
Pouch of Douglas, 1226
relation of, to uterus, 1319
surgical anatomy of, 1435, 1436
branchial, 42
duodenal, 1185, 1186
pharyngeal, 42
of Prussak, 842
of Rathke, 49
recto-genital, 1226
recto-vesical, 1226
surgical anatomy of, 1434
utero-vesical, 1238, 1317
vessels, 42
Poupart, inguinal ligament of, 477
surface anatomy of, 1458
line of, 1411
plane of, 1411
Prsecentral sulci, 665
sulcus, surface anatomy of, 1360
Preecordial area, outline of, 1403
Praecuneus, 662
Prse-interparietal bone, 277
Praelaminar arteries, 926
PrEeputium clitoridis, 1324, 1326
penis, 1299
Proevertebral fascia, 448
muscles, 467
Pre-aortic lymph glands, 1012
Pre -auricular lymph gland, 998
point, 1359
Pre-basi-occipital bone, 278
Precentral line, 1360
Precervical duct, 43
sinus, 43, 76
sulcus, 43
Prechordal part of basis cranii, 291
portion of skull, 291
Precoracoid, 295
Precostal anastomoses, 1044
Prehallux, 295
Prelaminar anastomoses, 926
Prelaryngeal lymph glands, 1001
Premaxillse, 150
ossification of, 150
Premaxillary suture, 150
Premolar teeth, 1117
Preneural anastomoses, 1044
Prepatellar bursa, 1460
Prepollex, 295
Prepuce, 1326
Preputial glands, 1299
Presphenoid bone, 291
Presternum, 107
Pretracheal glands, 1001
Prevertebral arteries, 896
fascia, 448, 467, 1386
muscles, 467
Prickle -cells, 857
Primary optic vesicle, 33
Primitive alimentary canal, 41
aortae, 67
branches of, 1027
morphology of, 1040
brain, fate of cavities of, 36
cerebral vesicles, 33
groove, 23
heart, 1026
streak, 26
vascular system, 1025
Primordial bones, 292
Princeps cervicis artery, 895
pollicis artery, 921
Prismata adamantina, 1245, 1247
Pro-atlas, 278
Process or Processes ; Processus
accessory, of the vertebras, 96
acromion, 203, 204
alar, of ethmoid, 140
alveolar, of maxilla, 148
absorption of, 197
angular medial, of frontal bone, 115
surface anatomy of, 1360
anterior mallei, 840
articular, 89
of cervical vertebrae, 91
of lumbar vertebras, 96
of sacrum, 97
of thoracic vertebras, 93
basilar, 120, 123
of calcaneus, 259
capitular, of vertebra, 284
ciliary, 812
clinoideus anterior, 135
medius, 135
posterior, 135
cochleariformis, 128
surgical anatomy of, 1368
conchal, of ethmoid, 141
surgical anatomy of, 1378
condyloid, of mandible, 156
coracoid, 201
morphology of, 295
ossification of, 204
surface anatomy of, 1445
variations in, 280
coronoid, 156, 210
surface anatomy of, 1325
dens, 92
ossification of, 105
epicondylic, of humerus, 280
surface anatomy of, 1449
ethmoidal, of inferior concha, 143
facial, of parotid gland, 1136
falciformis, of sacro-tuberous ligament, 337
frontal, of maxilla, 145, 148
of frontal bone, 117
100
1562
INDEX,
Processor Processes (contd.), Iron to-nasal, 49
fronto-sphenoidal, of zygoma tic bone, 153
funicular, of peritoneum, 1409
globular, 49
hamulus, of lacrimal, 143
of os hamatum, 221
of sphenoid, 138
surgical anatomy of, 1385
intermaxillary, 49
intrajugular, 122
jugular, 172, 177
lacrimal process of inferior concha, 143
lateralis mallei, 840
nasal is, 49
tali, 254
tuberis calcanei, 259
lenticularis incudis, 840
mamillary, of the vertebra, 96
marginal, of zygomatic bone, 153
mastoid, 128
maxillary, of inferior concha, 143
of mandibular arch, 48, 49, 50, 149
first appearance of, 48, 149
of palate bone, 152
medialis tuberis calcanei, 259
muscular, of vertebrae, 89
muscularis of arytaenoid, 1065, 1074
olecranon, 210
surface anatomy of, 1449
orbital, of palatine bone, 152
palatine, 50, 148, 149
paramastoid, 278
paroccipital, 278
petrosal, 135
phalangeal, of lamina reticularis, 851
of rods of Corti, 851
post-auditory, 133
pterygoid, 137, 174
pterygo-spinous, 137
pyramidal, of palate bone, 152
reticularis, 524
sphenoidal, of palate bone, 152
septi cartilaginous, 801
spinous, of cervical vertebrae, 90
of lumbar, 95
of sacral, 97
serial homology of, 283
surface anatomy of, 1436
of thoracic vertebrae, 93
styloid, 177
of radius, 216
surface anatomy of, 1450
temporal, 127
ossification of, 132
relation of, to jugular foramen, 177
root of, 177
of third metacarpal bone, 225
of ulna, 213
temporal, of zygomatic bone, 153
of Tomes, 1247
transverse, of atlas, 1391
of the cervical vertebrae, 90
lumbar, 95
sacral, 98
serial homology of, 284
surface anatomy of, 1437
thoracic, 93
trochlear, 260
of calcaneus, 260
tubarius, of pterygoid process, 838
tubercular, of vertebrae, 284
uncinate, of ethmoid, 141
Process or Processes, uncinate (contd.),
pancreas, 1203
vaginal, of the peritoneum, 1295, 1319
surgical anatomy of, 1409
of sphenoid bone, 177
of temporal bone, 127
vermiform, 1215
vocal, of arytaenoid, 1070
xiphoid, 108
zygomatic, of frontal, 115
of maxilla, 148
of temporal, 126
Proctodaeum, 42
derivative of, 50
Profunda brachii artery, 918
branch of ulnar artery, 918
cervicis artery, 914
clitoridis artery, 942
femoris artery, 949
abnormalities of, 1057
branches of, 949
linguae artery, 892, 1130
penis artery, 942
Prognathous skulls, 287
Projection fibres of cerebrum, 651
Prominentia canalis facialis, 833
laryngea, 1062, 1077
surface anatomy of, 1387
spiralis, 849
styloidea, 834
Promontorium cochleae, 1368
of sacrum, 98
surgical anatomy of, 1444
tympani, 832
Pronation, 328, 401
Pronator quadratus muscle, 390
action of, 391
teres muscle, 385
action of, 385
Pronephros, 1327
Pronucleus, female, 16
male, 20
Pro-otic part of temporal bone, 131-132
Prophase, 9
Prosencephalon, 514, 607
development of, 33, 514
diencephalon of, 608
development of parts of, 608
telencephalon of, 608
Prostate, 1301
anterior surfaces of, 1301
apex of, 1302
base of, 1301
capsule of, 1429
development of, 1335
ducts of, 1303
fibrous sheath of, 1302
glandular part of, 1301, 1303
lateral lobes of, 1302
surfaces of, 1301
middle lobe of, 1302
nerves of, 1304
posterior surface of, 1302
pudendal plexuses of, 1302
senile hypertrophy of, 1429
sheath of, 1429
structure of, 1303
surgical anatomy of, 1429
vessels and nerves of, 1304
Prostatectomy, 1429
perineal, 1430
supra-pubic, 1429
INDEX.
1563
Prostatectomy (contd,), total, 1430
Prostatic urethra, 1305
development of, 1335
utricle, 1306
Prostatico-vesical venous plexus, 985
Prosthion, 288
Protoplasm, 8
Protoplasmic process of Deiters, 507
Protovertebral somites, 28
Protuberance, mental, 155
occipital, external, 121
internal, 121 *
Prussak, pouch of, 842
Psoas abscess, 1439
major muscle, 410
actions of, 411
minor, 410
actions of, 411
Pterion, 166, 179, 285
surface anatomy of, 1360
Pterotic part of temporal bone, 132
Pterygoid artery of internal maxillary, 900
of internal carotid, 902
canal, 138, 175
fossa, 174
lamina, lateral, 137
medial, 137
muscles, 455-457
actions of, 458
nerves, 457
notch, 137
plexus, venous, 968
process, 137
ridge, 137
tubercle, 138
venous plexus, 968
Pterygo-palatine canal, 147
fossa, 138
sulcus, 138
Pterygo-spinous ligament, 313
process, 137
Pubic branch of inferior epigastric artery, 945
of obturator artery, 940
crest, 233
sexual difference of, 238
surface anatomy of, 1458
ligaments, 337
lymph glands, 1015
sinus, 197
tubercle, 233
surface anatomy of, 1458
vein, 988
Pubis, 232
morphology of, 296
Pubo-capsular ligament, 340
Pubo-cavernosus muscle, 488
Pubo-coccygeus muscle, 494
Pubo-prostatic ligaments, 493, 1429
Pubo-rectalis muscle, 494
Pudendal artery, accessory, 1056
external, deep, 948
superficial, 948
internal, 940
surgical anatomy of, 1428
nerve, 738
plexus, 766
veins, 985
venous plexus, 735, 1439
branches of, 736
morphology of, 740
Pudendum muliebre, 1324
Pulled elbow, 1449
Pulmonary artery, 882, 1097, 1405
abnormalities of, 1051
development of, 68
morphology of, 1047
surface anatomy, 1408
nerves, 786, '788, 791
orifice, 878
surface anatomy of, 1405
plexus, 786, 788
anterior, 788, 791
posterior, 786, 791
valve, 877
vascular system, 882, 958
vein, 958, 1097
orifices of, 875
vessels, 1099
Pulp cavity of spleen, 1353
of tooth, 1114
Pulvinar of thalamus, 611
Puncta lacrimalia, 825
surgical anatomy of, 1377
Pupilla, 814
dilator of, 814
sphincter of, 814
Pupillary border, 814
membrane, 813
Purkinje", cells of cerebellum, 580, 581
fibres of, 879
Purple, visual, 815
Putamen of lentiform nucleus, 639
Pyloric antrum, 1169
artery, 930
morphology of, 1047
canal, 1169
changes in, during digestion, 1173
ligaments, 1174
portion of stomach, 1165, 1166, 1169, 1173
sphincter, 1163, 1166, 1173
valve, 1173, 1174
vein, 992
morphology of, 1048
Pylorus, 1169
surgical anatomy of, 1416, 1417
Pyramid of cerebellum, 576
of medulla oblongata, 545
Pyramidal cells, 645
lobe of thyreoid gland, 1347
process of palatine bone, 152
tract, 538, 545, 565
Pyramidalis abdominis muscle, 481
Pyramids of medulla oblongata, 545, 557,
558
decussation of, 557
renal, 1265
of tympanic cavity, 834
of vestibule, 843
Pyrenin, 8
Quadrate lobe of liver, 1193, 1194
Quadratus femoris muscle, 418
action of, 418
labii inferioris muscle, 451
superioris muscle, 450
angular head, 450
action of, 454
infraorbital head, 451
action of, 452
lumborum muscle, 485
Quadriceps (extensor) femoris muscle, 406
action of, 409
Quadrigeminal bodies, 585, 586
development of, 34, 592
1564
INDEX.
Racemose glands, 1132
Radial artery, 919
fossa, 211
groove in upper arm, 207
nerve, 710
surgical anatomy of, 1448
variations, 742
Radiale, os, 295
Radialis indicis dorsalis artery, 920
Radiatio or Radiation
acoustic, 643, 656
of corpus collosum, 631
pars occipitalis of, 631
striatum, 639
occipito-thalamic, 620, 643, 658
optic, 620, 643, 658
thalamic, 610
thalamo-occipital, 658
thalamo-temporal, 656
Radicular cells, 528
veins of medulla oblongata, 972
Radii lentis, 820
Radio-carpal joint, 328
movements at, 329
surgical anatomy of, 1450
synovial stratum of, 329
Radiography of stomach, 1417
Radio-humeral joints, 323
Radio-ulnar joint, distal, 327
proximal, 326
Radius, 214
architecture of, 272
connexions of, 213
homology of, 295
movements of, on ulna, 213
ossification of, 217
surgical anatomy of, 1449, 1450
variations in, 272
Radix or Root, anterior nervorum spinalium,
685
arcus vertebrae, 88, 90, 93, 95, 97
brevis ganglii ciliaris, 759
cochlearis nervi acustici, 604, 852
dentis, 1114
descendens mesencephalica n. trigemini, 569,
601, 602
lateralis tractus optici, 378, 384
linguae, 1125
longa ganglii ciliaris, 773
medialis tractus optici, 378, 574
mesenterii, 1208
nasi, 799
nervi facialis, 781
penis, 1299
pili, 859
posterior nervorum spinalium, 685
pulmonis, 1096
sympathica ganglii ciliaris, 759
submaxillaris, 757
unguis, 858
Rami communicantes, gray, 694, 754
cervical, 694, 759
development of, 681
functions of, 755
lumbar, 719
of plexus, brachial, 700
cervical, 694, 759
lumbo-sacral, 719
pudendal, 736
of thoracic nerves, 716, 717, 761
Rami communicantes, white, 680, 692
cervical, 697
Rami communicantes, white (contd.\ develop-
ment of, 680
lumbar part of, 762
of lumbo-sacral plexus, 719, 762
of pelvic plexus, 762
of pudendal plexus, 737
of sacral plexus, 719
of solar plexus, 762
of thoracic sympathetic, 759, 760, 761
Ramus, Rami or Branches (of arteries)
acetabuli, 949
acromialis of thoraco-acromial artery, 916
of transverse scapular artery, 912
ad pontem, 907
anterior A. thyreoideae superioris, 892
ascendens A. circumflexae femoris lateralis
949
A. transversae colli, 911
auriculares anteriores, 896
atiricularis arteriae occipitalis, 895
posterioris, 896
bronchial, 925
calcanei, 953
medial, 955
carotico-tympanicus, 902
carpeus dorsalis A. radialis, 920
dorsalis A. ulnaris, 923
volaris A. radialis, 920
ulnaris, 922
circumflexus A. coronariae sinistrae, 887
cochlearis A. auditivse internae, 853, 907
communicans A. tibialis posterioris, 953
communicans A. peroneae, 953
cricothyreoideus, 892
cutanei anteriores (pectorales et abdominis),
926
deltoideus, 916
descendens anterior A. coronariae sinistrae,
887
A. circumflexae femoris lateralis, 949
A occipitalis, 895
A. transversae colli, 911
posterior A. coronarise sinistrae, 887
dexter A. hepaticae, 930
dorsalis A. costo-cervicalis, 914
A. linguae, 892
A lumbalium, 935
duodenales A. gastroduodenalis, 930
epiploici A. gastroepiploicae dextrae, 930
fibularis, 956
frontalis A temporalis superficialis, 897
glandulares A. maxillaris externae, 893
A. thyreoideae inferioris, 911
hyoideus A. thyroideae superioris, 892
hyoideus A. lingualis, 892
iliacus A. iliolumbalis, 938
intercostales A. mammariae internee, 913
intestini tennis, 932
mammarii externi A. thoracalis lateralis,
916
mammarii A. mammariae internae, 913
mammarii laterales A. intercos tali tun,
926
mediales A. intercostaliuin, 926
mastoideus A. occipitalis, 895
A. auricularis posterioris, 895
mediastinales aortae, 925
meningeus accessorius, 899
A. occipitalis, 895
A vertebralis, 907
mylohyoideus, 899
occipitalis A. auricularis posterioris, 896
INDEX.
1565
Ram us, Kami or Branches (of arteries) (contd.\
03sophagei aortse, 925
A. gastricae sinistrae, 929
ovarii A. uterinae, 940
pancreatici A. lienalis, 929
A. pancreaticoduodenalis superioris, 930
parotidei A. temporalis superficialis, 896
parietalis A, temporalis superficialis,
897
pectorales A. thoracoacromialis, 916
perforans A. tibialis posterioris, 953
A. mammariae internae, 913
A. metacarpalium volarium, 924
A. metatarsalium plantarium, 955
pericardiaci aortae, 925
petrosus superficialis A. maxillaris internae,
898
pharyngei A. pharyngeae ascendentis, 896
posterior A. thyreoideae superioris, 892
A. obturatorise, 940
A. intercostalium, 926
pterygoidei A. maxillaris internae, 899
pubic A. epigastricae inferioris, 945
pubicus A. epigastricae inferioris, 945
pubicus A. obturatoriae, 940
saphenus, 951
sinister A. hepaticae, 930
spinalis A. iliolumbalis, 938
A. intercostalis supremae, 914
A. intercostalium, 926
A. lumbalium, 935
A. sacralis lateralis, 938
A. vertebralium, 907
stapedius A. stylomastoideae, 895
sternomastoideus A. thyreoideae superioris,
892
suprarenales superiores, 933
tonsillares A. maxillaris externae, 893
tracheales A. thyreoideae inferioris, 911
tubarius A. uterinae, 940
vestibular A. auditivae internae, 853
volaris profuiidus, 923
superficialis, 919
Ramus or Rami or Branches (of nerves)
alveolares superiores anteriores, 777
posteriores, 775
alveolaris superior medius, 777
anastomotici cum nervo faciali, 780
hypoglosso, 780
anastomoticus cum chorda tympani, 781
nervo auriculo-temporali, 781
N. facialis cum nervo glossopharyngeo,
782
N. mediani cum nervo ulnari, 707
N. vagi cum nervo glossopharyngeo, 788
cum nervo laryngeo inferiore, 789
cum ramo auriculari nervi vagi, 788
anastomoticus peronaeus, 730
anterior nervi obturatorii, 722
anterior iiervorum spinalium, 692
rami cutanei lateralis (pectoralis et ab-
dominalis), 692, 714, 716, 717
anteriores N. thoracalium, 692, 713, 714-717
nervorum cervicalium, 692
lumbalium, sacralium, coccygeorum, 719
auricularis N. vagi, 788
buccales N". facialis, 784
calcanei mediales, 734
cardiaci inferiores N. vagi, 789
superiores N. vagi, 789
cceliaci N. vagi, 789
colli N. facialis, 784
Ramus or Rami or Branches (of nerves) (contd.},
communicans nervorum spinalium,
687
communicantes ganglii submaxillaris cum
nervo linguali, 780
cutanei anteriores nervi femoralis, 724
cruris mediales, 724
cutaneus anterior (pectoralis et abdominalis),
692, 714, 716, 717
cutaneus anterior nervi ilio-hypogastrici, 720
lateralis (pectoralis et abdominalis), 720
nervi ilio-hypogastrici, 720
nervorum thoracalium, posterior rami
of, lateral cutaneous branch of, 716,
717
medialis nervorum thoracalium, 690
medial cutaneous branch of, 690
nervi obturatorii, 723
volaris nervi ulnaris, 709
den tales inferiores, 780
superiores, 775
descendens N. hypoglossi, 794
digastricus N. facialis, 783
dorsalis manus nervi ulnaris, 709
externus nervi accessorii, 793
laryngei superioris, 788
frontal is nervi ophthalmici, 772
gastrici N. vagi, 789
hepatici N. vagi, 789
inferior nervi oculomotorii, 770
inferiores nervi cutanei colli, 618
infrapatellaris, 726
internus, nervi accessorii, 793
laryngei superioris, 788
isthmi faucium, 780
labiales inferiores N. mentalis, 770
superiores N. maxillaris, 777
laryngo-pharyngei, 756
lateralis ramorum posteriorum nervorum
cervicalium, 688, 690
K lumbalium, 690
nervorum sacralium et coccygei, 691
lienales nervi vagi, 789
linguales N. glossopharyngei, 786
N. hypoglossi, 795
N. lingualis, 780
marginalia mandibulae, 784
mediales ramorum posteriorum N. cervi-
calium, 688, 690
medialis ramorum posteriorum N. lumba-
lium, 690
nervorum sacralium et coccygei, 691
membranae tympani N. auriculo -temporal is,
780
meningeus nervi vagi, 788
nervorum spinalium, 686
mentales nervi mentalis, 780
musculares nervi axillaris, 710
femoralis, 724
ilio-hypogastrici, 720
ilio-inguinalis, 721
ischiadici, 728
mediani, 705
musculo-cutanei, 704
peronaei, 730
profundi, 730
superficialis, 731
radialis, 633
tibialis, 732
ulnaris, 709
nervorum thoracalium, 716, 717
plexus lumbalis, 720
1566
INDEX.
Ramus or Kami or Branches (of nerves) (contd.),
nasales extern! N. naso-ciliaris, 773
intern! N. naso-ciliaris, 773
laterales N. naso-ciliaris, 773
mediales N. naso-ciliaris, 773
occipitalis N. auricularis posterioris, 783
resophagei N. vagi, 788
orbitales ganglii spheno-palatini, 778
palmaris nervi mediani, 705
palpebrales inferiores nervi maxillaris, 777
palpebralis inferior nervi infra -trochlearis, 773
superior nervi infra-trochlearis, 773
parotidei nervi auriculo-temporalis, 780
pericardiacus nervi phrenici, 699
perineales nervi cutanei femoris posterioris,
737
pharyngei nervi glosso-pharyngei, 786
nervi vagi, 788
phrenico-abdominales nervi phrenici, 699
posterior nervi obturatorii, 723
nervorum spinalium, 687
posteriores nervorum cervicalium, 688, 690
lumbalium, sacralium, coccygeorum, 690,
691
thoracalium, 690
profundus nervi plantaris lateralis, 734
radialis, 712
ulnaris, 709
pulmonalis partis thoracalis sympathici,
761
renales N. vagi, 789
renalis nervi splanchnic! minoris, 765
stylohyoideus, 783
stylopharyngeus, 786
submaxillares ganglii submaxillaris, 780
superficialis N. plantaris lateralis, 735
nervi radialis, 712
N. ulnaris, 709
superior N. oculomotorii, 770
superiores nervi cutanei colli, 696
temporales N. facialis, 783
superficiales N. auriculo-temporalis, 780
thyreohyoideus N. hypoglossi, 795
tonsillares N. glossopharyngei, 786
tracheales nervi recurrentis N. vagi, 789
tubes plexus tympanici, 786
ulnaris nervi cutanei antibrachii medialis,
710
volaris nervi cutanei antibrachii medialis,
710
zygomatici N. facialis, 784
zygomatico-facialis, 776
zygomatico-temporalis, 776
Ramus anterior ascendens fissurae cerebri
lateralis, 653
anterior horizontalis fissurae cerebri lateralis,
653
posterior fissures cerebri lateralis, 653
Ramus bronchialis eparterialis, 1097
bronchialis hyperarterialis, 1097
Ramus ossis ischli inferior, 232
superior, 232
mandibulae, 156
surgical anatomy of, 1375
pubis inferior, 234
superior, 233
Raphe medullas oblongata, 554, 561
palati, 1110
pharyngis, 464, 1149
pontis, 558
scroti, 1297
of tongue, 1129
Rathke, pouch of, 49
Recess or Recessus, aqueductus vestibuli, 843
cochlearis, 843
duodenojejunal, 1185
ellipticus vestibuli, 843
epitympanic, 832
ileocaecal, 1218
inferior, 1218
superior, 1218
infundibuli, 618
intersigmoid, 1223
labyrinthi, 858
lateral, of fossa rhomboidea, 57 1
of pharynx, 1144
naso-palatine, 802
optic, 618
paracolic, 1219
parotid, 1133
pharyngeus, 1144
pinealis, 618
piriformis, 1069, 1147
retrocaecalis, 1219
sacciformis articulationis radio-ulnaris dis-
talis, 327
sphaericus vestibuli, 843
spheno-ethmoidalis, 802
supra -pinealis, 618
utriculi, 846
Recesses of Troltsch, 842
Rectal examination, 1430, 1431
fascia, 1228
of female, 1436
lymph glands, 1015, 1016, 1017
triangle of perinaeum, 1427
Recto -coccygeus muscle, 1229
Recto-genital folds, 1317
pouch, 1226
Recto-uterine fold, 1317
muscle, 1238
Recto- vaginal fold, 1317
Recto-vesical fascia, 493
pouch, 1226
surgical anatomy of, 1434
Rectum, 1224
ampulla of, 1226, 1227
anal orifice of, 1230
in child, 1228
columns of, 1230
course of, 1224
curvatures of, 1224
development of, 1252
general relations of, 1228
lateral flexures of, 1224
nerves of, 1233
pars analis of, 1228
peritoneal relations of, 1226
pits of, 1230
plicae transversales of, 1225, 1230
removal of, 1433
sphincter of, 1229
structure of, 1229
surgical anatomy of, 1430
valves of, 1230, 1231
variations in, 1233
vessels of, 1232
Rectus abdominis muscle, 481
capitis anterior muscle, 468
lateralis muscle, 470
posterior major muscle, 444
minor muscle, 444
femoris muscle, 407
action of, 409
INDEX.
15GV
Rectus muscles of orbit, inferior, 453
lateral, 453
medial, 453
superior, 453
actions of, 454
Recurrent artery, 924
nerve, surgical anatomy of, 1394
Red marrow, 83
nucleus, 613
origin of, 516
Refracting media of the eye, 819
Region, frontal,: 667
of brain, 665
hypothalamic, 613
prsecentral, 660
Regiones abdominis, 1158
Reichert, cartilage of, 159
Reid, base line of, 1360
Reil, island of, 654, 655
Reissner, membrane of, 849
Renal artery, 927
corpuscles of kidney, 1266
development of, 1331
fascia, 1425
impression on liver, 1194
plexus, 765
vein, 982
Reproduction of cells, 8
Reproductive cells, 11
organs, female, 1310
male, 1286
bulbo-urethral glands, 1286
duct, ejaculatory, 1286
ductus deferens, 1286
epididymis, 1286, 1287
penis, 1286
prostate, 1286
scrotum, 1286
testis, 1286
vesicula seminalis, 1286 .
Reserve germs of teeth, 1244
Respiration, movements of, 474
muscles 'of, 470, 474
organs of, 1061
Respiratory system, 1061
development of the, 42, 44
Restiform body, 547, 562
development of, 562
functions of, 563
structure of, 562
Rete testis, 1288
venosum dorsalis maims, 978
pedis, 989
vertebrarum, 976
Reticular process, 524
substance, 524
structure of, 564
Retina, 814
bacillary layer of, 817
bipolar cells of, 816
blind spot of, 815
blood-vessels of, 818
cone -granules of, 817
cones of, 817
development of, 827
excavatio nervi optici, 815
fovea centralis of, 815
ganglionic layer of, 816
granule layer of, 817, 818
horizontal cells of, 817
inner molecular layer of, 816
nuclear layer of, 816, 817
Retina (contd.), macula lutea, 815
membranse limitantes of, 817
nervous lamina of, 814
optic cup of, 815
disc of, 815
ora serrata of, 815
papilla nervi optici, 815
pars ciliaris retinae, 815
iridica retinae, 815
optica retinas, 815
pigment of, 817
relation of optic fibres to, 620
rod -granules of, 817
rods of, 817
spongioblasts of, 817
stratum opticum of, 815
pigmenti of, 817
structure of, 815
of macula lutea of, 818
of ora serrata of, 818
sustentacular fibres of, 815, 817
vessels of the, 818
visual purple of, 815, 817
Retinacula cutis, 856
of hip -joint, 340
Retinaculum, superior peroneal, 422
Retinal layer of optic vesicle, 825
Retro-ceecal fossae, 1218
Retro-colic fossae, 1219
Retro-pharyngeal abscess, 1386
Retzius, space of, 493, 1429
striae of, 1122
Rhinencephalon, 627, 682
development of, 33
Rhinion, 285
Rhinoscopy, anterior, 1378
posterior, 1385
Rhodopsin, 815
Rhombencephalon, 514, 515
development of parts of, 515
isthmus of, 515
Rhombic lip, 554
Rhomboideus major muscle, 368
minor muscle, 368
actions of, 369
Rib, eleventh, 113
first, 109
second, 112
tenth, 113
twelfth, 113
surface anatomy of, 1437, 1442
Ribs, 109
angle of, 109
architecture of, 109
cartilages of, 113, 315
cervical, 90, 104
false, 109
floating, 109, 112
head of, 109
lumbar, 104, 277, 284
movements of, 317
ossification of, 112
peculiar, 109
shaft of, 109
surface anatomy of, 1401
true, 109
tubercle of, 109
typical, 109
variations in, 276
vertebral, 109
vertebro-chondral, 109
vertebro-sternal, 109
1568
INDEX.
Ridge, epicondylic, 207
surface anatomy of, 1449
interosseous, of fibula, 252
of tibia, 248
intertrochanteric, 240
pectoral, 206
pterygoid, 137
superciliary, 116
surface anatomy of, 1374
temporal, 116
trapezoid, 199
Wolffian, 39
Riedel's lobe of liver, 1195
Rima glottidis, 1070
surface anatomy of, 1388
oris, 1106
palpebrarum, 821
pudendi, 1324
vestibule, 1070
Ring, abdominal inguinal, 1408
femoral, 405
fibro-cartilaginous, of membrana tympani,
834
subcutaneous inguinal, 477, 1408
crura of, 477
intercrural fibres of, 477
tympanic, 133
Riolan, muscle of, 823
Risorius muscle, 451
Rivinus, ducts of, 1139
notch of, 834
Rod-bipolars of retina, 816
Rod -granules of retina, 816
Rods of Corti, 850
head-plate of, 850
phalangeal processes of, 851
retinal, 817
Roof of fourth ventricle, 578
Roof-nucleus, 577
Roof-plate, 31, 502
Root of lung, 1096
surface anatomy of, 1442, 1440
Roots of aortic arch, 1027, 1028
of nerves, 519
of vertebral arches, 88
cervical, 90, 92
lumbar, 95
thoracic, 93
Rosenmuller, fossae of, 1144
surgical anatomy of, 1434
organ of, 1315
Rostrum of corpus callosum, 630
of sphenoid, 135
Rotation of joints, 303
Rotator humeri muscles, 373, 377
Rotatores dorsi muscles, 445
Round ligament of liver, 1197
of uterus, 1319
surgical anatomy of, 1434
Rubro-spinal tract, 534, 588
Rudiment of the processus vaginalis, 1296
Rufl&ni, corpuscles of, 865
Rugae of palate, 1110, 1111
of scrotum, 1297
of stomach, 1165
vaginales, 1323
Running, movements of, 437
Sac, lacrimal, 825
development of, 49
surgical anatomy of, 1377
tooth, 1245, 1246
Sacculus of membranous labyrinth, 846, 848
development of, 52, 854
ductus endolymphaticus of, 847
reuniens of, 847, 854
utriculo-saccularis of, 847
macula acustica of, 847
sinus utricularis of, 847
Saccus endolymphaticus, 847
development of, 52
Sacral arteries, lateral, 938
middle, 935
canal, 99
crest, 97, 98
ganglia, 763
index, 99, 289
lymph glands, 1016
nerves, 691, 702, 727, 735
notch, 96
plexus, 727
anterior branches of, 727
articular branches of, 728
branches of, 727
communications of, with sympathetic, 727
formation of, 727
muscular branches of, 728
nerves of distribution from, 728
position and constitution of, 727
sympathetic, 766
terminal branches of, 729
veins, 983
Sacro-coccygeal joint, 308
nerves, 691, 738
Sacro-genital fold, 1283, 1318
Sacro-iliac joint, 335
surface anatomy of, 1455
ligaments, 336
Sacro-spinalis, muscles, 439
actions of, 442
surface anatomy of, 1437
Sacro-vertebral angle, 109
sexual differences in, 238
Sacrum, 96
ala of, 98
auricular surface of, 99
canal of, 99
lateral part of, 96
ossification of, 106
posterior surface of, 97
promontory of, 98
level of, 1443
serial homology of, 284
sex differences of, 99
variations in, 275
Sagittal fontanelle, 194
plane, 5
sulcus, 117, 119, 121
suture, 118, 119, 171
Salivary glands, 1113
development of, 1249
structure of, 1140
Salpingo-palatine fold, 838, 1143
Salpingo-pharyngeal fascia, 838
fold, 838, 1143
muscle, 465
Santorini, cartilages of, 1065
ducts of, 1108, 1138, 1207
tubercle of, 1069
Saphenous artery, 951
nerve, 726
surface anatomy of, 1461, 1463
veins, 988, 989
Sartoriiis muscle, 406
INDEX.
1569
Sartorius muscle (contd.}, action of, 406
Scala tympani, 845
vestibuli, 845
Scalene tubercle, 111
Scalenus anterior muscle, 467
medius muscle, 467
posterior muscle, 467
actions of these, 468
Scalp, 448
arteries of, 894, 895, 897
. lymph vessels of, 1003, 1357
muscles of, 448
surgical anatomy of, 1357
veins of, 967, 1357
Scapha auriculae, 828
Scapula, 200
acromion, 200
architecture of, 271
axillary margin, 201
connexions of, 204
glenoid cavity of, 201
homology of, 295
ligaments of, 320
movements of, 319
notch of, 201, 202
ossification of, 204
surface anatomy of, 1436, 1444, 1445
variations in, 280
Scapular arteries, circumflex, 917
subscapular, 917
transverse, 911
index, 288
line, 1397
notch, 201, 202
Scapulo-clavicular joint, 318
Scarpa, fascia of, 1427
foramina of, 149, 174
ganglion of, 853
Scheme of the nervous system, 498
Schindylesis, 300
Schneiderian membrane, 804
Schreger, lines of, 1123
Schultze, comma tract of, 533
Sciatic foramen, greater, 229, 337
lesser, 232, 337
foramina, 229, 232, 335
ligaments, 337
nerve, 728
surgical anatomy of, 1456
notch, 229, 252
greater, 229, 232
lesser, 232
Sclera, 807
canal of Schlemm of, 808
development of, 743
foramina of, 808
lamina cribrosa of, 808
fusca of, 808
sinus venosus of, 808
spatium perichorioideale of, 808
structure of, 808
sulcus of, 807
vascular and nerve-supply of, 808
venae vorticosae of, 808
Scleratogenous segment, 29
Sclero-corneal junction, 809
Scrotal arteries, 1298
Scrotum, 1297
development of, 1295
raphe of, 1297
tunica dartos of, 1298
Sebaceous glands, 861
Sebum cutaiieum, 861
Secondary bones, 292
chorionic villi, 53
tympanic membrane, 833
Secretory nerves of salivary glands, origin of,
598
Sectiones cerebelli, 579
corporum quadrigeminorum, 584, 586
medullas oblongatae, 555, 565
spinalis 523, 539
pontis, 565, 570
telencephali, 633, 636, 638, 641
Segmental arteries, 66, 1043
anastomoses of, 1044, 1045
somatic, 1043, 1045
splanchnic, 1046
type, 2
veins, 1048, 1049
Segmentation cavity, 21
nucleus, 21
of ovum, 15, 21
Sella turcica, 134
Semicanalis m. tensoris tympani, 834
tubae auditivaa, 834, 838
Semicircular bony canals, 844
ampullae of, 847
crista ampullaris of, 848
crus commune of, 844
cupola terminalis of, 848
development of, 854
lateral, 844
posterior, 844
superior, 844
ducts, 847
development of, 52
Semilunar ganglion, 722
space of Traube, 1418
Semimembranosus muscle, 420
action of, 421
bursa, 1458
surface anatomy of, 1458
Seminal vesicles, 1292, 1294
development of, 1335
structure of, 1294
vessels and nerves of, 1295
Seminiferous tubules, 1288
Semispinalis muscle, 442
capitis, 442
dorsi, 442
Semitendinosus muscle, 419
action of, 420
surface anatomy of, 1450
Senses, organs of the, 799
Sensory area of the brain, 662
cells, 497
decussation, 562, 566
tracts of brain, 657
Separation of proximal epiphyses of humerus,
1445
Septal artery of nose, 805
Septo-marginal tract, 535
Septula testis, 1288
Septum or Septa, of aortic bulb, 1035
of aorto-pulmonary artery, 1035
atriorum, 1033
of auricles, 1032, 1033
development of, 1033
canalis musculo-tubarii, 833
cartilagineum nasi, 802
corporum cavernosorum, 1300
femoral, 405
glandis penis, 1298
1570
INDEX.
Septum or Septa (contd.), intermuscular, of
arm, 378
of foot, 423
of leg, 422
of thigh, 403
intermusculare femoris laterale, 404
mediale, 404
fibulae anterius, 422
posterius, 422
humeri laterale, 378
mediale, 378
interventricular, 1035
linguae, 1129
mediastinal, 1083
membranaceum ventriculorum, 878
musculare ventriculorum, 878
nasi, 185, 802
cartilage of, 800
development of, 40, 1033
surgical anatomy of, 1378
orbitale, of eyelids, 822
pectiniform, of penis, 1300
pellucidum, 628, 632
posterior median of, 521
posterius of arachnoid, 672
primum, 1033
scroti, 485
secundum, 1033
sinuum frontalium, 270
sphenoidalium, 271
spurium of heart, 1032
of tongue, 1129
transversum, 68, 74
of semicircular ducts, 848
-tubas, 833
g,of uterus, 1320
jj of vagina, 1320
^ventricular, 878
development of, 1035
Serial homology, 3
of vertebrae, 283
Serous glands, 1132
Serratus anterior muscle, 372
action of, 372
surgical anatomy of, 1446
posterior inferior muscle, 439
superior muscle, 438
actions of, 439
Sesamoid bones, 228, 269
patella, 245
of short muscles of thumb, 228
cartilages of larynx, 1062
of nose, 800
Sexual eminence, 1336
Shaft of the femur, to expose the, 1456
of humerus, exposure of, 1449
Sheath, axillary, 1447
carotid, 447
dentinal, 1123
digital, 384
surgical anatomy of, 1453, 1454
of toes, 424
femoral, 405, 475
of flexor longus pollicis, 1453
medullary, 508, 532
mitochondrial, 18
primitive, 508
of prostate, 493
of rectus muscle, 483
Shin, 248
Short bones, 82
Shoulder, bony parts of, 1444
Shoulder (contd.), fasciae of, 373
muscles of, 373
surgical anatomy of, 1444
Shoulder-blade, 200
girdle, 317
movements of, 319
joint, 320
Shoulder-joint, bursse connected with, 323
movements at, 323, 377
nerves of, 703
Shrapnell, membrane of, 835
Sigmoid artery, 933
colon, 1223
mesocolon, 1223
Sigmoidoscope, examination by, 1433
Sinus, air, 84
aortic, 884
of Arlt, 825
cavernous, 975
circularis, 974
coronary, 959
abnormalities of, 1057
development of, 1032
morphology of, 1049
tributaries of, 959
costo-mediastinal, 1094
of dura mater, 972
of epididymis, 1287
ethmoidal, 185
frontal, 186, 1371
surgical anatomy of, 1371
great oblique, of pericardium, 882
transverse, of pericardium, 882
intercavernosus anterior, 974
posterior, 974
lactiferi, 1338
longitudinal vertebral, 976
of Maier, 825
maxillary, 149, 186
surgical anatomy of, 1379
oblique, of pericardium, 882
occipital, 183, 974
of palate bone, 186
parasinoidal, 974
petrosal, inferior, 975
superior, 975
phrenico-costal, 1093
piriform, 1069, 1147
of portal vein, 990
precervical, 43
rectal, 1231
rectus, 974
renalis, of kidney, 1265
rhomboid, 550
sagittal inferior, 668, 669, 974
abnormalities of, 1058
superior, 668, 973
surgical anatomy of, 1364
sphenoidal, 135, 183, 185, 1373
extent of, 133
opening into, 135
relation of, to nasal fossae, 185
to orbit, 163
spheno-parietal, 975
squamo-petrosal, 1058
straight, 974
superior, of utricle, 846
tarsi, 355
tonsillar, 1145
transverse, 974
morphology of, 1040
surgical anatomy of, 1357, 1358
INDEX.
1571
Sinus (contd.), tympani, 833
urogenital, 1328
[T utricular, 763
^ of Valsalva, 797
^venosus, 1031, 1033
sclerae, 808
Sinuses, lymph, 994, 995
venous, of cranium, 808
Skein, chromatin, 10
Skeletal muscles, development of, 495
structures, 81
Skeleton, 81
appendicular, 82
morphology of, 294
axial, 82, 87
development of, 28, 29, 102, 106
splanchnic, 43, 81, 1062
Skin, 856
appendages of, 858
coriurn of, 857
development of, 861
of embryo, 78, 79, 862
epidermis of, 857
papillae of, 857
pigment of, 858
retinacula of, 857
tactile corpuscles of, 865, 866
discs of, 865
Skull, age differences in, 197
akanthion, 285
akrocephalic, 286
alveolar point, 285
apertura piriformis, 163
asterion, 285
base of, 172, 179
basion, 285
at birth, 194
bones of, 115
brachycephalic, 171, 285
brachyfacial, 286
brachyuranic, 287
breadth of, 286
bregma, 285
capacity of, 284
chamsecephalic, 286
chordal, 290
cryptozygous, 171, 286
dacryon, 285
dermic, 292
development of, 290
dolicho-cephalic, 171, 285
dolicho-facial, 286
dolicho-uranic, 287
facial angle of, 286
fixed points of, 285
floor of orbit, 168
fontanelles of, 194
frontal sections of, 186
front of, 160
glabella, 285
height of, 286
female, 194
horizontal circumference, 286
section, 192
hypsicephalic, 286
indices of, 284
alveolar index, 287
dental index, 287
gnathic index, 287
nasal index, 287
orbital index, 287
orthocephalic index, 286
Skull, indices of (contd.\ palato - maxillary
index, 287
superior facial index, 286
total facial index, 286
vertical index, 286
infra-temporal fossa, 168
inion, 285
interior of, 179
lambda, 285
lateral aspect of, 164
wall of orbit, 162
length of, 285
leptoprosopic, 286
leptorhine, 287
ligaments of, 312, 313
longitudinal arc of, 286
macrodont, 288
measurements of, 286
medial wall of orbit, 163
median sagittal section of, 183
megacephalic, 284
megadont, 288
megaseme, 287
mesaticephalic, 285
mesocephalic, 284
mesodont, 288
mesognathous, 287
mesorhine, 287
mesoseme, 287
mesuranic, 287
metopic, 172
metriocephalic, 286
microcephalic, 284
microdont, 288
microseme, 287
morphology of, 293
nasion, 285
obelion, 285
ophryon, 285
opisthion, 285
orbital fossae, 160
orthocephalic, 286
orthognathous, 287
phsenozygous, 171, 286
platyrhine, 287
posterior aspect of, 171
prechordal, 291
primordial, 292
prognathous, 287
pterion, 285
pterygo-palatine fossa, 170
rhinion, 285
roof of orbit, 160
in section, 179
sexual differences in, 193
skeleton of face, 163
stephanion, 285
sub-nasal point, 285
surgical anatomy of, 1358
tapeinocephalic, 286
temporal fossa, 166
trabecular portion of, 290, 291
upper aspect of, 171
vertebral portion of, 293
vertebrate theory of, 293
vertex, 285
as a whole, 159
Smegma embryonum, 79
praeputii, 1299
" Snuff-box," anatomical, 400
Soleus muscle, 429
action of, 429
1572
INDEX.
Soleus muscle (contd.), surgical anatomy of,
1461, 1462
Solitary glands, 1179, 1181
Someesthetic area, 645
Somatic mesoderm, 25, 27
segmental arteries, 1043, 1044
Somites, mesodermic, 28, 29, 75, 76
Sounds of heart, 1405
Space of Burns, 967
epidural, 669
intercostal, 114, 470
interpleural, 1089
mediastinal, 1089, 1090
of Nuel, 852
of Ketzius, 1410, 1429
subarachnoid, 671
cisternee of, 671
communications of, with ventricles, 553, 67 1
fluid of, 671
ligamenta denticulata of, 672, 675
septum posterius of, 672, 675
spinal, 672
trabecular tissue of, 671
subdural, 670
surgical anatomy of, 1362
Spaces of Fontana, 810
interglobular, of ivory, 1247
lymph, 867
perilymphatic, 846
perivascular, 870
Spatia anguli iridis, 810
intercostalia, 114, 470
perichorioidealia, 811
perilymphatica auris internae, 846
zonularia, 819
Sperm cells, 11, 12, 16, 1288
Spermatic artery, internal, 928
abnormalities of, 1053
morphology of, 1047
fascia, 475, 477
funiculus, 1290, 1296
surgical anatomy of, 1430
vein, internal, 983
abnormalities of, 1058
development of, 1040
morphology of, 1048
surgical anatomy of, 1427
Spermatids, 17
accessory body of, 17
centrosomes of, 17
development of, 18
Spermatocyte, 12
of first order, 12, 16
of second order, 17
Spermatozoa, 17
axial filament, 17, 18
body, 18
centrosomes, 17
head, 17
neck, 17
sheath, mitochondrial, of, 18
spiral, of, 18
tail, end-piece, 18
end-ring, 18
Spheno-ethmoidal recess, 802
Sphenoid bone, 133
alae, development of, 138
angular spine of, 135, 136
architecture of, 271
body of, 133
connexions of, 138
crest of, 133
Sphenoid bone (contd.), great wings of, 134
orbital fissure, inferior, 137
ossification of, 138
pterygoid laminae of, 137
small wings of, 135
variations in, 278
Sphenoidal angle of parietal bone, 119
conch se, 139
Sphenoidal crest of sphenoid bone, 135
process of palate, 152
sinuses, 271
skiagraphs of, 1372
surgical anatomy of, 1372
Spheno-mandibular ligament, 312
Spheno-palatine artery, 900
foramen, 185, 192, 152
ganglion, 775, 777
nerves, 775
notch, 152
roots of, 777
vein, 968
Spheno-parietal sinus, 975
suture, 164, 166
Spheno-petrous fissure, 176
Spheno-squamous suture, 176
Spheno-vomerine canal, 279
Spheno-zygomatic suture, 163
Sphere, attraction, 20
Sphincter ani externus, 486, 1232
action of, 1232
internus, 1232
pupillse, 814
pyloric, 1166, 1174
recti, 1229
vaginae, 487
vesicae, 1284
Spina or Spine, angular, of sphenoid, 136, 167
frontal, 116
helicis, 828
iliaca anterior inferior, 229
superior, 228
posterior inferior, 229
superior, 229
surface anatomy of, 1455
ischiadica, 232
sexual differences of, 237
surface anatomy of, 1456
mentalis, 156
nasal, 116
nasalis anterior, 146, 164
posterior, 174
peroneal, 260
variations in, 282
pubic, 233, 1458
scapulas, 202
Sphenoidal, 136, 167
suprameatal, 126, 1366
of tibia, 246
trochlear, of frontal bone, 117
tympanica major, 831
minor, 831
Spinal arteries, 938
formation of, 1029
of intercostals, 926
of lateral sacral, 938
of vertebral, 907
column, 100, 102
foramen of cervical vertebrae, 90
of lumbar vertebrae, 95
of thoracic vertebrae, 93
ganglia, 685
medulla, 517, 539
INDEX.
1573
Spinal medulla (contd.), anterior median fissure
of, 521
surgical anatomy of,- 1443
antero-lateral column, 529
antero-median column of, 529
arrangement of nerve-fibres of white matter
in tracts, 532
cauda equina of, 519, 526
cell column, intermedio-lateral, 530
central canal of, 521, 523, 526
cervical enlargement of, 519, 524
cervix of, 523
changes in gray matter of, 524
columns of, 22, 520, 523, 528
anterior, 523, 528
aiitero-lateral, 529
central, 529
intermedio-lateral, 530
lateral, 523, 529
posterior, 522, 523, 525, 529
postero -lateral, 529
retro-postero-lateral, 529
commissure of, anterior white, 523, 539
gray, 523, 539
posterior, 523
component parts of white matter of, 531
conns medullaris of, 518, 524, 525
development of, 31, 33, 35, 520 .
dorsal nucleus of, 531, 538
enlargements of, 519, 524
surgical anatomy of, 1443
fasciculi of, anterior proprius, 535, 537, 538
lateral, 535
bulbo-spinal, 537, 538
collateral fibres of, 534, 535, 539
lateralis proprius, 538
olivo-spinal, 538
fasciculus cuneatus of, 526, 533
gracilis of, 526, 533
solitarius of, 598
(fasciculus of) posterior proprius, 535
rubro-spinal, 537, 538
septo-marginal, 535
spino-cerebellar anterior, 537, 538
posterior, 537, 538
spino-tectal, 537
(fasciculus of) spino-thalamic, 535, 537
anterior, 537, 538
posterior, 537
tecto-spinal, 537, 538
vestibulo-spinal, 537, 538
filum terminale of, 518, 526
externum, 526
internum, 526
fissures of, 522
antero-median, 522
intermedius posterior, 522
lateralis posterior, 522
postero-median (septum), 522
fimiculi or tracts of, 535
anterior, 522, 525, 528, 539
antero-lateral, 522
of Burdach, 522
of Goll, 522
lateral, 522, 525
posterior, 521, 522, 525
postero-lateral, 584
solitarius, 598
gray matter of, 523, 525
inferior limit of, in child, 517
internal structure of, 523
intersegmental association fibres of, 535,538
Spinal medulla (contd.), length of, 517
ligamenta denticulata of, 518, 675
longitudinal commissural fibres of, 537, 538
lumbar enlargement of, 519, 524
membranes of, 518, 669, 675
nerve-cells of, 528 et seq.
nerve-fibres in. gray matter of, 531
nerve -fibres of, 531 et seq.
neuroglia of, 527
origin of nerves from, 519, 529, 533
posterior paramedian sulcus of, 522
postero-lateral column, 529
sulcus of, 522
postero-median column, 529
processus reticularis of, 524
regional differences in, 519, 527
regions of, 519
relation of, to vertebrae, 517, 1422
segments of, 519
sensory and motor distribution of various
segments of, 744, 752
septa of, 521, 522
substantia gelatinosa Rolandi, 523, 528
grisea, 520
substantia grisea centralis of, 528
reticularis of, 564
sulci of, 522
sulcus lateralis posterior of, 522
summary of chief characters, 527
surgical anatomy of, 1443, 1444
theca of, 518
tract or tracts of Burdach, 526, 533
anterior cerebro-spinal, 536, 539
cerebello-spinal, 531, 536
comma (fasciculus interfascicularis), 533
of Goll, 526, 533
of Gowers (fasciculus antero-lateral
superficial), 536
lateral cerebro-spinal (crossed), 536,
538
of Lissauer (postero-lateral), 534
trigeminal root-fibres in, 601
veins of, 977
ventriculus terminalis of, 526
white matter of, 524, 531
Spinal nerves, 519, 678
anterior rami of, 692
anterior root, 520
development of nerve-roots, 679
distribution of the, 687
distribution of, to muscles and skin of the
limbs, 744
lower limb, cutaneous nerves, 747
muscular nerves, 748
upper limb, cutaneous nerves, 744
muscular nerves, 745
white rami communicantes of, 687
divisions or rami of, 686
formation of, 680
posterior rami of, 687
roots of, 520, 533
splanchnic parts of, 680
venous plexus, anterior, 976
posterior, 970
Spinalis dorsi muscle, 442
Spindle, achromatic, 10, 13
Spine, somatic parts of, 680
Spino-glenoid ligament, 320
Spino-thalamic tract, 537, 538
Spinous process of cervical vertebras, 90, 93
of lumbar vertebrae, 95
of sacrum, 97
1574
INDEX.
Spinous process (contd.), of thoracic vertebrae, 93
homology of spinous processes, 283
surgical anatomy of spinous processes,
1436, 1442, 1443
Spiral fasciculi of cochlear nerve, 852
ganglion, 785, 845, 852
line of femur, 242
organ of cochlea, 849, 850
tubules of kidney, 1266
Splanchnic ganglion, 761
mesoderm, 27
. nerve, 761
greater, 761, 764
lowest, 761, 764
scgmental arteries, 1027, 1046
skeleton, 81
Splanchnology, 3
Spleen, 1352
accessory, 1353
angles of, 1352
blood and lymph vessels of, 1353
borders of, 1352
development of, 1253, 1353
excision of, 1442
hilum of, 1352
lymph nodules of, 1353
nerves of, 1353
notches and fissures of, 1352
peritoneal relations of, 1353
pulp of, 1353
structure of, 1353
surfaces of, 1352
sustentaculum of, 1353
Splenic artery, 929
lymph glands, 1020
plexus, 765
vein, 922
Splenium of corpus callosum, 630
Splenius capitis muscle, 439
action of, 439
Spongioblasts, 503, 817
Spongioplasm, 8
Spongy bone, 83
Spur of malleus, 839
Squama occipitalis, 120, 121
temporalis, 125
Squamo-petrosal sinus, 1369
Squamosal bone, 292
Squamoso-mastoid suture, 125
Squamous suture, 127
Stalk, allantoic, 38
body, 38
optic, 682, 825, 826
of thalamic radiation, 610, 612
Stapedial artery, 841
Stapedius muscle, 841
Stapes, 840
annular ligament of, 841
development of, 841
foot-plate of, 840
ligaments of, 841
movements of, 842
surgical anatomy of, 1368
Staphylorrhaphy, 1385
secondary haemorrhage after, 1385
Stenson, canals of, 149
duct of, 1136, 1137
foramen of, 149, 174
Stephanion, 166, 172, 285
Sternal angle, 107
articulations, 317
furrow, 1397
Sternal line of pleural reflexion, 1085
1086
lines, 1397
lymph glands, 1010
veins, 963
Sternalis muscle, 370
Sterno-clavicular joint, 317
movements at, 319
muscle, 372
Sterno-cleido-mastoid muscle, 458
action of, 458
surgical anatomy of, 1390
Sterno-hyoid muscle, 459
action of, 460
Sterno-mastoid artery of occipital, 895
of superior thyreoid, 892
muscle, 458
Sterno-pericardial ligaments, 881
Sterno- thyreoid muscle, 459
action of, 460
Sternum, 106
architecture of, 270
body of, 107
infrasternal angle, 114
manubrium, 107
movements of, 317
ossification of, 108
surgical anatomy of, 1397, 1405
variations in, 276
xiphoid process of, 108
Stigmata of capillaries, 867
Stilling, canal of, 819
Stomach, 1163
anterior surface of, 1167
areae gastricae of, 1176
arteries of, 1176
bed of, 1170
body of, 1168
capacity of, 1171
cardia, 1164
cardiac orifice of, 1164
surgical anatomy of, 1416, 1417
portion of, 1163
of child, 1171
curvatures of, 1166, 1167
development of, 47, 1249
displaced, 1171
in female, 1171
form of, 1163
foveolae of, 1176
fundus of, 1168, 1163
surgical anatomy of, 1416
gastro-phrenic ligament of, 1170
glands of, 1176
greater curvature of, 1167
surgical anatomy of, 1417
hour-glass, 1171
incisura angularis of, 1 166
cardiaca of, 1165
lesser curvature of, 1166
surgical anatomy of, 1417
lymph vessels of, 1177
mucous membrane of, 1179
muscular coat of, 1174
nerves of, 1177
partial resection of, 1418
peritoneal relations of, 1170
pit of, 108, 114
plicae villosae of, 1176
position of, 1063, 1172
posterior surface of, 1167
pyloric antrum of, 1161,ill67, 1169
INDEX.
1575
Stomach (contd.), pyloric canal of, 1169
ligaments of, 1170
orifice of, 1169, 1173
surface anatomy of, 1416, 1417
surgical anatomy from the back, 1439
portion of, 1169
position of, 1416
surgical anatomy of, 1416, 1417
sphincter of, 1166, 1174
valve of, 1174
pylorus, 1165
radiography of, 1417
relations of, 1416
rugae of, 1165
serous coat of, 1174
size of, 1171
at birth, 1171
structure of, 1174
submucous coat of, 1173
sulcus intermedius of, 1167
surfaces of, 1163
surgical anatomy of, 1416-1418
topography of, 1416, 1417, 1439
uncovered area of, 1170
veins of, 1991
X-ray examination of, 1173
Stomach -bed, 1170
Stomach-chamber, 1169
relations and connexions of, 1169
Stomata of capillaries, 867
Stomatodseum, 25, 27, 41
derivatives of the, 48
separation into nose and mouth, 49
Straight sinus, 974
Strand fronto-pontine, 653
Stratum bacillare retinae, 816, 818
circulare membranae tympani, 835
musculare ventriculi, 879
compactum, 57
corneum epidermis, 857, 859
unguis, 859
cutaneum inembranse tympani, 835
filamentosum, 858
germinativum epidermis, 857
unguis, 859
granulosum cerebelli, 581
epidermis, 858
ovarii, 1314
griseum centrale pedunculi cerebri, 584
colliculi superioris, 586
interolivary, 556
lemnisci, 586
longitudinale musculare ventriculi, 879
lucidum, 858
mucosum epidermis, 857
membranae tympani, 835
opticum, 586, 815
colliculi cerebelli, 580
superioris, 586
papillare of skin, 857
pigmenti retinae, 816, 817
radiatum membranae tympani, 835
reticulare of skin, 857
spongiosum, 57
synovial, 302
development of, 304
of ankle-joint, 353
of carpo-metacarpal joints, 333
of elbow-joint, 325
of hip -joint, 341
of intercarpal joints, 331
interosseous, of leg, 350
Stratum, synovial (contd.}, of intertarsal joints,
358
of knee-joint, 348
of mandibular joint, 312
of metacarpo-phalangeal joints, 333
of radio-carpal joint, 329
of radio-ulnar joint, 327
of shoulder-joint, 322
zonale cerebri, 585
sectionum corporum quadrigeminorum, 586
thalamencephali, 611
Streak, primitive, 23, 26
Strength of bones, 83
Stretching the sciatic nerve, 1457
Stria or Striae, of Gennari, 644, 659
longitudinalis lateralis, 630
of corpus callosum, 629
medialis, 630
medullares, 615
fossae rhomboideae, 550
of thalamus, 611
olfactorii lobi intermedia, 624
lateralis, 624
of Retzius, 1122
terminalis, 610, 635, 636, 642
transversae corporis callosi, 631
vascularis auris internee, 849
Striate arteries, 905
veins, 970, 971
Stripe of Hensen, 850
Stroma of iris, 813
ovarii, 1313
vitreum, 819
Structure of bones, 83
cerebral hemispheres, 644
teeth, 1122
urethra, 1428
Stylo-auricularis muscle, 830
Styloid process of fibula, 250
of metacarpal bone, 225
variations in, 280
of radius, 216
surgical anatomy of, 1450
of temporal bone, 127, 168, 177
development of, 43, 44, 159
ossification of, 132
of ulna, 213
surface anatomy of, 1451
Stylo-glossus muscle, 463
Stylo-hyals, 132, 159
Stylo-hyoid ligament, 313, 1134
muscle, 461
action of, 462
Stylo-mandibular ligament, 313, 1134
Stylo-mastoid artery, 895
foramen, 129, 177
Stylo-pharyngeus muscle, 465
Subacromial bursa, 323
Subanconeus muscle, 382
Subarachnoid fluid, 671
space, 671, 672
surgical anatomy of, 1227
Subarcuate fossa, 130, 131
Subclavian artery, 909
abnormalities of, 1055
branches of, 910
development of, 1027-1028
ligature of, 1394
morphology'of, 1046
surgical anatomy of, 1252, 1255
groove, 111
loop, 759
1576
INDEX.
Subclavian lymph trunk, 998
plexus, 759
vein, 965, 966
abnormalities of, 1058
danger of injury to, 1394
morphology of, 1048, 1049
surgical anatomy of, 1395
Subclavius muscle, 371
action of, 371
Subcoracoid centre, 204, 296
Subcostal angle, 1397, 1407
artery, 926
groove, 110
line, 1407
muscles, 470
plane, 1407
Subcrureus (O.T.), 408
Subdeltoid bursa, 323
Subdural space, 670
surgical anatomy of, 1362
Subinguinal lymph glands, 1459
Sublingual artery, 893
gland, 1138
development of, 1243
surgical anatomy of, 1383
region, 1383
Submalleolar apophysis, 282
Submaxillary artery, 893
duct, 1138
fossa, 155
ganglion, 780
gland, 1137
development of, 1243
duct of, 1138
surgical anatomy of, 1391
lymph glands, 1000
Submental artery, 894
triangle, 1387
Subnasal point, 285
Suboccipital nerve, 688
triangle, 444
boundaries of, 444
Subphrenic abscess, 1412
Subpleural plexus, 913
Subscapular artery, 917
of transverse scapular, 912
bursa, 377
fossa, 203
lymph glands, 1008
nerve, inferior, 713
superior, 713
Subscapularis muscle, 377
action of, 377
minor muscle, 377
Substantia adamantina, 1122
corticalis lentis, 820
lympho-glandulae, 995
sectionum cerebelli, 576
telencephali, 644
eburnea, 1122
ferruginea, 570
gelatinosa (spinal medulla), 528
grisea centralis (spinal medulla), 528
lentis, 820
medullaris lympho-glandulse, 995
nigra, 614
perforata anterior. 34, 541, 624
relation of, to olfactory tract, 624
posterior, 541, 615
relation of, to third ventricle, 616
propria corneae, 810
Suctorial pad, 446, 1109
Sudoriferous glands, 861
Sulcus or Sulci, 646, 653
alar, 799
alveolo-glossal, 1383
angular, 665, 666
anthelicis transversus, 829
arteriae occipitalis, 128
temporalis mediae, 125
vertebralis, 89
auris anterior, 828
basilar, of pons, 548
bicipital, lateral, 1448
medial, 1446, 1447
calcanei, 259
calcarine, 659
lateralis, 659
posterior, 659
carotic, 135
central, of brain, 663
insulae, 654
of cerebral cortex, 646
axial, 646
development of, 646
operculate, 646
terminal, 646
hemispheres, 653
chiasmatis, 135
chorioidal, of eye, 621, 637, 675, 826
cinguli, 666
circular, 654
collateral, 661, 662
transverse, 662
costae, 110
cruris helicis, 829
diagonal, 566
ethmoidalis ossis nasalis, 145
fimbrio-dentate, 627
floccular, of cerebellum, 572
frontal, of brain, 665
inferior, 665, 668
middle, 665
superior, 665, 668
surface anatomy of, 1360
of frontal bone, 116
fronto-marginal, 665
hamuli pterygoidei, 138
hippocampi, 626
horizontal, of cerebellum, 573
hypothalamicus, 618
inferior interventricular, 872
intermedius posterior medullas oblongatae,
544
of stomach, 1167
intertubercular, of humerus, 206
interventricular, 618
intraparietal, 661, 644, 664
lacrimal, of maxilla, 147
ossis lacrimalis, 147
lateral, of brain, 653, 1359, 1360
lateralis mesencephali, 584
posterior medullae oblongatse, 544, 547
spinalis, 522
limiting, of Keil, 654
longitudinal, of cerebrum, 540, 676
longitudinalis, of heart, 618
lunatus, 660
malleolaris, 253, 249
medianus posterior medullae spinalis, 522
mento-labial, of lips, 1108
musculi flexoris hallucis longi calcanei, 260
tali, 257
peronaei calcanei, 260
INDEX.
1577
Sulcus or Sulci musculi perouaei (contrf.), ossis
cuboidei, 263
mylo-hyoideus, 155
iiaso-labialis, 1108
naso-lacrimal, 49
nervi octilo-motorii, 584
petrosi stiperficialis majoris, 130
minoris, 130
radial, 207
ulnaris, 207
obturatorius, 234
occipitalis lateralis, 661
anterior, 665
paramedial, 661
transverse, 644
oculo -nasal, 49
- olfactory, 666
orbital (of brain), 666
paracentral, 664
para-cingular, 665
paramedial, 661
para-pyramidal, 573
of parietal region, 662
parietal, superior, 665
parieto-occipital, 661
paroccipital, 644, 661
peronaei, 253, 260, 263
petrosus inferior ossis occipitalis, 123
tempo ralis, 128
superior, 128
polares, 660
post-central, 662
inferior, 664
superior, 664
surface anatomy of, 1360
post-lunar, 573
post-nodular, 571
praecentral, 665
inferior, 664, 665
superior, 664, 665
surface anatomy of, 1360
praecunei, 665
precervical, 43
primary, of cerebellum, 572
of promontory, 832
pterygoid, 138
pterygo-maxillary, 168, 192
pterygo-palatine, 138, 192
rhinalis, 624
sagittal, of frontal bone, 118, 119, 171
of occipital, 121
of parietal, 119
secondary, of cerebellum, 572
sigmoid, 123
simial, 660
of spinal medulla, 522
spiralis externus cochleae, 849
internus cochleae, 849
subclavian, 111
subclavius pulmonis, 1093
subparietal, 665
suprapyramidal, 573
tali, 256
temporal, inferior, 658
middle, 658
superior, 657
surface anatomy of, 1360
topography of, 1360, 1361
terminalis atrii dextri (His), 874
significance of, 874
of heart, 873
linguae, 1125, 1126
Sulcus or Sulci (contd.), transverse (of brain),
674
of occipital bone, 121
of parietal bone, 119
tubae auditivae, 128, 838
of vallecula, 574
Superciliary ridge, 116, 160
sexual differences of, 116, 193
surface anatomy of, 1358
Superficial volar artery, 919
Superior temporal sulcus, 657
topography of, 1360, 1361
vena cava, 1405
Supination, 328, 401
Supinator muscle, 398
action of, 399
Supra -auricular point, 286
Supraclavicular nerves, 696
Suprahyoid artery, 892
lymph glands, 1002
muscles, 460
Supramandibular nerve (O.T.), 784
Supramarginal triangle, 1360
Supramastoid crest, 125
Suprameatal spine, 126, 1366, 1369
surgical importance of, 1366, 1369
triangle, 126
Supranasal bone, 277
Supraoccipital bone, 124
development of, 292
Supraorbital artery, 903
foramen, 116, 160
margin, 115, 160
nerve, 772
notch, 116, 160
surface anatomy of, 1358
ridge, 116
vein, 968
Suprarenal artery, 927, 933
gland, 1343
development of, 1341, 1343
forms and relations of, 1344
in foetus, 1343
hilum of, 1345
medullary portion of, 1343
nerves of, 765, 1346
relations of, 1340
structure of, 1346
surgical anatomy of, 1425
impression of liver, 1192
plexus, 765
vein, 982
abnormalities of, 1059
development of, 1040
morphology of, 1049
Suprascapular nerve, 703
region, 1436
Suprascleral lymph space, 808
Supraspinatus muscle, 375
action of, 375
Supraspinous artery, 913
fossa, 202
ligament, 308
Suprasternal artery, 912
notch, 107
region, 1397
Supratonsillar fossa, 1145, 1147
Supratrochlear foramen, 280
lymph glands, 1007
nerve, 778
Sural arteries, 952
nerves, 730, 732
101
1578
INDEX.
Surface and surgical anatomy, 1357
of abdomen, 1407
of abdominal aorta, 1426
of abdominal wall, 1407
of accessory nerve, 1393
of ankle, 1411, 1463
of arm, 1447
of axilla, 1446
of back, 1436
of bregma, 1358
of buttock, 1455
of central sulcus of brain, 1359
of cranium, 1357
of ear, 1360
of elbow, 1449
of face, 1374
of female pelvis, 1434
of foot, 1463
of forearm, 1450
of hand, 1450
of head and neck, 1357
of heart, 1403
of inferior end of central sulcus, 1359
of junction of motor areas, arm, and face, 1359
of knee, 1460
of lambda, 1358
of lateral fissure of brain, 1359
of lateral ventricle, 1362
of leg, 1461
of lungs, 1398
of meningeal arteries, 1364
of middle meningeal artery, 1359
of neck, 1385
of perineum, 1427
of popliteal space, 1457
of scalp, 1357
blood-supply of, 1357
of shoulder, 1444
of thigh, 1458
of thorax, 1395
of transverse sinus, 1365
Surgical neck of humerus, 206
Suspensory ligament of clitoris, 1326
of lens, 819
of ovary, 1312
of penis, 1299
muscle of duodenum, 1187
Sustentaculum lienis, 1353
tali, 260
architecture of, 274
position of, 1464
surface anatomy of, 1465
variation in, 282
Sutural bones, 145, -146
Suture or Sutura, 300
coronal, 164, 172
synostosis of, 197
dentate, 300
development of, 304
frontal, 160
fronto-maxillary, 160
fronto-zygomatic, 160
harmonia, 300
infraorbital, 279
intermaxillary, 163
internasal, 145
lambdoid, 165, 171
surgical anatomy of, 1360
limbosa, 300
masto-squamosal, 128
metopic, 118, 277
naso-f rental, 160
Suture or Sutura (contd.}, iiotha, 300
occipito-mastoid, 165, 171
orbito-maxillary -frontal, 277
palatine, 174
transverse, 174
parieto-mastoid, 164
petro-squamous, 125, 126
surgical anatomy of, 1366
premaxillary, 150
sagittal, 119, 171
serrata, 300
spheno-parietal, 164
spheno-squamous, 168
spheno-zygomatic, 163
squamosa, 164, 300
squamoso-mastoid, 125, 126
vera, 300
zygomatico-frontal, 160
zygomatico-maxillary, 160
Swallowing, movements in, 467
Sweat glands, 861
development of, 862
ducts of, 861
glomerulus of, 861
orifice of, 861
Sylvian (O.T.) (lateral cerebral) fissure, 653,
654
development of, 655, 656
surgical anatomy of, 1359, 1360
fossa, 624
point, 1360
veins, 971
Symmetry, 4
Sympathetic nervous system, 678, 753, 1342
cephalic and cervical parts of, 756
central communicating branches, 762
peripheral branches of distribution
762
connecting cords of, 755, 756, 759, 761,
762, 763
development of, 681
functions of, 755, 762
ganglia of, 504, 753
gangliated trunk of, 753
general structure of, 753
gray rami communicantes of, 678, 681
lumbar, 761
morphology of, 766, 795
medullated nerve-fibres of, 754
non-medullated, 754 '
peripheral branches of, 755
plexuses of, 763
rami communicantes of, 754, 756, 759,
761, 762, 763
sacral, 762
central communicating branches of,
763
peripheral branches of distribution,
763
thoracic part of, 759, 761
aortic branches, 761
central communicating branches of,
761
functions of, 761
peripheral branches of distribution,
761
pulmonary branches, 761
splanchnic branches, 761
white rami communicantes of, 678, 680,
681
Symphysis menti, 155
ossinm pubis, 337
INDEX.
1579
Symphysis pubis, 337
cavity of, 337
fibro-cartilage, interpubic of, 337
ligaments of, 337
sacro-coccygea, 308
Synarthrosis, 299
Synchondrosis, 299
cranii, 300
epiphyseos, 300
nemo-central, 104
pet ro- jugular, 300
spheno -occipital, 300
sternal, 317
Syndesmology, 299
Syndesmosis, tibio-fibular, 351
ligaments of, 351
Synovia, 301, 304
Synovial bursae, 302
fat-pads, 302, 325, 341, 348
pouches posterior to the condyles of the
femur, 1461
sheaths at wrist, 388, 389
strata of joints of lower limb, 341, 348, 350,
351, 353
of pelvis, 336
of thorax, 314, 315, 316
of upper limb, 322, 325, 327, 329
of mandibular joint, 312
stratum of the knee-joint, 1461
System, blood -vascular, morphology of, 1042
primitive formation of, 64
Systema lymphaticum, 993
nervorum centrale, 497
periphericum, 677
sympathicum, 753
Systematic anatomy, 3
Systemic circulation, 882, 959
Table of relations of structures to vertebral
spines, 1442, 1448
Tactile corpuscles, 863
discs, 864
Taenia coli, 1211
pontis, 615
thalami, 610
Tail, 48
fold, 38
gut, 48
Talo-calcaneal joint, 354
ligaments, 355
Talo-calcaneo-navicular joint, 355
Talo-fibular ligaments, 352
Talo-navicular joint, 355
surgical anatomy of, 1464
ligaments of, 355
Talo-tibial ligaments, 353
Talus, 254
architecture of, 274
articular surfaces of, 255
development of, 265
facets of head, 257
head of, 257
homology of, 295
ossification of, 265
Tapeinc cephalic skulls, 286
Tapetum of brain, 631
of chorioid, 812
cellulosum, 812
fibrosum, 812
Tarsal arches of eyelids, 823
artery, lateral, 957
glands, 822, 823
Tarsal glands (contd.), surgical anatomy of, 1377
ligaments of eyelid, 822
Tarsale, os, 295
Tarso-metatarsal joints, 359
line of, 1464
surgical anatomy of, 1464
Tarsus, 254, 821
architecture of, 274
ossification of, 265
transverse articulation of, 357
variations in, 282
as a whole, 264
Taste buds, 854, 1128
fibres, course of, 598
gustatory hair, 855
pore of, 854
nerves of, 855
nuclei of, 598
organs, 854
structure of, 854
supporting cells of, 854
Tectorial membrane, 851, 852
Tectum, 516
Teeth, 1112
adamant, 1113, 1122
composition of, 1122
prisms of, 1122
alveolar periosteum, 1115, 1123
alveoli of, 1115
apical foramen of, 1114
arrangement of, in jaws, 1119
canine, 1117
cavity, 1114
cingulum of, 1116
contact surface of, 1115
crown of, 1114, 1116, 1118, 1119, 1120
cuticle of, 1122
composition of, 1123
dental canaliculi, 1123
deciduous, 1113, 1114, 1121
dental arches, 1119
index of, 1248
lamina of, 1026
dermal, 1244
development of, 1244
eruption of, 1120, 1246
eye, 1117
fangs of, 1114
follicles of, 1245, 1246
general form and structure, 1114
germs of, 1245
grinding surfaces of, 1115
gubernaculum of, 1247
incisor, 1115, 1116
ivory of, 1113, 1122, 1123
lingual tubercle of, 1116
lymph vessels of, 1005
molar, 1117
lower, 1118
roots of, 1118
upper, 1118
morphology of, 1248
multitubercular, 1248
Nasmyth's membrane of, 1122
neck of, 1114
nerves of, alveolar, anterior superior, 777
inferior, 780
middle, superior, 777
posterior superior, 775
osseous substance, 1123
papilla of, 1244
parts of adamant, 1113
1580
INDEX.
Teeth, parts of (contd.), ivory, 1113
period of eruption of the permanent, 1120
permanent, 1115, 1119
descriptive terms for, 1115
premolar, 1117
pulp of, 1114, 1123
cavity of, 1114
relative sizes of, 1116, 1117, 1118, 1119,
1120, 1121
reserve germs of, 1246
root of, 1114, 1116, 1117, 1118, 1119
canal, 1114, 1115
serotinus, 1113, 1118, 1119
structure of, 1122
substantia ossea of, 1113, 1123
tartar of, 1115
tubercles of, 1114, 1116, 1118, 1119, 1128
of crown, 1114, 1118, 1119
variations in number of, 1121
auditory, 850
Tegmen tympani, 192, 271, 832
surgical anatomy of, 1366
Tegmen ventriculi quarti, 549
Tegmental region, hypothalamic, 613-
Tegmentum, 586
Tela chorioidea ventriculi quarti, 571, 674
tertii, 617, 674
serosa intestine, 1178
submucosa intestini, 1179
ventriculi, 1175
subserosa, 1158
Telencephalon, 608
development of, 34
Telolecithal ova, 11
Telophase, 10
Temporal area, 656, 658
artery, deep, anterior, 899
middle, 897
of posterior cerebral, 908
of retina, 818
superficial, 896
bone, 125
angles and petrous part of, 128
architecture of, 271
articular tubercle of, 167
at birth, 133
connexions of, 131
external acoustic meatus of, 127
ossification of, 131
parts of, at birth, 125
petromastoid part of, 128
petrous part, anterior surface, 130
inferior surface, 129
squamous part of, 125
tympanic antrum of, 832
part of, 127
variations in, 278
zygomatic process of, 166
canal, 154
crest, 116, 118, 166
fascia, 455
fossa, 145, 166
lateral wall, 167
medial wall, 166
gyri, 657, 658
line, 116, 118, 166
muscle, 455
nerve of auriculo-temporal, 780
deep, 779
of facial, 783
plane, 118
process, 153
Temporal region, 656, 658
surgical anatomy of, 1360
ridge, 118, 166
sulci, 958
veins, 967, 968
Temporo-mandibular arch, 279
joint, 312
surgical anatomy of, 1366, 1375
Temporo-pontine tract, 643
Tendinum inscriptiones, 1407
Tendo calcaneus (Achillis), 428, 429
surgical anatomy of, 1463
Tensor fasciae latae muscle, 415
action of, 416
surgical anatomy of, 1459
tarsi muscle, 450
tympani muscle, 841
canal for, 128
veli palatini muscle, 466
Tentorium cerebelli, 669
Teres major muscle, 376
minor muscle, 375
actions of, 376
Terms in use in limbs, 5
Testicular artery, 928
Testis, 1286
appendices of, 1287
coni vasculosi of, 1289
descent of, 1295
development of, 1333
ductuli efferentes, 1288
ductus deferens of, 1289
development of, 1296
efferent ductules of, 1288
epididymis of, 1286, 1287
gubernaculum of, 1295
lobes of, 1288
lymph vessels of, 1289
mediastinum of, 1288
mesorchium, 1295
nerves and vessels; of, 1287
paradidyinis of, 1287
processus vaginalis of, 1295
rete of, 1288
seminiferous tubules of, 1288
septula of, 1288
sinus epididymidis, 1287
structure of, 1288
tubuli recti of, 1288
seminiferi contorti, 1288
tunica albuginea of, 1288
vaginalis of, 1287
vasculosa of, 1288
undescended, 1296
vessels and nerves of, 1289
Thalamencephalon, 608, 609
Thalamic radiation, 610, 612, 613
Thalamo-cortical fibres, 612, 613
Thalamo-striate fibres, 612, 641, 642
Thalamus, 541, 609
anterior nucleus of, 612
tubercle of, 611
central nucleus of, 612
connexions of, 612, 641
with cerebral cortex, 612, 613
with hippocampus, 625
with optic tract, 658
cortico-thalamic fibres of, 612, 613
development of, 35
grey matter of, 611
inferior surface of, 610
internal medullary lamina of, 611
INDEX.
1581
Thalamus (contd.), intimate structure of, 611
lamina medullaris externa of, 611
interna of, 611
lateral geniculate body of, 611, 613
medullary lamina of, 610
nucleus of, 611
surface of, 610
lemniscus fibres of, 586
massa intermedia of, 611
medial nucleus of, 611
nuclei of, 611, 612
origin of, 517
position and connexions of, 610, 611, 612, 613
pulvinar of, 611
radiation of, 610, 612, 613
stalks of, 612
stratum zonale of, 611
stria medullaris of, 611
superior surface of, 610
surfaces of, 610
taenia of, 610
thalamo-mamillary tract of, 612
tuberculum anterius of, 611
Thebesius, valve of, 874
Theca folliculi, 1314
of spinal medulla, 518
Theory of nerve components, 505-506
Thigh bone, 239
Third ventricle, 616
development of, 36
Thoracic aorta, 884
branches of, 924
surface anatomy of, 140
arteries, lateral, 916
supreme, 916
duct, 993, 996
abnormalities of, 1060
course of, 997
length and diameter, 997
relations of, 997
tributaries of, 997
surgical anatomy of, 1394
ganglia, 759
part of sympathetic, 759
nerves, 713
anterior rami, 713
posterior rami of, 690
first thoracic, 713
communications of, 713
intercosto-brachial, 714, 716
second thoracic, 714
communications of, 716
third thoracic, 716
fourth to sixth thoracic, 716
branches of, 716
seventh to eleventh thoracic, 717
branches of, 717
twelfth thoracic, 717
branches of, 717
vertebrae, 93
Thoraco-acromial artery, 916
Thoraco -dorsal nerve, 713
Thorax, 113
anterior wall of, 113
aortic area of, 1405
apertures of, 114
at birth, 114
cavity of, 1083
division of, into regions, 1397
foetal condition, 114
in foetus, 114
joints of, 313
Thorax (contd.), lateral walls of, 114
lines of, 1089
lymph vessels of, 1013
mediastinum of, 1089
mitral area of, 1405
muscles of, 470
posterior wall of, 113
precordial area of, 1403
pulmonary area of, 1405
regions of, 1397
sexual differences in, 114
sternal furrow of, 1397
surgical anatomy of, 1395
tricuspid area of, 1405
walls of, 113
Thrombosis of femoral vein, 1427
Thumb, movements of, 402
muscles of, 392, 393
Thymus, 1350
blood-vessels of, 1351
development of, 44, 1351
structure of, 1351
vestiges, cervical, 1351
Thyreo-arytaenoid ligaments, 1067
muscle, 1073
action of, 1076
Thyreo-epiglottic ligament, 1068
muscle, 1075
action of, 1076
Thyreo-glossal duct, 44, 1348
surgical anatomy of, 1348
Thyreo-hyal, 146
Thyreo-hyoid arch, 42, 43
bar, 44, 159
membrane, 1066
muscles produced from, 460
action of, 460
nerve of, 796
Thyreoid artery, inferior, 910
abnormalities of, 1037
superior, 891
morphology of, 1047
cartilage, 1062
development of, 1100
incisura of, 1062
inferior cornua of, 1063
laminse of, 1062
linea obliqua of, 1063
ossification of, 1065
prominentia of, 1062
superior cornua of, 1063
tubercle, inferior, of, 1063
superior of, 1063
fascia, 1389
gland, 1347
accessory, 1348
blood and lymph vessels, 1348
capsule of, 1388
development of, 43, 44, 1348
fascial connexions of, 1388
isthmus of, 1347
size of, 1347
surgical anatomy of, 1388
leva tor muscle of, 460, 1347
lobes of, 1347
pyramidal lobe of, 1347
structure of, 1348
surgical anatomy of, 1388
variations in, 1347, 1348
rudiments, 1348
veins, 964, 965
Thyreoidea ima artery, 888
1582
INDEX.
Thyreotomy, 1388
Tibia, 246
anterior crest of, 248
architecture of, 274
condyles of, 246
connexions of, 249
fibular notch of, 249
fossae of, 247
homology of, 295
intercondyloid eminence of, 247
interosseons crest of, 248
medial malleolus of, 249
nutrient foramina of, 249
ossification of, 250
platyknemia, 281
popliteal line of, 249
shaft of, 248
surgical anatomy of, 1461
tubercles of, 247
tuberosity of, 248
variations in, 281
Tibial artery, anterior, 955
posterior, 952
recurrent, 956
nerve, 729, 732
articular branches of, 732
cutaneus suras lateralis, 732
Tibiale, os, 295
Tibialis anterior muscle, 424
action of, 424
surface anatomy of, 1465
posterior muscle, 431
action of, 431
surface anatomy of, 1465
Tibio-fascialis anterior muscle, 424
Tibio-femoral index, 289
Tibio-fibular articulation, 349
movements at, 349, 350
ligament, interosseotis, 349
transverse, 349
syndesmosis, 351
Tibio-navicular ligament, 353
Toes, digital sheaths of, 430
movements of, 436
Tomes, fibrils of, 1247
processes of, 1247
Tongue, 1124
anterior glands of, 1382
arteries of, 1130
development of, 45, 1249
dorsum of', 1124, 1125, 1126
folia of, 1124
foramen caecum of, 45, 1126, 1249, 1381
frenulum of, 1128
surgical anatomy of, 1383
glands of, 1130
inferior surface of, 1128
lateral margin, 1125
lingual duct of, 1139
lymph follicles of, 1126
vessels of, 1005, 1130, 1383
mucous membrane of, 1129
muscles of, 462
surgical anatomy of, 1382
nerves of, 1131
oral part of, 1126
papillae of, 1126
pharyngeal part of, 1126
plicae fimbriatse of, 1128
raphe of, 1129
septum of, 1129
structure of, 1129
Tongue (contd.), sulcus terminalis of, 1125
surgical anatomy of, 1381
taste-buds of, 854
thyreo-glossal duct of, 42, 46, 1348
surgical anatomy of, 1381
vessels of, 1130
Tonsil or Tonsilla, of auditory tube, 838
cerebelli, 575
lingual, 1126
palatine, 1145
arteries of, 1147
development of, 1249
lymph vessels of, 1147
nerves of, 1147
plica triangularis of, 1146
relations of, 1147
surgical anatomy of, 1383
pharyngea, 1143
surgical anatomy of, 1385
Tonsillar arteries, 1147
lymph gland, 1392
nerve, 786, 1147
plexus, 1147
Tooth-band, 1245
Torus levatorius, 1143
occipitalis transversus, 277
palatinus, 279
tubarius, 1143
uretericus, 1277
Touch, organs of, 858, 863-866
Trabeculae lienis, 1353
carneae, 877
corporum cavernosorum, 1300
cranii, 290
Trachea, 1078
bifurcation of, 1076, 1402
cartilaginous rings of, 1081
development of, 1100
fibro-elastic membrane of, 1081
mucous glands of, 1082
membrane of, 1082
muscle of, 1081.
relations of, 1079
structure of wall of, 1081
surface and surgical anatomy of, 1388, 1402
thoracic part of, 1080
Tracheal arteries, 911
cartilages, 1081
Tracheotomy, high, 1388
. low, 1388
Tracts or Tractus, see also under Spinal
medulla
antero-lateral, 535
bulbo-spinal, 537, 538
bulbo-thalamic, 591
Burdach, 531, 533, 537, 5'47, 559
callosal, crossed, 631
central tegmental, of pons, 568
cerebellar, 536, 537, 546, 563, 578
sensory, 538, 546
cerebello-olivary, 556, 560
cerebro-pontine, 566
cerebro-spinal, lateral (crossed pyramidal),
338, 545, 557, 565
cerebro-spinal, anterior (direct pyramidal),
536, 539, 545
in cerebral hemispheres, 642, 643
in internal capsule, 642
in medulla oblongata, 538, 545
in pons, 565
circum-olivary, 557
of corpus trapezoideum, 567
INDEX.
1583
Tracts or Tractus (contd.), cortico-poiitine, 653
fronto-pontine, in internal capsule, 642
of Gowers, 535, 536, 546
gracilis, 533, 547, 559
ilio-tibial, 404
surface anatomy of, 1461
interfascicular, 533, 587
of lemniscus, 568, 570, 585, 586
medial longitudinal, 562, 568, 570, 588
myelinisation of, 532, 533
olfactory, 623
lateral root of, 624
medial root of, 560
structure of, 623
olivo-spinal, 538
optic, 619
cerebral connexions of, 620
commissural fibres of, 619
efferent fibres of, 619
lateral root of, 620
medial root of, 619
postero-lateral (of Lissauer), 534
proprius, 537
rubro-spinal, 538, 588
septo-marginal descending, 535
solitarius, 597
spinalis of trigeminal nerve, 547, 601
spino-tectal, 537
spino-thalamic, 535, 537, 562, 591
spiralis foraminosus, 844, 845
superficial, antero-lateral, 536, 546
tecto-spinal, 537, 562
temporo-pontine, 653
thalamo-olivary, 556
vestibulo-spinal, 537, 538
Tragicus muscle, 829
Tragus, 828
Transpyloric plane, 1411
Transverse artery of basilar, 907
cervical artery, 911
carpal articulation, 330
fissure of brain, 604
humeral ligament, 321
intermetacarpal ligament, 332
ligament of acetabulum, 339
of knee, 348
metacarpal ligaments, 333
metatarsal ligament, 360
perineal ligament, 338
processes of vertebrae, cervical, 90, 92, 93
lumbar, 90
sacral, 98
surgical anatomy of, 1393
thoracic, 93, 94
scapular artery, 911
ligaments, superior and inferior, 320
vein, 911
tarsal articulation, 357
vesical fold, 1283
Transversalis fascia, 475
Transversus abdominis muscle, 480
auriculas muscle, 830
perinei profundus muscle, 488
superficialis muscle, 487
thoracis muscle, 470
of tongue, 463
vaginae muscle, 489
Trapezius muscle, 365
surgical anatomy of, 1437
Trapezoid ligament, 319
ridge of clavicle, 199
Traube, semilunar space of, 1418
Triangle of auscultation, 367
carotid, 1390, 1391
"digastric, 1390, 1391
epigastric, 1397
femoral, 414
of Hesselbach, 483, 1235, 1408
lower carotid, 1393
lumbar, 478
of Petit, 367
surgical anatomy of, 1437
of Macewen, 126, 168
medial supracondylar, 1447
rectal, of perineum, 1427
submental, 1387
suboccipital, 444
supramarginal, 1359
suprameatal, 126, 168
urogenital, 1427
Triangles of neck, 1387
Triangular ligament of liver, left, 1196
right, 1196
Triangularis (oris) muscle, 451
Triceps brachii muscle, 381
surgical anatomy of, 1437
surae muscle, 428
Tri cuspid area, 1405
orifice, 874, 877
surface anatomy of, 1405
valve, 877
Trigeminal nerve, 771
development of, 683
main sensory nucleus of, 600
mesencephalic root of, 601
nature of, 602
motor nucleus of, 601
sensory root of, 600
tractus spinalis of, 601
Trigonum acustici, 551
collaterale, of lateral ventricle, 636, 637
femorale, 414, 1291
habenulas, 611, 614
hypoglossi, 551, 594
olfactorium, 623
vagi, 551
vesicae, 1277
Triquetral bone of hand, 219
morphology of, 295
ossification of, 223
Trochanter major, 241, 1455
minor, 242
tertius, 242, 281
Trochlea, 206
of humerus, 208
of superior oblique muscle, 453
tali, 254
Trochlear fossa, 117
nerve, 770
development of, 683
nucleus of, 602
spine, 117
surface, 204, 208
Trochoid rotatory joint, 301
Trolard, anastomotic vein of, 971
Troltsch, recesses of, 842
Trophoblast, 21
Trunci lumbales (lymphatic), 997
Truncus corporis callosi, 630
costo-cervical, 914
intestinal, 997, 1210
jugular lymphatic, 998
lumbo-sacral, 727
subclavius, 998
1584
INDEX.
Truncus sympathicus, 753
Trunks of brachial plexus, 700, 742
of sacral plexus, 720, 727, 742
Tubal artery, 928
Tube, auditory, 44, 50, 52, 176
neural, 33
uterine, 1314
Tuber ; Tuberculum or Tuberositas ; Tubercle
or Tuberosity
accessory, 96
adductor, 242, 245
surgical anatomy of, 1461
amygdaloid, 636
anterior of the atlas, 91
helicis, 52, 828
thalami, 611
vertebrarum cervicalium, 90
anthelicis, 52, 828
antitragicum, 52, 828
articular, of temporal bone, 125
of atlas, 91
of the auricle, 828
auriculae Darwin ii, 828
calcanei, 259
caroticum, 1395
cinereum, 541, 547, 615
development of, 34
cloacal, 1328, 1336
coracoid, of clavicle, 199
corniculate, of larynx, 1069
of Wrisberg, 1069
costal, of clavicle, 199
of cuboid, 263
cuneate, 547
cuneiform, 1069
deltoid, 207
of clavicle, 198
dental, 1114
dentis, 1114
dorsal, of radius, 1450
epiglottic, 1069
of femur, 241, 242, 243
of fifth metacarpal bone, 226, 1451
of fifth metatarsal, 267
frontal, 115
genital, 78, 1328
of humerus, 204, 206, 207
iliaca, 230
impar, 45, 46
infraglenoidal, 201
intercondyloid lateral, 247
medial, 247
intermedium helicis, 828
intervenosum, 875
of ischium, 232
surgical anatomy of, 1455
jugular, 122
labial, 1109
lobular, 52, 828
majus humeri, 206
maxillary, 147, 148
mental, 155
minus humeri, 206
of navicular bone of hand, 218
surgical anatomy of, 1451
of foot, 261
surgical anatomy of, 1464
obturatorium anterius, 234
posterius, 234
olfactory, 623
omentale hepatis, 1193
pancreatis, 1206
Tuber ; Tuberculum or Tuberositas ; Tubercle
or Tuberosity (contd.}
papillare hepatis, 1192
parietal, 118
peroneal, 1464
pharyngeal, 123, 176, 179
posterius atlantis, 91
vertebrarum cervicalium, 90
post-glenoid, 126, 278
pterygoid, 138, 175
pubicum, 233, 237
for the quadratus, 240
of radius, 215
of rib, 109, 111, 112
of Santorini, 1069
scalene, 111
supraglenoidal, 201
supratragicum, 52, 828
of talus, 254
of tibia, 246, 248
tragicum, 52, 828
ulnae, 210
vermis cerebelli, 575
vertebrarterial, 1395
of Wrisberg, 1069
of zygoma, 153
Tubercular point of hip, 1455
process of vertebra, 284
Tubes, bronchial, in lung, 1097
dentinal, 1045, 1247
Tubular glands, 1132
Tubules of kidney, 1266
of par-oophoron, 1316
Wolffian, 1328
Tubuli recti testis, 1288
renales, 1266
seminiferi contorti, 1288
Tunica albuginea, 1288, 1300
of corpus cavernosum penis, 1300
conjunctiva bulbi, 823
palpebrarum, 823
dartos, 1298
externa or adventitia of arteries, 868
of lymph vessels, 994
of veins, 869
fibrosa of kidneys, 1257
interna or intima of arteries, 868
of lymph vessels, 994
of veins, 869
media of arteries, 868
of lymph vessels, 994
of veins, 869
mucosa linguae, 1129
tubae auditivae, 838
tympanica, 842
serosa, 1234
vaginalis, 1287
vasculosi oculi, 810, 814
Tunnel of Corti, 850
Tympanic antrum, 834, 836, 1369, 1371
aditus of, 834, 1369
development of, 133
relation of, to supra-meatal triangle, 1369
to tympanum, 834
surgical anatomy of, 1369
arteries, anterior, of internal maxillary, 898
inferior, of pharyngeal ascending, 896
of internal carotid, 902
posterior, of stylo-mastoid, 895
superior, of middle meningeal, 898
attic, 832, 1368, 1369
canal, 129
INDEX.
1585
Tympanic cavity, 52, 191, 192, 832
atrium of, 832
danger of injury to lateral semicircular
duct in, 1371
development of, 842
facial nerve in, 1371
formation of, 842
membrana tympani secundaria of, 833
mucous membrane of, 842
muscles of, 841
nerves of, 842
opening of, 1371
orifice of auditory tube in, 750
pouch of Prussak, 842
promontory of, 832
pyramid of, 834
recesses of Troltsch, 842
recessus epitympanicus of, 832, 1368
relation of, to tympanum, 834
surgical anatomy of, 1368
vessels of, 842
walls of, 832
carotic, 834
jugular, 832
labyrinthic, 832
mastoid, 834
membranous, 834
tegmental, 832
groove, 834
membrane, 834
folds of, 835
paracentesis of, 1368
surgical anatomy of, 1367
triangular cone of, 835
nerve, 836
ossicles, 838
part of temporal bone, 127, 132, 133
ossification of, 132, 133
sexual difference in, 194
plate, fibrous, 831
plexus, 759
ring, 133
Tympano-hyal, 132
Tympano-mastoid fissure, 127
Typical segmental nerve, 692
Ulna, 210
architecture of, 272
connexions of, 213
homology of, 295
ossification of, 213
surgical anatomy of, 1449, 1451
variations in, 280
Ulnar artery, 921
collateral artery, 899
furrow, 213
nerve, 708
notch, 216
veins, 977
Ulnare, os, 295
Ultimo-branchial body, 44, 1352
Umbilical arteries, 65, 939
cord, 55
fissure, 1191
fossa, 1191
notch, 1191
region, 1411
vein, 1036, 1037
vesicle, 22, 53
zone, 1411
Umbilicus, development of, 39
primitive orifice of, 38
Umbo mernbranae tympani, 835
Uncinate process of ethmoid, 141
of pancreas, 1205
Uncus, 629
Ungual phalanges of fingers, 227
surgical anatomy of, 1444
of toes, 268
Ungues, 858
Urachus, 48, 1283, 1332
Ureter, 1268
abdominal part of, 1268
calibre of, 1270
development of, 1331
in female, 1270
surgical anatomy of, 1434
orifice of, 1277, 1278, 1428
pelvic part of, 1269
position of, 1426
posterior position of, 1437
structure of, 1270
surgical relations of, 1426
variations in, 1271
vessels and nerves of, 1271
Ureteral artery of internal spermatic and
ovarian, 928
of renal, 927
Urethra, 1284
bulb of, 1308
cavernous part, 1304, 1308, 1309
crista urethralis of, 1284, 1303, 1306
male, 1306
development of, 1333, 1334
external orifice of, 1284
surgical anatomy of, 1427
female, 1284
development of, 1333
fossa navicularis urethras, 1308
glands of, 1285, 1304, 1309
internal orifice of, 1277, 1278
lacunae of, 1285, 1309
male, 1304
surgical anatomy of, 1428
membranous part, 1304, 1307
surgical anatomy of, 1427
para-urethral duct of, 1285
prostatic part, 1304, 1305
rupture of, 1427
structure of, 1285, 1309
surgical anatomy of, 1427
utriculus prostaticus, 1306
Urinary bladder, 1271, 1278
capacity of, 1277
development of, 1328, 1332
distended, 1276
empty, 1275
in female, 1278
in infant, 1279
interior of, 1277
urachus of, 1280, 1283
ureteral orifices of, 1278
urethral orifice of, 1273, 1274
Urogenital canal, 1329
cleft, 1336
diaphragm, 489, 491
relation of, to fascia of pelvis, 489, 491
fissure, 1336
organs, development of, 1327
space, 1335
system, 1257
triangle of perineum, 1427
Uterine artery, 928
of ovarian, 928
1586
INDEX.
Uterine artery (contd.}, surgical anatomy of,
1435
decidua, 57
glands, 1230
plexus, 765, 766
tube, 1310, 1314
abdominal ostium of, 1314
ampulla of, 1314
appendices vesiculosi of, 1316
development of, 1335
fimbriae of, 1314
infundibulum of, 1314
isthmus of, 1314
mesosalpinx of, 1314
nerves of, 1315
ovarian fimbria of, 1314
pars uterina of, 1315
plicae of, 1315
structure of, 1315
surgical anatomy of, 1436
uterine ostium of, 1315
vessels of, 1315
veins, 985
venous plexuses, 985
Utero-sacral ligaments, 1318
Utero-vesical fold, 1317
pouch, 1238, 1317
Uterus, 1316
age differences in, 1320
anteflexed, 1319
anteverted, 1319
arbor vitae of, 1317
body of, 1316
broad ligaments of, 1238
surgical anatomy of, 1434
cavity of, 1317
cervical canal of, 1317
ganglion of, 1321
cervix of, 1316
connexions of, 1317
development of, 1335
at different ages, 1320
external orifice of, 1316
fundus of, 1316
glands of, 1320
horns of, 1320
internal orifice of, 1317
intestinal surface of, 1316
lips of cervix, 1316
lymph vessels of, 1321
masculinus, 1306
in menstruation, 1320
nerves of, 1321
orifice, external of, 1317
internal of, 1316
periodic changes in wall of, 1320
peritoneal relations of, 1317
plicae palmatsB of, 1317
position of, 1319
pregnant, 1321
relations of, 1319
retroverted, 1319
round ligament of, 1319
septum of, 1320
structure of, 1320
supra-vaginal part of cervix, 1316
surgical anatomy of, 1434, 1435
vaginal part of cervix, 1316
variations in, 1320
vesical surface of, 1316
vessels and nerves of, 1321
Utricle, 846
Utricle (contd.}, development of, 52
macula acustica of, 846, 857
recessus of, 846
sinus superior of, 846
Utriculus prostaticus, 1292, 1306
Uvula cerebelli, 576
palatina, 1111
vesicae, 1277
Vagina, 1321
bulbs of, 1326
carina urethralis of, 1323
carunculss hymenales of, 1322
columns of, 1323
development of, 1335
digital exploration of, 1435
examination of, 1435
fornix of, 1321
hymen of, 1322
introitus of, 1325
lymph vessels of, 1324
mucous membrane of, 1323
muscular coat of, 1323
nerves of, 1324
orifice of, 1325
relations of, 1322
rugae of, 1323
septum of, 1320
structure of, 1323
variations in, 1320
vessels and nerves of, 1324
vestibule of, 1325
Vagina mucosa iiitertubercularis musculi bi-
cipitis brachii, 380
musculi recti abdominis, 482
nervi optici, 808
processus styloidei, 127
tendinis musculi extensoris carpi ulnaris, 384
digiti quinti, 384
hallucis longi, 431
pollicis longi, 384
flexoris hallucis longi, 431
pollicis longi, 390
peronaei longi plantaris, 426
tibialis anterioris, 424
posterioris, 431
tendinum digitalis, 388, 389
pedis, 430
musculi extensoris digitorum pedis longi,
425
flexoris digitorum pedis longi, 430
musculorum abductoris longi et extensoris
brevis pollicis, 383
extensoris digitorum commuiiis et ex-
tensoris indicis, 384
extensorum carpi radialium, 384
peronaeorum communes, 423
Vaginal artery, 939, 1324
ligaments, 384
plexus, 766, 985
process of temporal bone, 127, 177
sphenoid bone, 177
veins, 985
venous plexuses, 985
Vagus nerve, 786, 788
abdominal branches, 789
auricular branch of, 788
cardiac nerves, inferior, of vagus, 789
superior, of vagus, 789
communications of, 788
development of, 684
lingual branch of, 788
INDEX.
1587
Vagus nerve (contd.), meningeal branch of, 788
nuclei of, 596
phaiyngeal branch of, 788
superior laryngeal nerve, 788
external branch of, 788
internal branch of, 788
thoracic branches, 789
Vallate papillae, 1127
vallum of, 1127
Vallecula, 574
cerebelli, 1126
epiglottica, 1068
Valve or Valves, anal, 1230, 1231
aortic, 878
cusp of, 878
of Beraud, 825
of colon, 1214, 1215
lips of, 1214
position of, 1214
structure of, 1214
surface anatomy of, 1421, 1443
of the coronary sinus, 875
fossae navicularis, 1309
of Hasner, 825
of heart, positions of, 1405
ileo-caecal, 1215
of the inferior vena cava, 875
lunule of, 877
of lymph vessels, 994
mitral, 878
pulmonary, 877
processus vermiformis, 1216
pyloric, 1166, 1173, 1174
rectal, 1230, 1231
semilunar, 877
sinus coronarii, 875
spiral, of gall-bladder, 1201
structure of, 1202
tricuspid, 871
of veins, 869
venae cavae inferioris, 874, 875
venous, of heart, 1032
Vas afferens renis, 1267
efferens renis, 1267
prouiinens, 849
spirale, 849
Vasa aberrantia, 1055
efferentia testis, 1288
intestini tennis, 932
sanguinea retinae, 818
vasorum, 870
Vascular area, 64
system, 64, 867
abnormalities of, 1050
blood, 867
development of, primitive, 63
divisions of, 870
lymph, 867
morphology of, 1042, 1048
primitive, 65, 1025
Vastus intermedius muscle, 409
lateralis muscle, 407
medialis, 408
Vein or Veins ; Vena or Venae, 958
abnormalities of, 1058
advehentes, 1037
allantoic, 68
alveolar, 968
anal, 984
anastomotic, posterior, 971
great, of Trolard, 971
angular, 965
Vein or Veins (contd.)
anonymae dextra et sinistra, 962
anterior pyloric, of Mayo, 1416
appendicular, 1421
aquaeductus vestibuli, 853
arciform, of kidney, 1267
auditory, internal, 853
auricular, anterior, 830, 967
posterior, 967
axillary, 977
abnormality of, 1447
development of, 1042
relations of, 977
surface anatomy of, 1447
tributaries of, 978
azygos, 960
abnormality of, 1058
development of, 1041
morphology of, 1049
basal, 971
basilic, 979
abnormalities of, 1059
development of, 1042
morphology of, 1050
surface anatomy of, 1447, 1448
basis of vertebrae, 976
of bones, 87
brachial, 977
of brain, 970
bronchial, anterior, 961
posterior, 961
morphology of, 1049
canaliculi cochleae, 965
canalis pterygoidei, 968
capillary, 867
cardiac, anterior, 960
great, 959
inferior, 960
middle, 960
oblique, of left atrium, 960
small, 959
smallest, 960
cardinal, anterior, 69, 1038
morphology of, 1049
posterior, 69, 1041
cava inferior, 980, 983, 1042
abnormality of, 1058
development of, 70, 1041
fossa of, 1192, 1195
morphology of, 1049
orifice of, 873, 875
surface anatomy of, 1426
superior, 960
abnormality of, 1058
development of, 70, 1035, 1036
morphology of, 1049
orifice of, 873, 874
surface anatomy of, 1405
centralis retinae, 818
cephalic, 978
abnormality of, 1059
development of, 1043
morphology of, 1050
surface anatomy of, 1448
cerebellar, 971
deep, 971
cerebral, 970,971
anterior, 971
basal, 971
deep, 971
middle, 971
inferior, 971
1588
INDEX.
Vein or Veins (contd.)
cerebral (contd.), magna Galeni, 674, 976
superficial, 971
middle, 971
superior, 971
cervical, transverse, 967
cervical, deep, anterior, 963
posterior, 963
transverse, 967
chorioid, 970
ciliary, 814
circumflex iliac, deep, 988
superficial, 989
colic, left, 992
middle, 992
right, 992
comitans, 959, 1049, 1059
conjunctiva!, 824
coronaria ventriculi, 991, 998
of corpus striatum, 970
of cranium, 969-976
cystic, 990, 992
deep, of trunk and limbs, 963
development of, 1035
digital, of foot, 988
morphology of, 1049
of hand, 978
diploic, 969
frontal, 969
occipital, 970
temporal, 969
dorsal, of clitoris, 942
linguae, 965
of penis, 985
deep, 985
superficial, 985
duodenal, 992
elastic layer of, 869
emissary, 975
parietal, 968
endothelium of, 869
epigastric, inferior, 988
superficial, 986
superior, 968
of extremities, development of, 1042
facial, anterior, 965
surface anatomy of, 1391
common, 965
surface anatomy of, 1392
posterior, 968
deep, 965
femoral, 986
morphology of, 1049
tributaries of, 987
of forearm and arm, superficial, 978
frontal, 967, 969
gastric, right, 992
gastro-epiplok, 992
gluteal, inferior, 984
superior, 984
great cerebral, 970
hsemorrhoidal, inferior, 984
(media), 984
superior, 992
of head and neck, 964
of heart, 959
morphology of, 1048
hemiazygos, 961, 1041, 1049, 1058
accessoria, 961, 1041, 1049, 1058
hepatic, 982
abnormalities of, 1058
development of, 1037
Vein or Veins (contd.)
hepatic (contd.), morphology of, 1049
interlobular, 1200
sublobular, 1200
hypogastric, 984
development of, 1040, 1041
morphology of, 1048
ileo-csecal, 990
ileo-colic, 990
iliac, common, 983
abnormalities 'of, 1059
development of, 1041
left, 983
morphology of, 1048
right, 983
surface anatomy of, 1427
tributaries, 983
external, 986-988
ilio-lumbar, 983
infra-orbital, 968
innominate, 962
left, 962
development of, 1040
morphology of, 1048
right, 962
development of, 1040
intercostal, 961
anterior, 961
left superior, 961
development of, 1041
morphology of, 1048
posterior, 961
first left, 961
first right, 961
right superior, 963
morphology of, 1049
right superior, 961
interdigital, of foot, 954
of hand, 924
interlobar, of the kidney, 1267
interlobular, hepatic, 982
of the kidney, 1267
internal cerebral, 970
interosseous, of hand, 978
interventricular, inferior, 960
intervertebral, 976
intestinal, 992, 1210
jugular, anterior, 967
abnormalities of, 1058
external, 966
abnormalities of, 1058
development of, 1040
surgical anatomy of, 1394
internal, 964
abnormalities of, 1058
bulb of, 964
development of, 1040
morphology of, 1049
surgical anatomy of, 1391
posterior external, 966
primitive, 1040
labial, 1109
of large intestine, 992, 993
lingual, 965, 1130
surgical anatomy of, 1382
of liver, 980, 990
of Idwer limb, 985
abnormalities of, 1060
deep, 986
development of, 1042
morphology of, 1050
superficial, 988, 990
INDEX.
1589
Vein or Veins (contd.}
of lower limb, superficial (contd.}, develop-
ment of, 1042
lumbar, 982
abnormalities of, 1059
development of, 1041
morphology of, 1049
ascending, 961, 982
lymph vessels of, 870
magna cerebri, 970
mammary, internal, 962, 977
mandibular, 993
masseteric, 965
maxillary, internal, 968
morphology of, 1049
median, of bulb, 972
anterior, 972
antibrachii, 980
abnormalities of, 1059
development of, 1042
surgical anatomy of, 1450
I basilic, 979, 980
surgical anatomy of, 1450
cephalic, 980
abnormalities of, 1059
cubital, 979
surgical anatomy of, 1450
of forearm, 980
posterior, 972
mediastinal, 961, 963
of medulla oblongata, 972
meningeal, 970
mesenteric, inferior, 992
morphology of, 1050
superior, 992
tributaries of, 992, 993
morphology of, 1050
metacarpal, dorsal, 978
of mid-brain, 971
minimse cordis, 960
morphology of, 1048
muscle-fibres of, 869
musculo-phrenic, 963
nasal, 806
nerves of, 870
of the nose, 988
obliqua atrii sinistri (Marshalli), 70, 872,
960
obturator, 984
occipital, 967, 970
cesophageal, 1155
ophthalmic, inferior, 968
superior, 968
of orbit, 968
ovarian, 1048
abnormality of, 1058
morphology of, 1049
palatine, posterior, 965
palpebral, 824
pancreatic, 1208
pancreati co-duodenal, 1208
parotid, 965, 1137
pharyngeal, 965
canal, 968
phrenic, 982
of the pons, 971
popliteal, 986
abnormalities of, 1060
portal, 990
branches of, 991
capillaries of, 990
development of, 1037
Vein or Veins (contd.)
portal (contd.), morphology of, 1049
primitive development of, 1026
sinus of, 990
surgical anatomy of, 1416
tributaries, 991
primary head, 1039
primitive head, 69
profunda clitoridis, 984
penis, 984
pterygoid, 968
of pterygo-palatine region, 968
pterygo-palatine, 968
pubic, 988
pudendal, internal, 985
superficial, 988
pulmonary, 109, 958
development of, 1050
morphology of, 1050
orifices of, 875
relations of, 958
pyloric, 992
morphology of, 1049
radial, 919
abnormalities of, 1059
development of, 1042
morphology of, 1050
radicular, of medulla oblongata, 972
ranine, 965, 1130
surgical anatomy of, 1383
of rectum and anus, 1233
renal, 982
abnormalities of, 1059
development of, 1040
morphology of, 1049
revehentes, 1037
sacral, 983
middle, 983
saphena magna, 988, 989
abnormalities of, 1060
development of, 1043
morphology of, 1050
parva, development of, 1043
morphology of, 1050
surgical anatomy of, 1459, 1463
of scalp, 967
surgical anatomy of, 1357
scapular, transverse, 967
sciatic, 984
of scrotum, 1298
segmental, 1048, 1049
sigmoid, 993
special dorsal digital, 978
special volar digital, 978
spermatic, 983
abnormalities of, 1059
development of, 1040
surgical anatomy of, 1430
spheno-palatine, 968
spinal, 977
longitudinal, anterior, 977
posterior, 977
of spinal medulla, 977
splenic, 992
sternal, 963
of stomach, 991, 992
stria te, inferior, 971
structure of, 869
subcardinal, 1041
subclavian, 965
abnormalities of, 1059
development of, 1040
1590
INDEX.
Vein or Veins (contd.)
subclavian (contd.), morphology of, 1050
relations of, 965
surgical anatomy of, 1395
tributaries of, 966
superficial, of trunk and limbs, 978, 988
supra -orbital, 967
suprarenal, 982
abnormalities of, 1059
development of, 1040
systemic, general arrangement of, 959
temporal, deep, 968
anterior, 969
posterior, 969
superficial, 967
terminalis, 674, 970
testicular, 983
thyreoid, inferior, 964
morphology of, 1050
surgical anatomy of, 1389
middle, 965
superiores, 965
tibial, anterior, 986
posterior, 986
tonsillar, 1147
transverse cervical, 967
scapular, 967
tunica externa of, 869
intima of, 869
valves of, 869
media of, 869
tympanic, 842
ulnar, 977
development of, 1042
morphology of, 1050
umbilical, 68
impar, 66, 68, 1037
lateral, 66, 1036
development, 1036
of upper limb, 977
abnormalities of, 1059
deep branches of, 977
development of, 1042
morphology of, 1050
superficial branches of, 978
abnormalities of, 1058
uterine, 985
vaginal, 985
valves of, 869
of vertebrae, 976
vertebral, 963, 976
vesical, 1284
vessels of, 870
vestibular, 853
visceral, 1049
morphology of, 1049
vitelline, 56
vitello-umbilical, 69
vorticosae, 808
Velum, anterior medullary, 549, 569
development of, 33
palatinum, 1111
posterior medullary, 576
Vena azygos, 960
cava, inferior, 980
relations of, 980
tributaries of, 981
Venous arch, dorsal, of foot, 988
of hand, 918
transverse, of foot, 989
ligament (Arantius) of liver, 1196
sinuses of cranium, 969
Venous sinuses of cranium, development of, 1039
system, portal, 990
primitive development of, 68
valves of heart, 874, 875
Ventral aorta, 1026, 1027
Ventricles, cerebral, development of, 514, 517
fourth, 36, 549
acoustic area of, 551
area postrema of, 551
calamus scriptorius of, 550
chorioid plexuses of, 674
eminentia medialis, 551
floor of, 550
fossa rhomboidea of, 550
fovea, inferior of, 550
superior, of, 551
funiculus separans of, 551
lateral apertures of, 553
recess, 549
locus coeruleus of, 551
medial apertures of, 553
obex of, 579
roof of, 549, 578
striae medullaris of, 550
substantia ferruginea of, 551
tegmen of, 549
trigonum acustici of, 551
hypoglossi of, 551
vagi of, 551
lateral, 621, 632
anterior cornu of, 632, 634
body of, 633
chorioid plexus of, 636
cornu posterius, 633, 635
bulb of, 635
calcar avis of, 635
development of, 621
eminentia collateralis of, 636
floor of, 636
foramina of, 621, 632
hippocampus of, 636
horns of, 633, 635
surgical anatomy of, 1359
inferior cornu of, 633, 635
nuclei of, 635, 636, 637, 638, 639
pars centralis of, 633, 634
shape of, 633
trigonum of, 636
third, 616
anterior wall of, 617
chorioid plexus of, 674
floor of, 616
foramina of, 618
infundibulum of, 616
development of, 616
massa intermedia of, 617
recessus opticus of, 618
pinealis of, 618
suprapinealis of, 618
roof of, 617
side wall of, 617
sulcus hypothalamicus, 618
tela chorioidea of, 617
walls of, 617
of heart, 876
development of, 1032
left, 877
aortic orifice of, 878
valve, 878
mitral cusps of, 878
orifice of, 878
valve of, 878
INDEX.
1591
Ventricles of heart (contd.}, muscle of, 878
right, 876, 877
atrio- ventricular orifice of, 877
chordae tendineae of, 877
conns arteriosus of, 876
infimdibulum of, 876
moderator band of, 877
musculi papillares of, 877
pulmonary orifice of, 877
valve, 877
trabeculae carnese, 877
tricuspid valve, 877
septum of, 876
abnormality of, 1051
development of, 1032
of larynx, 1071
Ventricular septum of heart, 876, 898
Ventriculus terminalis of spinal medulla, 526
Vermiform process, 1215
in animals, 1217
blood-vessels of, 1217, 1421
cavity of, 1216
development of, 48
at different ages, 1216
lymph nodules of, 1217
vessels of, 1217
mesenteriolum of, 1216
morphology of, 1217
orifice of, 1216
position of, 1421
size of, 1216
structure of, 1217
surgical anatomy of, 1421
valve of, 1216
vessels of, 1217
Vermis cerebelli, 572, 574
Vernix caseosa, 862
Vertebra or Vertebrae, 87
accessory process of, 96
anticlinal, 101
arch of, -88
architecture of, 81
articular processes, 89
cervical, 90, 91
characteristics of, 90
coccygeal, 88, 99
ossification of, 106
common characters of, 88
epiphyses of, 104
false, 85
fifth lumbar, 96
fixed, 88
furcalis, 276
laminae, 89
lumbar, 95
characteristics of, 95
mamillary processes of, 96
movable, 88
ossification of, 104
prominens, 93
pseudo-sacral, 284
relation of, to spinal medulla, 519
important structures to spines of, 1442,
1443
to spinal nerves, 678
sacral, 96-98
ossification of, 104
serial homology of, 283
special (9th, 10th, llth, 12th), 94
thoracic, 93
characteristics of, 93
true, 88
Vertebra or Vertebrae (contd.), typical, 88
variations in, 275
veins of, 963
Vertebral aponeurosis, 365
arch, 88
arterial tubercle, 1395
artery, 910
border of scapula, 199
bow, 103
canal, 88
development, early, of, 29
membranous, 29
column, 87
articulation of, with cranium, 310
canal-of, 102
cartilaginous, 103
curves of, 100
development of, 102
intervertebral foramina, 102
length of, 102
ligaments of, 305
membranous, 29, 102
movements of, 309
surgical anatomy of, 1442, 1443
variations in, 275
as a whole, 100
foramen, 88
formula, 88
line of pleural reflexion, 1086
plexus, 759
vein, 963
Vertebrarterial foramen, 88, 89, 90
serial homology of, 283
variation in, 275
Vertebrate theory of skull, 293
Vertebro-chondral ribs, 109
Vertebro-sternal ribs, 109
Vertex, 285
Vertical plate of palate bone, 150
Vesalius, foramen of, 136
Vesica fellea, 1201
fossa for, 1191
urinaria, 1271
body of, 1274
fundus of, 1274
internal urethral orifice of, 1273
peritoneal relations of, 1272
position of, 1272
vertex of, 1274
Vesical arteries, 939
inferior, 939, 1284, 1295
middle, 939
of obturator, 940
superior, 1284, 1295
plexus of nerves, 766
venous, inferior, 985
superior, 985
Vesicle, auditory, 506
cerebral, 514
germinal, 22
optic, 825
otic, 51, 853
recessus labyrinthi of, 853
umbilical, 55
Vesico-vaginal artery, 939
Vesicula seminalis, 1286, 1290, 1295
development of, 1327, 1336
structure of, 1286
vessels of, 1289
Vestibular area, 846
ganglion, 785
gland, greater, 1326, 1327
1592
INDEX.
Vestibular gland (conld.), lesser, 1326
nerve, 853
Vestibule or vestibulum, aortic, 843
bulb of, 1326
pars intermedia of, 1326
bursse omentalis, 1239
of labyrinth, 843
aqueduct of, 843
crista of, 843
development of, 853
fissura of, 844
lamina spiralis ossea of, 844
secundaria, 844
macula cribrosa of, 84
pyramis vestibuli, 843
recessus cochlearis of, 843
ellipticus of, 843
sphericus of, 843
of larynx, 1069
of mouth, 1107
nasi, 802
oris, 1106
vaginae, 1325
bulb of, 1326
glands of, 1326
Vestigial fold of Marshall, 882
of pericardium, 872, 882
Vibrissse, 802
Villi, absorbent, 59
anchoring, 59
arachnoideal, 672
chorionic, 54
intestinal, 1179
primary chorionic, 53, 58
secondary chorionic, 58
Vincula accessoria, 430
brevia, 389
of flexor digitorum longus, 430
digitorum profundus, 389
sublimis, 388
longa, 389
tendinum, 388
Visceral arches, 42
clefts, 42, 46
intermediate arteries, 1043, 1046
veins, 1049
Visual areas and fibre tracts, 658
purple, 815
Vitelline body, 14
duct, 48, 55
membrane, 13
veins, 66
Vitello-intestinal duct, 38, 48, 55
Vitellus, 14
Vitreous body, 819
arteria hyaloidea, 819
canalis hyaloideus of Stilling, 819
composition of, 819
development of, 826
fossa patellaris of, 819
hyaloid fossa of, 819
membrane of, 819
spatia zonularia, 819
zonula ciliaris of, 819
Vocal folds, 1070
Voice, organs of, 1061
Volaris profunda artery, 923
superficial artery, 922
Vomer, 144
alse of, 144
architecture of, 271
connexions of, 147
Vomer (contd.), ossification of, 144
variations in, 279
Vomerine cartilage, 801
Vulva, 1324
anterior commissure of, 1324
bulbus vestibuli of, 1326
clitoris of, 1326
development of, 1335
fossa navicularis of, 1325
frenulum clitoridis of, 1326
labia majora of, 1324
minora of, 1324
mons Veneris of, 1324
nerves of, 1324
posterior commissure of, 1324
praeputium clitoridis of, 1326
surgical anatomy of, 1436
urogenital space of, 1325, 1328, 1336
vessels of, 1326
vestibular glands of, 1326, 1327
vestibule of, 1326
Wagner, corpuscles of, 865
Walking, movements of, 436
Wallerian degeneration, 532
Weight of the brain, 667
of the heart, 880
Wharton, duct of, 1138
surgical anatomy of, 1383
White line of anus, 1232
of pelvis, 491, 493
White matter of cerebellum, 516
of cerebral hemispheres, 647, 653
development of, 503, 505
of medulla oblongata, 557, 560, 562
of spinal medulla, 531, 539
Willis, circle of, 908
Windpipe, 1078
Wing, of sphenoid, orbital, 135
temporal, 136
Wirsung, duct of, 1206
Wisdom teeth, 1114, 1118
Wolffian body, 1329
duct, 1329
glomeruli, 1329
ridge, 39
tubules, 1329
Womb, 1316
Wormian bones, 145, 277, 278
Wounds of the scalp, 1357
Wrisberg, ganglion of, 790
Wrist, arterial arches of, 920, 922, 923
bones of, 217
ligaments of, 329
movements at, 334
synovial sheaths at, 388, 389
Wry neck, 1390
X-ray examination of the stomach, 1173
Xiphisternal joint, 316
surface anatomy of, 1397, 1407
Xiphoid artery, 914
cartilage, 108
Y-shaped ligament of Bigelow, 340
Yellow marrow, 83
Yolk, 14
nutritive, 14
sac, 38, 48, 55
Zahnleiste, 1245
Zona arcuata, 850
fasciculata of suprarenal gland, 1346
INDEX.
1593
Zona glonierulosa of suprarenal gland, 1346
orbicularis of hip-joint, 340
pectinata, 850
pellucida, 11
reticularis of suprarenal gland, 1346
stria ta, 11
Zones, abdominal, 1411
costal, 1158
epigastric, 1159
hypochondriac, 1159
hypogastric, 1158, 1159
iliac, 1159
lumbar, 1159
umbilical, 1158, 1159
Zonula ciliaris, 819
Zygapophyses, 283
of vertebra*, 89, 284
Zygomatic arch, 167, 169
surface anatomy of, 1364, 1365, 1367,
1375
bone, 153
architecture of, 271
Zygomatic bone (contd.}, connexions of, 154
ossification of, 154
processes of, 153
relation of, to orbit, 162, 164
tuberosity, 153
variations in, 279
centre, 150
crest, 137, 154
fossa, 168, 175
'head of quadra tus labii superioris muscle,
451
lymph glands (anterior auricular), 998
nerves, of facial, 784
of maxillary, 778
process, 148
Zygomatico-facial canal, 154
Zygomatico-orbital artery, 897
canal, 154
Zygomatico- temporal canal, 154
Zygomaticus muscle, 451
actions of, 452
Zygote, 13, 16
THE END
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